DE102020110635B4 - Method for fixing battery cells in a battery module - Google Patents

Abstract

A method is provided for fixing battery cells in a battery module, comprising: introducing battery cells (4) into a battery module housing (1), with between at least two battery cells (4) and / or between a battery cell (4) and an inner wall of the battery module housing (1) a bag (5) is or is arranged, the bag (5) having a first valve (51) through which the bag (5) can be filled with a fluid, and a second valve (52) which the fluid can escape when the pressure inside the bag (5) exceeds a predetermined threshold value; Filling a first fluid into the bag (5) in order to brace the battery cells (4) arranged in the battery module housing (1) against the inner walls of the battery module housing (1); and filling a second fluid into the bag (5) filled with the first fluid, the first fluid being displaced from the bag (5) through the second valve (52).

Description

The present invention relates to a method for fixing battery cells in a battery module, in particular in a battery module for a traction battery.

One of the most important characterization parameters for an electric vehicle is its range, which, in addition to the dimensions of the electric machine, is largely determined by its energy source, the so-called traction battery. The traction battery is a rechargeable battery with a large capacity. The traction battery usually has a modular structure and consists of a large number of battery modules. Each battery module in turn has a number of battery cells. Nowadays, lithium-ion technology is used in battery cells, which offers both a high energy density and a long service life.

During the manufacture of the battery modules, the battery cells are currently placed in one-piece battery module housings. In order to ensure stable storage of the battery cells within a battery module housing, the battery cells are arranged together with compression elements (compression pads) in a stacked arrangement in the battery module housing. The compression elements are usually made from a foamed polymer such as polyurethane foam. The dimensions of the stack of battery cells and compression elements, for example its width, are larger than the installation space provided for this in the battery module housing. For this reason, the stack of battery cells and the not yet compressed compression elements is pressed with a tool outside the module housing and positioned on the module housing. The compression is then released and the components are pushed into the battery module housing under high frictional forces. However, such a procedure has the disadvantage that the battery cells can be damaged by the high frictional forces that occur when the component stack is pushed into the battery housing.

To counteract this problem, alternative insertion concepts have been developed. For example, it is known to use additional elements with a non-stick coating to reduce friction. However, these have the disadvantage that, due to their use, there is less space available for the arrangement of battery cells in the battery cell module and thus the energy density in the battery module is reduced.

From block letters DE 10 2013 223 085 A1 For example, a method for assembling a battery module assembly is known which has a plurality of battery cell stacks which are arranged in a battery housing. Each battery cell stack is built up by positioning a pre-compressed foam unit sandwiched between two adjacent battery cells. After the battery cell stack has been inserted into a receiving frame and positioned in the receiving frame, the pre-compressed foam unit is expanded.

Pamphlet DE 10 2014 217 425 A1 discloses a clamping device for battery cells with a receptacle, which comprises a space with a variable volume, for receiving a fluid, wherein: the receptacle is designed such that a battery cell or a plurality of battery cells can be clamped.

Pamphlet US 2017/0133705 A1 discloses a pressurizing device having a housing that houses a plurality of battery cells and a plurality of spacers attached to the housing at regular intervals in the direction of thickness and forming pouch shapes that can expand and contract in response to air pressure.

Pamphlet DE 10 2014 206 813 A1 discloses an electrical energy store and a method for operating the same, the electrical energy store having a housing; comprises at least one energy storage element arranged in the housing and at least one gastight cavity arranged in the housing, which can be subjected to an internal pressure and by means of which pressure can be exerted on at least a portion of the energy storage element by applying the internal pressure to the cavity.

Further on is the printed matter JP 2012 - 221 773 A referred to as state of the art.

Against this background, the invention is based on the object of providing a method for providing a battery module fitted with battery cells, by means of which a battery module can be constructed flexibly and simply and in which the risk of damage to the battery cells is minimized.

This object is achieved by means of the method for fixing battery cells in a battery module according to the independent claim. Further preferred embodiments can be found in the dependent claims.

In various embodiments, a method for fixing battery cells in a battery module is provided which can be understood in particular as a method for tensioning battery cells in a battery housing.

The method according to the invention includes the introduction of battery cells into a battery module housing, a bag being arranged between at least two battery cells and / or between a battery cell and an inner wall of the battery module housing (ie already when the battery cells are inserted into the battery module housing) or is (ie separately after inserting the Battery cells). Although the majority of the description speaks of a pouch, several pouches can and will of course also be expediently used within the scope of the method according to the invention for arrangement in the battery module housing, the pouches being preferred, but not necessarily in the same orientation / orientation along one dimension can be arranged, for example along the width of the battery module housing.

For example, a bag can be arranged between each two battery cells within the battery cell stack arranged in a battery module housing. Alternatively or additionally, a bag can be arranged between an outer battery cell and an inner wall of the battery module housing at one or both ends of the battery cell stack (with or without a bag arranged in between). Furthermore, a bag can be arranged every two, three, four etc. battery cells, for example in particular when several battery cells (e.g. two or three) are provided in connected assemblies. In principle, any number of bags can be arranged in the battery cell stack between the battery cells and / or between (at least one outer) battery cell of the battery cell stack and an inner wall of the battery module housing. As a rule, but not by way of limitation, up to n + 1 bags can be used, where n indicates the number of battery cells in the battery housing. In this case, only one bag can expediently be arranged between two battery cells and / or between a battery cell and an inner wall of the battery module housing.

The bag used in the context of the invention can have any shape. The bag can preferably have a rectangular base area which can correspond approximately to the base area of a battery cell. The base area of a battery cell can be understood to mean that area which, within the battery cell stack, faces the base area of an adjacent battery cell. The bag can consist of a plastic, for example a film.

In general, a suitable number of the bags can already be arranged between the battery cells before the battery cell stack is introduced. In this case, the bags are placed in the battery module housing together with the battery cells. Alternatively, however, the bags can be introduced in a separate step, which takes place after the battery cells have been inserted into the battery module housing. In the latter case, for example, suitable holding templates can be used by means of which a bag can be inserted into its target position without creasing (i.e. between two battery cells or between a battery cell and an inner wall of the battery module housing).

The method according to the invention further comprises filling the bag with a fluid in order to brace the battery cells arranged in the battery module housing against the inner walls of the battery module housing. By pouring a fluid into the bag or bags arranged in the battery housing, the volume occupied by a bag can be increased, whereby the battery cell stack arranged within the battery module housing takes up more space overall and is thus braced against the inner walls of the battery module housing. The fluid can be a liquid, a gas, or a mixture of both.

The bag used in the context of the method according to the invention has at least one first valve through which the bag can be filled with the fluid. The first valve can consequently correspond to a filling valve. The first valve can be arranged, for example, on an edge surface of the bag so that it is exposed to the opening of the battery cell housing through which the battery cells have been inserted into the battery cell housing.

The bag used in the context of the method according to the invention has (at least) a second valve through which the first fluid can escape when the pressure inside the bag exceeds a predetermined threshold value. The second valve can therefore be a pressure relief valve.

The filling of the previously mentioned fluid into the bag corresponds to the filling of a first fluid and the method according to the invention further comprises filling a second fluid into the bag filled with the first fluid. The second fluid can be a liquid, for example a viscous liquid, for example a gel. The second fluid can preferably have a (viscous) liquid polymer foam, for example polyurethane foam. The second fluid may also preferably be a hardening fluid such as a hardening polymer foam (e.g.

Polyurethane foam). In general, the first fluid can have a physical state that differs from the second fluid. In this context, it should be mentioned that the at least one second valve, which is set up to discharge the first fluid from the bag in the event of excess pressure, selectively allows only the first fluid, but not the second fluid, to escape from the bag. For example, when the second fluid is being filled into the bag, the first fluid can be displaced out of the bag through the at least one second valve. If, for example, polyurethane foam is filled in, the first fluid, for example (pressure) air, escapes from the bag or is displaced from the bag at the same time and the polyurethane foam hardens, whereby the cells are tensioned within the battery module housing. By pre-filling the bag with the first fluid, it can be brought from its collapsed or, in a first approximation, two-dimensional shape into a three-dimensional shape, whereby the second fluid can be poured into the bag more easily and more evenly.

In further embodiments of the method, this can initially include the provision of a battery module housing for receiving battery cells.

According to further embodiments of the method, the battery module housing can be a one-piece battery module housing (“monoframe”), in other words, a one-piece housing that cannot be disassembled or opened accordingly for inserting the battery cells.

According to further embodiments of the method, the bag can be in an unfilled (unfilled) or in a partially filled state before being filled with the fluid. In other words, if the fluid is, for example, compressed air, the bag can be in an uninflated state until it is filled with the fluid. In the unfilled state, the bag takes up little space and does not make it difficult to insert the cell module stack into the battery module housing.

For example, the bag can be in a flat, but evacuated state before it is filled with the fluid, so that its side surfaces lie tightly against one another. The lateral extent of the bag, i.e. its expansion in the direction of the distance between the battery cells then corresponds to a first approximation of twice the wall thickness and is therefore minimal. In general, the bag can be designed such that when it is filled with the fluid, the increase in volume by enlarging the bag occurs essentially along only one dimension, for example laterally / laterally (along the direction of the distance between the battery cells in the battery cell stack). This can be achieved in that the corresponding side surfaces of the bag are made correspondingly rigid / inflexible.

According to further embodiments of the method, the filling of the fluid into the bag can include the filling of a gas, preferably air, into the bag. The fluid can in particular comprise compressed air. Consequently, the filling of the fluid into the bag can correspond to an inflation of the bag.

According to further embodiments of the method, the second fluid can be filled into the bag by means of a filling element which is fluid-mechanically coupled to the bag. The filling element can be an additional element which is attached to the bag and which is removed from the battery module housing after the second fluid has been filled into the bag.

According to further embodiments of the method, the filling element can have a plurality of nozzles which are fluid-mechanically coupled to corresponding valves provided on the bag. The valves can, for example, be arranged uniformly along an edge of the bag, so that the bag is evenly filled with the second fluid from one side of the edge, for example from below (against the force of gravity).

The features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 zeigt ein Batteriemodulgehäuse und eine darin einzusetzende Anordnung aus Batteriezellen, zwischen welchen Beutel angeordnet sind.
• 2 zeigt eine schematische Darstellung des im Rahmen des erfindungsgemäßen Verfahrens verwendbaren Beutels.

Further advantages and embodiments of the invention emerge from the description and the accompanying drawings.

• 1 shows a battery module housing and an arrangement of battery cells to be inserted therein, between which bags are arranged.
• 2 shows a schematic representation of the bag which can be used in the context of the method according to the invention.

In 1 a possible starting scenario for the implementation of the method according to the invention is illustrated. It is one side of a battery module case 1 shown which one opening 2 has through which the battery cells 4th , in the example shown a total of six battery cells 4th , into the battery housing module 1 should be inserted / inserted. Depending on the dimensions of the battery module housing 1 can of course have a different number of battery cells 3 can be used to equip it. The battery case 1 usually has a cuboid shape, but this is not mandatory. The relevant dimension of the battery module housing 1 which here the width 3 the opening 2 is larger than the corresponding width 6th of the component stack, which contains the battery cells to be used 4th and the bags therebetween 5 includes. The bags 5 are in an unfilled state and therefore hardly take up any space. The component stack can pass through the opening without problems, in particular without excessive expenditure of force and thus without significant frictional forces 2 into the battery case 1 be inserted. Although in the example shown there is only a bag on the right edge of the component stack 5 is arranged, a bag can in further embodiments 5 also be arranged on the left edge of the component stack. It should also be pointed out that the method according to the invention is not limited to an embodiment in which the bags 5 already when inserting the battery cells 4th are arranged between these.

After introducing the component stack into the battery module housing 1 , will be the bags 5 filled with a fluid so that they take on a larger volume. As a result, they exert pressure on the neighboring battery cells 5 and, if necessary, the corresponding inner wall of the battery module housing 1 the end. This increases the width 6th of the component stack and the battery cells 4th are against the inner walls of the battery module housing 1 pressed or tensioned. It should be noted that the bags 5 not before inserting the battery cells 4th into the battery module housing 1 must be arranged in their intended positions. The battery cells can do just as well in one step 4th into the battery module housing 1 are inserted and in a subsequent step the bags 5 be arranged in their intended positions. Generally the bags can 5 be designed as a flat bag, the volume of which increases essentially in only one dimension when the fluid is poured in - in the example shown laterally / laterally, that is, parallel to the direction of the arrangement of the battery cells 4th .

After filling the bag 5 with a first fluid, the bags 5 be filled with a second fluid in a further step. It can while the second fluid in the bag 5 is filled, the first fluid from the bag 5 escape or be displaced from this. As already mentioned, the second fluid can harden over time and thus for a stable tensioning of the battery cells for the duration of the use of the battery module 4th inside the battery module housing 1 care for.

In 2 Figure 3 is a side perspective view of one possible embodiment of the bag 5 shown, which can be used in the process of the invention described herein. As shown, the pouch can 5 have a flat, generally cuboid shape. On one side of the edge 53 of the bag 4th are a first valve 51 and a second valve 52 arranged. The first valve 51 can be set up as a filling valve and consequently be set up to fill in the first and optionally also the second fluid. The second valve 52 can be set up as a pressure relief valve, through which the first fluid from the interior of the bag 5 can escape when the pressure inside the bag reaches a certain threshold value. This threshold value can in particular be reached when after filling the bag 5 with the first fluid, the second fluid into the bag 5 is filled. Consequently, the second valve 52 can be used specifically to exchange the first fluid with the second fluid. The edge of the bag 5 which is the large side surface 56 of the bag 5 surrounding it may be stiffened, causing the pouch 5 easier between the battery cells 4th can be inserted and positioned. In one embodiment, the large side surface 56 of the bag 5 be stiff or inflexible and the surrounding edges, including the edge side 53 , can be made soft, so that the volume increase of the bag 5 when filling takes place essentially perpendicular to the side surface.

In 2 is also an optional with the bag 5 fluid mechanically coupled filling element 54 shown. The filling element 54 has a plurality of nozzles 55 with the corresponding additional valves on the bag 5 (in 2 not shown) are fluid-mechanically coupled. By means of the filling element 54 can the second fluid in the bag 4th be filled. After filling the bag 5 the filling element can with the second fluid 54 removed. The filling element 54 does not necessarily have to be according to the in 2 Image shown at the bottom of the bag 5 be coupled with this fluid mechanically, but can also be used in the in 2 The representation shown can be coupled with this at the rear edge of the page or at the top of the page if necessary. By means of the filling element 54 can the second fluid evenly in the bag 5 be filled.

Claims (6)

A method for fixing battery cells (4) in a battery module, comprising: introducing battery cells (4) into a battery module housing (1), wherein between at least two battery cells (4) and / or between a battery cell (4) and an inner wall of the battery module housing ( 1) a bag (5) is or will be arranged, wherein the bag (5) has a first valve (51) through which the bag (5) can be filled with a fluid, and a second valve (52) through which the fluid can escape when the pressure inside the bag (5) exceeds a predetermined threshold; Filling a first fluid into the bag (5) in order to brace the battery cells (4) arranged in the battery module housing (1) against the inner walls of the battery module housing (1); and filling a second fluid into the bag (5) filled with the first fluid, the first fluid being displaced from the bag (5) through the second valve (52). Procedure according to Claim 1 , wherein the battery module housing (1) is a one-piece battery housing module. Procedure according to Claim 1 or 2 wherein the bag (5) is in an unfilled or in a partially filled state before being filled with the first fluid. Method according to one of the Claims 1 until 3 wherein the filling of the first fluid into the bag (5) comprises the filling of a gas, preferably air, into the bag (5). Method according to one of the Claims 1 until 4th wherein the second fluid is filled into the bag (5) by means of a filling element (54) which is fluid-mechanically coupled to the bag (5). Procedure according to Claim 5 wherein the filling element (54) has a plurality of nozzles (55) which are fluid-mechanically coupled to corresponding valves on the bag (5).

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