Ultrathin NiCo2S4@graphene with a core–shell structure as a high performance positive electrode for hybrid supercapacitors

Feng Yu; Zheng Chang; Xinhai Yuan; Faxing Wang; Yusong Zhu; Lijun Fu; Yuhui Chen; Hongxia Wang; Yuping Wu; Weishan Li

doi:10.1039/C8TA00835C

Ultrathin NiCo₂S₄@graphene with a core–shell structure as a high performance positive electrode for hybrid supercapacitors†

Feng Yu,^abc Zheng Chang,^d Xinhai Yuan,^b Faxing Wang,^b Yusong Zhu,^b Lijun Fu,

*^ab Yuhui Chen,*^ab Hongxia Wang,

*^c Yuping Wu

*^abe and Weishan Li

^e

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* Corresponding authors

^a State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, Jiangsu Province, China
E-mail: cheny@njtech.edu.cn, wuyp@fudan.edu.cn

^b School of Energy Science and Engineering, Institute for Electrochemical Energy Storage, Nanjing Tech University, Nanjing 211816, Jiangsu Province, China

^c School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland QLD4001, Australia
E-mail: hx.wang@qut.edu.au

^d CAS Key Laboratory of Materials for Energy Conversion, State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China

^e School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China

Abstract

NiCo₂S₄ is a promising material for supercapacitors owing to its merits of high conductivity and activity in redox reactions. However it suffers poor cycling stability due to structural degradation of the electrode through the redox process. Herein we demonstrate a facile method for the synthesis of a NiCo₂S₄/graphene composite where NiCo₂S₄ is encapsulated with an ultrathin graphene layer to form a core/shell structure (NiCo₂S₄@G). Transmission electron microscopy (TEM) indicates that the shell is only 3–5 layers of graphene and the NiCo₂S₄ particle core has a uniform size of around 5–7 nm. The NiCo₂S₄@G composite exhibits excellent electrochemical performance with a specific capacitance of 1432 F g⁻¹ at a current density of 1 A g⁻¹. A hybrid supercapacitor assembled using the synthesized NiCo₂S₄@G as a positive electrode and porous carbon as a negative electrode demonstrates a high energy density of 43.4 W h kg⁻¹ at a power density of 254.3 W kg⁻¹ in the voltage range 0–1.35 V. After 5000 charge/discharge cycles, the device still retains 83.4% of its initial capacitance.

Journal of Materials Chemistry A

Ultrathin NiCo₂S₄@graphene with a core–shell structure as a high performance positive electrode for hybrid supercapacitors†

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Ultrathin NiCo₂S₄@graphene with a core–shell structure as a high performance positive electrode for hybrid supercapacitors

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Journal of Materials Chemistry A