Comparing Ion Conductivity and Transference Number of Single-ion and Salt-doped Block Copolymer Electrolytes

Nanostructured block copolymer electrolytes with both ion conductive and mechanically robust microphases are strong candidates for solid battery electrolytes. However, their performance is limited by their low cation transference number (fractional contribution of the cation to the overall conductivity). Experimental work has showed a potential route of increasing transference number by tethering anions to the polymer backbone of the conducting segment of block copolymers. Due to the synthetic challenges of such materials, the design space has yet to be well explored. It is unclear how to optimize their conductivity and under what conditions these single-ion block copolymer electrolytes can more efficiently conduct lithium ion than the salt-doped materials. In this work, we perform coarse-grained molecular dynamics simulations with an applied electric field to calculate ion conductivity and transference number in both single-ion and salt-doped block copolymers. We aim to show how the choices of molecular weight, ion loading, and anion type impact ion transport to guide design of new materials.