High-voltage battery system

Abstract

High-voltage battery system comprising a plurality of lithium-ion battery cells (11), in the cell housing of which active material and a liquid electrolyte (15) are located, wherein the high-voltage battery system has an electrolyte circuit in which the battery cells (11) are fluidically integrated, so that an electrolyte flow through the respective battery cell (11) is enabled by means of an inlet pump (37) and an outlet pump (43), wherein the battery cells (11) are arranged in parallel in the electrolyte circuit, wherein each battery cell (11) has an inlet (21) and an outlet (23) for connection to the electrolyte circuit, and wherein a shut-off valve is assigned to each inlet (21) and outlet (23), characterized in that the shut-off valve is a check valve (25, 27), and that the check valve (25) assigned to the inlet (21) is designed to allow pressure build-up in the cell housing towards the interior of the cell housing. (92) opens,provided that a pressure threshold is reached, and blocks in the opposite direction, and that the check valve (27) associated with the outlet (23) blocks towards the cell housing interior (92) and opens in the opposite direction for pressure relief in the cell housing, provided that a pressure threshold is reached, and that the pressure thresholds of the two check valves (25, 27) are equal and / or greater than the ambient pressure.

Description

[0001] High-voltage battery system with a plurality of lithium-ion battery cells according to the preamble of claim 1, the independent claim 10, the independent claim 11 and the independent claim 12.

[0002] Such a high-voltage battery system comprises electrically interconnected battery modules. Each battery module contains a cell stack of electrically interconnected lithium-ion battery cells. The cell housings of the battery cells of this type of high-voltage battery system contain active material, consisting of stacked layers of a cathode, an anode, and a separator, and a liquid electrolyte. The electrolyte ensures the transport of ions between the electrodes of the active material.

[0003] In pouch battery cells, the cell housing is completely sealed gas-tight by means of sealed seams. This results in the following disadvantages: Internal gas pressure, which arises, for example, due to a temperature increase in the cell housing, cannot be relieved. Furthermore, the pouch battery cells stacked in a battery module are usually only thermally coupled to cooling / heating surfaces via their narrow top and / or bottom surfaces. Given this, the achievable heating or cooling performance is suboptimal.

[0004] US 2016 / 0133914 A1 discloses a battery system with a gas discharge element and an electrolyte injection element. US 2020 / 0052267 A1 discloses another battery system. US 2019 / 355960 A1 discloses a generic battery cell in which an electrolyte can be refilled. Further battery systems with electrolyte circuits are known from US 6 106 968 A, DE 10 2011 088 682 A1, and ITPD0020090236A.

[0005] The object of the invention is to provide a high-voltage battery system that enables improved heat dissipation from the battery cell compared to the prior art. Furthermore, thermal runaway of the respective battery cell should be delayed in the event of a cell defect and increased battery cell safety should be provided. The problem is solved by the features of claims 1, 10, 11 and 12. Preferred developments are disclosed in the subclaims.

[0006] The invention is based on a high-voltage battery system comprising a plurality of lithium-ion battery cells. Each of these cells contains active material and a liquid electrolyte in its cell housing. According to claim 1, the high-voltage battery system is equipped with an electrolyte circuit in which the battery cells are fluidically integrated. An inlet pump and / or a drain pump enable electrolyte flow through the respective battery cell. Depending on the control of the inlet pump and / or drain pump, a circulation process is enabled in which the electrolyte in the battery cell can be circulated. Alternatively, a filling process is enabled in which new electrolyte can be fed into the respective battery cell. Furthermore, a draining process can be performed in which used electrolyte can be removed from the respective battery cell.

[0007] The pouch battery cell according to the invention is no longer gas-tight, but rather open, meaning it is not gas-tight. The pouch cell can be gas-tight on all sides, except for two locations where valves for the inlet and outlet of electrolyte and generated gas are installed. This allows the electrolyte to continuously flow into and out of the pouch cell, depending on the temperature and / or pressure setting of the valve. Furthermore, there is no need for cooling plates and a thermally conductive emulsion to cool the battery.

[0008] An electrolyte reservoir may also be provided. The electrolyte in the electrolyte reservoir has the same composition as the electrolyte present in the cell. The electrolyte reservoir is cooled or heated by a thermocouple (Peltier element). If the cell temperature rises, new, cool electrolyte flows into the cell, while hot electrolyte is pumped from the cell into the electrolyte reservoir. The entire electrolyte circuit is leak-free, so no electrolyte can escape to the outside. Along with the electrolyte, the gas generated by the heated electrolyte or by the SEI development is also transported to the tank (i.e., the electrolyte reservoir). In the tank, the gas trapped in the electrolyte is removed. This keeps the electrolyte circuit free of gas.

[0009] For example, the following five different arrangements are feasible, allowing for controlled inflow and outflow of electrolyte. These are explained in detail below: Each module can be connected to a directional control valve. This controls the flow of electrolyte inside and outside the cell of the respective module.

[0010] Each cell has check valves, which are attached to each module in addition to the directional control valve. The directional control valve directs the electrolyte to the affected module. However, only the cell whose internal pressure has increased is filled with new electrolyte. This solution works for every cell.

[0011] Alternatively, the module may not have a directional control valve installed. In this case, each cell can have two check valves. An inlet check valve allows electrolyte to flow into the cell. An outlet check valve allows electrolyte and trapped gas to flow out of the cell. The check valve pressure settings control the electrolyte flow. The inlet and outlet pumps always maintain a constant pressure. This option operates based on the pressure differential. If the pressure in the cell increases compared to the check valve pressure setting, electrolyte exchange occurs.

[0012] In another design variant, the cell may have no check valves. The inlet and outlet pumps can be connected directly to each cell. The pump can operate based on temperature sensor readings. When the temperature rises, the pumps circulate the electrolyte inside and outside the cell. This option operates at the cell level based on a temperature differential. The electrolyte of the entire cell is circulated. This option is useful when the electrolyte needs to be drained from all cells in the event of a sudden temperature increase.

[0013] As an additional alternative, two check valves can be installed on each cell. The pump directs the fluid to each cell based on the temperature difference. The check valve on each cell only opens when the pressure within the cell is higher than required. Therefore, only cells whose temperature and internal pressure have risen are supplied with electrolyte. This option works with both temperature and pressure differences.

[0014] Each check valve can be piloted by a signal from the temperature sensor. A pilot signal opens and closes the check valve, allowing electrolyte to flow to the individual cells depending on the temperature.

[0015] Two pumps can be attached to the tank. The inlet pump supplies the electrolyte to the cell. The drain pump draws the electrolyte out of the cell and transports it to the tank.

[0016] As soon as the battery management system detects a possible thermal runaway, the inlet pump, which supplies electrolyte to the cell, is deactivated. The drain pump, which pumps the electrolyte from the cell to the tank, runs at a high flow rate. This allows all the electrolyte to be removed from the cells and the tank to be filled. The battery management system also shuts down the empty cells / modules for further operation.

[0017] Typically, electrolyte transfer is preferentially performed when the cells are not delivering power. The battery management system temporarily shuts down individual cells or modules and allows electrolyte to flow through them for cooling. In addition to cell balancing, the battery management system also plays an important role in sequential electrolyte replenishment.

[0018] The electrolyte tank is an additional component. It contains an electrolyte reservoir. The electrolyte tank can be made of carbon fiber reinforced plastic, making it resistant to damage in the event of a vehicle crash. The electrolyte tank can be integrated into an electrolyte treatment system. This system can include various modules for filtration, degassing, and heating / cooling the tank.

[0019] Refilling the electrolyte in the cell / module can be done while it is disconnected from the power supply. This temporary disconnection of the cell / module from the power supply for cooling purposes is performed by the battery management system. Cooling is not recommended while the cells are delivering power. During cell / module operation, lithium ions move around in the electrolyte. Changing the electrolyte during operation also removes these ions from the electrolyte.

[0020] According to a first option, each cell can be assigned two fixed check valves. In this case, each cell can be equipped with two check valves. The check valves can have a diameter of approximately 2-3 mm and a length of 4-5 mm. Their housings can be made of stainless steel and mounted in a plastic housing. The plastic housing is made of acrylic or polycarbonate, making it chemically inert to hydraulic hydrofluoric acid. Typically, the plastic housing should be heated, and then the check valve should be pressed into the plastic housing. The inlet check valve allows electrolyte to flow into the cell, but not out of it. The outlet check valve allows electrolyte and gas to flow from inside the cell to outside the cell. It does not allow electrolyte or air to flow inside.

[0021] The outlet check valve is designed to control the flow of electrolyte and gas from within the cell to the outside. The pressure of the check valve is spring-loaded to approximately 1.2 bar. Only when the pressure within the cell exceeds this 1.2 bar does the outlet check valve open, and the electrolyte and gas are pumped into the tank by the drain pump. As the electrolyte flows out with the gas, a further pressure drop occurs. The outlet check valve closes as soon as the pressure drops below 1.2 bar. As soon as the drain pump starts, the inlet pump starts at the same time. This pumps new electrolyte into the cell. The inlet check valve is also set to 1.2 bar absolute. The inlet pump feeds new electrolyte until the pressure in the cell returns to 1.2 bar. The mass of the inlet (electrolyte) and the outflow (electrolyte and gas) are kept the same.The flow continues until a pressure of 1.2 bar is reached in the cell. Once this pressure is reached, both check valves close automatically. The entire electrolyte circuit is at a pressure of 1.2 bar. As soon as the pressure in the cell rises due to temperature or internal pressure, the hot electrolyte and the hot gas from the cell flow into the tank, and the new, cold electrolyte immediately flows into the cell. In this way, the pressure difference causes the cell to cool very quickly. Because the cell temperature is maintained at an overpressure (for example, 1.2 bar), outside air cannot penetrate the cell. Pouch cells can normally withstand an internal pressure of up to 6-8 bar. Therefore, the permissible internal pressure in the cell is well below a critical pouch cell pressure at which pouch cell destruction occurs.Since cooling is pressure-dependent, individual cells in the module can be filled with new electrolyte. Only the cells that show a pressure increase experience an inflow and outflow of electrolyte. The top plate (i.e., the module's top wall) of the module has grooves or channels for the flow of electrolyte. The grooves have threaded connections that fit into the check valves. The threaded connections ensure leak-free attachment of the check valve to the top plate of the module. The top plate is connected to the pumps via flexible plastic hoses. The plastic hoses, in turn, are connected to the top plate via threaded connections. One threaded connection is connected to the plastic hose that is connected to the inlet pump. This ensures the inflow of electrolyte within the top plate in the module. The other threaded connection is connected to the drain pump via a plastic hose.This is where electrolyte and gas from the cell are fed into the tank. The tank can be part of an electrolyte treatment system with its many functions (filtration, degassing, heating, and cooling), which will be explained later. The threaded connection ensures a leak-free connection of the plastic tube to the top plate in the module. The module does not have a cooling plate like conventional modules. Compression pads are placed between the cells to provide thermal and electrical insulation and to maintain uniform pressure during cell expansion and contraction during cycling and discharging. They are made of polyurethane or silicone material and have high compressibility. There is no temperature sensor in the cell, as the temperature is controlled indirectly by the pressure difference within the cell. The fixed pressure setting in the check valve reacts to even the smallest changes in the pressure within the cell.The pumps ensure that a constant pressure is always maintained in the system. A check valve C1 is located between the drain pump and the tank. It is also set to 1.2 bar. A check valve C4 is located between the feed pump and the tank. This check valve is also set to 1.2 bar. The check valve C1 allows electrolyte and gas to flow to the tank. Electrolyte can be pumped out of the tank via the check valve C4. The pressure of 1.2 bar can also be set to any other overpressure. It should be more than 1 bar. Here, for example, 1.2 bar is suggested. It is recommended to keep the pressure in the range of 1.1 to 1.3 bar. Both pumps start and stop at the same time.

[0022] The electrolyte treatment system is described below. It consists of the tank, a degassing system, a heater, a cooler, and a filtration system. As the electrolyte flows from the cell to the tank via the drain pump, it carries with it gas and some solid particles (formed during SEI or during delamination of the active material of the cathode and anode). The electrolyte can also have a high temperature of approximately 60°C (depending on the cell temperature). Furthermore, in cold climates, when the temperature is below -10°C, the electrolyte must be heated. Therefore, it is important that the electrolyte is filtered, degassed, and cooled before being fed to the cell (to lower the cell temperature) or that it is heated and then fed to the cell (so that the cell operates optimally at cold temperatures below -10°C without the risk of lithium plating).All four of these functions are fulfilled by the electrolyte treatment system. The electrolyte is first passed through the filter elements, where the solid particles are separated from the electrolyte. The filter should have a porosity in the range of 10 micrometers and can be made of synthetic plastic, polyester, or liquid-permeable paper. The filter is in the form of a cartridge, which allows for easy cleaning or replacement of the filter when it becomes clogged. The filter is connected to the drain pump, which pumps the electrolyte into the tank. This has the advantage that the electrolyte flow is virtually pressureless, thus preventing any pressure drop across the filter. The check valve C1 is located between the drain pump and the filtration chamber. This opens at a pressure of 1.2 bar. This means that the entire drain line is pressurized to 1.2 bar.The drain pump generates a pressure of more than 1.2 bar, which opens the check valve C1, allowing the electrolyte to flow into the filtration chamber. After the electrolyte has passed through the filter, it is free of solid deposits but still contains trapped gas. This gas must be removed. Degassing is carried out in two steps. In the first step, the electrolyte, after filtration, enters an ultrasonic chamber where ultrasonic waves are generated. The ultrasonic waves create cavitation in the electrolyte, causing gas bubbles to form. The gases trapped in the electrolyte are drawn out of the electrolyte along with this gas bubble. The gas bubble moves upwards, degassing the electrolyte.

[0023] Once the gas reaches the top of the ultrasonic chamber, it is passed through the gas-liquid separation membrane. This membrane is made of PTFE or silicon with a pore diameter in the range of 1 micrometer. The gas flows through this membrane (gas-liquid separation membrane) and is collected at the top of the ultrasonic chamber. The degassed electrolyte remains in the ultrasonic chamber. This then flows into the electrolyte reservoir. A check valve C3 is located between the ultrasonic chamber and the electrolyte reservoir. This prevents the degassed and filtered electrolyte from flowing back into the ultrasonic chamber. The gas collected above the gas-liquid separation membrane is extracted by the vacuum compressor and collected in an airtight chamber. This housing can be changed periodically or replaced when it is full. A check valve C2 is located between the vacuum pump and the gas collection chamber.This check valve C2 prevents gas from entering the vacuum pump. Degassed electrolyte is collected in the electrolyte reservoir, which has a nitrogen pressure of 1.1 bar. This prevents air from entering the tank. The nitrogen pressure is built up by a small nitrogen tank. A pressure reducing valve is located between the nitrogen tank and the electrolyte tank. This valve reduces the nitrogen pressure to 1.1 bar. This 1.1 bar nitrogen pressure remains in the tank. This purified electrolyte is pumped by the feed pump and transported to each cell. A check valve between the feed pump and the tank ensures that the entire supply line from the feed pump to the cell is kept at 1.2 bar.

[0024] Nitrogen gas is optional. If the connections are gas-tight, no air can enter the tank. In this case, nitrogen gas may not be required. The electrolyte is heated by a thermocouple. The thermocouple heats or cools the tank depending on the direction of the current. The current for heating and cooling is supplied by two high-voltage batteries. Based on the current flow, the surface of the tank is heated or cooled. Thermocouples are usually made of Peltier elements. Typically, Peltier elements are PN semiconductors. They have the advantage of precise temperature control through the current flow. The cooling or heating performance of the module is directly dependent on the applied electrical current and can therefore be controlled with high precision. Simple switching between cooling and heating functions is also possible. Reversing the current flow produces a change in the cooling or heating function.Peltier elements, also called thermocouples, maintain the electrolyte temperature within the optimal range of 20–40°C. Peltier elements can heat and cool the tank (and thus the electrolyte) very quickly based on the current flow. The current flow is regulated by a control unit that receives input from a temperature sensor placed in the tank.

[0025] In a second option, the electrolyte is supplied to each cell in the module via a directional control valve, although the installation of check valves on each cell is optional. Here, four temperature sensors are placed in each module. These detect a temperature increase in the module. The information from the temperature sensor is forwarded to the controller, which compares the set temperature value with the actual value. If the difference is greater than permissible, the difference signal is amplified and the directional control valve is moved from the open to the closed position. The supply pump allows the electrolyte to flow through the directional control valve into the cell. In the same way, the drain pump pumps the electrolyte and gas in the cell. The electrolyte circuit is always under pressure. Only the directional control valve can start and stop the flow. As soon as the temperature in the module returns to normal, there is no longer a signal to the directional control valve.The directional valve will return to the open state under spring pressure. The check valves on each cell are optional. Cells whose internal pressure has remained unchanged will not be refilled. Only those cells whose pressure has risen above the pressure set in the check valve will be filled with new electrolyte. By using the directional valve in combination with the check valve, it is possible to maintain both the temperature and pressure within each cell at the desired level. This means that not all cells in the module receive new electrolyte, but only those cells whose internal pressure is above the set value of the check valve. This means that the electrolyte filling is temperature and pressure controlled. It is possible to have this option without a check valve on each cell. In this case, all cells in the module will be filled with new electrolyte by the feed pump only when the directional valve is closed.The directional valve is controlled by temperature sensors in the module. Each module has its own directional valve. As soon as the temperature sensor detects a temperature higher than the desired value, the battery management system shuts down the corresponding module. The directional valve is closed. The pumps are started. The inlet pump fills with electrolyte. The outlet pump drains the electrolyte. The electrolyte is replenished until the temperature returns to normal. After that, the directional valve switches back to the open position. Electrolyte stops flowing. The battery management system reconnects the module to the power grid. The battery management system allows the cell / module to be refilled if they are disconnected.

[0026] In a third option, at least one temperature sensor can be placed in the module. This detects a temperature increase in the module. The information from the temperature sensors is transmitted to the controller, which compares the set temperature value with the actual value. If the difference is greater than permitted, the difference signal is amplified and the feed pump and drain pump are started. The feed pump fills new electrolyte from the tank into each individual cell of each module. The drain pump removes electrolyte and returns it to the tank. This means that the electrolyte filling is based on the temperature difference. This option can be used when the vehicle is stationary and no cells are in use. This method allows the electrolyte to be circulated in each cell. This option maintains the temperature in all cells of each module at the desired temperature.It is also possible to install a check valve on each cell. In this case, only those cells that have built up pressure in the cell are supplied with new electrolyte by the inlet pump. Likewise, the drain pump only removes electrolyte from cells whose internal pressure is higher than the desired pressure in the cell. This means that electrolyte is refilled when both a temperature and pressure difference are present. Only those cells whose temperature and pressure difference exceed the set values ​​receive new electrolyte. Both pumps must operate simultaneously. This option allows the electrolyte to be removed from all cells. This option is desirable when the ionic conductivity of the cell is significantly reduced. In this case, new electrolyte with optimal ionic conductivity can replace the old electrolyte from each cell. As already mentioned, a check valve can be installed in each cell if necessary.This option is also useful when a module / cell is thermally overloaded. To prevent the thermal path from spreading, the electrolyte is quickly released into the tank by the drain pump. In this case, no new electrolyte is added by the feed pump. Because the tank must hold all of the cell's electrolyte, the tank is larger than in previous versions. It is important to note that during normal cooling, both the feed pump and the drain pump operate simultaneously. In the event of a thermal runaway, only the drain pump operates.

[0027] In a fourth option, the electrolyte is supplied to each cell through a pilot-operated check valve. Here, the concept is similar to the first option, except that both cell valves in the cell are controlled by a pilot signal. Each cell has a temperature sensor, the signal from which is fed to the control unit. The control unit detects the temperature deviation and sends a pilot signal to the check valve. Both check valves are opened, and the electrolyte flows into the cell through the inlet pump and is pumped out of the cell by the drain pump. The pumps circulate the electrolyte until the temperature in the cell returns to normal. If the temperature does not return to normal within, for example, 4-5 minutes, only the drain pump operates, removing all the electrolyte from the cell. The cell is disconnected from the supply line by the battery management system.The main difference between this variant and previous variants is that the earlier variants were primarily pressure-controlled. The check valve opens and closes based on the pressure difference. Here, the check valve can also be opened externally based on the cell temperature. This provides additional safety. Normally, a rise in temperature inside the cell leads to gas formation inside the cell. This causes a rise in pressure inside the cell. The check valve should normally open with this increase in pressure. Therefore, the pressure-controlled version explained previously also indirectly regulates the temperature. It is possible that the pilot signal to the check valve can be given independently of the pressure difference. For example, if the ionic conductivity of the cell has decreased. This pilot signal can be given to the check valve by the battery management system. The electrolyte of all cells or a specific cell can be replaced.A pilot-operated check valve can be installed in a very simple way by incorporating a push and pull mechanism attached to the ball of the check valve into threaded connections.

[0028] In the fourth option above, the operation of a pilot-operated check valve is as follows: Temperature sensors are placed near each cell. They measure the temperature and transmit the information to a control unit. If the temperature difference between the measured value and the setpoint is greater, the control unit closes a switch. Current flows from the battery to, for example, a steel pin. The steel pin becomes magnetized. It presses on the spring attached to the top of the steel plunger. The spring is fully compressed until it reaches the block. After that, it moves the steel piston downward. The spring piston presses on the pin attached to the check valve ball. The check valve moves downward, compressing the check valve spring. The check valve opens, and the electrolyte is pumped into the cell by the feed pump.This means that the check valve is opened by an external magnetic force acting on the check valve ball. The pin attached to the check valve ball is also made of stainless steel and welded to the ball. As soon as the feed pump starts, the drain pump will start simultaneously and draw the electrolyte out of the cell. The feed pump generates a pressure that is higher than the check valve pressure of 1.2 bar. Therefore, the electrolyte is pumped out of the cell. As soon as the cell temperature returns to the normal range, the control unit opens the switch. The steel pin is demagnetized. It is moved back to its original position by the spring. The steel plunger also moves upwards. The check valve is closed and the flow of electrolyte in the cell is stopped. When the feed pump stops, the drain pump also stops.The steel pin, coil, spring, and steel plunger are integrated into the threaded connection. Only the check valve attached to the supply pump requires pilot control. When the supply pump starts operating, the drain pump starts running immediately.

[0029] Aspects of the invention are highlighted again in detail below: The battery cells are arranged in parallel in the electrolyte circuit. Each battery cell has an inlet and an outlet for connection to the electrolyte circuit. A shut-off valve is assigned to the inlet and outlet, respectively. The shut-off valve is an automatically operating check valve. The inlet check valve (i.e., assigned to the battery cell inlet) opens to build up pressure in the cell housing towards the interior of the cell housing, provided a pressure threshold is reached. The inlet check valve closes in the opposite direction. In addition, the outlet check valve (i.e., assigned to the battery cell outlet) closes towards the interior of the cell housing and opens to relieve pressure in the cell housing in the opposite direction, provided a pressure threshold is reached. The pressure thresholds of the two check valves are of the same size.In addition, the pressure threshold values ​​of the two check valves are larger than the ambient pressure.

[0030] To ensure the high-voltage battery system has the highest possible energy content, the battery cells can be stacked in a module housing of a battery module. The high-voltage battery system can have a plurality of such battery modules. The module housing of each battery module can be closed with a cover wall in the vertical direction of the module. To ensure a structurally simple integration of the battery cells into the electrolyte circuit, the following measures can be implemented: The module housing cover wall can have an inlet channel to which the battery cell inlets are connected. In addition, the cover wall can have a drain channel to which the battery cell outlets are connected. The inlet channel formed in the module housing cover wall can be connected to a pressure line of the inlet pump via a connection.In the same way, the drain channel formed in the module housing cover wall can be connected to a suction line of the drain pump via a connection.

[0031] An electrolyte reservoir can be integrated into the electrolyte circuit, in which old electrolyte from the battery cells is stored and from which new electrolyte is fed into the battery cells. For this purpose, the suction line of the inlet pump and the pressure line of the drain pump can be connected to the electrolyte reservoir. It is preferred if a check valve is arranged in the suction line of the inlet pump, which blocks the flow towards the electrolyte reservoir and opens the flow towards the inlet pump when the pressure threshold is reached. Alternatively and / or additionally, a check valve can be arranged in the pressure line of the drain pump, which blocks the flow towards the drain pump and opens the flow towards the electrolyte reservoir when the pressure threshold is reached. In this way, the pressure in the entire electrolyte circuit can be kept approximately at the pressure threshold, which is greater than the ambient pressure.

[0032] The electrolyte circuit can be designed so that a circulation process starts when the pressure in a battery cell increases. During the circulation process, the heated old electrolyte is drained from the battery cell and, at the same time, cool new electrolyte is fed into the battery cell. In one design variant, temperature sensors for detecting the temperature in the battery cell can be omitted. Instead, the circulation process can start depending on the internal pressure of the cell housing, which correlates with the temperature. In this case, the circulation process is started when the internal pressure of the cell housing exceeds the pressure threshold. This opens the drain check valve and activates the drain pump. The heated old electrolyte is drained from the cell housing until the internal pressure of the cell housing falls below the pressure threshold and the drain check valve closes.Simultaneously with the activation of the drain pump, the inlet pump is activated. The inlet pump feeds fresh electrolyte into the cell housing. This continues until the internal pressure in the cell housing exceeds the pressure threshold and the inlet check valve closes.

[0033] In a further embodiment, the electrolyte reservoir can be part of an electrolyte treatment system. In the electrolyte treatment system, a filter unit and a degassing unit can be installed upstream of the electrolyte reservoir. In this case, the used electrolyte discharged from the battery cell can first be freed of solids in the filter unit. The used electrolyte, freed of solids, can then be degassed in the degassing unit.

[0034] The interior of the electrolyte reservoir can preferably be pressurized with a protective gas, especially nitrogen. In this case, an oxygen-free protective gas atmosphere is provided in the electrolyte reservoir. Its pressure is, in particular, greater than ambient pressure to prevent air from entering the interior of the electrolyte reservoir.

[0035] The electrolyte reservoir may comprise a thermocouple, in particular a Peltier element, by means of which the electrolyte can be cooled or alternatively heated.

[0036] In a further embodiment, a directional control valve can be assigned to the electrolyte circuit. The directional control valve can be adjusted to a closed or open position using a control unit. In the closed position, both the pressure line of the supply pump and the suction line of the drain pump are closed. Alternatively, in the open position, both the pressure line of the supply pump and the suction line of the drain pump are open. The directional control valve is controlled by an electronic control unit. This can be in signal communication with at least one temperature sensor that detects the actual temperature of the battery cell or battery module. The control unit can control the two-way valve to the open position if the detected actual temperature is greater than a temperature threshold stored in the control unit.Alternatively, the control unit can control the directional control valve to the closed position if the actual temperature is lower than or equal to the temperature threshold. This allows both temperature-dependent and pressure-dependent cooling of the battery cells.

[0037] Such both temperature-dependent and pressure-dependent cooling is also possible in the following design variant: the inlet check valves and / or the outlet check valves can not only operate automatically, but can also be controlled by an additional control unit. The control unit can be connected to a temperature sensor that detects the actual temperature of the battery cell or battery module. The control unit can control the inlet and / or outlet check valve from its spring-loaded closed position to the open position if the actual temperature exceeds a temperature threshold stored in the control unit. In this way, temperature-dependent cooling of the battery cell can be achieved in addition to pressure-dependent cooling (depending on the internal pressure of the cell housing).

[0038] Embodiments of the invention are described below with reference to the attached figures.

[0039] They show: Fig. 1 to 5 each show views of a first embodiment for cooling battery cells in a battery module; Fig. 6 to 10 each show views of further embodiments.

[0040] In the Fig. 1 to 3, a battery module 1 is indicated to the extent necessary for understanding the invention. Accordingly, the battery module 1 has a module housing with a housing base 5, from which housing side walls 7 are raised. The housing top is closed with a cover wall 9. A total of six battery cells 11 are stacked in the module housing 3, with elastic intermediate layers 13 arranged therebetween. The battery cells 11 are integrated into an electrolyte circuit in which a liquid electrolyte 15 can be circulated. In the exemplary embodiments shown, the battery cells 11 are implemented, for example, as pouch cells, which have anodes 17 and cathodes 19 ( Fig. 3) which are electrically interconnected via busbars not shown.

[0041] In the battery module 1, the battery cells 11 are arranged in parallel in the electrolyte circuit. Each of the battery cells 11 has an inlet 21 and an outlet 23 ( Fig. 3), via which the cell housing interior 92 is connected to the electrolyte circuit. An inlet check valve 25 is arranged in the battery cell inlet 21, while an outlet check valve 27 is assigned to the battery cell outlet 23. All battery cell inlets 21 open into an inlet channel 29, which is formed in the module housing cover wall 9. Likewise, all battery cell outlets 23 open into an outlet channel 31, which is also formed in the module housing cover wall 9. The inlet channel 29 is connected via a connection 33 to a pressure line 35 of an inlet pump 37, while the outlet channel 31 is connected via a further connection 39 to a suction line 41 of a drain pump 43. The suction line 41 of the supply pump 37 and the pressure line 35 of the discharge pump 43 are connected to an electrolyte treatment system 49. The electrolyte treatment system 49 has an electrolyte reservoir 51.Upstream of the electrolyte reservoir 51 there is a filter unit 53 and a degassing unit 55.

[0042] In the in the Fig. In the electrolyte treatment system 49 shown in Figure 1, the electrolyte 15 fed from the battery cells 11 is filtered, degassed, and cooled or alternatively heated, before being fed back to the battery cells 11. For this purpose, the filter unit 53 has an indicated filter cassette 57, in which solids are separated from the electrolyte 15. The electrolyte, freed of solids, is then fed to the degassing unit 55. Degassing takes place in two process steps. In the first process step, the electrolyte 15 is subjected to ultrasonic treatment in an ultrasonic chamber 59, in which ultrasonic waves generate gas bubbles with the aid of a generator 61. The gas bubbles are separated from the electrolyte 15 at a gas / liquid separation membrane 63 and collected in a gas space 65. The gas space 65 is connected to a gas reservoir 69 via a gas line 67.A vacuum pump 71 is located in the gas line, along with a check valve C2 downstream of it. The degassed electrolyte 15 located in the ultrasonic chamber 59 is fed into the electrolyte reservoir 51 via an inlet line 75. A check valve C3 is located in the inlet line 75. Additional check valves C1 and C4 are located in the pressure line of the drain pump 43 and in the suction line of the inlet pump 37, respectively.

[0043] As from the Fig. As further shown in Figure 1, the interior of the electrolyte reservoir 51 is pressurized with protective gas, i.e., nitrogen. In this way, an oxygen-free protective gas atmosphere is provided in the electrolyte reservoir 51. For this purpose, a nitrogen container 77 is connected to the interior of the electrolyte reservoir 51 via a supply line 79. An overpressure of, for example, 2 bar prevails in the nitrogen container 77. This pressure is released to approximately 1.1 bar in the interior of the electrolyte reservoir 51 via a pressure reducing valve 81 arranged in the supply line 79.

[0044] A Peltier element 83, by means of which the electrolyte 15 can be cooled or heated, is also arranged on the housing base of the electrolyte reservoir 51. For this purpose, an actual temperature in the electrolyte reservoir 51 is detected by a temperature sensor 85. Based on the detected actual temperature, a control unit 87 generates a corresponding control signal for the Peltier element 83 to cool or heat the electrolyte 15.

[0045] In the Fig. 4 and Fig. 5, an inlet check valve 25 and an outlet check valve 27 are shown in detail. Accordingly, a spherical valve element 89 is brought into fluid-tight contact with a valve seat 91 by means of a preload force exerted by a spring 90. The inlet check valve 25 ( Fig. 4) opens to build up pressure inside the cell housing 92, provided a pressure threshold (corresponding to the spring preload) is reached. In the opposite direction, the inlet check valve 25 closes. In contrast, the outlet check valve 27 ( Fig. 5) toward the cell housing interior 92. To relieve pressure in the cell housing, the outlet check valve 27 opens when a pressure threshold (corresponding to the spring preload) is reached. According to the invention, the pressure thresholds of the two check valves 25, 27 and the additional check valves C1 to C4 are coordinated with one another and are preferably equal to and greater than the ambient pressure. The check valves C1 to C4 are essentially functionally identical to the check valves 25, 27.

[0046] When the temperature in one of the battery cells 11 rises, a circulation process starts, in which the old electrolyte 15 heated in the battery cell 11 is led out of the battery cell 11 and cool new electrolyte 15 is fed into the battery cell 11. Fig. 1 to 4, temperature sensors for detecting the battery cell temperature are omitted. Instead, the circulation process occurs solely depending on the internal cell housing pressure, which correlates with the battery cell temperature. The circulation process is started when the internal cell housing pressure exceeds the pressure threshold (e.g., 1.2 bar). This opens the drain check valve 27 and activates the drain pump 43. This causes the heated used electrolyte 15 to be drained from the cell housing until the internal cell housing pressure falls below the pressure threshold (e.g., 1.2 bar) and the drain check valve 27 closes. Simultaneously with the activation of the drain pump 43, the inlet pump 37 is also activated. By means of the inlet pump 37, new electrolyte 15 is fed into the cell housing until the internal pressure of the cell housing exceeds the pressure threshold (1.2 bar) and the inlet check valve 25 closes.

[0047] In the Fig. 6 shows an electrolyte circuit according to a second embodiment. Its basic structure and operation are identical to those shown in the Fig. 1 to 5 shown structure and its function. Therefore, reference is made to the previous description. In contrast to Fig. 1, the electrolyte circuit is provided without electrolyte treatment system 49. Instead, in the Fig. 6, only one electrolyte reservoir 51 is connected to the electrolyte circuit. In addition, the electrolyte circuit has Fig. 6 has a two-way valve 93, which can be adjusted by means of an electronic control unit 94 into a shown closed position or an open position. In the shown closed position, the pressure line 35 of the inlet pump 37 and the suction line 41 of the drain pump 43 are closed. In contrast, in the open position (not shown), the pressure line 35 of the inlet pump 37 and the suction line 41 of the drain pump 43 are open. The control unit 94 is in the Fig. 6 in signal connection with temperature sensors 85, which detect an actual temperature in the battery module 1. The control unit 94 controls the two-way valve 93 to the open position if the actual temperature is greater than a temperature threshold stored in the control unit 94. Alternatively, the control unit 94 controls the two-way valve 93 to the shown closed position if the actual temperature is less than or equal to the temperature threshold. According to the Fig. In the embodiment shown in Figure 6, in addition to the automatic pressure-dependent cooling (using the inlet check valves 25 and the outlet check valves 27), temperature-dependent cooling can also be carried out using the control unit 94.

[0048] In the same way, in the Fig. 7 both pressure-dependent and temperature-dependent cooling can be carried out. Accordingly, in the Fig. 7 the inlet pump 37 and the drain pump 43 are in signal connection with a control unit 96. The control unit 96 can activate the inlet pump 37 and / or the drain pump 43 depending on the actual temperatures detected by the temperature sensors 85.

[0049] In the Fig. 8 also shows an electrolyte circuit, which allows for both temperature-dependent cooling and pressure-dependent cooling. The pressure-dependent cooling is carried out as already described in the Fig. 1 to 3. In the, in the Fig. In the further development shown in Figure 8, both the inlet check valves 25 and the outlet check valves 27 can be controlled by means of a control unit 97, as shown in the Fig. 9 and Fig. 10. According to the Fig. 9, the inlet check valve 25 is assigned an electromechanical actuator 98, which opens a fluid path against the spring force of the preload spring 90. In the same way, the outlet check valve 27 ( Fig.10) is assigned such an electromechanical actuator 98, which can be controlled by the control unit 97. In this way, the inlet check valves 25 and the outlet check valves 27 can be adjusted to an open position with the aid of the control unit 97, regardless of the internal pressure of the cell housing. The control unit 97 is in signal communication with temperature sensors 95, which detect the actual temperature of the battery cells 11. The control unit 97 controls the inlet and / or outlet check valves 25, 27 to the open position if the detected actual temperature exceeds a temperature threshold stored in the control unit 97. List of reference symbols 1 battery module 5 Case back 7 Housing side panels 9 Housing cover wall 11 battery cells 13 elastic intermediate layers 15 Electrolyte 17 anodes 19 cathodes 21 Entrance 23 Outlet 25 Inlet check valve 27 Outlet check valve 29 Inlet channel 31 Drain channel 33 connection 35 Inlet pump pressure line 37 Inlet pump 39 connection 41 Drain pump suction line 43 Drain pump 49 Electrolyte treatment plant 51 Electrolyte reservoir 53 Filter unit 55 Degassing unit 57 filter cassette 59 Ultrasound Chamber 61 Ultrasonic generator 63 Gas / liquid separation membrane 65 Gas room 67 Gas pipeline 69 Gas reservoir 71 Vacuum pump 75 Inlet line 77 protective gas containers 79 supply line 81 Pressure reducing valve 83 Core element 85 Temperature sensor 87 Control unit 92 Cell housing interior 93-way valve 94 Control unit 95 Temperature sensor 96 Control unit 97 Control unit 98 electromechanical actuator 99 Temperature sensor C1 to C4 check valves

Claims

[1] A high-voltage battery system comprising a plurality of lithium-ion battery cells (11), in the cell housing of which there is active material and a liquid electrolyte (15), wherein the high-voltage battery system comprises an electrolyte circuit into which the battery cells (11) are fluidically integrated, so that an electrolyte flow through the respective battery cell (11) is enabled by means of an inlet pump (37) and a drain pump (43), wherein the battery cells (11) are arranged in parallel in the electrolyte circuit, wherein each battery cell (11) has an inlet (21) and an outlet (23) for connection to the electrolyte circuit, and wherein a shut-off valve is each assigned to the inlet (21) and the outlet (23), characterized bythat the blocking valve is a check valve (25, 27), that the check valve (25) assigned to the inlet (21) opens in the direction of the cell housing interior (92) to build up pressure in the cell housing if a pressure threshold value is reached, and closes in the opposite direction, and that the check valve (27) assigned to the outlet (23) closes in the direction of the cell housing interior (92) and opens in the opposite direction to relieve pressure in the cell housing if a pressure threshold value is reached, and that the pressure threshold values ​​of the two check valves (25, 27) are equal to and / or greater than the ambient pressure. [2] High-voltage battery system according to claim 1, characterized bythat the battery cells (11) are stacked in a module housing of a battery module (1) which is closed in the vertical direction of the module by a cover wall (9), that the cover wall (9) has an inlet channel (29) to which the battery cell inlets (21) are connected, and a drain channel (31) to which the battery cell outlets (23) are connected, and that the inlet channel (29) is connected via a connection (33) to a pressure line (35) of the inlet pump (37), and / or that the drain channel (31) is connected via a connection (39) to a suction line (41) of the drain pump (43). [3] High-voltage battery system according to one of the preceding claims, characterized bythat an electrolyte reservoir (51) is integrated into the electrolyte circuit, that the suction line of the inlet pump (37) and the pressure line of the drain pump (43) are connected to the electrolyte reservoir (51), that a check valve (C4) is arranged in the suction line of the inlet pump (37), which blocks in the direction of the electrolyte reservoir (51) and opens in the direction of the inlet pump (37) when the pressure threshold is reached, and / or that a check valve (C1) is arranged in the pressure line of the drain pump (43), which blocks in the direction of the cell housing and opens in the direction of the electrolyte reservoir (51) when the pressure threshold is reached. [4] High-voltage battery system according to one of the preceding claims, characterized bythat when the temperature in a battery cell (11) rises, a circulation process starts, in which the heated old electrolyte (15) is formed from the battery cell (11) and cool new electrolyte (15) is fed into the battery cell (11), and / or that a temperature sensor for detecting the temperature in the battery cell (11) is dispensed with and / or instead the circulation process is started depending on the cell housing internal pressure, which correlates with the temperature, and that the circulation process is started when the cell housing internal pressure exceeds the pressure threshold, so that the outlet check valve (27) opens and the drain pump (43) is activated, and that the heated old electrolyte (15) is guided out of the cell housing until the cell housing internal pressure falls below the pressure threshold and the outlet check valve (27) closes, and / or that simultaneously with the activation of the drain pump (43) the inlet pump (37) is activated,by means of which new electrolyte (15) is fed into the cell housing until the internal pressure of the cell housing exceeds the pressure threshold and the inlet check valve (25) closes. [5] High-voltage battery system according to claim 4, characterized by that the electrolyte reservoir (51) is a component of an electrolyte treatment system (49) in which a filter unit (53) and a degassing unit (55) are arranged upstream of the electrolyte reservoir (51), and that the used electrolyte (15) discharged from the battery cell (11) is freed of solids in the filter unit (53) and is then degassed in the degassing unit (55). [6] High-voltage battery system according to one of the preceding claims 4 or 5, characterized bythat the interior of the electrolyte reservoir (51) is pressurized with protective gas, whereby an oxygen-free protective gas atmosphere is provided in the electrolyte reservoir (51), the pressure of which is greater than the ambient pressure, and / or that the electrolyte reservoir (51) has a thermocouple (83) by means of which the electrolyte (15) can be cooled or heated. [7] High-voltage battery system according to one of the preceding claims, characterized bythat the electrolyte circuit has a directional control valve (93) which can be adjusted into a blocking position or into an open position by means of a control unit (94), and that in the blocking position the pressure line (35) of the inlet pump (37) and the suction line (41) of the drain pump (43) are blocked, or in the open position the pressure line (35) of the inlet pump (37) and the suction line (41) of the drain pump (43) are open, and that the control unit (94) is in signal connection with at least one temperature sensor (85) which detects an actual temperature of the battery cell (11) or of the battery module (1), and that the control unit (94) controls the directional control valve (93) into the open position if the actual temperature is greater than a temperature threshold stored in the control unit (94). [8] High-voltage battery system according to one of the preceding claims, characterized bythat the inlet pump (37) and the outlet pump (43) are in signal connection with a control unit (96), and that the control unit (96) activates the inlet pump (37) and / or the outlet pump (43) depending on actual temperatures detected by means of temperature sensors (85). [9] High-voltage battery system according to one of claims 1 to 8, characterized by that the inlet check valves (25) and / or the outlet check valves (27) can be adjusted into an open position by means of a control unit (97), independently of the cell housing pressure, that the control unit (97) is in signal connection with at least one temperature sensor (95) which detects an actual temperature of the battery cell (11) or of the battery module (1), and that the control unit (97) controls the inlet and / or outlet check valve (25, 27) into the open position if the actual temperature exceeds a temperature threshold value stored in the control unit (97). [10] High-voltage battery system, with a plurality of lithium-ion battery cells (11), in the cell housing of which there is active material and a liquid electrolyte (15), wherein the high-voltage battery system has an electrolyte circuit, in which the battery cells (11) are fluidically integrated, so that an electrolyte flow through the respective battery cell (11) is enabled by means of an inlet pump (37) and a drain pump (43), wherein an electrolyte reservoir (51) is integrated into the electrolyte circuit, wherein the suction line of the inlet pump (37) and the pressure line of the drain pump (43) are connected to the electrolyte reservoir (51), and wherein when the temperature in a battery cell (11) rises, a circulation process starts, in which the heated old electrolyte (15) is formed from the battery cell (11) and cool new electrolyte (15) is pumped into the battery cell (11), characterized bythat the electrolyte reservoir (51) is a component of an electrolyte treatment system (49) in which a filter unit (53) and a degassing unit (55) are arranged upstream of the electrolyte reservoir (51), and that the used electrolyte (15) discharged from the battery cell (11) is freed of solids in the filter unit (53) and is then degassed in the degassing unit (55). [11] High-voltage battery system, with a plurality of lithium-ion battery cells (11), in the cell housing of which there is active material and a liquid electrolyte (15), wherein the high-voltage battery system has an electrolyte circuit in which the battery cells (11) are fluidically integrated, so that an electrolyte flow through the respective battery cell (11) is possible by means of an inlet pump (37) and a drain pump (43), characterized bythat the electrolyte circuit has a directional control valve (93) which can be adjusted into a blocking position or an open position by means of a control unit (94), that in the blocking position the pressure line (35) of the inlet pump (37) and the suction line (41) of the drain pump (43) are blocked, and in the open position the pressure line (35) of the inlet pump (37) and the suction line (41) of the drain pump (43) are open, that the control unit (94) is in signal connection with at least one temperature sensor (85) which detects an actual temperature of the battery cell (11) or of the battery module (1), and that the control unit (94) controls the directional control valve (93) into the open position if the actual temperature is greater than a temperature threshold stored in the control unit (94). [12] High-voltage battery system, with a plurality of lithium-ion battery cells (11), in the cell housing of which there is active material and a liquid electrolyte (15), wherein the high-voltage battery system has an electrolyte circuit into which the battery cells (11) are fluidically integrated, so that an electrolyte flow through the respective battery cell (11) is possible by means of an inlet pump (37) and a drain pump (43), characterized by that the inlet pump (37) and the outlet pump (43) are in signal connection with a control unit (96), and that the control unit (96) activates the inlet pump (37) and the outlet pump (43) depending on actual temperatures detected by means of temperature sensors (85).

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