Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1990-10-24
1992-03-10
Tufariello, T. M.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204140, C25C 124
Patent
active
050947389
DESCRIPTION:
BRIEF SUMMARY
Rechargeable cells/batteries with an anode of Li/Al receive increasing attention due to the facts among other things that they have high energy density and power density, work over a great temperature bracket, including room temperature, and have good storage capability.
Reference is in this context made to the publications U.S. Pat. No. 4,690,840 and 4,056,885.
In U.S. Pat. No. 4,690,840 description is made of the production of an Li/Al anode in that a metallic Al-body is immersed into a free radical solution, comprising Li-salt solved in an organic solvent. After a certain immersion time an Li/Al alloy is obtained which depending on the shape of the metallic body can form or be formed into an anode.
In U.S. Pat. No. 4,056,885 description is also made of the production of an Li/Al anode in sheet form in that a laminate of Li and Al is immersed into an anhydrous organic solvent with lithium salt therein.
These publications are incorporated into this specification by means of reference, especially as regards chemical reactions, electrolytes, anode and cathode materials, and separator materials.
The main problem behind the present invention is to accomplish a method by which it is possible to produce in a simple and rational way an anode of an alloy of an alkaline metal or alkaline earth metal and a host metal therefore, where the anode has a larger contact area than is possible to attain by the techniques according to the above mentioned pulications. A larger contact area gives a larger power/energy density.
For the sake of simplicity and for the reason that at present Li/Al is considered to be the most usable anode material in anodes of an alkaline metal or an alkaline earth metal and a host metal, the combination of the metals is below called Li/Al. As an alternative to Al special mention of Sn is made.
Behind the invention are also the problems that the separator in a cell with Li/Al anode, which is brittle and easliy falls apart, is exposed to pressure variations at charge/discharge, which means that the separator is stressed, and that the arrangement of the separator in a cell between the anode and cathode, for example according to the above mentioned publications, involves an additional and thus costly step.
According to the invention, as defined in the claims, an Li/Al anode unit is accomplished in situ in a flexible enclosure in the form of an at least somewhat elastic, micro-porous hollow fiber of plastic material, which is suitable for forming a separator relative to a cathode in a cell/battery. The enclosure constitutes a mold for establishing the Li/Al anode unit as well as a separator between this unit and the cathode in the cell/battery. Due to its flexibility and elastic character the enclosure/separator can adapt to the volume changes occurring when the anode unit is produced and when it is used as an electrode in a cell, so that the anode is prevented from falling apart. In a battery the anode is formed of one or more or a plurality of such anode units electrically connected to each other.
The basic Al element can contain a core of another metal which does not form an alloy with Li, for example Cu; this core constitutes the current collector in the anode.
Suitable separator materials or raw materials and techniques for producing separator materials with the above specified character are already on the market. A suitable separator material is polypropylene, which is solid by Celanese Corporation under the trademark Celgard.RTM.. The Pore size should be in the bracket 0.01-100 mm, preferably 0.1-20 mm, inner diameter 0.005-10 mm, preferably 0.05-3 mm - with corresponding outer cross sectional dimension for the basic Al element -, a thickness in the bracket 0.005-5 mm and a porousity of >10%. The electrochemical contact is preferably accomplished by short-circuiting and electrochemical cell with Al as electrode and Li as counter electrode. It is, however, also possible to choose to apply a voltage on one of those electrodes.
Two embodiments of the invention will now be further described und
REFERENCES:
patent: 4056885 (1977-11-01), Rao
patent: 4690840 (1987-09-01), Gauthier
Malling Jesper
Rothman Ulf
Brown Laurence R.
Inclusion AB
Tufariello T. M.
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