A method and system for testing gassing porosity of test tabs

Abstract

The application provides a method and system for testing liquid absorption porosity of an electrode sheet. The mass of electrolyte absorbed by the electrode sheet is measured, the density of the corresponding electrolyte is obtained, and the volume of the electrolyte absorbed by the electrode sheet is calculated. The mass of the electrode sheet is measured, the compaction density of the electrode sheet is obtained, and the volume of the electrode sheet is calculated. The ratio of the volume of the electrolyte absorbed by the electrode sheet to the volume of the electrode sheet is the liquid absorption porosity.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material evaluation technology, and in particular relates to a method and system for testing the liquid absorption porosity of electrode sheets. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Electrodes possess porous characteristics, enabling them to absorb electrolyte. In material and battery development, electrode porosity is a crucial parameter, closely related to battery internal resistance and electrolyte injection volume in battery design. In this application, porosity refers to the effective porosity of the electrode for electrolyte absorption under normal pressure. Excessive electrode porosity results in a weaker conductive network and higher internal resistance; conversely, insufficient porosity leads to lower electrolyte absorption, affecting battery electrolyte retention. Therefore, electrode porosity is an important parameter for material selection and battery design.

[0004] Currently, mercury intrusion porosimetry (MIP) is commonly used to test electrode porosity. While MIP can accurately measure electrode porosity, it is complex and expensive, and because it typically tests only a single sample, the results can be somewhat limited. Furthermore, what is actually needed to evaluate is the porosity of the electrode absorbing the electrolyte, while MIP measures the porosity of the electrode absorbing mercury, whose density is 13.59 g / cm³. 3 Electrolyte density 1.22 g / cm³ 3 The two are not the same, and the data obtained from this cannot be accurately equated to the porosity of the electrolyte. Furthermore, existing gas adsorption methods are time-consuming and cannot meet the needs of rapid testing of a large number of electrodes, resulting in low efficiency. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for testing the liquid absorption porosity of electrode sheets, providing a reference for battery material selection and battery development and design.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0007] In the first aspect, a method for testing the liquid absorption porosity of an electrode is disclosed, including:

[0008] Measure the mass of electrolyte absorbed by the electrode, obtain the density of the corresponding electrolyte, and calculate the volume of electrolyte absorbed by the electrode.

[0009] Measure the mass of the electrode to obtain its compaction density and calculate its volume;

[0010] The ratio of the volume of electrolyte absorbed by the electrode to the volume of the electrode is called the electrolyte porosity.

[0011] As a further technical solution, the ratio of the mass of electrolyte absorbed by the electrode to the mass of the electrode is used to obtain the relative percentage of the electrolyte absorbed by the electrode.

[0012] As a further technical solution, before measurement, the following steps are also included: electrode adhesive application: green adhesive of selected width is applied in parallel segments to the electrode.

[0013] As a further technical solution, the selected width of green adhesive is segmented and parallelly adhered to the electrode sheet before the electrode sheet is cut: the electrode sheet is cut after the adhesive is applied to form small pieces of a certain size.

[0014] As a further technical solution, after the electrode is cut, it is dried by placing the cut electrode in a set temperature range for a set time.

[0015] As a further technical solution, after the electrode is dried, it is weighed and soaked in electrolyte. The electrode with good surface after inspection is weighed and its mass is recorded. The electrode with measured mass is stored in the corresponding sealed container in sequence.

[0016] Pour the electrolyte that matches the electrode into the appropriate container. The electrolyte should completely cover the electrode. Record the soaking start time. After a certain soaking time, remove the electrode, wipe it dry with lint-free paper, and weigh the electrode that has absorbed the electrolyte.

[0017] As a further technical solution, the quality of the electrolyte absorbed by the electrode plate excludes the quality of the electrolyte absorbed by the green adhesive.

[0018] As a further technical solution, the quality of the electrode sheet excludes the quality of the current collector and the quality of the green adhesive. When testing the weight of the electrode sheet, it is necessary to ensure that the electrolyte on the surface of the green adhesive has been wiped clean.

[0019] As a further technical solution, the processes of electrode application, drying, and soaking must all ensure that the electrode is flat, wrinkle-free, and free of air bubbles.

[0020] In a first aspect, a system for testing the liquid absorption porosity of an electrode is disclosed, comprising:

[0021] Green glue, weight measuring equipment, cutting equipment, drying equipment, and host computer;

[0022] The green adhesive is adhered to the electrode in segments in parallel.

[0023] The cutting equipment cuts the electrode sheet after it has been coated with green adhesive into small pieces of a certain size;

[0024] The drying equipment places the cut electrode sheets at a set temperature and dries them for a set time.

[0025] The drying equipment weighs the dried electrode sheets with good surface inspection, and also weighs the electrode sheets after soaking in electrolyte, thus measuring the mass of the electrode sheets that have absorbed the electrolyte.

[0026] The host computer obtains the density of the electrolyte by measuring the mass of the electrolyte absorbed by the electrode, and calculates the volume of the electrolyte absorbed by the electrode.

[0027] Based on the mass of the electrode, the compaction density of the electrode is obtained, and the volume of the electrode is calculated.

[0028] The liquid absorption porosity is the ratio of the volume of electrolyte absorbed by the electrode to the volume of the electrode.

[0029] The above one or more technical solutions have the following beneficial effects:

[0030] The porosity tested by the method of this invention is the effective porosity of the electrode for absorbing electrolyte under normal pressure, which is closer to the actual design requirements of the battery. It provides an accurate reference for battery material selection and battery development and design. It is simple to operate, has low testing cost, and can test multiple parallel samples at the same time. It overcomes the problems of high cost of mercury porosimetry and the one-sidedness of test results caused by single sampling.

[0031] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 This is a schematic diagram of the adhesive application for cutting the electrode sheet required for testing the liquid absorption weight percentage and liquid absorption porosity of the electrode sheet in an embodiment of the present invention; the active material layer is the positive and negative electrode material of the battery cell, which is coated on the current collector and becomes the electrode sheet after coating.

[0034] Figure 2 This is a flowchart illustrating the method for testing the liquid absorption weight percentage and liquid absorption porosity of the electrode according to an embodiment of the present invention. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0037] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0038] Example 1

[0039] This embodiment discloses a method for testing the liquid absorption porosity of an electrode, including:

[0040] The volume of electrolyte absorbed by the electrode (V0) can be calculated by measuring the mass of electrolyte absorbed by the electrode (W0, excluding the mass of electrolyte absorbed by the green adhesive) and the corresponding electrolyte density (ρ). The volume of the electrode (V1) can be calculated by measuring the mass of the electrode (W1, excluding the mass of the current collector and the green adhesive) and the compacted density of the electrode (P). The relative percentage of liquid absorbed by the electrode (θ) and the liquid absorption porosity (Φ) can be obtained using the formulas θ = (W0 / W1)*100% and Φ = (V0 / V1)*100%.

[0041] During the test, the electrolyte density can be obtained by measuring with a densitometer; specifically, the electrolyte used (and paired with) the electrode being tested in the lithium-ion battery can also be used.

[0042] The specific steps of the method for testing the liquid absorption porosity of electrode sheets in this embodiment include:

[0043] (1) Prepare the electrode raw materials to be tested, as well as instruments and equipment such as green glue, electronic scale, and oven; the electronic scale used for testing should have an accuracy of 0.1mg.

[0044] The aforementioned green adhesive can be selected from the insulating tape (green adhesive) - L 40mm wide from Jiangsu Rongqi Optoelectronic Materials Technology Co., Ltd.; it is used to protect the electrode from falling off when soaked in electrolyte, while allowing the electrolyte to pass through.

[0045] (2) The 40mm wide green adhesive segments were adhered parallel to the electrode sheet to obtain the following: Figure 1 The adhesive electrode shown.

[0046] (3) After the electrode is coated with adhesive, use a scalpel to cut small pieces of 30mm*50mm size. The cut pieces should have a flat blade and few burrs.

[0047] (4) Place the cut electrode sheet at 85℃ and dry for 4 hours to remove moisture.

[0048] (5) Weigh the electrodes with good surfaces after inspection and record the mass of blank green adhesive (0.1885g, 0.1916g, 0.1924g...) and the mass of the electrodes (0.6179g, 0.6135g, 0.6145g...). Store the electrodes that have been weighed in the corresponding sealed containers in order.

[0049] Pour the electrolyte solution matching the electrode into the appropriate container, ensuring the electrolyte completely covers the electrode, and soak for 24 hours. Weigh the green gel after absorbing the electrolyte (0.1951g, 0.1980g, 0.2000g...) and the electrode after absorbing the electrolyte (0.7267g, 0.7214g, 0.7152g...).

[0050] (6) Data processing: θ = (W0 / W1)*100% and Φ = (V0 / V1)*100% = (W0 / ρ) / (W1 / p)*100%, where W0 is the mass of electrolyte absorbed by the electrode (excluding the mass of electrolyte absorbed by the green glue, which needs to be prepared as a standard sample and weighed in advance), W1 is the mass of the electrode (excluding the mass of the current collector and the mass of the green glue, which can be calculated based on density, area and thickness), V0 is the volume of electrolyte absorbed by the electrode, and V1 is the volume of the electrode. In this example, the electrolyte density ρ = 1.185 g / cm3 and the electrode compaction density P = 1.65 g / cm3.

[0051] The calculation results are shown in Table 1 below:

[0052] Table 2

[0053]

[0054] It should be noted that the processes of applying adhesive, drying, and soaking the electrode must all ensure that it is flat, wrinkle-free, and free of air bubbles. When testing the weight of the electrode, ensure that the electrolyte on the surface of the green adhesive has been wiped clean. The mass of electrolyte absorbed by the electrode (W0) excludes the mass of electrolyte absorbed by the green adhesive. The mass of the electrode (W1) excludes the mass of the current collector and the mass of the green adhesive.

[0055] The commonly used principle of mercury porosimetry (MPA) is based on the well-known Washburn equation, Pr = -2γcosθ. With θ and γ remaining constant, as the pressure gradually increases, mercury will gradually enter pores with smaller diameters. θ is the contact angle of mercury with the solid, and γ is the surface tension of mercury. If the pressure changes from P1 to P2, corresponding to pore diameters r1 and r2 respectively, and the volume of mercury (ΔV) injected per unit mass of sample into the pore between the two diameters is measured, then by continuously changing the measuring pressure, the amount of mercury entering pores of different sizes can be measured, thus obtaining the pore size distribution. Pore types: There are open pores and closed pores. Mercury porosimetry measures the porosity of open pores (channels connected to the outer surface of the sample) that absorb mercury.

[0056] The porosity tested by the sub-technical solution in this embodiment is the effective porosity of the electrode for absorbing electrolyte under normal pressure, which is closer to the actual design requirements of the battery. It provides an accurate reference for battery material selection and battery development and design. It is also simple to operate, has low testing cost, and can test multiple parallel samples at the same time. It overcomes the problems of high cost of mercury porosimetry and the one-sidedness of test results caused by single sampling.

[0057] Example 2

[0058] The purpose of this embodiment is to provide a system for testing the liquid absorption porosity of electrode sheets, including:

[0059] Green glue, weight measuring equipment, cutting equipment, drying equipment, and host computer;

[0060] The green adhesive is adhered to the electrode in segments in parallel.

[0061] The cutting equipment cuts the electrode sheet after it has been coated with green adhesive into small pieces of a certain size;

[0062] The drying equipment places the cut electrode sheets at a set temperature and dries them for a set time.

[0063] The drying equipment weighs the dried electrode sheets with good surface inspection, and also weighs the electrode sheets after soaking in electrolyte, thus measuring the mass of the electrode sheets that have absorbed the electrolyte.

[0064] The host computer obtains the density of the electrolyte by measuring the mass of the electrolyte absorbed by the electrode, and calculates the volume of the electrolyte absorbed by the electrode.

[0065] Based on the mass of the electrode, the compaction density of the electrode is obtained, and the volume of the electrode is calculated.

[0066] The liquid absorption porosity is the ratio of the volume of electrolyte absorbed by the electrode to the volume of the electrode.

[0067] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for testing the liquid absorption porosity of an electrode, characterized in that, include: Measure the mass of electrolyte absorbed by the electrode, obtain the density of the corresponding electrolyte, and calculate the volume of electrolyte absorbed by the electrode. Measure the mass of the electrode to obtain its compaction density and calculate its volume; The ratio of the volume of electrolyte absorbed by the electrode to the volume of the electrode is called the liquid absorption porosity. The ratio of the mass of electrolyte absorbed by the electrode to the mass of the electrode itself yields the relative percentage of electrolyte absorbed by the electrode. Before measurement, the process also includes: electrode adhesive application: applying green adhesive of selected width in parallel segments to the electrode; electrode drying after cutting: placing the cut electrode in a set temperature range for a set time to dry; electrode weighing and electrolyte immersion after drying: weighing the electrode and recording the mass of the electrode with good surface after inspection; and storing the electrode with measured mass in the corresponding sealed container in order. Pour the electrolyte that matches the electrode into the appropriate container. The electrolyte should cover the electrode. Record the soaking start time. After a certain soaking time, take out the electrode, wipe it dry with lint-free paper, and weigh the electrode that has absorbed the electrolyte. The formula for calculating the liquid absorption porosity is as follows: Φ = (V0 / V1) * 100% = (W0 / ρ) / (W1 / p) * 100%; where W0 is the mass of electrolyte absorbed by the electrode, W1 is the mass of the electrode, V0 is the volume of electrolyte absorbed by the electrode, V1 is the volume of the electrode; ρ is the electrolyte density, and P is the electrode compaction density; where W0 excludes the mass of electrolyte absorbed by the electrode, and W1 excludes the mass of the current collector and the mass of the electrode.

2. The method for testing the liquid absorption porosity of an electrode as described in claim 1, characterized in that, After the selected width of green adhesive is applied in parallel segments to the electrode, the electrode is cut: the electrode is cut after the adhesive is applied to form small pieces of a certain size.

3. The method for testing the liquid absorption porosity of an electrode as described in claim 1, characterized in that, When testing the weight of the electrode, ensure that the electrolyte on the surface of the green adhesive has been wiped clean.

4. The method for testing the liquid absorption porosity of an electrode as described in claim 1, characterized in that, The processes of applying adhesive to the electrode, drying, and soaking must all ensure that the electrode is flat, wrinkle-free, and free of air bubbles.

5. A system for testing the liquid absorption porosity of an electrode, characterized in that, include: Green adhesive, weight measuring equipment, cutting equipment, drying equipment, and host computer; The green adhesive is adhered to the electrode in segments in parallel. The cutting equipment cuts the electrode sheet after it has been coated with green adhesive into small pieces of a certain size; The drying equipment places the cut electrode sheets at a set temperature and dries them for a set time. The drying equipment weighs the dried electrode sheets with good surface inspection, and also weighs the electrode sheets after soaking in electrolyte, measuring the mass of the electrode sheets that have absorbed the electrolyte. The host computer obtains the density of the electrolyte by measuring the mass of the electrolyte absorbed by the electrode, and calculates the volume of the electrolyte absorbed by the electrode. The ratio of the mass of electrolyte absorbed by the electrode to the mass of the electrode itself yields the relative percentage of electrolyte absorbed by the electrode. Based on the mass of the electrode, the compaction density of the electrode is obtained, and the volume of the electrode is calculated. The ratio of the volume of electrolyte absorbed by the electrode to the volume of the electrode is called the liquid absorption porosity. The formula for calculating the liquid absorption porosity is as follows: Φ = (V0 / V1) * 100% = (W0 / ρ) / (W1 / p) * 100%; where W0 is the mass of electrolyte absorbed by the electrode, W1 is the mass of the electrode, V0 is the volume of electrolyte absorbed by the electrode, V1 is the volume of the electrode; ρ is the electrolyte density, and P is the electrode compaction density; where W0 excludes the mass of electrolyte absorbed by the electrode, and W1 excludes the mass of the current collector and the mass of the electrode.

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