Configuring cations–doped cobalt lanthanum LDH nanoarray-on-nanoarray platforms for supercapacitors

Abstract

Modifying the chemistry of earth-abundant compounds is a viable strategy for producing low-crystalline active electrodes with robust interfaces for hybrid supercapacitor technologies. Doping engineering provides a trustworthy method for enhancing the electronic configuration and electrochemical properties of transition metal layered double hydroxides (LDHs). Hierarchical nanoelectrodes featuring several redox-active sites are essential for overcoming charge storage limitations and gaining superior energy density. This study presents a simple room-temperature electrodeposition method employing Zn²⁺ and Mg²⁺ or Al³⁺ cations in the hierarchically structured cobalt lanthanum LDH (CoLa LDH) through interfacial chemical bonding to establish a suitable system for realizing fast Faradaic redox reactions. This method enables the in-situ stabilization of nanostructured dual-layered nanoarray-on-nanoarray platforms including hierarchical porous Zn/CoLa LDH, Al/CoLa LDH, Mg/CoLa LDH, and CoLa LDH films on a nickel foam (NF) conductive core for large-scale applications. The availability of electrochemically reactive centers/interfaces, together with strong intercomponent synergy and close integration between vertically oriented frameworks and the NF skeleton, facilitates rapid charge transfer kinetics for exceptional charge storage capacity. The free-standing Zn/CoLa LDH nanoarray-on-nanoarray network electrode has superior performance, achieving a high capacity of 226.7 mAh g⁻¹ at 1 A g⁻¹, in contrast to Al/CoLa LDH (195.7 mAh g⁻¹), Mg/CoLa LDH (169.6 mAh g⁻¹), and CoLa LDH (125.6 mAh g⁻¹). The synthesized Zn/CoLa LDH exhibits advantageous synergistic effects and significant intrinsic reactivity, demonstrating a commendable rate capability of 150 mAh g⁻¹ at 40 A g⁻¹ and adequate durability with around 82.4 % capacity retention over 7000 cycles at a high current density of 20 A g⁻¹. The density functional theory (DFT) simulation results reveal that Zn dopants can substantially modify the electronic structure and electrical conductivity, hence enhancing the efficiency of electrochemical charge transfer. Additionally, the Zn/CoLa LDH-based asymmetric supercapacitor cell delivers peak energy and power densities of 59.9 Wh kg⁻¹ and 16 kW kg⁻¹, respectively. The battery cell retains 86.4 % of its original capacity over 12,000 charge-discharge cycles. Our findings delineate a reliable approach and potential for customizing low-cost, simply manufactured, binder-free integrated electrodes for sustainable energy systems.