Pole piece, battery cell, battery and electric device

Abstract

This utility model discloses an electrode, a battery cell, a battery, and an electrical device, relating to the field of electrical device technology, and aims to solve the problem of how to reduce uneven current distribution on an electrode. The electrode includes a current collector, a conductive layer, and an active material layer. The current collector is connected to a tab. The conductive layer is disposed on the current collector. The portion of the current collector with the conductive layer is a first current collector portion. Within the plane of the current collector, the first current collector portion and the tab are spaced apart. The portion of the current collector portion located between the first current collector portion and the tab is a second current collector portion. The active material layer is disposed on the conductive layer and the second current collector portion.

Description

Technical Field

[0001] This application relates to the field of electrical equipment technology, and in particular to electrode sheets, battery cells, batteries and electrical equipment. Background Technology

[0002] With the rapid development of new energy technologies, electrical equipment such as electric vehicles has been widely used, and these devices typically require batteries to provide power. The battery cell is the core component of a battery. A battery cell includes electrodes, which may include current collectors and active materials disposed within the current collectors. The active materials participate in the charge-discharge reaction. The current collectors are connected to tabs, used to lead the collected electricity from the current collectors to the external circuitry of the battery, or to introduce the external circuitry of the battery into the current collector circuitry.

[0003] In the prior art, the current needs to travel a long distance from the tab to a region far from the tab, resulting in a large ohmic voltage drop and uneven current density distribution on the electrode. Utility Model Content

[0004] The purpose of this application is to provide an electrode, a cell, a battery, and an electrical device, which aims to solve the problem of how to reduce uneven current distribution on the electrode.

[0005] In a first aspect, an electrode is provided, which includes a current collector, a conductive layer and an active material layer. The current collector is connected to a tab, the conductive layer is disposed on the current collector, the portion of the current collector with the conductive layer is a first current collector portion, the first current collector portion and the tab are spaced apart in the plane where the current collector is located, the portion of the current collector located between the first current collector portion and the tab is a second current collector portion, and the active material layer is disposed on the conductive layer and the second current collector portion.

[0006] In this way, the conductivity of the first current collector section can be enhanced, the impedance reduced, the conductivity difference between the first current collector section and the electrode at the tab reduced, and the ohmic voltage drop reduced, so that the current density distribution inside the cell is uniform and lithium plating at the electrode at the tab is avoided due to uneven potential.

[0007] In some embodiments, the conductive layer is a porous material layer.

[0008] In some embodiments, the conductive layer is a conductive carbon layer.

[0009] In some embodiments, the thickness of the conductive layer is greater than or equal to 0.5 μm and less than or equal to 5 μm.

[0010] In some embodiments, the thickness of the conductive layer is greater than or equal to 1 μm.

[0011] In some embodiments, along the arrangement direction of the first current collector, the second current collector, and the tab, the size of the first current collector is a first size B, and the size of the second current collector is a second size A. The second size and the first size satisfy: 0.2×(A+B / 2)≤A≤0.4×(A+B / 2).

[0012] In some embodiments, the electrode is a positive electrode or a negative electrode.

[0013] In some embodiments, the portion of the active material layer disposed on the conductive layer is the first active material portion, and the portion of the active material layer disposed on the first current collector portion and the second current collector portion is the second active material portion; when the electrode is a positive electrode, the specific capacity of the second active material portion is lower than that of the first active material portion, or when the electrode is a negative electrode, the specific capacity of the second active material portion is higher than that of the first active material portion. In some embodiments, the active material layer is a graphite layer.

[0014] In some embodiments, the portion of the active material layer disposed on the conductive layer is a first active material portion, and the surface of the first active material portion facing away from the conductive layer is provided with a groove.

[0015] In some embodiments, the groove is a circular groove; or, the groove is a long groove extending along a straight line, a broken line, or a curve.

[0016] In some embodiments, the width of the groove is greater than or equal to 20 μm and less than or equal to 80 μm; and / or, the thickness of the conductive layer is a first thickness, the thickness of the first active material portion is a second thickness, and the depth of the groove is greater than or equal to 0.2 times the sum of the first thickness and the second thickness and less than or equal to 0.45 times the sum of the first thickness and the second thickness.

[0017] In some embodiments, the number of grooves is multiple, and the multiple grooves are spaced apart.

[0018] In some embodiments, the distance between two adjacent grooves is greater than or equal to 500 μm and less than or equal to 1000 μm.

[0019] In some embodiments, the current collector further includes a third current collector portion, which is located on the side of the first current collector portion away from the second current collector portion in the plane where the current collector is located, and an active material layer is also disposed in the third current collector portion.

[0020] Secondly, a battery cell is also provided, which includes the electrode sheets as described in any of the above technical solutions.

[0021] Thirdly, a battery is also provided, which includes the battery cell as described in the above technical solutions, or the electrode sheet as described in any of the above technical solutions.

[0022] Fourthly, an electrical device is also provided, which includes the battery as described in the above technical solution, or the battery cell as described in the above technical solution, or the electrode sheet as described in any of the above technical solutions.

[0023] Since the battery cells, batteries, and electrical devices provided in this application include the electrode sheets described in any of the above technical solutions, they can solve the same technical problems and achieve the same effects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of this application;

[0026] Figure 2 A schematic diagram of the structure of a battery cell with opposite tabs provided for some embodiments of this application;

[0027] Figure 3 A schematic diagram of the structure of a battery cell on the same side as the tab provided in some embodiments of this application;

[0028] Figure 4 for Figure 2 A top view of the electrode plates in the battery cell shown;

[0029] Figure 5 for Figure 3 A top view of the electrode plates in the battery cell shown;

[0030] Figure 6 for Figure 4 A schematic diagram of the cross-section of the electrode shown;

[0031] Figure 7 for Figure 5 A schematic diagram of the cross-section of the electrode shown.

[0032] Figure label:

[0033] 1000, Vehicle; 100, Battery cell; 101, Positive electrode; 102, Negative electrode; 103, Separator; 10, Electrode;

[0034] 1. Current collector; 11. First current collector section; 12. Second current collector section; 13. Third current collector section;

[0035] 2. Conductive layer; 21. Conductive carbon layer;

[0036] 3. Active material layer; 31. First active material portion; 311. Groove; 32. Second active material portion;

[0037] 4. Electrode; 41. First Electrode; 42. Second Electrode. Detailed Implementation

[0038] In the embodiments of this application, the terms "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," "fourth," "fifth," and "sixth" may explicitly or implicitly include one or more of that feature.

[0039] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0040] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0041] In the embodiments of this application, "parallel," "perpendicular," and "equal" include the described situation and situations similar to the described situation, the range of which is within an acceptable deviation range, said acceptable deviation range being determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range for approximate parallelism may be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range for approximate perpendicularity may also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range for approximate equality may be, for example, a difference between the two equals being less than or equal to 5% of either one.

[0042] This application provides an electrical device, which can be a mobile phone, ship, aircraft, vehicle 1000, energy storage system, etc. This application uses vehicle 1000 as an example for illustration. Vehicle 1000 can be a hybrid vehicle, a pure electric vehicle, etc. Vehicle 1000 can also be a sedan, bus, truck, etc.

[0043] like Figure 1 As shown, Figure 1 This is a structural schematic diagram of a vehicle 1000 provided for some embodiments of this application. The vehicle 1000 may include a body, wheels, and a drive assembly. The body is used to carry people or goods, and the wheels are connected to the underside of the body and are capable of rolling on the road surface to move the body. The drive assembly is connected to the body and is used to drive the wheels to rotate, thereby causing the wheels to roll on the road surface. For example, the drive assembly may be a drive motor, or it may include a drive motor and an engine, or it may include a drive motor, an engine, and a generator.

[0044] The drivetrain may also include a battery, which can be connected to the vehicle body and to a drive motor to provide electrical power to the drive motor, thereby enabling the drivetrain to drive the wheels. The battery may also be connected to a generator to charge the battery by generating electricity from the generator.

[0045] Batteries can be lithium-ion batteries, nickel-metal hydride batteries, lead-acid batteries, lithium polymer batteries, fuel cells, etc. Batteries are the core device for storing electrical energy in vehicles.

[0046] The battery may also include at least one cell 100, that is, the number of cells 100 can be one or more. When the number of cells 100 is multiple, the multiple cells 100 can be connected in series and parallel. The cell 100 may also include at least one of the following auxiliary components: integrated battery management system (BMS), thermal management system, casing, etc., to provide stable power to the electrical equipment and ensure safe operation.

[0047] Cell 100 is the core component of a battery. It is usually an electrochemical device encapsulated in a metal casing. It is the unit that stores and releases electrical energy, converting chemical energy into electrical energy through internal chemical reactions.

[0048] In some embodiments, please refer to Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of the structure of a cell 100 on the opposite side of the tab 4, provided in some embodiments of this application. Figure 3This is a schematic diagram of the structure of a battery cell 100 on the same side as the tab 4, provided for some embodiments of this application. The battery cell 100 may include a positive electrode 101, a negative electrode 102, and a separator 103. The positive electrode 101 and the negative electrode 102 are the two polar ends of the battery cell 100. The positive electrode 101 and the negative electrode 102 are respectively coated on a current collector 1, and are separated from each other by the separator 103. The separator 103 allows ions to pass between the positive electrode 101 and the negative electrode 102 while preventing direct contact between them to prevent short circuits. The electrolyte is the transport medium for ion migration and is suitable for maintaining ion flow within the battery cell 100. The working principle of the battery cell 100 is mainly based on the movement of lithium ions between the positive electrode 101 and the negative electrode 102. During charging, lithium ions are extracted from the positive electrode, pass through the electrolyte, and embed into the negative electrode, thus placing the negative electrode in a lithium-rich state. During discharging, lithium ions are extracted from the negative electrode, pass through the electrolyte, and embed into the positive electrode, completing the release of electrical energy. This back-and-forth embedding and de-embedding process of lithium ions between the positive electrode 101 and the negative electrode 102 enables the battery cell 100 to store and release electrical energy.

[0049] In some embodiments, please refer to Figures 4 to 7 , Figure 4 for Figure 2 The top view of electrode 10 in cell 100 shown. Figure 5 for Figure 3 The top view of electrode 10 in cell 100 shown. Figure 6 for Figure 4 A schematic diagram of the cross-section of electrode 10 is shown. Figure 7 for Figure 5 The diagram shows a cross-sectional view of the electrode 10. The electrode 10 may include a current collector 1, a conductive layer 2, and an active material layer 3. The current collector 1 is connected to a tab 4. The current collector 1 serves as the conductive substrate of the electrode 10, and it can carry the active material layer 3 and the conductive layer 2, while collecting electrical energy. The tab 4 is used to lead the electrical energy collected by the current collector 1 to the external circuit of the battery, or to introduce the external circuit of the battery into the circuit of the current collector 1. The active material layer 3 is suitable for participating in the charging and discharging reaction of the battery.

[0050] The conductive layer 2 is disposed on the current collector 1. The portion of the current collector 1 with the conductive layer 2 is the first current collector portion 11. In the plane where the current collector 1 is located, the first current collector portion 11 and the tab 4 are spaced apart. The portion of the current collector 1 located between the first current collector portion 11 and the tab 4 is the second current collector portion 12. The active material layer 3 is disposed on the conductive layer 2 and the second current collector portion 12.

[0051] In this way, this arrangement can enhance the conductivity of the first current collector 11, reduce the impedance, narrow the conductivity difference between the first current collector 11 and the electrode 10 at the tab 4, reduce the ohmic voltage drop, so that the current density distribution inside the cell 100 is uniform and lithium deposition at the electrode 10 at the tab 4 is avoided due to uneven potential.

[0052] The electrode 10 can be either the positive electrode 101 or the negative electrode 102 mentioned above.

[0053] In some embodiments, the current collector 1 further includes a third current collector portion 13. In the plane where the current collector 1 is located, the third current collector portion 13 is located on the side of the first current collector portion 11 away from the second current collector portion 12, and the active material layer 3 is also disposed on the third current collector portion 13.

[0054] In this way, by placing the third current collector 13 on the side of the first current collector 11 away from the second current collector 12, and the active material layer 3 is also placed in the third current collector 13, the active material layer 3 of the third current collector 13 and the electrolyte jointly participate in the charging and discharging reaction of the battery.

[0055] For ease of explanation, the tab 4 of the current collector 1 connected to the positive electrode 101 is the first tab 41, and the tab 4 of the current collector 1 connected to the negative electrode 102 is the second tab 42.

[0056] exist Figure 2 In the illustrated embodiment, the first tab 41 and the second tab 42 are located along the first direction of the current collector 1 (e.g., ...). Figure 2 On opposite sides of direction A), for example, the first tab 41 can be located at the upper end of the current collector 1 along the first direction, and the second tab 42 can be located at the lower end of the current collector 1 along the first direction. In the region near the first tab 41 (i.e., the second current collector portion 12), the active material layer 3 of the positive electrode 101 and the electrolyte jointly participate in the battery's charge-discharge reaction. In the region near the second tab 42 (i.e., the third current collector portion 13), the active material layer 3 on the negative electrode 102 and the electrolyte jointly participate in the battery's charge-discharge reaction. A conductive layer 2 is provided in the region away from the tab 4 (i.e., the first current collector portion 11). This arrangement can enhance the conductivity of the first current collector portion 11, reduce impedance, narrow the conductivity difference between the first tab 41 and the second tab 42 and the first current collector portion 11, and reduce the ohmic voltage drop, so that the current density distribution inside the cell 100 is uniform, preventing the electrode potential of the first current collector portion 11 from falling below the lithium plating potential too early, thus preventing lithium plating and affecting battery performance.

[0057] exist Figure 3 In the illustrated embodiment, the first tab 41 and the second tab 42 are located along the first direction of the current collector 1 (e.g., ...). Figure 3On the same side as direction A), for example, the first tab 41 and the second tab 42 can both be located at the upper end of the current collector 1 along the first direction. In the area close to the first tab 41 and the second tab 42 (i.e., the second current collector portion 12), the active material layer 3 of the positive and negative electrode plates 102 and the electrolyte jointly participate in the charging and discharging reaction of the battery. The area away from the tab 4 (i.e., the first current collector portion 11) is provided with a conductive layer 2. This can also enhance the conductivity of the first current collector portion 11, reduce the impedance, narrow the conductivity difference between the first tab 41 and the second tab 42 and the first current collector portion 11, and reduce the ohmic voltage drop, so that the current density distribution inside the cell 100 is uniform, and the potential of the electrode plate 10 of the first current collector portion 11 is prevented from falling below the lithium plating potential too early, resulting in lithium plating and affecting the performance of the battery.

[0058] In some examples, both the conductive layer 2 and the active material layer 3 can be disposed on both sides of the current collector 1 along its length (e.g., Figure 6 In some other examples, the conductive layer 2 and the active material layer 3 can both be disposed on one side of the current collector 1 along the length direction (as shown in the figure, B1).

[0059] This application provides an exemplary description using the example that both the conductive layer 2 and the active material layer 3 can be disposed on opposite sides of the current collector 1 along its length.

[0060] In some embodiments, the conductive layer 2 is a porous material layer.

[0061] This improves the electrolyte retention capacity of electrode 10. Furthermore, the porous structure of the porous material layer allows for thorough electrolyte wetting, enhancing charge and discharge performance.

[0062] In some embodiments, the conductive layer 2 is a conductive carbon layer 21.

[0063] In this way, the voltage drop between the conductive carbon layer 21 and the current collector 1 is smaller, which can improve the performance of the electrode 10.

[0064] It is known that if the thickness D of the conductive layer 2 is thin, the conductivity of the electrode 10 will be poor; if the thickness D of the conductive layer 2 is thick, under the premise that the thickness of the electrode 10 is constant, the thickness of the active material layer 3 will be reduced, the amount of active material per unit area on the first current collector 11 will be reduced, and the energy density of the cell 100 will be affected.

[0065] In some embodiments, the thickness D of the conductive layer 2 can be greater than or equal to 0.5 μm and less than or equal to 5 μm. When the thickness D of the conductive layer 2 is within this range, the thickness is moderate and can balance conductivity and energy density.

[0066] For example, the thickness D of the conductive layer 2 can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0067] In some embodiments, the thickness D of the conductive layer 2 is greater than or equal to 1 μm. When the thickness D of the conductive layer 2 is within this range, the thickness D of the conductive layer 2 is moderate, which can better balance conductivity and energy density.

[0068] Define the arrangement direction along the first current collector 11, the second current collector 12 and the tab 4. The size of the first current collector 11 is defined as the first size B, and the size of the second current collector 12 is defined as the second size A. Under the premise that the length of the current collector is constant, the larger the first size B is, the more it will compress the second size A, affecting the lithium intercalation capability. The larger the second size A is, the more it will compress the first size B, resulting in a reduction in the size of the conductive layer, affecting the conductivity.

[0069] In some embodiments, the second dimension A and the first dimension B satisfy: 0.2×(A+B / 2)≤A≤0.4×(A+B / 2). When the lengths of the first current collector 11 and the second current collector 12 are within this range, the lengths are moderate and can balance conductivity and lithium intercalation capability.

[0070] In some embodiments, the active material layer 3 is a graphite layer.

[0071] In this way, the conductivity of the first current collector 11 and the second current collector 12 can be improved. In addition, the low cost of graphite can reduce the cost of the electrode 10 and further reduce the cost of the cell 100.

[0072] In some embodiments, the portion of the active material layer 3 disposed on the conductive layer 2 is the first active material portion 31, and the portion of the active material layer 3 disposed on the first current collector 11 and the second current collector 12 is the second active material portion 32. When the electrode is a positive electrode 101, the specific capacity of the second active material portion 32 is lower than that of the first active material portion 31; or when the electrode is a negative electrode 102, the specific capacity of the second active material portion 32 is higher than that of the first active material portion 31. Specific capacity refers to the amount of electrical capacity that can be released per unit mass (typically one gram) of active material.

[0073] In this way, when the electrode is a positive electrode 101, the specific capacity of the second active material portion 32 is lower than that of the first active material portion 31; in other words, the specific capacity of the first active material portion 31 is higher than that of the second active material portion 32. When the electrode is a negative electrode 102, the specific capacity of the second active material portion 32 is higher than that of the first active material portion 31; in other words, the specific capacity of the first active material portion 31 is lower than that of the second active material portion 32. This can compensate for the reduction in capacitance generated by the active material due to the conductive layer, thereby reducing the difference in capacitance generated by the active material at different locations on the electrode and improving charge / discharge efficiency.

[0074] In some other embodiments, the first active material portion 31 and the second active material portion 32 may also be the same material.

[0075] In some embodiments, the portion of the active material layer 3 disposed on the conductive layer 2 is a first active material portion 31, and the surface of the first active material portion 31 facing away from the conductive layer 2 is provided with a groove 311.

[0076] In this way, by providing a groove 311 on the surface of the first active material portion 31 facing away from the conductive layer 2, the groove 311 can increase the contact area between the active material layer 3 and the electrolyte, improve the wetting effect of the electrode 10 of the first current collector portion 11, and the electrolyte stored in the groove 311 can replenish the electrolyte consumed during the cycle in a timely manner, thereby improving the fast charging performance.

[0077] The groove 311 can be formed by laser etching technology.

[0078] In some embodiments, the groove 311 is a circular groove 311; or, the groove 311 is a long groove extending along a straight line, a broken line, or a curve. This structure is simple and easy to process.

[0079] It is known that if the width E of the groove 311 is too narrow, the penetration range of the electrolyte in the electrode 10 is limited, and the wetting effect of the electrode 10 in the first current collector 11 is not good; if the width E of the groove 311 is too wide, more space will be occupied for the active material, resulting in a decrease in volumetric energy density and affecting the performance of the battery.

[0080] In some embodiments, the width E of the groove 311 is greater than or equal to 20 μm and less than or equal to 80 μm. When the width E of the groove 311 is within this range, the electrolyte can uniformly wet the electrode 10 of the first current collector 11, thereby taking into account both the wetting effect of the electrolyte and the volumetric energy density.

[0081] For example, the width E of the groove 311 can be 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, etc.

[0082] It is known that if the depth G of the groove 311 is too shallow, the electrolyte may not be able to fully penetrate the electrode 10 of the first current collector 11. Incomplete wetting may cause local lithium plating, leading to a short circuit and affecting the battery performance. If the depth G of the groove 311 is too deep, it may occupy more space for the active material, resulting in a decrease in volumetric energy density.

[0083] In some embodiments, the thickness D of the conductive layer 2 is a first thickness, the thickness of the first active material portion 31 is a second thickness, and the depth G of the groove 311 is greater than or equal to 0.2 times the sum of the first thickness and the second thickness, and less than or equal to 0.45 times the sum of the first thickness and the second thickness. When the depth G of the groove 311 is within this range, the electrolyte can uniformly wet the entire electrode 10, thereby taking into account both the wetting effect of the electrolyte and the volumetric energy density of the battery.

[0084] In some embodiments, the number of grooves 311 can be multiple, and the multiple grooves 311 are spaced apart. For example, the number of grooves 311 can be 2, 3, 4, 5, 6, 7, etc.

[0085] In this way, the electrolyte can uniformly and quickly wet the entire electrode 10, thereby improving the wetting effect of the electrolyte and the performance of the battery, and rapidly improving the wetting effect of the electrode 10 of the first current collector section 11.

[0086] It is known that if the distance F between two adjacent grooves 311 is too small, the density of the grooves 311 will be greater, occupying more space of active material, or the distribution will be concentrated, thus affecting the volumetric energy density of the battery or the uniformity of wetting. If the distance F between two adjacent grooves 311 is too large, the larger distance may lead to poor wetting effect of the electrolyte on the electrode 10 of the first current collector 11.

[0087] In some embodiments, the distance F between two adjacent grooves 311 is greater than or equal to 500 μm and less than or equal to 1000 μm. When the distance F between two adjacent grooves 311 is within this range, the distance is moderate, and the electrolyte can uniformly and quickly wet the entire electrode 10, thereby taking into account both the wetting effect of the electrolyte and the volumetric energy density of the battery.

[0088] For example, the distance F between two adjacent grooves 311 can be 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm, etc.

[0089] The above describes various implementation methods of the electrode 10. Specifically, the battery with different electrode 10s in this application can have the following 9 embodiments.

[0090] Example 1:

[0091] 1. The positive electrode sheet is prepared with slurry according to the formula. The positive electrode adopts the lithium supplementation scheme. The negative electrode is prepared with two kinds of slurry: conductive carbon layer slurry and pure graphite slurry.

[0092] 2. The positive electrode is first coated with a conductive coating, then coated with a positive electrode paste. After coating, the electrode sheet is baked, rolled, slit, and die-cut, and then stacked with the negative electrode sheet.

[0093] 3. The negative electrode sheet uses a conductive carbon layer slurry coated on the bottom layer of the first current collector section. The length of the conductive carbon layer is B = 147 mm, and the thickness of the conductive carbon layer is D = 2 μm. The length of the second current collector section is A = 50 mm. A graphite slurry is coated on the top layer. The thickness of the graphite slurry in the second current collector section is C = 64 μm, and the thickness of the graphite slurry in the first current collector section is CD = 62 μm. After coating, baking, rolling, and slitting, the rolled and slit electrode sheet is laser-etched to form grooves. After die-cutting, it is stacked with the positive electrode. The width of the groove is E = 20 μm, the spacing between two adjacent grooves is F = 500 μm, and the depth of the groove is G = 0.3C.

[0094] 4. Positive and negative electrode sheets and separators are stacked and hot-pressed to form a battery cell. After the battery cell is assembled with structural components, it forms a dry cell. The battery is then subjected to electrolyte injection, pre-charging, wetting, formation, electrolyte replenishment, charging, aging, and capacity testing to prepare a finished battery.

[0095] Example 2:

[0096] The difference from Example 1 is that the spacing between two adjacent grooves is F = 800 μm, the groove depth is G = 0.4C, and the rest is the same as Example 1.

[0097] Example 3:

[0098] The difference from Example 1 is that the spacing between two adjacent grooves is F = 1000 μm, the groove depth is G = 0.4C, and the rest is the same as Example 1.

[0099] Example 4:

[0100] The difference from Example 1 is that the width of the groove is E = 50 μm, the distance between two adjacent grooves is F = 800 μm, and the depth of the groove is G = 0.4C. The rest is the same as Example 1.

[0101] Example 5:

[0102] The difference from Example 4 is that the thickness of the conductive carbon layer is D = 3 μm, and the spacing between two adjacent grooves is F = 1000 μm, but otherwise it is the same as Example 4.

[0103] Example 6:

[0104] The difference from Example 1 is that the thickness of the conductive carbon layer is D = 3 μm, and the spacing between two adjacent grooves is E = 80 μm, but otherwise it is the same as Example 1.

[0105] Example 7:

[0106] The difference from Example 6 is that the spacing between two adjacent grooves is F = 800 μm, the groove depth is G = 0.45 C, and the rest is the same as Example 6.

[0107] Example 8:

[0108] The difference from Example 4 is that the region far from the electrode, B, is 167 mm, and the region close to the electrode, A, is 30 mm. Otherwise, it is the same as Example 4.

[0109] Example 9:

[0110] The difference from Example 4 is that the region far from the electrode, B, is 107 mm, and the region close to the electrode, A, is 90 mm; otherwise, they are the same as in Example 4.

[0111] Comparative Group Implementation Scheme:

[0112] The positive and negative electrode sheets are prepared with slurry according to the formula. The active material of the negative electrode sheet adopts the graphite scheme. The negative electrode sheet adopts single-layer coating. The electrode sheet is not laser etched. Other aspects are the same as in Example 1.

[0113] The blade batteries described in Examples 1-9 and the comparative examples were subjected to continuous fast charging cycle at a constant temperature of 25±2℃, with a maximum fast charging rate of 8C, a rest period of 30 minutes, and then discharged to 3.0V at a rate of 0.5C. This charge-discharge cycle was repeated 800 times, and the discharge capacity and lithium plating status of the 800th cycle were recorded. The capacity retention rate (%) after the cycle was calculated as: discharge capacity after 800 cycles / initial discharge capacity × 100%. The capacity retention rate and lithium plating status of the blade batteries described in Examples 1-9 and the comparative examples are shown in Table 1.

[0114] Table 1. Test results of the schemes described in Examples 1-9 and the schemes described in the comparative examples.

[0115]

[0116]

[0117] The test results from the schemes described in Examples 1-9 and the schemes described in the comparative group show that setting a conductive carbon layer and grooves in the first current collector (i.e., the area away from the tab) can improve the battery cycle performance. After 800 cycles, except for Examples 7, 8 and 9, no lithium plating was observed in the other schemes.

[0118] The test results of the schemes described in Examples 1-4 show that, for the same conductive carbon layer design, when the width E of the groove is small, the depth G of the groove needs to be increased and the spacing F between two adjacent grooves needs to be shortened; otherwise, the electrolyte wetting path will be less and the improvement in cycle performance will not be significant.

[0119] The test results of the schemes described in Examples 3, 5, and 7 show that when the groove design is the same, if the thickness D of the conductive carbon layer is too thick, it will lead to greater capacity loss during the cycle process. This is mainly because the conductive battery will consume some active lithium. Therefore, the thickness D of the conductive carbon layer is best controlled between 1-5 μm.

[0120] The test results of the schemes described in Examples 4, 8, and 9 show that when the groove design is the same, the thickness D of the conductive carbon layer in the first current collector section (i.e., the area away from the tab) exceeds the design range, and the battery has slight lithium plating.

[0121] In the description of the embodiments of this application, specific features, structures, materials or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0122] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electrode sheet, characterized in that, It includes a current collector (1), a conductive layer (2), and an active material layer (3); The current collector (1) is connected to a tab (4), the conductive layer (2) is disposed on the current collector (1), the portion of the current collector (1) with the conductive layer (2) is the first current collector portion (11), in the plane where the current collector (1) is located, the first current collector portion (11) and the tab (4) are spaced apart, the portion of the current collector (1) located between the first current collector portion (11) and the tab (4) is the second current collector portion (12), and the active material layer (3) is disposed on the conductive layer (2) and the second current collector portion (12).

2. The electrode sheet according to claim 1, characterized in that, The conductive layer (2) is a porous material layer.

3. The electrode sheet according to claim 2, characterized in that, The conductive layer (2) is a conductive carbon layer (21).

4. The electrode sheet according to claim 1, characterized in that, The thickness D of the conductive layer (2) is greater than or equal to 0.5 μm and less than or equal to 5 μm.

5. The electrode sheet according to claim 4, characterized in that, The thickness D of the conductive layer (2) is greater than or equal to 1 μm.

6. The electrode sheet according to claim 1, characterized in that, Along the arrangement direction of the first current collection part (11), the second current collection part (12) and the tab (4), the size of the first current collection part (11) is a first size B, and the size of the second current collection part (12) is a second size A. The second size and the first size satisfy: 0.2×(A+B / 2)≤A≤0.4×(A+B / 2).

7. The electrode sheet according to claim 1, characterized in that, The electrode is either a positive electrode (101) or a negative electrode (102).

8. The electrode sheet according to claim 1, characterized in that, The portion of the active material layer (3) disposed on the conductive layer (2) is the first active material portion (31), and the portion of the active material layer (3) disposed on the first current collection portion (11) and the second current collection portion (12) is the second active material portion (32). When the electrode is a positive electrode (101), the specific capacity of the second active material portion (32) is lower than that of the first active material portion (31), or when the electrode is a negative electrode (102), the specific capacity of the second active material portion (32) is higher than that of the first active material portion (31).

9. The electrode sheet according to claim 1, characterized in that, The active material layer (3) is a graphite layer.

10. The electrode sheet according to claim 1, characterized in that, The portion of the active material layer (3) disposed on the conductive layer (2) is the first active material portion (31), and the surface of the first active material portion (31) facing away from the conductive layer (2) is provided with a groove (311).

11. The electrode according to claim 10, characterized in that, The groove (311) is a circular groove (311); Alternatively, the groove (311) may be a long groove that extends along a straight line, a broken line, or a curve.

12. The electrode sheet according to claim 10, characterized in that, The width E of the groove (311) is greater than or equal to 20 μm and less than or equal to 80 μm; And / or, the thickness of the conductive layer (2) is a first thickness, the thickness of the first active material portion (31) is a second thickness, and the depth G of the groove (311) is greater than or equal to 0.2 times the sum of the first thickness and the second thickness, and less than or equal to 0.45 times the sum of the first thickness and the second thickness.

13. The electrode sheet according to claim 10, characterized in that, The number of grooves (311) is multiple, and the multiple grooves (311) are arranged at intervals.

14. The electrode sheet according to claim 13, characterized in that, The distance F between two adjacent grooves (311) is greater than or equal to 500 μm and less than or equal to 1000 μm.

15. The electrode sheet according to claim 1, characterized in that, The current collector (1) further includes a third current collector section (13). In the plane where the current collector (1) is located, the third current collector section (13) is located on the side of the first current collector section (11) away from the second current collector section (12). The active material layer (3) is also provided on the third current collector section (13).

16. A battery cell, characterized in that, Includes the electrode sheet as described in any one of claims 1-15.

17. A battery, characterized in that, It includes the electrode sheet as described in any one of claims 1-15, or the battery cell as described in claim 16.

18. An electrical appliance, characterized in that, It includes the electrode sheet according to any one of claims 1-15, the cell according to claim 16, or the battery according to claim 17.

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