Patent Description:
Rechargeable batteries are widely used in many technology fields, e.g. low-capacity rechargeable batteries are used as power supply for small electronic devices, such as cellular phones, notebook computers and camcorders, while high-capacity rechargeable batteries are used as the power supply for hybrid vehicles and the like.

Rechargeable batteries or secondary batteries differs from primary batteries in that they can be repeatedly charged and discharged, while the latter provide only an irreversible conversion of chemical to electrical energy.

A unit battery cell includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, a case receiving the electrode assembly, and an electrode terminal electrically connected to the electrode assembly. Furthermore, the battery cell comprises positive and negative terminals electrically connected to the positive and negative electrodes, respectively, and extending outside the case.

In general, a battery module is formed of a plurality of unit battery cells coupled in series and/or in parallel so as to provide the required energy density, e.g. a high-power rechargeable battery for an electric vehicle. In order to connect the battery cells in series or in parallel, the electrode terminals of adjacent battery cells are connected by so-called "bus bars". Bus bars are usually metal plates electrically connected to the electrode terminals of two or more battery cells and are manually fixed thereto by means of screws or the like. Therefore, the application of the bus bars between the battery cells may result long and laborious. For instance, <CIT>, <CIT> and <CIT> disclose battery assemblies comprising a plurality of battery cells and a plurality of bus bars electrically connecting at least two battery cells. <CIT> is directed to a battery system wherein a connection member located above an upper cover plate electrically connects the two end plates to each other. Furthermore, <CIT> is directed a battery module including a plurality of secondary batteries each having an electrode lead and a bus bar electrically connecting the electrode lead to a power terminal.

Alternatively, a holding frame for the bas bars, a so-called cell connection unit (CCU), may be used. A CCU is made of an electric insulating material, such as plastic, and the bus bars are pre-assembled in the CCU. The bus bars can be then mounted on the respective electrode terminals in a single step. Since the CCU holds the bus bars in their position before they are mounted on the terminals, the application of the cell connection unit is simplified as compared to the application of single bus bars.

However, since the single bus bars have to be manually pre-assembled on the cell connection unit, the overall manufacturing process is still rather difficult and time-consuming. Furthermore, because the bus bars are fixed to the CCU, previous to the mounting on the battery cells, it is not possible to compensate for accidental fluctuations in the cell height. Thus, the tolerance in the position and height of the battery cells is very low when using a CCU. Additionally, the use of a plastic frame increases the overall volume inside the battery module.

It is an object of the present invention to overcome or reduce at least some of the drawbacks of the prior art and to provide a battery module with a simplified assembly procedure and which may compensate for small variations in the height of the battery cells.

One or more of the drawbacks of the prior art could be avoided or reduced by the battery module of the present invention, which comprises a housing with integrated bus bars, and by the method of manufacturing the battery according to the present invention.

In particular, according to an aspect of the present invention a battery module is provided which comprises a plurality of secondary battery cells, each battery cell comprising a first terminal and a second terminal spaced apart and electrically isolated from one another, the first and second terminals having opposite polarities, a housing comprising an upper housing part and a lower housing part assembled together to completely surround the plurality of battery cells, and a plurality of bus bars integrated in the upper housing part, wherein each of the plurality of bus bars is connected to one of the first and second terminals of at least two battery cells. The bus bars are metallic plates embedded in the upper housing part. The upper housing part is formed as a single piece of plastic material and covers a top side and the four lateral sides of the battery module.

For instance, a bus bar may be connected to the first terminal of a first battery cell and to the second terminal of a second battery cell adjacent to the first battery cell.

The upper housing part covers all sides of the battery module except one side and the lower housing preferably part covers the open side of the upper housing part. Preferably, the lower housing part covers a bottom side of the battery module.

Preferably, the upper housing part has the shape of a rectangular hexahedron (or rectangular box) comprising a top portion covering the top side of the battery module and four side portions extending from the four edges of the top portion and covering the four lateral sides of the battery module.

The top portion may comprise openings for at least partially exposing the bus bars. The exposed portions of the bus bars may correspond to the positions where the first and second terminals contact the bus bars. The bus bars may be made of conductive material. Preferably, the bus bars may be made of aluminum.

Preferably, the upper housing part further comprises partition walls for separating the battery cells inside the battery module.

Preferably, the battery module further comprises a heat exchange member provided between the plurality of battery cells and the lower housing part for cooling down the battery cells. The heat exchange member may include a cooling plate with a passage. Preferably, the cooling plate is made of aluminum. The cooling plate may be connected to the lower housing part by means of clips. Preferably, a thermally conductive layer is further provided between the plurality of battery cells and the heat exchange member for ensuring a thermal contact between the plurality of battery cells and the heat exchange member.

Preferably, the bus bars are welded to the corresponding first and second terminals of the battery cells.

According to another aspect of the present invention, a vehicle including a battery module as defined above is provided.

According to a further aspect of the present invention, a method of manufacturing a battery module includes: providing an upper housing part with integrated bus bars, the upper housing part having the shape of a rectangular hexahedron with a side open, inserting a plurality of battery cells into the upper housing part through the open side so that the first and second terminals of the battery cells extend downwards to contact the bus bars, assembling a lower housing part on the upper housing part to form a housing enclosing the battery cells.

The upper housing part comprises a top portion and four side portions extending from the four edges of the top portion. Preferably, the bus bars are integrated in the top portion of the upper housing part.

The upper housing part is formed by injection molding a plastic material. The plastic material may be PP GF30 or PA GF30. Preferably, the plurality of bus bars is formed as a leadframe integrated in the top portion of the upper housing part. The upper housing part is formed by over-molding the bus bars. The top portion of the upper housing part may comprise openings exposing at least a part of the bus bars.

Preferably, the bus bars may be attached to respective first and second terminals of the battery cells by welding. Preferably, the welding is automatically performed from outside the housing through the openings in the top portion of the upper housing part.

Preferably, before assembling the lower housing part to the upper housing part, a heat exchange member is provided on a first surface of the lower housing part for cooling the battery cells and the lower housing part is assembled on the upper housing part so that the heat exchange member faces the battery cells.

Preferably, a thermally conductive layer is provided on the heat exchange member after inserting the battery cells into the upper housing part and before assembling the lower housing part to the upper housing part. The thermally conductive layer may be made of thermal conductive glue or elastic thermal interface material (TIM), i.e. thermally conductive layer may be made of thermally conductive one or two component adhesives or pads such as polyurethane, epoxy resin or silicone, containing thermal conductive substances (e.g. aluminium hydroxide or aluminium oxide).

Effects and features of the exemplary embodiments, and implementation methods thereof will be described with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and redundant descriptions are omitted.

It will be understood that when a film, a region, or an element is referred to as being "above" or "on" another film, region, or element, it can be directly on the other film, region, or element, or intervening films, regions, or elements may also be present.

Herein, the terms "upper" and "lower" are defined according to the z-axis. For example, the upper housing is positioned at the upper part of the z-axis, whereas the lower housing is positioned at the lower part thereof. In the drawings, the sizes of elements may be exaggerated for clarity. For example, in the drawings, the size or thickness of each element may be arbitrarily shown for illustrative purposes, and thus the embodiments of the present invention should not be construed as being limited thereto.

Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and the written description, and thus, descriptions thereof will not be repeated.

Referring to <FIG>, a conventional battery module <NUM> is shown, which includes a plurality of battery cells <NUM> aligned in one direction (X direction). <FIG> shows a cross-sectional view of an exemplary battery cell <NUM> in <FIG> taken along the YZ-plane.

As depicted in <FIG>, a battery cell <NUM> includes an electrode assembly <NUM> and a case <NUM> for accommodating the electrode assembly <NUM>. The battery cell <NUM> may also include a cap assembly <NUM> for sealing an opening of the case <NUM>. The battery cell <NUM> will be described as a non-limiting example of a lithium ion secondary battery configured to have a prismatic shape, i.e. a rectangular hexahedron shape. However, the shape of the case may be varied according to the intended purpose and design of the device, e.g. the cell may also have a cylindrical shape.

The electrode assembly <NUM> may be formed as a jelly roll type electrode assembly by spirally winding a positive electrode <NUM> and a negative electrode <NUM> with a separator <NUM> therebetween. The positive electrode <NUM> and the negative electrode <NUM> may respectively include coated regions of current collectors formed of a thin metal foil, on which an active material may be coated, and may respectively include positive and negative electrode uncoated regions 81a and 82a of the current collectors on which no active material is coated. As a non-limiting example, the coated region of the positive electrode <NUM> may be formed by coating a base material formed of a metal foil, such as an aluminum foil, with an active material, such as transition metal oxide or the like. Also, the coated region of the negative electrode <NUM> may be formed by coating a base material formed of a metal foil, such as a copper or nickel foil, with an active material, such as carbon, graphite, or the like.

The positive electrode uncoated region 81a and the negative electrode uncoated region 82a may be on sides that are opposite to each other with respect to the coated regions. The electrode assembly <NUM> may be accommodated in the case <NUM> together with an electrolyte solution. The electrolyte solution may be made of a lithium salt, such as LiPF6 or LiBF4 with an organic solvent, such as EC, PC, DEC, EMC, or EMC. The electrolyte solution may be in a liquid, solid, or gel state. The case <NUM> may be configured to have a substantially cuboidal shape, and an opening may be formed at one side thereof. The case <NUM> may be formed of a metal, such as aluminum.

The cap assembly <NUM> is provided with positive and negative electrode terminals <NUM> and <NUM> (first and second terminals, respectively) having different polarities, and a vent <NUM>. The positive terminal <NUM> and the negative terminal <NUM> are electrically connected to the positive electrode <NUM> and the negative electrode <NUM>, respectively. The vent <NUM> is a safety means of the battery cell <NUM>, which acts as a passage through which gas generated in the battery cell <NUM> is exhausted to the outside of the battery cell <NUM>. Usually, the battery cells <NUM> are all arranged to have the electrode terminals <NUM> and <NUM> extending in the same direction. In the present case, the electrode terminals <NUM> and <NUM> extend upwards.

The battery module <NUM> includes a housing <NUM> enclosing the battery cells <NUM> for protecting the battery cells <NUM>. The housing <NUM> comprises an upper housing part <NUM> formed in the shape of a rectangular hexahedron with an open side at the bottom and a lower housing part <NUM> located at a bottom side of the battery module <NUM> and adapted to be assembled to the upper housing part <NUM> to form the housing <NUM>.

Generally, the battery cells <NUM> generate a large amount of heat while being charged/discharged. The generated heat is accumulated in the battery cells <NUM>, thereby accelerating the deterioration of the battery cells <NUM>. Therefore, the battery module <NUM> further includes a heat exchange member <NUM>, which is provided adjacent to the bottom surface of the battery cells <NUM> so as to cool down the battery cells <NUM>.

The heat exchange member <NUM> may include a cooling plate provided to have a size corresponding to that of the bottom surface of the plurality of battery cells <NUM>, e.g., the cooling plate may completely overlap the entire bottom surfaces of all the battery cells <NUM> in the battery module <NUM>. The cooling plate usually includes a passage through which a coolant can flow. The coolant performs a heat exchange with the battery cells <NUM> while circulating inside the heat exchange member <NUM>, i.e., inside the cooling plate. In addition, an elastic member <NUM> made of rubber or other elastic materials may be interposed between the lower housing part <NUM> and the heat exchange member <NUM>.

The battery cells <NUM> are connected in series and/or in parallel by means of conventional bus bars <NUM>, which are metal plates connecting the positive and negative electrode terminals <NUM> and <NUM> of neighboring battery cells <NUM>. Thus, the battery module <NUM> may be used as power source unit by electrically connecting the plurality of battery cells <NUM> as one bundle.

Conventional bus bars <NUM> like the ones depicted in <FIG> are usually fixed to the electrode terminals with nuts <NUM> and screws or by welding, i.e. they have to be manually mounted on the battery module <NUM>. Therefore, the application of the bus bars <NUM> between the battery cells may result long and laborious.

According to the present invention an improved bus bar is employed, which is integrated in the housing <NUM> of the battery module <NUM>.

<FIG> shows a schematic perspective view of an exemplary embodiment of a bus bar <NUM> according to the present invention and <FIG> shows a schematic perspective view of an exemplary embodiment of a housing with integrated bus bar <NUM> according to the present invention.

According to an embodiment of the present invention the bus bars <NUM> are formed as a lead frame to be integrated in the upper housing part <NUM> of the battery module <NUM>. In the specific embodiment illustrated in <FIG> a 12s3p configuration is shown, i.e. a configuration wherein twelve groups of battery cells <NUM> are connected in series, each group comprising three battery cells connected in parallel. However, the invention is not limited thereto and other configurations as well as different amount of battery cells are possible.

The bus bars <NUM> are integrated in a top portion 32a of the upper housing part <NUM>, i.e. the bus bars <NUM> are integrated in a portion of the upper housing part <NUM>, which is covering the upper side of the battery module <NUM>.

<FIG> shows a schematic perspective view of an upper housing part <NUM> with integrated bus bar <NUM>. The upper housing part <NUM> has the form of a rectangular hexahedron, i.e. of a rectangular box, comprising a top portion 32a and four side portions 32b, 32c extending from the top portion 32a. The bottom side of the upper housing part <NUM>, which is opposite to the top portion 32a, is open. The bus bars <NUM> consist of metallic plates embedded in the top portion 32a of the upper housing part <NUM>. The bus bars <NUM> are made of conductive material, for instance, the bus bars <NUM> may be made of aluminum. The battery housing <NUM> is formed by injection molding. The bus bars <NUM> are inlaid in a lower tooling side and when the injection-mold-tool is closed with an upper tooling side, the bus bars <NUM> are clamped between lower and upper tooling-side. Then the plastic material is injected. After removal of the part from the tooling, the clamping surface on the bus bars <NUM> builds the connecting and welding-area to the terminals of the battery-cells.

The battery housing <NUM> is made of insulating material, such as reinforced plastic. For instance, the battery housing <NUM> may be made of PP GF30, PA GF30, or the like. The battery housing <NUM> includes a plurality of openings <NUM> in the top portion 32a exposing the bus bars <NUM> for welding.

In the following, a manufacturing method of a battery module according to the present invention will be illustrated referring to <FIG>, <FIG> and <FIG>.

<FIG> shows the assembly of the battery cells <NUM> into the housing <NUM>. In a first step, the upper housing part <NUM> is turned upside-down, so that the top portion 32a including the bus bars <NUM> is located at the bottom. Then, the plurality of battery cells <NUM> are inserted in the upper housing part <NUM> with the first and second terminals <NUM> and <NUM> extending downwards toward the top portion 32a of the upper housing part <NUM>, so that the first and second terminals <NUM>, <NUM> of the battery cells <NUM> are in contact with the exposed parts of the corresponding bus bars <NUM>. The bus bars <NUM> are fixed to the corresponding first and second terminals <NUM>, <NUM> by welding.

Since the battery cells <NUM> are inserted into the housing <NUM> with the electrode terminals <NUM>, <NUM> extending downwards, a contact between the electrode terminals <NUM>, <NUM> and the corresponding of the bus bars <NUM> is achieved for all battery cells <NUM> because of the gravity force acting on the battery cells <NUM> or of an individual force on the bottom side of each battery cell <NUM>, irrespective of the height of the individual battery cell <NUM>. Therefore, the welding can be automatically performed, i.e. by means of a machine or robot, for all battery cells <NUM> through the openings <NUM> in the top portion 32a of the housing <NUM>.

Hence, according to the present invention, the assembly of the bus bars <NUM> to the electrode terminals <NUM>, <NUM> can be simplified because the bus bars <NUM> are integrated in the top portion 32a of the housing <NUM>, so that the bus bars <NUM> are held in the required position by the housing and the contact between the electrode terminals of the battery cells <NUM> and the corresponding bus bar occurs automatically when inserting the battery cells into the housing.

Since the assembly of the battery cells is performed upside-down, a contact between the electrode terminals and the bus bars can be easily achieved, even when the battery cells have different heights. Thus, a tolerance to height fluctuations of the battery cells is enhanced.

Furthermore, sine no additional CCU is required for pre-assembling the bus bars and holding the bus bars in their positions, an overall size of the battery module can be reduced.

<FIG> shows a perspective view of the upper housing part <NUM>, wherein the battery cells <NUM> have been inserted, and the lower housing part <NUM> before assembling the lower hosing part <NUM> onto the upper housing part <NUM>. Since the battery cells <NUM> are upside-down, a difference in cell height between the battery cells <NUM> in the upper housing part may occur at the side of the battery cells <NUM> opposite to the top portion 32a of the upper housing part <NUM>. In order to compensate for said difference, a thermally conductive layer <NUM> is deposited on the heat exchange member <NUM> located on the lower housing part <NUM> to ensure thermal connection between the cell case <NUM> of the battery cells <NUM> and the heat exchange member <NUM>. The thermally conductive layer <NUM> may be made of thermally conductive glue or elastic thermal interface material, such as thermally conductive one or two component adhesives or pads such as polyurethane, epoxy resin or silicone, containing thermal conductive substances (e.g. aluminium hydroxide or aluminium oxide).

The heat exchange member <NUM> is located on the lower housing part <NUM>. The heat exchange member <NUM> may comprise an aluminum cooler connected to lower housing part <NUM> by means of clips or the like.

Finally, the lower housing part <NUM> with the heat exchange member <NUM> is assembled to the upper housing part <NUM> to seal the battery.

<FIG> shows a bottom perspective view of the assembled battery module <NUM>. The lower housing part <NUM> comprises cooling openings 31a corresponding to coolant feed interfaces <NUM> of the heat exchange member <NUM> through which the coolant is input into or discharged from the heat exchange member <NUM>.

<FIG> show sectional views of the battery module <NUM> in the upright position. According to the illustrated embodiment the battery cells <NUM> are assembled in the housing <NUM> in two rows including <NUM> battery cells each, wherein the battery cells <NUM> are divided into <NUM> groups, each group including <NUM> battery cells connected in parallel. The housing <NUM> also includes partition walls <NUM> separating a group of battery cells <NUM> from the other groups. In the present case, one longitudinal partition wall 34c parallel to the long side portion 32c of the upper housing part <NUM> and six short partition walls 34b parallel to the short side 32b of the upper housing part <NUM>. However, the present invention is not limited thereto and a different number of battery cells or different configurations are possible.

Claim 1:
A battery module (<NUM>), comprising:
- a plurality of secondary battery cells (<NUM>), each battery cell (<NUM>) comprising a first terminal (<NUM>) and a second terminal (<NUM>) spaced apart and electrically isolated from one another;
- a housing (<NUM>) comprising an upper housing part (<NUM>) and a lower housing part (<NUM>) assembled together to enclose the plurality of battery cells (<NUM>);
- a plurality of bus bars (<NUM>) integrated in the upper housing part (<NUM>) for electrically connecting adjacent battery cells (<NUM>);
wherein each of the plurality of bus bars (<NUM>) is connected to one of the first and second terminals (<NUM>, <NUM>) of at least two battery cells (<NUM>),
characterized in that
the upper housing part (<NUM>) is formed as a single piece of plastic material having the shape of a rectangular hexahedron comprising a top portion (32a) and four side portions (32b, 32c) extending from the four edges of the top portion (32a), and
the bus bars (<NUM>) are metallic plates embedded in the upper housing part (<NUM>), wherein the top portion (32a) of the upper housing part (<NUM>) comprises openings (<NUM>) for at least partially exposing the bus bars (<NUM>).