Polymorphs of Nb₂O₅ Compound and Their Electrical Energy Storage Applications

Niobium pentoxide (Nb₂O₅), as an important dielectric and semiconductor material, has numerous crystal polymorphs, higher chemical stability than water and oxygen, and a higher melt point than most metal oxides. Nb₂O₅ materials have been extensively studied in electrochemistry, lithium batteries, catalysts, ionic liquid gating, and microelectronics. Nb₂O₅ polymorphs provide a model system for studying structure-property relationships. For example, the T-Nb₂O₅ polymorph has two-dimensional layers with very low steric hindrance, allowing for rapid Li-ion migration. With the ever-increasing energy crisis, the excellent electrical properties of Nb₂O₅ polymorphs have made them a research hotspot for potential applications in lithium-ion batteries (LIBs) and supercapacitors (SCs). The basic properties, crystal structures, synthesis methods, and applications of Nb₂O₅ polymorphs are reviewed in this article. Future research directions related to this material are also briefly discussed.