B-coating modulation strategy serving ultrahigh nickel cathodes

To satisfy the demand for low-cost and long-range electric vehicles by the market, the commercialization of ultrahigh nickel cathode materials with high specific capacity and a wide electrochemical window is expected to facilitate the development of lithium-ion batteries. However, residual lithium compounds with a strong alkalinity cause difficulty in cathode preparation and indirectly affect the cycling stability of the cathode during cycling. Given the inevitability of the formation of residual alkali, a lithium-borate coating with an adjustable thickness was selected 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, which rendered the cathode with better cycle stability. As a result, the percentage of peak area of lithium carbonate on the surface-modified cathode surface exhibited a considerable decrease from 38.07% to 28.26%. The etching results show the formation of a uniform coating layer after boric acid treatment. The initial capacity of the treated cathode was 214.6 mAh·g⁻¹ owing to the favorable effect of the surface coating, and the capacity retention raised from 59.35% to 90.75% and from 63.81% to 91.94% after cycling at 0.5 and 1 C current densities, respectively. The boric acid coating-modified strategy proposed in this paper considerably ameliorates the cycling stabilization of cathodes and provides superior commercial application value for ultrahigh nickel cathode materials.