FR2512276A1 - COMPOSITE ELECTRODE FOR ALKALINE ACCUMULATORS - Google Patents

Abstract

THIS ELECTRODE HAS THE ADVANTAGE OF BETTER USE OF ITS ACTIVE MATERIAL, OR INCREASE IN CAPACITY. THE ELECTRODE INCLUDES: A METAL GRID WITH BARS 1 AND INTERVALS 2 BETWEEN BARS, A PLASTIC SUPPORT 3 ON EACH SIDE OF THE GRID, ACTIVE MATERIAL 4, A COVER 5 IN A FELT OR NON-WOVEN FELT. IN ADDITION, AN INTERMEDIATE LAYER 6, CONDUCTIVE AND PERMEABLE TO ELECTROLYTE IS ARRANGED BETWEEN SUPPORT 3 AND COVER 5. THIS INTERMEDIATE LAYER 6, MAY BE IN PERFORATED METAL SHEET, WOVEN OR MESH FABRIC, OR UNWISSNED FABRIC, ITS BEING METALLIC OR METALLIC. ALKALINE ACCUMULATORS.

Description

The invention relates to a composite electrode for alkaline accumulators,

  in particular for iron / nickel accumulators, this electrode comprising a metal grid with bars and intervals between bars, a plastic support on each of the two sides of the metal grid, the mass or active material, and a cover made of a fabric Of the kind felt or nonwoven web Preferably the plastic supports arranged on both sides are welded to each other in the intervals between bars of the grid, so that they constitute almost "pockets" for the material active ingredient brought into the electrode, these pockets being closed by the cover made

  a felt-like fabric or non-woven fabric.

  Composite electrodes of the kind under consideration (German Patent Nos. 2,710,907, 2,710,908, 2,833,725, 2,833,771).

  can in principle be used both in

  lead-acid emulators only in alkaline storage batteries (eg iron / nickel, cadmium / nickel

  zinc / silver) It is particularly in the field of accumula-

  In such composite electrodes, the "shielding" of the active mass, without metal "encapsulation", has the advantage of a very improved electrolyte permeability. encloses the active mass

  With metal, for example, there are openings whose im-

  In the composite electrodes of the type considered, the nonwoven fabric cover allows, by its porosity, an opening greater than 80%. On the other hand, in the case of accumulators

  alkaline, there are difficulties due to other causes.

  Only a small percentage of the active mass is used for the electrochemical process of charging and discharging,

  so that this active mass is misused.

  The object of the invention is to develop an elec-

  Composite trode of the kind considered, so that the active mass is better used when it comes to such

  electrode in an alkaline accumulator.

  To achieve this goal, the invention recommends that there is between plastic support and cover (made of a felt-like fabric or nonwoven web), a

  intermediate layer which is metallically conductive but permeable

  It is already known that, in composite electrodes for alkaline accumulators (Patent Application No. 2,254,319 in Germany), a layer of

  felt or non-woven fabric, with a metallic layer

conductive

  as a perforated metal foil.

  However, in this known embodiment, it is a metal coating, the perforated metal sheet being

  applied externally on the nonwoven fabric layer.

  In detail, several configurations and achievements of the

  intermediate layer are possible within the framework of the

  This is how the intermediate layer can be

  The intermediate layer can, however, also be in the form of a woven fabric, a mesh fabric, or a fabric. of the kind felt or fleece nonwoven, of fibers and / or natural and / or synthetic non-metallic yarns, such fibers and / or

  at least partially metallised yarns According to another

  According to the invention, the intermediate layer is a metallization layer which the cover made of a fabric of the felt or nonwoven fleece type has received on its side facing the plastic support. This embodiment is particularly appreciable because, in this case, there is no

  need additional components for the intermediate layer.

  for example in the form of a sheet, a sheet, a woven or mesh fabric or a special nonwoven fabric 3 The metallization of fabric blankets of the kind felt or nonwoven web is known per se in the

  composite electrodes (US Pat. No. 2,985,701).

  However, in the context of the invention, if the intermediate layer is produced by means of a metallization, this can be carried out in various ways. The appropriate metals can in particular be applied by spraying or deposited.

by electroplating.

  In the context of the invention, it may be appropriate,

  to stabilize the contact conditions between

  medium and active mass, to give a particular configuration

  For this purpose, the invention recommends that in combination with the above-mentioned provisions the fabric cover of the felt or nonwoven web type have a pore width of only 1 to 10 microns (1 to 1 micron). OV) This avoids any possibility of the active mass passing through the cover in the free electrolyte during charging and discharging processes. Moreover, it goes without saying that a composite electrode according to the 'invention,

  intended for an alkaline accumulator, particularly an accumulator

  iron / nickel, must also have the necessary mechanical robustness taking into account that volume variations

  inherent to the use of alkaline accumulators, in particular

  iron / nickel accumulators, is a cause of significantly greater swelling pressure than in

  the case of an active mass of lead accumulator.

  If it is an iron / nickel

  recommends that the intermediate layer be in one

  nickel bonding or a nickel-plated steel alloy For example,

  Nickel-plated steel mesh can be used, or

  For other alkaline accumulators, the intermediate layer is advantageously constructed of

  function of the metals used In all cases, it is advantageous

  that the intermediate layer is put in con-

  ductive with metal mesh This form of realization

  of the invention is particularly important.

  The advantages achieved lie in the fact that with a composite electrode according to the invention, used in an alkaline accumulator, the active mass is substantially

  better used It is easy to obtain a user rate

  more than 50%, referring to the theo-

  according to Faraday's law This applies in particular

  The nickel electrode is the electrode according to the invention.

  It is an open-encapsulated composite electrode for alkaline storage batteries. As the active mass cooperates not only with internal current flows constituted by the metal grid, but also with current flows provided by the metal intermediate layer.

  As a result, this composite electrode has a capacitance

  Stable for many charging and discharging cycles Surprisingly, it is not essential for the intermediate layer to be connected to the internal current supply,

  that is to say to the metal grid, although as indicated -

  such a link is recommended.

  The description that follows, next to the drawing

  annexed by way of nonlimiting examples, will allow a good understanding of how the present invention can be put into practice. Figure 1 shows a partial sectional view

  of a composite electrode according to the invention.

  Figure 2 represents another form of reality

the object of Figure 1.

  Figure 3 represents another form of reali-

  tion. The composite electrode shown in the figures

  is basically constituted by a metal grid 1,2 -

  with bars 1 and intervals 2 between bars, by a

  port or support 3 made of plastic material on each of the two sides of the metal grid 1, with an arrangement such that the two lateral supports 3 are welded to each other in

  the intervals 2 between bars, and by the active mass 4 -

  placed inside, as well as by a blanket made of a

  fabric of the felt, mat or nonwoven fabric type.

  It can be seen that an intermediate layer 6,

  tallically conductive at the same time as it is permeable

  to the electrolyte, is arranged between support 3 and cover 5.

  In the embodiment according to FIG. 1, the intermediate layer 6 can be made in the form of a sheet or

  metal sheet with holes 7 for the passage of the electro-

  lyte It is also here a woven fabric, a knitted fabric or a fabric of the kind felt or non veil

  In this respect, FIG. 1 is merely schematic.

  The intermediate metal layer 6 can also be entirely

  However, it may also consist of natural and / or synthetic non-metallic yarns or fibers, at least partially metallized by coating, which are mutually associated in the form of a woven or meshed fabric or of a felt or non-woven fabric. In FIG. 2, it is indicated that the metallization, and with it the intermediate layer 6, can also be applied directly to the blanket 5 of the felt-like or non-woven fabric, 3 made of material on the side facing the support. In this case, only the fibers within the fabric of the felt or nonwoven web type are coated with metal, and the cover remains generally permeable to the electrolyte. The pores of this cover may have a width of 1 to

microns (1 to 10 A-).

  Figure 3 shows that the

  intermediate 6 is, as a whole, passed in a S-shaped pattern and can then also pass through the middle part * of the S, on the metal grid 1 Thus, in a simple manner, a conductive connection of the intermediate layer 6 to the

  In addition, with this form of embodiment,

  In addition to the intermediate layer 6, the mechanical stability of the electrode can be further improved, so that this intermediate layer 6 is constituted by woven fabric, mesh material or felt-like fabric.

  mat or non woven sail, or by sheet.

Claims (6)

  1 Composite electrode for accumulators   alkali, in particular for iron / nickel accumulators, cete e-   the electrode comprising a metal grid with bars and intervals between bars, a plastic support on both sides of the metal grid, the mass or active material placed in this electrode, and a cover made of a fabric of the felt or sail type nonwoven, this electrode being characterized by the fact that there is, between   support (3) made of plastic and cover (5), a cover   intermediate che (6) metallically conductive and permeable to the electrolyte.   2- Electrode according to claim 1, characterized   characterized by the fact that the intermediate layer (6) is   made of sheet or sheet metal and has holes for the passage of the electrolyte.   3 Electrode according to claim 1, characterized   characterized in that the intermediate layer (6) is of woven fabric, or of knitted fabric, or of the kind of felt or fleece nonwoven, and is made of fibers and / or yarns metal.   4 Electrode according to claim 1, characterized   characterized in that the intermediate layer (6) is of woven or knitted fabric or fabric of the kind leutre or voule nonwoven, and is made of natural and / or synthetic non-metallic fibers and / or non-metallic threads , synthetic and / or natural, these fibers and / or son being metallized.   Electrode according to claim 1, characterized   because the intermediate layer is a   metallization that the cover (5) made of a felt-like fabric or non-woven fabric to regue the side opposite   support (3) made of plastic.   6 Electrode according to any one of   claims 1 to 5, characterized in that furthermore   the blanket (5) made of a felt-like fabric or a nonwoven web has pores with a width of 1 to 10 microns (1 to 10 -).   7 Electrode according to any one of   Claims 1 to 6, for an iron / nickel battery,   characterized in that the intermediate layer (6) is made of nickel alloy or nickel-plated steel alloy, for example in nickel-plated steel mesh.   8 Electrode according to any one of the   1 to 7, characterized by the fact that   intermediate (6) is electrically connected to the metal grid (1)