Anionically charged, Li+ neutralized dry polymers have been studied as a means to create an electrolyte in which most (or all) ionic current is carried by the Li+ ion during electrochemical measurements. These high transference number electrolytes could enable high charge and discharge rates in lithium ion batteries, in addition to minimizing concentration polarization. Current state of the art polymer electrolytes designed to enhance the transference number still suffer from low conductivity at moderate to room temperature. In this presentation, we use a single-ion conducting polysulfone-co-poly(ethylene glycol) copolymer (PSf-co-PEG) that has a large miscible composition window to probe the established understanding of ion conduction. We show that blending of a small molecule diluent breaks the apparent tradeoff between segmental dynamics and charge carrier concentration in the PSf-co-PEG system, indicating a clear path to an electrolyte with optimal transport properties. When this strategy is fully extended to electrolytes in which single-ion conducting polymers are entirely dissolved in nonaqueous solvents to create polyelectrolyte solutions, liquid-like conductivities and high Li+ transference numbers can be obtained for certain electrolyte compositions. We will discuss attempts to prepare polyelectrolyte compositions in which liquid carbonates (typical solvents for binary salt Li-ion battery electrolytes) are used as solvents for PSf-co-PEG, as well as other, more highly dissociating anionically-charged polymers that possess sidechains comprised of triflimide anions.

Designing polymer-based Li+ electrolytes with high conductivity and Li+ transference number

2019 Fall National Meeting

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