Low‐cost BPO4 In Situ Synthetic Li3PO4 Coating and B/P‐Doping to Boost 4.8 V Cyclability for Sulfide‐Based All‐Solid‐State Lithium Batteries

Abstract

AbstractStructural damage of Ni‐rich layered oxide cathodes such as LiNi0.8Co0.1Mn0.1O2 (NCM811) and serious interfacial side reactions and physical contact failures with sulfide electrolytes (SEs) are the main obstacles restricting ≥4.6 V high‐voltage cyclability of all‐solid‐state lithium batteries (ASSLBs). To tackle this constraint, here, a modified NCM811 with Li3PO4 coating and B/P co‐doping using inexpensive BPO4 as raw materials via the one‐step in situ synthesis process is presented. Phosphates have good electrochemical stability and contain the same anion (O2−) and cation (P5+) as in cathode and SEs, respectively, thus Li3PO4 coating precludes interfacial anion exchange, lessening side reactivity. Based on the high bond energy of B─O and P─O, the lattice O and crystal texture of NCM811 can be stabilized by B3+/P5+ co‐doping, thereby suppressing microcracks during high‐voltage cycling. Therefore, when tested in combination with Li─In anode and Li6PS5Cl solid electrolytes (LPSCl), the modified NCM811 exhibits extraordinary performance, with 200.36 mAh g−1 initial discharge capacity (4.6 V), cycling 2300 cycles with decay rate as low as 0.01% per cycle (1C), and 208.26 mAh g−1 initial discharge capacity (4.8 V), cycling 1986 cycles with 0.02% per cycle decay rate. Simultaneously, it also has remarkable electrochemical abilities at both −20 °C and 60 °C.