Decoupling activation from passivation in high-rate Li-rich Mn-based layered oxides through the construction of a conductive LiFePO4 island architecture

Abstract

Although Li-rich Mn-based layered oxides (LMRs) exhibit high specific capacities (>250 mAh g(-1)) through anionic redox activity and are therefore promising next-generation cathode materials for high-energy Li-ion batteries, their commercialization is severely hindered by voltage fading, structural degradation, and safety concerns arising from surface instability. To address these problems, we deposited an insular protective layer of carbon-coated LiFePO4 (C-LFP) nanoparticles on LMR secondary particles using a scalable solvent-free mechanofusion strategy. The optimal coating (C-LFP loading = 0.75 wt%) notably enhanced electrochemical performance, resulting in a capacity retention of 60.7% at 3C (cf. 38% for pristine LMR) and 93.43% after 200 cycles at 0.5C while suppressing voltage fading. According to the proposed synergistic mechanism, C-LFP provided electronic conductivity exceeding that of bare LMR, the insular morphology preserved direct electron transport pathways, and the nanoscale C-LFP particle size enabled rapid Li-ion transport and shortened diffusion lengths. The C-LFP coating prevented the formation of highly resistive rock-salt degradation layers, maintained a low interfacial impedance, and suppressed Mn dissolution (>95% reduction) and O-2 evolution. Thus, this work demonstrates that rationally designed surface modification can unlock the full potential of LMR cathodes for next-generation energy storage applications.