Lithium polymer electrolytes

Fig. 11.14 Lithium polymer electrolyte cell configuration (Linford, 1991).

Lithium polymer electrolytes formed by dissolving a lithium salt LiX (where X is preferably a large soft anion) in poly(ethylene oxide) PEO can find useful application as separators in lithium rechargeable polymer batteries.Thin films must be used due to the relatively high ionic resistivity of these polymers. For example, the lithium-ion conductivity of PEO—Li salt complexes at 100 °C is still only about Viooth the conductivity of a typical aqueous solution. 

A practical use of a microelectrode The advantages of microelectrode techniques are especially pronounced for systems with limited conductivity (e.g., polymer electrolytes), which are popular candidates for state-of-the-art lithium ion batteries, normally with room-temperature conductivities K - 10-4 S/cm. (a) A researcher is evaluating a newly synthesized lithium polymer electrolyte. He uses a two-electrode cell in which an electrolyte disk of 0.1 cm X 1.0 cm is... 

L1XV2O5 is a non-stoichiometric compound (x 1) and acts as a Li atom store. When a small potential is applied across the cell, Li ions migrate from the lithium polymer electrolyte into the WO3 layer forming a tungsten bronze (see equation 22.42 and discussion). Its formation results in a colour change from colourless to blue. 

Macklin, W. J., and Neat, R. J. (1992). Performance of titanium dioxide-based cathodes in a lithium polymer electrolyte cell. Solid State Ionics, 53, pp. 694-700. 

Historically, the first types of lithium polymer electrolytes to be considered for battery applications were those formed by blending high molecular weight poly(ethylene oxide) (PEO), with a lithium salt LiX, where X is preferably a large anion [9-12], Various books and extensive review articles have been published on these polymer electrolytes [5, 13-16] and thus only their essential properties will be briefly recalled. 

Fauteux, D Massuco, A., Malin, M., Busen, M., and Shi, J., Lithium polymer electrolyte rechargeable battery, Electrochim. Acta, 40, 2184-2190 (1995). 

This lithium electrode/electrolyte interfacial problem can be circumvented by replacing liquid organic electrolyte with a solid state, solvent free lithium polymer electrolyte (Scrosati, 1993). 

One of the major problems of lithium polymer electrolyte systems is the development of high interfacial resistance at the lithium/polymer electrolyte interphase. This resistance grows with time and could be as high as 10 kO cm. This resistance layer is due to the reactions of lithium with water, other impurities, and the salt anions. Similar to nonaqueous electrolytes, the solid electrolyte interphase (SET) also exists in the lithium/polymer electrolyte systems. In this case, the solid electrolyte interface (SEI) consists of the inorganic reduction products of the polymer electrolyte and its impurities. 

Lampe-Onnerud C, Thomas JO, Hardgrave M, Yde-Andersen S (1995) The Performance of single phase VgOis in the lithium/polymer electrolyte battery. J Electrochem Soc 142 3648-3651... 

E. Peled, D. Golodnitsky,G. Ardeland V. Eshkenazy, These model—Application to lithium-polymer electrolyte batteries, EJectrochim. Acta 40,1995,2197-2204. 

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