CN113394515B - Composite diaphragm for lithium battery, preparation method and detection method thereof - Google Patents
Composite diaphragm for lithium battery, preparation method and detection method thereof Download PDFInfo
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- CN113394515B CN113394515B CN202110940653.8A CN202110940653A CN113394515B CN 113394515 B CN113394515 B CN 113394515B CN 202110940653 A CN202110940653 A CN 202110940653A CN 113394515 B CN113394515 B CN 113394515B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6402—Atomic fluorescence; Laser induced fluorescence
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the technical field of lithium batteries, in particular to a composite diaphragm for a lithium battery, a preparation method and a detection method thereof. The method comprises the following steps: a separator substrate; the inorganic particle layer is coated on at least one surface of the diaphragm base material and comprises inorganic particles, and the inorganic particles contain inert fluorescent particles; and the bonding layer is coated on the inorganic particle layer. The composite diaphragm for the lithium battery, the preparation method and the detection method thereof can effectively detect whether the bonding layer is not coated, and the detection method is simple and effective.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a composite diaphragm for a lithium battery, a preparation method and a detection method thereof.
Background
The diaphragm is one of the main components of the lithium ion battery, and plays a role in separating the anode and the cathode to avoid short circuit and realizing lithium ion conduction by penetrating through electrolyte in the lithium ion battery. With the continuous popularization of lithium ion battery applications, the safety and electrochemical performance of lithium batteries need to be improved. In the existing lithium battery, a diaphragm is usually a porous PE or PP diaphragm, and the thickness of the diaphragm is 4-20 micrometers. However, at higher temperatures, e.g., above 100 ℃, porous PE or PP separators are prone to shrinkage, which leads to a safety problem in lithium batteries where short circuits between the positive and negative electrodes occur at high temperatures. Therefore, the separator is required to have a heat shrinkage resistance at high temperature. CN200580044583.7 discloses a separator having an inorganic/organic composite structure, in which inorganic particles bonded with a polymer binder are disposed on the surface of a polyolefin substrate to improve the thermal shrinkage capability of the separator. Typically, the inorganic particles are alumina, magnesium hydroxide, boehmite, or the like. On the other hand, since the lithium battery undergoes volume expansion during charging and discharging, a polymer bonding layer is usually further disposed on the inorganic particle layer of the separator to bond the separator and the electrode together, so as to reduce interfacial resistance and keep the structure of the battery from being damaged after charging and discharging. Typically this layer of binder is PVDF. As can be seen from the above discussion, the prior art separators generally include a polyolefin separator substrate/heat resistant inorganic particle layer/tie layer. In order to ensure that the separator has heat shrinkage resistance, the heat-resistant inorganic particle layer is required to be completely covered on the surface of the polyolefin separator substrate.
The existing bonding layer is coated by adopting a gravure roll coating method. Due to the unevenness of the diaphragm, equipment vibration and roll jump, uneven sizing agent, dry material on the surface of the gravure roll and the like, the adhesive layer generates a missing coating condition. The omission of the adhesive layer leads to no adhesive force between the diaphragm and the pole piece, and the battery performance is obviously influenced. Therefore, the adhesive leakage must be detected in the production.
The existing diaphragm coating detection method is X-ray transmission detection, and the principle of the X-ray transmission detection is that an X-ray emission source is arranged on one side of a coated diaphragm, and a receiver is arranged on the other side of the coated diaphragm. In the region of the missing coating, the amount of absorbed X-rays is reduced and the intensity of the X-rays detected by the receiver is significantly increased.
The bleed-over areas are essentially identified by measuring the change in intensity of transmitted light, however, bleed-over of a tie layer of porous PVDF cannot be effectively detected.
PVDF itself absorbs X-rays and visible light much less than inorganic materials, so the inorganic particle layer absorbs X-rays or visible light more strongly than the adhesive layer, and the adhesive layer is porous, further reducing absorption. In the missing coating area, the influence of the X-ray intensity or the transmitted light intensity is small, the resolution of the missing coating of the bonding layer is low, and the missing coating area is difficult to accurately identify and detect.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method solves the technical problem that the existing composite diaphragm detection method in the prior art is difficult to detect the bonding layer coated on the inorganic particle layer. The invention provides a composite diaphragm for a lithium battery, a preparation method and a detection method thereof, which can effectively detect whether a bonding layer is not coated, and the detection method is simple and effective.
The technical scheme adopted by the invention for solving the technical problems is as follows: a composite separator for a lithium battery, comprising: a separator substrate; an inorganic particle layer coated on at least one surface of the diaphragm base material, wherein the inorganic particle layer comprises inorganic particles, and the inorganic particles contain inert fluorescent particles; and the bonding layer is coated on the inorganic particle layer.
Preferably, the inert fluorescent particles comprise greater than or equal to 5% by weight of the inorganic particles.
Preferably, the inert fluorescent particles are uniformly distributed in the inorganic particle layer;
specifically, the inert fluorescent particles are calcium tungstate or chromium tungstate.
Specifically, the tie layer is a porous layer of PVDF.
Specifically, the diaphragm base material is a PP or PE material.
The composite diaphragm for the lithium battery has the following specific effects: the inorganic particles contain inert fluorescent particles, and are inert, so that the inert fluorescent particles cannot react with substances in the battery, and the fluorescent particles can perform a fluorescent reaction under the irradiation of exciting light of the fluorescent particles, so that the detection of the coating on the diaphragm is facilitated.
A method for preparing the above composite separator for a lithium battery, comprising:
s1, mixing inorganic particles containing inert fluorescent particles, a binder, sodium carboxymethyl cellulose, deionized water and a wetting agent to form inorganic particle layer slurry, coating the inorganic particle layer slurry on at least one surface of the diaphragm base material, and drying after coating to form an inorganic particle layer on the diaphragm base material;
s2, dissolving PVDF in a DMAC or NMP solvent to form bonding layer slurry, uniformly coating the bonding layer slurry on the inorganic particle layer, and immersing the inorganic particle layer in deionized water after coating, wherein the PVDF precipitates on the surface of the inorganic particle layer to form a bonding layer.
Specifically, in step S1, the inorganic particles containing inert fluorescent particles: adhesive: sodium carboxymethylcellulose: deionized water: the weight ratio of the wetting agent is 30: 6: 0.5: 63: 0.5.
specifically, after the bonding layer slurry is uniformly coated on the inorganic particle layer in step S2, the undried coated membrane is immersed in 50% DMAC-deionized water for 30 seconds, then immersed in deionized water for 30 seconds, and then dried.
The preparation method of the composite diaphragm for the lithium battery has the following specific effects: the preparation method is simple, and the composite diaphragm can be prepared by only doping inert fluorescent particles into inorganic particles and performing a traditional preparation process.
The detection method for the composite diaphragm of the lithium battery comprises the following steps:
the light source is arranged on one side of the composite diaphragm, the side is set as side A, the side A is coated with an inorganic particle layer, the inorganic particle layer is coated with a bonding layer, the light source faces the bonding layer and can emit exciting light, the exciting light can enable inert fluorescent particles in the inorganic particle layer to generate a fluorescent reaction, and the inert fluorescent particles emit fluorescence after the reaction;
the CCD detector is arranged on the side A of the composite diaphragm, faces the bonding layer, receives fluorescence emitted after the reaction of the inert fluorescent particles, and converts the intensity of the received fluorescence into a gray value;
the detection method of the composite diaphragm for the lithium battery comprises the following steps:
si, the light source emits exciting light, the exciting light enables inert fluorescent particles in the inorganic particle layer to perform a fluorescent reaction, and the inert fluorescent particles generate fluorescence;
sii, the CCD detector receives the fluorescence and converts the intensity of the received fluorescence into a gray value;
siii, comparing whether the gray values in the test area are consistent or not, and if the gray values are inconsistent and the gray difference value is larger than 20, judging that the bonding layer is not coated in the area with the high gray value.
Preferably, a filter is arranged on the CCD detector to block the reflected light of the excitation light.
The detection method for the composite diaphragm of the lithium battery has the following specific effects:
in the application, exciting light is emitted by a light source to irradiate one side of the composite diaphragm coated with the coating, inert fluorescent particles of the inorganic particle layer generate a fluorescent effect to emit fluorescent light, under the condition that the bonding layer generates missing coating, the exciting light emitted by the light source directly irradiates the inorganic particle layer to react with the inert fluorescent particles in the inorganic particle layer to emit fluorescent light, the emitted fluorescent light is directly received by a CCD detector, and the CCD detector converts a fluorescent intensity value into a gray value a;
under the condition that no missing coating is generated on the bonding layer, exciting light emitted by the light source penetrates through the bonding layer, reaches the surface of the inorganic particle layer, reacts with inert fluorescent particles in the inorganic particle layer and emits fluorescence; the fluorescence passes through the bonding layer, the fluorescence part is absorbed by the bonding layer, the unabsorbed fluorescence is emitted from the bonding layer and received by the CCD detector, the CCD detector converts the fluorescence intensity value into a gray value b, under the condition that the bonding layer does not produce the missing coating, part of the fluorescence is absorbed by the bonding layer, the fluorescence intensity value received by the CCD detector is smaller than the fluorescence intensity value produced by the missing coating bonding layer, the larger the fluorescence intensity value is, the stronger the light spot is produced, the larger the converted gray value is, and the gray value a obtained by normally coating the bonding layer is also smaller than the gray value b obtained by converting the missing coating bonding layer.
And when the gray values in the detection areas are inconsistent and the gray difference value is larger than 20, namely the gray value b-gray value a is larger than 20, judging that the areas with high gray values are not coated with the bonding layer.
The detection method can not be affected by the absorption of the inorganic particle layer, and in addition, the reaction of the inert fluorescent particles to exciting light is particularly sensitive, so that the detection method for the composite diaphragm of the lithium battery can effectively detect the missing coating of the bonding layer.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic illustration of prior art detection of a membrane coating;
fig. 2 is a schematic view of a detection method of a composite separator for a lithium battery.
Reference numerals:
10. a separator substrate; 20. an inorganic particle layer; 30. a bonding layer; 100. a light source; 200. a CCD detector; 300. an X-ray emission source.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
According to a preferred embodiment of the present invention, a composite separator for a lithium battery includes:
the diaphragm substrate 10, the diaphragm substrate 10 is a PP or PE material.
An inorganic particle layer 20, wherein the inorganic particle layer 20 is coated on at least one surface of the diaphragm base material 10, the inorganic particle layer 20 comprises inorganic particles, and the inorganic particles comprise inert fluorescent particles; the inert fluorescent particles account for more than or equal to 5 percent of the inorganic particles by weight, are uniformly distributed in the inorganic particle layer 20, and are calcium tungstate or chromium tungstate.
And the bonding layer 30, wherein the bonding layer 30 is coated on the inorganic particle layer 20, and the bonding layer 30 is a PVDF porous layer.
A method for preparing the above composite separator for a lithium battery, comprising:
s1, mixing inorganic particles containing inert fluorescent particles, a binder, sodium carboxymethyl cellulose, deionized water, and a wetting agent to form an inorganic particle layer slurry, coating the inorganic particle layer slurry on at least one surface of the diaphragm substrate 10, drying after coating, and forming an inorganic particle layer 20 on the diaphragm substrate 10, in step S1, the inorganic particles containing inert fluorescent particles: adhesive: sodium carboxymethylcellulose: deionized water: the weight ratio of the wetting agent is 30: 6: 0.5: 63: 0.5.
s2, dissolving PVDF in a DMAC or NMP solvent to form bonding layer slurry, uniformly coating the bonding layer slurry on the inorganic particle layer 20, immersing the inorganic particle layer 20 in deionized water after coating, precipitating the PVDF on the surface of the inorganic particle layer 20 to form a bonding layer 30, uniformly coating the bonding layer 30 slurry on the inorganic particle layer 20 in step S2, immersing an undried coated diaphragm in 50% DMAC-deionized water for 30 seconds, immersing the diaphragm in the deionized water for 30 seconds, and drying the diaphragm.
The detection method for the composite diaphragm of the lithium battery comprises the following steps:
the light source 100 is arranged on one side of the composite diaphragm, the side is an A side, the A side is coated with the inorganic particle layer 20, the inorganic particle layer 20 is coated with the bonding layer 30, the light source 100 faces the bonding layer 30, the light source 100 can emit exciting light, the exciting light can enable inert fluorescent particles in the inorganic particle layer 20 to react, and the inert fluorescent particles emit fluorescence after reaction;
the CCD detector 200 is arranged on the side A of the composite diaphragm, the CCD detector 200 faces the bonding layer 30, the CCD detector 200 receives fluorescence emitted after the reaction of the inert fluorescent particles and converts the intensity of the received fluorescence into a gray value;
the detection method of the composite diaphragm for the lithium battery comprises the following steps:
si, the light source 100 emits exciting light, the exciting light causes the inert fluorescent particles in the inorganic particle layer 20 to perform a fluorescent reaction, and the inert fluorescent particles generate fluorescence;
the Sii and CCD detector 200 receives the fluorescence and converts the intensity of the received fluorescence into a gray value;
siii, comparing whether the gray values in the test area are consistent or not, and if the gray values are inconsistent and the gray difference value is larger than 20, judging that the adhesive layer 30 is not coated in the area with the high gray value.
The existing diaphragm coating detection method in the background art of the application is that the bonding layer coated on the inorganic particle layer is difficult to identify through X-ray transmission detection, and the specific reasons are as follows:
as shown in fig. 1, one side of a diaphragm substrate 10 is coated with an inorganic particle layer 20, the inorganic particle layer 20 is coated with an adhesive layer 30, the side where the inorganic particle layer 20 and the adhesive layer 30 are coated on the diaphragm substrate 10 is a side a, the other side of the diaphragm substrate 10 is a side B, the X-ray emission source 300 is disposed on the side B of the diaphragm substrate 10, and the receiver is disposed on the side a of the diaphragm substrate 10.
Intensity of incident X-ray or visible light QIncident lightTransmission intensity of QTransmission throughThe absorption intensity of the base material is QBase materialThe inorganic particle layer 20 has an absorption strength of QInorganic substanceThe absorption strength of the adhesive layer 30 is QBonding of。QTransmission through=QIncident light-QBase material-QInorganic substance-QBonding of. When the adhesive layer 30 is missing, there is QBonding of=0, transmission intensity Q of the holiday regionTransmission through holiday= QIncident light-QBase material-QInorganic substance. Resolution for the missing coating region is QTransmission through holiday/QTransmission through=1＋QBonding of/（QIncident light-QBase material-QInorganic substance-QBonding of）。QBonding ofThe absorption is very small relative to the substrate and the inorganic layer, the resolving power is almost 1, i.e. it is difficult to distinguish QTransmission through holidayAnd QTransmission through. Therefore, the prior art detects whether the adhesive layer 30 is missing coating by a transmission detection method due to the inorganic particlesThe detection influence of the layer 20 on the bonding layer 30 is large, and the detection method in the prior art has low resolution capability, so that the coating missing area on the bonding layer 30 cannot be effectively identified.
In addition, for better heat-resistant effect and security performance, the both sides of diaphragm substrate 10 all can coat inorganic particle layer 20, and the coating has tie coat 30 respectively on the inorganic particle layer 20 of both sides, and the X ray transmission that so structure was again through prior art detects, and double-sided inorganic particle layer 20 influences the testing result more greatly, is difficult to discern inorganic layer's holiday more.
As shown in fig. 2, in the present application, the light source 100 emits excitation light to irradiate one side of the composite membrane coated with the coating, the inert fluorescent particles of the inorganic particle layer 20 generate a fluorescence effect to emit fluorescence, in the case that the adhesive layer 30 generates a missing coating, the excitation light emitted by the light source 100 directly irradiates the inorganic particle layer 20, reacts with the inert fluorescent particles in the inorganic particle layer 20 to emit fluorescence, the emitted fluorescence is directly received by the CCD detector 200, and the CCD detector 200 converts the fluorescence intensity value into a gray value a;
under the condition that no leakage coating is generated on the adhesive layer 30, the light source 100 emits exciting light which passes through the adhesive layer 30, reaches the surface of the inorganic particle layer 20, reacts with inert fluorescent particles in the inorganic particle layer 20 and emits fluorescence; the fluorescence passes through the adhesive layer 30, the fluorescence is partially absorbed by the adhesive layer 30, the unabsorbed fluorescence is emitted from the adhesive layer 30 and received by the CCD detector 200, the CCD detector 200 converts the fluorescence intensity value into a gray value b, and because the adhesion layer 30 does not produce the missing coating, part of the fluorescence is absorbed by the adhesive layer 30, the fluorescence intensity value received by the CCD detector 200 is smaller than the fluorescence intensity value produced by the missing coating adhesive layer 30, the larger the fluorescence intensity value is, the stronger the light spot is produced, the larger the converted gray value is, so the gray value a obtained by normally coating the adhesive layer 30 is also smaller than the gray value b obtained by converting the missing coating adhesive layer 30.
When the gray values in the detection areas are inconsistent and the gray difference value is larger than 20, namely the gray value b-gray value a is larger than 20, the area with high gray value is judged to be not coated with the bonding layer 30.
The detection method of the application cannot be affected by the absorption of the inorganic particle layer 20, and the reaction of the inert fluorescent particles to the exciting light is particularly sensitive, so that the detection method of the composite diaphragm for the lithium battery can effectively detect the missing coating of the bonding layer 30. In addition, for better heat-resisting effect and security performance, inorganic particle layer 20 can all be coated to the both sides of diaphragm substrate 10, has coated tie coat 30 on the inorganic particle layer 20 of both sides respectively, has detected one side through the detection device of this application after, carries out the turn-over with compound diaphragm, detects compound diaphragm's opposite side, can not receive inorganic particle layer 20's influence, causes detection error.
Example 1: using calcium tungstate (CaWO)4) As the fluorescent material, the excitation light was ultraviolet light, and the emission light was 430nm blue light and 535nm green light. The inorganic particles are calcium tungstate and alumina in a weight ratio of 5: 95. The particle size of calcium tungstate D50 was 0.5 microns, and the particle size of alumina D50 was 0.8 microns. The binder is SBR emulsion with solid content of 25 percent, and the wetting agent is Fuile DS-960E.
The method for manufacturing the inorganic particle layer 20 comprises the following steps: the preparation method comprises the following steps of (1) mixing inorganic particles: adhesive: sodium carboxymethylcellulose: deionized water: wetting agent = 30: 6:0.5: and (3) uniformly mixing the components in a ratio of 63:0.5 to form inorganic particle layer slurry, uniformly coating the slurry on a 7-micron TNS diaphragm, and drying to obtain the inorganic particle layer 20 with the thickness of 2 microns.
The method for manufacturing the bonding layer 30 comprises the following steps: PVDF with the mark of LBG of the Achima company is dissolved in DMAC to form bonding layer slurry, the solid content of the PVDF is 5%, the bonding layer 30 slurry is uniformly coated on the inorganic particle layer 20, then the undried coating membrane is immersed in 50% DMAC-deionized water for 30 seconds, then is immersed in the deionized water for 30 seconds, and then is dried. The porous bonding layer 30 was formed to a thickness of 2 microns.
The model of the light source 100 of the detection device is LY-LH1400-UV-1924, and the model of the CCD detector 200 is Defect view-2;
the light source 100 is arranged on one side of the composite diaphragm, the side is an A side, the A side is coated with the inorganic particle layer 20, the inorganic particle layer 20 is coated with the bonding layer 30, the light source 100 faces the bonding layer 30, the light source 100 can emit exciting light, the exciting light can enable inert fluorescent particles in the inorganic particle layer 20 to react, and the inert fluorescent particles emit fluorescence after reaction;
the CCD detector 200 is arranged on the side A of the composite diaphragm, the CCD detector 200 faces the bonding layer 30, the CCD detector 200 receives fluorescence emitted after the reaction of the inert fluorescent particles and converts the intensity of the received fluorescence into a gray value;
the composite diaphragm is prepared by the method, the composite diaphragm is completely coated with the bonding layer 30, and the composite diaphragm for testing is taken, and the gray value measured by the CCD detector 200 is 69;
example 2:
the composite membrane adopted in the embodiment 2 is different from the composite membrane adopted in the embodiment 1 in that the composite membrane of the embodiment 2 is partially coated with the adhesive layer 30 in a missing way, the composite membrane for testing is taken, the gray value of the detection area is detected by the CCD detector 200, the gray value of the missing coating area is 114, and the difference value of the gray value of the non-missing coating area is 69 is 45;
example 3:
example 3 differs from example 2 in that the composite membrane of example 3 was filled with calcium tungstate and alumina in a weight ratio of 3:97 (the weight ratio of inert fluorescent particles to inorganic particles is less than 5%), the gray value of the detection region was detected by the CCD detector 200, the gray value of the missing coating region was 94, the gray value of the non-missing coating region was 69, and the difference was 25;
example 4:
example 4 differs from example 2 in that the composite membrane of example 4 was filled with calcium tungstate and alumina in a weight ratio of 10:90 (the weight ratio of inert fluorescent particles to inorganic particles is greater than 5%), the gray value of the detection region was detected by the CCD detector 200, the gray value of the missing coating region was 124, the gray value of the non-missing coating region was 69, and the difference was 55;
comparative example 1:
the composite membrane adopted in comparative example 1 is different from that of example 2 in that the gray value of the detection area is detected by the CCD detector 200 without adding calcium tungstate (inert fluorescent particles) in comparative example 1, the gray value of the non-leakage-coated area is 69, and the difference is 0; the measured gray values before and after the coating are equal, and it is impossible to detect whether the adhesive layer 30 is not coated.
Comparative example 2:
the difference between the comparative example 2 and the comparative example 1 is that the detection mode is different, the comparative example 2 adopts X-ray transmission detection in the prior art, the model of an adopted X-ray emission source 300 is RXG1200L, and the model of a receiver is a CCD detector 200 and is Defect view-2; by placing an X-ray emission source 300 on one side of the coated membrane and a CCD detector 200 on the other side. The gray value of the light transmission of the neglected coating area measured by the CCD detector 200 is 75, and the gray value of the light transmission of the un-neglected coating area measured by the receiver is 73; the values of the light transmission amounts measured before and after the coating are approximately equal, and it is impossible to detect whether the adhesive layer 30 is not coated.
According to the data, the detection method for the composite diaphragm of the lithium battery can not be influenced by the absorption of the inorganic particle layer 20, the detection precision is improved, and the reaction of the inert fluorescent particles to the exciting light is particularly sensitive, so that the detection method for the composite diaphragm of the lithium battery can effectively detect the missing coating of the bonding layer 30, the detection precision is improved, the detection method is simple and easy to implement, and the production cost can be effectively saved.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (9)
1. A composite separator for a lithium battery, comprising:
a separator substrate (10);
an inorganic particle layer (20), wherein the inorganic particle layer (20) is coated on at least one surface of the diaphragm base material (10), the inorganic particle layer (20) comprises inorganic particles, and the inorganic particles comprise inert fluorescent particles;
an adhesive layer (30), wherein the adhesive layer (30) is coated on the inorganic particle layer (20);
the inert fluorescent particles account for more than or equal to 5% of the inorganic particles by weight;
the inert fluorescent particles are uniformly distributed in the inorganic particle layer (20);
the inert fluorescent particles emit fluorescence through exciting light irradiation, and whether the bonding layer (30) is not coated or not is judged through converting the fluorescence into a gray value.
2. The composite separator for a lithium battery as claimed in claim 1, wherein the inert fluorescent particles are calcium tungstate or chromium tungstate.
3. The composite separator for a lithium battery as claimed in claim 1, wherein the adhesive layer (30) is a porous layer of PVDF.
4. The composite separator for a lithium battery as claimed in claim 1, wherein the separator substrate (10) is a PP or PE material.
5. A method of preparing a composite separator for a lithium battery as claimed in claim 1, comprising:
step S1, mixing inorganic particles containing inert fluorescent particles, a binder, sodium carboxymethyl cellulose, deionized water and a wetting agent to form inorganic particle layer slurry, coating the inorganic particle layer slurry on at least one surface of the diaphragm base material (10), and drying after coating to form an inorganic particle layer (20) on the diaphragm base material (10);
step S2, dissolving PVDF in DMAC or NMP solvent to form bonding layer slurry, uniformly coating the bonding layer slurry on the inorganic particle layer (20), and immersing the inorganic particle layer in deionized water after coating, wherein PVDF precipitates on the surface of the inorganic particle layer (20) to form the bonding layer (30).
6. The method according to claim 5, wherein in step S1, the inorganic particles containing inert fluorescent particles: adhesive: sodium carboxymethylcellulose: deionized water: the weight ratio of the wetting agent is 30: 6: 0.5: 63: 0.5.
7. the method of claim 6, wherein the step S2 is performed by immersing the undried coated separator in 50% DMAC-DI water for 30 seconds, then in DI water for 30 seconds, and then drying after the adhesive layer (30) slurry is uniformly coated on the inorganic particle layer (20).
8. The method for inspecting a composite separator for a lithium battery as set forth in claim 1, wherein the inspection apparatus for a composite separator for a lithium battery comprises:
the light source (100) is arranged on one side of the composite diaphragm, the side is an A side, the A side is coated with the inorganic particle layer (20), the inorganic particle layer (20) is coated with the bonding layer (30), the light source (100) faces the bonding layer (30), the light source (100) can emit exciting light, the exciting light can enable inert fluorescent particles in the inorganic particle layer (20) to react, and the inert fluorescent particles emit fluorescence after reaction;
the CCD detector (200) is arranged on the side A of the composite diaphragm, the CCD detector (200) faces the bonding layer (30), and the CCD detector (200) receives fluorescence emitted after the inert fluorescent particles react and converts the intensity of the received fluorescence into a gray value;
the detection method of the composite diaphragm for the lithium battery comprises the following steps:
step Si, the light source (100) emits exciting light, the exciting light enables inert fluorescent particles in the inorganic particle layer (20) to perform fluorescence reaction, and the inert fluorescent particles generate fluorescence;
sii, the CCD detector (200) receives the fluorescence and converts the intensity of the received fluorescence into a gray value;
step Siii, comparing whether the gray values in the test area are consistent or not, and if the gray values are inconsistent and the gray difference value is larger than 20, judging that the adhesive layer (30) is not coated in the area with the high gray value.
9. The detection method according to claim 8, wherein a filter is provided on the CCD detector (200) to block reflected light of the excitation light.
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| CN202110940653.8A CN113394515B (en) | 2021-08-17 | 2021-08-17 | Composite diaphragm for lithium battery, preparation method and detection method thereof |
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| CN202110940653.8A CN113394515B (en) | 2021-08-17 | 2021-08-17 | Composite diaphragm for lithium battery, preparation method and detection method thereof |
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| CN116073004B (en) * | 2021-10-29 | 2024-02-02 | 宁德时代新能源科技股份有限公司 | Isolation film, secondary battery, battery module, battery pack and electricity utilization device |
| CN114284641A (en) * | 2021-11-09 | 2022-04-05 | 江苏卓高新材料科技有限公司 | Composite coating diaphragm, preparation method thereof, battery with composite coating diaphragm and object with composite coating diaphragm |
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