Conformal phosphating hierarchical interface of CC/CoNiMn–P for hybrid supercapacitors with high cycling stability†

Abstract

Transition metal phosphides (TMPs) have gained widespread applications in the field of electrochemical energy storage. However, controlled morphology and multi-site dynamic activation remain challenging. Herein, a thin-walled, hollow, and porous ternary Co–Ni–Mn metal phosphide was synthesized on carbon cloth (CC/CoNiMn–P) via a mixed-solvent-assisted etching method combined with gas-phase phosphidation, using Co-MOF and CoNiMn(OH)₂ triangular nanosheet arrays as templates. The mild phosphating process maintained the hollow porous structure of the master plate. The DFT calculation further demonstrated that the hollow conformal phosphide improved the adsorption of OH⁻ to the electrode, thereby increasing the conductivity and thermal stability. Combined with the synergistic effect of ternary metals, the electrode showed a high specific capacity 2247 F g⁻¹ at a current density of 1 A g⁻¹, and excellent rate performance (with 90.2% retention at 8 A g⁻¹). When used in hybrid supercapacitors (HSCs), the CC/CoNiMn–P-500//AC HSC achieves a high energy density of 45.7 W h kg⁻¹ at a power density of 344.8 W kg⁻¹, with a capacitance retention of 84.3% after 10 000 cycles. This work provides a novel approach for constructing electrode materials with well-defined hierarchical structures for supercapacitor and energy storage applications.