A Plastic‐Crystal Electrolyte Layer Promotes Interfacial Stability of Ni‐Rich Oxide Cathode in Li6PS5Cl‐Based All‐Solid‐State Rechargeable Li Batteries

Unfavorable parasitic reactions between the Ni‐rich layered oxide cathode and the sulfide solid electrolyte have plagued the realization of all‐solid‐state rechargeable Li batteries. The accumulation of inactive by‐products (P2Sx, S, POxn− and SOxn−) at the cathode‐sulfide interface impedes fast Li‐ion transfer, which accounts for sluggish reaction kinetics and significant loss of cathode capacity. Herein, we proposed an easily scalable approach to stabilize the cathode electrochemistry via coating the cathode particles by a uniform, Li+‐conductive plastic‐crystal electrolyte nanolayer on their surface. The electrolyte, which simply consists of succinonitrile and Li bis(trifluoromethanesulphonyl)imide, serves as an interfacial buffer to effectively suppress the adverse phase transition in highly delithiated cathode materials, and the loss of lattice oxygen and generation of inactive oxygenated by‐products at the cathode‐sulfide interface. Consequently, an all‐solid‐state rechargeable Li battery with the modified cathode delivers high specific capacities of 168 mAh g−1 at 0.1 C and a high capacity retention >80 % after 100 cycles. Our work sheds new light on rational design of electrode‐electrolyte interface for the next‐generation high‐energy batteries. A uniform plastic‐crystal electrolyte nanolayer is coated onto the surface of Ni‐rich oxide cathode particles and serves as a buffer to effectively suppress the adverse phase transition, loss of lattice oxygen and interfacial parasitic reactions with a sulfide solid electrolyte at highly delithiated cathode, which contributes improved electrochemical performance of an all‐solid‐stare rechargeable Li battery.