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Confinement of sulfur species into heteroatom-doped, porous carbon container for high areal capacity cathode
... [11,12] Much effort has been devoted to solve these problems in the past several years, which can be divided into either physical confinement or chemical confinement. In terms of physical confinement, porous sulfur host such as carbon nanotubes, [13,14] carbon nanofibers, [15] carbon spheres, [16,17] graphene, [18] hierarchical porous carbon [19,20] are often used to physically block the diffusion of polysulfides. Nevertheless, a gradual decrease in capacity with prolonged battery cycling is still observed due to the weak interaction between polar polysulfides and non-polar porous host. ...
Sulfur‐rich copolymers have gained a great deal of attention as promising cathode materials in Li−S batteries due to their low cost and naturally uniform sulfur dispersion. However, the poor electrical conductivity and shuttle effect cause rapid capacity decay and low sulfur utilization especially under high sulfur loading and low electrolyte/sulfur ratio. Herein, the Fe1‐xS/C dispersed and Se‐containing sulfur‐rich copolymer (FSP) was synthesized by one‐pot reaction of ferrocene, trithiocyanuric acid with SexSy. In such process, the trithiocyanuric acid reacts with SexSy to form Se‐containing sulfur‐rich copolymers. Simultaneously, ferrocene reacts with sulfur to form highly dispersed Fe1‐xS/C within sulfur‐rich copolymers. The covalent chemical binding of sulfur in the FSP effectively suppress the shuttle effect of polysulfides by chemical binding. Meanwhile, the Se improves the conductivity of FSP, which enhances the reaction kinetics. Moreover, the highly dispersed Fe1‐xS/C in the FSP is able to effectively catalyze polysulfide conversion and inhibit the shuttle effect. As a result, the optimized FSP electrode exhibits a high capacity of 1330 mAh g⁻¹ at 0.2 C. Even under high sulfur loading (4.08 mg cm⁻²) and low E/S ratio (6 μL mg⁻¹), the FSP cathode demonstrates a remarkable capacity of 734.7 mAh g⁻¹ at 0.2 C.
... Researchers have conducted a lot of research on lithium-sulfur battery cathode materials. Non-polar porous carbon materials or polar porous carbon doped with B, N, O, P, S and other elements were used to load sulfur to improve the electrical conductivity of cathode materials [11][12][13][14][15]. For example, carbon nanotubes (CNTs) or carbon nanofibers (CNFs) [16], graphene carbon nanosheets [17], and porous carbons and their complexes [18] used to prepare sulfur composite cathode materials can significantly improve the cycle stability and rate performance of lithium-sulfur batteries. ...
Lithium-sulfur batteries with high theoretical energy density and cheap cost can meet people’s need for efficient energy storage, and have become a focus of the research on lithium-ion batteries. However, owing to their poor conductivity and “shuttle effect”, lithium-sulfur batteries are difficult to commercialize. In order to solve this problem, herein a polyhedral hollow structure of cobalt selenide (CoSe2) was synthesized by a simple one-step carbonization and selenization method using metal-organic bone MOFs (ZIF-67) as template and precursor. CoSe2 is coated with conductive polymer polypyrrole (PPy) to settle the matter of poor electroconductibility of the composite and limit the outflow of polysulfide compounds. The prepared CoSe2@PPy-S composite cathode shows reversible capacities of 341 mAh g−1 at 3 C, and good cycle stability with a small capacity attenuation rate of 0.072% per cycle. The structure of CoSe2 can have certain adsorption and conversion effects on polysulfide compounds, increase the conductivity after coating PPy, and further enhance the electrochemical property of lithium-sulfur cathode material.
... The surface chemical properties are important factors that affects the surface wettability. 6,15,146,147 Thus, recent studies have focused on the introduction of more lithiophilic sites on the carbon matrix, including the addition of metal oxide, metal particles and polymers. According to the Wenzel model, reasonable materials (Al, Cu, CNT, and NiO) with strong binding energy between molten Li and matrix materials may improve wettability. ...
Lithium metal anodes are ideal for realizing high-energy-density batteries owing to their advantages, namely high capacity and low reduction potentials. However, the utilization of lithium anodes is restricted by the detrimental lithium dendrite formation, repeated formation and fracturing of the solid electrolyte interphase (SEI), and large volume expansion, resulting in severe "dead lithium" and subsequent short circuiting. Currently, the researches are principally focused on inhibition of dendrite formation toward extending and maintaining battery lifespans. Herein, we summarize the strategies employed in interfacial engineering and current-collector host designs as well as the emerging electrochemical catalytic methods for evolving-accelerating-ameliorating lithium ion/atom diffusion processes. First, strategies based on the fabrication of robust SEIs are reviewed from the aspects of compositional constituents including inorganic, organic, and hybrid SEI layers derived from electrolyte additives or artificial pretreatments. Second, the summary and discussion are presented for metallic and carbon-based three-dimensional current collectors serving as lithium hosts, including their functionality in decreasing local deposition current density and the effect of introducing lithiophilic sites. Third, we assess the recent advances in exploring alloy compounds and atomic metal catalysts to accelerate the lateral lithium ion/atom diffusion kinetics to average the spatial lithium distribution for smooth plating. Finally, the opportunities and challenges of metallic lithium anodes are presented, providing insights into the modulation of diffusion kinetics toward achieving dendrite-free lithium metal batteries.
... Even the uniform Li metal corrosion caused by the dissolution and diffusion of LiPSs in the electrolyte could result in the fluctuation of Coulombic efficiency with limited Li, but the pouch cell still shows high Coulombic efficiency of >96% and stable cycle life, further suggesting the function of the outer layer Ta 2 O 5 in restraining the dissolution of LiPSs in organic electrolyte and eliminating Li metal corrosion. Our TiN@C/S/Ta 2 O 5 pouch cell exhibits a superior electrocatalytic sulfur reduction reaction (SRR) and represents a significant advance in the light of specific capacity, good cycling life, and capacity retention when compared with some reported data (Table S2) [29][30][31][32]. Despite the substantial progress made in our work, there is much room to further enhance the energy densities by optimizing both the mass-production process and cell configuration for making the pouch cell. ...
Lithium-sulfur (Li-S) batteries are deemed to be one of the most optimal solutions for the next generation of high-energy-density and low-cost energy storage systems. However, the low volumetric energy density and short cycle life are a bottleneck for their commercial application. To achieve high energy density for lithium-sulfur batteries, the concept of synergistic adsorptive-catalytic sites is proposed. Base on this concept, the TiN@C/S/Ta2O5 sulfur electrode with about 90 wt% sulfur content is prepared. TiN contributes its high intrinsic electron conductivity to improve the redox reaction of polysulfides, while Ta2O5 provides strong adsorption capability toward lithium polysulfides (LiPSs). Moreover, the multidimensional carbon structure facilitates the infiltration of electrolytes and the motion of ions and electrons throughout the framework. As a result, the coin Li-S cells with TiN@C/S/Ta2O5 cathode exhibit superior cycle stability with a decent capacity retention of 56.1% over 300 cycles and low capacity fading rate of 0.192% per cycle at 0.5 C. Furthermore, the pouch cells at sulfur loading of 5.3 mg cm-2 deliver a high areal capacity of 5.8 mAh cm-2 at low electrolyte/sulfur ratio (E/S, 3.3 μL mg-1), implying a high sulfur utilization even under high sulfur loading and lean electrolyte operation.
... Figure 1B shows that SACo/ADFS@HPSC exhibits a cross-linked network nanostructure with hierarchical macropores and mesopores, which is potentially beneficial for the electrolyte immersion and Li + transfer. 13,14,40,43 In the highresolution SEM image ( Figure 1C), large numbers of nanoparticles are observed and distributed in a nanocarbon matrix. The TEM images of SACo/ADFS@HPSC in Figure 1D and Figure S1A also reveal the porous structure of HPSC and the small size of in situ formed nanoparticles with a domain size of about 100 nm. ...
Lithium metal electrodes have shown great promise for high capacity and the lowest potential. However, wide application is restricted by uncontrollable plating/stripping lithium behaviors, an uneven solid electrolyte interphase, and a lithium dendrite. Herein, the highly active single metal atom anchored in vacant catalyst is synthesized on the hierarchical porous nanocarbon (SACo/ADFS@HPSC). Acting as an artificial protective modulation layer on the lithium surface, the numerous atomic sites show the superiority in modulating lithium ion behaviors and smoothing the lithium surface without dendrite growth. As a consequence, the SACo/ADFS@HPSC-modified Li electrode lowers nucleation barrier (15 mV), extends the smooth plating lifespan (1600 h), and improves Coulombic efficiency, significantly accelerating the horizonal deposition of plated lithium. Coupled with a sulfur cathode, the fabricated pouch cell with 5.4 mg cm-2 delivers a high capacity of 3.78 mA h cm-2 corresponding to 1505 Wh kg-1, showing the promising practical application.
... The observation of higher D Li + for S@CNTs/HNC-800 than S@HNC-800 suggests a faster reaction kinetics for the S@CNTs/HNC-800 based electrode, probably due to the presence of abundant pores and tunnels in CNTs/HNC as well as the catalysis of N-doped carbon matrix towards the reversible conversion of sulfur and lithium polysulfides. As for the electrochemical impedance spectra recorded with in the frequency range of 0.01 Hz to 100 kHz (Figure 4f), the Nyquist plots of all the three investigated samples display a semicircle that corresponds to charge-transfer resistance (R 1 ) [49][50][51] in the high frequency region. Based on the corresponding equivalent circuit model (insetto the upper right of Figure 4f), the R 1 of electrolyte-electrode interface is determined to be 22.72 Ω for S@CNTs/HNC-800 electrode (Figure 4f), which is much smaller than that of S@HNC-800 (57.02 Ω) and S@CNTs (75.50 Ω) electrodes, signifying a faster reaction kinetics for lithium polysulfides conversion and lower interfacial resistance for charge transfer in the S@CNTs/HNC-800 electrode, most likely due to the effective catalysis of N-doped carbon towards lithium polysulfides conversion and sufficient infiltration of electrolyte intothe abundant mesopores of S@CNTs/HNC-800 electrode. ...
Effectively confining lithium polysulfides inside porous material matrix with a high electrical conductivity represents a judicious way to extend lifespan and enhance rate performance of lithium‐sulfur (Li‐S) batteries. Herein, nitrogen‐doped hollow carbon polyhedrons with a thin CNTs conductive surface layer (CNTs/HNC) were prepared by directly pyrolyzing the CNTs coated ZIF‐8 polyhedrons crystallite precursors, and subsequently served as sulfur hosts in Li‐S batteries. The resulted product CNTs/HNC‐800 comprises a nitrogen content of 4.94 at.% as well as a high electrical conductivity of 8.43 × 10 ‐1 S cm ‐1 , which help to effectively adsorb/confine lithium polysulfides and substantially improve the rate capacity of Li‐S batteries. With a sulfur loading of 1.60 mg cm ‐2 , the S@CNTs/HNC based cathode shows a discharge capacity of 870.7 mAh g ‐1 at 1 C, and can maintain 76.4% of its initial capacity after 500 charge‐discharge cycles, corresponding to a capacity fade rate of only 0.047% per cycle. While with a higher sulfur loading of 2.46 mg cm ‐2 , a discharge capacity of 649.7 mAh g ‐1 can be achieved at 0.5 C, along with a capacity fade rate of merely 0.044% per cycle during 200 cycles. When sulfur loading is further increased to 5.39 mg cm ‐2 , it can also maintain a considerable initial discharge capacity of 812 mAh g −1 at 0.1C. This work enriches the ways to prepare complicate nanostructured sulfur hosts for long‐life and high‐rate Li‐S batteries.
... 23 In 2017, an intensive literature research within a perspective article on Li-S cells revealed that studies on practical cells need to be intensified as results obtained in bottom or coin cells are very often misleading, as discussed in detail in Cleaver et al. 15 Since 2017, an increasing number of articles published pouch cell results analyzing the translation from coin to pouch cell for lithium-metal batteries in general [24][25][26][27] and Li-S batteries in particular. 16,21,22,[28][29][30][31][32][33][34][35][36][37] Nevertheless, values for Wh/kg on cell level, practical cathode areal capacities, low electrolyte amounts, and transparent calculations on components 13,16,28,30,35,36 are rarely found and require more consideration. Moreover, developments in regard of electrolyte formulations with low polysulfide solubility working under lean conditions have been made. ...
Lithium-sulfur (Li-S) technology was identified as a promising candidate to overcome energy density limitations of common lithium-ion batteries given the world-wide abundance of sulfur as a low-cost alternative to state-of-the-art active materials, such as Ni and Co. Li-S cells have received tremendous recognition in recent years, both from a scientific and industrial perspective. However, only few data on adequate multilayer-pouch cell characterization are available so far, and transparent calculations on components require more consideration. Because of the gap of lab cell characterization and prototype cell development, misinterpretations and false expectations are frequently reported, mostly resulting from lithium and electrolyte excess. For the commercialization of the Li-S technology, rapid transfer of new concepts on the prototype cell level is essential. Furthermore, fundamental studies should concentrate on fundamental scientific questions related to the main bottlenecks of Li-S cells: understanding anode and electrolyte degradation phenomena and realistic evaluation of stabilizing interfaces.
... The design and fabrication of advanced sulfur cathodes based on carbon materials are widely accepted to be the workable way to conquer those problems due to their desirable features including excellent conductivity and chemical stability. [11][12][13][14][15][16][17][18][19][20][21][22][23] With the in-depth research, the simply combination of excellent conductivity and adsorption sites within the carbon host is not good enough to satisfy the increasing demands of rapid charge/discharge for developing fast and long cycling life of the batteries. As is well known, electron transfer and lithium ion transport across the interfaces are quite decisive to the battery performance. ...
Rechargeable lithium‐sulfur (Li‐S) batteries with high areal capacity are hindered by ion/electron pathway and sluggish reaction kinetics of sulfur species resulting from high energy barriers. Inspired by the nature of biomass on efficient nutrition transfer, we have presented a high‐performance sulfur cathode based on nanocarbon tunnels with natural polar catalytic sites. The inherited tunnels can propel lithium ion transport across the interface to reach the active materials and the interior heteroatom dopants provide abundant catalytic sites to further reduce the energy barriers. The as‐fabricated sulfur cathode displays much higher rate performance of 565 mA h g ‐1 at 6 C and a low decay rates of 0.029% per cycle for 2000 cycles at 3 C. Most importantly, a high initial areal capacity of 5.1 mA h cm ‐2 with enhancing loading up to 5.8 mg cm ‐2 at 1 C is achieved, corresponding to volumetric capacity of 638 A h L ‐1 .
The intricate sulfur redox chemistry involves multiple electron transfers and complicated phase changes. Catalysts have been previously explored to overcome the kinetic barrier in lithium–sulfur batteries (LSBs). This work contributes to closing the knowledge gap and examines electrocatalysis for enhancing LSB kinetics. With a strong chemical affinity for polysulfides, the electrocatalyst enables efficient adsorption and accelerated electron transfer reactions. Resulting cells with catalyzed cathodes exhibit improved rate capability and excellent stability over 500 cycles with 91.9% capacity retention at C/3. In addition, cells were shown to perform at high rates up to 2C and at high sulfur loadings up to 6 mg cm⁻². Various electrochemical, spectroscopic, and microscopic analyses provide insights into the mechanism for retaining high activity, coulombic efficiency, and capacity. This work delves into crucial processes identifying pivotal reaction steps during the cycling process at commercially relevant areal capacities and rates.
The extremely depressive conversion kinetics of polysulfides due to sluggish Li+ diffusion kinetics remain to be resolved for low-temperature Li-S batteries (LT-LSB). Herein, the strategy of electron-delocalization nanocatalyst has been...
Lithium‐ion batteries (LIBs) are extensively used everywhere today due to their prominent advantages. However, the safety issues of LIBs such as fire and explosion have been a serious concern. It is important to focus on the root causes of safety accidents in LIBs and the mechanisms of their development. This will enable the reasonable control of battery risk factors and the minimization of the probability of safety accidents. Especially, the chemical crosstalk between two electrodes and the internal short circuit (ISC) generated by various triggers are the main reasons for the abnormal rise in temperature, which eventually leads to thermal runaway (TR) and safety accidents. Herein, this review paper concentrates on the advances of the mechanism of TR in two main paths: chemical crosstalk and ISC. It analyses the origin of each type of path, illustrates the evolution of TR, and then outlines the progress of safety control strategies in recent years. Moreover, the review offers a forward‐looking perspective on the evolution of safety technologies. This work aims to enhance the battery community's comprehension of TR behavior in LIBs by categorizing and examining the pathways induced by TR. This work will contribute to the effective reduction of safety accidents of LIBs.
High‐energy‐density lithium metal batteries (LMBs) are limited by reaction or diffusion barriers with dissatisfactory electrochemical kinetics. Typical conversion‐type lithium sulfur battery systems exemplify the kinetic challenges. Namely, before diffusing or reacting in the electrode surface/interior, the Li(solvent)x⁺ dissociation at the interface to produce isolated Li⁺, is usually a prerequisite fundamental step either for successive Li⁺ “reduction” or for Li⁺ to participate in the sulfur conversions, contributing to the related electrochemical barriers. Thanks to the ideal atomic efficiency (100 at%), single atom catalysts (SACs) have gained attention for use in LMBs toward resolving the issues caused by the five types of barrier‐restricted processes, including polysulfide/Li2S conversions, Li(solvent)x⁺ desolvation, and Li⁰ nucleation/diffusion. In this perspective, the tandem reactions including desolvation and reaction or plating and corresponding catalysis behaviors are introduced and analyzed from interface to electrode interior. Meanwhile, the principal mechanisms of highly efficient SACs in overcoming specific energy barriers to reinforce the catalytic electrochemistry are discussed. Lastly, the future development of high‐efficiency atomic‐level catalysts in batteries is presented.
Low‐temperature vanadium‐based zinc ion batteries (LT‐VZIBs) have attracted much attention in recent years due to their excellent theoretical specific capacities, low cost, and electrochemical structural stability. However, low working temperature surrounding often results in retarded ion transport not only in the frozen aqueous electrolyte, but also at/across the cathode/electrolyte interface and inside cathode interior, significantly limiting the performance of LT‐VZIBs for practical applications. In this review, a variety of strategies to solve these issues, mainly including cathode interface/bulk structure engineering and electrolyte optimizations, are categorially discussed and systematically summarized from the design principles to in‐depth characterizations and mechanisms. In the end, several issues about future research directions and advancements in characterization tools are prospected, aiming to facilitate the scientific and commercial development of LT‐VZIBs.
Sn-based anodes are promising high-capacity anode materials for low-cost lithium ion batteries. Unfortunately, their development is generally restricted by rapid capacity fading resulting from large volume expansion and the corresponding structural failure of the solid electrolyte interphase (SEI) during the lithiation/delithiation process. Herein, heterostructural core-shell SnO2-layer-wrapped Sn nanoparticles embedded in a porous conductive nitrogen-doped carbon (SOWSH@PCNC) are proposed. In this design, the self-sacrificial Zn template from the precursors is used as the pore former, and the LiF-Li3N-rich SEI modulation layer is motivated to average uniform Li+ flux against local excessive lithiation. Meanwhile, both the chemically active nitrogen sites and the heterojunction interfaces within SnO2@Sn are implanted as electronic/ionic promoters to facilitate fast reaction kinetics. Consequently, the as-converted SOWSH@PCNC electrodes demonstrate a significantly boosted Li+ capacity of 961 mA h g-1 at 200 mA g-1 and excellent cycling stability with a low capacity decaying rate of 0.071% after 400 cycles at 500 mA g-1, suggesting their great promise as an anode material in high-performance lithium ion batteries.
The viability of lithium‐sulfur (Li–S) batteries toward real implementation directly correlates with unlocking lithium polysulfide (LiPS) evolution reactions. Along this line, designing promotors with the function of synchronously relieving LiPS shuttle and promoting sulfur conversion is critical. Herein, the nitrogen evolution on hierarchical and atomistic Ni–N–C electrocatalyst, mainly pertaining to the essential subtraction, reservation and coordination of nitrogen atoms, is manipulated to attain favorable Li–S pouch cell performances. Such rational evolution behavior realizes the “nitrogen balance” in simultaneously regulating the Ni–N coordination environment, Ni single atom loading, abundant vacancy defects, active nitrogen and electron conductivity, and maximizing the electrocatalytic activity elevation of Ni–N–C system. With such merit, the cathode harvests favorable performances in a soft‐packaged pouch cell prototype even under high sulfur mass loading and lean electrolyte usage. A specific energy density up to 405.1 Wh kg⁻¹ is harvested by the 0.5‐Ah‐level pouch cell.
Lithium metal is considered as the most prospective electrode for next‐generation energy storage systems due to high capacity and the lowest potential. However, uncontrollable spatial growth of lithium dendrites and the crack of solid electrolyte interphase still hinder its application. Herein, Schottky defects are motivated to tune the 4f‐center electronic structures of catalysts to provide active sites to accelerate Li transport kinetics. As experimentally and theoretically confirmed, the electronic density is redistributed and affected by the Schottky defects, offering numerous active catalytic centers with stronger ion diffusion capability to guide the horizontal lithium deposition against dendrite growth. Consequently, the Li electrode with artificial electronic‐modulation layer remarkably decreases the barriers of desolvation, nucleation, and diffusion, extends the dendrite‐free plating lifespan up to 1200 h, and improves reversible Coulombic efficiency. With a simultaneous catalytic effect on the conversions of sulfur species at the cathodic side, the integrated Li–S full battery exhibits superior rate performance of 653 mA h g−1 at 5 C, high long‐life capacity retention of 81.4% at 3 C, and a high energy density of 2264 W h kg−1 based on sulfur in a pouch cell, showing the promising potential toward high‐safety and long‐cycling lithium metal batteries. The electronic structure of CeO2 is initially modulated by introducing Schottky defects, providing more active sites for interacting with lithium ion/atom. Higher Schottky defect concentration is more beneficial to motivate charge transfer effect on manipulating horizontal deposition, achieving uniform and smooth plating Li surface with long‐term cycling of 1200h and ultra‐low overpotentials.
Abstract Lithium–sulfur (Li–S) batteries, although a promising candidate of next‐generation energy storage devices, are hindered by some bottlenecks in their roadmap toward commercialization. The key challenges include solving the issues such as low utilization of active materials, poor cyclic stability, poor rate performance, and unsatisfactory Coulombic efficiency due to the inherent poor electrical and ionic conductivity of sulfur and its discharged products (e.g., Li2S2 and Li2S), dissolution and migration of polysulfide ions in the electrolyte, unstable solid electrolyte interphase and dendritic growth on anodes, and volume change in both cathodes and anodes. Owing to the high specific surface area, pore volume, low density, good chemical stability, and particularly multimodal pore sizes, hierarchical porous carbon (HPC) materials have received considerable attention for circumventing the above problems in Li–S batteries. Herein, recent progress made in the synthetic methods and deployment of HPC materials for various components including sulfur cathodes, separators and interlayers, and lithium anodes in Li–S batteries is presented and summarized. More importantly, the correlation between the structures (pore volume, specific surface area, degree of pores, and heteroatom‐doping) of HPC and the electrochemical performances of Li–S batteries is elaborated. Finally, a discussion on the challenges and future perspectives associated with HPCs for Li–S batteries is provided.
Rechargeable lithium–sulfur (Li–S) full batteries hold practical promise for nextgeneration energy storage system owing to low cost and unparalleled theoretical energy density of 2600Wh kg-1. However, wide commercialization is severely hampered by the poor conductivity of S/Li2S, worrisome polysulfide shuttling effect, sluggish multistep reaction kinetics, and uncontrolled lithium dendrite growth. 2D materials show the advantages in suppressing polysulfide shuttling
and boosting lithium diffusion kinetics through rational modifications of surface chemistry and nanostructure design, greatly enhancing battery performances. In this review, the recent developments of 2D graphene-based materials in propelling the conversion/plating kinetics of Li–S full batteries are highlighted from intrinsic conductive property to adsorption and catalysis modifications. Specifically, with the functionalization of the pore morphology and heteroatom/metal atom doping in the pristine/hybrid matrix, the adsorption ability and the
lithium diffusion kinetics are significantly enhanced in both cathodic and anodic side, so that the interconversion kinetics of sulfur species are propelled to inhibit polysulfide shuttling and lithium-ion flux is homogenized to realize uniform deposition without any dendrite growth. Furthermore, challenges and opportunities for future fully development of Li–S batteries based on 2D graphene-based materials are prospected from interfacial mechanisms at the atomic/molecular level to large-scale production.
Lithium–sulfur batteries (LSBs) are considered one of the most promising candidates for next-generation energy storage owing to their large energy capacity. Tremendous effort has been devoted to overcoming the inherent problems of LSBs to facilitate their commercialization, such as polysulfide shuttling and dendritic lithium growth. Pouch cells present additional challenges for LSBs as they require greater electrode active material utilization, a lower electrolyte–sulfur ratio, and more mechanically robust electrode architectures to ensure long-term cycling stability. In this review, the critical challenges facing practical Li–S pouch cells that dictate their energy density and long-term cyclability are summarized. Strategies and perspectives for every major pouch cell component—cathode/anode active materials and electrode construction, separator design, and electrolyte—are discussed with emphasis placed on approaches aimed at improving the reversible electrochemical conversion of sulfur and lithium anode protection for high-energy Li–S pouch cells.
Lithium sulfur batteries have exhibited unparalleled advantages in energy density. However, the sulfide oxidation reactions (SORs) in sulfur cathode is much more sluggish, which is mainly restricted by high conversion barriers. Herein, the catalytic “Li-N” bond sites are designed to activate SORs in high areal loading cathode with the multi-functions of bridging the active materials and carbon matrix tightly. The presence of catalytic “Li-N” bonds is co-revealed by X-ray photoelectronic spectroscopy and electronic energy loss spectroscope. As unraveled by theoretical physical van der Waals interaction analysis and various electrochemical tests, the improved kinetics and mechanism of SORs are achieved by motivating polysulfide interconversions and propelling lithium ion diffusion. Consequently, the so-fabricated electrode with abundant Li-N bond catalytic sites deliveries 900 mA h g⁻¹ at 0.05 C and a stable retention of 74.3% at 1 C after 300 cycles. More impressively, high-loading with high-weight-content cathodes still remain rapid SORs kinetics, high capacity utilization and retention from 3.0 to 6.9 mg cm⁻². At 6.5 mg cm⁻², the cathode displays 550 mA h g⁻¹ at 0.76 mA cm⁻² corresponded to 3.58 mA h cm⁻², which is better than many reports. These results shed light on using intrinsic catalytic sites to realize application of batteries.
Lithium‐sulfur (Li‐S) batteries exhibit unparalleled merits in theoretical energy density (2600 Wh kg‐1) among next‐generation storage systems. However, the sluggish electrochemical kinetics of sulfur reduction reactions (SRRs), sulfide oxidation reactions (SORs) in the sulfur cathode and the lithium dendrite growth resulted from uncontrollable lithium behaviors in lithium anode have inhibited high‐rate conversions and uniform deposition to achieve high performances. Thanks to the “adsorption‐catalysis” synergetic effects, the reaction kinetics of SRRs/SORs composed of the delithiation of Li2S and the interconversions of sulfur species are propelled by lowering the delithiation/diffusion energy barriers, inhibiting polysulfide shuttling. Meanwhile, the anodic plating kinetic behaviors modulated by the catalysts tends to uniformize without dendrite growth. In this review, the various active catalysts in modulating lithium behaviors are summarized, especially for the defect‐rich catalysts (DRCs) and single atomic catalysts (SACs). The working mechanisms of these highly active catalysts revealed from theoretical simulation to in‐situ/operando characterizations are also highlighted. Furthermore, the opportunities of future higher performance enhancement to realize practical applications of Li‐S batteries are prospected, shedding light on the future practical development.
Lithium-sulfur(Li–S)batteries have received extensive attention due to the high theoretical energy density. However, tremendous works have been made to improve the three major problems of Li–S batteries. Namely, electrical insulation of sulfur, shuttle effect of polysulfide, and volume expansion of sulfur. However, there are still huge challenges to solve these problems and improve capacity. Here, we propose a strategy to prepare a double-shelled structure [email protected]2O5 spheres @GO composite.The polar hollow V2O5 sphere can realize the chemical adsorption of polysulfides and graphene oxide facilitates good electronic conductivity, thereby improving rate capability and cycling performance. The cycle capacity of [email protected]2O5 spheres @GO composite remains 895.7 mAh/g at 0.1C after 100 cycles and low capacity decay of 0.015% after 200 cycles at 1C rate, attributed to the double-shelled structure of the [email protected]2O5 spheres @ GO, the resulting electrode exhibits better performance. Offering a potential candidate for practical application of Li–S batteries in the future.
The development of lithium/sulfur batteries has been hindered by notorious shuttling effect and sluggish electrochemical conversion kinetics owing to high barrier of lithium ion transport behaviors. In this work, anionic oxygen vacancies in niobium oxide nanoparticle is fabricated on a high-conductive hierarchical porous nanocarbon as a sulfur anchor and lithium ion accelerator. As evidenced by optical coloration and electrochemical measurement, the oxygen-deficient electrocatalyst shows much stronger interaction ability to polysulfides and endows superior catalytic ability of propelling ion kinetics and facilitating the precipitation of Li2S. Theoretical simulations have also revealed that Nb-S bonds are formed when polysulfides interacts with AOV-Nb2O5-x catalyst. Consequently, the as-prepared sulfur cathode exhibits a high initial capacity of 1489 mA h g⁻¹, corresponding to the theoretical utilization of 89%, and a long life for 600 cycles at 1 C. Enhancing rate to 5 C, a rate capacity of 899 mA h g⁻¹ is obtained, demonstrating rapid conversion kinetics. Impressively, even increasing the areal loading to 4.2 mg cm⁻² with the lean electrolyte, the pouch cell can still exhibit the initial areal capacity of 3.54 mA h cm⁻² at 0.343 mA cm⁻² and stabilize for several tens of cycles, providing the promise for fast-charge batteries.
The volumetric energy density of lithium–sulfur (Li–S) batteries is particularly important to accommodate the ever-shrinking space of practical devices. A feasible path for improving the volumetric energy density of the cathode is to increase the utilization of active materials within a limited volume. However, the sluggish conversion kinetics and severe migration of polysulfides hinder its development. Herein, different from simple additives with large aggregation, we propose in situ growth of ultra-small tungsten carbide nanoparticles on highly conductive nanocarbon in a relatively low-temperature process. As evidenced by the comprehensive density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS) and electrochemical kinetic analyses, the in situ formed WC nanoparticles could strongly enhance the absorption ability of the sulfur species and reduce the reaction energy barriers, boosting the whole interconversion kinetics. Benefiting from these advantages, the as-synthesized hybrid cathode delivered a high rate capability of 6C (627 mA h g⁻¹) and enabled a long-term cycling lifespan of 500 cycles with a low decay rate of 0.039% at 5C. Moreover, a high volumetric capacity up to 625 mA h cm⁻³ (volumetric energy density of 1312 W h L⁻¹) was reached at the cathode-level with a high sulfur loading of 5.9 mg cm⁻² at 1C, suggesting a great promise in the development of Li–S batteries with high volumetric energy density.
The enhanced chemical immobilization and catalytic conversion of polysulfides (LiPS) intermediates are considered a promising solution to improve the electrochemical performance in lithium-sulfur batteries. However, the role of catalysts on catalytic mechanism of distinctive selectivity is still not understood and overlooked. Herein, a dual-functional strategy, composed of Fe3O4 nanoparticles/hierarchical porous carbon (Fe3O4/HPC) cathode and FeP/HPC modified separator, is proposed to improve anchoring and catalyzing of LiPS, ensure uniform Li2S deposition and reduce the dead sulfur. The systematic theoretical calculation reveals that the Fe3O4 has the stronger binding energy with LiPS (Li2S4 and Li2S6) due to the Fe-S bonds and Li-O bonds. The variations in the catalytic performance of Fe3O4 and FeP are due to the shifts of p band center. Especially, Fe3O4 and FeP tend to selectively catalyze the solid-liquid reaction and liquid-liquid-solid conversion, respectively. Thus, the synergistic effects of dual-catalysts in spatial separation help to achieve excellent cycling stability with an ultralow capacity decay rate of 0.083% over 1000 cycles at 1 C. Even with a high areal sulfur loading of 5.73 mg cm⁻² and a cruel current density of 0.01 C, the cells can still keep a low shuttle factor of 0.08, demonstrating the effective inhibition of shuttle effect. This work offers novel insights for designing a dual-functional structure in lithium-sulfur batteries.
The sluggish redox kinetics and shuttling effect result in low sulfur utilization, large polarization and rapid capacity decay of lithium-sulfur batteries. Here, we develop iron phosphide nanoparticles and reduced graphene oxide composites (FeP/rGO) as sulfiphilic host materials, which not only immobilize the polysulfides but also facilitate the fast charge transport kinetics. The FeP nanoparticles undergo superficial oxidation are beneficial to enhance the catalytic effect that leads to a higher coulombic efficiency and the rGO buffer the volume expansion of the sulfur electrode. Thus, the synergistic effect of FeP/rGO reduces the voltage overpotential and provides high adsorption–diffusion–conversion of polysulfides. Under the optimized condition, the S@FeP/rGO exhibits a high initial capacity of 1467.1 mAh g−1 at 0.1 C with a sulfur utilization of 87.7% and stable cycling stability with a capacity retention of 645.6 mAh g−1 at 1C after 500 cycles. In addition, the FeP/rGO composite has been used as a separator that exhibits excellent electrochemical performance. The current work provides a proof-of-concept study and practical application of S@FeP/rGO cathode in the lithium-sulfur batteries.
A strategy to produce sulfur (S) cathodes with ultrahigh areal capacity for lithium-sulfur (Li–S) batteries is proposed. Porous carbon nanotube (CNT) [email protected]2S8 cathodes are obtained by dropping Li2S8 solution into the CNT aerogels that are prepared through a freeze-drying method. The three-dimensional (3D) porous structure of the CNT aerogel provides a complete electron transport network and rapid ion transport channels. Moreover, the rich mesoporous structure has an extreme capillary action on the electrolyte. Numerical simulation shows that in a surprisingly short time (2 μs), the electrolyte can be absorbed into the mesopores by capillary action and reach a stable state, limiting the “shuttle effect” of polysulfides. Based on these unique characteristics, the CNT [email protected]2S8 cathode exhibits excellent electrochemical performance. With an extremely high areal S loading of 20 mg cm⁻², the cathode shows an ultrahigh areal specific capacity of 22.9 mAh cm⁻². For the pouch cell with an areal S loading of 10 mg cm⁻² and a low electrolyte/sulfur (E/S) ratio of 7.8 μL mg⁻¹, the areal specific capacity reaches a high value of 10.4 mAh cm⁻².
The performance of lithium-sulfur (Li-S) batteries is strongly limited by the sluggish lithium polysulfides (LiPSs) conversion kinetics and LiPSs shuttling. Herein, mesoporous Co3S4 hexagonal nanosheets with sulfur-atom vacancy defects (Co3S4-DHS) are synthesized via hydrothermally treating the Co3(VO4)2 hexagonal nanosheet parent in the presense of Na2S. The sulfur-atom vacancy defects endow Co3S4-DHS with a significantly enhanced electronic conductivity and superior LiPSs adsorbability. Moreover, the abundant mesoporous textures of Co3S4-DHS help to maximize the exposure of catalytically active sites toward LiPSs conversion and buffer the negative effects of large volume fluctuation of loaded sulfur during cycling. Benefiting from these aspects, the Li-S batteries employing Co3S4-DHS/S based cathodes exhibit a reversible specific capacity of 1090 mA h g-1 at 0.1 C and 750 mA h g-1 at 1 C, as well as a high capacity of 699 mAh g−1 after 400 charge-discharge cycles at 1 C, corresponding to a low capacity fade rate of 0.17% per cycle. This work enriches the way to fabricate defect-rich transition metal sulfides as efficient sulfur host materials for high-rate, long-lifespan rechargeable Li-S batteries.
Lithium–sulfur batteries are among the most promising candidates for next‐generation energy‐storage systems due to its high theoretical energy density. However, the shuttle effect of polysulfides and sluggish reaction kinetics severely hinder the development of practical Li–S batteries. Merely depending on an adsorption strategy to resist the shuttle effect is insufficient to boost the overall electrochemical conversion reaction. Recently, single atom catalysts (SACs) have been used to solve this problem by decreasing the energy barriers of sulfur‐species interconversion and Li2S decomposition. Herein, the research progress made in using SACs in Li–S batteries is discussed, focusing on their functions and catalytic mechanism. The challenges and prospects for future application of SACs in electrochemical energy‐storage systems are also discussed.
Lithium-sulfur (Li-S) batteries have received increasing attention due to their high energy density. However, it is still challenging to inhibit the diffusion of polysulfide and achieve high sulfur utilization. Herein, we designed and prepared a free-standing and binder-free electrode for high-performance Li-S batteries by in situ growth of 3D ordered macroporous MoO2 on carbonized nonwoven cloth (MoO2/CC). After the uptake of Li2S6, the obtained MoO2/CC-Li2S6 electrode with high sulfur loading of 3.26 mg cm-2 delivers a large discharge capacity of 1267 mA h g-1 at 0.1 C. A high discharge capacity of 621 mA h g-1 is still retained after 500 cycles at 2 C. The excellent electrochemical performance of this MoO2/CC-Li2S6 electrode is attributed to the unique nanostructure and strong chemical interaction between MoO2 and polysulfides. The 3DOM MoO2 not only guarantees the high loading of sulfur but also suppresses the diffusion of polysulfides. The carbonized nonwoven cloth (CC) functions as the basic support for the 3DOM MoO2, increasing the electronic conductivity and mechanical property of the free-standing electrodes. This work provides a feasible strategy for the construction of high-performance free-standing binder-free Li-S electrodes.
Rational design of functional interlayer is highly significant in pursuit of high-performance Li-S batteries. Herein, a nanocrystalline niobium carbide (NbC) is developed via a facile and scalable autoclave technology, which is, for the first time, employed as the advanced interlayer material for Li-S batteries. Combining the merits of strong polysulfides (PS) anchoring with high electric conductivity, the NbC-coated membrane enables efficiently tamed PS shuttling and fast sulfur electrochemistry, achieving outstanding cyclability with negligible capacity fading rate of 0.037% cycle−1 over 1500 cycles, superb rate capability up to 5 C, high areal capacity of 3.6 mA h cm−2 under raised sulfur loading, and reliable operation even in soft-package cells. This work offers a facile and effective method of promoting Li-S batteries for practical application.
How to exert the energy density advantage is a key link in the development of lithium–sulfur batteries. Therefore, the performance degradation of high-sulfur-loading cathodes becomes an urgent problem to be solved at present. In addition, the volumetric capacities of high-sulfur-loading cathodes are still at a low level compared with their areal capacities. Aiming at these issues, two-dimensional carbon yolk-shell nanosheet is developed herein to construct a novel self-supporting sulfur cathode. The cathode with high-sulfur loading of 5 mg cm⁻² and sulfur content of 73 wt% not only delivers an excellent rate performance and cycling stability, but also provides a favorable balance between the areal (5.7 mAh cm–2) and volumetric (1330 mAh cm–3) capacities. Remarkably, an areal capacity of 11.4 mAh cm–2 can be further achieved by increasing the sulfur loading from 5 to 10 mg cm–2. This work provides a promising direction for high-energy-density lithium–sulfur batteries.
While lithium–sulfur batteries are poised to be the next-generation high-density energy storage devices, the intrinsic polysulfide shuttle has limited their practical applications. Many recent investigations have focused on the development of methods to wrap the sulfur material with a diffusion barrier layer. However, there is a trade-off between a perfect preassembled wrapping layer and electrolyte infiltration into the wrapped sulfur cathode. Here, we demonstrate an in situ wrapping approach to construct a compact layer on carbon/sulfur composite particles with an imperfect wrapping layer. This special configuration suppresses the shuttle effect while allowing polysulfide diffusion within the interior of the wrapped composite particles. As a result, the wrapped cathode for lithium–sulfur batteries greatly improves the Coulombic efficiency and cycle life. Importantly, the capacity decay of the cell at 1000 cycles is as small as 0.03% per cycle at 1672 mA g–1.
Lithium-sulfur (Li-S) batteries with high energy density and long cycle life are considered to be one of the most promising next-generation energy-storage systems beyond routine lithium-ion batteries. Various approaches have been proposed to break down technical barriers in Li-S battery systems. The use of nanostructured metal oxides and sulfides for high sulfur utilization and long life span of Li-S batteries is reviewed here. The relationships between the intrinsic properties of metal oxide/sulfide hosts and electrochemical performances of Li-S batteries are discussed. Nanostructured metal oxides/sulfides hosts used in solid sulfur cathodes, separators/interlayers, lithium-metal-anode protection, and lithium polysulfides batteries are discussed respectively. Prospects for the future developments of Li-S batteries with nanostructured metal oxides/sulfides are also discussed.
A CO2 in water nanoparticle stabilized Pickering emulsion is used to template micrometer sized hollow porous nitrogen doped carbon particles for high rate performance lithium sulfur battery. For the first time, nanoparticles serve the dual role of an emulsion stabilizer and a pore template for the shell, directly utilizing in situ generated CO2 bubbles as template for the core. The minimalistic nature of this method does not require expensive surfactants or additional core templates. Upon polymerization of melamine formaldehyde onto CO2, a robust polymer/silica composite shell is formed and transformed into a porous shell upon washing. The micrometer-sized hollow morphology in combination with its nitrogen rich porous shell demonstrates impressive rate capabilities of 670 and 500 mAh g−1 even at a high rate of 7C and 9C, respectively. This material also possesses excellent cycle durability, exhibiting a low capacity decay of 0.088%/cycle over 300 cycles. Measurement of the shuttle current and impedance provides interesting insight into the polysulfide mass transfer mechanism of hollow structured sulfur hosts.
Sulfur-carbon composites are promising next generation cathode materials for high energy density lithium batteries and thus, their discharge and charge properties have been studied with increasing intensity in recent years. While the sulfur-based redox reactions are reasonably well understood, the knowledge of deleterious side reactions in lithium-sulfur batteries is still limited. In particular, the gassing behavior has not yet been investigated, although it is known that lithium metal readily reacts with the commonly used ethereal electrolytes. Herein, we describe, for the first time, gas evolution in operating lithium-sulfur cells with a diglyme-based electrolyte and evaluate the effect of the polysulfide shuttle-suppressing additive LiNO3. The use of the combination of two operando techniques (pressure measurements and online continuous flow differential electrochemical mass spectrometry coupled with infrared spectroscopy) demonstrates that the additive dramatically reduces, but does not completely eliminate gassing. The major increase in pressure occurs during charge, immediately after fresh lithium is deposited, but there are differences in gas generation during cycling depending on the addition of LiNO3. Cells with LiNO3 show evolution of N2 and N2O in addition to CH4 and H2, the latter being the main volatile decomposition products. Collectively, these results provide novel insight into the important function of LiNO3 as a stabilizing additive in lithium-sulfur batteries.
Although lithium−sulfur (Li−S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and insulating nature of sulfur. Here, we report a rationally designed Li−S cathode with a dual-confined configuration by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transport and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior electrochemical performance, including a large reversible capacity of 1,328 mAh g−1 in the first cycle, excellent cycling stability (maintaining a reversible capacity of 647 mAh g−1 at 0.2 C after 300 cycles) with nearly 100% Coulombic efficiency, and a high rate capability of 512 mAh g−1 at 8 C for 30 cycles, which is among the best reported rate capabilities.
Nitrogen and sulfur co-doped porous carbon spheres (NS-PCSs) were prepared using l-cysteine to control the structure and functionalization during the hydrothermal reaction of glucose and the subsequent activation process. As the sulfur hosts in Li-S batteries, NS-PCSs combine strong physical confinement and surface chemical interaction to improve the affinity of polysulfides to the carbon matrix.
A facile hard-templating method has been developed to prepare highly N-doped carbon/sulfur cathodes with thickness < 200 [small micro]m and large areal mass loading (> 2.5 mgsulfur cm-2). Lithium-sulfur batteries using this free-standing and binder-free hierarchical hybrid design exhibit good cycling performance, with stable areal capacities of 3.0 mAh cm-2, owing to favorable properties of the carbon host.
Herein, we report the construction of three-dimensional hollow [email protected] structure composed of N-doped CNT-assembled dodecahedra core derived from ZIF-67 and Ni(OH)2 nanosheet shell as the sulfur scaffold for Li-S batteries. The obtained sulfur cathode demonstrates outstanding electrochemical performance, including a high reversible capacity (1321 mAh g⁻¹ at 0.1 C), excellent rate capability (1030 and 753 mAh g⁻¹ at 1 and 3 C, respectively), and superior cycling stability (611 mAh g⁻¹ after 1000 cycles at 3 C). The enhancement in electrochemical performance can be ascribed to the unique [email protected] architecture: the interconnected CNT-assembled dodecahedra core provides rapid Li⁺/e⁻ transport and sufficient free space for volume change; the Ni(OH)2 nanosheet shell not only acts as a durable physical barrier, but also serves as the polar material to restrain the dissolution of polysulfides with chemical interaction. In addition, in-situ nitrogen doping in CNTs introduces rich defects and active sites for polysulfides adsorption. This work provides a promising direction for high performance Li-S batteries by coating strong polar material on carbon materials.
Exploring a stable and high-efficiency sulfur cathode with strong polarity and robust porous conductive framework is a critical challenge to develop advanced lithium-sulfur (Li-S) batteries. Herein, a multidimensional N-doped porous carbon/MoS2/CNTs (FSC/MoS2/CNTs) nano-architecture hybrid is rationally designed and successfully fabricated by the facile pyrolysis and hydrothermal process. For the nano-architecture composite, the porous carbon with electroconductive acid-CNTs imbedding effectively enhances the flexibility and construct a conductive network for rapid ions/electrons transfer; specifically, a synergistic action of polar MoS2 and electronegative doped N atoms significantly strengthens the chemical affinity with polysulfides; furthermore, MoS2 exhibits a strong catalytic effect that can improve the redox kinetics of polysulfides. On account of the merits mentioned above, the as-built N-doped porous carbon/MoS2/CNTs@S (FSC/MoS2/CNTs@S) composite, utilized as Li-S batteries cathode, delivers a high discharge capacity of 1313.4 mAh g-1 at 0.1 C, glorious rate performance with 671.6 mAh g-1 at 2.0 C and remarkable cycling stability with capacity fade rate of 0.059% per cycle for 500 cycles at 1.0 C. This work provides a novel and simple strategy to design a doped porous carbon/transition metal sulfide with CNTs decorating polar and conductive network hybrid for excellent performance Li-S batteries and numerous energy storage fields.
Antibiotic bacterial residue is a kind of hazardous waste generated during the extraction of antibiotic. Due to the large amount, difficult disposal and horrible impacts on environment and human health of antibiotic bacterial residues, it is of great significance to find an efficient treatment and resource technology. In an effort to recycle antibiotic bacterial residues from tough trash to treasure and target high value application, in this study, antibiotic bacterial residues were utilized for the fabrication of nitrogen doped porous carbon followed by modifying separator in the configuration of lithium‐sulfur batteries. Due to the high nitrogen doping, large surface area and abundant pores, the obtained lithium‐sulfur batteries delivered a high initial discharge capacity of 1426 mAh g‐1 at 0.2 C and a low fading rate of 0.077% per cycle within 700 cycles at 0.5 C with pure sulfur cathode.
h i g h l i g h t s 3D porous NSG is synthesized under ammonia and sulfide ion modulation. The surface chemistry and pore morphology of NSG is simultaneously optimized. The S@NSG cathode exhibits long cycle life and high capacity. a b s t r a c t Lithium/sulfur (Li/S) battery is a promising next-generation energy storage system owing to its high theoretical energy density. However, for practical use there remains some key problems to be solved, such as low active material utilization and rapid capacity fading, especially at high areal sulfur loadings. Here, we report a facile one-pot method to prepare porous three-dimensional nitrogen, sulfur-codoped graphene through hydrothermal reduction of graphene oxide with multi-ion mixture modulation. We show solid evidence that the results of multi-ion mixture modulation can not only improve the surface affinity of the nanocarbons to polysulfides, but also alter their assembling manner and render the resultant 3D network a more favorable pore morphology for accommodating and confining sulfur. It also had an excellent rate performance and cycling stability, showing an initial capacity of 1304 mA h g À1 at 0.05C, 613 mA h g À1 at 5C and maintaining a reversible capacity of 462 mA h g À1 after 1500 cycles at 2C with capacity fading as low as 0.028% per cycle. Moreover, a high areal capacity of 5.1 mA h cm À2 at 0.2C is achieved at an areal sulfur loading of 6.3 mg cm À2 , which are the best values reported so far for dual-doped sulfur cathodes.
Heteroatom-doped carbon hybrids containing sp²-hybridizedand sp³-hybridized nanocarbons have attracted immense interest as the sulfur hosts due to their unique 3D conductive networks and synergistic effect of physical absorption and chemical interaction in suppressing the dissolution of polysulfides. However, the reported carbon hybrids always require tedious fabrication process, including a multistep chemical vapor deposition and a thermally stable catalyst. Therefore, it is highly desirable to exploit a simple, renewable, and scalable strategy to fabricate 3D heteroatom-doped carbon hybrids. Herein, a N, P-co-doped 3D carbon hybrid was successfully fabricated via one-pot pyrolysis process. Due to the rapid Li+/e- transport among the 3D interconnected porous frameworks and effectively suppressed polysulfides dissolution by physical confinement and chemical interaction, the assembled Li-S batteries exhibit excellent electrochemical performance. The as-obtained cell delivers an ultrahigh initial discharge capacity of 1446 mAh g⁻¹ at 0.1 C as well as an excellent rate capability of 921 mAh g⁻¹ at 1 C. Additionally, a reversible and stable discharge capacity of 795 mAh g⁻¹ is remained after 400 cycles at 1C, corresponding to an extremely low capacity decay of 0.034% per cycle. Such design strategy is eco-friendly and generally applicable to combine the sp² nanocarbon with sp³ amorphous carbon, which is crucial to construct 3D interconnected hierarchical porous carbon in advanced energy storage, such as lithium batteries, catalysis and hydrogen storage.
The present work reports the preparation of activated carbon fibers (ACFs) from pineapple plant leaves, and its application on caffeine (CFN) removal from aqueous solution. The preparation procedure was carried out using the H3PO4 as activating agent and slow pyrolysis under N2 atmosphere. The characterization of materials was performed from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Boehm titration and pHpzc method. ACFs showed high BET surface area value (SBET = 1031m(2) g(-1)), well-developed mesoporous structure (mesopore volume of 1.27cm³ g(-1)) and pores with average diameter (DM) of 5.87nm. Additionally, ACFs showed features of fibrous material with predominance of acid groups on its surface. Adsorption studies indicated that the pseudo-second order kinetic and Langmuir isotherm models were that best fitted to the experimental data. The monolayer adsorption capacity was found to be 155.50mgg(-1). thermodynamic studies revealed that adsorption process is spontaneous, exothermic and occurs preferably via physisorption. The pineapple leaves are an efficient precursor for preparation of ACFs, which were successful applied as adsorbent material for removal of caffeine from the aqueous solutions.
High performance cathode with sufficiently high areal sulfur loading is still a major challenge for practical Li/S batteries. Herein, we propose a 3D nanocarbon architecture with robust electrical “highway” network for high sulfur mass loading and efficient sulfur utilization. The structure is constructed by “welding” highly conductive nitrogen-doped graphene (NG) and nitrogen-doped carbon nanotubes (NCNT) together through in-situ polymeric crosslinking and nitrogen-doped carbon shell (NCS) formation. The highly sulfur-absorptive NCS provides strong physical and chemical confinements to sulfur and polysulfides, which is confirmed by in-situ Raman and electrochemical analysis. At a moderate sulfur loading, the [email protected]@S cathode exhibits a high initial discharge capacity of 1421 mA h g⁻¹, excellent rate performance of 750 mA h g⁻¹ at 2 C and 465 mA h g⁻¹ at 5 C, and a capacity fading rate as low as 0.037% per cycle at 2 C for 1400 cycles. At high areal sulfur loading up to 10.2 mg cm⁻², the cathode retains a high areal capacity of 5.43 mA h cm⁻² after 150 cycles at a high current rate (1 C). A large areal cathode (77 × 50 mm²) with sulfur loading of 8.5 mg cm⁻² delivers a record-high capacity of 9.04 mA h cm⁻² at 0.1 C, demonstrating its great potential for practical application in Li/S batteries.
The most important challenge in the practical development of lithium-sulfur (Li−S) batteries is finding the suitable cathode materials. Due to the complexity of this system, various factors have been investigated during the last years, but still, the roadmap for designing the best cathode candidates is not vivid. This review attempts to create a better picture of the cathode process to pave the path for developing more practical cathode materials. The most promising candidate as the host cathode material is porous carbon nanomaterials, which are highly conductive and lightweight while having the capability of fabricating the freestanding electrodes. In this case, there is no need for a binder and current collector, and thus, a significantly higher energy density can be expected. Despite the good performance of these carbon-based sulfur cathodes, the presence of some additives anchoring the sulfur molecules to the electrode backbone seems necessary for the practical performance. Metal oxides and sulfides are among the best options, as they act as mediators in the electrochemical redox system of Li/S. Despite their similarities, these additives might mediate in the battery system via entirely different mechanisms. In addition to carbon nanomaterials, other porous materials such as metal-organic frameworks can also provide the cage-like architecture for the construction of sulfur cathode.
Here, we demonstrate a strategy to produce high areal loading and areal capacity sulfur cathodes by using vapor phase infiltration of low-density carbon nanotube (CNT) foams pre-formed by solution processing and freeze drying. Vapor phase capillary infiltration of sulfur into pre-formed and binder-free low-density CNT foams leads to mass loading of ~ 79 wt.% arising from interior filling and coating of CNTs with sulfur while preserving conductive CNT-CNT junctions that sustains electrical accessibility through the thick foam. Sulfur cathodes are then produced by mechanically compressing these foams into dense composites (ρ > 0.2 g/cm3), revealing specific capacity of 1039 mAh/gS at 0.1 C, high sulfur areal loading of 19.1 mg/cm2, and high areal capacity of 19.3 mAh/cm2. This work highlights a technique broadly adaptable to a diverse group of nanostructured building blocks where pre-formed low-density materials can be vapor infiltrated with sulfur, mechanically compressed, and exhibit simultaneous high areal and gravimetric storage properties. This provides a route for scalable, low-cost, and high energy density sulfur cathodes based on conventional solid electrode processing routes.
Self-healing capability helps biological systems to maintain their survivability and extend their lifespan. Similarly, self-healing is also beneficial to next-generation secondary batteries because high-capacity electrode materials, especially the cathodes such as oxygen or sulfur, suffer from shortened cyclic lives resulting from irreversible and unstable phase transfer. Herein, by mimicking a biological self-healing process, fibrinolysis, we introduced an extrinsic healing agent, polysulfide, to enable the stable operation of sulfur microparticle (SMiP) cathodes. An optimized capacity (~3.7 mAh cm-2) with nearly no decay after 2000 cycles at a high sulfur loading of 5.6 mg(S) cm-2 was attained. The inert SMiP is activated by the solubiliza-tion effect of polysulfides whereas the unstable phase transfer is mediated by mitigated spatial heterogeneity of polysulfides, which induces uniform nucleation/growth of solid compounds. The comprehensive understanding of the healing process, as well as of the spatial heterogeneity, could further guide the design of novel healing agents (e.g. lithium iodine) towards high-performance rechargeable batteries.
For the Lithium-Sulfur (Li-S) battery to be competitive in commercialization, it is requested that the sulfur electrode must have deliverable areal capacity > 8 mAh cm⁻², which corresponds to a sulfur loading > 6 mg cm⁻². At this relatively high sulfur loading, we evaluated the impact of binder and carbon type on the mechanical integrity and the electrochemical properties of sulfur electrodes. We identified hydroxypropyl cellulose (HPC) as a new binder for the sulfur electrode because it offers better adhesion between the electrode and the aluminum current collector than the commonly used polyvinylidene fluoride (PVDF) binder. In combination with the binder study, multiple types of carbon with high specific surface area were evaluated as sulfur hosts for high loading sulfur electrodes. A commercial microporous carbon derived from wood with high pore volume showed the best performance. An electrode with sulfur loading up to 10 mg cm⁻² was achieved with the optimized recipe. Based on systematic electrochemical studies, the soluble polysulfide to insoluble Li2S2/Li2S conversion was identified to be the major barrier for high loading sulfur electrodes to achieve high sulfur utilization.
The use of monolithic carbons with structural hierarchy and varying amounts of nitrogen and oxygen functionalities as sulfur host materials in high-loading lithium-sulfur cells is reported. The primary focus is on the strength of the polysulfide/carbon interaction with the goal of assessing the effect of (surface) dopant concentration on cathode performance. The adsorption capacity - which is a measure of the interaction strength between the intermediate lithium polysulfide species and the carbon - was found to scale almost linearly with the nitrogen level. Likewise, the discharge capacity of lithium-sulfur cells increased linearly. This positive correlation can be explained by the favorable effect of nitrogen on both the chemical and electronic properties of the carbon host. The incorporation of additional oxygen-containing surface groups into highly nitrogen-functionalized carbon helped to further enhance the polysulfide adsorption efficiency, and therefore the reversible cell capacity. Overall, the areal capacity could be increased by almost 70% to around 3 mA h cm(-2). We believe that the design parameters described here provide a blueprint for future carbon-based nanocomposites for high-performance lithium-sulfur cells.
Lithium-sulfur batteries, notable for high theoretical energy density, environmental benignity and low cost, hold great potentials for next-generation energy storage. Polysulfides, the intermediates generated during cycling, may shuttle between electrodes, compromising the energy density and cycling life. We report herein a class of regenerative polysulfide-scavenging layers (RSL), which effectively immobilize and regenerate polysulfides, especially for electrodes with high sulfur loadings (e.g. 6 mg cm-2). The resulted cells exhibit high gravimetric energy density of 365 Wh kg-1, initial areal capacity of 7.94 mAh cm-2, low self-discharge rate of 2.45% after resting for 3 days and dramatically prolonged cycling life. Such blocking effects have been thoroughly investigated and correlated with the work functions of the oxides, as well as their bond energies with polysulfides. This work offers not only a novel class of RSL to mitigate shuttling effect, but also a quantified design framework for advanced lithium-sulfur batteries.
Despite high theoretical energy density, the practical deployment of lithium-sulfur (Li-S) batteries is still not implemented because of the severe capacity decay caused by polysulfide shuttling and the poor rate capability induced by low electrical conductivity of sulfur. Herein, we report a novel sulfur host material based on “sea urchin”-like cobalt nanoparticle embedded and nitrogen-doped carbon nanotube/nanopolyhedra (Co-NCNT/NP) superstructures for Li-S batteries. The hierarchical micro-mesopores in Co-NCNT/NP can allow efficient impregnation of sulfur and block diffusion of soluble polysulfides by physical confinement, and the incorporation of embedded Co nanoparticles and nitrogen doping (~4.6 at.%) can synergistically improve the adsorption of polysulfides, as evidenced by beaker cell tests. Moreover, the conductive networks of Co-NCNT/NP interconnected by nitrogen-doped carbon nanotubes (NCNTs) can facilitate electron transport and electrolyte infiltration. Therefore, the specific capacity, rate capability and cycle stability of Li-S batteries are significantly enhanced. As a result, the Co-NCNT/NP based cathode (loaded with 80 wt% sulfur) delivers a high discharge capacity of 1240 mAh g–1 after 100 cycles at 0.1 C (based on the weight of sulfur), high rate capacity (755 mAh g–1 at 2.0 C) and ultralong cycling life (a very low capacity decay of 0.026% per cycle over 1500 cycles at 1.0 C). Remarkably, the composite cathode with high areal sulfur loading of 3.2 mg cm–2 shows high rate capacities and stable cycling performance over 200 cycles.
The practical use of lithium-sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulted poor rate capabilities. Here, we report a sulfur-carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Served as cathode material for Li-S battery, the elaborately designed S/C composite leads to “kinetically stable” transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance. In this way, the S/C composite has been proved a promising cathode material for high-rate Li-S batteries targeted at automobile storage.
Lithium-sulfur (Li-S) battery is expected to be the high-energy battery system for next generation. Nevertheless, the degradation of lithium anode in Li-S battery is the crucial obstacle for practical application. In this work, a porous carbon paper obtained from corn stalks via simple treating procedures is used as interlayer to stabilize the surface morphology of Li anode in the environment of Li-S battery. A smooth surface morphology of Li is obtained during cycling by introducing the porous carbon paper into Li-S battery. Meanwhile, the electrochemical performance of sulfur cathode is partially enhanced by alleviating the loss of soluble intermediates (polysulfides) into the electrolyte, as well as the side reaction of polysulfides with metallic lithium. The Li-S battery assembled with the interlayer exhibits a large capacity and excellent capacity retention. Therefore, the porous carbon paper as interlayer plays a bi-functional role in stabilizing the Li anode, and enhancing the electrochemical performance of the sulfur cathode for constructing a stable Li-S battery.
Theoretical and experimental studies together show phosphorene as a highly potent polysulfide immobilizer for lithium sulfur batteries, enabling a high capacity, good rate capability, and excellent cycling stability.
For the first time, nitrogen and phosphorus codoped hierarchically porous carbon (NPHPC) has been explored as an efficient host for sulfur. The material is fabricated based on a scalable, one-step process involving the pyrolysis of melamine polyphosphate synthesized via a simple and versatile organic approach by using low cost industrial raw materials (melamine and polyphosphoric acid). The key features of NPHPC are the hierarchically porous structure and high surface area (1398 m² g⁻¹) that not only benefit for maximum sulfur loading but also capable of suppressing the dissolution of polysulfides through physisorption. Meanwhile, the N and P codopants together with the thermally stable functionalities are favorable for binding polysulfides via chemisorption. Benefitting from the synergistic effect of structural confinement (physisorption) and chemical binding (chemisorption), the NPHPC/S composite with a high sulfur content of 73 wt% delivers high capacity (1580 mAh g⁻¹ at 0.02 C) and long lifespan (200 cycles with 71% retention) for Li-S batteries. The present work highlights the importance of adopting heteroatom-doped hierarchically porous carbon for improving the performance of Li-S batteries, which may further stimulate more efforts in exploring advanced carbon-based hosts in the near future.
Due to their high energy density and low material cost, lithium-sulfur batteries represent a promising energy storage system for a multitude of emerging applications, ranging from stationary grid storage to mobile electric vehicles. This review aims to summarize major developments in the field of lithium-sulfur batteries, starting from an overview of their electrochemistry, technical challenges and potential solutions, along with some theoretical calculation results to advance our understanding of the material interactions involved. Next, we examine the most extensively-used design strategy: encapsulation of sulfur cathodes in carbon host materials. Other emerging host materials, such as polymeric and inorganic materials, are discussed as well. This is followed by a survey of novel battery configurations, including the use of lithium sulfide cathodes and lithium polysulfide catholytes, as well as recent burgeoning efforts in the modification of separators and protection of lithium metal anodes. Finally, we conclude with an outlook section to offer some insight on the future directions and prospects of lithium-sulfur batteries.
Compared with a two dimensional graphene sheet, a three dimensional (3D) graphene sponge has a continuous conductive structure and numerous pores, which are beneficial for sulfur utilization and anchoring. However, strategies for the construction of 3D graphene sponges composited with sulfur nanoparticles (3DGS) are either energy consuming or involve toxic reagents. Herein, a 3DGS is fabricated via a reduction induced self-assembly method, which is simple but facile and scalable. The structural design of this 3DGS promises fast Li(+) transport, superior electrolyte absorbability and effective electrochemical redox reactions of sulfur. As a result, this 3DGS achieves a stable capacity of 580 mA h g(-1) after 500 cycles at a high rate of 1.5 A g(-1), which corresponds to a low fading rate of 0.043% per cycle. The present study effectively demonstrates that the 3D construction strategy is propitious for obtaining flexible high performance Li-S batteries.
A unique nanostructure of 3D and vertically aligned and interconnected porous carbon nanosheets (3D-VCNs) is demonstrated by a simple carbonization of agar. The key feature of 3D-VCNs is that they possess numerous 3D channels with macrovoids and mesopores, leading to high surface area of 1750 m2 g-1, which play an important role in loading large amount of sulfur, while vertically aligned microporous carbon nanosheets act as the multilayered physical barrier against polysulfides anions and prevent their dissolution in the electrolyte due to strong adsorption during cycling process. As a result, the 3D hybrid (3D-S-VCNs) infiltered with 68.3 wt% sulfur exhibits a high and stable reversible capacity of 844 mAh g-1 at the current density of 837 mA g-1 with excellent Coulombic efficiency ≈100%, capacity retention of ≈80.3% over 300 cycles, and good rate ability (the reversible capacity of 738 mAh g-1 at the high current density of 3340 mA g-1). The present work highlights the vital role of the introduction of 3D carbon nanosheets with macrovoids and mesopores in enhancing the performance of LSBs.
An ultrahigh-loading lithium polysulfide cathode is developed to investigate the electrochemical behaviors of high-energy Li-S batteries. With this design, Li-S batteries with an ultrahigh areal sulfur loading (18.1 mg cm–2) are achieved with low polarization, high areal capacity, and promising cycling performance. It is further demonstrated that the challenge for high sulfur loading cells is the serious lithium-metal corrosion and electrolyte depletion.
Lithium–sulfur batteries can deliver significantly higher specific capacity than standard lithium ion batteries, and represent the next generation of energy storage devices for both electric vehicles and mobile devices. However, the lithium–sulfur technology today is plagued with numerous challenges, including poor sulfur conductivity, large volumetric expansion, severe polysulfide shuttling and low sulfur utilization, which prevent its wide-spread adoption in the energy storage industry. Here we report a freestanding three-dimensional (3D) graphene framework for highly efficient loading of sulfur particles and creating a high capacity sulfur cathode. Using a one-pot synthesis method, we show a mechanically robust graphene–sulfur composite can be prepared with the highest sulfur weight content (90% sulfur) reported to date, and can be directly used as the sulfur cathode without additional binders or conductive additives. The graphene–sulfur composite features a highly interconnected graphene network ensuring excellent conductivity and a 3D porous structure allowing efficient ion transport and accommodating large volume expansion. Additionally, the 3D graphene framework can also function as an effective encapsulation layer to retard the polysulfide shuttling effect, thus enabling a highly robust sulfur cathode. Electrochemical studies show that such composite can deliver a highest capacity of 96 mAh·g–1, a record high number achieved for all sulfur cathodes reported to date when normalized by the total mass of the entire electrode. Our studies demonstrate that the 3D graphene framework represents an attractive scaffold material for a high performance lithium sulfur battery cathode, and could enable exciting opportunities for ultra-high capacity energy storage applications.
A 3D graphene-foam-reduced-graphene-oxide hybrid nested hierarchical network is synthesized to achieve high sulfur loading and content simultaneously, which solves the "double low" issues of Li-S batteries. The obtained Li-S cathodes show a high areal capacity two times larger than that of commercial lithium-ion batteries, and a good cycling performance comparable to those at low sulfur loading.
A sulfur electrode exhibiting strong polysulfide chemisorption using a porous N, S dual-doped carbon is reported. The synergistic functionalization from the N and S heteroatoms dramatically modifies the electron density distribution and leads to much stronger polysulfide binding. X-ray photoelectron spectroscopy studies combined with ab initio calculations reveal strong Li(+) -N and Sn (2-) -S interactions. The sulfur electrodes exhibit an ultralow capacity fading of 0.052% per cycle over 1100 cycles.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A facile method was presented to synthesize three-dimensional carbon nanotubes/graphene-sulfur (3DCGS) sponge with high sulfur loading of 80.1%. In the well-designed 3D architecture, the two-dimensional graphene nanosheets functions as the 3D porous backbone and the one-dimensional (1D) highly conductive carbon nanotubes (CNT) can not only significantly enhance the conductivity, but also effectively tune the mesopore structure. Compared to the three-dimensional graphene-sulfur (3DGS) sponge without CNT, the conductivity of 3DCGS is enhanced by 324.7%; most importantly, compared to the monomodal mesopores (with a size of 3.5 nm) formed in the 3DG, the bimodal mesopores (with sizes of 3.5 and 32.1 nm) were formed in 3DCG; the bimodal mesopores, especially the newly formed 32.1-nm mesopores, provide abundant electrochemical nanoreactors, accommodate plenty of sulfur and polysulfides, and facilitate the charge transportation and electrolyte penetration. The significantly enhanced conductivity and the unique bimodal-mesopore structure in 3DCGS, result in its superior electrochemical performance. The reversible discharge capacity for sulfur is 1217 mAh g-1; corresponding capacity for the whole electrode (including the 3DCGS, the conductive additive and the binder) is 877.4 mAh g_e^(-1), which is the highest ever reported. In addition, the capacity decay is as low as 0.08% per cycle, and the high-rate capacity up to 4 C is as large as 653.4 mAh g-1. The 3DCGS sponge with high sulfur loading is promising as superior-capacity cathode for lithium-sulfur batteries.
The lithium–sulfur (Li–S) battery is regarded as the most promising rechargeable energy storage technology for the increasing applications of clean energy transportation systems due to its remarkable high theoretical energy density of 2.6 kWh kg−1, considerably outperforming today&s lithium-ion batteries. Additionally, the use of sulfur as active cathode material has the advantages of being inexpensive, environmentally benign, and naturally abundant. However, the insulating nature of sulfur, the fast capacity fading, and the short lifespan of Li–S batteries have been hampered their commercialization. In this paper, a functional mesoporous carbon-coated separator is presented for improving the overall performance of Li–S batteries. A straightforward coating modification of the commercial polypropylene separator allows the integration of a conductive mesoporous carbon layer which offers a physical place to localize dissolved polysulfide intermediates and retain them as active material within the cathode side. Despite the use of a simple sulfur–carbon black mixture as cathode, the Li–S cell with a mesoporous carbon-coated separator offers outstanding performance with an initial capacity of 1378 mAh g−1 at 0.2 C, and high reversible capacity of 723 mAh g−1, and degradation rate of only 0.081% per cycle, after 500 cycles at 0.5 C.
Battery technologies involving Li-S chemistries have been touted as one of the most promising next generation systems. The theoretical capacity of sulfur is nearly an order of magnitude higher than current Li-ion battery insertion cathodes and when coupled with a Li metal anode, Li-S batteries promise specific energies nearly five-fold higher. However, this assertion only holds if sulfur cathodes could be designed in the same manner as cathodes for Li-ion batteries. Here, the recent efforts to engineer high capacity, thick, sulfur-based cathodes are explored. Various works are compared in terms of capacity, areal mass loading, and fraction of conductive additive, which are the critical parameters dictating the potential for a device to achieve a specific energy higher than current Li-ion batteries (i.e., >200 Wh kg−1). While an inferior specific energy is projected in the majority of cases, several promising strategies have the potential to achieve >500 Wh kg−1. The challenges associated with the limited cycle-life of these systems due to both the polysulfide shuttle phenomenon and the rapid degradation of the Li metal anode that is experienced at the current densities required to charge high specific energy batteries in a reasonable timeframe are also discussed.
Sulfur stands as a very promising cathode candidate for the next-generation rechargeable batteries due to its high energy density, natural abundance, low cost and environmental friendliness. However, the application of lithium–sulfur batteries suffers from low sulfur utilization and poor cycle life of the sulfur cathode. The problems are mainly ascribed to the electrically insulating nature of sulfur and the discharge products, and to the dissolution of the reaction intermediates of polysulfides. Among various approaches, fabricating sulfur–carbon composite cathodes with sulfur embedded within conductive carbon frameworks has been proven promising. Carbon materials, including nanoporous carbon, carbon nanotubes, graphene nanosheets and some other forms, have excellent conductivity, robust chemistry, good mechanical stability, and great abundance. By constraining sulfur within carbon frameworks, the conductivity of the sulfur electrode can be greatly enhanced, and the dissoluble loss of intermediate sulfur species in the liquid electrolyte can also be restrained due to the sorption properties of carbon, leading to a much improved electrochemical performance. This review summarizes the progresses in the sulfur–carbon composite cathodes for lithium–sulfur batteries in recent years, and introduces the roles and the effectiveness of various carbon structures on the electrochemical properties.
A novel carbon/sulfur composite has been fabricated by means of thermal and hydro-thermal treatments to serve as the cathode in Li-S batteries. The carbon matrix consists of graphene nanosheet (GS) and multiwalled carbon nanotube (MWCNT). The “GS/MWCNT@S” composite allows for infiltration of electrolyte into the cathode, assists in entrapment of polysulfide intermediates, and accommodates some of the stress and volume expansion that occurs during charge-discharge processes. In addition, the uniform distribution of sulfur in the conductive carbon matrix promotes utilization of the active materials. A Li-S cell containing the GS/MWCNT@S cathode delivered a capacity of 1290.8 mAh/g and exhibited stable specific capacities up to 612.1 mAh/g after 200 cycles at 0.1 C. These results demonstrate that this cathode material is a promising candidate for rechargeable lithium batteries with high energy density.
High energy and cost-effective lithium sulfur (Li–S) battery technology has been vigorously revisited in recent years due to the urgent need of advanced energy storage technologies for green transportation and large-scale energy storage applications. However, the market penetration of Li–S batteries has been plagued due to the gap in scientific knowledge between the fundamental research and the real application need. Here, a facile and effective approach to integrate commercial carbon nanoparticles into microsized secondary ones for application in high loading sulfur electrodes is proposed The slurry with the integrated particles is easily cast into electrode laminates with practically usable mass loadings. Uniform and crack-free coating with high loading of 2–8 mg cm−2 sulfur are successfully achieved. Based on the obtained thick electrodes, the dependence of areal specific capacity on mass loading, factors influencing electrode performance, and measures used to address the existing issues are studied and discussed.
Development of advanced energy-storage systems for portable devices, electric vehicles, and grid storage must fulfill several requirements: low-cost, long life, acceptable safety, high energy, high power, and environmental benignity. With these requirements, lithium-sulfur (Li-S) batteries promise great potential to be the next-generation high-energy system. However, the practicality of Li-S technology is hindered by technical obstacles, such as short shelf and cycle life and low sulfur content/loading, arising from the shuttling of polysulfide intermediates between the cathode and anode and the poor electronic conductivity of S and the discharge product Li2 S. Much progress has been made during the past five years to circumvent these problems by employing sulfur-carbon or sulfur-polymer composite cathodes, novel cell configurations, and lithium-metal anode stabilization. This Progress Report highlights recent developments with special attention toward innovation in sulfur-encapsulation techniques, development of novel materials, and cell-component design. The scientific understanding and engineering concerns are discussed at the end in every developmental stage. The critical research directions needed and the remaining challenges to be addressed are summarized in the Conclusion.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Batteries with high energy and power densities along with long cycle life and acceptable safety at an affordable cost are critical for large-scale applications such as electric vehicles and smart grids, but is challenging. Lithium–sulfur (Li-S) batteries are attractive in this regard due to their high energy density and the abundance of sulfur, but several hurdles such as poor cycle life and inferior sulfur utilization need to be overcome for them to be commercially viable. Li–S cells with high capacity and long cycle life with a dual-confined flexible cathode configuration by encapsulating sulfur in nitrogen-doped double-shelled hollow carbon spheres followed by graphene wrapping are presented here. Sulfur/polysulfides are effectively immobilized in the cathode through physical confinement by the hollow spheres with porous shells and graphene wrapping as well as chemical binding between heteronitrogen atoms and polysulfides. This rationally designed free-standing nanostructured sulfur cathode provides a well-built 3D carbon conductive network without requiring binders, enabling a high initial discharge capacity of 1360 mA h g−1 at a current rate of C/5, excellent rate capability of 600 mA h g−1 at 2 C rate, and sustainable cycling stability for 200 cycles with nearly 100% Coulombic efficiency, suggesting its great promise for advanced Li–S batteries.
The lithium-sulfur (Li-S) battery is one of the most promising candidates for the next generation of rechargeable batteries owing to its high theoretical energy density which is four- to five-fold greater than those of state-of-the-art Li-ion batteries. However, its commercial applications have been hampered by the insulating nature of sulfur and by the poor cycling stability caused for the polysulfide shuttle phenomenon. In this work, we show that Li-S batteries with a mesoporous carbon interlayer placed between the separator and the sulfur cathode not only reduces the internal resistance of the cells but also that its intrinsic mesoporosity provides a physical place for trapping soluble polysulfides as well as to alleviate the negative impact of the large volume change of sulfur. This improvement of the active material reutilization allows to obtain a stable capacity of 1015 mAh g-1 at 0.2 C after 200 cycles despite the use of a conventional sulfur-carbon black mixture as cathode. Furthermore, we observe an excellent capacity retention (~0.1% loss per cycle, after the second cycle), thus making one step closer towards feasible Li-S battery technology for applications in electric vehicles and grid-scale stationary energy storage systems.
A facile and unique layer-by-layer strategy for high-areal-capacity sulfur cathodes was reported, in which commercial sulfur powders are directly splinted between porous carbon nanofiber (PCNF) layers. The pristine carbon nanofiber (CNF) sheets were prepared via a vacuum-filtrate, peel-off, and punch-out process using commercial CNF powder as the starting material without any additional binder. During the CO2 activation process, part of the solid carbon is consumed to produce CO gas, thus leading to carbons with enhanced pore volume and specific surface area. To prepare the layer-by-layer cathodes, sulfur powder was first spread onto the carbon layers as uniform as possible to form sulfur-particle-spread carbon layers, which were used as the bottom layer or middle layers for the cathodes. Finally, the stacked layers were pressed slightly to ensure that the sulfur particles are embedded well in the carbon layers. After the first scan, all the CV curves display the typical two-step reactions in both the cathodic and anodic sweeps; the stable peak positions and currents demonstrate that the layer-by-layer cathodes are efficient in trapping the soluble polysulfides. Also, the sharp peaks imply that the active material has been confined with a highly ion/charge accessible environment successfully after the first discharge/charge processes.
An effective strategy was developed to obtain flexible Li-S battery electrodes with high energy density, high power density, and long cyclic life by adopting graphene foam.•The graphene foam can provide a highly electrical conductive network, mechanical support and enough space for high sulfur loading.•The electrode with 10.1 mg cm−2 sulfur loading could deliver extremely high areal capacity of 13.4 mAh cm−2 at 300 mA g−1 and 9.3 mAh cm−2 at 1500 mA g−1.•Stable cyclic performance with ~0.07% capacity decay per cycle over 1000 cycles at 1500 mA g−1 was obtained.
For lithium-sulfur batteries, the commercial application is hindered by the insulating nature of sulfur and the dissolution of the reaction intermediates of polysulfides. Here, we present an ordered meso-microporous core-shell carbon (MMCS) as sulfur container, which combines the advantages of both mesoporous and microporous carbon. With large pore volume and highly ordered porous structure, the "core" promises a sufficient sulfur loading and a high utilization of the active material, while the "shell" containing microporous carbon and smaller sulfur acts as a physical barrier and stabilizes the cycle capability of the entire S/C composite. Such S/MMCS composite exhibits a capacity as high as 837 mAh g-1 at 0.5 C after 200 cycles with a capacity retention of 80% vs. the 2nd cycle (a decay of only 0.1% per cycle), demonstrating that the diffusion of the polysulfides into the bulk electrolyte can be greatly reduced. We believe that the tailored highly ordered meso-microporous core-shell structured carbon can also be applicable for designing some other electrode materials for energy storage.