Co3O4@Mn-Ni(OH)2 core–shell heterostructure for hybrid supercapacitor electrode with high utilization

Abstract

It is of great importance to rationally design and fabricate electrode materials with high utilization and unexceptionable re-cycling performance in energy storage device including supercapacitors (SCs). Herein, Mn-doped Ni(OH)2 nanosheets with oxygen vacancies in-situ grow on the Co3O4 nanorods on carbon cloth (CC) to form a core–shell heterostructure (Co3O4@Mn-Ni(OH)2/CC). The obtained Co3O4@Mn-Ni(OH)2/CC electrode has an outstanding specific capacity of 313.4 mA h g−1 (1128.4 C g−1 or 2051.6 F g−1) at 1 A g−1, ca. 6.4 times that of the Ni(OH)2/CC electrode (48.9 mA h g−1). The hybrid supercapacitor (HSC) constructed by activated carbon (AC) and Co3O4@Mn-Ni(OH)2/CC displays a marvelous energy density of 65.5 W h kg−1 at 800 W kg−1, and 93.0% of the capacity retention over 10,000 repeated charging/discharging cycles at 5 A g−1, superior to the Co3O4@Ni(OH)2/CC//AC HSC (36.5%) and Mn-Ni(OH)2/CC//AC HSC (53.9%). The results of the characterizations and density functional theory (DFT) calculation show that the Mn-doping and subsequent induced oxygen vacancies promote the conductivity, and inhibit the irreversible phase transition of Ni(OH)2 during the charging/discharging process which contributes to the long-time cycling stability of the electrode. Moreover, the core–shell heterostructure fosters the exposure of active sites and reduces the charge transfer resistance due to the interfacial interaction. This work provides some insight into the rational design and fabrication of electrode materials with high utilization in SCs.