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The association of ions describes the formation of ion species in electrolyte solutions and is strongly related to the salt concentration. However, the discussion of ion species and their transport is ambiguous in some studies on electrolyte materials due to the assumption of ideal solutions. Accordingly, in this work, molecular dynamics simulations are used to study ion association and transport properties of poly­(ethylene)­oxide (PEO)–lithium bis­(trifluoromethanesulfonyl)­imide electrolytes over a range of salt concentrations (r = [Li]/[EO]) from 0.01 to 0.20. Based on the analysis of the solvation environment and ion species, it is revealed that the distinct ion–ion correlations exist in two different characteristic areas, with a salt concentration of 0.10 as the limit. Below the critical concentration, the dynamic equilibrium between free ions and ion pairs is the most important process affecting the transport properties of electrolytes, but the process may have a minor influence on the applicability of the Nernst–Einstein relation. In concentrated solutions, a large number of ion pairs, triplets, and so forth appear in the electrolytes. The high-order ion clusters, with an average size of 3.95 at r = 0.20, are the main stable structures for transporting Li+, but the trapped free ions are the most abundant ion species. Meanwhile, the effect of salt concentrations on the average transport of ion clusters is to increase their average lifetime, but their transport rates remain unchanged. In addition, the coupling dynamics between ions and polymers is also discussed in order to gain a complete insight into the importance of salt concentrations.

Polymer dielectrics possess excellent flexibility compared with inorganic ceramic materials.However, the relatively low dielectric constant and working temperature significantly constrains their widespread application. Here, we report a low-cost facile strategy to develop flexible polymer-based composite films with high dielectric constant over a broad temperature.Polyacrylonitrile (PAN) nanofiber mats containing graphene oxide (GO) with core-shell microstructure were firstly prepared via coaxial electrospinning and then hot-pressed into dense composite films. It was revealed that hot-pressing assisted by a stretching force under appropriate temperature and pressure can generate local conformational changes of PAN, leading to the formation of an electroactive phase with increased dielectric constant.Meanwhile, the GO transformed into reduced graphene oxide (rGO) under heat reduction, serving as conductive nanofillers to further promote the increase of dielectric constant.Consequently, the optimized rGO/PAN composites displayed thermally stable dielectric properties with a high dielectric constant (ɛ'=23, 80℃; ɛ'=40, 150℃) and low loss (tanδ=0.13, 80℃; tanδ=0.55, 150℃) over a broad temperature range. This work offers an efficient method for the synthesis of flexible composite dielectric films that hold great potential in high-temperature electronic applications.

An elastomer, poly (n-butyl methacrylate), coated liquid metal (LM) nanodroplets (EGaIn@PBMA) was successfully fabricated via a facile in-situ free radical polymerization method. The as prepared soft nanoparticles can be directly...

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