Facile Alignment of Amorphous Poly(ethylene oxide) Microdomains in a Liquid Crystalline Block Copolymer Using Magnetic Fields: Towards Ordered Electrolyte Membranes

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Edited by Qichao Hu

October 4th, 2010

reference: [1]

The hydrophilic Poly(ethylene oxide) (PEO) polymer is water-soluble and semicrystalline, and has many applications. One of the main applications is used as a solid polymer electrolyte in lithium batteries. When lithium salts are introduced to the PEO polymer, the lithium ions are complexed by the ether oxygen atoms, and can migrate along the PEO side chains and result in ion conducting electrolyte.

However, due to the crystalline nature of PEO, ion transport is slow, since the lithium ion conductivity is related to the segmental motion of the PEO side chains. The effect of increasing ion concentration in PEO is unclear, while it suppresses the crystallinity, it also increases the glass transition temperature of the polymer. Thus amorphous and liquid-like PEO is desired for high conductivity polymer electrolyte. However, a certain mechanical strength is also needed in lithium batteries to overcome the dendrite growth problem. As a consequence, one approach of using PEO-based polymer as an electrolyte in lithium battery, is to use block copolymer, where microphase separation between PEO and another block results in a copolymer that is liquid on the nano-scale, but solid on the macro-scale.