Unlocking the ultra-high capacity and cost-effectiveness of cobalt-free lithium-rich cathode materials

Abstract

Cobalt-free Li- and Mn-rich layered (LMR) cathode materials have the merits of being low-cost and environmentally compatible. However, their practical discharge capacities are much lower than the theoretical ones because the lack of cobalt reduces the anion redox activity. Furthermore, the issues related to anionic redox reactions, such as irreversible oxygen loss and phase transitions, hinder their commercialization. In this study, we present a novel method that involves premixing active materials and conductive agents followed by post-processing using spark plasma sintering (SPS). This rapid treatment (10 min) significantly enhances the discharge capacity of Co-free LMR materials. Specifically, the treated materials can achieve 319.4 mAh g⁻¹ at 0.1C, approximately 90 mAh g⁻¹ higher than the untreated LMR. Noticeably, the SPS-treated LMR exhibits excellent capacity retention of 71.8% after 800 cycles at 5C. Multi-angle characterizations demonstrate that SPS treatment induces a reconstructed surface with cationic disordering increasing from the bulk to the surface. This interlayer cationic disordering effectively enhances oxygen redox activity and the reconstructed rock-salt surface protects the interior layered structure. This study develops a new approach to activating the oxygen activity and enhancing the capacity in cathode materials through an innovative SPS technology.