Unveiling the role of Ti substitution in improving safety of high voltage LiNi_0.5Mn_1.5-xTi_xO₄ 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 LiNi_0.5Mn_1.5O₄(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.