Hybrid carbon nanofiller/polymer composites as self-healable current collector electrodes for use in high-performance flexible metal-free supercapacitors

Abstract

Supercapacitors with multiple features, such as high capacitance, high-rate capability, high flexibility, and self-healing properties, are regarded as good candidates for powering portable and wearable electronics. Herein, a symmetric supercapacitor with multiple functions is fabricated by sandwiching a highly conductive self-healable composite current collector electrode with an active material, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/multiwalled carbon nanotubes (PEDOT:PSS/MWNTs), and a poly(vinyl alcohol)/ phosphoric acid (PVA/H3PO4) electrolyte. The novelty of this work lies in the synergy arising from the combination of two conducting carbon nanofillers, referred to as hybrid carbon nanofiller (HCF), coupled with healable polymer matrices (HCF/HPU) to fabricate self-healing high-conductivity composite current collector electrodes. These can be used in flexible metal-free supercapacitors, which have not been specifically considered previously. The use of two geometrically varied nanofillers with proper selection of the nanofiller content ratio can induce the formation of an effectively conductive co-supporting network, which drastically enhances the electrical properties and mechanical strength of the composite current collector compared to that of single nanofillers. More importantly, the supercapacitor assembled by the HCF/HPU composite current collector delivers high specific capacitance and energy density. In addition, noticeable cycling stability with only ∼ 10 % capacitance loss was observed after 20,000 consecutive charge/discharge cycles at a high current density of 10 mA cm–2. Furthermore, at a medium temperature of 60 °C, supercapacitors with this HCF/HPU composite current collector restore at least 96.2 % of their capacitance properties even after 5 cycles of severing/healing. The capacitive retention rate after 2000 bending cycles was 97.4 % at a bending radius of 4.0 mm. These properties indicate this HCF/HPU composite current collector is a promising candidate for use in high-performance flexible energy storage devices.