Self-doped Block Polymer Electrolytes for Lithium-ion Batteries

As a result of their ability to self-assemble on nanometer length scales, block polymer (BP) electrolytes offer an attractive strategy to tackle the competing constraints of high conductivity and mechanical/thermal stability that hamper optimization of traditional electrolyte materials. Herein, we report on the behavior of a new self-doped diblock terpolymer electrolyte, in which one block was a high modulus material and the other was comprised of high ion-conductivity and self-doped monomer segments. Unlike traditional salt-doped BP electrolytes, which require the addition of a lithium salt to bestow conductivity, these self-doped BPs minimize counterion motion that reduce efficiency and cause concentration polarization in the electrolyte. These single-ion BPs were synthesized with a series of self-doped lithium concentrations, and the nanoscale morphologies were determined using small angle X-ray scattering and transmission electron microscopy. Electrolyte transport properties were measured via AC impedance spectroscopy and DC polarization. With this enhanced physical understanding, the chemistries, monomer segment distribution, and ion content of the self-doped BP can be used to inform BP electrolyte designs.