Controllable synthesis of coaxial nickel hexacyanoferrate/carbon nanotube nanocables as advanced supercapcitors materials

• Nickel hexacyanoferrate/carbon nantubes nanocables were prepared by co-precipitation.
• Nickel hexacyanoferrate was covered on carbon nanotubes with controllable thickness.
• Their energy storage performance is superior to pure Nickel hexacyanoferrate.
• Their energy density is close to or better than those of conventional batteries.

The transition metal hexacyanoferrate (MHCF, M represents as Fe, Co, Ni, et al), has been studied and applied intensively in biosensor, catalysts, ion exchanger, molecular magnets and gas storage, but as yet remains largely unexplored for electrochemical energy storage device. This study shows that NiHCF can be uniformly deposited into the matrix of poly(4-vinylpyridine) grafted onto multiwalled carbon nanotubes (MWCNTs), and forms coaxial NiHCF/MWCNT nanocables with MWCNTs as core and NiHCF as shell. A different NiHCF content was loaded onto MWCNTs, and their electrochemical behavior and capacitive performance were determined. The as-prepared NiHCF/P4VP-g-MWCNT hybrids can possess a huge specific capacitance up to 1035 F·g−1 at a discharge density of 0.05 A·g−1. These capacitance will decay by 10% at 25.6 A·g−1. They remain 92.7% of its initial capacitance at 2 A·g−1 after 10000 discharge/charge cycles. Their energy density is nearly 56.2 Wh·kg−1 at a power density of 10 W·kg−1. Their good electrochemical reversibility, high cyclic stability and excellent capacitive performance suggest a promising use as an advanced material for supercapacitors.

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