Lithium polymer cells

Fig. 1. Configuration for a soHd polymer electrolyte rechargeable lithium cell where the total thickness is 100 pm.

Lithium-Ion Cells. Lithium-ion cells and the newer alternative, lithium-ion-polymer, can usually run much longer on a charge than comparable-size Nicad and nickel-metal hydride batteries. Usually is the keyword here since it depends on the battery s application. If the product using the battery requires low levels of sustained current, the lithium battery will perform very well however, for high-power technology, lithium cells do not perform as well as Nicad or nickel-metal hydride batteries. 

Lithium oxide(s), 15 134, 141 Lithium perchlorate, 3 417 15 141-142 dessicant, 3 360 in lithium cells, 3 459 Lithium peroxide, 15 142 18 393 Lithium phosphate, 15 142 Lithium-polymer cells, 3 551 in development, 3 43 It Lithium primary cells, 3 459-466 Lithium production, 9 640 Lithium products, sales of, 15 121 Lithium salts, 15 135-136, 142 Lithium secondary cells, 3 549-551 ambient temperature, 3 541-549 economic aspects, 3 551-552 high temperature, 3 549-551 Lithium silicate glass-ceramics, 12 631-632... 

Redox shuttles based on aromatic species were also tested. Halpert et al. reported the use of tetracyano-ethylene and tetramethylphenylenediamine as shuttle additives to prevent overcharge in TiS2-based lithium cells and stated that the concept of these built-in overcharge prevention mechanisms was feasible. Richardson and Ross investigated a series of substituted aromatic or heterocyclic compounds as redox shuttle additives (Table 11) for polymer electrolytes that operated on a Li2Mn40g cathode at elevated temperatures (85 The redox potentials of these... 

In addition to the criticisms from Anderman, a further challenge to the application of SPEs comes from their interfacial contact with the electrode materials, which presents a far more severe problem to the ion transport than the bulk ion conduction does. In liquid electrolytes, the electrodes are well wetted and soaked, so that the electrode/electrolyte interface is well extended into the porosity structure of the electrode hence, the ion path is little affected by the tortuosity of the electrode materials. However, the solid nature of the polymer would make it impossible to fill these voids with SPEs that would have been accessible to the liquid electrolytes, even if the polymer film is cast on the electrode surface from a solution. Hence, the actual area of the interface could be close to the geometric area of the electrode, that is, only a fraction of the actual surface area. The high interfacial impedance frequently encountered in the electrochemical characterization of SPEs should originate at least partially from this reduced surface contact between electrode and electrolyte. Since the porous structure is present in both electrodes in a lithium ion cell, the effect of interfacial impedances associated with SPEs would become more pronounced as compared with the case of lithium cells in which only the cathode material is porous. 

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.)...

The necessary porosity for thicker layers was introduced by appropriate current densities [321-323], by co-deposition of composites with carbon black [28, 324] (cf. Fig. 27), by electrodeposition into carbon felt [28], and by fabrication of pellets from chemically synthesized PPy powders with added carbon black [325]. Practical capacities of 90-100 Ah/kg could be achieved in this way even for thicker layers. Self-discharge of PPy was low, as mentioned. However, in lithium cells with solid polymer electrolytes (PEO), high values were reported also [326]. This was attributed to reduction products at the negative electrode to yield a shuttle transport to the positive electrode. The kinetics of the doping/undoping process based on Eq. (59) is normally fast, but complications due to the combined insertion/release of both ions [327-330] or the presence of a large and a small anion [331] may arise. Techniques such as QMB/CV(Quartz Micro Balance/Cyclic Voltammetry) [331] or resistometry [332] have been employed to elucidate the various mechanisms. 

S. Panero, P. Prosperi and B. Scrosati, Characteristics of electrochemically synthesized polymer electrodes in lithium cell. VI. Effects of synthesis conditions on the performance... 

Another lithium-ion polymer cell recently tested as a laboratory-scale prototype [88] has the configuration KCg/LiC104-EC-PC-PAN/LiMn204. 

Peramunage and Abraham have recently reported an advanced lithium-ion polymer cell [106, 107]. In this case, a material of the Li [Lij/3Tij/3]04 family [108, 109], e.g., the Li4Ti50i2, intercalation compound, has been used as an anode. The lithium intercalation-deintercalation process in this compound is shown in Equation 7.14. 

Panero, S., et al. 1992. Properties of electrochemically synthesized polymer electrodes. Part VII Kinetics of poly-3-methylthiophene in lithium cells. J Appl Electrochem 22 189. 

Other recent developments include the incorporation of a fire retardant, which retards the combustion of the solvent, and a new additive to improve the wetting of the separator. It is difficult to use these additives in the gel-type electrolytes employed in lithium-ion polymer cells. This may be one reason for the lower market share experienced by lithium-ion polymer cells. 

Most lithium cells available in the market utilize nonaqueous electrolyte solutions, where lithium salts are dissolved in organic solvents. The gelled electrolytes used in lithium-ion polymer batteries are also regarded as an organic electrolyte immobilized with a high molecular weight polymer. 

Scrosati, B., et al. 1987. Kinetics of semiconducting polymer electrodes in lithium cells. / Power Sources 19 (1) 27. 

Also launched in late 2010, the Chevrolet Volt uses a 16 kWh battery based on LG Chem s lithium-ion polymer cells. The Volt is an EREV, which means that the vehicle has both a 1.4-1 ICE and a 16 kWh Li-ion battery pack. The ICE acts as a generator operating the motors once the battery charge has dropped to a minimum level determined by the system controller. This combination of Li-ion battery and ICE allows the vehicle a total range comparable to a standard ICE. 

Ion exchange membranes work in the temperature range of conventional fluid electrolytes, e.g., in electric cars from 0 °C to -1-80 °C and perhaps in the future up to -1-130 °C. This must not be confused with solid electrolytes, which are used in solid oxide fuel cells (SOFC) as oxygen ion conductors at up to 1,000 °C. Lithium ionconducting polymers are important components of high-power lithium ion secondary batteries, but that is not object of this entry. 

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