New cathode material of NiCo2Crx-OH (x=0, 1, 1.5, 2.0) and anode material of one-off chopsticks derived carbon for high performance supercapacitor

Highlights: • A kind of novel NiCO₂Crx-OH (X = 0, 1, 1.5, 2) electrode material is synthesized by simple hydrothermal method. • Biomass derived activated carbon material is fabricated by simple heat-treatment of disposable chopsticks. • The synthesized NiCO₂Crx-OH and carbon electrode materials show high specific capacitance of 1011, and 422 F g^-1. • The device NiCo₂Cr_1.5-OH Carbon-4 has an energy density of 33.6 Wh kg^-1 at power density of 374.6 W kg^-1. -- Abstract: Here, we prepare a ternary hydroxide composite (NiCo₂Cr_X-OH) by a simple one-step hydrothermal method, and the effect of the ratio of Cr on the final composite morphology and electrochemical performance are systematically studied. We find that NiCo₂Cr_1.5-OH in 6 M KOH has the best electrochemical performance, the mass capacitance is 1101 F g⁻¹ at a current density of 0.5 A g⁻¹, and the specific capacitance of NiCo₂–OH under the same conditions is 323.7 F g⁻¹. A biomass activated carbon with a porous structure is prepared by the KOH activation method with one-off chopsticks, and it has a specific capacitance of 422.0 F g⁻¹ at 0.5 A g⁻¹. Using this carbon as the negative electrode material and NiCo₂Cr_1.5-OH as the positive electrode material, an asymmetric supercapacitor is assembled and it has an energy density of 33.6 Wh kg⁻¹ (power density, 374.6 W kg⁻¹) when the current density is 0.5 A g⁻¹ in 6 M KOH. To prevent the leakage of the electrolyte in the actual application process, the prepared gel electrolyte is used instead of aqueous electrolyte.