Solid electrolytes polymer gels

Stoddart and co-workers have developed molecular switch tunnel junctions [172] based on a [2]rotaxane, sandwiched between silicon and metallic electrodes. The rotaxane bears a cyclophane that shuttles along the molecular string toward the electrode and back again driven by an electrochemical translation. They used electrochemical measurements at various temperatures [173] to quantify the switching process of molecules not only in solution, but also in self-assembled monolayers and in a polymer electrolyte gel. Independent of the environment (solution, self-assembled monolayer or solid-state polymer gel), but also of the molecular structure - rotaxane or catenane - a single and generic switching mechanism is observed for all bistable molecules [173]. 

The electrolytes currently in use and under research include liquid electrolytes, all-solid electrolytes, and gel-type polymer electrolytes. 

Lithium secondary batteries can be classified into three types, a liquid type battery using liquid electrolytes, a gel type battery using gel electrolytes mixed with polymer and liquid, and a solid type battery using polymer electrolytes. The types of separators used in different types of secondary lithium batteries are shown in Table 1. The liquid lithium-ion cell uses microporous polyolefin separators while the gel polymer lithium-ion cells either use a PVdF separator (e.g. PLION cells) or PVdF coated microporous polyolefin separators. The PLION cells use PVdF loaded with silica and plasticizer as separator. The microporous structure is formed by removing the plasticizer and then filling with liquid electrolyte. They are also characterized as plasticized electrolyte. In solid polymer lithium-ion cells, the solid electrolyte acts as both electrolyte and separator. 

Development efforts are under way to displace the use of microporous membranes as battery separators and instead use gel electrolytes or polymer electrolytes. Polymer electrolytes, in particular, promise enhanced safety by eliminating organic volatile solvents. The next two sections are devoted to solid polymer and gel polymer type lithium-ion cells with focus on their separator/electrolyte requirements. 

Wang P, Zakeeruddin SM, Moser JE, Nazeeruddin MK, Sekiguchi T, Gratzel M (2003) A stable-quasi-solid state dye-sensitized solar cell with amphiphilic ruthenium sensitizer and polymer gel electrolyte. Nature Mater 2 402-406... 

The EDLCs, which use all-solid-state ion-conducting polymer [e.g., polyethylene oxide)/LiC104] or polymer gel electrolyte, have also been developed [3],... 

There are two classes of materials which may be used as electrolytes in all-solid-state cells polymer electrolytes, materials in which metal salts are dissolved in high molar mass coordinating macromolecules or are incorporated in a polymer gel, and ceramic crystalline or vitreous phases which have an electrical conductance wholly due to ionic motion within a lattice structure. The former were described in Chapter 7 in this... 

A variety of dimensionally stable solid electrolytes consisting of a mixture of organic plasticizers such as EC, PC etc., along with structurally stable polymers such as poly( acrylonitrile) (PAN) or poly( vinyl sulfone) (PVS), or polyvinyl pyrrolidine (PVP) or polyvinyl chloride (PVC) and several lithium salts have been tested and found to have excellent ionic conductivities at ambient temperatures [155-156]. In these gel type electrolytes the primary role of the polymers PAN, PVS, PVP or PVC is to immobilize the lithium salt solvates of the organic plasticizer liquids. However, with polymers such as PAN a coordination interaction with Li+ is also quite likely. 

Small LL interfaces have been used by Girault and co-workers (33-38) and by Senda et al. (39, 40). We have used a small hole formed in a thin glass wall (41-43). Figure 16 shows the voltammetric response of lauryl sulfate anion transport between water and nitrobenzene. Recent analytical applications of these microinterfaces have resulted in construction of gel-solidified probes. The advantage of such a modification is ease of handling (44-47). The immobilization can be extended further to studies of frozen interfaces, or even to solid electrolytes. Significantly, ITIES theory also applies to interfaces that are encountered in ion-doped, conductive, polymer-coated electrodes. 

Alkaline polymer gel electrolytes are commonly used in all- solid-state alkaline rechargeable batteries and supercapacitors. The typically used electrode materials for supercapacitors... 

Lu, W., Henry, K., Turchi, C., Pellegrino, J., 2008. Incorporating ionic liquid electrolytes into polymer gels for solid-state ultracapacitors. J. Electrochem. Soc. 155, A361-A367. 

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