Electro-deposition of Co-Ni sulfide nanosheet arrays on nickel foam and investigation of the pseudocapacitive performance

The bimetallic sulfides of Co
_1.5
Ni
_1.5
S
₄
flower-like nanosheets have been successfully synthesized on Ni foam via one-step electrodeposition method and used as electrode for high-performance supercapacitance. The effect of raw materials proportion on the electrochemical performance of the products was systematically investigated. Results showed that when the ratio of CoCl
₂
and NiCl
₂
was 1:1, the resultant Co
_1.5
Ni
_1.5
S
₄
flower-like nanosheets have formed, which demonstrated higher specific capacitance than Co
₉
S
₈
, NiCo
₂
S
₄
and CoNi
₂
S
₄
, and showed good rate capability. All-solid-state asymmetric supercapacitor device was fabricated using the Co
_1.5
Ni
_1.5
S
₄
flower-like nanosheets and active carbon as electrodes. The device retained 91 % of its original specific capacitance after 1000 charge-discharge cycles at a current density of 5 A g
^-1
, which demonstrated that the long-term cycling stability of Co
_1.5
Ni
_1.5
S
₄
flower-like nanosheets are outstanding. These excellent properties can be mainly attributed to the unique architecture with large surface area and interspaces. The device in series could light a red LED indicator. Our strategy provides a remarkable way to fabricate all-solid-state energy storage devices for various applications including wearable microelectronics.