Nickel hydroxide/chemical vapor deposition-grown graphene/nickel hydroxide/nickel foam hybrid electrode for high performance supercapacitors

Rational design of electrode structures has been recognized as an effective strategy to improve the electrochemical performance of electrode materials. Herein, we demonstrate an integrated electrode in which nickel hydroxide (Ni(OH)₂) nanosheets are deposited on both sides of chemical vapor deposition-grown graphene on Ni foam, which not only effectively optimizes electrical conductivity of Ni(OH)2, but also accommodates the structural deformation assciated with the large volume change upon cycling. The synthesized Ni(OH)₂/graphene/Ni(OH)₂/Ni foam electrode exhibits a high specific capacity of 991 C g⁻¹ at a current density of 1 A g⁻¹, which is higher than the theoretical specific capacity of additive sum of Ni(OH)₂ and graphene, and retains 95.4% of the initial capacity after 5000 cycles. A hybrid supercapacitor is constructed by using Ni(OH)₂/graphene/Ni(OH)₂/Ni foam as the positive electrode and activated carbon on Ni foam as the negative electrode, which achieves a maximum energy density of 49.5 W h kg⁻¹ at a power density of 750 W kg⁻¹, and excellent cycling lifespans with 89.3% retention after 10000 cycles at 10 A g⁻¹.