Stabilization of the polymer electrolyte/lithium metal electrode interface with increased ion conduction using PEO polymer/low molecular weight PE-b-PEO diblock copolymer composite bi-layer films

Abstract

A method of stabilizing the interface of PEO polymer electrolytes with respect to lithium metal, using a composite bi-layered, hybrid film is described. This method utilizes a low molecular weight PE-b-PEO diblock copolymer having a general chemical formula of H-(CH2)32-(O-CH2CH2)10-OH that can be positioned at the PEO polymer electrolyte surface. These hybrid films are fabricated by making a thin layer of the PE-b-PEO materials by solvent casting and then casting a second layer of standard PEO polymer electrolyte on the PE-b-PEO film. This PE-b-PEO layer adheres to the polymer electrolyte surface, making a stabilized interface with lithium. This hybrid system not only stabilize the lithium/polymer electrolyte interface but also has the desirable property of increasing ion conduction by almost three orders of magnitude over a standard PEO polymer electrolyte system. The stabilization of the lithium/polymer electrolyte interface and the increase in ionic conduction has been studied by using AC impedance spectroscopy, AFM phase imaging, and attenuated total reflection IR, which allow the mechanism for stabilization and increased ionic conduction to be discussed.