Copper nanoparticles anchored onto boron-doped graphene nanosheets for use as a high performance asymmetric solid-state supercapacitor

Abstract

There is a high demand for high energy and power density in the field of energy storage devices. To rectify these limitations, a novel asymmetric solid-state supercapacitor (ASSC) was designed and fabricated using a copper anchored boron doped graphene nanosheet (CuBG) as a negative electrode and reduced graphene nanoplatelets as a positive electrode with H₂SO₄/PVA as the quasi-solid electrolyte. The CuBG was prepared using a two step hydrothermal process followed by pyrolysis at different temperatures using chemical vapour deposition (CVD), using copper sulphate (CuSO₄) and boron-trioxide (B₂O₃) as precursors, for doping in graphene oxide. Owing to the remarkable structure and morphology of Cu nanoparticles on nanosheets of boron intercalated with graphene oxide, the nanosheets exhibit a high specific capacitance of 483 Fg⁻¹ at 1 Ag⁻¹ with a capacitance retention of 96% after 5000 cycles, respectively, in a two-electrode system. In addition, the designed and fabricated solid state ASSC device of rGO//CuBG exhibited a high energy and power density of 132.5 W h kg⁻¹ and 1000 W kg⁻¹, respectively, in a wide potential window of 2.0 V, with an excellent stability, retaining 91% of its initial specific capacitance after 5000 cycles. The electrochemical capacitance of CuBG was also evaluated in a three and two electrode system using a KOH and KOH/PVA solid electrolyte respectively. A specific capacitance of 87.5 Fg⁻¹ was achieved at 1 Ag⁻¹ using the fabricated asymmetric device with a 31.1 W h kg⁻¹ energy density at a corresponding power density of 800 W kg⁻¹ and an 85% capacitance was retained after 5000 cycles. The kinetics of the interfacial charge transport phenomena were analysed using a Nyquist plot of the electrochemical impedance analysis.