Surface Engineering Strategy Enables 4.5 V Sulfide-Based All-Solid-State Batteries with High Cathode Loading and Long Cycle Life

Sulfide-based all-solid-state lithium batteries (ASSLBs) with LiCoO 2 (LCO) operating at high voltage (≥4.5 V vs Li + /Li) hold promise in realizing high energy density while maintaining safety. Here, we propose a solid electrolyte coating strategy to stabilize the cathode electrolyte interface and demonstrate the benefit of lithium difluoro(oxalate)borate (LiDFOB) as coating layer on the surface of Li 6 PS 5 Cl (LPSCl) to improve the performance of LCO at 4.5 V. 89.3% of initial discharge capacity can be retained after 1500 cycles at 1 C (1 C = 150 mA g –1 ). ASSLBs with high cathode loading (35.7 mg cm –2 ) could deliver an areal capacity over 6 mAh cm –2 (167 mAh g –1 ) at 0.1 C and keep 85% capacity retention after 200 cycles at 0.3 C . The investigation of the improvement mechanism further verifies that in situ decomposition of LiDFOB would build an (electro)chemomechanically stable interface, which not only suppresses interfacial side reactions but also buffers the cathode cracking.