Triggering the phase transition and capacity enhancement of Nb2O5 for fast-charging lithium-ion storage

Abstract

Developing high energy density and high-power density electrode materials is of great importance for lithium-ion batteries to satisfy the requirements of the customer market. We report that introducing Mo into Nb₂O₅ at a low temperature leads to phase transition from bronze-phase T to crystallographic shear-phase H. The resulting Nb₁Mo_0.1O_2.8 exhibits higher energy density than T-Nb₂O₅ and improved rate-performance and cycling-stability compared to H-Nb₂O₅. Neutron diffraction was applied to Nb₁Mo_0.1O_2.8 to characterize the structure and two-phase ratios of the mixed metal oxide together with the first-principles method to calculate the possible Mo substitution sites. The Nb₁Mo_0.1O_2.8 anode displays intrinsic pseudocapacitive lithium-ion intercalation with a high energy density of 362 mA h g⁻¹ at 0.2C. In situ XRD results suggest that Nb₁Mo_0.1O_2.8 is able to intercalate more lithium ions with smaller structure expansion compared with H-Nb₂O₅; furthermore, a computational method reveals that the introduction of Mo into the oxide increases Li atom adsorption energies and decreases the diffusion barrier. Therefore, Nb₁Mo_0.1O_2.8 is a promising anode material for high-capacity and high-rate lithium-ion energy storage.