Enhanced elevated-temperature performance of LiAlxSi0.05Mg0.05Mn1.90-xO4 (0≤x≤0.08) cathode materials for high-performance lithium-ion batteries

In order to significantly enhance the elevated-temperature performance of LiSi0.05Mg0.05Mn1.90O4, the LiAlxSi0.05Mg0.05Mn1.90-xO4 (0 ≤ x ≤ 0.08) samples were firstly prepared via sol-gel technique. All the obtained samples showed the intrinsic spinel structure without any other detectable impurity phases. Among these samples, the LiAl0.05Si0.05Mg0.05Mn1.85O4 sample was found to be optimal possessing regular crystal morphology with clean surfaces and presented much better elevated-temperature cycling stability and rate capability. When carried out at 55 °C, the LiAl0.05Si0.05Mg0.05Mn1.85O4 sample exhibited the initial discharge capacity of 123.6 mAh g−1 at 0.5C between 3.20 and 4.35 V. After 100 cycles, the discharge capacity could still reach up to 115.9 mAh g−1 with capacity retention of 93.8%, which was much higher than that of LiSi0.05Mg0.05Mn1.90O4. At the higher discharge rate of 10C, a high discharge capacity of 82.5 mAh g−1 could be obtained with capacity retention of 95.6% after 50 cycles at 55 °C. By contrast, the LiSi0.05Mg0.05Mn1.90O4 sample only exhibited 43.7 mAh g−1 with lower capacity retention of 61.8%. These results indicate that the introduction of appropriate amount of aluminium ions in the magnesium and silicon co-doped spinel can make up for the shortage of co-doping with magnesium and silicon ions in term of the elevated-temperature performance.