Pressure holding device and battery system including the same

Abstract

To provide a pressure holding device for maintaining an internal pressure of a battery structure to a constant level even when a cubic volume of a battery cell changes, and to provide a battery system including the pressure holding device.SOLUTION: A pressure holding device according to the disclosure may include: a hydraulic device which is located within a housing of a battery module with multiple battery cells and whose cubic volume is changed so as to cancel pressure change in the housing caused by deformation of the multiple battery cells; an accumulator which stores a fluid, is connected to the hydraulic device through a pipe, and discharges the fluid in the pipe or stores the fluid flowing in from the pipe according to volumetric change of the hydraulic device; a heater which heats the accumulator; and a controller which controls the heater according to an outside air temperature.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a pressure holding device and a battery system including the same.

Background Art

[0002] A secondary battery is different from a primary battery that provides only an irreversible conversion of chemical substances into electrical energy in that charging and discharging can be repeated. Low-capacity secondary batteries are used as power sources for small electronic devices such as mobile phones, notebook computers, and camcorders, and high-capacity secondary batteries are used as power sources for hybrid vehicles and the like.

[0003] Generally, a secondary battery cell 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 housing the electrode assembly, and electrode terminals electrically connected to the electrode assembly. An electrolytic solution is injected into the case to enable charging and discharging of the battery cell by an electrochemical reaction of the positive electrode, the negative electrode, and the electrolyte solution. The shape of the case, such as a cylindrical shape or a hexahedron, varies depending on the use of the battery cell.

[0004] As the secondary battery cell repeatedly contracts and expands as charging and discharging are repeated, a direct fatigue load is applied to the battery structure. In addition, as the secondary battery cell continuously expands as deterioration progresses, such continuous expansion increases the pressure applied to the structure in the later stage of the life compared to the initial stage of the life, and safety problems due to performance degradation and structural deformation may occur.

Summary of the Invention

Problems to be Solved by the Invention

[0005] A technical problem to be solved by the present disclosure is to provide a pressure holding device for maintaining a constant internal pressure of a battery structure even with a volume change of a battery cell, and a battery system including the same.

Means for Solving the Problems

[0006] A pressure holding device according to an embodiment for solving the above-described problems is located inside a housing of a battery module together with a plurality of battery cells, and has a hydraulic device whose volume changes to cancel out a pressure change inside the housing due to deformation of the plurality of battery cells, stores a fluid, is connected to the hydraulic device via a pipe, and discharges the fluid to the pipe or stores the fluid flowing in from the pipe according to a volume change of the hydraulic device, a heater for heating the accumulator, and a controller for controlling the heater according to an outside air temperature.

[0007] The hydraulic device can contract when the plurality of battery cells expand and discharge the fluid to the pipe, and can expand when the fluid flows in from the pipe when the plurality of battery cells contract.

[0008] The hydraulic device can be a hydraulic cylinder or a hydraulic bag.

[0009] The pressure holding device may further include a temperature sensor for detecting the outside air temperature.

[0010] The pressure holding device may further include a holding valve connected to the pipe and replenishing the fluid to the pipe when opened.

[0011] The pressure holding device may further include a pressure reducing valve connected to the pipe and opened when the pressure in the pipe exceeds a predetermined value to discharge the fluid from the pipe.

[0012] The pressure holding device may further include a replenishing pipe, a solenoid valve connected between the pipe and the replenishing pipe and supplying the fluid in the replenishing pipe to the pipe when opened, and an auxiliary accumulator that stores the fluid and discharges the fluid to the replenishing pipe when the internal pressure of the replenishing pipe becomes low due to the opening of the solenoid valve. The solenoid valve can be opened when the internal pressure of the pipe is lower than the internal pressure of the replenishing pipe by a predetermined value or more.

[0013] The pressure holding device may further include a holding valve that is connected to the replenishing pipe and replenishes the replenishing pipe with fluid when opened.

[0014] The pressure holding device may further include a first pressure sensor coupled to the pipe to detect the internal pressure of the pipe and a second pressure sensor coupled to the replenishing pipe to detect the internal pressure of the replenishing pipe. When the first pressure detected by the first pressure sensor is lower than the second pressure detected by the second pressure sensor, the controller may open the solenoid valve.

[0015] The pressure holding device may further include a first pressure sensor coupled to the accumulator to detect the internal pressure of the accumulator and a second pressure sensor coupled to the auxiliary accumulator to detect the internal pressure of the auxiliary accumulator. When the first pressure detected by the first pressure sensor is lower than the second pressure detected by the second pressure sensor, the controller may open the solenoid valve.

[0016] The pressure holding device may further include a pump coupled to the pipe to additionally supply fluid to the pipe and a motor for driving the pump. When the internal pressure of the pipe drops below a predetermined value, the controller may control the motor to drive the pump.

[0017] A battery system according to an embodiment may include the pressure holding device described above and the battery module. The battery module may include the plurality of battery cells stacked on each other and the housing in which an airtight space where the plurality of battery cells and the hydraulic device are located is formed.

Advantages of the Invention

[0018] According to the present disclosure, even if swelling of the battery cell occurs, the internal pressure of the battery structure can be kept constant.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The effects, features, and implementation methods of the embodiments will be described in detail with reference to the accompanying drawings below. In the drawings, the same reference numerals denote the same components, and redundant descriptions thereof are omitted. However, the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those of ordinary skill in the art.

[0021] Therefore, processes, elements, and techniques that are considered unnecessary for those of ordinary skill in the art to fully understand the aspects and features of the present invention are not described. In the drawings, the relative sizes of elements, layers, and regions can be exaggerated for clarity.

[0022] In the present invention, the term "and / or" includes all combinations or any combination of a plurality of items listed in relation thereto. When describing embodiments of the present invention, the use of "can be" or "can be" means "one or more embodiments of the present invention". In the present invention, singular terms can include the plural form unless otherwise indicated by the context.

[0023] In the present invention, terms including ordinal numbers such as "first", "second", "third", etc. are used to describe various components, but these components are not limited by these terms. These terms are only used for the purpose of distinguishing one component from another. For example, unless it exceeds the scope of the rights of the present invention, the second component may be named the first component, and similarly, the first component may also be named the second component.

[0024] When in the present invention one component or layer is described as "above", "connected to", or "coupled to" another component or layer, "above", "connected to", and "coupled to" all include being formed directly or through one or more other components or layers intervening. Also, when one component or layer is described as being "between" two components or layers, it must be understood as being either the only component or layer between the two components or layers, or having one or more intervening other elements or layers.

[0025] In the present invention, electrically connecting two components can include not only the case where the two components are directly connected, but also the case where they are connected through other components between the two components. The other components can include switches, resistors, capacitors, etc. In the description of the embodiments, the expression "connect" means electrically connecting when there is no expression of direct connection.

[0026] Hereinafter, a pressure holding device according to an embodiment and a battery system including the same will be described in detail with reference to the necessary drawings.

[0027] FIG. 1 is a diagram schematically showing a battery system including a pressure holding device according to an embodiment.

[0028] Referring to FIG. 1, a battery system 1a according to an embodiment can include a battery module and a pressure holding device for the battery module.

[0029] The battery module can include a plurality of battery cells 11 connected in series or in parallel with each other, and a module housing 12 which is a structure for accommodating the plurality of battery cells 11. The plurality of battery cells 11 can be arranged in a stacked shape inside the module housing 12.

[0030] An airtight space (or compartment) 14 is formed inside the module housing 12. Inside the internal space 14 of the module housing 12, a plurality of battery cells 11 and a hydraulic device 21 of a pressure holding device 20 described later are accommodated. A buffer plate 13 can be further positioned between the hydraulic device 21 and the battery cells 11 in the internal space 14 of the module housing 12. The buffer plate 13 can be deformed or its position can be moved according to the volume change of the battery cells 11. The buffer plate 13 can be moved or deformed toward the battery cells 11 by the expansion pressure of the hydraulic device 21 when the battery cells 11 contract. The buffer plate 13 can be moved or deformed toward the hydraulic device 21 by the expansion pressure of the battery cells 11 when the battery cells 11 expand.

[0031] The pressure holding device according to one embodiment can include a hydraulic device 21, an accumulator (22), a fluid pipe 23, a holding valve 24, a pressure reducing valve 25, a heater 26, a temperature sensor 27, and a controller 28.

[0032] The hydraulic device 21 can cancel out the pressure change inside the module housing 12 due to the deformation (volume change) of the battery cells 11 and minimize the fatigue load on the module housing 12. When the battery cells 11 contract, the hydraulic device 21 can expand and move or deform the buffer plate 13 toward the battery cells 11. When the battery cells 11 expand, the hydraulic device 21 can contract by the expansion pressure transmitted from the battery cells 11 via the buffer plate 13.

[0033] The hydraulic device 21 can include devices that can expand and contract by hydraulic pressure, such as a hydraulic bag and a hydraulic cylinder. The hydraulic device 21 can expand or contract by the inflow and discharge of a fluid (for example, oil). When the hydraulic device 21 contracts, the fluid can be discharged from the hydraulic device 21. When the hydraulic device 21 expands, the fluid can flow into the hydraulic device 21.

[0034] The accumulator 22 stores the pressurized fluid and offsets the hydraulic pressure changes generated by the expansion and contraction of the hydraulic device 21. That is, when a hydraulic pressure change occurs inside the fluid pipe 23 due to the expansion and contraction of the hydraulic device 21, the accumulator 22 can discharge the fluid to the fluid pipe 23 or allow the fluid to flow from the fluid pipe 23 into the accumulator 22 to offset the hydraulic pressure change in the fluid pipe 23. When the battery cell 11 contracts and the hydraulic device 21 expands, the accumulator 22 can discharge the fluid to the fluid pipe 23 to prevent a decrease in hydraulic pressure. When the battery cell 11 expands and the hydraulic device 21 contracts, the accumulator 22 can allow the fluid to flow from the hydraulic device 21 into the accumulator 22 to prevent an increase in hydraulic pressure. Therefore, the internal pressure of the accumulator 22 can change in proportion to the change in the internal pressure of the battery cell 11. That is, when the internal pressure of the battery cell 11 rises (expands), the pressure of the accumulator 22 rises due to the inflow of the fluid, and when the internal pressure of the battery cell 11 decreases (contracts), the pressure of the accumulator 22 decreases due to the discharge of the fluid.

[0035] The fluid pipe 23 penetrates and is connected to the module housing 12 and can be respectively connected to the fluid inlets and outlets (not shown) of the hydraulic device 21 and the accumulator 22. The fluid pipe 23 can be used as a passage for fluid exchange between the hydraulic device 21 and the accumulator 22.

[0036] The holding valve 24 is connected to the fluid inlet (not shown) of the fluid pipe 23 to replenish the fluid inside the fluid pipe 23. The holding valve 24 operates manually or automatically.

[0037] The holding valve 24 is opened by the manual operation of the user to supply fluid into the fluid pipe 23.

[0038] The holding valve 24 can also be controlled to open and close by the controller 28. In this case, when the pressure inside the fluid pipe 23 drops below a predetermined value or reaches a set period, the controller 28 opens the holding valve 24 to supply the fluid stored in a fluid tank (not shown) into the fluid pipe 23. For this purpose, the pressure holding device can further include a pressure sensor (see reference numeral 34 in FIG. 2) for detecting the internal pressure of the fluid pipe 23 or the accumulator 22. When the internal pressure of the fluid pipe 23 or the accumulator 22 detected by the pressure sensor drops below a predetermined value, the controller 28 can open the holding valve 24 to additionally supply fluid to the fluid pipe 23.

[0039] The pressure reducing valve 25 is connected to a fluid discharge port (not shown) of the fluid pipe 23 to discharge the fluid inside the fluid pipe 23 to the outside of the fluid pipe 23. The pressure reducing valve 25 can be opened when the pressure inside the fluid pipe 23 exceeds a predetermined value to discharge the fluid inside the fluid pipe 23 to the outside. The pressure reducing valve 25 can also be closed to interrupt fluid discharge when the pressure inside the fluid pipe 23 drops below a predetermined value.

[0040] The fluid pipe 23 can maintain an airtight state except when the holding valve 24 is opened to supply fluid into the fluid pipe 23 or when the pressure reducing valve 25 is opened to discharge the fluid inside the fluid pipe 23 to the outside. Therefore, with the holding valve 24 and the pressure reducing valve 25 closed, the fluid inside the fluid pipe 23 is only allowed to exchange with the hydraulic device 21 and the accumulator 22.

[0041] The heater 26 heats the accumulator 22.

[0042] The temperature sensor 27 measures the outside air temperature outside the accumulator 22.

[0043] The controller 28 detects the outside air temperature with the temperature sensor 27, and adjusts the current flowing through the heater 26 to heat the accumulator 22. The controller 28 can minimize the internal temperature change of the accumulator 22 by controlling the operation of the heater 26 according to the detected outside air temperature in order to prevent a pressure change from occurring inside the accumulator 22 due to the temperature change inside the accumulator 22. When nitrogen is filled inside the accumulator 22, since the energy required to raise the temperature of 1 L of nitrogen pressurized at 200 bar by 30 degrees is approximately 2 Wh, the internal temperature change of the accumulator 22 can be minimized with less energy.

[0044] According to the above-described embodiment, the displacement of the battery cell 11 can be absorbed by the pressure holding device, and the fatigue load applied to the module housing 12 due to charge and discharge can be minimized. Further, even if swelling occurs due to the life deterioration of the battery cell 11, the pressure inside the module housing 12 can be maintained constant as compared with the initial stage of the life, and the structural deformation of the module housing 12 can be minimized. Further, the fastening force of the battery cell 11 can be improved by pressurizing the battery cell 11 using the pressure holding device when installing the battery module. Further, it is possible to cope with outside air temperature variables, fluid leakage, etc. using the accumulator 22, the heater 26, etc.

[0045] FIG. 2 is a diagram schematically showing a battery system including a pressure holding device according to another embodiment.

[0046] In the battery system 1b of FIG. 2, the same reference numerals as those of the battery system 1a of FIG. 1 described above denote the same components, and the overlapping descriptions thereof are omitted.

[0047] Compared with FIG. 1, the battery system 1b can further include a replenishing pipe 31, an auxiliary accumulator 32, a solenoid valve 33, and pressure sensors 34, 35.

[0048] The supplementary pipe 31 can be used as a fluid passage between the solenoid valve 33, the auxiliary accumulator 32, and the holding valve 24.

[0049] The auxiliary accumulator 32 stores fluid in a pressurized state. When fluid is supplied to the supplementary pipe 31 via the holding valve 24, the auxiliary accumulator 32 stores the supplied fluid inside. When the solenoid valve 33 is opened and the hydraulic pressure inside the supplementary pipe 31 becomes low, the auxiliary accumulator 32 discharges the fluid stored inside and supplies fluid to the supplementary pipe 31.

[0050] The opening degree of the solenoid valve 33 is controlled by the controller 28 to control the flow of fluid between the fluid pipe 23 and the supplementary pipe 31.

[0051] The pressure sensor 34 is coupled to the fluid pipe 23 to detect the internal hydraulic pressure P1 of the fluid pipe 23. The pressure sensor 35 is coupled to the supplementary pipe 31 to detect the internal hydraulic pressure P2 of the supplementary pipe 31.

[0052] The controller 28 compares the pressures detected by the pressure sensors 34 and 35. When the internal hydraulic pressure P1 of the fluid pipe 23 becomes lower than the internal hydraulic pressure P2 of the supplementary pipe 31, the controller 28 opens the solenoid valve 33 to allow the fluid in the supplementary pipe 31 to flow into the fluid pipe 23. When fluid is supplied from the supplementary pipe 31 to the fluid pipe 23, the hydraulic pressure inside the supplementary pipe 31 becomes low, and thereby the fluid stored in the auxiliary accumulator 32 can be discharged into the supplementary pipe 31.

[0053] On the one hand, the opening of the solenoid valve 33 was described above by taking as an example the determination using the pressure sensors 34 and 35 coupled to the fluid pipe 23 and the replenishment pipe 31. However, the pressure sensors 34 and 35 for determining the opening of the solenoid valve 33 can also be coupled to the accumulators 22 and 32, respectively. In this case, the pressure sensors detect the internal pressures of the accumulator 22 and the auxiliary accumulator 32, respectively, and the controller 28 can compare these pressures to determine the opening of the solenoid valve 33. That is, when the internal pressure of the accumulator 22 becomes lower than the internal pressure of the auxiliary accumulator 32, the controller 28 can open the solenoid valve 33 so that the fluid in the replenishment pipe 31 flows into the fluid pipe 23.

[0054] According to this embodiment, the auxiliary accumulator 32 can be used to replenish the fluid when the pressure of the main accumulator 22 drops, and the maintenance period can be increased.

[0055] FIG. 3 is also a diagram schematically showing a battery system including a pressure holding device according to another embodiment.

[0056] In the battery system 1c of FIG. 3, the same reference numerals as those of the battery system 1a of FIG. 1 described above denote the same components, and the overlapping descriptions thereof are omitted.

[0057] Compared with FIG. 1, the battery system 1c can further include a pump 41 for replenishing the fluid to the fluid pipe 23 and a motor 42 for driving the pump 41 instead of the holding valve 24.

[0058] When the pressure inside the fluid pipe 23 drops below a predetermined value or reaches a set period, the controller 28 drives the pump 41 by the motor 42 to supply the fluid stored in a fluid tank (not shown) into the fluid pipe 23. For this purpose, the pressure holding device can further include a pressure sensor (see reference numeral 34 in FIG. 2) for detecting the internal pressure of the fluid pipe 23 or the accumulator 22. When the internal pressure of the fluid pipe 23 or the accumulator 22 detected by the pressure sensor drops below a predetermined value, the controller 28 can drive the pump 41 to additionally supply fluid to the fluid pipe 23.

[0059] According to this embodiment, when it is determined that fluid replenishment is necessary, the pressure holding device can drive the pump 41 even during running to automatically replenish the accumulator 22 with fluid.

[0060] The above detailed description of the invention with reference to the drawings is merely illustrative of the invention, which is used solely for the purpose of explaining the invention and is not used to limit the meaning or the scope of the invention described in the claims. Therefore, those of ordinary skill in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the invention should be determined by the technical idea of the appended claims.

Explanation of Reference Numerals

[0061] 1a, 1b, 1c Battery system 11 Battery cell 12 Module housing 13 Buffer plate 21 Hydraulic device 22 Accumulator 23 Fluid pipe 24 Holding valve 25 Pressure reducing valve 26 Heater 27 Temperature sensor 28 Controller 31 Replenishment pipe 32 Auxiliary accumulator 33 Solenoid valve 34, 35 Pressure sensor 41 Pump 42 Motor

Claims

1. A hydraulic device located inside the housing of a battery module together with a plurality of battery cells, the volume of which changes to counteract a change in pressure inside the housing due to deformation of the plurality of battery cells. An accumulator that stores fluid, is connected to the hydraulic device via a pipe, and discharges fluid into the pipe or stores the fluid flowing into the pipe in response to a change in volume of the hydraulic device. A heater that heats the accumulator. A temperature sensor that detects the outside air temperature, and A pressure holding device including a controller that controls the heater according to the outside air temperature.

2. The hydraulic device according to claim 1, wherein when the plurality of battery cells expand, it contracts and discharges fluid into the pipe, and when the plurality of battery cells contract, fluid flows into the pipe and it expands.

3. The hydraulic device according to claim 2, wherein the hydraulic device is a hydraulic cylinder or a hydraulic bag.

4. A hydraulic device located inside the housing of a battery module together with a plurality of battery cells, the volume of which changes to counteract a change in pressure inside the housing due to deformation of the plurality of battery cells. An accumulator that stores fluid, is connected to the hydraulic device via a pipe, and discharges fluid into the pipe or stores the fluid flowing into the pipe in response to a change in volume of the hydraulic device. A heater that heats the accumulator. A controller that controls the heater according to the outside air temperature, and A pressure holding device including a holding valve that is connected to the pipe and replenishes the pipe with fluid when opened.

5. A hydraulic device located inside the housing of a battery module together with a plurality of battery cells, the volume of which changes to counteract a change in pressure inside the housing due to deformation of the plurality of battery cells. An accumulator that stores fluid, is connected to the hydraulic device via a pipe, and discharges fluid into the pipe or stores the fluid flowing into the pipe in response to a change in volume of the hydraulic device. A heater that heats the accumulator. A controller that controls the heater according to the outside air temperature, and A pressure holding device including a pressure reducing valve that is connected to the pipe and is opened when the pressure in the pipe exceeds a predetermined value to discharge fluid from the pipe. Claim 6: A hydraulic device located inside the housing of a battery module together with a plurality of battery cells, the volume of which changes to cancel out a pressure change inside the housing due to deformation of the plurality of battery cells. An accumulator that stores a fluid, is connected to the hydraulic device via a pipe, and discharges the fluid into the pipe or stores the fluid flowing in from the pipe in response to a volume change of the hydraulic device. A heater that heats the accumulator. A controller that controls the heater according to the outside air temperature. A replenishment pipe. A solenoid valve connected between the pipe and the replenishment pipe, and supplying the fluid in the replenishment pipe to the pipe when opened. And An auxiliary accumulator that stores a fluid and discharges the fluid into the replenishment pipe when the internal pressure of the replenishment pipe becomes low due to the opening of the solenoid valve. The solenoid valve is a pressure holding device that is opened when the internal pressure of the pipe is lower than a predetermined value or more than the internal pressure of the replenishment pipe. Claim 7 The pressure holding device according to claim 6, further including a holding valve connected to the replenishment pipe and replenishing the fluid into the replenishment pipe when opened. Claim 8 A first pressure sensor coupled to the pipe to detect the internal pressure of the pipe. And The pressure holding device according to claim 6, further including a second pressure sensor coupled to the replenishment pipe to detect the internal pressure of the replenishment pipe. The controller opens the solenoid valve when a first pressure detected by the first pressure sensor is lower than a second pressure detected by the second pressure sensor. Claim 9 A first pressure sensor coupled to the accumulator to detect the internal pressure of the accumulator. And The pressure holding device according to claim 6, further including a second pressure sensor coupled to the auxiliary accumulator to detect the internal pressure of the auxiliary accumulator. The controller opens the solenoid valve when a first pressure detected by the first pressure sensor is lower than a second pressure detected by the second pressure sensor. Claim 10: A hydraulic device located inside the housing of a battery module together with a plurality of battery cells, the volume of which changes to cancel out a pressure change inside the housing due to deformation of the plurality of battery cells. An accumulator that stores a fluid, is connected to the hydraulic device via a pipe, and discharges the fluid into the pipe or stores the fluid flowing in from the pipe in response to a volume change of the hydraulic device. A heater that heats the accumulator. A controller that controls the heater according to the outside air temperature, a pump that is coupled to the pipe and additionally supplies fluid to the pipe, and a motor that drives the pump, wherein the controller controls the motor to drive the pump when the internal pressure of the pipe drops below a predetermined value, a pressure holding device.

11. The pressure holding device according to any one of Claims 1 to 10, and including the battery module, the battery module includes the plurality of battery cells stacked on each other, and a battery system including the housing in which an airtight space where the plurality of battery cells and the hydraulic device are located is formed.

Images