• A lithium-borate coating with adjustable thickness is formed by controlling residual alkali, effectively reducing surface Li2CO3 from 38.07% to 28.26%.
• The boric acid treatment creates a uniform coating layer, significantly enhancing cycling stability: capacity retention improves from 59.35% to 90.75% at 0.5C and from 63.81% to 91.94% at 1C.
• The modified cathode delivers an initial capacity of 214.6 mAh·g−1, demonstrating the coating's beneficial effect on electrochemical performance.
• This strategy offers a commercially viable solution to mitigate residual alkali issues in ultrahigh nickel cathodes, advancing lithium-ion battery technology for electric vehicles.