Thiourea-derived coating enabled lithium-rich manganese oxide positive electrode in solid-state batteries

Solid-state batteries employing lithium-rich manganese oxide positive electrodes are a highly promising candidate for next-generation high-energy-density energy storage systems. However, the practical deployment of lithium-rich manganese oxide positive electrodes is hindered by several critical challenges, including poor initial-cycle reversibility, rapid capacity decay, structural collapse due to oxygen release, and interfacial instability at high potentials. Here, we introduce a thiourea-derived surface modification strategy for lithium-rich manganese oxide positive electrodes, which significantly enhances the electrochemical performance of solid-state batteries (SSBs). The modified lithium-rich manganese oxide positive electrodes exhibit an initial discharge capacity of 220.2 mAh g^-1, an initial Coulombic efficiency of 84.83 %, and capacity retention of 97 % after 600 cycles at 1 C under 4.6 V (vs. Li⁺/Li). The improved cycling performance is shown to be attributed to a dual modification of lithium-rich manganese oxide particles, i.e., the application of sub-nm-thick S-rich coating layer and formation of a spinel-like structure in the surface near proximity, which prevents oxygen-related degradation and accelerates Li⁺ transport, respectively. These findings present a scalable surface modification strategy that potentially addresses key limitations of lithium-rich manganese oxide-based SSBs, paving the way for the development of stable, high-energy-density batteries.