Stable Ni-rich layered oxide cathode for sulfide-based all-solid-state lithium battery

Sulfide-based all-solid-state lithium-ion batteries (ASSLIBs) are one of the most promising energy storage technologies due to their high safety and ionic conductivity. To achieve greater energy density, a Ni-rich layered oxide LiNixCoyM1-x-yO2 (NCM, M ​= ​Mn/Al, x ​≥ ​0.6) is desirable due to its relatively high voltage and large capacity. However, interfacial side reactions between the NCM and sulfide solid electrolytes lead to undesirable interfacial passivation layers and low ionic conductivity, thereby degrading the electrochemical performance of NCM sulfide all-solid-state batteries. Herein, a time-/cost-effective sulfidation strategy is exploited to sulfidize a Ni-rich NCM88 cathode in a mixed gas atmosphere of N2 and CS2. A new type of cathode (NCM88-S) with an ultrathin (∼2 ​nm) surface layer is obtained, which significantly reduces the interfacial side reactions/resistance and improves the interfacial stability. The resulting NCM88-S/Li6PS5Cl/Li4Ti5O12 ASSLIB exhibits superior performance, including a high discharge specific capacity (200.7 mAh g−1) close to that of liquid batteries, excellent cycling performance (a capacity retention of 87% after 500 cycles), and satisfactory rate performance (158.3 mAh g−1 at 1C).