Puncture needle for internal short-circuit acupuncture test and test method

Abstract

The invention provides a pricking needle for an internal short-circuit acupuncture test and a test method, the pricking needle comprises a needle head which is at least partially conductive and a needle rod which is at least surface-insulated, and the height of the conductive part of the needle head is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units. When the needle head and the needle rod of the pricking needle pierce into the battery, only the conductive part of the needle head enables one battery reaction unit or fewer battery reaction units to be conductively communicated, and the insulating part of the pricking needle avoids large-area internal short circuit in the battery to a certain extent; therefore, the condition that the lithium dendrites in the battery pierce the diaphragm to cause local micro short circuit of the battery reaction unit is simulated. In the test method, the pricking needle rapidly pierces into the battery cell, so that the insulating part of the pricking needle can rapidly block the diaphragm of the battery reaction unit punctured by the needle head in the early stage, and simultaneous short circuit of a large number of battery reaction units can be further prevented.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, and more specifically to a needle and a testing method for internal short-circuit penetration testing. Background Technology

[0002] With the rapid development of the energy industry in recent years, lithium-ion batteries have gradually become the main energy storage medium due to their high energy density and long cycle life. However, lithium-ion batteries also contain a large number of active materials and easily decomposed flammable substances, making them highly susceptible to thermal runaway, fire, and explosion under abuse conditions, seriously endangering public safety. Therefore, conducting reasonable abuse tests on large-capacity energy storage lithium-ion batteries is of great significance. Among these tests, internal short-circuit testing is more dangerous than other abuse tests and is most likely to cause battery thermal runaway. Currently, the methods for nail penetration testing are mainly for automotive power batteries. The test standards mainly consider that sharp objects on the ground may pierce the bottom of the car during vehicle operation and penetrate the battery pack, causing internal short circuits in individual cells. Therefore, a conductive steel needle is used to penetrate the battery from a direction perpendicular to the battery plates, causing a large-area internal short circuit within the cell. However, energy storage lithium-ion batteries are placed in a static energy storage system, where the environmental operating conditions are singular and they are not exposed to foreign object intrusion. Internal short circuits in energy storage lithium-ion batteries mainly occur because lithium deposits deposit inside the battery after prolonged charge-discharge cycles, forming lithium dendrites that pierce the separator and cause micro-short circuits in localized battery reaction cells. Therefore, for testing micro-short circuits in energy storage lithium-ion batteries, there is an urgent need for testing devices and methods that are significantly different from traditional nail penetration testing methods. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a needle and testing method for internal short-circuit needle penetration testing. The needle includes at least a partially conductive needle tip and at least a surface-insulated needle shaft. The height of the conductive portion of the needle tip is greater than or equal to the thickness of one battery reaction cell and less than or equal to the thickness of ten battery reaction cells. When the needle tip and needle shaft penetrate the battery, only the conductive portion of the needle tip enables one or fewer battery reaction cells to conduct electricity, while the insulating portion of the needle prevents large-area internal short circuits within the battery to a certain extent, thus simulating the situation where lithium dendrites pierce the separator inside the battery, leading to micro-short circuits in localized battery reaction cells. In the testing method, the needle quickly penetrates the cell, allowing the insulating portion of the needle to quickly seal the separator of the battery reaction cells previously pierced by the needle tip, further preventing a large number of battery reaction cells from short-circuiting simultaneously.

[0004] The technical solution provided by this invention is as follows:

[0005] According to the present invention, a needle for internal short-circuit needle penetration testing is provided. The needle includes a needle tip with a pointed end that is at least partially conductive and a needle shaft that is at least surface-insulated. The height of the conductive portion of the needle tip is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units. The battery reaction unit includes a positive electrode, a negative electrode, and an insulating layer located between the positive and negative electrode. The diameter of the needle shaft is approximately 1-10 mm. Specifically, the needle includes a needle tip and a needle shaft. A portion of the needle tip is conductive or the entire needle tip is conductive. The material of the conductive portion can be steel materials such as tungsten carbide or low-carbon steel. The surface of the needle shaft is insulated or the entire needle shaft is insulated. The height of the conductive portion of the needle tip should be greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units. Preferably, the height of the conductive portion of the needle tip is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of three battery reaction units. The length ratio of the needle tip to the needle shaft can be, for example, 1:20 to 1:60. The thicker diameter of the needle shaft makes it less prone to deformation or breakage when the needle quickly penetrates the battery cell. Furthermore, the thicker needle is less susceptible to damage and can be reused, thus saving costs. When the needle tip first pierces the battery cell and enters its interior, the needle shaft follows. Depending on the speed and force of the penetration, the needle can penetrate to different depths within the battery cell. The conductive portion of the needle tip connects the positive and negative electrodes of one or a few battery reaction units whose insulating layer has been pierced. The insulating portion of the needle seals the holes in the remaining battery reaction units, effectively preventing short circuits between the positive and negative electrodes in the battery reaction units corresponding to the insulating portion of the needle. Unlike traditional needle penetration tests, the needle of this invention only triggers internal short circuits in one or a few battery reaction units, i.e., micro-short circuits within the battery cell. This avoids a large number of battery reaction units simultaneously generating short-circuit currents, thereby simulating the internal short-circuit conditions of real-world lithium-ion batteries. In addition, due to the insulated design of the needle shaft, the insulated needle body will not generate current. Therefore, the needle will not generate a lot of heat as a heat source, which can avoid non-battery heat generation and can more accurately reflect the heat spread phenomenon caused by micro-short circuits inside the battery.

[0006] The needle shaft can be surface-insulated. The needle shaft may include a core and an outer layer. The core is integrally formed with the needle tip, and both the core and needle tip are made of conductive material. The outer layer of the needle shaft is made of insulating material. According to one embodiment, the outer layer of the needle shaft is a sleeve, and the sleeve is made of insulating material, such as high-temperature resistant polypropylene, high-density polyethylene, or glass fiber-doped composite materials. Preferably, the sleeve is made of a plastic material with low thermal conductivity (≤0.5 W / (m·K)) and high temperature resistance (≥180℃), such as reinforced nylon, aromatic nylon, polyphenylene sulfide, polyaryletherketones, tetrafluoroethylene, etc. More preferably, the sleeve can be an insulating material with an elastic foam layer structure, thereby more effectively sealing the hole pierced by the needle tip. The core may include a necked portion connected to the needle tip and a cylindrical portion connected to the necked portion. The diameter of the necked portion is smaller than the diameter of the cylindrical portion, and the sleeve is fitted onto the necked portion and the cylindrical portion. The thickness of the sleeve can be approximately 1–3 mm. The diameter of the end of the sleeve after it is fitted onto the necked section is smaller than the maximum diameter of the needle. The diameter of the sleeve after it is fitted onto the cylindrical section is approximately equal to the maximum diameter of the needle, and the difference between the diameter of the sleeve after it is fitted onto the cylindrical section and the maximum diameter of the needle is approximately ±0.1 mm. This prevents the sleeve from detaching from the core and allows the needle shaft to better seal the holes pierced by the spikes in the battery cell. The sleeve can be fitted onto the core by heat fusion, bonding, or other methods. According to another embodiment, the outer layer of the needle shaft is an insulating plating layer, and the material of the insulating plating layer can be an oxide ceramic material or a nitride ceramic material, such as alumina, zirconium oxide, silicon nitride ceramic layers, etc.

[0007] The needle shaft can also be integrally insulated. The needle tip and shaft can be integrally molded and made of insulating material. A conductive strip is provided on the tip or conical wall of the needle tip, and the conductive strip is attached to the needle tip by means of coating, electroplating, bonding, or embedding. That is, the needle tip and shaft can be integrally molded using insulating materials such as insulating plastic or insulating ceramic. The conductive strip is provided on portions of the needle tip, such as the tip or conical wall, and the height of the conductive strip can be less than or equal to the height of the needle tip. The conductive strip can be in the form of conductive material foil, powder, etc. The conductive strip can be continuous rings, discontinuous rings, or a single segment or several segments. Additionally, multiple conductive strips can be provided on the needle tip to simulate multiple micro-short circuits. The height of each conductive strip is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units.

[0008] The present invention also provides a test method for internal short-circuit needle penetration testing, wherein the test method uses the needle described above to perform the internal short-circuit needle penetration test.

[0009] In the test method used for internal short-circuit needle penetration testing, the initial velocity of the needle penetrating the battery is approximately 20–500 mm / s. The rapid penetration of the needle into the cell allows the insulating portion of the needle to quickly seal the separator of the battery reaction unit previously punctured by the needle, thereby further preventing a large number of battery reaction units from short-circuiting simultaneously. The needle can be driven into the battery using a nail gun or a hydraulic mechanism.

[0010] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention.

[0011] The advantages of this invention are:

[0012] 1) In the battery needle penetration test, the present invention will only trigger a short circuit in a single or a small number of battery reaction units inside the battery, avoiding the simultaneous generation of short circuit current in a large number of battery reaction units, and can simulate the internal short circuit conditions of real energy storage lithium-ion batteries.

[0013] 2) The design of the needle shaft insulation can ensure that the overall current of the needle is small during the battery needle penetration test. Only the needle tip generates a weak current due to connecting the positive and negative terminals of the battery reaction unit. The other insulated parts of the needle body will not generate current. Therefore, the needle itself will not generate a lot of heat as a heat source, which can avoid non-battery heat generation. This allows the needle penetration test using this invention to more accurately reflect the heat spread phenomenon inside the battery.

[0014] 3) Using this invention for needle penetration testing eliminates the need for a large-volume needle penetration test bench. A common pneumatic gun can be used to inject the needle into the battery cell, simplifying the operation and achieving rapid penetration. The rapid penetration of the needle into the battery cell allows the insulating portion of the needle to quickly seal the membrane of the battery reaction unit that was previously punctured by the needle, further preventing a large number of battery reaction units from short-circuiting simultaneously. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a needle according to the first embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of a needle according to a second embodiment of the present invention;

[0017] Figures 3(a) to 3(c) This is a schematic diagram of a needle according to a third embodiment of the present invention;

[0018] Figure 4This is a schematic diagram of the needle piercing the battery cell according to the present invention.

[0019] List of reference numerals

[0020] 1 - Needle

[0021] 101, 101a, 101b — Conductive bands

[0022] 2—Needle bar

[0023] 201 - Core

[0024] 202 - Casing

[0025] 203 - Coating

[0026] 2a—Neck constriction

[0027] 2b - Cylindrical section

[0028] 3—Battery Reaction Unit

[0029] 301 - Positive Electrode Tablet

[0030] 302 - Isolation Layer

[0031] 303 - Negative electrode plate Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 This is a schematic diagram of a needle according to a first embodiment of the present invention. Figure 1 As shown, the needle includes a needle tip 1 and a needle shaft 2, the needle shaft 2 further including a core 201 and a sleeve 202. The needle tip 1 and the core 201 are integrally formed and are made of conductive low-carbon steel, while the sleeve 202 is made of tetrafluoroethylene with an elastic foam layer structure. The needle tip 1 may include a conical tip portion and a cylindrical body portion, and the core 201 may include a thinner necked portion 2a and a thicker cylindrical portion 2b. The sleeve 202 can be heat-fused onto the necked portion 2a and the cylindrical portion 2b. The resulting needle has a conductive needle tip 1 and an insulated needle shaft 2. After the cannula 202 is fitted onto the necked portion 2a and the cylindrical portion 2b, the total end diameter D2 of the necked portion 2a and the cannula 202—that is, the portion of the necked portion 2a and the cannula 202 near the needle 1—is less than the maximum diameter D1 of the needle 1, and the total diameter D3 of the cylindrical portion 2b and the cannula 202 is approximately equal to the maximum diameter D1 of the needle 1.

[0034] Figure 2 This is a schematic diagram of a needle according to a second embodiment of the present invention. Figure 2As shown, the needle includes a needle head 1 and a needle shaft 2. The needle shaft 2 further includes a core 201 and a plating layer 203. The needle head 1 and the core 201 are integrally formed and are made of conductive tungsten steel. The plating layer 203 is made of alumina ceramic. The needle head 1 can be conical, and the core 201 can be cylindrical. The insulating plating layer 203 is plated on the core portion. This results in a needle with a conductive needle head 1 and an insulating needle shaft 2. The diameter of the core 201 can be 8 mm, and the thickness of the plating layer 203 can be 1 mm.

[0035] Figures 3(a) to 3(c) This is a schematic diagram of a needle according to a third embodiment of the present invention. As shown in Figures 3(a), 3(b), and 3(c), the needle includes a needle tip 1 and a needle shaft 2. The needle tip 1 and the needle shaft 2 are integrally formed and are made of reinforced nylon with low thermal conductivity (≤0.5W / (m·K)) and high temperature resistance (≥180℃). The needle tip 1 can be conical, and the needle shaft can be cylindrical. A conductive strip is provided on the needle tip 1. The conductive strip is made of aluminum and is deposited on the needle tip by vapor deposition. This results in a needle with a conductive needle tip and an insulated needle shaft. As shown in Figure 3(a), the conductive strip 101 can be disposed on the conical wall of the needle 1; as shown in Figure 3(b), the conductive strip 101 can be disposed on the tip of the needle 1; as shown in Figure 3(c), multiple conductive strips 101a and 101b can be disposed on the needle 1, and the multiple conductive strips 101a and 101b are spaced apart along the height direction of the needle 1. The height of each conductive strip is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units, thereby simulating the situation where multiple battery reaction units spaced apart from each other simultaneously experience internal short circuits.

[0036] Figure 4 This is a schematic diagram of the needle piercing the battery cell according to the present invention. Figure 4 As shown, the battery cell includes multiple battery reaction units 3, each of which includes a positive electrode 301, a separator 302, and a negative electrode 303. After prolonged use, lithium dendrites may form inside the battery. These dendrites can puncture the separator, leading to micro-short circuits in localized battery reaction units. To simulate this situation, and distinguish it from large-area internal short circuits within the battery, a needle of this invention can be inserted into the battery. The height H of the conductive portion of the needle tip is approximately equal to the thickness of a single battery reaction unit or a few battery reaction units. Internal short circuits occur in battery reaction units located on the conductive portion of the needle tip, while the holes in battery reaction units located on the insulating portion of the needle are sealed by the insulating portion of the needle, mitigating the occurrence of internal short circuits.

[0037] Furthermore, according to the test method for internal short-circuit needle penetration testing according to the present invention, the needle is inserted into the battery at a relatively fast initial speed, for example, 200 mm / s, and quickly penetrates into the battery. This allows for rapid and timely sealing of the diaphragm of the battery reaction unit 3 punctured by the needle, avoiding the situation where a large number of battery reaction units may be short-circuited simultaneously due to slow needle insertion.

[0038] The specific embodiments described herein are not intended to limit the scope of the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, shall still fall within the protection scope of the present invention.

Claims

1. A needle for internal short-circuit needle penetration testing, characterized in that, The needle includes a needle tip with a point that is at least partially conductive and a needle shaft with at least surface insulation. The height of the conductive portion of the needle tip is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of ten battery reaction units. The battery reaction unit includes a positive electrode, a negative electrode, and an insulating layer located between the positive electrode and the negative electrode. The diameter of the needle shaft is 1 to 10 mm.

2. The needle for internal short-circuit needle penetration testing according to claim 1, wherein, The height of the conductive portion of the needle is greater than or equal to the thickness of one battery reaction unit and less than or equal to the thickness of three battery reaction units.

3. The needle for internal short-circuit needle penetration testing according to claim 1, wherein, The needle bar includes a core and an outer layer. The core and the needle tip are integrally formed. Both the core and the needle tip are made of conductive material, and the outer layer of the needle bar is made of insulating material.

4. The needle for internal short-circuit needle penetration testing according to claim 3, wherein, The outer layer is a sleeve made of plastic. The rod core includes a necked portion connected to the needle and a cylindrical portion connected to the necked portion. The diameter of the necked portion is smaller than the diameter of the cylindrical portion. The sleeve is fitted onto the necked portion and the cylindrical portion.

5. The needle for internal short-circuit needle penetration testing according to claim 4, wherein, The thickness of the sleeve is 1-3 mm, and the diameter of the end of the sleeve after it is fitted with the necked portion is smaller than the maximum diameter of the needle.

6. The needle for internal short-circuit needle penetration testing according to claim 4, wherein, The difference between the diameter of the sleeve after it is fitted onto the cylindrical part and the maximum diameter of the needle is ±0.1 mm.

7. The needle for internal short-circuit needle penetration testing according to any one of claims 4 to 6, wherein, The sleeve is fitted onto the rod core by heat fusion.

8. The needle for internal short-circuit needle penetration testing according to claim 3, wherein, The outer layer is an insulating coating, and the material of the insulating coating is an oxide ceramic material or a nitride ceramic material.

9. The needle for internal short-circuit needle penetration testing according to claim 1, wherein, The needle tip and the needle shaft are integrally formed and made of insulating material. A conductive strip is provided on the tip or conical wall of the needle tip. The conductive strip is provided on the needle tip by means of covering, electroplating, bonding or embedding.

10. The needle for internal short-circuit needle penetration testing according to claim 9, wherein, Multiple conductive strips are provided on the needle tip.

11. A test method for internal short-circuit needle penetration testing, characterized in that, The test method uses the needle as described in any one of claims 1 to 10 to perform an internal short-circuit needle puncture test.

12. The test method for internal short-circuit needle penetration testing according to claim 11, wherein, The initial velocity at which the needle pierces the battery is 20–500 mm / s.

13. The test method for internal short-circuit needle penetration testing according to claim 12, wherein, The needle is inserted into the battery using a nail gun or a hydraulic mechanism.

Images