B-coating modulation strategy serving ultra-high Ni cathodes

To satisfy the demand for low-cost and long-range in the electric vehicle market, ultra-high nickel cathode materials with high specific capacity and a wide electrochemical window are expected to be commercialized to facilitate the development of lithium-ion batteries in the electric vehicle market. However, residual lithium compounds with strong alkalinity make cathode preparation difficult and indirectly affect the cycling stability of the cathode during the cycle. Since the formation of residual alkali is inevitable, the lithium borate coating with adjustable thickness was chosen by controlling the formation of residual alkali. An additional lithium source was added to the synthesis process and converted into a thicker and more complete coating structure, giving the cathode better cycle stability. As a result, the surface-modified cathode exhibited a significant decrease in the percentage of lithium carbonate on its surface from 38.07% to 28.26%. The etching results showed that a uniform coating layer was formed after boric acid treatment. The initial capacity of the treated cathode was 214.6 mA h g-1 owing to the favorable effect of the surface coating, and the capacity retention raised from 59.35% to 90.75% after cycling at 0.5 C current density and from 63.81% to 91.94% after cycling at 1 C current density. The boric acid coating modified strategy proposed in this paper significantly ameliorates the cycling stabilization of cathode, providing superior commercial application value for ultra-high nickel cathode materials.