Boosting high-rate capacity and long-cycle stability of spinel LiMn2O4 by the Cr-Al co-doping strategy

Jahn-Teller distortion and Mn dissolution are easily generated at a high current density, whilst hindering the elevation of high-rate capacity and long-cycle performance of spinel LiMn2O4. Herein, a Cr-Al co-doping strategy is proposed for preparing a series of LiCr0.04AlxMn1.96-xO4 (0 < x < 0.08) cathode materials using facile solid-state combustion. Crystalline structure and particle morphology are regulated by changing the Al doping contents. After optimizing the Al-doping, the LiCr0.04Al0.01Mn1.95O4 cathode shows a unique truncated octahedron with the preferred growth of {111} crystal surfaces, which is conducive to reducing the Mn dissolution. Meanwhile, the LiCr0.04Al0.01Mn1.95O4 also exhibits a relatively high Mn average valence (+3.53) and lattice shrinkage, which can stabilize the spinel structure of the LiMn2O4 by inhibiting the Jahn-Teller to improve the electrochemical performance. Therefore, the optimized LiCr0.04Al0.01Mn1.95O4 cathode delivers the high-rate discharge capacity of 103.0 mAh/g and maintains the capacity retention of 67.0 % after 2000 cycles at 10C. Even at an ultra-high current rate of 30C, a long cycle life with a capacity retention of 78.0 % is also obtained after 1000 cycles.