Preparation and Supercapacitive Performance of K⁺-Doped Nickel-Cobalt-Based Perovskite Fluoride/Double Hydroxide Heterojunction with Ultra-Long Cycling Stability and High Mass Loading

Abstract

NiCo-LDH's low conductivity and structural instability limit its stability and cycle life, especially under high-mass-loading conditions. In this paper, a KCoNiF₃/NiCo-LDH supported on activated carbon cloth (KCNF-LDH/ACC) heterojunction structural composite material is in situ synthesized on carbon cloth by doping K⁺ into nickel-cobalt double hydroxide, and the loading amount can reach 12 mg cm⁻². The doping of K⁺ can enhance the stability and rate performance of NiCo-LDH. The electrode with the optimal K⁺ doping amount (KCNF-LDH-3/ACC) exhibits a capacitance of 10.1 F cm⁻² / 841 F g⁻¹ at 1 mA cm⁻². When the current increases to 50 mA cm⁻², capacitance can still maintain 85% of the initial capacity. The capacity retention rate reaches 91% after 20 000 cycles. An asymmetric supercapacitor is assembled with KCNFo-LDHo-3/ACC as the positive electrode and AC as the negative electrode. It outperformed the previously published NiCo-LDH supercapacitors with an energy density of 1.14 mWh cm⁻² at a power density of 4 mW cm⁻². This demonstrated the viability of doping alkali metal cations into NiCo-LDH and explored the application potential of perovskite fluoride (ABF₃) in the field of supercapacitors.