Test method for battery electrolyte wetting degree and wetting path

Abstract

The present invention discloses a method for testing the degree of electrolyte infiltration and the infiltration path of a battery. The method for testing the degree of electrolyte infiltration of the present invention comprises: taking a battery containing a fluorescent agent in the electrolyte, disassembling the battery, wherein the battery further comprises a positive electrode plate, a negative electrode plate and a diaphragm, taking out the diaphragm in the battery, and volatilizing the electrolyte; the diaphragm comprises a first surface and a second surface, irradiating the first surface of the diaphragm with blue light, the blue light penetrating the diaphragm, photographing the second surface of the diaphragm, and recording the color distribution in the second surface of the diaphragm; and determining the degree of electrolyte infiltration. The present invention utilizes the scattering phenomenon when blue light penetrates the diaphragm and the fluorescent powder, and distinguishes the infiltration of the electrolyte in the battery by observing the color presented on the diaphragm. The electrolyte distribution map can be obtained with high precision, thereby establishing a fast, low-cost and accurate method for testing the degree of electrolyte infiltration.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for testing the degree of infiltration and infiltration path of battery electrolyte. Background Art

[0002] Lithium-ion batteries have high specific energy density and capacity retention, and are gradually being widely used in the field of on-board power supplies. As consumers' requirements for the endurance and safety of electric vehicles increase, the energy density and safety standards of electric vehicle batteries have also been greatly improved. Increasing the thickness of the electrode (such as the positive electrode and / or the negative electrode) and the size of the battery can effectively improve the energy density of the battery, but at the same time it increases the difficulty of electrolyte infiltration. During the injection and standing process, the electrolyte will penetrate from the edge of the electrode through the diaphragm into the electrode pores and the center of the battery. Due to the increase in the thickness and area of the electrode, the electrolyte infiltration distance is lengthened and the infiltration speed is slowed down. The optimal parameters for injection, standing and formation are also difficult to explore, and a large number of experimental verifications are required.

[0003] In addition, the amount of electrolyte injection and the infiltration conditions have a huge impact on battery performance. Too little electrolyte will increase the internal resistance of the battery, reduce the capacity and life, and even worse, may cause safety issues such as capacity drop and lithium precipitation. Too much electrolyte will increase the weight of the battery and reduce the energy density of the battery. Moreover, because the electrolyte is a flammable substance, excessive electrolyte also increases the safety risks of the battery. The electrolyte infiltration speed is affected by the viscosity of the electrolyte, the amount of electrolyte, the diaphragm, the porosity of the electrode, the vacuum degree during injection, the temperature, etc., and slows down with the increase of the infiltration depth. The consumption of electrolyte during battery formation will also change the distribution of electrolyte in the battery. Therefore, when conducting experiments to optimize the parameters and conditions of electrolyte injection, static and formation, it is necessary to have an accurate and fast method to understand the distribution of electrolyte in the battery in order to maximize the battery cycle performance and safety. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for testing the degree and infiltration path of battery electrolyte. This method uses the scattering phenomenon when blue light penetrates the diaphragm and phosphor to perform accurate testing according to different colors corresponding to different infiltration degrees. It can intuitively understand the electrolyte distribution in the battery, and can further optimize the electrolyte injection and infiltration parameters to improve the battery's cycle performance and safety.

[0005] The present invention provides a method for testing the degree of battery electrolyte infiltration, comprising:

[0006] Taking a battery containing a fluorescent agent in an electrolyte, disassembling the battery, wherein the battery further comprises a positive electrode sheet, a negative electrode sheet, and a separator, removing the separator from the battery, and volatilizing the electrolyte;

[0007] The diaphragm comprises a first surface and a second surface, the first surface of the diaphragm is irradiated with blue light, the blue light penetrates the diaphragm, and the second surface of the diaphragm is photographed, and the color distribution on the second surface of the diaphragm is recorded;

[0008] The degree of wetting of the electrolyte is determined.

[0009] Furthermore, the fluorescent agent comprises at least one of acridine orange, rhodamine (Rhodamine phosphor), hoechst, DAPI (4',6-diamidino-2-phenylindole), Alexa Fluor, DyLight, Cy3 (Sulfo-Cyanine3), Cy5 (Sulfo-Cyanine5) and fluorescent orange.

[0010] Furthermore, the mass percentage of the fluorescent agent in the electrolyte is less than 0.1%.

[0011] In the above method, the wavelength of the blue light may be 350 nm to 600 nm.

[0012] In the above method, the criteria for determining the degree of electrolyte infiltration are: the area on the diaphragm that is blue in color and has no fluorescent effect is an area that is not infiltrated by the electrolyte; the area on the diaphragm that is blue in color and has a fluorescent effect is an area with poor electrolyte infiltration; the area on the diaphragm that is not blue in color and has a fluorescent effect is an area with good electrolyte infiltration.

[0013] As an example, the fluorescent agent is Cy3, and the criteria for determining the degree of electrolyte infiltration are: the area on the diaphragm that is dark blue in color is the area not infiltrated by the electrolyte; the area on the diaphragm that is bright blue in color is the area with poor electrolyte infiltration; and the area on the diaphragm that is bright orange in color is the area with good electrolyte infiltration.

[0014] In the criteria for determining the degree of electrolyte wetting, a boundary between the electrolyte non-wetting area and the electrolyte poorly wetting area appears white.

[0015] In the above method, the electrolyte is volatilized by drying or air-drying.

[0016] In the above method, the battery disassembly is performed after any process of liquid filling, standing, formation, aging, charging, discharging, storage or cycling.

[0017] The present invention further provides a method for testing a battery electrolyte infiltration path, comprising:

[0018] By testing the electrolyte infiltration degree using any of the methods described above, the electrolyte infiltration path can be determined.

[0019] The present invention has the following beneficial effects:

[0020] (1) The present invention utilizes the scattering phenomenon when blue light penetrates the diaphragm and phosphor, and distinguishes the infiltration of the battery electrode by observing the color presented on the diaphragm. The electrolyte distribution area and distribution gradient map can be obtained with high precision, and a fast, low-cost and accurate electrolyte infiltration test method is established. The distribution of the electrolyte on the positive electrode or negative electrode in the battery is reflected during the injection, standing, formation and post-processing to adjust the battery design, manufacturing parameters and conditions.

[0021] (2) The method of the present invention can visually analyze the electrolyte distribution of the core before disassembly after the battery is disassembled, the core is unfolded, and the electrolyte volatilizes. The method has high resolution and can reflect the liquid deficiency position that cannot be identified conventionally.

[0022] (3) In the method of the present invention, the mass percentage of the phosphor in the electrolyte containing the phosphor is less than or equal to 0.0095%. The viscosity of the electrolyte after adding the phosphor is similar to the viscosity of the electrolyte without adding the phosphor, which does not affect the wetting properties of the electrolyte. Moreover, no additional wetting agent needs to be added, and the overall liquid injection volume can be maintained.

[0023] (4) Based on the electrode liquid wettability test method of the present invention, by photographing and recording the changes in the color distribution on the diaphragm over time during the electrolyte infiltration process, the electrolyte infiltration path is determined according to the color change, which can be used to study the electrolyte infiltration path in the battery and develop corresponding innovative infiltration methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0025] Figure 1 Schematic diagram of a method for testing the degree of battery electrolyte infiltration in an embodiment of the present invention.

[0026] Figure 2 These are the wettability test results in Example 1 of the present invention. From left to right, they are the wettability test results of the present invention (a photo of the diaphragm after blue light passing through the infiltration), the interface after the negative electrode is disassembled before formation, the interface after the positive electrode is disassembled before formation, and the negative electrode surface irradiated with blue light.

[0027] Figure 3 These are the wettability test results of the present invention before and after optimizing the process parameters in Example 2 of the present invention and the corresponding negative electrode plate interface at 100% SOC.

[0028] Figure 4 This is the test result after adjusting the phosphor content in the electrolyte to 0.0095% in Example 3 of the present invention and optimizing the process parameters according to Example 2.

[0029] Figure 5 This is the test result after adjusting the phosphor content in the electrolyte to 0.1% in Comparative Example 1 of the present invention and optimizing the process parameters according to Example 2. DETAILED DESCRIPTION

[0030] In the existing technology, pigments are added to the electrolyte to determine the degree of electrolyte penetration based on the color area distribution, or fluorescent agents are added to the electrolyte to determine the degree of electrolyte penetration based on the intensity of fluorescence. However, there are problems such as large experimental errors and low resolution.

[0031] To understand the distribution of electrolyte within a battery, one can disassemble the battery after filling, standing, or forming, unfolding the electrodes and separator to visually observe the degree of electrolyte penetration. However, due to the high volatility of the electrolyte, this test method has low accuracy and cannot assess the actual degree of electrolyte penetration.

[0032] This method uses a colored wetting agent to perform injection, infiltration, and formation with the electrolyte. The color distribution on the diaphragm and electrode is then used to determine the degree of electrolyte wetting. This method requires a relatively large amount of pigment (0.1%) to achieve effective differentiation. Adding large amounts of pigment increases electrolyte viscosity, thus altering its wetting ability. Furthermore, since the wetting agent is not very volatile, it may flow during disassembly, resulting in large experimental errors and discrepancies with actual results.

[0033] After filling and soaking the battery with a fluorescent electrolyte, the battery material, such as the positive or negative electrode, is removed from the battery casing and unfolded. The surface of the battery material fluoresces under illumination. The intensity of the fluorescence emitted from the surface of the battery material is used to determine the consistency of the electrolyte's soaking of the battery. Using fluorescence intensity to determine wettability has a low resolution, requiring a significant difference in the amount of phosphor to produce a clear difference. However, excessive phosphor content can affect the viscosity of the electrolyte, thereby affecting its wettability. Furthermore, fluorescence intensity can be affected by the illumination and reflection angle of the light source, making it difficult to accurately distinguish between well-wetted and poorly wetted areas of the battery with the naked eye.

[0034] In order to solve the above technical problems, the present invention provides a method for testing the degree of electrolyte infiltration in a battery, comprising: taking a battery containing a fluorescent agent in the electrolyte, disassembling the battery, the battery also comprising a positive electrode plate, a negative electrode plate and a separator, removing the separator from the battery, and volatilizing the electrolyte; the separator comprises a first surface and a second surface, irradiating the first surface of the separator with blue light, the blue light penetrating the separator, photographing the second surface of the separator, and recording the color distribution on the second surface of the separator; determining the degree of electrolyte infiltration. Figure 1As shown, the diaphragm is placed flat on top of a blue light source, and the first side (back side) of the diaphragm is illuminated with blue light. The blue light emitted by the blue light lamp passes through the diaphragm soaked with the electrolyte containing fluorescent powder, and is photographed on the second side (front side) of the diaphragm to record the color distribution on the second side of the diaphragm. Among them, the diaphragm is a porous light-transmitting material, which appears dark blue when penetrated by blue light. The fluorescent electrolyte soaks the diaphragm and evaporates and then is penetrated by blue light. It shows a fluorescent color, which forms a sharp color difference with the blue position of the lack of liquid. Therefore, it can accurately distinguish between the electrode lacking liquid and the well-infiltrated area. The present invention utilizes the sharp contrast of blue light scattering and fluorescence. By observing the color presented on the entire diaphragm, the infiltration of the electrode in the battery can be distinguished, which can greatly improve the resolution and test accuracy of the well-infiltrated and poorly infiltrated areas.

[0035] In order to make the color contrast more obvious, the fluorescent agent of the present invention contains fluorescent powder, preferably at least one of acridine orange, rhodamine, hoechst, DAPI, Alexa Fluor, DyLight, Cy3, Cy5 and fluorescent orange.

[0036] According to some embodiments of the present invention, the mass percentage of phosphor in the electrolyte is less than 0.1%, such as 0.00001% to 0.09%. The viscosity data of the electrolyte with phosphor within this range is similar to that of conventional electrolyte. In some embodiments, the mass percentage of phosphor in the electrolyte is 0.00001% to 0.05%. In some embodiments, the mass percentage of phosphor in the electrolyte is 0.00001% to 0.01%. In some embodiments, the mass percentage of phosphor in the electrolyte is 0.00001% to 0.095%. When the phosphor content is within the above range, the viscosity of the electrolyte can be less affected by the phosphor, and the wetting properties of the electrolyte can be better reflected. In embodiments of the present invention, the viscosity of electrolytes with a phosphor content of 0.00001% to 0.1% was tested. The results are shown in Table 1. Excessive phosphor content will affect the viscosity of the electrolyte, thereby affecting its wetting properties. In the present invention, the amount of phosphor can be appropriately adjusted within the above range according to the actual dissolution of the phosphor in the electrolyte.

[0037] According to the present invention, the wavelength of the blue light used in the present invention is 350-600 nm. In at least one embodiment of the present invention, the wavelength of the blue light is 450-550 nm.

[0038] According to the present invention, the criteria for determining the degree of electrolyte wetting are as follows: an area on the diaphragm that is blue and has no fluorescence effect is an area not wetted by the electrolyte; an area on the diaphragm that is blue and has a fluorescence effect is an area with poor electrolyte wetting; and an area on the diaphragm that is not blue and has a fluorescence effect is an area with good electrolyte wetting. The colors of the areas not wetted by the electrolyte, the areas with poor electrolyte wetting, and the areas with good electrolyte wetting are different and can be distinguished by the naked eye. In at least one embodiment of the present invention, Cy3 is used as a fluorescent agent. When the electrolyte containing this fluorescent agent is penetrated by blue light after the electrolyte evaporates from the diaphragm, the fluorescent color exhibits a bright orange color. The criteria for determining the degree of electrolyte wetting are as follows: an area on the diaphragm that is dark blue is an area not wetted by the electrolyte; an area on the diaphragm that is bright blue is an area with poor electrolyte wetting; and an area on the diaphragm that is bright orange is an area with good electrolyte wetting. In addition, the boundary between the electrolyte non-wetted area and the electrolyte poorly wetted area appears white.

[0039] According to the present invention, the battery in the testing method of the present invention may be a wound lithium battery or a laminated lithium battery.

[0040] The electrolyte in the testing method of the present invention can be any electrolyte commonly used in lithium-ion batteries.

[0041] The separator in the testing method of the present invention can be any separator commonly used in lithium-ion batteries. For example, in at least one embodiment of the present invention, the separator is a PP separator.

[0042] To avoid affecting the electrolyte distribution, the electrolyte is evaporated by drying or air-drying. When the battery is disassembled, as the electrolyte evaporates, the phosphor crystallizes in its original position and remains in the separator. This prevents the color infiltrant from flowing after disassembly, reducing test errors and greatly improving test reliability.

[0043] According to the present invention, the battery is disassembled after the filling is completed. Specifically, the battery can be disassembled after the filling, standing, capacity separation, formation, aging, charging, discharging, storage or circulation processes to reflect the distribution of the electrolyte in the coil after different processes, optimize the electrolyte filling, standing and formation parameters and conditions experiments, and adjust the battery design, manufacturing parameters and conditions. Specifically, the test results of different filling and infiltration or formation process parameters are compared to find the key factors affecting the battery infiltration (for example, the battery infiltration degree is compared using different standing times, temperatures, etc., to find the injection and infiltration conditions that have the greatest impact on the infiltration degree and are easier to achieve and economical); the test results of different design parameters, such as different surface densities, different compaction densities, etc., can also be compared to find the influence of battery design on battery infiltration; it can also be applied to other applicable scenarios.

[0044] Based on the above-mentioned electrolyte wetting degree testing method, the present invention also provides a method for testing the battery electrolyte wetting path, including: using the above-mentioned method to test the electrolyte wetting degree and determine the electrolyte wetting path. Specifically, the changes in the electrolyte non-wetted area, the electrolyte poorly wetting area and / or the electrolyte well-wetted area on the diaphragm during the electrolyte wetting process are recorded and recorded, and the electrolyte wetting path can be determined based on the changes. This method can be used to study the electrolyte wetting paths of different battery designs and develop corresponding innovative wetting methods.

[0045] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0047] Preparation of positive electrode

[0048] The positive electrode active material NCM622, the conductive agent acetylene black, and the binder PVDF were mixed in a mass ratio of 96:2:2, and the solvent NMP was added. The mixture was stirred under the action of a vacuum mixer until the system became uniform to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain positive electrode sheets.

[0049] Preparation of negative electrode sheet

[0050] The negative electrode active material graphite, the conductive agent acetylene black, the thickener CMC, and the binder SBR are mixed in a mass ratio of 96.5:1:1:1.5, and deionized water solvent is added. The mixture is stirred under the action of a vacuum mixer until the system becomes uniform to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain a negative electrode sheet.

[0051] Preparation of electrolyte

[0052] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 was dissolved in the above organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L. Based on the total mass of the electrolyte, 2% vinylene carbonate and the phosphor described in the examples were added.

[0053] Preparation of isolation membrane

[0054] Polypropylene film was selected as the separator.

[0055] Preparation of lithium-ion batteries

[0056] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrode sheets to provide insulation. The stack is then wound to form a core. The core is placed in an outer packaging shell, dried, and then filled with electrolyte. The lithium-ion battery is obtained through vacuum packaging, resting, and formation. The blue light used in the following examples is all 500nm in wavelength.

[0057] Example 1

[0058] This embodiment is used to illustrate a method for testing the degree of liquid infiltration of battery electrodes.

[0059] Follow the steps below to test the battery electrolyte infiltration level:

[0060] 1) Add phosphor Cy3 into the electrolyte and dissolve it. The amount of phosphor Cy3 is 0.001%.

[0061] 2) Use the above-mentioned electrolyte containing fluorescent components to inject the electrolyte. After injection, disassemble the battery, remove the core and unfold it, separate the separator from the core, and allow the electrolyte on the separator to evaporate naturally.

[0062] 3) After the electrolyte has completely evaporated (dry naturally), Figure 1 As shown, place the diaphragm flat on a blue light lamp, illuminate the back of the diaphragm with blue light, and let the blue light penetrate the diaphragm. Observe the color distribution on the front of the diaphragm penetrated by the blue light and take photos to record it, so as to determine the degree of electrolyte infiltration.

[0063] The experimental results are as follows Figure 2 As shown, the diaphragm soaked in fluorescent electrolyte shows different colors after being penetrated by blue light, as follows: the bright orange area is the well-wetted area, the bright blue position is the poorly wetting area, the dark blue position is the liquid-free area, and the boundary between the lack of liquid and the no-liquid area is white. The well-wetted area and the blue position of the lack of liquid form a clear color difference, so the lack of liquid and the well-wetted area can be accurately distinguished. The areas of different colors can correspond to the wettability of the electrode one by one. Because the electrode cannot transmit light, the method of blue light penetration of the present invention cannot be used, and this effect cannot be achieved by irradiating the surface of the electrode.

[0064] Example 2

[0065] This example is used to study the effects of different infiltration processes on the battery infiltration results, and their corresponding effects on the negative electrode interface after high-rate cycling.

[0066] The method of the present invention is used to evaluate the electrolyte infiltration condition before the infiltration process is optimized. The specific steps are as follows:

[0067] 1) The pre-injection batteries were divided into two groups for injection: one group used a conventional electrolyte, and the other group used an electrolyte containing 0.00001% Cy3 phosphor. After injection, both groups were allowed to stand and undergo formation. The standing temperature and time were 40°C for 1 hour, the formation voltage range was 0-4V, and the magnification was 0.1C. The formation temperature and vacuum were 40°C and -50kPa.

[0068] 2) After formation, the battery filled with fluorescent electrolyte is disassembled, the reel is opened to separate the diaphragm from the electrode, and the electrolyte on the diaphragm is allowed to evaporate naturally. Then, blue light is used to penetrate the diaphragm and photos are taken to record the color distribution on the diaphragm.

[0069] 3) After formation, the battery was subjected to 10 charge-discharge cycles at a rate of 5C and a voltage range of 2.8-4.4V. After ten cycles, the battery was disassembled at 100% SOC to observe the interface of the fully charged negative electrode.

[0070] The electrolyte wettability test results in step 2) show that ( Figure 3 -wetting test results before optimization), a bright blue horizontal line appears in the center of the diaphragm, a fishtail-shaped bright blue area appears at the end of the horizontal line, and the rest of the area is bright orange. This result shows that using the above injection, infiltration and formation methods, a horizontal line and a fishtail-shaped poor infiltration area appear in the center of the core. In step 3), after the battery is cycled at a high rate, the fully charged negative electrode interface results show ( Figure 3 - Optimization of the negative electrode interface at 100% SOC before and after cycling. A dark yellow horizontal line at the center of the negative electrode appears with a fishtail-shaped line at the end. Spots of lithium deposition are observed near the dark line, while the rest of the negative electrode appears golden yellow, consistent with a fully charged state. The abnormal location in the negative electrode interface results matches the electrolyte wettability test results from step 2), indicating that the dark yellow horizontal line, fishtail-shaped line, and lithium deposition are related to poor electrolyte wettability at that location.

[0071] Based on the above experimental results, the battery rest and formation conditions were optimized. Take the same pre-filled batteries as those used in the above experiment and divide them into two groups for filling. Note: the rest and formation temperatures are increased to 60°C to improve the electrolyte wetting ability. The other parameters and operation methods are exactly the same as in step 1) above. Then proceed to steps 2) and 3). After optimizing the rest and formation temperatures, the electrolyte wetting test results show that the diaphragm is evenly distributed bright orange ( Figure 3 -wetting test results after optimization), indicating that the electrode is well wetted overall; after high-rate cycling, the fully charged negative electrode interface is in good condition, with the entire surface showing a uniform golden color and no abnormalities ( Figure 3 -100% SOC negative electrode plate interface after optimization cycle). The optimized fully charged negative electrode plate interface is uniform, which corresponds to the bright orange color of the separator in the electrolyte wettability test results.

[0072] The above results demonstrate that the electrolyte wetting test method of the present invention accurately reflects the distribution of electrolyte within the winding core and can be effectively applied to optimize battery wetting parameters and conditions. It can also be applied to other scenarios requiring understanding of electrolyte wetting.

[0073] Example 3

[0074] The battery electrolyte wetting degree was tested according to the steps in Example 2, except that the phosphor content in the phosphor-containing electrolyte was adjusted to 0.0095%. After optimizing the standing and formation temperatures, the electrolyte wetting degree test results showed that the separator was evenly distributed bright orange.

[0075] The experimental results are shown in Figure 4 , Figure 4 and Figure 3 -The wettability test results after optimization are basically consistent, indicating that the electrolyte with this phosphor content does not affect the wettability of the electrolyte.

[0076] Comparative Example 1

[0077] The battery electrolyte wetting degree was tested according to the steps in Example 1, except that the phosphor content in the phosphor-containing electrolyte was adjusted to 0.1%. After optimizing the standing and formation temperatures, the electrolyte wetting degree test results showed that a bright blue area with poor wetting appeared on the diaphragm.

[0078] The experimental results are shown in Figure 5 , Figure 5 and Figure 3 - The results of the infiltration test after optimization showed poorer infiltration.

[0079] The viscosity of the electrolytes before and after the addition of phosphors in the above examples and comparative examples was tested, and the percentage increase in viscosity was calculated. The experimental results are shown in Table 1. It can be seen that excessive phosphor content can lead to excessive viscosity, which affects the electrolyte's wetting ability.

[0080] Table 1. Electrolyte viscosity growth with different phosphor contents

[0081]

[0082] Example 5

[0083] This embodiment is used to illustrate a method for testing the battery electrode liquid infiltration path.

[0084] like Figure 3 The results of the wettability test before and after optimization show that before optimization, a bright blue horizontal line appears at the center of the diaphragm, with a fishtail-shaped bright blue area at the end of the line, and the rest of the area appears bright orange. After optimization, the diaphragm exhibits a uniform distribution of bright orange. This indicates that the wettability path moves from the periphery of the diaphragm toward the center.

[0085] The present invention has been described in detail above. It will be apparent to those skilled in the art that the present invention can be practiced over a wide range of parameters, concentrations, and conditions without departing from the spirit and scope of the present invention and without unnecessary experimentation. Although specific embodiments have been described herein, it should be understood that further modifications may be made to the present invention. In short, according to the principles of the present invention, this application is intended to cover any variations, uses, or improvements to the present invention, including those made using conventional techniques known in the art that depart from the scope disclosed herein. Applications of the essential features may be made within the scope of the appended claims.

Claims

1. A method for testing the degree of battery electrolyte infiltration, comprising: Taking a battery containing a fluorescent agent in an electrolyte, disassembling the battery, wherein the battery further comprises a positive electrode sheet, a negative electrode sheet, and a separator, removing the separator from the battery, and volatilizing the electrolyte; The diaphragm comprises a first surface and a second surface, the first surface of the diaphragm is irradiated with blue light, the blue light penetrates the diaphragm, and the second surface of the diaphragm is photographed, and the color distribution on the second surface of the diaphragm is recorded; determining a degree of wetting of the electrolyte; The fluorescent agent comprises at least one of acridine orange, rhodamine, hoechst, 4',6-diamidino-2-phenylindole, Alexa Fluor, DyLight, Cy3, Cy5 and fluorescent orange; The mass percentage of the fluorescent agent in the electrolyte is less than 0.1%.

2. The method for testing the degree of battery electrolyte infiltration according to claim 1, wherein: The wavelength of the blue light is 450nm~550nm.

3. The method for testing the battery electrolyte infiltration degree according to claim 1, wherein: The criteria for determining the degree of electrolyte infiltration are as follows: the area on the diaphragm that is blue in color and has no fluorescent effect is an area that is not infiltrated by the electrolyte; the area on the diaphragm that is blue in color and has a fluorescent effect is an area with poor electrolyte infiltration; the area on the diaphragm that is not blue in color and has a fluorescent effect is an area with good electrolyte infiltration.

4. The method for testing the battery electrolyte infiltration degree according to claim 1, wherein: The fluorescent agent is Cy3, and the criteria for determining the degree of electrolyte infiltration are: the area on the diaphragm that is dark blue in color is the area not infiltrated by the electrolyte; the area on the diaphragm that is bright blue in color is the area with poor electrolyte infiltration; and the area on the diaphragm that is bright orange in color is the area with good electrolyte infiltration.

5. The method for testing the battery electrolyte infiltration degree according to claim 4, wherein: In the criteria for determining the degree of electrolyte wetting, a boundary between the electrolyte non-wetting area and the electrolyte poorly wettable area appears white.

6. The method for testing the battery electrolyte infiltration degree according to claim 1, wherein: The electrolyte is volatilized by drying or air-drying.

7. The method for testing the degree of battery electrolyte infiltration according to any one of claims 1 to 6, characterized in that: The battery disassembly is performed after any process of liquid filling, standing, formation, aging, charging, discharging, storage or circulation.

8. A method for testing a battery electrolyte wetting path, comprising: The electrolyte infiltration degree is tested using the method according to any one of claims 1 to 7 to determine the electrolyte infiltration path.

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