Intercalation pseudocapacitive electrochemistry of Nb-based oxides for fast charging of lithium-ion batteries

Niobium-based oxides, i.e., Nb2O5, TiNbxO2+2.5x compounds, etc., have become very promising candidates for application in electrochemical energy storage due to the unique intercalation pseudocapacitance mechanism. Beneficial to the stable and open Wadsley–Roth shear crystal structure, niobium-based oxides could realize fast ion insertion and extraction, result in outstanding rate capability. Therefore, niobium-based oxides are expected to accomplish both high power density and high energy density to bridge the gap between batteries and capacitors. However, the intrinsic poor electronic conductivity limits its practical applications. Here, we systematically discuss the mechanisms and characteristics of pseudocapacitance for Nb-based oxides, and thoroughly distinguish the intrinsic differences between intercalation pseudocapacitance and conventional pseudocapacitance. More importantly, the main strategies for enhancing the pseudocapacitive kinetics of niobium-based oxides are especially emphasized. Overall, we provide our perspective and analyze the challenges and prospects of pseudocapacitive materials in future development and industrial applications.