GB2154786A

GB2154786A - Single-cell gas-tight primary battery

Info

Publication number: GB2154786A
Application number: GB08504165A
Authority: GB
Inventors: Paul Wyser; Casar Battilana
Original assignee: Renata AG
Current assignee: Renata AG
Priority date: 1984-02-20
Filing date: 1985-02-19
Publication date: 1985-09-11
Also published as: FR2559961B1; CH654718GA3; DE3505321A1; GB8504165D0; GB2154786B; FR2559961A1; JPS60193259A

Abstract

Both the cover (1) and the can (2) of the primary battery, in the form of a button cell, preferably a lithium battery, have a substantially cylindrical edge flange (3, 11), between which a sealing and insulating ring (6) is located for gas-tight sealing of the battery. The sealing and insulating ring (6) consists preferably of a substantially dimensionally stable plastic and has an approximately L-shaped cross-section. Due to the sealing insulating ring, the can (2) and the cover (1) are at both an axial and a radial distance from one another and are mutually joined mechanically by firm seating. The primary battery according to the invention is conceived as a high-power button cell of small diameter and small overall height and is intended to achieve an extremely long life. <IMAGE>

Description

SPECIFICATION Single-cell gas-tight primary battery The invention relates to a single-cell gas-tight primary battery.

In gas-tight primary batteries, in particular those in the form of button cells, it is conventional to use readily coid-deformable plastic materials for both the sealing components and other insulating components. The gas-tight sealing of the battery can be effected by flanging the cover in or out on the housing.

Single cells of this type can conveniently be assembled in-various ways into multi-cel cascades and used for diverse purposes.

The disadvantages of a conventional sealing and insulating closure, which can be produced virtually without any problems, is that primary batteries fitted out in this way are not suitable for long-term operation and storage.

This has an adverse effect in particular in batteries of high energy density, such as, for example, lithium/manganese dioxide batteries, mercury batteries of silver oxide batteries etc., where a long life would be expected under extremely small loading. The electrolyte leakage loss, which occurs even using materials which are absolutely resistant to chemicals for the can, the cover and the sealing and insulating closure, results in not only a reduction in the power output of the active battery material, but also, due to oxidation phenomena, external tracking current paths which can lead to a discharge of the battery. Moreover, the applicance in which the battery is installed can be damaged by the egress of chemicals.

Viewed from one aspect the invention provides a single-cell gas tight primary battery having a housing which contains the active battery material and comprises a substantially flat metallic cover, a substantially flat metallic can, and a sealing and insulating ring retained between the cover and can under mechanical pre-tension, wherein both the cover and the can have an edge flange substantially at right angles to the flat parts thereof, wherein the sealing and insulating ring consists of a material which is substantially dimensionally stable under a compressive stress and has an approximately L-shaped cross-section, the radially oriented arm of which is formed as an axial spacer element between the cover and the can and the axially oriented arm of which is formed as a radial spacer element between the cover and the can, and wherein the edge flange of the cover is locked radially on the inside of the sealing and insulating ring and the edge flange of the can is locked radially on the outside on the axially oriented arm, the upper end of the can flange terminating in an at least approximately cylindrical form.

One illustrative embodiment of a primary battery according to the invention is explained below by reference to the drawing in which Figure 1 shows a battery, partially in section, in the state of being manufactured just before sealing, and Figure 2 shows a battery according to Fig.

1 in the finished state.

In the drawing, 1 denotes the cover of the housing of a single-cell button battery, which cover forms at the same time the positive (+) pole plate and consists of a corrosion-resistant material, for example stainless steel or a steel which has been made rustproof by a surface treatment. The negative (-), substantially flat pole plate is formed by the bottom of the can 2. The polarities can also be selected to be the converse.

The substantially flat cover 1 carries a peripheral edge flange 3, on the outer end of which a radially oriented circular end bead 4 is formed. The latter engages in an engagement groove 5 of a sealing and insulating ring 6 having an approximately L-shaped crosssection and arms of virtually the same thickness. The end bead 4 and the engagement groove 5 are matched cross-sectionally and functionally in such a way that, in a first assembly step, the insulating ring 6 can be placed tightly and in a defined position onto the cover edge flange 3. A covering lacquer filling 7 between the edge bead 4 and the radial arm or base section 6.1 of the sealing and insulating ring 6 represents a first safety measure for optimizing the gas seal between the cover 1 and the insulating ring 6.The base section 6.1 also forms a support member for the edge flange 3 against the bottom of the can 2, and its radially inner boundary surface 6.1 ' serves at the same time as a boundary zone for the cathode material 9, which expands during the discharge of the battery, of the active material of the battery.

The sealing and insulating ring 6 is preferably made from an injection-moldable thermoplastic material. Essential features of the materials which can be used for the sealing an insulating ring 6 are resistance to electrolyte solvents, low water absorption in the case of electrolytes for lithium batteries, for example 1, 2-dimethoxyethane (DME) or propylene carbonate (PC), a high dielectric constant and low cold-flow properties or a high compressive strength. In this connection, a high melting point is also of considerable importance, because the compressive strength of conventional materials decreases rapidly with increasing temperature. Examples of plastic materials of this type are polymeric or aromatic polyethers. The use of a polyether-ether ketone (PEEK), which has been developed by ICI Plastics Division, has proved to be particularly advantageous.

During the manufacture of the battery shown in the drawings, the sealing and insulating ring 6 is first pushed, with elastic expansion, over the bead 4 until the latter engages in the groove 5. The covering lacquer filling 7 is then intoduced. It can be appropriate to introduce the covering lacquer filling 7 into the groove 5 before the sealing and insulating ring 6 is placed on, in order to ensure that the sealing effect is also obtained in the groove region. Excess covering lacquer then settles, as shown, in front of the curvature of the bead.After the cathode material 9 of the active battery material has been filled into the cover 1 preferably standing on the cover bottom, the separator 10 and, if appropriate, an electrolyte reserve have been inserted, and the anode material 8 has been filled in, the can 2 is slipped over the insulating ring 6 such that the semi-finished state shown in Fig. 1 results. Under a closing pressure A applied to the top of the cover, the inside of the can bottom is then in full-face contact with the outside of the arm or base section 6.1, and the can edge flange 11 elastically forces the lower cylindrical section 6.2 of the sealing and insulating ring 6 radialy inward against the cover edge flange 3.In this way, optimum sealing conditions can be obtained even in a preparatory phase, because the material of relativley high compressive strength used for the sealing and insulating ring 6 and its low cold-flow tendency create ideal conditions for an excellent sealing effect.

While maintaining the closing pressure A, the distal end 11', projecting beyond the cylindrical arm or section 6.2 of the sealing and insulating ring 6, of the can edge flange 11 is then pressd or flanged radially inward in such a way that it makes tight-seating contact on the clamping shoulder 6.3 of the sealing and insulating ring 6, which shoulder runs initially conically inward and then cylindrically upward. This results in the battey closure of mechanically high stability, as shown in Fig. 2 on the left, the upper end of the can flange 11' terminating in at least apprximately cylindrical form and thus fixing an insulating section 12 of virtually the same width all round, opposite the cover flange 3.As an additional sealing element and in order to avoid places where dirt could collect between the flanges 3 and 11, which are at the full battery potential, a a covering lacquer layer 13 is finally applied to the insulating section 12, and this layer also prevents access of moisture to the otherwise exposed surface of the sealing and insulating ring 6.

The construction of the battery in accordance with this description in particular permits the manufacture of high-capacity batteries of small diameter and small overall height, coupled with a relatively long life. Typically diameters are 6-12 mm at overall heights of 1 to 3 mm. Such batteries are suitable especially for very flat watches, in particular wrist watches, hearing aids and other miniaturized applicances. Compared with known batteries of the same volume, 15-25% high energy capacities can be obtained.

It will thus be seen that the invention, at least in its preferred forms, provides a singlecell primary battery with a housing, the sealing and insulating closure of which is, on the one hand, sufficiently elastic to absorb without damage any closing forces mechanically applied between the cover edge and can edge of the battery and, on the other hand, is able to exert such a high deformation resistance that the closing force allows a gas-tight seal between the cover edge zone and the can edge zone to be obtained, but without making the distance of the said edge zones dependent on the closing force applied. Furthermore in its preferred forms the invention permits the manufacture of gas-tight single-cell primary batteries of small to extremely small dimensions, in which the pole insulation strength cannot be varied or cannot deteriorate due to flow properties of the sealing element.

Claims

1. A single-cell gas-tight primary battery having a housing which contains the active battery material and comprises a substantially flat metallic cover, a substantially flat metallic can, and a sealing and insulating ring retained between the cover and can under mechanical pre-tension, wherein both the cover and the can have an edge flange substantially at right angles to the flat parts thereof, wherein the sealing and insulating ring consists of a material which is substantially dimensionally stable under a compressive stress and has an approximately L-shaped cross-section, the radially oriented arm of which is formed as an axial spacer element between the cover and the can and the axially oriented arm of which is formed as a radial spacer element between the cover and the can, and wherein the edge flange of the cover is locked radially on the inside of the sealing and insulating ring and the edge flange of the can is locked radially on the outside on the axially oriented arm, the upper end of the can flange terminating in at least approximately cylindrical form.

2. A primary battery as claimed in claim 1, wherein the cover edge flange has a radially outward-pointing end bead on its outer end and the axially oriented arm has, on the inside of the ring, a circular groove for engagement with the bead.

3. A primary battery as claimed in claim 2, wherein the end bead is formed as a support region for the cover edge flange against the radial arm.

4. A primary battery as claimed in claim 3, wherein the end bead and the circular groove are sealed by a covering lacquer.

5. A primary battery as claimed in any preceding claim, wherein the axially oriented arm of the sealing and insulating ring is provided with a clamping shoulder located on the outside and offset radially inward, and wherein the distal end of the can edge flange is deformed radially inwared onto the clamping shoulder.

6. A primary battery as claimed in claim 5, wherein an insulation section on the outer end of the axial arm is sealed by means of a layer of covering lacquer.

7. A primary battery as claimed in any preceding claim wherein the sealing and insulating ring consists of a polymer plastic.

8. A primary battery as claimed in claim 7, wherein said polymer plastic is an aromatic polyether.

9. A primary battery as claimed in claim 8, wherein the plastic material is a polyetherether ketone.

10. A primary battery as claimed in any preceding claim, wherein the radially inner boundary surface of the radially oriented arm is formed as a radial boundary for the active battery material introduced into the can.

11. A primary battery substantially as hereinbefore described with reference to the accompanying drawing.