Unveiling the role of Ti substitution in improving safety of high voltage LiNi0.5Mn1.5-Ti O4 cathode material by ameliorating Structure-stability and enhancing Elevated-temperature properties

The proposal of net-zero emissions policy promotes the research on safety property of cathode material in lithium ion batteries. Herein, to improve the safety of high voltage LiNi0.5Mn1.5O4(LNMO) as cathode material in lithium ion batteries, Ti4+ ions were doped into LNMO(LNMTO) and the enhancement mechanisms on safety property were investigated from aspects of structure stability and elevated-temperature properties by experimental and theoretical study. In experimental, the influence of Ti4+ doping on cathode/electrolyte interface stability and cathode thermal stability is explored by differential scanning calorimetry test(DSC), thermal diffusion and In-situ-XRD. Ti4+ doping can effectively improve the structure-stability of LNMO by infusing the stronger Ti-O bands, promoting thermal diffusion and suppressing the unexpected two-phase reactions. Compared with LNMO, LNMTO exhibits superior cycling stability at elevated-temperature with the 100th capacity of 124.1 mAh·g−1, which is equal to 98.8% of the 1st discharge capacity under 2C at 55 °C. Furthermore, we also verified the effectiveness of Ti4+ doping on improving thermal stability in LNMO/Li4Ti5O12(LTO) full cells. This work systematically investigates the effect of Ti4+ doping on safety of LNMO from aspects of structure-stability and elevated-temperature properties, which can be easily stretched into other cathode materials and speed up wider application of LIBs.