Electric vehicles, conductive polymers

PEM Proton-exchange-membrane fuel cell (Polymer-electrolyte-membrane fuel cell) Proton- conducting polymer membrane (e.g., Nafion ) H+ (proton) 50-80 mW (Laptop) 50 kW (Ballard) modular up to 200 kW 25-=45% Immediate Road vehicles, stationary electricity generation, heat and electricity co-generation, submarines, space travel... 

More recently, solid state batteries with lithium conducting polymer electrolytes have been extensively studied. The development has focused on secondary batteries for an electric vehicle, because lithium polymer batteries have a theoretical energy density that approaches 800 W h kg ... 

Fig. 13.48. Conceptual diagram of the discharge process of a lithium cell that includes an organosulfur-based cathode. (Reprinted from J. M. Pope, T. Sotomura, and N. Oyama, Characterization and Performance of Organosulfur Cathodes for Secondary Lithium Cells Composites of Organosulfur, Conducting Polymer, and Copper Ion, in Batteries for Portable Applications and Electric Vehicles, C. F. Holmes and A. R. Landgrebe, eds., Electrochemical Society Proc. PV97-18, pp. 116-123, Fig. 1, 1977. Reprinted by permission of The Electrochemical Society, Inc.)...

Because the conductivity of polymer electrolytes is generally low, thin batteries are assembled (50-200 pm) with electrolyte thickness ranging from 20 to 50 pm. Conventional polymer electrolytes based on PEO and lithium salts, owing to their high crystallinity, reach useful conductivity values only at temperatures above 60 °C, i.e., above the melting temperature of the crystalline phase. If the low conductivity at room temperature prevents their application for consumer electronics, this does not represent an obstacle for electric vehicles, for which an operating temperature higher than that of the transition in the amorphous phase is expected. 

Supercapacitors containing electronically conducting polymer electrodes are of great interest, in particular for hybrid and electric vehicles due to their potential in the storage of large amounts of energy in a small volume. The largest hurdles towards marketable products are material development, production scale up and quality control. 

A solid polymer electrolyte may be defined as electrically conducting solution of a salt in a polymer. Solid polymer electrolytes are popular and practical applications in portable telecommunication devices, computers, and hybrid electric vehicles and for the possibility of using them in compact, lightweight, high-energy-density rechargeable lithium batteries. 

Crosslinked sulfonated PI types have been developed for use as cation exchange membranes. The sulfonated Pis have excellent proton conductivity and a low cost of preparation. These membranes can be used as polymer electrolyte membranes in hydrogen or a direct methanol fuel cell for electric vehicles and portable electric power sources [99]. 

There has been growing interest in the field of supercapacitors due to their possible applications in medical devices, electrical vehicles, memory protection of computer electronics, and cellular communication devices. Their specific energies are generally greater than those of electrolytic capacitors and their specific power levels are higher than those of batteries. Supercapacitors can be divided into redox supercapacitors and electrical double layer capacitors (EDLCs). The former uses electroactive materials such as insertion-type compounds or conducting polymers as the electrode, while the latter uses carbon or other similar materials as the blocking electrode. 

The ionic conductivity of most solid polymer electrolytes is significantly lower than that of the liquid electrolytes. Cells must he designed with thin electrodes and cell components to minimize the internal cell resistance. The total thickness of a cell assembly is as low as 200 fim or thinner. An alternative is to operate at higher temperatures where the conductivity is higher. While this may he acceptahle for electric-vehicle and stand-by batteries, it will not be acceptable for many portable consumer applications. Newer polymer electrolytes are being developed using plasticizers or gel-type polymers. These methods increase the conductivity of the polymers, but since they contain organic solvents, they will be more reactive with the lithium anode. 

Avestor spent hundreds of millions of dollars to develop a lithium metal polymer battery, but the company went out of business. The battery used a low-voltage LiV30g positive to stabilize the polymer electrolyte, which consisted of a PE oxide polyether copolymer and hthium perfluorosulfonimide (Li(CF3S0CNS02CF3)). The battery was heated above 40 °C in order to achieve a conductivity of 10 S cm . The battery proved ineffective for use in electric vehicles, but showed some promise in telecommunications applications where cycling was limited. However, even the telecommunications apphcation did not work out. 

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