Mass-balancing strategy enhances the cycling stability of rice husk-derived activated carbon-based supercapacitors in KOH electrolyte

Abstract

Rice husk-derived activated carbon prepared via KOH activation usually has high specific capacitance due to its high oxygen content and high specific surface area, which is regarded as a promising candidate for supercapacitor electrodes. However, the poor cycling stability of supercapacitors based on rice husk-derived activated carbon in KOH electrolyte severely limit its commercial application. In this study, the influence of different positive-to-negative electrode mass ratios on the cycling stability of supercapacitors was systematically investigated using rice husk-derived activated carbon as electrode materials. The results show that increasing the positive-to-negative electrode mass ratios significantly enhances the cycling stability of supercapacitors. In this process, the continuous increase in positive electrode potential is effectively suppressed, which avoid the oxidation of the positive electrode. When the positive-to-negative electrode mass ratio is increased from 1 to 2, the capacitance retention of the supercapacitors significantly increases from 27.9% to 96.4% after 10 000 charge-discharge cycles. Meanwhile, the specific capacitance is only reduced by 9.1%. The supercapacitor with positive-to-negative electrode mass ratio s of 1 and 2 shows energy densities of 10.68 W h kg−1 and 9.54 W h kg−1 at 0.5 A g−1, retaining 46.8% and 43.4% of energy densities at 20 A g−1. Adjusting the positive-to-negative electrode mass ratio does not significantly affect the electrochemical properties of supercapacitors. Thus, this work unfolds a new strategy for enhancing the cycling stability of activated carbon-based supercapacitors in alkaline electrolytes and a viable route for practical energy storage applications of rice husk-derived activated carbon in supercapacitors.