Coordination-derived nickel cobalt sulfide porous ball-like structure consisting of particles and pores for high-performance asymmetric supercapacitors

Bimetallic sulfides are effective cathode materials for asymmetric supercapacitors because of their excellent electrochemical properties. However, the low utilisation ratio of the electrode materials and their low energy storage capacitance restrict their use. In this study, Ni and Co were hydrothermally reacted with terephthalic acid and isonicotinic acid, hydrolyzed in 1 M KOH, and sulfurated in thiourea to yield a CoNi2S4 porous ball-like structure with particles and pores. These structural and morphological features compensate for the shortcomings of bimetallic sulfide electrodes. The specific capacitance of the proposed electrode reaches 268.8 and 162.6 C/g at specific currents of 1 and 20 A/g, respectively. The specific current increases 20 times, and the capacitance retention rate reaches 60.5%, thereby improving the rate performance. After 5000 charge/discharge cycles, the capacitance retention rate reaches 96.78%. This superior electrochemical performance significantly increases the competitiveness of CoNi2S4 electrodes in the electrochemical energy storage field.