| Summary: | In order to enhance the electrochemical performance and mechanical properties of poly(ethylene oxide) (PEO)-based solid polymer electrolytes, composite solid electrolytes (CSE) composed of single-ion conducting polymer-modified SiO<sub>2</sub>, PEO and lithium salt were prepared and used in lithium-ion batteries in this work. The pyridyl disulfide terminated polymer (py-ss-PLiSSPSI) is synthesized through RAFT polymerization, then grafted onto SiO<sub>2</sub> via thiol-disulfide exchange reaction between SiO<sub>2</sub>-SH and py-ss-PLiSSPSI. The chemical structure, surface morphology and elemental distribution of the as-prepared polymer and the PLiSSPSI-<i>g</i>-SiO<sub>2</sub> nanoparticles have been investigated. Moreover, CSEs containing 2, 6, and 10 wt% PLiSSPSI-<i>g</i>-SiO<sub>2</sub> nanoparticles (PLi-<i>g</i>-SiCSEs) are fabricated and characterized. The compatibility of the PLiSSPSI-<i>g</i>-SiO<sub>2</sub> nanoparticles and the PEO can be effectively improved owing to the excellent dispersibility of the functionalized nanoparticles in the polymer matrix, which promotes the comprehensive performances of PLi-<i>g</i>-SiCSEs. The PLi-<i>g</i>-SiCSE-6 exhibits the highest ionic conductivity (0.22 mS·cm<sup>−1</sup>) at 60 °C, a large t<sub>Li+</sub> of 0.77, a wider electrochemical window of 5.6 V and a rather good lithium plating/stripping performance at 60 °C, as well as superior mechanical properties. Hence, the CSEs containing single-ion conducting polymer modified nanoparticles are promising candidates for all-solid-state lithium-ion batteries.
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