Patent Application
20200112013
The invention relates to a contact with a composite material containing an elastic polymeric material and a metal material which is introduced into the polymeric material to conduct an electric current of a battery cell.
Contacts made of a composite material containing an elastic polymeric material and a metal material are previously known from the prior art. The publication WO 2014/016393 A1 discloses an energy storage device for a vehicle which is equipped with correspondingly formed contacts. In the case of the disclosed energy storage device, an energy storage system such as a battery cell, for example, is connected to a circuit board via a plurality of elastic contacts. The contacts consist of an elastomer into which metal particles are introduced. The contacts establish an elastic effect between the energy storage system and the circuit board. This allows electric contacting between the battery cell and the circuit board. The contacts are also electrically conductive due to the metal particles introduced therein.
However, it has been found that no or only few fully highly conductive tracks form in such a composite material if normal operating voltages are applied to the contacts. As a result, a desired low electric resistance is not set between the circuit board and the energy storage system. Therefore, the object of the present invention is to provide an elastic contact which has a very high electric conductivity.
The object is achieved by a contact of the generic type described at the outset, wherein according to the invention the metal material forms a metal body with a cohesive geometric structure which extends through the composite material such that an electric and a thermal current can be conducted through the composite material via the metal body. Since the metal body has a cohesive geometric structure, highly conductive tracks are present in the composite material for conducting an electric current. Furthermore, a thermal current can also be conducted via the metal body since metals have an exceptionally good thermal conductivity. Nevertheless, according to the invention, the thermal current can be conducted by the polymeric material.
The contact is elastic due to the elastic material used inside the composite material. In this case, the elastic material fills intermediate spaces, gaps, holes or other imperfections of the metal structure located in the composite material. In order to achieve a particularly good elasticity of the contact, the composite material should have less than 20 vol. % metal material. The composite material preferably has less than 15 vol. %. Particularly preferably, it has less than 10 vol. % metal material.
The elastic material is preferably formed such that it can readopt its original length due to a length change of 20% or more as a result of a compression. According to the invention, the elastic material should have an elasticity modulus of less than or equal to 0.5 N/m2, preferably less than or equal to 0.1 N/m2 and quite particularly preferably less than or equal to 0.05 N/m2.
The contact being formed to conduct an electric current of a battery cell is understood to mean that the contact can conduct a charge and/or discharge current of a battery cell. The current is conducted permanently by the contact. The charge or discharge current is in particular a current which typically occurs in battery cells (for example an energy cell or a power cell) of a battery of a mobile or stationary energy storage system, for example for a home or industrial storage system or for a motor vehicle, which is driven with electric power.
Thus, the contact is formed such that it can conduct a (recommended) charge current permanently received and/or discharge current permanently emitted by the battery without damage. For example, the contact is formed such that it can also conduct a maximum charge current received and/or maximum discharge current emitted by the battery cell permanently or at least briefly.
The contact is formed and suitable for this purpose due to the specific electrical properties of the material used, in particular in combination with the geometry used (in particular the cross-sectional geometry). In particular, a sufficiently low transition resistance or contact resistance for this purpose is achieved. In this case, sufficient heat dissipation (in particular into the electrically conductive connecting plate) can also be achieved from heat resulting during operation.
For example, a mentioned permanent charge current is at least 500 mA, preferably at least 1000 mA. Exemplary permanent charge currents are 1010 mA, 1020 mA, 1700 mA, 1675 mA or in particular in the case of power cells also 2000 mA or 3000 mA. For example, a mentioned maximum charge current is at least 1500 mA, preferably at least 2000 mA. Exemplary maximum charge currents are 2000 mA, 3000 mA, 3400 mA, 4000 mA, 5000 mA or 6000 mA.
For example, a mentioned permanent discharge current is at least 500 mA, preferably at least 1000 mA. Examples of permanent discharge currents are 670 mA or 680 mA. For example, a mentioned maximum discharge current is at least 5000 mA, preferably at least 8000 mA. Exemplary maximum discharge currents are 8000 mA, 10000 mA, 13000 mA or in particular in the case of power cells also 15000 mA, 30000 mA or 35000 mA.
As mentioned, the cross-sectional surface of the contact is in particular dimensioned such that a sufficient low transition resistance or contact resistance and therefore a current flow, as described, and sufficient heat dissipation (with respect to the material used in each case) is achieved. For example, the cross-sectional surface of the contact (as far as provided in particular in the region of at least one of the contacting regions or one of the contact elements) is at least in sections, preferably continuously at least 15 mm2, preferably at least 35 mm2, further preferably at least 75 mm2 and further preferably at least 175 mm2. In the case of a substantially round cross-sectional geometry of the contact, the diameter of the contact is therefore at least 5 mm, preferably at least 7 mm, further preferably at least 10 mm, further preferably at least 15 mm.
The metal body preferably forms an uninterrupted electric conductor. It is advantageous if the metal body consists of copper or of silver. Both copper and silver have an exceptionally good electric and thermal conductivity. However, silver or copper do not necessarily have to be used. The use of other metals is also possible. According to the invention, a silver alloy, a copper alloy or another metal alloy can be used.
The elastic material can, according to the invention, be a natural rubber or a synthetic rubber. Rubbers are materials which have very good elastic properties and good durability which means in particular a long lifetime. Rubber can be brought to an increased temperature, at which it is liquid, when producing the contact. The metal body can now be introduced into the rubber. Then, the rubber hardens and forms an electrically and thermally conductive contact in the composite with the metal body.
The elastic material is preferably a nitrile butadiene rubber, a hydrated nitrile rubber, an ethylene propylene diene rubber, a silicone rubber, a fluorine silicone rubber, a perfluorine rubber, a chlorine rubber, a chlorsulphonated polyethylene rubber, a polyester urethane rubber or a butyl rubber. The mentioned materials have, with respect to their elasticity modulus, their hardness, their flammability, their ageing resistance and further parameters, different properties and can be selected taking into account the purpose of use of the contact according to the invention. Additives can be added to the mentioned rubbers to improve their elasticity.
According to a particular embodiment of the invention, the elastic material is electrically conductive. More recently, various polymeric materials were developed which are electrically conductive. A composite material, which contains both a metal body and electrically conductive elastic material, has a particularly high electric conductivity. The use of such an elastic material is therefore desired. The electrically conductive elastic material does not necessarily have to be a polymer; the use of other elastic, electrically conductive materials is also possible according to the invention. According to the invention, the use of elastic materials is also possible which are only electrically conductive from a certain limit temperature or from a certain breakdown voltage.
According to the invention, the elastic material can be formed from doped polyacetylene, from polypyrrole, from polyaniline, from polythiophene or from poly-3, 4-ethylenedioxythiophene. Additives can be added to these materials to improve their elasticity. The mentioned materials have, with respect to their electric conductivity, their elasticity modulus, their hardness, their flammability, their ageing resistance and further parameters, different properties and can be selected taking into account the purpose of use of the contact according to the invention.
It is advantageous when the metal structure on surfaces of the elastic material is exposed in at least two contacting regions. If the metal body is exposed in the contacting regions, a current can be conducted directly into the metal body via a first contacting region of the contact without it having to penetrate the elastic material. The current is conducted through the contact via the metal body and can be led out of the contact in the region of a second contacting region. The metal body can be exposed in the contacting regions in each case at multiple points. According to possible embodiments of the invention, sections of the metal body can emerge from the metal body in the contacting regions. The two contacting regions are preferably arranged on opposing sides of the contact. The contact can consequently be electrically contacted on two opposing sides. In the case of the intended use, the contact is normally elastically deformed such that a distance is reduced between the two contacting regions owing to the elastic deformation.
The contact preferably has two electrodes which are designated below as contact elements and can in particular be contacting surfaces. The contact elements are connected in an electrically and thermally conductive manner on opposing sides of the composite material to the composite material. It is also possible according to the invention that a contact element is arranged only on one side of the composite material. The contact elements can, according to the invention, be connected in an electrically and thermally conductive manner to the contacting regions of the composite material. The contact elements can be metal plates. The contact elements provide a well-defined contact resistance to the composite material.
The metal body is preferably a metal fleece, a metal mesh or a metal foam. The metal fleece is a metal body which consists of disorderly arranged metal fibres and/or other fine metal structures. The metal mesh is a metal body which consists of metal fibres interwoven together or other fine metal structures. The metal foam is a metal body which has a number of cavities. The metal foam has a sponge-like structure.
It is also possible for the metal body to consist of directionally arranged metal fibres. Unlike the metal fleece, individual fibres are in this case not arranged randomly, but in a directional manner. This material is therefore also direction dependent with respect to its mechanical properties. The material can for example consist of a multitude of metal fibres which are aligned parallel to one another.
The metal foam is elastic and can therefore contribute to the elasticity of the composite material. A metal body, which is formed as a metal fleece or as a metal mesh, can, according to particular embodiments, also have elastic properties. The person skilled in the art can produce metal fleeces, metal meshes and metal bodies from directionally arranged metal fibres owing to his knowledge in such a manner that they are elastic. The elasticity of the metal fleeces, metal meshes or metal bodies results in an advantageous manner substantially from the geometric arrangement of the individual metal fibres to one another.
The metal body can, according to the invention, also have a grid structure or a lattice structure. A metal body, which has a grid structure or a lattice structure, consists of a number of metal wires which are connected to one another at nodal points. A metal body made of a grid structure or of a lattice structure can also be equipped such that the metal body is elastically deformable in particular owing to the elastic properties of the individual metal wires and therefore contributes to the elasticity of the composite material.
The invention also relates to an electrically conductive connecting plate which has a contact, as described.
The invention also relates to a battery with at least one battery cell, an electrically conductive connecting plate and a contact to connect a battery pole of the battery cell to the circuit board. The contact is a contact according to the invention as described above. The battery preferably contains a number of battery cells which are connected to a connecting plate in an electrically and thermally conductive manner via a contact according to the invention. The connecting plate is preferably a circuit board. According to the invention, the connecting plate is, however, also a metal plate. The connecting plate is particularly preferably a copper plate.
The elastic material of the composite material preferably has an elasticity modulus which is set such that the connecting plate is not damaged when contacting the battery cells through a force effect of the battery poles of the battery cells on the connecting plate. The elasticity modulus is preferably also set such that a battery cell can be clamped on the contacts between two connecting plates of a battery spaced apart from one another, which are provided with contacts according to the invention, and can be held by the contacts between the connecting plates, advantageously also in the case of forces acting for example due to vibrations of the battery on the battery cells.
According to a further embodiment of the invention, the contact is applied on the connecting plate. The contact can be applied on the connecting plate on regions which are provided in order to be contacted with battery cells of the battery in an electrically and thermally conductive manner.
It is also possible according to the invention for the contact to be applied on a circuit board of the battery. The contact can be covered on the surface facing the circuit board by a contact element. If a pressure is exerted on the contact element by a battery pole of a battery cell, the contact can be elastically deformed and a low-impedance contact transfer ensured between the battery cell and the circuit board.
Further advantageous embodiments of the invention are represented in the drawings, wherein:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 107 928.9 | Apr 2017 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/059465 | 4/12/2018 | WO | 00 |
