In Situ Welding Ionic\nConductive Breakpoints for Highly\nReversible All-Solid-State Lithium–Sulfur Batteries

Poly(ethylene oxide) (PEO)-based solid-state lithium–sulfur\nbatteries (SSLSBs) have garnered considerable interest owing to their\nimpressive energy density and high safety. However, the dissolved\nlithium polysulfide (LiPS) together with sluggish reaction kinetics\ndisrupts the electrolyte network, bringing about ionic conductive\nbreakpoints and severely limiting battery performance. To cure this,\nwe propose an in situ welding strategy by introducing phosphorus pentasulfide\n(P<sub>2</sub>S<sub>5</sub>) as the welding filler into PEO-based\nsolid cathodes. P<sub>2</sub>S<sub>5</sub> can react with LiPS to\nform ion-conducting lithium polysulfidophosphate (LSPS), which suppresses\nthe interaction with PEO and in situ weld breakpoints within the ionic\nconductive network. Of interest, LSPS also shows another function,\nthat is, to catalyze sulfur redox reactions by decreasing the activation\nenergy of sulfur reduction reaction from 0.87 to 0.75 eV, mitigating\nthe shuttle effect. The in situ welding strategy helps the assembled\nSSLSB to feature exceptional cycling stability and a high energy density\nof up to 358 Wh·kg<sup>–1</sup> due to the high sulfur\nutilization. Our findings pave an avenue for practical high-performance\nSSLSBs with a novel welding filler for in situ welding of ionic conductive\nnetwork.