Ni–Mo-Layered Double Hydroxide with Nanowall Morphology as the Positive Electrode in Asymmetric Supercapacitors

Layered double hydroxides (LDHs) have gained significant attention, typically as cathodic electrode materials in renewable energy storage technologies such as supercapacitors because of their anion intercalation effect between stacked layers, which undergoes a surface redox reaction leading to enhanced capacitance. However, the electronic conductivity of LDH is highly dependent on shape and morphology (nanostructure) because it hinders interlayer electron transport and ion migration, leading to a significant decrease in energy/power densities. Herein, the shape and morphology of NiMo-based LDHs are tuned by varying the anion precursors (chloride/nitrate) in order to obtain homogeneous layered nanowall-like morphology via an in situ hydrothermal method without agglomeration. Under optimized conditions, NiMo-LDH (2:1) possesses a diffusion-controlled process, reflecting the battery-type charge storage mechanism and retaining a high specific capacity of about 2394 C g–1 at 1 A g–1. To improve the capacity and energy density, a hybrid cell is designed using a pseudocapacitive V2CTx film as the negative electrode and NiMo-LDH (2:1)/NF as the positive electrode, which provides an excellent energy density (77.6 Wh kg–1), good power density (450 W kg–1), and retains 125.3% of its initial capacity over 10,000 continuous cycles. By extension of the pseudocapacitive layered materials as negative electrodes, design of asymmetric hybrid devices with higher capacity retention is established.