Interstitial nanoclusters within graphene sheets for highly conductive, strong and electrochemically active fiber-shaped supercapacitors

Abstract

Developing free-standing fibers with excellent flexibility, mechanical strength and electrical conductivity is of paramount importance for successful implementation of wearable electronic power sources. Herein, graphene fibers with interstitial nanoclusters of 3D Graphene (3DG) nanoflakes were fabricated through wet-spun method. We present the stepwise formation of nanoclusters which heavily depends upon the composition of 3DG nanoflakes. Initially, cavities are formed when the nanoflakes circumvent the graphene-graphene sheet stacking under low compositions. At the intermediate loading, nanoflakes produce interstitial pores by controlling the graphene sheet orientations during wet spinning injection. Finally, the nanoflakes can be seen impregnated inside the interstitial pores forming ‘nanoclusters’ at higher nanoflakes loadings. This unique hybrid structure possesses high electrical conductivity of 1.5(104) Sm−1, mechanical strength of 126 MPa and results in the high volumetric capacity of 90.6 Fcm−3 for H3PO4/PVA-gel based supercapacitor application; which is 25 times better than that of pristine graphene fibers. Though, 3DG has already been explored for supercapacitor application, nevertheless, our novelty is the encapsulation of 3DG inside the interstitial sites of the fibers resulting in ‘internally decorated pores’. Moreover, we show that our nanoclusters supersede vacant-pores in terms of electrical, mechanical and capacitive properties. Therefore, we emphasize on these nanoflake-impregnated-pores over the vacant-pores. This strategy can lay the foundation of novel ‘internally decorated porous structures’ for developing next-generation electrochemical fibers.