Probing the Electrochemical Processes of Niobium Pentoxides (Nb 2 O 5 ) for High‐Rate Lithium‐ion Batteries: A Review

The rising demand to electrify power-intensive energy devices and systems, as well as fast charging, has imposed a great challenge in current chemistries for lithium-ion batteries (LIBs), whose rate capabilities are predominantly restricted by the conventional graphite anode. Niobium pentoxide (Nb₂O₅) is a promising high-rate anode material for LIBs with extraordinary rate performance beyond 5 C and good theoretical capacity (~202 mAh ⋅ g⁻¹). With many possible crystal structures, Nb₂O₅ has a complicated family of different polymorphs, each of which can possess distinct electrochemical properties, specific capacity, cycling stability, and rate capability. This special feature of Nb₂O₅ makes it a challenging material to understand and requires a comprehensive investigation of every one of its polymorphs. In this paper, we summarize the state-of-the-art research on Nb₂O₅ polymorphs for LIBs, with an emphasis on the advanced characterisation techniques that have been used to probe the electrochemical processes of Nb₂O₅. Key findings related to Nb₂O₅ that have emerged from the previous studies are highlighted, and new scientific questions that are important for its scale-up and commercialization are proposed for future research.