title: Synthesis of Capsule-like Porous Hollow Nanonickel Cobalt Sulfides via Cation Exchange Based on the Kirkendall Effect for High-Performance Supercapacitors.
abstract: To construct a suitable three-dimensional structure for ionic transport on the surface of the active materials for a supercapacitor, porous hollow nickel cobalt sulfides are successfully synthesized via a facile and efficient cation-exchange reaction in a hydrothermal process involving the Kirkendall effect with γ-MnS nanorods as a sacrificial template. The formation mechanism of the hollow nickel cobalt sulfides is carefully illustrated via the tuning reaction time and reaction temperature during the cation-exchange process. Due to the ingenious porous hollow structure that offers a high surface area for electrochemical reaction and suitable paths for ionic transport, porous hollow nickel cobalt sulfide electrodes exhibit high electrochemical performance. The Ni(1.77)Co(1.23)S4 electrode delivers a high specific capacity of 224.5 mAh g(-1) at a current density of 0.25 A g(-1) and a high capacity retention of 87.0% at 10 A g(-1). An all-solid-state asymmetric supercapacitor, assembled with a Ni(1.77)Co(1.23)S4 electrode as the positive electrode and a homemade activated carbon electrode as the negative electrode (denoted as NCS//HMC), exhibits a high energy density of 42.7 Wh kg(-1) at a power density of 190.8 W kg(-1) and even 29.4 Wh kg(-1) at 3.6 kW kg(-1). The fully charged as-prepared asymmetric supercapacitor can light up a light emitting diode (LED) indicator for more than 1 h, indicating promising practical applications of the hollow nickel cobalt sulfides and the NCS//HMC asymmetric supercapacitor.
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Yongfu
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Shunji
authors.initials: S
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan, 430070, China.
authors.forename: Shichun
authors.initials: S
authors.lastname: Mu
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Teng
authors.initials: T
authors.lastname: Chen
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Qiao
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Shengxue
authors.initials: S
authors.lastname: Yu
authors.affiliation: Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao, Hebei 066004, China.
authors.forename: Faming
authors.initials: F
authors.lastname: Gao
keywords: Kirkendall effect; cation-exchange reaction; hollow structure; hydrothermal synthesis; nickel cobalt sulfide; supercapacitor