Enabling stable and high areal capacity solid state battery with Ni-rich cathode via failure mechanism study

Sulfide based all solid state batteries (ASSBs) with Ni-rich layered oxide cathode are one of the most promising next-generation battery technologies due to their high energy density and improved safety. However, its electrochemical performance is still unsatisfactory, especially with high cathode mass loading. Herein, the failure mechanisms of single crystal LiNi0.8Co0.1Mn0.1O2 (NCM811) in ASSBs are systematically investigated from three aspects: interfacial side reactions, micro-distribution of cathode composite and mechanical failure. In addition to the commonly reported interfacial side reactions, we find micro-heterogeneity in cathode composite has detrimental effects on electrochemical performance. Three strategies are proposed and are effective to achieve excellent electrochemical performance of the batteries: ASSBs with bare NCM811 retains 88.5 % of its capacity after 2000 cycles at 1C (1C = 200 mA g–1). Moreover, ASSBs with high cathode loading of 35.7 mg cm−2 (30 °C) and 71.4 mg cm−2 (60 °C) is explored, which deliver a record-breaking areal capacity of 6.4 mAh cm−2 and 13 mAh cm−2, respectively.