CN113451666A

CN113451666A - Battery system, method of operating the same, and battery pack and vehicle including the same

Info

Publication number: CN113451666A
Application number: CN202110324284.XA
Authority: CN
Inventors: A.戈卢布科夫
Original assignee: Samsung SDI Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 2020-03-27
Filing date: 2021-03-26
Publication date: 2021-09-28

Abstract

The invention relates to a battery system (100) comprising: comprises a plurality of battery units (10)₁、……、10₁₂) A stack of (a); a fluid spring (30); and a fluid pressure adjusting mechanism (12). A fluid spring (30) is located between the first end plate (40a) and the second end plate (40b) and is configured to apply pressure to the battery cell. At least one of the fluid springs (30) comprises resilient means having a predetermined young's modulus. A fluid pressure regulating mechanism (12) connected withTo one or more fluid springs (30) comprising resilient means configured to create a negative pressure in the fluid within the connected fluid spring (30). Furthermore, the battery system allows to avoid or minimize the risk of thermal runaway overflowing between different units of the battery system. The invention also relates to a method for operating the battery system.

Description

Battery system, method of operating the same, and battery pack and vehicle including the same

Technical Field

The present invention relates to a battery system or a battery module including a stack of battery cells. Furthermore, the invention relates to a battery pack comprising a battery system, and to a vehicle comprising a battery pack or a battery system as defined above.

Background

In recent years, vehicles for transportation of goods and people using electric power as a moving source have been developed. Such an electric vehicle is an automobile propelled by an electric motor using energy stored in a rechargeable battery. The electric vehicle may be powered by a battery only, or may be in the form of a hybrid vehicle powered by, for example, a gasoline generator. Further, the vehicle may include a combination of an electric motor and a conventional internal combustion engine. In general, an Electric Vehicle Battery (EVB) or traction battery is a battery used to power the propulsion of a Battery Electric Vehicle (BEV). Electric vehicle batteries are different from starting batteries, lighting batteries, and ignition batteries because they are designed to power for sustained periods of time. A rechargeable or secondary battery differs from a primary battery in that it can be repeatedly charged and discharged, while a primary battery provides only irreversible conversion of chemical energy into electrical energy. A low-capacity rechargeable battery is used as a power source for small electronic devices such as cellular phones, notebook computers, and camcorders, and a high-capacity rechargeable battery is used as a power source for hybrid vehicles and the like.

In general, a rechargeable battery includes: an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a case receiving the electrode assembly; and electrode terminals electrically connected to the electrode assembly. An electrolyte solution is injected into the case so that the battery can be charged and discharged by an electrochemical reaction of the positive electrode, the negative electrode and the electrolyte solution. The shape of the housing, such as cylindrical or rectangular, depends on the intended use of the battery. Lithium ion (and similar lithium polymer) batteries, which are well known for their use in notebook computers and consumer electronics, dominate the latest batch of electric vehicles under development.

As an alternative to the electrolyte solution described above, a solid-state cell may be employed in the battery. The solid-state battery can be defined by the following characteristics. The main difference between conventional lithium ion cells and all solid-state lithium ion cells is that all solid-state lithium ion batteries do not contain a liquid electrolyte. Alternatively, the electrolyte is a solid electrolyte. The solid electrolyte may be a ceramic (e.g., sulfide, oxide, phosphate) or a solid polymer (e.g., polyethylene oxide (PEO)) or a polymer gel (e.g., poly (vinylidene fluoride) -hexafluoropropylene (pvdf (hfp))).

The cathode material arranged in the solid state may be the same as in a conventional lithium ion battery. However, the cathode particles are not soaked by the liquid electrolyte, but are embedded in a solid electrolyte matrix. Furthermore, the anode of the solid-state cell is different from the anode of the conventional lithium-ion cell. In conventional units, the anode is composed of graphite or silicon particles. However, in solid state cells, the anode comprises a thin lithium metal film. Furthermore, solid state cells do not have dedicated separators. The solid electrolyte acts as a separator (thus, the solid electrolyte is not conductive).

The rechargeable battery may be used as a battery module formed of a plurality of unit battery cells coupled in series and/or parallel, thereby providing high energy density, particularly, for motor driving of a hybrid vehicle. That is, the battery module is formed by interconnecting electrode terminals of the plurality of unit battery cells depending on the required amount of electric power and in order to realize a high-power rechargeable battery.

A battery pack is a group of any number of (preferably identical) battery modules. They may be configured in series, parallel, or a mixture of both to provide a desired voltage, capacity, or power density. The components of the battery pack include individual battery modules and interconnects that provide electrical conductivity therebetween.

The mechanical integration of such battery packs requires suitable mechanical connections between the individual components of, for example, the battery module and between them and the supporting structure of the vehicle. These connections must remain functional and safe during the average service life of the battery system. Furthermore, the requirements of installation space and interchangeability must be met, especially in mobile applications.

The mechanical integration of the battery module may be achieved by providing a carrier frame and by placing the battery module thereon. The fixation of the battery cells or battery modules may be achieved by mating recesses in the frame or by mechanical interconnects such as bolts or screws. Alternatively, the battery module is restrained by fastening the side plates to the sides of the carrier frame. In addition, the cap plate may be fixed at the top and under the battery module.

The carrier frame of the battery pack is mounted to a load-bearing structure of the vehicle. In the case of a battery pack that is to be fastened to the vehicle underbody, the mechanical connection can be established from the underside by means of, for example, bolts that pass through the carrier frame of the battery pack. The frame is typically made of aluminum or an aluminum alloy to reduce the overall weight of the structure. Furthermore, the frame may be made of a steel alloy to improve safety and robustness.

Regardless of any modular construction, battery systems according to the prior art typically include a battery housing that serves as a shell to seal the battery system from the environment and to provide structural protection to the components of the battery system. The housed battery system is generally integrally mounted into its application environment, such as an electric vehicle. Therefore, the replacement of defective system parts, such as defective battery submodules, requires the first disassembly of the entire battery system and the removal of its housing. Even a defect in small and/or inexpensive system components can then lead to the removal and replacement of the entire battery system and its individual servicing. The process is rendered cumbersome because high capacity battery systems are expensive, large and heavy, and storage of large volume battery systems, for example in a mechanic's shop, becomes difficult.

In order to meet the dynamic power demands of the various electrical consumers connected to the battery system, static control of the battery power output and charging is not sufficient. Therefore, a stable information exchange between the battery system and the controller of the electrical consumer is required. Such information includes the actual state of charge (SoC), potential electrical performance, charging capability and internal resistance of the battery system, and the actual or anticipated power demand or surplus of the consumer.

The battery system generally includes a Battery Management System (BMS) and/or a Battery Management Unit (BMU) for processing the aforementioned information. The BMS/BMU CAN communicate with the controllers of the various electrical consumers via a suitable communication bus, for example an SPI or CAN interface. The BMS/BMU may also communicate with each battery sub-module, in particular with a battery supervision circuit (CSC) of each battery sub-module. The CSC may also be connected to a battery connection and sensing unit (CCU) of the battery sub-modules that interconnect the battery cells of the battery sub-modules.

Thus, the BMS/BMU is provided for managing the battery pack, for example, by protecting the battery from operating outside its safe operating range, monitoring its status, calculating auxiliary data, reporting this data, controlling its environment, authenticating it, and/or equalizing it.

To provide thermal control of the battery pack, a thermal management system is needed to safely use at least one battery module by efficiently dissipating, draining, and/or dissipating heat generated from its rechargeable battery. If the heat dissipation/discharge/dissipation is not sufficiently performed, a temperature deviation occurs between the respective battery cells such that at least one battery module cannot generate a desired amount of power. In addition, an increase in internal temperature may cause an abnormal reaction to occur therein, so that rechargeable charge and discharge performance is deteriorated and the life of the rechargeable battery is shortened. Therefore, there is a need for cell cooling for efficiently dissipating/exhausting/dissipating heat from the cells.

As already indicated above, most automotive lithium ion (Li-ion) battery packs used, i.e. battery packs employed in electric vehicles or hybrid vehicles, are composed of several battery modules. A typical automotive battery module (hereinafter also simply referred to as "module") is constructed of several stacked units. To achieve the desired module capacity and voltage, bus bars electrically connect the cells in series or in parallel. The modules may also be connected in series until a desired system voltage of the battery pack is reached.

To reduce aging, the stack of modules is pressed with mechanical pressure (e.g., 100kPa) to press each of the battery cells included in the stack. Solid state battery cells (see definition thereof above) require higher mechanical pressures (typically in the range of 2MPa to 3 MPa) to operate.

However, a battery cell (hereinafter also simply referred to as "cell") may expand during charging and contract (e.g., 5%) during discharging, particularly resulting in a thickness variation of the cell. In addition to the reversible thickness variation during charging/discharging, the thickness of the cell is also superimposed by a slow irreversible swelling due to aging of the electrode material.

Since the cells of the battery module are arranged in a stack, the thickness variation of the cells causes the size variation of the stack. However, the stack is typically accommodated in a carrier frame or packaging frame (see above) having limited dimensions, so that the carrier frame acts as a restraint, which imposes mechanical constraints on the stack and the units comprised in the stack. Therefore, the expansion or contraction of the battery cells affects the pressure that the battery cells exert on each other in the stack. Thus, the dimensional changes of the stack impose mechanical constraints on the stack and different stresses on the cells. The stress variation depends on the stiffness of the unit and the restraint; the relationship between the stress variation and the stiffness of the unit and of the restraint can be described in good approximation by hooke's law.

However, this reveals the disadvantages of (a) not being able to actively control or adjust the stress after assembly of the stack and (b) the mechanical pressure is not constant over the lifetime of the cell.

One possibility to control the stress on the units used in the prior art is to apply pressure by means of flat pressure plates, e.g. end plates arranged in front of the first unit of the stack and behind the last unit of the stack. However, when high forces are applied, those plates may bend and the resulting pressure on the outermost cell or cells becomes uneven. However, uneven pressure reduces the performance of the cell stack, especially in terms of safety and/or ageing. The aforementioned disadvantages are particularly evident in stacks having solid-state cells that require higher pressures during operation (see above).

One possibility to obtain an improved control of the pressure prevailing in the stack of battery cells is to integrate a fluid spring, such as an air spring or an air cushion, in the cell stack. The pressure of the fluid within the fluid spring can be controlled from the outside, which allows to adapt the total pressure exerted on the units in the stack.

One disadvantage of using simple fluid springs is that the fluid pressure in the fluid springs has to be actively maintained during the entire life of the battery module, for example by means of a compressor. On the one hand, this is energy intensive due to the constantly required power consumption of the compressor. On the other hand, the compressor must be able to provide at least the required pressure required in the cell stack (see above).

Furthermore, in the event of a thermal event within a unit in the stack (such as a thermal runaway), the heat transfer from the affected unit to an adjacent unit may be so great that even when the unit is cooled by the cooling system, the adjacent unit absorbs more heat than the cooling system can expel, which often results in the adjacent unit being infected with a thermal runaway, i.e. a thermal runaway may occur in the adjacent unit.

It is therefore desirable to provide a battery module or battery system that allows for active control of the pressure exerted on the cells in the battery module, but at the same time reduces the need or requirement for energy/power consumption and for the layout of the mechanism for controlling the pressure in the fluid spring (with respect to the strength and/or strength of the pressure provided). Furthermore, it is desirable to provide a battery module or a battery system which avoids or at least reduces the risk of thermal runaway occurring in a cell of the battery system propagating to adjacent cells.

It is therefore 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 system that allows an active control of the pressure exerted on the cells in the battery module, but at the same time reduces the energy/power consumption and the need or requirement for the layout of the mechanism for controlling the pressure in the fluid spring (with respect to the strength and/or strength of the pressure provided). It is also an object of the invention to provide a battery module or battery system which avoids or at least reduces the risk of thermal runaway occurring in a cell of the battery system propagating to adjacent cells. These objects are achieved by a battery system (battery module) and a method for operating the battery system as disclosed in the independent claims.

Disclosure of Invention

Embodiments of the present disclosure seek to address, at least to some extent, at least one of the problems presented in the prior art. Specifically, a battery system or a battery module for use in a vehicle is provided, which includes: a stack including a plurality of battery cells stacked along a virtual reference axis; a packing frame including a first end plate and a second end plate; one or more fluid springs configured to contain a fluid; one or more fluid pressure adjustment mechanisms for adjusting fluid pressure within the at least one fluid spring; and a control unit configured to control the one or more fluid pressure adjustment mechanisms. The stack is placed between the first end plate and the second end plate. Each of the one or more fluid springs is located between the first end plate and the second end plate and is configured to apply pressure to at least one of the battery cells in a direction along the reference axis. Each fluid pressure adjustment mechanism is connected to one or more fluid springs. In accordance with a first alternative of the battery system according to the invention, at least one of the fluid springs comprises elastic means. Each of the fluid pressure adjustment mechanisms connected to one or more fluid springs including elastic means is configured to generate or adjust a negative pressure in the fluid within the connected fluid spring when the connected one or more fluid springs each contain fluid. In accordance with a second alternative of the battery system according to the invention, the control unit is configured to receive a safety check signal from at least one safety check sensor. The control unit is further configured for evaluating whether the received safety check signal may indicate a safety critical situation and for operating the fluid pressure regulating mechanism such that the fluid pressure in the fluid spring is reduced after the safety check signal(s) are evaluated as being indicative of a safety critical situation.

Note that the expression "battery cell placed next to an end plate" does not exclude that a different element, such as a fluid spring, is placed between the battery cell and the end plate.

Furthermore, the term "pressure" as used throughout this document shall refer to a mechanical contact pressure, wherein the mechanical contact pressure may be caused by direct contact between two elements, or the pressure is transmitted from one element to another element through one or more intervening elements.

The term "negative pressure" of the fluid spring shall refer here and throughout the entire document to a pressure range that is less than or at most equal to the pressure of the surrounding atmosphere of the fluid spring. The pressure of the ambient atmosphere of the fluid spring typically corresponds to the pressure of the ambient air of the battery system.

Of course, the actual pressure applied from the fluid spring to one or two adjacent battery cells corresponds to the (counter) pressure applied from the adjacent battery on the fluid spring. Thus, if a fluid spring is filled with a certain amount of fluid, the pressure provided by the fluid spring depends on the situation, in particular on the space left for the fluid spring between two elements (e.g. cells) adjacent to the fluid spring along the reference axis.

The expression "may indicate a safety hazard situation" may particularly denote an evaluation of the safety check signal(s) performed by the control unit, a probability or likelihood of a safety hazard event in or of the vehicle being estimated, the measured/received safety check signal(s) being classified as safety hazard if said probability or likelihood exceeds a predetermined value, e.g. 50%, 80% or 90%. Furthermore, the term "safety critical situation" shall refer to every event that entails a risk for the vehicle itself and/or the passengers/drivers of the vehicle.

In one embodiment, the resilient means has a predetermined young's modulus. The young's modulus may be a function depending on temperature. Furthermore, the young's modulus may also be a function depending on spatial position. Preferably, the young's modulus is selected to be constant over the entire extension of the elastic means in a plane perpendicular to the reference direction.

According to one embodiment of the battery system, the stack is placed between the first end plate and the second end plate such that a first battery cell of the stack is located next to the first end plate when viewed along the reference axis and a last battery cell of the stack is located next to the second end plate when viewed along the reference axis.

The battery system may further include at least one fluid pressure sensor configured to measure a fluid pressure present in at least one of the fluid springs; wherein the control unit is configured to receive a pressure signal corresponding to the pressure measured from each fluid pressure sensor; and wherein the control unit is further configured to control the one or more fluid pressure regulating mechanisms in dependence on the received one or more pressure signals.

The control unit may be configured to detect a pressure change in the fluid of the fluid spring to which the fluid pressure sensor is connected from the pressure signal provided from each fluid pressure sensor. Further, the control unit is further configured to control at least one of the fluid pressure adjusting mechanisms such that, upon detection of an increase in pressure by at least one of the fluid pressure sensors, the fluid pressure adjusting mechanism reduces the pressure of the fluid within the fluid spring connected to the respective fluid pressure adjusting mechanism.

In other words, when a pressure increase occurs in the stack, the negative pressure increases (i.e. the pressure decreases), resulting in a decrease of the total pressure consisting of the pressure caused by the elastic means and the pressure within the fluid. If in the initial state no negative pressure of the fluid is present in the respective fluid spring (i.e. the fluid pressure is equal to the pressure of the surrounding atmosphere or higher), a negative pressure (i.e. a pressure lower than or equal to the pressure of the surrounding atmosphere) is generated in the fluid after detecting the pressure increase in the stack.

The relationship between the measured pressure increase and the pressure decrease in the fluid spring(s) triggered in response to the measured pressure increase may be linear.

Note that in this context, the expression "pressure change" shall cover both the case of pressure increase and the case of pressure decrease.

According to another aspect of the present disclosure, the control unit is further configured to control at least one of the fluid pressure adjusting mechanisms such that, upon detection of a decrease in pressure by at least one of the fluid pressure sensors, the fluid pressure adjusting mechanism increases the pressure of the fluid within a fluid spring connected to the respective fluid pressure adjusting mechanism.

This may require that the pressure prevailing in the fluid spring(s) is already a negative pressure after a pressure reduction is detected.

The relationship between the measured pressure decrease and the pressure increase in the fluid spring(s) triggered in response to the measured pressure decrease may be linear, at least up to a pressure equal to the pressure of the surrounding atmosphere.

In one embodiment of the battery system according to the invention, the resilient means is a foam.

According to another aspect of the present disclosure, at least one of the fluid springs is placed between two adjacent battery cells, as seen along the reference axis. In particular, in this case, the battery system may include only a single fluid spring.

According to another aspect of the present disclosure, one of the fluid springs is disposed between the (N/2) th battery cell and the (N/2+1) th battery cell if the number of battery cells in the stack is N and N is an even integer, or between the ((N-1)/2) th battery cell and the ((N +1)/2) th battery cell if the number of battery cells in the stack is N and N is an odd integer, wherein the battery cells are counted from the first battery cell in the stack to the last battery cell in the stack. In particular, in this case, the battery system may include only a single fluid spring.

In one embodiment of the battery system according to the present invention, one fluid spring is placed between the first end plate and the first battery cell stacked; another fluid spring is placed between the second end plate and the last battery cell in the stack. In particular, in this case, the battery system may comprise only two fluid springs.

According to another aspect of the present disclosure, at least one positioning plate is placed between two adjacent battery cells, as viewed along the reference axis. In particular, in this case, the battery system may include only a single positioning plate.

According to another aspect of the present disclosure, one of the positioning plates is disposed between the (N/2) th battery cell and the (N/2+1) th battery cell if the number of battery cells in the stack is N and N is an even integer, or between the ((N-1)/2) th battery cell and the ((N +1)/2) th battery cell if the number of battery cells in the stack is N and N is an odd integer, wherein the battery cells are counted from the first battery cell in the stack to the last battery cell in the stack. In particular, in this case, the battery system may include only a single positioning plate.

According to another aspect of the present disclosure, each fluid spring is in fluid communication with each other. This embodiment has the following advantages: a single fluid pressure adjustment mechanism is sufficient to control each fluid spring and the negative pressure of the fluid within the fluid spring is equal for each fluid spring.

The fluid may be an incompressible fluid or a compressible fluid. The incompressible fluid may be air.

According to another aspect of the present disclosure, at least one of the fluid pressure adjustment mechanisms includes a vacuum pump, a valve, or a compressor.

According to another aspect of the present disclosure, at least one fluid pressure sensor is connected to one or more of the fluid springs.

According to another aspect of the present disclosure, the battery cell is a solid-state battery cell.

According to another aspect of the invention, each battery cell has a prismatic geometry or a cylindrical geometry, wherein the base region extends perpendicular to the reference axis.

According to a further aspect of the invention, each fluid spring has a prismatic or cylindrical geometry, wherein the base region extends perpendicular to the reference axis; and each fluid spring is positioned such that for each battery cell in contact with the fluid spring, the entire base region of the battery cell is in contact with the adjacent base region of the fluid spring. This has the following advantages: for each fluid spring, pressure is provided from the fluid spring over the entire adjacent area of the adjacent battery cell, i.e. pressure is applied to each point of the adjacent area of each battery cell adjacent to the fluid spring.

According to another aspect of the present disclosure, the control unit is integrated into a BMU or BMS of the battery system or the battery pack including the battery system.

According to another aspect of the present disclosure, the at least one safety check sensor is an acceleration sensor configured to detect a negative acceleration having an absolute acceleration value equal to or greater than a predetermined positive value.

The acceleration sensor serves as a collision sensor. For example, the acceleration sensor may detect-and send a safety check signal to a connected control unit-that is equal to or lower than-90 m/s for the vehicle (or equivalently, for a battery system employed in the vehicle)²Or in other words, detected to have a negative acceleration equal to or greater than +90m/s²Negative acceleration of the absolute value of (a). Of course, the acceleration sensor may also send a measured acceleration, for example within a predetermined time interval, independent of its value, and the control unit evaluates whether the measured acceleration or acceleration pattern may indicate a collision of the vehicle. The term "acceleration pattern" may in this context refer to a function of measured acceleration values plotted over the last M acceleration measurement times (where, for example, M ═ 4).

According to another aspect of the present disclosure, the at least one safety check sensor is a temperature sensor configured to measure a temperature of the stack of battery cells or to measure a temperature of at least one of the battery cells included in the stack; and the control unit evaluates whether the temperature or the temperature pattern measured by the at least one temperature sensor may indicate a safety critical thermal event, such as thermal runaway.

In this context, the term "temperature pattern" may refer to a function of measured temperature values plotted over the last M temperature measurement times (where, for example, M ═ 4).

In one embodiment of the battery system, the at least one safety check sensor is a cell voltage sensor configured to measure a voltage or voltage pattern across one or more cells of the battery system.

In this context, the term "voltage pattern" may refer to a function of measured voltage values plotted over the last M voltage measurement times (where, for example, M ═ 4).

In one embodiment of the battery system, the at least one safety check sensor is a current sensor configured to measure a current or a current pattern generated by the battery system or at least by one unit of the battery system.

In this context, the term "current mode" may refer to a function of measured current values plotted over the last M current measurement times (where, for example, M ═ 4).

In one embodiment of the battery system, the at least one safety check sensor is an insulation monitor.

According to another aspect of the present disclosure, a Battery Management Unit (BMU) of a battery system detects a safety critical state of a battery pack/battery system by combining and processing at least two of the following signals: cell voltage, cell temperature, system current, gas pressure in the battery system, gas temperature in the battery system.

Another aspect of the present disclosure relates to a method for operating a battery system according to the present invention, the method comprising the steps of:

a) creating a negative pressure in the fluid of at least one of the fluid springs;

b) the fluid pressure of at least one of the fluid springs is regulated according to the state of at least one of the battery cells, wherein the fluid pressure is regulated to a negative pressure.

Step a) also covers the case where a (negative) pressure of 0Pa is maintained in the fluid spring, i.e. the pressure inside the fluid spring is equal to the pressure of the surrounding atmosphere; see the definition of the term "negative pressure" given above. In other words, step a) sets or defines an initial negative pressure in at least one of the fluid springs. Preferably, in step b), the fluid pressure of the fluid springs is adjusted to be equal for each fluid spring at any time.

In one embodiment of the method, step b) is repeated continuously or within a predetermined time interval or when triggered by a predetermined event.

In one embodiment of the method, the state of at least one of the battery cells is dependent on the age of the at least one battery cell; step b) includes decreasing the fluid pressure of at least one of the fluid springs as the age of the battery cell increases.

Note that in this context, the expression "reducing the fluid pressure" shall refer to an increase of the negative pressure. In other words, as the negative pressure increases, the absolute pressure within the fluid decreases.

In one embodiment of the method, the state of at least one of the battery cells is dependent on the charging or discharging condition of the at least one battery cell.

In one embodiment of the method, step b) includes reducing the fluid pressure of at least one of the fluid springs when the battery cell is in a charging condition; step b) includes increasing a fluid pressure of at least one of the fluid springs when the battery cell is in a discharge condition.

Another aspect of the present disclosure relates to a method for operating a battery system, comprising the steps of:

a) adjusting a pressure in the fluid of at least one of the fluid springs;

b) checking, by the control unit, whether a security check signal has been received from the at least one security check sensor;

c) evaluating, by the control unit, whether the received safety check signal may indicate a safety critical situation; and

d) the fluid pressure regulating mechanism is operated by the control unit after evaluating the safety check signal(s) may indicate a safety critical situation such that the fluid pressure in the fluid spring is reduced.

According to one embodiment of the method, step b) comprises: if the at least one security check sensor is an acceleration sensor: it is checked whether the received safety check signal from at least one of the acceleration sensors indicates a negative acceleration having an absolute acceleration value equal to or greater than a predetermined positive value. Further, if the at least one safety check sensor is a thermal sensor configured to measure a temperature of the stack of battery cells or to measure a temperature of at least one of the battery cells included in the stack, step b) may include: it is evaluated whether the temperature or the temperature pattern measured by the at least one temperature sensor may indicate a safety critical thermal event, such as thermal runaway. Further, if the at least one safety check sensor is a cell voltage sensor configured to measure a voltage across at least one cell of the battery system, step b) may comprise: it is evaluated whether the voltage or the voltage pattern measured by the at least one cell voltage sensor may indicate a safety critical event. Furthermore, if the at least one safety check sensor is a current sensor configured for measuring a current generated by the battery system or at least by one unit of the battery system, step b) may comprise: it is evaluated whether the current or the current pattern measured by the at least one current sensor may indicate a safety critical event. Further, if the at least one safety check sensor is an insulated sensor, the step b) may include: it is evaluated whether the insulation measured by the at least one insulation sensor is below a predetermined critical value.

Another aspect of the present disclosure relates to a battery pack including the battery system according to the present invention.

Yet another aspect of the present disclosure relates to a vehicle comprising a battery pack or battery system as defined above.

Further aspects of the disclosure may be gleaned from the following description.

Drawings

Features will become apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, wherein:

fig. 1A shows a schematic view (longitudinal cut) of a battery system according to an embodiment of the invention;

fig. 1B shows a schematic view (longitudinal cut) of a battery system according to an embodiment of the present invention connected to a safety check sensor;

fig. 2 shows a schematic view (longitudinal cut) of a battery system according to another embodiment of the present invention;

fig. 3 shows a schematic view (longitudinal cut) of a battery system according to a further embodiment of the invention;

fig. 4 shows a schematic view (longitudinal cut) of a battery system according to a further embodiment of the invention; and

fig. 5 shows a schematic view (longitudinal cutting) of a battery system according to still another embodiment of the present invention.

Reference symbols

100 Battery system (Battery module)

10₁、10₂、……、10_NBattery cell designed as a metal can

20₁、20₂、……、20_NBattery cell designed as a flat pouch cell

12 mechanism for controlling pressure (negative pressure) in a fluid spring

14 pressure sensor

16 fluid connection

18. 18a, 18b external fluid connection

30. 30a, 30b fluid spring

32 outer wall of fluid spring

34a, 34b resilient support element

36a, 36b, 36c cavity

40a first end plate

40b second end plate

50 positioning plate

60 safety check sensor

90 control unit

92. 94, 96 signal connecting wire

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. Effects and features of exemplary embodiments and methods of implementing the same will be described with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and redundant description is omitted. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Furthermore, "may" be used in describing embodiments of the invention to mean "one or more embodiments of the invention.

It will be understood that, although the terms first and second are used to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention.

It will be further understood that the terms "comprises," "comprising," "includes … …," or "including … …," specify the presence of stated features, regions, integers, steps, processes, elements, components, and combinations thereof, but do not preclude the presence or addition of other features, regions, integers, steps, processes, elements, components, and combinations thereof.

In the drawings, the size of elements may be exaggerated for clarity. For example, in the drawings, the size or thickness of each element may be arbitrarily shown for the purpose of illustration, and thus the embodiments of the present invention should not be construed as being limited thereto.

As used herein, the terms "substantially," "about," and the like are used as approximate terms and not as degree terms, and are intended to account for inherent deviations in measured or calculated values that would be recognized by one of ordinary skill in the art. Furthermore, if the term "substantially" is used in connection with a feature that can be expressed using a numerical value, the term "substantially" means a range of +/-5% of the value centered on the value. Furthermore, "may" be used in describing embodiments of the invention to mean "one or more embodiments of the invention.

An electronic or electrical device and/or any other related device or component in accordance with embodiments of the invention described herein may be implemented using any suitable hardware, firmware (e.g., application specific integrated circuits), software, or combination of software, firmware and hardware. For example, various components of these devices may be formed on one Integrated Circuit (IC) chip or on separate IC chips. In addition, the respective components of these devices may be implemented on a flexible printed circuit film, a Tape Carrier Package (TCP), a Printed Circuit Board (PCB), or formed on one substrate. Further, the various components of these apparatuses may be processes or threads that execute on one or more processors in one or more computing devices, execute computer program instructions, and interact with other system components to perform the various functions described herein. The computer program instructions are stored in a memory, which may be implemented in the computing device using standard memory devices, such as, for example, a Random Access Memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as CD-ROM, flash drives, and the like. In addition, those skilled in the art will recognize that the functionality of the various computing devices may be combined or integrated into a single computing device, or that the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the exemplary embodiments of this invention.

The present invention is adapted to include a metal can element 10 such as a prismatic metal can element₁、10₂、……、10₁₂(see fig. 1-4) or flat bag-type unit 20₁、20₂、……、20₁₈(see fig. 5) of the battery cells. The invention is particularly suitable for Li-ion cells, especially for solid-state cells (batteries) which require high mechanical pressure during operation.

As shown in fig. 1-5, one or more fluid springs 30, 30a, 30b are integrated into the stack of units. The fluid springs 30, 30a, 30b may have a flat shape. Thus, the stack includes the battery cell 10₁、10₂、……、10₁₂、20₁、20₂、……、20₁₈And one or more fluid springs 30, 30a, 30 b. The stack is defined by

fixed end plates

40a, 40b on either side of the stack. The fluid springs 30, 30a, 30b have the shape of a cushion and comprise fluid-tight bellows or bladders. The fluid springs 30, 30a, 30b include resilient means that may be formed within a bellows or bladder of the fluid spring. The elastic means may be the bellows or the bladder itself, or embedded in the bellows or the bladder. The resilient means may comprise foam or may be made entirely of foam.

Due to the elastic means comprised in the fluid springs 30, 30a, 30b, the fluid springs, when integrated in a stack as shown in fig. 1-5, provide a pressure force exerted on the stack of battery cells, which pressure force acts along the longitudinal axis z of the stack (also referred to throughout this document as reference axis; this axis is only depicted in fig. 1A, but is used to explain the other figures in a similar way), i.e. along the axis from the first end plate 40a to the second end plate 40 b. It is noted in this context that if a first element (fluid spring, unit, location plate or end plate) in a stack of elements provides a pressure on an adjacent second element (also fluid spring, unit, location plate or end plate) in a first direction along the longitudinal axis, the second element exerts the same pressure on the first element in the opposite direction. Furthermore, the pressure of one element is transferred through one or more intervening elements to other elements of the stack that are not in direct contact with the first element. Further, if the non-fixed element (unit or fluid spring) receives a first pressure from one side (e.g., from the left side in the drawing) and a second pressure from the opposite side (e.g., from the right side in the drawing), the non-fixed element is displaced along the axis (i.e., to the left or right side in the drawing) as long as the absolute value of the pressure applied to the element from the one side is not equal to the absolute value of the pressure applied to the element from the other side. For the reasons described above, the pressure exerted on the non-fixed elements arranged in the stack between two fixed elements (end plates, positioning plates) is essentially the same for each of these non-fixed elements. Furthermore, if the pressure changes at some point between two fixed elements (typically due to a change in thickness of one or more non-fixed elements therebetween) such that the pressure exerted on the non-fixed elements is not the same for all non-fixed elements, the non-fixed elements are displaced until each non-fixed element is again subjected to the same pressure. In order to control the pressure in the stack of non-fixed elements confined between two fixed elements, it is therefore sufficient to control the pressure at one (or a limited) position between the fixed elements.

For the above reasons, the battery cell 10 in the battery system₁、10₂、……、10_N、20₁、20₂、……、20_NIn the stack ofEqual to the adjustable pressure provided by one or more fluid springs 30, 30a, 30b to the adjacent element (cell, end plate or spacer plate). The pressure provided by the fluid springs 30, 30a, 30b consists of: (i) pressure provided by elastic means consisting of a fluid spring; and (ii) the fluid pressure prevailing within the fluid spring. The pressure sensor 14 may be used to measure the fluid pressure within the fluid spring.

The resilient means provides pressure in the stack even when the fluid pressure within the fluid spring is equal to the pressure of the surrounding atmosphere. The pressure provided by the resilient means depends on the young's modulus of the resilient means (which in turn depends on the position in a direction perpendicular to the longitudinal axis of the stack and/or on the temperature of the resilient means) and the thickness of the resilient means (measured along the longitudinal axis of the stack) consisting of a fluid spring confined between adjacent elements in the stack. Hooke's law gives a good approximation of the relationship between pressure and thickness of the elastic means comprised in the fluid spring.

The resilient means may constitute the maximum pressure applied to adjacent elements of the fluid springs 30, 30a, 30b in the stack. The total pressure exerted by the fluid springs-the pressure provided by the resilient means plus the total pressure given by the fluid pressure within the fluid in the fluid springs-may be controlled by controlling the pressure in the fluid springs 30, 30a, 30 b. According to the invention, a negative pressure is generated in the fluid of the fluid spring. Herein, the negative pressure of the fluid is defined as the pressure in the fluid being at most equal to the pressure of the surrounding atmosphere, i.e. the fluid pressure is equal to or less than the pressure of the surrounding atmosphere. In other words, the mechanical total pressure may be reduced by evacuating the fluid-tight bellows or bladder of the fluid spring with a vacuum pump.

In order to control the (negative) pressure in the fluid springs 30, 30a, 30b, a fluid

pressure regulating mechanism

12, 12a, 12b is employed. The fluid pressure regulating mechanism 12 may be a combination of a vacuum pump and a valve. In other words, the fluid pressure regulating mechanism 12 regulates the pressure to a desired set point.

Due to the resilient means, one or more fluid springs 30, 30a, 30b in the stack will also provide pressure in case of a loss or leakage of air pressure.

The

fluid spring

30, 30a, 30b employed in the embodiment of the present invention may have a structure similar to the battery cell 10₁、10₂、……、10_N，20₁、20₂、……、20_NThe same cross section and preferably may be attached directly to adjacent units within the stack. Throughout this document, the term "cross-section" shall refer to the lateral area of an element (fluid spring, cell, positioning plate or end plate) perpendicular to the longitudinal axis z of the stack as defined above. The width (i.e., the thickness measured along the longitudinal axis z of the stack) of each of the fluid springs 30, 30a, 30b employed may be in the range of 5mm to 50 mm. The working medium (i.e., the fluid in the fluid spring) may be any compressible or incompressible fluid. For example, the working medium may be air. The most cost effective medium for inflating an air spring is ambient air.

Fig. 1A is a schematic diagram of a battery system or battery module 100 according to a first embodiment of the present invention. The battery system 100 of fig. 1 includes a battery cell 10 confined between a first end plate 40a and a second end plate 40b₁、10₂、……、10_NWhere the subscript N denotes the number of cells in the stack, i.e. fig. 1 shows an example where N-12, i.e. twelve battery cells 10 are employed₁、10₂、……、10₁₂). The

end plates

40a, 40b are part of a carrier frame or encasement frame of the battery system or battery module 100. Thus, the

end plates

40a, 40b provide fixation and restraint to both outer sides of the stack. According to a first embodiment, the fluid spring 30 is located on one side of the stack of cells. More specifically, the fluid spring 30 is located between one of the end plates (in the example of FIG. 1: the first end plate 40a) and the cell 10 closest to that end plate 40a₁In the meantime.

If the first end plate is due to the closest cell 10₁The force/pressure applied to it bends, which is compensated by the flexible fluid spring 30, since the flexible fluid spring 30 changes its shape accordingly. Thus, to the cell surface (in particular to the first cell 10)₁) Is still uniform in pressureIn (1).

Through the conduit 16, the fluid in the bellows or bladder of the fluid spring 30 is in fluid communication with the fluid pressure regulating mechanism 12, which may include a vacuum pump and a valve. The fluid pressure regulating means 12 has a second connection 18 to a reservoir (not shown) for a working medium, i.e. a fluid. In the case of using ambient air as the working medium, the connection 18 is simply an outlet to the ambient atmosphere. Further, a pressure sensor 14 may be arranged at a branch of the conduit 16 to measure the fluid pressure in the fluid spring 30.

The pressure sensor 14 and the fluid pressure regulating mechanism 12 may each be connected (electrically or wirelessly) with a control unit (not shown) such that the control unit may receive signals from the pressure sensor 14 encoding the measured pressure and may send signals to the fluid pressure regulating mechanism 12 to control the fluid pressure. The control unit may be integrated in a BMU or a BMS including the battery pack of the battery system 100 shown in fig. 1.

In the example of fig. 1, the bellows or bladder of the fluid spring 30 is made of or at least includes an outer wall 32 adapted to be filled with a fluid. In other words, the outer wall 32 embeds one or

more cavities

36a, 36b, 36c suitable for liquid intake. The outer wall may be formed of an elastic material such that the bellows or bladder itself forms the elastic means. To support the elasticity of the fluid spring 30, in particular in the z-direction, one or more

elastic support elements

34a, 34b may be formed inside the bellows or bladder of the fluid spring 30. The

resilient support elements

34a, 34b may be made of the same material as the outer wall 32, or the

resilient support elements

34a, 34b may be made of a different material than the material of the outer wall 32. In the latter case, the elasticity (i.e., young's modulus) of the material of the outer wall 32 may be different from the elasticity of the

elastic support elements

34a, 34 b.

The one or more

elastic support elements

34a, 34b may be strip-shaped (each strip having a longitudinal central axis pointing in the z-direction) and arranged inside the bellows or bladder of the fluid spring 30 such that only one single cavity is formed inside the outer wall 32, in which case only a section cut through this cavity is interrupted into

several cavities

36a, 36b, 36c as shown in fig. 1A, which

several cavities

36a, 36b, 36c are, however, connected to each other in front of and behind the plane of the figure. Alternatively, the elastic support element may be wall-shaped, so that the bellows of the bladder of the fluid spring 30 is divided into several chambers. In any event, each of the one or more chambers formed within the bellows or bladder of the fluid spring 30 must be fluidly connected to the fluid pressure regulating mechanism 12 (and the pressure sensor 14).

The assembly of fluid springs 30 as described above with reference to fig. 1A is also applicable to each of the fluid springs shown in fig. 1B and 2-4. In addition, the principle of the assembly can be easily applied to the fluid springs 30a and 30b shown in fig. 5. Accordingly, the description of the construction of the fluid spring will not be repeated throughout the description of the following drawings.

In order to control the fluid pressure adjusting mechanism 12 for controlling the pressure (negative pressure) in the fluid spring 30, a control unit 90 may be provided as shown in fig. 1B. The control unit 90 may be integrated in a Battery Management Unit (BMU) of the battery system. The control unit 90 may be connected to the fluid pressure adjusting mechanism 12 for controlling the pressure (negative pressure) in the fluid spring 30 through a signal connection line 92. Alternatively, the signal from the control unit 90 to the fluid pressure adjustment mechanism 12 for controlling the pressure may be transmitted wirelessly. To monitor the pressure inside the fluid spring 30, the control unit 90 is also connected to the pressure sensor 14 by means of a further signal connection 94. Alternatively, the signal from the pressure sensor 14 to the control unit 90 may be transmitted wirelessly.

In addition, at least one security check sensor 60 may be provided. The at least one safety check sensor 60 may be part of the battery system 100, or the safety check sensor(s) 60 may be disposed externally (as shown in fig. 1B and indicated by the dashed box). The at least one security check sensor 60 may be adapted to measure any physical/technical variable or entity that may be used to assess the security of the scene. For example, the safing check sensor 60 may include an acceleration sensor to detect whether a sudden (negative) acceleration occurs that may indicate a vehicle collision. Alternatively or additionally, the safety check sensor 60 may include a temperature sensor to monitor the temperature of the ambient air of the battery system. When (a plurality of) is safeThe actual evaluation of the measurement data provided by the inspection sensor 60 is performed by the control unit 90, the control unit 90 being connected to the safety inspection sensor(s) 60 by one or more signal connection lines 96. Alternatively, the signal from the security check sensor(s) 60 to the control unit 90 may be transmitted wirelessly. Fig. 2 is a schematic diagram of a battery system or battery module 100 according to a second embodiment of the present invention. As in the case of the first embodiment described above, the battery system of fig. 2 also includes the battery cell 10 that is restrained between the first end plate 40a and the second end plate 40b₁、10₂、……、10_N(subscript N denotes the number of units in the stack, where N ═ 12). According to the second embodiment, the first fluid spring 30a is located on one exterior side of the stack of cells and the second fluid spring 30b is located on the opposite exterior side of the stack of cells. More specifically, the first fluid spring 30a is located in the first end plate 40a and the first cell 10 disposed closest to the first end plate 40a in the stack₁The second fluid spring 30b is located between the second end plate 40b and the last unit 10 in the stack that is disposed closest to the second end plate 40b_NIn the meantime.

In the example shown in fig. 2, fluid in the bellows or bladder of the first fluid spring 30a is in fluid communication with the first fluid pressure regulating mechanism 12a, which may include a vacuum pump and a valve, through the first conduit 16 a. The first fluid pressure regulating means 12a has a second connection 18a to an (external) reservoir (not shown) for the working medium, i.e. fluid. Further, a first pressure sensor 14a may be disposed at a branch of the first conduit 16a to measure the fluid pressure in the first fluid spring 30 a.

A further assembly comprising a second fluid pressure regulating mechanism 12b, a second conduit 16b, a further connection 18b to an external fluid reservoir (not shown) and optionally a second pressure sensor 14b is connected in a fully corresponding manner to the second fluid spring 30b by a second conduit 16 b.

In the embodiment of fig. 2, the two

fluid springs

30a and 30b should preferably always be pressurized to the same pressure to prevent all cells from shifting to one side. However, the two

fluid springs

30a, 30b are not connected and can therefore be controlled independently of each other.

Typically, the same working medium (fluid) is used to operate the first and second fluid springs 30a, 30 b. However, in an embodiment of the battery system according to the present invention, different working media may be used to operate the first and second fluid springs 30a and 30 b.

Of course, in alternative embodiments, the fluid springs 30a, 30b may be connected to each other, for example, by the same conduit 16 as shown in the example of fig. 3; see also the corresponding discussion regarding the advantages of such components described below in the context of fig. 3.

The first pressure sensor 14a and the first fluid pressure adjustment mechanism 12a may each be connected (electrically or wirelessly) to a control unit (not shown) such that the control unit may receive signals from the pressure sensor 14a encoding the measured pressure within the first fluid spring 30a and may send signals to the first fluid pressure adjustment mechanism 12a to control the fluid pressure. In a similar manner, the second pressure sensor 14b and the second fluid pressure regulating mechanism 12b may each be connected (electrically or wirelessly) to a control unit (not shown). The control unit may be integrated in a BMU or a BMS including the battery pack of the battery system 100 shown in fig. 2.

If the

end plates

40a, 40b are from the respective nearest adjacent cells 10₁、10_NBending from the applied force/pressure, the bending of the

end plates

40a, 40b is compensated by the fluid springs 30a and 30b, since the fluid springs 30a, 30b each change shape accordingly. Thus, on the cell surface (particularly the first cell 10 in the stack)₁And a last unit 10_NAbove) is still uniform.

Fig. 3 is a schematic diagram of a battery system or battery module 100 according to a third embodiment of the present invention. The embodiment shown in fig. 3 largely corresponds to the embodiment described above in the context of the second embodiment depicted in fig. 2. Thus, the above is with respect to the including unit 10₁、10₂、……、10_N(subscript N denotes the number of cells in the stack, where N is 12) stackThe discussion of the assembly of the stack, the

end plates

40a, 40b and the fluid springs 30a, 30b correspondingly applies in the context of fig. 3. However, the stack of the third embodiment includes the positioning plate 50 in addition to the stack shown in fig. 2. The alignment plate 50 may be part of a load-bearing frame or frame packaging and thus have a fixed position. However, the positioning plate 50 may also be arranged displaceable or movable along the longitudinal axis of the stack. Preferably, the positioning plate 50 may be located in the middle of the battery stack, i.e., in the example shown in fig. 3, when viewed from the left unit (the first unit 10) in the stack₁) Starting to the right cell (last cell 10)₁₂) The number of cells is between the 6 th cell and the 7 th cell. In general, when the stack is composed of N units and N is an even integer, the positioning plate 50 may be located between the (N/2) th battery cell and the (N/2+1) th battery cell, and if N is an odd integer, the positioning plate 50 may be located between the ((N-1)/2) th battery cell and the ((N +1)/2) th battery cell.

The third embodiment, as shown in fig. 3, in which the fluid springs 30a, 30b are placed on both outer sides of the cell stack and the positioning plate 50 is placed in the center of the cell stack, provides the best pressure uniformity. In this case, the two

fluid springs

30a, 30b should preferably be pressurized to the same pressure in order to counteract any force/pressure on the positioning plate 50.

The working media (fluid) of the two

fluid springs

30a, 30b can be communicated to equalize the pressure. To this end, the fluid springs 30a, 30b may be connected to each other by a conduit 16, which conduit 16 is also used for establishing fluid communication with the fluid pressure regulating mechanism 12. As already described in the context of the previous figures, the fluid pressure regulating mechanism 12 may be a vacuum pump and a valve. Since the two

fluid springs

30a, 30b are connected by (branches of) the same conduit 16, in this case it is sufficient to use only a single fluid pressure regulating means 12.

The pressure sensor 14 may be connected to the conduit 16 to measure the pressure in both the first fluid spring 30a and the second fluid spring 30b that are in pressure equilibrium due to the assembly. Furthermore, the fluid pressure regulating mechanism 12 and the pressure sensor 14 may be connected (electrically or wirelessly) to a control unit to supervise the pressure and control the pressure, as described in the context of the previous figures.

The fluid spring 30 may also be placed in the middle of the stack to reduce the number of components. Such an assembly is shown in fig. 4, and fig. 4 shows a schematic view of a battery system or a battery module according to a fourth embodiment of the present invention. The arrangement of the components of the battery module of fig. 4 corresponds to the first embodiment shown in fig. 1, except for the position of the (single) fluid spring 30. However, unlike the first embodiment, the fluid spring 30 is placed in the center of the stack of battery cells. In the example shown in fig. 4, when the left cell (first cell 10) within the stack is counted₁) Starting to the right cell (last cell 10)₁₂) When numbering the cells, the fluid spring 30 is disposed between the 6 th cell and the 7 th cell. In general, when the stack is composed of N units and N is an even integer, the fluid spring 30 may be located between the (N/2) th battery cell and the (N/2+1) th battery cell, and if N is an odd integer, the fluid spring 30 may be located between the ((N-1)/2) th battery cell and the ((N +1)/2) th battery cell. Due to the placement of the fluid spring in the center of the stack, an even distribution of the pressure along the longitudinal axis of the stack is improved.

Finally, fig. 5 shows a schematic view of a battery system or a battery module according to a fifth embodiment of the present invention. The embodiment of the battery module 100 shown in fig. 5 corresponds to the third embodiment of the battery module shown in fig. 3, except for the battery cells, which in the case of the module of fig. 5 are 18 flat pouch-shaped cells 20₁、20₂、……、20₁₈Instead of the 12 prismatic metal can units 10 as shown in fig. 3₁、10₂、……、10₁₂. Further, in fig. 5, the positioning plate 50 is placed at the center of the stack of the battery cells. The function of the positioning plate 50 corresponds to the function already described in the context of fig. 3. Since the pouch cells are smaller (relative to the longitudinal axis), the assembly of the fifth embodiment is generally smaller, despite the use of more battery cells than in the third embodiment.

The invention is particularly suitable for long cell stacks (e.g. for stacks comprising 12 or more cells) so that only one or two fluid springs may be used for many cells. Of course, more fluid springs could be used if desired.

The fluid springs apply uniform pressure to the outer surface as compared to pressure plates (such as end plates) that may bend and apply uneven pressure under high loads. When the pressure on the stack is uniform, the performance, safety and/or ageing of the stack is improved. However, when the fluid spring comprises elastic means (for example foam embedded in a bellows or a pocket of the fluid spring), the elastic means may exhibit a young's modulus depending on the position on a plane perpendicular to the longitudinal axis (reference axis) of the stack. In an embodiment of the battery system or the battery module according to the invention, the young's modulus is selected to be constant over the plane, i.e. the young's modulus is independent of the position on the plane. In other embodiments, the young's modulus is selected as a function of the position of a plane perpendicular to the longitudinal axis. For example, the young's modulus may be selected such that, when the fluid spring is arranged in a stack of cells having a centre point relative to a vertical plane, the young's modulus has a maximum at the location of the centre point (relative to the vertical plane) and decreases with increasing distance from the centre point. In the latter case, the young's modulus may be rotationally symmetric about an axis passing through the centre point and pointing in the direction of the longitudinal axis of the stack. For example, if z represents the direction of the longitudinal axis in a cartesian coordinate system, and if x and y represent positions on a plane perpendicular to the z direction, where (x, y) ═ 0,0 represents the center point of the unit with respect to the perpendicular plane, the young's modulus of the elastic device can be determined by the function E (x, y, z) ═ f (x, y, z), for example²+y²) Where f (r) has a maximum at r-0 and decreases monotonically as r increases. Then, the pressure provided by the fluid spring has a maximum at the center of the cell, i.e., at (x, y) — (0,0), where the pressure of the cell has a maximum due to the bending of the outer case of the battery cell caused by the internal pressure of the battery cell.

Over the life of the cell, due to aging, the cell may exhibit irreversible expansion and elongation of the stack, or, if limited in length, excessive build-up of pressure in the stack. The accumulation of excessive pressure may cause Li plating on the anode of the Li-ion cell. Li plating is safety critical and reduces battery capacity. By means of the fluid spring, expansion can be compensated and elongation in the stack or build-up of excessive pressure can be prevented.

The pressure may be adjusted as desired, for example, different pressures for charging and discharging of the cell, or different pressures depending on the state of charge (SoC) of the cell, or different pressures depending on the state of health of the cell.

If thermal runaway is detected, the fluid springs may be depressurized to reduce contact between the cells and to reduce heat transfer at the interface between the cells. Reduced heat transfer has the advantage of preventing or slowing down the propagation of thermal runaway from unit to unit.

The control software of the battery pack that calculates the pressure set point can be easily updated if field data indicates that it is necessary to adjust the algorithm for optimal cell pressurization. If the pressure needs to be adjusted, the mechanical parts may not be changed.

Claims

1. A battery system (100), comprising:

stack comprising a plurality of battery cells (10) stacked along a virtual reference axis (z)₁、10₂、……、10₁₂、20₁、20₂、……、20₁₈)；

A packing frame comprising a first end panel (40a) and a second end panel (40 b);

one or more fluid springs (30, 30a, 30b) configured to contain a fluid;

one or more fluid pressure adjustment mechanisms (12, 12a, 12b) for adjusting the fluid pressure within the at least one fluid spring (30, 30a, 30 b);

a control unit (90) configured for controlling the one or more fluid pressure regulating mechanisms (12, 12a, 12 b);

wherein the stack is placed between the first end plate (40a) and the second end plate (40 b);

wherein each of the one or more fluid springs (30, 30a, 30b) is located between the first and second end plates and is configured for applying a pressure to at least one of the battery cells in a direction along the reference axis (z);

wherein each of the fluid pressure adjustment mechanisms (12, 12a, 12b) is connected to one or more fluid springs (30, 30a, 30 b); wherein

At least one of the fluid springs (30, 30a, 30b) comprises elastic means, and wherein each of the fluid pressure adjustment mechanisms (12, 12a, 12b) is configured to create or adjust a negative pressure in the fluid within the connected fluid spring (30, 30a, 30b) when the connected one or more fluid springs each contain fluid; and/or

The control unit (90) is configured for receiving a safety check signal from at least one safety check sensor (60), and wherein the control unit (90) is further configured for assessing whether the received safety check signal may indicate a safety critical situation, and for operating the pressure regulating means (12, 12a, 12b) such that the fluid pressure in the fluid spring (30, 30a, 30b) is reduced after assessing that the safety check signal may indicate a safety critical situation.

2. The battery system (100) of claim 1, further comprising at least one fluid pressure sensor (14, 14a, 14b), the at least one fluid pressure sensor (14, 14a, 14b) configured to measure a fluid pressure present in at least one of the fluid springs;

wherein the control unit is configured to receive a pressure signal corresponding to the pressure measured from each of the fluid pressure sensors (14, 14a, 14 b); and

wherein the control unit is further configured to control the one or more fluid pressure regulating mechanisms (12, 12a, 12b) in dependence on one or more received pressure signals.

3. The battery system (100) of claim 2,

wherein the control unit is configured to detect pressure changes in the fluid of the fluid spring to which the fluid pressure sensor (14, 14a, 14b) is connected from the pressure signal provided from each of the fluid pressure sensors (14, 14a, 14 b);

wherein the control unit is further configured to control at least one of the fluid pressure regulating mechanisms (12, 12a, 12b) such that, upon detection of an increase in pressure by at least one of the fluid pressure sensors (14, 14a, 14b), the fluid pressure regulating mechanism (12, 12a, 12b) decreases the pressure of fluid within the fluid spring (30, 30a, 30b) connected to the respective fluid pressure regulating mechanism (12, 12a, 12 b); and

wherein the control unit is further configured to control at least one of the fluid pressure regulating mechanisms (12, 12a, 12b) such that, upon detection of a decrease in pressure by at least one of the fluid pressure sensors (14, 14a, 14b), the fluid pressure regulating mechanism (12, 12a, 12b) increases the pressure of fluid within the fluid spring (30, 30a, 30b) connected to the respective fluid pressure regulating mechanism.

4. A battery system (100) according to any of claims 1-3, wherein the resilient means is foam.

5. The battery system (100) of any of claims 1 to 3,

wherein the first cell (10) of the stack is seen along the reference axis (z)₁、20₁) Is located next to the first end plate (40a), the last battery cell (10) of the stack when seen along the reference axis (z)₁₂、20₁₈) Positioned adjacent to the second end plate (40 b);

wherein one fluid spring (30a) is placed between the first end plate (40a) and the first battery cell (10) of the stack₁、20₁) To (c) to (d); and

wherein another fluid spring (30b) is placed between the second end plate (40b) and the last battery cell (10) of the stack₁₂、20₁₈) In the meantime.

6. The battery system (100) of any of claims 1-3, wherein each of the fluid springs (30, 30a, 30b) are in fluid communication with each other.

7. A battery system (100) according to any of claims 1 to 3, wherein at least one of the fluid pressure regulating means (12, 12a, 12b) comprises a vacuum pump and/or a valve and/or a compressor.

8. The battery system (100) according to any one of claims 1 to 3, wherein at least one safety check sensor is an acceleration sensor configured to detect a negative acceleration having an absolute acceleration value equal to or greater than a predetermined positive value.

9. The battery system (100) of any of claims 1 to 3,

wherein at least one safety check sensor is a temperature sensor configured to measure a temperature of the stack of battery cells or to measure a temperature of at least one of the battery cells included in the stack; and

wherein the control unit evaluates whether the temperature or the temperature pattern measured by the at least one temperature sensor may indicate a safety critical thermal event.

10. A method for operating a battery system (100) according to claim 1, comprising the steps of:

a: generating a negative pressure in the fluid of at least one of the fluid springs (30, 30a, 30 b);

b: according to the battery cell (10)₁、10₂、……、10₁₂；20₁、20₂、……、20₁₈) To regulate the fluid pressure of at least one of the fluid springs (30, 30a, 30b), wherein the fluid pressure is regulated as a negative pressure.

11. The method for operating a battery system (100) according to claim 10,

wherein the battery cell (10)₁、10₂、……、10₁₂；20₁、20₂、……、20₁₈) The state of the at least one battery cell in (a) depends on the age of the at least one battery cell; and

wherein step b comprises decreasing the fluid pressure of at least one of the fluid springs (30, 30a, 30b) as the age of the battery cell increases.

12. The method for operating a battery system (100) according to claim 10 or 11,

wherein the battery cell (10)₁、10₂、……、10₁₂；20₁、20₂、……、20₁₈) The state of the at least one battery cell in (a) depends on a charging or discharging condition of the at least one battery cell;

wherein step b comprises reducing the fluid pressure of at least one of the fluid springs (30, 30a, 30b) when the battery unit is in a charging condition; and

wherein step b comprises increasing the fluid pressure of at least one of the fluid springs (30, 30a, 30b) when the battery cell is in a discharged condition.

13. A method for operating a battery system (100) according to claim 1, comprising the steps of:

a: adjusting the pressure in the fluid of at least one of the fluid springs (30, 30a, 30 b);

b: checking, by the control unit, whether a security check signal has been received from at least one security check sensor;

c: evaluating, by the control unit, whether the received safety check signal may indicate a safety critical condition; and

d: operating, by the control unit, the fluid pressure regulating mechanism (12, 12a, 12b) such that the fluid pressure in the fluid spring (30, 30a, 30b) is reduced after evaluating that the safety check signal may indicate a safety critical situation.

14. The method for operating a battery system (100) according to claim 13, wherein step b comprises:

if the at least one security check sensor is an acceleration sensor: checking whether the received safety check signal from at least one of the acceleration sensors indicates a negative acceleration having an absolute acceleration value equal to or greater than a predetermined positive value; and/or

If at least one safety check sensor is a thermal sensor configured to measure a temperature of the stack of battery cells or to measure a temperature of at least one of the battery cells included in the stack: evaluating whether the temperature or temperature pattern measured by the at least one temperature sensor may indicate a safety critical thermal event; and/or

If at least one safety check sensor is a cell voltage sensor configured to measure a voltage across at least one cell of the battery system: evaluating whether a voltage or voltage pattern measured by at least one cell voltage sensor may indicate a safety critical event; and/or

If at least one safety check sensor is a current sensor configured to measure a current generated by the battery system or at least by one cell of the battery system: evaluating whether the current or current pattern measured by the at least one current sensor may indicate a safety critical event; and/or

If the at least one security check sensor is an insulated sensor: it is evaluated whether the insulation measured by the at least one insulation sensor is below a predetermined critical value.

15. The method for operating a battery system (100) according to claim 10 or 13, wherein step b is repeated continuously or within a predetermined time interval or upon being triggered by a predetermined event.

16. A battery pack comprising the battery system of claim 1.

17. A vehicle comprising the battery system of claim 1 or the battery pack of claim 16.