Device and method for testing swelling ratio of binder

Abstract

The invention belongs to the technical field of lithium ion battery testing, and particularly relates to a binder swelling rate testing device and method. Comprising a glass cover (1), a filter bag (2), a lifting frame rod (3), a hook (6), a tension sensor (7), a swelling chamber (8) and a weighing table (9), the swelling chamber is arranged on the weighing table and used for containing electrolyte, the hook is arranged on the lifting frame, the lifting frame is lifted through an internal connecting frame rod structure, and the tension sensor (7) is arranged on the lifting frame. The lower part of the hook is sequentially connected with a tension sensor (7) and a filter bag (2) through a rope, the filter bag (2) can be used for accommodating an object and enabling electrolyte to pass through, and the glass cover (1) is made of a glass material and is used for covering the outside of the whole testing device. When the device is used for testing the swelling rate of the binder, the swelling saturation state of the binder sample can be determined in real time, the electrolyte in the swelling chamber can be replaced, the swelling rates of the binder in different electrolytes can be tested, and the principle and equipment are simple and convenient.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery testing technology, and particularly relates to a binder swelling rate testing device and method. Background Technology

[0002] As a core energy storage device in the new energy field, the electrochemical performance of lithium batteries directly depends on the stability of electrode materials. Binders, as key materials in the electrodes, are crucial for the strong bond between active materials, conductive agents, and current collectors. Currently, most binders used in lithium batteries are cross-linked polymer materials. These materials, due to their three-dimensional cross-linked network structure, typically do not dissolve in the electrolyte but can absorb electrolyte and swell, specifically manifested as volume expansion and mass increase. The swelling behavior of the binder has a significant impact on the overall performance of lithium batteries. Excessive swelling may cause battery bulging, increasing electrode thickness and exacerbating C-corner wrinkles. Insufficient swelling can lead to internal battery looseness, negatively affecting battery performance. Therefore, the swelling rate of the binder in the electrolyte is a very important evaluation indicator. However, since adhesive materials are mostly polymers with heterogeneous compositions, the degree of crosslinking and component proportions vary in different regions. Therefore, the degree of swelling differs across regions, leading to irregular morphological changes after swelling, making it impossible to determine the swelling volume through simple calculations and measurements. Existing methods for testing adhesive swelling rates mostly employ offline weighing or volumetric measurement, which have several limitations. Offline weighing requires removing the swollen adhesive from the electrolyte and drying it before weighing, which can easily result in electrolyte residue or adhesive loss, leading to significant measurement errors. Volumetric measurement typically involves visually observing changes in electrolyte level and then converting them to volume, but this method also introduces significant errors and makes it difficult to determine the saturation state of the adhesive after immersion in the electrolyte. Furthermore, most existing methods can only measure mass swelling rate or volumetric swelling rate separately, failing to achieve simultaneous and accurate detection of both indicators and thus failing to comprehensively reflect the swelling characteristics of the adhesive. To address the aforementioned technical deficiencies, there is an urgent need to develop a high-precision, real-time device and method for testing the swelling rate of binders. This device and method should be able to simultaneously measure the volumetric swelling rate and mass swelling rate of binders in electrolytes, accurately determine the swelling saturation state, improve the accuracy and reliability of test data, and provide scientific and effective technical support for the performance evaluation of lithium battery binders. Summary of the Invention

[0003] In view of this, this application provides an adhesive swelling rate testing device and method. By observing the readings of the tensile sensor and the weighing display screen, the swelling saturation state and the swelling degree are determined. It can measure the volume of irregular polymers during and after swelling in real time. Moreover, it does not require repeatedly removing the adhesive from the electrolyte to determine the swelling saturation state during the measurement process. Furthermore, the electrolyte in the swelling chamber can be changed to test the swelling degree of the adhesive in different electrolytes. The principle and equipment are simple and convenient, solving the problem in the prior art that it is impossible to accurately test the irregular swelling volume changes and determine the swelling saturation state in real time.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This application provides an adhesive swelling rate testing device, including a glass cover 1, a filter bag 2, a lifting frame 3, a hook 6, a tension sensor 7, a swelling chamber 8, and a weighing platform 9. The swelling chamber is disposed on the weighing platform and is used to contain electrolyte. The hook is disposed on the lifting frame, which is raised and lowered by an internal connecting frame structure. The hook is connected to the tension sensor 7 and the filter bag 2 in sequence by ropes. The filter bag 2 can hold objects and allow electrolyte to pass through. The glass cover 1 is made of glass and is used to cover the entire testing device.

[0005] Preferably, the weighing platform also includes a weighing display panel 10, function buttons 5, and a tension sensor display panel 4 below it.

[0006] In another aspect, the test method using the above-mentioned adhesive swelling rate testing device includes the following steps: S1: By placing the swelling chamber 8 on the weighing platform 9, after tareing, pouring in a fixed volume of electrolyte, weighing and reading the mass of the electrolyte on the weighing display panel 10 as m0, the electrolyte density ρ0 is calculated. S2: Use a tablet press mold to make an adhesive sample, and make the density of the pressed adhesive sample ρ1 > ρ0. Calculate the minimum mass m1 of the adhesive sample, and use the cylinder volume formula to calculate the volume V1. S3: Drive the lifting frame 3 to descend, so that the filter bag 2 is completely immersed in the electrolyte, and the weighing platform 9 reads the mass reading m2; S4: Place the adhesive sample in the filter bag 2 and immerse it completely in the electrolyte in the swelling chamber 8. Cover it with a glass cover 1 to reduce environmental interference. When the adhesive sample reaches the swelling saturation state, read the mass reading m3 through the weighing platform 9. S5: Remove filter bag 2 containing the adhesive sample from the electrolyte surface. After the adhesive sample dries and the tensile sensor reading remains stable for 10 minutes, calculate the mass m after swelling and saturation using the formula F=G=mg. 4，Read the reading m5 on the weighing display panel 10 at this time; S6: Calculate the volume swelling rate and mass swelling rate based on the above test results.

[0007] Preferably, the specific calculation method for the electrolyte density ρ0 in step S1 is as follows: the volume of electrolyte poured in is recorded as V, and the electrolyte density ρ0 is calculated according to the formula ρ0=m0 / V.

[0008] Preferably, in step S2, the volume V1 of the adhesive sample is determined by the mold with a fixed size of the tablet press, and the minimum mass m1 of the adhesive sample is obtained according to the formula m1=ρ1V1.

[0009] Preferably, in step S3, the lifting rod 3 is driven to descend by rotating the lifting knob 31 to completely immerse the filter bag 2 in the electrolyte. The reading on the weighing platform is m2, then the volume of electrolyte displaced by the filter bag is V2 = (m2 - m0) / ρ0.

[0010] Preferably, the evaluation method for the adhesive sample reaching the swelling saturation state in step S4 specifically involves: real-time observation of the tensile force value F on the tensile sensor display panel 4. 拉 If the reading does not fluctuate or fluctuates within ±0.01N, the adhesive sample is considered to have reached the swelling saturation state.

[0011] Preferably, when the adhesive sample reaches the swelling saturation state in step S4, the formula for calculating the total electrolyte volume V3 displaced by the filter bag and adhesive sample is: V3=(m3-m5) / ρ0, then the volume of electrolyte displaced by the swollen adhesive sample is V4=V3-V2=(m3-m5-m2+m0) / ρ0.

[0012] Preferably, the formula for calculating the volume swelling ratio Q1 in step S6 is: Q1 = (V4 - V1) / V1 × 100%; the formula for calculating the mass swelling ratio Q2 is: Q2 = (m4 - m1) / m1 × 100%.

[0013] Preferably, the adhesive swelling rate testing device has a function button 5 that integrates peeling, power on / off, and zeroing operation functions.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This application uses a tensile sensor to determine the swelling saturation state of the adhesive sample, and weighs the sample on a weighing platform to obtain the difference between the mass of the adhesive sample at saturation and the mass before swelling. The mass swelling rate is calculated, and using Archimedes' principle, the volume of electrolyte displaced by the adhesive sample at saturation is calculated. The volume swelling rate is then calculated based on the volume difference before and after swelling. This application offers the following advantages: 1) Accurate measurement with small error: By placing electrolyte in the swelling chamber and using a weighing platform, the mass of the electrolyte and the mass change of the system during the soaking process can be accurately measured, which is the basis for the calculation of volume swelling rate.

[0015] 2) The device has a reasonable structural design: the filter bag design takes into account both sample support and electrolyte flow, which can not only stably place the binder sample, but also ensure that the electrolyte fully contacts the sample during the swelling process, avoiding the problem of sample falling off or insufficient swelling.

[0016] 3) Quantitative determination of swelling saturation state: The force sensor can monitor the force change of the sample during the swelling process in real time, providing a quantitative basis for the determination of "swelling saturation", which solves the drawback of "saturation time is judged by experience" in traditional swelling test.

[0017] 4) Minimal interference from external environment: By setting up a glass cover, the interference of environmental factors such as airflow and dust on the tension sensor is reduced, thus improving data accuracy.

[0018] In summary, this application achieves an upgrade from "experience-based" to "precision-based" testing through an innovative combination of "integrated device + tensile sensing quantitative saturation determination + simultaneous testing of volume swelling rate / mass swelling rate dual indicators + standardized calculation". This not only improves testing efficiency and result accuracy but also reduces testing costs. It can be widely applied in industrial production and research fields and is suitable for large-scale promotion and use. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the adhesive swelling rate testing device of this application.

[0020] In the diagram: 1. Glass cover; 2. Filter bag; 3. Lifting frame; 31. Lifting knob; 4. Tension sensor display panel; 5. Function button; 6. Hook; 7. Tension sensor; 8. Swelling chamber; 9. Weighing platform; 10. Weighing display panel. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0022] It should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the invention. In the description of the invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," and "fixed connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. In the description of the invention, unless otherwise stated, "a number" means two or more. For those skilled in the art, the specific meaning of the above terms in the invention can be understood through specific circumstances, and several improvements and modifications can be made without departing from the principle of the invention.

[0023] This application discloses an adhesive swelling rate testing device, such as... Figure 1 As shown: The system includes a glass cover 1, a filter bag 2, a lifting frame 3, a hook 6, a tension sensor 7, a swelling chamber 8, and a weighing platform 9. Below the weighing platform 9 are a weighing display panel 10, function buttons 5, and a tension sensor display panel 4. Specifically: The swelling chamber 8 is disposed on the weighing platform 9 and is used to contain the electrolyte. The weighing display panel 10 is used to display the weighing reading of the weighing platform 9 in real time.

[0024] The hook 6 is mounted on the lifting frame for placing and removing test samples, while also ensuring stable transmission of tensile force. This facilitates the placement and removal of test samples by operators and ensures stable transmission of tensile force, guaranteeing accurate and reliable force data acquired by the tensile sensor.

[0025] The lifting frame 3 achieves lifting and lowering through an internal connecting frame structure. By rotating the lifting knob 31, the frame can be driven to move up and down, thereby adjusting the height of the detection components associated with the lifting frame 3, such as filter bags and tension sensors, to adapt to different detection needs and sample conditions.

[0026] The hook 6 is connected to the tension sensor 7 and the filter bag 2 in sequence by a rope. The tension data detected by the tension sensor 7 will be displayed in real time on the corresponding tension sensor display panel 4. The tension on the rope can be read directly, which is convenient for the operator to observe and record.

[0027] The filter bag 2 is used to hold the test sample and allow the electrolyte to pass through. It serves to support the test sample while effectively transmitting force, thus enabling accurate detection of the sample under specific conditions.

[0028] The tensile sensor display panel 4 displays the tensile force change in real time, which is used to determine the swelling and saturation state of the adhesive sample in real time.

[0029] The glass cover 1, made of glass, is used to enclose the entire testing device. It effectively isolates external environmental factors such as airflow and dust, preventing them from interfering with the detection accuracy of the tensile sensor and providing a stable environmental foundation for testing. The function button 5 integrates tare, power on / off, and zeroing operation functions.

[0030] In summary, the weighing platform of this application can display the corresponding detection data on the weighing display panel in real time when measuring the mass of the sample placed on it. At the same time, it can form a synchronous detection feedback with the tensile data measured by the tensile sensor, and can simultaneously obtain the tensile and mass change information of the sample under the electrolyte environment.

[0031] The specific steps of the testing method in this application are as follows: S1: Place the empty swelling chamber 8 on the weighing platform 9, press the tare function button 5, and then add 50mL of electrolyte to the swelling chamber. Read the mass m0 of the electrolyte as 60g through the weighing display panel 10. Calculate the electrolyte density as ρ0=1.2g / mL using ρ0=m0 / V.

[0032] S2: Take the styrene-butadiene rubber (SBR) powder as the adhesive, and compress it into small round adhesive samples using a die of fixed size (diameter d = 1 cm, thickness h = 0.2 cm) in a tablet press. Specific steps: S21: The initial volume V1 of the adhesive sample is calculated: V1 = πr 2 h = 3.14 × (5 mm) 2 ×2mm=0.157cm 3 ; S22: To ensure the sample does not float after immersion, the designed post-compression binder density ρ1 > ρ0 (1.2 g / cm³). 3 ), select ρ1=1.5g / cm 3 Therefore, the minimum mass of the adhesive sample is m1 = ρ1V1 = 1.5 g / cm³. 3 ×0.157cm 3 ≈0.236g.

[0033] S3: When the filter bag 2 is completely submerged in the electrolyte by rotating the lifting knob 31, its mass is measured to be m2 = 60.5g. Therefore, the volume of electrolyte displaced by the filter bag is V2 = (m2 - m0) / ρ0 = 0.416 cm³. 3 (This m2 is the value displayed on the indicator panel, which is the sum of the initial electrolyte mass and the mass after immersion in the filter bag).

[0034] S4: Turn the lifting knob 31 again to raise the filter bag 2, placing the adhesive sample pressed into a small round disc. Simultaneously, drive the lifting rod 3 to lower the filter bag 2 containing the adhesive sample, completely immersing it in the electrolyte of the swelling chamber 8. Cover the filter bag with the glass cover 1 to reduce environmental interference. After two hours of saturated swelling, the tensile sensor reading stabilizes at F. 拉 =0.3642N (fluctuation ±0.0001N, which meets the ±0.01N requirement), at this time the weighing platform reading m3=60.6521g.

[0035] S5: Rotate the lifting knob 31 to lift the filter bag containing the adhesive sample out of the electrolyte surface. After lifting the adhesive, wait for the reading of the tension sensor to stabilize at 2.3873N. Using the formula F=G=mg (gravity coefficient g is 9.8N / kg), calculate the mass of the adhesive sample as m4=0.2436g. At this time, the reading of the weighing platform is m5=59.9532 (mass of the remaining electrolyte).

[0036] S6: Based on the above test results, the following can be calculated: 1) The volume of electrolyte displaced by the filter bag, V2 = (m2 - m0) / ρ0, 2) The formula for calculating the total electrolyte volume V3 displaced by the filter bag and adhesive sample is: V3 = (m3 - m5) / ρ0. Therefore, the electrolyte volume displaced by the swollen adhesive sample is V4 = V3 - V2 = [m3 - m5 - (m2 - m0)] / ρ0 = (m3 - m5 - m2 + m0) / ρ0 = (60.6521 - 59.9532 - 60.5 + 60) / 1.2 ≈ 0.166 cm² 3 , Therefore, the volume swelling ratio Q1 can be calculated as follows: Q1 = (V4 - V1) / V1 × 100% ≈ 5.73%. Mass swelling rate Q2 = (m4 - m1) / m1 × 100% ≈ 3.22%.

[0037] In summary, using the testing device of this application, the swelling and saturation state of the adhesive sample is determined in real time by a tensile sensor, and the mass difference of the adhesive sample before and after swelling and saturation is read in real time by the weighing display panel under the weighing platform. Combining Archimedes' principle, the volume change of the displaced electrolyte is calculated, and finally, the volume swelling rate is obtained. Alternatively, the mass swelling rate can be calculated by directly measuring the mass difference of the adhesive sample before and after swelling using the weighing platform.

[0038] It should be noted that: 1) This application uses a tablet press to press the adhesive material into a disc with a density greater than that of the electrolyte, ensuring that the adhesive sample can be fully immersed in the electrolyte and swell. This optimizes the method of using adhesive film or other counterweights, which are prone to errors, and is simpler and lower in cost.

[0039] 2) This application does not require visual reading of changes in liquid level, as even using a magnifying glass to observe the scale will result in errors. The swelling rate can be calculated solely based on the readings on the weighing platform and the principle of the water displacement method.

[0040] 3) This application uses a tensile sensor to determine the swelling saturation state, which can ensure that the swelling saturation state can be determined without repeatedly pulling the adhesive sample out of the liquid surface, thus reducing errors.

[0041] 4) This application does not require testing the diameter of the adhesive sample, and the swelling of the material is not necessarily linear, nor is the volume after swelling necessarily regular. This invention can be applied to swollen products with irregular shapes.

[0042] 5) This application adds a glass protective cover to the outside of the test device. The main purpose is that the swelling process is a long process. Exposing the electrolyte and tension rope to the surrounding environment can easily cause tension disturbance or dust and adhesive materials. Adding a glass protective cover eliminates interference factors.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit it. It should be noted that those skilled in the art can still modify the technical solutions described above or make equivalent substitutions for some of the technical features without departing from the principle of the present invention, and such modifications or substitutions all fall within the protection scope of the present invention.

Claims

1. A device for testing the swelling rate of an adhesive, characterized in that, The device includes a glass cover (1), a filter bag (2), a lifting frame (3), a hook (6), a tension sensor (7), a swelling chamber (8), and a weighing platform (9). The swelling chamber is located on the weighing platform and is used to contain the electrolyte. The hook is located on the lifting frame, which is lifted and lowered by an internal connecting frame structure. The hook is connected to the tension sensor (7) and the filter bag (2) in sequence by ropes. The filter bag (2) can hold objects and allow the electrolyte to pass through. The glass cover (1) is made of glass and is used to cover the outside of the entire testing device.

2. The adhesive swelling rate testing device according to claim 1, characterized in that, The weighing platform also includes a weighing display panel (10), function buttons (5), and a tension sensor display panel (4) below it.

3. A test method using the adhesive swelling rate testing apparatus according to any one of claims 1-2, characterized in that, Includes the following steps: S1: By placing the swelling chamber (8) on the weighing platform (9), after tareing, pour in a fixed volume of electrolyte, weigh and read the mass of the electrolyte on the weighing display panel (10) as m0, and calculate the electrolyte density ρ0. S2: Use a tablet press mold to make an adhesive sample, and make the density of the pressed adhesive sample ρ1 > ρ0. Calculate the minimum mass m1 of the adhesive sample, and use the cylinder volume formula to calculate the volume V1. S3: Drive the lifting frame (3) to descend, so that the filter bag (2) is completely immersed in the electrolyte, and the weighing platform (9) reads the mass reading m2; S4: Place the adhesive sample in the filter bag (2) and immerse it completely in the electrolyte of the swelling chamber (8). Cover it with a glass cover (1) to reduce environmental interference. When the adhesive sample reaches the swelling saturation state, read the mass reading m3 through the weighing platform (9). S5: Remove the filter bag (2) containing the adhesive sample from the electrolyte surface. After the adhesive sample dries and the reading of the tensile sensor remains stable within 10 minutes, calculate the mass m after swelling and saturation using the formula F=G=mg. 4， Read the reading m5 on the weighing display panel (10) at this time; S6: Calculate the volume swelling rate and mass swelling rate based on the above test results.

4. The method according to claim 3, characterized in that, The specific calculation method for the electrolyte density ρ0 in step S1 is as follows: the volume of electrolyte poured in is recorded as V, and the electrolyte density ρ0 is calculated according to the formula ρ0=m0 / V.

5. The method according to claim 3, characterized in that, In step S2, the volume V1 of the adhesive sample is determined by the mold with a fixed size of the tablet press. According to the formula m1=ρ1V1, the minimum mass m1 of the adhesive sample is obtained.

6. The method according to claim 3, characterized in that, In step S3, the lifting rod (3) is driven to descend by rotating the lifting knob (31) to completely immerse the filter bag (2) in the electrolyte. The reading on the weighing platform is m2. Then the volume of electrolyte displaced by the filter bag is V2 = (m2-m0) / ρ0.

7. The method according to claim 3, characterized in that, The evaluation method for the adhesive sample reaching the swelling saturation state in step S4 is as follows: real-time observation of the tensile force value F on the tensile sensor display panel (4). 拉 If the reading does not fluctuate or fluctuates within ±0.01N, the adhesive sample is considered to have reached the swelling saturation state.

8. The method according to claim 3, characterized in that, When the adhesive sample reaches the swelling saturation state in step S4, the formula for calculating the total electrolyte volume V3 displaced by the filter bag and adhesive sample is: V3=(m3-m5) / ρ0. Then, the electrolyte volume displaced by the swollen adhesive sample is V4=V3-V2=(m3-m5-m2+m0) / ρ0.

9. The method according to claim 3, characterized in that, The formula for calculating the volume swelling ratio Q1 in step S6 is: Q1 = (V4 - V1) / V1 × 100%; the formula for calculating the mass swelling ratio Q2 is: Q2 = (m4 - m1) / m1 × 100%.

10. The adhesive swelling rate testing device according to claim 2, characterized in that, The function button (5) integrates tare, power on / off, and zeroing functions.

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