Cation mixing regulation of cobalt-free high-nickel layered cathodes enables stable and high-rate lithium-ion batteries

The cobalt-free high-nickel layered oxide possesses high capacity and controllable cost, positioning it as a prospective option for cathode materials in the future lithium-ion batteries (LIBs). However, the charge compensation effect and high nickel content usually cause serious cation mixing, resulting in poor capacity stability, and hindering its practical application. Here, three types of LiNi0.9Mn0.1O2 microspheres with varying levels of cation mixing are constructed by simply adjusting the calcination temperatures, and the impacts of cation mixing on the electrochemical performance in LIBs are systematically investigated. By using XRD and cross-section STEM to characterize the levels of cation mixing, the resulting LiNi0.9Mn0.1O2 after treated at 780 °C (denoted as NM91-780) shows a lower degree of cation mixing compared to other samples (NM91-720 and NM91-840). As a proof-of-concept application in LIBs, the NM91-780 exhibits remarkable cycling stability with 92.4% capacity retention after 100 cycles, along with excellent rate capability of 132.5 mAh g−1 at 10 C. In situ XRD analysis shows that the low cation mixing of NM91-780 inhibits harmful volumetric strain during the electrochemical process, providing structural and chemical stability for its long-term cycling. This investigation contributes to the advancement of commercializing cobalt-free high-nickel layered oxide LiNi0.9Mn0.1O2 for use in LIBs.