High‐Entropy Argyrodite‐Type Sulfide Electrolyte with High Conductivity and Electro‐Chemo‐Mechanical Stability for Fast‐Charging All‐Solid‐State Batteries

Abstract Inorganic solid electrolytes offer inherently unique transport, thermal, and mechanical attributes that can potentially address the fast‐charging barriers of safety, performance, and degradation exhibited by their liquid counterparts; however, to achieve reliable fast charging while retaining long cycle life remains a challenge for all‐solid‐state lithium batteries (ASSLBs), which is hindered by the electro‐chemo‐mechanical and transport issues at solid–solid interface. Herein, a high‐entropy strategy is reported to design ideal argyrodite electrolytes for fast‐charging ASSLBs with boosted transport kinetics and mitigated electrolyte‐electrode reactions via anionic site disordering. As proof of concept, multiple aliovalent cations (Si⁴⁺/Ge⁴⁺/Sn⁴⁺) and anions (Cl⁻) are introduced to Li₆PS₅Br (LPSBr) to prepare its high‐entropy counterpart, HE‐LPSBrCl. As the configuration entropy increases from 1.35 to 2.29 R, the disordering increases by 6.83‐fold and ionic conductivity increases by nearly one order of magnitude (7.96 mS cm⁻¹ at 30 °C for HE‐LPSBrCl). The HE‐LPSBrCl full cells deliver a high capacity of 67.7 mA h g⁻¹ at 10 C, 61.5 times higher than that of LPSBr counterparts, and retain 85.6% of the capacity (96.2 mA h g⁻¹ at 5 C) after 1400 cycles. Unwanted mechanical penetration of Li and interfacial delamination and particle cracking of composite cathode at high rates are successfully suppressed.