Facile solid-state combustion synthesis of Al–Ni dual-doped LiMn2O4 cathode materials

Abstract

A series of aluminum and nickel (Al–Ni) co-doped LiAl0.15NixMn1.85−xO4 composites are prepared through a facile solid-state combustion method. All the as-obtained materials show a spinel structure and analogous spherical morphology with uniform particle distribution. Moreover, the synergistic merits of Al and Ni dual substitutions endow the spinel LiMn2O4 with an elevated Mn average valence state of 3.59 and relatively alleviative Jahn–Teller distortion. Among these samples, the LiAl0.15Ni0.03Mn1.82O4 (LANMO-0.03) cathode exhibits an optimal electrochemical performance with the discharge capacities of 103.3 mAh g−1 and 102 mAh g−1 at 1 C and 5 C in the first cycle, and the capacity retentions are 72.0% and 68.6% after 1000 cycles, respectively. Even at 1 C and high temperature of 55 °C, an excellent capacity retention remained to be 76.6% after 200 cycles. Furthermore, the LANMO-0.03 has good Li+ diffusion capability during charge/discharge, the DLi+ value of the LANMO-0.03 (1.65 × 10–11 cm2∙s−1) is higher than that of the LiAl0.15Mn1.85O4 (LAMO) (8.12 × 10–12 cm2∙s−1), and the charge transfer resistances of the LAMO and LANMO-0.03 samples are almost the same at 150 Ω before cycling but decrease to 130 Ω and 95 Ω after 1000 cycles at 1 C, respectively. These results demonstrate that the Al–Ni co-doped strategy can enhance the structural stability and provide stable Li+ diffusion channel during the long cycles even at elevated temperature. Meanwhile, the facile solid-state combustion approach can also be extended to the preparation of other dual cation-doped electrode materials.