Synthesis And Electrochemical Studies Of Nb-O Type Composites

Intercalation pseudocapacitance in Nb₂O₅ has been confirmed as an intrinsic property of the material, which is capable of exhibiting high capacitance and high rate capability through a bulk Li-ion insertion process. However, the poor electric conductivity may limits its electrochemical utilization and high-rate capability. In this work, different materials with Nb-O component were investigated to develop more intercalation psuedocapacitive materials for high-rate energy storage. In addition, the conductive Nb₂O₅/carbon nanocomposites were constructed to improve the electrochemical performance. The main conclusions are as follows:?1? Electrochemical studies on commercial Nb-O materials including Nb₂O₅, LiNbO3, NaNbO3 and NbO2 revealed that the intrinsic capacitive intercalation of Nb₂O₅ can be extended to other Nb-O crystalline materials. Compared to Nb₂O₅, LiNbO3, NaNbO3 and NbO2 could retain higher capacity retention as the sweep rate increasing and higher level of pseudocapacitance contribution. LiNbO3, NaNbO3 and KNbO3 nano-particles were prepared by one-pot hydrothermal method. These nano-architecture materials show higher capacitance and rate performance than their commercial counterparts. Furthermore, LiNbO3 nano-particles were coupled with conductive graphene to increase their capacitance up to 115 C/g ?2 m V/s?.?2? Nb₂O₅@rGO nanocomposites were prepared by one-pot solvethermal method, and partially-reduced Nb₂O₅@graphene was obtained by post-treatment of Nb₂O₅@rGO at 800? in H2 atmosphere. Compared with Nb₂O₅@graphene, partially-reduced Nb₂O₅@graphene showed broader intercalation energy distribution, higher capacitance retention ?343 C/g at 100 mV/s? and better rate performance ?306 C/g at 20 A/g?.?3? Nb₂O₅@CNTs nanocomposites were also prepared by one-pot solvethermal method, which delivered a high specific capacitance of 681 C/g ?0.5 A/g? and good kinetics performance. Influence of Carbon contents in Nb₂O₅@CNTs nanocomposites was further investigated:While CNT contents increased from 20% to 30%, specific capacitance of Nb₂O₅@CNTs increased from 534 C/g to 642 C/g ?2 mV/s?.