Homologous Strategy: Fabrication of a High-Performance Dual-Carbon Potassium Ion Hybrid Capacitor

Abstract

Potassium ion hybrid capacitors (PIHC) have attracted a significant amount of interest in recent years because of their excellent overall performance and the abundance of potassium resources. The search for kinetically matched and high-performing anode and cathode materials is the key to the development of PIHCs. Hereby, we present a homologous preparation method for dual-carbon electrode materials of PIHCs with the single precursor nitrilotriacetic acid trisodium salt (NTA-3Na) by different preparation routes. The 3NaC-700 obtained by high-temperature calcination as the anode exhibits excellent kinetics performance for potassium ion storage due to its three-dimensional, large layer spacing and N-doped structure. 3NaC can be converted to a 3NaAC cathode with a high specific surface area (SSA, 3014 m2 g–1) and superior capacitance properties by further KOH activation. As a result of the advantages of the 3NaC and 3NaAC electrodes mentioned above, a high-performance dual-carbon PIHC is fabricated. It delivers a high energy and power density of 149.2 Wh kg–1 at 200 W kg–1. A high energy density of 67.2 Wh kg–1 is maintained even at a high power density of 20 kW kg–1. The PIHC device also exhibits excellent cycling stability with 81% capacity retention after 8000 cycles at a current density of 2.0 A g–1.