Conductive polymers rechargeable batteries

Applications of conducting polymers include batteries (2), antistatic transparent films to protect sensitive microelectronic devices (2), antistatic fabrics (3), and sensors (4). Moreover, conducting polymers that change color when oxidized or reduced are the basis of smart windows (3). Blends of electrically conducting polymers have also been developed for applications such as rechargeable batteries (5), chemical and optical sensors (6), nonlinear optical devices (7), and light-emitting diodes (8). 

By the time the next overview of electrical properties of polymers was published (Blythe 1979), besides a detailed treatment of dielectric properties it included a chapter on conduction, both ionic and electronic. To take ionic conduction first, ion-exchange membranes as separation tools for electrolytes go back a long way historically, to the beginning of the twentieth century a polymeric membrane semipermeable to ions was first used in 1950 for the desalination of water (Jusa and McRae 1950). This kind of membrane is surveyed in detail by Strathmann (1994). Much more recently, highly developed polymeric membranes began to be used as electrolytes for experimental rechargeable batteries and, with particular success, for fuel cells. This important use is further discussed in Chapter 11. 

The enormous efforts put into the basic research and development of conducting polymers are naturally related to hopes of feasible technical apphcations The starting point of this development was the discovery that PA can fimction as an active electrode in a rechargeable polymer battery. Since then, the prospects of technical application have grown considerably Apart from the battery electrode, conducting polymers are discussed as potential electrochromic displays... 

There are difficulties in analysing conductive polymers, and information on the relationship between structure and properties somewhat difficult to obtain. These materials have already found a variety of uses, including flat panel displays, antistatic packaging and rechargeable batteries, and other applications are likely to emerge in the future. 

Polymer Batteries The discovery that doping of polyacetylene produced a highly conducting material was followed swiftly by the realization that this material was a rechargeable battery material which, optimistically, might lead to lightweight... 

The mechanisms and reasons of catalytic activity of polyaniline (PANI)-type conducting polymers toward oxygen reduction in acidic and saline solutions are investigated by electrochemical and quantum-chemical methods. The PANI/thermally expanded graphite compositions were developed for realization of fully functional air gas-diffusion electrodes. Principally new concept for creation of rechargeable metal-air batteries with such type of catalysts is proposed. The mockups of primary and rechargeable metal-air batteries with new type of polymer composite catalysts were developed and tested. 

Conducting polymers, polyaniline, catalytic activity, PANI/expanded graphite composites, metal-air batteries, primary rechargeable cells. 

Although conjugated polymers can be both n-doped and p-doped - and thus, in principle, be capable of behaving either as negative or as positive electrodes - the majority of applications have been confined to the p-doping, positive side. Conductive polymers have been proposed and tested in a variety of advanced electrochemical devices. Due to lack of space, we will confine our attention to the description of the most illustrative examples which are rechargeable lithium batteries and multi-chromic optical displays. 

Technically important electrochemical reactions of pyrrole and thiophene involve oxidation in non-nucleophilic solvents when the radical-cation intermediates react with the neutral molecule causing polymer growth [169, 191], Under controlled conditions polymer films can be grown on the anode surface from acetonitrile. Tliese films exhibit redox properties and in the oxidised, or cation doped state, are electrically conducting. They can form the positive pole of a rechargeable battery system. Pyrroles with N-substituents are also polymerizable to form coherent films [192], Films have been constructed to support electroactive transition metal centres adjacent to the electrode surface fomiing a modified electrode,... 

There is a large potential for conducting polymers as corrosion-inhibiting coatings. For instance, the corrosion protection ability of polyaniline is pH-dependent. At lower pH polyaniline-coated steel corrodes about 100 times more slowly than noncoated steel. By comparison, at a pH of about 7 the corrosion protection time is only twice for polyaniline-coated steel. Another area of application involves creation of solid state rechargeable batteries and electrochromic cells. Polyheterocycles have been cycled thousands of times with retention of over 50% of the electrochromic activity for some materials after 10,000 cycles. IR polarizers based on polyaniline have been shown to be as good as metal wire polarizers. 

As a conducting polymer, polyaniline has many electronics-related applications, such as rechargeable batteries (Tsutsumi et al. 1995), multilayer heterostructure light-emitting diode devices (Onoda Yoshino 1995), biosensors (Bartlett Whitaker 1987), elec-trochromic windows (Nguyen Dao 1989), and nonlinear optical materials (Papacostadi-nou Theophilou 1991). Polyaniline may be prepared from aniline by both electrochemi-... 

As important as batteries are to modern civilization, a number of inherent problems are associated with them. For example, the lead-storage battery present in all modern motor vehicles is very heavy (it contains one of the densest of common metals, lead) and it must be continually recharged, eventually wears out, and presents serious environmental problems during its manufacture and disposal. After the discovery of conductive polymers, many scientists hoped and dreamed that these materials could he used to make efficient, lightweight plastic batteries. 

Activity in the battery area using electronically conducting polymers has been intense (see Fig. 11.19). The possibilities (MacDiarmid, 1997) point to the provision of cheap (because of the relative cheapness of organic compounds) batteries, e.g., for massive use as a power source for bicycles. The counter-point is the limited stability and hence lifetime of such structures, and the availability of, e.g., rechargeable MnOj-Li cells, in which the (bismuth doped) Mn02 is also a relatively cheap material. 

In the case of ion conductive polymers, gel polymer electrolytes which consist of a polymer matrix, organic solvents and supporting electrolyte, were introduced as novel nonaqueous electrolyte systems in electrochemical applications, such as rechargeable batteries and electric double layer capacitors [3-5], Recently, considerable attention has been devoted to the application of gel poly-... 

---