Morphology reconstruction of nickel cobalt layered double hydroxides induced by electrolyte concentrations triggers high performance of supercapattery storage

Abstract

Nickel cobalt layered double hydroxides (NiCo LDHs) have emerged as ideal electrode materials for supercapattery due to their high specific surface area and excellent cycling stability. Morphology control plays a unique role in regulating the performance of the NiCo LDHs. Herein, the morphology of NiCo-LDHs electrode is optimized for enhancing energy storage by a simple activation process with different concentrations of the electrolyte. During the activation process, electrochemical morphology reconstruction occurs on the electrode surface. With a 2 m KOH electrolyte, the NiCo-LDH electrode transforms from nanosheets to nanoflower, which aids in reducing the distance of ion transport. The reconstructed NiCo-LDH exhibits an ultra-high specific capacity of 2809 C g⁻¹ at a current density of 1 A g⁻¹, outperforming most of NiCo LDHs. At a high current density of 10 A g⁻¹, the capacity retention rate remains above 72.7% after 3000 cycles. An asymmetric supercapacitor is fabricated with activated carbon material as the negative electrode, the energy density is 36 Wh kg⁻¹ at the power density of 732 W kg⁻¹. The strategy proposed in the study, which involves concentration-controlled morphology optimization for energy storage enhancement, holds great practical significance for the field of supercapatteries.