Patent Description:
In the recent years, vehicles for transportation of goods and peoples have been developed using electric power as a source for motion. Such an electric vehicle is an automobile that is propelled by an electric motor, using energy stored in rechargeable batteries. An electric vehicle may be solely powered by batteries or may be a form of hybrid vehicle powered by for example a gasoline generator or a hydrogen fuel power cell. Furthermore, the vehicle may include a combination of electric motor and conventional combustion engine. In general, an electric-vehicle battery, EVB, or traction battery is a battery used to power the propulsion of battery electric vehicles, BEVs. Electric-vehicle batteries differ from starting, lighting, and ignition batteries because they are designed to give power over sustained periods of time. A rechargeable or secondary battery differs from a primary battery in that it can be repeatedly charged and discharged, while the latter provides only an irreversible conversion of chemical to electrical energy. 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 electric and hybrid vehicles and the like.

Rechargeable batteries may be used as a battery module formed of a plurality of unit battery cells coupled in series and/or in parallel so as to provide a high energy content, in particular for motor driving of a hybrid vehicle. That is, the battery module is formed by interconnecting the electrode terminals of the plurality of unit battery cells depending on a required amount of power and in order to realize a high-power rechargeable battery.

Battery modules can be constructed either in block design or in modular design. In block designs each battery is coupled to a common current collector structure and a common battery management system and the unit thereof can be arranged in a housing. In modular designs, pluralities of battery cells are connected to form submodules and several submodules are connected to form the battery module. In automotive applications, battery systems often consist of a plurality of battery modules connected in series for providing a desired voltage, or alternatively, cells are directly stacked into the housing without an intermediate module structure. The battery modules may comprise submodules with a plurality of stacked battery cells, each stack comprising cells connected in parallel that are connected in series (XpYs) or multiple cells connected in series that are connected in parallel (XsYp). Therein, term stacked means that equally or similarly shaped battery cells are brought into contact in a specific order. Typically, a stack can be formed of a plurality of prismatic battery cells, i.e., battery cells having three surfaces that are perpendicular to each other. Therein, the stack is formed by repeatedly arranging one surface a battery cell in contact with, or in thermal contact with but separated by a spacer from, a surface of a neighboring battery cell.

They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power.

The mechanical integration of a battery module requires appropriate mechanical connections between the individual components, e.g. between battery cells. These connections must be functional, in particular with respect to heat conductance, and safe during the average service life of the battery system. Further, installation space and interchangeability requirements must be met, especially in mobile applications.

Exothermic decomposition of cell components may lead to a so-called thermal runaway. In general, thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. In rechargeable battery systems, thermal runaway is associated with strongly exothermic reactions that are accelerated by temperature rise. These exothermic reactions can include combustion of flammable gas compositions within the battery pack housing. For example, when a cell is heated above a critical temperature (typically above <NUM>) it can transit into a thermal runaway. The initial heating may be caused by a local failure, such as a cell internal short circuit, heating from a defect electrical contact, short circuit to a neighboring cell. During the thermal runaway, a failed battery cell, i.e., a battery cell which has a local failure, may reach a temperature exceeding <NUM>. Further, large quantities of hot gas are ejected from inside of the failed battery cell through the venting opening of the cell housing into the battery pack. The main components of the vented gas are H<NUM>, CO<NUM>, CO, electrolyte vapor and other hydrocarbons. The vented gas is therefore burnable and potentially toxic. The vented gas also causes a gas-pressure increase inside the battery pack.

According to the prior art, two typical types of cell integration concepts for prismatic cells into a battery pack are: with a module structure and in a cell-to-pack fashion. The latter can avoid extra interfaces and, thus, extra cost. In either of these arrangements battery cells all are typically oriented in the same way. However, high energy densities of the cells, a high packing density of the cells within the battery pack, and relatively good thermal contact between the cells lead to increased safety issues in case of thermal runaway of at least one cell. When a battery cell goes into thermal runaway, e.g. triggered by overtemperature, overcharging, internal or external short circuit, its stored electrical and chemical energy will be released in a sudden chemical reaction. This leads to a heat-up of the battery cell in thermal runaway to up to <NUM> or more, depending on the energy density (see, e.g., Table <NUM> in <NPL>). With typical battery cell masses of around <NUM> and a heat capacity of roughly <NUM> kJ/K kg, a heat-up from <NUM> to <NUM> corresponds to an energy of <NUM> MJ. In the conventional arrangement as shown in <FIG>, typically a battery cell will mostly transfer the heat to its two nearest neighbors, i.e., two battery cells within the battery cell group which are touched via a longitudinal side surface of the battery cell (in its x-direction, see <FIG>). Assuming adiabatic conditions on all other surfaces (which is a good approximation if there is a good thermal insulation on the other surfaces), each neighbor battery cell gets half of the released energy (500kJ) and consequently heats up by <NUM>, which is enough to trigger thermal runaway (this happens at ca. <NUM>-<NUM>). The propagation continues until all battery cells in the cell stack and/or the battery module have entered thermal runaway. The prior art intends to avoid thermal runaway propagation by, e.g., compartmentalization of battery cells. However, compartmentalization is expensive and takes up a lot of space.

<CIT> discloses an electric vehicle power battery including a box body provided with a partition that divides an inner cavity of the box body into a plurality of battery installation chambers. Battery groups are installed in the installation chambers, wherein the battery cells accommodated in one installation chamber are arranged orthogonally to the battery cells accommodated in the remaining installation chambers, i.e., a plurality of battery cell groups is equally stacked and a single battery cell group is stacked differently. Prevention of thermal runaway could be improved over <CIT>. In <CIT> a battery module is disclosed in which the cells include a first group including cells stacked along a first direction and a second group including cells stacked along a second direction. The <CIT> discloses a battery module with first and second cell group which arranged in two stages and where long side faces of the first cell group and the long side faces of the second cell group are perpendicular to each other.

According to the invention, a battery module is provided according to claim <NUM>.

According to another aspect of the invention, a battery pack is provided, comprising at least one battery module according to claim <NUM>.

Another aspect of the present disclosure refers to an electric vehicle comprising at least one battery module and/or at least one battery pack according to the invention.

Yet another aspect of the present disclosure refers to a method for assembling a battery module according to claim <NUM>.

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.

According to one aspect of the present disclosure, a battery module is provided. The battery module comprises a plurality of first battery cell groups and a plurality of second battery cell groups. Each of the battery cell groups is formed by the arrangement of a plurality of battery cells forming the battery cell group. The first battery cell groups and the second battery cell groups are separated from each other by a cell group boundary that defines the spatial domains of the battery cell groups without necessarily being provided by a physical, i.e., mechanical, boundary arrangement. At least one of the first battery cell groups is arranged adjacent to at least one of the second battery cell groups, i.e., at least one of the first battery cell groups is adjacent to at least one of the second battery cells. Thus, said first battery cell and said second battery cell are separated from each other by a cell group boundary, and at least one battery cell of said first battery cell group is in contact with at least one battery of said neighboring second battery cell group. The adjacent arrangement of first battery cell groups and second battery cell groups ensures a thermal contact between adjacently arranged battery cell groups so that heat can be transferred from one battery cell group to its adjacent, i.e., neighboring, battery cell group. Each of the first battery cell groups and each of the second battery cell groups comprises a plurality of stacked prismatic battery cells. , each of the first battery cell groups can also be called a first battery cell stack, and each of the second battery cell groups can also be called a second battery cell stack. Therein, the first battery cell groups and second battery cell groups are alternatingly stacked. , the stacking pattern of each of the first battery cell groups is different than the stacking pattern of each of the second battery groups. The adjacent arrangement of the first and second battery cell groups and the alternating arrangement means that from battery cell group to battery cell group the stacking of battery cells within the battery cell groups varies periodically in a discrete manner. In particular, the battery cells of the first battery cell groups are stacked so that they are oriented differently than the battery cells of the second battery cell groups. The difference in the stacking pattern distinguishes the first battery cell groups from the second battery cell groups. In other words, the battery module comprises different battery cell groups which are distinguishable from each other by their stacking pattern of stacking battery cells, and the different battery cell groups form domains in which the stacking pattern alternates from domain to domain. That is, the battery cell groups are arranged in a checkerboard pattern, wherein sites of the checkerboard are alternatingly occupied by either a battery cell group of the first battery cell groups or by a battery cell group of the second battery cell groups.

The alternating stacking of the first battery cell groups and the second battery cell groups can improve the thermal conductance between battery cells at the cell group boundaries between a first battery cell group and a neighboring second battery cell group. The alternating stacking implies that a battery cell of the first battery cell group is in thermal contact with a plurality of battery cells of a neighboring second battery cell group. Thus, the battery cells of the first battery cell group can transport its thermal energy to the plurality of battery cells of the neighboring second battery cell group which improves heat conduction between battery cell groups and prevents a thermal runaway. The alternating stacking implies that the above holds analogously for a second battery group, i.e., due to the alternating stacking a battery cell of the second battery cell group is in thermal contact with a plurality of battery cells of a neighboring first battery cell group. Thus, the battery cells of the second battery cell group can transport its thermal energy to the plurality of battery cells of the neighboring first battery cell group. Potentially additional thermally isolating spacers between battery cell groups can be dispensed with or can be smaller than in the prior art.

The battery cells of the first battery cell group are oriented orthogonally to the battery cells of the second battery cell group. In other words, the battery cells of the first battery cell group are stacked and arranged to be orthogonal to battery cells of the second battery cell group, i.e., battery cells of the first battery cell group are rotated by <NUM>° against the battery cells of the second battery cell group. This arrangement can improve the effectiveness of avoiding thermal runaway by providing improved thermal contact between neighboring battery cell groups and is particularly space-saving and cost-effective to manufacture. In this arrangement, a battery cell of a first battery cell group contacts, compared with other orientations, a maximal number of battery cells of a second battery cell group which provides an effective heat conductance.

Optionally, each of the first battery cell groups comprises at least one neighboring second battery cell group, wherein each of the neighboring first battery cell groups and second battery cell groups are alternatingly stacked. This provides an alternating arrangement of first battery cell groups and second battery cell groups extending specifically among neighboring battery cell groups. Therein, optionally, at least one of the first battery cell groups comprises at least another one of the first battery cell groups as next-nearest neighbor, wherein said first battery cell group and the next-nearest first battery cell group are stacked in the same manner. For example, the battery module can comprise a one-dimensional arrangement of battery cell groups, wherein battery cell groups are first battery cell groups or second battery cell groups alternatingly.

Optionally, the first battery cell groups and the secondary battery cell groups are arranged on a two-dimensional lattice; wherein the lattice comprises lattice sites arranged in at least two rows and at least two columns. In this embodiment, the term lattice does not refer to a physical structure, e.g., for mounting the battery cell groups. The lattice refers to the arrangement of battery cell groups in a mathematical sense to define that the battery cell groups are arranged in a regular pattern on the lattice sites. Therein, either one of the first battery cell groups or one of the second battery cell groups is arranged on each lattice site. This provides an effective arrangement of battery cell groups in a regular pattern that can improve the mountability of the battery module.

Optionally, the battery module comprises thermally insolating spacers arranged between the battery cell groups. This improve avoiding the thermal runaway further. A spacer might be electrically insolating to improve electrical safety, i.e., to avoid creepage and/or to provide electrical clearance.

The first battery cell groups and the second battery cell groups are arranged so that one battery cell of the first battery cell group is arranged to touch a plurality of, or each of, the cells of a neighboring second battery cell group. In this embodiment, the first battery cell group can be arranged so that a battery cell of the first battery cell group and its boundary touches a plurality of, or each of, the cells of a neighboring second battery cell group to achieve improved heat conductance between said battery cell of the first battery group and the neighboring second battery cell group. Each of the battery cells has a narrow side surface and a longitudinal side surface; and the first battery cell groups and the second battery cell groups are arranged so that one battery cell of the first battery cell group is arranged to touch, with its longitudinal side surface, a plurality of, or each of, the cells of a neighboring second battery cell group at their narrow side surfaces.

Optionally, one battery cell of one of the first battery cell groups has a longitudinal side surface that contacts a plurality of narrow side surfaces of battery cells of a neighboring second battery group, wherein the sum of the areas of the narrow side surfaces is less or equal then the area of the longitudinal side surface. This embodiment can improve heat conductance between the battery cell with its longitudinal side surface and the battery cells with their respective narrow side surfaces as the battery cell of the first battery cell group is, or can be brought, in contact with the plurality of battery cells of the second battery cell group.

Optionally, for each of the battery cells, the elongation of a battery cell in a first direction is a integer multiple of the elongation of said battery cell in a second direction. This embodiment allows an efficient arrangement of alternatingly stacked battery cell groups, wherein one battery can contact with its plane surface extending along the first direction a plurality of battery cells of a neighboring battery cell group with their plane surfaces extending along the second direction.

Optionally, each of the battery cells has an equal shape, and/or each of the first and second battery cell groups has an equal shape with a square cross-section. Equally shaped battery cells can provide an efficient stacking of battery cells to form battery groups, and can improve an alternating arrangement of first battery cell groups and second battery cell groups. Equally shaped first battery cell groups and second battery cell groups with a square cross-section each can improve the arrangement of the battery groups in an alternating manner, wherein the equal shape of the battery cell groups and the alternating arrangement leads to a checkerboard pattern with equally-sized square sites on the checkerboard at which battery cell groups are arranged.

Optionally, the number of battery cells comprised by each of the first battery cell groups and the number of battery cells comprised by each of the second battery cell groups equal each other. In this embodiment, the size of each of the first battery cell group and the size of each of the second battery cell groups equal if they comprise the same number of battery cells with the same aspect ratio. This allows an effective arrangement of battery groups.

According to another aspect of the present disclosure, a battery pack is provided. The battery pack comprises at least one battery module as described above. Thus, technical effects and optional features as describe above apply to the battery pack.

Another aspect of the present disclosure refers to an electric vehicle. The electric vehicle comprises at least one battery module as described above and/or at least one battery pack as described above. Thus, technical effects and optional features as describe above apply to the electric vehicle.

Yet another aspect of the present disclosure refers to a method for assembling a battery module according to an aspect of the present disclosure, wherein the method comprises the steps of.

<FIG> illustrates a schematic view of an electric vehicle <NUM> according to an embodiment of the invention. The electric vehicle <NUM> is propelled by an electric motor <NUM>, using energy stored in rechargeable batteries arranged in a battery pack <NUM>. The battery pack <NUM> is a set of any number of battery modules <NUM>. Rechargeable batteries are used as a battery module <NUM> formed of a plurality of secondary battery cells <NUM> (in <FIG>, only one of the secondary battery cells <NUM> is indicated with a reference numeral for an illustrative purpose only). Components of the battery pack <NUM> include the individual battery modules <NUM>, and interconnects <NUM>, which provide electrical conductivity between the battery modules <NUM>.

Each of the battery modules <NUM> comprises two first battery cell groups <NUM> and two second battery cell groups <NUM>. The two first battery cell groups <NUM> and two second battery cell groups <NUM>, and a two-dimensional arrangement of battery cell groups <NUM>, <NUM> are shown in <FIG> only for illustrative purposes. However, each of the battery modules <NUM> can, depending on the size of the battery cells <NUM>, the aspect ratio of the battery cells <NUM> and on the number of battery cells <NUM> within the battery cell groups <NUM>,<NUM>, comprise another suitable number of first battery cell groups <NUM> and/or of second battery cell groups <NUM> than illustrated in the figures, and the first battery cell groups <NUM> and the second battery cell groups <NUM> can be arranged differently than shown in <FIG>. The battery modules <NUM> as shown in <FIG> are described further with reference to <FIG>.

<FIG> illustrates a schematic perspective view of a battery cell <NUM> according to prior art. The battery cell <NUM> is prismatic, i.e., the battery cell <NUM> comprises three pairs of oppositely arranged and basically flat surfaces that are perpendicular to each other. The battery cells <NUM> comprises a pair of longitudinal side surfaces <NUM> (i.e. the largest flat surface of the battery cell <NUM>), a pair of narrow side surfaces <NUM>, and a bottom surface <NUM>. The components together build a sealed case to contain the electrochemical components of the battery cell <NUM>. The opening of the case is tightly sealed with a casing cover <NUM> with a pair of battery connectors <NUM> at its top.

As shown in <FIG> and explained with reference thereto, battery cells <NUM> are arranged so that the longitudinal side surface <NUM> contacts the longitudinal side surface <NUM> of a neighboring battery cell <NUM> within the same battery cell group <NUM>, <NUM>, <NUM>, <NUM> or so that the longitudinal side surface <NUM> contacts the plurality of smaller flat surfaces, e.g., the narrow side surfaces <NUM>, of a plurality of battery cells <NUM> of a neighboring battery cell group <NUM>, <NUM>, <NUM>, <NUM>. The sum of the areas of the narrow side surfaces <NUM> is less than or equal to the area of the longitudinal side surface <NUM>.

As shown in <FIG>, the battery cell <NUM> comprises electrical connectors <NUM> to electrically interconnect the battery cell <NUM> with, e.g., another battery cell <NUM> and/or a battery management module, e.g., via one or more a current collector structures, e.g., busbars <NUM> (see <FIG>), that are electrically connected to the electrical connectors <NUM>.

<FIG> illustrates a schematic view of a battery module <NUM> according to prior art. The exemplary battery module <NUM> comprises two battery cell groups <NUM> and <NUM>, each with a plurality of battery cells <NUM> being stacked onto each other. High energy densities of the battery cells <NUM> and a high packing density of the battery cells <NUM> within the module <NUM> in thermal contact between the battery cells <NUM> lead to increased safety issues in case of thermal runaway. If the battery cell <NUM> goes into thermal runaway, this leads to a heat-up of said battery cell <NUM> in thermal runaway and said battery cell <NUM> transfers the heat to its two nearest neighbors, i.e., two battery cells <NUM>, <NUM> within the battery cell group <NUM> or <NUM> which are touched via a longitudinal side surface <NUM> of the battery cell <NUM> (in its x-direction, see <FIG>). Each neighboring battery cell <NUM>, <NUM> gets half of the released energy and consequently heats up, which is enough to trigger thermal runaway. The propagation continues until all battery cells <NUM> in the cell stack, i.e., the cell group <NUM> or <NUM>. The battery module <NUM> comprises a cross-beam <NUM> as a part of a supporting structure of the battery module <NUM>. The cross-beam <NUM> leads to a compartmentalization of the battery module <NUM>, i.e., a plurality of chambers is formed in which the battery groups <NUM> are arranged. By using suitable measures, it may be prevented that the thermal runaway spreads across the cross-beam <NUM> throughout the entire battery module <NUM>. However, in principle, the thermal runaway may also propagate across the cross-beam <NUM> from one of the two battery cell groups <NUM> to the other cell group <NUM>. To achieve a compartmentalization also in the stacking direction in the conventional arrangement, spacers are typically used in the stacking direction. A sufficiently thick spacer, e.g., every seventh cell would lead to a similar compartmentalization as shown the arrangement in <FIG>.

The dots indicate that the battery module <NUM> can comprise more battery cells <NUM> than illustrated in <FIG>. Any number of battery cells <NUM> can be comprised by the battery module <NUM>.

<FIG> illustrates a schematic view of a battery module <NUM> according to an embodiment of the invention.

The battery module <NUM> comprises two first battery cell groups <NUM>, <NUM> and two second battery cell groups <NUM>, <NUM>. Each of the first battery cell groups <NUM>, <NUM> and each of the second battery cell groups <NUM>, <NUM> comprises a plurality of stacked prismatic battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The dots indicate that the battery module <NUM> can comprise more battery cell groups <NUM>, <NUM>, <NUM>, <NUM> than illustrated in <FIG>. Also the number of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> can be different than illustrated. Any suitable number of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and/or battery cell groups <NUM>, <NUM>, <NUM><NUM> can be comprised by the battery module <NUM>.

The numbers of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in any of the first battery cell groups <NUM>, <NUM> equal to each other. The numbers of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in any of the second battery cell groups <NUM>, <NUM> equal to each other. The number of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in any of the first battery cell groups <NUM>, <NUM> equals the number of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in any of the second battery cell groups <NUM>, <NUM>. Each of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> has the same prismatic shape. This enables an effective arrangement of the battery groups <NUM>, <NUM>, <NUM>, <NUM> in the battery module <NUM>.

Each of the first battery cell groups <NUM>, <NUM> is arranged adjacent to two second battery cell groups <NUM>, <NUM>. , each one of the first battery cell groups <NUM>, <NUM> is arranged side-by-side with the two second battery cell groups <NUM>, <NUM>. In other words, the two first battery cell groups <NUM>, <NUM> and the two second battery cell groups <NUM>, <NUM> are neighboring battery cell groups <NUM>, <NUM>, <NUM>, <NUM>. Similarly, each of the second battery cell groups <NUM>, <NUM> is arranged adjacent to two first battery cell groups <NUM>, <NUM>.

The first battery cell groups <NUM>, <NUM> and second battery cell groups <NUM>. , <NUM> are arranged to be alternatingly stacked. The battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the first battery cell groups <NUM>, <NUM> are oriented orthogonally to the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the second battery cell groups <NUM>, <NUM>.

The first battery cell groups <NUM>, <NUM> and the secondary battery cell groups <NUM>, <NUM> are arranged on a two-dimensional lattice, wherein the lattice comprises lattice sites arranged in at least two rows and at least two columns, wherein either one of the first battery cell groups <NUM>, <NUM> or one of the second battery cell groups <NUM>, <NUM> is arranged on each lattice site. Between two columns, a cross beam <NUM> is provided that is comprised by the battery module <NUM>. The cross beams <NUM> can support enduring side-crush loads. Given the expected values for the swelling force that a battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> generates in its x-direction, the necessary strength of the battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> housing in y-direction can be determined; if it is not sufficient in a given battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, additional support structures can be built in. Optionally and not shown in the figures, the battery module <NUM> comprises at least two cross-beams <NUM>, wherein two cross-beams <NUM> are arranged orthogonally to each other. This leads to a compartmentalization of the battery module <NUM> into compartments. Therein, the cross-beams <NUM> are arranged so that a width of the compartments match the width of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Thus, the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are to be stacked perpendicular to the width of the compartments.

The battery module <NUM> comprises thermally insolating spacers arranged between the battery cell groups <NUM>, <NUM>, <NUM>, <NUM> (not shown in the Figures).

Each of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> has a longitudinal side surface <NUM> and a narrow side surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> being smaller than the longitudinal side surface <NUM>. Within each of the first battery cell groups <NUM>, <NUM> and each of the second battery cell groups <NUM>, <NUM>, the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are stacked so that the longitudinal side surfaces <NUM> of two contacting battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> touch each other. This allows an efficient stacking of battery cell groups <NUM>, <NUM>, <NUM>, <NUM> and an efficient heat transfer between battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> within the respective battery cell group <NUM>, <NUM>, <NUM>, <NUM>. The first battery cell groups <NUM>, <NUM> and the second battery cell groups <NUM>, <NUM> are arranged so that one battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the first battery cell group <NUM>, <NUM> is arranged to touch a plurality of, or each of, the cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of a neighboring second battery cell group <NUM>, <NUM>, specifically with their narrow side surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. This allows an efficient heat transfer between battery cells <NUM> of adjacent battery cell groups <NUM>, <NUM>, <NUM>, <NUM>.

The battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> dimensions, i.e., elongation, perpendicular to the x- and y-direction match in the sense that its dimension perpendicular to the x-direction is an integer multiple of the dimension perpendicular to the y-direction (see <FIG> for coordinate system). Thus, the surface area of the longitudinal side surface <NUM> is an integer multiple of the surface area of the narrow side surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. For contacting the plurality of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the second battery cell group <NUM>, <NUM>, the longitudinal side surface <NUM> of the battery cell <NUM> of the first battery cell groups <NUM> contacts a plurality of narrow side surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the neighboring second battery group <NUM>. Each of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the second battery cell group <NUM>, <NUM> is arranged so that the narrow side surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> contacts the longitudinal side surface <NUM> of the battery cell <NUM> of the first battery cell group <NUM>. The sum of the areas of the narrow side surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is less or equal then the area of the longitudinal side surface <NUM>.

Alternatively, if the battery cell <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> dimensions do not match in the above-mentioned sense, additional spacers at the end of the cell stacks or between the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> can be introduced to enable an effective arrangement of battery cell groups <NUM>, <NUM>, <NUM>, <NUM> in the battery module <NUM>.

Arranging the battery cell groups <NUM>, <NUM>, <NUM>, <NUM> so that they are alternatingly stacked leads to a checkerboard pattern. In case of a thermal runaway each of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> within one square, i.e., site, of the checkerboard within one of the battery cell groups <NUM>, <NUM>, <NUM>, <NUM>, will likely go into thermal runaway one after the other. However, the last battery cell <NUM>, <NUM> being arranged at the boundary of the battery cell group <NUM>, <NUM>, <NUM>, <NUM> will transport its energy, via its longitudinal side surface <NUM> (perpendicular to the x-direction according to <FIG>), to a plurality of battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the neighboring battery cell group <NUM>, <NUM>, <NUM>, <NUM> via their narrow side surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (perpendicular to the y-direction according to <FIG>), e.g. seven in <FIG>. By distributing the energy of the thermal runaway to seven cells of the neighboring battery cell group <NUM>, <NUM>, <NUM>, <NUM>, each will heat up by for example ca. <NUM>, which is safe regarding triggering of thermal runaway.

Each of the first battery cell groups <NUM>, <NUM> and each of the second battery cell groups <NUM>, <NUM> is illustrated as having a square cross-section. However, it is also possible that the battery cell groups <NUM>, <NUM>, <NUM>, <NUM> have another rectangular cross-section by providing spacers between neighboring battery cell groups <NUM>, <NUM>, <NUM>, <NUM>. The prismatic shape of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> implies that the battery cell groups <NUM>, <NUM>, <NUM>, <NUM> have a rectangular cross-section or specifically a square cross-section is shown in the figures. Each of the battery cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> has an equal shape, and each of the first and second battery cell groups <NUM>, <NUM>, <NUM>, <NUM> has an equal shape with a square cross-section.

<FIG> illustrates a schematic view of a battery module <NUM> according to another embodiment of the invention. The embodiment of <FIG> will be explained with reference to the embodiment of <FIG>, wherein the differences are explained. In <FIG>, it is referred to battery cells <NUM> and to narrow side surfaces <NUM>, if appropriate.

Each of the first battery cell groups <NUM>, <NUM> comprises at least another one of the first battery cell groups <NUM>, <NUM> as next-nearest neighbor, wherein said first battery cell group <NUM> and the next-nearest neighboring first battery cell group <NUM> are stacked in the same manner. One of the second battery cell groups <NUM>, <NUM> is arranged between any pair of next nearest neighboring first battery cell groups <NUM>, <NUM>.

The battery module <NUM> comprises busbars <NUM> which are depicted for illustrative purpose to electrically interconnect the battery cells <NUM> of the battery cell groups <NUM>, <NUM>, <NUM>, <NUM>, and to electrically interconnect the battery cell groups <NUM>, <NUM>, <NUM>, <NUM>. The busbars <NUM> are connected to the battery cell connectors <NUM> of the battery cells <NUM>. In another embodiment, other current collector structures can be provided. <FIG> shows an exemplary busbar layout for part of a cell stack.

In this embodiment, the battery cell groups <NUM>, <NUM>, <NUM>, <NUM> are arranged on lattice sites of a one-dimensional lattice, i.e., battery cell groups <NUM>, <NUM>, <NUM>, <NUM> form a one-dimensional checkerboard pattern and are alternatingly arranged on the lattice sites of the one-dimensional lattice.

Claim 1:
A battery module (<NUM>), comprising
- a plurality of first battery cell groups (<NUM>, <NUM>, <NUM>) and a plurality of second battery cell groups (<NUM>, <NUM>, <NUM>); wherein
- at least one of the first battery cell groups (<NUM>, <NUM>, <NUM>) is arranged adjacent to at least one of the second battery cell groups (<NUM>, <NUM>, <NUM>); wherein
- each of the first battery cell groups (<NUM>, <NUM>, <NUM>) and each of the second battery cell groups (<NUM>, <NUM>, <NUM>) comprises a plurality of stacked prismatic battery cells (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); wherein
- the first battery cell groups (<NUM>, <NUM>, <NUM>) and second battery cell groups (<NUM>, <NUM>, <NUM>) are alternatingly stacked; and wherein
- the battery cells (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of the first battery cell group (<NUM>, <NUM>, <NUM>) are oriented orthogonally to the battery cells (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of the second battery cell group (<NUM>, <NUM>, <NUM>),
- each of the battery cells (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) has a narrow side surface (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and a longitudinal side surface (<NUM>), wherein the longitudinal side surfaces correspond to the largest flat surfaces of the battery cells;
characterized in that,
- the first battery cell groups (<NUM>, <NUM>, <NUM>) and the second battery cell groups (<NUM>, <NUM>, <NUM>) are arranged so that one battery cell (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of the first battery cell group (<NUM>, <NUM>, <NUM>) is arranged to touch, with its longitudinal side surface (<NUM>), a plurality of, or each of, the cells (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of a neighboring second battery cell group (<NUM>, <NUM>, <NUM>) at their narrow side surfaces (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>).