Cobalt-Based Layered Hydroxides with Modulated Electronic and Thermodynamic Properties for High-Performance Supercapacitors

The layered transition metal hydroxides can potentially incorporate high-density anions in an aqueous solution, leading to good performance applicable in supercapacitors. However, the practical application of these materials is hindered due to the low utilization rate of the binding sites and the low conductivity of these materials. To improve the capacitance of these materials, we propose a rational way to dope typical ions, modify the material atomic/electronic properties, and boost the anion intercalation process. Herein, the layered Co(OH)2 as a prototypical sample is chosen to be doped by [K]+/[Cl]− ions within its framework. We perform both theoretical and experimental investigations to validate this protocol, and the [K]+/[Cl]−-modified Co(OH)2 shows capacitance with 139.6% improvement compared with that of the pristine Co(OH)2 (3.21 F/cm2 vs 2.31 F/cm2 at 5 mA/cm2). Thereafter, we assemble a hybrid supercapacitor device with an extremely high active material loading of 8.36 mg, and the device presents an energy density of 39.8 Wh/kg at a power density of 478.6 W/kg, much higher than previously reported cobalt hydroxide-based materials as supercapacitors. Our study demonstrates effective methods in developing high-performance layered hydroxide electrode materials for supercapacitors.