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

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 & horbar;O & horbar;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 Nb2O5 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. A carbon-covalent amorphous niobium oxide via formation of Nb & horbar;O & horbar;C bonds is prepared, which can effectively prevent phase transition and maintains its structure during cycling. Conversely, crystalline carbon-coated Nb2O5 and pure amorphous Nb2O5 all experience an irreversible phase transition, which is detrimental to structural stability. The a-Nb2O5-C exhibits a high reversible capacity, ultrafast lithium storage and long cycling stability as a LIBs anode. image