Order-disorder transition mechanism for high-capacity amorphous anodes of lithium-ion batteries

Abstract

As potential electrode materials with a high specific capacity, vanadium-based amorphous materials have attracted a great deal of attention in lithium-ion batteries (LIBs). Herein, different valence states of manganese, MnO2 and Mn2O3 are utilized to replace V in V2O5. The results reveal that the MnO2-substituted glass exhibits a high initial capacity of 1029.8 mAh g−1 and preserves a capacity of 210.3 mAh g−1 after 50 cycles at the current density of 10 mA g−1. After Mn substitution, the content of V4+ increases from 15.6% to 57.3% and 60.9%. Moreover, it is demonstrated that the increase in average valence state of Mn effectively suppresses the Jahn-Teller effect in the local structure. For instance, both VO and Li3MnO4 nano-crystals are identified after 50 charge/discharge cycles, whose synergistic effect with the amorphous matrix ameliorates the conductivity of the electrode and enhances the reaction kinetics. Furthermore, density functional theory calculations reveal that the substitution of Mn moves the Fermi level close to the conduction band to reduce the bond gap, corresponding to an increase in conductivity, and facilitates the charges transfer from Li to O contrarily, improving the cyclic stability of the anode material. The order-disorder transition mechanism presents a novel perspective for the selection of materials for LIBs.