Composite adhesive, electrode plate, battery and electric equipment

Abstract

The invention relates to a composite adhesive, an electrode plate, a battery and electric equipment. The composite adhesive comprises a plurality of adhesive particles, each adhesive particle comprises an adhesive core and a shell, and the glass transition temperature Tg of each adhesive core is larger than or equal to-60 DEG C and smaller than or equal to 0 DEG C; the shell wraps the surface of the bonding inner core, and the bonding force of the bonding inner core is larger than that of the shell.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a composite binder, an electrode sheet, a battery and an electrical device. Background Art

[0002] In the lithium battery industry, the dry electrode has great development space. For example, in the manufacturing process of the dry electrode technology, no solvent is used, avoiding solvent recovery and reducing environmental pollution. The preparation of the dry electrode does not require a drying process, which can save a large amount of energy, and at the same time avoid problems such as the floating of the binder and the cracking of the electrode sheet caused by the wet process coating and drying. However, the binder in the dry electrode is prone to side reactions with lithium ions, resulting in a low capacity retention rate of the dry electrode cell. Summary of the Invention

[0003] In view of this, the present application provides a composite binder, an electrode sheet, a battery and an electrical device. The composite binder has good bonding performance and can reduce the amount of polytetrafluoroethylene binder in the electrode sheet, so as to reduce the side reaction between the polytetrafluoroethylene binder and the active material while ensuring the bonding performance.

[0004] The present application provides a composite binder, which includes a plurality of bonding particles. Each bonding particle includes a bonding core and a shell. The glass transition temperature Tg of the bonding core ranges from -60°C to 0°C. The shell wraps around the surface of the bonding core, and the bonding force of the bonding core is greater than that of the shell.

[0005] Further, the composite binder has a first bonding force. After a preset pressure is applied to the composite binder, the composite binder has a second bonding force, and the first bonding force is less than the second bonding force. Wherein, the range of the preset pressure F is 10N ≤ F ≤ 20N.

[0006] Further, the material of the bonding core is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-methylol acrylamide.

[0007] Further, the material of the shell is selected from at least one of alumina, silica, lithium carbonate, carbon-containing substances and polyethylene wax.

[0008] Further, the range of the thickness h of the shell is 1μm ≤ h ≤ 10μm; the range of the particle size D of the bonding particle is 10μm ≤ D ≤ 100μm.

[0009] Further, the swelling ratio α of the composite binder ranges from 80% ≤ α ≤ 150%.

[0010] This application provides an electrode tab, which includes a current collector layer and an active material layer. The active material layer is disposed on at least one side of the current collector layer. The active material layer includes an active material, a polytetrafluoroethylene binder, and the composite binder provided by this application. In the active material layer, the mass fraction m1 of the polytetrafluoroethylene binder and the mass fraction m2 of the composite binder satisfy the relationship: 2 ≤ m1 / m2 ≤ 5.

[0011] Further, in the active material layer, the range of the mass fraction m1 of the polytetrafluoroethylene binder is: 0.5% ≤ m1 ≤ 10%; the range of the mass fraction m2 of the composite binder is: 1% ≤ m2 ≤ 2.5%.

[0012] Further, when the electrode tab is a positive electrode tab, in the active material layer, the range of the mass fraction m1 of the polytetrafluoroethylene binder is: 2% ≤ m1 ≤ 10%; and / or, when the electrode tab is a negative electrode tab, in the active material layer, the range of the mass fraction m1 of the polytetrafluoroethylene binder is: 0.5% ≤ m1 ≤ 2.5%.

[0013] This application provides a battery, which includes the electrode tab provided by this application and an electrolyte, and the electrolyte is used to infiltrate the electrode tab.

[0014] This application provides an electrical device, which includes a device body and the battery provided by this application, and the battery powers the device body.

[0015] In the present application, the adhesive particles include an adhesive core, and the glass transition temperature Tg of the adhesive core satisfies the range -60°C ≤ Tg ≤ 0°C. Then, the adhesive core exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, which is convenient for maintaining good adhesive performance. When the composite adhesive is applied to the active material layer, it can exhibit good adhesive performance and cooperate with the polytetrafluoroethylene adhesive to bond the inside of the active material layer and bond the active material layer to the current collector layer, thereby reducing the amount of the polytetrafluoroethylene adhesive used and reducing the side reaction between the polytetrafluoroethylene adhesive and the active material, so that the electrode tab has a high capacity retention rate and good adhesive performance. In addition, an adhesive with a glass transition temperature between -60°C and 0°C will agglomerate during spray drying granulation, increasing the processing difficulty. In the present application, the adhesive particles further include a shell, the shell wraps around the surface of the adhesive core, and the adhesive force of the adhesive core is greater than that of the shell. In other words, the shell can serve as an anti-sticking layer to wrap around the outer periphery of the adhesive core, so that during the processing of the composite adhesive, the adhesive cores can be prevented from sticking to each other, facilitating the dispersion and subsequent processing of the composite adhesive, and improving the processing performance of the composite adhesive. Further, due to the low glass transition temperature of the adhesive core, the temperature at which the composite adhesive produces an adhesive effect through hot pressing is relatively low. In other words, by pressing the composite adhesive at a relatively low temperature, the adhesive particles can exert an adhesive effect. When the composite adhesive is compounded with the polytetrafluoroethylene adhesive and applied to the electrode tab, the temperature for hot pressing the electrode tab can be reduced, the processing parameters of the electrode tab can be optimized, the processing cost of the electrode tab can be reduced, and at the same time, the adhesive performance between the active material layer and the current collector layer in the electrode tab can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic structural diagram of the adhesive particles according to an embodiment of the present application;

[0018] Figure 2 is a partial cross-sectional structural diagram of the electrode tab according to an embodiment of the present application;

[0019] Figure 3 is a scanning electron micrograph of the composite adhesive applied to the active material layer and compacted according to an embodiment of the present application;

[0020] Figure 4 Schematic partial cross-sectional structure diagram of a battery according to an embodiment of the present application;

[0021] Figure 5 Schematic structure diagram of an electrical device according to an embodiment of the present application;

[0022] Figure 6 Circuit block diagram of an electrical device according to an embodiment of the present application.

[0023] Explanation of reference numerals:

[0024] 100 - adhesive particle, 110 - adhesive core, 120 - outer shell, 200 - electrode tab, 210 - current collector layer, 220 - active material layer, 300 - battery, 310 - electrolyte, 400 - electrical device, 410 - device body. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0026] The terms "first", "second", etc. in the specification and claims of the present application and the above accompanying drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0027] Referring to "embodiment" or "embodiment manner" herein means that a specific feature, structure or characteristic described in connection with the embodiment or embodiment manner may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0028] In the lithium battery industry, dry electrodes have great development potential. For example, during the manufacturing process of dry electrode technology, solvents are not used, avoiding solvent recovery and reducing environmental pollution. The preparation of dry electrodes does not require a drying process, which can save a large amount of energy. At the same time, problems such as the floating of adhesives and cracks in the electrode sheets caused by the coating drying in the wet process are avoided. However, the preparation of dry electrodes also has certain shortcomings. Among them, the selection range of polymer adhesives used in the electrode sheets is small, and the most commonly used one is polytetrafluoroethylene (PTFE). The inventor's research found that the molecular structure of PTFE is composed of carbon atoms and fluorine atoms connected by covalent bonds, forming a highly symmetric helical structure, and PTFE contains a relatively large number of fluorine atoms. This structure makes the electron distribution in the PTFE molecule very uniform, and the non-polar regions and polar regions of the molecular chain are alternately distributed. This uniform electron distribution and symmetric molecular structure make the lowest unoccupied molecular orbital (LUMO) of PTFE very low, and it is easy to have side reactions with Li+ in the negative electrode, affecting the capacity retention rate of the dry electrode battery cell.

[0029] In addition, if PTFE adhesive is used alone, in the negative electrode sheet, the addition amount of PTFE adhesive needs to be increased to more than 3% to better compound and prevent the surface of the negative electrode sheet from shedding powder. However, the more PTFE adhesive is used, the higher the probability of side reactions with lithium ions, which will affect the capacity of the battery cell and the stability and cycle performance of the electrode sheet. Therefore, it is necessary to reduce the usage amount of PTFE adhesive on the premise of ensuring the film-forming and bonding performance of the negative electrode sheet.

[0030] Please refer to Figure 1 , this application provides a composite adhesive. The composite adhesive includes a plurality of adhesive particles 100. The adhesive particles 100 include an adhesive core 110 and a shell 120. The range of the glass transition temperature Tg of the adhesive core 110 is: -60°C ≤ Tg ≤ 0°C; the shell 120 wraps the surface of the adhesive core 110, and the adhesive force of the adhesive core 110 is greater than the adhesive force of the shell 120.

[0031] It can be understood that the composite adhesive is applied to the active material layer 220 of the electrode sheet 200. The active material layer 220 also includes active materials and PTFE adhesive. The composite adhesive cooperates with the PTFE adhesive to bond the active materials and can also bond the active material layer 220 and the current collector layer 210.

[0032] It can be understood that the adhesive particles 100 are of a core-shell structure.

[0033] Understandably, when the composite binder is applied to the active material layer 220 of the electrode tab 200, the plurality of adhesive particles 100 are dispersed in the active material layer 220.

[0034] Specifically, the value of the glass transition temperature Tg of the adhesive core 110 can be, but is not limited to, -60°C, -55°C, -50°C, -48°C, -44°C, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, etc.

[0035] In this embodiment, the adhesive particle 100 includes an adhesive core 110, and the glass transition temperature Tg of the adhesive core 110 satisfies the range -60°C ≤ Tg ≤ 0°C. Then, the adhesive core 110 exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, which is convenient for maintaining good adhesive performance. When the composite binder is applied to the active material layer 220, it can exhibit good adhesive performance and cooperate with the polytetrafluoroethylene binder to bond the inside of the active material layer 220 and bond the active material layer 220 to the current collector layer 210, thereby reducing the amount of the polytetrafluoroethylene binder used and reducing the side reaction between the polytetrafluoroethylene binder and the active material. Moreover, the composite binder does not react with the active material, so that the electrode tab 200 has a high capacity retention rate and good adhesive performance. In addition, the binder with a glass transition temperature between -60°C and 0°C will agglomerate during spray drying granulation, increasing the processing difficulty. In this embodiment, the adhesive particle 100 further includes a shell 120, the shell 120 wraps around the surface of the adhesive core 110, and the adhesive force of the adhesive core 110 is greater than that of the shell 120. In other words, the shell 120 can serve as an anti-sticking layer to wrap around the outer periphery of the adhesive core 110, so that during the processing of the composite binder, the adhesive cores 110 can be prevented from sticking to each other, facilitating the dispersion and subsequent processing of the composite binder, and improving the processing performance of the composite binder. Further, due to the low glass transition temperature of the adhesive core 110, the temperature at which the composite binder is hot-pressed to produce an adhesive effect is relatively low. In other words, by pressing the composite binder at a relatively low temperature, the adhesive particles 100 can exert an adhesive effect. When the composite binder is compounded with the polytetrafluoroethylene binder and applied to the electrode tab 200, the hot-pressing temperature of the electrode tab 200 can be reduced, the processing parameters of the electrode tab 200 can be optimized, the processing cost of the electrode tab 200 can be reduced, and at the same time, the adhesive performance between the active material layer 220 and the current collector layer 210 in the electrode tab 200 can be improved, that is, the peel strength between the active material layer 220 and the current collector layer 210 can be increased.

[0036] Understandably, when the glass transition temperature Tg of the adhesive core 110 is too high, it is difficult to effectively bond the active material layer 220 by hot pressing, making it difficult to form the electrode sheet 200. Even if the electrode sheet 200 is formed, the peel strength of the electrode sheet 200 is extremely low, reducing the performance of the electrode sheet 200. When the glass transition temperature Tg of the adhesive core 110 is too low, on the one hand, the adhesive core 110 is difficult to form or easily dissolves in the electrolyte, thus reducing the structural stability of the electrode sheet 200 and the cycle capacity retention rate of the battery 300 when the electrode sheet 200 is applied to the battery 300.

[0037] Understandably, in some embodiments, when using only the polytetrafluoroethylene adhesive, the hot pressing temperature of the electrode sheet 200 is greater than or equal to 120 °C to enable the polytetrafluoroethylene adhesive to exhibit adhesive performance and bond the active material layer 220 and the current collector layer 210. In other embodiments, when the composite adhesive and the polytetrafluoroethylene adhesive are used in combination, the hot pressing temperature of the electrode sheet 200 is less than or equal to 100 °C, which can enable the composite adhesive and the polytetrafluoroethylene adhesive to exhibit adhesive performance and bond the active material layer 220 and the current collector layer 210. Among them, preferably, the hot pressing temperature of the electrode sheet 200 is 80 °C.

[0038] In some embodiments, the composite adhesive has a first adhesive force. After applying a preset pressure to the composite adhesive, the composite adhesive has a second adhesive force, and the first adhesive force is less than the second adhesive force. Among them, the range of the preset pressure F is: 10 N ≤ F ≤ 20 N.

[0039] Understandably, the first adhesive force is the adhesive force of the composite adhesive before compaction, and the second adhesive force is the adhesive force of the composite adhesive after compaction.

[0040] Understandably, the composite adhesive does not play an adhesive role before compaction, and the outer shell can act as an anti-adhesive layer, that is, the first adhesive force is almost 0; the composite adhesive plays an adhesive role after compaction.

[0041] Specifically, the value of the preset pressure can be, but is not limited to, 10 N, 10.5 N, 10.8 N, 11 N, 11.2 N, 11.5 N, 11.8 N, 12 N, 12.5 N, 13 N, 14 N, 14.5 N, 15 N, 15.5 N, 16 N, 16.5 N, 17 N, 17.5 N, 18 N, 19 N, and 20 N, etc.

[0042] In this embodiment, before applying a preset pressure to the composite adhesive, the composite adhesive has a first adhesive force. Since the outer shell 120 covers the outer periphery of the adhesive core 110, the outer shell 120 plays an anti-sticking role, and the first adhesive force is small or almost zero, which is convenient for the processing of the composite adhesive and also convenient for the composite adhesive to be evenly dispersed in the active material layer 220, thus facilitating the composite adhesive to exhibit better adhesive performance. When a preset pressure is applied to the composite adhesive, wherein the preset pressure F satisfies the range of 10N ≤ F ≤ 20N, the composite adhesive has a second adhesive force. After the composite adhesive is compacted, the outer shell 120 partially cracks to expose at least part of the adhesive core 110. The adhesive force of the adhesive core 110 is greater than that of the outer shell 120, and the adhesive core 110 is exposed to bond the active material and / or the current collector layer 210, so that the second adhesive force of the composite adhesive is greater than the first adhesive force. The composite adhesive can fully exhibit its adhesive performance to better bond the active material and can play a bonding role between the active material layer 220 and the current collector layer 210. When the composite adhesive is applied to the electrode plate 200, the amount of polytetrafluoroethylene adhesive can be reduced, thereby reducing the side reaction between the polytetrafluoroethylene adhesive and the active material, which is beneficial to improving the capacity retention rate and adhesive performance of the electrode plate 200 when the composite adhesive is applied to the electrode plate 200.

[0043] Optionally, in some embodiments, the material of the adhesive core 110 is selected from at least one of ester monomers, alcohol monomers or polyamide monomers, so as to facilitate the regulation of the glass transition temperature of the adhesive core 110, so that the glass transition temperature Tg of the adhesive core 110 satisfies the range of -60°C ≤ Tg ≤ 0°C.

[0044] In some embodiments, the material of the adhesive core 110 is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-methylolacrylamide.

[0045] In the terms of this application, "at least one" means one or more, and "a plurality" means two or more, which can be but are not limited to two, three or four, etc.

[0046] In this embodiment, isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate and diphenylmethane diisocyanate are ester monomers, all having a polar group, the ester group, polyester polyol and polyether polyol are alcohol monomers, all having a polar group, the hydroxyl group, and N-methylolacrylamide is a polyamide monomer having an amide group. The above monomers are relatively active, facilitating the control of the degree of polymerization and molecular structure of the polymer formed by at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-methylolacrylamide, so as to regulate the glass transition temperature of the adhesive core 110, such that the glass transition temperature of the adhesive core 110 satisfies the range of -60°C ≤ Tg ≤ 0°C. The adhesive core 110 exhibits a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, facilitating the maintenance of good adhesive performance, and ultimately enabling the composite adhesive to have good adhesive performance. Further, when the composite adhesive is applied to the electrode tab 200, the composite adhesive can also improve the liquid retention performance of the electrode tab 200. The electrolyte 310 of the battery 300 contains more lipophilic monomers, and the adhesive core 110 of the composite adhesive has a relatively low glass transition temperature. The monomers in the electrolyte 310 easily enter the composite adhesive and cause the adhesive core 110 to swell, thereby enabling the electrode tab 200 to have good liquid retention performance, facilitating the full infiltration of the electrolyte 310 into the electrode tab 200, reducing the side reactions between the electrolyte 310 and the electrode tab 200, and ultimately enabling the battery 300 to have good cycling performance.

[0047] In some embodiments, the material of the outer shell 120 is selected from at least one of alumina, silica, lithium carbonate, carbon-containing substances and polyethylene wax.

[0048] In this embodiment, the material of the outer shell 120 is selected from at least one of alumina, silica, lithium carbonate, carbon-containing substances, and polyethylene wax. Alumina, silica, lithium carbonate, carbon-containing substances, and polyethylene wax are in a solid state in the range of -60°C to 0°C. Compared with the adhesive core 110 whose glass transition temperature satisfies -60°C ≤ Tg ≤ 0°C, the outer shell 120 is harder and covers the outer periphery of the highly elastic adhesive core 110. The outer shell 120 can serve as an anti-sticking layer to prevent multiple adhesive cores 110 from sticking to each other and agglomerating, thereby facilitating the uniform dispersion of the composite adhesive in the active material layer 220, enabling the composite adhesive to fully exert its adhesive performance, and making the electrode sheet 200 have better overall performance. In addition, alumina, silica, lithium carbonate, carbon-containing substances, and polyethylene wax are porous materials. When the outer shell 120 is selected from at least one of alumina, silica, lithium carbonate, carbon-containing substances, and polyethylene wax, the porous structure of the outer shell 120 allows the electrolyte 310 to easily pass through. The cooperation of the outer shell 120 and the adhesive core 110 is conducive to the easier entry of the electrolyte 310 into the adhesive particles 100, thereby making the adhesive particles 100 more likely to swell, and ultimately making the electrode sheet 200 have better liquid retention performance.

[0049] Specifically, if the material of the outer shell 120 includes lithium carbonate, lithium carbonate can also provide active lithium ions for the electrode sheet 200, that is, the outer shell 120 can also serve as a lithium supplement agent to supplement the lithium ions lost during the charge and discharge process of the battery 300 when the composite adhesive is applied to the electrode sheet 200 and assembled in the battery 300, thereby improving the capacity and energy density of the battery 300.

[0050] Specifically, if the material of the outer shell 120 is selected from alumina, silica, etc., the outer shell 120 has a porous structure, which is conducive to improving the liquid retention performance of the electrode sheet 200.

[0051] In some embodiments, the range of the thickness h of the outer shell 120 is: 1μm ≤ h ≤ 10μm.

[0052] Specifically, the value of the thickness h of the outer shell 120 can be, but is not limited to, 1μm, 1.2μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, and 10μm, etc.

[0053] In this embodiment, when the thickness h of the outer shell 120 satisfies the range of 1 μm ≤ h ≤ 10 μm, the thickness of the outer shell 120 is within a reasonable range. On the one hand, it can prevent the multiple bonding cores 110 from bonding together into a mass during the processing due to the too small thickness of the outer shell 120, which is conducive to uniformly dispersing the multiple bonding particles 100 in the active material layer 220, so that the composite binder can exhibit better bonding performance. On the other hand, after the composite binder is compacted, the outer shell 120 cracks and exposes the bonding cores 110, so that the bonding cores 110 can exhibit bonding performance, thereby reducing the amount of polytetrafluoroethylene binder used. When the thickness of the outer shell 120 is too large, after the composite binder is applied to the electrode plate 200, when the multiple bonding particles 100 are pressed together under a preset pressure, it is difficult to break the outer shell 120, so that the bonding cores 110 are difficult to be exposed to exhibit bonding performance, weakening the bonding performance of the composite binder. When the thickness of the outer shell 120 is too small, the anti-sticking effect of the outer shell 120 as an anti-sticking layer is weak. In other words, during the processing of the composite binder, it is difficult for the outer shell 120 to completely cover the bonding cores 110, resulting in the multiple bonding cores 110 sticking together into a mass, which is not conducive to uniformly dispersing the multiple bonding particles 100 in the active material layer 220, thereby weakening the bonding performance of the composite binder.

[0054] In some embodiments, the range of the particle size D of the bonding particle 100 is: 10 μm ≤ D ≤ 100 μm.

[0055] It can be understood that when the bonding particle 100 is spherical, the particle size of the bonding particle 100 is the diameter of the bonding particle 100; when the bonding particle 100 is quasi-spherical, the particle size of the bonding particle 100 is the maximum radial dimension of the bonding particle 100.

[0056] Specifically, the value of the particle size D of the bonding particle 100 can be, but is not limited to, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0057] In this embodiment, when the value of the particle size D of the adhesive particles 100 satisfies the range 10 μm ≤ D ≤ 100 μm, the particle size D of the adhesive particles 100 is within a reasonable range. The adhesive particles 100 not only have good adhesive properties but also can be evenly dispersed in the active material layer 220, so that the inside of the active material layer 220 has good adhesive properties, and there is also good adhesive performance between the active material layer 220 and the current collector layer 210. At the same time, it is also beneficial to the processing of the adhesive particles 100.

[0058] Optionally, the thickness h of the outer shell 120 and the particle size D of the adhesive particles 100 satisfy the relationship: 0.005 ≤ h / D ≤ 0.15.

[0059] Specifically, the value of h / D can be, but is not limited to, 0.005, 0.008, 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.1, 0.12, 0.15, etc.

[0060] In this embodiment, when the thickness h of the outer shell 120 and the particle size D of the adhesive particles 100 satisfy the relational expression: 0.005 ≤ h / D ≤ 0.15, both the thickness h of the outer shell 120 and the particle size D of the adhesive particles 100 are within a reasonable range. On the one hand, it can prevent the multiple adhesive cores 110 from adhering to each other in a mass during the processing due to the too small thickness of the outer shell 120, thereby facilitating the uniform dispersion of the multiple adhesive particles 100 in the active material layer 220, so that the composite adhesive can exhibit good adhesive performance. On the other hand, after the composite adhesive is compacted, the outer shell 120 cracks and exposes the adhesive cores 110, and the amount of the exposed adhesive cores 110 is within a reasonable range, so that the adhesive cores 110 can exhibit adhesive performance, thereby reducing the amount of polytetrafluoroethylene adhesive used. When h / D is too large, the thickness of the outer shell 120 is too large or the particle size of the adhesive particles 100 is too small. In other words, when the thickness of the outer shell 120 is too large or the particle size of the adhesive cores 110 is too small, then after the composite adhesive is applied to the electrode plate 200 and the multiple adhesive particles 100 are pressed together under a preset pressure, it is difficult to break the outer shell 120, making it difficult for the adhesive cores 110 to be exposed, or even if the adhesive cores 110 leak out, the content is insufficient, so that the adhesive cores 110 are difficult to exhibit adhesive performance or the exhibited adhesive performance is too poor, weakening the adhesive performance of the composite adhesive. When h / D is too small, the thickness of the outer shell 120 is too small or the particle size of the adhesive particles 100 is too large. In other words, when the thickness of the outer shell 120 is too small or the particle size of the adhesive cores 110 is too large, the anti-adhesive effect of the outer shell 120 as an anti-adhesive layer is weak. In other words, during the processing of the composite adhesive, it is difficult for the outer shell 120 to completely cover the adhesive cores 110, so that the multiple adhesive cores 110 adhere to each other in a mass, which is not conducive to the uniform dispersion of the multiple adhesive particles 100 in the active material layer 220, thereby weakening the adhesive performance of the composite adhesive.

[0061] In some embodiments, the swelling ratio α of the composite adhesive ranges from 80% ≤ α ≤ 150%.

[0062] Specifically, the value of the swelling ratio α of the composite adhesive can be, but is not limited to, 80%, 82%, 85%, 90%, 92%, 95%, 100%, 105%, 110%, 114%, 118%, 120%, 125%, 130%, 135%, 140%, 145%, and 150%, etc.

[0063] It can be understood that the swelling ratio of the composite adhesive is an index to measure the swelling ability of the composite adhesive after absorbing the electrolyte 310. Its calculation formula is: α = (m b -ma ) / m a , where m a is the total weight of the composite binder before absorbing the electrolyte 310, and m b is the total weight of the composite binder after absorbing the electrolyte 310.

[0064] It can be understood that the electrolyte 310 in the embodiments of the present application is selected from the formulations of common electrolytes 310, and the component parameters of the electrolyte 310 are not specifically limited herein.

[0065] In this embodiment, the swelling rate α of the composite binder satisfies the range of 80% ≤ α ≤ 150%. The composite binder has good liquid retention performance and swelling performance. The composite binder includes a plurality of bonding particles 100, and the bonding particles 100 include a bonding core 110 and a shell 120. The shell 120 is a porous material, which facilitates the electrolyte 310 to enter the bonding core 110; the material of the bonding core 110 is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylol acrylamide. Thus, the bonding core 110 can absorb the lipophilic monomers in the electrolyte 310 and swell, so that the composite binder has a high swelling rate, and the electrode sheet 200 has good liquid retention performance, which is beneficial to the full infiltration of the electrolyte 310 into the electrode sheet 200, reducing the side reaction between the electrolyte 310 and the electrode sheet 200, so that the battery 300 has good cycle performance.

[0066] Optionally, the present application also provides a preparation method of a composite binder for preparing the composite binder provided in this embodiment. The preparation method of the composite binder includes:

[0067] S101, providing a polymerization monomer and an aqueous solution containing an emulsifier, adding the polymerization monomer to the aqueous solution containing the emulsifier to form a mixed solution, and adding an initiator or an azo compound to the mixed solution for emulsion polymerization to obtain an emulsion with a solid content of 15%.

[0068] It can be understood that the solid content of the emulsion affects the molecular weight of the bonding core 110 in the formed composite binder, thereby affecting the glass transition temperature of the bonding core 110.

[0069] Optionally, the polymerization monomer includes at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylol acrylamide.

[0070] Optionally, the emulsifier includes at least one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, or sodium dodecyl sulfonate.

[0071] Optionally, the initiator includes, but is not limited to, peroxides, and the peroxides include, but are not limited to, benzoyl peroxide.

[0072] Optionally, the azo compound includes, but is not limited to, azobisisobutyronitrile.

[0073] Optionally, in step S101, based on the total mass of the emulsifier, the polymerization monomer, and the initiator being 100%, the mass ratio of the emulsifier is 1% to 5%, the mass ratio of the polymerization monomer is 70% to 99.8%, and the mass ratio of the initiator is 0.01% to 5%.

[0074] Optionally, in step S101, in the mixed solution, the total mass of the emulsifier, the polymerization monomer, and the initiator accounts for 1% to 30% of the mixed solution.

[0075] Optionally, the reaction temperature of the emulsion polymerization is 60°C to 90°C, and the time of the emulsion polymerization is 4 h to 9 h.

[0076] S102, spray-dry the emulsion using a spray-drying device, add an anti-sticking agent during the spray-drying process. The anti-sticking agent is sprayed into the drying chamber through a nozzle, and at the same time, hot air is provided to the drying chamber to quickly evaporate the droplets in the chamber and form multiple adhesive particles 100. The adhesive particles 100 include an adhesive core 110 and a shell 120. The range of the glass transition temperature Tg of the adhesive core 110 is: -60°C ≤ Tg ≤ 0°C, and the adhesive force of the adhesive core 110 is greater than the adhesive force of the shell 120.

[0077] Optionally, the material of the adhesive core 110 is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, and N-methylol acrylamide.

[0078] Optionally, the material of the shell 120 is selected from at least one of alumina, silica, lithium carbonate, carbon-containing substances, and polyethylene wax.

[0079] In the preparation method provided in this embodiment, the composite adhesive obtained by the preparation method includes a plurality of adhesive particles 100. The adhesive particles 100 include an adhesive core 110 and a shell 120. The glass transition temperature Tg of the adhesive core 110 satisfies the range of -60°C ≤ Tg ≤ 0°C. Then the adhesive core 110 presents a highly elastic state at a relatively low temperature, showing higher flexibility and elasticity, which is convenient for maintaining good adhesive performance. When the composite adhesive is applied to the active material layer 220, it can exhibit good adhesive performance and cooperate with the polytetrafluoroethylene adhesive to bond the inside of the active material layer 220 and bond the active material layer 220 to the current collector layer 210, thereby reducing the amount of the polytetrafluoroethylene adhesive used and reducing the side reaction between the polytetrafluoroethylene adhesive and the active material. Moreover, the composite adhesive does not react with the active material, so that the electrode tab 200 has a high capacity retention rate and good adhesive performance. Further, the outer periphery of the adhesive core 110 has a shell 120, and the shell 120 serves as an anti-sticking layer. Thus, during the processing of the composite adhesive, the adhesive cores 110 can be prevented from sticking to each other, which is convenient for the dispersion and subsequent processing of the composite adhesive, and improves the processing performance of the composite adhesive. When the composite adhesive is applied to the active material layer 220 and before being compacted, the shell 120 can also prevent the plurality of adhesive particles 100 from sticking to each other, which is beneficial to uniformly disperse the plurality of adhesive particles 100 in the active material layer 220 to improve the adhesive performance of the composite adhesive to the electrode tab 200.

[0080] Please refer to Figure 2 , this application provides an electrode tab 200, which includes: a current collector layer 210 and an active material layer 220. The active material layer 220 is disposed on at least one side of the current collector layer 210. The active material layer 220 includes an active material, a polytetrafluoroethylene adhesive, and the composite adhesive provided by this application. In the active material layer 220, the mass fraction m1 of the polytetrafluoroethylene adhesive and the mass fraction m2 of the composite adhesive satisfy the relationship: 2 ≤ m1 / m2 ≤ 5.

[0081] Specifically, the value of m1 / m2 can be, but is not limited to, 2, 2.1, 2.2, 2.5, 2.8, 3, 3.1, 3.4, 3.5, 3.8, 4, 4.2, 4.5, 4.8, and 5, etc.

[0082] It can be understood that in some embodiments, the active material layer 220 is disposed on one side of the current collector layer 210; in other embodiments, the active material layer 220 is two layers, and the two active material layers 220 are respectively disposed on opposite sides of the current collector layer 210.

[0083] Optionally, in some embodiments, the electrode sheet 200 is a positive electrode sheet; in other embodiments, the electrode sheet 200 is a negative electrode sheet.

[0084] In this embodiment, the active material layer 220 includes the active material, which is used to store and provide active ions. The polytetrafluoroethylene binder and the composite binder cooperate to bond the active material and to bond the active material layer 220 and the current collector layer 210, so that there is good bonding performance both inside the active material layer 220 and between the active material layer 220 and the current collector layer 210. In addition, in the active material layer 220, the mass fraction m1 of the polytetrafluoroethylene binder and the mass fraction m2 of the composite binder satisfy the relational expression: 2 ≤ m1 / m2 ≤ 5. The mass fractions of the polytetrafluoroethylene binder and the composite binder are both within a reasonable range. On the one hand, the polytetrafluoroethylene binder can preferentially form a bonding film to be distributed among the active materials. The composite binder is distributed among the active materials and connects the polytetrafluoroethylene binders. The bonding core 110 of the composite binder has a low glass transition temperature, so the bonding core 110 presents a high elastic state at a lower temperature, showing higher flexibility and elasticity, which is convenient for maintaining good bonding performance. When the composite binder is applied to the active material layer 220, it can exhibit good bonding performance and cooperate with the polytetrafluoroethylene binder to bond the inside of the active material layer 220 and to bond the active material layer 220 and the current collector layer 210, thereby reducing the dosage of the polytetrafluoroethylene binder and reducing the side reaction between the polytetrafluoroethylene binder and the active material, so that the electrode sheet 200 has a high capacity retention rate and good bonding performance. Further, compared with the scheme of using the polytetrafluoroethylene binder alone, the compounding of the polytetrafluoroethylene binder and the composite binder can increase the peel force between the active material layer 220 and the current collector layer 210. In other words, the cooperation of the polytetrafluoroethylene binder and the composite binder has better bonding performance. This is because the surface energy of polytetrafluoroethylene is low and the critical surface tension is small, while the bonding core 110 of the bonding particle 100 has a low glass transition temperature and has good flexibility and fluidity even at a lower temperature to contact the polytetrafluoroethylene binder and form a bonding network, thereby increasing the bonding strength between the active material layer 220 and the current collector layer 210.

[0085] Specifically, in some embodiments, if the polytetrafluoroethylene adhesive is used alone, the peel strength between the active material layer 220 and the current collector layer 210 is about 5 N / m. If the polytetrafluoroethylene adhesive and the composite adhesive are used simultaneously, the peel strength between the active material layer 220 and the current collector layer 210 is about 10 N / m.

[0086] Optionally, compared with the scheme of using the polytetrafluoroethylene adhesive alone, the compounding of the polytetrafluoroethylene adhesive and the composite adhesive can increase the peel strength between the active material layer 220 and the current collector layer 210 by more than 50%.

[0087] It can be understood that "contacting with the polytetrafluoroethylene adhesive and forming an adhesive network" can be that the polytetrafluoroethylene adhesive has a fibrous structure and is dispersed in the active material layer 220, and multiple fibrous structures at least partially overlap to form an adhesive network, and the adhesive core 110 of the composite adhesive can adhere to the adhesive network and exert its adhesive performance.

[0088] Optionally, the active material layer 220 further includes a conductive agent, and the conductive agent includes but is not limited to conductive carbon black, which is used to improve the conductivity of the active material layer 220.

[0089] It can be understood that, please refer to Figure 3 , in Figure 3 the SEM image shows that in the embodiment where the composite adhesive is applied to the active material layer 220 and compacted, the core-shell structure with a brighter outer layer and a darker inner core is the composite adhesive, where the brighter outer layer corresponds to the outer shell 120 and the darker inner core corresponds to the adhesive core 110.

[0090] In some embodiments, in the active material layer 220, the mass fraction m1 of the polytetrafluoroethylene adhesive ranges from 0.5% ≤ m1 ≤ 10%.

[0091] It can be understood that in the active material layer 220, the mass fraction of the polytetrafluoroethylene adhesive is the ratio of the mass of the polytetrafluoroethylene adhesive to the mass of the active material layer 220.

[0092] Specifically, the value of the mass fraction m1 of the polytetrafluoroethylene adhesive can be but is not limited to 0.5%, 0.6%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.1%, 2.2%, 2.3%, 2.5%, 2.6%, 2.7%, 2.9%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% and 10%, etc.

[0093] Understandably, if the active material layer 220 only includes polytetrafluoroethylene binder and does not include the composite binder, the mass fraction of the polytetrafluoroethylene binder should be higher than 3%. Correspondingly, the larger the mass fraction of the polytetrafluoroethylene binder, the greater the probability of side reaction between the polytetrafluoroethylene binder and the active material.

[0094] In the active material layer 220 provided in this embodiment, when the mass fraction m1 of the polytetrafluoroethylene binder satisfies the range of 0.5% ≤ m1 ≤ 10%, the mass fraction of the polytetrafluoroethylene binder is within a reasonable range. Compared with the solution where the active material layer 220 only includes polytetrafluoroethylene binder, the solution of compounding the composite binder and the polytetrafluoroethylene binder in this embodiment, while ensuring the adhesion performance of the composite binder and the polytetrafluoroethylene binder to the active material layer 220 and the current collector layer 210, reduces the mass fraction of the polytetrafluoroethylene binder, making the minimum mass fraction of the polytetrafluoroethylene binder decrease, thereby reducing the side reaction between the polytetrafluoroethylene binder and the active material, which is beneficial to maintaining the capacity retention rate of the electrode sheet 200 and improving the energy efficiency of the battery 300 when the electrode sheet 200 is applied to the battery 300. When the mass fraction of the polytetrafluoroethylene binder is too large, there are too many fluorine atoms in the polytetrafluoroethylene binder. Fluorine atoms have a strong electron affinity, so that the polytetrafluoroethylene binder is more likely to accept electrons and react with the lithium ions of the active material, thereby reducing the capacity retention rate of the electrode sheet 200. When the mass fraction of the polytetrafluoroethylene binder is too small, it is difficult for the polytetrafluoroethylene binder to preferentially form an adhesion network, so that the polytetrafluoroethylene is difficult to cooperate with the composite binder to achieve better adhesion performance.

[0095] In some embodiments, in the active material layer 220, the range of the mass fraction m2 of the composite binder is: 1.5% ≤ m2 ≤ 2.5%.

[0096] Understandably, in the active material layer 220, the mass fraction of the composite binder is the ratio of the mass of the composite binder to the mass of the active material layer 220.

[0097] Specifically, the value of the mass fraction m2 of the composite binder can be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4% and 2.5%, etc.

[0098] In the active material layer 220 provided in this embodiment, when the mass fraction m2 of the composite binder satisfies the range of 1.5% ≤ m2 ≤ 2.5%, the mass fraction of the composite binder is within a reasonable range. The bonding core 110 of the composite binder has a relatively low glass transition temperature, so that the composite binder can exhibit good bonding performance at a relatively low temperature. In addition, the composite binder can reduce the addition amount of the polytetrafluoroethylene binder in the active material layer 220 to reduce the side reaction between the polytetrafluoroethylene binder and the active material, thereby enabling the electrode tab 200 to have a high capacity retention rate. When the mass fraction of the composite binder is too large, the amount of the active material will be reduced, thereby affecting the capacity of the battery 300 and increasing the impedance of the battery 300. In addition, after the excessive composite binder is infiltrated by the electrolyte 310, the thickness of the electrode tab 200 increases due to swelling, increasing the cyclic expansion force of the electrode tab 200 and reducing the cyclic stability of the battery 300. When the mass fraction of the composite binder is too small, correspondingly, in the active material layer 220, the mass fraction of the polytetrafluoroethylene binder is still too large, and there are still many side reactions between the polytetrafluoroethylene binder and the active material, reducing the capacity retention rate of the electrode tab 200.

[0099] Optionally, in some embodiments, the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a positive electrode tab is equal to the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a negative electrode tab; in other embodiments, the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a positive electrode tab is not equal to the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a negative electrode tab, and the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a positive electrode tab is greater than the mass fraction of the polytetrafluoroethylene binder when the electrode tab 200 is a negative electrode tab. This is because: the particles of the active material in the positive electrode tab are smaller, and the larger the mass fraction of the polytetrafluoroethylene binder, the more conducive it is to form a bonding network on the surface of the active material, thereby improving the bonding performance when the polytetrafluoroethylene binder cooperates with the composite binder.

[0100] In some embodiments, when the electrode plate 200 is a positive electrode plate, in the active material layer 220, the mass fraction m1 of the polytetrafluoroethylene binder ranges from 2% ≤ m1 ≤ 10%. Compared with the solution where only the polytetrafluoroethylene binder is included in the active material layer 220 and no composite binder is included, the solution of the present application includes a polytetrafluoroethylene binder and a composite binder. The composite binder and the polytetrafluoroethylene binder have better bonding performance when combined. The polytetrafluoroethylene binder forms a bonding network and combines with the composite binder. The combination of the polytetrafluoroethylene binder and the composite binder can also reduce the hot pressing temperature of the electrode plate 200, thereby facilitating the improvement of the processing performance of the electrode plate 200. In addition, when the mass fraction of the polytetrafluoroethylene binder is relatively low, the side reaction between the polytetrafluoroethylene binder and the active material can be effectively reduced, and the capacity retention rate of the electrode plate 200 can be improved.

[0101] In some embodiments, when the electrode plate 200 is a negative electrode plate, in the active material layer 220, the mass fraction m1 of the polytetrafluoroethylene binder ranges from 0.5% ≤ m1 ≤ 2.5%. Similarly, compared with the solution where only the polytetrafluoroethylene binder is included in the active material layer 220 and no composite binder is included, the solution of the present application includes a polytetrafluoroethylene binder and a composite binder. The composite binder and the polytetrafluoroethylene binder have better bonding performance when combined, and can also reduce the hot pressing temperature of the electrode plate 200, so that the electrode plate 200 has good bonding performance. In addition, when the mass fraction of the polytetrafluoroethylene binder is relatively low, the side reaction between the polytetrafluoroethylene binder and the active material can be effectively reduced, and the capacity retention rate of the electrode plate 200 can be improved.

[0102] Please refer to Figure 4 , the present application provides a battery 300, and the battery 300 includes: the electrode plate 200 provided by the present application and an electrolyte 310, and the electrolyte 310 is used to infiltrate the electrode plate 200.

[0103] In this embodiment, the electrolyte 310 is used to infiltrate the electrode sheet 200. The active material layer 220 of the electrode sheet 200 includes a polytetrafluoroethylene binder and the composite binder provided in this application. The polytetrafluoroethylene binder and the composite binder cooperate to bond the active material and bond the active material layer 220 and the current collector layer 210, so that there is good bonding performance both inside the active material layer 220 and between the active material layer 220 and the current collector layer 210. In addition, in the active material layer 220, the polytetrafluoroethylene binder has a fibrous structure, and multiple fibrous structures at least partially overlap to form a bonding network, which is distributed among the active materials. The composite binder is distributed among the active materials and connects the polytetrafluoroethylene binder. The bonding core 110 of the composite binder has a low glass transition temperature, so the bonding core 110 exhibits a highly elastic state at a lower temperature, showing higher flexibility and elasticity, which is convenient for maintaining good bonding performance. When the composite binder is applied to the active material layer 220, it can exhibit good bonding performance and cooperate with the polytetrafluoroethylene binder to bond the inside of the active material layer 220 and bond the active material layer 220 and the current collector layer 210, thereby reducing the amount of the polytetrafluoroethylene binder used and reducing the side reaction between the polytetrafluoroethylene binder and the active material, so that the electrode sheet 200 has a high capacity retention rate, good bonding performance, and finally enables the battery 300 to have a high energy efficiency and good cycling performance.

[0104] Optionally, the battery 300 further includes a separator. The number of the electrode sheets 200 is two, which are a positive electrode sheet and a negative electrode sheet respectively. The separator is disposed between the positive electrode sheet and the negative electrode sheet. The electrolyte 310 is used to infiltrate the positive electrode sheet, the separator, and the negative electrode sheet.

[0105] The technical solution of this application will be further introduced in multiple embodiments as follows:

[0106] Examples 1 to 5, Comparative Examples 1 to 4:

[0107] 1. Preparation of the composite binder:

[0108] A polymerization monomer and an initiator are added to an aqueous solution containing an emulsifier for emulsion polymerization. The polymerization monomer includes at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, 2-hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol, N-methylol acrylamide, etc. The reaction temperature of the emulsion polymerization reaction is 60°C to 90°C, and the time is 4h to 9h. Finally, an emulsion with a solid content of 15% is obtained.

[0109] The emulsion is spray-dried using a spray drying device. During the spray drying process, in order to prevent adhesion between the rubber particles, an anti-sticking agent is added and sprayed into the drying chamber through a nozzle. At the same time, hot air is provided to the drying chamber to cause the droplets to evaporate rapidly in the chamber, and composite adhesives of Examples 1 to 5 and Comparative Examples 1 to 4 are formed. The composite adhesive includes a plurality of adhesive particles 100, and the adhesive particles 100 include an adhesive core 110 and a shell 120. The range of the glass transition temperature Tg of the adhesive core 110 is: -60°C ≤ Tg ≤ 0°C, and the adhesive force of the adhesive core 110 is greater than the adhesive force of the shell 120.

[0110] 2. Preparation of the electrode sheet 200:

[0111] Taking the negative electrode sheet as an example. The active material (graphite), conductive agent (conductive carbon black), polytetrafluoroethylene adhesive, and composite adhesive are mixed and pre-fibrillated under certain process conditions to form a mixture, which is pressed using a multi-stage roller. The roller temperature is maintained at 80°C. When the tensile strength of the formed film sheet > 0.088 Mpa, an active material layer 220 is formed, and it is respectively compounded with a base-coated current collector layer 210 (copper foil), and the temperature is set at 80°C. After compounding, roller pressing is performed to obtain the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4. The compaction density of the electrode sheet 200 is 1.5 g / cm 3 。

[0112] Among them, the composite adhesive of Example 1 is applied to the electrode sheet 200 of Example 1, the composite adhesive of Example 2 is applied to the electrode sheet 200 of Example 2, the composite adhesive of Comparative Example 1 is applied to the electrode sheet 200 of Comparative Example 1, and so on.

[0113] Among them, in the active material layers 220 of the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4, the mass fractions of the active material, conductive agent, polytetrafluoroethylene adhesive, and composite adhesive are shown in Table 1.

[0114] 3. Preparation of the battery 300:

[0115] A positive electrode sheet, a separator, and an electrolyte are provided. Among them, the separator and the electrolyte are conventional formulations in the art and are not limited herein. Only the Examples 1 to 5 and Comparative Examples 1 to 4 of the present application need to be controlled for variables.

[0116] Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence so that the separator is located between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind them into a bare electrode assembly; after welding the electrode tabs, place the bare battery in the outer packaging case, inject the above-mentioned electrolyte after drying, and perform vacuum packaging, standing, forming, shaping, etc., and finally prepare implementation batteries 1 to 5 and comparative batteries 1 to 4.

[0117] Among them, the electrode sheet 200 (negative electrode sheet) of Example 1 is assembled into implementation battery 1, the electrode sheet 200 (negative electrode sheet) of Example 2 is assembled into implementation battery 2, the electrode sheet 200 (negative electrode sheet) of Comparative Example 1 is assembled into comparative battery 1, and so on.

[0118] Table 1: Composition parameters of the active material layer 220 of the electrode sheet 200 in Examples 1 to 5 and Comparative Examples 1 to 4.

[0119]

[0120]

[0121] Performance test of the electrode sheet 200:

[0122] 1. Peel strength test:

[0123] Use a tensile testing machine to test the peel strength of the electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 4. The test method is as follows: Step 1, lay the electrode sheet 200 flat, and use a ruler and a utility knife to prepare the electrode sheet 200 into strips with a specification of 200 mm × 25 mm. Generally, 3 to 5 test strips need to be prepared for a group of samples; Step 2, stick one side of the double-sided tape to the middle of the steel plate, and roll it back and forth with a roller 3 times to firmly bond it to the test steel plate; Step 3, make one end of the test strip flush with the steel plate, with the double-sided tape slightly wider on both sides, and fit it parallel and centered to the other side of the double-sided tape. Roll it with a roller 3 times in one direction to make it fit flat. Manually peel the test strip 5 mm to 10 mm from the bottom, and use a tensile testing machine with a 180° fixture for peeling to obtain the peel force of the test strip.

[0124] Among them, the peel force of the test strip can characterize the peel force of the electrode sheet 200. More specifically, it can characterize the peel force between the active material layer 220 and the current collector layer 210 in the electrode sheet 200. The greater the peel force of the electrode sheet 200, the better the bonding performance of the composite adhesive. The peel force values of the electrode sheets 200 in Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Table 2.

[0125] 2. Wettability test:

[0126] Respectively take the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4 prepared, cut them into square sheets with a specification of 4 cm × 4 cm, and perform the contact angle test of the electrolyte 310 with a contact angle tester, and record the time required for the contact angle between the electrode sheet 200 and the electrolyte 310 to be 10°.

[0127] Among them, the shorter the time required for the contact angle between the electrode sheet 200 and the electrolyte 310 to be 10°, the better the wetting performance and the better the liquid retention performance of the electrode sheet 200. The values of the time required for the contact angle between the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4 and the electrolyte 310 are shown in Table 2.

[0128] Performance test of the battery 300:

[0129] Perform constant power charge and discharge cycle tests on the above-mentioned Implementing Batteries 1 to 5 and Comparative Batteries 1 to 4 on a charge and discharge instrument. The test temperature is 25 °C, and the charge and discharge rate is 0.5C (the magnitude of the charge and discharge current is usually represented by the charge and discharge rate, and the calculation formula for the charge and discharge current is: charge and discharge power = voltage platform of the battery 300 (3.2 V) × rated capacity of the battery 300). The charge and discharge voltage window is 2.5 V to 3.65 V (that is, the charge cut-off voltage of the battery 300 is 3.65 V, and the discharge cut-off voltage of the battery 300 is 2.5 V; it is generally considered that when the charge cut-off voltage ≥ 4 V, the charge cut-off voltage of the battery 300 is relatively high). Calculate the capacity retention rate after 600 cycles. The calculation formula is: capacity retention rate after the Nth cycle = (discharge capacity after the Nth cycle / discharge capacity of the first cycle) × 100%.

[0130] Among them, usually a complete charge and discharge is called a charge and discharge cycle, that is, the battery 300 first charges from 2.5 V to 3.65 V, and then discharges from 3.65 V to 2.5 V, thus forming a charge and discharge cycle. Cycling N times means repeating the above process N times.

[0131] The following Table 2 shows the performance parameters of the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4 and the performance parameters of the Implementing Batteries 1 to 5 and Comparative Batteries 1 to 4.

[0132] Table 2: Performance parameters of the electrode sheets 200 of Examples 1 to 5 and Comparative Examples 1 to 4 and performance parameters of the Implementing Batteries 1 to 5 and Comparative Batteries 1 to 4.

[0133]

[0134]

[0135] Among them, the electrode tab 200 in Comparative Example 4 is difficult to form into a sheet, and the capacity retention rate of the battery 300 after 600 cycles cannot be obtained.

[0136] Please refer to Table 1 and Table 2. From the data of Examples 1 to 5, Comparative Example 1 and Comparative Example 2, it can be seen that the electrode plates 200 in Examples 1 to 5 all include polytetrafluoroethylene binder and composite binder, while the electrode plates 200 in Comparative Example 1 and Comparative Example 2 only include polytetrafluoroethylene binder and do not include composite binder. This makes the peel strength of the electrode plates 200 in Examples 1 to 5 significantly greater than that of the electrode plates 200 in Comparative Example 1 and Comparative Example 2, and the time required for the contact angle between the electrode plates 200 in Examples 1 to 5 and the electrolyte 310 to reach 10° is shorter than that of the electrode plates 200 in Comparative Example 1 and Comparative Example 2. The capacity retention rates of Battery 1 to Battery 5 after 600 cycles are higher than those of Comparative Battery 1 to Comparative Battery 2 after 600 cycles. This shows that: compared with the solution where the electrode plate 200 only includes one kind of binder, i.e., polytetrafluoroethylene binder, through the combination of polytetrafluoroethylene binder and composite binder, the polytetrafluoroethylene binder and the composite binder can exert better bonding effects to improve the peel strength of the electrode plate 200 and make the electrode plate 200 have better liquid retention performance. Specifically, the composite binder includes a plurality of bonding particles 100, and the bonding particles 100 include a bonding core 110 and a shell 120. The glass transition temperature Tg of the bonding core 110 satisfies the range -60°C ≤ Tg ≤ 0°C, then the bonding core 110 presents a high elastic state at a lower temperature, showing higher flexibility and elasticity, which is convenient for maintaining good bonding performance. When the composite binder is applied to the active material layer 220, it can exert good bonding performance and cooperate with the polytetrafluoroethylene binder to bond the inside of the active material layer 220 and bond the active material layer 220 to the current collector layer 210, thereby reducing the usage amount of the polytetrafluoroethylene binder, reducing the side reaction between the polytetrafluoroethylene binder and the active material, and the composite binder does not react with the active material, so that the electrode plate 200 has a high capacity retention rate and good bonding performance. Moreover, when the composite binder is applied to the electrode plate 200, the composite binder can also improve the liquid retention performance of the electrode plate 200. The porous structure of the shell 120 makes it easy for the electrolyte 310 to pass through. There are more lipophilic monomers in the electrolyte 310 of the battery 300, and the bonding core 110 of the composite binder has a lower glass transition temperature. The monomers in the electrolyte 310 easily enter the composite binder and cause the bonding core 110 to swell, so that the electrode plate 200 has better liquid retention performance, which is beneficial to the full infiltration of the electrolyte 310 into the electrode plate 200, reducing the side reaction between the electrolyte 310 and the electrode plate 200, and thus making the battery 300 have better cycling performance.

[0137] More specifically, please refer to Examples 1 to 3. The electrode plates 200 in Examples 1 to 3 all include polytetrafluoroethylene binder and composite binder. In the active material layer 220, the mass fractions of both the polytetrafluoroethylene binder and the composite binder are within a reasonable range. As the mass fraction of the composite binder gradually increases, the peel force of the corresponding electrode plate 200 gradually increases, and the time required for the contact angle between the electrode plate 200 and the electrolyte 310 to be 10° gradually decreases, and the capacity retention rate of the corresponding battery 300 after 600 cycles gradually increases. This is because: the bonding core 110 of the composite binder has a low glass transition temperature, so that the composite binder can exhibit good bonding performance at a relatively low temperature. In addition, as the mass fraction of the composite binder increases, the addition amount of the polytetrafluoroethylene binder in the active material layer 220 decreases to reduce the side reaction between the polytetrafluoroethylene binder and the active material, thereby enabling the electrode plate 200 and the battery 300 to have a high capacity retention rate.

[0138] More specifically, please refer to Example 1, Example 4, Example 5, Comparative Example 3, and Comparative Example 4. Under the same other conditions, the glass transition temperature Tg of the adhesive core 110 in Example 1, Example 4, and Example 5 satisfies the range of -60°C ≤ Tg ≤ 0°C. However, the glass transition temperature Tg of the adhesive core 110 in Comparative Example 3 is too small, and the glass transition temperature Tg of the adhesive core 110 in Comparative Example 4 is too large. This makes the peel strength of the electrode sheet 200 in Example 1, Example 4, and Example 5 significantly greater than that of the electrode sheet 200 in Comparative Example 3 and Comparative Example 4, and the time required for the contact angle between the electrode sheet 200 in Example 1, Example 4, and Example 5 and the electrolyte 310 to reach 10° is shorter than the time required for the contact angle between the electrode sheet 200 in Comparative Example 3 and Comparative Example 4 and the electrolyte 310 to reach 10°. The capacity retention rates of Battery 1, Battery 4, and Battery 5 after 600 cycles are higher than those of Comparative Battery 3 to Comparative Battery 4 after 600 cycles. This shows that: when the glass transition temperature of the adhesive core 110 of the composite adhesive satisfies a reasonable range, the adhesive core 110 presents a high elastic state at a lower temperature, showing higher flexibility and elasticity, which is convenient for maintaining good adhesive performance. When the composite adhesive is applied to the active material layer 220, it can exhibit good adhesive performance and cooperate with the polytetrafluoroethylene adhesive to bond the inside of the active material layer 220 and bond the active material layer 220 to the current collector layer 210, thereby reducing the amount of the polytetrafluoroethylene adhesive used, reducing the side reaction between the polytetrafluoroethylene adhesive and the active material, and the composite adhesive does not react with the active material, so that the electrode sheet 200 and the battery 300 have a high capacity retention rate. When the glass transition temperature of the adhesive core 110 is too high, it is difficult to effectively bond the active material layer 220 by hot pressing, so that it is difficult to form the electrode sheet 200. Even if the electrode sheet 200 is formed, the peel strength of the electrode sheet 200 is extremely low, reducing the use performance of the electrode sheet 200. When the glass transition temperature of the adhesive core 110 is too low, on the one hand, the adhesive core 110 is difficult to form or is easily dissolved in the electrolyte, thereby reducing the structural stability of the electrode sheet 200 and reducing the cycle capacity retention rate of Comparative Battery 3.

[0139] Please refer to Figure 5 and Figure 6 , the present application provides an electrical device 400, which includes: a device body 410 and the battery 300 provided by the present application, and the battery 300 supplies power to the device body 410.

[0140] It can be understood that the battery 300 is electrically connected to the device body 410.

[0141] In this embodiment, the battery 300 includes the electrode plate 200, and the electrode plate 200 has a high capacity retention rate and good adhesion performance, and finally enables the battery 300 to have high energy efficiency and good cycling performance. When the battery 300 is applied to the electrical device 400, the battery 300 can provide stable electric energy for the device body 410, which is beneficial to improving the user experience.

[0142] Optionally, the electrical device 400 in the embodiment of the present application may be, but is not limited to, portable electronic devices such as mobile phones, tablet computers, laptop computers, desktop computers, smart bracelets, smart watches, e-readers, game consoles, etc. It may also be means of transportation such as cars, trucks, sedans, vans, trucks, bullet trains, high-speed rails, electric scooters, etc. In addition, it may also be various household appliances, etc. The present application Figure 5 The electrical device 400 in the embodiment of the present application is an energy storage battery cabinet.

[0143] It can be understood that the electrical device 400 described in this embodiment is only one form of the electrical device 400 to which the battery 300 is applied, and should not be construed as a limitation on the electrical device 400 provided by the present application, nor should it be construed as a limitation on the electrical device 400 provided by each embodiment of the present application.

[0144] When "embodiment" or "embodiment mode" is mentioned in the present application, it means that the specific features, structures or characteristics described in combination with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application may be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in each embodiment of the present application can be combined arbitrarily without contradiction to form another embodiment that does not depart from the spirit and scope of the technical solution of the present application.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A composite adhesive, characterized in that: The composite adhesive comprises a plurality of adhesive particles, wherein the adhesive particles comprise an adhesive core and an outer shell, wherein the glass transition temperature Tg of the adhesive core is in the range of -60°C ≤ Tg ≤ 0°C; the outer shell is wrapped around the surface of the adhesive core, and the adhesive force of the adhesive core is greater than the adhesive force of the outer shell.

2. The composite adhesive according to claim 1, characterized in that: The composite adhesive has a first adhesive force. When a preset pressure is applied to the composite adhesive, the composite adhesive has a second adhesive force. The first adhesive force is smaller than the second adhesive force. The preset pressure F is in the range of 10N≤F≤20N.

3. The composite adhesive according to claim 1, characterized in that: The material of the bonding core is selected from at least one of isooctyl acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid, hydroxyethyl methacrylate, toluene diisocyanate, diphenylmethane diisocyanate, polyester polyol, polyether polyol and N-hydroxymethyl acrylate.

4. The composite adhesive according to claim 1, characterized in that: The material of the shell is selected from at least one of alumina, silicon dioxide, lithium carbonate, carbonaceous material and polyethylene wax.

5. The composite adhesive according to claim 1, characterized in that: The range of the thickness h of the shell is: 1 μm≤h≤10 μm; the range of the particle size D of the bonding particles is: 10 μm≤D≤100 μm.

6. The composite adhesive according to claim 1, characterized in that: The swelling rate α of the composite adhesive is in the range of 80%≤α≤150%.

7. An electrode plate, characterized in that: The electrode plate comprises: a current collector layer; and An active material layer, wherein the active material layer is disposed on at least one side of the current collector layer, the active material layer comprises an active material, a polytetrafluoroethylene adhesive and the composite adhesive according to any one of claims 1 to 6, wherein in the active material layer, the mass fraction m1 of the polytetrafluoroethylene adhesive and the mass fraction m2 of the composite adhesive satisfy the relationship: 2≤m1 / m2≤5.

8. The electrode plate according to claim 7, characterized in that: In the active material layer, the mass fraction m1 of the polytetrafluoroethylene binder is in the range of 0.5%≤m1≤10%; the mass fraction m2 of the composite binder is in the range of 1%≤m2≤2.5%.

9. The electrode plate according to claim 8, characterized in that: When the electrode plate is a positive electrode plate, in the active material layer, the mass fraction m1 of the polytetrafluoroethylene binder is in the range of 2%≤m1≤10%; and / or, when the electrode plate is a negative electrode plate, in the active material layer, the mass fraction m1 of the polytetrafluoroethylene binder is in the range of 0.5%≤m1≤2.5%.

10. A battery, characterized in that: The battery comprises: The electrode sheet according to any one of claims 7 to 9, An electrolyte is used to soak the electrode plates.

11. An electrical device, characterized in that: The electrical equipment includes: The device itself; and The battery of claim 10, wherein the battery is used to power the device body.

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