Fig 2 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Summary of the main characteristics and challenges of MSBs. As highlighted in red, research should focus on a reduction of the high overpotentials at the Mg anode and the S cathode, as well as the realization of low E:S ratios. The molecular structures contain Mg (gray), S (yellow), O (red), C (cyan), H (white), and N (blue). Blocked pathways are indicated by red crosses. (Molecular structures are redrawn from Bieker et al. 84 . Copyright American Chemical Society. Reused with permission).
Source publication
Following in the footsteps of lithium-sulfur batteries, magnesium-sulfur batteries offer a high theoretical energy content and are composed of cheap and more environmentally-friendly electrode materials. In comparison to lithium-sulfur, however, current magnesium-sulfur batteries suffer from higher overpotentials at the magnesium anode and the sulf...
Citations
... 6,7 Unlike the general Sbased Li-S batteries using S 8 as the cathode active material, Li 2 S-based Li-S batteries contain a Li source at the cathode before cycling. Therefore, Li-free anodes, such as graphite, Si, and alloying composites, can be adopted, thus evading safety concerns and uncontrollable side reactions on the surface of metallic Li. [6][7][8][9][10] To achieve the high energy density expected from Li-S batteries, it is essential to manufacture high-sulfurloading electrodes with high sulfur contents that have high sulfur utilization. As the loading level of the electrode increases, however, the electrode inevitably thickens, thereby retarding electron transfer toward the whole electrode. ...
Realizing a lithium sulfide (Li2S) cathode with both high energy density and a long lifespan requires an innovative cathode design that maximizes electrochemical performance and resists electrode deterioration. Herein, a high‐loading Li2S‐based cathode with micrometric Li2S particles composed of two‐dimensional graphene (Gr) and one‐dimensional carbon nanotubes (CNTs) in a compact geometry is developed, and the role of CNTs in stable cycling of high‐capacity Li–S batteries is emphasized. In a dimensionally combined carbon matrix, CNTs embedded within the Gr sheets create robust and sustainable electron diffusion pathways while suppressing the passivation of the active carbon surface. As a unique point, during the first charging process, the proposed cathode is fully activated through the direct conversion of Li2S into S8 without inducing lithium polysulfide formation. The direct conversion of Li2S into S8 in the composite cathode is ubiquitously investigated using the combined study of in situ Raman spectroscopy, in situ optical microscopy, and cryogenic transmission electron microscopy. The composite cathode demonstrates unprecedented electrochemical properties even with a high Li2S loading of 10 mg cm–2; in particular, the practical and safe Li–S full cell coupled with a graphite anode shows ultra‐long‐term cycling stability over 800 cycles. A high‐loading lithium sulfide (Li2S)‐based cathode composed of graphene, carbon nanotubes (CNTs), and Li2S in compact geometry is developed for high‐energy Li–S batteries. A dimensionally combined fine carbon matrix provides fast electron diffusion pathways and a sustainable electrical network. The composite cathode showed unprecedented high areal capacity and cycling stability at ultrahigh Li2S loading, in which the role of the CNTs is emphasized for stable cycling of Li–S batteries.
... This includes large-scale stationary storage systems, where cost (both for acquisition and for operation) is more important than energy density [3]. One transition-metal-free battery technology, which offers a high theoretical specific energy (2654 Wh kg −1 ) is the sulfur ‖ Li metal battery (LSBs) [3,6,7]. However, challenges such as inhomogeneous electrodeposition and -dissolution of Li metal, as well as transport of soluble polysulfides (PSs) from the sulfur-based positive electrode to the Li metal negative electrode and reactions thereof limit the Coulombic efficiency (C Eff ) and cycle life of LSBs [6,[8][9][10]. ...
... One transition-metal-free battery technology, which offers a high theoretical specific energy (2654 Wh kg −1 ) is the sulfur ‖ Li metal battery (LSBs) [3,6,7]. However, challenges such as inhomogeneous electrodeposition and -dissolution of Li metal, as well as transport of soluble polysulfides (PSs) from the sulfur-based positive electrode to the Li metal negative electrode and reactions thereof limit the Coulombic efficiency (C Eff ) and cycle life of LSBs [6,[8][9][10]. Based on the comparably low potential of sulfur reduction and Li 2 S oxidation (≈2.2 V vs. Li|Li + ), however, sulfur-based electrodes can also be considered as the negative electrode in combination with a high-potential positive electrode. ...
... Based on the comparably low potential of sulfur reduction and Li 2 S oxidation (≈2.2 V vs. Li|Li + ), however, sulfur-based electrodes can also be considered as the negative electrode in combination with a high-potential positive electrode. In the past, several approaches combined negative electrodes based on elemental sulfur [11,12] or sulfurized polyacrylonitrile (SPAN) [13][14][15][16] in combination with different positive electrodes (≈3.7 to 4.1 V [17] vs. LiLi + ) including LiMn 2 O 4 (LMO) [11,13,14], Na 0.44 MnO 2 [12], LiCoO 2 (LCO) [11], LiNi x Mn y Co z O 2 (NMC) [15] and anion intercalating graphite (4.0 to 4.6 V vs. Li|Li + ) [16], and achieved average discharge cell voltages between 1.5 and 2.0 V. Great advantages of sulfur as negative electrode are its high theoretical capacity (1672 mAh g −1 ) [6], low price (0.09 USD kg −1 ) [18] and potential sustainability (sulfur is a waste product of the petrochemical industry [19]). Furthermore, reductively less stable electrolytes including concentrated aqueous ones can be used [11,15]. ...
In this work, a cell concept comprising of an anion intercalating graphite-based positive electrode (cathode) and an elemental sulfur-based negative electrode (anode) is presented as a transition metal- and in a specific concept even Li-free cell setup using a Li-ion containing electrolyte or a Mg-ion containing electrolyte. The cell achieves discharge capacities of up to 37 mAh g ⁻¹ and average discharge cell voltages of up to 1.9 V. With this setup, more than 100 cycles with a high capacity retention (> 90% of the highest achieved value) and Coulombic efficiencies up to 95% could be achieved, which opens a broad new field for energy storage approaches.
... Bieker et al. [37] reported that, unlike hard-case cell housings, pouch cells do not allow too much excess of liquid electrolyte without losing shape and stability. ...
Nowadays, rechargeable batteries utilizing an S cathode together with an Mg anode are under substantial interest and development. The review is made from the point of view of materials engaged during the development of the Mg–S batteries, their sulfur cathodes, magnesium anodes, electrolyte systems, current collectors, and separators. Simultaneously, various hazards related to the use of such materials are discussed. It was found that the most numerous groups of hazards are posed by the material groups of cathodes and electrolytes. Such hazards vary widely in type and degree of danger and are related to human bodies, aquatic life, flammability of materials, or the release of flammable or toxic gases by the latter.
... [75][76][77] In cases of metal-S batteries with multivalent metal anodes (e.g., Mg, Ca, and Al), the polysulfide dissolution and shuttle are also involved, but are not significant as alkali-metal sulfur batteries. [78][79][80][81] The reason is that the solubility of multivalent-metal polysulfides (e.g., CaS x , MgS x , and AlS x ) is much lower than that of LiPS, NaPS, and KPS in the commonly used ether-based electrolytes. 54,82,83 For example, evidence was shown that the UV-vis signals of polysulfides in the electrolyte from cycled Al-S cells are significantly lower than those of Li-S and Na-S cells. ...
Rechargeable metal–sulfur batteries with the use of low‐cost sulfur cathodes and varying choice of metal anodes (Li, Na, K, Ca, Mg, and Al) represent diverse energy storage solutions to satisfy different application requirements. In comparison to the highly‐regarded lithium–sulfur batteries, the use of nonlithium‐metal anodes in metal–sulfur batteries offers multiple advantages in terms of abundance, cost, and volumetric energy density. Although with the same sulfur cathode, metal–sulfur batteries show considerably differences in the electrochemical reaction pathway and capacity fading mechanism. Herein, we provide an overview of correlations and differences in metal–sulfur batteries, highlighting the knowledge and experience that can be transplanted from lithium–sulfur to other metal–sulfur batteries. We first discuss the historical development and the electrochemical reaction mechanism of various metal–sulfur batteries. This is then followed by an analysis of key challenges of metal–sulfur batteries including polysulfide shutting, cathode passivation, and anode stability. Finally, a short perspective is presented about the possible future development of metal–sulfur batteries. Deciphering the correlations and differences between the lithium–sulfur battery and other metal–sulfur batteries is essential to broaden the knowledge of lithium–sulfur batteries and contribute to other metal–sulfur batteries. This work presents an overview of correlations and differences in metal–sulfur batteries, highlighting the knowledge and experience that can be transplanted from lithium–sulfur to other metal–sulfur batteries.
... The shuttle of polysulfide, inactive materials, excessive demand of electrolytes, limited compatible electrolyte with electrophilic sulfur, and sluggish kinetic conversion reaction for Mg-ion storage are essential challenges to realize practical technology. 7 In this regard, recent innovative strategies have been devoted toward developing nonnucleophilic electrolytes to be compatible with the electrophilic nature of sulfur; for example, Mg(CF 3 SO 3 ) 2 −AlCl 3 dissolved in a cosolvent of tetrahydrofuran and tetraglyme, 8 Mg(CF 3 SO 3 ) 2 , MgCl 2 , and AlCl 3 in 1,2-dimethoxyethane (DME), 9−11 organic magnesium borate-based electrolyte, 12 and halogen-free electrolyte (HFE) like Mg[B(hfip) 4 ] 2 . 13,14 However, shortcomings and unsolved problems such as poor chemical stability, the corrosion nature of Cl on battery components, the cost and complex synthesis constitution of Mg[B(hfip) 4 ] 2 , and self-discharge restrict the commercialization of the electrolyte. ...
... Sulfur element recently received much attention as one of the best promising cathode materials for Mg-ion batteries, because of its advantages of low cost, abundance, and nontoxicity, as well as the high theoretical specific capacity of 1673 mAh g −1 . However, the shuttle of polysulfide and the limited compatible electrolyte with electrophilic sulfur are fundamental challenges to be overcome for practical use of this technology [7,8]. Attempts to design an appropriate sulfur host to suppress polysulfideshuttling and improve the electrochemical kinetics included hosting S in the framework of metal-organic derivative carbon to trap soluble polysulfides [9] and Co 3 S 4 @MXene heterostructure to promote the electrochemical kinetics [10]. ...
... HE electrolyte was chosen for assembling Mg-S full cells at room temperature, Fig. 7a shows CV curves of Mg-S cells using HE electrolyte; the cathodic current and the area under the cathodic peak are very large compared to that of the anodic current. This confirms that the S cathode can host magnesium ions numbers during discharge higher than the number released during recharge, which may be attributed to the partial reduction of sulfur to S 2 2− directly forming polysulfide [7]. Figure 7b shows the Cole-Cole plot of Mg-S coin cells before and after CV and the inset are fitting equivalent circuits. ...
Realizing practical magnesium-ion batteries (MIBs) is hindered by parasitic formation processes on the surface of the magnesium anode from contaminants typically from the electrolyte. Aiming to address this issue, we investigate the addition of water scavengers like hexamethyldisilazane (HMDS) and 2,2-dimethoxypropane (DMP) into a non-aqueous electrolyte-based magnesium perchlorate. The addition of water scavengers greatly reduces the overpotential of Mg deposition/dissolution, improves the ionic transfer number, and enhances the electrochemical performance of the electrolyte. In addition, a buffer layer interface from ionic conductive polymer–based magnesium chloride and polyvinylidene difluoride (PVDF) was applied between the liquid electrolyte and magnesium anode to protect the surface of the Mg anode from the direct contact with the liquid electrolyte to further inhibit Mg metal corrosion. The Mg symmetric cells deliver low overpotential compared with the liquid electrolytes by introducing the buffer layer, with and without scavengers. The value of the ion transference increased compared with analogs of liquid electrolytes. Mg-S coin cell assembled with an electrolyte-based HMDS can deliver a high initial discharge/charge specific capacity of ~ 520/530 mAhg⁻¹.
Lithium-sulfur batteries are compelling candidates for overcoming the resource and sustainability limitations of current batteries. Regulating complex polysulfide chemistry is a critical challenge in achieving a practical lithium-sulfur battery with high cycle life and minimal electrolyte weight. Drawing inspiration from cell biology, here we propose the concept of bespoke membranes for making practical lithium-sulfur batteries. The membrane devised herein utilizes conductive reduced graphene oxide as a brick-like framework, with an elastic polymer liquid—rich in ion hopping and lithiophilic sites—as the mortar. The membrane mimics cell plasma membranes by integrating rapid and permselective Li⁺ channels alongside catalytic electrochemical reactions. Employing our reactive permselective membranes, we attain areal capacities of 4.8–8.1 mAh cm⁻² with 450 stable cycles in coin cells and 202 Wh kg⁻¹ with over 100 stable cycles in pouch cells. This behavior is achieved with efficient electrolyte/capacity ratios (4.9–5.3 μL mAh⁻¹).
