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.