Diffusion lithium alloys

It is thus much better to measure the chemical diffusion coefficient directly. Descriptions of electrochemical methods for doing this, as well as the relevant theoretical background, can be found in the literature [33, 34]. Available data on the chemical diffusion coefficient in a number of lithium alloys are included in Table 3. 

Table 3. Data on chemical diffusion in lithium alloy phases.

Annually, sessions are held on advanced aluminum alloys as part of the conference on Advanced Aerospace MaterialsAProcesses and Exposition." Topics discussed have included rapid-solidilication alloys, very low density alloys, laminates, new alloying elements, such as lithium, and such processes as diffusion bonding and means to improve fracture toughness and reduce fatigue and corrosion. 

There are reports that the surface chemistry of Li alloys is indeed largely modified, compared with Li metal electrodes [303], It appears that they are less reactive with solution species, as is expected. The morphology of Li deposition on Li alloys may also be largely modified and smooth, compared with Li deposition on Li substrates [302,304], A critical point in the use of Li alloys as battery anodes is the lithium diffusion rates into the alloys. Typical values of Li diffusion coefficient into alloys are 3-LiAl —> 7 16 9 cm2/s [305], Li44Sn —> 2 10 9 cm2/s [306], LiCd and LiZn —> 1010 cm2/s [307], It should be emphasized that it is very difficult to obtain reliable values of Li diffusion coefficient into Li alloys, and thus the above values provide only a rough approximation for diffusion rates of Li into alloys. However, it is clear that Li diffusion into Li alloys is a slow process, and thus is the rate-limiting process of these electrodes. Li deposition of rates above that of Li diffusion leads to the formation of a bulk metallic lithium layer on the alloy s surface which may be accompanied by mas-... 

The lithium is in the form of an alloy with magnesium or aluminium which retains much of the tritium until it is released by treatment with acid. Alternatively the tritium can be produced by neutron irradiation of enriched LiF at 450° in a vacuum and then recovered from the gaseous products by diffusion through a palladium barrier. As a result of the massive production of tritium for thermonuclear devices and research into energy production by fusion reactions, tritium is available cheaply on the megacurie scale for peaceful purposes. The most convenient way of storing the gas is to react it with finely divided uranium... 

The concentration of lithium in the alloy at a potential is c . After application of a potential pulse dE and increasing of the potential from to + j, the lithium concentration at the electrolyte-electrode interface is raised to c + j. A concentration profile expands into the alloy phase. At the middle of the aluminum electrode the two diffusion waves meet. Boundary conditions for this situation are... 

For species in solution undergoing diffusion (without forced convection) the lowest frequency that can be used depends also on the hydrodynamic conditions. It is well known that the chronoamperometric curves in solutions might be measured up to 60 s, after which natural convection affects the linearity of diffusion. This means that measurements of the mass transport impedance are limited to approximately 0.1 Hz (or slightly lower). However, measuring diffusion in solid materials (e.g., hydrogen absorption in metals and alloys, lithium intercalation) is not influenced by convection, and the measurements might be carried out to the... 

More interesting is the commonly encountered situation where an ion diffuses in a majority electronic conductor. Thus, diffusion in metallic and semiconducting alloys or of inserted species in transition metal oxides and chalcogenides fall into this category. Many electrode reactions are of this type. Lithium diffusion in j5-LiAl and other alloys is of interest in negative electrode reactions for advanced hthium batteries hydrogen and lithium diffusion in oxides (e.g. VeOn) and sulfides (e.g. TiSa) are of importance as positive electrode reactions for batteries and elec-trochromic devices. 

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