A method for detecting battery pole piece adhesive

Abstract

The present invention relates to a battery pole piece adhesive detection method, which uses a physical vapor deposition method to modify the lithium ion battery pole piece, so that each component in the battery pole piece is evaporated with a metal layer, especially the metal layer is evaporated on the adhesive surface with poor electronic conductivity, and then the active material particles are profiled using a focused ion beam, and the pole piece surface and active material particles are characterized by a scanning electron microscope. By comparing the surface and particle cross-section morphology, the distribution of the pole piece adhesive can be determined, and the structure and state of the adhesive can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of battery detection, and in particular relates to a battery pole piece adhesive detection method. Background Art

[0002] The binder of lithium-ion batteries plays a bonding role between the active materials and other components of lithium-ion battery pole pieces, and is the main component that supports the mechanical properties of the positive and negative pole pieces of lithium-ion batteries. In lithium-ion batteries, binders need to withstand the swelling of small molecules and the corrosion of solvents and electrolyte additives. In addition, during the battery charging and discharging process, binders also need to withstand electrochemical redox effects. The binder accounts for a very small proportion in the battery, but its function in lithium-ion batteries is crucial. At present, the most widely used lithium-ion battery binders mainly include: polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) emulsion / carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), etc.

[0003] The main functions of binders in the positive and negative pole pieces of lithium-ion batteries include: first, connecting electrode materials such as active material particles and conductive agent particles; second, connecting active materials and foil current collectors such as copper and aluminum foil; third, the intermolecular force between binder molecules. The performance evaluation of binders is divided into three parts: the mechanical properties of the binder body, the bonding strength of the binder to the current collector, and the bonding strength of the binder to the active material. It can be seen that the uniformity of the distribution of the binder in the pole piece and the distribution state of the binder have a greater impact on the performance of lithium-ion batteries. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for detecting a battery pole piece adhesive.

[0005] The technical solution adopted by the present invention is: a method for detecting a battery pole piece adhesive, forming a pole piece modified with a metal layer on the surface of the battery pole piece by physical vapor deposition, and then characterizing its morphology by a scanning electron microscope.

[0006] Preferably, the specific method is as follows:

[0007] Step 1: Perform surface modification on the battery electrode by physical vapor deposition to form a metal layer on the electrode surface;

[0008] Step 2: Use a focused ion beam to profile the active material particles, and use a scanning electron microscope to characterize the morphology of the electrode surface and the cross section of the active material particles;

[0009] Step 3: Analyze the characterization results to determine the binder distribution.

[0010] Preferably, the vacuum degree of vacuum coating in step 1 is 10-4 -10 -1 Pa, the temperature of vacuum coating is 500-1000℃, and the time of vacuum coating is 1min-5h.

[0011] Preferably, the vacuum coating has a film thickness of 10 nm-3 μm.

[0012] Preferably, the evaporated metal source is lithium, aluminum, magnesium, zinc, manganese, calcium or silver.

[0013] Preferably, the adhesive in the battery pole piece is a combination of one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), emulsion / carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI) and polyacrylamide (PAM).

[0014] Preferably, the battery electrode is a positive electrode, which is a ternary positive electrode, LCO or LFP;

[0015] Alternatively, the negative electrode at the tail of the battery is a graphite negative electrode or a silicon negative electrode.

[0016] Application of battery pole piece adhesive detection method in battery pole piece evaluation.

[0017] The advantages and positive effects of the present invention are: this detection method overcomes the disadvantage that the binder insulation cannot respond to the electron beam, maintains the original structural morphology of the binder through non-destructive surface modification means, and can quickly and truly characterize the distribution and state of the binder of the lithium-ion battery pole piece; thereby realizing the evaluation of the battery pole piece quality from the perspective of microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the surface characterization of the sample prepared in Example 1;

[0019] Figure 2 This is a partial enlarged SEM image of the surface characterization of the sample prepared in Example 1;

[0020] Figure 3 This is a SEM image of the cross section of the sample prepared in Example 1;

[0021] Figure 4 This is a SEM image of the surface characterization of the sample prepared in Example 2;

[0022] Figure 5 This is the SEM image of the surface characterization of the sample prepared in Example 3. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0024] The present invention relates to a battery pole piece adhesive detection method, which uses a physical vapor deposition metal source method to modify the lithium ion battery pole piece, so that each component in the battery pole piece is evaporated with a metal layer, especially the metal layer is evaporated on the adhesive surface with poor electronic conductivity, and then the active material particles are profiled using a focused ion beam, and the pole piece surface and active material particles are characterized by a scanning electron microscope. By comparing the surface and particle cross-section morphology, the distribution of the pole piece adhesive can be determined, and the structure and state of the adhesive can be obtained.

[0025] Applicable binders may be a mixture of one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), emulsion / carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyimide (PI), polyacrylamide (PAM), etc. Applicable positive electrode sheets may be ternary positive electrodes, LCO, LFP, etc.; Applicable negative electrode sheets may be graphite negative electrodes, silicon negative electrodes, etc. The metal source used for evaporation may be metal lithium, aluminum, magnesium, zinc, manganese, calcium, silver, etc.;

[0026] The specific detection methods are as follows:

[0027] Step 1: Surface modification of lithium-ion battery electrodes is performed by physical vapor deposition of metals, and the thickness of the metal layer is controlled by adjusting the deposition conditions; the vacuum degree of vacuum coating is 10 -4 -10 -1 Pa, the temperature of vacuum coating is 500-1000℃, the time of vacuum coating is 1min-5h; the film thickness of vacuum coating is 10nm-3μm;

[0028] Step 2: Use a focused ion beam to profile the active material particles, and use a scanning electron microscope to characterize the morphology of the electrode surface and the cross section of the active material particles;

[0029] Step three: By comparing the surface and particle cross-section morphology, the distribution of the electrode adhesive can be determined, and the structure and state of the adhesive can be obtained.

[0030] This detection method overcomes the shortcoming that the binder insulation cannot respond to the electron beam. Through non-destructive surface modification, the original structural morphology of the binder is maintained, and the distribution and state of the binder in the lithium-ion battery pole piece can be quickly and truly characterized; thereby realizing the evaluation of the battery pole piece quality from a microstructural perspective.

[0031] The scheme of the present invention is described below in conjunction with the accompanying drawings, wherein the experimental methods without specific operating steps are all carried out in accordance with the corresponding product instructions, and the instruments, reagents, and consumables used in the examples can all be purchased from commercial companies unless otherwise specified.

[0032] Example 1

[0033] Characterize the distribution of binders in the negative electrode of lithium-ion batteries. The binders in the negative electrode are SBR and CMC, specifically 1% SBR and 1.2% CMC. The lithium-ion battery electrode is modified by physical vapor deposition of lithium metal, with a vacuum degree of 0.1 Pa, a temperature of 1000°C, and a vacuum deposition time of 0.5 h.

[0034] The modified negative electrode was subjected to a focused ion beam profile treatment on the active material particles, and a scanning electron microscope was used to characterize the morphology of the electrode surface and the cross section of the active material particles. Figure 1-3 As shown, Figure 1 This is the SEM image of the negative electrode surface. Figure 2 It is a local enlarged picture, such as Figure 3 The figure shows a cross-section SEM image of the negative electrode sheet; the active components and conductive agent are both known materials, and their microstructures are also known. Since the adhesive part is also covered by the evaporated metal lithium, the distribution of the adhesive in the negative electrode sheet can also be clearly distinguished through the SEM image. Figure 1-3 As shown in , the distribution of the binder in the negative electrode sheet is relatively uniform, proving that it has better quality.

[0035] In addition, through the electrode adhesion test, the adhesion of the 4cm wide electrode is 50gf, which also proves that the electrode has a better use effect. The adhesion test results and the microstructure test structure have the same trend in the evaluation of battery electrode performance.

[0036] Example 2

[0037] Characterize the distribution of binder on the surface of negative electrode. The negative electrode binder is PI, and the binder content is 1.5%. The lithium-ion battery electrode is modified by physical vapor deposition of lithium metal. The vacuum degree of vacuum coating is 0.1Pa, the temperature of vacuum coating is 1000℃, and the vacuum coating time is 0.5h.

[0038] The modified negative electrode was profiled using a focused ion beam to profile the active material particles in the electrode, and a scanning electron microscope was used to characterize the morphology of the electrode surface, particle cross section, and active material particles. Figure 4 As shown, the SEM images of the surface and particle cross-section morphology show that the distribution of the electrode adhesive is uneven.

[0039] The electrode bonding test shows that the 4cm wide electrode bonding is 10gf, which indicates that the electrode bonding agent is not effective. The evaluation of the negative electrode is consistent with the microstructure evaluation trend.

[0040] Example 3

[0041] Characterize the distribution of the binder on the surface of the positive electrode. The positive electrode binder is PVDF, and the binder content is 3%. The lithium-ion battery electrode is modified by physical vapor deposition of lithium metal. The vacuum degree of vacuum coating is 0.01Pa, the temperature of vacuum coating is 500℃, and the vacuum coating time is 2h.

[0042] The modified positive electrode was subjected to a focused ion beam profile treatment on the active material particles, and a scanning electron microscope was used to characterize the morphology of the electrode surface and the cross section of the active material particles. Figure 5 As shown, through the surface SEM image, it can be judged that the distribution of the pole piece adhesive on the surface is uniform and dense.

[0043] The electrode bonding force test was then conducted, and the 4cm wide electrode bonding force was 120gf, which indicates that the electrode bonding agent has a good effect. The evaluation of the positive electrode is consistent with the microstructure evaluation trend.

[0044] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A battery pole piece adhesive detection method, characterized in that: A metal layer-modified electrode is formed on the surface of the battery electrode by physical vapor deposition, and its morphology is then characterized by scanning electron microscopy.

2. The battery electrode adhesive detection method according to claim 1, characterized in that: The specific method is as follows: Step 1: Perform surface modification on the battery electrode by physical vapor deposition to form a metal layer on the electrode surface; Step 2: Use a focused ion beam to profile the active material particles, and use a scanning electron microscope to characterize the morphology of the electrode surface and the cross section of the active material particles; Step 3: Analyze the characterization results to determine the binder distribution.

3. The battery electrode adhesive detection method according to claim 2, characterized in that: The vacuum degree of vacuum coating in step 1 is 10 -4 -10 -1 Pa, the temperature of vacuum coating is 500-1000℃, and the time of vacuum coating is 1min-5h.

4. The battery electrode adhesive detection method according to claim 3, characterized in that: The film thickness of vacuum coating is 10nm-3μm.

5. The battery electrode adhesive detection method according to claim 2, characterized in that: The evaporation metal source is lithium, aluminum, magnesium, zinc, manganese, calcium or silver.

6. The battery pole piece adhesive detection method according to any one of claims 1 to 5, characterized in that: The adhesive in the battery pole piece is a combination of one or more of polyvinylidene fluoride, styrene-butadiene rubber, emulsion / carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyimide and polyacrylamide.

7. The battery electrode adhesive detection method according to claim 6, characterized in that: The battery pole piece is a positive pole piece, which is a ternary positive electrode, LCO or LFP; Alternatively, the negative electrode at the tail of the battery is a graphite negative electrode or a silicon negative electrode.

8. Application of the battery pole piece adhesive detection method according to any one of claims 1 to 7 in battery pole piece evaluation.

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