Controllable preparation of hydrangea-shaped CoAl-LDHs/CoF₂ composite for supercapacitor electrode with superior performance

Exploring the method for rational design of hierarchical structures such as hollow, sphere, and core–shell structures is a crucial challenge for enhancing the electrochemical performance of supercapacitor electrodes. In this study, we demonstrate a facile method for controllable preparation of hydrangea-shaped CoAl-LDHs/CoF₂ composite and used as a positive electrode for supercapacitor. A series of contrast tests are performed to select optimal experiment condition. CoAl-LDHs obtained at a metal ratio of 2:1, reacting 8 h with the addition of NH₄F, display optimal performance associated with the hierarchical structure, where NH₄F plays a vital role in regulating this uniform generation process. The fabricated working electrode shows a high specific capacitance of 827.8 Fg⁻¹, with excellent capacitance retention of 62.8% after current density increases ten times. At last, an asymmetric supercapacitor using C2A1-8 h sample as positive electrode and activated carbon as negative electrode is assembled and delivers an outstanding energy density of 53.7 Wh kg⁻¹ at a power density of 239.9 kW kg⁻¹, and energy density reaches 27.8 Wh kg⁻¹ at maximum power density of 12,000 W kg⁻¹, indicating C2A1-8 h is a potential candidate for energy storage and conversion systems.