A modification strategy for 4.6V LiCoO2: Uniform nano-coating and multi-level structure via high-temperature calcination

Abstract

Increasing the charge cut-off voltage is an effective means to boost the energy density of LiCoO₂. However, high voltage induces severe interfacial side reactions and degradation of the layered structure in LiCoO₂. The erosion of the interface by the by-product HF exacerbates this process, leading to battery failure. This study proposes suppressing the agglomeration of surface nano-coatings through applying a carbon source in combination with high-temperature calcination and forming a spinel-like transition layer to prevent the shedding of the nano-coating. Consequently, a multi-level modified structure comprising a Ta-O rock-salt phase nano-coating and Ta-Mg-Al gradient co-doped spinel phase is constructed. The uniformly coated Ta-O nano-coating serves as a physical barrier to effectively resist interfacial side reactions and HF corrosion. Additionally, Ta-Mg-Al co-doping that inhibits harmful phase transitions also enhances interfacial transport kinetics. The Ta element doped in the bulk phase inhibits the harmful H1-3 phase transition and stabilizes lattice oxygen. Therefore, the modified LiCoO₂ exhibits excellent electrochemical performance at 4.6 V, with a capacity retention rate of 92.8 % after 100 cycles at 0.5C and a discharge specific capacity of 143.0 m h g⁻¹ at 10 C. This work provides new ideas for the optimization of lithium-ion batteries.