Device for measuring internal pressure of battery

Abstract

The invention discloses a battery internal pressure measuring device, the battery internal pressure measuring device comprises a puncture piece and a sealing mechanism, the sealing mechanism comprises an air pressure joint and a flexible pipe, the air pressure joint is connected with the outer surface of a battery shell, the air pressure joint is provided with an air passage, the flexible pipe is fixedly connected to the air pressure joint, and the puncture piece is arranged on the puncture piece. The sealing mechanism is arranged in the battery shell and is communicated with the air channel, the puncturing piece is arranged in the flexible pipe, the puncturing piece can move in the flexible pipe, and the puncturing piece is used for puncturing the battery shell so as to enable air in the battery shell to enter the sealing mechanism. The battery internal pressure measuring device provided by the invention is simple in structure and can accurately measure the internal pressure of the battery.

Description

Technical Field

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

[0002] With the widespread application of lithium-ion batteries, their safety has received more and more attention. The outer shell of a lithium-ion battery is a closed cavity. Gas will be generated due to internal chemical or physical reactions. The accumulation of gas will cause the internal pressure of the battery to increase. When the limit pressure value in the battery is too high, the gas inside the battery cannot be discharged in time, which will cause the battery to explode and cause a safety accident. If the pressure value is too low, the battery will fail prematurely and reduce its service life. Therefore, it is necessary to measure the internal pressure of the battery. The existing technical solution for measuring the internal air pressure of the battery is to make a hole on the surface of the battery, implant a trachea, and then connect an air pressure sensor to measure the internal air pressure of the battery. The problem of uncontrollable gas leakage during the hole-making process will make the test results inaccurate. Therefore, it is urgent to provide a device that can accurately measure the internal air pressure of the battery. Summary of the invention

[0003] The battery internal pressure measurement provided in this application can accurately measure the pressure inside the battery.

[0004] A battery internal pressure measuring device provided in the present application includes: a puncture piece and a sealing mechanism, wherein the sealing mechanism includes a gas pressure joint and a flexible tube, wherein the gas pressure joint is connected to the outer surface of the battery shell, the gas pressure joint has an air passage, the flexible tube is fixedly connected to the gas pressure joint and communicates with the air passage, the puncture piece is arranged in the flexible tube, the puncture piece can move in the flexible tube, and the puncture piece is used to puncture the battery shell so that the gas in the battery shell enters the sealing mechanism.

[0005] In the above embodiment, the sealing mechanism forms a closed space outside the battery. After the battery is punctured, since the air pressure inside the battery is higher than the air pressure of the sealing mechanism, the gas inside the battery enters the sealing mechanism until the sealing mechanism is filled, thereby preventing the gas from leaking into the external environment. The flexible tube is flexible and can change its posture at will. Therefore, during the movement of the puncture member toward the battery, the flexible tube can be deformed and will not hinder the movement of the puncture member. During the specific operation, the flexible tube and the puncture member can be held at the overlapped part so that the puncture member passes through the airway and punctures the battery housing. The gas in the battery enters the airway and the flexible tube to prevent it from escaping to the outside of the sealing mechanism. The gas enters the limited sealed space of the sealing mechanism, which can improve the accuracy of the air pressure measurement.

[0006] In one embodiment, the puncture member has a limiting structure, which is located on the side wall of the puncture member. The puncture member includes a tip and a tail end. The limiting structure is spaced a preset distance from the tip, and the limiting structure is used to limit the distance that the tip is inserted into the battery housing.

[0007] In one embodiment, the preset distance a and the thickness b of the battery housing satisfy 1<a / b<50.

[0008] In one embodiment, the battery internal pressure measuring device further comprises a measuring mechanism connected to an end of the flexible tube away from the air pressure connector.

[0009] In one embodiment, the measuring mechanism includes an air pressure sensor and a data collector, wherein the air pressure sensor is connected to the flexible tube, and the air pressure sensor is used to collect the pressure of the sealing mechanism and send the data to the data collector.

[0010] In one embodiment, a ratio r of the volume of the sealing mechanism to the volume of the battery housing satisfies: r<1 / 200.

[0011] In one embodiment, the piercing element has a length of 3 cm to 5 cm.

[0012] In one embodiment, the length of the flexible tube is 3 cm to 5 cm.

[0013] In one embodiment, the flexible tube is made of silicone or plastic. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a structure in which a battery internal pressure measuring device provided in an embodiment of the present application is installed on a battery;

[0015] Figure 2 A schematic diagram of a structure in which another battery internal pressure measuring device provided in an embodiment of the present application is installed on a battery;

[0016] Figure 3 A schematic diagram of a battery internal pressure measuring device provided in an embodiment of the present application puncturing a battery housing;

[0017] Figure 4 A schematic structural diagram of a battery internal pressure measuring device installed in a battery according to another embodiment of the present application.

[0018] Reference numerals:

[0019] 100-battery housing; 101-battery cell; 1-puncture piece; 2-sealing mechanism; 21-air pressure connector; 22-flexible tube; 211-airway; 212-connecting part; 213-connecting ring; A-tip end; B-tail end; 11-limiting structure; 3-air pressure sensor; 4-data collector. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings.

[0021] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "an", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context.

[0022] References to "one embodiment" or "a specific embodiment" in this specification mean that one or more embodiments of the present application include a particular feature, structure or characteristic described in conjunction with the embodiment. The terms "include", "comprises", "has" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0023] Lithium batteries are mainly composed of positive electrode sheets, negative electrode sheets, diaphragms and electrolytes. The positive electrode sheets and negative electrode sheets are respectively arranged on both sides of the diaphragm and are immersed in the electrolyte. The lithium ions of the positive electrode are released and enter the electrolyte during charging, and then pass through the microporous structure of the diaphragm, migrate to the negative electrode and combine with the electrons that reach the negative electrode through the external circuit. In this process, lithium ions escape from the positive electrode material, enter the electrolyte, and migrate to the negative electrode under the action of the external electric field, forming a compound with the carbon material of the negative electrode. During discharge, electrons and lithium ions move at the same time, but in different paths. Electrons flow from the negative electrode to the positive electrode through the external circuit, while lithium ions enter the electrolyte from the negative electrode, migrate to the positive electrode through the diaphragm, and combine with electrons that have already arrived.

[0024] The battery involves chemical reactions in the above-mentioned charging and discharging process, which will produce gas. In particular, when the battery is charged, the positive electrode material releases oxygen ions, which react with the electrolyte to produce gas. These gases accumulate inside the battery and form pressure inside the shell. In addition, during the charging and discharging process of the battery, the battery cell will also expand, and the expansion force mainly acts on the shell wall part in contact with the battery cell, further increasing the pressure inside the shell. Therefore, the structural strength of the battery shell must be sufficient to resist the expansion force of the battery cell without rupture. At the same time, the reaction force is added to the battery cell to fix the battery cell, and this reaction force will also affect the electrochemical reaction inside the battery.

[0025] The measurement of the internal pressure of the lithium battery shell is crucial to ensure the safety and performance of the battery. This change in pressure can reflect the health of the battery, the state of charge, and potential safety hazards. In some related technologies, the method of measuring the internal pressure of the lithium battery shell is to directly measure the internal pressure by drilling a hole in the battery and connecting a pressure sensor. This method can directly observe the changes in the internal air pressure of the battery during the charging and discharging process, thereby analyzing the performance and safety of the battery. This method has some shortcomings: for batteries whose internal pressure is greater than the ambient air pressure, uncontrollable gas leakage will inevitably occur during the battery opening process under ambient air pressure, resulting in an unassessable difference between the measured value of the pressure sensor and the true value of the internal pressure of the battery, resulting in inaccurate measurement. In addition, in order to ensure airtightness, after the battery is opened and the trachea is implanted, the trachea and the opening need to be sealed with glue, which may cause part of the glue to flow into the battery, react chemically with the electrolyte, cause changes in the internal environment of the battery, and cause uncertainty inside the battery.

[0026] To solve the above problems, an embodiment of the present application provides a battery internal pressure measuring device that can accurately measure the pressure inside the battery.

[0027] Figure 1 A schematic diagram of a battery internal pressure measuring device provided in an embodiment of the present application is installed in a battery, as shown in FIG. Figure 1 As shown, a battery internal pressure measuring device provided by an embodiment of the present application includes: a puncture member 1 and a sealing mechanism 2. The sealing mechanism 2 includes a gas pressure connector 21 and a flexible tube 22. The gas pressure connector 21 is a rigid connector, which is connected to the outer surface of the battery housing 100, and can be fixedly connected to the outer surface of the battery housing 100 by bonding. The gas pressure connector 21 has an airway 211, and the flexible tube 22 is fixedly connected to the gas pressure connector 21 and communicates with the airway 211. The puncture member 1 is disposed in the flexible tube 22, and the puncture member 1 can move in the flexible tube 22. The puncture member 1 is used to puncture the battery housing 100 so that the gas in the battery housing 100 enters the sealing mechanism 2.

[0028] In the above embodiment, the sealing mechanism 2 forms a closed space outside the battery. After the battery is punctured, since the air pressure inside the battery is higher than the air pressure of the sealing mechanism 2, the gas inside the battery enters the sealing mechanism 2 until the sealing mechanism 2 is filled, thereby preventing the gas from leaking to the external environment. The flexible tube 22 is flexible and can change its posture at will. For example, it can be bent into an S shape, a U shape, a wavy shape, etc., or wrinkles can be generated. Therefore, during the movement of the puncture member 1 toward the battery, the flexible tube 22 can be deformed and will not hinder the movement of the puncture member 1. During the specific operation, the flexible tube 22 can be held at the overlapped part with the puncture member 1, so that the puncture member 1 passes through the airway 211 and punctures the battery housing 100. The gas in the battery enters the airway 211 and the flexible tube 22 to prevent it from escaping to the outside of the sealing mechanism 2. The gas enters the limited sealed space inside the sealing mechanism 2, which can improve the accuracy of the air pressure measurement.

[0029] When connecting the air pressure connector 21 to the battery housing 100, bonding can be used. Specifically, the air pressure connector 21 has a connecting portion 212, which is located on the peripheral side of the airway 211. When bonding, the connecting portion 212 is connected to the battery housing 100, and no adhesive is set at the position of the airway 211, so that when puncturing, the puncture member 1 will not bring the adhesive into the battery housing 100, no new substances are added to the electrolyte, and no other chemical reactions will occur. In addition, in some related technologies, a clamp is usually used to clamp the battery and the measuring device to fix them together. The clamp applies a certain pressure to the battery, which will cause a certain change in the pressure inside the battery. The battery internal pressure measuring device of the present application does not use a clamp or other device to connect the sealing mechanism 2 to the battery, so as to avoid the clamp or other devices from causing pressure on the battery housing 100, affecting the change of its internal air pressure, and improving the accuracy and safety of the measurement.

[0030] In one embodiment, the inner diameter r of the air channel 211 and the inner diameter R of the flexible tube 22 satisfy r<R. When preparing the flexible tube 22 and the air pressure connector 21, the inner diameter r of the air channel 211 can be made slightly smaller than the inner diameter R of the flexible tube 22, so that after the flexible tube 22 is connected to the air channel 211, the gas inside the battery is not easy to leak out, thereby improving the accuracy of the measurement.

[0031] Figure 2 Another battery internal pressure measuring device provided in an embodiment of the present application is installed in a battery. Figure 2As shown, the flexible tube 22 and the air pressure connector 21 can also be connected by bonding, or, in one embodiment, a connecting ring 213 can be provided on the side of the air pressure connector 21 facing the flexible tube 22, and the connecting ring 213 can be an integrally formed structure with the air pressure connector 21. The inner through hole of the connecting ring 213 is connected to the airway 211, and the outer diameter of the connecting ring 213 can be equal to or slightly larger than the inner diameter of the flexible tube 22. Since the flexible tube 22 is flexible, when the outer diameter of the connecting ring 213 is slightly larger than the inner diameter of the flexible tube 22, the flexible tube 22 is sleeved on the connecting ring 213 and the connecting ring 213 is interference fit, thereby improving the reliability and convenience of the assembly of the flexible tube 22 and the air pressure connector 21. It can also prevent the flexible tube 22 from falling off the air pressure connector 21 when it is deformed. To improve reliability, the flexible tube 22 can be sleeved and bonded to the outer wall of the connecting ring 213, or, after the flexible tube 22 is sleeved on the outer wall of the connecting ring 213, a hoop is used to fix the flexible tube and the connecting ring 213.

[0032] Figure 3 A schematic diagram of a battery internal pressure measuring device provided in an embodiment of the present application piercing a battery housing, as shown in FIG. Figure 3 As shown, in one embodiment, the puncture member 1 can be a rigid needle-like structure, which includes a tip A and a tail B. The tip A is used to puncture the battery housing 100. In order to prevent the puncture member 1 from piercing too deeply into the battery housing 100, causing the electrode sheet or diaphragm of the battery cell 101 to be punctured. The puncture member 1 is provided with a limiting structure 11, which is located on the side wall of the puncture member 1 and close to the tip A. The limiting structure 11 is spaced a preset distance from the tip A, and the limiting structure 11 can limit the distance that the tip A is inserted into the battery. The limiting structure 11 can be a plate-like or block-like structure. After the tip A pierces the inside of the battery housing 100, it continues to slide into the battery housing 100 until the limiting structure 11 abuts against the outer surface of the battery housing 100, and the puncture member 1 is restricted from continuing to move into the battery housing 100, thereby achieving a limiting effect.

[0033] In a specific embodiment, the preset distance a between the above-mentioned limiting structure 11 and the tip A, and the shell thickness b of the battery, satisfy 1<a / b<50. The ratio of the preset distance a to the shell thickness b needs to be greater than 1 so that the puncture member 1 can pierce the battery shell 100. When measuring pressure, the puncture position can be the position of the explosion-proof valve on the battery shell 100. The thickness of the explosion-proof valve on the conventional square shell lithium-ion battery shell is 0.1mm. This position is the thinnest position of the battery shell and is easier to pierce. The distance between the explosion-proof valve and the pole piece is 5mm. Therefore, the ratio of the preset distance a to the shell thickness b satisfies 1<a / b<50, which can pierce the battery shell 100 without piercing the pole piece. The ratio of the above-mentioned preset distance a to the shell thickness b can be specifically 1.2, 10, 30, 40, 45, 48 or 49.5.

[0034] In one embodiment, the battery internal pressure measuring device further comprises a measuring mechanism, which is connected to an end of the flexible tube 22 away from the air pressure connector 21 and is used to measure the air pressure value in the sealing mechanism 2 .

[0035] Figure 4 A schematic diagram of a battery internal pressure measuring device installed in a battery according to another embodiment of the present application is shown in FIG. Figure 4 As shown, in a specific embodiment, the above-mentioned measuring mechanism includes an air pressure sensor 3 and a data collector 4. The air pressure sensor 3 is connected to the flexible tube 22. The air pressure sensor 3 is used to collect the pressure of the sealing mechanism 2 and send the data to the data collector 4. Specifically, the air pressure sensor 3 is connected to the end of the flexible tube 22 away from the gas interface to block the flexible tube 22. The air pressure sensor 3 can convert the gas pressure into a readable electrical signal and output it to the data collector 4. The above-mentioned air pressure sensor 3 can be a piezoresistive sensor, a capacitive sensor or a piezoelectric sensor.

[0036] Among them, the piezoresistive sensor consists of two thin film resistors, which are sandwiched by piezoelectric materials. When gas pressure is applied to the sensor surface, the resistance value of the thin film resistor changes because the pressure causes the thin film resistor to deform, thereby changing the resistance. By measuring the change in resistance value, the pressure of the gas can be determined. Capacitive sensors use the effect of gas pressure on capacitors. The capacitor in the sensor usually consists of an air gap between two metal plates. When gas pressure is applied to the sensor surface, the distance between the metal plates changes slightly, thereby changing the capacitance of the capacitor. The pressure of the gas can be inferred by measuring the change in capacitance value. Piezoelectric sensors use the piezoelectric effect to measure the pressure of the gas. Piezoelectric material is a material with a special crystal structure that produces charge separation and polarization when pressure is applied. In a piezoelectric sensor, the piezoelectric material is usually fixed in a mechanical structure so that it can be deformed when subjected to gas pressure. This deformation causes charge separation inside the piezoelectric material and produces a potential difference. By measuring the change in potential difference, the pressure of the gas can be determined. The above three pressure sensors can be selected as needed, and this application does not make specific restrictions.

[0037] In one embodiment, the ratio r of the volume of the sealing mechanism 2 to the battery housing 100 satisfies r<1 / 200. The sealing mechanism 2 can be regarded as a part of the battery, and its volume is set as small as possible to improve the sensitivity and accuracy of the test. For example, the volume of the battery housing 100 is 400cm 3 , then the volume of the sealing mechanism can be set to less than 2cm 3By setting the volume of the sealing mechanism 2 within the above-mentioned ratio range, the gas leakage in the battery housing 100 can be controlled within a smaller range, thereby improving the accuracy of the test.

[0038] In a specific embodiment, the volume of the sealing mechanism 2 is set to 1 cm 3 , through the formula PV = nRT, where: p is the pressure (Pa), V is the volume of the gas (m 3 ), n is the amount of gas substance (mol), R is the molar gas constant (also called universal gas constant) (J / (mol.K)), and T is the temperature (K), and the pressure inside the battery casing 100 before the hole is opened can be measured.

[0039] In one embodiment, the length of the flexible tube 22 is greater than the length of the piercing member 1. The length of the piercing member 1 may be 3 cm to 5 cm, preferably 3 cm. The length of the flexible tube 22 may be 3 cm to 5 cm, preferably 4 cm.

[0040] In one embodiment, the material of the flexible tube 22 can be silicone or plastic, preferably silicone, which is soft and convenient for puncture operation.

[0041] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A battery internal pressure measuring device, characterized in that: include: A puncture piece and a sealing mechanism, wherein the sealing mechanism comprises a gas pressure joint and a flexible tube, wherein the gas pressure joint is connected to the outer surface of the battery shell, the gas pressure joint has an airway, the flexible tube is fixedly connected to the gas pressure joint and communicates with the airway, the puncture piece is arranged in the flexible tube, the puncture piece can move in the flexible tube, and the puncture piece is used to puncture the battery shell so that the gas in the battery shell enters the sealing mechanism.

2. The battery internal pressure measuring device according to claim 1, characterized in that: The piercing member has a limiting structure, which is located on the side wall of the piercing member. The piercing member includes a tip and a tail. The limiting structure is spaced a preset distance from the tip, and the limiting structure is used to limit the distance that the tip is inserted into the battery housing.

3. The battery internal pressure measuring device according to claim 2, characterized in that: The preset distance a and the thickness b of the battery housing satisfy 1<a / b<50.

4. The battery internal pressure measuring device according to claim 1, characterized in that: The battery internal pressure measuring device further comprises a measuring mechanism connected to an end of the flexible tube away from the air pressure connector.

5. The battery internal pressure measuring device according to claim 4, characterized in that: The measuring mechanism comprises an air pressure sensor and a data collector. The air pressure sensor is connected to the flexible tube. The air pressure sensor is used to collect the pressure of the sealing mechanism and send the data to the data collector.

6. The battery internal pressure measuring device according to claim 1, characterized in that: A ratio r of the volume of the sealing mechanism to the volume of the battery housing satisfies r<1 / 200.

7. The battery internal pressure measuring device according to claim 1, characterized in that: The length of the piercing element is 3-5 cm.

8. The battery internal pressure measuring device according to claim 1, characterized in that: The length of the flexible tube is 3-5 cm.

9. The battery internal pressure measuring device according to claim 1, characterized in that: The flexible tube is made of silicone or plastic.

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