A high-precision lithium-ion battery puncture testing device and method based on electrical signals

Abstract

The application provides a high-precision needle-punching test device and method for a lithium ion battery based on an electric signal, which comprises a needle-punching execution mechanism, a stroke monitoring circuit and a sample fixing tool. The needle-punching execution mechanism is provided with a metal needle, the sample fixing tool is provided with a conductive area, and part of the conductive area is located below the metal needle. One end of the stroke monitoring circuit is connected with the metal needle, and the other end is connected with the conductive area. When the metal needle contacts the conductive area, the metal needle, the stroke monitoring circuit and the conductive area form a closed loop, and a positioning signal is output from the stroke monitoring circuit to the needle-punching device. By adding the stroke monitoring circuit, the initial position of the needle is accurately positioned based on the electric signal, the accuracy and repeatability of the initial position are ensured, and thus the time when the needle contacts the battery and the stroke after entering the battery can be accurately controlled and judged, so that the consistency of the actual penetration depth in the needle-punching test is ensured, and the accuracy and consistency of the needle-punching test result are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery testing, in particular to a high-precision needle puncture testing device and method for lithium ion batteries based on an electric signal. BACKGROUND

[0002] Lithium ion batteries have been widely used in various portable electronic products due to their high energy and power density, long cycle life and other advantages, and are gradually applied to new energy vehicles and various forms of energy storage base stations. With the increasing energy density of lithium ion batteries and their increasing popularity in various application terminals, the risk of failure and the damage caused by failure are becoming more and more serious.

[0003] For the above reasons, lithium ion battery manufacturers need to conduct safety performance sampling inspection at the development process, type test, factory inspection and other links, and needle puncture testing is very important; related domestic and foreign test standards such as GB / T 31485:2015, SAE J2464:2009, SAND2005-3123, AIS-048:2009, PV8450:2018, IEC 62660-4, etc. also contain the requirements of needle puncture testing.

[0004] There are currently many safety equipment manufacturers on the market that can produce needle puncture testing equipment, but the existing needle puncture testing equipment has simple stroke monitoring logic, poor displacement detection precision, and no determination of the initial position of the needle, so it is difficult to control the actual contact time of the needle with the battery and the stroke after the needle penetrates the battery, resulting in poor test consistency and greatly reducing the repeatability of the needle puncture test.

[0005] Related patents such as CN201922017349 and CN202210240070 have also developed new types of high-precision needle puncture testing equipment, but the current conventional needle puncture operation still mainly relies on visual inspection to adjust the initial position of the needle, with an error of generally 0.3-0.5 mm. No one has paid attention to how to accurately control the initial position of the needle to monitor the actual time of the needle contacting the battery and measure the actual stroke of the needle in the battery.

[0006] The thickness of a single layer of lithium ion battery electrode sheet is 0.1-0.15 mm, and the error of the existing equipment is 0.3-0.5 mm, which may cause a difference of ±2-4 layers of electrode sheets; some test standards require the puncture depth to be controlled at 1-2 mm, and the error of the existing equipment is 0.3-0.5 mm, which is equivalent to a difference of up to 20%-50%; both of the above may bring huge differences to the test results, and even directly affect whether to fail. SUMMARY

[0007] The technical problem solved by the present application is: in order to clearly explain the technical scheme of the present application, first introduce the existing needle test process. Needle test is a destructive test, its main process is to use metal needle to pierce into the battery sample, the purpose is to investigate whether different products will appear unsafe situation in the test and after the test, such as smoking, fire or explosion, etc. Because of the destructiveness to the sample, each sample can only be tested once, so it is required to ensure that the depth of each penetration is the same, so as to evaluate the needle penetration performance and safety performance of the product, thereby providing guidance for product design and engineering development.

[0008] During the needle test, the metal needle needs to be fixed on the needle test equipment, and the sample to be tested also needs to be fixed by using a fixing tool, and the fixing needs to be re-performed before each test. Due to the assembly error between the tool and the product, the distance from the needle surface of the product to the metal needle is different. For example: according to the conventional needle process, the travel of the metal needle is set to 8mm each time, but due to the assembly error of the fixing tool and the error of the initial positioning by the naked eye, it may appear that 7.2mm is penetrated this time and 7.8mm is penetrated next time, so that the penetration depth cannot be guaranteed to be consistent, and the test results, test data and conclusions analyzed from the data also introduce a large inaccuracy (the data here is only for illustration, not for real data).

[0009] Because the conventional needle position confirmation is controlled by visual means, there is a serious lack of consistency and repeatability, which leads to poor repeatability of needle test of samples in the same batch; the present application provides a high-precision needle test device and method for lithium ion battery based on electrical signal, which can improve the consistency of lithium ion battery needle test results to a certain extent, greatly improve the efficiency of product development and test, and avoid misjudgment caused by test results in the development process.

[0010] The technical solution adopted by the present application to solve its technical problem is: a high-precision needle test device for lithium ion battery based on electrical signal, comprising a needle execution mechanism, a stroke monitoring circuit and a sample fixing tool, the needle execution mechanism has a metal needle, at least part of the area of the sample fixing tool is a conductive area, and at least part of the conductive area is located below the metal needle, one end of the stroke monitoring circuit is connected with the metal needle through a line, and the other end is connected with the conductive area through a line, when the metal needle contacts with the conductive area, the metal needle, the stroke monitoring circuit and the conductive area form a closed loop, and a positioning signal is outputted from the stroke monitoring circuit to the needle equipment, and the travel of the needle execution mechanism is controlled by the needle equipment.

[0011] Further, the stroke monitoring circuit comprises at least a power supply and a signal monitoring unit, the power supply provides working voltage for the stroke monitoring circuit, and the signal monitoring unit is used for monitoring the electric signal in the closed loop, and the operator controls the action of the needle puncture actuator of the needle puncture device according to the monitoring result of the signal monitoring unit.

[0012] The stroke monitoring circuit uses the principle of circuit on-off to determine the position of the metal needle, and when the metal needle contacts the conductive tape, a closed loop is formed to generate an electric signal, which is used as the positioning signal of the metal needle, thereby ensuring the consistency of the initial position of the metal needle and reducing the influence of the initial position error of the metal needle on the test result.

[0013] The power supply uses a small external power supply to provide voltage for the signal monitoring unit and the signal judgment unit, and the voltage should generally not be higher than 12V for safety; the signal monitoring unit includes but is not limited to light-emitting diodes, buzzers and other components, as long as it can form a closed loop and has a prompt function.

[0014] If the stroke monitoring circuit does not include a signal judgment unit, the initial position of the metal needle during testing can be controlled by manually controlling the needle puncture device to stop, for example, stopping the needle puncture device immediately after seeing the diode light or hearing the buzzer alarm. Manual control may have some reaction error, but considering that the error is much smaller than the test requirement, it can be considered within the error allowed range.

[0015] Since manual adjustment is relatively slow and needs to pay attention to the position of the metal needle and the state of the signal monitoring unit at all times, although manually controlling the needle puncture device to stop can meet the testing needs, in order to further reduce measurement error, the stroke monitoring circuit further comprises a signal judgment unit. The signal input end of the signal judgment unit is connected with the closed loop for receiving the electric signal generated in the closed loop, and outputs the positioning signal of the metal needle to the needle puncture device according to the electric signal. The needle puncture device controls the action of the needle puncture actuator according to the positioning signal, i.e. controls the metal needle to descend or stop. After adding the signal judgment unit, the automatic control and linkage of the testing device and the needle puncture device are realized, and the electric signal can be directly provided to the needle puncture device through the signal judgment unit. Compared with manual observation, the transmission of the electric signal is more accurate and fast, and the control is more accurate and convenient. As a preferred embodiment, the signal judgment unit can use a single-chip microcomputer as a signal receiving and judging control unit, which analyzes the electric signal to determine whether the loop is closed and whether the metal needle is at the initial position.

[0016] Specifically, the sample fixing tool includes a sample lower fixing tool and a sample upper fixing tool, and the sample to be tested is fixed between the sample lower fixing tool and the sample upper fixing tool during testing, and the sample upper fixing tool faces the needling surface of the sample to be tested, the sample upper fixing tool is provided with a needling hole, the needling hole is located directly below the metal needle, the needling hole corresponds to the position of the needle and can be penetrated by the metal needle, and a conductive adhesive tape is pasted on the needling hole, the conductive adhesive tape forms a conductive area, and is connected with the travel monitoring circuit through a circuit.

[0017] The test device of the application can be used for different types of batteries or cells, and the sample to be tested includes but is not limited to soft package cells, square shell cells, cylindrical cells, soft package modules, square shell modules, cylindrical modules and battery packs, etc. Wherein, the cells can form a module, the module can form a battery pack, and both small units and large units can be tested.

[0018] Preferably, the metal needle includes but is not limited to a steel needle, an aluminum needle or a copper needle, and the material is a metal that can form a conduction loop.

[0019] Further, the conductive adhesive tape is a copper foil tape, an aluminum foil tape, a silver tape or a carbon paper tape. The conductive adhesive tape is generally a metal tape with a thickness of less than 0.2 mm, so the deformation caused by stretching and other operations during pasting is relatively small, and the introduced error is much smaller than the allowable error of the test, so it will not have a great impact on the test results.

[0020] A high-precision needle puncture test method for lithium ion batteries based on electrical signals, which uses the above needle puncture test device for testing, and further includes the following test steps:

[0021] S1: using the sample fixing tool to fix the sample to be tested (such as a cell) on the needle puncture equipment, ensuring that the needle puncture position of the sample to be tested is aligned with the needle puncture hole on the sample upper fixing tool, and the needle puncture hole is located directly below the metal needle;

[0022] S2: paste the conductive adhesive tape on the upper surface of the sample upper fixing tool, and cover the needle puncture hole with the conductive adhesive tape, and try to ensure that the conductive adhesive tape covering the hollow area of the needle puncture hole is in a flat state; then, connect the travel monitoring circuit at both ends with the metal needle and the conductive adhesive tape, and ensure that the travel monitoring circuit can be turned on;

[0023] S3: determine the distance L1 between the needle puncture surface of the sample to be tested at the needle puncture position and the upper surface of the conductive adhesive tape;

[0024] In the scheme, the distance L1 is the sum of the thickness of the upper sample fixing tool and the thickness of the conductive tape. In actual testing, the thickness of the upper sample fixing tool is fixed, so it can be measured before assembly or determined according to the design size; the thickness of the conductive tape can be the theoretical thickness of the product. Although the conductive tape has small deformation, there will be small errors due to different pasting states. Therefore, in actual operation, in order to minimize the error, the distance L1 can be measured after the conductive tape is pasted, that is, the overall thickness of the conductive tape and the upper sample fixing tool is directly measured.

[0025] S4: Start the needle punching equipment, and drive the metal needle to punch the part of the upper sample fixing tool pasted with the conductive tape at a slow speed; and observe the position of the metal needle and the state of the signal monitoring unit. When the metal needle contacts the conductive tape, the circuit is connected and current flows, at this time, the signal monitoring unit gives an indication, and controls the needle punching actuator of the needle punching equipment to stop moving, then the position of the metal needle at this time is the critical point that the metal needle contacts the conductive tape, that is, the initial position of the metal needle; at this time, it is considered that the vertical height from the needle tip of the metal needle to the position to be tested is equal to L1.

[0026] S5: Drive the metal needle upward by the needle punching actuator to disconnect the conductive circuit, and remove the conductive tape from the upper sample fixing tool, and determine the lifting height L2, which is the distance from the needle tip of the metal needle to the surface of the conductive tape; the lifting height L2 should be large enough to provide enough space to conveniently remove the conductive tape on the surface of the tool before the actual needle punching test in the next step.

[0027] S6: Then perform the needle punching test according to the specified speed and process of the original needle punching test requirement, and the stroke of the needle punching equipment is set to x+L1+L2, wherein x is the penetration depth, which is determined according to the test requirement and is a known parameter, and the sample needs to be replaced and the clamp needs to be reinstalled, and the needle needs to be retracted and the conductive tape needs to be removed, so L1 and L2 are likely to change, and therefore need to be measured again each time.

[0028] S7: After completing the test of one sample to be tested, replace the new sample, and perform the test again according to the process of steps S1-S6 until the test of all samples to be tested is completed.

[0029] Preferably, the speed range of the needle punching actuator driving the metal needle to punch the conductive tape in step S4 is 0.1-1 mm / s.

[0030] Preferably, the lifting height L2 in step S5 should be large enough to provide enough space between the metal needle and the sample fixing tool to facilitate the removal of the conductive tape from the sample fixing tool.

[0031] The application has the beneficial effect that the application provides a high-precision needle-punching test device and method for lithium ion batteries based on electrical signals, which can accurately position the starting position of the needle before the needle-punching test of the lithium ion battery based on electrical signals by adding a stroke monitoring circuit, ensure the accuracy and repeatability of the initial position, and thus accurately control and judge the time when the needle contacts the battery cell and the stroke after entering the battery cell, thereby ensuring the consistency of the actual penetration depth in the needle-punching test and improving the accuracy of the needle-punching test result. BRIEF DESCRIPTION OF DRAWINGS

[0032] The application will be further described below in conjunction with the drawings and examples.

[0033] Figure 1 Fig. 1 is a structural schematic diagram of a test device according to an embodiment of the application.

[0034] Figure 2 Fig. 2 is a structural schematic diagram of a test device according to another embodiment of the application.

[0035] Figure 3 Fig. 3 is a schematic diagram of a needle-punching process of a metal needle.

[0036] Figure 4 Fig. 4 is a flowchart of a test method according to the application.

[0037] In the drawings: 11, lower sample fixing tool, 12, upper sample fixing tool, 2, sample to be tested, 3, conductive tape, 4, stroke monitoring circuit, 41, power supply, 42, signal monitoring unit, 43, signal judging unit, 5, metal needle. DETAILED DESCRIPTION

[0038] The application will now be further described in detail in conjunction with the drawings. These drawings are all simplified schematic diagrams, which only schematically illustrate the basic structure of the application, and thus only show the structures related to the application, and the directions and references (such as up, down, left, right, etc.) can only be used to help the description of the features in the drawings. Therefore, the following detailed description is not in a limiting sense, and the scope of the claimed subject matter is only defined by the appended claims and their equivalents.

[0039] Example 1

[0040] As Figure 1As shown, the high-precision needle-punching test device for lithium ion battery based on electric signal of the application comprises a needle-punching execution mechanism, a stroke monitoring circuit 4 and a sample fixing tool. The needle-punching execution mechanism can use a general needle-punching device or be newly developed according to the requirements; the stroke monitoring circuit 4 can be manually built using a power supply 41, a circuit board and a signal line or be built in the needle-punching test device. The needle-punching execution mechanism is provided with a metal needle 5, which is a steel needle, an aluminum needle or a copper needle. At least part of the sample fixing tool is an electrically conductive area, and at least part of the electrically conductive area is located below the metal needle 5. One end of the stroke monitoring circuit 4 is connected with the metal needle 5 through a line, and the other end is connected with the electrically conductive area through a line. When the metal needle 5 contacts with the electrically conductive area, the metal needle 5, the stroke monitoring circuit 4 and the electrically conductive area form a closed loop, and a positioning signal is output from the stroke monitoring circuit 4 to the needle-punching device.

[0041] The sample fixing tool comprises a sample lower fixing tool 11 and a sample upper fixing tool 12. During the test, the sample 2 to be tested is fixed between the sample lower fixing tool 11 and the sample upper fixing tool 12. The sample upper fixing tool 12 is provided with a needle-punching hole on the needle-punching surface facing the sample 2 to be tested. The needle-punching hole is located directly below the metal needle 5 and can be penetrated by the metal needle 5 at the needle-punching position. The needle-punching hole is pasted with an electrically conductive adhesive tape 3, which forms an electrically conductive area and is connected with the stroke monitoring circuit 4 through a line. The electrically conductive adhesive tape 3 is a copper foil adhesive tape, an aluminum foil adhesive tape, a silver adhesive tape or a carbon paper adhesive tape.

[0042] The travel monitoring circuit 4 includes at least a power supply 41, a signal sampling unit, and a signal judgment unit 43. The power supply 41 provides operating voltage to the signal sampling unit and the signal judgment unit 43. The signal sampling unit collects electrical signals in a closed loop and sends the electrical signals to the signal judgment unit 43. The signal judgment unit 43 outputs a positioning signal of the metal needle 5 to the acupuncture device based on the electrical signals. The acupuncture device controls the acupuncture actuator to operate based on the positioning signal. The power supply 41 is a small external power supply used to provide voltage to the signal monitoring unit 42 and the signal judgment unit 43. For safety reasons, it should generally not exceed 12V. The signal monitoring unit 42 includes, but is not limited to, components such as LEDs and buzzers, as long as they can form a closed loop and have a prompting function. In this embodiment, the signal monitoring unit 42 uses an LED. After the loop is connected, the LED lights up, indicating that this is the initial position of the metal needle 5. With the addition of the signal judgment unit 43, automatic control and linkage between the testing device and the acupuncture equipment are achieved. The generated electrical signal can be directly provided to the acupuncture equipment through the signal judgment unit 43. Compared with manual observation, the transmission of electrical signals is more accurate and faster, thus making control more accurate and convenient. Preferably, the signal judgment unit 43 can be a microcontroller, serving as the control unit for signal reception and judgment. Through the analysis of the electrical signal by the microcontroller, it determines whether the circuit is closed, i.e., whether the metal needle 5 has reached the initial position.

[0043] The testing device of the present invention can test different types of batteries or cells. The test sample 2 includes, but is not limited to, pouch cells, prismatic cells, cylindrical cells, pouch modules, prismatic modules, cylindrical modules, and battery packs.

[0044] Example 2:

[0045] like Figure 2 As shown, the difference between this embodiment and Embodiment 1 lies in that the acupuncture actuator of the acupuncture device is manually controlled to stop during the initial position calibration. Acupuncture devices generally have a stop button; pressing the stop button directly stops the operation of the acupuncture actuator. Therefore, considering this function of the acupuncture device, the stroke monitoring circuit 4 in this embodiment only includes the power supply 41 and the signal monitoring unit 42, excluding the signal judgment unit 43. The signal monitoring unit 42 uses a light-emitting diode (LED). When the tip of the metal needle 5 contacts the conductive tape 3, the circuit is completed, the LED lights up, and the operator immediately presses the stop button upon seeing the light, stopping the movement of the acupuncture actuator. At this time, the position of the metal needle 5 is the initial position.

[0046] like Figure 3 and Figure 4As shown, the lithium ion battery high-precision needle punching test method based on an electric signal of the present application adopts the above-mentioned needle punching test device for testing, and further includes the following test steps:

[0047] S1: The sample to be tested 2 is fixed on the needle punching equipment using a sample fixing tool, so as to ensure that the needle punching position of the sample to be tested 2 is aligned with the needle punching hole on the upper sample fixing tool 12, and the needle punching hole is located directly below the metal needle 5.

[0048] S2: The conductive tape 3 is pasted on the upper surface of the sample upper fixing tool 12, and the conductive tape 3 covers the needle punching hole, and the conductive tape 3 across the hollow area of the needle punching hole is kept in a flat state as much as possible; then, the travel monitoring circuit 4 is connected to the metal needle 5 and the conductive tape 3 at both ends, and it is ensured that the travel monitoring circuit 4 can be turned on.

[0049] S3: The distance L1 between the needle punching surface of the sample to be tested 2 at the needle punching position and the upper surface of the conductive tape 3 is determined; in this embodiment, the distance L1 is the sum of the thickness of the sample upper fixing tool 12 and the thickness of the conductive tape 3.

[0050] S4: The needle punching equipment is started, and the needle punching actuator drives the metal needle 5 to punch the part of the sample upper fixing tool 12 pasted with the conductive tape 3 at a slow speed; as an optimization, the speed range of the needle punching actuator driving the metal needle 5 to punch the conductive tape 3 is 0.1mm / s-1mm / s. The position of the metal needle 5 and the state of the signal monitoring unit 42 are observed, when the metal needle 5 contacts the conductive tape 3, the loop is turned on and there is current flowing through, at this time, the signal monitoring unit 42 gives an indication, and controls the needle punching actuator of the needle punching equipment to stop moving, then the position of the metal needle 5 at this time is the critical point that the metal needle 5 contacts the conductive tape 3, that is, the initial position of the metal needle 5; at this time, it is considered that the vertical height of the needle tip of the metal needle 5 from the position to be punched of the sample to be tested 2 is equal to L1.

[0051] S5: The needle punching actuator of the needle punching equipment is controlled to drive the metal needle 5 to lift up to disconnect the conductive loop, and the conductive tape 3 is taken off from the sample upper fixing tool 12, and the lifting height L2 is confirmed, which refers to the distance from the needle tip of the metal needle 5 to the surface of the conductive tape 3. The lifting height L2 should be large enough to provide sufficient space between the metal needle 5 and the sample fixing tool, so as to facilitate taking off the conductive tape 3 from the sample fixing tool.

[0052] S6: Then, the needle punching test is performed according to the specified speed and process of the original needle punching test requirement, and the travel of the needle punching equipment is set to x+L1+L2, wherein x is the penetration depth.

[0053] S7: When the test of one sample 2 is completed, replace the new sample, and then test again according to the procedures of steps S1-S6 until the test of all samples 2 is completed.

[0054] As shown in Figure 3 the actual test, the travel distance of the metal needle 5 should be set to x+L1+L2, x is the depth of the metal needle 5 into the test sample, and the arrow in the figure indicates the direction of movement of the metal needle 5.

[0055] The key technical point in the present application is:

[0056] (1) The actual position of the needle is determined by the electrical signal. The position of the needle in the conventional needle test is mostly determined by visual observation, which has a large human factor and poor repeatability. It is difficult to obtain the actual distance of the initial state of the needle from the sample. The electrical signal detection is accurate and fast, which can reduce human intervention.

[0057] (2) The actual needle penetration depth is determined by the initial position and the pre-measured clamp height. The inaccurate initial position will cause the actual penetration depth into the sample to be different even if the same process is used for needle penetration. On a microscopic level, it may be the difference between whether the number of layers of the electrode plate is penetrated. The present application can avoid the above problems.

[0058] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the scope of the present application. The technical scope of the present application is not limited to the contents of the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A high-precision pin test device for lithium-ion batteries based on electrical signals, characterized by: The needle puncture test device comprises a needle puncture actuator, a stroke monitoring circuit and a sample fixing tool, the needle puncture actuator is provided with a metal needle, at least part of the sample fixing tool is an electrically conductive area, and at least part of the electrically conductive area is located below the metal needle, one end of the stroke monitoring circuit is connected with the metal needle through a wire, and the other end is connected with the electrically conductive area through a wire, when the metal needle contacts the electrically conductive area, the metal needle, the stroke monitoring circuit and the electrically conductive area form a closed loop, and a positioning signal is output by the stroke monitoring circuit to the needle puncture device, and the needle puncture device controls the movement of the needle puncture actuator according to the positioning signal. The stroke monitoring circuit further comprises a signal judgment unit, the signal input end of the signal judgment unit is connected with the closed loop, the signal judgment unit is used for receiving the electric signal generated in the closed loop, and outputs the positioning signal of the metal needle to the needle puncture device according to the electric signal, and the needle puncture device controls the movement of the needle puncture actuator according to the positioning signal. The sample fixing tool comprises a sample lower fixing tool and a sample upper fixing tool, during testing, the sample to be tested is fixed between the sample lower fixing tool and the sample upper fixing tool, and the sample upper fixing tool faces the needle puncture surface of the sample to be tested, the sample upper fixing tool is provided with a needle puncture hole, the needle puncture hole is located directly below the metal needle, and the needle puncture hole is pasted with an electrically conductive adhesive tape, the electrically conductive adhesive tape forms an electrically conductive area, and is connected with the stroke monitoring circuit through a wire.

2. The high precision electrical signal based lithium ion battery pin test device of claim 1, wherein: The stroke monitoring circuit comprises at least a power supply and a signal monitoring unit, the power supply provides working voltage for the stroke monitoring circuit, and the signal monitoring unit is used for monitoring the electric signal in the closed loop.

3. The high precision electrical signal based lithium ion battery pin test device of claim 1, wherein: The sample to be tested comprises a soft package battery cell, a square shell battery cell, a cylindrical battery cell, a soft package battery module, a square shell battery module, a cylindrical battery module and a battery pack.

4. The high precision electrical signal based lithium ion battery pin test device of claim 1, wherein: The metal needle is a steel needle, an aluminum needle or a copper needle.

5. The high precision electrical signal based lithium ion battery pin test device of claim 1, wherein: The electrically conductive adhesive tape is a copper foil adhesive tape, an aluminum foil adhesive tape, a silver adhesive tape or a carbon paper adhesive tape.

6. A high-precision pin test method for lithium-ion batteries based on electrical signals, characterized by: The needle puncture test device is used for testing, and the testing further comprises the following steps: S1: fixing the sample to be tested on the needle puncture device by using the sample fixing tool, ensuring that the needle puncture position of the sample to be tested is aligned with the needle puncture hole on the sample upper fixing tool, and making the needle puncture hole located directly below the metal needle; S2: pasting the electrically conductive adhesive tape on the upper surface of the sample upper fixing tool, covering the needle puncture hole with the electrically conductive adhesive tape, and ensuring that the electrically conductive adhesive tape crossing the hollow area of the needle puncture hole is in a flat state; then, connecting the stroke monitoring circuit with the metal needle and the electrically conductive adhesive tape respectively, and ensuring that the stroke monitoring circuit can be turned on; S3: measuring the distance L1 between the needle puncture surface of the sample to be tested at the needle puncture position and the upper surface of the electrically conductive adhesive tape. S4: Start the needle-punching device, and drive the needle-punching actuator to punch the metal needle to the part of the sample upper fixing tool to which the conductive tape is adhered at a slow speed; and observe the position of the metal needle and the state of the signal monitoring unit. When the metal needle contacts the conductive tape, the circuit is conducted and current flows, at this time, the signal monitoring unit gives an indication, and the needle-punching actuator of the needle-punching device is controlled to stop running. At this time, the position of the metal needle is the critical point at which the metal needle contacts the conductive tape, that is, the initial position of the metal needle; S5: Drive the needle-punching actuator to lift the metal needle upward to disconnect the conductive circuit and take the conductive tape off the sample upper fixing tool by the needle-punching device, and determine the lifting height L2, which refers to the distance from the needle tip of the metal needle to the surface of the conductive tape; S6: Then, perform the needle-punching test according to the specified speed and process of the original needle-punching test requirement, and the stroke of the needle-punching device is set to x+L1+L2, wherein x is the penetration depth; S7: After completing the test of one sample to be tested, replace the new sample, and perform the test again according to the process of steps S1-S6 until the test of all samples to be tested is completed.

7. The high precision pin test method for lithium ion batteries based on electrical signals as claimed in claim 6, wherein: The speed range of the needle-punching actuator driving the metal needle to punch the conductive tape in step S4 is 0.1 mm / s-1 mm / s.

8. The high precision pin test method for lithium ion batteries based on electrical signals as claimed in claim 6, wherein: The lifting height L2 in step S5 should be large enough to provide sufficient space between the metal needle and the sample fixing tool, so as to facilitate taking the conductive tape off the sample fixing tool.

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