High-performance and thermostable wire supercapacitors using mesoporous activated graphene deposited on continuous multilayer graphene†
Wire supercapacitors are promising flexible power sources for wearable devices because of their high power density, long cycle life, and mechanical flexibility. However, obtaining high energy density along with thermal stability is essential for developing sustainable wire supercapacitors that use a charge storage mechanism based on electric double-layer (EDL) formation. In this study, activated graphene (AG) was coated onto continuous graphene deposited on Cu wire current collectors using electrophoretic deposition, forming wire supercapacitors with high power and energy density as well as outstanding thermal stability and chemical resistance. The incorporation of AG, which has a high specific surface area, enabled nearly ideal capacitive behaviors of the devices with high specific areal capacitances of up to 130.3 mF cm−2. Multilayer graphene grown by chemical vapor deposition (CVD) on Cu wires worked as a multifunctional intermediate layer for enhancing the interfacial contact between the electrode and the current collector as well as the electrical conductivity, chemical resistance, and thermal stability of the Cu wire. The great synergy between the AG electrode material and CVD-grown graphene on Cu current collectors achieved high energy densities of up to 4.54 μW h cm−2 and outstanding power densities of up to 1.61 mW cm−2 with excellent cycling stability (∼93.8% capacitance retention over 10 000 cycles). Furthermore, the wire supercapacitors exhibited stable EDL charge storage capability for temperatures ranging from 7 to 80 °C. This unique architecture of wire supercapacitors promises great potential for high-performance and thermostable energy storage, and can be embedded in future wearable electronics and smart textiles.