The Optimal Arm Length for Star Polymer Electrolytes

The wide application of lithium batteries requires safe and stable electrolyte materials. Recently, there has been an emergence of advanced polymer electrolytes that combine polyethylene oxide with other components in complex architectures including block, bottlebrush, and star structures. However, the conduction mechanisms within these non-linear architectures are yet to be rigorously examined and there lack transferable principles to aid the design and optimization of polymer electrolytes with non-linear architectures. Therefore, in this work, we utilized star polymer as an example to obtain fundamental understandings on how the desired high ionic conductivity evolves with the changes in the arm structures of star polymers. Specifically, we identified a delicate balance between the high flexibility provided by long arms and the low crystallinity caused by shorter arms, leading to an optimal chain length for ion-conduction. Based upon this finding, we proposed a set of general design rules that we anticipate could inform the designs of other polymer electrolytes with complex architectures moving forward.