The LiCuxMn1.95-xSi0.05O₄ (x = 0, 0.02, 0.05, 0.08) samples have been obtained by a simple solid-state method. XRD and SEM characterization results indicate that the Cu-Si co-doped spinels retain the inherent structure of LiMn₂O₄ and possess uniform particle size distribution. Electrochemical tests show that the optimal Cu-doping amount produces an obvious improvement effect on the cycling stability of LiMn1.95Si0.05O₄. When cycled at 0.5 C, the optimal LiCu0.05Mn1.90Si0.05O₄ sample exhibits an initial capacity of 127.3 mAh g-1 with excellent retention of 95.7% after 200 cycles. Moreover, when the cycling rate climbs to 10 C, the LiCu0.05Mn1.90Si0.05O₄ sample exhibits 82.3 mAh g-1 with satisfactory cycling performance. In particular, when cycled at 55 °C, this co-doped sample can show an outstanding retention of 94.0% after 100 cycles, whiles the LiMn1.95Si0.05O₄ only exhibits low retention of 79.1%. Such impressive performance shows that the addition of copper ions in the Si-doped spinel effectively remedy the shortcomings of the single Si-doping strategy and the Cu-Si co-doped spinel can show excellent cycling stability.
Keywords: Cu-Si co-doping; LiMn2O4; cathode material; cycling stability; lithium-ion batteries.