A high-performance asymmetric supercapacitor using composite electrodes of layered double hydroxides and holey reduced graphene oxide

Abstract

Layered double hydroxide (LDH) materials are promising candidates to achieve high specific capacities of supercapacitors (SCs). However, their electrical conductivities are low, restricting their SC performance. Herein, a one-step solvothermal technique is employed to synthesize a hybrid material of nickel‑manganese LDH/holey reduced graphene oxide (NiMn-LDH/hrGO). The addition of hrGO improves the conductivity and surface area of the NiMn-LDH/hrGO electrode. It thus exhibits a specific capacity of as high as 302.0 C g−1 at a current density of 1 A g−1 and excellent capacity retention even after 2000 cycles. In an asymmetric supercapacitor (ASC), the NiMn-LDH/hrGO electrode is assembled with a Bi(OH)3/hrGO electrode. This ASC exhibits a specific capacity of 237.6 C g−1 at a current density of 1 A g−1, cycling stability of 80.5% after 2000 cycles at a current density of 10 A g−1, and an energy density of as high as 59.9 Wh kg−1 at a power density of 901.5 W kg−1. The proposed method handles the challenges posed by electrochemical capacitors and paves a way to ensemble high performance SCs.