Abstract
Li- and Mn-rich layered oxides exhibit high specific capacity due to the cationic and anionic reaction process during high-voltage cycling (≥ 4.6 V). However, they face challenges such as low initial coulombic efficiency (~70%) and poor cycling stability. Here, we propose a combination of H3BO3 treatment and low temperature calcination to construct a shell with cationic vacancy on the surface of Li1.2Ni0.2Mn0.6O2 (LLNMO). The H3BO3 treatment produces cationic vacancy and lattice distortion, forming an oxidized On- (0<n<2) on the surface, accompanied by electrons redistribution. Low temperature calcination eliminates lattice distortion, activates metastable On- and promotes coherent lattice formation. In addition, the cationic vacancy shell reduces the diffusion energy barrier of Li+, allowing more Li+ and oxygen to participate in deeper reactions and increasing the oxidation depth of oxygen. The modified material (LLNMO-H10-200) exhibits an initial coulombic efficiency of up to 88% and a capacity of 256 mAh g-1. Moreover, similar enhancements were observed with Co-containing lithium-rich materials, with a 280 mAh g-1 discharge capacity and 89% coulombic efficiency. These findings reveal the correlation between cationic vacancy, metastable oxygen activation and bulk phase activity, offering a novel approach to enhancing the initial coulombic efficiency and cycle stability of Li-rich materials.
Published Version
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