## 1 Introduction  
Polymers based on ethylene oxides such as poly(ethylene oxide) (PEO) and nitrile groups such as polyacrylonitrile (PAN) have traditionally been used to prepare solid polymer electrolytes for use in all solid-state batteries [1, 2]. However, as the solvent casting method is typically used in research settings to dissolve the polymers and lithium salts that comprise these electrolytes, significant quantities of solvent and energy for solvent evaporation are consumed during the synthesis of these electrolytes [3, 4, 5, 6]. This would result in a significant financial and environmental cost to produce \"green\" devices. Therefore, a cost effective and solvent-free method for the preparation of solid polymer electrolytes is of interest [7]. Although hot pressing methods for the preparation of solid polymer electrolytes do exist, these require specialized equipment and are mostly limited to thermoplastic materials which impacts the widespread application of this technique. A solution to this dilemma is to investigate polymerization reactions that allow films to be produced in the absence of solvents. One such reaction is the ring opening polymerization reaction of epoxides which can be catalyzed by lithium salts and/or amine-containing reagents and can yield crosslinked films that tend to have superior mechanical strength and decreased crystallinity relative to typical PEO-based solid polymer electrolytes [7]. Additionally, the ring opening polymerization reaction of epoxides is useful in the generation of ether oxygen-containing polymers which yields ionic conductivity pathways that are similar to those that are found in PEO-based polymer electrolytes [8,9]. The lithium salt-catalyzed ring opening polymerization reaction falls under the category of cationic ring opening polymerization reactions because both the initiating and propagating species are positively charged [10]. Polymers originating from epoxide-containing monomers tend to have desirable characteristics for solid electrolyte applications, in addition to being compatible with solvent-free preparation techniques: they are highly flexible, have low glass transition temperature (T\({}_{\text{g}}\)), low crystallinity, low polymer chain entanglement and high hydrophilicity relative to polymers with hydrocarbon-based backbones [8]. Additionally, similar to other classes of electrolytes that are suitable for use in all solid-state batteries, epoxide-based polymer electrolytes can provide significant safety advantages over traditional liquid electrolytes. These electrolytes are non-flammable and possess sufficient flexibility and mechanical strength to both prevent leakage and inhibit dendrite growth which can cause short-circuits [11, 12, 13]. However, as epoxide-based polymer electrolytes are an emerging technology, a full analysis of all potential safety issues and benefits has yet to be widely demonstrated Epoxide-based polymer electrolytes have the possibility of out-performing PEO-based solid electrolytes at room temperature as they are non-crystalline and tend to have high polymer chain mobility [9,14]. Another advantage of epoxide-based solid polymer electrolytes is the possibility for considerable synthetic variability as a result of the variety of epoxide-functionalized monomers that are amenable to polymerization [9]. The viability of many different epoxide-containing monomers for ring opening polymerization means that several characteristics of the resultant polymer electrolytes including ionic conductivity, crystallinity and thermal and electrochemical stability are highly tunable [9]. The receptivity of various epoxide monomers toward the ring opening polymerization reaction depends on the molecular structure of the monomer. Cycloaliphatic epoxides, which have significant ring strain, tend to crosslink rapidly, while those with nucleophilic groups tend to crosslink more slowly [15].