Rechargeable energy storage systems with merits of durable, powerful, and inexpensive are urgently desired along with the rapid development in portable electronics and electric vehicles. Herein, a facile electrochemical method is employed to prepare a free-standing exfoliated graphite (EG) electrode with significantly enhanced surface area and pore volume. Then a binder-free composite electrode is fabricated by a double-phase (DP) electrochemical deposition of vertical arrays of Ni(OH)2 throughout the EG hydrogel electrode in an organic electrolyte. The obtained composite, Ni(OH)2@EG-DP, exhibits battery-type capacitive behavior and much higher capacity than its counterparts fabricated either by single-phase electrochemical deposition or with non-exfoliated graphite foil. Ni(OH)2@EG-DP also exhibits remarkable rate capability and cycling stability, due to the well-dispersed ultrathin Ni(OH)2 nanoplatelets and the graphene-like expanded gallery of EG, enabling the efficient transportation of both electrons and ions. When coupling with an active carbon anode, the assembled asymmetric supercapacitor shows 84.5% capacity retention after 20000 cycles at 8 A g−1, and a high energy density of 34.7 Wh kg−1 at the power density of 15 kW kg−1. This work opens an avenue towards the efficient construction of free-standing three-dimensional (3D) conductive substrates and high-performance 3D hybrid electrodes using electrochemistry.
Bibliographical noteFunding Information:
The work was supported by the National Natural Science Foundation of China (No. 21576138 , 51572127 , 51702162 ); China-Israel Cooperative Program ( 2016YFE0129900 ); the program for Science and Technology Innovative Research Team in Universities of Jiangsu Province, China ; China Postdoctoral Science Foundation ( 2018M632309 ). H.Q.D. acknowledges the financial support from the PBC Fellowship jointly sponsored by the Planning and Budgeting Committee of the Council for Higher Education in Israel and the Hebrew University of Jerusalem .
© 2019 Elsevier B.V.
- 3D electrode
- Asymmetric supercapacitor
- Double-phase electrochemical deposition
- Exfoliated graphite
- Graphene hydrogel