Discharge process, lithium alloys

Nanostructnred materials comprising 3-d transition metal oxide nanoparticles or alloys have been investigated extensively for their potential application as anode materials in lithium-ion batteries. A serious drawback of such systems is the substantial volume change of the active phase (up to 300%) during the charge/discharge process, which leads to mechanical disintegration of the electrode. The use of the polymeric matrix could stabilize the nanoparticles within the nanocomposite. 

Thus, in the process of Li+ reaction with tin, theoretical capacity of Li-Sn alloys can reach up to 790 mA-h/g. Theoretical capacity of pure Sn is 994 mA-h/g (7234 mA-h/cm3). Formation of such alloys occurs in the range of potentials from 0 to 0.8V versus lithium (Table 2) or in the temperature window 0-800°C. Charge-discharge curves have an inclined form. 

The processes taking place in the first intercalation of lithium into an alloy anode in a lithium-ion battery assembled in the discharged state are expected to be similar to those in a disordered carbon anode. 

Polymers. Electronically conductive polymers may also be used as cathode materials in rechargeable lithium batteries. The most popular polymers are polyacetylene, polypyrrole, polyaniline, and polythiophene, which are made conductive by doping with suitable anions. The discharge-charge process is a redox reaction in the polymer. The low specific energy, high cost, and their instability, however, make these polymers less attractive. They have been used in small coin-type batteries with a lithium-aluminum alloy as the anode. 

These metals are all produced by electrolysis of a mixture of molten metal chlorides the electrolyte composition is selected to minimize the process temperature and to ensure that it is the desired metal that is discharged at the cathode. The estimated annual world production of sodium and magnesium is a few hundred thousand tons while that for lithium is only a few thousand tons. The major uses are (a) sodium-manufacture of lead alkyls, isolation of titanium metal, production of several organic and inorganic substances (b) magnesium-organic synthesis, metal alloys (c) lithium - polymer initiation, organic synthesis and batteries. 

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