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

• Published in: Electrochimica acta 2021-11, Vol.395, p.139167, Article 139167
• Main Authors: Zhang, Wen, Fan, Hefei, Liu, Qianfeng, Ta, Na, Pu, Yuguang, Chen, Xize, Sui, Yanwei, Wang, Erdong, Cao, Peng
• Format: Article
• Language: English
• Subjects: Carbon; Chemical precipitation; Chemical synthesis; Crystal structure; Crystallinity; Diffusion rate; Electrochemical performance; Electrode materials; Electrokinetics; Energy storage mechanism; Hollow structure; Intermetallic compounds; Ion diffusion; Nickel; Nickel-rich NiCo LDHs; Reagents; Supercapacitors
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.139167

•Hollow carbon (HC) supported NiCo LDHs was synthesized via a solvothermal method.•High nickel concentration induces the uniform growth of a hydrangea-like structure.•Excessive divalent nickel ions contribute to higher pseudocapacitance.•The HC@NiCo LDHs electrode exhibits excellent capacitance of 758 C g−1 at 2 A g−1. Hydrangea-like hollow carbon shell-supported NiCo LDHs (HC@NiCo 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 HC@NiCo 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 HC@NiCo LDHs//AC asymmetrical supercapacitor maintains 70% capacitance after 4000 cycles and possesses rapid electrokinetics. [Display omitted]