Accelerating the activation of Li2MnO3 in Li-rich high-Mn cathodes to improve its electrochemical performance

Abstract

Li-rich high-Mn oxides, xLi₂MnO₃·(1 − x)LiMO₂ (x ≥ 0.5, M = Co, Ni, Mn…), have attracted extensive research interest due to their high specific capacity and low cost. However, slow Li₂MnO₃ activation and poor cycling stability have affected their electrochemical performance. Herein, to solve these problems, morphology regulation and LiAlF₄ coating strategies have been synergistically applied to a Li-rich high-Mn material Li_1.7Mn_0.8Co_0.1Ni_0.1O_2.7 (HM-811). This dual-strategy successfully promotes the activation process of the Li₂MnO₃ phase and thus improves the electrochemical performance of HM-811. Theoretical computation indicates that the LiAlF₄ layer has a lower Li⁺ migration barrier than the HM-811 matrix, so it could boost the diffusion of Li⁺ ions and promote the activation of the Li₂MnO₃ phase. Benefiting from the morphology regulation and LiAlF₄ coating, the HM-811 cathode shows a high initial charge capacity of >300 mA h g⁻¹. In addition, the modified HM-811 could deliver superior electrochemical performance even at a low temperature of −20 °C. This work provides a new approach for developing high performance cathode materials for next-generation Li-ion batteries.