Journal of Energy Chemistry 26 (2017) 129–138 http://www.journals.elsevier.com/ journal-of-energy-chemistry/ Contents lists available at ScienceDirect Journal of Energy Chemistry journal homepage: www.elsevier.com/locate/jechem Development of flexible zinc–air battery with nanocomposite electrodes and a novel separator Zhiqian Wang, Xianyang Meng, Zheqiong Wu, Somenath Mitra ∗ Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 161 Warren St, Newark, NJ 07102, USA a r t i c l e i n f o Article history: Received 11 July 2016 Revised 26 August 2016 Accepted 31 August 2016 Available online 7 September 2016 Key words: Flexible zinc–air battery Carbon nanotube Poly (acrylic acid) Paper based battery a b s t r a c t In this paper, we present the development of flexible zinc–air battery. Multiwalled carbon nanotubes (MWCNTs) were added into electrodes to improve their performance. It was found that MWCNTs were ef- fective conductive additive in anode as they bridged the zinc particles. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was applied as a co-binder to enhance both the conductivity and flexi- bility. A poly (acrylic acid) (PAA) and polyvinyl alcohol (PVA) coated paper separator was used to enhance the battery performance where the PVP–PAA layer facilitated electrolyte storage. The batteries remained functional under bending conditions and after bending. Multiple design optimizations were also carried out for storage and performance purposes. © 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved. 1. Introduction The development of flexible electronic devices such as flexible circuits, displays, and wearable electronics requires the devel- opment of flexible power supplies [1–5]. Efforts are underway to develop different flexible power sources including batteries [6–11] and super capacitors [12–15]. There have been sev- eral reported studies on the development of flexible versions of conventional batteries including zinc–carbon, alkaline, and lithium-ion. Researchers have used novel nanoparticles, polymeric materials, have utilized techniques such as screen and 3D printing [16,17]; to make batteries on substrates such as fabrics and paper [7,12,15,18–20]. Aqueous electrolyte based batteries offer several advantages. These include safety, lower costs and the ease of fabrication. Zinc based flexible batteries are the most widely used aqueous battery systems for their lower costs [8,10]. However, most of the zinc batteries have low energy/capacity densities, where MnO 2 serves as the cathode active material along with zinc anode. For com- mercially available Zn–MnO 2 batteries, the typical energy density was 85 Wh/kg (zinc–carbon) or 105 Wh/kg (alkaline) [21]. As alter- natives, zinc–air batteries utilizing the O 2 from the air have been developed, which feature lightweight, higher energy and capacity, and are suitable for lower power continuous discharges. The common zinc–air cells have energy densities of around 350 Wh/kg [22]. Limited reports on flexible zinc–air batteries [23,24] including ∗ Corresponding author. Fax: +1 973 596 3586. E-mail address: somenath.mitra@njit.edu (S. Mitra). cable batteries [25,26] are available, and there is need to explore novel designs for composite electrodes, separators as well as fabrication techniques. The objective of this paper is to develop a flexible primary zinc–air battery with carbon nanotube enhanced composite electrodes using a low-cost metal oxide catalyst and novel separator with high electrolyte storage capacity. 2. Experimental 2.1. Preparation of electrodes The standard cathode paste was prepared by mixing electrolytic manganese dioxide powder (EMD, TRONOX, ≥ 92%, AB Grade), binder, and multiwalled carbon nanotubes (MWCNTs). Before electrode preparation, MWCNTs (purity 95%, diameter 20–30 nm, length 10–30 μm, Cheap Tubes Inc. Brattleboro, VT, USA) were purified in a Microwave Accelerated Reaction System (Mode: CEM Mars) using previously reported method [27,28]. Polymers such as polyethylene oxide (PEO, Sigma Aldrich, Mv∼400,000) and polyvinylpyrrolidone (PVP, Sigma Aldrich, average mol wt 10,000) were purchased and used without further treatment. The powders were added into the solvent, mixed for 30 min to form homogeneous slurry, and then sonicated for 30 min using OMNI SONIC RUPTOR 250 ultrasonic homogenizer. The dry formulation for the cathode comprised of MWCNTs (6%, wt%), binder (10%, wt%) and the rest EMD (84%, wt%). The anode paste was prepared by mixing zinc, polymer binder, Bismuth (III) oxide (Sigma Aldrich, 90–210 nm particle size, ≥ 99.8%) and purified MWCNTs. Both chemical grade zinc (Sigma Aldrich, ≤10 μm, ≥ 98%) and industrial battery grade zinc (Umicore, BIA 100 200 65 d140, ≤425 μm) were http://dx.doi.org/10.1016/j.jechem.2016.08.007 2095-4956/© 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.