Battery internal pressure measuring device and method and cylindrical battery

Abstract

The invention provides a battery internal pressure measuring device and method and a cylindrical battery, and relates to the technical field of battery tests.The battery internal pressure measuring device comprises a shell, one end, facing the interior of a gas production area, of the shell is provided with a gas-permeable and liquid-impermeable film, and the other end of the shell is covered with a first sealing piece; a second sealing piece sliding in the axial direction of the shell is connected into the shell in a sliding mode, and the second sealing piece and the first sealing piece are connected with the two ends of the elastic element respectively. The battery has the beneficial effects that when gas generated by the battery enters the shell through the gas-permeable and liquid-impermeable membrane, pressure is generated on the second sealing element, so that the elastic element deforms, the second sealing element displaces, the change condition of the internal pressure of the battery can be determined by detecting the displacement degree, the sealing performance of the battery is not damaged, and the service life of the battery is prolonged. An external sensor is not needed, leakage of air pressure and electrolyte in the testing process is avoided, meanwhile, the original internal space of the cylindrical battery is not changed, the change condition of the internal pressure of the battery can be measured more accurately, and the method is simple and high in realizability.

Description

Technical Field

[0001] The present invention relates to the technical field of battery testing, and in particular to a battery internal pressure measuring device, method and cylindrical battery. Background Art

[0002] The lifespan of lithium-ion batteries is determined by the rate of capacity decay, which is primarily driven by factors such as side reactions between internal battery materials, battery structural design, manufacturing processes, and operating conditions. Side reactions between the electrolyte and the positive and negative electrode materials are a significant contributor to rapid capacity decay. During the cycling and storage of lithium-ion batteries, gases generated by these side reactions accumulate within the battery, causing volume expansion, electrode / diaphragm misalignment, and increased polarization. This accelerates capacity decay and can even pose safety risks.

[0003] In recent years, in order to improve the energy density of batteries, high-nickel positive electrode materials (such as NCM811, NCA) and graphite / silicon composite negative electrode systems have become research hotspots. However, the side reactions of such highly active material systems with the electrolyte are more intense under high pressure or high capacity conditions, resulting in a significant increase in gas production. In steel-shell cylindrical batteries, gas accumulation will cause the internal pressure to continue to rise, and the negative electrode cover (such as the top cover or explosion-proof valve assembly) is prone to bulging and deformation due to its low structural strength. If the internal pressure exceeds the design threshold, it may cause electrolyte leakage or premature opening of the explosion-proof valve, seriously affecting the safety and reliability of the battery.

[0004] At present, the main methods for measuring the internal pressure of lithium-ion batteries include destructive puncture of the battery and bolted external pressure sensors. However, the destructive puncture method requires puncturing the battery casing to access the measuring equipment, which may cause electrolyte leakage or gas escape during the process, causing the measurement results to deviate from the actual aging state, and it is impossible to perform long-term dynamic monitoring of the same battery. The bolted external sensor method requires processing and installing interfaces on the battery casing, which not only occupies internal space and changes the volume of the air chamber, but may also introduce the risk of leakage or gas leakage due to poor sealing. In addition, the mechanical installation of the external sensor may interfere with the internal structure of the battery (such as squeezing the diaphragm or electrode), affecting the normal aging behavior of the battery.

[0005] Therefore, the existing technology lacks a non-destructive method for detecting the internal pressure of the battery, which makes it difficult to meet the needs of high-energy-density battery systems in gas production behavior analysis and safety assessment. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a battery internal pressure measuring device, which is plugged into the gas-generating area of ​​the battery and includes a housing, one end of the housing facing the interior of the gas-generating area is provided with a gas-permeable and liquid-impermeable membrane, and the other end cover is provided with a first sealing member;

[0007] A second sealing member is slidably connected inside the housing and slides along the axial direction of the housing. The second sealing member and the first sealing member are respectively connected to two ends of the elastic element.

[0008] Preferably, the shape of the shell is adapted to the shape of the gas production area, and the length of the shell is smaller than the width of the electrode of the battery.

[0009] Preferably, the pressure resistance of the shell is not less than 3 MPa.

[0010] Preferably, the shell is made of one or more of nylon, polyester fiber, fluororubber, polytetrafluoroethylene and polyphthalamide.

[0011] Preferably, the material of the air-permeable and liquid-impermeable membrane is one or more of high-density polyethylene, polytetrafluoroethylene and non-woven fabric.

[0012] Preferably, the second sealing member is made of rubber, polytetrafluoroethylene, or metal.

[0013] The present invention further provides a battery internal pressure measurement method, which is applied to the above-mentioned battery internal pressure measurement device, comprising:

[0014] Step S1, during the battery preparation process, inserting the battery internal pressure measuring device into the gas generating area of ​​the battery;

[0015] Step S2: During the battery test, monitor the displacement of the second sealing member in the axial direction of the housing, and calculate the real-time pressure inside the battery based on the displacement.

[0016] Preferably, the step S2 includes:

[0017] Step S21, collecting an image of the battery in an initial state, and performing image recognition to obtain an initial position of the second sealing member;

[0018] Step S22, collecting images of the battery during the test, performing image recognition to obtain a current position of the second sealing member, and calculating the displacement of the second sealing member in the axial direction of the housing using the current position and the initial position;

[0019] Step S23: Calculate the real-time pressure inside the battery according to the displacement and the cross-sectional area of ​​the second sealing member.

[0020] Preferably, the image is an ultrasound image or a CT image.

[0021] The present invention also provides a cylindrical battery, wherein the center hole of the cylindrical battery is used as the gas production area and the above-mentioned battery internal pressure measuring device is plugged into the center hole of the cylindrical battery.

[0022] The above technical solution has the following advantages or beneficial effects:

[0023] 1) By inserting the battery internal pressure measuring device of the present invention into the gas-generating area inside the battery, the gas generated by the battery enters the interior of the housing through the gas-permeable and liquid-impermeable membrane, generating pressure on the second sealing member, thereby causing the elastic element to deform. The second sealing member is displaced as the elastic element deforms. By detecting the degree of this displacement, the change in the internal pressure of the battery can be determined. This method is simple and highly feasible.

[0024] 2) The battery internal pressure measuring device based on the present invention performs non-destructive measurement of the internal pressure of the battery without destroying the sealing of the battery, without the need for external sensors, and avoids air pressure and electrolyte leakage during the test. At the same time, it does not change the original internal space of the cylindrical battery, and can more accurately measure the changes in the internal pressure of the battery, meeting the needs of high-energy-density battery systems in gas production behavior analysis and safety assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a battery internal pressure measuring device in a preferred embodiment of the present invention;

[0026] Figure 2 FIG1 is a flow chart of a method for measuring internal pressure of a battery in a preferred embodiment of the present invention;

[0027] Figure 3 Schematic diagram of a sub-flow chart of step S2 in a preferred embodiment of the present invention;

[0028] In the figure, 1, shell; 2, air-permeable and liquid-tight membrane; 3, first sealing member; 4, second sealing member; 5, elastic element. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0030] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a battery internal pressure measuring device is provided, which is plugged into the gas generating area of ​​the battery, such as Figure 1 As shown, it comprises a shell 1, an end of the shell 1 facing the interior of the gas production area is provided with a gas-permeable and liquid-impermeable membrane 2, and the other end cover is provided with a first sealing member 3;

[0031] A second sealing member 4 that slides along the axial direction of the housing 1 is slidably connected inside the housing 1 . The second sealing member 4 and the first sealing member 3 are respectively connected to two ends of the elastic element 5 .

[0032] Specifically, in this embodiment, the battery internal pressure measurement principle is described by taking the battery internal pressure measurement device of the present invention applied to a cylindrical battery as an example:

[0033] First, the gas-generating area of ​​a cylindrical battery is located at the center hole. During the trial production of cylindrical batteries, the battery internal pressure measuring device can be inserted into the center hole of the cylindrical battery, achieving a built-in battery internal pressure measuring device. In a preferred embodiment of the present invention, the shape of the housing 1 is adapted to the shape of the gas-generating area, and the length of the housing 1 is less than the width of the battery electrode.

[0034] In this embodiment, since the center hole area is cylindrical, the shell 1 of the battery internal pressure measuring device of the present invention also needs to be set to a cylindrical shape accordingly, and since it needs to be inserted into the center hole, the outer diameter of the shell 1 needs to be smaller than the inner diameter of the center hole. The fitting clearance between the shell 1 and the center hole is preferably 0.1mm-0.3mm, which ensures that the shell 1 can be smoothly inserted into the center hole and can avoid gas leakage. In addition, in order not to interfere with the pole piece winding structure, the length of the shell 1 needs to be less than the pole piece width of the battery. Preferably, the length of the shell 1 can be 80%-90% of the pole piece width, so that the measurement area is located in the middle position where gas production is most concentrated. For example, for a 21700 battery (pole piece width 50mm), the device length is designed to be 42.5mm.

[0035] Taking the aging test of the battery as an example, after the battery internal pressure measuring device is installed, the internal pressure change of the battery can preferably be monitored by ultrasonic image or CT image recognition. Specifically, in the initial state of the battery, an ultrasonic image or CT image can be collected from the outside of the battery, and then the position X1 of the second seal 4 in the shell 1 can be obtained through image recognition. Subsequently, after the aging test, the gas generated by the aging of the battery will enter the interior of the shell 1 from one end of the shell 1 where the air-permeable and liquid-impermeable membrane 2 is set along the direction indicated by the arrow. As the gas production gradually increases, the internal pressure of the shell 1 gradually increases, thereby generating pressure on the second seal 4. Under the action of the gradually increasing pressure, the elastic element 5 will deform, and then the second seal 4 will move following the elastic element 5. At this time, an ultrasonic image or CT image is collected from the outside of the battery again, and then the position X2 of the second seal 4 in the shell 1 is obtained through image recognition. The displacement x of the two measurements is x1-x2.

[0036] Furthermore, the displacement x of the second sealing member 4 and the pressure F generated by the gas satisfy Hooke's law, that is, F=Kx, where K is a constant.

[0037] The pressure F generated by the gas and the real-time pressure P inside the battery satisfy P=F / A, where A is the cross-sectional area of ​​the second sealing member 4 .

[0038] Therefore, the real-time pressure inside the battery can be achieved by measuring the displacement of the second seal 4. The entire process will not destroy the sealing of the battery, does not require external sensors, and will not change the original internal space of the cylindrical battery. It can more accurately measure the changes in the internal pressure of the battery and meet the needs of high-energy-density battery systems in gas production behavior analysis and safety assessment.

[0039] In practice, ultrasound or CT images can be collected simultaneously during battery charge and discharge tests or aging tests, enabling real-time monitoring. However, this is costly and complex. Preferably, ultrasound or CT images can be collected after a specific number of cycles, such as every 100 cycles, to monitor internal pressure throughout the battery's lifecycle.

[0040] In addition, considering that there are differences in gas production between different batteries, and even differences in gas production at different stages of the aging process, when selecting the elastic element 5, an elastic element 5 of a suitable range can be selected according to the battery size. The elastic element 5 includes but is not limited to a spring, such as a 46 cylindrical battery spring that can withstand a pressure range of 0-2 MPa.

[0041] In a preferred embodiment of the present invention, the pressure resistance of the housing 1 is not less than 3 MPa.

[0042] Specifically, in this embodiment, since the internal expansion force of the cylindrical battery is generally less than 3 MPa, when the shell 1 is prepared, its pressure resistance is required to be no less than 3 MPa, so that the shell 1 is less deformed by extrusion within the 3 MPa stress range, avoiding side extrusion.

[0043] In a preferred embodiment of the present invention, the shell 1 and the first seal 3 need to be made of materials with high strength, high elasticity and resistance to electrolyte corrosion. Based on this, the material of the shell 1 and the first seal 3 can be the same, preferably one or more of nylon, polyester fiber, fluororubber, polytetrafluoroethylene and polyamide.

[0044] In a preferred embodiment of the present invention, one end of the shell 1 is sealed and the other end is sealed with a gas-permeable and liquid-tight membrane 2, which can ensure that the gas generated inside the battery can enter the interior of the shell 1, but the liquid will not enter, thereby preventing the electrolyte from entering the interior of the shell 1. The material of the gas-permeable and liquid-tight membrane 2 is one or more of high-density polyethylene, polytetrafluoroethylene and non-woven fabric.

[0045] In a preferred embodiment of the present invention, the second sealing member 4 needs to be displaced along with the deformation of the elastic element 5 while ensuring sealing performance. The second sealing member 4 is made of rubber, polytetrafluoroethylene, or metal.

[0046] The present invention also provides a battery internal pressure measurement method, which is applied to the above-mentioned battery internal pressure measurement device, such as Figure 2 As shown, including:

[0047] Step S1: During the battery preparation process, a battery internal pressure measuring device is plugged into the gas generating area of ​​the battery;

[0048] Step S2: During the battery test, the displacement of the second sealing member in the axial direction of the housing is monitored, and the real-time pressure inside the battery is calculated based on the displacement.

[0049] In a preferred embodiment of the present invention, Figure 3 As shown, step S2 includes:

[0050] Step S21, collecting an image of the battery in an initial state, and performing image recognition to obtain an initial position of the second sealing member;

[0051] Step S22, collecting images of the battery during the test, performing image recognition to obtain the current position of the second seal, and calculating the displacement of the second seal in the axial direction of the housing based on the current position and the initial position;

[0052] Step S23 , calculating the real-time pressure inside the battery according to the displacement and the cross-sectional area of ​​the second sealing member.

[0053] In a preferred embodiment of the present invention, the image is an ultrasound image or a CT image.

[0054] The present invention also provides a cylindrical battery, wherein the center hole of the cylindrical battery is used as a gas production area and the battery internal pressure measuring device is plugged in.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A battery internal pressure measuring device, characterized in that: Inserted in the gas production area of ​​the battery, comprising a shell, one end of the shell facing the interior of the gas production area is provided with a gas-permeable and liquid-impermeable membrane, and the other end cover is provided with a first sealing member; A second sealing member is slidably connected inside the housing and slides along the axial direction of the housing. The second sealing member and the first sealing member are respectively connected to two ends of the elastic element.

2. The battery internal pressure measuring device according to claim 1, characterized in that: The shape of the shell is adapted to the shape of the gas production area, and the length of the shell is smaller than the width of the electrode of the battery.

3. The battery internal pressure measuring device according to claim 1, characterized in that: The pressure resistance of the shell is not less than 3MPa.

4. The battery internal pressure measuring device according to claim 1, characterized in that: The shell is made of one or more of nylon, polyester fiber, fluororubber, polytetrafluoroethylene and polyphthalamide.

5. The battery internal pressure measuring device according to claim 1, characterized in that: The material of the air-permeable and liquid-impermeable membrane is one or more of high-density polyethylene, polytetrafluoroethylene and non-woven fabric.

6. The battery internal pressure measuring device according to claim 1, characterized in that: The second sealing member is made of rubber, polytetrafluoroethylene, or metal.

7. A method for measuring battery internal pressure, characterized in that: The battery internal pressure measuring device according to any one of claims 1 to 6 comprises: Step S1, during the battery preparation process, inserting the battery internal pressure measuring device into the gas generating area of ​​the battery; Step S2: During the battery test, monitor the displacement of the second sealing member in the axial direction of the housing, and calculate the real-time pressure inside the battery based on the displacement.

8. The battery internal pressure measurement method according to claim 7, characterized in that: The step S2 comprises: Step S21, collecting an image of the battery in an initial state, and performing image recognition to obtain an initial position of the second sealing member; Step S22, collecting images of the battery during the test, performing image recognition to obtain a current position of the second sealing member, and calculating the displacement of the second sealing member in the axial direction of the housing using the current position and the initial position; Step S23: Calculate the real-time pressure inside the battery according to the displacement and the cross-sectional area of ​​the second sealing member.

9. The battery internal pressure measurement method according to claim 8, characterized in that: The image is an ultrasound image or a CT image.

10. A cylindrical battery, characterized in that: The battery internal pressure measuring device according to any one of claims 1 to 6 is inserted into the center hole of the cylindrical battery as the gas production area.

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