The key role of microscopic structure and graphene sheet-high homogenization in the high rate capability and cycling stability of Ni–Co LDH

Abstract

As a typical electrode material in Faraday supercapacitors (FSs), Ni(OH)₂ has some intrinsic issues such as low electrical conductivity and structural instability, resulting in its low performance. In view of these issues, we design a multifunctional nanostructure, rigid nanosheet-interlaced structure of Ni–Co LDH/graphene to improve the electrical conductivity and structural stability of Ni(OH)₂. Under the high shear applied by a high shear mixer (HSM) and the regulation of polyvinylpyrrolidone (PVP), the designed structure is realized. Benefitting from the well-designed structure and improved electrical conductivity of the graphene sheet-high homogenization, Ni–Co LDH/graphene presents the expected performance. It exhibits a high specific capacity of 1020 C g⁻¹ at a low current density of 2.7 A g⁻¹ and excellent high rate performance (637.5 C g⁻¹ at 62.5 A g⁻¹). The asymmetrical supercapacitors (ASCs) assembled with the composite as the positive material show high energy density (86.5 W h kg⁻¹ at a power density of 695.7 W kg⁻¹). Due to the improved structural stability, the ASCs also exhibit high cycling stability (a capacity retention of 97.8% after 10 000 charge–discharge cycles).