Poly /lithium salt systems

A second class of important electrolytes for rechargeable lithium batteries are soHd electrolytes. Of particular importance is the class known as soHd polymer electrolytes (SPEs). SPEs are polymers capable of forming complexes with lithium salts to yield ionic conductivity. The best known of the SPEs are the lithium salt complexes of poly(ethylene oxide) [25322-68-3] (PEO), —(CH2CH20) —, and poly(propylene oxide) [25322-69-4] (PPO) (11—13). Whereas a number of experimental battery systems have been constmcted using PEO and PPO electrolytes, these systems have not exhibited suitable conductivities at or near room temperature. Advances in the 1980s included a new class of SPE based on polyphosphazene complexes suggesting that room temperature SPE batteries may be achievable (14,15). 

The effect of penultimate units on the rate constants of anionic propagation is observed also in other systems. For example, the addition of styrene to the lithium salt of 1-phenyl-n-hexyl anion is 4 times faster than to polystyryl lithium 51). Similarly, the addition of monomer to the lithium salt of 1,1-diphenyl-n-hexyl lithium is faster than the addition to 1,1,3-triphenyl-n-octyl lithium or 2-poly-sty ry 1-1,1-diphenyl ethyl lithium, the latter two salts having comparable reactivities52 . See also Ref.53)... 

If a mercury cathode is expected to be necessary, the aprotic solvent-alkali-metal salt system appears to be inconvenient since many compounds are cathodically cleaved, reduced, or/and deprotected at potentials beyond that of alkali-metal amalgam formation. nevertheless, in certain cases the use of lithium salts as an electrolyte possessing strong electrophilic properties appears necessary in order to avoid the possibility of a Hofmann degradation of the tetraalkylammonium ion by electrogenerated bases. Under such experimental conditions, the cathodic synthesis of some aza and aza-oxa ligands [31] has been successfully achieved from the corresponding and readily obtained poly-... 

Scheme 9.19). The enantioselectivity during the polymerisation was estimated to be over 80% enantiomeric excess. During the course of their study on the stereocontrolled synthesis of poly(2,3-dihydroxynaphthalene) by AOCP, Habaue found that the novel system, VO(stearate)2-D-tartaric acid lithium salt, showed a catalytic activity with much higher stereocontrol than that of the above-mentioned vanadyl sulfate-Phbox catalyst. However, Habaue s catalytic system exhibited no activity for the oxidative coupling of other 2-naphthol derivatives. 

Systems based on the simple combination of high molecular weight polymer hosts (e.g. poly(ethylene oxide), PEO) and lithium salts (LiX), which may be classified as first generation polymer ionic membranes ... 

The concept of SPE dates back to 70s, when Armand firstly proposed a new ion conductor based on a lithium salt properly complexed by a polar and aprotic polymer matrix without the use of any liquid component (additives or liquid electrolytes) [65]. At the beginnings, the research on SPEs was exclusively focused on poly(ethyleneoxide) (PEO) as the complexing polymer [66]. Ever since, a lot of polymer/salt systems were deeply investigated, such as those based on PMMA, PAN, PVDF [66-69]. In principle, SPEs must satisfy some basic requirements (i) ionic conductivity higher than 10 " S/cm at room temperature, (ii) good thermal, chemical and mechanical stability, (iii) lithium transport number close to the unity, and (iv) compatibility with the electrodes and consequently wide electrochemical windows [67]. 

Ionic conductivity of alkali metal salt complexes of poly(ethylene oxide) was noted in studies three decades ago by Wright [217, 218]. The interest in this observation has surged, due to the commercial success of lithium ion batteries. Poly(ethylene oxide) plus lithium salts have been the preferred system for solid polyelectrolyte layers, although the commercial systems... 

Solid polymer electrolytes for lithium batteries applications are commonly prepared by dissolving a lithium salt in poly(ethylene oxide) (PEO)-based materials. Chiappone et al. investigated these systems by a Li and NMR study yielding local dynamics and mass transport by temperature-dependent Ti and PFG-NMR diffusion measurements. 

These critical attributes are necessary if the materials are to be considered as practical replacements for their liquid counterparts. In addition, their properties, particularly conductivity and transport properties, should be sufficiently practical to stimulate their development when compared with other highly conducting solid electrolyte materials. Since 1978, when Michel Armand first introduced polyether-alkali-metal salt complexes to the solid state community as potential materials for electrochemical devices, there has been an enormous amount of research carried out on these (particularly high molecular weight poly(ethylene oxide)-lithium salt) systems, to obtain... 

Water-soluble derivatives of polythiophene have been made allowing counterions bound to the polymer backbone to self-dope with the protons (e.g., lithium and sodium ions) injecting electrons into the pi-system. Thus, combinations of sodium salts and proton salts (e.g., prepared from poly-3-(2-ethanesulfonate)thiophene) have been prepared that are both water-soluble and conducting. 

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