Co-free/Co-poor high-Ni cathode for high energy, stable and low-cost lithium-ion batteries

Advanced cathode materials have been considered as the key to significantly improve the energy density of lithium-ion batteries (LIBs). High-Ni layer-structured cathodes, especially with Ni atomic content above 0.9 (LiNi x M 1− x O 2 , x ≥ 0.9), exhibit high capacity to be commercially available in electric vehicles (EVs). However, the intrinsic structure instability of high-Ni materials and the negative impacts severely restrict their further application. In addition, Co has various effective efforts to stabilize the layered structure. Nevertheless, due to the high cost of Co, it is required to be replaced. Therefore, modification methods on increasing the stability of high-Ni cathode with the reduction of Co content have been widely investigated. In this review, we summarized various effective research progresses and several potential modification strategies of Co-free/Co-poor layered cathodes with Ni content over 0.9. The challenges and development opportunities of high-Ni, Co-free/Co-poor cathodes are further overviewed to meet the future commercial energy demands. Graphical abstract