Lithium-ion batteries are a promising energy storage technology due to their high energy density, high open-circuit potential, low self-discharge rates, and minimal memory effects. However, despite their potential benefits, lithium-ion batteries tend to suffer from problems with safety and stability. Block polymers can be designed to improve the stability of electrolyte materials such that one domain is glassy at operating temperature while another efficiently conducts lithium ions, which are doped into the electrolyte through the addition of a lithium salt. Previous work in our group has shown that the choice of counter-ion in the salt has a significant impact on both conductivity and effective segregation strength of the electrolyte. Even with the careful selection of salts, in traditional block polymer lithium-ion batteries, over half of all ion motion is done by ions that do not participate in the energy-generating reaction. This work describes the synthesis and characterization of a novel polymer electrolyte, known as a single-ion conductor, in which the flow of ions across the electrolyte is heavily biased towards lithium ions because the counter-ions are immobilized on the polymer chains. Starting from a polymer block with a high glass transition temperature, the single-ion conductor was copolymerized with a good ion-conductor by atom transfer radical polymerization. The kinetics of this copolymerization were monitored to ensure even incorporation of the two monomers. The resulting single-ion conducting polymer was characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, and microwave plasma-atomic emission spectrometry. The performance of the electrolyte material was measured using AC impedance spectroscopy to determine the conductivity and lithium ion transference number.

Synthesis and characterization of single-ion conducting polymers for lithium-ion batteries

251st National Meeting (2016)

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