Low‐cost BPO<sub>4</sub> In Situ Synthetic Li<sub>3</sub>PO<sub>4</sub> Coating and B/P‐Doping to Boost 4.8 V Cyclability for Sulfide‐Based All‐Solid‐State Lithium Batteries
Jie Shi, Zhihui Ma, Di Wu, Yue Yu, Zhen Wang, Yixing Fang, Dishuang Chen, Shuai Shang, Xuanhui Qu, Ping Li
Abstract
Abstract Structural damage of Ni‐rich layered oxide cathodes such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (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 Li 3 PO 4 coating and B/P co‐doping using inexpensive BPO 4 as raw materials via the one‐step in situ synthesis process is presented. Phosphates have good electrochemical stability and contain the same anion (O 2− ) and cation (P 5+ ) as in cathode and SEs, respectively, thus Li 3 PO 4 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 B 3+ /P 5+ co‐doping, thereby suppressing microcracks during high‐voltage cycling. Therefore, when tested in combination with Li─In anode and Li 6 PS 5 Cl 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.