| Summary: | Three new crosslinked polystyrene nanoparticles covalently attached with low lattice energy lithium salt moieties were synthesized: poly(styrene lithium trifluoromethane sulphonyl imide) (PSTFSILi), poly(styrene lithium benzene sulphonyl imide) (PSPhSILi), and poly(styrene lithium sulfonyl-1,3-dithiane-1,1,3,3-tetraoxide) (PSDTTOLi). A series of solid polymer electrolytes (SPEs) were formulated by mixing these lithium salts with high molecular weight poly(ethylene oxide), poly(ethylene glycol dimethyl ether), and lithium bis(fluorosulfonyl)imide. The crosslinked nano-sized polymer salts improved film strength and decreased the glass transition temperature (T<sub>g</sub>) of the polymer electrolyte membranes. An enhancement in both ionic conductivity and thermal stability was observed. For example, the SPE film containing PSTFSILi displayed ionic conductivity of 7.52 × 10<sup>−5</sup> S cm<sup>−1</sup> at room temperature and 3.0 × 10<sup>−3</sup> S cm<sup>−1</sup> at 70 °C, while the SPE film containing PSDTTOLi showed an even better performance of 1.54 × 10<sup>−4</sup> S cm<sup>−1</sup> at room temperature and 3.23 × 10<sup>−3</sup> S cm<sup>−1</sup> at 70 °C.
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