Abstract: Solid-polymer electrolytes, methods of making solid-polymer electrolytes, and uses of solid-polymer electrolytes. A solid-polymer electrolyte comprises a cross-linked polymer network. A cross-linked polymer network may comprise a plurality of groups, which may be cross-linked groups, such as, for example, cross-linked difunctional polyether groups, cross-linked difunctional ionic groups, non-crosslinked groups, which may be referred to as “dangling” groups, or a combination thereof, and a plurality of cross-linked multifunctional crosslinker groups. A solid polymer electrolyte can be formed by polymerization. A solid polymer electrolyte can be formed in situ in a device. A solid polymer electrolyte can be used in devices such as, for example, batteries, supercapacitors, fuel cells, and the like.