Insight into the action mechanism of Ce4+ doping in improving cycling stability of LiNi0.5Mn1.5O4 from internal stress and structure stability

The higher requirements for power sources in electric vehicles promote the further research on high voltage cathode material LiNi0.5Mn1.5O4(LNMO), especially for its cycle stability. As previously reported, doping has achieved some promotion in enhancing cycle stability, but little attention paid to the side effects on the change of internal stress induced by the differences in ionic radius between Mn4+ and doping elements, leading to the little cognitive advances in enhancement mechanism. Thus, in this paper, Ce4+ ion was chosen as the research subject; the effect of Ce4+ doping on the internal stress change was investigated through monitoring lattice parameter changes by in situ XRD. In addition, the content of Ce4+ doping on electrochemical property was explored; the results exhibit that Li0.99Ni0.05Mn1.5Ce0.01O2 (LNMCO-0.01) shows superior cycling stability compared with LNMO for its better crystal structure stability during cycle process, as demonstrated by SEM and TEM. For example, under 10 C, the 1000th discharge capacity is 88.2 mAh/g much larger than that of LNMO (73.5 mAh/g). This work provides new perspectives for choosing doping element for cathode material in improving its cycling stability, which may contribute a lot to the further application of high voltage LNMO as cathode material in LIBs.