Pole piece, battery cell, battery and electric device

Abstract

The utility model discloses a kind of pole piece, battery cell, battery and electric equipment, it is related to electric equipment technical field, to solve how to reduce the problem of uneven current distribution on pole piece. The pole piece includes current collector, conductive layer, first active material layer and second active material layer, current collector is connected with tab, conductive layer is set in current collector, the part of current collector with conductive layer is first current collection part, in the plane where current collector is located, first current collection part is spaced apart from tab, the part of current collector between first current collection part and tab is second current collection part, first active material layer is set in second current collection part, second active material layer is set in conductive layer and first active material layer, the gram capacity of first active material layer is different from the gram capacity of second active material layer.

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, comprising a current collector, a conductive layer, a first active material layer, and a second active material layer. The current collector is connected to a tab, and 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. In the plane where the current collector is located, the first current collector portion and the tab are spaced apart. The portion of the current collector located between the first current collector portion and the tab is a second current collector portion. The first active material layer is disposed on the second current collector portion, and the second active material layer is disposed on the conductive layer and the first active material layer. The specific capacity of the first active material layer is different from that of the second active material layer.

[0006] In this way, by placing the conductive layer in the first current collector section, the conductivity of the area far from the tab (i.e., 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 narrowed, and the ohmic voltage drop decreased. By placing the first active material layer in the second current collector section and the second active material layer in both the conductive layer and the first active material layer, and by placing the specific capacity of the first active material layer different from that of the second active material layer, the lithium intercalation capability of the area near the tab 6 (i.e., the second current collector section 12) can be changed, thus preventing lithium plating on the electrode 10 of the second current collector section 12.

[0007] In some embodiments, the specific capacity of the first active material layer is greater than that of the second active material layer.

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

[0009] In some embodiments, the conductive layer is a conductive carbon layer.

[0010] 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.

[0011] In some embodiments, the thickness of the conductive layer is greater than or equal to 1 μm.

[0012] 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).

[0013] In some embodiments, the first active material layer is an active material layer doped with a first type of material, which is used to enhance the lithium intercalation space.

[0014] In some embodiments, the first type of material includes at least one of silicon-based materials, tin-based materials, and hard carbon.

[0015] In some embodiments, the mass percentage of the first type of material in the first active material layer is greater than or equal to 3% and less than or equal to 8%.

[0016] In some embodiments, the first current collector is directed toward the tab, and the mass percentage of the first type of material in the first active material layer gradually increases.

[0017] In some embodiments, the electrode is a positive electrode or a negative electrode.

[0018] In some embodiments, the current collector further includes a third current collection portion. In the plane where the current collector is located, the third current collection portion is located on the side of the first current collection portion away from the second current collection portion. The electrode also includes a third active material layer. The third active material layer is disposed in the third current collection portion. The second active material layer is also disposed in the third active material layer. The specific capacity of the third active material layer is different from that of the second active material layer.

[0019] Secondly, a battery cell is also provided, which includes the electrode sheets as described in any of the above technical solutions.

[0020] 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.

[0021] 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.

[0022] 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

[0023] 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.

[0024] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of this application;

[0025] Figure 2 A schematic diagram of the structure of a battery cell with opposite tabs provided for some embodiments of this application;

[0026] 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;

[0027] Figure 4 for Figure 2 A top view of the electrode plates in the battery cell shown;

[0028] Figure 5 for Figure 3 A top view of the electrode plates in the battery cell shown;

[0029] Figure 6 for Figure 4 A schematic diagram of the cross-section of the electrode shown;

[0030] Figure 7 for Figure 5 A schematic diagram of the cross-section of the electrode shown.

[0031] Figure label:

[0032] 1000, Vehicle; 100, Battery cell; 101, Positive electrode; 102, Negative electrode; 103, Separator; 10, Electrode;

[0033] 1. Current collector; 11. First current collector section; 12. Second current collector section; 13. Third current collector section;

[0034] 2. Conductive layer; 21. Conductive carbon layer;

[0035] 3. First active material layer;

[0036] 4. Second active material layer;

[0037] 5. Third active material layer;

[0038] 6. Electrode; 61. First electrode; 62. Second electrode. Detailed Implementation

[0039] 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.

[0040] 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.

[0041] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0042] 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.

[0043] 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.

[0044] like Figure 1 As shown, Figure 1This 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.

[0045] 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.

[0046] 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.

[0047] 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 auxiliary components such as an integrated battery management system (BMS), a thermal management system, and a casing, to provide stable power to the electrical equipment and ensure safe operation.

[0048] 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.

[0049] 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 6, 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 6, 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 the 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.

[0050] 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, a first active material layer 3, and a second active material layer 4. The current collector 1 is connected to a tab 6. The current collector 1 serves as the conductive substrate of the electrode 10. The current collector 1 can carry the first active material layer 3, the second active material layer 4, and the conductive layer 2, and collect electrical energy. The tab 6 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 current collector circuit. The first active material layer 3 and the second active material layer 4 are suitable for participating in the charging and discharging reactions of the battery.

[0051] A conductive layer 2 is disposed on a 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 6 are spaced apart. The portion of the current collector 1 located between the first current collector portion 11 and the tab 6 is the second current collector portion 12. A first active material layer 3 is disposed on the second current collector portion 12. A second active material layer 4 is disposed on the conductive layer 2 and the first active material layer 3. The specific capacity of the first active material layer 3 is different from that of the second active material layer 4.

[0052] In this way, by placing the conductive layer 2 on the first current collector 11, the conductivity of the area far from the tab 6 (i.e., the first current collector 11) can be enhanced, the impedance reduced, the conductivity difference between the first current collector 11 and the electrode 10 at the tab 6 narrowed, and the ohmic voltage drop decreased. By placing the first active material layer 3 on the second current collector 12, and the second active material layer 4 on the conductive layer 2 and the first active material layer 3, the specific capacity of the first active material layer 3 is different from that of the second active material layer 4, so as to change the lithium intercalation capability of the area near the tab 6 (i.e., the second current collector 12) and avoid lithium plating on the electrode 10 of the second current collector 12.

[0053] In some examples, the specific capacity of the first active material layer 3 may be greater than that of the second active material layer 4. In other examples, the specific capacity of the first active material layer 3 may be less than that of the second active material layer 4.

[0054] This application is illustrated by taking the example that the specific capacity of the first active material layer 3 is greater than that of the second active material layer 4.

[0055] In this way, by making the specific capacity of the first active material layer 3 greater than that of the second active material layer 4, in other words, the specific capacity of the second active material layer 4 less than that of the first active material layer 3, the lithium intercalation capability of the region near the tab 6 (i.e., the second current collector 12) can be improved, thereby enhancing the charge and discharge efficiency.

[0056] In some other embodiments, the first active material layer 3 and the second active material layer 4 may also be made of the same material.

[0057] 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. The electrode 10 further includes a third active material layer 5. The third active material layer 5 is disposed in the third current collector portion 13. The second active material layer 4 is also disposed in the third active material layer 5. The specific capacity of the third active material layer 5 is different from that of the second active material layer 4.

[0058] In this way, the lithium intercalation capability of the area near the tab 6 (i.e., the third current collector section 13) can be changed, and lithium plating can be avoided on the electrode 10 of the third current collector section 13.

[0059] For example, the specific capacity of the third active material layer 5 can be greater than that of the second active material layer 4, so as to provide more lithium intercalation space for the electrode 10 in the region close to the tab 6 (i.e., the third current collector 13).

[0060] The electrode 10 can be either the positive electrode 101 or the negative electrode 102 mentioned above.

[0061] For ease of explanation, the tab 6 of the current collector 1 connected to the positive electrode 101 is the first tab 61, and the tab 6 of the current collector 1 connected to the negative electrode 102 is the second tab 62.

[0062] exist Figure 2 In the illustrated embodiment, the first tab 61 and the second tab 62 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 61 can be located at the upper end of the current collector 1 along the first direction, and the second tab 62 can be located at the lower end of the current collector 1 along the first direction. In the region near the first tab 61 (i.e., the second current collector section 12), the active material layer of the positive electrode 101 and the electrolyte jointly participate in the battery's charge-discharge reaction. In the region near the second tab 62 (i.e., the third current collector section 13), the active material layer 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 6 (i.e., the first current collector section 11). This arrangement can enhance the conductivity of the first current collector section 11, reduce impedance, narrow the conductivity difference between the first tab 61 and the second tab 62 and the first current collector section 11, and reduce ohmic voltage drop, so that the current density distribution inside the cell 100 is uniform, preventing the electrode potential of the first current collector section 11 from falling below the lithium plating potential too early, thus preventing lithium plating and affecting battery performance.

[0063] exist Figure 3 In the illustrated embodiment, the first tab 61 and the second tab 62 are located along the first direction of the current collector 1 (e.g., ...). Figure 3 On the same side as direction A), for example, the first tab 61 and the second tab 62 can both be located at the upper end of the current collector 1 along the first direction. In the region close to the first tab 61 and the second tab 62 (i.e., the second current collector portion 12), the active material layers of the positive and negative electrode plates 102 and the electrolyte jointly participate in the charging and discharging reaction of the battery. The region away from the tab 6 (i.e., the first current collector portion 11) is provided with a conductive layer 2, which can also enhance the conductivity of the first current collector portion 11, reduce the impedance, narrow the conductivity difference between the first tab 61 and the second tab 62 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.

[0064] In some examples, the conductive layer 2, the first active material layer 3, and the second active material layer 4 can all be disposed on both sides of the current collector 1 along its length (e.g., Figure 6In the direction shown (B), in some other examples, the conductive layer 2, the first active material layer 3, and the second active material layer 4 can all be disposed on one side of the current collector 1 along its length. Figure 6 It is not shown in the text.

[0065] This application provides an exemplary description using the example that the conductive layer 2, the first active material layer 3, and the second active material layer 4 can all be disposed on opposite sides of the current collector 1 along its length.

[0066] In some embodiments, the conductive layer 2 is a porous material layer.

[0067] 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.

[0068] In some embodiments, the conductive layer 2 is a conductive carbon layer 21.

[0069] 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.

[0070] 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, it will lead to a reduction in the thickness of the active material layer, a reduction in the amount of active material per unit area on the first current collector 11, and an impact on the energy density of the cell 100.

[0071] 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.

[0072] For example, the thickness D of the conductive layer 2 can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0073] 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.

[0074] Define the arrangement direction along the first current collector 11, the second current collector 12 and the tab 6. 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 1 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 2, affecting the conductivity performance.

[0075] 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.

[0076] In some examples, the second active material layer 4 and the third active material layer 5 can both be made of the same material; for example, both the second active material layer 4 and the third active material layer 5 can be graphite layers.

[0077] In this way, the conductivity of the first current collector 11, the second current collector 12 and the third current collector 13 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.

[0078] In some embodiments, the first active material layer 3 may be an active material layer doped with a first type of material, which is used to enhance the lithium intercalation space of the electrode 10 in the region near the tab 6 (i.e., the second current collector portion 12), thereby further improving the charging and discharging efficiency.

[0079] In some embodiments, the first type of material includes at least one of silicon-based material, tin-based material and hard carbon. That is, the first type of material may include silicon-based material, or tin-based material, or hard carbon, or any combination thereof, which can further increase the lithium intercalation space of the electrode 10 of the second current collector 12 to improve the charging and discharging efficiency.

[0080] This application uses silicon-based materials as an example to illustrate the first type of materials. The theoretical specific capacity of silicon carbide electrode 10 material is 1600mAh / g, which is much higher than that of graphite electrode 10 material. This can further increase the lithium intercalation space of electrode 10 in the second current collector 12, thereby improving the charging and discharging efficiency.

[0081] It is known that if the mass proportion of the first type of material in the first active material layer 3 is too large, it may consume too much active lithium. If the mass proportion of the first type of material in the first active material layer 3 is too small, the lithium intercalation space is insufficient, resulting in lithium plating and affecting the charging and discharging efficiency.

[0082] In some embodiments, the mass percentage of the first type of material in the first active material layer 3 is greater than or equal to 3% and less than or equal to 8%. When the mass percentage of the first type of material in the first active material layer 3 is within this range, the mass percentage is moderate and can improve the charging and discharging efficiency.

[0083] For example, the mass percentage of the first type of material in the first active material layer 3 can be 3%, 4%, 5%, 6%, 7%, 8%, etc.

[0084] In some examples, the first current collector 11 points in the direction of the tab 6, and the mass percentage of the first type of material in the first active material layer 3 gradually increases. In other examples, the first current collector 11 points in the direction of the tab 6, and the mass percentage of the first type of material in the first active material layer 3 gradually decreases or remains unchanged.

[0085] This application uses the example of the first current collector 11 pointing towards the tab 6, with the mass ratio of the first type of material in the first active material layer 3 gradually increasing, as an example. This can provide more lithium intercalation space for the electrode 10 in the area close to the tab 6 (i.e., the second current collector 12) to improve the charge and discharge efficiency.

[0086] The above describes various implementation methods of the electrode sheet. Specifically, the battery with different electrode sheets in this application can have the following 7 embodiments.

[0087] Example 1:

[0088] 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 three kinds of slurry: conductive carbon layer slurry, graphite slurry with 3% silicon carbon doping and pure graphite slurry.

[0089] 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.

[0090] 3. The lower layer of the negative electrode uses a segmented coating technology, simultaneously extruding conductive carbon slurry and 3% silicon-doped graphite slurry. The first current collector section is coated with conductive carbon slurry at the bottom, with a length B = 147 mm and a thickness D = 2 μm. The second current collector section is coated with 3% silicon-doped graphite slurry, with a length A = 50 mm. The upper layer of the negative electrode is coated with graphite slurry, with a total coating thickness C = 64 mm and a graphite slurry thickness CD = 62 μm. After coating, baking, and rolling, the rolled electrode is slit, die-cut, and then stacked with the positive electrode.

[0091] 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, immersion, formation, electrolyte replenishment, charging, aging, and capacity testing to prepare a finished battery.

[0092] Example 2:

[0093] Unlike Example 1, the area near the tab 6 region uses a 0.2% silicon-carbon doping scheme, otherwise it is the same as Example 1.

[0094] Example 3:

[0095] Unlike Example 1, the area near the tab 6 region uses an 8% silicon-carbon doping scheme, otherwise it is the same as Example 1.

[0096] Example 4:

[0097] The difference from Example 1 is that the thickness of the conductive carbon layer is D = 1 μm, but everything else is the same as in Example 1.

[0098] Example 5:

[0099] The difference from Example 1 is that the thickness of the conductive carbon layer is D = 5 μm, but the rest is the same as in Example 1.

[0100] Example 6:

[0101] The difference from Example 1 is that the length of the conductive carbon layer in the first current collector section is B = 167 mm, and the length of the 3% silicon-doped graphite paste in the second current collector section is A = 30 mm. The rest is the same as in Example 1.

[0102] Example 7:

[0103] The difference from Example 1 is that the length of the conductive carbon layer in the first current collector section is B = 107 mm, and the length of the 3% silicon-doped graphite paste in the second current collector section is A = 90 mm. The rest is the same as in Example 1.

[0104] Comparative Group Implementation Scheme:

[0105] The positive and negative electrode sheets are prepared with slurry according to the formula. The first and second active material layers of the negative electrode sheet adopt the graphite scheme. The negative electrode sheet adopts single-layer coating. Other aspects are the same as in Example 1.

[0106] The blade batteries described in Examples 1-7 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 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 of the blade batteries described in Examples 1-7 and the comparative examples are shown in Table 1.

[0107] Table 1. Test results of the schemes described in Examples 1-7 and the schemes described in the comparative examples.

[0108]

[0109] The test results from the schemes described in Examples 1-7 and the schemes described in the comparative group show that the battery cycle performance of all silicon-carbon doped schemes in the second current collector section (i.e., near the tab 6 region) is improved. After 800 cycles, except for Examples 2, 6 and 7, no lithium plating is observed in the other schemes.

[0110] The test results of the schemes described in Examples 1-3 show that if the amount of silicon-carbon doping in the second current collector section (i.e., the area near the tab 6 region) is too high, it will consume too much active lithium. If the amount of silicon-carbon doping in the second current collector section is too low, the improvement effect is not obvious. Therefore, the silicon-carbon doping amount under the double-layer coating scheme is best controlled between 3% and 8%.

[0111] The test results of the schemes described in Examples 1, 4 and 5 show that if the thickness of the conductive carbon layer in the scheme with 3% silicon-carbon doping is too thick, it will consume too much active lithium. Therefore, the thickness of the conductive carbon layer should be controlled between 1-5 μm for optimal results.

[0112] The test results of the schemes described in Examples 1, 6, and 7 show that when the width of the conductive carbon layer in the first current collector section (i.e., the area far from the tab 6) exceeds the design range, the battery experiences slight lithium plating.

[0113] 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.

[0114] 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), a first active material layer (3), and a second active material layer (4); The current collector (1) is connected to a tab (6), and 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 (6) are spaced apart. The portion of the current collector (1) located between the first current collector portion (11) and the tab (6) is the second current collector portion (12). The first active material layer (3) is disposed on the second current collector portion (12), and the second active material layer (4) is disposed on the conductive layer (2) and the first active material layer (3). The specific capacity of the first active material layer (3) is different from the specific capacity of the second active material layer (4).

2. The electrode sheet according to claim 1, characterized in that, The specific capacity of the first active material layer (3) is greater than that of the second active material layer (4).

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

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

5. 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.

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

7. 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 (6), 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).

8. The electrode sheet according to claim 1, characterized in that, The first active material layer (3) is an active material layer doped with a first type of material, which is used to enhance the lithium intercalation space.

9. The electrode sheet according to claim 8, characterized in that, The first type of material includes at least one of silicon-based materials, tin-based materials, and hard carbon.

10. The electrode according to claim 8, characterized in that, The mass percentage of the first type of material in the first active material layer (3) is greater than or equal to 3% and less than or equal to 8%.

11. The electrode sheet according to claim 8, characterized in that, From the direction of the first current collection section (11) toward the tab (6), the mass ratio of the first type of material in the first active material layer (3) gradually increases.

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

13. The electrode sheet according to claim 1, characterized in that, 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). The electrode also includes a third active material layer (5). The third active material layer (5) is disposed on the third current collector portion (13). The second active material layer (4) is also disposed on the third active material layer (5). The specific capacity of the third active material layer (5) is different from the specific capacity of the second active material layer (4).

14. A battery cell, characterized in that, Includes the electrode sheet as described in any one of claims 1-13.

15. A battery, characterized in that, It includes the electrode sheet as described in any one of claims 1-13, or the battery cell as described in claim 14.

16. An electrical appliance, characterized in that, It includes the electrode sheet according to any one of claims 1-13, the cell according to claim 14, or the battery according to claim 15.

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