Branched polyethylene/poly(ethylene oxide) as a host matrix for Li-ion battery electrolytes: A molecular dynamics study

This article discusses the structural and dynamic properties of a model polymer electrolyte system suitable for Li-ion batteries, investigated by Molecular Dynamics simulations at 293 K. It consists of a non-polar polyethylene backbone, onto which polar oligomeric polyethylene oxide side-chains of length 4–15 EO units are attached. LiPF6 salt is dissolved into the matrix to a concentration corresponding to a Li:EO ratio of 1:12. It is found that the system display significantly higher mobility values that linear PEO using the same concentration, which is attributed to the high side-chain dynamics and the polar/non-polar topology of the system. An optimum side-chain length of 10 EO units is found for many properties, such as the dissolution of salt, although the Li+ ion diffusion was found to be the highest for side-chain lengths of 15 EO units: 1.54 × 10−13 m2 s−1.

► We use Molecular Dynamics to model a Li-battery polymer electrolyte with different polarities. ► The polymeric system has a tendency to phase-separate at the nano-scale level. ► The ionic conductivity is significantly higher in the bipolar system than in linear poly(ethylene oxide).