Polymer Blend Separators

In this chapter, we have presented the fundamentals, fabrication, and functions of polymer blend separators with novel structures for lithium-sulfur battery applications. Polymer blend membranes are prepared by mixing two or more polymers with complementary properties. A separator is typically a porous polymer membrane preventing internal short-circuit without disrupting the ion diffusion channels. Polyolefin membranes are commonly used as separators in Li–S batteries owing to their easy availability, low cost, and good mechanical and chemical stability. However, the polysulfide shuttle effect caused by the dissolution and diffusion of the polysulfides (PS) cannot be impeded using traditional polyolefin separators. In order to confine the diffusion of PS species, many efforts have been made by functionalizing the commercial polyolefin separators by introducing a variety of barrier layer coatings such as carbon, metal oxides, polymer, and their composites. However, the coated separators suffer from weak interfacial adhesions between the polyolefin substrate and functional coating layer, and inadequacy of interfacial pores. Therefore, developing polymer blend membranes as independent separators or as integrated components is an effective strategy to alleviate the PS shuttle effect in the Li–S system. A brief introduction to the polymer blend separators, their fabrication methods, functions either as an inactive or as an active component, and recent developments are discussed in detail.