A battery cell and an electrochemical device

Abstract

The present application provides a battery cell and an electrochemical device, wherein the battery cell includes a first pole piece, a second pole piece, and a diaphragm disposed between the first pole piece and the second pole piece, wherein the first pole piece includes a first current collector and a first active material layer disposed on at least one side of the first current collector, and the first pole piece includes at least part of a first sub-pole piece, and the first sub-pole piece includes a first current collector, a first active material layer, and an adhesive layer, wherein: the adhesive layer is located between the first current collector and the first active material. The first pole piece includes at least part of a sub-pole piece, and the first sub-pole piece includes a first current collector, a first active material layer, and an adhesive layer, and the adhesive layer is disposed between the first current collector and the first active material layer. In this way, the stability of the bonding between the first current collector and the first active material layer can be improved, thereby reducing the amount of the active material layer falling off from the current collector, and even preventing the active material layer from falling off, thereby alleviating the problems of reduced battery capacity and cycle attenuation.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical devices, and in particular to a battery cell and an electrochemical device. Background Art

[0002] With the rapid development of lithium-ion batteries, during the battery charge and discharge cycle, the active material layer coated on both sides of the current collector in the electrode of the battery cell will expand. During the long-term charge and discharge process of the battery cell, the active material layer may fall off from the current collector; and in the process of assembling the electrode into the battery cell, the active material layer may also fall off from the current collector; this leads to the problem of reduced battery capacity and cycle attenuation. Utility Model Content

[0003] In view of this, the present application provides a battery cell, aiming to solve the problem of battery capacity reduction and cycle attenuation. The present application also provides an electrochemical device including the battery cell.

[0004] In order to achieve the above objectives, this application provides the following technical solutions:

[0005] A battery cell, comprising a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, wherein the first pole piece comprises a first current collector and a first active material layer disposed on at least one side of the first current collector, the first pole piece comprises at least part of a first sub-pole piece, the first sub-pole piece comprises the first current collector, the first active material layer, and an adhesive layer, wherein:

[0006] The adhesive layer is located between the first current collector and the first active material.

[0007] Optionally, the first sub-pole sheet is located at the outermost side of the battery cell.

[0008] Optionally, the adhesive layer is located on a side of the first current collector facing the center of the battery cell.

[0009] Optionally, the first pole piece includes a second sub-pole piece, the second sub-pole piece includes the first current collector and the first active material layer, and the second sub-pole piece is not provided with the adhesive layer.

[0010] Optionally, the first sub-pole sheet is located at the outermost layer of the battery cell, and the second sub-pole sheet is located on a side of the first sub-pole sheet facing the center of the battery cell.

[0011] Optionally, the first electrode is a negative electrode.

[0012] Optionally, the battery cell is a stacked battery cell, the first pole sheet and the second pole sheet are alternately stacked in sequence, the first sub-pole sheet is located at the outermost side of the stacking direction of the stacked battery cell, and the second sub-pole sheet is located in the middle of the battery cell stacking direction.

[0013] Optionally, the bonding layer includes an adhesive and a conductive agent.

[0014] Optionally, in a direction perpendicular to the first current collector, the thickness of the adhesive layer is 0.5 μm to 5 μm; preferably, the thickness of the adhesive layer is 1 μm to 2 μm.

[0015] Optionally, in a direction perpendicular to the first current collector, the thickness of the bonding layer is less than the thickness of the first active material layer, and the thickness of the first active material layer is 20-100 μm.

[0016] Optionally, the battery cell is a wound battery cell, the first sub-pole sheet is the portion of the first pole sheet located at the outermost layer of the wound battery cell, and the second sub-pole sheet is the remaining portion of the first pole sheet located inside the outermost layer.

[0017] An electrochemical device comprises the battery cell described in any one of the above.

[0018] The battery cell provided by the present application comprises a first pole piece including at least part of a sub-pole piece, the first sub-pole piece comprises a first current collector, a first active material layer and an adhesive layer, and the adhesive layer is arranged between the first current collector and the first active material layer. In this way, the stability of the bonding between the first current collector and the first active material layer can be improved, thereby reducing the amount of the active material layer falling off from the current collector, and even preventing the active material layer from falling off, thus alleviating the problem of reduced battery capacity and cycle attenuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0020] Figure 1 A front view of the laminated battery cell provided in this embodiment;

[0021] Figure 2 This is a front view of the wound battery cell.

[0022] exist Figure 1-Figure 2 middle:

[0023] 1-first pole piece, 2-second pole piece, 3-diaphragm;

[0024] 11 - first sub-pole sheet, 12 - second sub-pole sheet, 21 - second current collector, 22 - second active material layer; 111 - first current collector, 112 - first active material layer, 113 - adhesive layer. DETAILED DESCRIPTION

[0025] The present application provides a battery cell and an electrochemical device comprising the battery cell.

[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] like Figure 1 to Figure 2 As shown, an embodiment of the present application provides a battery cell, which can be combined with a shell and components to form a battery, and the battery is installed on an electrical device and provides electrical energy to the electrical device. The battery cell includes a first pole piece 1, a second pole piece 2, and a diaphragm 3 disposed between the first pole piece 1 and the second pole piece 2. The first pole piece 1 includes a first current collector 111 and a first active material layer 112 disposed on at least one side of the first current collector 111. The corresponding second pole piece 2 includes a second current collector 21 and a second active material layer 22 disposed on at least one side of the second current collector 21.

[0028] Specifically, at least part of the first pole piece 1 is the first sub-pole piece 11, that is, part of the first pole piece 1 is the first sub-pole piece 11 or all of the first pole piece 1 is the first sub-pole piece 11. The first sub-pole piece 11 includes a first current collector 111, a first active material layer 112, and an adhesive layer 113, wherein the adhesive layer 113 is located between the first current collector 111 and the first active material layer 112. Specifically, the adhesive layer 113 is provided between the first current collector 111 and the first active material layer 112 of the first sub-pole piece 11. It should be noted that the first active material layer 112 can be provided on only one side of the first current collector 111, or on both sides of the first current collector 111; and there is no limitation on the setting position of the adhesive layer 113. The adhesive layer 113 can be provided between the first current collector 111 and the first active material layer 112 on one of the two sides of the first current collector 111, or between the first current collector 111 and the first active material layer 112 on both sides of the first current collector 111.

[0029] It should be noted that the first pole piece 1 is not limited here, and the first pole piece 1 can be a positive pole piece or a negative pole piece. Also, the arrangement of the first sub-pole piece 11 is not limited. When the battery cell is a laminated battery cell, the first sub-pole piece 11 can be located in the direction of pole piece stacking ( Figure 1 When the battery cell is a wound battery cell, the first sub-pole sheet 11 can be located at any area on the outermost or inner side in the winding direction of the pole sheet.

[0030] In the battery cell of the above structure, at least part of the first pole piece 1 is set as a sub-pole piece, and the first sub-pole piece 11 includes a first current collector 111, a first active material layer 112 and an adhesive layer 113, and the adhesive layer 113 is set between the first current collector 111 and the first active material layer 112. In this way, the stability of the bonding between the first current collector 111 and the first active material layer 112 can be improved, thereby reducing the amount of the active material layer falling off from the current collector, and even preventing the active material layer from falling off, so as to alleviate the problems of reduced battery capacity and cycle attenuation.

[0031] In some embodiments, the first sub-electrode sheet 11 is located at the outermost side of the battery cell. Figure 1 The outermost side of the battery cell refers to the direction of battery cell stacking ( Figure 1 The end of the battery is in the direction indicated by the double-headed arrow X in the figure); when the battery cell is a wound battery cell (such as Figure 2 The outermost side of the battery cell refers to the outermost circle in the winding direction of the battery cell. When the battery cell is a laminated battery cell, the first sub-pole sheet 11 is the pole sheet located at the end of the battery cell; when the battery cell is a wound battery cell, the first sub-pole sheet 11 is the portion of the first pole sheet 1 located at the outermost circle of the winding core.

[0032] When the battery cell is in the process of charging and discharging, lithium ion migration occurs between the first active material layer 112 near the center of the battery cell and the adjacent second active material layer 22 of the first sub-pole sheet 11 located at the outermost side of the battery cell. As the battery cell is charged and discharged for a long time, the first active material layer 112 near the center of the battery cell of the first sub-pole sheet 11 will expand, while the other side of the first sub-pole sheet 11 located at the outermost side will not expand because lithium ion migration does not occur. This will cause the first sub-pole sheet 11 to curl from the side close to the center of the battery cell to the side away from the center of the battery cell, which may cause the first active material layer 112 near the center of the battery cell of the first sub-pole sheet 11 located at the outermost side to fall off. In this embodiment, an adhesive layer 113 is provided between the first current collector 111 of the first sub-pole sheet 11 and the first active material layer 112, thereby improving the firmness of the bonding between the first current collector 111 of the first sub-pole sheet 11 and the first active material layer 112, thereby reducing the probability of the first active material layer 112 falling off, and even preventing the first active material layer 112 from falling off.

[0033] It should also be noted that the center of the laminated cell is Figure 1 The area indicated by arrow A is the center of the wound cell. Figure 2 The area indicated by arrow B.

[0034] Furthermore, the adhesive layer 113 is located on the side of the first current collector 111 facing the center of the battery cell. Specifically, since the first active material layer 112 on the side of the first current collector 111 facing the center of the battery cell has a large amount of shedding, the adhesive layer 113 is arranged on the side of the first current collector 111 facing the center of the battery cell, so that the first current collector 111 and the first active material layer 112 can be firmly bonded, thereby preventing the first active material layer 112 on this side from shedding, thereby preventing the battery capacity from being reduced.

[0035] In some embodiments, the first pole piece 1 includes a second sub-pole piece 12, the second sub-pole piece 12 includes a first current collector 111 and a first active material layer 112, and the second sub-pole piece 12 is not provided with an adhesive layer 113. Specifically, the first pole piece 1 includes a first sub-pole piece 11 and a second sub-pole piece 12, at least a portion of the first pole piece 1 is the first sub-pole piece 11 and the rest is the second sub-pole piece 12, the second sub-pole piece 12 includes a first current collector 111 and a first active material layer 112 disposed on at least one side of the first current collector 111, and the adhesive layer 113 is not disposed in the second sub-pole piece 12, so that the size of the second sub-pole piece 12 in the direction perpendicular to the current collector can be reduced, so as to reduce the thickness of the second sub-pole piece 12, so as to increase the energy density of the battery cell.

[0036] In some embodiments, the first sub-electrode sheet 11 is located at the outermost layer of the battery cell, and the second sub-electrode sheet 12 is located on the side of the first sub-electrode sheet 11 facing the center of the battery cell. Specifically, when the battery cell is a laminated battery cell, the first sub-electrode sheet 11 is located at the outermost layer of the battery cell, which means that the first sub-electrode sheet 11 is arranged in the direction of the battery cell stacking ( Figure 1 At the two ends of the battery cell (in the direction indicated by the double-headed arrow X), the second sub-pole sheet 12 is arranged on the side of the first sub-pole sheet 11 facing the center of the battery cell, and the second sub-pole sheet 12 is arranged between the two first sub-pole sheets 11 located at the ends; when the battery cell is a wound battery cell, the first sub-pole sheet 11 is located at the outermost layer of the battery cell, which means that the first sub-pole sheet 11 is the partial structure of the outermost circle of the first pole sheet 1 wound on the winding core, and the second sub-pole sheet 12 refers to the remaining structure of the first pole sheet 1 on the inner side of the winding of the winding core.

[0037] In this embodiment, by setting the first sub-pole sheet 11 at the outermost side of the battery cell, the active material layer at the outermost side of the battery cell can be prevented from falling off; by locating the second sub-pole sheet 12 on the side of the first sub-pole sheet 11 facing the center of the battery cell, the number of adhesive layers in the battery cell can be reduced, thereby preventing the energy density of the battery cell from being reduced too much.

[0038] In some embodiments, the first electrode sheet 1 is a negative electrode sheet. Specifically, the first electrode sheet 1 is set as a negative electrode sheet, and when the negative electrode sheet is a silicon-carbon negative electrode sheet, that is, when the active material layer of the negative electrode sheet is a silicon-based layer, the negative electrode of the battery made of silicon-carbon material has a large amount of expansion during the charging and discharging process. The first electrode sheet 1 is set as a negative electrode sheet, and the first sub-electrode sheet 1 is also a negative electrode sheet. In this way, the stability of the bonding between the first active material layer 112 and the first current collector 111 can be improved, the amount of the first active material layer 112 falling off from the first current collector 111 can be alleviated, and the excessive reduction in the battery capacity can be reduced.

[0039] In addition, the first pole piece 1 can also be a positive pole piece, and the corresponding second pole piece 2 can be a negative pole piece.

[0040] Further, in some embodiments, see Figure 1 , the battery cell is a laminated battery cell, the first electrode sheet 1 and the second electrode sheet 2 are alternately stacked in sequence, the first sub-electrode sheet 11 is located at the outermost side in the stacking direction of the laminated battery cell, and the second sub-electrode sheet 12 is located in the middle of the stacking direction of the battery cell. Specifically, taking the first electrode sheet 1 as a negative electrode sheet, the second electrode sheet 2 as a positive electrode sheet, and the battery cell being a laminated battery cell as an example, the negative electrode sheets and the positive electrode sheets are alternately stacked in sequence, and a diaphragm 3 is arranged between adjacent positive and negative electrode sheets, and the first sub-electrode sheet 11 is arranged at the outermost side in the stacking direction of the laminated battery cell, and the second sub-electrode sheet 12 is arranged in the middle of the stacking direction of the laminated battery cell, that is, the second sub-electrode sheet 12 is arranged between the first sub-electrode sheets 11 located at both ends.

[0041] In some embodiments, the adhesive layer 113 includes an adhesive and a conductive agent. Specifically, since the adhesive layer 113 is disposed between the first current collector 111 and the first active material layer 112 of the first sub-electrode sheet 11, the first current collector 111 and the first active material layer 112 need to be electrically connected when the battery cell is charged and discharged. Since the adhesive layer 113 is usually non-conductive, the adhesive layer 113 is configured as an adhesive and a conductive agent, so that the adhesive layer 113 prevents the first current collector 111 from falling off from the first active material layer 112, and can also achieve electrical connection between the first current collector 111 and the first active material layer 112.

[0042] Exemplarily, the adhesive can be a water-washable adhesive or an oil-based adhesive. The water-based adhesive includes one or a combination of carboxymethyl cellulose acid (salt), styrene-butadiene rubber, polyacrylonitrile, polyacrylamide, polyacrylate, polyacrylic acid (salt), polyvinyl alcohol, alginic acid (salt), perfluorosulfonic acid (salt), etc. The oil-based adhesive includes one or a combination of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and its derivatives. The conductive agent includes at least one of conductive carbon black (SP), Ketjen black, acetylene black, graphite conductive agent (KS-6, KS-15, SO, SEG-6), carbon fiber (VGCG), carbon nanotube (CNT), and graphene.

[0043] In this embodiment, further, the proportion of the adhesive in the bonding layer 113 is greater than the proportion of the conductive agent. The proportion of the adhesive is within the above range. On the premise that the bonding layer 113 realizes electrical connection between the first current collector 111 and the first active material layer 112, the content of the adhesive in the bonding layer 113 can be increased to enhance the bonding strength between the first end current collector and the first active material layer 112, thereby further preventing the first active material layer 112 from falling off.

[0044] In some embodiments, the proportion of the conductive agent is 0% to 50%. Setting the conductive agent to the above range can ensure the conductivity between the first current collector 111 and the first active material layer 112 after the first current collector 111 and the first active material layer 112 are bonded together by the adhesive layer 113; the proportion of the adhesive is 20% to 100%. Setting the adhesive to the above range can ensure the bonding strength between the first current collector 111 and the first active material layer 112 while ensuring the conductivity between the first current collector 111 and the first active material layer 112.

[0045] For example, the proportion of the conductive agent may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc. The proportion of the adhesive may be 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, etc.

[0046] In some embodiments, in the direction perpendicular to the first current collector 111, the thickness of the adhesive layer 113 is 0.5 μm to 5 μm; preferably, the thickness of the adhesive layer 113 is 1 μm to 2 μm. Specifically, the thickness of the adhesive layer 113 is within the above range, which can ensure the firmness of the adhesion between the first current collector 111 and the first active material layer 112, prevent the first active material layer 112 from falling off the first current collector 111, and prevent the adhesive layer 113 from being too thick, thereby preventing the energy density of the battery cell from being excessively reduced.

[0047] Illustratively, the thickness of the adhesive layer 113 may be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0048] It should be noted that in the laminated cell, the direction perpendicular to the first current collector 111 is the same as the direction of the electrode stacking. Figure 1 In the wound cell, when the first current collector 111 is in the area shown by the straight section, the direction perpendicular to the first current collector 111 is Figure 2 In the direction indicated by the double-headed arrow Y, the straight section refers to the straight area of ​​the wound battery cell.

[0049] In some embodiments, in the direction perpendicular to the first current collector 111, the thickness of the adhesive layer 113 is less than the thickness of the first active material layer 112, and the thickness of the first active material layer 112 is 20-100 μm. Specifically, the thickness of the adhesive layer 113 is ensured to be less than the thickness of the first active material layer 112, and on the premise that the adhesive layer 113 ensures that the first current collector 111 and the first active material layer 112 are firmly bonded, the thickness of the adhesive layer 113 can be avoided to be too large, thereby avoiding excessive reduction in the energy density of the battery cell.

[0050] It should be noted that when the battery cell is a laminated battery cell, the direction perpendicular to the first current collector 111 refers to Figure 1 The direction indicated by the double-headed arrow X in the figure; when the battery cell is a straight section of a wound battery cell, the direction perpendicular to the first current collector 111 refers to Figure 2 The direction is indicated by the double-headed arrow Y.

[0051] For example, the thickness of the first active material layer 112 may be 20 μm, 30 μm, 40 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, etc.

[0052] In some embodiments, the first active material layer 112 includes an active material; the active material is a silicon-based layer, and the silicon-based layer includes at least one of silicon, nano-silicon, silicon carbide, a silicon-carbon composite material, or silicon monoxide.

[0053] Specifically, a conductive agent is also provided in the first active material layer 112 to increase the conductivity of the first active material layer 112, and a conductive agent is also provided in the bonding layer 113 to enhance the conductivity between the first active material layer 112 and the first current collector 111; an adhesive is also provided in the first active material layer 112, and an adhesive is also provided in the bonding layer 113 to further enhance the firmness of the bonding between the first active material layer 112 and the adhesive; and at the same time, the bonding strength between the first current collector 111 in the middle of the battery cell and the first active material layer 112 can also be enhanced.

[0054] It should be noted that the first active material layer 112 in the first pole piece 1 located in the middle of the battery cell and the first end active material layer in the first end pole piece located at the end of the battery cell have the same composition, which is active material, conductive agent and adhesive. In this way, the first current collector 111 is coated with the same can material to form the first active material layer 112, which ensures the uniformity of the first current collector 111, can ensure the manufacturing speed and yield of the first pole piece 1, and improve production efficiency.

[0055] In some embodiments, the proportion of the conductive agent is 0.5% to 2%, and / or the proportion of the adhesive is 1% to 4%. Specifically, ensuring that the conductive agent is within the above range can improve the conductivity between the first active material layer 112 and the first current collector 111, and avoid excessive content of the conductive agent, and avoid excessive reduction in the energy density of the battery cell; correspondingly, ensuring that the adhesive is within the above range can improve the bonding strength between the first active material layer 112 and the adhesive layer 113 or the first current collector 111, and avoid the first active material layer 112 from falling off the first current collector 111, and avoid excessive content of the adhesive, and avoid excessive reduction in the energy density of the battery cell.

[0056] Exemplarily, the proportion of the conductive agent can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc.; the proportion of the adhesive can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0057] Furthermore, in some embodiments, the ratio of active material: conductive agent: adhesive agent is 96:3:1. Specifically, the ratio of active material, conductive agent and adhesive agent is within the above range, the first active material layer 112 has certain adhesion and conductivity, and the ratio of active material layer is the highest, so that the energy density of the battery cell is reduced less.

[0058] In some embodiments, the active material is a silicon-based layer, and the silicon content in the silicon-based layer is greater than 5%. Specifically, the active material layer is set as a silicon-based layer, which has a higher capacity than the silicon in the graphite layer silicon-based layer, and can store more lithium ions to increase the capacity of the battery cell; when the battery cell is charged and discharged, the lithium ions move between the positive and negative electrodes, and the active material layer will expand. Silicon has good expansion tolerance, reducing the risk of stress damage; and silicon has good conductivity. Ensuring that the silicon content is greater than 5% can further increase the capacity of the battery cell, further reduce the risk of stress damage, and further improve conductivity.

[0059] For example, the silicon content in the silicon-based layer may be 5%, 8%, 10%, 15%, 20%, 25%, 30%, etc.

[0060] In some embodiments, the battery cell is a wound battery cell, the first sub-pole sheet 11 is a portion of the first pole sheet 1 located at the outermost layer of the wound battery cell, and the second sub-pole sheet 12 is the remaining portion of the first pole sheet 1 located inside the outermost layer. Specifically, taking the first pole sheet 1 as a negative pole sheet, the second pole sheet 2 as a positive pole sheet, and the battery cell being a wound battery cell as an example, at this time, the first sub-pole sheet 11 is a portion of the first pole sheet 1 located at the outermost circle of the wound battery cell, and the second sub-pole sheet 12 is the remaining portion of the first pole sheet 1 located inside the outermost circle of the wound battery cell. In this way, when the battery composed of the above-mentioned battery cells undergoes charge and discharge reactions, since the active material layer on the side of the negative electrode sheet on the outermost circle of the wound battery cell facing away from the center of the battery cell does not react, the active material layer on the side of the negative electrode sheet on the outermost circle of the wound battery cell close to the center of the battery cell reacts and expands, the negative electrode sheet on the outermost circle of the wound battery cell curls up, which may cause the active material layer close to the center of the battery cell to fall off. The negative electrode sheet located on the outermost circle of the winding core is the first sub-pole sheet 11, and an adhesive layer 113 is provided between the first active material layer 112 on the side of the first sub-pole sheet 11 close to the center of the battery cell and the first current collector 111. This can ensure the stability of the adhesion between the first active material layer 112 and the first current collector 111, thereby avoiding the falling off of the first active material layer 112.

[0061] An electrochemical device includes any one of the above-mentioned battery cells. Since the electrochemical device includes the above-mentioned battery cell, the beneficial effects of the electrochemical device brought by the battery cell can be found in the above content and will not be described in detail here.

[0062] The method for preparing the first pole piece 1 comprises at least the following steps:

[0063] S101, mixing a water-based or oil-based binder and a conductive agent, and obtaining a uniformly dispersed mixture by high-speed stirring. The mixture is made into a slurry using water or N-methylpyrrolidone (NMP) as a solvent. The slurry is uniformly coated on one side of the first current collector 111 of the first sub-pole sheet 11, and after drying, the first current collector 111 of the first sub-pole sheet 11 with an adhesive layer 1135 set on one side is obtained.

[0064] S102, mixing the first end active material graphite and silicon-based material, binder and conductive agent, and obtaining a uniformly dispersed mixture by high-speed stirring. The mixture is made into a first active material slurry using water or N-methylpyrrolidone (NMP). The slurry is evenly coated on both sides of the first current collector 111 of the second sub-pole sheet 12 to obtain the first current collector 111 of the second sub-pole sheet 12. The slurry is evenly coated on both sides of the first current collector 111 of the first sub-pole sheet 11 with the adhesive layer 1135 set on one side in step 1, and after drying, the first current collector 111 of the first sub-pole sheet 11 is obtained.

[0065] Further, the silicon-based negative electrode material in S102 is one or a combination of pure silicon, nano-silicon, silicon carbide, silicon-carbon composite material or silicon oxide. The graphite in S102 is one or a combination of natural graphite, artificial graphite, mesophase carbon microspheres, soft carbon, and hard carbon.

[0066] In this embodiment, the battery comprises a first pole piece 1, a second pole piece 2 and an electrolyte or an electrolyte solution.

[0067] On the basis that the first electrode sheet 1 is a negative electrode sheet, the second electrode sheet 2 is a positive electrode sheet, and the battery cell is a laminated battery cell, the following experiment is performed, and the specific steps are as follows:

[0068] Example 1

[0069] (1) Preparation of the first sub-electrode sheet 11 and the second sub-electrode sheet 12 at the ends of the laminated cell

[0070] The aqueous binder SBR and the conductive agent are mixed, the binder ratio is 30%, and a uniformly dispersed mixture is obtained by high-speed stirring. The mixture is made into a slurry using water as a solvent, and the solid content of the slurry is 15%. The slurry is evenly coated on one side of the first current collector 111 of the first sub-pole sheet 11 with a thickness of 1.5 μm, and after drying, a first end current collector of the first sub-pole sheet 11 with a single-sided adhesive layer 1135 is obtained.

[0071] The negative electrode active material graphite is mixed with 10% SiOx silicon-based material, aqueous SBR binder and conductive agent, and a uniformly dispersed mixture is obtained by high-speed stirring. The mixture is made into a first active material layer 112 slurry using an aqueous solvent, and the slurry has a solid content of 50%. The slurry is evenly coated on both sides of the first current collector 111 of the second sub-pole sheet 12 to obtain the second sub-pole sheet 12 located in the middle of the laminated battery cell. The slurry is evenly coated on both sides of the first current collector 111 of the first sub-pole sheet 11 coated with the adhesive layer 113 on one side in step 1, and after drying, the first sub-pole sheet 11 of the outermost layer of the laminated battery cell is obtained.

[0072] (2) Preparation of the Second Sub-Pole Sheet 12

[0073] The positive electrode active material ternary nickel cobalt manganese NCM, binder PVDF and conductive carbon black are mixed and stirred at high speed to obtain a uniformly dispersed mixture. In the mixture, the solid components include 95wt% NCM, 2wt% binder PVDF and 3wt% conductive carbon black. The mixture uses N-methylpyrrolidone as a solvent to prepare a second active material slurry, and the solid content in the slurry is 70wt%. The slurry is evenly coated on both sides of the second current collector 21, and after drying and roller pressing, the second pole piece 2 is obtained.

[0074] (3) Assembly of Example Battery C1

[0075] After punching the first pole piece 1 and the second pole piece 2, a Z-shaped stack is used to form a bare cell, with the first sub-pole piece 11 at both ends, and the adhesive layer 113 facing the second pole piece 2. The aluminum tabs and the copper-plated nickel tabs are turned out respectively. The bare cell is clamped with a glass clamp with a strength of 100MPa / m2, and vacuum-baked at 85°C for 24 hours, and then encapsulated with an aluminum-plastic film. The electrolyte uses a 1M lithium hexafluorophosphate electrolyte, and the solvent is a mixed solvent of ethylene carbonate / dimethyl carbonate / 1,2-propylene glycol carbonate-1:1:1 (volume ratio). After packaging, the battery is formed and aged to obtain a square soft-package battery with a length, width and thickness of 160mm×60mm×10mm, which is recorded as the comparison group C1. The design capacity of the stacked structure battery cell is 8000mAh.

[0076] The difference between Example 2 and Example 1 is that one of the two first sub-pole sheets 11 at the two side ends of the laminated battery cell is replaced with a second sub-pole sheet 12, and the prepared battery is C2.

[0077] The difference between Example 3 and Example 1 is that the thickness of the adhesive layer 113 in the first sub-electrode sheet 11 is changed to 0.5 μm, and the prepared battery is C3.

[0078] The difference between Example 4 and Example 1 is that the proportion of the adhesive in the adhesive layer 113 in the first sub-electrode sheet 11 is reduced from 30% to 10%, and the prepared battery is C4.

[0079] The difference between Example 5 and Example 1 is that the proportion of silicon in the first active material layer 112 is increased from 10% to 20%, and the prepared battery is C5.

[0080] The difference between Comparative Example 6 and Example 1 is that the two first sub-pole sheets 11 at both ends of the laminated battery cell are replaced with second sub-pole sheets 12, and the prepared battery is C6.

[0081]

[0082] Table 1

[0083] C1 C2 C3 C4 C5 C6 100T / ％ 99.9％ 98.2％ 99.2％ 99.1％ 99.9％ 97.3％ 1000T / ％ 86.4％ 83.2％ 84.3 83.9％ 85.4％ 79.3％

[0084] Table 2

[0085] After conducting the above experiments, the following conclusions were obtained:

[0086] Table 1 is a data table of curling and de-molding and capacity utilization of the outermost pole pieces of C1, C2, C3, C4, C5 and C6 after the chemical composition selection. Compared with the conventional silicon-carbon laminated battery cell of group C6, after the chemical composition selection is completed, cracks appear on both sides of the battery cell, the outermost pole piece curls and de-moldes and loses powder, causing the electron channel to break, and the outermost first active material cannot exert its capacity, resulting in a decrease in capacity. After the adhesive layer 113 is introduced, it buffers the expansion stress of the silicon negative electrode on one side of the first current collector 111 of the first sub-pole piece 11, and there will be no curling and de-molding problems, and the capacity will not be reduced. Both C1 and C5 batteries can reach the designed capacity. However, the thickness of the adhesive layer 1135 and the specific gravity of the adhesive can affect the effect of buffering stress. Too thin a thickness of the adhesive layer and a low specific gravity of the adhesive will weaken the buffering effect. Both C3 and C4 batteries have slight de-molding problems and a decrease in capacity. The design of the C2 battery cell proves the effect of the carbon-coated adhesive layer. There is no problem of film peeling when the adhesive layer 113 is set using the first sub-pole sheet 11, but there is a serious problem of curling and film peeling when the adhesive layer 1135 is not set.

[0087] Table 2 is a comparison chart of 1C / 1C 100% DOD cycle performance at room temperature for C1, C2, C3, C4, C5 and C6 cells, with a voltage window of 2.5V-4.3V. As can be seen from the cycle chart, the cells C2, C3, C4 and C6 cells with outer layer curling and delamination have more or less problems of fast early cycle attenuation and poor overall cycle, especially for conventional silicon-carbon negative electrode stacked cells, whose 100T capacity attenuates by about 97%, and 1000T capacity attenuates to less than 80%. When the adhesive layer 1135 is introduced at the end of the stacked cell, such as C1 to C5 cells, there is no problem of early attenuation, and the cycle performance is also improved to 1000T, with a retention rate of more than 85%.

[0088] Among them, the test method for the battery cell cycle is to charge to 4.3V at 1C at room temperature, then discharge to 2.5V at 1C, record the discharge capacity values ​​of different cycle numbers, and calculate the capacity retention rates of 100T and 1000T.

[0089] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0090] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0091] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0092] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0093] It should be understood that the qualifiers "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present application are only used to more clearly explain the technical solutions and cannot be used to limit the scope of protection of the present application.

[0094] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A battery cell, comprising a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, wherein the first pole piece comprises a first current collector and a first active material layer disposed on at least one side of the first current collector, characterized in that: The first pole piece includes at least part of a first sub-pole piece, and the first sub-pole piece includes the first current collector, the first active material layer, and an adhesive layer, wherein: The adhesive layer is located between the first current collector and the first active material.

2. The battery cell according to claim 1, characterized in that: The first sub-electrode sheet is located at the outermost side of the battery cell.

3. The battery cell according to claim 2, characterized in that: The adhesive layer is located on a side of the first current collector facing the center of the battery cell.

4. The battery cell according to claim 1, characterized in that: The first pole piece includes a second sub-pole piece, the second sub-pole piece includes the first current collector and the first active material layer, and the second sub-pole piece is not provided with the adhesive layer.

5. The battery cell according to claim 4, characterized in that: The first sub-pole sheet is located at the outermost layer of the battery cell, and the second sub-pole sheet is located at a side of the first sub-pole sheet facing the center of the battery cell.

6. The battery cell according to claim 1, characterized in that: The first electrode is a negative electrode.

7. The battery cell according to claim 4, characterized in that: The battery cell is a laminated battery cell, wherein the first pole piece and the second pole piece are alternately stacked in sequence, the first sub-pole piece is located at the outermost side in the stacking direction of the laminated battery cell, and the second sub-pole piece is located in the middle in the stacking direction of the battery cell.

8. The battery cell according to claim 1, characterized in that: The adhesive layer includes an adhesive and a conductive agent.

9. The battery cell according to claim 8, characterized in that: In a direction perpendicular to the first current collector, the thickness of the adhesive layer is 0.5 μm to 5 μm.

10. The battery cell according to claim 9, characterized in that: The thickness of the adhesive layer is 1 μm to 2 μm.

11. The battery cell according to claim 8, characterized in that: In a direction perpendicular to the first current collector, the thickness of the bonding layer is less than the thickness of the first active material layer, and the thickness of the first active material layer is 20-100 μm.

12. The battery cell according to claim 1, characterized in that: The battery cell is a wound battery cell, the first sub-pole sheet is the portion of the first pole sheet located at the outermost layer of the wound battery cell, and the second sub-pole sheet is the remaining portion of the first pole sheet located inside the outermost layer.

13. An electrochemical device, characterized in that: Comprising the battery cell as described in any one of claims 1 to 12.

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