New highly conductive organiceinorganic hybrid electrolytes based on star-branched silica based architectures Diganta Saikia a , Hao-Yiang Wu b , Chi-Pin Lin a , Yu-Chi Pan a , Jason Fang c , Li-Duan Tsai c , George T.K. Fey d , Hsien-Ming Kao a, * a Department of Chemistry, National Central University, Chung-Li 32054, Taiwan, ROC b Department of Neurological Surgery, Tri-Service General Hospital, National Defense Medical Center, 325, Sec. 2, Cheng-Kung Rd, Nei-Hu Dist, Taipei 11490, Taiwan, ROC c Department of Fuel Cell Materials and Advanced Capacitors, Division of Energy Storage Materials and Technology, Material and Chemical Laboratories, Industrial Technology Research Institute, Hsin-Chu 300, Taiwan, ROC d Department of Chemical and Materials Engineering, National Central University, Chung-Li 32054, Taiwan, ROC article info Article history: Received 7 August 2012 Received in revised form 2 November 2012 Accepted 3 November 2012 Available online 9 November 2012 Keywords: Organiceinorganic hybrid electrolyte Ionic conductivity Poly(oxyalkylene) diamine abstract A new type of organiceinorganic hybrid electrolyte has been developed by a solegel process through the reaction of cyanuric chloride with poly(oxyalkylene) diamine and 3-isocyanatepropyltriethoxysilane, followed by co-condensation of 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane. A maximum ionic conductivity of 1.0  10 4 Scm 1 at 30  C has been achieved with the solid hybrid electrolyte. The results of solid-state NMR not only confirm the structural framework of the hybrids, but also provide a microscopic view of the effects of salt concentrations on the dynamic behavior of the polymer chains. The hybrid materials are blended with PVdF-HFP to form the blend hybrid membrane, followed by plasticization with various electrolyte solvents, with the purpose of increasing ionic conductivity. The plasticized blend hybrid electrolyte exhibits a maximum room temperature ionic conductivity of 8.8  10 3 Scm 1 . Such a high ionic conductivity allows it as a potential candidate for applications in lithium ion batteries. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The research on lithium ion secondary batteries becomes important due to the requirements of reliable energy storage systems. Recently, major research efforts have been focused on developing efficient electrolytes and electrode materials for rechargeable batteries. In that regard, polymer electrolytes are very crucial materials with an extraordinary technological potential in high energy density rechargeable batteries, dye-sensitized solar cells, fuel cells, supercapacitors, electrochromic displays, etc. [1e5]. The area of polymer electrolytes has gone through various developmental stages, e.g., from dry solid polymer electrolytes (SPEs) to plasticized, rubbery, and micro/nano-composite polymer electrolytes [1e3]. Although dry solid polymer electrolytes have many advantages such as no leakage, flexibility, and easy handling, their ionic conductivities are relatively low and thus often hinder their practical applications in batteries, as compared to gel or plasticized electrolytes whose conductivities are around 10 3 e10 2 Scm 1 [6e8]. In addition, micro/nano-composite polymer electrolytes with enhanced mechanical integrity have been intensively studied and few of them exhibit a room temperature ionic conductivity value up to 10 4 Scm 1 [9e11]. Poly(ethylene oxide) (PEO) and its derivatives have been used in most of the studies since PEO contains ether coordination sites, which assist the dissociation of salts incorporated in the polymer as well as a flexible structure that promotes facile ionic transport [1e 3,12,13]. The earliest works on the ionic conductivities of PEO complexed with alkali metal salts were made by Wright and Armand [12,13]. However, PEO-based SPEs with LiClO 4 , LiCF 3 SO 3 , and LiAsF 6 salts show comparatively low ionic conductivity (w10 7 e10 6 Scm 1 ) at ambient temperatures due to the existence of crystalline domains which prohibits the ionic transport. Never- theless, the PEO- lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) polymer electrolyte system attracted attention because of the high dissociating ability and plasticizing ability of LiTFSI. However, these electrolytes exhibit ionic conductivities greater than 10 5 Scm 1 at 25  C and achieve reasonable conductivity values at higher temperature only [14,15]. Incorporation of boroxine polymers, plasticizing lithium borate or addition of ionic liquids into PEO- LiTFSI system increases the room temperature conductivity value * Corresponding author. Tel.: þ886 3 4275054; fax: þ886 3 4227664. E-mail address: hmkao@cc.ncu.edu.tw (H.-M. Kao). Contents lists available at SciVerse ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymer.2012.11.012 Polymer 53 (2012) 6008e6020