Composite\nCathode Design for High-Energy All-Solid-State\nLithium Batteries with Long Cycle Life

Abstract

All-solid-state batteries (ASSBs) consisting of a 4 V\nclass layered\noxide cathode active material (CAM), an inorganic solid-state electrolyte\n(SE), and a lithium metal anode are considered the future of energy\nstorage technologies. To date, aside from the known dendrite issues\nat the anode, cathode instabilities due to oxidative degradation of\nthe SE and reactivities between the SE and CAM as well as loss of\nmechanical integrity are considered to be the most significant barriers\nin ASSB development. In the present study, we address these challenges\nby developing composite cathode structures featuring two key design\nelements: (1) a halide SE with high oxidative stability to enable\ndirect use of an uncoated 4 V class CAM and (2) a single-crystal (SC)\nCAM to eliminate intergranular cracking associated with volume changes\nand mechanical instability. We demonstrate exceptional performance\nachieved on such ASSB cells incorporating an uncoated SC-LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) CAM,\na Li₃YCl₆ (LYC) SE, and a Li–In alloy\nanode, delivering a high discharge capacity of 170 mAh/g at C/5 and\nan impressive capacity retention of nearly 90% after 1000 cycles.\nThrough comparative studies on polycrystalline and single-crystal\nNMC811 composite cathodes, we reveal the working mechanism that enables\nsuch stable cycling in the latter cell design. The study highlights\nthe importance of proper cathode composite design and provides key\ninsights in the future development of better-performing ASSB cells.