Ionically conducting polymer membranes (polymer electrolytes) might enhance lithium-battery technology by replacing the liquid electrolyte currently in use and thereby enabling the fabrication of flexible, compact, laminated solid-state structures free from leaks and available in varied geometries1. Polymer electrolytes explored for these purposes are commonly complexes of a lithium salt (LiX) with a high-molecular-weight polymer such as polyethylene oxide (PEO). But PEO tends to crystallize below 60 °C, whereas fast ion transport is a characteristic of the amorphous phase. So the conductivity of PEO–LiX electrolytes reaches practically useful values (of about 10−4 S cm−1) only at temperatures of 60–80 °C. The most common approach for lowering the operational temperature has been to add liquid plasticizers, but this promotes deterioration of the electrolyte's mechanical properties and increases its reactivity towards the lithium metal anode. Here we show that nanometre-sized ceramic powders can perform as solid plasticizers for PEO, kinetically inhibiting crystallization on annealing from the amorphous state above 60 °C. We demonstrate conductivities of around 10−4 S cm−1 at 50 °C and 10−5 S cm−1 at 30 °C in a PEO–LiClO4 mixture containing powders of TiO2 and Al2O3 with particle sizes of 5.8–13 nm. Further optimization might lead to practical solid-state polymer electrolytes for lithium batteries.

Nanocomposite polymer electrolytes for lithium batteries

Poly(ethylene oxide) (PEO) based materials are widely considered as promising candidates of polymer hosts in solid-state electrolytes for high energy density secondary lithium batteries. They have several specific advantages such as high safety, easy fabrication, low cost, high energy density, good electrochemical stability, and excellent compatibility with lithium salts. However, the typical linear PEO does not meet the production requirement because of its insufficient ionic conductivity due to the high crystallinity of the ethylene oxide (EO) chains, which can restrain the ionic transition due to the stiff structure especially at low temperature. Scientists have explored different approaches to reduce the crystallinity and hence to improve the ionic conductivity of PEO-based electrolytes, including blending, modifying and making PEO derivatives. This review is focused on surveying the recent developments and issues concerning PEO-based electrolytes for lithium-ion batteries.

Poly(ethylene oxide)-based electrolytes for lithium-ion batteries

Recent advances in all-solid-state rechargeable lithium batteries

https://krc.cecri.res.in/ro_2006/034-2006.pdf

Review on gel polymer electrolytes for lithium batteries

In this review, state-of-the-art polymer electrolytes are discussed with respect to their electrochemical and physical properties for their application in lithium polymer batteries. We divide polymer electrolytes into the two large categories of solid polymer electrolytes and gel polymer electrolytes (GPE). The performance requirements and ion transfer mechanisms of polymer electrolytes are presented at first. Then, solid polymer electrolyte systems, including dry solid polymer electrolytes, polymer-in-salt systems (rubbery electrolytes), and single-ion conducting polymer electrolytes, are described systematically. Solid polymer electrolytes still suffer from poor ionic conductivity, which is lower than 10−5 S cm−1. In order to further improve the ionic conductivity, numerous new types of lithium salt have been studied and inorganic fillers have been incorporated into solid polymer electrolytes. In the section on gel polymer electrolytes, the types of plasticizer and preparation methods of GPEs are summarized. Although the ionic conductivity of GPEs can reach 10−3 S cm−1, their low mechanical strength and poor interfacial properties are obstacles to their practical application. Significant attention is paid to the incorporation of inorganic fillers into GPEs to improve their mechanical strength as well as their transport properties and electrochemical properties.

J.E. Weston

Papers

Effects of inert fillers on the mechanical and electrochemical properties of lithium salt-poly(ethylene oxide) polymer electrolytes

Effects of preparation method on properties of lithium salt-poly(ethylene oxide) polymer electrolytes

Thermal history — conductivity relationship in lithium salt-poly (ethylene oxide) complex polymer electrolytes

Investigation of the electrode/electrolyte interface for the Cu+ ion solid electrolyte N,N′-dimethyl-triethylene diamine-copper(1) bromide

Thermodynamics and mobility of copper in bornite (Cu5FeS4)