Examples of Lithium Alloy Systems

Examples of Lithium Alloy Systems 415 Table 14.3 Data on chemical diffusion in lithium alloy phases. 

The small size of lithium frequently confers special properties on its compounds and for this reason the element is sometimes termed anomalous . For example, it is miscible with Na only above 380° and is immiscible with molten K, Rb and Cs, whereas all other pairs of alkali metals are miscible with each other in all proportions. (The ternary alloy containing 12% Na, 47% K and 41% Cs has the lowest known mp, —78°C, of any metallic system.) Li shows many similarities to Mg. This so-called diagonal relationship stems from the similarity in ionic size of the two elements / (Li ) 76pm, / (Mg ) 72pm, compared with / (Na ) 102pm. Thus, as first noted by Arfvedson in establishing lithium as a new element, LiOH and LiiCOs are much less soluble than the corresponding... 

Polyaniline is frequently used in r.b.s with lithium negative electrodes. However, in the course of the development of a commercialized system (Seiko/Bridgestone), there have only been a few examples with true lithium-metal negative electrodes, but many for the more practical LiAl alloy electrodes. The redox processes of RANI are basically the same in aqueous electrolytes and in Li -containing organic solutions. 

To overcome this problem without using a metallic lithium layer, an active-active concept has been proposed. It also strove to avoid the presence of inactive solid phases that considerably reduce the overall anode capacity. Such an example is the multiphase system - Sn/SnSb - proposed by Besenhard s research group. It was revealed that this alloy reacts with LF according to the following scheme ... 

Although the term mass transfer as used in liquid metal technology normally refers to the phenomenon described above, a second type of mass transfer has been observed in isothermal liquid metal systems due to the presence of more than one container metal or alloy. For example, nickel will transfer to and deposit on molybdenum in sodium at 1800°F and will dissolve from type 304 stainless steel to precipitate on iron in lithium at 1800°F. The possibility of such dissimilar metal mass transfer must be considered every time an additional material is proposed for use in an engineering system as a valve seat, impeller bearing, and so forth. Not much data are available on usable material combinations, and the tendency is to design for a single container alloy whenever possible. 

Alloys of zinc, aluminum, and lithium have also been considered for special-purpose seawater batteries. Zinc can be used as the anode in low-current, low-power long-Ufe batteries. It has the advantage of not sludging, but the disadvantage of being a low-power-density system. Zmc/sUver chloride seawater batteries have been used as the power source for repeaters for submarine telephone cables (for example, 5 mA at 0.9-1.1 V for 1 year of operation). 

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