**1.2 Applications of solid polymer electrolytes**

SPEs are of great interests in the technology field, especially the area of electrical power generation and storage systems. It is primarily due to their wider range of applications, ranging from small scale production of commercial secondary lithium ion batteries (also known as the rechargeable batteries) to advanced high energy electrochemical devices, such as chemical sensors, fuel cells, electrochromic windows (ECWs), solid state reference electrode systems, supercapacitors, thermoelectric generators, analog memory devices and solar cells (Gray, 1991; Rajendran et al., 2004). As for the commercial promises of lithium rechargeable batteries, there is a wide range of applications which ranges from portable electronic and personal communication devices such as laptop, mobile phone, MP3 player, PDA to hybrid electrical vehicle (EV) and start–light–ignition (SLI) which serves as traction power source for electricity (Gray, 1997a; Ahmad et al., 2005).

#### **1.3 Advantages of solid polymer electrolytes**

A force had been driven in the development of SPEs to replace conventional liquid electrolytes due to its attractive advantages. These features include the elimination of the problems of corrosive solvent leakage and harmful gas production, ease of processability due to elimination of liquid component, and suppression of lithium dendrite growth as well (Rajendran et al., 2004; Ramesh et al., 2010). Besides safety performance, SPE is also a promising candidate because of its intrinsic characteristics, such as ease to configure in any shape due to its high flexibility of polymer matrix, high automation potential for electrode application and no new technology requirement as well as light in weight (Xu and Ye, 2005; Gray, 1991). The other advantages of SPEs are viz., negligible vapor pressure, ease of handling and manufacturing, wide operating temperature range, low volatility, high energy density and high ionic conductivity at ambient temperature (Baskaran et al., 2007; Rajendran et al., 2004). In addition, they exhibit excellent electrochemical, structural, thermal, photochemical and chemical stabilities without the combustible reaction products at the electrode surface by comparing with conventional liquid electrolyte (Adebahr et al., 2003; Nicotera et al., 2006; Stephan, 2006). Moreover, they produce miniaturized structures via fabrication methods and provide longer shelf–lives with no internal shorting (Gray, 1997a; Stephan, 2006).
