A Lyotropic Liquid-Crystal-Based Assembly Avenue toward Highly Oriented Vanadium Pentoxide/Graphene Films for Flexible Energy Storage

A novel lyotropic liquid-crystal (LC) based assembly strategy is developed for the first time, to fabricate composite films of vanadium pentoxide (V 2 O 5 ) nanobelts and graphene oxide (GO) sheets, with highly oriented layered structures. It is found that similar lamellar LC phases can be simply established by V 2 O 5 nanobelts alone or by a mixture of V 2 O 5 nanobelts and GO nanosheets in their aqueous dispersions. More importantly, the LC phases can be retained with any proportion of V 2 O 5 nanobelts and GO, which allows facile optimization of the ratio of each component in the resulting films. Named VrGO, composite films manifest high electrical conductivity, good mechanical stability, and excellent flexibility, which allow them to be utilized as high performance electrodes in flexible energy storage devices. As demonstrated in this work, the VrGO films containing 67 wt% V 2 O 5 exhibit excellent capacitance of 166 F g −1 at 10 A g −1 ; superior to those of the previously reported composites of V 2 O 5 and nanocarbon. Moreover, the VrGO film in flexible lithium ion batteries delivers a high capacity of 215 mAh g −1 at 0.1 A g −1 ; comparable to the best V 2 O 5 based cathode materials.