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.