Lithium ion battery pole piece and battery

Abstract

The invention discloses a lithium ion battery pole piece, the pole piece comprises a current collector, at least one surface of the current collector is provided with an active material layer, and the surface of the active material layer is provided with a groove. According to the pole piece disclosed by the invention, by arranging the surface grooves, active sites and lithium ion diffusion channels of the negative electrode on the surface of the pole piece are increased, so that the active substance layer can be fully infiltrated by electrolyte, and lithium precipitation is improved.

Description

[0001] This application is a divisional application of patent application No. 202503170079389.0, filed on February 21, 2025, entitled "Lithium-ion Battery Electrode and Battery". Technical Field

[0002] This application belongs to the field of lithium-ion battery technology, specifically relating to a lithium-ion battery electrode and a battery. Background Technology

[0003] Lithium-ion batteries possess high energy and power densities, making them the preferred technology for portable electronic devices, power tools, and hybrid / fully electric vehicles. Therefore, as consumers demand increasingly higher product performance, the market's need for high-performance lithium-ion batteries is becoming more urgent.

[0004] Lithium-ion battery electrode sheets are generally made by forming an active material layer on the electrode current collector. Conventional electrode sheets have low porosity of the active material layer, resulting in low wetting and absorption efficiency of the electrolyte. The ion diffusion path in the electrode sheet is increased, ion polarization is increased, and it is also easy to cause problems such as slow lithium ion migration speed and high battery internal resistance. This leads to a deterioration in the kinetic performance of the electrochemical device, which in turn causes problems such as poor rate performance, poor cycle performance, and easy lithium deposition. Especially under low temperature charge and discharge and high current density conditions, lithium dendrites are more likely to form, which also poses a significant safety hazard to the electrochemical device. These problems become more prominent as the thickness of the active material layer of the electrode sheet increases.

[0005] Graphite is a common anode material for lithium-ion batteries. The specific surface area of ​​graphite refers to the total area per unit mass of graphite. High specific surface area graphite can lead to increased side reactions and a risk of reduced initial efficiency of the electrochemical device. Conversely, low specific surface area graphite has poor kinetic properties, which can cause lithium deposition on the anode surface. Furthermore, its larger particle size and poor interparticle bonding result in a sparse and unstable SEI film, leading to decreased cycle performance. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this application provides a lithium-ion battery electrode and a battery.

[0007] The first aspect of this application provides a lithium-ion battery electrode, the electrode including a current collector, the current collector including a first surface and a second surface opposite to each other along its thickness direction, the first surface being provided with an active material layer, the surface of the active material layer having a plurality of trenches, the direction from the active material layer to the current collector along the thickness direction of the electrode being a first direction, and when viewed along the first direction, the total area of ​​the plurality of trenches is 1%-10% of the surface area of ​​the active material layer, and / or the total volume of the trenches in the active material layer is 0.05%-10% of the total volume of the negative electrode active material layer.

[0008] According to the electrode of the first aspect, the active material layer has two or more grooves, and the multiple grooves are arranged along the length of the electrode.

[0009] According to the electrode in the first aspect, the angle between the length direction of the groove and the length direction of the electrode is 45°~90°.

[0010] According to the electrode in the first aspect, the cross-sectional shape of the trench perpendicular to its length direction is rectangular; When viewed along the first direction, the groove shape is one of rectangle, parallelogram, or trapezoid; and / or, multiple grooves are parallel to each other and are evenly distributed along the length of the electrode in the active material layer of the electrode.

[0011] According to the first aspect, the electrode is a negative electrode, and the active material layer is a negative active material layer.

[0012] According to the electrode in the first aspect, the trench satisfies the following formula: 0.00001×V0≤V≤0.003×V0, V = H×L×Y×L0 / (L+S), V0 = B × m × H0, The vertical distance between the deepest point of the trench and the electrode surface is H mm, the trench width on the electrode surface is L mm, the trench length on the electrode surface is Y mm, the length of the negative electrode active material layer is L0 mm, the spacing between two adjacent trenches is S mm, and the specific surface area of ​​the negative electrode active material is B mm. 2 / g, the coating mass of the negative electrode active material in the negative electrode active material layer is mg / mm 2 The total volume of all the trenches is V mm. 3 The thickness of the negative electrode active material layer is H0, and 0 < H <H0。

[0013] According to the electrode in the first aspect, the groove width L on the electrode surface also satisfies: 0.1×Dv10≤L≤100×Dv90, Wherein, Dv10 is the particle size corresponding to a cumulative particle size distribution percentage of 10% for the negative electrode active material, and Dv90 is the particle size corresponding to a cumulative particle size distribution percentage of 90% for the negative electrode active material.

[0014] According to the first aspect of the electrode, the groove width L on the electrode surface satisfies: 0.5×Dv10≤L≤50×Dv90.

[0015] According to the first aspect of the electrode, the groove is perpendicular to the length direction of the electrode.

[0016] According to the first aspect of the electrode, the length of the groove on the electrode surface Y ≤ Y0, where Y0 is the width of the negative electrode active material layer.

[0017] According to the first aspect of the electrode sheet, the negative electrode active material is graphite.

[0018] According to the first aspect of the electrode, the specific surface area B of the negative electrode active material is < 3 m². 2 / g.

[0019] A second aspect of this application provides a lithium-ion battery comprising the electrode of the first aspect.

[0020] The lithium-ion battery electrode of this application has, but is not limited to, the following beneficial effects: This application creates channels by trenching on the electrode, particularly the negative electrode, which increases the diffusion channels for lithium ions and also increases the active sites in the low specific surface area graphite negative electrode, thus avoiding the surface lithium deposition problem of low specific surface area graphite during charge and discharge. The trenching increases the reaction sites between graphite and the electrolyte, allowing for the formation of a denser SEI film, slowing down cycle degradation, and improving battery performance. By adjusting the relationship between the trenches and the active material layer, the electrolyte wetting and energy density of the lithium-ion battery can be further adjusted, resulting in an electrode with both good wetting effect and high energy density. Attached Figure Description

[0021] Figure 1 A schematic diagram of a lithium-ion battery electrode sheet according to this application is shown, wherein, Figure 1 (a) shows a top view of the electrode. Figure 1 (b) shows a cross-sectional view of the electrode.

[0022] Figure 2 A schematic diagram of a lithium-ion battery electrode sheet according to this application is shown, wherein, Figure 2 (a) shows a top view of the electrode. Figure 2 (b) shows a cross-sectional view of the electrode.

[0023] Explanation of reference numerals in the attached figures: 1. Active material layer; 2. Current collector; 3. Groove; X - length direction of electrode; Y - width direction of electrode; Z - thickness direction of electrode (first direction). Detailed Implementation

[0024] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0025] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0026] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0027] This application provides a lithium-ion battery electrode, which includes a current collector 2. At least one surface of the current collector 2 is provided with an active material layer 1. The surface of the active material layer 1 has a plurality of trenches 3. The direction from the active material layer 1 to the current collector 2 along the thickness direction of the electrode is a first direction (Z-axis direction). When viewed along the first direction, the total area of ​​the plurality of trenches 3 is 1%-10% of the surface area of ​​the active material layer 1, and / or the total volume of the plurality of trenches 3 in the active material layer 1 is 0.05%-10% of the total volume of the active material layer 1.

[0028] This application utilizes laser processing technology to create a uniform trench structure in the active material layer of the electrode, thereby improving lithium plating and cycle degradation in the battery. The total area of ​​the multiple trenches 3 is 1%-10% of the surface area of ​​the active material layer 1, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. The larger the total trench area relative to the surface area of ​​the active material layer 1, the better the diffusion effect of lithium ions. Simultaneously, the ratio of the total volume of the multiple trenches 3 in the active material layer 1 to the total volume of the active material layer 1 can be 0.05%-10%, for example, 0.05%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 2%, 5%, 8%, 10%. However, if the total volume of the multiple trenches 3 is too large relative to the total volume of the active material layer 1, it will lead to a significant loss in the battery's volumetric energy density. Preferably, the total volume of the multiple trenches 3 in the active material layer 1 is 0.05%-5% of the total volume of the negative electrode active material layer 1. Specifically, this application involves trenching on the surface of the negative electrode sheet, which increases the active sites and lithium-ion diffusion channels for low specific surface area negative electrode active materials such as graphite, overcoming the problem of surface lithium plating during charge and discharge. The trenching increases the reaction sites between the low specific surface area graphite and the electrolyte, enabling the formation of a denser SEI film and slowing down cycle degradation. If the number of trenches 3 in the negative electrode active material layer 1 is too large, it will lead to a decrease in battery capacity; if the number of trenches 3 in the negative electrode active material layer 1 is too small, it will not be able to provide active sites and diffusion channels, and the lithium plating problem cannot be overcome.

[0029] In this application, the total area of ​​the trenches refers to the total area of ​​the multiple trenches 3 on the surface of the electrode sheet measured along the first direction (Z-axis direction). The surface area of ​​the active material layer 1 refers to the area of ​​the surface of the active material layer 1 without trenches along the thickness direction of the electrode sheet, that is, the projected area of ​​the active material layer 1 on the current collector 2. The total volume of the trenches refers to the sum of the volumes of all trenches on the surface of the active material layer 1. For example, the volume of each trench 3 can be calculated by the length × width × height of the trench, and the total volume of the trenches can be obtained by summing the volumes of all trenches. The total volume of the active material layer 1 refers to the volume of the active material layer 1 without trenches, which can be calculated by the length × width × height of the active material layer 1 without trenches.

[0030] In one embodiment, the active material layer 1 has two or more trenches 3, and the multiple trenches 3 are arranged along the length direction of the electrode sheet. Preferably, the angle between the length direction of the groove 3 and the length direction of the electrode is 45°~90°.

[0031] This application does not specifically limit the shape of the trench 3; the top view distribution shape of the trench 3 can be a straight line, a broken line, a curve, etc. Although the trench 3 on the surface of the active material layer 1 can be in any direction, considering the actual grooving process (such as laser grooving, mechanical grooving, etc.), setting multiple trenches 3 in a parallel distribution facilitates processing, reduces processing difficulty, and is beneficial to improving the processing efficiency of the trench 3. Setting the angle between the length direction of the trench 3 and the length direction of the electrode sheet to 45°~90°, compared to the case where the angle is less than 45°, allows the electrolyte to wet the center of the electrode sheet more quickly through the trench 3, improving the wetting effect.

[0032] In the embodiments of this application, parallel trench distribution refers to the axes along the length direction of any two trenches 3 (e.g., Figure 1 The grooves on the left (shown by the dashed center line) are parallel to each other, but due to process errors, measurement errors, etc., a certain angle is allowed between the axes of the two grooves, which is ±5°. These embodiments are all included within the protection scope of the claims of this application.

[0033] In a preferred embodiment, the groove 3 has a rectangular cross-sectional shape perpendicular to its length direction.

[0034] In a preferred embodiment, when viewed along the first direction, the shape of the groove 3 is one of a rectangle, a parallelogram, or a trapezoid.

[0035] In a preferred embodiment, the multiple trenches 3 are parallel to each other and are uniformly distributed along the length of the electrode in the electrode active material coating area.

[0036] In one specific embodiment, a plurality of trenches 3 are evenly distributed parallel to each other on the surface of the active material layer 1 of the electrode.

[0037] The above settings allow for the uniform distribution of multiple trenches 3 in the active material layer 1 of the electrode, increasing the active sites and lithium ion diffusion channels on the electrode surface. This enables the electrolyte to fully wet the active material layer 1 and improve lithium plating.

[0038] The parallelism of multiple grooves 3 means that they are roughly parallel, and there is a process tolerance, with a tolerance range of ±10°. The uniform distribution means that the multiple grooves 3 are distributed at approximately equal intervals, and there is a process tolerance between the intervals, with a tolerance range of ±0.3mm.

[0039] Figure 1 A schematic diagram of the lithium-ion battery electrode of this application is shown. An active material layer 1 is formed on the current collector 2, and grooves are cut on the active material layer 1 to obtain trenches 3. Multiple trenches are distributed in parallel. The angle between the length direction of the trenches 3 and the length direction (Y-axis direction) of the electrode is 90°. The length direction of the trenches 3 is perpendicular to the length direction of the electrode. The cross-sectional shape of the trenches 3 perpendicular to its extension direction (X-axis direction, i.e., the width direction of the electrode) is rectangular. When viewed along the first direction (Z-axis direction), the shape of the trenches 3 is rectangular. The trenches 3 are uniformly distributed along the length direction (Y-axis direction) of the electrode in the active material coating area of ​​the electrode.

[0040] Figure 2 Another schematic diagram of the lithium-ion battery electrode of this application is shown. An active material layer 1 is formed by coating a current collector 2, and grooves are cut into the active material layer 1 to obtain trenches 3. Multiple trenches 3 are distributed in parallel, and the angle θ between the length direction of the trenches 3 and the length direction (Y-axis direction) of the electrode is 45°. The cross-sectional shape of the trenches 3 perpendicular to its extension direction (X-axis direction, i.e., the width direction of the electrode) is rectangular; when viewed along the first direction (Z-axis direction), the shape of the trenches 3 is parallelogram and trapezoid; the trenches 3 are uniformly distributed along the length direction (Y-axis direction) of the electrode active material layer.

[0041] In one embodiment, the electrode sheet is a negative electrode sheet, and the active material layer is a negative active material layer.

[0042] In one specific embodiment, the trench 3 satisfies the following formula: 0.00001×V0≤V≤0.003×V0, V = H×L×Y×L0 / (L+S), V0 = B × m × H0, The vertical distance between the deepest point of the trench and the electrode surface is H mm, the trench width on the electrode surface is L mm, the trench length on the electrode surface is Y mm, the length of the negative electrode active material layer is L0 mm, the spacing between two adjacent trenches is S mm, and the specific surface area of ​​the negative electrode active material is B mm. 2 / g, the coating mass of the negative active material in the negative active material layer is m g / mm 2 , the total volume of all the grooves is V mm 3 , the thickness of the negative active material layer is H0, and 0 < H < H0, and the preferred range of the depth is 0 < H ≤ 0.5H0.

[0043] Among them, V is the total volume of all the grooves (mm 3 ), H×L×Y is the volume of a single groove 3 (mm 3 ), L0 / (L + S) is the total number of grooves 3, and the total volume V of all the grooves, the specific surface area B of the negative active material, the mass m of the negative active material in the negative active material layer 1, and the thickness H0 of the negative active material layer 1 satisfy the above relationship 0.00001×V0 ≤ V ≤ 0.003×V0. When V < 0.00001×V0, the total volume of multiple grooves 3 is too small to allow the electrolyte to fully infiltrate the electrode sheet, resulting in lithium deposition. When V > 0.003×V0, the total volume of grooves 3 is too large, resulting in too little negative active material content, thus resulting in insufficient volumetric energy density. At the same time, as the depth of the groove 3 increases, the grooving process may cause a large thermal effect near the groove 3, causing the negative active material to fall off and form dust, resulting in an increase in the internal resistance of the battery, an electrochemical reaction imbalance, and even piercing the diaphragm, which has an adverse impact on the battery performance.

[0044] In this application, the vertical distance H from the deepest part of the groove 3 to the surface of the electrode sheet can be obtained by the following method: Cut the negative electrode sheet and measure it using a scanning electron microscope (SEM) to obtain the vertical distance from the deepest part of the groove 3 to the surface of the electrode sheet. Accumulate the numerical values of the vertical distances at 10 positions inside the groove 3 and take the average value to obtain the vertical distance H1 from the deepest part of the groove 3 to the surface of the electrode sheet. In the case of having n grooves 3, use the same method to measure the vertical distances H2, H3,..., H from the deepest parts of the other grooves 3 to the surface of the electrode sheet n , calculate the average value of the vertical distances H1~H from the deepest parts of all the grooves 3 to the surface of the electrode sheet n to obtain H.

[0045] The width L of the groove on the surface of the electrode sheet can be obtained by the following method: Measure the electrode sheet using a scanning electron microscope (SEM) to obtain the width of the groove on the surface of the electrode sheet. Accumulate the numerical values at 10 positions and take the average value to obtain the width L1 of the groove on the surface of the electrode sheet of the groove 3. In the case of having n grooves 3, use the same method to measure the widths L2, L3,..., L of the grooves on the surface of the electrode sheet of the other grooves 3 n , calculate the average value of the widths L1~L of the grooves on the surface of the electrode sheet of all the grooves 3 n to obtain L.

[0046] The trench length Y on the electrode surface can be obtained by the following method: The electrode is measured using a scanning electron microscope (SEM) to obtain the trench length. Ten measurements are taken, and the average value is taken to obtain the trench length Y1 for trench 3. With n trenches 3, the same method is used to measure the trench lengths Y2, Y3, ..., Y... of the other trenches. n Calculate the trench lengths Y1~Y2 on the electrode surface of all trenches 3. n Y is obtained by averaging the values.

[0047] The distance S between two adjacent grooves 3 can be obtained by the following method: The electrode is measured using a scanning electron microscope (SEM) to obtain the distance between two adjacent grooves 3. Ten measurements are taken, and the average value is used to obtain the distance S1 between the two adjacent grooves. With n grooves 3, the distances S2, S3, ..., S between other adjacent grooves 3 are measured using the same method. n-1 Calculate the trench lengths S1~S on the electrode surface of all trenches 3. n-1 The average value is S.

[0048] In particular, such as Figure 2 As shown, when viewed along the first direction (Z-axis direction), i.e., with the electrode thickness direction as the top view, when there is a certain angle between the length direction of the groove 3 and the length direction of the electrode, the top view shape of the groove 3 on the electrode surface is a parallelogram or trapezoid. The width L of the groove 3 on the electrode surface is the distance between the two parallel walls formed by the groove and the active material layer 1. The distance S between two adjacent grooves 3 is the perpendicular distance between the two adjacent walls of the two adjacent grooves 3. Y is the length of the centerline of the two parallel walls formed by the groove 3 and the active material layer 1, and the straight line containing the centerline is the middle parallel line of the straight lines containing the two parallel walls. When the top view shape of the groove 3 is a parallelogram, Y is the length of the aforementioned two parallel walls. When the top view shape is a trapezoid, Y is the length of the median line of the trapezoid, as shown. Figure 2 The Y' shown.

[0049] In this application, when the trenches 3 are uniformly and parallelly distributed in the active material coating area, the parameters of the trenches 3 can be obtained by testing using the following methods: Five samples were randomly taken from the electrode, each with the same area. The sample size could be adjusted according to the coverage of the active material layer 1, for example, 2cm×2cm, 3cm×3cm, 4cm×4cm, 5cm×5cm, and 6cm×6cm. Cross-sectional and surface samples were prepared respectively. The parameters of the trenches 3 on the electrode were measured using a scanning electron microscope (ZEISS Sigma / X-max). The depth H, width L, length Y, and spacing S of the trenches 3 were averaged from five measurements.

[0050] In this application, the length L0, width Y0, and thickness H0 of the active material layer 1 are all the thickness of a single layer of active material after cold pressing.

[0051] In this application, the specific surface area (B) of graphite can be obtained by the following method: using a specific surface area analyzer (TriStarⅡ3020X), the powder sample is pretreated at 200℃ for 2h before the test, and the test environment is nitrogen.

[0052] In one specific embodiment, the trench width L on the surface of the negative electrode sheet also satisfies: 0.1×Dv10≤L≤100×Dv90, preferably, 0.5×Dv10≤L≤50×Dv90. Wherein, Dv10 is the particle size corresponding to a cumulative particle size distribution percentage of 10% for the negative electrode active material, and Dv90 is the particle size corresponding to a cumulative particle size distribution percentage of 90% for the negative electrode active material. When the width L of trench 3 is less than 0.1 × Dv10, the width of trench 3 is too small, which is not conducive to electrolyte wetting; when the width of trench 3 is greater than 100 × Dv90, the width of trench 3 is too large, which will result in too little negative electrode active material, leading to a reduction in battery capacity.

[0053] In this application, the particle size can be obtained by the following method: The particle size of graphite is tested using a laser particle size analyzer (Malvern2000). Approximately 5g of graphite powder sample is placed in a 50ml clean beaker, 1-2 drops of 1% surfactant P40 are added, and the sample is stirred to wet it. Then, approximately 20ml of water is added to completely disperse the powder in the water. The sample is then placed in an ultrasonic cleaner with a power of 120W and a frequency of 53kHz and sonicated for 5 minutes. After stirring evenly, the sample is injected for testing.

[0054] In this application, the shape of the projection of the groove 3 onto the current collector along the first direction can be regular or irregular, both of which can achieve good results. The terms "width," "length," and "spacing" have their conventional meanings in the art: "Width" is generally understood to mean that when the projection of the groove 3 onto the current collector along the first direction is rectangular, the width is the width of that rectangle; when the projection of the groove 3 onto the current collector along the first direction is non-rectangular, the width is an equivalent width to the width of a rectangle with the same area. "Length" is generally understood to mean that when the projection of the groove 3 onto the current collector along the first direction is rectangular, the length is the length of that rectangle; when the projection of the groove 3 onto the current collector along the first direction is non-rectangular, the length is an equivalent length to the length of a rectangle with the same area. "Spacing" refers to the shortest distance between the edges of two adjacent grooves 3.

[0055] In one embodiment, the trench 3 is perpendicular to the length direction of the electrode sheet; Preferably, the length Y of the trench on the electrode surface is less than or equal to Y0, where Y0 is the width of the active material layer 1. In this application, the trench 3 is formed on the active material layer 1 and is constrained by the width of the active material layer 1; therefore, the length Y of the trench 3 is less than or equal to Y0. Simultaneously, changes in the length of the trench 3 will cause corresponding changes in the total area and total volume of the trench 3, thereby affecting the electrolyte wetting effect and the volumetric energy density of the battery.

[0056] It should be noted that the perpendicularity of the trench 3 to the length direction of the electrode sheet means that the axis of the trench 3 along its length is theoretically perpendicular to the length direction (X-axis) of the electrode sheet, i.e., θ=90°. However, due to unavoidable process errors and measurement errors, there is a certain angular error in the perpendicularity between the trench 3 and the length direction (X-axis) of the electrode sheet, with an error range of ±5°. Due to the expansion and contraction of the active material after cycling and unavoidable process errors and measurement errors, the measurement errors of the length, width, depth, and spacing of the trench 3 after cycling are within ±5%. In one embodiment, the negative electrode active material is graphite. Preferably, the specific surface area B of the negative electrode active material is less than 3 m². 2 / g.

[0057] This application also provides a method for preparing lithium-ion electrodes, including: (1) A negative electrode slurry containing active material is coated on one surface of the current collector 2, and the active material layer 1 is formed by cold pressing; (2) Grooving is made on the surface of the active material layer 1. Preferably, the grooving is made by laser processing or mechanical processing.

[0058] The current collector 2 in this application can be a metal foil, such as copper foil, aluminum foil, etc.

[0059] In one specific implementation, the electrode is a negative electrode.

[0060] In one specific embodiment, in step (1), the negative electrode slurry further includes a binder and / or a thickener; Preferably, the adhesive is selected from one or more of the following: styrene-butadiene rubber latex (SBR), styrene-acrylic rubber, polyacrylic acid; and / or Preferably, the thickener is selected from one or more of the following: sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0061] In one embodiment, the negative electrode slurry contains 94% to 98% by mass of the negative electrode active material.

[0062] This application also provides a lithium-ion battery comprising the aforementioned electrode or an electrode prepared according to the aforementioned method.

[0063] This application does not impose any special restrictions on the source of any raw materials. Unless otherwise specified, all raw materials are conventional products that can be obtained through commercial purchase.

[0064] Battery System The battery systems used in the comparative and example embodiments employ lithium cobalt oxide as the positive electrode active material, graphite as the negative electrode active material, along with a separator, electrolyte, and packaging shell. They are manufactured through processes including mixing, coating, assembly, electrolyte injection, and formation. Specifically: (1) Positive electrode plate: The positive electrode slurry of the battery is composed of 97.6% lithium cobalt oxide (LiCoO2) as the positive electrode active material, 1.3% polyvinylidene fluoride (PVDF) as the binder, and 1.1% conductive carbon black (SP) as the conductive agent. The positive electrode slurry is coated onto the positive electrode current collector aluminum foil with a coating weight of 235 mg / 1540.25 mm. 2 The thickness of the positive electrode active material layer after cold pressing is 36 μm.

[0065] (2) Negative electrode plate: The battery's negative electrode slurry is composed of 98% graphite as the negative electrode active material, 1.0% styrene-butadiene rubber latex (SBR) as a binder, and 1.0% sodium carboxymethyl cellulose (CMC) as a thickener. The negative electrode slurry is coated onto the copper foil of the negative electrode current collector, with a coating weight of 130 mg / 1540.25 mm². 2 The coating weight m of the negative electrode active material graphite is Y0×L0÷1540.25×130×98%=8.7061g / mm. 2 The negative electrode coating has a width Y0 of 71.7 mm and a length L0 of 1468 mm. After cold pressing, the thickness H0 of the negative electrode active material layer 1 is 44 μm. The surface area of ​​the negative electrode active material layer 1 is Y0 × L0 = 105255.6 mm². 2 The total volume of the negative electrode active material layer 1 is Y0×L0×H0=4631.25mm. 3 .

[0066] (3) Electrolyte: The electrolyte is a solution prepared by mixing LiPF6 and solvent (ethylene carbonate: diethyl carbonate: methyl ethyl carbonate: vinyl carbonate in a mass ratio of 8:85:5:2) in a mass ratio of 8:92.

[0067] (4) Diaphragm: The substrate of the separator is a 9μm thick polypropylene separator, and the adhesive layer is 15μm thick.

[0068] The negative electrode sheet, separator, and positive electrode sheet are stacked in sequence and then wound to form a bare cell. After encapsulation, electrolyte injection (i.e., injection of electrolyte), and standing, a cell that is to be fully wetted is obtained. After formation and other steps, a lithium-ion battery is obtained.

[0069] The charging limit voltage U of the batteries in the comparative examples and embodiments of this application is 4.5V. It is hereby stated that the electrode processing method of this application is applicable to batteries of various voltage systems and is not limited to the 4.5V system. By comparing the prior art negative electrode processing method (without laser processing) used in the comparative examples with the laser processing method for the electrode used in the embodiments provided in this application, the lithium plating interface after 10 cycles and the capacity retention rate after 500 cycles are compared.

[0070] Examples and Comparative Examples Grooves are etched on the active material layer of the electrode using laser processing according to the parameters in Table 1.

[0071] Laser processing method: Fiber laser is used for processing. Laser process parameters: Power: 10%~90%, Laser speed: 1000~70000mm / s.

[0072] Trench parameters obtained in each embodiment and comparative example, and performance testing of lithium-ion batteries. The performance of the lithium-ion batteries and positive / negative electrode trench parameters prepared in each embodiment and comparative example were tested using the following methods, and the test results are listed in Table 2.

[0073] 1. Comparison method for lithium plating interfaces: At an ambient temperature of 25°C, both the comparative and example batteries were cycled 10 times using the same charging and discharging process. The batteries were then disassembled for comparative observation of the negative electrode, revealing the lithium plating interface. Charging process: Step 1: Charge the battery to 4.5V using a constant current of 2C; Step 2: Charge the battery to 0.05C using a constant voltage of 4.5V; Step 3: Let the battery sit for 5 minutes; Step 4: Discharge the battery to 3.0V using a constant current of 0.5C; Step 5: Let the battery sit for 5 minutes; Step Six: Repeat steps one through five 10 times.

[0074] The battery cells that have undergone 10 cycles were disassembled, and the interface of the negative electrode was observed for comparison. To describe the lithium plating at the interface, the interface conditions were graded. By visual inspection, if the surface of the negative electrode is golden yellow and shows no abnormalities, it is determined to be non-lithium plating; if the negative electrode shows intermittent punctate purple spots, lithium plating, or lithium plating on purple spots, it is determined to be slight lithium plating; if the main body of the negative electrode shows large areas of continuous purple spots, lithium plating, or lithium plating on purple spots, and the abnormal area percentage is <50%, it is determined to be lithium plating; if the main body of the negative electrode shows large areas of continuous purple spots, lithium plating, or lithium plating on purple spots, and the abnormal area percentage is ≥50%, it is determined to be severe lithium plating.

[0075] 2. Cycle performance testing of lithium-ion batteries: The capacity retention rate is calculated as follows: At a test ambient temperature of 25°C, both the comparative and example batteries are charged and discharged 500 times using the same charging process. The discharge capacity after 500 charge-discharge cycles is then divided by the discharge capacity at the start of the first cycle to obtain the capacity retention rate. Charging process: Step 1: Charge the battery to 4.5V using a constant current of 2C; Step 2: Charge the battery to 0.05C using a constant voltage of 4.5V; Step 3: Let the battery sit for 5 minutes; Step 4: Discharge the battery to 3.0V using a constant current of 0.5C; Step 5: Let the battery sit for 5 minutes; Step Six: Repeat steps one through five 500 times.

[0076] 3. Battery volumetric energy density test: Methods for testing volumetric energy density include: Battery cell capacity test: The battery cell was left to stand at 25℃ for 30 minutes to ensure that the temperature of the battery cell was 25℃. Then the battery was discharged at a constant current of 0.2C to 3.0V. After standing for 10 minutes, the battery cell was charged at a constant current of 0.5C to 4.53V. The constant voltage charging was continued at 4.53V until the current was 0.02C. After standing for 10 minutes, the battery cell was discharged at a constant current of 0.2C to 3.0V. The discharge capacity C and discharge plateau voltage U of the battery cell in this discharge step were recorded.

[0077] Battery cell volume measurement: Use calipers to measure the length, width, and height of the battery's outer surface, and calculate the volume V of a single battery cell. d .

[0078] Volumetric energy density calculation: E = C × U / V d The unit is Wh / L.

[0079] Table 1

[0080] Table 2

[0081] The test results above show that: (1) By comparing the ungrooved Comparative Examples 1 and 2 with Examples 1-17, it can be seen that the grooving treatment of the electrode can improve the lithium plating interface and cycle retention rate; comparing Comparative Examples 1 and 2, it can be seen that the specific surface area B of the negative electrode active material is <3 m² 2 At / g, it can improve the lithium plating interface.

[0082] (2) By comparing Examples 1-17, when the trench parameters of the laser-treated electrode meet the corresponding relationship, the active sites and lithium ion diffusion channels of the low specific surface area graphite anode are increased, which improves the surface lithium plating problem of low specific surface area graphite during charging and discharging, and significantly improves the lithium plating interface and cycle capacity retention of the battery.

[0083] The larger the grooved area on the electrode surface, the more electrolyte transport paths there are in all directions, and the more significant the improvement. When the total volume of trench 3 is large, the volumetric energy density loss of the battery is significant, therefore there is an optimal range for each parameter.

[0084] In Comparative Examples 1 and 2, the surface wetting effect of the ungrooved electrode was poor, leading to lithium plating. The capacity retention rate was also significantly lower compared to the examples using graphite as the negative electrode material with the same surface area. In Comparative Example 3, the excessively narrow groove width resulted in a small proportion of the total volume of the groove 3 to the total volume of the negative electrode active material layer 1, leading to severe lithium plating on the electrode. The excessively narrow groove widths in Comparative Examples 3 and 4 not only resulted in a small proportion of the total volume of the groove 3 to the total volume of the negative electrode active material layer 1, but also caused V < 0.00001 × V0, which negatively impacted the performance of the electrode. In Comparative Example 3, 0.00001×V0=3.064547, V=0.3154513; in Comparative Example 4, 0.00001×V0=3.064547, V=1.31241397, resulting in severe lithium plating on the electrode and low capacity retention; in Comparative Example 5, 0.3×V0=919.36416, V=935.6053, V>0.003×V0, the excessively large groove volume leads to excessive loss of active material on the electrode surface, resulting in a significant reduction in the energy density of the battery.

[0085] Similarly, in the embodiments, when the total volume of the trench 3 is too small as a proportion of the total volume of the negative electrode active material layer 1, the number of reaction sites of graphite and electrolyte on the electrode surface increases less, and lithium plating still occurs; while when the total volume of the trench 3 is too large as a proportion of the total volume of the active material, it will lead to a decrease in the volumetric energy density of the battery. The embodiments within the above preferred range have better wetting effect, capacity retention rate and energy density.

[0086] In summary, the electrode processing method of this application increases the reaction sites between graphite and electrolyte, which, within the preferred parameter range, can improve the lithium plating interface and slow down the cycle decay process.

[0087] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A lithium-ion battery electrode, characterized in that, The electrode includes a current collector, which includes a first surface and a second surface opposite to each other along its thickness direction. The first surface is provided with an active material layer, and the surface of the active material layer has a plurality of grooves. A first direction is defined as the direction from the active material layer to the current collector along the thickness direction of the electrode. When viewed along the first direction, the total area of ​​the plurality of grooves is 1%-10% of the surface area of ​​the active material layer, and / or, the total volume of the grooves in the active material layer is 0.05%-10% of the total volume of the active material layer. Wherein, the width L of the groove satisfies: 0.1×Dv10≤L≤100×Dv90, Wherein, Dv10 is the particle size corresponding to a cumulative particle size distribution percentage of 10% for the negative electrode active material, and Dv90 is the particle size corresponding to a cumulative particle size distribution percentage of 90% for the negative electrode active material.

2. The electrode sheet according to claim 1, characterized in that, The plurality of grooves are arranged along the length of the electrode.

3. The electrode sheet according to claim 1, characterized in that, The angle between the length direction of the groove and the length direction of the electrode is 45°~90°.

4. The electrode sheet according to claim 3, characterized in that, The groove has a rectangular cross-sectional shape perpendicular to its length. When viewed along the first direction, the trench shape is one of a rectangle, a parallelogram, or a trapezoid; and / or, a plurality of the trenches are parallel to each other and uniformly distributed along the length of the electrode in the active material layer.

5. The electrode sheet according to any one of claims 1 to 4, characterized in that, The electrode sheet is a negative electrode sheet, and the active material layer is a negative active material layer.

6. The electrode sheet according to claim 4, characterized in that, The trench satisfies the following formula: 0.00001×V0≤V≤0.003×V0, V = H×L×Y×L0 / (L+S), V0 = B × m × H0, The vertical distance between the deepest point of the trench and the electrode surface is H mm, the trench width on the electrode surface is L mm, the trench length on the electrode surface is Y mm, the length of the negative electrode active material layer is L0 mm, the spacing between two adjacent trenches is S mm, and the specific surface area of ​​the negative electrode active material is B mm. 2 / g, the coating mass of the negative electrode active material in the negative electrode active material layer is mg / mm 2 The total volume of all the trenches is V mm. 3 The thickness of the negative electrode active material layer is H0, and 0 < H <H0。 7. The electrode sheet according to claim 1, characterized in that, The width L of the groove on the electrode surface satisfies: 0.5×Dv10≤L≤50×Dv90.

8. The electrode sheet according to claim 1, 6, or 7, characterized in that, The groove is perpendicular to the length direction of the electrode.

9. The electrode sheet according to claim 8, characterized in that, The length of the groove on the electrode surface is Y≤Y0, where Y0 is the width of the negative electrode active material layer.

10. The electrode sheet according to claim 6, characterized in that, The negative electrode active material is graphite.

11. The electrode according to claim 10, characterized in that, The specific surface area B of the negative electrode active material is less than 3 m². 2 / g.

12. A lithium-ion battery comprising the electrode sheet according to any one of claims 1 to 11.

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