Pushing the Energy Limits of Lithium Ion Batteries through Fluorinated Materials 2019-01-0595

The use of electrolytes containing small fluorinated molecules to enable stable high voltage (>4.3 V) battery operation is the focus of this project. Previously, it has been shown that it is possible to operate lithium ion batteries utilizing several different cathode chemistries up to 4.5 V. Energy gains of 30-50% have been demonstrated when the battery is cycled at 4.5 V. High voltage cycling is accomplished by reducing the gas generation originating from electrolyte decomposition at high voltage. The primary mechanism for this is not completely understood, but the hypothesis is that the fluorinated molecules form a film on the highly oxidizing cathode. The protective film formation allows stable cycle life during high voltage operation. In addition, fluorinated electrolytes have the added benefit of being less flammable which increases safety performance of lithium ion batteries.

Highly fluorinated binder materials offer a variety of advantages (lower modulus, higher chemical resistance, better temperature stability) over the conventional PVDF binders used in current lithium ion batteries. Use of these highly fluorinated binder additives has a direct impact on battery manufacturing costs through decreased scrap rate. This is achieved through higher slurry stability (improved mixing, coating) and more flexible physical characteristics (improved winding). The trend towards higher voltage battery operation will also require increased binder stability.

This paper will address the advantages of both fluorinated electrolytes and binder materials as well as their role in future battery production.