Polyethylene oxide -based electrolyte system

In addition, various gel electrolytes were investigated for EDLC as well. Polyethylene oxide) (PEO)-, poly(acrylonitrile) (PAN)-, polymethylmethacrylate) (PMMA)- and poly(vinylidene flouride) (PVdF)-based gel electrolytes, which have been applied for secondary lithium batteries [5-7,50,51,64], were also studied as electrolyte systems for EDLC with carbon electrodes [65-68],... 

Here, the polymeric species are designed to interact with Li salts, leading to the necessary ionic separation for electrolyte systems, and therefore, the presence of hquid solvents can be avoided. In order to obtain dissolution of Li salts, the polymers have to contain ethers, ester or other polar groups. Indeed, the most important polymeric electrol) es of this kind are based on polyethylene oxide and its derivatives [36 ]. These polymers have the reactivity of ethers towards Li and Uthiated carbon surfaces, which is much lower as compared with that of alkyl carbonates. However, since battery systems with solid-state electrolyte matrices are usually operated at elevated temperatures (>60 °C), it is obvious that there are surface reactions between the polyethers and the Uthiated carbons which form of surface films. We should also mention problems of hmited electrochemical windows when using solvent-free polymeric electrolytes, since the oxidation potentials of polyethers are similar to those of ethers which are usually in the 4-5 V range (v5. 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

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