Porous CoFe-LDH free-standing electrodes for high-performance asymmetric supercapacitors

Abstract

Designing highly active, high-rate, and stable layered double hydroxides (LDHs) as electrode materials for asymmetric supercapacitors holds significant potential for efficient energy storage applications. Herein, we employed a simple one-step hydrothermal method to prepare a novel porous CoFe-LDH supported on nickel foam as a free-standing electrode for supercapacitors. In a three-electrode system, Co₂Fe₂-LDH/NF exhibited a high specific capacitance of 4108 mF cm⁻² at 5 mA cm⁻², and a specific capacitance of 2646 mF cm⁻² when the current density increased to 30 mA cm⁻² (rate performance of 64.4%). To investigate the dynamic changes in Co₂Fe₂-LDH/NF during the charge/discharge process, we employed in situ Raman spectroscopy to study its species composition at various constant voltages, confirming the high reversibility and stability of Co₂Fe₂-LDH/NF. Subsequently, Co₂Fe₂-LDH/NF was used as the anode in an assembled asymmetric supercapacitor device, achieving a specific capacitance of 953.1 mF cm⁻² at a current density of 5 mA cm⁻², and an energy density of up to 338.9 mW h cm⁻² at an output power of 4000 mW cm⁻². Furthermore, both the capacitance retention rate and Coulombic efficiency of the device were close to 100% after 10 000 cycles of stable operation at 15 mA cm⁻².