Inhibition of Phase Transition in Amorphous Niobium Oxide by Covalent Carbon Reinforcement Enables Fast‐Charge and Long‐Duration Lithium Storage

Abstract Niobium oxides are potential anode materials for ultrafast and safe lithium‐ion batteries due to their high ionic conductivity and relatively high operation voltage. However, the electrochemically induced phase transformations that involve multi‐electron redox reactions in a wide voltage window cause rapid capacity degradation and poor rate capability. Here, a novel carbon‐covalent amorphous niobium oxide anode is reported to greatly suppress the phase transition during cycling via formation of strong Nb─O─C bonds, achieving high‐capacity, fast‐charge and long‐duration lithium storage. This amorphous structure and forming covalent carbon contribute to good volume accommodation and high electron conductivity. The carbon‐covalent amorphous Nb 2 O 5 displays a high reversible capacity of 361.5 mAh g −1 at 0.1 A g −1 and excellent cycling stability with a capacity of 189.8 mAh g −1 at a high rate of 10 A g −1 after 9000 cycles. Structure characterizations reveal that the well‐preserved amorphous structure without phase transition during repeated Li + insertion/desertion is responsible for the superior performance. This work opens a new avenue on rational design of high‐performance amorphous electrode materials for next‐generation batteries.