Enhancing high-rate and elevated-temperature properties of Ni-Mg co-doped LiMn2O4 cathodes for Li-ion batteries.

The improvements of cyclability and rate capability of lithium ion batteries with spinel LiMn2O4 as cathode are imperative demands for the large-scale practical applications. Herein, a nickel (Ni) and magnesium (Mg) co-doping strategy was employed to synthesize LiNi0.03Mg0.05Mn1.92O4 cathode material via a facile solid-state combustion approach. The effects of the Ni-Mg co-doping on crystalline structure, micromorphology and electrochemical behaviors of the as-prepared LiNi0.03Mg0.05Mn1.92O4 are investigated by a series of physico-chemical characterizations and performance tests at high-rate and elevated-temperature. The resultant LiNi0.03Mg0.05Mn1.92O4 has the intrinsic spinel structure with no any impurities, and exhibits an elevated average valence of manganese in comparison to the pristine LiMn2O4. Owing to the Ni and Mg dual-doped merits, the LiNi0.03Mg0.05Mn1.92O4 sample demonstrates a robust spinel structure and high first discharge specific capacity of 112.3 mAh g-1, whilst undergoing a long cycling of 1000 cycles at 1 C. At a high current rate of 20 C, the capacity of 91.2 mAh g-1 with an excellent retention of 77% is obtained after 1000 cycles. Even at 10 C under 55 °C, an excellent capacity of 97.6 mAh g-1 is also delivered. These results offer a new opportunity for developing high-performance lithium ion batteries with respect to the Ni-Mg co-doping strategy.