CoNi2S4 Electrode with High Mass‐Loading for High‐Energy‐Density Supercapacitor: Role of S‐Containing Anions Exchange

Anion exchange is recognized as an effective method to regulate the composition, electronic conductivity, and electrochemical behavior of the transition metal-based compounds. In this work, anion exchange is adopted as a rational post-treatment route to facilitate the capacitive activity of CoNi2 S4 nanoparticle arrays grown on carbon cloth (CC) with high mass-loading. As soaked in saturated Na2 S solution, the CoNi2 S4 /CC electrode showed an increased capacity from 483 C g-1 to 841 C g-1 at 10 mA cm-2 with excellent rate performance and stable cycling performance, which was superior to the CoNi2 S4 /CC electrode activated by NaBH4 reduction. Anion exchange was beneficial for enhancing the crystallinity, retaining the adhesion of nanoarrays, and realizing low resistance nature in a mild route. The as-assembled CoNi2 S4 /CC//activated CC hybrid supercapacitor delivered a high areal capacitance of 1.28 F cm-2 at 5 mA cm-2 , and achieved an energy density of 0.58 mWh cm-2 at a power density of 4.5 mW cm-2 with excellent cycle stability with 90.6 % capacity retention after 10000 cycles.