A Systematic Study of NiCo Layered Double Hydroxides Grown on Porous Carbon for Hybrid Battery-like Supercapacitor Electrodes: Growth Method, Morphology, and Composition

Transition metal layered double hydroxides (LDHs) are often hybridized with conductive materials for supercapacitor electrodes to facilitate charge transport. Although diverse forms of LDH hybridized carbon electrodes have been designed, it has not yet been systematically studied how morphology and composition simultaneously affect the performance of supercapacitors. Herein, we synthesize LDHs grown on nitrogen-doped porous carbon (NPC) as hybrid battery-like supercapacitor electrodes via both electrodeposition and solvothermal methods, where we systematically investigate the effect of the electrode morphology, composition, and loading mass on the electrochemical performance. Electrodeposition is advantageous in a systematic study since the total deposited charge (100, 300, 500, 800, and 1000 mC) and ratio of metals (Ni:Co = 1:0, 0:1, 1:1, 2:1, and 1:2) in LDHs can be easily controlled. Among these, the NiCo LDH grown on NPC with a total deposited charge of 500 mC (NiCo500 LDH/NPC) shows the highest specific capacitance (1420.0 C g–1 at a current density of 1 A g–1). It might be attributed to (i) fast ion transport via the vertically arranged morphology of the LDH, (ii) multiple redox reactions by the coexistence of Ni–Co, and (iii) facilitated ion accessibility due to the broad interlayer of LDH. The NiCo500 LDH/NPC||NPC asymmetric supercapacitor shows a maximum specific energy density of 86.44 Wh kg–1 at a specific power density of 914.45 W kg–1 and cycling stability with 83.99% capacity retention after 20 000 cycles at a current density of 10 A g–1.