Self-Grading and Surface-Preservation to Enhance the Compaction Density and Structural Stability of Li-Rich Mn-Based Cathode

Li-rich Mn-based (LRM) cathode materials are considered promising candidates for next-generation lithium-ion batteries due to their high specific capacity and cost-effectiveness. However, they exhibit deficiencies in volumetric energy density, largely attributable to their lower compaction density, which constrains their application in space-limited devices such as electric vehicles and portable devices. In this study, (NH₄)₂S₂O₈ surface treatment is proposed to enhance the compaction density and stability performance of LRM cathode materials. This (NH₄)₂S₂O₈ treatment induces the formation of surface Li/O vacancies and spinel structure, leading to an increase in the initial Coulombic efficiency (ICE) from 75.62% to 89.07%, as well as an increase in discharge capacity from 214.2 to 266.01 mAh g⁻¹ compared with the untreated sample. Furthermore, due to the self-grading generated by the crushing of cathode particles during the treatment process, which results in the enhancement of the compaction density to 3.18 g cm⁻³ and the volumetric energy density of 3145 Wh L⁻¹, significantly surpassing the 2487 Wh L⁻¹ of commercial LRM cathode materials. The present work provides new perspectives for the development of LRM cathode materials with high volumetric energy density.