A quantitative reconstruction strategy for the surface structure of LiNi_0.80Co_0.15Al_0.05O₂ cathode material

To address the detrimental impact of residual LiOH on the electrochemical performance of LiNi0.80Co0.15Al0.05O2 (NCA) cathode material, it is imperative to optimize its surface structure. Adding a Li-reactant to react with residual LiOH on the cathode surface not only removes residual LiOH but also forms new surface structure layers. However, this reaction process not only necessitates evaluating the compatibility between the newly formed surface layer and the crystal structure of the NCA cathode material but also requires careful determination of the optimal amount of Li-reactant. Currently, there remains a lack of well-established theoretical guidance for determining the optimal addition amount of lithium reactants. In this study, the quantitative addition of 6,000 ppm Al2O3 as a Li-reactant to react with the residual 3,156 ppm LiOH on the NCA surface not only effectively reduces the residual LiOH but also facilitates the formation of a LiAlO2@NCA heterostructure on the NCA cathode materials. This approach provides a theoretical foundation for the addition of Li-reactant, overcomes the limitations of empirical trial-and-error methods, and achieves quantitative reconstruction of the NCA cathode materials surface structure. Based on an in-depth analysis of the surface structure, first-principles calculations and electrochemical performance tests, the LiAlO2@NCA heterostructure not only serves as an efficient Li+ diffusion channel and reduces the Li+ migration energy barrier, but also provides a stable protection of the surface of the cathode material, thereby enhancing its stability and reversibility.