The Capacitive Performance of α-Ni(OH)₂-Based Composites for Hybrid Supercapacitors

Abstract

This study provides new data on the fabrication of hybrid battery-supercapacitor with an excellent cycling stability based on composites of α-Ni(OH) 2 and activated carbon (AC). The α-phase, Ni(OH) 2 .0.3H 2 O, consists of charged Ni(OH) 2-x layers, SO 2- 4 anions being intercalated in the interlayer spaces. The hydroxide has a mesoporous structure and contains nanometric primary particles bounded into micrometric aggregates. The supercapacitor performance of α-Ni(OH) 2 mixed with AC is tested by galvanostatic experiments in KOH-LiOH electrolyte. The ratio between α-Ni(OH) 2 and AC is varied in a whole concentration range: 0≤x≤100 wt.%. In comparison with the symmetrical supercapacitor, the composite electrodes containing α-Ni(OH) 2 between 6 and 35 wt. % demonstrate higher and more stable discharge capacitance, as well as a higher effectiveness of charge-discharge process. α-Ni(OH) 2 has a better cycling stability in comparison with the β-phase. The supercapacitor performance is discussed in terms of structure and morphology stability of α-Ni(OH) 2 in alkaline electrolyte.