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LiFePO4/Carbon Nanomaterial Composites for Cathodes of High-Power Lithium Ion Batteries

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... Under microscope observation, it can be seen that its structure includes pores and crystals. [5]. The sintering process may affect the properties of the original material, because it will affect the size of the pores of the object, the size of the crystalline particles, and the distribution and shape of the grain boundaries. ...
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Li metal batteries are revived as the next-generation batteries beyond Li-ion batteries. The Li metal anode can be paired with intercalation-type cathodes LiMO2 and conversion-type cathodes such as sulfur and oxygen. Then, energy densities of Li/LiMO2 and Li/S,O2 batteries can reach 400 Whkg⁻¹ and more than 500 Whkg⁻¹, respectively, which surpass that of the state-of-the-art LIB (280 Whkg⁻¹). However, replacing the intercalation-type graphite anode with the Li metal anode suffers from low coulombic efficiency during repeated Li plating/stripping processes, which leads to short cycle lifetime and potential safety problems. The key solution is to construct a stable and uniform solid electrolyte interphase with high Li⁺ transport and high elastic strength on the Li metal anode. This review summarizes recent progress in improving the solid electrolyte interphase by tailoring liquid electrolytes, a classical but the most convenient and cost-effective strategy.
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The wide usage of LiFePO 4 batteries makes their recovery and recycling urgent. Here, a novel, efficient and environmentally friendly recycling process has been developed to recover high performance LiFePO 4 nano composites from spent LiFePO 4 materials. The process comprises an intensive mechanochemical activation through mixing with precursor mixture and one-step solid state heat treatment. Spent LiFePO 4 , V 2 O 5 , Li 2 CO 3 , and NH 4 H 2 PO 4 are mixed according to the molar ratio of 1-xLiFePO 4 @xLi 3 V 2 (PO 4 ) 3 (x = 0, 0.005, 0.01, 0.03 and 0.1). In the typical process, the decomposition of self-contained binder and the conductive carbon provide a reducing environment as well as an in-situ coating carbon source. The SEM, XRD and XPS results illustrate that V ⁵⁺ is doped in the Fe ²⁺ site when x < 0.01, with co-existence of V ⁵⁺ doping and Li 3 V 2 (PO 4 ) 3 when x ≥ 0.03. Sole V ⁵⁺ doping assisted in-situ carbon coating displays the best electrochemical performance. The optimized sample shows discharge capacities of 154.3 mA h g ⁻¹ and 142.6 mA h g ⁻¹ at 0.1 and 1 C rates, respectively, with a high capacity retention of nearly ∼100% after 100 cycles. All results indicate that intensive mechanochemical activation assisted V ⁵⁺ doping is a promising strategy for spent LiFePO 4 recycling.
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Lithium-ion batteries (LIBs) have become energy storage tools in our daily lives, and high energy and power densities as well as long lifespan are necessary for next-generation batteries for transportation technologies and smart grids. Newly emerging electrode materials fabricated with rational component design are coming close to achieving this feat, but essential drawbacks such as insufficient electron/ion-transport efficiency, large volume variations and various side reactions hinder their practical applications. Although carbon coating has long been considered an effective method to improve the electrochemical performance by increasing conductivity, buffering volume expansion and/or stabilizing the reaction interface, it has been proven that a single species of carbon is unable to meet all requirements in terms of conformal coverage for active materials and a continuous conductive network for electrodes. In this review, we mainly focus on recent developments in dual or multi carbonaceous coating strategies, aiming to summarize the hierarchical construction of complex structures and consequently discuss the multifunctionality of each carbonaceous material for the rational design of electrodes not only for LIBs but also for other rechargeable batteries to be developed in the future.
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With the increasing consumption of lithium ion batteries (LIBs) in electric and electronic products, the recycling of spent LIBs has drawn significant attention due to their high potential of environmental impacts and waste of valuable resources. Among different types of spent LIBs, the difficulties for recycling spent LiFePO4 batteries rest on their relatively low extraction efficiency and recycling selectivity in which secondary waste is frequently generated. In this research, mechanochemical activation was introduced to improve the recycling efficiencies of cathode scrap from spent LiFePO4 batteries. By using weak acidic leaching solutions, the leaching efficiency of Fe and Li can be significantly improved to be 97.67% and 94.29%, respectively. In order to understand the Fe and Li extraction process and the mechanochemical activation mechanisms, the effects of various parameters during Fe and Li recovery were comprehensively investigated, including activation time, cathode powder to additive mass ratio, acid concentration, the liquid-to-solid ratio and leaching time. Subsequently, the metal ions after leaching can be selectively recovered. In the whole process, about 93.05% Fe and 82.55% Li could be recovered as FePO4·2H2O and Li3PO4, achieving selective recycling of metals for efficient use of resources from spent lithium ion batteries.
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In this study, we report a promising structural design of the 3D graphene-encapsulated Li3V2(PO4)3 microspheres (3D-Li3V2(PO4)3/G) by using a facile spray-drying method with one-step calcination. XRD results indicate that the as-prepared composite shows a single monoclinic Li3V2(PO4)3 without any impurity phases. SEM and TEM images reveal that all the particles of 3D-Li3V2(PO4)3/G are spherical with diameters of about 5 μm and the surface of Li3V2(PO4)3 particles are tightly covered by soft graphene sheets, forming a conductive network. This unique structure of the composite offers a synergistic effect to facilitate the transport of electrons and Li⁺ ions. As the advanced cathode for lithium-ion batteries, the obtained 3D-Li3V2(PO4)3/G displays good high-rate capability and long cycling performance between 3.0 and 4.8 V (vs. Li/Li⁺). It delivers an initial specific capacity of 187 mAh g⁻¹ at 0.1 C, which is close to the theoretical maximum value (197 mAh g⁻¹). More remarkably, it presents a superior discharge capacity of 146 mAh g⁻¹ at 20 C with capacity retention of about 95.7% over 100 cycles. Combined with the advantages of high voltage and high theoretical capacity, the 3D-Li3V2(PO4)3/G cathode material would be a potential cathode material for next-generation lithium-ion batteries.
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Development of alternative energy sources is one of the main trends of modern energy technology. Lithium-ion batteries and fuel cells are the most important among them. The increase in the energy and power density is the essential aspect which determined their future development. We provide a brief review of the state of developments in the field of nanosize electrode materials and electrolytes for lithium-ion batteries and hydrogen energy. The presence of relatively inexpensive and abundant elements, safety and low volume change during the lithium intercalation/deintercalation processes enables the application of lithium iron phosphate and lithium titanate as electrode materials for lithium-ion batteries. At the same time, they exhibit low ionic and electronic conductivity. To overcome this problem the following main approaches have been applied: use of nanosize materials, including nanocomposites, and heterovalent doping. Their impact in the property change is analyzed and discussed. Hybrid membranes containing inorganic nanoparticles enable a significant progress in the fuel cell development. Different approaches to their preparation, the reasons for ion conductivity and selectivity change, as well as the prospects for their application in low-temperature fuel cells are discussed. This review may provide some useful guidelines for development of advanced materials for lithium ion batteries and fuel cells.
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LiFePO4, as the most famous member of the family of olivine-type lithium transition metal phosphates, is one of the promising candidates for the cathodes of lithium-ion batteries. However, its battery performance is limited by its low electrical conductivity and slow Li solid-state diffusion. Various methods have been attempted to improve the battery performance of lithium iron phosphate. Among them, compositing the LiFePO4 with carbon nanomaterials seems to be the most promising, as it is facile and efficient. Carbon nanomaterials usually serve as a conductive agent to improve the electrical conductivity while increasing the material porosity in which the solid-state diffusion distances are significantly shortened. Owing to the popularity of various carbonaceous nanomaterials, there is no straightforward line of research for comparing the LiFePO4/C nanocomposites. This review aims to provide a general perspective based on the research achievements reported in the literature. While surveying the research findings reported in the literature, controversial issues are also discussed. The possible contribution of pseudocapacitance as a result of functionalized carbon or LiFePO4 lattice defects is described, since from a practical perspective, a LiFePO4/C electrode can be considered as a supercapacitor at high C rates (with a specific capacitance as large as 200 F g⁻¹). The Li diffusion in LiFePO4 has not been well understood yet; while the Li diffusion within the LiFePO4 lattice seems to be quite fast, the peculiar interfacial electrochemistry of LiFePO4 slows down the diffusion within the entire electrode by a few orders of magnitude.
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The three-dimensional porous LiFePO4 modified with uniformly dispersed nitrogen-doped carbon nanotubes has been successfully prepared by a freeze-drying method. The morphology and structure of the porous composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performances are evaluated using the constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The nitrogen-doped carbon nanotubes are uniformly dispersed inside the porous LiFePO4 to construct a superior three-dimensional conductive network, which remarkably increases the electronic conductivity and accelerates the diffusion of lithium ion. The porous composite displays high specific capacity, good rate capability and excellent cycling stability, rendering it a promising positive electrode material for high-performance lithium-ion batteries.
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Monodisperse LiFePO4 microspheres embedded with well dispersed nitrogen doped carbon nanotubes (N-CNTs) are synthesized by chemical lithiation of the pre-synthesized FePO4/N-CNTs precursor. The morphology and structure of the composite microspheres are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performances are evaluated using constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The nitrogen-doped carbon nanotubes are uniformly dispersed inside the LiFePO4 microsphere to construct a superior three-dimensional conductive network, which allows for efficient charge transfer, ensures short lithium-ion diffusion distance, and facilitates the ion and electron transport throughout the active materials. The LiFePO4/N-CNTs microsphere composites display a reversible discharge capacity of 153 mAh g⁻¹ at 0.1C, a rate capability of 106 mAh g⁻¹ at a high rate of 10C, and an excellent cycling stability (>97% capacity retention after 500 cycles), which are promising positive electrode materials for application in high-performance lithium-ion batteries.
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In the past two decades, LiFePO4 has undoubtly become a competitive candidate for the cathode material of the next-generation LIBs due to its abundant resources, low toxicity and excellent thermal stability, etc. However, the poor electronic conductivity as well as low lithium ion diffusion rate are the two major drawbacks for the commercial applications of LiFePO4 especially in the power energy field. The introduction of highly graphitized advanced carbon materials, which also possess high electronic conductivity, superior specific surface area and excellent structural stability, into LiFePO4 offers a better way to resolve the issue of limited rate performance caused by the two obstacles when compared with traditional carbon materials. In this review, we focus on advanced carbon materials such as one-dimensional (1D) carbon (carbon nanotubes and carbon fibers), two-dimensional (2D) carbon (graphene, graphene oxide and reduced graphene oxide) and three-dimensional (3D) carbon (carbon nanotubes array and 3D graphene skeleton), modified LiFePO4 for high power lithium ion batteries. The preparation strategies, structure, and electrochemical performance of advanced carbon/LiFePO4 composite are summarized and discussed in detail. The problems encountered in its application and the future development of this composite are also discussed.
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This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors.
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A novel process has been demonstrated to recycle LiFePO4 from spent lithium-ion batteries. The spent LiFePO4 cathode materials were leached by phosphoric acid (H3PO4) solution and followed by subsequent heat treatment to obtain FePO4·2H2O hierarchical microflowers. Furthermore, new LiFePO4/C sample was prepared via a carbothermal reduction process of calcining the obtained FePO4·2H2O precursor with Li2CO3 and glucose in N2 atmosphere. The re-synthesized LiFePO4/C sample inherits the hierarchical microflower structure of the FePO4·2H2O precursor, with a diameter of 1–2 μm. Electrochemical test indicates that the re-synthesized LiFePO4/C shows excellent electrochemical performance as cathode material for lithium ion batteries. The discharge capacity can reach 159.3 mAh g−1 at 0.1C rate and 86.3 mAh g−1 even at 20C rate, respectively. After 500 cycles at 5C, they still can deliver a discharge capacity of 105 mAh g−1 with a high capacity retention rate of 95.4%. Moreover, the lithium element was also recovered in the form of LiH2PO4 from the filtrate after collecting the FePO4·2H2O precipitate. This work provides a promising route for large scale recovery and reuse of spent LiFePO4 cathode materials of lithium-ion batteries.
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The state-of-the-art in the field of cathode and anode nanomaterials for lithium-ion batteries is considered. The use of these nanomaterials provides higher charge and discharge rates, reduces the adverse effect of degradation processes caused by volume variations in electrode materials upon lithium intercalation and deintercalation and enhances the power and working capacity of lithium-ion batteries. In discussing the cathode materials, attention is focused on double phosphates and silicates of lithium and transition metals and also on vanadium oxides. The anode materials based on nanodispersions of carbon, silicon, certain metals, oxides and on nanocomposites are also described.
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(LiFe1-xMxPO4)-P-II/C (M-II = co, Ni, Mg) composites had been-obtained by sol-gel method. Structure and morphology of the obtained materials have been studied with the use of the XRD-analysis, SEM and Mossbauer spectroscopy. Their electrochemical behavior has been investigated with the use of charge/discharge tests. The materials doped by cobalt and nickel were shown to be characterized by an increased lithium intercalation and deintercalation rates, and retain a high capacity during charge and discharge the battery at high currents densities (LiFe0.9Ni0.1PO4 capacity amounts to 145 and 62 mAh/g at a discharge current 50 and 3000 mA/g). Mg2+ incorporation into LiFePO4/C cathode material results in the slight increase of charge/discharge rate and significant capacity decrease. Mossbauer spectroscopy has shown that M-II ions in the (LiFe1-xMxPO4)-P-II/C (M-II = Co, Ni) materials are orderly distributed both in charged and discharged states, each iron ion has no more than one M-II ion in the nearest environment. In the case of Ni-doped samples the ordering is less pronounced. The reasons of the changes observed in the electrochemical performances and charge/discharge rate have been discussed on the base of Mossbauer spectroscopy and XRD data.
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Integrating variable and non-dispatchable renewable power generation into existing power systems will have consequences for their operation and future expansion. These impacts will depend on two factors: (1) the variability of the total renewable power generation on different time scales and (2) the possibilities of accurately forecasting these fluctuations. In this paper, previous research on variability assessment and forecasting of solar, wind, wave and tidal energy resources is reviewed. The aim is to summarize the state of knowledge in each area and to compare the approaches used for the respective resources. For temporal variability, methods and models used for assessing the variability are surveyed, as well as what is known about the variability at individual sites and for larger aggregates of sites. For forecasting, an overview of forecasting methods for the different resources is made, and selected forecasting methods are compared over different time horizons. An important finding is that it is hard to draw strong conclusions from the existing studies due to differences in approaches and presentation of results. There is a need for further, more coherent studies that analyze the variability for the different resources in comparable ways, using data with the same resolution, and for studies that evaluate the smoothing effect and complementarity of combinations of several renewable energy resources. For forecasting, future research should suggest ways to evaluate forecasts from different renewable energy sources in easily comparable ways, using data from the same locations or regions, with the same temporal and spatial resolution, and with comparable metrics for the forecasting errors.
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The high-energy consumption in our day-to-day life can be balanced not only by harvesting pollution-free renewable energy sources, but also requires proper storage and distribution of energy. In this regard, lithium ion battery is currently considered as an effective energy storage device and involved most active research. There exist several review articles dealing with various sections of LIB, such as anode, cathode, electrolytes, electrode-electrolyte interface etc. However, anode is considered to be a crucial component effecting the performance of LIB as evident from the tremendous amount of current research work carried out in this area. In last few years, advancements are focused more on the fabrication of nanostructured anode owing to special properties, such as, high surface area, short Li+ ion diffusion path length, high electron transportation rate etc. As the work in this area is growing very fast, the present review paper deliberates the recent developments of anode materials in the nanoscale dimensions. Different types of anode materials, such as, carbon-based material, alloys, Si-based materials, transition metal oxides, and transition metal chalcogenides with their unique physical and electrochemical properties are discussed. Various approaches on designing materials in the form of 0, 1 and 2D nanostructures and their effect of size and morphology on the performance as anode material in LIB are reviewed. Moreover, the article emphasizes the smart approaches of making core-shell, nanoheterostructures, nanocomposites or nanohybrids with the combination of electrochemically active materials and conductive carbonaceous or electrochemically inactive material to achieve LIBs with high capacity, high rate capability, and excellent cycling stability. We believe the review paper will provide an updated scenario to the reader about recent progress on the nanostructured anode material of LIB.