Borate based lithium conducting glasses

Borate based lithium conducting glasses are reviewed. The glass former is B2O3 to which Li2O is usually added as a modifier. Various lithium salts can be present in order to enhance the conductivity such as lithium halides, sulfate or orthophosphate. Their preparation procedures are described. The local structure is discussed on the basis of crystallized lithium borate data, Raman spectroscopy and sound velocity measurements. The conduction mechanisms are still not completely established and two models have been proposed. One can consider either that a dissociation equilibrium yields a limited number of mobile lithium ions the mobility of which is not dependent on the composition or that all ions present are equally mobile, their mobility being influenced by the local structure. Mixed conducting glasses incorporating a transition element oxide are mentioned. The main practical applications of such glasses as thin films are described.