The performance of solid polymer electrolytes is characterized by lower ionic conductivity than conventional liquid electrolytes but provides advantages in terms of operational safety. A quasi-solid polymer electrolyte (QSPE) based on a new plasticizer 4,7,10,13-tetraoxahexadecane-1,16-dinitrile (bCN-PEG4) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) incorporated into a polyacrylates matrix was successfully prepared via UV-induced copolymerization. The matrix consists of units of trimethylolpropane ethoxylate triacrylate (ETPTA), poly(ethylene glycol) diacrylate (PEGDA), and the monoacrylate poly(ethylene glycol) methyl ether acrylate (mPEGa). The QSPE containing 55 wt% bCN-PEG4 exhibits highly uniform morphology, thermal stability > 200 °C, ionic conductivity of 1.8 × 10−4 S cm−1 at 30 °C, and 1.3 × 10−3 S cm−1 at 80 °C, coupled with very high electrochemical stability (> 5 V vs. Li/Li+) and a low glass transition temperature (− 55.7 °C). A cycling experiment in a Li/QPSE/Li cell setup demonstrated the compatibility toward lithium metal additionally. The bCN-PEG4 offers an overall satisfying performance as a plasticizer in a poly(ethylene oxide)-based solid polymer electrolyte. The new QSPE is an alternative to dinitrile-based (e.g., succinonitrile) or glycol ether-based (e.g., tetraglyme) plasticizers with application potential in high-voltage lithium-ion batteries.
Graphical abstract
Diphenyliodonium ions (Ph2I+) form donor-acceptor ion pairs with suitable cyanometallates such as [Mo(CN)8]4-, [W(CN)8]4-, [Ru(CN)6]4- and [Os(CN)6]4-. Such ion pairs are characterized by new spectroscopic transitions due to second-sphere interactions between donor ([M(CN)x]4-, x=6, 8) and acceptor (Ph2I+) ions. Photochemical excitation of these ion-pair charge-transfer (IPCT) states leads to efficient electron transfer reactions that yield short-lived diphenyliodyl radicals (Ph2I*) and oxidized cyanometallates ([M(CN)x]3-). Diphenyliodyl radicals decay to iodobenzene and phenyl radicals. This very convenient source for generating phenyl radicals was applied to the photoinduced chain oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones, respectively. However, unexpected side reactions led to undesired chain-terminating reactions. Adduct formation of diphenyliodonium ions with alpha-hydroxyalkyl radicals was verified by pulse radiolysis studies. These relatively longlived adducts give rise to chain-terminating reactions because of interactions with [M(CN)x]4- complexes that lead to oxidized cyanometallates [M(CN)x]3- upon regeneration of the starting alcohols.
The reaction of N, N-diaryl-substituted formamides with oxalyl chloride gives rise, instead to the formation of the expected salt-like formamide chlorides, to the formation of corresponding non-ionic N-dichloromethyl-substituted diarylamines.
Other than triarylamines, which are protonated by strong acids both at their N-atom and aromatic rings, pyrrole and its Nsubstituted derivatives were exclusively protonated at the carbon atoms of their heteroaromatic rings. Whereas with the strong trifluoromethane sulfonic acid (TFS) stable pyrrolium salts were obtained, with the weaker trifluoroacetic acid (TFA) oligomers are formed. E.g., from the N-(tert-butyl)pyrrole a dimeric compound could be unambiguously identified and structural characterised by means of 1 H NMR measurements. Treatment of N-aryl substituted pyrroles with deuterated TFS revealed an H/D exchange not only at the pyrrole rings but also at their aryl moieties even.
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