Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries Rupesh Rohan a , Yubao Sun b , Weiwei Cai a , Yunfeng Zhang a , Kapil Pareek a , Guodong Xu a , Hansong Cheng a,b, ⁎ a Department of Chemistry, National University of Singapore, Singapore b Sustainable Energy Laboratory, China University of Geosciences Wuhan, 388 Lumo RD, Wuhan 430074, China abstract article info Article history: Received 26 July 2013 Received in revised form 12 October 2014 Accepted 13 October 2014 Available online xxxx Keywords: Single ion electrolyte Conductivity Electrochemical stability Lithium poly(4-styrene sulfonyl (phenylsulfonyl)imide) (PSSPSI) was synthesized through the Hinsberg reaction. Since the bis(sulfonyl)imide anion is immobilized in the polymer chain, the lithium cation transference number was measured to be 0.87. The weight average number molecular weight (M w ) was found to be 105,343 determined by gel permeation chromatography (GPC). A gel polymer electrolyte membrane, comprising of PVDF and PSSPSI, was successfully prepared with the ionic conductivity of 1.1 × 10 -3 S cm -1 at room temperature. The membrane exhibits a wide electrochemical window up to 4.5 V (vs. Li + /Li) and is thermally and mechanically stable. The material is well suited for applications in lithium-ion batteries. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The steady exhaustion of fossil fuels and its adverse effects on the environment have compelled intense research efforts to search for clean energy resources and to improve energy efficiency to cope with the increasingly pressing energy demand [1,2]. To this end, renewable energy sources necessitate intermittent such as batteries and capacitors with high energy capacity, which require development of novel electrode materials and electrolytes to meet the market demands [3,4]. The high specific capacity (3.86 Ah g -1 ) coupled with the low gravimetric density (0.534 g cm -3 ) of lithium metal makes it a superior choice for negative electrode, in particular, to work with high capacity cathode materials in tandem [4]. However, the formation of lithium dendrites on the anode can be highly hazardous [1,5]. Furthermore, the movement of both cat- ions and anions of a liquid electrolyte upon charging and discharging hampers the amount of useful work and ultimately the performance of battery devices [6]. Solid polymer electrolytes (SPE) provide an important alternative to conventional liquid electrolytes to address the issues on battery safety and efficiency. Unfortunately, the inability of achieving both high ionic conductivity and strong mechanical strength, coupled with the problem of concentration potential, impeded its chance to replace the liquid elec- trolytes [7]. The conductivity and mechanical robustness issues can be partially resolved by introducing either lithium ion salts in organic carbonate solvents, such as ethyl carbonate (EC) and propyl carbonate (PC), or ionic liquids into the polymer matrix such as polyethylene oxide (PEO), polyvinylene difluoride (PVDF), which serve as a binder, to form gel polymer electrolytes (GPEs) [8–10]. Nevertheless, despite these improvements, the low transport number of cations still remains a serious issue affecting the battery performance. To deal with this prob- lem, the concept of single-ion conducting electrolyte, with or without an organic solvent, was recently coined [6]. A single ion electrolyte is made of a polymeric or copolymeric lithium salt [11–20]. The polymeric part of the lithium salt serves as immobile anions in the framework and allows transport of lithium ions only upon charging or discharging. Conse- quently, the problem of concentration polarization is minimized [6]. In this paper, we report a synthesis of a novel polystyrene based single ion gel polymer electrolyte with ionic conductivity of 1.1 × 10 -3 S cm -1 at room temperature. The ionic conductivity of the membrane is among the highest values of the single ion polymer electrolytes reported to date and comparable to the conductivity of liquid electrolytes [21–24]. The fabricated membrane displays a sufficiently high mechanical strength for serving as a separator to block lithium dendrite formation on anode and high electrochemical stability in the operating voltage range of lithium ion batteries. 2. Experimental 2.1. Materials Polystyrene powder, Mw 65,000 g mol -1 (Alfa-Aesar), chlorosulfonic acid (Fluka), thionyl chloride(Tee Hai), benzenesulfonamide (Sigma- Aldrich), lithium hydroxide (Sigma-Aldrich), polyvinylidene fluoride (PVDF) (Solef 6020), Mw 680,000 g mol -1 (Solvay), dichloroethane (DCE) (Alfa-Aesar), ethoxylated natural fatty alcohol with 12 carbon atom chain based non-ionic surfactant (commercial name Brij L23) Solid State Ionics xxx (2014) xxx–xxx ⁎ Corresponding author at: Department of Chemistry, National University of Singapore, Singapore. E-mail address: chmch@nus.edu.sg (H. Cheng). SOSI-13498; No of Pages 6 http://dx.doi.org/10.1016/j.ssi.2014.10.013 0167-2738/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Solid State Ionics journal homepage: www.elsevier.com/locate/ssi Please cite this article as: R. Rohan, et al., Solid State Ionics (2014), http://dx.doi.org/10.1016/j.ssi.2014.10.013