Lithium-air cells

Fig. 6.8 Photograph of a lithium-air cell, left the air cathode, right (courtesy of Yardney Technical Products, Inc.)...

With regard to France, in addition to institutional laboratories, EDF has coordinated a National Research Agency project - Z/O. Faisabilite d um batterie Lithium-air (Feasibility of a Lithium-air battery) (project director Ph. Stevens) devoted to the development of a complete aqueous-electrolyte lithium-air cell with all its components. The metal lithium is protected by a first surface layer of LIPON (lithium phosphoms oxynitride) and then by a ceramic membrane of LISICON (Li Super Ionic Conductor LiM2(P04)3 with M=Ti, Zr, Ge, Hf). The declared performances are 100 mAh/cm (sufficient to deliver 500 Wh/kg) for current strength of 2 mA/cm at 30 C, and up to 6 mA/cm at 60°C. The lifetime is 38 cycles with a current strength of 10 mAh/cm. ... 

We shall also touch upon the increasing rapid evolution of the technologies, particularly as regards lithium batteries, for which the avenues of research are extremely varied. The substance couples used in tomorrow s world will probably be different to those widely used today. These advances will be discussed in Chapter 7 for lithium-ion elements. Then we shall go on to describe the promising lithium-sulfur batteries (Chapter 9) and lithium-air cells (Chapter 10). 

The theoretical open-circuit voltage of the lithium/air cell is 3.35 V, but in practice, this value is not achieved because the lithium anode and the air cathode exhibit mixed potentials. Figure 38.45 shows that the actual open-circuit voltage is near 2.85 V. It is also evident that the major voltage loss is at the air cathode and that the cell cannot be discharged efficiently at voltages much above 2.2 V unless a substantial reduction in cathode polarization is achieved. 

FIGURE 38.45 Typical individual electrode and cell polarization curve of lithium/air cell. 

Imanishi and co-workers of Mie University, Japan, [68] have examined the charge discharge performance of an aqueous lithium-air cell with 0-LATP and saturated LiOH with 10 M LiCl aqueous solution with a third electrode for the OER, as proposed by Stevens [50]. Rechargeable hthium-air batteries require a bi-functional air electrode for the oxygen reduction reaction (ORR) and the OER. When an air electrode is used for the OER, it is exposed to a highly corrosive potential. Arai et al. [69] examined a high surface area carbon black (Ketjen black KB) electrode for the ORR and OER in aqueous 8 M KOH and observed electrode deterioration during the OER, which they claimed was due to a loss of the electrochemicaUy active surface... 

Fig. 14 a Schematic diagram of the Gakushuin aqueous lithium-air cell with LLTO and b cycling performance at 1 mA (0.05 mA cm ) and room temperature (from Ref [67])... 

FIGURE 1.5 A lithium-air cell s discharge is depicted here in pure oxygen gas using a manganese oxide catalyst. The cell could provide additional energy past tlie 1.5 V cutoff. 

FIGURE 1.6 Different specific capacities are determined by the catalysts present in the air cathodes. These were lithium-air cells run in oxygen gas with variables constant except the catalyst present. 

Figure 22.13 Voltage profile as a function of capacity for a lithium-air cell. The specific energy of the complete cell (including the package) was 362 Wh kg . (Reproduced from Zhang et at. [21].)...

The oxygen reduction process involves a sequence of intermediates steps, including a radical anion 62" that readily decomposes the organic carbonate solutions used as electrolytes in the early development of the lithium-air cells. 

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