A battery cross-section sample preparation method

Abstract

A battery cross-section sample preparation method, comprising the steps of: S1 battery embedding sample preparation: winding the battery cell with adhesive tape or film, then placing the battery cell into a mold, pouring a wrapping material into the mold to wrap the battery cell, and obtaining an inlay block; S2 wire cutting: wire cutting the inlay block to obtain a battery cross-section inlay block; S3 grinding and polishing: grinding and polishing the battery cross-section inlay block to obtain a battery cross-section inlay block with a flat cross-section; S4 argon ion polishing: placing the battery cross-section inlay block on a sample stage and polishing it using an argon ion polishing device, wherein the emission direction of the argon ion beam of the argon ion polishing device forms an angle of 0-45° with the plane in which the cross-section of the battery cross-section inlay block lies, and the battery cross-section inlay block can rotate around the horizontal direction during polishing; and S5 battery cross-section sample removal, thereby obtaining an actual battery whole cross-section with sub-micron level flatness, centimeter level observation area and undamaged components, which lays a solid foundation for subsequent multi-modal non-in-situ and in-situ observation.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, and specifically to a method for preparing battery cross-section samples. Background Technology

[0002] Batteries are widely used in various electronic devices, bringing great convenience to people's lives. How to prepare qualified battery cross-sections for characterization studies has always been a goal pursued by those skilled in the art. However, there are currently very few reports on the preparation and study of overall battery cross-sections. This is because, on the one hand, research on mesoscale battery reaction behaviors occurring at the battery scale, such as the reaction uniformity and failure uniformity of electrodes and separators at different spatial locations in actual commercial batteries under different charge-discharge conditions, is currently scarce. On the other hand, in-situ reaction studies on the overall battery cross-section are also rare. It is worth noting that research is needed using actual batteries as the research object to explore the relevant battery and electrode reaction behaviors under both in-situ and ex-situ conditions. Therefore, it is necessary to develop a battery cross-section sample preparation technique targeting the macroscopic battery as a whole, providing technical support for studying electrochemical reaction mechanisms occurring at the battery and electrode levels. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a novel method for preparing battery cross-section samples.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a battery cross-section sample, comprising the following steps:

[0006] S1 Battery Pack Embedding Sample Preparation: The battery cell is wrapped with tape or film, and the wrapped and sealed battery cell is placed in a mold. A wrapping material is poured into the mold to wrap the battery cell. After the wrapping material solidifies, an embedding block is obtained.

[0007] S2 Wire Cutting: The inlay block is wire cut using a wire cutting device to obtain a battery cross-section inlay block;

[0008] S3 Polishing: Polish the side of the battery cross-section of the battery cross-section inlay block that exposes the battery cross-section by using sandpaper of different grits from low grit to high grit to obtain a battery cross-section inlay block with a flat cross-section.

[0009] S4 Argon Ion Polishing: The battery cross-section mounting block is fixedly placed on the sample stage, and the battery cross-section mounting block is polished using an argon ion polishing device. The emission direction of the argon ion beam of the argon ion polishing device makes an angle of 0 to 45° with the plane of the cross-section of the battery cross-section mounting block. During the argon ion polishing process, the battery cross-section mounting block can rotate around the horizontal direction.

[0010] S5 Battery Cross-Section Sample Removal: The encapsulation outside the battery cross-section inlay block is cut using a wire cutting device to remove the battery cross-section sample.

[0011] In some embodiments, the argon ion polishing device has two argon ion guns, which are symmetrically arranged on both sides of the battery cross-section mounting block in step S4.

[0012] In some embodiments, in step S4, the battery cross-section insert can rotate 360° around the horizontal direction.

[0013] In some embodiments, the emission direction of the argon ion beam of the argon ion polishing device is at an angle of 0° to the plane containing the cross-section of the battery cross-section insert, the argon ion beam is emitted by an argon ion gun, and the cross-section of the battery cross-section insert remains horizontal and aligned with the center hole of the argon ion gun.

[0014] In some embodiments, the battery type is one of a pouch battery, a cylindrical battery, a prismatic battery, or a single-cell battery.

[0015] In some embodiments, the battery cell is a dry cell without liquid filling, or a cell that has been charged and discharged.

[0016] In some embodiments, when the battery cell is wound, the entire battery cell is wound and sealed, and no part of the battery cell is exposed.

[0017] In some embodiments, the encapsulation is a mixture of resin and curing agent, wherein the mass ratio of resin to curing agent is 10:2 to 3.

[0018] In some embodiments, step S4 involves cryogenic argon ion polishing at a freezing temperature ≤ -20°C.

[0019] In some embodiments, in step S5, before using diamond wire cutting to cut the encapsulation outside the battery cross-section inlay block, it is necessary to cover and protect the battery cross-section with a blue film.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] This invention discloses a multi-technology combined sample preparation method for battery cross-sections, which integrates embedding technology, wire cutting technology, grinding and polishing technology, argon ion polishing technology, etc. It can directly or indirectly prepare samples of dry cells that have not been charged and discharged and cells that have been charged and discharged, to obtain an overall battery cross-section with nanoscale flatness, so as to further conduct in-situ and non-in-situ characterization for charging and discharging mechanism research. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a wire EDM (Electrical Discharge Machining) machine.

[0023] Figure 2 This is a schematic diagram of an argon ion polishing device.

[0024] Figure 3 A scanning electron microscope image of a cross-section of a battery after polishing with an argon-ion polishing device;

[0025] In the picture:

[0026] 1—Battery cell; 2—Diamond wire cutting equipment; 3—Argon ion gun; 4—Argon ion polishing equipment sample stage; 5—Battery cross-section inlay block; 6—Argon ion beam; 7—Argon ion polishing equipment sample stage base. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0028] like Figure 1 and Figure 2 As shown, this invention provides a method for preparing a battery cross-section sample. Taking a commercially available 350mAh Bluetooth headset battery cell without electrolyte filling as an example, the method includes the following steps:

[0029] S1 Battery Embedding Sample Preparation: The battery cell 1 of the Bluetooth headset was removed and embedded. The sides, top, and bottom of the battery cell 1 were tightly wrapped and completely sealed with raw rubber tape. It was fixed with clips and a 50µm stainless steel sheet and placed vertically in a soft rubber mold with an inner diameter of 30mm. A resin and curing agent mixed in a mass ratio of 10:3 was poured in and embedded. The mixture was then placed in a 30℃ oven for 24 hours to obtain the embedded block.

[0030] S2 wire cutting: See Figure 1 The insert block was wire-cut using a diamond wire cutting machine 2 to obtain the battery cross-section insert block 5. During the wire cutting process, the cutting speed was 2 mm / min, the cutting position was the exact center of the battery cell, and the cutting speed was 250 revolutions per minute.

[0031] S3 Polishing: Manually polish the side of the battery section of the above-mentioned battery section inlay block 5 that exposes the battery section. Use 240 grit, 600 grit, 1000 grit, 1500 grit and 2000 grit sandpaper to slowly polish, and then use 3000 grit and 5000 grit sponge sandpaper to automatically polish at a speed of 600 rpm to obtain a battery section inlay block 5 with a flat cross section.

[0032] S4 Cryogenic Argon Ion Polishing. An argon ion polishing device equipped with two argon ion guns 3 is selected. The battery cross-section embedding block is fixed on the sample stage 4 of the argon ion polishing device. The argon ion guns 3 are symmetrically arranged on both sides of the battery cross-section embedding block 5. The cross-section of the battery cross-section embedding block 5 is kept horizontal and aligned with the center hole of the argon ion gun 3. The emission direction of the argon ion beam 6 makes an angle of 0° with the plane of the cross-section of the battery cross-section embedding block 5. The ambient freezing temperature is -30°C. The sample stage 4 of the argon ion polishing device drives the battery cross-section embedding block 5 to rotate horizontally. The rotation angle is in the range of 0 to 360°, resulting in a battery cross-section with nanometer-level flatness.

[0033] S5 Battery Cross-Section Sample Removal: The argon-ion polished battery cross-section mounting block 5 was covered with a blue film containing lint-free paper to conceal the exposed portion of the battery cross-section. Both sides were cut using a diamond wire cutter 2, and then the sample was pried open with two pliers to remove and preserve it. The sample was then placed in a specific in-situ charge-discharge device for in-situ electrochemical reaction behavior observation.

[0034] S6 battery cross-sectional sample morphology characterization: The battery cross-sectional sample was fixed on the sample stage and placed in a field emission scanning electron microscope (SEM) to observe the battery microstructure. The SEM imaging parameters were low voltage (1 kV) and low vacuum mode. Figure 3 As shown, it can be clearly seen that the inside of the Bluetooth headset battery is wound, with a smooth and flat cross-section. The cross-sectional shape of the battery cell can be clearly and intuitively seen, and the positive electrode, negative electrode and separator areas can be distinguished. The width of the above three areas can also be measured.

[0035] In step S1, battery cell 1 is either a dry cell without electrolyte filling or a cell that has undergone charge-discharge cycles. The cell after charge-discharge cycles needs to be centrifuged 3-5 times using a high-speed centrifuge to obtain a cell with trace amounts of electrolyte salts. For cells that have undergone charge-discharge cycles, all steps of centrifugation, embedding, wire cutting, grinding, and argon ion polishing must be completed in a drying room or inert glove box. For dry cells without electrolyte filling, the indoor humidity needs to be maintained at ≤30%. In some embodiments, the battery capacity of the present invention is ≤10000mAh. In some embodiments, the insert is obtained by curing in an oven at 20-45°C for ≤24 hours.

[0036] In step S4, in some embodiments, the emission direction of the argon ion beam 6 forms an angle of 0–45° with the plane containing the cross-section of the battery cross-section inlay block 5. In other embodiments, the angle is 0–35°. That is, the argon ion beam 6 can extend obliquely from bottom to top, from top to bottom, or horizontally. In some embodiments, the accelerating voltage of the argon ion gun 3 is ≤10.0kV, the polishing time is ≤24h, and the ambient freezing temperature is controlled at ≤-20℃. Preferred polishing conditions are: accelerating voltage and time of the argon ion gun 3 are 8.0kV-60min, 7.0kV-90min, and 5.0kV-120min respectively; the ambient freezing temperature is controlled at -30℃; the angle between the argon ion gun 3 and the horizontal plane is 0°; and the horizontal rotation angle of the battery cross-section inlay block 5 is 360°. By setting the emission direction of the argon ion beam 6 as parallel as possible to the plane containing the cross-section of the battery cross-section inlay block 5, the flatness of the cross-section of the battery cross-section inlay block 5 after polishing can be improved. By setting the battery cross-section inlay block to be able to rotate horizontally 360°, the polishing of its cross-section is made more uniform.

[0037] In some embodiments, the battery type is one of a pouch battery, a cylindrical battery, a prismatic battery, or a single-cell battery. In some embodiments, the battery is specifically a lithium battery. The thickness of the positive electrode ranges from 1 to 500 μm, the thickness of the negative electrode ranges from 1 to 500 μm, and the thickness of the separator ranges from 1 to 200 μm.

[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a battery cross-section sample, characterized in that, Including the following steps: S1 Battery Pack Embedding Sample Preparation: The battery cell is wrapped with tape or film, and the wrapped and sealed battery cell is placed in a mold. A wrapping material is poured into the mold to wrap the battery cell. After the wrapping material solidifies, an embedding block is obtained. The battery cell is a lithium battery cell, which includes a positive electrode, a negative electrode, and a separator. When wrapping the battery cell, the entire battery cell is wrapped and sealed, and no part of the battery cell is exposed. S2 Wire Cutting: The inlay block is wire cut using a wire cutting device to obtain a battery cross-section inlay block; S3 Polishing: Polish the side of the battery cross-section of the battery cross-section inlay block that exposes the battery cross-section by using sandpaper of different grits from low grit to high grit to obtain a battery cross-section inlay block with a flat cross-section. S4 Argon Ion Polishing: The battery cross-section mounting block is fixedly placed on the sample stage, and the battery cross-section mounting block is polished using an argon ion polishing device. The emission direction of the argon ion beam of the argon ion polishing device forms an angle of 0 to 45° with the plane of the cross-section of the battery cross-section mounting block. During the argon ion polishing process, the battery cross-section mounting block can rotate around the horizontal direction. The argon ion polishing device has two argon ion guns. In step S4, the argon ion guns are symmetrically arranged on both sides of the battery cross-section mounting block. In step S4, the battery cross-section mounting block can rotate 360° around the horizontal direction. The emission direction of the argon ion beam of the argon ion polishing device forms an angle of 0° with the plane of the cross-section of the battery cross-section mounting block. The argon ion beam is emitted by the argon ion guns, and the cross-section of the battery cross-section mounting block remains horizontal and aligned with the center hole of the argon ion gun. S5 Battery cross-section sample removal: Use the wire cutting equipment to cut the wrapping material outside the battery cross-section inlay block and remove the battery cross-section sample; In step S1, the battery cell is either a dry cell without liquid filling or a cell that has undergone charge and discharge. The cell that has undergone charge and discharge needs to be centrifuged 3 to 5 times using a high-speed centrifuge. For the cell that has undergone charge and discharge, all steps of centrifugation, embedding, wire cutting, grinding and polishing, and argon ion polishing need to be completed in a dry room or inert glove box. For the dry cell without liquid filling, the indoor humidity needs to be maintained at ≤30%.

2. The battery cross-section sample preparation method according to claim 1, characterized in that: The battery type is one of the following: pouch battery, cylindrical battery, prismatic battery, or single cell battery.

3. The method for preparing a battery cross-section sample according to claim 1, characterized in that: The encapsulation is a mixture of resin and curing agent, wherein the mass ratio of resin to curing agent is 10:2 to 3.

4. The battery cross-section sample preparation method according to claim 1, characterized in that: In step S4, cryogenic argon ion polishing is performed, with a freezing temperature ≤ -20℃.

5. The method for preparing a battery cross-section sample according to claim 1, characterized in that: In step S5, before using diamond wire cutting to cut the outer covering of the battery cross-section inlay block, the battery cross-section needs to be covered and protected with a blue film.

Images