Synthesis and Characterization of a New Class of Mono-lithium Salts for PEO-Based Solid Polymer Electrolytes

摘要

Lithium ion conducting polymer electrolytes have significant potential in the field of secondary lithium batteries, including display and sensor devices. We report here a new class of lithium sulfonimide salts for use in lithium-ion battery electrolytes. These salts, prepared by a two- to three-step synthetic strategy from inexpensive and readily available starting materials, were characterized by H-NMR, FTIR and elemental analysis. The thermal properties of the salts were determined by thermogravimetric analysis and showed stabilities up to 300°C. Earlier studies demonstrated that the ionic conductivity of solid polymer electrolytes could be improved by use of a borate ester plasticizer. In order to optimize conductivity, solid polymer electrolyte films were prepared by incorporating this plasticizer with each of the new salts in a PEO matrix. We observed that the Li:O ratio of 1:20 exhibits maximum ionic conductivity (2.05×10{sup}(-6)S/cm at 30°C for the salt ALT01). A trend of decreasing conductivity with increasing size of the anionic moiety was also noted. It was found that 1g of plasticizer can be loaded in a film containing 1g of PEO without deterioration of mechanical properties. An improved ionic conductivity of 3.82×l0{sup}(-5)S/cm at 30°C was observed. The films also exhibited good thermal and electrochemical stabilities. Glass transition temperature of the films were determined using differential scanning calorimetry.