electrolytes were discovered by Michael Faraday in the nineteenth century, these being silver sulfide (Ag₂S) and lead(II) fluoride (PbF₂). The first polymeric material able to conduct ions at the solid-state was PEO, discovered in the 1970s by V. Wright. The importance of the discovery was recognized in the early 1980s.

However, unresolved fundamental issues remain in order to fully understand