Modulating electronic and interface structure of CuO/CoNi-LDH via electrochemical activation for high areal-performance supercapacitors

The inferior charge transfer kinetics and self-agglomerate issues have challenged the commercialization of nickel‑cobalt layered double hydroxides (NiCo-LDHs) in supercapacitors. In this study, we designed and constructed a hierarchical core-shell structure with CuO/NiCo-LDHs as electrode material on a highly conductive Cu foam substrate. To further boost its energy storage performance, electrochemical activation method was adopted to modify the electronic structure of CuO/NiCo-LDHs. Remarkably, this process led to a noticeable change in the interface structure between CuO and NiCo-LDHs, resulting in hierarchical double-shelled heterostructures. This unique structure concurrently promotes rapid electron conduction and ion diffusion within a high areal-loading electrode. The obtained EA(CuO/NiCo-LDH) electrode exhibited significantly enhanced areal-capacitance (7791 mF cm−2 at 10 mA cm−2, 762C g−1 at 2.17 A g−1) and rate capability (64.1 % capacitance retention at 60 mA cm−2). Furthermore, the hybrid supercapacitor (HSC) constructed with the EA(CuO/LDH30) and porous activated carbon (PAC) electrodes achieved a maximum energy density of 393.69 mW h cm−2 at power density of 3.70 mW cm−2 (39.2 Wh kg−1 at 368.3 W kg−1). This work paves the way for the modification of electronic and interface structure of electrode materials using an electrochemical activation strategy, and also expected to make great contributions to the application of LDHs in energy storage, catalyst and other fields.