Chapter 11 - Electrolytes for lithium batteries

Abstract

This chapter begins by stating that most electrolytes for lithium batteries are aprotic organic solvents containing lithium salts like propylene carbonate, ethylene carbonate, and diethyl carbonate. Dielectric constants of these solvents are relatively high, but are smaller as compared to water. In order to dissolve more electrolyte salts, a pair of large and small ions is required. Therefore, most lithium salts that can easily dissolve into aprotic organic solvents involve various large anions containing F elements. The chapter introduces lithium salts including F elements. Reactions in lithium batteries are discussed first. An analysis of ionic conductivity of aprotic solvent containing electrolyte salt is also included in the chapter. Electrolytes containing new salts with F element are described in the chapter. The stability of fluorinated electrolyte salt is discussed, and the role of electrolyte salts is explained. The development of new electrolyte salts is briefly referred to along with the solvent for electrolyte. The chapter concludes that several kinds of electrolyte salts containing F element used in practical primary and rechargeable lithium batteries provide high ionic conductivities of organic electrolytes. It adds that the surface state of electrodes is also influenced by the presence of F in the electrolytes.