## 3 Varieties of Epoxide-Based Polymer Electrolyte
### Silicone-Based Reagents
As GLYMO was combined with another epoxide-containing silane, PEO-methyl-propyltrimethoxysilane (PEO-MP), a binary polymer electrolyte was produced [14]. The resultant electrolyte material was thermally stable up to 250 \({}^{\circ}\)C and had a room temperature conductivity on the order of 10\({}^{-4}\) S/cm with some variation based on the ratio of LiClO\({}_{4}\) to ether oxygen [22]. This material had a transport number (determined using the Bruce-Vincent method) of 0.5 which is significantly higher than the \(\sim\)0.2 that is generally reported for PEO-based electrolytes [22]. This was attributed to the amorphous nature of the crosslinked polymer electrolyte. In addition, these electrolytes were electrochemically stable up to 4.0 to 4.5 V relative to Li\({}^{+}\)/Li depending on the lithium to ether oxygen ratio thus demonstrating that the incorporation of inorganic polymers can also improve the electrochemical stability of polymer electrolytes [22]. Differences in ionic conductivity and electrochemical stability between silicone-containing systems and those that contain PEO can be demonstrated by comparing the work of [PERSON] et al. where PEO, GLYMO and LiTFSI were combined to produce a polymer electrolyte via the hot pressing method [23]. This material was thermally stable up to 230 \({}^{\circ}\)C [23]. The most conductive electrolyte, with a lithium to ether oxygen ratio of 20, had an ionic conductivity of 5.56 \(\times\) 10\({}^{-5}\) S/cm at 30 \({}^{\circ}\)C and a T\({}_{\text{g}}\) of \(-\)45.5 \({}^{\circ}\)C [23]. The electrochemical stability relative to Li\({}^{+}\)/Li was 3.75 V, it is anticipated that the inclusion of PEO in the polymer blend made the properties of the resultant electrolyte more similar to those of PEO-based polymer electrolytes than those of silane-containing polymer electrolytes. [PERSON] et al. prepared a GLYMO-based polymer electrolyte with improved thermal stability using ethylene diglycidyl ether (EDGE) and LiTFSI [24]. The resultant polymer electrolyte was thermally stable up to 400 \({}^{\circ}\)C [24]. However, the T\({}_{\text{g}}\) was found to be dependent on the lithium to ether oxygen ratio with the T\({}_{\text{g}}\) increasing from \(-\)61 \({}^{\circ}\)C when the lithium to ether oxygen ratio was 7 to 45 \({}^{\circ}\)C when the lithium to ether oxygen ratio was 20 [24]. This increase was attributed to decreasing polymer chain mobility as a result of increased polymer chain crosslinking that was caused by the affinity of the polymer backbone for the lithium ions [24]. This impacted the ionic conductivity of the material. The highest room temperature conductivity, 2.6 \(\times\) 10\({}^{-5}\) S/cm, was obtained when the lithium to ether oxygen ratio was equal to 10 [24]. This resulted in a lithium transference number of 0.37, which is higher than what is typically observed in PEO-based electrolytes and activation energies for lithium ion transport between 0.5 and 0.6 eV [24]. Ionic conductivity decreased at higher lithium salt loadings as a result of increased polymer crystallinity. The electrochemical stability of this polymer electrolyte was determined to be 4.9 V with respect to Li\({}^{+}\)/Li [24]. Cycling an asymmetric Li-LTO cell for 500 cycles revealed that the polymer electrolyte is moderately stable with respect to the lithium anode. This was investigated using electrochemical impedance spectroscopy where an observed increase in resistance was attributed to the growth of a solid electrolyte interface layer [24]. In addition to forming polymer electrolytes with polyether-based epoxide reagents via the ring opening polymerization reaction, GLYMO is compatible with other film-forming reactions. [PERSON] and Liu produced solid polymer electrolytes using the sugar agarose, GLYMO and LiTFSI [25]. In this case, linkages were formed between the methoxy groups on the silane and the OH groups on the sugar via a substitution reaction [25]. The resultant polymer was thermally stable up to 150 \({}^{\circ}\)C and had good electrochemical properties.