Metal working – Method of mechanical manufacture – Electrical device making
Patent
1991-12-30
1996-01-16
Skapars, Anthony
Metal working
Method of mechanical manufacture
Electrical device making
419 67, 429140, H01M 404
Patent
active
054844614
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for producing a Li(Al) anode for a lithium battery, in which Li and Al are pyrometallurgically alloyed in inert atmosphere and the formed alloy after cooling is ground to a homogeneous powder.
TECHNICAL BACKGROUND
At the present time there is a growing interest for lithium batteries. The interest is not limited to primary batteries, which so far have been most common on the market, but is increasingly focused also on secondary batteries. Lithium metal is attractive as a battery anode material because of its light weight, high voltage, high electrochemical equivalence, and good conductivity.
However, the use of pure lithium as anode material creates numerous and difficult problems, which are well known in the art. Especially, the difficulty with rechargeability and low melting point should be mentioned. The safety problems with batteries having pure lithium negative electrodes can certainly not be neglected.
For improving the qualities of negative electrodes having lithium as the active material the use of different lithium alloys has been investigated. Especially the use of aluminum as host metal for the highly reactive lithium has been found to provide certain advantages, for example with regard to the absence of dendrite formation and a high melting point. The present invention accordingly relates to a new and improved method for producing a Li(Al) anode for use in a primary or secondary battery.
The production of a Li(Al) powder in the way set forth in the introduction above is known from GB-A-1 484 650, but this powder is then pressed on a current conductive mesh.
In Journal of Electrochemical Society, Volume 124, No 10, 1977, M. L. Rao et al, "Lithium-Aluminium Electrode", p 1490-1492, a method to sinter Li(Al) powder on current conductive grids is disclosed.
In Journal of Electrochemical Society, Volume 131, No 8, 1984, A. S. Baranski et al, "The Cycling Efficiency of Lithium-Aluminium Electrodes in Nonaqueous Media", p 1750-1755, the electrodeposition of lithium on aluminium or nickel wires is disclosed.
By US-A-4 011 372 it is known to east a Li(Al) alloy on a conductive substrate.
Also DE-A-1 049 949 regarding the production of a certain electrode by pressing active lead paste on a lead thread, followed by the step of providing the electrode with a separator should be mentioned as another example of the prior art.
All these publications fail to disclose any totally satisfactory method of practically producing a Li(Al) anode for a lithium battery with the properties and qualities now sought for.
THE INVENTION
Such a method is according to the invention obtained in that the Li(Al) powder produced in the way set forth above is pressed or extruded to an elongated anode element around a current conductive thread, preferably of nickel, and that the anode element is provided with an enclosure of microporous separator material.
The enclosure can according to a further aspect of the invention be provided in a least two different ways: A separator material sheet can be placed at either side of an anode complex, comprising anode elements and connector rails, and pressed and line welded around the separate anode elements. Alternatively and preferably, a plurality of separate anode elements at certain intervals on a current conductive thread is formed in a continuous process, including the provision of the enclosures of microporous separator material.
The utilized microporous separator material is quite sensitive. Accordingly, each anode element may be provided with a protective web or net outside the separator material, especially when the anodes are to be used for a secondary battery.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in further detail below reference being made to the accompanying drawings, in which FIG. 1 illustrates a thread length with anode elements according to the invention thereon, FIG. 2 shows an anode element to a larger scale, FIG. 3 is a plan view of an embodiment of an anode according to the invention, F
REFERENCES:
patent: 2251913 (1941-08-01), Brennan
patent: 2754348 (1956-07-01), Berchielli
patent: 4011372 (1977-03-01), Tomczuk et al.
Malling Jesper
Rothman Ulf
Brown Laurence R.
Inclusion AB
Skapars Anthony
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