Perspective on the Preparation Methods of Single Crystalline High Nickel Oxide Cathode Materials

Li(NixCoyMnz)O2 (x + y + z = 1, NCM), as one of the most dominant cathode materials in electric vehicle (EV) batteries, faces the challenges of poor cycling stability and safety concerns with the increase of Ni content and charge/discharge capacity. Single crystalline NCM (SC‐NCM) materials have been developed to mitigate these challenges, owing to their lower surface areas, fewer grain boundaries, and better morphological stability. Here, the preparation strategies of SC‐NCM are summarized, including continuous high‐temperature sintering (CHTS), molten salt method, pulse high‐temperature sintering (PHTS), and controllable growth with special orientations or sizes. CHTS produces irregular SC‐NCM particles, but is accompanied by Li‐volatilization and agglomeration during long‐term sintering. The molten salt helps to lower calcination temperature and generate well‐defined crystalline material, but generally causes large capacity loss due to the Li/H exchange in the following water rinsing procedure. To address the above challenges, the PHTS strategy has recently been recently proposed, which mitigates Li‐loss through shortened high‐temperature stage and avoids further water rinsing steps. For improving the C‐rate performance, controllable crystal growth with specific sizes and crystal orientations is highly desired, which calls for further investigation and upgrading of current large‐scale preparation technology. Considering the importance of single crystalline high nickel oxide cathode materials, their various preparation strategies are outlined according to different sintering modes, the corresponding electrochemical performance, underlying mechanisms, and respective challenges are discussed as well.