Compact self-standing layered film assembled by V 2 O 5 ·nH 2 O/CNTs 2D/1D composites for high volumetric capacitance flexible supercapacitors

Abstract

Flexible supercapacitors (SCs) are attractive energy storage devices for wearable electronics, but their applications are hindered by their low volumetric energy densities. Two dimensional (2D) non-carbon nanomaterials are the most promising pseudocapacitive materials for high volumetric capacitance electrodes. However, they are poorly conductive and prone to self-stacking, which results in unsatisfactory electrochemical performance. In this work, large-scale V 2 O 5 ·nH 2 O ultrathin nanosheets are synthesized by a facile and scalable method and transformed into layered and compact composite films with one-dimensional carbon nanotubes (CNTs). The self-standing films show an optimized volumetric capacitance of 521.0 F cm −3 with only 10 wt% of CNTs, which is attributed to dramatically enhanced electrical conductivity beyond the electrical percolation threshold, high dispersion of pseudocapacitive V 2 O 5 ·nH 2 O nanosheets, and high mass density of the films. All-solid-state flexible SCs made of V 2 O 5 ·nH 2 O/CNTs films show a maximum energy density of 17.4 W h L −1 .