Unveiling the influential factors and inhibition strategies of the electrodeposition behavior on the negative electrode in aqueous nickle‑carbon supercapacitors

It has been generally accepted that the negative electrode of aqueous nickel‑carbon asymmetric capacitors underwent capacitive reactions. However, through further research, we have unveiled an additional electrochemical reaction occurring on the negative electrode. Nickel ions were reduced to nickle and deposited on the surface of the negative electrode, which subsequently transformed to nickel oxides. This previously unrecognized phenomenon significantly impacted the energy density and cycle life of nickel‑carbon supercapacitors . The introduction of anion exchange membranes between the positive and negative electrodes was demonstrated as an effective solution in inhibiting the uncontrolled diffusion of nickel ions onto the surface of the negative electrodes. This modification led to a remarkable increase in capacity retention rate of the alkaline nickel‑carbon supercapacitor , rising from 70.45 % to 97.76 % after 10,000 cycles. Furthermore, the modified supercapacitor continued to operate reliably for over 45,000 cycles, extending the cycle life by nearly fivefold. The suppression of nickel deposition on the negative electrode represented a critical advancement in enhancing the performance and lifespan of nickel‑carbon supercapacitors.