Effects of ammonium chloride on structural stability of cobalt carbonate hydroxide and their improved electrochemical performance for supercapacitor

Abstract

Transition metal salts are potential materials for energy storage and conversion. However, their application is limited by poor morphology retention and performance stability during charge/discharge processes. Herein, the interlaced rod-like Co(CO3)0.5(OH)·0·11H2O (CCO) are prepared on nickel foam (NF) by hydrothermal method. During the experiment, the reaction solution is changed from weak basic to weak acidity with the increase of NH4Cl, and it has obvious influence on the growth and electrochemical performance of the as-prepared CCO. When the molar ratio of CO(NH2)2/NH4Cl in solution is 1:2.8 (the pH value of solution is 5.42), the microstructure of CCO nanorods (NRs) are obviously different from that obtained by other molar ratios, and many nanofloccules surrounded on their surface. Moreover, they show improved electrochemical performance, and the specific capacities are 2115.1 and 1400 C/g at 1 and 20 A/g, respectively. Especially, the structure of CCO NRs is remained after 3000 electrochemical cycles, and the specific capacity only lost 3% of the initial value, showing their good cycle stability. In addition, an assembled hybrid CCO NRs/NF//AC device can output a specific energy of 41.8 Wh/kg at 850.7 W/kg. These results can fully prove that the as-prepared CCO NRs is a good candidate for high-performance electrode material.