Negative pole piece, battery and electric equipment

Abstract

The invention relates to a negative pole piece, a battery and electric equipment. The negative pole piece comprises a current collector layer and an active material layer, the active material layer comprises an active material and an adhesive, the active material comprises hard carbon, the hard carbon is provided with a plurality of pores, the adhesive comprises an inner core and an adhesive layer, the adhesive layer is adhered to the surface of the inner core, and the adhesive layer is arranged between the inner core and the adhesive layer. The hardness of the inner core is larger than that of the bonding layer, and the radial size of the pores is smaller than the particle size of the inner core.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode plate, a battery and an electrical device. Background Art

[0002] With the continuous development of battery technology, sodium-ion batteries have shown great application potential due to their superior electrical properties. However, the current negative electrode sheets of sodium-ion batteries have the problem of low peeling force after rolling, and conventional adhesives are not enough to meet the bonding requirements of negative electrode sheets. It is necessary to prepare new sodium-ion battery adhesives. Summary of the invention

[0003] In view of this, the present application provides a negative electrode sheet, a battery and an electrical device, wherein the adhesive of the negative electrode sheet has good bonding performance so that the negative electrode sheet has a greater peeling force.

[0004] The present application provides a negative electrode plate, which 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 size of the pore is smaller than the particle size of the core.

[0005] Furthermore, the inner core includes silicon dioxide, the adhesive layer includes polyacrylate, and the particle size D1 of the adhesive is in the range of 3 μm≤D1≤4 μm.

[0006] Furthermore, the particle size D2 of the inner core is in the range of 1 μm≤D2≤2 μm.

[0007] Furthermore, the radial dimension of the pore is D3, which satisfies the relationship: 0.25≤D3 / D2<1.

[0008] Furthermore, the thickness h of the adhesive layer is in the range of 1 μm≤h≤2 μm.

[0009] Furthermore, the molecular weight M of the polyacrylate is in the range of 5×10 5 g / mol≤M≤10×10 5 g / mol.

[0010] Furthermore, the inner core has a plurality of mesopores, and the radial dimension d of the mesopores is in the range of 4nm≤d≤10nm.

[0011] Furthermore, the porosity α of the inner core is in the range of 15%≤α≤50%.

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

[0013] The present application provides an electrical device, which includes: a device body and a battery provided in the present application, wherein 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, so that the hard carbon has a high sodium storage capacity, which is conducive to improving the energy density of the battery when the negative electrode sheet is applied to the battery. In addition, the adhesive includes a core and an adhesive layer, the adhesive layer is bonded to the surface of the core, and the hardness of the core is greater than the hardness of the adhesive layer. On the first hand, the hardness of the core is relatively large. During the rolling process of the negative electrode sheet, even if the adhesive layer is rolled and deformed to a certain extent, the core can still maintain its original appearance, so that the adhesive can still exert its adhesive properties. On the second hand, the radial size of the pore is smaller than the particle size of the core, and the core occupies a certain volume in the adhesive. During the rolling process of the negative electrode sheet, due to the limitation of the size of the pore, the adhesive can be prevented from being filled into the pore. The adhesive can still bond to the adjacent hard carbon, thereby exerting the bonding performance to the hard carbon, and finally making the negative electrode sheet have a higher peeling force. When the negative electrode plate is applied to a battery, it is beneficial to improve the cycle stability of the battery. BRIEF 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 use in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A schematic diagram of a partial cross-sectional structure of a negative electrode sheet according to an embodiment of the present application; Figure 2 This is a schematic diagram of the structure of an adhesive according to an embodiment of the present application; Figure 3 A partial cross-sectional structural schematic diagram of a battery according to an embodiment of the present application; Figure 4 This is a schematic diagram of the structure of an electrical device according to an embodiment of the present application; Figure 5 This is a circuit block diagram of an electrical device according to an embodiment of the present application.

[0017] Description of reference numerals: 100 - negative electrode plate, 110 - current collector layer, 120 - active material layer, 121 - adhesive, 1211 - core, 1212 - adhesive layer, 200 - battery, 210 - diaphragm, 220 - positive electrode plate, 230 - electrolyte, 300 - electrical equipment, 310 - equipment body. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any of their variations 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 includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0020] Reference to "embodiment" or "implementation" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment or implementation may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] With the continuous development of battery technology, sodium-ion batteries have shown great application potential due to their superior electrical properties. However, the current negative electrode sheets of sodium-ion batteries have the problem of low peeling force after rolling. Conventional adhesives are not sufficient to meet the bonding requirements of negative electrode sheets, and it is necessary to prepare new sodium-ion battery adhesives.

[0022] In the field of sodium-ion battery technology, styrene-butadiene rubber (SBR) is often used as a binder for negative electrode sheets, while hard carbon is often used as the active material of negative electrode sheets. On the one hand, hard carbon is harder and styrene-butadiene rubber is softer. After rolling, styrene-butadiene rubber is easily squeezed and deformed and loses its bonding sites, thereby weakening the bonding performance of styrene-butadiene rubber to hard carbon; secondly, there are many pores on the surface of hard carbon, while the regular size of styrene-butadiene rubber is less than 500nm. Styrene-butadiene rubber is easily filled into the pores on the surface of hard carbon and loses its bonding performance to the adjacent hard carbon, resulting in a lower peeling force for the negative electrode sheet using styrene-butadiene rubber.

[0023] See also Figure 1 and Figure 2 The present application provides a negative electrode plate 100, which includes: a current collector layer 110 and an active material layer 120, wherein the active material layer 120 includes an active material and a binder 121, wherein the active material includes hard carbon, and the hard carbon has a plurality of pores, and the binder 121 includes a core 1211 and a bonding layer 1212, wherein the bonding layer 1212 is bonded to the surface of the core 1211, the hardness of the core 1211 is greater than the hardness of the bonding layer 1212, and the radial size of the pore is smaller than the particle size of the core 1211.

[0024] It can be understood that the active material layer 120 is arranged on at least one surface of the current collector layer 110. In other words, in some embodiments, the active material layer 120 has one layer and is arranged on one side of the current collector layer 110; in other embodiments, the active material layer 120 has two layers and the two active material layers 120 are arranged on opposite sides of the current collector layer 110.

[0025] 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 is coated on the periphery of the core 1211, and the adhesive layer 1212 has bonding properties to the hard carbon.

[0026] It can be understood that the adhesive 121 is used to bond the hard carbon to improve the peeling force of the negative electrode sheet 100. In the terminology of the present application, the peeling force of the negative electrode sheet 100 is the firmness of the 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 arranged 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. The peeling force of the negative electrode sheet 100 is positively correlated with the bonding performance of the adhesive 121.

[0027] Optionally, in some embodiments, when the negative electrode plate 100 is applied to a battery 200, the battery 200 is a sodium ion battery.

[0028] 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, so that the hard carbon has a high sodium storage capacity, which is beneficial to improve the energy density of the battery 200 when the negative electrode plate 100 is applied to the battery 200. In addition, the adhesive 121 includes a core 1211 and an adhesive layer 1212, and 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. In the first aspect, the hardness of the core 1211 is relatively large. During the rolling process of the negative electrode plate 100, even if the adhesive layer 1212 is rolled and deformed to a certain extent, the core 1211 can still maintain its original appearance, so that the adhesive 121 can still exert its bonding performance. In the second aspect, the radial size of the pore is smaller than the particle size of the core 1211, and the core 1211 occupies a certain volume in the adhesive 121. During the rolling process of the negative electrode sheet 100, the adhesive 121 can be prevented from being filled into the pore due to the limitation of the size of the pore. The adhesive 121 can still bond to the adjacent hard carbon, thereby exerting the bonding performance to the hard carbon, and finally making the negative electrode sheet 100 have a higher peeling 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.

[0029] In some embodiments, the core 1211 comprises silicon dioxide and the adhesive layer 1212 comprises polyacrylate.

[0030] In this embodiment, the core 1211 includes silicon dioxide, which has greater hardness and rigidity. When silicon dioxide is applied to the adhesive 121, silicon dioxide can provide support for the adhesive layer 1212, so that the adhesive 121 still has a larger particle size. During the rolling process of the negative electrode plate 100, even if the adhesive layer 1212 is rolled and deformed to a certain extent, the silicon dioxide can still maintain a complete structure to prevent the adhesive 121 from completely filling the pores of the hard carbon. The adhesive 121 can still be distributed on the surface of the hard carbon and bonded to the adjacent hard carbon, and the adhesive 121 has good bonding properties. In addition, the bonding layer 1212 includes polyacrylate. On the first hand, polyacrylate has a high viscosity and good chemical stability. When the negative electrode plate 100 is applied to the battery 200, the polyacrylate can give full play to its bonding performance to bond the adjacent hard carbon, thereby improving the peeling force of the negative electrode plate 100; in addition, when the electrolyte 230 infiltrates the negative electrode plate 100, the bonding layer 1212 can be prevented from being damaged, thereby ensuring that the adhesive 121 can give full play to its bonding performance. On the second aspect, polyacrylate is coated on the periphery of silica, and the surface of silica has more hydroxyl groups (-OH), while polyacrylic acid has more carboxyl groups (-COOH). During the preparation of the adhesive, as the double bond addition polymerization reaction occurs between acrylic acid and acrylate, the carboxyl groups of polyacrylic acid further undergo esterification reaction with the hydroxyl groups on the surface of silica, and a stable chemical bond is formed between polyacrylic acid and silica, which is conducive to enhancing the adhesion between polyacrylic acid and the surface of silica, so that during the preparation of the adhesive, polyacrylate is not easy to fall off from the surface of silica. In addition, the hydroxyl groups on the surface of silica can also form hydrogen bonds with the ester groups or other polar groups in polyacrylate, and this hydrogen bonding effect is also conducive to further enhancing the adhesion between polyacrylate and the surface of silica, thereby improving the stability of the adhesive layer 1212 coated on the periphery of the core 1211, so that the adhesive 121 has better performance and a longer service life. Furthermore, during the rolling process of the negative electrode sheet 100, the core 1211 and the adhesive layer 1212 can be prevented from separating, ensuring that the adhesive 121 can fully exert its adhesive properties to hard carbon. Compared with the solution of setting other adhesive layers 1212 on the surface of the core 1211, polyacrylate is more easily bonded to the surface of silicon dioxide and has better adhesive properties, which is conducive to reducing the processing difficulty of the adhesive 121, thereby saving the processing cost of the adhesive 121.

[0031] In some embodiments, the particle size D1 of the adhesive 121 is in the range of 3 μm≤D1≤4 μm.

[0032] It can be understood that the size of the adhesive 121 is at the micron level.

[0033] Specifically, the particle size D1 of the adhesive 121 may 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.

[0034] In this embodiment, when the particle size D1 of the adhesive 121 satisfies the range of 3μm≤D1≤4μm, 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 plate 100, even if the adhesive layer 1212 undergoes a certain degree of deformation, the adhesive 121 can still maintain a relatively large particle size to avoid the adhesive 121 being completely filled into the pores of the hard carbon, thereby ensuring the adhesive performance of the adhesive 121 to the hard carbon. When the particle size of the adhesive 121 is too large, it will increase the difficulty of preparing the core 1211, as well as the difficulty and cost of preparing 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 plate 100 is applied to the battery 200. When the particle size of the adhesive 121 is too small, the adhesive layer 1212 will deform to a certain extent during the rolling process of the negative electrode plate 100 in order to exert the adhesive performance, which may make the particle size of the adhesive 121 smaller than the radial size of the pores of the hard carbon. In this case, the adhesive 121 may be completely filled into the pores of the hard carbon, and the adhesive 121 cannot contact the adjacent hard carbon and cannot exert the adhesive effect, so that the peeling force of the negative electrode plate 100 is still small, which may cause the active material to fall off from between the active material layers 120, thereby reducing the capacity retention rate of the battery 200 when the negative electrode plate 100 is applied to the battery 200.

[0035] In some embodiments, the particle size D2 of the core 1211 is in the range of 1 μm≤D2≤2 μm.

[0036] It can be understood that the size of the core 1211 is in the micron level.

[0037] Specifically, the particle size D2 of the inner core 1211 may 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.

[0038] In this embodiment, the size of the core 1211 is micrometer-level. Compared with the solution of using nanometer-level silicon dioxide as the core 1211 of the binder 121, the core 1211 of this solution has advantages. First, the micrometer-level silicon dioxide is larger in size and has a relatively small specific surface area. It is easier to disperse in the binder 121 and is not easy to agglomerate, so that the binder 121 can be evenly distributed between the active material layers 120 to have a better bonding effect on the hard carbon. Second, the micrometer-level silicon dioxide is larger in size than the nanometer-level silicon dioxide, and has higher mechanical strength and wear resistance. During the rolling process of the negative electrode plate 100, the core 1211 can be prevented from being crushed, and the binder 121 can be further prevented from being squeezed into the pores of the hard carbon, which is conducive to the binder 121 to give full play to the bonding performance of the hard carbon, so that the negative electrode plate 100 has a greater peeling 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, the particle size of the core 1211 can be greater than the radial size of the pores of the hard carbon to prevent the adhesive 121 from completely entering the pores and failing to exert its adhesive properties. On the other hand, the micron-level core 1211 has greater mechanical strength, which can reduce the risk of the core 1211 being crushed during the rolling process of the negative electrode plate 100, so that the adhesive 121 can also be set on the surface of the hard carbon and bond the adjacent hard carbon, giving full play to the adhesive properties of the adhesive 121, so that the negative electrode plate 100 has a greater peeling force. The core 1211 with a larger size can occupy a larger volume of the adhesive 121, so that the particle size of the adhesive 121 is larger, avoiding the adhesive 121 from being squeezed into the pores of the hard carbon, and ensuring that the adhesive 121 can exert its adhesive properties on the hard carbon. When the particle size of the core 1211 is too large, the processing difficulty of the core 1211 will increase, which is not conducive to the industrial preparation of the adhesive 121 and increases the production cost of the adhesive 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 of the thickness of the adhesive layer 1212 is limited, which makes the particle size of the adhesive 121 too small. During the rolling process of the negative electrode plate 100, the adhesive layer 1212 will be deformed to a certain extent, so that the particle size of the adhesive 121 may be smaller than the radial size of the pores of the hard carbon, and the adhesive 121 may completely fill the pores of the hard carbon, and then the adhesive 121 cannot exert its bonding performance.On the other hand, the particle size of the core 1211 is too small, and accordingly, the mechanical strength of the core 1211 is reduced. During the rolling process of the negative electrode plate 100, the core 1211 is crushed, and the core 1211 cannot provide support for the bonding 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 bonding properties, thereby reducing the peeling force of the negative electrode plate 100.

[0039] In some embodiments, the radial dimension of the pore is D3, and the relationship is satisfied: 0.25≤D3 / D2<1.

[0040] It can be understood that the radial size of the pore 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 pore, which can prevent the core 1211 from being stuck in the pore.

[0041] 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 and 0.98, etc.

[0042] In this embodiment, when the radial dimension D3 of the pore and the particle size D2 of the core 1211 satisfy the relationship 0.25≤D3 / D2<1, when the radial dimension of the pore is constant, 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 plate 100, the core 1211 can still maintain structural integrity and the particle size of the core 1211 is larger than the radial dimension of the pore. Even if the bonding layer 1212 undergoes a certain degree of deformation, the particle size of the adhesive 121 is still larger than the radial dimension of the pore. Then, the adhesive 121 will not completely fill the pores of the hard carbon. The adhesive 121 can be arranged between two adjacent hard carbons and give full play to the bonding performance, so that the negative electrode plate 100 has better bonding performance. When the value of D3 / D2 is too large, under the condition that the radial size of the pore is constant, the particle size of the core 1211 is too small. If the particle size of the core 1211 is smaller than the radial size of the pore, then during the rolling process of the negative electrode plate 100, the bonding layer 1212 will deform to a certain extent, so that the particle size of the adhesive 121 may be smaller than the radial size of the pore of the hard carbon, and the adhesive 121 may completely fill the pore of the hard carbon, thereby making the adhesive 121 unable to exert its bonding performance. If the particle size of the core 1211 is larger than the radial size of the pore, but the particle size of the core 1211 is still small, then the mechanical strength of the core 1211 is relatively poor, and the risk of the core 1211 being crushed increases during the rolling process of the negative electrode sheet 100. The core 1211 is difficult to provide a stable support for the bonding layer 1212, thereby increasing the risk of the adhesive 121 being filled into the pores of the hard carbon, making the adhesive 121 unable to exert its bonding performance, and ultimately reducing the peeling force of the negative electrode sheet 100. When the value of D3 / D2 is too small, the particle size of the core 1211 is too large when the radial size of the pore is constant, which increases the difficulty of processing the core 1211, is not conducive to the industrial preparation of the adhesive 121, and increases the production cost of the adhesive 121.

[0043] Optionally, the radial dimension D3 of the pore is in the range of 0.5 μm≤D3≤1 μm.

[0044] Specifically, the value of the radial dimension D3 of the pore can be but is not limited to 0.5μm, 0.52μm, 0.55μm, 0.58μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.81μm, 0.83μm, 0.85μm, 0.88μm, 0.9μm, 0.92μm, 0.93μm, 0.94μm, 0.95μm, 0.96μm, 0.97μm, 0.98μm, 0.99μm and 1μm, etc.

[0045] In this embodiment, when the radial dimension D3 of the pore satisfies the range of 0.5 μm ≤ D3 ≤ 1 μm, the radial dimension of the pore is within a reasonable range. On the one hand, the pore is convenient for providing sodium storage sites for the active material, so that the active material has a higher sodium storage capacity, and improves the energy density of the battery 200 when the negative electrode plate 100 is applied to the battery 200. On the other hand, the pore is not too large to allow the adhesive 121 to be squeezed into the pore during the rolling process. The adhesive 121 can contact the surfaces of two adjacent hard carbons and exert adhesive properties, so that the negative electrode plate 100 has better adhesive properties and greater peeling force.

[0046] In some embodiments, the thickness h of the adhesive layer 1212 is in the range of 1 μm≤h≤2 μm.

[0047] Specifically, the thickness h of the adhesive layer 1212 may 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.

[0048] 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 bonding performance, and during the rolling process of the negative electrode plate 100, the adhesive layer 1212 can still firmly adhere to the periphery of the core 1211, avoiding the separation of the adhesive layer 1212 from the 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, so that the negative electrode plate 100 has a large peeling force. On the other hand, it can be avoided that the thickness of the adhesive layer 1212 is too large to increase the internal resistance of the negative electrode plate 100. When the thickness of the adhesive layer 1212 is too large, on one hand, the side of the adhesive layer 1212 away from the core 1211 has a tendency and risk of falling off from the periphery of the core 1211. If part of the adhesive layer 1212 is separated from the core 1211, without the support of the core 1211 with good rigidity, the part of the polymethacrylate separated from the adhesive layer 1212 may be completely embedded in the pores of the hard carbon during the rolling process, thereby being unable to contact the surrounding hard carbon, and then making the part of the polymethacrylate separated from the adhesive layer 1212 unable to exert the adhesive performance, resulting in a 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 plate 100 is applied to the battery 200, it may increase the resistance of the active ions in the battery 200 to diffuse in the active material layer 120, increase the internal resistance of the negative electrode plate 100, and thus deteriorate the rate performance of the battery 200. When the thickness of the bonding layer 1212 is too small, the bonding layer 1212 is difficult to exert its bonding performance to the active material, thereby increasing the risk of the active material falling off from the active material layer 120 and reducing the cycle stability of the battery 200 when the negative electrode plate 100 is applied to the battery 200.

[0049] In some embodiments, the molecular weight M of the polyacrylate is in the range of 5×10 5 g / mol≤M≤10×10 5 g / mol.

[0050] Specifically, the molecular weight M of the polyacrylate may 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.

[0051] In this embodiment, the polyacrylate is an unbranched linear polymer. As the molecular weight of the polyacrylate gradually increases, the bonding strength of the bonding layer 1212 gradually increases. However, when the molecular weight of the polyacrylate reaches a certain critical value, the bonding strength of the bonding layer 1212 tends to be stable. When the molecular weight M of the polyacrylate satisfies the range of 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 bonding layer 1212 has good bonding strength, which is conducive to the bonding layer 1212 being firmly bonded to the periphery of the core 1211, and the bonding agent 121 being firmly bonded to the active material, so that the negative electrode plate 100 has a large peeling force. On the other hand, as the molecular weight of the polyacrylate gradually increases, the cohesive strength of the bonding layer 1212 gradually increases, and the polyacrylate has reasonable fluidity to form a uniform bonding layer 1212 on the periphery of the core 1211, so that the bonding layer 1212 is firmly arranged on the periphery of the core 1211, so as to avoid the bonding layer 1212 being directly squeezed into the pores of the hard carbon and causing waste, and the bonding agent 121 has good performance. When the molecular weight of the polyacrylate is too large, the processing difficulty of the polyacrylate is increased, and the cohesive strength of the polyacrylate is increased, thereby reducing the coating and fluidity of the adhesive layer 1212 during the preparation process, reducing the processing performance of the adhesive layer 1212, and ultimately affecting the bonding 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 be bonded to the periphery of the core 1211, so that the adhesive layer 1212 cannot be firmly bonded to the core 1211. In addition, the smaller the molecular weight of the polyacrylate, the worse the bonding performance of the polyacrylate, and the polyacrylate is difficult to effectively bond to the active material, thereby reducing the bonding performance of the adhesive 121.

[0052] In some embodiments, the inner core 1211 has a plurality of mesopores, and the radial dimension d of the mesopores is in the range of 4 nm ≤ d ≤ 10 nm.

[0053] Specifically, the value of the radial dimension d of the mesopore can be but is not limited to 4nm, 4.2nm, 4.3nm, 4.5nm, 4.8nm, 5nm, 5.2nm, 5.5nm, 5.8nm, 6nm, 6.2nm, 6.5nm, 7nm, 7.2nm, 7.8nm, 8nm, 8.2nm, 8.5nm, 9nm, 9.2nm, 9.5nm and 10nm, etc.

[0054] Optionally, in some embodiments, part of the mesopores penetrate the inner core 1211 , and part of the mesopores are disposed on the surface of the inner core 1211 .

[0055] It can be understood that the electrolyte can enter the inner core 1211 through the adhesive layer 1212 .

[0056] In this embodiment, when the radial dimension d of the mesopores of the inner core 1211 satisfies the range of 4nm≤d≤10nm, the radial dimension of the mesopores is within a reasonable range. When the negative electrode plate 100 is applied to the battery 200, the battery 200 also includes an electrolyte 230 and infiltrates the negative electrode plate 100. The mesopores in the inner core 1211 can be used to store the electrolyte 230, so that the adhesive 121 has a strong liquid retention ability, which is beneficial to improve the degree of wetting of the negative electrode plate 100 by the electrolyte 230, and is beneficial to improve the efficiency of transmission of active ions between the negative electrode plate 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 mesopore is too large, accordingly, the volume of the core 1211 occupied by the mesopore 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 plate 100, the core 1211 may be crushed and cannot 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 cannot play the adhesive function, thereby being unfavorable for improving the peeling force of the negative electrode plate 100. When the radial dimension of the mesopore is too small, when the negative electrode plate 100 is applied to the battery 200, the amount of electrolyte 230 that can be stored in the mesopore is small, so that the liquid retention capacity of the adhesive 121 is poor, which is unfavorable for improving the efficiency of the transmission of active ions between the negative electrode plate 100 and the electrolyte 230.

[0057] It can be understood that the size of the mesopores of the core 1211 can be adjusted by adjusting the surfactant type, hydrothermal temperature and other conditions in the preparation process of silica, so that the radial size d of the mesopores of the core 1211 satisfies the range of 4nm≤d≤10nm.

[0058] In some embodiments, the porosity α of the inner core 1211 is in the range of 15%≤α≤50%.

[0059] Specifically, the porosity α of the inner core 1211 may be, but is not limited to, 15%, 16%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 44%, 45%, 48% and 50%, etc.

[0060] In this embodiment, when the porosity α of the core 1211 satisfies the range of 15%≤α≤50%, the porosity of the core 1211 is within a reasonable range, and the core 1211 has both good liquid retention performance to improve the degree of wetting 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 solid support for the bonding layer 1212, so as to ensure that the adhesive 121 can exert its bonding performance to hard carbon, so that the negative electrode sheet 100 has a greater peeling force. When the porosity of the core 1211 is too large, accordingly, the mesopores of the core 1211 occupy too much volume of the core 1211, thereby reducing the structural stability and strength of the core 1211. During the rolling process of the negative electrode sheet 100, the core 1211 may be crushed and cannot 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 cannot play the adhesive function, thereby being unfavorable for improving the peeling force of the negative electrode sheet 100. When the porosity of the core 1211 is too small, when the negative electrode sheet 100 is applied to the battery 200, the amount of electrolyte 230 that can be stored in the mesopores is small, so that the liquid retention capacity of the adhesive 121 is poor, which is unfavorable for improving the efficiency of the transmission of active ions between the negative electrode sheet 100 and the electrolyte 230.

[0061] See also Figure 3 The present application provides a battery 200, which includes: the negative electrode plate 100 provided in the present application, as well as a separator 210, a positive electrode plate 220, and an electrolyte 230, wherein the electrolyte 230 is used to infiltrate at least a portion of the negative electrode plate 100, the separator 210, and the positive electrode plate 220.

[0062] It can be understood that the negative electrode sheet 100 , the separator 210 , and the positive electrode sheet 220 are stacked in sequence and then wound.

[0063] It can be understood that the electrolyte 230 includes active ions, and during the charge and discharge cycle of the battery 200 , the active ions are transferred between the positive electrode plate 220 and the negative electrode plate 100 .

[0064] Optionally, the battery 200 is a sodium ion battery.

[0065] In this embodiment, the battery 200 includes the negative electrode plate 100 provided in the present application, as well as a diaphragm 210, a positive electrode plate 220 and an electrolyte 230. The electrolyte 230 is used to infiltrate at least a portion of the negative electrode plate 100, the diaphragm 210 and the positive electrode plate 220, so that the active ions can be transmitted between the positive electrode plate 220 and the negative electrode plate 100, thereby realizing the charging and discharging process of the battery 200. The active material layer 120 of the negative electrode plate 100 provided in the present application includes an active material and a binder 121, wherein the active material includes hard carbon, and the hard carbon has a plurality of pores. The binder 121 includes a core 1211 and a bonding layer 1212, wherein the bonding 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 bonding layer 1212, and 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 plate 100, even if the bonding layer 1212 is rolled and deformed to a certain extent, the core 1211 can still maintain its original appearance, and the binder 121 can be prevented from being filled into the pores. The binder 121 can still bond to the adjacent hard carbon, thereby exerting the bonding performance to the hard carbon, and finally making the negative electrode plate 100 have a higher peeling force, and the battery 200 has better cycle stability.

[0066] The technical solution of this application is further introduced in the following with multiple embodiments: Example 1 to Example 12, Comparative Example 1 to Comparative Example 5: 1. Preparation of adhesive 121: (1) Mesoporous silica, part of acrylic acid, part of acrylic ester and initiator (ammonium persulfate) are added to a reaction container for preliminary polymerization, wherein the mass fraction of mesoporous silica is 5% to 10%, the mass fraction of acrylic acid is 40% to 45%, the mass fraction of acrylic ester is 2% to 5%, and the mass fraction of initiator is 2% to 5%; (2) After reacting for 2 hours at 75°C, the remaining acrylic acid, remaining acrylic ester and remaining initiator (ammonium persulfate) were continuously added dropwise. The reaction was stopped after 10 hours. The mass fraction of the remaining acrylic acid was 40% to 45%, the mass fraction of the remaining acrylic ester was 2% to 5%, and the mass fraction of the remaining initiator was 2% to 5%.

[0067] (3) Washing: Wash the precipitate 2 to 3 times to remove unreacted monomers and small molecular impurities; (4) Neutralization: using sodium carbonate to neutralize the reaction product to a pH of 6-8; (5) Filling of finished products.

[0068] Through the above steps, the adhesive 121 of Examples 1 to 12 and Comparative Examples 1 to 5 is obtained.

[0069] The particle size D1 of the adhesive 121 , the particle size D2 of the core 1211 , and the radial dimension d of the mesopores are directly calculated by scanning with an electron microscope.

[0070] Among them, the values ​​of the particle size of the adhesive 121, the particle size of the core 1211, and the radial dimension d of the mesopores in Examples 1 to 12 and Comparative Examples 1 to 5 are shown in Table 1.

[0071] 2. Preparation of negative electrode sheet 100: Active material (hard carbon), conductive agent (conductive carbon black), binder 121, and solvent water are prepared into negative electrode slurry according to a kneading process, and the active material layer 120 is coated on the bottom coating current collector layer 110 (copper foil) by a coating machine. The water is removed by high-temperature baking, and the obtained negative electrode sheet 100 is rolled to obtain the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 5. The compaction density of the negative electrode sheet 100 is 1.5 g / cm 3 .

[0072] Among them, the adhesive 121 of Example 1 is applied to the negative electrode sheet 100 of Example 1, the adhesive 121 of Example 2 is applied to the negative electrode sheet 100 of Example 2, the adhesive 121 of Comparative Example 1 is applied to the negative electrode sheet 100 of Comparative Example 1, and so on.

[0073] Wherein, the hard carbon of the active material has pores, and the value of the radial dimension D3 of the pores satisfies the range of 0.5um≤D3≤1um. The test method of the radial dimension D3 of the pores and the value of the porosity α of the core 1211 is as follows: ① The negative electrode plate 100 is subjected to argon ion beam polishing, and its cross section is scanned by a scanning electron microscope (SEM); through SEM imaging, the pore values ​​between 50 hard carbons are measured using ImageJ software, and the radial dimension D3 of the pores is obtained by taking the average value. ② The porosity α of the core 1211 is tested by a mercury intrusion instrument, where mercury is pressed into the pores of the core 1211 by high pressure, and the porosity α of the core 1211 is calculated based on the relationship between pressure and the pore size of the core 1211 (Washburn equation), wherein the measurement of the pore size of the core 1211 refers to the radial dimension test method of the hard carbon pores.

[0074] Among them, in Examples 1 to 12 and Comparative Examples 1 to 5, the radial dimension D3 of the pores of the inner core 1211 of the adhesive 121 and the porosity α of the inner core 1211 are as shown in Table 1.

[0075] 3. Preparation of battery 200: A positive electrode sheet 220 , a separator 210 and an electrolyte 230 are provided, wherein the positive electrode sheet 220 , the separator 210 and the electrolyte 230 are conventional formulas in the art and are not limited here.

[0076] The positive electrode sheet 220, the separator 210, and the negative electrode sheet 100 are stacked in order so that the separator 210 is located between the positive electrode sheet 220 and the negative electrode sheet 100 to play an isolating role, and then they are wound into a bare electrode assembly; after welding the pole ears, the bare battery 200 is placed in an outer packaging shell, and after drying, the above-mentioned electrolyte 230 is injected, and after vacuum packaging, standing, forming, shaping, etc., finally, implementation batteries 1 to implementation batteries 12 and comparison batteries 1 to comparison batteries 5 are prepared.

[0077] The negative electrode sheet 100 of Example 1 is assembled in the implementation battery 1, the negative electrode sheet 100 of Example 2 is assembled in the implementation battery 2, the negative electrode sheet 100 of Comparative Example 1 is assembled in the comparison battery 1, and so on.

[0078] The following Table 1 is a table of structural parameters of the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 5.

[0079]

[0080] It can be understood that in Comparative Examples 1 and 2, the adhesive 121 does not have a core 1211, and the particle size D1 of the adhesive 121 in Comparative Examples 1 and 2 is much smaller than 3 μm.

[0081] Performance test of negative electrode sheet 100 and battery 200: 1. Peel strength test of negative electrode sheet 100: A tensile testing machine is used to test the peel strength of the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 5, and the testing method is as follows: Step 1, lay the negative electrode sheet 100 flat, and use a ruler and a utility knife to prepare the negative electrode sheet 100 into a strip of 200mm×25mm. A group of samples generally needs to prepare 3 to 5 test strips; 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 make it firmly bonded to the test steel plate; Step 3, make one end of the test strip flush with the steel plate, with slightly wider double-sided tape on both sides, and fit it parallel and centered to the other side of the double-sided tape, and roll it 3 times in one direction with a roller to make it fit flat, manually peel off 5mm to 10mm from the bottom, and peel it off with a tensile testing machine using a 90° clamp to obtain the peeling force of the test strip.

[0082] The peeling force of the test strip can represent the peeling force of the negative electrode sheet 100, and more specifically, can represent the peeling force between the active material layer 120 and the current collector layer 110 in the negative electrode sheet 100. The greater the peeling force of the negative electrode sheet 100, the better the bonding performance of the adhesive 121. The peel strength refers to the peeling force required for the bonding surface of the adhesive 121 of unit width in the direction perpendicular to the bonding surface. In other words, the peel strength is the ratio of the peeling force to the width of the bonding surface of the adhesive 121. In the present application, the peel strength of the negative electrode sheet 100 is the ratio of the peeling force to the width (20 mm) of the test strip, thereby obtaining the peel strength values ​​of the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 5.

[0083] The peel strength values ​​of the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 4 are shown in Table 2.

[0084] 2. Liquid retention performance test of negative electrode sheet 100: Determination of the oil absorption value of the negative electrode sheet 100: Scrape the prepared negative electrode sheet 100 into powder, accurately weigh 1g of the powder sample, place the powder sample on a glass plate, pour DBP (dibutyl phthalate, analytical grade) into a burette, and adjust the burette scale to zero. Add DBP to the sample at a uniform speed, stir and roll with a glass rod until a specific shape (noodles or strips) appears, and record the volume of DBP consumed in the burette. The oil absorption value of the negative electrode sheet 100 = the volume of DBP consumed (mL) / (mass of powder sample (g) × 100), and the unit of oil absorption value is mL / 100g.

[0085] The oil absorption value of the negative electrode plate 100 represents the liquid retention performance of the negative electrode plate 100 . The greater the oil absorption value of the negative electrode plate 100 , the better the liquid retention performance of the negative electrode plate 100 .

[0086] 3. Battery 200 cycle performance test: The above-mentioned implementation batteries 1 to implementation batteries 12 and comparison batteries 1 to comparison batteries 5 were subjected to constant power charge and discharge cycle tests on a charge and discharge instrument. The test temperature was 25°C, the charge and discharge rate was 0.5P (the size of the charge and discharge current is usually expressed by the charge and discharge rate, and the calculation formula of the charge and discharge current is: charge and discharge power = voltage platform of battery 200 (3.2V) × rated capacity of battery 200), the charge and discharge voltage window was 2.5V to 3.65V (that is, the charge cut-off voltage of battery 200 is 3.65V, and the discharge cut-off voltage of battery 200 is 2.5V; it is generally believed that when the charge cut-off voltage is ≥4V, the charge cut-off voltage of battery 200 is higher), and the capacity retention rate after 1000 cycles was calculated. The calculation formula is: capacity retention rate after the Nth cycle = (discharge capacity after the Nth cycle / discharge capacity of the first cycle) × 100%.

[0087] A complete charge and discharge is usually called a charge and 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 and discharge cycle. Cycle N times means repeating the above process N times.

[0088] The capacity retention rates of implementation batteries 1 to implementation batteries 12 and comparison batteries 1 to comparison batteries 5 after 1000 cycles are shown in Table 2.

[0089] Table 2 below shows the performance parameters of the negative electrode sheets 100 of Examples 1 to 12 and Comparative Examples 1 to 4, and the performance parameters of Implementation Batteries 1 to 12 and Comparative Batteries 1 to 5.

[0090]

[0091] It can be understood that in Table 2, the higher the capacity retention rate of the battery 200 after 1000 cycles, the better the cycle stability of the battery 200.

[0092] Please refer to Table 1 and Table 2. From the data of Examples 1 to 12, Comparative Examples 1 and 2, it can be seen that the adhesive 121 of Examples 1 to 12 includes a core 1211 and an adhesive layer 1212, and the adhesive layer 1212 is bonded to the surface of the core 1211. The particle size D1 of the adhesive 121 satisfies the range of 3μm≤D1≤4μm, and the particle size D2 of the core 1211 satisfies the range of 1μm≤D2≤2μm. The adhesive 121 of Comparative Examples 1 and 2 does not include the core 1211. In other words, the adhesive 121 does not have the core 1211 as a support, so that the negative electrode sheet 100 of Examples 1 to 12 is The peel strength is significantly greater than the peel strength of the negative electrode plate 100 of Examples 1 and 2, and the capacity retention rates of Implementation Battery 1 to Implementation Battery 12 after 1000 cycles are significantly higher than the capacity retention rates of Comparative Battery 1 and Comparative Battery 2 after 1000 cycles. This is because: the adhesive 121 of Examples 1 to 12 includes a core 1211 and an adhesive layer 1212. On the first hand, the hardness of the core 1211 is relatively large. During the rolling process of the negative electrode plate 100, even if the adhesive layer 1212 is rolled and deformed to a certain extent, the core 1211 can still maintain its original appearance, so that the adhesive 121 can still exert its adhesive properties. Secondly, the radial dimension of the pore is smaller than the particle size of the core 1211, and the core 1211 occupies a certain volume in the adhesive 121. During the rolling process of the negative electrode plate 100, the adhesive 121 can be prevented from being filled into the pore due to the limitation of the size of the pore. The adhesive 121 can still bond to the adjacent hard carbon, thereby exerting the bonding performance to the hard carbon, and ultimately making the negative electrode plate 100 have a higher peel strength, and the corresponding battery 200 has better cycle stability. However, as conventional adhesives 121, Comparative Examples 1 and 2 do not have a core 1211 with greater rigidity, and due to the limitation of the degree of polymerization, polyacrylate cannot form an adhesive 121 with a radial dimension satisfying the range of 3μm≤D1≤4μm. In addition, there is no rigid support inside the polyacrylate. During the rolling process of the negative electrode sheet 100, the adhesive 121 of Comparative Examples 1 and 2 is easily completely filled into the pores of the hard carbon, so that the adhesive 121 cannot exert its bonding performance, and ultimately the peel strength of the negative electrode sheet 100 of Comparative Examples 1 and 2 is too small, the active material is easy to fall off from the active material layer 120, and the cycle stability of Comparative Battery 1 and Comparative Battery 2 is too poor.

[0093] It can be seen from the data of Examples 1 to 3 and Comparative Example 3 that, under the same other conditions, the particle size D1 of the adhesive 121 of Examples 1 to 3 satisfies the range of 3μm≤D1≤4μm, and the particle size D1 of the adhesive 121 of Comparative Example 3 is too small, so that the peel strength of the negative electrode sheet 100 of Examples 1 to 3 is greater than the peel strength of the negative electrode sheet 100 of Comparative Example 3. In addition, as the particle size of the adhesive 121 continues to increase, 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 a trend of increasing. This is because: when the particle size D1 of the adhesive 121 satisfies the range of 3μm≤D1≤4μm, the particle size of the adhesive 121 is much larger than the radial size of the pores of the hard carbon, and during the rolling process of the negative electrode plate 100, even if the adhesive layer 1212 undergoes a certain degree of deformation, the adhesive 121 can still maintain a larger particle size to avoid the adhesive 121 being completely filled into the pores of the hard carbon, thereby ensuring the bonding performance of the adhesive 121 to the hard carbon, and the negative electrode plate 100 has a greater peel strength, and the corresponding battery 200 has better cycle stability. When the particle size of the adhesive 121 is small, during the rolling process of the negative electrode plate 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 adhesive 121 smaller than the radial size of the pores of the hard carbon. In this case, the adhesive 121 may be completely filled into the pores of the hard carbon, and the adhesive 121 cannot contact the adjacent hard carbon and cannot exert the bonding effect, so that the peel strength of the negative electrode plate 100 of Example 1 is still small, which may cause the active material to fall off from between the active material layers 120, resulting in a low capacity retention rate of the implemented battery 1 after 1000 cycles. Similarly, it can be seen from the data of Examples 9 and 10 that, under the same other conditions, the particle size D2 of the core 1211 in Example 9 is smaller than the particle size D2 of the core 1211 in Example 10, and the peel strength of the negative electrode sheet 100 of Example 9 is smaller than the peel strength of the negative electrode sheet 100 of Example 10, and the capacity retention rate of battery 9 after 1000 cycles is smaller than the capacity retention rate of battery 10 after 1000 cycles.

[0094] It can be seen from the data of Example 1, Example 4, Example 5 and Comparative Example 4 that, under the same other conditions, the particle size D2 of the core 1211 of Example 1, Example 4 and Example 5 satisfies the range of 1μm≤D2≤2μm, and the particle size D2 of the core 1211 of Comparative Example 4 is too small, so that the peel strength of the negative electrode sheet 100 of Example 1, Example 4 and Example 5 is greater than the peel strength of the negative electrode sheet 100 of Comparative Example 4. In addition, as the particle size of the core 1211 continues to increase, its The peel 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. This is because: 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, which can satisfy that the particle size of the core 1211 is larger than the radial size of the pores of the hard carbon, so as to avoid the adhesive 121 completely entering the pores and failing to exert the adhesive performance. In addition, the core 1211 has a large mechanical strength, and during the rolling process of the negative electrode sheet 100, the risk of the core 1211 being crushed can be reduced, so that the adhesive 121 can also be set on the surface of the hard carbon and bonded to the adjacent hard carbon, giving full play to the bonding performance of the adhesive 121, so that the negative electrode sheet 100 has a large peel strength. When the particle size of the inner core 1211 is smaller, the mechanical strength of the inner core 1211 decreases accordingly. During the rolling process of the negative electrode plate 100, the inner core 1211 is crushed. The inner core 1211 cannot provide support for the bonding 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 bonding properties. As a result, the peel strength of the negative electrode plate 100 of Example 1 is still relatively small, which may cause the active material to fall off from between the active material layers 120, resulting in a low capacity retention rate of the battery 1 after 1000 cycles.

[0095] It can be seen from the data of Example 5, Example 6 and Example 7 that, under the same other conditions, the core 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 4nm≤d≤10nm. Under the condition that the radial size of the mesopores satisfies the reasonable range, as the radial size of the mesopores increases, the oil absorption value of the corresponding negative electrode plate 100 shows an increasing trend, that is, the liquid retention performance of the corresponding negative electrode plate 100 is getting better and better. This is because: when the negative electrode plate 100 is applied to the battery 200, the battery 200 It also includes an electrolyte 230 and infiltrates the negative electrode plate 100. The mesopores in the inner core 1211 can be used to store the electrolyte 230. Under the premise of ensuring the structural strength of the inner core 1211, as the radial size of the mesopores gradually increases, the liquid retention capacity of the adhesive 121 gradually increases, which is beneficial to improving the degree of infiltration of the negative electrode plate 100 by the electrolyte 230, and is beneficial to improving the efficiency of transmission of active ions between the negative electrode plate 100 and the electrolyte 230, thereby helping to reduce the internal resistance of the battery 200 and improve the cycle stability of the battery 200.

[0096] It can be seen from the data of Example 1, Example 8, Example 9, and Comparative Example 5 that, under the same other conditions, the radial size D3 of the pores of the core 1211 of Example 1, Example 8, and Example 9 satisfies the range of 0.5μm≤D3≤1μm, and the radial size of the pores of the core 1211 of Comparative Example 5 is too large, which makes the peel strength of the negative electrode sheet 100 of Example 1, Example 8, and Example 9 greater than the peel strength of the negative electrode sheet 100 of Comparative Example 5, and the capacity retention rate of the implementation battery 1, the implementation battery 8, and the implementation battery 9 after 1000 cycles is higher than the capacity retention rate of the comparative battery 5 after 1000 cycles, and as the radial size of the pores of the core 1211 increases, the capacity retention rate of the negative electrode sheet 100 of the implementation battery 1, the implementation battery 8, and the implementation battery 9 ... The peeling strength of the corresponding negative electrode plate 100 is continuously increased, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows an increasing trend. This is because: when the radial dimension D3 of the pore satisfies the range of 0.5μm≤D3≤1μm, the radial dimension of the pore is within a reasonable range, and the pore is not too large to allow the adhesive 121 to be squeezed into the pore during the rolling process. The adhesive 121 can contact the surfaces of two adjacent hard carbons and exert its bonding properties, so that the negative electrode plate 100 has better bonding properties and greater peeling force, which can avoid the falling of active materials, thereby making the corresponding battery 200 have better cycle performance. In comparative example 5, the radial dimension D3 of the pores of the inner core 1211 is too large, and the adhesive 121 may be squeezed into the pores during the rolling process. The adhesive 121 is difficult to contact the surfaces of two adjacent hard carbons, thereby weakening the bonding performance, resulting in poor bonding performance and small peeling force of the negative electrode sheet 100.

[0097] It can be seen from the data of Example 1, Example 11 and Example 12 that, under the same other conditions, the porosity α of the core 1211 of 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 continues to increase, the oil absorption value of the negative electrode sheet 100 continues to increase, and the capacity retention rate of the corresponding battery 200 after 1000 cycles shows a trend of gradually increasing. This is because: when the porosity α of the core 1211 satisfies the range: When 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 degree of infiltration of the electrolyte 230 into 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 bonding layer 1212 to ensure that the adhesive 121 can exert its bonding performance to the hard carbon, so that the negative electrode sheet 100 has 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 is gradually enhanced.

[0098] It can be understood that in Comparative Example 3, although the adhesive 121 includes a core 1211, the radial size d of its mesopores is too small, and the radial size D3 of the pores of the core 1211 is too large, so that the corresponding negative electrode sheet 100 has a small peeling force. Correspondingly, in Comparative Example 4, although the adhesive 121 includes a core 1211, the particle size D2 of the core 1211 is too small, the radial size d of the mesopores is too large, and the radial size D3 of the pores of the core 1211 is too large, so that the corresponding negative electrode sheet 100 has a small peeling force.

[0099] See also Figure 4 and Figure 5 The present application provides an electrical device 300 , which includes: a device body 310 and a battery 200 provided in the present application, and the battery 200 supplies power to the device body 310 .

[0100] It can be understood that the battery 200 is electrically connected to the device body 310 .

[0101] In this embodiment, the battery 200 includes the negative electrode plate 100 provided in the present application. The adhesive 121 of the negative electrode plate 100 has good bonding properties to the active material, so that the negative electrode plate 100 has a large peeling force and peeling strength. The battery 200 has good cycle stability, so as to provide stable electric energy to the electrical device 300, which is beneficial to improving user experience.

[0102] Optionally, the power-consuming device 300 in the embodiment of the present application may be, but is not limited to, a portable electronic device such as a mobile phone, a tablet computer, a laptop computer, a desktop computer, a smart bracelet, a smart watch, an e-reader, a game console, etc. It may also be a vehicle such as a car, a truck, a car, a truck, a motor vehicle, a high-speed train, an electric vehicle, etc. In addition, it may also be various household appliances, etc. The present application Figure 4 The electrical equipment 300 of the embodiment is an energy storage battery cabinet.

[0103] It can be understood that the electric device 300 described in this embodiment is merely a form of the electric device 300 used by the battery 200, and should not be understood as a limitation on the electric device 300 provided in this application, nor should it be understood as a limitation on the electric device 300 provided in each embodiment of this application.

[0104] Mentioning "embodiment" and "implementation method" in this application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, provided that there is no contradiction between them.

[0105] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the above preferred implementation modes, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution 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, wherein the active material layer includes an active material and a binder, wherein the active material includes hard carbon, wherein the hard carbon has a plurality of pores, wherein the binder includes a core and a bonding layer, wherein the bonding layer is bonded to the surface of the core, wherein the hardness of the core is greater than the hardness of the bonding layer, and wherein the radial size of the pores is smaller than the particle size of the core.

2. The negative electrode sheet according to claim 1, characterized in that: The inner core includes silicon dioxide, the adhesive layer includes polyacrylate, and 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 particle size D2 of the inner core is in the range of 1 μm≤D2≤2 μm.

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

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

6. The negative electrode sheet according to claim 2, 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.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The inner core has a plurality of mesopores, and the radial dimension d of the mesopores is in the range of 4nm≤d≤10nm.

8. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The porosity α of the inner core is in the range of 15%≤α≤50%.

9. A battery, characterized in that: The battery comprises: The negative electrode sheet according to any one of claims 1 to 8; 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.

10. An electrical device, characterized in that: The electrical equipment includes: The device itself; and The battery as claimed in claim 9, wherein the battery is used to power the device body.

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