Mechanical property testing device for diaphragm

Abstract

The utility model provides a mechanical property testing device for a diaphragm. The mechanical property testing device comprises a fixing unit, a piercing unit and a data acquisition unit, the fixing unit comprises a bearing seat and a pressing piece, the bearing seat is used for bearing a pole group with a diaphragm to be tested, and the pressing piece is arranged above the pole group and is detachably connected with the bearing seat, so that the pole group is fixed between the pressing piece and the bearing seat. The piercing unit comprises a piercing needle arranged above the pressing piece in a sliding mode, the piercing needle can be driven to be close to the pole set to pierce the diaphragm, the data acquisition unit acquires resistance between the pole set and the piercing needle, or the data acquisition unit at least can acquire voltage and current between the pole set and the piercing needle. According to the mechanical property testing device for the diaphragm, the puncturing needle in the puncturing unit punctures the diaphragm, and the resistance between the pole group and the puncturing needle is directly or indirectly acquired through the data acquisition unit, so that the mechanical property of the diaphragm of a lithium ion battery can be effectively tested, and the mechanical property testing device has relatively high testing precision.

Description

Technical Field

[0001] The utility model relates to the technical field of power battery testing, in particular to a mechanical performance testing device for a diaphragm. Background Art

[0002] The safety of lithium-ion batteries is an important factor affecting the promotion of electric vehicles. In lithium-ion batteries, the diaphragm is one of the important main materials, which is located between the positive electrode and the negative electrode to separate the two. The performance of the diaphragm determines the capacity, cycle performance and safety performance of the battery, so high-quality diaphragms play an important role in improving the comprehensive performance of the battery. Lithium-ion batteries are prone to foreign matter during assembly. During long-term charge and discharge cycles, foreign matter in the battery will squeeze the diaphragm under the action of the expansion force of the battery cell, causing damage to the diaphragm. If the diaphragm ruptures, the battery will short-circuit, leading to safety problems, so it is particularly important to test the mechanical properties of the diaphragm.

[0003] Currently, the performance of the diaphragm is usually evaluated by piercing the diaphragm with a needle and collecting pressure. However, this test method does not take into account the damage to the diaphragm caused by foreign matter introduced during the battery cell manufacturing process, resulting in the test results being of low reference value. Utility Model Content

[0004] In view of this, the utility model aims to provide a mechanical property testing device for a diaphragm, so as to facilitate the puncture test of the diaphragm and have high test accuracy.

[0005] In order to achieve the above object, the technical solution of the utility model is implemented as follows:

[0006] A mechanical property testing device for a diaphragm, comprising a fixing unit, a piercing unit and a data acquisition unit; the fixing unit comprises a supporting seat and a pressing member, the supporting seat is used to support a pole group having a diaphragm to be tested, the pressing member is arranged above the pole group and is detachably connected to the supporting seat to fix the pole group between the pressing member and the supporting seat; the piercing unit comprises a needle slidably arranged above the pressing member, the needle can be driven to approach the pole group and pierce the diaphragm; the data acquisition unit is electrically connected to the needle and the pole group respectively, and the data acquisition unit can at least collect the resistance between the pole group and the needle, or the data acquisition unit can at least collect the voltage and current between the pole group and the needle. Further, the pressing member is connected to the supporting seat through a screw structure; and / or the pressing member is a pressing plate, and a through hole is provided on the pressing plate for the needle to pass through.

[0007] Furthermore, the screw connection structure includes bolts respectively passing through two ends of the pressing member, and threaded holes provided on the supporting seat and corresponding to the bolts.

[0008] Furthermore, it also includes a shell having a cavity inside, and the fixing unit and the piercing unit are both arranged in the cavity.

[0009] Furthermore, the piercing unit includes a horizontal plate slidably arranged on the shell along a vertical direction, and the puncture needle is arranged on the horizontal plate.

[0010] Furthermore, a guide portion is provided between the shell and the transverse plate, and the guide portion is used to guide the transverse plate to slide in a vertical direction.

[0011] Furthermore, a connecting column extending in a vertical direction is provided at the bottom of the horizontal plate, and the pricking needle is detachably connected to the connecting column.

[0012] Furthermore, the thorn needle is made of tungsten steel or stainless steel.

[0013] Furthermore, the needle head of the puncture needle is round, flat or conical.

[0014] Furthermore, the diameter D of the needle tip of the puncture needle satisfies: D≤0.5 mm; and / or the thickness d of the pressing member and the length L of the puncture needle satisfy: Ld>2 mm.

[0015] Compared with the prior art, the utility model has the following advantages:

[0016] The mechanical property testing device for the diaphragm described in the utility model is provided with a supporting seat and a piercing unit for fixing the electrode group, so that the piercing needle in the piercing unit pierces the diaphragm, and at the same time directly or indirectly collects the resistance between the electrode group and the piercing needle through the data acquisition unit, thereby simulating the damage to the diaphragm caused by foreign matter introduced during the battery cell manufacturing process, thereby providing a basis for evaluating the influence of foreign matter on the safety of the battery cell from the perspective of the diaphragm.

[0017] In addition, the lower pressure piece is a lower pressure plate, and is connected to the supporting seat through a screw structure. At the same time, a through hole for the puncture needle to pass through is provided on the lower pressure plate, which can compress the electrode group during the puncture of the puncture needle to ensure the stability of the electrode group fixation. In addition, the screw structure includes bolts provided through both ends of the lower pressure piece, which is convenient for disassembly and assembly of the lower pressure plate, thereby facilitating the disassembly of the electrode group on the supporting seat. By arranging the fixing unit and the puncture unit in the cavity of the shell, it is convenient to protect both of them and further improve the test accuracy. By arranging the puncture needle on a horizontal plate slidably provided on the shell, it is convenient to arrange and implement the puncture needle.

[0018] In addition, the guide part between the shell and the horizontal plate is conducive to improving the stability of the needle during sliding. The needle is detachably arranged on the connecting column, so as to facilitate the replacement of needles of different specifications to meet the needs of mechanical property testing of the diaphragm. The needle is made of tungsten steel or stainless steel, which is conducive to extending the service life of the needle. The needle head is round, flat or conical, has a good piercing effect, and is easy to arrange and implement. The setting of the diameter range of the needle head is conducive to improving the piercing effect on the diaphragm; the relationship between the thickness of the lower pressure piece and the length of the needle is conducive to further ensuring the piercing effect of the needle on the electrode group. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the accompanying drawings:

[0020] Figure 1 It is a structural schematic diagram of the mechanical properties testing device for the diaphragm described in an embodiment of the utility model.

[0021] Description of reference numerals:

[0022] 1. Support seat; 2. Pressing piece; 3. Pole group; 4. Needle; 5. Data acquisition unit; 6. Screw structure; 7. Shell; 8. Horizontal plate; 9. Guide part; 10. Connecting column. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0024] In the description of the present invention, it should be noted that if there are terms indicating orientation or positional relationship such as "upper", "lower", "inner", "back", etc., they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, if there are terms such as "first", "second", etc., they are also used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0026] This embodiment relates to a mechanical properties testing device for a diaphragm, which is used to test the diaphragm of a battery. Figure 1 As shown, the mechanical property testing device for the diaphragm of this embodiment includes a fixing unit, a piercing unit and a data acquisition unit 5.

[0027] The fixing unit includes a supporting seat 1 and a pressing member 2. The supporting seat 1 is used to support a pole group 3 having a diaphragm to be tested. The pressing member 2 is disposed above the pole group 3 and is detachably connected to the supporting seat 1 to fix the pole group 3 between the pressing member 2 and the supporting seat 1. The piercing unit includes a needle 4 slidably disposed above the pressing member 2. The needle 4 can be driven to approach the pole group 3 to pierce the diaphragm. The data acquisition unit 5 is electrically connected to the needle 4 and the pole group 3, respectively, and the data acquisition unit 5 can at least collect the resistance between the pole group 3 and the needle 4, or the data acquisition unit 5 can at least collect the voltage and current between the pole group 3 and the needle 4.

[0028] The mechanical properties testing device for the diaphragm of the present embodiment is provided with a supporting seat 1 for fixing the electrode group 3 and a piercing unit, so that the piercing needle 4 in the piercing unit pierces the diaphragm, and at the same time, the resistance between the electrode group 3 and the piercing needle 4 is directly or indirectly collected by the data acquisition unit 5, thereby simulating the damage to the diaphragm caused by foreign matter introduced during the battery cell manufacturing process, thereby providing a basis for evaluating the influence of foreign matter on the safety of the battery cell from the perspective of the diaphragm.

[0029] Based on the above overall introduction, continue to combine Figure 1 As shown, the electrode group 3 of this embodiment is composed of a plurality of positive and negative electrode sheets stacked alternately, and the positive and negative electrode sheets are separated by a diaphragm, and the center positions of the positive and negative electrode sheets and the diaphragm are on the same vertical line. During the test, the puncture needle 4 first punctures the diaphragm on the upper surface of the electrode group 3. The puncture needle 4 punctures the diaphragm on the upper surface of the electrode group 3 to simulate the damage caused to the diaphragm by metal foreign matter in the battery or the electrode group 3 during the actual charge and discharge process of the battery, thereby testing the mechanical properties of the diaphragm.

[0030] In addition, the data acquisition unit 5 in this embodiment is connected to the needle 4 and the electrode of the electrode group 3 through a wire, and the data collected by the data acquisition unit 5 is the resistance value between the electrode group 3 and the needle 4. During the test, since the membrane is punctured by the needle 4, the resistance value between the needle 4 and the electrode group 3 changes, and the mechanical properties of the tested membrane are evaluated according to the change in the resistance value.

[0031] In addition, the data collected by the data acquisition unit 5 may also be other values ​​associated with the electrode group, such as the voltage or current value between the needle 4 and the electrode group 3. In specific implementation, the data acquisition unit 5 may preferably adopt a conventional acquisition unit with data storage function well known to those skilled in the art, such as a Fluke data acquisition unit, etc., which can collect the resistance value between the electrode group 3 and the needle 4 or other values ​​associated with the resistance.

[0032] In addition, as an optional embodiment, the pressing member 2 is connected to the supporting seat 1 through a screw structure 6, and the pressing member 2 is a pressing plate, and the pressing plate is provided with a through hole for the needle 4 to pass through. The pressing member 2 is connected to the supporting seat 1 through the screw structure 6, so that the pressing member 2 is easy to disassemble and assemble, thereby facilitating the loading of the electrode group 3 to be tested, that is, the diaphragm on the electrode group 3.

[0033] At the same time, the lower pressing member 2 adopts a lower pressing plate, and the lower pressing plate is provided with a through hole for the puncture needle 4 to pass through, so as to tightly fix the electrode group 3 on the supporting seat 1, and tightly fit the diaphragm with the bottom of the lower pressing plate, so as to ensure the flatness of the diaphragm, avoid uneven force on the diaphragm during the puncture process, and cause the diaphragm to deform and deviate, thereby affecting the test results. In the specific implementation, the lower pressing plate can preferably be made of metal or non-metallic materials with higher strength, such as stainless steel, nylon, etc., to improve the durability and structural strength of the fixing unit.

[0034] As a preferred implementation form, the screw connection structure 6 of this embodiment includes bolts respectively passing through the two ends of the lower pressing member 2, and threaded holes provided on the supporting seat 1 and corresponding to the bolts. In specific implementation, the four corners of the lower pressing plate are each provided with a fixing hole for the bolts to pass through, and the lower pressing plate presses the electrode group 3 against the supporting seat 1 through the four fixing holes, so that the diaphragm on the electrode group 3 can be subjected to more uniform force, thereby preventing the diaphragm from deforming and deviating, which affects the test results.

[0035] In this embodiment, as a preferred implementation form, the mechanical property testing device for the diaphragm of this embodiment also includes a shell 7 with a cavity inside, and the fixing unit and the puncture unit are both arranged in the cavity. In the specific implementation, the shell 7 is a square frame structure, and is preferably made of conventional materials with a certain strength, such as stainless steel, etc., with a certain structural strength, so as to facilitate loading the fixing unit and the puncture unit. Among them, the data acquisition unit 5 can be preferably arranged outside the shell 7, and the wire of the data acquisition unit 5 passes through the shell 7 and is connected to the puncture needle 4 and the electrode group 3, so as to facilitate connecting the data acquisition unit 5 with other external devices and reading the data collected by the data unit.

[0036] Specifically, as a preferred implementation form, the piercing unit includes a horizontal plate 8 slidably arranged on the housing 7 in a vertical direction, and the puncture needle 4 is arranged on the horizontal plate 8. It can be understood that when the horizontal plate 8 moves in the vertical direction, the horizontal plate 8 can drive the puncture needle 4 to move toward the electrode group 3, so that the puncture needle 4 punctures the diaphragm on the upper surface of the electrode group 3, thereby completing the mechanical property test of the diaphragm.

[0037] In order to improve the stability of the needle 4 during movement, a guide portion 9 is provided between the housing 7 and the horizontal plate 8 of this embodiment. The guide portion 9 is used to guide the horizontal plate 8 to slide in the vertical direction, thereby driving the horizontal plate and the needle 4 arranged on the horizontal plate to move, so as to puncture the diaphragm. In a specific implementation, the guide portion 9 may include guide blocks arranged at both ends of the horizontal plate 8, and guide grooves arranged on the inner wall of the housing 7 for each guide block to slide into. Here, the structure of the guide block and the guide groove is simple, easy to process and form, and the guiding effect of the two is good. The horizontal plate 8 can be made of stainless steel to ensure the stability and structural strength of the horizontal plate 8 during movement.

[0038] In addition, the mechanical property testing device in this embodiment further includes a driving unit, the power end of which is connected to the horizontal plate 8 to drive the horizontal plate 8 to drive the needles 4 to move up and down. The driving unit here can be, for example, a linear motor, an electric push rod, etc., which can guide and drive the horizontal plate 8 to slide in the vertical direction.

[0039] As a preferred implementation form, the bottom of the horizontal plate 8 of this embodiment is provided with a connecting column 10 extending in the vertical direction, and the thorn needle 4 is detachably connected to the connecting column 10, so as to facilitate the replacement of thorn needles 4 of different specifications to meet different test requirements. Specifically, the thorn needle 4 is made of tungsten steel or stainless steel to ensure that the thorn needle 4 has a high structural strength to complete the puncture of the diaphragm and has a long service life. As a preferred implementation form, the needle head of the thorn needle 4 of this embodiment is a round head, a flat head or a cone head, and different needle head shapes are used to simulate the damage of different metal foreign bodies to the diaphragm to meet various test requirements.

[0040] Specifically, the diameter D of the needle meets: D≤0.5mm. It can be understood that, due to the small volume of the metal foreign matter in the battery or the electrode group 3, when the diameter D of the needle does not exceed 0.5mm, it can simulate the damage caused by the metal foreign matter to the diaphragm under the actual working condition of the battery, and has a more complex and practical simulation test effect. In addition, the thickness d of the lower pressing member 2 and the length L of the puncture needle 4 meet: Ld>2mm, so as to ensure that the puncture needle 4 can penetrate the lower pressing member 2 and puncture into the electrode group 3 to a certain depth to meet the test requirements.

[0041] The following is an explanation of the method for using the above-mentioned diaphragm mechanical properties testing device.

[0042] First, place the electrode group 3 to be tested on the supporting seat 1, and place the pressing piece 2 horizontally on the upper surface of the electrode group 3, and fix it by the screw structure 6 to ensure that the electrode group 3 will not move in any direction along the horizontal plane when the needle 4 pierces the diaphragm;

[0043] Then, the needle 4 is installed under the connecting column 10, and the acupuncture parameters are set, including the speed of the needle 4, the size of the holding force of the needle 4, the holding time of the needle 4 under this force, and the number of cycles of the needle 4. In specific implementation, for example, the speed of the needle 4 can be set not more than 20mm / min, the holding force of the needle 4 can not exceed the maximum pressure that the diaphragm can withstand, the holding time of the acupuncture force of the needle 4 is between 1min-60min, and the cycle is 1000 times. The value of the resistance between the needle 4 and the electrode group 3 is recorded by the data acquisition unit 5.

[0044] Before the diaphragm is punctured, due to the electronic insulation properties of the diaphragm itself, the resistance R0 between the needle 4 and the electrode group 3 is very large, about the MΩ level. After the diaphragm is punctured by the needle 4, the needle 4 is connected to the electrode sheet under the diaphragm. The resistivity of the electrode sheet is much smaller than that of the diaphragm, so the resistance between the needle 4 and the electrode group 3 will be greatly reduced. Record the number of acupuncture cycles N5, N10, N20, and N50 in which the resistance R0 decreases by more than 5%, 10%, 20%, and 50%.

[0045] By comparing the N5, N10, N20 and N50 of different types of diaphragms, under the same test conditions, the larger the N5, N10, N20 and N50 of the diaphragm, the better the long-term mechanical properties of the diaphragm and the stronger its ability to resist damage from foreign matter.

[0046] The mechanical properties testing device for the diaphragm of this embodiment is provided with a support seat 1 for fixing the electrode group 3 and a piercing unit, so that the piercing needle 4 in the piercing unit pierces the diaphragm, and the resistance between the electrode group 3 and the piercing needle 4 is directly or indirectly collected by the data acquisition unit 5, thereby effectively testing the mechanical properties of the lithium-ion battery diaphragm, ensuring the battery quality, and having good usability. The long-term mechanical properties of the diaphragm are also compared by comparing the number of cycles of different types of diaphragms under the same test conditions.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A mechanical properties testing device for a diaphragm, characterized in that: It includes a fixing unit, a piercing unit and a data acquisition unit; The fixing unit comprises a supporting seat and a pressing member, wherein the supporting seat is used to support the electrode group having the diaphragm to be tested, and the pressing member is arranged above the electrode group and is detachably connected to the supporting seat to fix the electrode group between the pressing member and the supporting seat; The piercing unit comprises a puncture needle slidably disposed above the pressing member, and the puncture needle can be driven close to the electrode group to puncture the diaphragm; The data acquisition unit is electrically connected to the needle and the electrode group, respectively, and the data acquisition unit can at least acquire the resistance between the electrode group and the needle, or the data acquisition unit can at least acquire the voltage and current between the electrode group and the needle.

2. The mechanical properties testing device for a diaphragm according to claim 1, characterized in that: The pressing member is connected to the supporting seat via a screw connection structure; and / or, The pressing member is a pressing plate, and the pressing plate is provided with a through hole for the needle to pass through.

3. The mechanical properties testing device for a diaphragm according to claim 2, characterized in that: The screw connection structure includes bolts respectively passing through two ends of the pressing member, and threaded holes arranged on the supporting seat and corresponding to the bolts.

4. The mechanical properties testing device for a diaphragm according to claim 1, characterized in that: It also includes a shell having a cavity inside, and the fixing unit and the piercing unit are both arranged in the cavity.

5. The mechanical properties testing device for a diaphragm according to claim 4, characterized in that: The piercing unit comprises a transverse plate slidably arranged on the housing along a vertical direction, and the puncture needle is arranged on the transverse plate.

6. The mechanical properties testing device for a diaphragm according to claim 5, characterized in that: A guide portion is provided between the shell and the transverse plate, and the guide portion is used to guide the transverse plate to slide in a vertical direction.

7. The mechanical properties testing device for a diaphragm according to claim 5, characterized in that: A connecting column extending in a vertical direction is provided at the bottom of the transverse plate, and the pricking needle is detachably connected to the connecting column.

8. The mechanical properties testing device for a diaphragm according to claim 1, characterized in that: The pricking needle is made of tungsten steel or stainless steel.

9. The mechanical properties testing device for a diaphragm according to claim 1, characterized in that: The needle head of the puncture needle is a round head, a flat head or a cone head.

10. The mechanical property testing device for a diaphragm according to any one of claims 1 to 9, characterized in that: The diameter D of the needle tip of the puncture needle satisfies: D≤0.5 mm; and / or, The thickness d of the pressing member and the length L of the needle satisfy: Ld>2mm.

Images