Li2O–V2O5–MoO3–Fe2O3 amorphous cathode material for lithium-ion batteries based on coordinated multi-electron effect and stable network structure

Abstract

The amorphous cathode materials Li2O–V2O5–MoO3 and Li2O–V2O5–MoO3–Fe2O3 were produced via melt quenching. By analyzing the structure, elemental valence, and electrochemical characteristics of Li2O–V2O5–MoO3 at different ratios, the effects of MoO3 addition on vanadium-based amorphous cathode materials were explored. 20Li2O–60V2O5–20MoO3 has a high initial capacity (268.0 mAh/g for the first reversible discharge at a current density of 50 mA/g), which is based on the properties that MoO3 supplies additional oxidation reductions and has [MoO6] structural units to widen the diffusion channels for lithium ions in the network structure. Unfortunately, the network of the structural elements [MoO6] and [VO4] is unstable, which causes the material to have poor cycle stability and exhibit an unsatisfactory current response. The network structure stability of Li2O–V2O5–MoO3–Fe2O3 is increased by adding Fe2O3 to provide [FeO4], which strengthens the link between each structural unit. Vanadium oxidation reductions are promoted, and iron oxidation reductions replace the role of molybdenum in the charge/discharge. The discharge product transforms from LiVMoO5 to Li2FeV3O8 with increased de-embedding Li efficiency. The 20Li2O–60V2O5–10MoO3–10Fe2O3 achieves an initial reversible specific capacity of 255.2 mAh/g at 50 mA/g, 139.7 mAh/g additional specific capacity after 100 cycles, and 110.5 mAh/g specific capacity at a high current density of 400 mA/g. The test findings show that 20Li2O–60V2O5–10MoO3–10Fe2O3 efficiently increases high-current responsiveness and cycle stability while retaining a high capacity. In this study, we propose a compositional design strategy, which is based on the coordinated multi-electronic effect of multiple transition metal elements and the design of a stable disordered network structure, to incorporate MoO3 and Fe2O3 into vanadium-based amorphous to create a novel cathode material. This work offers a fresh perspective on investigating innovative lithium-ion battery cathode materials.