Solid State Polymer Electrolytes

Gel and solid polymer electrolytes aim to combine the function of the electrolyte and separator into a single component to reduce the number of parts in an ES and increase the potential window through the higher stability offered by a polymer matrix. A gel electrolyte incorporates a liquid electrolyte into a microporous polymer matrix that holds in the liquid electrolyte through capillary forces, creating a solid polymer film. The chosen separator must be insoluble in the desired electrolyte and provide adequate ionic conductivity. Non-polar rigid polymers such as PTFE, PVA, PVdF, and cellulose acetate offer good ion conductivity when used as gel electrolytes [114]. Based on the data in Table 4.9, the ionic conductivity of EtMeIm+Bp4 is 14 mS.cm . Ionic conductivity of the same imidazolium salt used as a gel electrolyte in a PVdF matrix retains 5 mS.cm [115]. 

Modern electrolytes need increased stability and ion mobility to operate at high potential windows. Gel electrolytes allow incorporation of aqueous, organic, and ionic liquids, depending on the requirements of the ES. Separators are used in conjimction with the electrolyse to help provide structured channels and prevent short circuits between the electrodes. The presence of solid electrolyte layers results in a reduced need for robust encapsulation technologies. 

In order to combine the two structures, electrolyse is trapped within the polymer matrix during polymerization. The result is a solid, thin, flexible electrolyte. Gel electrolytes have clear manufacturing and assembly advantages because of their simplified forms and dual functionalities. However, the performance is a large factor in the ability of such ideas to proliferate. 

Gel polymers offer slightly lower conductance than liquid electrolytes, but they provide structural improvement that improves the efficiency of ion transport mechanisms and cycle life [116,117]. Polyvinyl acetate (PVA) has been shown to offer good results in trapping aqueous electrolytes [116,118,119]. 

Thickness dependence of capacitance per area for CNT films comparing liquid (1 M H2SO4) and gel (PVA/H3P04) electrolytes. (Source Kaempgen, M. et al. 2009. Journal the American Chemical Society, 9,1872-1876. With permission.) 

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The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

It is the purpose of this chapter to introduce photoinduced charge transfer phenomena in bulk heterojunction composites, i.e., blends of conjugated polymers and fullerenes. Phenomena found in other organic solar cells such as pristine fullerene cells [11,12], dye sensitised liquid electrolyte [13] or solid state polymer electrolyte cells [14], pure dye cells [15,16] or small molecule cells [17], mostly based on heterojunctions between phthalocyanines and perylenes [18] or other bilayer systems will not be discussed here, but in the corresponding chapters of this book. 

Battery electrodes for aqueous [306a-g], non-aqueous [306h-p], ambient molten salt [306q], and all-solid state polymer electrolyte batteries [306r-t]. As long as the redox chemistry of a polymer is reversible and both oxidized and reduced forms of the polymer are not soluble in a solvent with which a battery is to be constructed, it can be used as a battery electrode material. Numerous applications have been published for PPy, PTh, and other conducting polymers as well. 

FIGURE 2.81 Schematic diagrams of (a) dry solid-state polymer electrolyte (e.g., PEO/Li+), (b) gel polymer electrolyte, and (c) polyelectrolyte. (Zhong, C. et al. 2015. A review of electrolyte materials and compositions for electrochemical supercapacitors. Chemical Society Reviews 44 7484-7539. Reproduced by permission of The Royal Society of Chemistry.)... 

In the 1960s, the use of solid-state polymer electrolytes instead of the liquid electrolytes normally used in alkaline electrolysis led to the development of novel concepts for water electrolysis. The US company General Electric was the first to realize solid polymer electrolyte water electrolysis (SPE) with the aid of the solid polymer electrolyte membrane (Nafion ) developed by DuPont [16]. At the same time, ABB [17, 18] in Switzerland and Fuji Electric [19] in Japan also developed PEM electrolyzers with single electrode areas of up to 2500 cm. These... 

Solid polymer electrolytes made of polyethylene oxide (PEO) and polypropylene oxide (PPO) are considered because of their strong thermal conduction and electrochemical properties over a wide operating temperature range [114,115]. However, the low room temperature ionic conductivities exhibited by PEO and PPO solid state polymer electrolytes prevents successful application in ESs. When PEO was incorporated into a gel electrolyte to boost conductivity, the result indicated that PEO and PPO are actually found inferior compared to PVA and PVdF for gel electrolytes because the oxygen atoms in the polymer backbone limit ion mobility [115]. 

Generally, lead dioxide (Pb02) and platinum (Pt) electrodes are used as electrocatalysts for ozone generation [2-4]. The electrolytic cell consists of a porous anode, a porous cathode and a solid-state polymer electrolyte membrane instead of an electrolyte solution these are stacked, as shown schematically in Fig. 24.1(a). Pure water, or tap water without additives as an electrolyte, is directly supplied to the anode compartment, the electrolysis of water occurs, and the electrolyzed water containing dissolved ozone is directly drained. Electrolytic ozonizers based on this system have already become available on the market. 

For water electrolysis, the self-standing perforated diamond electrode was used as the anode, being set as shown in Fig. 24.1 (a). Platinum mesh (55 mesh, Nilaco Co., Japan) was used as the cathode. Nafion films (DuPont, USA) were used as the solid-state polymer electrolyte membrane to separate the anode and cathode compartments, to which the anode and cathode adhered firmly and uniformly. Ultrapure water (purified by a Milli-Q system, Millipore Japan, Ltd.) was continuously supplied into each compartment at a flow rate of 0.1 L min. The electrolysis was performed by the constant current method. The ozone concentration was checked with an ozone meter (03 2Z, Kasahara Chemical Instruments Co., Japan). 

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 most promising fuel cell for transportation purposes was initially developed in the 1960s and is called the proton-exchange membrane fuel cell (PEMFC). Compared with the PAFC, it has much greater power density state-of-the-art PEMFC stacks can produce in excess of 1 kWA. It is also potentially less expensive and, because it uses a thin solid polymer electrolyte sheet, it has relatively few sealing and corrosion issues and no problems associated tvith electrolyte dilution by the product water. 

F.R. Kalhammer, Polymer Electrolytes and the Electric Vehicle, Solid State Ionics 135, 315-323 (2000). 

Matsumoto M, Miyazaki H, Matsuhiro K, Kumashiro Y, Takaoka Y (1996) A dye sensitized Ti02 photoelectrochemical cell constructed with polymer solid electrolyte. Solid State Ionics 89 263-267... 

State-of-the-art thin film Li" cells comprise carbon-based anodes (non-graphitic or graphite), solid polymer electrolytes (such as those formed by solvent-free membranes, for example, polyethylene oxide, PEO, and a lithium salt like LiPFe or LiCFsSOs), and metal oxide based cathodes, in particular mixed or doped oxides... 

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