Advances on Defect Engineering of Niobium Pentoxide for Electrochemical Energy Storage

The reasonable design of advanced anode materials for electrochemical energy storage (EES) devices is crucial in expediting the progress of renewable energy technologies. Nb₂O₅ has attracted increasing research attention as an anode candidate. Defect engineering is regarded as a feasible approach to modulate the local atomic configurations within Nb₂O₅. Therefore, introducing defects into Nb₂O₅ is considered to be a promising way to enhance electrochemical performance. However, there is no systematic review on the defect engineering of Nb₂O₅ for the energy storage process. This review systematically analyzes first the crystal structures and energy storage mechanisms of Nb₂O₅. Subsequently, a systematical summary of the latest advances in defect engineering of Nb₂O₅ for EES devices is presented, mainly focusing on vacancy modulation, ion doping, planar defects, introducing porosity, and amorphization. Of particular note is the effects of defect engineering on Nb₂O₅: improving electronic conductivity, accelerating ion diffusion, maintaining structural stability, increasing active storage sites. The review further summarizes diverse methodologies for inducing defects and the commonly used techniques for the defect characterization within Nb₂O₅. In conclusion, the article proposes current challenges and outlines future development prospects for defect engineering in Nb₂O₅ to achieve high-performance EES devices with both high energy and power densities.