Investigation of the Effects of Crosslinking on the Properties of Poly(ethylene oxide) Based Solid Polymer Electrolytes

Solid polymer electrolytes (SPEs) promise to provide many benefits for lithium ion batteries including enhancing safety, enabling the use of a solid lithium anode, and facilitating the development of flexible and stretchable batteries. Traditional SPEs use high molecular weight polymers cast into amorphous films. Two very important properties relating to the ionic conductivity of the SPEs are the degree of crystallinity of the polymer as well as the glass transition temperature. Unfortunately, these properties lead to tradeoffs in other important properties such as mechanical toughness and stability. Here, we demonstrate the use of UV crosslinked poly(ethylene oxide) and its derivatives to create a network polymer electrolyte structure. These networked polymers demonstrate interesting properties compared to traditional linear chain SPEs. Notably, the crosslinked polymer networks allow for tuning of the glass transition temperature, mechanical properties, and ionic conductivities of the polymers. This study will demonstrate a methodical and rigorous exploration of the effects of salt concentration, crosslink network density, and molecular additives on the properties of interest for SPEs. A general framework for designing network SPEs will be presented. These principles will be contrasted to those known for linear chain SPEs, elucidating further knowledge of the fundamental mechanisms of ion transport in SPEs. Preliminary results indicate that network SPEs allow the incorporation of conductivity enhancing plasticizers without experiencing substantial deterioration of mechanical properties, providing a substantial advantage to traditional SPEs.