Nickel-rich NiCo LDHs supported on hollow carbon shells for hybrid supercapacitors

Hydrangea-like hollow carbon shell-supported NiCo LDHs ([email protected] LDHs) have been readily synthesized via a chemical co-precipitation process without extra alkaline reagent added. Different molar ratios of Ni/Co (1:4, 2:3, 3:2 and 4:1) in the initial reactants were applied to explore its effect on a series of as-synthesized electrode materials. The optimized [email protected] LDHs with an actual Ni/Co molar ratio of ∼4.8:1 (reactant ratio of 4:1) exhibited the highest specific capacity of 758 C g−1 at 2 A g−1 and displayed excellent rate performance with 79% capacity retention at 20 A g−1. The much improved supercapacitive performance results from the high Ni concentration, which has induced the uniform growth and intimate contact of NiCo LDHs with weak crystallinity on hollow carbon shells to form a hydrangea-like structure. This unique structure and crystalline phase exposes more active sites and facilitates faster ion diffusion. Meanwhile, the Ni-rich NiCo LDHs increases divalent metal cations to achieve high pseudocapacitance. In addition, the assembled [email protected] LDHs//AC asymmetrical supercapacitor maintains 70% capacitance after 4000 cycles and possesses rapid electrokinetics.