Two‐Step Electrodeposition Synthesis of Heterogeneous Coral‐Like NiCo(OH) ₄ @NiS on Nickel Foam for High‐Performance Supercapacitors

Layered nickel–cobalt‐based hydroxides (NiCo(OH) ₄ ) have high charge storage capacity. However, single NiCo(OH) ₄ electrode materials have poor electrical conductivity, low active site density. Transition metal sulfides can improve electrochemical properties due to their high electrical conductivity, multivalency, and low price, as well as their sulfidation effect. In this article, the electrode material NiCo(OH) ₄ @NiS is synthesized by loading NiS material on the surface of NiCo‐LDH, constructing hierarchical structure and introducing sulfur elements. Coral‐like NiCo(OH) ₄ @NiS electrode materials are prepared by adjusting the scanning speed (40 mV S ⁻¹ ), deposition voltage (2.2 V), and cycle period (six times). At a current density of 1 A g ⁻¹ , it achieves a high specific capacitance of 2149 F g ⁻¹ . After 5000 cycles at a current density of 20 A g ⁻¹ , it retains 99.8% of its Coulomb efficiency. In addition, the NiCo(OH) ₄ @NiS//AC asymmetric supercapacitor exhibits an energy density of 44.36 Wh kg ⁻¹ at a power density of 584.93 W kg ⁻¹ . After 5000 cycles of high current (20 A g ⁻¹ ), the capacitance retention is still 80.42%. The electrode material composed of NiCo(OH) ₄ and NiS can compensate the shortcomings of the single electrode material, which is the reference for the selection of capacitor electrode materials.