Chloride-ion-engineered nickel-cobalt bimetallic chloride: A tunable electrode material for high-energy-density supercapacitors

The development of metal-based materials for supercapacitor electrodes garners significant attention in energy storage research due to their potential to achieve high energy and power density. This study presents a one-step solvothermal synthesis of nickel-cobalt bimetallic chlorides (NCC) with ethanol as the solvent. By precisely tuning the Cl-content, the material's structural, morphological, and electrochemical properties are optimized. Among the synthesized samples, NCC-8, prepared with a Ni:Co:Cl molar ratio of 1:1:8, demonstrates superior performance, delivering a remarkable specific capacitance of 1385.4 F g- 1 at 1 A g- 1, which is more than twice that of its chloride-free counterpart. Furthermore, an asymmetric supercapacitor (NCC-8//AC), constructed with NCC-8 as the positive electrode and activated carbon (AC) as the negative electrode, achieves an exceptional energy density of 80.1 Wh kg- 1 at a power density of 800 W kg- 1. The device also exhibits excellent cycling stability, retaining 74.1 % of its initial capacitance after 10,000 charge-discharge cycles at 10 A g- 1. These findings highlight the potential of chloride-ion-modified nickel-cobalt materials as high-performance electrode candidates, paving the way for developing next-generation energy storage systems with enhanced longevity and superior performance.