title: Aqueous manganese dioxide ink for paper-based capacitive energy storage devices.
abstract: We report a simple approach based on a chemical reduction method to synthesize aqueous inorganic ink comprised of hexagonal MnO2 nanosheets. The MnO2 ink exhibits long-term stability and continuous thin films can be formed on various substrates without using any binder. To obtain a flexible electrode for capacitive energy storage, the MnO2 ink was printed onto commercially available A4 paper pretreated with multiwalled carbon nanotubes. The electrode exhibited a maximum specific capacitance of 1035 F g(-1) (91.7 mF cm(-2)). Paper-based symmetric and asymmetric capacitors were assembled, which gave a maximum specific energy density of 25.3 Wh kg(-1) and a power density of 81 kW kg(-1). The device could maintain a 98.9% capacitance retention over 10 000 cycles at 4 A g(-1). The MnO2 ink could be a versatile candidate for large-scale production of flexible and printable electronic devices for energy storage and conversion.
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Jiasheng
authors.initials: J
authors.lastname: Qian
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Huanyu
authors.initials: H
authors.lastname: Jin
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Bolei
authors.initials: B
authors.lastname: Chen
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Mei
authors.initials: M
authors.lastname: Lin
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Wing Man
authors.initials: WM
authors.lastname: Tang
authors.affiliation: School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, 693 Xiongchu Road, Wuhan 430073 (P.R. China).
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Lai Wa Helen
authors.initials: LW
authors.lastname: Chan
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR.|Shenzhen Research Institute, The Hong Kong Polytechnic University, Shenzhen 518057 (P.R. China).
authors.forename: Shu Ping
authors.initials: SP
authors.lastname: Lau
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong SAR. jikang.yuan@polyu.edu.hk.
authors.forename: Jikang
authors.initials: J
authors.lastname: Yuan
keywords: MnO2 ink; electrochemistry; energy-storage devices; metal oxides; thin films