Ultrahigh cobalt-loading composite electrode material for wearable supercapacitors

Abstract

Cobalt nanocomposites have garnered significant attention for high-performance supercapacitors due to their high redox activity, multi-electron transfer capability, and wide operating voltage window. However, their practical application remains hindered by limited nanoparticle loading and poor cycling stability. This study reports the synthesis of a metal ionic liquid-mediated carbon composite with ultrahigh loading of cobalt nanoparticles (denoted as H-Co-CF) and its application as a supercapacitor electrode material. The optimized nanoparticle-rich nanofiber composite membrane structure enhances electronic conductivity, expands the voltage window to 1.8 V, and ensures operational stability. The H-Co-CF electrode demonstrates a high specific capacitance of 759.3 F·g⁻¹ at a current density of 1 A·g⁻¹, along with an outstanding rate capability of 303.7 F·g⁻¹ even at 50 A·g⁻¹. A symmetric supercapacitor fabricated using H-Co-CF achieves remarkable performance metrics: a specific capacitance of 751.9 F·g⁻¹ at 1 A·g⁻¹, which retains 300.8 F·g⁻¹ at 50 A·g⁻¹, and delivers an energy density of 169.2 Wh·kg⁻¹ at a power density of 900 W·kg⁻¹. These advancements originate from the synergistic effect between the uniquely structured fibrous membrane and the high-loading cobalt nanoparticles, positioning H-Co-CF as a promising transformative material for next-generation wearable energy storage devices.