title: High-energy MnO2 nanowire/graphene and graphene asymmetric electrochemical capacitors.
abstract: In order to achieve high energy and power densities, we developed a high-voltage asymmetric electrochemical capacitor (EC) based on graphene as negative electrode and a MnO(2) nanowire/graphene composite (MGC) as positive electrode in a neutral aqueous Na(2)SO(4) solution as electrolyte. MGC was prepared by solution-phase assembly of graphene sheets and α-MnO(2) nanowires. Such aqueous electrolyte-based asymmetric ECs can be cycled reversibly in the high-voltage region of 0-2.0 V and exhibit a superior energy density of 30.4 Wh kg(-1), which is much higher than those of symmetric ECs based on graphene//graphene (2.8 Wh kg(-1)) and MGC//MGC (5.2 Wh kg(-1)). Moreover, they present a high power density (5000 W kg(-1) at 7.0 Wh kg(-1)) and acceptable cycling performance of ∼79% retention after 1000 cycles. These findings open up the possibility of graphene-based composites for applications in safe aqueous electrolyte-based high-voltage asymmetric ECs with high energy and power densities.
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China.
authors.forename: Zhong-Shuai
authors.initials: ZS
authors.lastname: Wu
authors.forename: Wencai
authors.initials: W
authors.lastname: Ren
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Bilu
authors.initials: B
authors.lastname: Liu
authors.forename: Hui-Ming
authors.initials: HM
authors.lastname: Cheng