Si-Al co-doping synergistically enhances the high-rate capacity and long-cycle life of spinel LiMn2O4

The drawbacks of Jahn-Teller (J-T) effect, capacity decay at high temperature and the dissolution of Mn generated at elevated current density limit the large-scale application of LiMn 2 O 4 batteries . Herein, a Si 4+ /Al 3+ co-doping strategy of LiMn 2 O 4 is carefully developed to stabilize the [MnO 6 ] framework, thereby inhibiting the J-T distortion and ultimately alleviating Mn dissolution. The incorporation of Si 4+ and Al 3+ in LiMn 2 O 4 promotes the formation of a single-crystal truncated octahedral structure, with preferential grain growth along the {111}, {100} and {110} crystal plane, which decreases Mn dissolution and enhances the Li + transfer pathways. Furthermore, the integration of Si 4+ /Al 3+ co-doping producing smaller particles can shorten the migration paths of electrons and ions. Consequently, the optimized LiSi 0.05 Al 0.09 Mn 1.86 O 4 displays a decent initial discharge specific capacity of 103.2 mAh·g −1 and an excellent capacity storage percentage of 79.7 % after 1000 cycles at 10 C. Meanwhile, the optimal sample also exhibits respectable first discharge capacities of 91.9 mAh·g −1 and 61.8 mAh·g −1 at ultra-high rates of 20 C and 40 C, along with superior capacity storage ratios of 70.9 % and 70.7 % after 1000 cycles. More importantly, the optimized sample shows remarkable first discharge specific capacity of 107.1 mAh·g −1 at 55 °C and 10 C and exciting capacity storage rate of 61.9 % after 500 cycles. This study serves as a guide for advancing high-performance, high-stability LiMn 2 O 4 cathode materials for use in lithium-ion batteries.