Lithium cell

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

Advanced Systems. Apphcations for the coin and button secondary lithium cells is limited. However, researchers are working to develop practical "AA"-sized and larger cells. Several systems have reached advanced stages of development. 

Efforts to commercialize larger versions of rechargeable lithium cells have been fmstrated by concerns over product safety. MoH Energy Ltd. briefly introduced "AA" Li—M0S2 cells for OEM use in laptop computers and cellular phones. However, safety issues resulted in a product recall and a halt to commercialization of this product. 

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. 

It should be noted that the rechargeable cells discussed later have the same construction and differ only in separator type, electrode composition and cathode / anode balance. For comparison, Fig. 3 shows the design of an AA-size lithium cell. The construction with a spirally rolled electrode increases the power output. 

There are distinct differences in the electrochemical behavior of lithium cells constructed with /1-Mn02 electrodes prepared by acid treatment and those containing Li[Mn2]04 electrodes [120].Cells with A-Mn02 electrodes show an essentially featureless voltage profile at 4V on the initial discharge on subsequent cycling, the cells show a profile more consistent with that expected from an Li[Mn2]04 electrode. 

Although LiJMn2]04 appears to have the ideal structure for an insertion electrode in 4V lithium cells, the cells lose capacity slowly when operated over the high voltage range. Several reasons have... 

The figure of merit (FOM) for lithium cycling efficiency [24] also is often used to evaluate the cyclability of a lithium cell. The FOM is defined as the number of cycles completed by one atom of lithium before it becomes electrochemically inactive. Equation (2) is derived from the above definition. 

Another influence that electrolyte materials have on the cycle life of a practical lithium cell results from the evolution of gas as a result of solvent reduction by lithium. For example, EC and PC give rise to [53] evolution of ethylene and propylene gas, respectively. In a practical sealed-structure cell, the existence of gas causes irregular lithium deposition. This is because the gas acts as an electronic insulator and lithium is not deposited on an anode surface where gas has been absorbed. As a result, the lithium cycling efficiency is reduced and shunting occurs. 

Whereas there had been a significant amount of work on the properties of lithium alloys in the research community for a number of years, this alternative did not receive much attention in the commercial world until about 1990, when Sony began producing batteries with lithium-carbon negative electrodes. Since then, there has been a large amount of work on the preparation, structure, and properties of various carbons in lithium cells. 

The composition, structure, and formation process of the SEI on metallic lithium depend on the nature of the electrolyte. The variety of possible electrolyte components makes this topic very complex it is reviewed by Peled, Golodnitsky, and Penciner in Chapter III, Sec.6 of this handbook. The types and properties of liquid nonaqueous electrolytes, that are commonly used in lithium cells are reviewed by Barthel and Gores in Chapter III, Sec.7. 

Figure 2. Redox potentials for lithium insertion into/removal from several anode materials for lithium cells.

The first electrolytes used for primary lithium cells [47, 48] were based on lith-... 

Some problems associated with the use of these anions have stimulated the search for substitutes [6], especially for rechargeable lithium cells. 

The electrolyte used in lithium cells, i.e., for aU hthium couples, must be completely anhydrous (< 20 ppm H2O) alkali metals in general are compatible with neutral salt solutions in aprotic solvents or neutral molten salts or solid ion-conductors. 

Further, tungsten oxysulfide films, WOyS, have shown promising behavior as positive electrodes in microbatteries, unlike WS2 that is not suitable as cathode in lithium cells. Using amorphous thin films of WO1.05S2 and WO1.35S2.2 in the cell Li/LiAsFe, 1 M ethyl-methyl sulfone (EMS)/W03,Sz, Martin-Litas et al. [80] obtained current densities up to 37 xA cm between 1.6 and 3 V. In these cathode materials, 0.6 and 0.8 lithium per formula unit, respectively, could be intercalated and de-intercalated reversibly. 

Kanehori K, Matsumoto K, Miyauchi K, Kudo T (1983) Thin film solid electrolyte and its application to secondary Lithium cell. Solid State Ionics 9-10 1445-1448 Py MA, Haering RR (1983) Structural destabilization induced by lithium intercalation in M0S2 and related compounds. Can J Phys 61 76-84... 

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