Highly Reversible Anion Redox of Manganese-Based Cathode Material Realized by Electrochemical Ion Exchange for Lithium-Ion Batteries

Anion energy storage provides the possibility to achieve higher specific capacity in lithium-ion battery cathode materials, but the problems of capacity attenuation, voltage degradation, and inconsistent redox behavior are still inevitable. In this paper, a novel O2-type manganese-based layered cathode material Li_xLi_0.2Mn_0.8]O₂ with a ribbon superlattice structure is prepared by electrochemical ion exchange, which realizes the highly reversible redox of anions and excellent cycle performance. Through low-voltage pre-cycling treatment, the specific capacity of the material can reach 230 mAh g⁻¹ without obvious voltage attenuation. During the electrochemical ion exchange, the precursor with P2 structure transforms into Li_xLi_0.2Mn_0.8]O₂ with O2 structure through the slippage and shrink of adjacent slabs, and the special superlattice structure in Mn slab is still retained. Simultaneously, a certain degree of lattice mismatch and reversible distortion of the MnO₆ octahedron occur. In addition, the anion redox catalyzes the formation of the solid electrolyte interface, stabilizing the electrode/electrolyte interface and inhibiting the dissolution of Mn. The mechanism of electrochemical ion exchange is systematically studied by comprehensive structural and electrochemical characterization, opening an attractive path for the realization of highly reversible anion redox.