Electrolytes lithium alloys

Attention has been given for some time to the use of lithium alloys as an alternative to elemental lithium. Groups working on batteries with molten salt electrolytes that operate at temperatures of 400-450 °C, well above the melting point of lithium, were especially interested in this possibility. Two major directions evolved. One involved the use of lithium-aluminium alloys [5, 6], whereas another was concerned with lithium-silicon alloys [7-9]. 

A series of experiments have been undertaken to evaluate the relevant thermodynamic properties of a number of binary lithium alloy systems. The early work was directed towards determination of their behavior at about 400 °C because of interest in their potential use as components in molten salt batteries operating in that general temperature range. Data for a number of binary lithium alloy systems at about 400 °C are presented in Table 1. These were mostly obtained by the use of an experimental arrangement employing the LiCl-KCl eutectic molten salt as a lithiumconducting electrolyte. 

It is now well established that in lithium batteries (including lithium-ion batteries) containing either liquid or polymer electrolytes, the anode is always covered by a passivating layer called the SEI. However, the chemical and electrochemical formation reactions and properties of this layer are as yet not well understood. In this section we discuss the electrode surface and SEI characterizations, film formation reactions (chemical and electrochemical), and other phenomena taking place at the lithium or lithium-alloy anode, and at the Li. C6 anode/electrolyte interface in both liquid and polymer-electrolyte batteries. We focus on the lithium anode but the theoretical considerations are common to all alkali-metal anodes. We address also the initial electrochemical formation steps of the SEI, the role of the solvated-electron rate constant in the selection of SEI-building materials (precursors), and the correlation between SEI properties and battery quality and performance. 

Solid electrolyte interphase (SEI), electrolyte additive, lithium ion battery, Li metal, graphite, lithium alloy. 

Wang J., Raistrick ID., Huggins RA., Behavior of some Binary Lithium Alloys as Negative Electrodes in Organic Solvent-Based Electrolytes. J. Electrochem. Soc. 1986 133 457-60. 

Battery technology has developed enormously in recent years. One of the most useful types of batteries is known as the lithium battery, but there are actually several designs only one of which will be described. In one of the types, the anode is constructed of lithium or a lithium alloy hence the name. A graphite cathode is used, and the electrolyte is a solution of Li[AlCl4] in thionyl chloride. At the anode, lithium is oxidized,... 

The Other Five Candidates. All the molten salt SBs reviewed above have either a Li anode or a lithium alloy, one in which Li prevails quantitatively. As to the other 5 light metals they are seldom mentioned in the literature as candidates for anodes in these SBs, except Al. In (82) it is stated that molten salt batteries with Ca or Mg anodes yield only a small proportion of their theoretical energy because (a) Ca anodes react chemically with the electrolyte, and (b) both Ca and Mg anodes are passivated at high current drains, becoming coated with resistive films of solid salts. In a melt containing Li salts, Ca replaces Li ions by the displacement reaction Ca + 2LiCl = CaCl2 + 2Li. 

Other common anode materials for thermal batteries are lithium alloys, such as Li/Al and Li/B, lithium metal in a porous nickel or iron matrix, magnesium and calcium. Alternative cathode constituents include CaCr04 and the oxides of copper, iron or vanadium. Other electrolytes used are binary KBr-LiBr mixtures, ternary LiF-LiCl-LiBr mixtures and, more generally, all lithium halide systems, which are used particularly to prevent electrolyte composition changes and freezing out at high rates when lithium-based anodes are employed. 

Wang J, Raistrick ID, Huggins RA. Behavior of some binary lithium alloys as negative electrodes in organic solvent-based electrolyte. J Electrochem Soc 1986 133 457-460. 

Switching to lithium-alloy negative electrodes, some voltage loss must be noted. LiAl has Uu = -1-385 mV, Li4.5Pb has Uu = 388 mV. Entries 18-20 in Table 10(b) represent three examples of rechargeable cells, which have been, at least temporarily, commercialized. The first (No. 18) is due to a lithium alloy/carbon black battery conunercialized by the Matsushita Co. [248]. The lithium alloy components are Pb -I- Cd -I- Bi -h Sn (Wood s alloy). Button cells in the range 0.3 to 2.5 mAh were offered. The electrolyte was LiC104 in an unknown solvent. The practical energy densities, 2Wh/kg, were rather low. The c.b. positive electrode acts as a double... 

If the device is not designed to use a heat resistant material, a loss of its functionality during reflow soldering may occur. The lithium alloy may react with the electrolytic solution and other components of the battery to cause abrupt bulging or explosion. Therefore, materials resistant to the reflow temperature must be used for the electrolytic solution, separator, or gasket... 

In 1994, Tadiran, an Israeli company, made the discovery described as follows This cell comprises as main components a negative electrode which is Lithium or Lithium alloy, a positive cathode which includes MnOa and an electrolyte which is 1,3-Dioxolane (148) with Lithium hexafluoroarsenate (LiAsFe) and a polymerization inhibitor [143]. 

After a 12-year research work on electroacoustic materials, I resumed investigating novel electrochemical cells. My efforts were focused on cells utilizing nonaqueous electrolytes, especially those with carbon/lithium alloy anodes. The result was a high-performance cell with LiCo02 (LCO) cathodes and lithiated carbon anodes. We named this battery system LIB. 

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