Negative electrode sheet production method, negative electrode sheet, and battery

Abstract

The application provides a negative electrode sheet preparation method, a negative electrode sheet and a battery. The negative electrode sheet preparation method comprises the following steps: providing a copper foil; performing ultrasonic shot blasting on the copper foil to form a microcrystalline wrinkle layer on the surface of the copper foil; performing coating on the microcrystalline wrinkle layer to form a rough active material layer on the surface of the copper foil, thereby obtaining a negative electrode sheet semi-product; and performing rolling on the negative electrode sheet semi-product, thereby obtaining a negative electrode sheet. The negative electrode sheet preparation method increases the contact area of the copper foil and the active material and increases the active point position, thereby increasing the transfer probability of the electric charge between the copper foil and the active material layer, improving the charge transmission efficiency of the contact interface between the copper foil and the active material layer, improving the cycle performance of the battery, obtaining a battery with good electrical performance and cycle performance, and improving the phenomenon that the negative electrode sheet of the battery is difficult to infiltrate.

Description

Technical Field

[0001] This invention relates to the field of battery processing technology, and in particular to a method for preparing a negative electrode, the negative electrode, and a battery. Background Technology

[0002] With the rapid development of new energy vehicles, portable power tools, and the demand for miniaturization of various electrical devices, the energy density requirements for lithium batteries are also increasing. To improve the energy density of lithium batteries, high-capacity, high-density battery electrodes are typically developed for use in lithium batteries to better adapt to market trends.

[0003] Currently, in the manufacturing process of battery electrodes, the active material is typically coated onto positive and negative current collectors. The coated current collectors are then rolled and slit to produce high-energy-density battery electrodes. However, due to the weak adhesion between the copper foil current collector and the active material in the negative electrode, the active material is prone to detachment during coating, thus affecting the battery's electrical performance.

[0004] Furthermore, in pursuit of high energy density battery electrodes, a large coating surface density and compaction density are typically employed. This can make it difficult for the electrolyte to fill the electrodes, resulting in poor electrode wetting. Consequently, the wetting effect of the battery cell is poor, affecting the battery's electrical and cycle performance. This leads to lower battery capacity, failing to meet market trends. This is especially true for wound high-energy-density batteries, where the tightly packed and compacted winding structure makes electrode wetting even more difficult, resulting in longer wetting times and poorer wetting effects, making it impossible to guarantee batteries with good electrical and cycle performance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a negative electrode sheet with good wetting effect, strong adhesion between the active material layer and the copper foil, and good cycle performance, as well as the negative electrode sheet and the battery.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a negative electrode includes the following steps:

[0008] Provide copper foil;

[0009] The copper foil is subjected to ultrasonic shot peening to form a microcrystalline wrinkled layer on the surface of the copper foil;

[0010] The microcrystalline wrinkled layer is coated to form a rough active material layer on the surface of the copper foil, thereby obtaining a negative electrode semi-finished product.

[0011] The negative electrode semi-finished product is subjected to a rolling operation to obtain a negative electrode sheet.

[0012] In one embodiment, the copper grain size of the microcrystalline wrinkled layer is 50 μm to 150 μm.

[0013] In one embodiment, the thickness of the active material layer is 120 μm to 125 μm.

[0014] In one embodiment, the step of performing ultrasonic shot peening on the copper foil to form a microcrystalline wrinkled layer on the surface of the copper foil includes the following specific steps:

[0015] The copper foil surface is subjected to ultrasonic shot peening using an ultrasonic shot peening device.

[0016] In one embodiment, the step of performing ultrasonic shot peening on the surface of the copper foil using an ultrasonic shot peening device includes the following specific steps:

[0017] The copper foil is placed at the ultrasonic window of the ultrasonic shot peening device and subjected to ultrasonic vibration to form a microcrystalline wrinkled layer on the surface of the copper foil.

[0018] In one embodiment, the ultrasonic frequency is 16Hz to 20Hz and the duration is 9s to 15s.

[0019] In one embodiment, the thickness of the copper foil is 6 μm to 9 μm.

[0020] In one embodiment, the step of rolling the negative electrode semi-finished product includes the following specific steps:

[0021] The negative electrode semi-finished product is rolled by a rolling device to make the active material laminated firmly on the surface of the copper foil.

[0022] A negative electrode sheet is produced using the negative electrode sheet preparation method described in any of the above embodiments.

[0023] A battery comprising the negative electrode sheet described in one of the above embodiments.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] 1. The above-mentioned method for preparing the negative electrode involves ultrasonic shot peening of copper foil. This process allows the copper foil to be bombarded with ultrasonic energy, easily forming a microcrystalline wrinkled layer on its surface. This microcrystalline wrinkled layer increases the contact area between the copper foil and the active material, thereby increasing the amount of active material coated on the copper foil and ensuring a high-energy-density negative electrode. This also reduces the charge diffusion resistance and charge transfer resistance of the active material layer. Furthermore, the microcrystalline wrinkled layer provides good adhesion points for the active material, allowing it to be well coated and embedded on the surface of the copper foil within the microcrystalline wrinkled layer, forming a continuous, interlocking structure. This results in a tighter and stronger bond between the copper foil and the active material layer, improving the adhesion strength and effectively preventing the active material from easily detaching during the coating process. This ensures that the battery subsequently prepared has a high capacity. Therefore, with the same area, the copper foil not only increases the contact area with the active material, but also increases the number of active sites, thereby increasing the probability of charge transfer between the copper foil and the active material layer. This improves the charge transfer efficiency at the contact interface between the copper foil and the active material layer, and thus improves the cycle performance of the battery, resulting in a battery with better electrical and cycle performance.

[0026] 2. The above-mentioned negative electrode preparation method involves coating the microcrystalline wrinkled layer. Due to the fluidity of the active material, when coating the copper foil, the active material can form an active material layer with a similar wrinkle curvature to the wrinkle curvature of the microcrystalline wrinkled layer, so that the side of the active material layer facing away from the copper foil can form a rough surface. Then, after the negative electrode semi-finished product is rolled, the active material can be compacted and embedded on the copper foil to obtain a high-energy-density negative electrode with a rough surface. When the negative electrode is wound with the positive electrode and the separator to form a battery cell, multiple tiny channels will be formed between the rough surface of the negative electrode and the separator. This facilitates the simultaneous flow of electrolyte into the battery cell from multiple tiny channels, thereby improving the phenomenon of difficult wetting of the battery negative electrode, and is especially suitable for wetting of wound high-energy-density batteries. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of a method for preparing a negative electrode sheet according to an embodiment of the present invention;

[0029] Figure 2A schematic diagram of the structure of a copper foil subjected to ultrasonic shot peening according to an embodiment of the present invention;

[0030] Figure 3 SEM image of a copper foil according to an embodiment of the present invention;

[0031] Figure 4 A cross-sectional view of an ultrasonic shot peening device according to an embodiment of the present invention in one direction.

[0032] Figure 5 A cross-sectional view of the negative electrode sheet according to one embodiment of the present invention.

[0033] Attached Figures: 10. Ultrasonic shot peening device; 100. Mounting bracket; 200. Ultrasonic component; 210. Ultrasonic vibrating element; 220. Ultrasonic processing chamber; 221. Ultrasonic window; 230. Cover; 231. Positioning post; 232. Cavity; 300. Shot peening; 400. Magnetic suction element; 500. Copper foil;

[0034] 20. Negative electrode sheet; 21. Copper foil layer; 22. Microcrystalline wrinkled layer; 23. Active material layer; 24. Rough surface; 25. Embedded pillar. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0037] Unless otherwise defined, 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. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] This application provides a method for preparing a negative electrode sheet, comprising the following steps: providing copper foil; performing ultrasonic shot peening on the copper foil to form a microcrystalline wrinkled layer on the surface of the copper foil; performing a coating operation on the microcrystalline wrinkled layer to form a rough active material layer on the surface of the copper foil, thereby obtaining a negative electrode sheet semi-finished product; and performing a roll pressing operation on the negative electrode sheet semi-finished product to obtain a negative electrode sheet.

[0039] The aforementioned method for preparing the negative electrode involves ultrasonic peening of copper foil. This process bombards the copper foil with ultrasonic energy, creating a microcrystalline wrinkled layer on its surface. This microcrystalline wrinkled layer increases the contact area between the copper foil and the active material, thereby increasing the amount of active material coated on the copper foil and ensuring a high-energy-density negative electrode. This also reduces the charge diffusion and charge transfer resistance of the active material layer. Furthermore, the microcrystalline wrinkled layer provides good adhesion points for the active material, allowing it to be well coated and embedded on the surface of the copper foil, forming a continuous, interlocking structure. This results in a tighter and stronger bond between the copper foil and the active material layer, effectively preventing the active material from detaching during coating and ensuring that the resulting battery has a high capacity. Therefore, with the same area, the copper foil not only increases the contact area with the active material, but also increases the number of active sites, thereby increasing the probability of charge transfer between the copper foil and the active material layer. This improves the charge transfer efficiency at the contact interface between the copper foil and the active material layer, and thus improves the cycle performance of the battery, resulting in a battery with better electrical and cycle performance. Furthermore, by coating the microcrystalline wrinkled layer, due to the fluidity of the active material, when coating the copper foil, the active material can form an active material layer with a similar wrinkle curvature to the wrinkle curvature of the microcrystalline wrinkled layer, so that the side of the active material layer facing away from the copper foil can form a rough surface. Then, after the negative electrode semi-finished product is rolled, the active material can be compacted and embedded on the copper foil to obtain a negative electrode sheet with high energy density and a rough surface. When the negative electrode sheet is wound with the positive electrode sheet and the separator to form a battery cell, multiple tiny channels will be formed between the rough surface of the negative electrode sheet and the separator. This facilitates the simultaneous flow of electrolyte into the battery cell from multiple tiny channels, thereby improving the phenomenon of difficult wetting of the battery negative electrode sheet, which is especially suitable for the wetting of wound high energy density batteries.

[0040] Please see Figure 1 To better understand the technical solution and beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments. One embodiment of the negative electrode preparation method includes some or all of the following steps:

[0041] S110, Provides copper foil as a substrate for the negative electrode.

[0042] S120. The copper foil is subjected to ultrasonic shot peening to form a microcrystalline wrinkled layer on the surface of the copper foil.

[0043] It is understandable that the smooth surface of the copper foil results in insufficient adhesion between the copper foil and the active material, which in turn leads to high impedance at the interface between the copper foil and the active material, thus limiting the electrochemical performance of the active material. Therefore, this invention involves ultrasonic peening of copper foil, allowing the copper foil to be bombarded with ultrasonic energy. According to the law of kinetic energy, the copper foil will plastically deform to counteract the ultrasonic energy, forming a microcrystalline wrinkled layer on the surface of the copper foil. This microcrystalline wrinkled layer increases the contact area between the copper foil and the active material, thereby increasing the amount of active material coated on the copper foil, ensuring a high-energy-density negative electrode. This also reduces the charge diffusion resistance and charge transfer resistance of the active material layer. Furthermore, the microcrystalline wrinkled layer provides better adhesion points for the active material, allowing it to be well coated and embedded on the surface of the copper foil, forming a continuous, interlocking structure. This results in a tighter and stronger bond between the copper foil and the active material, improving the adhesion strength between them and effectively preventing the active material from easily detaching during the coating process. This ensures that the battery subsequently manufactured has a high capacity.

[0044] S130. The microcrystalline wrinkled layer is coated to form a rough active material layer on the surface of the copper foil, thereby obtaining a negative electrode semi-finished product.

[0045] It is understandable that when a uniformly mixed active material is coated onto a copper foil with a microcrystalline wrinkled layer, the active material has a certain fluidity. When the copper foil is coated, the active material can form an active material layer with a similar wrinkle curvature to the wrinkle curvature of the microcrystalline wrinkled layer. This allows the side of the active material layer facing away from the copper foil to form a rough surface, thus obtaining a rough active material layer. This ensures that a high-energy-density negative electrode sheet with a rough surface can be obtained subsequently.

[0046] S140. The negative electrode semi-finished product is rolled to obtain a negative electrode sheet. It can be understood that because a rough active material layer forms on the surface of the copper foil, when the negative electrode semi-finished product is rolled, the high-energy-density negative electrode sheet with a rough surface is wound with the positive electrode sheet and separator to form a battery cell. Multiple tiny channels are formed between the rough surface of the negative electrode sheet and the separator, which facilitates the simultaneous flow of electrolyte into the battery cell through these tiny channels. This improves the difficulty of wetting the battery negative electrode sheet, ensuring a better wetting effect and thus ensuring the battery's electrical and cycle performance, better adapting to market development.

[0047] The aforementioned method for preparing the negative electrode involves ultrasonic peening of copper foil. This process bombards the copper foil with ultrasonic energy, creating a microcrystalline wrinkled layer on its surface. This microcrystalline wrinkled layer increases the contact area between the copper foil and the active material, thereby increasing the amount of active material coated on the copper foil and ensuring a high-energy-density negative electrode. This also reduces the charge diffusion and charge transfer resistance of the active material layer. Furthermore, the microcrystalline wrinkled layer provides good adhesion points for the active material, allowing it to be well coated and embedded on the surface of the copper foil, forming a continuous, interlocking structure. This results in a tighter and stronger bond between the copper foil and the active material layer, effectively preventing the active material from detaching during coating and ensuring that the resulting battery has a high capacity. Therefore, with the same area, the copper foil not only increases the contact area with the active material, but also increases the number of active sites, thereby increasing the probability of charge transfer between the copper foil and the active material layer. This improves the charge transfer efficiency at the contact interface between the copper foil and the active material layer, and thus improves the cycle performance of the battery, resulting in a battery with better electrical and cycle performance.

[0048] The above-described method for preparing the negative electrode involves coating the microcrystalline wrinkled layer. Due to the fluidity of the active material, when coating the copper foil, the active material can form an active material layer with a similar wrinkle curvature to the microcrystalline wrinkled layer, so that the side of the active material layer facing away from the copper foil can form a rough surface. Then, after rolling the negative electrode semi-finished product, the active material can be compacted and embedded on the copper foil to obtain a high-energy-density negative electrode with a rough surface. When the negative electrode is wound with the positive electrode and the separator to form a battery cell, multiple tiny channels will be formed between the rough surface of the negative electrode and the separator. This facilitates the simultaneous flow of electrolyte into the battery cell from multiple tiny channels, thereby improving the difficulty of wetting the battery negative electrode, and is especially suitable for wetting of wound high-energy-density batteries.

[0049] Please see Figure 2 and Figure 3 In this embodiment, the microcrystalline wrinkled layer is a continuous microcrystalline wrinkled layer. It can be understood that because the microcrystalline wrinkled layer is continuous, it allows for a continuous and uninterrupted intercalation structure with the active material. This means a complete and continuous active material layer can be formed on the surface of the copper foil. On the one hand, this ensures that the active material can be more tightly intercalated onto the continuous microcrystalline wrinkled layer; on the other hand, it ensures that more active material can participate in charge transfer, thereby improving the charge mobility on the copper foil and thus improving the cycle performance of the battery.

[0050] In one embodiment, the microcrystalline wrinkled layer comprises multiple copper crystals spaced apart on the surface of a copper foil to form a continuous microcrystalline wrinkled layer. It is understood that because the multiple copper crystals are spaced apart on the copper foil, each pair of copper crystals in each adjacent gap can form multiple grooves. These grooves provide better positioning for the active material, allowing it to fill the grooves effectively and forming multiple active sites on the copper foil. This improves the charge transfer efficiency between the copper foil and the active material layer, thereby improving the battery's cycle performance and electrical performance.

[0051] In one embodiment, the copper grain size of the microcrystalline wrinkled layer is 50 μm to 150 μm. It is understood that if the copper grain size of the microcrystalline wrinkled layer is less than 50 μm, the microcrystalline wrinkled layer is too small, thus failing to provide good bonding strength to the active material layer. If the copper grain size of the microcrystalline wrinkled layer is greater than 150 μm, on the one hand, it will affect the compaction between the subsequent negative electrode and the separator and positive electrode, resulting in a larger compacted volume, making it impossible to obtain a miniaturized high-capacity battery. On the other hand, since the copper foil itself is thin, if the copper grain size is greater than 150 μm, the copper foil is prone to cracking during shot peening, resulting in a large waste of copper foil. Therefore, this invention controls the copper crystal grain size of the microcrystalline wrinkled layer to be 50μm to 150μm, so that multiple grooves with a depth of 50μm to 150μm can be formed between each two adjacent copper crystals. In this way, the side of the active material layer facing the copper foil can be well embedded in the grooves with a depth of 50μm to 150μm, so that the active material layer and the copper foil can form a continuous structure of mutual embedding, thereby ensuring the bonding strength between the active material layer and the copper foil. Furthermore, the side of the active material layer facing away from the copper foil can form a rough surface with a similar wrinkle curvature to the wrinkle curvature of the microcrystalline wrinkled layer, so as to ensure that a high energy density negative electrode sheet with a rough surface can be obtained subsequently.

[0052] It should be further explained that if the copper crystal grain size is greater than 150μm, the wrinkle curvature of the side of the active material layer facing away from the copper foil will also be correspondingly increased, thereby increasing the roughness of the active material layer. This will increase the flow rate of multiple tiny channels formed between the rough surface and the separator, which is more conducive to the flow of electrolyte in the vertical direction of the active material layer. However, due to the relatively high compaction density of the side of the active material layer facing the copper foil, it is more difficult for the electrolyte to flow in the horizontal direction of the active material layer. By using a copper crystal grain size of 50μm to 150μm in the microcrystalline wrinkled layer, it is possible to ensure that the electrolyte has a faster flow rate in both the vertical and horizontal directions of the active material layer, so as to ensure that the electrolyte can flow more fully and comprehensively in the negative electrode, further improving the wetting effect of the negative electrode.

[0053] In one embodiment, the plurality of copper crystals comprises at least two different particle sizes. It is understood that because the plurality of copper crystals comprises at least two different particle sizes, grooves of at least two different depths can be formed in the microcrystalline wrinkled layer. On the one hand, this allows the active material layer facing the copper foil to form a continuous structure with interlocking shallow and deep grooves, ensuring good adhesion between the active material layer and the copper foil. This effectively prevents the active material from easily detaching from the copper foil surface, thus avoiding capacity decay and shortened cycle life. On the other hand, it allows multiple channels with different flow rates to be formed between the rough surface of the active material layer facing away from the copper foil and the separator. This effectively reduces electrolyte flow in the vertical direction of the active material layer while increasing electrolyte flow in the horizontal direction, enabling good bidirectional flow in both the horizontal and vertical directions. This ensures that the electrolyte can more fully and comprehensively enter the micropores of the active material layer, further improving the problem of difficult wetting of the battery electrodes.

[0054] In one embodiment, the thickness of the active material layer is 120 μm to 125 μm. It is understood that since the copper foil, after shot peening, can obtain a 50 μm to 150 μm microcrystalline wrinkled layer, the active material can be well coated on this layer to form an active material layer with a thickness of 120 μm to 125 μm. That is, for the same area of ​​copper foil, a relatively thick active material layer can be obtained, whereas the thickness of traditional active materials is below 117 μm. This increases the density of the copper active material layer per unit area, better adapting to the development of high-energy-density battery electrodes. This increases the number of active sites per unit area of ​​the active material and copper foil, thereby reducing the charge diffusion resistance and charge transfer resistance of the active material layer, increasing the probability of electron transfer between the copper foil and the active material layer, and thus improving the cycle performance of the battery.

[0055] In one embodiment, the step of coating the microcrystalline wrinkled layer to form a rough active material layer on the surface of the copper foil to obtain a negative electrode semi-finished product includes the following specific steps: coating the surface of the copper foil on which the microcrystalline wrinkled layer is formed by a coating device.

[0056] It is understandable that by using a coating device to uniformly coat and fill the surface of the copper foil with the microcrystalline wrinkled layer, the active material can be quickly and uniformly coated on the microcrystalline wrinkled layer to obtain an active material layer with a rough surface that has a similar wrinkle curvature to the microcrystalline wrinkled layer. This also enables a rapid coating operation on the copper foil and improves the production efficiency of the negative electrode sheet.

[0057] In one embodiment, the step of performing ultrasonic shot peening on the copper foil to form a microcrystalline wrinkled layer on the surface of the copper foil includes the following specific steps: performing ultrasonic shot peening on the surface of the copper foil using an ultrasonic shot peening device, so that the copper foil can be bombarded by shot carrying ultrasonic energy. According to the law of kinetic energy, the copper foil will plastically deform to offset the ultrasonic energy, so that a microcrystalline wrinkled layer can be formed on the surface of the copper foil.

[0058] In one embodiment, the step of performing ultrasonic peening on the surface of the copper foil using an ultrasonic peening device includes the following specific steps: placing the copper foil at the ultrasonic window of the ultrasonic peening device for ultrasonic vibration operation to form a microcrystalline wrinkled layer on the surface of the copper foil.

[0059] It is understandable that by fixing the copper foil at the ultrasonic window of the ultrasonic shot peening device, the ultrasonic shot peening device can perform ultrasonic vibration operation on one side of the copper foil, thereby realizing the ultrasonic shot peening operation on the copper foil.

[0060] Please see Figure 4 In one embodiment, the ultrasonic shot peening device 300 10 includes a mounting frame 100 and an ultrasonic component 200. The ultrasonic component 200 includes an ultrasonic vibrator 210, an ultrasonic processing chamber 220, and a cover 230. The ultrasonic vibrator 210 is disposed on the mounting frame 100 and has an ultrasonic vibration section. The ultrasonic processing chamber 220 has an ultrasonic window 221 facing the ultrasonic vibration section. The ultrasonic window 221 is used to place a copper foil 500, and the ultrasonic vibration section is used to place the shot peening 300. The cover 230 is detachably connected to the ultrasonic window 221 and is used to fix the copper foil 500 in the ultrasonic window 221.

[0061] It is understandable that, since the ultrasonic processing chamber 220 has an ultrasonic window 221 facing the ultrasonic vibration unit, meaning the ultrasonic window 221 is positioned opposite the ultrasonic vibration unit, when the copper foil 500 is placed in the ultrasonic window 221, and because the cover 230 is detachably connected to the ultrasonic window 221, the cover 230 can fix the copper foil 500 in place in the ultrasonic window 221. This also effectively prevents the copper foil 500 from shifting during the shot peening 300 process. When the user needs to perform shot peening 300 on the copper foil 500... Remove the cover 230, place the copper foil 500 at the ultrasonic window 221, and then press the cover 230 back into the ultrasonic window 221. Start the ultrasonic shot peening device 10, so that the shot peening device 300 can collide with the copper foil 500 at the ultrasonic window 221 as the ultrasonic vibrating part vibrates. According to the law of kinetic energy, the impact force on the surface of the copper foil 500 will cause plastic deformation of the surface of the copper foil 500, thereby forming a microcrystalline wrinkled layer on the surface of the copper foil 500, thus realizing the ultrasonic shot peening operation on the copper foil 500.

[0062] In one embodiment, the ultrasonic window 221 is recessed inward at the end of the ultrasonic processing chamber 220 facing the cover 230. It is understood that because the ultrasonic window 221 is recessed inward at the end of the ultrasonic processing chamber 220 facing the cover 230, a positioning ultrasonic window 221 can be formed at the end of the ultrasonic processing chamber 220 facing the cover 230, so that the copper foil 500 can be placed and fixed at the ultrasonic window 221.

[0063] In one embodiment, the cover 230 is provided with a magnetic suction member 400, which is magnetically connected to the end of the ultrasonic processing chamber 220 to achieve a detachable connection between the cover 230 and the end of the ultrasonic processing chamber 220. In this embodiment, the ultrasonic processing chamber 220 is made of stainless steel to achieve a magnetic connection with the magnetic suction member 400.

[0064] In one embodiment, the end of the ultrasonic processing chamber 220 facing the cover 230 is provided with a positioning groove, which is offset from the ultrasonic window 221. A positioning post 231 is correspondingly provided on the cover 230, and the magnetic suction member 400 is provided on the positioning post 231. The positioning groove is adapted to the positioning post 231, and the positioning post 231 is magnetically connected to the side wall of the positioning groove through the magnetic suction member 400.

[0065] It is understandable that by providing positioning posts 231 on the cap 230, users can quickly and accurately close the cap 230 into the positioning groove, thereby achieving rapid fixation of the copper foil 500. Furthermore, since the magnetic suction component 400 is magnetically connected to the side wall of the positioning groove, compared to the threaded connection of the traditional shot peening device 300, the operation is simpler and faster, and replacement is easier. This makes the production process of shot peening 300 operation and coating operation more compact, thus better adapting to modern automated production.

[0066] In one embodiment, the cover 230 is recessed inwards towards the window to form a cavity 232. It is understood that, since the copper foil 500 is relatively thin, if the cover 230 directly covers the entire copper foil 500, the copper foil 500 is easily deformed and adheres to the cover 230 under the impact of the shot peening 300, making it difficult to separate the copper foil 500 from the cover 230. Therefore, by forming a cavity 232 inwards towards the window on the cover 230, the present invention allows the cover 230 and the copper foil 500 to be spaced apart by a distance, effectively avoiding the phenomenon that the copper foil 500 is easily deformed and adheres to the cover 230 under the impact of the shot peening 300, making it difficult to separate the copper foil 500 from the cover 230. Furthermore, since the copper foil 500 is not blocked by the cap 230 during the shot peening process 300, the impact force during the shot peening process can be fully applied to the copper foil 500, thereby quickly obtaining a relatively uniform and continuous micron-level microcrystalline wrinkled layer.

[0067] In one embodiment, the shot peening is a steel ball, which impacts the copper foil, thereby enabling the copper foil to undergo good plastic deformation.

[0068] In one embodiment, the diameter of the shot peening is 1 mm to 2 mm, so that the shot peening can obtain tiny copper crystals on the surface of the copper foil, thereby ensuring the formation of a micron-scale microcrystalline wrinkled layer.

[0069] In one embodiment, the ultrasonic frequency is 16Hz–20Hz, and the duration is 9s–15s. It is understood that because the copper foil used is relatively thin, if the shot peening time is greater than 15s, the thin copper foil is prone to breakage during prolonged ultrasonic shot peening, resulting in waste. If the shot peening time is less than 9s, the microcrystalline wrinkle layer on the surface of the copper foil is small, which cannot provide good adhesion strength to the active material layer and cannot ensure a good negative electrode sheet with a good rough surface, thus failing to effectively improve the difficulty of wetting the battery negative electrode sheet. Therefore, this invention controls the ultrasonic frequency to 16Hz–20Hz, the duration to 9s–15s, and uses a shot peening diameter of 1mm–2mm to form a microcrystalline wrinkle layer with a particle size of 50μm–150μm on the surface of the copper foil.

[0070] In one embodiment, the ultrasonic shot peening operation includes a first shot peening operation and a second shot peening operation. The ultrasonic frequency of the first shot peening operation is 16Hz to 18Hz and the duration is 6s to 10s. The ultrasonic frequency of the second shot peening operation is 19Hz to 20Hz and the duration is 3s to 5s.

[0071] It is understandable that when copper foil is initially shot-peened, it is not deformed, resulting in a relatively close distance between the copper foil and the ultrasonic vibrating element. However, with continuous shot peening, the copper foil gradually deforms, increasing the distance between the ultrasonic vibrating element and the copper foil. Using the same ultrasonic frequency cannot guarantee that the shot peening will impact the surface of the copper foil. Therefore, this invention performs a first shot peening operation and a second shot peening operation on the copper foil. The ultrasonic frequency of the second shot peening operation is 19Hz-20Hz, which is higher than the ultrasonic frequency of 16Hz-18Hz in the first shot peening operation. Furthermore, the ultrasonic duration of the second shot peening operation is 3s-5s, which is longer than the ultrasonic duration of the first shot peening operation (6s-10s). This ensures that the shot peening can better impact the surface of the copper foil, resulting in a dense microcrystalline wrinkled layer with various copper crystal grain sizes at the micron level.

[0072] Furthermore, in order to ensure the formation of a continuous micron-scale microcrystalline wrinkled layer, in one embodiment, the number of shot peenings is multiple, so that multiple shot peenings can simultaneously impact the surface of the copper foil to obtain a continuous micron-scale microcrystalline wrinkled layer.

[0073] It should be noted that if a large number of shot peens are added, the force generated by multiple shot peens simultaneously impacting the surface of the copper foil will be significant. Furthermore, because the copper foil is relatively thin, it is prone to cracking. Therefore, in one embodiment, the number of shot peens is... By taking integer values, it can be ensured that the added shot can simultaneously perform ultrasonic shot peening on the copper foil. With an ultrasonic frequency of 16Hz to 20Hz, a duration of 9s to 15s, and a copper foil thickness of 6μm to 9μm, a continuous micron-level microcrystalline wrinkled layer can be obtained on the surface of the copper foil without any cracking.

[0074] In one embodiment, the copper foil has a thickness of 6 μm to 9 μm to maintain a certain thickness so that a microcrystalline wrinkled layer with a particle size of 50 μm to 150 μm can be formed on the surface of the copper foil during subsequent ultrasonic shot peening.

[0075] Furthermore, in a preferred embodiment, the copper foil has a thickness of 8 μm and an area of ​​37 mm². 2 The shot peening process involved 20 steel balls with a particle size of 1 mm. The first shot peening operation used an ultrasonic frequency of 18 Hz for 7 seconds, while the second operation used an ultrasonic frequency of 20 Hz for 5 seconds. This resulted in a continuous micron-level microcrystalline wrinkled layer with a particle size of 50 μm to 150 μm on the surface of the copper foil. The resulting bonding strength between the active material layer of the negative electrode and the copper foil was 4.92 N / cm. -1 .

[0076] In one embodiment, the step of rolling the semi-finished negative electrode sheet includes the following specific steps: rolling the semi-finished negative electrode sheet using a rolling device to compact the active material layer onto the surface of the copper foil. It is understood that rolling the semi-finished negative electrode sheet using a rolling device allows the active material to be tightly compacted onto the copper foil with the microcrystalline wrinkled layer, quickly obtaining a negative electrode sheet with high energy density and a rough surface, thus better adapting to automated production.

[0077] Please see Figure 5 This application also provides a negative electrode 20, which is produced using the negative electrode 20 preparation method described in any of the above embodiments. It is understood that the negative electrode 20 obtained using the negative electrode 20 preparation method of the present invention includes a copper foil layer 21 and an active material layer 23. A microcrystalline wrinkled layer 22 is formed on the side of the copper foil layer 21 facing the active material layer 23. The microcrystalline wrinkled layer 22 has multiple grooves. Multiple embedded posts 25 are provided on the protrusions of the active material layer 23 facing the copper foil layer 21. Each embedded post 25 is engaged in a corresponding groove. The side of the active material layer 23 facing away from the copper foil layer 21 is a rough surface 24.

[0078] It is understandable that, because the copper foil layer 21 has a microcrystalline wrinkled layer 22 on the side facing the active material layer 23, and because the microcrystalline wrinkled layer 22 has multiple grooves, the multiple embedded pillars 25 of the active material layer 23 can be engaged and set in the corresponding grooves, thereby achieving a continuous structure in which the active material layer 23 and the copper foil layer 21 are interlocked. This increases the contact area between the copper foil and the active material, and also increases the number of active sites, thereby increasing the probability of charge transfer between the copper foil and the active material layer 23. This improves the charge transfer efficiency at the contact interface between the copper foil and the active material layer 23, thus improving the cycle performance of the battery. Furthermore, it makes the copper foil layer 21 and the active material layer 23 more tightly and firmly bonded, thereby improving the adhesion strength between the copper foil and the active material layer 23. The resulting negative electrode sheet 20 has an adhesion strength of 4.35 N / cm. -1 ~4.92 N·cm -1 This effectively avoids the phenomenon that the active material is easy to fall off during the coating process of copper foil. Furthermore, since the side of the active material layer 23 facing away from the copper foil layer 21 is a rough surface 24, it is beneficial that multiple tiny channels will be formed between the rough surface 24 of the negative electrode sheet 20 and the separator when the battery cell is immersed in electrolyte. This allows the electrolyte to flow into the battery cell from multiple tiny channels at the same time, thereby improving the phenomenon that the battery negative electrode sheet 20 is difficult to wet.

[0079] In one embodiment, there are two active material layers, namely a first active material layer and a second active material layer, and there are two microcrystalline wrinkled layers, namely a first microcrystalline wrinkled layer and a second microcrystalline wrinkled layer. The first microcrystalline wrinkled layer and the second microcrystalline wrinkled layer are respectively formed on opposite sides of the copper foil layer. The first active material layer is stacked on the first microcrystalline wrinkled layer, and the second active material layer is stacked on the second microcrystalline wrinkled layer. It is understandable that by setting a first active material layer and a second active material layer on the copper foil layer, the unit density of the active material layer on the copper foil layer is greatly improved, thereby better improving the high energy density of the negative electrode sheet. At the same time, while improving the unit density of the active material layer on the copper foil layer, it also ensures the bonding strength between the first active material layer and the first microcrystalline wrinkled layer, and the bonding strength between the second active material layer and the second microcrystalline wrinkled layer, so as to obtain a negative electrode sheet with high energy density and good bonding strength. It is also beneficial to form multiple tiny channels on both sides of the negative electrode sheet during subsequent electrolyte immersion, so that the electrolyte can better enter the battery cell, thereby reducing the immersion time and improving the immersion effect, thus improving the phenomenon of difficult immersion of battery negative electrode sheets, which is especially suitable for wound high energy density batteries.

[0080] This application also provides a battery including the negative electrode sheet described in the above embodiment. It is understood that the battery includes a battery cell and a battery casing, with the battery cell housed within the battery casing. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator, and the positive electrode sheet, the separator, and the negative electrode sheet are wound together to form the battery cell. It is understood that because the positive electrode sheet, separator, and negative electrode sheet are wound together to form the battery cell, the rough surface of the active material layer on the negative electrode sheet can form multiple tiny channels with the separator, allowing the electrolyte to better enter the battery cell, thereby reducing the wetting time and improving the wetting effect. This improves the difficulty of wetting the negative electrode sheet, resulting in a battery with good electrical performance and cycle performance. Furthermore, the negative electrode sheet obtained by this invention is assembled into a battery, and the battery is subjected to cycle performance testing. After 800 cycles, the battery retains more than 90% of its capacitance, exhibiting good electrical performance and cycle performance.

[0081] Compared with the prior art, the present invention has at least the following advantages:

[0082] 1. The above-mentioned method for preparing the negative electrode involves ultrasonic shot peening of copper foil. This process allows the copper foil to be bombarded with ultrasonic energy, easily forming a microcrystalline wrinkled layer on its surface. This microcrystalline wrinkled layer increases the contact area between the copper foil and the active material, thereby increasing the amount of active material coated on the copper foil and ensuring a high-energy-density negative electrode. This also reduces the charge diffusion resistance and charge transfer resistance of the active material layer. Furthermore, the microcrystalline wrinkled layer provides good adhesion points for the active material, allowing it to be well coated and embedded on the surface of the copper foil within the microcrystalline wrinkled layer, forming a continuous, interlocking structure. This results in a tighter and stronger bond between the copper foil and the active material layer, improving the adhesion strength and effectively preventing the active material from easily detaching during the coating process. This ensures that the battery subsequently prepared has a high capacity. Therefore, with the same area, the copper foil not only increases the contact area with the active material, but also increases the number of active sites, thereby increasing the probability of charge transfer between the copper foil and the active material layer. This improves the charge transfer efficiency at the contact interface between the copper foil and the active material layer, and thus improves the cycle performance of the battery, resulting in a battery with better electrical and cycle performance.

[0083] 2. The above-mentioned negative electrode preparation method involves coating the microcrystalline wrinkled layer. Due to the fluidity of the active material, when coating the copper foil, the active material can form an active material layer with a similar wrinkle curvature to the wrinkle curvature of the microcrystalline wrinkled layer, so that the side of the active material layer facing away from the copper foil can form a rough surface. Then, after the negative electrode semi-finished product is rolled, the active material can be compacted and embedded on the copper foil to obtain a high-energy-density negative electrode with a rough surface. When the negative electrode is wound with the positive electrode and the separator to form a battery cell, multiple tiny channels will be formed between the rough surface of the negative electrode and the separator. This facilitates the simultaneous flow of electrolyte into the battery cell from multiple tiny channels, thereby improving the phenomenon of difficult wetting of the battery negative electrode, and is especially suitable for wetting of wound high-energy-density batteries.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a negative electrode, characterized in that, Includes the following steps: We offer copper foil with a thickness of 6μm to 9μm; The copper foil is subjected to ultrasonic shot peening to form a microcrystalline wrinkled layer on the surface of the copper foil; wherein the microcrystalline grain size of the microcrystalline wrinkled layer is 50μm~150μm; The microcrystalline wrinkled layer includes a plurality of copper crystals, which are spaced apart on the surface of the copper foil to form a continuous microcrystalline wrinkled layer; the plurality of copper crystals contain at least two different grain sizes, thereby enabling the formation of grooves at least two different depths in the microcrystalline wrinkled layer; The number of shot peenings is Take the integer part; The ultrasonic frequency of the ultrasonic shot peening operation is 16Hz~20Hz, and the duration is 9s~15s. The microcrystalline wrinkled layer is coated to form a rough active material layer on the surface of the copper foil, resulting in a negative electrode semi-finished product; wherein, the thickness of the active material layer is 120μm~125μm; the side of the active material layer facing the copper foil can form a continuous structure with interlocking shallow and deep layers; multiple channels with different flow rates are formed between the rough side of the active material layer facing away from the copper foil and the separator. The negative electrode semi-finished product is subjected to a rolling operation to obtain a negative electrode sheet.

2. The method for preparing the negative electrode sheet according to claim 1, characterized in that, The step of performing ultrasonic shot peening on the copper foil to form a microcrystalline wrinkled layer on the surface of the copper foil includes the following specific steps: The copper foil surface is subjected to ultrasonic shot peening using an ultrasonic shot peening device.

3. The method for preparing the negative electrode sheet according to claim 2, characterized in that, The step of performing ultrasonic shot peening on the surface of the copper foil using an ultrasonic shot peening device includes the following specific steps: The copper foil is placed at the ultrasonic window of the ultrasonic shot peening device and subjected to ultrasonic vibration to form a microcrystalline wrinkled layer on the surface of the copper foil.

4. The method for preparing a negative electrode sheet according to claim 1, characterized in that, The rolling operation of the semi-finished negative electrode sheet includes the following specific steps: The negative electrode semi-finished product is rolled by a rolling device to make the active material laminated firmly on the surface of the copper foil.

5. A negative electrode sheet, characterized in that, The negative electrode is produced using the method described in any one of claims 1 to 4.

6. A battery, characterized in that, Includes the negative electrode sheet as described in claim 5.

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