CN108627387B - Method and combined device for testing puncture resistance of battery diaphragm - Google Patents
Method and combined device for testing puncture resistance of battery diaphragm Download PDFInfo
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- CN108627387B CN108627387B CN201810688253.0A CN201810688253A CN108627387B CN 108627387 B CN108627387 B CN 108627387B CN 201810688253 A CN201810688253 A CN 201810688253A CN 108627387 B CN108627387 B CN 108627387B
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Abstract
The invention relates to a method for testing the puncture resistance of a battery diaphragm, which comprises the steps of placing a diaphragm sample between two electrode plates to form a test piece, wherein the surface of at least one electrode plate is provided with a burr surface, the burr surface comprises a plurality of conductive hard particles protruding out of the surface of the electrode plate, the diaphragm sample is placed corresponding to the contact burr surface, and the two electrode plates are respectively and electrically connected to the two ends of an insulation resistance tester. The test piece is placed in an environment with changeable and controllable temperature, the pressure value of mutual forward extrusion of the two electrode plates is increased by external force, when the insulation resistance tester measures the short circuit of the two electrode plates of the test piece, the pressure value at the moment is recorded, and the pressure value is used for representing the puncture resistance of the diaphragm sample. Preferably, the present invention replaces two electrode plates with two pieces of dry-abrasive paper having conductive cemented carbide particles on the surfaces thereof. The invention also relates to a test combination device for testing the puncture resistance of the battery diaphragm.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a method for testing the puncture resistance of a battery diaphragm.
Background
The separator is one of the key internal layer components in the structure of a lithium battery. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The diaphragm popular point is described as a porous plastic film, which is a high value-added material with the highest technical barrier in lithium battery materials and accounts for about 20% -30% of the cost of lithium batteries. The diaphragm divides the electrolytic chamber into a cathode area and an anode area, lithium ions can migrate through the diaphragm, the anode and cathode are prevented from being in contact with each other to generate short circuit, once the diaphragm is subjected to mechanical breakdown or damage, the internal short circuit of the battery can be directly caused, the local temperature of a short circuit area is rapidly increased, and even thermal runaway can be possibly caused. Because the aging or low-temperature charging of the battery can cause the deposition of metal lithium on the surface of the negative electrode to generate lithium dendrites, and the lithium dendrites can puncture a diaphragm to cause the internal short circuit of the battery; or the battery is not manufactured well, metal burrs exist around the pole piece or metal particles are mixed in the pole piece, and the burrs or the metal particles can pierce the diaphragm under certain conditions to cause short circuit in the battery. Therefore, good puncture resistance of the separator is critical to the safety performance of the battery.
Most of lithium ion battery separators commercially used at present are polyolefin separators (polypropylene and polyethylene), and the puncture resistance of the lithium ion battery separators changes along with the change of environmental temperature. The characterization of the diaphragm puncture resistance in the prior art is basically to test the diaphragm puncture resistance by adopting an ASTM F1306-90 film puncture strength standard test method, the test method is to vertically press a conical pressure head with the diameter of 3.2mm into a diaphragm fixed on a clamping device at the moving speed of 25mm/min, the pressure when the diaphragm is punctured is recorded as the diaphragm puncture resistance, the diameter of the puncture pressure head used by the test method is obviously hundreds of times larger than that of lithium dendrites, pole piece metal burrs or foreign particles in a battery, and the influence of the battery manufacturing process temperature or the use temperature on the diaphragm puncture resistance is ignored. Therefore, the test method is to directly use the puncture indenter to test the puncture resistance of the diaphragm sample in a room temperature environment, and the test result is greatly different from the actual situation and is not enough to accurately evaluate the actual puncture resistance of the diaphragm in the battery.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for testing the puncture resistance of a battery diaphragm, which simulates the actual environment of the diaphragm in the battery, more objectively tests the puncture resistance of the diaphragm in the battery against electrode particles or foreign particles, is used for evaluating the performance of the diaphragm and the probability of short circuit of the battery, can better predict the safety and reliability of the diaphragm in the battery, and has important significance for lithium battery research and development, diaphragm evaluation and failure analysis. The invention also provides a testing combination device for testing the puncture resistance of the battery diaphragm.
In order to achieve the purpose, the invention adopts the main technical scheme that:
a method for testing the puncture resistance of a battery diaphragm comprises the steps of placing a diaphragm sample between two electrode plates to form a test piece, wherein the surface of at least one electrode plate is provided with a burr surface, the burr surface comprises a plurality of conductive hard particles protruding out of the surface of the electrode plate, the diaphragm sample is correspondingly contacted with the burr surface, and the two electrode plates are respectively and electrically connected to two ends of an insulation resistance tester; the test piece is placed in an environment capable of simulating the internal temperature condition of the battery, the pressure of mutual forward extrusion of the two electrode plates is increased through external force, when the insulation resistance tester measures the short circuit of the two electrode plates of the test piece, the pressure value at the moment is recorded, and the pressure value is used for representing the puncture resistance of the diaphragm sample.
According to a preferred embodiment of the present invention, each of the two electrode plates is a sand paper, the sand paper includes a base paper and a sand layer covering the base paper, the sand layer forms the burr surface, sand of the sand layer is conductive hard alloy particles, and the sand paper is connected to the insulation resistance tester via lead wires respectively led from the sand layer.
According to a preferred embodiment of the present invention, the sand grains of the sand grain layer are one or more conductive cemented carbide grains selected from tungsten carbide, titanium nitride and chromium carbide.
According to a preferred embodiment of the present invention, the sand grain size of the sand grain layer is 5 to 100 μm, preferably 30 to 40 μm.
According to a preferred embodiment of the invention, the peripheral edges of the diaphragm sample extend out of the region where the two electrode plates overlap. Preventing direct contact between the two electrode plates outside the region blocked by the separator sample.
According to a preferred embodiment of the present invention, the separator is a separator conventionally used in the art, such as a polypropylene separator or a polyethylene separator, and has a thickness of 1 to 40 μm.
According to a preferred embodiment of the present invention, the environment capable of simulating the internal temperature condition of the battery is provided by a high-low temperature universal tester. The internal environment temperature of the high-low temperature universal testing machine is set to be-20-130 ℃.
During testing, the test piece needs to be flatly placed in the high-low temperature universal testing machine, and the test piece is kept stand for 5-60 min, preferably 30min, at a set internal environment temperature, so that the temperature of a diaphragm sample in the test piece is consistent with the internal environment temperature of the high-low temperature universal testing machine.
According to a preferred embodiment of the invention, the external force is provided by a ball-type pressure head of the high and low temperature universal testing machine. In specific implementation, the test piece is horizontally placed on the test platform of the high-low temperature universal testing machine, so that the spherical pressure head applies downward pressure to the electrode plate positioned at the upper part of the component to be tested. Preferably, the pushing speed of the spherical pressure head of the high-low temperature universal testing machine is 0.01-0.1 mm/min, and preferably 0.01 mm/min.
According to a preferred embodiment of the invention, the diameter of the spherical pressure head is 1-2 cm, preferably 1.5 cm.
According to a preferred embodiment of the present invention, the insulation resistance tester has a voltage setting range of 10 to 250V, preferably 100V, and a resistance setting range of 0.1 to 0.5M Ω, preferably 0.1M Ω.
According to a preferred embodiment of the present invention, 3 to 10 test pieces are further fabricated for each membrane sample according to the above method, and the average value of the measured values corresponding to the 3 to 10 test pieces is used as the final puncture resistance data of the membrane sample. Therefore, the influence of external factors on the test result can be eliminated, and the reliability and the accuracy of the test result are further improved.
The invention also provides a method for testing the puncture resistance of the battery diaphragm, which comprises the following steps:
s1: assembling a test piece: cutting a diaphragm sample and placing the diaphragm sample between two laminated electrode plates to form a test piece; one surface of at least one of the electrode plates is provided with a burr surface, the burr surface comprises a plurality of conductive hard particles protruding out of the surface of the electrode plate, and the diaphragm sample is correspondingly contacted with the burr surface;
and S2, connecting the test piece with an insulation resistance tester: connecting the two electrode plates to two ends of an insulation resistance tester by leads respectively;
s3 testing in a simulated environment: setting the environmental temperature in a high-low temperature universal tester, placing the test piece in the high-low temperature universal tester, standing for more than 5min, and then pressing an electrode plate on the upper layer of the test piece by using a pressure head of the high-low temperature universal tester; when the insulation resistance tester measures that the two electrode plates of the test piece are short-circuited, the pressure value of the pressure head pressing the test piece at the moment is recorded, and the pressure value represents the puncture resistance of the diaphragm sample at a specific temperature.
In step S1:
preferably, each of the two electrode plates is a piece of sandpaper, such as conventionally used dry-grinding sandpaper, the sandpaper includes base paper and a sand layer covering the base paper, the sand layer forms the burr surface, sand of the sand layer is conductive hard alloy particles, and the conductive hard alloy particles are selected from one or more of tungsten carbide, titanium nitride and chromium carbide.
Preferably, the size of the membrane sample is as large as possible larger than the two pieces of sandpaper, so as to prevent the two pieces of sandpaper from directly contacting at a position outside the barrier region of the membrane sample, thereby causing errors in the test results.
Preferably, the grain size of the sand grains is 5-100 μm, and preferably 30-40 μm.
Preferably, the separator is a separator conventionally used in the art, and has a thickness of 1 to 40 μm.
In step S2:
and the sand paper is respectively connected with the insulation resistance tester through a lead by the sand grain layer. Preferably, the voltage setting range of the insulation resistance tester is 10-250V, preferably 100V, and the resistance setting range is 0.1-0.5M omega, preferably 0.1M omega.
In step S3:
preferably, the set range of the environmental temperature in the high-low temperature universal tester is-20-130 ℃.
Preferably, the standing time of the test piece is 5-60 min, preferably 30 min. The test piece is ensured to reach the temperature consistent with the temperature set by the high-low temperature universal testing machine.
Preferably, the pressure head of the high-low temperature universal testing machine is a spherical pressure head, and the pressing speed of the pressure head is 0.01-0.1 mm/min, preferably 0.01 mm/min. Preferably, the diameter of the spherical pressure head is 1-2 cm, and preferably 1.5 cm.
According to the concept of the present invention, the present invention also provides a test assembly for testing the puncture resistance of a battery separator, comprising:
the test piece comprises two electrode plates and a diaphragm sample clamped between the two electrode plates, wherein one surfaces of the two electrode plates, which correspond to the diaphragm sample, are provided with sand grain layers, and sand grains of the sand grain layers are conductive hard particles;
the insulation resistance tester is respectively and electrically connected with the two electrode plates of the test piece;
the high-low temperature universal testing machine can set the internal environment temperature, a testing platform and a pressure head are arranged in the high-low temperature universal testing machine, the testing platform provides the horizontal position of a testing piece, the pressure head is used for pressing the testing piece at a preset speed, when the insulation resistance tester measures the short circuit between two electrode plates of the testing piece, the pressure value of the pressure head pressing the testing piece at the moment is recorded, and the pressure value is used for representing the puncture resistance of the diaphragm sample.
Preferably, the two electrode plates are respectively one piece of sand paper, the sand paper comprises base paper and a sand grain layer covering the base paper, sand grains forming the sand grain layer are one or more conductive hard alloy particles of tungsten carbide, titanium nitride or chromium carbide, the grain size of the sand grains is 5-100 micrometers, preferably 30-40 micrometers, one surface of the sand grain layer of the sand paper is electrically connected with the insulation resistance tester through a lead.
The invention has the beneficial effects that:
(1) the invention simulates the actual environment and state of a diaphragm in a battery, simulates a battery core lamination mode by clamping the diaphragm between two overlapped electrode plates, simulates the temperature of the diaphragm in the actual manufacturing and using processes of the battery by using the internal temperature set by a high-low temperature universal testing machine, and simulates the piercing effect of burrs, lithium dendrites or foreign particles on the surface of an electrode on the diaphragm by using a sand layer on the surface of the electrode plate. Therefore, the capability of the diaphragm in the battery for resisting the penetration of electrode particles or foreign particles is tested more objectively, the anti-penetration performance of the diaphragm and the actual probability of short circuit of the battery are evaluated more comprehensively, and the safety and reliability of the diaphragm in the battery are predicted better.
(2) The invention has simple and convenient operation, reasonable combination and matching use are carried out on the basis of the existing test equipment, special equipment does not need to be purchased, the detection repeatability is good, the standardized test can be carried out, the detection personnel can independently operate, the test results of different types of diaphragms have comparability and are closer to the actual condition, the puncture effect of the diaphragms under different environments and different working conditions can be quickly analyzed, and the invention has important significance for lithium battery research and development, diaphragm evaluation and failure analysis.
Drawings
Fig. 1 is a schematic structural diagram of a testing assembly for testing the puncture resistance of a battery separator according to a preferred embodiment of the invention.
100-test combination device, 10 test pieces, 2-sand paper, 21-base paper of sand paper, 22-sand grain layer of sand paper, 3-diaphragm sample, 4-high and low temperature universal test machine, 41-test platform, 42 spherical pressure head, 51, 52-lead and 6-insulation resistance tester.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
Referring to fig. 1, a schematic structural diagram of a testing assembly 100 for testing the puncture resistance of a battery separator according to a preferred embodiment of the present invention is shown, which includes:
a test piece 10 comprising two sheets of sandpaper 2 and a membrane sample 3 sandwiched between the two sheets of sandpaper 2. The separator sample 3 is a separator conventionally used in the art, such as a polyethylene separator or a polypropylene separator, and has a thickness of 1 to 40 μm. The sand paper 2 is a conventionally used dry grinding sand paper, which comprises a base paper 21 and a sand grain layer 22, wherein the base paper 21 is a base material for adhering the sand grain layer 22, and is generally insulated kraft paper and latex paper, sand grains forming the sand grain layer 22 are selected from one or more conductive hard alloy particles of tungsten carbide, titanium nitride and chromium carbide, and the grain size of the sand grains is 5-100 μm, preferably 30-40 μm. The membrane sample 3 is clamped between the upper and lower sandpaper 2 and is in contact with the grit layer 22. When the diaphragm sample 3 is cut, the size of the diaphragm sample 3 is preferably larger than that of the sand paper 2, so that the two pieces of sand paper 2 are prevented from being in direct contact in the testing process, and the insulation resistance tester 6 gives an alarm. One end of the wire 51 was led out from the surface of the separator sample 3 on which the sand paper 2 was provided, and one end of the wire 52 was led out from the surface of the separator sample 3 on which the sand paper 2 was provided, the sand layer 22.
The insulation resistance tester 6 is electrically connected to the other ends of the wires 51 and 52, respectively. The voltage setting range of the insulation resistance tester is 10-250V, preferably 100V, and the resistance setting range is 0.1-0.5M omega, preferably 0.1M omega.
The high-low temperature universal testing machine 4 is provided with a testing box and a testing platform 41, and the environmental temperature of the testing box where the testing platform 41 is located is set through a control panel of the high-low temperature universal testing machine 4, so that the set temperature range is-20-130 ℃. The high-low temperature universal tester 4 further comprises a pressure head 42, as shown in fig. 1, which is a spherical pressure head with a diameter of 1-2 cm, preferably 1.5cm, and the spherical pressure head is not easy to mechanically damage the test piece 10 in the pressurizing process.
When testing the anti puncture ability of diaphragm sample 3, locate this insulation resistance tester 6 the test box outside of this high low temperature testing machine 4 (through wire connection test 10, in order to avoid the inside temperature variation of test box to influence this insulation resistance tester 6's normal use state, also be convenient for the tester to observe this insulation resistance tester 6 more), this test 10 is placed on test platform 41 in high low temperature testing machine 4 test box, 5~ 60min stews earlier, wait when the temperature of this test 10 is unanimous with the environmental temperature of setting for in the high low temperature universal testing machine 4, begin the test. During testing, the starting switch of the pressure head 42 is controlled, the spherical pressure head 42 is enabled to move downwards and press the test piece 10, in the process, the state of the insulation resistance tester 6 is continuously observed, and when the insulation resistance tester 6 sends out an alarm signal (displayed by a display or sends out an alarm sound) due to the short circuit between two electrode plates (namely the sand paper 2) of the test piece, the pressure value of the pressure head pressing the test piece at the moment is recorded. Wherein the pressing speed of the pressing head 42 is 0.01-0.1 mm/min, preferably 0.01 mm/min. The pressure values recorded are used to characterize the puncture resistance of the septum sample 3 at a particular temperature. The insulation resistance tester 6 is used for testing the insulator, so when the insulation resistance tester 6 sends an alarm signal, the pressure of the pressure head 42 at this time causes the membrane sample 3 to be pierced by fine sand grains on the sand paper 2, and the piercing causes the sand paper 2 on the upper layer and the lower layer of the membrane sample 3 to be electrically conducted, so that the test piece 10 becomes a non-insulator, and the alarm of the insulation resistance tester 6 is triggered.
The dry abrasive paper is a product prepared by bonding a high-hardness abrasive on latex by using synthetic resin as a bonding agent and coating an antistatic coating. The sand grains of the dry grinding abrasive paper have various optional fineness, and the base paper is generally made of special kraft paper and latex paper, and then natural and synthetic resin is selected as a binder, and the base paper is manufactured by an advanced high-static sand planting process.
In the sandpaper 2 (counter electrode plate) on the upper and lower layers of the separator sample 3, if the base paper 21 (the base paper 21 corresponds to the portion of the electrode plate other than the burr surface) is a conductor, since the indenter 42 is made of metal, in order to prevent the passage of current from the indenter 42 when a large voltage is applied to the insulation resistance meter, an insulating paste may be applied or an insulating coating may be applied to the surface of the base paper 21 opposite to the sand layer 22, or the indenter 42 may be replaced with an insulating material, or an insulating treatment such as an insulating paste application or an insulating coating may be applied to the outer surface thereof. If the indenter 42 is replaced with an insulating material (e.g., rigid plastic) or the outside of the indenter 42 is insulated, there is no need to insulate the side of the base paper 21 opposite the grit layer 22. The base paper 21 is a conductor, in this case, the test condition is satisfied as long as the sand layer 22 of one layer of sand paper in the two layers of sand paper 2 faces the diaphragm sample 3, and the leads 51 and 52 can be led out from the surface of the base paper 21 opposite to the sand layer 22 or from the sand layer 22, as long as the leads 51 and 52 can be electrically conducted when the diaphragm sample 3 is pierced. On the contrary, when the base paper 21 is an insulator, the sand grain layers 22 of the upper and lower sandpaper layers 2 should be correspondingly contacted with the membrane sample 3, and the leads 51 and 52 can only be led out from the sand grain layers 22, so as to ensure that the two electrode plates of the test piece 10 are short-circuited (converted into a non-insulator) when the membrane sample 3 is pierced. In short, it is necessary to ensure that the indenter 42 is in a non-conductive state with the upper surface of the test piece 10 being pressed.
In order to eliminate the influence of external factors on the test result and further improve the objectivity and accuracy of the test result, 3-10 diaphragm samples 3 can be cut for each diaphragm to be tested during testing, and the diaphragm samples are respectively manufactured into test pieces 10 according to the method. And then, connecting the sand grain layer 22 of the two layers of sand paper 2 with two ends of the insulation resistance tester 6 by leads 51 and 52 respectively, testing each test piece 10 according to the testing method to obtain 3-10 anti-puncture capability data of the same diaphragm to be tested, averaging the data, and taking the average value as the final anti-puncture strength data of a certain diaphragm.
The testing method is mainly technically characterized in that the testing method simulates the actual environment and state of a diaphragm in the battery, the mode that the diaphragm is clamped between two overlapped electrode plates (abrasive paper 2) is used for simulating a cell lamination mode, the temperature of the diaphragm in the actual manufacturing and using process of the battery is simulated by the temperature of a testing box and a testing platform set by a high-low temperature universal testing machine, and the piercing effect of burr, lithium dendrite or foreign matter particles on the surface of an electrode is simulated by a fine and hard sand grain layer on the surface of the abrasive paper. The method is simple, convenient and visual, can be independently operated by detection personnel, can be used for standardized test, and has comparability to test results of different samples at different temperatures.
The invention also skillfully applies the existing dry grinding abrasive paper as a tested electrode plate, the sand grains on the dry grinding abrasive paper have small grain size, high hardness and conductivity, and can be used for simulating burrs, lithium dendrites or foreign particles on the surfaces of the positive and negative electrode plates, and the insulation resistance tester 6 is combined to accurately test the puncture resistance of the diaphragm sample 3 in different states, so as to comprehensively evaluate the puncture resistance of the diaphragm. The device of the invention has simple requirements, only carries out reasonable collocation combination and utilization on the basis of the existing testing device, does not need to buy new devices, has good detection repeatability and has comparable testing results. The following description will use the testing assembly for testing the puncture resistance of the battery separator with the structure shown in fig. 1 in conjunction with the specific embodiments to illustrate the feasibility and technical effects of the present invention, but the present invention is not limited thereto.
Example 1
In this embodiment, the high-temperature puncture strength of a polyethylene wet-process separator with a thickness of 16 μm is tested, the process of baking a battery core is simulated, and the puncture strength of the separator during baking the battery core is tested, and the specific operation steps are as follows:
(1) the method comprises the steps of placing a 120mm multiplied by 120mm diaphragm sample on a copper foil (the burr-free surface is coated with an insulating layer or adhered with insulating glue) with micro burrs occupying 30% -40% of the surface area distributed on the upper side surface and the lower side surface of 100mm multiplied by 100mm, wherein the grain diameter of burrs on the copper foil is 50-80 mu m, the protruding height is 50-80 mu m, and the burr surface faces the diaphragm sample. The lead is bonded on the copper foil (bonded on one surface without the insulating layer or the insulating film) and connected with an insulation resistance tester, then the copper foil and the diaphragm are placed on a test platform in the high-low temperature universal tester together, and the insulation resistance tester is placed outside the high-low temperature universal tester.
(2) The diaphragm sample is stood in a high-low temperature universal tester at 80 ℃ for 30min, then a spherical pressure head of the high-low temperature universal tester is used for pressing the upper copper foil until an insulation resistance tester gives an alarm, the pressure value at the moment is recorded, the puncture strength values of 5 polyethylene wet-process diaphragm samples are tested repeatedly, the average value is taken, and the experimental result is shown in table 1, wherein the diameter of the spherical pressure head is 1.5cm, the compression speed of the high-low temperature universal tester is 0.01mm/min, the voltage of the insulation resistance tester is set to be 100V, and the resistance is set to be 0.1M omega.
Example 2
In this embodiment, the high-temperature puncture strength of a polyethylene wet-process separator with a thickness of 16 μm is tested, the process of baking a battery core is simulated, and the puncture strength of the separator during baking the battery core is tested, and the specific operation steps are as follows:
(1) placing a 120mm multiplied by 120mm diaphragm sample between an upper dry grinding abrasive paper and a lower dry grinding abrasive paper with the grain size of 100mm multiplied by 100mm, wherein the sand grains of the abrasive paper are tungsten carbide with the grain size of 40 mu m, bonding a lead on the sand grain layers of the two dry grinding abrasive papers and connecting the lead with an insulation resistance tester, then placing the two dry grinding abrasive papers and the diaphragm sample on a test platform in a high-low temperature universal tester together, and placing the insulation resistance tester outside the high-low temperature tester.
(2) The diaphragm sample is stood in a high-low temperature tester at 80 ℃ for 30min, then a ball-shaped pressure head of the high-low temperature universal tester is used for pressing the dry-grinding abrasive paper on the upper layer until an insulation resistance tester gives an alarm, the pressure value at the moment is recorded, the puncture strength values of 5 polyethylene wet-process diaphragm samples are tested repeatedly, the average value is taken, and the experimental result is shown in table 1, wherein the diameter of the ball-shaped pressure head is 1.5cm, the compression speed of the high-low temperature universal tester is 0.01mm/min, the voltage of the insulation resistance tester is set to be 100V, and the resistance is set to be 0.1M omega.
Example 3
In this embodiment, the low-temperature puncture strength of the polypropylene dry-process separator with the thickness of 40 μm is tested, the low-temperature service environment of the battery is simulated, and the puncture strength of the separator in the low-temperature charging and discharging process of the battery is tested, and the specific operation steps are as follows:
(1) the method comprises the steps of placing a 120mm multiplied by 100mm diaphragm sample between an upper dry grinding abrasive paper and a lower dry grinding abrasive paper which are 90mm multiplied by 80mm, wherein the sand grains of the abrasive paper are titanium carbide with the grain diameter of 80 microns, bonding a lead on the sand grain surfaces of the two dry grinding abrasive papers and connecting the lead with an insulation resistance tester, then placing the two dry grinding abrasive papers and the diaphragm sample on a test platform in a high-low temperature universal tester together, and placing the insulation resistance tester outside the high-low temperature universal tester.
(2) The diaphragm sample is stood in a high-low temperature universal tester at the temperature of minus 20 ℃ for 60min, then dry grinding abrasive paper on the upper layer of a spherical pressure head of the high-low temperature universal tester is used until an insulation resistance tester gives an alarm, the pressure value at the moment is recorded, the puncture strength values of 5 polypropylene dry-method diaphragm samples are tested repeatedly, the average value is taken, and the experimental result is shown in table 1, wherein the diameter of the spherical pressure head is 1cm, the compression speed of the high-low temperature universal tester is 0.1mm/min, the voltage of the insulation resistance tester is set to be 250V, and the resistance is set to be 0.5M omega.
Example 4
In this embodiment, the low-temperature puncture strength of the polyethylene wet-process separator with the thickness of 1 μm is tested, the high-temperature service environment of the battery is simulated, and the puncture strength of the separator in the high-temperature charging and discharging process of the battery is tested, and the specific operation steps are as follows:
(1) the method comprises the steps of placing a diaphragm sample with the diameter of 100mm between an upper dry grinding abrasive paper and a lower dry grinding abrasive paper with the diameter of 80mm, wherein the sand grains of the abrasive paper are titanium nitride with the grain diameter of 5 microns, bonding a lead on the sand grain surfaces of the two dry grinding abrasive papers and connecting the lead with an insulation resistance tester, then placing the two dry grinding abrasive papers and the diaphragm sample on a test platform in a high-low temperature universal tester together, and placing the insulation resistance tester outside the high-low temperature universal tester.
(2) The diaphragm sample is kept stand in a high-low temperature universal tester at 55 ℃ for 5min, then a ball-shaped pressure head of the high-low temperature universal tester is used for pressing dry grinding abrasive paper on the upper layer until an insulation resistance tester gives an alarm, the pressure value at the moment is recorded, the puncture strength values of 5 test samples are tested repeatedly, the average value of the puncture strength values is taken, and the experimental result is shown in table 1, wherein the diameter of the ball-shaped pressure head is 2cm, the compression speed of the high-low temperature universal tester is 0.02mm/min, the voltage of the insulation resistance tester is set to be 10V, and the resistance is set to be 0.1M.
Example 5
In this example, the low-temperature puncture strength of a polypropylene dry-process ceramic diaphragm with a thickness of 25 μm is tested, wherein the thickness of the coating is 2.5 μm × 2, a battery heating test is simulated, and the puncture strength of the diaphragm in the battery heating test process is tested, and the specific operation steps are as follows:
(1) the method comprises the steps of placing a 100mm multiplied by 100mm diaphragm sample between an upper dry grinding abrasive paper and a lower dry grinding abrasive paper with the diameter of 60mm, wherein the sand grains of the abrasive paper are chromium carbide with the grain diameter of 30 mu m, bonding a lead on the sand grain surfaces of the two dry grinding abrasive papers, connecting the lead with an insulation resistance tester, placing the two dry grinding abrasive papers and the diaphragm sample on a test platform in a high-low temperature universal tester together, and placing the insulation resistance tester outside the high-low temperature universal tester.
(2) The diaphragm sample is stood in a high-low temperature universal tester at 130 ℃ for 30min, then a ball-shaped pressure head of the high-low temperature universal tester is used for pressing dry grinding abrasive paper on the upper layer until an insulation resistance tester gives an alarm, the pressure value at the moment is recorded, the puncture strength values of 5 polypropylene dry-process ceramic diaphragm samples are tested repeatedly, the average value is taken, and the experimental result is shown in table 1, wherein the diameter of the ball-shaped pressure head is 1.5cm, the compression speed of the high-low temperature universal tester is 0.01mm/min, the voltage of the insulation resistance tester is set to be 100V, and the resistance is set to be 0.1M omega.
Example 6
The difference between the method for testing the puncture resistance of the lithium ion battery separator provided by the embodiment and the embodiment 2 is as follows: the grain size of the titanium carbide sand grains is 100 mu m.
Example 7
The difference between the method for testing the puncture resistance of the lithium ion battery separator provided by the embodiment and the embodiment 2 is as follows: the diaphragm sample is kept still for 1min in a high-low temperature universal tester at 25 ℃.
Example 8
The difference between the characterization method for the puncture resistance of the lithium ion battery separator provided by the embodiment and the embodiment 2 is as follows: the insulation resistance tester voltage was set to 1000V and the resistance was set to 0.01M Ω.
TABLE 1 puncture strength of membranes in examples 2-8 under different environments
In conclusion, by using the testing method, the actual environment and state of the diaphragm in the battery are simulated, the mode that the diaphragm is clamped between two overlapped electrode plates is used for simulating the cell lamination mode, the internal temperature set by a high-low temperature universal testing machine is used for simulating the temperature of the diaphragm in the actual manufacturing and using processes of the battery, and the sand layer on the surface of the electrode plate is used for simulating the piercing action of burrs, lithium dendrites or foreign particles on the surface of the electrode on the diaphragm, so that the capability of the diaphragm for resisting the piercing of the electrode particles or the foreign particles in the battery is tested more objectively, the piercing resistance of the diaphragm and the actual probability of short circuit of the battery are evaluated more comprehensively, and the safety and reliability of the diaphragm in the battery are predicted better.
The above description is only for the purpose of describing some embodiments of the present invention, and is not intended to limit the scope of the present invention, and one skilled in the art can make improvements or modifications to the above embodiments according to the present invention, but all fall within the scope of the present invention.
Claims (8)
1. A method for testing the puncture resistance of a battery diaphragm is characterized by comprising the following steps:
placing a diaphragm sample between two electrode plates to form a test piece, wherein the surface of at least one electrode plate is provided with a burr surface, the burr surface comprises a plurality of conductive hard particles protruding out of the surface of the electrode plate, the diaphragm sample is correspondingly contacted with the burr surface, and the two electrode plates are respectively and electrically connected to two ends of an insulation resistance tester;
placing the test piece in an environment capable of simulating the internal temperature condition of the battery, increasing the pressure of mutual forward extrusion of the two electrode plates through external force, and recording the pressure value at the moment when the insulation resistance tester measures that the two electrode plates of the test piece are short-circuited, wherein the pressure value is used for representing the puncture resistance of the diaphragm sample;
two electrode plates are equallyd divide and do not are abrasive paper, abrasive paper contains the body paper and covers the sand grain layer on the body paper, the sand grain layer constitutes promptly the burr face, the sand grain on sand grain layer is electrically conductive carbide granule, just abrasive paper is connected with insulation resistance tester with its sand grain layer lead-out wire respectively.
2. The test method according to claim 1, wherein the sand grains of the sand grain layer are one or more conductive cemented carbide particles selected from tungsten carbide, titanium nitride, and chromium carbide.
3. The test method according to claim 1 or 2, wherein the sand grain layer has a sand grain size of 5 to 100 μm.
4. The test method according to claim 1, wherein the peripheral edges of the separator sample each extend beyond the region where the two electrode plates overlap.
5. The test method according to claim 1, wherein the environment capable of simulating the internal temperature condition of the battery is provided by a high-low temperature universal tester, and the external force is provided by a ball-type indenter of the high-low temperature universal tester.
6. The method according to claim 1, wherein the insulation resistance tester has a voltage setting range of 10 to 250V and a resistance setting range of 0.1 to 0.5M Ω.
7. A method for testing the puncture resistance of a battery diaphragm comprises the following steps:
s1: assembling a test piece: cutting a diaphragm sample and placing the diaphragm sample between two laminated electrode plates to form a test piece; one surface of at least one of the electrode plates is provided with a burr surface, the burr surface comprises a plurality of conductive hard particles protruding out of the surface of the electrode plate, and the diaphragm sample is correspondingly contacted with the burr surface; the two electrode plates are respectively sand paper, the sand paper comprises base paper and a sand particle layer covering the base paper, the sand particle layer forms the burr surface, and sand particles of the sand particle layer are conductive hard alloy particles;
and S2, connecting the test piece with an insulation resistance tester: respectively leading out wires from the sand grain layer of the sand paper to be connected with an insulation resistance tester;
s3 testing in a simulated environment: setting the environmental temperature in a high-low temperature universal tester, placing the test piece in the high-low temperature universal tester, standing for more than 5min, and then pressing an electrode plate on the upper layer of the test piece by using a pressure head of the high-low temperature universal tester; when the insulation resistance tester measures that the two electrode plates of the test piece are short-circuited, the pressure value of the pressure head pressing the test piece at the moment is recorded, and the pressure value represents the puncture resistance of the diaphragm sample at a specific temperature.
8. A test assembly for testing the puncture resistance of a battery separator, comprising:
the test piece comprises two electrode plates and a diaphragm sample clamped between the two electrode plates, wherein one surfaces of the two electrode plates, which correspond to the diaphragm sample, are provided with sand grain layers, and sand grains of the sand grain layers are conductive hard particles; the two electrode plates are respectively sand paper, the sand paper comprises base paper and a sand particle layer covering the base paper, the sand particle layer forms a burr surface, and sand particles of the sand particle layer are conductive hard alloy particles;
the insulation resistance tester is respectively and electrically connected with the two electrode plates of the test piece; specifically, lead wires are led out of the sand layers of the sand paper and are connected with an insulation resistance tester;
the high-low temperature universal testing machine can set the internal environment temperature, a testing platform and a pressure head are arranged in the high-low temperature universal testing machine, the testing platform provides the horizontal position of a testing piece, the pressure head is used for pressing the testing piece at a preset speed until the pressure head records the pressure value of the pressure head pressing the testing piece when the insulation resistance tester measures the short circuit between two electrode plates of the testing piece, and the pressure value represents the anti-puncture capacity of the diaphragm sample at a specific temperature.
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