An apparatus and method for evaluating the flexibility of lithium-ion battery electrodes

Abstract

The present invention belongs to the technical field of lithium-ion battery detection, and specifically relates to a device and method for evaluating the flexibility of lithium-ion battery electrodes. S1. Cut the electrode to be detected; S2. Clamp one end of the electrode to be detected flatly between the rubber layer and the bottom plate, and the electrode to be detected deforms and sags under its own gravity, and the flexibility of the electrode is initially reflected according to the "sag"; S3. Turn on the motor to drive the electric telescopic rod to move upward in the vertical direction. The liquid crystal display screen real-time displays the displacement value and the pressure value received by the support beam to obtain the "stress-strain curve" of the electrode. When the electrode is in stage I of T1-T2, the greater the pressure value, the better the flexibility; when the electrode is in stage II of T2-T3, the smaller the pressure value, the better the flexibility. The present invention is simple, easy, fast, and the data is accurate and reliable; and the gravity of the electrode is incorporated into the flexibility data to further improve the test accuracy, and can also feedback and compare information such as the surface density and coating amount of the electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery detection, and particularly relates to a device and method for evaluating the flexibility of lithium-ion battery electrode sheets. Background Art

[0002] Lithium-ion batteries have many advantages such as high energy density, high output power, long charge-discharge life, no pollution, wide operating temperature range, and low self-discharge. As a new type of high-energy chemical power source, in recent years, lithium-ion batteries have been widely used in fields such as mobile phones, computers, and electric vehicles. Lithium-ion batteries have the advantages of long battery life, long service life, low self-discharge rate, and environmental friendliness.

[0003] There are many factors affecting the flexibility of lithium-ion battery electrode sheets, such as the type and proportion of materials, the areal density of the electrode sheets, the compaction of the electrode sheets, etc. When the flexibility of the electrode sheet is poor, it will affect its processing performance and the safety of the battery core. When the flexibility of the electrode sheet is poor, phenomena such as roller compaction material loss and cutting position material loss may occur, resulting in the scrapping of materials, affecting the cleanliness of the workshop, and increasing the risk of internal short circuit in the battery core; during hot pressing, the rolled core bears for ten to dozens of seconds between the pressing plates with a pressure of several tons. The poorer the flexibility of the electrode sheet, the more likely it is to cause microcracks, cracks, and even material loss at the inner corner of the rolled core, thus affecting the electrochemical performance and even the safety performance of the battery core. The flexibility of the electrode sheet can be improved by optimizing the materials and their proportions, selecting a more appropriate areal density and compaction density, and optimizing the hot pressing process. However, there is currently no unified method for evaluating and comparing the flexibility of electrode sheets at the initial stage. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a device for evaluating the flexibility of lithium-ion battery electrode sheets, which can accurately compare the flexibility between electrode sheets and provide data support for the electrode sheet softening process.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An apparatus for evaluating the flexibility of lithium-ion battery electrode sheets, comprising a horizontal stage, two electric telescopic rods, a support crossbeam, an electrode sheet fixing mechanism, a control panel, a liquid crystal display screen and a protective cover. The two electric telescopic rods are arranged perpendicular to the upper surface of the horizontal stage and can perform telescopic movement in the vertical direction. The tops of the two electric telescopic rods are respectively fixedly connected to the two ends of the support crossbeam. The two electric telescopic rods are respectively connected to the circuit inside the control panel. The control panel is embedded in the front of the horizontal stage. The protective cover is arranged on the tabletop of the horizontal stage and forms a cubic airtight space with its edge to prevent the detection process from being affected by external air flow, vibration, etc. Windows that can be opened and closed are respectively arranged on the front and top surfaces of the protective cover for loading and unloading the electrode sheet to be detected. One end of the electrode sheet to be detected is fixed on the electrode sheet fixing mechanism, and the electrode sheet fixing mechanism is fixed on the protective cover behind and above the support crossbeam.

[0007] Further, a pressure sensor and a displacement sensor are arranged side by side on the support crossbeam. The pressure sensor and the displacement sensor are connected to the liquid crystal display screen through a single-chip microcomputer and an A / D converter.

[0008] Further, a speed regulator is arranged inside the horizontal stage. The speed regulator is electrically connected to the motor that drives the electric telescopic rod and is connected to the circuit inside the control panel.

[0009] Further, the electrode sheet fixing mechanism includes a clamping plate and a bottom plate. The bottom plate is fixed on the protective cover behind and above the support crossbeam. The clamping plate is connected to the bottom plate through two groups of screws. The electrode sheet to be detected is clamped between the clamping plate and the bottom plate.

[0010] Even further, a rubber layer is fixed on the plane of the clamping plate facing the bottom plate.

[0011] Even further, the electrode sheet fixing mechanism is made of stainless steel material, and the protective cover is made of acrylic material.

[0012] Even further, speed regulation buttons for controlling the speed regulator, as well as a start button, a pause button and a reset button for respectively controlling the start, pause and reset of the motor are arranged on the control panel.

[0013] Based on a general inventive concept, another object of the present invention is to provide a method for evaluating the flexibility of lithium-ion battery electrode sheets by using the above-mentioned apparatus, comprising the following steps:

[0014] S1. Cut the electrode sheet to be detected into a fixed length and width;

[0015] S2. Open the switchable window on the front or top of the protective cover, loosen the screws on the pole piece fixing mechanism, place one end of the pole piece to be detected between the rubber layer on the clamping plate and the bottom plate, tighten the screws to clamp the pole piece to be detected flatly between the rubber layer and the bottom plate, and close the window of the protective cover;

[0016] Among them, the pole piece to be detected is deformed and sagged under its own gravity, and the flexibility of the pole piece is initially reflected according to the "sag";

[0017] The above "sag" can be visually judged or by setting a scale on the "horizontal stage". When pole pieces of the same size sag, the distance from the lowest end to the rear wall of the protective cover is used as the measurement standard.

[0018] S3. Click the start button to start the motor, drive the electric telescopic rod to move upward along the vertical direction at a rate of 10 - 50 mm / min. The liquid crystal display screen real-time displays the displacement value and the pressure value received by the support crossbeam, and obtains the "stress-strain curve" of the measured pole piece;

[0019] Among them, the state when the support crossbeam reaches the same level as the pole piece fixing mechanism is defined as T2. The state from T1 to T2 is regarded as stage I, and the state from T2 to T3 is regarded as stage II;

[0020] Judge the flexibility of the pole piece through the "stress-strain curve". When the pole piece to be detected is in stage I, the greater the pressure value, the better the flexibility of the pole piece to be detected; when the pole piece to be detected is in stage II, the smaller the pressure value, the better the flexibility of the pole piece to be detected.

[0021] The principle is as follows: Before the support crossbeam reaches the same level as the pole piece fixing mechanism, the force on the pressure sensor on the support crossbeam is the difference between the self-gravity of the pole piece to be detected and the deformation stress (less than the gravity of the corresponding pole piece); after the support crossbeam reaches the same level as the pole piece fixing mechanism, the force on the pressure sensor is the sum of the self-gravity of the pole piece to be detected and the deformation stress.

[0022] Preferably, in step S1, the pole piece to be detected is cut into a length of 50 - 150 mm and a width of 30 - 100 mm.

[0023] Preferably, in step S3, when the non-fixed end of the pole piece and the fixed end of the pole piece are at the same height, the pressure value obtained by the pressure sensor is regarded as half of the gravity of the pole piece, and the pole piece weight or coating amount data is obtained.

[0024] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0025] The device of the present invention is simple, easy to carry and operate; the method of the present invention records the corresponding relationship between the displacement value of the electric telescopic rod in the vertical direction and the pressure value received at its top, obtains the relevant data (stress-strain curve) of the flexibility of the pole piece, the test is simple, easy, fast, and the data is accurate and reliable; incorporating the gravity of the pole piece into the flexibility data further improves the test accuracy, and can feedback and compare information such as the surface density and coating amount of the pole piece. Through the method of the present invention, the flexibility of the lithium-ion battery pole piece can be effectively detected, and the flexibility of the pole piece can be quantitatively and data-processed and compared, providing an effective pole piece for subsequent continuous film-making processes, winding processes, etc., effectively avoiding the pole piece breakage caused by the brittleness of the pole piece, ensuring the electrochemical performance and safety performance of the lithium-ion battery, and at the same time providing convenience for the automated continuous manufacturing of lithium-ion batteries; it is convenient to use, highly reliable, accurate and fast, and can be applied to the flexibility test of pole pieces of different sizes and thicknesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the overall structure of the present invention;

[0027] Figure 2 Schematic diagram of the structure of the support crossbeam;

[0028] Figure 3 Schematic diagram of the structure of the pole piece fixing mechanism;

[0029] Figure 4 Schematic diagram of the deformation of the pole piece when the device of the present invention is working;

[0030] Figures 1-4 The meanings of the marks are as follows: 1 - horizontal stage, 2 - electric telescopic rod, 3 - support crossbeam, 4 - pole piece fixing mechanism, 5 - control panel, 6 - liquid crystal display screen, 7 - protective cover, 8 - pole piece to be detected, 9 - pressure sensor, 10 - displacement sensor, 11 - clamping plate, 12 - bottom plate, 13 - screw, 14 - rubber layer, 15 - speed control button, 16 - start button, 17 - pause button, 18 - reset button.

[0031] T1, T2 and T3 respectively indicate different states of the pole piece when the device of the present invention is working. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In the description of the present invention, it is necessary to understand that the orientation or positional relationship indicated by "upper", "lower", "top", "bottom", "inner", "outer", etc. is all based on the orientation or positional relationship shown in the drawings. The purpose is only to facilitate the description of the present invention and simplify the description, and does not indicate or imply that the indicated components must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0033] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0034] Embodiment 1

[0035] A device for evaluating the flexibility of lithium-ion battery electrodes, as Figure 1 shown, includes a horizontal stage 1, two electric telescopic rods 2, a support beam 3, an electrode fixing mechanism 4, a control panel 5, a liquid crystal display screen 6, and a protective cover 7. The two electric telescopic rods 2 are vertically arranged on the upper surface of the horizontal stage 1 and can perform telescopic movement in the vertical direction. The tops of the two electric telescopic rods 2 are respectively fixedly connected to both ends of the support beam 3. The two electric telescopic rods 2 are respectively connected to the circuit inside the control panel 5. The control panel 5 is embedded directly in front of the horizontal stage 1. The protective cover 7 is arranged on the tabletop of the horizontal stage 1 and forms a cubic closed space with its edge to prevent the detection process from being affected by external air flow and vibration, etc. The front and top surfaces of the protective cover 7 are respectively provided with switchable windows for loading and unloading the electrode to be detected 8. One end of the electrode to be detected 8 is fixed on the electrode fixing mechanism 4, and the electrode fixing mechanism 4 is fixed on the protective cover 7 behind and above the support beam 3.

[0036] Embodiment 2

[0037] This embodiment is a further optimization based on Embodiment 1. As Figure 2 shown, a pressure sensor 9 and a displacement sensor 10 are arranged in parallel on the support beam 3. The pressure sensor 9 and the displacement sensor 10 are connected to the liquid crystal display screen 6 through a single-chip microcomputer and an A / D converter.

[0038] Embodiment 3

[0039] This embodiment is a further optimization based on Embodiment 2. A speed regulator is arranged inside the horizontal stage 1. The speed regulator is electrically connected to the motor that drives the movement of the electric telescopic rod 2 and is connected to the circuit inside the control panel 5.

[0040] Embodiment 4

[0041] This embodiment is a further optimization based on Embodiment 3. As Figure 3 shown, the electrode fixing mechanism 4 includes a clamping plate 11 and a bottom plate 12. The bottom plate 12 is fixed on the protective cover 7 behind and above the support beam 3. The clamping plate 11 is connected to the bottom plate 12 through two groups of screws 13. The electrode to be detected 8 is clamped between the clamping plate 11 and the bottom plate 12.

[0042] Embodiment 5

[0043] This embodiment is a further optimization based on Embodiment 4. A rubber layer 14 is fixed on the plane of the clamping plate 11 facing the bottom plate 12.

[0044] Embodiment 6

[0045] This embodiment is a further optimization based on Embodiment 5. The pole piece fixing mechanism 4 is made of stainless steel, and the protective cover 7 is made of acrylic.

[0046] Embodiment 7

[0047] This embodiment is a further optimization based on Embodiment 6. On the control panel 5, there are speed adjustment buttons 15 for controlling the speed governor, and start button 16, pause button 17 and reset button 18 for respectively controlling the start, pause and reset of the motor.

[0048] Embodiment 8

[0049] This embodiment is a method for evaluating the flexibility of lithium-ion battery pole pieces using the device of Embodiment 7, including the following steps:

[0050] S1. Cut the pole piece 8 to be detected into a length of 100 mm and a width of 65 mm.

[0051] S2. Open the switchable window on the front or top surface of the protective cover 7, loosen the screw 13 on the pole piece fixing mechanism 4, place one end of the pole piece 8 to be detected between the rubber layer 14 on the clamping plate 11 and the bottom plate 12, tighten the screw 13 to clamp the pole piece 8 to be detected flatly between the rubber layer 14 and the bottom plate 12, and close the window of the protective cover 7.

[0052] Among them, the pole piece 8 to be detected deforms and sags under its own gravity, and the flexibility of the pole piece is initially reflected according to the "sag".

[0053] S3. Click the start button 16 to start the motor, drive the electric telescopic rod 2 to move upward in the vertical direction at a rate of 30 mm / min. The liquid crystal display screen 6 real-time displays the displacement value and the pressure value received by the support cross beam 3, and obtains the "stress-strain curve" of the measured pole piece.

[0054] As Figure 4 shown, there are three deformation states (T1, T2 and T3) of the pole piece during the test. Among them, the state when the support cross beam 3 reaches the same level as the pole piece fixing mechanism 4 (when the non-fixed end of the pole piece is at the same height as the fixed end of the pole piece) is defined as T2. The state from T1 to T2 is regarded as stage I, and the state from T2 to T3 is regarded as stage II.

[0055] The flexibility of the to-be-tested electrode sheet 8 is judged by the "stress-strain curve". When the to-be-tested electrode sheet 8 is in stage I, the greater the pressure value, the better the flexibility of the to-be-tested electrode sheet 8; when the to-be-tested electrode sheet 8 is in stage II, the smaller the pressure value, the better the flexibility of the to-be-tested electrode sheet 8.

[0056] Among them, when the electrode sheet is in the T2 state, the pressure value obtained by the pressure sensor 9 is regarded as half of the gravity of the electrode sheet to obtain the electrode sheet weight or coating amount data.

[0057] After the electric telescopic rod 2 reaches the end point, the detection process ends. The test can also be paused by clicking the pause button 17. After the test ends, the data will be stored in the form of an exportable text; the reset button 18 can be clicked, and the electric telescopic rod 2 can be retracted to its original position for repeated testing.

[0058] When performing a flexibility test on the to-be-tested electrode sheet 8, 3-5 to-be-tested electrode sheets 8 are tested in sequence, and the displacement value and the pressure value are obtained respectively. Through multiple detections, the average values of the displacement value and the pressure value are taken to effectively increase the accuracy and stability of the test results.

[0059] After the experiment ends, remove the electrode sheet clamped between the clamping plate 11 and the bottom plate 12, keep the equipment clean, close the window on the protective cover 7, and turn off the power supply.

[0060] The present invention can accurately measure the flexibility value of the to-be-tested electrode sheet, form measurement-type data, fill the blank of the flexibility evaluation of the electrode sheet in the process of winding the lithium-ion battery cell and manufacturing the electrode sheet, and effectively reduce the defective rate in the production process.

[0061] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. The standard parts used in the present invention can be purchased from the market. The special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part all adopt conventional means such as bolts, rivets, and welding that are mature in the prior art. The machines, parts, and equipment all adopt conventional models in the prior art. Coupled with the circuit connection adopting the conventional connection method in the prior art, it will not be elaborated here.

[0062] The above embodiments are only the preferred embodiments of the present invention. Any simple modification, modification, and alternative change made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. An apparatus for evaluating the flexibility of a lithium-ion battery electrode sheet, characterized in that, It includes a horizontal stage (1), two electric telescopic rods (2), a support crossbeam (3), a pole piece fixing mechanism (4), a control panel (5), a liquid crystal display screen (6) and a protective cover (7). The two electric telescopic rods (2) are arranged perpendicular to the upper surface of the horizontal stage (1) and can perform telescopic motion in the vertical direction. The tops of the two electric telescopic rods (2) are respectively fixedly connected to both ends of the support crossbeam (3). The two electric telescopic rods (2) are respectively connected to the circuit inside the control panel (5). The control panel (5) is embedded directly in front of the horizontal stage (1). The protective cover (7) is arranged on the tabletop of the horizontal stage (1) and forms a cubic airtight space with its edge. The front and top surfaces of the protective cover (7) are respectively provided with switchable windows for loading and unloading the pole piece to be detected (8). One end of the pole piece to be detected (8) is fixed on the pole piece fixing mechanism (4), and the pole piece fixing mechanism (4) is fixed on the protective cover (7) behind and above the support crossbeam (3); A pressure sensor (9) and a displacement sensor (10) are arranged in parallel on the support crossbeam (3). The pressure sensor (9) and the displacement sensor (10) are connected to the liquid crystal display screen (6) through a single-chip microcomputer and an A / D converter.

2. The device for evaluating the flexibility of the lithium-ion battery electrode sheet according to claim 1, characterized in that, A speed regulator is arranged inside the horizontal stage (1). The speed regulator is electrically connected to the motor that drives the electric telescopic rod (2) to move and is connected to the circuit inside the control panel (5).

3. A device for evaluating the flexibility of a lithium-ion battery electrode sheet according to any one of claims 1-2, characterized in that, The pole piece fixing mechanism (4) includes a clamping plate (11) and a bottom plate (12). The bottom plate (12) is fixed on the protective cover (7) behind and above the support crossbeam (3). The clamping plate (11) is connected to the bottom plate (12) through two groups of screws (13). The pole piece to be detected (8) is clamped between the clamping plate (11) and the bottom plate (12).

4. The device for evaluating the flexibility of a lithium-ion battery electrode sheet according to claim 3, characterized in that, A rubber layer (14) is fixed on the plane of the clamping plate (11) facing the bottom plate (12).

5. The device for evaluating the flexibility of a lithium-ion battery electrode sheet according to claim 4, characterized in that, The pole piece fixing mechanism (4) is made of stainless steel, and the protective cover (7) is made of acrylic material.

6. The device for evaluating the flexibility of a lithium-ion battery electrode sheet according to claim 2, characterized in that, The control panel (5) is provided with a speed regulation button (15) for controlling the speed regulator, and a start button (16), a pause button (17) and a reset button (18) for respectively controlling the start, pause and reset of the motor.

7. A method for evaluating the flexibility of a lithium-ion battery electrode sheet by using the device according to claim 6, characterized in that, It includes the following steps: S1. Cut the pole piece to be detected (8) into a fixed length and width; S2. Open the switchable window on the front or top surface of the protective cover (7), loosen the screw (13) on the pole piece fixing mechanism (4), place one end of the pole piece to be detected (8) between the rubber layer (14) on the clamping plate (11) and the bottom plate (12), tighten the screw (13) to clamp the pole piece to be detected (8) flatly between the rubber layer (14) and the bottom plate (12), and close the window of the protective cover (7); Among them, the pole piece to be detected (8) is deformed and sagged under the action of its own gravity, and the flexibility of the pole piece is preliminarily reflected according to the "sag"; S3. Click the start button (16) to start the motor, drive the electric telescopic rod (2) to move upward in the vertical direction at a rate of 10 - 50 mm / min. The liquid crystal display screen (6) displays the displacement value and the pressure value received by the support crossbeam (3) in real time, and obtain the "stress-strain curve" of the measured pole piece; Among them, the state when the support crossbeam (3) reaches the same level as the pole piece fixing mechanism (4) is defined as (T2). The state T1 - T2 is regarded as stage I, and the state T2 - T3 is regarded as stage II; Judge the flexibility of the pole piece through the "stress-strain curve". When the pole piece to be detected (8) is in stage I, the greater the pressure value, the better the flexibility of the pole piece to be detected (8); when the pole piece to be detected (8) is in stage II, the smaller the pressure value, the better the flexibility of the pole piece to be detected (8).

8. A method for evaluating the flexibility of a lithium-ion battery electrode sheet according to claim 7, characterized in that, In step S1, the pole piece to be detected (8) is cut into a length of 50 - 150 mm and a width of 30 - 100 mm.

9. The method for evaluating the flexibility of a lithium-ion battery electrode sheet according to claim 7, wherein In step S3, when the non-fixed end of the pole piece and the fixed end of the pole piece are at the same height, the pressure value obtained by the pressure sensor (9) is regarded as half of the gravity of the pole piece, and the pole piece weight or coating amount data is obtained.

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