Collaborative Research: SusChEM: Perfluoroether-based Polymer Electrolytes for Lithium Batteries

Nitash Balsara / Joseph DeSimone

1505669 / 1510579

Although electric and hybrid vehicles have the potential to reduce dependence on fossil fuels for transportation, the rechargeable lithium batteries that currently power them suffer from many problems. Current designs can hold 10% of their theoretical amount of energy content, contain highly flammable organic liquid electrolytes, are relatively costly, and do not last as long as a typical automobile. New battery materials are needed to address these problems. The objective of this project is to develop high-performance electrolytes for lithium batteries that have no flammable components, potentially leading to improved safety. These electrolytes will be based on nonflammable fluorinated polymers designed to dissolve lithium ions and maintain high ion conductivity for improved charging and discharging rates. The proposed research will make and test these new polymer materials for battery applications, and try to understand the fundamental science underlying their performance. The proposed educational activities associated with this project include an engineering summer camp for underserved high school students in the Oakland-Berkeley area that features hands-on projects related to lithium batteries.

The overall goal of the proposed research is to develop perfluoropolyether (PFPE)-based electrolytes for lithium batteries. It is believed that this material is a promising new electrolyte for two principal reasons. First, PFPE materials are a class of fluoropolymers that are intrinsically nonflammable and exhibit low vapor pressure as well as thermal, chemical and oxidative stability. Second, for lithium ion battery applications, PFPE-based electrolytes also can dissolve lithium salts with fluoridated anions. This electrolyte system possesses high conductivity dominated by molecular lithium ion (Li+) transport, owing to the low glass transition temperature of the PFPE materials, and the solvation of fluorinated anions by fluorinated polymers, which immobilizes the anion on the polymer. The proposed research will synthesize functionalized homo- and block co-polymer perfluoropolyethers and lithium salts, characterize the electrochemical properties of these electrolytes, and assess their ion transport and cycling performance in electrochemical energy storage test devices. Selected research outcomes will be used to support the development of a start-up company and provide entrepreneurial training for students involved on the project. Additional education and outreach activities are also planned in coordination with the Professional Development Program at UC Berkeley and with the Research Triangle Electrochemical Society Student Chapter.