The present invention relates to a housing for a battery cell, comprising a varnish coating for electrical insulation, a battery cell, a battery and a motor vehicle.
In vehicles with at least partial electric drive, electrical storage devices are used in order to store the electrical energy for the electric motor, which assists the drive or acts as the drive. So-called lithium-ion batteries find an application here in vehicles of the latest generation. These batteries are characterized by, among other things, high energy densities and an extremely low self-discharge. Lithium-ion battery cells have at least one positive and one negative electrode (cathode or anode), which possess the ability reversibly to store lithium ions (Li+) (intercalation) or to release them again (deintercalation).
According to the prior art, lithium-ion battery cells in particular are clamped securely to one another, so that any expansion during operation due to the intercalation and deintercalation of the ions is largely prevented. Clamping also ensures, in addition, that the interconnected battery cells are in contact with a component for temperature control and are in positive engagement during normal use of the product and in the event of a crash.
In order to ensure the functional performance of the described clamping, the surfaces of the cells lying in positive engagement must exhibit high friction values, depending on the construction of the lithium-ion battery, the value of which depends on the design of the lithium-ion battery.
In the event of excessively low frictional values between the cell surfaces lying in positive engagement, relative movements can occur between the cells, which can give rise to damage to the lithium-ion battery.
The use of a friction-increasing coating, for example a molybdenum coating, in order to obtain a stable connection of component parts is already known from DE 10 2010 009 901 A1.
According to the invention, a housing for a battery cell, preferably a lithium-ion battery cell, is made available which is provided with a varnish coating for electrical insulation, the varnish coating containing adhesive-containing particles, the adhesive of which can be activated under defined conditions.
As described previously, battery cells, in particular lithium-ion battery cells, are clamped together, the surfaces of the housings of the battery cells lying in positive engagement being required to exhibit defined friction values in order to ensure the stability of the batteries.
It is possible to increase the coefficients of friction of the housings of the battery cells specifically during assembly by bursting of the adhesive-containing particles of the varnish coating, which release adhesive under defined conditions, preferably with initiation by pressure or force, initiation by temperature, initiation by radiation or by chemical motivation, and particularly preferably with initiation by pressure or force. The adhesive reaches the surface of the varnish coating in this way.
The arrangement of the individual housings in relation to one another can thus be effected advantageously and without problems, and the possibility of an increase in the coefficient of friction by the activated adhesive only arises when the battery cells are clamped.
Also, only the adhesive-containing particles of the functional surfaces necessary for clamping are activated advantageously in connection with this, so that the clamped battery possesses a lower coefficient of friction on its outer surfaces, that is to say the coefficient of friction is only influenced on surfaces which lie in positive engagement. As a result, the handling or the production sequence of a corresponding battery is significantly facilitated.
Provision for the activation of the adhesive can also be made by contact of the battery with a cooling element, for example, on which the battery is conventionally arranged, since reliable contact for reliable temperature control of the battery is necessary in this case, too.
Materials for producing appropriate particles are already familiar from the prior art to a person skilled in the art, which materials can preferably be constituted by adhesive itself. For this purpose, for example, the outer layer of the adhesive can be hardened in order to form the particle. Activation causes this layer to burst, with the result that the adhesive contained therein is able to emerge and in so doing to become active.
The adhesive-containing particles can differ in their nature in other respects, there being a preference for an embodiment as a hollow body filled with adhesive.
It is also possible for the particles to possess a porous structure, in which the adhesive is present, the adhesive being able to emerge from or being forced from this structure by the activation.
Suitable adhesives from the field of physically bonding adhesives, chemically curing adhesives or adhesives without strengthening mechanisms are generally familiar to a person skilled in the art, which adhesives are selected depending on the requirements.
The use of 2-component adhesives is also possible, in which case only two different particles need to be integrated into the varnish coating for this purpose.
The desired chemical reaction to form the adhesive takes place upon release of the components, for example by pressure.
The size of the particles can fundamentally be selected freely as required and can lie on the macroscopic, microscopic or nanoscopic scale.
The desired coefficient of friction can be adjusted selectively by the size of the particles and the quantity used in relation to the surface area, as well as by the appropriate choice of adhesive.
Selective adaptation of the coefficient of friction can also be achieved by causing the number of burst adhesive-containing particles to be dependent on the initial surface pressure on the surfaces lying in the force flux, which means that a lower coefficient of friction is obtained for a lower initial surface pressure, and a higher coefficient of friction is obtained for a higher initial surface pressure. This behavior is possible through an appropriate choice of particles and the adhesive that is used, or by the use of particles of different sizes.
The choice of the varnish systems that are used for insulation purposes can be made advantageously primarily according to the insulation properties through the arrangement according to the invention of housings for battery cells.
According to a particularly preferred embodiment of the invention, the varnish coating exhibits two layers. A basic insulation is thus provided, which does not exhibit any particles and assures optimal insulation. This in turn can consist of a single layer or can exhibit a plurality of layers. Present on top of this is at least one second varnish layer, which contains the particles.
Both layers can consist of the same varnish. It is also possible, however, to specify different varnishes.
This preferred construction of the varnish coating permits an adaptation of the coefficient of friction to be undertaken advantageously without changing the properties of the basic insulation system.
Varnish systems with individually adaptable coefficients of friction, which increase the product reliability and exclude any risk as described by way of introduction, are thus available.
With reference to the above analysis, it is possible to make use of mixtures of particles which vary with regard to their geometry and size, mixtures of particles made of various materials, mixtures of particles with a varied structure, for example hollow bodies and porous bodies, mixtures of particles with different mechanical, electrical, chemical and thermal properties and combinations thereof.
The object of the present invention also includes a battery cell, which is arranged inside a housing according to the invention and is preferably a lithium-ion cell, a battery, which exhibits at least two of these battery cells, and a motor vehicle having an electric drive motor for driving the motor vehicle and a battery connected or connectable to the electric drive motor.
Advantageous further developments of the invention are indicated in the dependent claims and are described in the description.
Illustrative embodiments of the invention are explained in more detail on the basis of the drawings and the following description. In the drawings,
An explanation of the prior art has already been provided in
Depicted in
Number | Date | Country | Kind |
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10 2011 088 739.3 | Dec 2011 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2012/072767 | 11/15/2012 | WO | 00 | 6/10/2014 |