Microstructure-Controlled Li-Rich Mn-Based Cathodes by a Gas–Solid Interface Reaction for Tackling the Continuous Activation of Li2MnO3

Li-rich Mn-based cathodes have attracted much attention due to their high capacity stemming from anion redox above 4.5 V. However, the continuous activation of Li₂MnO₃ in Li-rich Mn-based materials, which correlates with O₂ release and TM migration, is usually unfavorable to structural stability. Herein, based on a gas-solid interface reaction, we tackle this continuous activation phenomenon by restricting the capacity release of Li₂MnO₃ via NH₄HCO₃ treatment in the Li_1.2Ni_0.36Mn_0.44O₂ cathode. After modification, oxygen vacancies associated with the spinel phase are introduced on the surface. The 4 mol % NH₄HCO₃-modified material's capacity starts at 182 mAh g^-1 at 1 C instead of increasing from 173 to 186 mAh g^-1 for 25 cycles in the pristine material. Meanwhile, it also exhibits an excellent capacity retention of 93.24% after 200 cycles (at 1 C), with a small voltage decay rate of 1.19 mV cycle^-1.