Ionic conductivity in crystalline polymer electrolytes

Abstract

Polymer electrolytes are the subject of intensive study, in part because of their potential use as the electrolyte in all-solid-state rechargeable lithium batteries. These materials are formed by dissolving a salt (for example LiI) in a solid host polymer such as poly(ethylene oxide) (refs 2, 3, 4, 5, 6), and may be prepared as both crystalline and amorphous phases. Conductivity in polymer electrolytes has long been viewed as confined to the amorphous phase above the glass transition temperature, Tg, where polymer chain motion creates a dynamic, disordered environment that plays a critical role in facilitating ion transport. Here we show that, in contrast to this prevailing view, ionic conductivity in the static, ordered environment of the crystalline phase can be greater than that in the equivalent amorphous material above Tg. Moreover, we demonstrate that ion transport in crystalline polymer electrolytes can be dominated by the cations, whereas both ions are generally mobile in the amorphous phase. Restriction of mobility to the lithium cation is advantageous for battery applications. The realization that order can promote ion transport in polymers is interesting in the context of electronically conducting polymers, where crystallinity favours electron transport.

Morphological, rheological and electrochemical studies of Poly(ethylene oxide) electrolytes containing fumed silica nanoparticles

“…Although it has been long recognized that ionic transportation is mainly through amorphous phases, there is new opinion that conductivity in crystalline phase could be even higher than that in the amorphous phase [9]. Golodnistsky et.al.…”

Carbonate-linked poly(ethylene oxide) polymer electrolytes towards high performance solid state lithium batteries

“…To develop dry solid polymer electrolytes with high ionic conductivity and interfacial stability, many strategies, such as synthesizing PEO copolymers [11][12][13][14][15][16], tailoring blend polymers [17], preparing branched PEO polymers [18][19][20] or cross-linked PEO polymers [21][22][23] and compositing ceramic fillers [8,[24][25][26][27][28][29][30][31][32] have been extensively studied [33]. A self-doped solid block copolymer electrolyte was synthesized combining a single-ion poly(lithium methacrylate-co-oligoethylene glycol methacrylate) (P(MALi-co-OEGMA)) and a structuring polystyrene block (PS).…”

A new class of Solvent-in-Salt electrolyte for high-energy rechargeable metallic lithium batteries

“…For instance, the use of solid polymer or inorganic electrolytes could potentially suppress the formation of the lithium dendrites. However, for solid-state electrolytes, the kinetic properties are limited, due to both low conductivity at room temperature and high interfacial resistance [24][25][26][27][28] . Recently, a breakthrough has been achieved in inorganic sulphide-based electrolytes with quite high room temperature conductivity of 10 À 2 S cm À 1 (ref.…”