Modification strategies improving the electrochemical and structural stability of high-Ni cathode materials

With the increasing spotlight in electric vehicles, there is a growing demand for high-energy-density batteries to enhance driving range. Consequently, several studies have been conducted on high-energy-density LiNixCoyMnzO2 cathodes. However, there is a limit to permanent performance deterioration because of side reactions caused by moisture in the atmosphere and continuous microcracks during cycling as the Ni content to express high energy increases and the content of Mn and Co that maintain structural and electrochemical stabilization decreases. The direct modification of the surface and bulk regions aims to enhance the capacity and long-term performance of high-Ni cathode materials. Therefore, an efficient modification requires a study based on a thorough understanding of the degradation mechanisms in the surface and bulk region. In this review, a comprehensive analysis of various modifications, including doping, coating, concentration gradient, and single crystals, is conducted to solve degradation issues along with an analysis of the overall degradation mechanism occurring in high-Ni cathode materials. It also summarizes recent research developments related to the following modifications, aims to provide notable points and directions for post-studies, and provides valuable references for the commercialization of stable high-energy-density cathode materials.