Aluminum Sulfate Surface Treatment Enabling Long Cycle Life and Low Voltage Decay Lithium-rich Manganese Based Oxide Cathode

Abstract

Lithium-rich manganese-based cathode materials (LRMs) represent promising candidates for high-energy-density lithium-ion batteries. Nevertheless, the significant voltage decay and inferior cycle performance resulting from irreversible oxygen redox processes have impeded the commercialization of LRMs. In this study, we demonstrate that surface aluminum doping, in situ formation of spinel structures, and amorphous lithium sulfate coatings can enhance lithium-ion diffusion and mitigate irreversible oxygen loss through a straightforward aluminum sulfate treatment applied to cobalt-free LRMs. The modified LRMs demonstrate a capacity retention of 93.8% and a voltage decay rate of 0.28 mV per cycle after 500 cycles. Additionally, the modified LRMs achieve a first discharge-specific energy density of 1016 Wh/kg (based on active materials), which is comparable to that of cobalt-containing LRMs (Li_1.2Ni_0.1Co_0.13Mn_0.54O₂) while offering superior energy density retention. This enhanced performance can be primarily attributed to increased reversible oxygen redox processes and reduced structural reorganization following prolonged cycling. This study presents a robust strategy for the synthesis of high-energy, high-stability cobalt-free LRMs tailored for advanced lithium-ion battery applications.