Negative plate and battery monomer

Abstract

The invention discloses a negative plate and a battery monomer, and relates to the technical field of batteries, the negative plate comprises a current collector, the current collector has a first surface and a second surface, and the first surface and the second surface are respectively located at two opposite sides of the current collector; and the two active material layers are respectively arranged on the first surface and the second surface, each active material layer comprises a plurality of sub active material layers, the plurality of sub active material layers are arranged in a laminated manner, an infiltration channel is formed in the active material layer, and the infiltration channel extends to the innermost sub active material layer from the surface, deviating from the current collector, of the active material layer. The active material layers are arranged on the first surface and the second surface of the current collector, and the infiltration channels extend from the surfaces, deviating from the current collector, of the active material layers to the innermost active material sub-layer, so that the infiltration capacity of an electrolyte and the reaction area of the active material layers can be improved, and meanwhile, the migration channels and the migration rate of lithium ions are increased; and the fast charging capability and the safety performance of the single battery are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode sheet and a battery cell. Background Art

[0002] In related technologies, as the application scope of new energy vehicles becomes wider and wider, and the cruising range of new energy vehicles has made great breakthroughs, higher requirements are also placed on the fast charging performance of the power batteries of new energy vehicles. The fast charging capability of existing power batteries is greatly affected by the lithium embedding rate of the battery cell negative electrode sheet (the migration speed of lithium ions during the battery charging and discharging process), and there is also the risk of lithium plating affecting the safety of the battery. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to provide a negative electrode sheet that can improve the wetting ability of the electrolyte and the reaction area of ​​the active material layer, while increasing the lithium ion migration channel and migration rate, reducing the risk of lithium precipitation, and improving the fast charging capability and safety performance of the battery cell.

[0004] The present invention further provides a battery cell having the negative electrode sheet.

[0005] According to an embodiment of the present invention, the negative electrode sheet includes: a current collector, the current collector has a first surface and a second surface, the first surface and the second surface are respectively located on opposite sides of the current collector; two active material layers, the two active material layers are respectively arranged on the first surface and the second surface, the active material layer includes a plurality of sub-active material layers, the plurality of sub-active material layers are stacked, the active material layer forms an infiltration channel, and the infiltration channel extends from the surface of the active material layer away from the current collector to the innermost sub-active material layer.

[0006] According to the negative electrode sheet of the embodiment of the present invention, an active material layer is arranged on the first surface and the second surface of the current collector, the active material layer includes a plurality of sub-active material layers, the plurality of sub-active material layers are stacked, and the active material layer forms an infiltration channel, which extends from the surface of the active material layer away from the current collector to the innermost sub-active material layer, thereby improving the infiltration ability of the electrolyte and the reaction area of ​​the active material layer, and at the same time increasing the lithium ion migration channel and migration rate, reducing the risk of lithium plating, and improving the fast charging capability and safety performance of the battery cell.

[0007] According to some embodiments of the present invention, along the thickness direction of the active material layer, the thickness of the innermost sub-active material layer is D1, and the depth of the infiltration channel formed by the innermost sub-active material layer is D2, satisfying the relationship: 0<D2 / D1≤0.3.

[0008] According to some embodiments of the present invention, at least two sub-active material layers in each active material layer have different surface densities.

[0009] According to some embodiments of the present invention, the sub-active material layers each include: a negative electrode active material, a conductive agent and a binder. The multiple sub-active material layers of each active material layer form a first material layer group and a second material layer group. The second material layer group is located between the first material layer group and the current collector. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layers of the first material layer group are 97%-98%, 0.3%-0.7%, and 1.5%-3%, respectively. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layers of the second material layer group are 95%-97%, 0.3%-0.7%, and 3%-5%, respectively. The first material layer group and the second material layer group each include at least one sub-active material layer.

[0010] According to some embodiments of the present invention, the mass ratios of negative electrode active materials in at least two sub-active material layers in each active material layer are different.

[0011] According to some embodiments of the present invention, the mass ratios of binders in at least two sub-active material layers in each active material layer are different.

[0012] According to some embodiments of the present invention, multiple sub-active material layers of each active material layer form a first material layer group and a second material layer group, the second material layer group is located between the first material layer group and the current collector, the porosity of the sub-active material layer of the first material layer group is greater than the porosity of the sub-active material layer of the second material layer group, and the first material layer group and the second material layer group each include at least one sub-active material layer.

[0013] According to some embodiments of the present invention, the porosity of the sub-active material layer of the first material layer group is greater than or equal to 25% and less than or equal to 35%, and the porosity of the sub-active material layer of the second material layer group is greater than or equal to 15% and less than or equal to 25%.

[0014] According to some embodiments of the present invention, the cross section of the infiltration channel is circular, and the cross section diameter of the infiltration channel is R, satisfying the relationship: 30 μm≤R≤80 μm.

[0015] According to some embodiments of the present invention, the depth of the wetting channel is D3, satisfying the relationship: 1.5≤R / D3≤2.5.

[0016] According to some embodiments of the present invention, the volume of the active material layer is V1, and the total volume of the infiltration channel is V2, satisfying the relationship: 0<V2 / V1<0.01, and / or, the cross-sectional area of ​​the active material layer is S1, and the total cross-sectional area of ​​the infiltration channel is S2, satisfying the relationship: 0<S2 / S1<0.05.

[0017] According to some embodiments of the present invention, at least two sub-active material layers in the active material layer have different thicknesses; and / or,

[0018] The compaction density of at least two sub-active material layers in the active material layer is different; and / or,

[0019] At least two sub-active material layers in the active material layer have different active material structures.

[0020] According to an embodiment of the present invention, the battery cell comprises: a shell and an electrode assembly, wherein the electrode assembly is arranged in the shell, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet, the negative electrode sheet and the separator are assembled to form the electrode assembly, and the negative electrode sheet is the negative electrode sheet of the above embodiment.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0023] Figure 1 is a top view of a negative electrode sheet according to an embodiment of the present invention;

[0024] Figure 2 is a cross-sectional view of a negative electrode sheet according to an embodiment of the present invention.

[0025] Reference numerals:

[0026] Negative electrode sheet 100;

[0027] Current collector 10; first surface 11; second surface 12;

[0028] Active material layer 20; first material layer group 21; second material layer group 22; sub-active material layer 23;

[0029] Wetting channel 30. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0031] Reference below Figure 1-Figure 2 A negative electrode sheet 100 and a battery cell according to an embodiment of the present invention are described.

[0032] According to an embodiment of the present invention, the negative electrode sheet 100 includes: a current collector 10, the current collector 10 has a first surface 11 and a second surface 12, the first surface 11 and the second surface 12 are respectively located on opposite sides of the current collector 10; two active material layers 20, the two active material layers 20 are respectively arranged on the first surface 11 and the second surface 12, the active material layer 20 includes a plurality of sub-active material layers 23, the plurality of sub-active material layers 23 are stacked, and the active material layer 20 is formed with an infiltration channel 30, the infiltration channel 30 extends from the surface of the active material layer 20 away from the current collector 10 to the innermost sub-active material layer 23.

[0033] Among them, the current collector 10 is the basic structure of the negative electrode sheet 100, which is used to collect and conduct current. It can be a metal foil, for example, the current collector 10 can be a copper foil. The current collector 10 has a first surface 11 and a second surface 12. Along the thickness direction of the current collector 10, the first surface 11 and the second surface 12 are respectively located on opposite sides of the current collector 10. The active material layer 20 is the core part of the negative electrode sheet 100, responsible for storing and releasing electrical energy. The current collector 10 is provided with two active material layers 20, and the two active material layers 20 are respectively arranged on the first surface 11 and the second surface 12. The active material layer 20 includes a plurality of sub-active material layers 23, for example, the active material layer 20 may include two, three, four, etc. sub-active material layers 23, but the present invention is not limited thereto, and the active material layer 20 may also include other numbers of sub-active material layers 23, as long as the active material layer 20 includes a plurality of sub-active material layers 23. Multiple sub-active material layers 23 are stacked to increase the capacity of the active material, thereby improving the energy density of the battery cell.

[0034] The active material layer 20 is formed with a wetting channel 30, which provides a channel for the electrolyte to be embedded from the surface of the negative electrode sheet 100 to the inside, ensuring that the electrolyte is evenly distributed in the negative electrode sheet 100, which helps to maintain the stability and safety of the battery cell. By forming the wetting channel 30 in the active material layer 20, the wetting channel 30 extends from the surface of the active material layer 20 away from the current collector 10 to the innermost sub-active material layer 23, so that the electrolyte can be more evenly penetrated into the active material layer 20, so that the active material layer 20 can be fully in contact with the electrolyte, thereby improving the wetting ability of the electrolyte and the reaction area of ​​the active material layer 20, and the wetting channel 30 can reduce the obstacles to charge transmission, and the lithium ions in the electrolyte are quickly transmitted in the active material layer 20 through the wetting channel 30, thereby improving the energy density, charge and discharge efficiency and performance of the battery cell.

[0035] According to the negative electrode sheet 100 of the embodiment of the present invention, an active material layer 20 is provided on both the first surface 11 and the second surface 12 of the current collector 10. The active material layer 20 includes a plurality of sub-active material layers 23. The plurality of sub-active material layers 23 are stacked. The active material layer 20 is formed with a wetting channel 30. The wetting channel 30 extends from the surface of the active material layer 20 away from the current collector 10 to the innermost sub-active material layer 23, which can improve the wetting ability of the electrolyte and the reaction area of ​​the active material layer 20, and at the same time increase the lithium ion migration channel and migration rate, effectively prevent lithium plating during fast charging, reduce the risk of lithium plating, and improve the fast charging ability and safety performance of the battery cell.

[0036] According to some embodiments of the present invention, Figure 2 As shown, the infiltration channel 30 and the active material layer 20 can be vertical, which can reduce the diffusion path of the electrolyte in the active material layer 20, and help the electrolyte to quickly and evenly penetrate the active material layer 20 to improve the permeability of the electrolyte. The uniform distribution of the electrolyte helps to achieve a more uniform charge and discharge reaction of the battery cell, which is beneficial to avoid the occurrence of local overcharge or over-discharge. It can also allow a larger area of ​​the active material layer 20 to participate in the charge and discharge reaction, which helps to improve the utilization rate of the active material layer 20, and thus can improve the energy output of the battery cell. In addition, the vertical infiltration channel 30 provides a more direct transmission path for charges (such as lithium ions), reduces the transmission obstacles of charges in the active material layer 20, thereby improving the charge transmission efficiency. Efficient charge transmission helps to achieve higher charge and discharge speeds and energy density, thereby improving the fast charging performance of the battery cell. The vertical infiltration channel 30 can also reduce the capacity decay of the battery cell during the cycle process and extend the service life of the battery cell. The vertical wetting channel 30 also helps to simplify the manufacturing process of the negative electrode sheet 100 . For example, a vertical channel structure can be easily formed by precise etching or deposition technology.

[0037] This application uses the example of etching a wetting channel 30 in the active material layer 20 through a laser etching process. Laser etching can form a fine wetting channel 30 in the active material layer 20, which helps the electrolyte to better infiltrate the active material, thereby improving the wettability of the battery cell. The enhanced wettability helps to reduce the internal resistance of the battery cell and improve the charge and discharge performance and cycle life of the battery cell. The laser etching process can accurately control the depth and shape of the etching, thereby achieving fine control of the negative electrode sheet 100, helping to optimize the porosity and specific surface area of ​​the negative electrode sheet 100, and thus can improve the energy storage performance and power density of the battery cell. The laser etching process does not require the use of chemical agents, and the operation process is relatively simple and safe, which helps to protect the environment and reduce production costs and safety risks.

[0038] According to some embodiments of the present invention, along the thickness direction of the active material layer 20, the thickness of the innermost sub-active material layer 23 is D1, and the depth of the infiltration channel 30 formed by the innermost sub-active material layer 23 is D2, which satisfies the relationship: 0<D2 / D1≤0.3. For example, D2 / D1 can be 0.1, 0.2, 0.3, etc., but the present invention is not limited thereto, and D2 / D1 can also be other values ​​between 0-0.3, as long as D2 / D1 satisfies the relationship: 0<D2 / D1≤0.3. Setting the ratio D2 / D1 of the thickness D1 of the innermost sub-active material layer 23 to the depth D2 of the wetting channel 30 formed by the innermost sub-active material layer 23 within a reasonable range of 0-0.3 can prevent the wetting channel 30 from extending to the current collector 10, avoid or reduce the direct contact between the electrolyte and the current collector 10, thereby reducing the polarization phenomenon caused by the contact between the electrolyte and the current collector 10 (polarization phenomenon is an unfavorable factor in the charging and discharging process of the battery cell, which will cause the performance of the battery cell to decline, such as reduced capacity, increased internal resistance, etc.), thereby reducing the capacity attenuation and internal resistance of the battery cell and improving the performance of the battery cell. It can also reduce the risk of corrosion and deformation of the current collector 10 caused by electrolyte penetration, thereby enhancing the mechanical stability and chemical stability of the battery cell, helping to extend the service life of the battery cell and improve the reliability and safety of the battery cell.

[0039] In addition, the ratio of the thickness D1 of the innermost sub-active material layer 23 to the depth D2 of the wetting channel 30 formed by the innermost sub-active material layer 23 is set within the range of 0-0.3, so that the wetting channel 30 can effectively guide the electrolyte into the interior of the active material layer 20, which helps to improve the wetting efficiency, and also helps to reduce the internal resistance of the battery cell, improve the charge and discharge performance and cycle stability of the battery cell. The depth of the wetting channel 30 is moderate and will not excessively weaken the structural strength of the active material layer 20, which helps to reduce the shedding of the active material during the charge and discharge process, and can also enhance the stability of the negative electrode sheet 100, reduce the risk of deformation or rupture of the negative electrode sheet 100 during the charge and discharge process, and help to improve the reliability and safety of the battery.

[0040] According to some embodiments of the present invention, at least two sub-active material layers 23 in each active material layer 20 have different surface densities. For example, each active material layer 20 may have two, three, four, or other numbers of sub-active material layers 23 with different surface densities. However, the present invention is not limited to this. Each active material layer 20 may also have other numbers of sub-active material layers 23 with different surface densities, as long as at least two sub-active material layers 23 in each active material layer 20 have different surface densities.

[0041] By reasonably adjusting the surface density of different sub-active material layers 23, the distribution of active materials in the negative electrode sheet 100 can be optimized, thereby improving the energy density of the battery cell. The difference in surface density can affect the expansion and contraction behavior of the active material during the charge and discharge process, thereby helping to alleviate the stress concentration and deformation of the negative electrode sheet 100, thereby extending the cycle life and stability of the battery cell. Sub-active material layers 23 with different surface densities can form a more uniform porosity distribution during the compaction process, thereby improving the consistency of the compaction density of the negative electrode sheet 100, helping to reduce the internal resistance of the negative electrode sheet 100, and thereby improving the charge and discharge performance of the battery cell. The surface density of the sub-active material layer 23 can be reasonably designed according to actual conditions. Through reasonable surface density design, the overall strength and toughness of the negative electrode sheet 100 can be enhanced, making the negative electrode sheet 100 less susceptible to damage during processing and use.

[0042] According to some embodiments of the present invention, the sub-active material layers 23 each include: a negative electrode active material, a conductive agent and a binder. The multiple sub-active material layers 23 of each active material layer 20 form a first material layer group 21 and a second material layer group 22. The second material layer group 22 is located between the first material layer group 21 and the current collector 10. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layer 23 of the first material layer group 21 are 97%-98%, 0.3%-0.7%, and 1.5%-3%, respectively. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layer 23 of the second material layer group 22 are 95%-97%, 0.3%-0.7%, and 3%-5%, respectively. The first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23.

[0043] Among them, the sub-active material layer 23 includes: negative electrode active material, conductive agent and binder. The negative electrode active material is used to provide capacity for the negative electrode sheet 100. The conductive agent is used to improve the conductivity inside the active material layer 20 to ensure that the current can smoothly pass through the active material layer 20 for charging and discharging. The binder is used to firmly bind the negative electrode active material to the current collector 10 and between the negative electrode active material and the negative electrode active material, reducing the risk of the negative electrode active material falling off during the charging and discharging process of the battery cell. The negative electrode active material can be graphite, silicon-based negative electrode and other materials, the conductive agent can be one or more of SUPER P (super conductive carbon black), carbon nanotubes, and graphene. The binder can be one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid binders. However, the present invention is not limited to this. The materials and compositions of the negative electrode active material, conductive agent, and binder can be reasonably selected according to actual conditions.

[0044] The multiple sub-active material layers 23 of each active material layer 20 can form a first material layer group 21 and a second material layer group 22, and the second material layer group 22 is located between the first material layer group 21 and the current collector 10. It can be explained that the second material layer is closer to the current collector 10 than the first material layer group 21, and the mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layer 23 of the first material layer group 21 are 97%-98%, 0.3%-0.7%, and 1.5%-3%, respectively. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent, and the mass ratio of the binder in the sub-active material layer 23 of the second material layer group 22 are 95%-97%, 0.3%-0.7%, and 3%-5%, respectively.

[0045] It can be explained that a higher proportion of negative electrode active material helps to improve the energy density and endurance of the battery cell. The mass ratio of the negative electrode active material in the second material layer group 22 is slightly lower than that in the first material layer group 21, but still maintains a high ratio, which can also ensure the stability of the battery cell.

[0046] The function of the conductive agent is to ensure smooth electron transmission inside the negative electrode sheet 100 and improve the charge and discharge efficiency of the battery cell. The mass ratio range of the conductive agent of the first material layer group 21 and the second material layer group 22 is the same. The conductive agent within this mass ratio range can fully play its role while avoiding excessive conductive agent from having a negative impact on the performance of the battery cell.

[0047] An appropriate amount of binder can ensure a firm bond between the active material and the current collector 10, so as to reduce the shedding of the active material and the degradation of the performance of the battery cell. The mass ratio range of the binder of the second material layer group 22 is larger than the mass ratio range of the binder of the first material layer group 21, which can further enhance the bonding force between the second material layer group 22 and the current collector 10, and further improve the cycle stability of the battery cell.

[0048] By rationally designing and optimizing the ratio of negative electrode active material, conductive agent and binder in each sub-active material layer 23, the energy density, charge and discharge efficiency and cycle stability of the battery cell can be significantly improved. The second material layer group 22 is located between the current collector 10 and the first material layer group 21, and its high ratio of binder helps to enhance the stability of the entire negative electrode sheet 100, thereby improving the safety of the battery cell.

[0049] The first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23. For example, the first material layer group 21 and the second material layer group 22 each may include one, two, three, or other sub-active material layers 23. However, the present invention is not limited thereto. The first material layer group 21 and the second material layer group 22 may also include other numbers of sub-active material layers 23, as long as the first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23. The first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23, which can improve the filling rate of the negative electrode active material, thereby increasing the energy density of the battery cell, and can also disperse the stress concentration of the battery cell during the charge and discharge process, reduce the shedding of the negative electrode active material and the damage to the structure, thereby extending the cycle life of the battery.

[0050] According to some embodiments of the present invention, the mass ratios of the negative electrode active materials in at least two sub-active material layers 23 in each active material layer 20 are different. For example, each active material layer 20 may have two, three, four, or other numbers of sub-active material layers 23 with different mass ratios of the negative electrode active materials, but the present invention is not limited to this. Each active material layer 20 may also have other numbers of sub-active material layers 23 with different mass ratios of the negative electrode active materials, as long as the mass ratios of the negative electrode active materials in at least two sub-active material layers 23 in each active material layer 20 are different.

[0051] By reasonably adjusting the mass ratio of the negative electrode active material in different sub-active material layers 23, the distribution of the negative electrode active material in the negative electrode sheet 100 can be optimized, thereby balancing the energy density and power density of the battery cell, and further helping to improve the battery life and fast charge and discharge performance of the battery cell. The difference in the mass ratio of the negative electrode active material can affect the expansion and contraction behavior of the negative electrode active material during the charge and discharge process. By reasonably adjusting the mass ratio of the negative electrode active material in different sub-active material layers 23, it is helpful to alleviate the stress concentration and deformation of the negative electrode sheet 100, extend the cycle life of the battery cell, and improve the reliability and stability of the battery cell. The optimized mass ratio distribution of the negative electrode active material can also promote the infiltration of the electrolyte and the transmission of lithium ions, reduce polarization, and thus improve the charge and discharge efficiency of the battery cell.

[0052] According to some embodiments of the present invention, in each active material layer 20, from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, the mass ratio of the negative electrode active material in the multiple sub-active material layers 23 gradually increases, which can improve the filling rate and utilization rate of the negative electrode active material, thereby helping to increase the energy density of the battery cell, and then help to improve the battery life of the battery cell, and also help to form a more stable battery cell structure to enhance the impact resistance and vibration resistance of the battery cell, improve the reliability and durability of the battery cell, and help to alleviate the stress concentration and deformation of the battery cell during the charging and discharging process. In particular, under the joint action of multiple layers of sub-active material layers 23, stress can be more effectively dispersed, and the cycle life of the battery cell can be extended. The thermal management of the battery cell during the charging and discharging process can also be effectively controlled to reduce the risk of thermal runaway, thereby improving the safety of the battery cell.

[0053] In addition, in each active material layer 20, the mass ratio of the negative electrode active material in multiple sub-active material layers 23 gradually increases from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, which helps to ensure that the electrolyte penetrates into the active material layer 20 more effectively, thereby improving the charging and discharging efficiency of the battery cell.

[0054] It can be explained that, in each active material layer 20, from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, the mass ratio of the negative electrode active material in the multiple sub-active material layers 23 can gradually increase in a fixed gradient or a non-gradient manner, and the design can be adjusted and optimized according to the actual situation and the performance results of the battery cell, as long as the mass ratio of the negative electrode active material in the multiple sub-active material layers 23 in each active material layer 20, from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, gradually increases.

[0055] According to some embodiments of the present invention, the mass ratios of the binders of at least two sub-active material layers 23 in each active material layer 20 are different. For example, each active material layer 20 may have two, three, four, or other numbers of sub-active material layers 23 with different mass ratios of the binders. However, the present invention is not limited to this. Each active material layer 20 may also have other numbers of sub-active material layers 23 with different mass ratios of the binders, as long as the mass ratios of the binders of at least two sub-active material layers 23 in each active material layer 20 are different.

[0056] By reasonably adjusting the mass ratio of the binder of different sub-active material layers 23, the bonding strength of each component of the negative electrode sheet 100 can be optimized, thereby enhancing the stability of the negative electrode sheet 100, helping to reduce the shedding of the negative electrode active material and the deformation of the negative electrode sheet 100, and thus improving the cycle life and reliability of the battery cell. Different mass ratios of the binder may affect the wettability of the electrolyte in the negative electrode sheet 100. Reasonable distribution of the binder can ensure that the electrolyte can penetrate into the active material layer 20 more effectively, and can also improve the transmission performance of lithium ions in the negative electrode sheet 100, reduce internal resistance, and thus improve the charge and discharge efficiency and performance of the battery cell.

[0057] In addition, the mass ratio of the binder in at least two sub-active material layers 23 in each active material layer 20 is different, and the mass ratio of the binder in each sub-active material layer 23 can be adjusted according to specific needs, thereby increasing the flexibility of the production process and helping to reasonably control the amount of raw materials while ensuring the performance of the battery cell, thereby helping to reduce production costs and improve production competitiveness.

[0058] It can be explained that in each active material layer 20, from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, the mass ratio of the binder in multiple sub-active material layers 23 can gradually decrease in a fixed gradient or non-gradient manner, and the design can be adjusted and optimized according to actual conditions and combined with the battery cell performance results.

[0059] According to some embodiments of the present invention, the multiple sub-active material layers 23 of each active material layer 20 form a first material layer group 21 and a second material layer group 22, the second material layer group 22 is located between the first material layer group 21 and the current collector 10, the porosity of the sub-active material layer 23 of the first material layer group 21 is greater than the porosity of the sub-active material layer 23 of the second material layer group 22, and the first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23.

[0060] Among them, the multiple sub-active material layers 23 of each active material layer 20 form a first material layer group 21 and a second material layer group 22, and the second material layer group 22 is located between the first material layer group 21 and the current collector 10. The porosity of the sub-active material layer 23 of the first material layer group 21 is greater than the porosity of the sub-active material layer 23 of the second material layer group 22. Specifically, the first material layer group 21 has a higher porosity, which helps the lithium ions in the electrolyte to pass more smoothly, thereby reducing the resistance to lithium ion transmission, further improving the infiltration ability of the electrolyte, and can improve the charge and discharge rate and energy efficiency of the battery cell. The second material layer group 22 is located between the first material layer group 21 and the current collector 10. The sub-active material layer 23 of the second material layer group 22 has a lower porosity, which means that the sub-active material layer 23 of the second material layer group 22 has a higher density and a tighter structure, which can reduce the shedding of the negative electrode active material and improve the cycle stability and life of the battery cell.

[0061] The first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23. For example, the first material layer group 21 and the second material layer group 22 each include one, two, three, or other sub-active material layers 23. However, the present invention is not limited thereto. The first material layer group 21 and the second material layer group 22 may also include other numbers of sub-active material layers 23, as long as the first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23. The first material layer group 21 and the second material layer group 22 each include at least one sub-active material layer 23, which can improve the filling rate of the negative electrode active material, thereby increasing the energy density of the battery cell, and can also disperse the stress concentration of the battery cell during the charge and discharge process, reduce the shedding of the active material and the damage to the structure, thereby extending the cycle life of the battery.

[0062] According to some embodiments of the present invention, in each active material layer 20, the porosity of multiple sub-active material layers 23 gradually increases from the innermost sub-active material layer 23 to the outermost sub-active material layer 23, which can reduce the resistance of lithium ion transmission, help improve the charge and discharge rate and energy efficiency of the battery cell, enable the battery cell to respond to load changes more quickly, and increase the contact area between the negative electrode active material and the electrolyte, thereby improving the utilization rate of the active material layer 20, helping to increase the capacity of the battery cell and extend the service life of the battery cell. It is also possible to optimize the stress distribution inside the active material layer 20, relieve the stress concentration of the battery cell during the charge and discharge process, reduce the shedding of the negative electrode active material and the deformation of the negative electrode sheet 100, improve the overall strength of the battery cell structure, help reduce the risk of damage to the battery cell due to excessive stress during the charge and discharge process, and thus improve the reliability and durability of the battery cell.

[0063] According to some embodiments of the present invention, the porosity of the sub-active material layer 23 of the first material layer group 21 is greater than or equal to 25% and less than or equal to 35%, and the porosity of the sub-active material layer 23 of the second material layer group 22 is greater than or equal to 15% and less than or equal to 25%.

[0064] Among them, the porosity of the sub-active material layer 23 of the first material layer group 21 is greater than or equal to 25% and less than or equal to 35%, that is, the porosity of the sub-active material layer 23 of the first material layer group 21 is between 25% and 35%, for example: the porosity of the sub-active material layer 23 of the first material layer group 21 can be 25%, 26%, 31%, 35%, etc., but the present invention is not limited thereto, the porosity of the sub-active material layer 23 of the first material layer group 21 can also be other values ​​between 25% and 35%, as long as the porosity of the sub-active material layer 23 of the first material layer group 21 is greater than or equal to 25% and less than or equal to 35%. The sub-active material layer 23 of the first material layer group 21 has a higher porosity, which is conducive to the rapid migration of lithium ions in the active material layer 20, and can also increase the lithium ion migration channel and reduce the lithium ion migration resistance, thereby improving the charge and discharge rate of the battery cell, and the higher porosity also helps the electrolyte to better infiltrate the active material layer 20, thereby improving the utilization rate of the active material layer 20.

[0065] The porosity of the sub-active material layer 23 of the second material layer group 22 is greater than or equal to 15% and less than or equal to 25%, that is, the porosity of the sub-active material layer 23 of the second material layer group 22 is between 15% and 25%. For example, the porosity of the sub-active material layer 23 of the second material layer group 22 can be 15%, 16%, 21%, 25%, etc., but the present invention is not limited thereto. The porosity of the sub-active material layer 23 of the second material layer group 22 can also be other values ​​between 15% and 25%, as long as the porosity of the sub-active material layer 23 of the second material layer group 22 is greater than or equal to 15% and less than or equal to 25%. The sub-active material layer 23 of the second material layer group 22 has a moderate porosity, which can provide sufficient structural support while ensuring the lithium ion migration rate. The moderate porosity helps to reduce the shedding and pulverization of the negative electrode active material during the charging and discharging process, and improve the structural stability of the battery cell.

[0066] Reasonable design of porosity helps to reduce heat accumulation in battery cells during the charging and discharging process, thereby reducing the risk of thermal runaway of battery cells. It can also improve the power density of the battery while ensuring the energy density of the battery cells.

[0067] According to some embodiments of the present invention, the cross section of the infiltration channel 30 may be circular or polygonal. When the cross section of the infiltration channel 30 is circular, the infiltration channel 30 has better stability and efficiency when transporting electrolyte. When the infiltration channel 30 with a circular cross section is subjected to external pressure, the pressure can be evenly distributed, reducing the risk of structural damage caused by stress concentration. In addition, the manufacturing and processing of the infiltration channel 30 with a circular cross section are relatively simple, reducing the manufacturing cost of the infiltration channel 30. When the cross section of the infiltration channel 30 is polygonal, the cross section of the infiltration channel 30 may be triangular, square, etc., which can have a larger heat exchange area to transfer heat more effectively, and the shape and size of the polygonal infiltration channel 30 can be customized according to specific needs to adapt to different application scenarios and performance requirements.

[0068] The cross section of the wetting channel 30 is circular or polygonal, which can improve the charge and discharge rate, energy density and cycle stability of the battery cell to a certain extent.

[0069] According to some embodiments of the present invention, the cross-section of the infiltration channel 30 may be circular, and the cross-sectional diameter of the infiltration channel 30 is R, satisfying the relationship: 30μm≤R≤80μm, that is, the cross-sectional diameter R of the infiltration channel 30 is 30μm-80μm, for example: the cross-sectional diameter R of the infiltration channel 30 may be 30μm, 31μm, 40μm, 50μm, 80μm and other values, but the present invention is not limited thereto, the cross-sectional diameter R of the infiltration channel 30 may also be other values ​​between 30μm-80μm, as long as the cross-sectional diameter R of the infiltration channel 30 satisfies the relationship: 30μm≤R≤80μm.

[0070] The cross-sectional diameter R of the wetting channel 30 is in the range of 30μm-80μm, which can make the flow of electrolyte in the wetting channel 30 more stable, reduce eddy currents and turbulence, and is beneficial to the uniform distribution and transmission of the electrolyte. It also helps to reduce the pressure loss of the electrolyte in the wetting channel 30, improve the transmission rate of the electrolyte, and also help to conduct heat between the wall of the wetting channel 30 and the electrolyte, thereby improving the heat exchange rate.

[0071] According to some embodiments of the present invention, the depth of the wetting channel 30 is D3, which satisfies the relationship: 1.5≤R / D3≤2.5, that is, the ratio R / D3 between the cross-sectional diameter R of the wetting channel 30 and the depth D3 of the wetting channel 30 is between 1.5-2.5, for example: R / D3 can be 1.5, 1.8, 2, 2.1, 2.5 and other values, but the present invention is not limited to this, R / D3 can also be other values ​​between 1.5-2.5, as long as the ratio R / D3 between the cross-sectional diameter R of the wetting channel 30 and the depth D3 of the wetting channel 30 satisfies the relationship: 1.5≤R / D3≤2.5.

[0072] The ratio R / D3 between the cross-sectional diameter R of the infiltration channel 30 and the depth D3 of the infiltration channel 30 is in the appropriate range of 1.5-2.5, and the electrolyte is more evenly distributed in the infiltration channel 30, which helps to reduce the retention and dead corners of the electrolyte in the infiltration channel 30. The appropriate ratio can balance the flow resistance and fluid transmission efficiency, thereby improving the transmission rate of the electrolyte. Within this ratio range, the structural strength of the infiltration channel 30 is relatively high, and the appropriate ratio of the cross-sectional diameter and the depth can make the wall of the infiltration channel 30 withstand greater pressure without deformation or rupture, thereby improving the safety and reliability of the negative electrode sheet 100.

[0073] According to some embodiments of the present invention, there may be multiple infiltration channels 30, and the interval distance between any two adjacent infiltration channels 30 is d, satisfying the relationship: 50 μm≤d≤1500 μm.

[0074] There may be multiple infiltration channels 30, for example, there may be two, three, four, etc. infiltration channels 30, but the present invention is not limited thereto, and there may be other numbers of infiltration channels 30, as long as there are multiple infiltration channels 30. The spacing distance d between any two adjacent infiltration channels 30 satisfies the relationship: 50μm≤d≤1500μm, that is, the spacing distance d between any two adjacent infiltration channels 30 may be any value between 50μm-1500μm, for example, the spacing distance d between any two adjacent infiltration channels 30 may be 50μm, 51μm, 80μm, 1000μm, 1201μm, 1500μm, etc., but the present invention is not limited thereto, and the spacing distance d between any two adjacent infiltration channels 30 may also be other values ​​between 50μm-1500μm, as long as the spacing distance d between any two adjacent infiltration channels 30 satisfies the relationship: 50μm≤d≤1500μm.

[0075] The provision of multiple wetting channels 30 can significantly improve the infiltration rate and uniformity of the electrolyte, and setting the spacing d between any two adjacent wetting channels 30 within a reasonable range of 50μm-1500μm can reduce the risk of excessive obstruction of the electrolyte during the infiltration process, help reduce local accumulation or drying of the electrolyte during the infiltration process, and improve the performance and stability of the battery cell.

[0076] According to some embodiments of the present invention, the volume of the active material layer 20 is V1, and the total volume of the infiltration channel 30 is V2, satisfying the relationship: 0<V2 / V1<0.01, and / or, the cross-sectional area of ​​the active material layer 20 is S1, and the total cross-sectional area of ​​the infiltration channel 30 is S2, satisfying the relationship: 0<S2 / S1<0.05.

[0077] Among them, as an embodiment of the present application, the volume of the active material layer 20 is V1, and the total volume of the infiltration channel 30 is V2, satisfying the relationship: 0<V2 / V1<0.01, that is, the ratio V2 / V1 of the total volume V2 of the infiltration channel 30 to the volume V1 of the active material layer 20 is in the range of 0-0.01, for example: the ratio V2 / V1 of the total volume V2 of the infiltration channel 30 to the volume V1 of the active material layer 20 can be 0.001, 0.005, 0.009 and other values, but the present invention is not limited to this, the ratio V2 / V1 of the total volume V2 of the infiltration channel 30 to the volume V1 of the active material layer 20 can also be other values ​​between 0-0.01, as long as the ratio V2 / V1 of the total volume V2 of the infiltration channel 30 to the volume V1 of the active material layer 20 satisfies the relationship: 0<V2 / V1<0.01. It should be noted that the volume of each active material layer 20 is V1, and the total volume of the infiltration channels 30 provided on the corresponding active material layer 20 is V2.

[0078] Since the volume of the infiltration channel 30 accounts for a smaller volume of the active material layer 20, the active material layer 20 can occupy a larger space, thereby improving the energy density of the battery cell, and further allowing the battery cell to store more energy. In addition, as a channel for the flow of electrolyte, the reasonable control of the volume of the infiltration channel 30 helps to maintain the stability of the battery cell structure. An overly large infiltration channel 30 may cause the internal structure of the battery cell to become loose, while an overly small channel may affect the infiltration effect of the electrolyte. Therefore, satisfying the above-mentioned proportional relationship between the volume of the infiltration channel 30 and the volume of the active material layer 20 helps to set an infiltration channel 30 with a more reasonable volume, which helps to improve the energy density, power output, cycle stability and production efficiency of the battery cell.

[0079] As another embodiment of the present application, the cross-sectional area of ​​the active material layer 20 is S1, and the total cross-sectional area of ​​the wetting channel 30 is S2, satisfying the relationship: 0<S2 / S1<0.05, that is, the ratio S2 / S1 of the total cross-sectional area S2 of the wetting channel 30 to the cross-sectional area S1 of the active material layer 20 is in the range of 0-0.05, for example: the ratio S2 / S1 of the total cross-sectional area S2 of the wetting channel 30 to the cross-sectional area S1 of the active material layer 20 can be 0.01, 0.02, 0.04 and other values, but the present invention is not limited to this, the ratio S2 / S1 of the total cross-sectional area S2 of the wetting channel 30 to the cross-sectional area S1 of the active material layer 20 can also be other values ​​between 0-0.05, as long as the ratio S2 / S1 of the total cross-sectional area S2 of the wetting channel 30 to the cross-sectional area S1 of the active material layer 20 satisfies the relationship: 0<S2 / S1<0.05. It should be noted that the cross-sectional area of ​​the active material layer 20 refers to the cross-sectional area obtained by cutting the active material layer 20 along a plane perpendicular to the thickness direction of the negative electrode sheet 100. The cross-sectional area of ​​each active material layer 20 is S1, and the total cross-sectional area of ​​the corresponding active material layer 20 on which the wetting channel 30 is arranged is S2.

[0080] Since the total cross-sectional area S2 of the infiltration channel 30 is relatively small, the electrolyte can form a higher internal pressure when passing through the infiltration channel 30, thereby quickly and fully infiltrating the active material layer 20. This high-pressure infiltration method helps to ensure that the electrolyte can penetrate into the fine parts of the active material layer 20, thereby improving the uniformity and integrity of the infiltration.

[0081] As another embodiment of the present application, the volume of the active material layer 20 is V1, and the total volume of the infiltration channel 30 is V2, satisfying the relationship: 0<V2 / V1<0.01, and the cross-sectional area of ​​the active material layer 20 is S1, and the total cross-sectional area of ​​the infiltration channel 30 is S2, satisfying the relationship: 0<S2 / S1<0.05. Such a setting not only helps to set a more reasonable volume of the infiltration channel 30, but also helps to improve the energy density, power output, cycle stability and production efficiency of the battery cell, and helps to ensure that the electrolyte can penetrate into the fine parts of the active material layer 20, thereby improving the uniformity and integrity of the infiltration.

[0082] According to some embodiments of the present invention, the distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is less than or equal to 2 mm. For example, the distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 can be 2 mm, 0.9 mm, 0.8 mm, 0.5 mm, etc., but the present invention is not limited thereto. The distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 can be other values, as long as the distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is less than or equal to 2 mm. It can be explained that the lower limit of the distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 can be reasonably designed according to actual conditions, as long as the wetting channels 30 located at the edge of the negative electrode sheet 100 among the multiple wetting channels 30 are spaced apart from the edge of the negative electrode sheet 100. The distance between any one of the multiple wetting channels 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is less than or equal to 2 mm. More wetting channels 30 can be provided to make more full use of the negative electrode sheet 100, so that the electrolyte can more fully penetrate the active material layer 20, which helps to reduce the electrolyte infiltration time and improve the infiltration efficiency, thereby ensuring that the negative electrode sheet 100 can fully and evenly absorb the electrolyte, thereby improving the energy density, cycle stability, and charge and discharge performance of the battery cell.

[0083] According to some embodiments of the present invention, at least two sub-active material layers 23 in the active material layer 20 have different thicknesses; and / or,

[0084] The compaction densities of at least two sub-active material layers 23 in the active material layer 20 are different; and / or,

[0085] In the active material layer 20 , at least two sub-active material layers 23 have different active material structures.

[0086] Here, the different active material structures refer to that at least one of the particle size and the shape of the active material in the sub-active material layer 23 is different.

[0087] The thicknesses of at least two sub-active material layers 23 in each active material layer 20 are different. For example, there may be two, three, four, or other numbers of sub-active material layers 23 with different thicknesses in the active material layer 20, but the present invention is not limited to this. The active material layer 20 may also have other numbers of sub-active material layers 23 with different thicknesses, as long as the thicknesses of at least two sub-active material layers 23 in the active material layer 20 are different.

[0088] The compaction densities of at least two sub-active material layers 23 in each active material layer 20 are different. For example, there may be two, three, four, or other numbers of sub-active material layers 23 with different compaction densities in the active material layer 20, but the present invention is not limited to this. The active material layer 20 may also have other numbers of sub-active material layers 23 with different compaction densities, as long as the compaction densities of at least two sub-active material layers 23 in the active material layer 20 are different.

[0089] The active material structures of at least two sub-active material layers 23 in each active material layer 20 are different. For example, there may be two, three, four, or other numbers of sub-active material layers 23 in the active material layer 20 with different active material structures. However, the present invention is not limited to this. The active material layer 20 may also have other numbers of sub-active material layers 23 with different active material structures, as long as at least two sub-active material layers 23 in the active material layer 20 have different active material structures.

[0090] The thickness of at least two sub-active material layers 23 in the active material layer 20 is different, or the compaction density of at least two sub-active material layers 23 in the active material layer 20 is different, or the active material material structure of at least two sub-active material layers 23 in the active material layer 20 is different. Or the thickness of at least two sub-active material layers 23 in the active material layer 20, the compaction density of at least two sub-active material layers 23 in the active material layer 20, and the active material material structure of at least two sub-active material layers 23 in the active material layer 20 are all different. Or two of the thickness of at least two sub-active material layers 23 in the active material layer 20, the compaction density of at least two sub-active material layers 23 in the active material layer 20, and the active material material structure of at least two sub-active material layers 23 in the active material layer 20 are different.

[0091] The present application takes the case where the thickness of at least two sub-active material layers 23 in the active material layer 20 is different, the compaction density of at least two sub-active material layers 23 in the active material layer 20 is different, and the active material material structure of at least two sub-active material layers 23 in the active material layer 20 is different as an example for explanation. By reasonably adjusting the thickness of different sub-active material layers 23, the distribution of active materials in the battery cell can be optimized, so that the battery cell can store more energy in a limited volume. Sub-active material layers 23 with different compaction densities can affect the porosity and electrolyte wettability of the negative electrode sheet 100. By reasonably adjusting the sub-active material layers 23 with different compaction densities, the utilization rate of the active material can be improved, thereby improving the energy density of the battery. Active material layers 20 with different material structures will exhibit different expansion and contraction characteristics during the charge and discharge process. By reasonably designing the material structure of the sub-active material layer 23, these characteristics can be balanced, reducing the structural changes of the battery cell during the cycle process, thereby improving the cycle stability of the battery cell.

[0092] According to some embodiments of the present invention, the active material slurry ratios of at least two sub-active material layers 23 in the active material layer 20 may be different. For example, there may be two, three, four, etc. sub-active material layers 23 in the active material layer 20 with different active material slurry ratios, but the present invention is not limited thereto. There may also be other numbers of sub-active material layers 23 in the active material layer 20 with different active material slurry ratios, as long as at least two sub-active material layers 23 in the active material layer 20 have different active material slurry ratios. By reasonably adjusting the slurry ratios of different sub-active material layers 23, the distribution and content of the active material in the battery can be optimized, thereby improving the energy density of the battery cell, and balancing the expansion and contraction characteristics of the active material, reducing the structural changes of the battery cell during the cycle, thereby improving the cycle stability of the battery cell.

[0093] The following is a detailed description of the embodiments and comparative examples of the present application.

[0094] Each example uses the same positive electrode sheet, the positive electrode active material is lithium iron phosphate, the conductive agent is SP and carbon nanotubes (carbon nanotubes), the binder is polyvinylidene difluoride (polyvinylidene fluoride), the solvent is N-Methylpyrrol idone (N-methylpyrrolidone), the ratio of each substance is 96.2%:2.2%:1.6%, and when preparing the slurry, the NMP solvent and the binder are first mixed to make a glue. After the glue solution is prepared, the conductive agent and the positive electrode main material are added in batches according to the process flow, and the positive electrode slurry is obtained after stirring. The slurry is coated and rolled to obtain a positive electrode roll. The rolled thickness of the roll is 170μm, and then the positive electrode sheet is obtained through a die-cutting process.

[0095] The negative electrode sheet 100 used in each example has a double-layer structure, the negative electrode active material is graphite, the conductive agent is SP, the binder is sodium carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, the solvent is deionized water, and the proportion of each material in the second material layer group 22 neutron active material layer 23 is graphite: SP: sodium carboxymethyl cellulose: styrene butadiene rubber: polyacrylic acid = 96.5%: 0.3%: 1.2%: 1.6%: 0.4%, and the first material layer group 21 neutron active material layer 23 is 96.5%: 0.3%: 1.2%: 1.6%: 0.4%. The proportions of the various materials in the material layer 23 are graphite: SP: sodium carboxymethyl cellulose: styrene-butadiene rubber: polyacrylic acid = 97.2%: 0.4%: 0.7%: 0.5%: 1.2%. The above materials are mixed, coated, and rolled to obtain a negative electrode coil with a rolled thickness of 115 μm. The negative electrode sheet 100 is then obtained through a die-cutting process. The porosity of the second material layer group 22 of the obtained negative electrode sheet 100 is approximately 23%, and the porosity of the first material layer group 21 is approximately 33%.

[0096] Comparative Example: The positive electrode sheet prepared above and the negative electrode sheet 100 that has not been etched are subjected to the processes of lamination, assembly, baking, liquid injection, formation, capacity division, etc. to obtain a finished battery cell as a comparative example.

[0097] The negative electrode sheet 100 is laser etched to form the infiltration channel 30, and the cross-sectional area of ​​the infiltration channel 30 is a circle as an example for explanation:

[0098] First embodiment: the diameter of the wetting channel 30 is 60 μm, the depth of the wetting channel 30 is 24 μm, the spacing between any two adjacent wetting channels 30 is 500 μm, and the distance between any wetting channel 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is 2 mm; after the negative electrode is etched and pore-formed, the etched negative electrode sheet 100 is obtained by die-cutting, and the positive electrode sheet and the etched negative electrode sheet 100 are stacked, assembled, baked, injected, formed, and divided into different capacities to obtain a finished battery cell.

[0099] Second embodiment: the diameter of the wetting channel 30 is 90 μm, the depth of the wetting channel 30 is 40 μm, the spacing between any two adjacent wetting channels 30 is 500 μm, and the distance between any wetting channel 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is 2 mm; after the negative electrode is etched and pore-formed, the etched negative electrode sheet 100 is obtained by die-cutting, and the positive electrode sheet and the etched negative electrode sheet 100 are stacked, assembled, baked, injected, formed, and divided into different capacities to obtain a finished battery cell.

[0100] The third embodiment: the diameter of the wetting channel 30 is 60 μm, the depth of the wetting channel 30 is 24 μm, the distance between any two adjacent wetting channels 30 is 1000 μm, and the distance between any wetting channel 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is 2 mm; after the negative electrode is etched and pore-formed, the etched negative electrode sheet 100 is obtained by die-cutting, and the positive electrode sheet and the etched negative electrode sheet 100 are stacked, assembled, baked, injected, formed, and divided into different capacities to obtain a finished battery cell.

[0101] Fourth embodiment: the diameter of the wetting channel 30 is 90 μm, the depth of the wetting channel 30 is 40 μm, the spacing between any two adjacent wetting channels 30 is 1000 μm, and the distance between any wetting channel 30 located at the edge of the negative electrode sheet 100 and the edge of the negative electrode sheet 100 is 2 mm; after the negative electrode is etched and pore-formed, the etched negative electrode sheet 100 is obtained by die-cutting, and the positive electrode sheet and the etched negative electrode sheet 100 are stacked, assembled, baked, injected, formed, and divided into different capacities to obtain a finished battery cell.

[0102] The comparison chart of the test results of the battery cells prepared in the above comparative example, the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment is as follows:

[0103]

[0104] According to the test results, it can be found that the electrolyte retention capacity of the battery cell prepared by laser etching the negative electrode sheet 100 to form the infiltration channel 30 is improved, and the fast charging test efficiency is higher under the same conditions. The surface condition of the electrode sheet after disassembly is good, thereby improving the fast charging capability and safety performance of the battery cell.

[0105] The battery cell according to the embodiment of the present invention comprises: a housing and an electrode assembly, wherein the electrode assembly is arranged in the housing, and the electrode assembly comprises a positive electrode sheet, a negative electrode sheet 100 and a separator, wherein the positive electrode sheet, the negative electrode sheet 100 and the separator are assembled to form the electrode assembly, and the separator is used as a separator between the positive electrode sheet and the negative electrode sheet 100, which not only prevents the short circuit caused by the direct contact between the positive electrode sheet and the negative electrode sheet 100, but also allows lithium ions to freely shuttle between the positive electrode sheet and the negative electrode sheet 100, thereby realizing the charging and discharging process of the battery cell. The negative electrode sheet 100 is the negative electrode sheet 100 of the above embodiment, which can improve the infiltration ability of the electrolyte and the reaction area of ​​the active material layer 20, while increasing the lithium ion migration channel and migration rate, and also reducing the risk of lithium plating, thereby improving the fast charging ability and safety performance of the battery cell.

[0106] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0107] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A negative electrode sheet (100), characterized in that: include: A current collector (10), the current collector (10) having a first surface (11) and a second surface (12), the first surface (11) and the second surface (12) being respectively located on two opposite sides of the current collector (10); Two active material layers (20), the two active material layers (20) are respectively arranged on the first surface (11) and the second surface (12), the active material layer (20) includes a plurality of sub-active material layers (23), the plurality of sub-active material layers (23) are stacked, and the active material layer (20) is formed with a wetting channel (30), and the wetting channel (30) extends from the surface of the active material layer (20) away from the current collector (10) to the innermost sub-active material layer (23).

2. The negative electrode sheet (100) according to claim 1, characterized in that: Along the thickness direction of the active material layer (20), the thickness of the innermost sub-active material layer (23) is D1, and the depth of the wetting channel (30) formed by the innermost sub-active material layer (23) is D2, satisfying the relationship: 0<D2 / D1≤0.

3.

3. The negative electrode sheet (100) according to claim 1, characterized in that: At least two of the sub-active material layers (23) in each of the active material layers (20) have different surface densities.

4. The negative electrode sheet (100) according to claim 1, characterized in that: The sub-active material layers (23) each include: a negative electrode active material, a conductive agent and a binder. The multiple sub-active material layers (23) of each active material layer (20) form a first material layer group (21) and a second material layer group (22). The second material layer group (22) is located between the first material layer group (21) and the current collector (10). The mass ratio of the negative electrode active material, the mass ratio of the conductive agent and the mass ratio of the binder in the sub-active material layers (23) of the first material layer group (21) are 97%-98%, 0.3%-0.7% and 1.5%-3%, respectively. The mass ratio of the negative electrode active material, the mass ratio of the conductive agent and the mass ratio of the binder in the sub-active material layers (23) of the second material layer group (22) are 95%-97%, 0.3%-0.7% and 3%-5%, respectively. The first material layer group (21) and the second material layer group (22) each include at least one sub-active material layer (23).

5. The negative electrode sheet (100) according to claim 1, characterized in that: The mass ratios of negative electrode active materials in at least two of the sub-active material layers (23) in each of the active material layers (20) are different.

6. The negative electrode sheet (100) according to claim 1, characterized in that: The mass ratios of the binders in at least two of the sub-active material layers (23) in each of the active material layers (20) are different.

7. The negative electrode sheet (100) according to claim 1, characterized in that: The multiple sub-active material layers (23) of each active material layer (20) form a first material layer group (21) and a second material layer group (22), the second material layer group (22) is located between the first material layer group (21) and the current collector (10), the porosity of the sub-active material layer (23) of the first material layer group (21) is greater than the porosity of the sub-active material layer (23) of the second material layer group (22), and the first material layer group (21) and the second material layer group (22) each include at least one sub-active material layer (23).

8. The negative electrode sheet (100) according to claim 7, characterized in that: The porosity of the sub-active material layer (23) of the first material layer group (21) is greater than or equal to 25% and less than or equal to 35%, and the porosity of the sub-active material layer (23) of the second material layer group (22) is greater than or equal to 15% and less than or equal to 25%.

9. The negative electrode sheet (100) according to claim 1, characterized in that: The cross section of the infiltration channel (30) is circular, and the cross section diameter of the infiltration channel (30) is R, satisfying the relationship: 30 μm≤R≤80 μm.

10. The negative electrode sheet (100) according to claim 9, characterized in that: The depth of the infiltration channel (30) is D3, satisfying the relationship: 1.5≤R / D3≤2.

5.

11. The negative electrode sheet (100) according to claim 1, characterized in that: The volume of the active material layer (20) is V1, and the total volume of the infiltration channel (30) is V2, satisfying the relationship: 0<V2 / V1<0.01; and / or, The cross-sectional area of ​​the active material layer (20) is S1, and the total cross-sectional area of ​​the wetting channel (30) is S2, satisfying the relationship: 0<S2 / S1<0.

05.

12. The negative electrode sheet (100) according to any one of claims 1 to 11, characterized in that: At least two of the sub-active material layers (23) in the active material layer (20) have different thicknesses; and / or, The compaction density of at least two of the sub-active material layers (23) in the active material layer (20) is different; and / or, At least two of the sub-active material layers (23) in the active material layer (20) have different active material structures.

13. A battery cell, characterized in that: include: A shell and an electrode assembly, wherein the electrode assembly is arranged in the shell, and the electrode assembly comprises a positive electrode sheet, a negative electrode sheet (100) and a separator, wherein the positive electrode sheet, the negative electrode sheet (100) and the separator are assembled together to form the electrode assembly, and the negative electrode sheet (100) is the negative electrode sheet (100) according to any one of claims 1 to 12.

Images