Solid Electrolyte with Oxidation Tolerance Provides a High‐Capacity Li₂S‐Based Positive Electrode for All‐Solid‐State Li/S Batteries

Abstract

The electrochemical window of solid electrolytes (SEs) plays a crucial role in designing active material-SE interfaces in high-energy-density all-solidstate batteries (ASSBs). However, the suitable electrochemical window for individual active materials is not yet investigated, as the electrochemical window of SEs is overestimated. In this study, the oxidation onset voltages (OOVs) of several SEs, namely those compatible with Li 2 S as a high-capacity positive electrode material are determined. Results reveal that SEs with low OOVs decrease the capacity and increase the interfacial resistance of the corresponding ASSBs. The OOVs of SEs must exceed that of Li 2 S by more than 0.2 V to achieve high capacity, which in turn depends on SE ionic conductivity. Therefore, an Li 2 S positive electrode is combined with pseudobinary Li-oxyacid salts as SEs, exhibiting high OOVs and ionic conductivities, to afford a high-capacity (500 Wh kg −1 ) ASSB with high Li 2 S content.

Li2S–LiI Solid Solutions with Ionic Conductive Domains for Enhanced All-Solid-State Li/S Batteries

“…The Li 2 S–LiI–C cell shows a higher capacity than that of the Li 2 S–LPS–C cell, which suggests that LiI is superior to LPS as an ionic conduction pathway, although LPS itself has a higher conductivity than LiI. Previously, we reported that the oxidation onset voltage of a nanosized ionic conduction pathway contributes to the charge–discharge capacity, and this experiment is consistent with our previous paper. Therefore, this positive electrode can be used to investigate the origin of the high utilization and full reversibility of the all-solid-state Li 2 S–LiI–C cell because it excludes the influence of the sulfide SE, including the contributions of the total capacity, reaction distribution, and overlapping peaks in the S2p XPS.…”

Can Substitutions Affect the Oxidative Stability of Lithium Argyrodite Solid Electrolytes?

“…18 In addition, LiX is found as one of the decomposition products, which has been recently proved to enhance the oxidative stability of thiophosphate, Li 3 PS 4 . 27 Clearly, the substitutions via the halide anion or substitution of the cation in PS 4 3− units do not significantly affect the stability of these sulfide argyrodite solid ionic conductors. To shed light on the relation between the electronic structure and electrochemical stability, we take a closer look at the contributions of all atoms to the band edges.…”

“…24−26 Although the former option has shown to be very effective, it is unclear if substitution in sulfide solid electrolytes can enhance their stability toward the electrode materials for operation. Further, recent reports have explored the role of electronically insulating additives to improve electrochemical stability of thiophosphates; 27 however the reason behind enhanced stability is not clear yet.…”

“…Therefore, two routes have emerged to promote long-term cycling that focuses either on incorporating protective coatings in active materials , or utilizing compositional changes in known solid electrolyte phases to achieve higher stabilities. − Although the former option has shown to be very effective, it is unclear if substitution in sulfide solid electrolytes can enhance their stability toward the electrode materials for operation. Further, recent reports have explored the role of electronically insulating additives to improve electrochemical stability of thiophosphates; however the reason behind enhanced stability is not clear yet.…”

Theoretical Consideration of Side Reactions between the VS₄ Electrode and Carbonate Solvents in Lithium–metal Polysulfide Batteries

“…To avoid the decomposition of organic solvents, replacing the electrolyte solution with a solid electrolyte also could improve the electrochemical performance of the Li|VS4 battery. 75,76 Therefore, we recommend reducing the reactivity at the VS4/carbonate solvent interface or replacing the carbonate solvents to improve the lifetime of the Li|VS4 battery.…”