High Energy Sulfide-Based All-Solid-State Lithium Batteries Enabled by Single-Crystal Li-Rich Cathodes

High-capacity Li-rich Mn-based oxides (LRMOs) show great potential for enhancing the energy density of all-solid-state lithium batteries (ASSLBs). However, the intrinsically low electronic/ionic conductivity of LRMOs and bulk structural degradation lead to an inferior electrochemical performance. Herein, a single-crystal Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (SC- LRMO) cathode is developed to address the challenges associated with charge-transport limitations and mechanical degradation of conventional polycrystalline (PC)-LRMO in ASSLBs. The results indicate that composite cathodes using small SC-LRMO achieve excellent electrochemical performance. Specifically, SC-LRMO not only delivers a high specific capacity of 316 mAh g^–1 at 0.05C but also exhibits a capacity retention of 86% after 300 cycles at 1C, outperforming the PC-LRMO (243 mAh g^–1, 84%). Comprehensive characterization reveals that the small single-crystal microstructure of SC-LRMO facilitates electrochemical reaction and mitigates detrimental mechanical degradation. Overall, this work expedites the practical application of LRMO cathodes in high-energy-density ASSLBs through dedicated morphology design.