Negative electrode sheet, battery and electrical equipment

Abstract

The present application relates to a negative electrode plate, a battery and an electrical device. The negative electrode plate includes: a current collector layer and an active material layer, the active material layer includes an active material and a binder, the active material includes hard carbon, the hard carbon has a plurality of pores, the binder includes a core and an adhesive layer, the adhesive layer is bonded to the surface of the core, the hardness of the core is greater than the hardness of the adhesive layer, and the radial dimension of the pores is smaller than the particle size of the core.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a negative electrode sheet, a battery, and an electrical device using the same. Background Art

[0002] With the continuous development of battery technology, sodium-ion batteries show great application potential due to their excellent electrical properties. However, the current negative electrode sheets of sodium-ion batteries have the problem of low peel strength after rolling, and conventional adhesives are not sufficient to meet the bonding requirements of the negative electrode sheets, so new sodium-ion battery adhesives need to be prepared. Summary of the Invention

[0003] In view of this, this application provides a negative electrode sheet, a battery, and an electrical device using the same, and the adhesive of the negative electrode sheet has good bonding performance, so that the negative electrode sheet has a large peel strength.

[0004] This application provides a negative electrode sheet, which includes a current collector layer and an active material layer. The active material layer includes an active material and an adhesive. The active material includes hard carbon, and the hard carbon has a plurality of pores. The adhesive includes a core and an adhesive layer. The adhesive layer is bonded to the surface of the core, the hardness of the core is greater than that of the adhesive layer, and the radial size of the pores is smaller than the particle size of the core.

[0005] Further, the core includes silicon dioxide, the adhesive layer includes polyacrylate, and the particle size D1 of the adhesive ranges from 3 μm ≤ D1 ≤ 4 μm.

[0006] Further, the particle size D2 of the core ranges from 1 μm ≤ D2 ≤ 2 μm.

[0007] Further, if the radial size of the pores is D3, the relational expression 0.25 ≤ D3 / D2 < 1 is satisfied.

[0008] Further, the thickness h of the adhesive layer ranges from 1 μm ≤ h ≤ 2 μm.

[0009] Further, the molecular weight M of the polyacrylate ranges from 5×10 5 g / mol ≤ M ≤ 10×10 5 g / mol.

[0010] Further, the core has a plurality of mesopores, and the radial size d of the mesopores ranges from 4 nm ≤ d ≤ 10 nm.

[0011] Further, the porosity α of the core ranges from 15% ≤ α ≤ 50%.

[0012] The present application provides a battery, which includes: a negative electrode sheet, a separator, a positive electrode sheet, and an electrolyte provided by the present application. The electrolyte is used to infiltrate at least part of the negative electrode sheet, the separator, and the positive electrode sheet.

[0013] The present application provides an electrical device, which includes: a device body and a battery provided by the present application. The battery supplies power to the device body.

[0014] In the present application, the active material includes hard carbon, and the hard carbon has a plurality of pores. The pore structure provides a large number of sodium storage sites, enabling the hard carbon to have a high sodium storage capacity, which is beneficial to improving the energy density of the battery when the negative electrode sheet is applied to the battery. In addition, the binder includes a core and a bonding layer. The bonding layer is bonded to the surface of the core, and the hardness of the core is greater than that of the bonding layer. First, the core has a relatively high hardness. During the rolling process of the negative electrode sheet, even if the bonding layer is rolled and undergoes a certain degree of deformation, the core can still maintain its original shape, so that the binder can still exert its bonding performance. Second, the radial dimension of the pores is smaller than the particle size of the core. The core occupies a certain volume in the binder. During the rolling process of the negative electrode sheet, due to the limitation of the pore size, the binder can be prevented from being filled into the pores, and the binder can still bond the adjacent hard carbon, thereby exerting the bonding performance on the hard carbon and finally enabling the negative electrode sheet to have a high peel strength. When the negative electrode sheet is applied to the battery, it is beneficial to improve the cycle stability of the battery. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the implementation 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.

[0016] Figure 1 Partial cross-sectional structure schematic diagram of the negative electrode sheet according to an embodiment of the present application;

[0017] Figure 2 Structure schematic diagram of the binder according to an embodiment of the present application;

[0018] Figure 3 Partial cross-sectional structure schematic diagram of the battery according to an embodiment of the present application;

[0019] Figure 4 Structure schematic diagram of the electrical device according to an embodiment of the present application;

[0020] Figure 5Circuit block diagram of an electrical device according to an embodiment of the present application.

[0021] Description of reference numerals:

[0022] 100 - negative electrode tab, 110 - current collector layer, 120 - active material layer, 121 - binder, 1211 - core, 1212 - adhesive layer, 200 - battery, 210 - separator, 220 - positive electrode tab, 230 - electrolyte, 300 - electrical device, 310 - device body. Detailed implementation manners

[0023] 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.

[0024] Terms such as "first" and "second" in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. 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.

[0025] Referring to "embodiment" or "embodiment manner" herein means that a specific feature, structure or characteristic described in connection with the embodiment or embodiment manner can 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 will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0026] With the continuous development of battery technology, sodium-ion batteries show great application potential due to their excellent electrical properties. However, the current negative electrode tabs of sodium-ion batteries have the problem of low peeling force after rolling, and conventional binders are not sufficient to bond the negative electrode tabs, so new sodium-ion battery binders need to be prepared.

[0027] In the field of sodium-ion battery technology, styrene-butadiene rubber (SBR) is commonly used as an adhesive for the negative electrode sheet, and hard carbon is commonly used as the active material of the negative electrode sheet. On the one hand, hard carbon is relatively hard and styrene-butadiene rubber is relatively soft. After rolling, the styrene-butadiene rubber is easily extruded and deformed, losing its bonding sites, thereby weakening the bonding performance of the styrene-butadiene rubber to hard carbon. Second, there are many fine pores on the surface of hard carbon, and the conventional size of styrene-butadiene rubber is less than 500 nm. The styrene-butadiene rubber is easily filled into the fine pores on the surface of hard carbon and loses its bonding performance to adjacent hard carbon, resulting in a low peel strength of the negative electrode sheet using styrene-butadiene rubber.

[0028] Please refer to Figure 1 and Figure 2 , the present application provides a negative electrode sheet 100, the negative electrode sheet 100 includes: a current collector layer 110 and an active material layer 120, the active material layer 120 includes an active material and an adhesive 121, the active material includes hard carbon, the hard carbon has a plurality of pores, the adhesive 121 includes a core 1211 and an adhesive layer 1212, the adhesive layer 1212 is bonded to the surface of the core 1211, and the hardness of the core 1211 is greater than the hardness of the adhesive layer 1212, and the radial size of the pores is less than the particle size of the core 1211.

[0029] It can be understood that the active material layer 120 is disposed on at least one surface of the current collector layer 110. In other words, in some embodiments, the number of layers of the active material layer 120 is one layer, disposed on one side of the current collector layer 110; in other embodiments, the number of layers of the active material layer 120 is two layers, and the two active material layers 120 are disposed on opposite sides of the current collector layer 110.

[0030] It can be understood that the adhesive layer 1212 is bonded to the surface of the core 1211. In other words, the adhesive layer 1212 covers the outer periphery of the core 1211, and the adhesive layer 1212 has an adhesive property to the hard carbon.

[0031] It can be understood that the adhesive 121 is used to bond the hard carbon to improve the peel strength of the negative electrode sheet 100. In the terms of the present application, the peel strength of the negative electrode sheet 100 is the degree of firm adhesion between the active material layer 120 and the current collector layer 110. The adhesive 121 not only bonds the active material, but also when the adhesive 121 is disposed on the surface of the active material layer 120 facing the current collector layer 110, the adhesive 121 is also used to bond the active material layer 120 and the current collector layer 110, and the peel strength of the negative electrode sheet 100 is positively correlated with the adhesive property of the adhesive 121.

[0032] Optionally, in some embodiments, when the negative electrode sheet 100 is applied to the battery 200, the battery 200 is a sodium-ion battery.

[0033] In this embodiment, the active material includes hard carbon, and the hard carbon has a plurality of pores. The pore structure provides a large number of sodium storage sites, enabling the hard carbon to have a high sodium storage capacity, which is beneficial to improving the energy density of the battery 200 when the negative electrode sheet 100 is applied to the battery 200. In addition, the binder 121 includes a core 1211 and a bonding layer 1212. The bonding layer 1212 is bonded to the surface of the core 1211, and the hardness of the core 1211 is greater than that of the bonding layer 1212. On the one hand, the core 1211 has a relatively high hardness. During the rolling process of the negative electrode sheet 100, even if the bonding layer 1212 is rolled and undergoes a certain degree of deformation, the core 1211 can still maintain its original shape, so that the binder 121 can still exert its bonding performance. On the other hand, the radial size of the pores is smaller than the particle size of the core 1211. The core 1211 occupies a certain volume in the binder 121. During the rolling process of the negative electrode sheet 100, due to the limitation of the pore size, the binder 121 can be prevented from being filled into the pores. The binder 121 can still bond the adjacent hard carbon, thereby exerting the bonding performance on the hard carbon and finally enabling the negative electrode sheet 100 to have a high peel force. When the negative electrode sheet 100 is applied to the battery 200, it is beneficial to improve the cycle stability of the battery 200.

[0034] In some embodiments, the core 1211 includes silicon dioxide, and the bonding layer 1212 includes polyacrylate.

[0035] In this embodiment, the core 1211 includes silica, which has relatively high hardness and stiffness. When the silica is applied to the binder 121, the silica can provide support for the adhesive layer 1212, so that the binder 121 still has a relatively large particle size. During the rolling process of the negative electrode sheet 100, even if the adhesive layer 1212 is rolled and undergoes a certain degree of deformation, the silica can still maintain a complete structure to prevent the binder 121 from completely filling the pores of the hard carbon. The binder 121 can still be distributed on the surface of the hard carbon and bond the adjacent hard carbon, and the binder 121 has good bonding performance. In addition, the adhesive layer 1212 includes polyacrylate. On the one hand, polyacrylate has a relatively high viscosity and good chemical stability. When the negative electrode sheet 100 is applied to the battery 200, the polyacrylate can fully exert its bonding performance to bond the adjacent hard carbon, thereby improving the peel strength of the negative electrode sheet 100. In addition, when the electrolyte 230 infiltrates the negative electrode sheet 100, it can prevent the adhesive layer 1212 from being damaged, ensuring that the binder 121 can fully exert its bonding performance. On the other hand, the polyacrylate coats the outer periphery of the silica. The silica surface has many hydroxyl groups (-OH), while the polyacrylic acid has many carboxyl groups (-COOH). During the preparation process of the binder, as acrylic acid and acrylate undergo a double bond addition polymerization reaction, the carboxyl group of the polyacrylic acid further undergoes an esterification reaction with the hydroxyl group on the silica surface, forming a stable chemical bond between the polyacrylic acid and the silica, which is beneficial to enhancing the adhesion force between the polyacrylic acid and the silica surface, so that during the preparation process of the binder, the polyacrylate is not easily detached from the silica surface. In addition, the hydroxyl group on the silica surface can also form hydrogen bonds with the ester group or other polar groups in the polyacrylate. This hydrogen bond effect is also beneficial to further enhancing the adhesion force between the polyacrylate and the silica surface, thereby improving the stability of the adhesive layer 1212 coating the outer periphery of the core 1211, making the binder 121 have good use performance and a long service life. Moreover, during the rolling process of the negative electrode sheet 100, it can also prevent the core 1211 from separating from the adhesive layer 1212, ensuring that the binder 121 can fully exert its bonding performance on the hard carbon. Compared with the scheme of setting other adhesive layers 1212 on the surface of the core 1211, the polyacrylate is more easily bonded to the silica surface and has better bonding performance, which is beneficial to reducing the processing difficulty of the binder 121, thereby saving the processing cost of the binder 121.

[0036] In some embodiments, the range of the particle size D1 of the binder 121 is: 3 μm ≤ D1 ≤ 4 μm.

[0037] It can be understood that the size of the binder 121 is at the micron level.

[0038] Specifically, the value of the particle size D1 of the adhesive 121 can be, but is not limited to, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, etc.

[0039] In this embodiment, when the particle size D1 of the adhesive 121 satisfies the range of 3 μm ≤ D1 ≤ 4 μm, the particle size of the adhesive 121 is much larger than the radial size of the pores of the hard carbon. During the rolling process of the negative electrode sheet 100, even if the adhesive layer 1212 undergoes a certain degree of deformation, the adhesive 121 can still maintain a relatively large particle size, so as to prevent the adhesive 121 from being completely filled into the pores of the hard carbon, thereby ensuring the bonding performance of the adhesive 121 to the hard carbon. When the particle size of the adhesive 121 is too large, it will increase the preparation difficulty of the core 1211, as well as the preparation difficulty and cost of the polyacrylate, which is not conducive to the industrial production of the adhesive 121, and may occupy too much volume of the active material layer 120, reducing the amount of active material in the active material layer 120, thereby reducing the capacity and rate performance of the battery 200 when the negative electrode sheet 100 is applied to the battery 200. When the particle size of the adhesive 121 is too small, during the rolling process of the negative electrode sheet 100, in order to exert the bonding performance, the adhesive layer 1212 will undergo a certain degree of deformation, which may cause the particle size of the adhesive 121 to be smaller than the radial size of the pores of the hard carbon, then the adhesive 121 may be completely filled into the pores of the hard carbon, and the adhesive 121 cannot contact adjacent hard carbon and cannot exert the bonding effect, so that the peel force of the negative electrode sheet 100 is still small, which may cause the active material to fall off between the active material layers 120, reducing the capacity retention rate of the battery 200 when the negative electrode sheet 100 is applied to the battery 200.

[0040] In some embodiments, the range of the particle size D2 of the core 1211 is: 1 μm ≤ D2 ≤ 2 μm.

[0041] It can be understood that the size of the core 1211 is at the micron level.

[0042] Specifically, the value of the particle size D2 of the core 1211 can be, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc.

[0043] In this embodiment, the size of the core 1211 is at the micron level. Compared with the solution using silica with a size at the nanometer level as the core 1211 of the binder 121, the core 1211 of this solution has advantages. Firstly, the silica at the micron level has a larger size and a relatively smaller specific surface area, and is more likely to be dispersed in the binder 121 and not easily agglomerate. As a result, the binder 121 can be evenly distributed between the active material layers 120, achieving a better bonding effect on the hard carbon. Secondly, the silica at the micron level has a larger size than the silica at the nanometer level, with higher mechanical strength and wear resistance. During the rolling process of the negative electrode sheet 100, the core 1211 can be prevented from being crushed, further avoiding the binder 121 being squeezed into the pores of the hard carbon, which is beneficial for the binder 121 to fully exert its bonding performance on the hard carbon, so that the negative electrode sheet 100 has a greater peel force. When the particle size D2 of the core 1211 satisfies the range of 1μm ≤ D2 ≤ 2μm, the particle size of the core 1211 is within a reasonable range. On the one hand, it can meet the requirement that the particle size of the core 1211 is larger than the radial size of the pores of the hard carbon, so as to prevent the binder 121 from completely entering the pores and losing its bonding performance. On the other hand, the core 1211 at the micron level has greater mechanical strength. During the rolling process of the negative electrode sheet 100, the risk of the core 1211 being crushed can be reduced, enabling the binder 121 to be also disposed on the surface of the hard carbon and bond the adjacent hard carbon, fully exerting the bonding performance of the binder 121, so that the negative electrode sheet 100 has a larger peel force. The larger-sized core 1211 can occupy a larger volume of the binder 121, making the particle size of the binder 121 larger and preventing the binder 121 from being squeezed into the pores of the hard carbon, ensuring that the binder 121 can exert its bonding performance on the hard carbon. When the particle size of the core 1211 is too large, it will increase the processing difficulty of the core 1211, which is not conducive to the industrial preparation of the binder 121 and increases the production cost of the binder 121. When the particle size of the core 1211 is too small, on the one hand, the particle size of the core 1211 is too small, and the degree of synthesis of the polyacrylate is limited. In other words, the upper limit value of the thickness of the bonding layer 1212 is limited, resulting in too small a particle size of the binder 121. During the rolling process of the negative electrode sheet 100, the bonding layer 1212 will undergo a certain degree of deformation, so that the particle size of the binder 121 may be smaller than the radial size of the pores of the hard carbon, and the binder 121 may completely fill the pores of the hard carbon, and then the binder 121 cannot exert its bonding performance.On the other hand, the particle size of the core 1211 is too small. Correspondingly, the mechanical strength of the core 1211 decreases. During the rolling process of the negative electrode sheet 100, the core 1211 is crushed, and the core 1211 cannot provide support for the adhesive layer 1212, so that the adhesive 121 is filled into the pores of the hard carbon, increasing the risk that the adhesive 121 cannot exert its adhesive performance, thereby reducing the peel strength of the negative electrode sheet 100.

[0044] In some embodiments, if the radial dimension of the pores is D3, the following relationship is satisfied: 0.25 ≤ D3 / D2 < 1.

[0045] It can be understood that the radial dimension of the pores is smaller than the particle size of the core 1211. In other words, the particle size of the core 1211 is larger than the pore size of the pores, which can prevent the core 1211 from being stuck in the pores.

[0046] It can be understood that the value of D3 / D2 can be, but is not limited to, 0.25, 0.28, 0.3, 0.32, 0.35, 0.4, 0.42, 0.45, 0.5, 0.55, 0.6, 0.68, 0.7, 0.75, 0.78, 0.8, 0.85, 0.88, 0.9, 0.95, 0.98, etc.

[0047] In this embodiment, when the radial dimension D3 of the pores and the particle size D2 of the core 1211 satisfy the relation 0.25 ≤ D3 / D2 < 1, with the radial dimension of the pores being fixed, the particle size of the core 1211 is within a reasonable range. On the one hand, the core 1211 has a relatively large hardness. During the rolling process of the negative electrode sheet 100, the core 1211 can still maintain its structural integrity and the particle size of the core 1211 is larger than the radial dimension of the pores. Even if the adhesive layer 1212 undergoes a certain degree of deformation, the particle size of the binder 121 is still larger than the radial dimension of the pores. Then, the binder 121 will not completely fill the pores of the hard carbon. The binder 121 can be disposed between two adjacent hard carbons and fully exert its bonding performance, so that the negative electrode sheet 100 has good bonding performance. When the value of D3 / D2 is too large, with the radial dimension of the pores being fixed, the particle size of the core 1211 is too small. If the particle size of the core 1211 is smaller than the radial dimension of the pores, then during the rolling process of the negative electrode sheet 100, the adhesive layer 1212 will undergo a certain degree of deformation, so that the particle size of the binder 121 may be smaller than the radial dimension of the pores of the hard carbon, and the binder 121 may completely fill the pores of the hard carbon, thereby making the binder 121 unable to exert its bonding performance. If the particle size of the core 1211 is larger than the radial dimension of the pores, but the particle size of the core 1211 is still small, then correspondingly, the mechanical strength of the core 1211 is poor. During the rolling process of the negative electrode sheet 100, the risk of the core 1211 being crushed is increased, and the core 1211 is difficult to provide stable support for the adhesive layer 1212, so that the risk of the binder 121 being filled into the pores of the hard carbon makes the binder 121 unable to exert its bonding performance, and finally reduces the peel strength of the negative electrode sheet 100. When the value of D3 / D2 is too small, with the radial dimension of the pores being fixed, the particle size of the core 1211 is too large, which increases the processing difficulty of the core 1211, is not conducive to the industrial preparation of the binder 121, and increases the production cost of the binder 121.

[0048] Optionally, the range of the radial dimension D3 of the pores is: 0.5 μm ≤ D3 ≤ 1 μm.

[0049] Specifically, the value of the radial dimension D3 of the pores can be, but is not limited to, 0.5 μm, 0.52 μm, 0.55 μm, 0.58 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.81 μm, 0.83 μm, 0.85 μm, 0.88 μm, 0.9 μm, 0.92 μm, 0.93 μm, 0.94 μm, 0.95 μm, 0.96 μm, 0.97 μm, 0.98 μm, 0.99 μm, 1 μm, etc.

[0050] In this embodiment, when the radial dimension D3 of the pores satisfies the range 0.5 μm ≤ D3 ≤ 1 μm, the radial dimension of the pores is within a reasonable range. On the one hand, the pores facilitate providing sodium storage sites for the active material, enabling the active material to have a high sodium storage capacity and improving the energy density of the battery 200 when the negative electrode sheet 100 is applied to the battery 200. On the other hand, the pores are not too large so that the binder 121 is not squeezed into the pores during the rolling process. The binder 121 can contact the surfaces of two adjacent hard carbons and exhibit the bonding performance, making the negative electrode sheet 100 have good bonding performance and a large peeling force.

[0051] In some embodiments, the range of the thickness h of the bonding layer 1212 is: 1 μm ≤ h ≤ 2 μm.

[0052] Specifically, the value of the thickness h of the bonding layer 1212 can be, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc.

[0053] In this embodiment, when the thickness h of the adhesive layer 1212 satisfies the range of 1 μm ≤ h ≤ 2 μm, the thickness of the adhesive layer 1212 is within a reasonable range. On the one hand, the adhesive layer 1212 has good adhesive properties, and during the rolling process of the negative electrode sheet 100, the adhesive layer 1212 can still firmly adhere to the outer periphery of the inner core 1211, avoiding the separation of the adhesive layer 1212 from the inner core 1211 and partially embedding into the pores of the hard carbon. The adhesive layer 1212 undergoes a certain degree of deformation to bond the adjacent active materials, thereby enabling the negative electrode sheet 100 to have a large peeling force. On the other hand, it can avoid increasing the internal resistance of the negative electrode sheet 100 due to the excessive thickness of the adhesive layer 1212. When the thickness of the adhesive layer 1212 is too large, on the one hand, there is a tendency and risk for the side of the adhesive layer 1212 facing away from the inner core 1211 to fall off from the outer periphery of the inner core 1211. If a part of the adhesive layer 1212 detaches from the inner core 1211, without the support of the relatively rigid inner core 1211, the part of polymethacrylate detached from the adhesive layer 1212 may be completely embedded into the pores of the hard carbon during the rolling process, thus unable to contact the surrounding hard carbon, and then the part of polymethacrylate detached from the adhesive layer 1212 cannot exert its adhesive performance, resulting in waste of the adhesive 121. On the other hand, the adhesive layer 1212 is an insulator. If the thickness of the adhesive layer 1212 is too large, when the negative electrode sheet 100 is applied to the battery 200, it may increase the resistance to the diffusion of active ions in the battery 200 in the active material layer 120, increase the internal resistance of the negative electrode sheet 100, and thus deteriorate the rate performance of the battery 200. When the thickness of the adhesive layer 1212 is too small, the adhesive layer 1212 is difficult to exert its adhesive performance on the active materials, thereby increasing the risk of the active materials falling off from the active material layer 120 and reducing the cycle stability of the battery 200 when the negative electrode sheet 100 is applied to the battery 200.

[0054] In some embodiments, the range of the molecular weight M of the polyacrylate is: 5 × 10 5 g / mol ≤ M ≤ 10 × 10 5 g / mol.

[0055] Specifically, the value of the molecular weight M of the polyacrylate can be, but is not limited to, 5 × 10 5 g / mol, 5.2 × 10 5 g / mol, 5.5 × 10 5 g / mol, 5.8 × 10 5 g / mol, 6 × 10 5 g / mol, 6.3 × 10 5 g / mol, 6.8 × 10 5g / mol, 7×10 5 g / mol, 7.2×10 5 g / mol, 7.5×10 5 g / mol, 8×10 5 g / mol, 8.5×10 5 g / mol, 9×10 5 g / mol, 9.2×10 5 g / mol, 9.5×10 5 g / mol and 10×10 5 g / mol, etc.

[0056] In this embodiment, the polyacrylate is a linear polymer without side chains. As the molecular weight of the polyacrylate gradually increases, the adhesive strength of the adhesive layer 1212 gradually increases. However, when the molecular weight of the polyacrylate reaches a certain critical value, the adhesive strength of the adhesive layer 1212 tends to be stable. When the molecular weight M of the polyacrylate satisfies the range: 5×10 5 g / mol ≤ M ≤ 10×10 5 g / mol, the molecular weight of the polyacrylate is within a reasonable range. On the one hand, the molecular weight of the polyacrylate is relatively high, so that the adhesive layer 1212 has good adhesive strength, which is beneficial to the firm adhesion of the adhesive layer 1212 to the outer periphery of the inner core 1211 and also beneficial to the firm adhesion of the adhesive 121 to the active material, thereby enabling the negative electrode plate 100 to have a large peeling force. On the other hand, as the molecular weight of the polyacrylate gradually increases, the cohesive strength of the adhesive layer 1212 gradually increases, and the polyacrylate has reasonable fluidity to form a uniform adhesive layer 1212 on the outer periphery of the inner core 1211, so that the adhesive layer 1212 is firmly arranged on the outer periphery of the inner core 1211 to avoid the adhesive layer 1212 being directly extruded into the pores of the hard carbon and causing waste, and the adhesive 121 has good usability. When the molecular weight of the polyacrylate is too large, it not only increases the processing difficulty of the polyacrylate but also increases the cohesive strength of the polyacrylate, thereby reducing the coating property and fluidity of the adhesive layer 1212 during the preparation process, reducing the processing performance of the adhesive layer 1212, and ultimately affecting the adhesion effect of the adhesive 121 on the active material. When the molecular weight of the polyacrylate is too small, the fluidity of the polyacrylate may be too good to adhere to the outer periphery of the inner core 1211, so that the adhesive layer 1212 cannot firmly adhere to the inner core 1211. In addition, the smaller the molecular weight of the polyacrylate, the worse the adhesion performance of the polyacrylate, and it is difficult for the polyacrylate to effectively adhere to the active material, thereby reducing the adhesion performance of the adhesive 121.

[0057] In some embodiments, the core 1211 has a plurality of mesopores, and the radial dimension d of the mesopores ranges from 4 nm ≤ d ≤ 10 nm.

[0058] Specifically, the value of the radial dimension d of the mesopores can be, but is not limited to, 4 nm, 4.2 nm, 4.3 nm, 4.5 nm, 4.8 nm, 5 nm, 5.2 nm, 5.5 nm, 5.8 nm, 6 nm, 6.2 nm, 6.5 nm, 7 nm, 7.2 nm, 7.8 nm, 8 nm, 8.2 nm, 8.5 nm, 9 nm, 9.2 nm, 9.5 nm, and 10 nm, etc.

[0059] Optionally, in some embodiments, some of the mesopores penetrate the core 1211, and some of the mesopores are disposed on the surface of the core 1211.

[0060] It can be understood that the electrolyte can enter the core 1211 through the adhesive layer 1212.

[0061] In this embodiment, when the radial dimension d of the mesopores of the core 1211 satisfies the range 4 nm ≤ d ≤ 10 nm, the radial dimension of the mesopores is within a reasonable range. When the negative electrode sheet 100 is applied to the battery 200, the battery 200 further includes an electrolyte 230 and wets the negative electrode sheet 100. The mesopores in the core 1211 can be used to store the electrolyte 230, so that the adhesive 121 has extremely strong liquid retention ability, which is beneficial to improving the wetting degree of the electrolyte 230 on the negative electrode sheet 100, and is beneficial to improving the efficiency of the transfer of active ions between the negative electrode sheet 100 and the electrolyte 230, thereby reducing the internal resistance of the battery 200 and improving the cycle stability of the battery 200. When the radial dimension of the mesopores is too large, correspondingly, the volume of the mesopores occupying the core 1211 is too large, which may lead to a decrease in the mechanical strength and structural stability of the core 1211. During the rolling process of the negative electrode sheet 100, the core 1211 may be crushed and unable to provide a stable support for the adhesive layer 1212, which may cause the adhesive 121 to be completely squeezed into the pores of the hard carbon and unable to perform the bonding function, thus being not conducive to the improvement of the peeling force of the negative electrode sheet 100. When the radial dimension of the mesopores is too small, when the negative electrode sheet 100 is applied to the battery 200, the amount of the electrolyte 230 that the mesopores can store is small, so that the liquid retention ability of the adhesive 121 is poor, which is not conducive to improving the efficiency of the transfer of active ions between the negative electrode sheet 100 and the electrolyte 230.

[0062] Understandably, the size of the mesopores of the core 1211 can be adjusted by conditions such as the type of surfactant and the hydrothermal temperature in the preparation process of silica, so that the radial size d of the mesopores of the core 1211 satisfies the range 4nm ≤ d ≤ 10nm.

[0063] In some embodiments, the porosity α of the core 1211 ranges from: 15% ≤ α ≤ 50%.

[0064] Specifically, the value of the porosity α of the core 1211 can be, but is not limited to, 15%, 16%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 44%, 45%, 48%, 50%, etc.

[0065] In this embodiment, when the porosity α of the core 1211 satisfies the range: 15% ≤ α ≤ 50%, the porosity of the core 1211 is within a reasonable range. The core 1211 has good liquid retention performance to improve the wetting degree of the electrolyte 230 on the negative electrode plate 100. The core 1211 can also maintain good structural strength, so that during the rolling process of the negative electrode plate 100, the core 1211 can still maintain structural integrity and provide a stable support for the adhesive layer 1212, so as to ensure that the adhesive 121 can exert the adhesive performance on the hard carbon, thereby enabling the negative electrode plate 100 to have a large peeling force. When the porosity of the core 1211 is too large, correspondingly, the mesopores of the core 1211 occupy too much volume of the core 1211, thus reducing the structural stability and structural strength of the core 1211. During the rolling process of the negative electrode plate 100, the core 1211 may be crushed and unable to provide a stable support for the adhesive layer 1212, which may cause the adhesive 121 to be completely squeezed into the pores of the hard carbon and unable to exert the adhesive function, thus being unfavorable for the improvement of the peeling force of the negative electrode plate 100. When the porosity of the core 1211 is too small, when the negative electrode plate 100 is applied to the battery 200, the amount of the electrolyte 230 that can be stored in the mesopores is small, so that the liquid retention ability of the adhesive 121 is poor, which is not conducive to improving the efficiency of the transfer of active ions between the negative electrode plate 100 and the electrolyte 230.

[0066] Please refer to Figure 3 , this application provides a battery 200, which includes: the negative electrode plate 100 provided by this application, a separator 210, a positive electrode plate 220, and an electrolyte 230. The electrolyte 230 is used to wet at least part of the negative electrode plate 100, the separator 210, and the positive electrode plate 220.

[0067] Understandably, after the negative electrode sheet 100, the separator 210, and the positive electrode sheet 220 are stacked in sequence, they are wound.

[0068] Understandably, the electrolyte 230 includes active ions. During the charge and discharge cycles of the battery 200, the active ions are transmitted between the positive electrode sheet 220 and the negative electrode sheet 100.

[0069] Optionally, the battery 200 is a sodium-ion battery.

[0070] In this embodiment, the battery 200 includes the negative electrode sheet 100 provided in the present application, as well as a separator 210, a positive electrode sheet 220, and an electrolyte 230. The electrolyte 230 is used to infiltrate at least part of the negative electrode sheet 100, the separator 210, and the positive electrode sheet 220, so that the active ions are transmitted between the positive electrode sheet 220 and the negative electrode sheet 100, realizing the charge and discharge process of the battery 200. The active material layer 120 of the negative electrode sheet 100 provided in the present application includes an active material and a binder 121. The active material includes hard carbon, and the hard carbon has a plurality of pores. The binder 121 includes a core 1211 and an adhesive layer 1212. The adhesive layer 1212 is bonded to the surface of the core 1211. The hardness of the core 1211 is greater than the hardness of the adhesive layer 1212. The radial dimension of the pores is smaller than the particle size of the core 1211. So that during the rolling process of the negative electrode sheet 100, even if the adhesive layer 1212 is rolled and deformed to a certain extent, the core 1211 can still maintain its original shape, and the binder 121 can be prevented from being filled into the pores. The binder 121 can still bond the adjacent hard carbon, thereby exerting the bonding performance on the hard carbon, and finally enabling the negative electrode sheet 100 to have a high peel force and the battery 200 to have good cycle stability.

[0071] The technical solution of the present application will be further introduced in multiple embodiments as follows:

[0072] Embodiments 1 to 12, Comparative Examples 1 to 5:

[0073] 1. Preparation of the binder 121:

[0074] (1) Mesoporous silica, part of acrylic acid, part of acrylate, and an initiator (ammonium persulfate) are added to a reaction vessel for preliminary polymerization, where the mass fraction of mesoporous silica is 5% - 10%, the mass fraction of acrylic acid is 40% - 45%, the mass fraction of acrylate is 2% - 5%, and the mass fraction of the initiator is 2% - 5%;

[0075] (2) After reacting for 2 h at 75 °C, the remaining acrylic acid, the remaining acrylate, and the remaining initiator (ammonium persulfate) were continuously added dropwise. The reaction was stopped after 10 h. Among them, the mass fraction of the remaining acrylic acid was 40% - 45%, the mass fraction of the remaining acrylate was 2% - 5%, and the mass fraction of the remaining initiator was 2% - 5%.

[0076] (3) Washing: The precipitate was washed 2 - 3 times to remove unreacted monomers and small molecule impurities.

[0077] (4) Neutralization: The reaction product was neutralized with sodium carbonate to pH = 6 - 8.

[0078] (5) Filling the finished product.

[0079] The adhesives 121 of Examples 1 to 12 and Comparative Examples 1 to 5 were obtained through the above steps.

[0080] Among them, the particle size D1 of the adhesive 121, the particle size D2 of the inner core 1211, and the radial size d of the mesopores were directly calculated by scanning electron microscopy.

[0081] Among them, the values of the particle size of the adhesive 121, the particle size of the inner core 1211, and the radial size d of the mesopores in Examples 1 to 12 and Comparative Examples 1 to 5 are shown in Table 1.

[0082] 2. Preparation of the negative electrode plate 100:

[0083] The active material (hard carbon), the conductive agent (conductive carbon black), the adhesive 121, and the solvent water were prepared into a negative electrode slurry according to the kneading process. The active material layer 120 was coated on the bottom-coated current collector layer 110 (copper foil) by a coater, and the moisture was removed by high-temperature baking. The obtained negative electrode plate 100 was roll-pressed to obtain the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 5. The compaction density of the negative electrode plate 100 was 1.5 g / cm 3 .

[0084] Among them, the adhesive 121 of Example 1 was applied to the negative electrode plate 100 of Example 1, the adhesive 121 of Example 2 was applied to the negative electrode plate 100 of Example 2, the adhesive 121 of Comparative Example 1 was applied to the negative electrode plate 100 of Comparative Example 1, and so on.

[0085] Among them, the hard carbon of the active material has pores, and the value of the radial size D3 of the pores satisfies the range of 0.5 μm ≤ D3 ≤ 1 μm. The test methods for the radial size D3 of the pores and the porosity α of the inner core 1211 are as follows: ① Polish the negative electrode plate 100 with an argon ion beam, and scan its cross-section through a scanning electron microscope (SEM); through SEM imaging, use ImageJ software to measure the pore values among 50 hard carbons, and take the average value to obtain the radial size D3 of the pores. ② The porosity α of the inner core 1211 is tested by a mercury intrusion porosimeter. Press mercury into the pores of the inner core 1211 under high pressure, and calculate the porosity α of the inner core 1211 according to the relationship between the pressure and the pore diameter of the inner core 1211 (Washburn equation), where the measurement of the pore diameter of the inner core 1211 refers to the test method for the radial size of the hard carbon pores.

[0086] Among them, in Examples 1 to 12 and Comparative Examples 1 to 5, the values of the radial size D3 of the pores and the porosity α of the inner core 1211 of the binder 121 are shown in Table 1.

[0087] 3. Preparation of the battery 200:

[0088] Provide a positive electrode plate 220, a separator 210 and an electrolyte 230, where the positive electrode plate 220, the separator 210 and the electrolyte 230 are of conventional formulations in the art and will not be limited here.

[0089] Stack the above positive electrode plate 220, separator 210, and negative electrode plate 100 in sequence, so that the separator 210 is located between the positive electrode plate 220 and the negative electrode plate 100 to play an isolation role, and then wind them into a bare electrode assembly; after welding the electrode tabs, place the bare battery 200 in an outer packaging case, inject the above electrolyte 230 after drying, and finally prepare the implementation batteries 1 to 12 and the comparative batteries 1 to 5 through vacuum packaging, standing, forming, shaping, etc.

[0090] Among them, the negative electrode plate 100 of Example 1 is assembled into the implementation battery 1, the negative electrode plate 100 of Example 2 is assembled into the implementation battery 2, the negative electrode plate 100 of Comparative Example 1 is assembled into the comparative battery 1, and so on.

[0091] The following Table 1 is a structural parameter table of the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 5.

[0092]

[0093] It can be understood that in Comparative Example 1 and Comparative Example 2, the binder 121 does not have the inner core 1211, so the particle size D1 of the binder 121 in Comparative Example 1 and Comparative Example 2 is much smaller than 3 μm.

[0094] Performance Test of Negative Electrode Plate 100 and Battery 200:

[0095] 1. Peel Strength Test of Negative Electrode Plate 100:

[0096] The peel strength of the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 5 was tested using a tensile machine. The test method was as follows: Step 1, lay the negative electrode plate 100 flat, and use a ruler and a utility knife to prepare the negative electrode plate 100 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, align one end of the test strip 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 machine with a 90° clamp for peeling to obtain the peel force of the test strip.

[0097] Among them, the peel force of the test strip can characterize the peel force of the negative electrode plate 100. More specifically, it can characterize the peel force between the active material layer 120 and the current collector layer 110 in the negative electrode plate 100. The greater the peel force of the negative electrode plate 100, the better the bonding performance of the adhesive 121.

[0098] The peel strength refers to the peel force required for the bonding surface of the adhesive 121 per unit width in the direction perpendicular to the bonding surface. In other words, the peel strength is the ratio of the peel force to the width of the bonding surface of the adhesive 121. In this application, the peel strength of the negative electrode plate 100 is the ratio of the peel force of the test strip to the width (20 mm), and thus the peel strength values of the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 5 are obtained.

[0099] Among them, the peel strength values of the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 4 are shown in Table 2.

[0100] 2. Liquid Retention Performance Test of Negative Electrode Plate 100:

[0101] Determination of the oil absorption value of the negative electrode plate 100: Scrape the prepared negative electrode plate 100 into powder, accurately weigh 1 g of the powder sample, place the powder sample on a glass plate, pour DBP (dibutyl phthalate, analytical pure) into the burette, and adjust the burette scale to zero. Slowly add DBP to the sample, and continuously stir and roll with a glass rod until a specific form (noodle-like or thin strip-like) appears. Record the volume of DBP consumed in the burette. Then, the oil absorption value of the negative electrode plate 100 = volume of DBP consumed (mL) / (mass of powder sample (g) × 100). The unit of the oil absorption value is mL / 100g.

[0102] Among them, the oil absorption value of the negative electrode plate 100 characterizes the liquid retention performance of the negative electrode plate 100. The larger the oil absorption value of the negative electrode plate 100, the better the liquid retention performance of the negative electrode plate 100.

[0103] 3. Cycling performance test of the battery 200:

[0104] Perform a constant-power charge-discharge cycling test on the above-mentioned implementation batteries 1 to 12 and comparative batteries 1 to 5 on a charge-discharge instrument. The test temperature is 25°C, and the charge-discharge rate is 0.5C (the magnitude of the charge-discharge current is usually represented by the charge-discharge rate. The calculation formula for the charge-discharge current is: charge-discharge power = voltage plateau of the battery 200 (3.2V) × rated capacity of the battery 200). The charge-discharge voltage window is 2.5V to 3.65V (that is, the charge cut-off voltage of the battery 200 is 3.65V, and the discharge cut-off voltage of the battery 200 is 2.5V; generally, it is considered that when the charge cut-off voltage ≥ 4V, the charge cut-off voltage of the battery 200 is relatively high). Calculate the capacity retention rate after 1000 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%.

[0105] Among them, usually, a complete charge-discharge is called a charge-discharge cycle, that is, the battery 200 is first charged from 2.5V to 3.65V, and then discharged from 3.65V to 2.5V, thus forming a charge-discharge cycle. Cycling N times means repeating the above process N times.

[0106] Among them, the values of the capacity retention rates of the implementation batteries 1 to 12 and the comparative batteries 1 to 5 after 1000 cycles are shown in Table 2.

[0107] The following Table 2 shows the performance parameters of the negative electrode plates 100 of Examples 1 to 12 and Comparative Examples 1 to 4 and the performance parameters of the implementation batteries 1 to 12 and the comparative batteries 1 to 5.

[0108]

[0109] Understandably, in Table 2, the higher the capacity retention rate of the battery 200 after 1000 cycles, the better the cycling stability of the battery 200.

[0110] Please refer to Table 1 and Table 2. From the data of Examples 1 to 12, Comparative Example 1 and Comparative Example 2, it can be seen that the binder 121 in Examples 1 to 12 includes a core 1211 and an adhesive layer 1212, and the adhesive layer 1212 is adhered to the surface of the core 1211. The particle size D1 of the binder 121 satisfies the range of 3μm ≤ D1 ≤ 4μm, and the particle size D2 of the core 1211 satisfies the range of 1μm ≤ D2 ≤ 2μm. In Comparative Example 1 and Comparative Example 2, the binder 121 does not include the core 1211. In other words, the binder 121 has no core 1211 as a support, resulting in the peel strength of the negative electrode sheet 100 in Examples 1 to 12 being significantly greater than that of the negative electrode sheet 100 in Comparative Example 1 and Comparative Example 2. The capacity retention rate of Battery 1 to Battery 12 after 1000 cycles is significantly higher than that of Comparative Battery 1 and Comparative Battery 2 after 1000 cycles. This is because: the binder 121 in Examples 1 to 12 includes a core 1211 and an adhesive layer 1212. On the one hand, the core 1211 has a relatively high hardness. During the rolling process of the negative electrode sheet 100, even if the adhesive layer 1212 is rolled and undergoes a certain degree of deformation, the core 1211 can still maintain its original shape, so that the binder 121 can still exert its adhesive performance. On the other hand, the radial size of the pores is smaller than the particle size of the core 1211. The core 1211 occupies a certain volume in the binder 121. During the rolling process of the negative electrode sheet 100, due to the limitation of the pore size, it can be avoided that the binder 121 is filled into the pores. The binder 121 can still adhere to the adjacent hard carbon, thereby exerting its adhesive performance on the hard carbon and ultimately enabling the negative electrode sheet 100 to have a relatively high peel strength, and its corresponding battery 200 to have better cycling stability. In Comparative Example 1 and Comparative Example 2, as conventional binders 121, they do not have a core 1211 with a relatively high stiffness. Moreover, due to the limitation of the degree of polymerization of polyacrylate, a binder 121 with a radial size satisfying the range of 3μm ≤ D1 ≤ 4μm cannot be formed. In addition, there is no rigid support inside the polyacrylate. During the rolling process of the negative electrode sheet 100, the binders 121 in Comparative Example 1 and Comparative Example 2 are easily completely filled into the pores of the hard carbon, resulting in the binder 121 being unable to exert its adhesive performance and ultimately causing the peel strength of the negative electrode sheets 100 in Comparative Example 1 and Comparative Example 2 to be too small, and the active material is easily detached from the active material layer 120, and the cycling stability of Comparative Battery 1 and Comparative Battery 2 is too poor.

[0111] As can be seen from the data of Examples 1 to 3 and Comparative Example 3, under the same other conditions, the particle size D1 of the binder 121 in Examples 1 to 3 satisfies the range of 3 μm ≤ D1 ≤ 4 μm. The particle size D1 of the binder 121 in Comparative Example 3 is too small, so that the peel strength of the negative electrode sheet 100 in Examples 1 to 3 is greater than that of the negative electrode sheet 100 in Comparative Example 3. In addition, as the particle size of the binder 121 continuously increases, the peel strength of the corresponding negative electrode sheet 100 shows an increasing trend, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows an increasing trend. This is because: when the particle size D1 of the binder 121 satisfies the range of 3 μm ≤ D1 ≤ 4 μm, the particle size of the binder 121 is much larger than the radial size of the pores of the hard carbon. During the rolling process of the negative electrode sheet 100, even if the adhesive layer 1212 undergoes a certain degree of deformation, the binder 121 can still maintain a relatively large particle size to prevent the binder 121 from being completely filled into the pores of the hard carbon, thus ensuring the bonding performance of the binder 121 to the hard carbon. Then the negative electrode sheet 100 has a large peel strength, and the corresponding battery 200 has good cycle stability. When the particle size of the binder 121 is small, during the rolling process of the negative electrode sheet 100, in order to exert the bonding performance, the adhesive layer 1212 will undergo a certain degree of deformation, which may make the particle size of the binder 121 smaller than the radial size of the pores of the hard carbon. Then the binder 121 may be completely filled into the pores of the hard carbon, and the binder 121 cannot contact adjacent hard carbon and cannot exert the bonding effect, so that the peel strength of the negative electrode sheet 100 in Example 1 is still small, which may cause the active material to fall off between the active material layers 120, resulting in a low capacity retention rate of the implemented battery 1 after 1000 cycles. Similarly, as can be seen from the data of Example 9 and Example 10, under the same other conditions, the particle size D2 of the inner core 1211 in Example 9 is smaller than the particle size D2 of the inner core 1211 in Example 10. Then the peel strength of the negative electrode sheet 100 in Example 9 is smaller than that of the negative electrode sheet 100 in Example 10, and the capacity retention rate of the implemented battery 9 after 1000 cycles is smaller than that of the implemented battery 10 after 1000 cycles.

[0112] As can be seen from the data of Example 1, Example 4, Example 5 and Comparative Example 4, under the same other conditions, the particle size D2 of the core 1211 in Example 1, Example 4 and Example 5 satisfies the range of 1 μm ≤ D2 ≤ 2 μm. The particle size D2 of the core 1211 in Comparative Example 4 is too small, resulting in the peeling strength of the negative electrode sheet 100 in Example 1, Example 4 and Example 5 being greater than that of the negative electrode sheet 100 in Comparative Example 4. In addition, as the particle size of the core 1211 continuously increases, the peeling strength of the corresponding negative electrode sheet 100 shows a trend of first increasing and then decreasing, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows a trend of first increasing and then decreasing. The reason is as follows: when the particle size D2 of the core 1211 satisfies the range of 1 μm ≤ D2 ≤ 2 μm, the particle size of the core 1211 is within a reasonable range, which can meet the requirement that the particle size of the core 1211 is greater than the radial size of the pores of the hard carbon, so as to prevent the binder 121 from completely entering the pores and losing its bonding performance. In addition, the core 1211 has a relatively high mechanical strength. During the rolling process of the negative electrode sheet 100, the risk of the core 1211 being crushed can be reduced, so that the binder 121 can also be disposed on the surface of the hard carbon and bond the adjacent hard carbon, giving full play to the bonding performance of the binder 121, so that the negative electrode sheet 100 has a relatively high peeling strength. When the particle size of the core 1211 is small, correspondingly, the mechanical strength of the core 1211 decreases. During the rolling process of the negative electrode sheet 100, the core 1211 is crushed, and the core 1211 cannot provide support for the bonding layer 1212, resulting in the binder 121 being filled into the pores of the hard carbon, increasing the risk that the binder 121 cannot exert its bonding performance, so that the peeling strength of the negative electrode sheet 100 in Example 1 is still relatively small, which may cause the active material to fall off between the active material layers 120, resulting in a relatively low capacity retention rate of the battery 1 after 1000 cycles.

[0113] As can be seen from the data of Example 5, Example 6 and Example 7, under the condition that other conditions are the same, the cores 1211 of Example 5, Example 6 and Example 7 all have mesopores, and the radial size d of the mesopores all satisfies the range of 4 nm ≤ d ≤ 10 nm. Under the condition that the radial size of the mesopores meets the reasonable range, as the radial size of the mesopores increases, the oil absorption value of the corresponding negative electrode sheet 100 shows an increasing trend, that is, the liquid retention performance of the corresponding negative electrode sheet 100 is getting better and better. This is because: when the negative electrode sheet 100 is applied to the battery 200, the battery 200 also includes an electrolyte 230 and wets the negative electrode sheet 100. The mesopores in the core 1211 can be used to store the electrolyte 230, and on the premise of ensuring the structural strength of the core 1211, as the radial size of the mesopores gradually increases, the liquid retention ability of the binder 121 gradually increases, which is beneficial to improving the wetting degree of the electrolyte 230 on the negative electrode sheet 100, and is beneficial to improving the efficiency of the transfer of active ions between the negative electrode sheet 100 and the electrolyte 230, thereby being beneficial to reducing the internal resistance of the battery 200 and improving the cycle stability of the battery 200.

[0114] As can be seen from the data of Example 1, Example 8, Example 9 and Comparative Example 5, under the condition that other conditions are the same, the radial size D3 of the pores of the cores 1211 in Example 1, Example 8 and Example 9 satisfies the range of 0.5 μm ≤ D3 ≤ 1 μm. The radial size of the pores of the core 1211 in Comparative Example 5 is too large, which makes the peeling strength of the negative electrode sheets 100 in Example 1, Example 8 and Example 9 greater than that of the negative electrode sheet 100 in Comparative Example 5. The capacity retention rates of Battery 1, Battery 8 and Battery 9 after 1000 cycles are all higher than that of Comparative Battery 5 after 1000 cycles. And as the radial size of the pores of the core 1211 continuously increases, the peeling strength of the corresponding negative electrode sheet 100 continuously increases, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows an increasing trend. This is because: when the radial size D3 of the pores satisfies the range of 0.5 μm ≤ D3 ≤ 1 μm, the radial size of the pores is within a reasonable range, and the pores are not too large to cause the binder 121 to be squeezed into the pores during the rolling process. The binder 121 can contact the surfaces of two adjacent hard carbons and play a bonding performance, so that the negative electrode sheet 100 has good bonding performance and a large peeling force, and the dropping of the active material can be avoided, so that the corresponding battery 200 has good cycle performance. In Comparative Example 5, the radial size D3 of the pores of the core 1211 is too large, and the binder 121 may be squeezed into the pores during the rolling process, and it is difficult for the binder 121 to contact the surfaces of two adjacent hard carbons, thereby weakening the bonding performance and making the bonding performance of the negative electrode sheet 100 poor and the peeling force small.

[0115] As can be seen from the data of Example 1, Example 11 and Example 12, under the same other conditions, the porosity α of the core 1211 in Example 1, Example 11 and Example 12 satisfies the range of 15% ≤ α ≤ 50%. And as the porosity of the core 1211 gradually increases, the peel strength of the corresponding negative electrode sheet 100 continuously increases, the oil absorption value of the negative electrode sheet 100 continuously increases, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows a gradually increasing trend. This is because: when the porosity α of the core 1211 satisfies the range: 15% ≤ α ≤ 50%, the porosity of the core 1211 is within a reasonable range. The core 1211 has good liquid retention performance to improve the wetting degree of the electrolyte 230 on the negative electrode sheet 100, and the core 1211 can also maintain good structural strength so that during the rolling process of the negative electrode sheet 100, the core 1211 can still maintain structural integrity and provide a stable support for the adhesive layer 1212 to ensure that the adhesive 121 can exert the bonding performance on the hard carbon, thereby making the negative electrode sheet 100 have a large peeling force. In addition, as the porosity of the core 1211 gradually increases, the liquid retention performance of the corresponding negative electrode sheet 100 gradually increases.

[0116] It can be understood that in Comparative Example 3, although the adhesive 121 includes the core 1211, the radial dimension d of its mesopores is too small, and the radial dimension D3 of the pores of the core 1211 is too large, resulting in a small peeling force of the corresponding negative electrode sheet 100. Correspondingly, in Comparative Example 4, although the adhesive 121 includes the core 1211, the particle size D2 of its core 1211 is too small, the radial dimension d of the mesopores is too large, and the radial dimension D3 of the pores of the core 1211 is too large, resulting in a small peeling force of the corresponding negative electrode sheet 100.

[0117] Please refer to Figure 4 and Figure 5 , the present application provides an electrical device 300, and the electrical device 300 includes: a device body 310 and the battery 200 provided by the present application, and the battery 200 supplies power to the device body 310.

[0118] It can be understood that the battery 200 is electrically connected to the device body 310.

[0119] In this embodiment, the battery 200 includes the negative electrode sheet 100 provided by the present application. The adhesive 121 of the negative electrode sheet 100 has good bonding performance for the active material, so that the negative electrode sheet 100 has a large peeling force and peel strength, and the battery 200 has good cycle stability to provide stable electric energy for the electrical device 300, which is beneficial to improving the user experience.

[0120] Optionally, the electrical device 300 in the embodiments 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 transportation means such as cars, trucks, sedans, freight trucks, bullet trains, high-speed rails, electric scooters, etc. In addition, it may also be various household appliances, etc. In the present application Figure 4 the electrical device 300 in the embodiments is an energy storage battery cabinet.

[0121] It can be understood that the electrical device 300 described in this embodiment is only one form of the electrical device 300 to which the battery 200 is applied, and should not be construed as a limitation on the electrical device 300 provided in the present application, nor should it be construed as a limitation on the electrical device 300 provided in each embodiment of the present application.

[0122] In the present application, the mention of "embodiment" and "embodiment mode" 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 can 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 deviate from the spirit and scope of the technical solution of the present application.

[0123] 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 negative electrode plate, characterized in that: The negative electrode plate comprises: a current collector layer; and An active material layer, the active material layer comprising an active material and a binder, the active material comprising hard carbon, the hard carbon having a plurality of pores, the binder comprising a core and a bonding layer, the bonding layer being bonded to a surface of the core, the hardness of the core being greater than the hardness of the bonding layer, and the radial size of the pore being smaller than the particle size of the core; the core comprising silicon dioxide, and the bonding layer comprising polyacrylate; Among them, the range of the particle size D2 of the inner core is: 1μm≤D2≤2μm; the range of the radial size D3 of the pore is: 0.5μm≤D3≤1μm; the inner core has a plurality of mesopores, and the range of the radial size d of the mesopores is: 4nm≤d≤10nm; the range of the porosity α of the inner core is: 15%≤α≤50%.

2. The negative electrode sheet according to claim 1, characterized in that: The particle size D1 of the adhesive is in the range of 3 μm≤D1≤4 μm.

3. The negative electrode sheet according to claim 1, characterized in that: The radial dimension of the pore is D3, which satisfies the relationship: 0.25≤D3 / D2<1.

4. The negative electrode sheet according to claim 1, characterized in that: The thickness h of the adhesive layer is in the range of 1 μm≤h≤2 μm.

5. The negative electrode sheet according to claim 1, characterized in that: The molecular weight M of the polyacrylate is in the range of 5×10 5 g / mol≤M≤10×10 5 g / mol.

6. A battery, characterized in that: The battery comprises: The negative electrode sheet according to any one of claims 1 to 5; Diaphragm; A positive electrode; and An electrolyte is used to soak at least a portion of the negative electrode plate, the separator and the positive electrode plate.

7. An electrical equipment, characterized in that: The electrical equipment includes: The device itself; and The battery as described in claim 6 is used to power the device body.

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