A novel strategy to accelerate electrochemical kinetics in polymorphic Nb2O5 nanosheets for highly stable and rate-capable lithium storage

Nb2O5-based nanomaterials are emerged as a promising electrode material for lithium-ion batteries. However, the rapid capacity loss during cycling and poor rate capability limits their usage in practical applications. In this work, a novel strategy is employed to address these issues. Polymorphic Nb2O5 nanosheets with surface carbon modification were synthesized. The developed nanosheets were coexist in orthorhombic (T), tetragonal (M) and monoclinic (H) phases with abundant interfaces and tunable amount of carbon contents. The combined effect of surface carbon coating along with coexistence of multiphases on the electrochemical performance of Nb2O5 nanosheets were investigated. It is found that the Nb2O5 nanosheets (Nb2O5 @C-2) with carbon coating thickness of 6 nm delivers enhanced reversible capacity (~187.7 mAh·g−1 at 5C with a capacity retention rate of 97.1 %.), outstanding rate capability (116.8 mAh·g−1 at 35C as compare to many states of art Nb2O5-based anode materials) and good cycling stability even after 700 cycles. The excellent performance of the Nb2O5@C-2 electrode owed to the synergy between Nb2O5 and ultrathin amorphous carbon layer with multiphases, creation of abundant interfaces, increase in ionic conductivity and stable structure. It is suggested that the lithium storage capabilities of Nb2O5 can be tuned by optimizing the thickness of carbon layer.