In-situ isomorphous recombination method to prepare isomorphic NiCo(CO3)(OH)2-Co(CO3)0.5(OH) nanowires for high-performance supercapacitors

Abstract

Nickel-cobalt carbonate hydroxides have been widely employed as battery-type electrode materials. However, in contrast to batteries, improvement in the electrochemical performance of these materials is still needed. Most studies have focused on improving the performance of basic nickel-cobalt carbonate by two means: compounding with conductive carbon materials or changing the nanostructure of the material by adjusting the Ni/Co ratio; however, these methods have the problems of requiring binder and complicated operation, respectively. At this point, the in-situ isomorphism method, especially the in-situ isomorphous recombination method, provides a new way of thinking. Hence, we proposed an in-situ isomorphous recombination method to improve the performance of basic nickel-cobalt carbonate. A facile, two-step hydrothermal strategy was utilized to synthesize isomorphic NiCo(CO3)(OH)2-Co(CO3)0.5(OH) (NCCH-CCH) nanowires on nickel foam. The electrochemical performances of the synthesized electrodes were tested with a three-electrode system. Impressively, the obtained composite electrode exhibited a large specific capacity of 937 C g−1 at 1 A g−1 (1.550 C cm−2 at 1 mA cm−2) and retains 80.9% capacity after 15000 cycles at 20 A g−1. Additionally, employing acid-etched carbon cloth (AECC) as the negative electrode, a NCCH-CCH//AECC hybrid supercapacitor (HSC), which delivers a high energy density of 156.7 μWh cm−2 at 0.8 mW cm−2, and exceptional cycling stability (88.9% of capacitance retention after 15000 cycles), is assembled. Moreover, the change in pH value at various stages of the reaction was applied to roughly analyse the cause of the disparate morphologies of the two-step hydrothermal products in this study.