Tailoring lithium concentration in alloy anodes for long cycling and high areal capacity in sulfide-based all solid-state batteries

Lithium–indium (Li-In) alloys are important anode materials for sulfide-based all-solid-state batteries (ASSBs), but how different Li concentrations in the alloy anodes impact the electrochemical performance of ASSBs remains unexplored. This paper systematically investigates the impact that different Li concentrations in Li-In anodes have on the performance of ASSBs. We show that In with 1 ​wt% Li (LiIn-1) exhibits the best performance for ASSBs among all the tested Li-In anodes. In essence, LiIn-1 not only provides sufficient Li to compensate for first-cycle capacity loss in the anode but also facilitates the formation of a LiIn alloy phase that has the best charge transfer kinetics among all the LixIn alloy phases. The ASSB with a LiIn-1 anode and a LiNi0.8Mn0.1Co0.1O2 cathode reached 3400 cycles at an initial capacity of 125 mAh/g. Remarkably, ASSBs with a high cathode active material (CAM) loading of 36 ​mg/cm2 delivered a high areal capacity of 4.05 mAh/cm2 at high current density (4.8 ​mA/cm2), with a capacity retention of 92% after 740 cycles. At an ultra-high CAM loading of 55.3 ​mg/cm2, the ASSB achieved a stable areal capacity of 8.4 mAh/cm2 at current density of 1.7 ​mA/cm2. These results bring us one step closer to the practical application of ASSBs.