Pole piece, battery and electric equipment

Abstract

The invention discloses a pole piece, a battery and electric equipment, the pole piece comprises a current collector and an active material layer, and the active material layer is arranged on at least one side of the current collector; the active material layer comprises N sub-active material layers, N is a positive integer greater than 1, the performance parameter of each sub-active material layer is Z, Zn is not less than Zn-1, and at least one Zn is greater than Zn-1, the performance parameter Z of the corresponding sub-active material layer is determined according to a formula Zn = (1-pn) * cn * 100 / (pi * (D50) n2), pn is the porosity of the nth sub-active material layer, cn is the compaction density of the nth sub-active material layer, and n is a positive integer greater than 1. And (D50) n is the corresponding particle size when the cumulative particle size distribution number of the active material in the nth sub active material layer reaches 50%. Therefore, the performance parameter Z of the N sub-active material layers satisfies that Zn is not less than Zn-1 and at least one Zn is greater than Zn-1, so that the compaction density, porosity and D50 of each sub-active material layer can be reasonably configured, electrolyte infiltration is facilitated, and the quick charge performance and stable cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a pole piece, a battery and an electrical device. Background Art

[0002] In related technologies, with the widespread application of new energy technologies in the fields of mobile power equipment and electric vehicles, higher requirements are placed on the performance of batteries. The performance of batteries is closely related to the porosity, compaction density, and particle size of the active material layer of the electrode. Therefore, how to improve the performance of batteries has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a pole piece that is conducive to electrolyte infiltration and can improve the fast charging performance and stable cycle performance of the battery.

[0004] The present invention further provides a battery having the pole piece.

[0005] The invention further provides an electrical device having the battery.

[0006] The pole piece according to the embodiment of the present invention comprises: a current collector and an active material layer, wherein the active material layer is disposed on at least one side of the current collector along the thickness direction of the current collector; the active material layer comprises N sub-active material layers, where N is a positive integer greater than 1, and the performance parameters of the sub-active material layers are Z, Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 , according to the formula Z n =(1-p n )×c n ×100 / (π×(D 50 ) n 2 ) determines the performance parameter Z corresponding to the sub-active material layer, wherein p n is the porosity of the nth active material layer, c n is the compaction density of the nth active material layer, (D50) n It is the particle size corresponding to the point where the cumulative particle size distribution of the active material in the n-th active material sub-layer reaches 50%.

[0007] According to the pole piece of the embodiment of the present invention, by making the performance parameter Z of the N-layer active material layer satisfy Z n Not less than Z n-1 And at least one Z n Greater than Z n-1, the compaction density, porosity and D50 of each sub-active material layer can be reasonably configured, which is beneficial to the infiltration of electrolyte and can improve the fast charging performance and stable cycle performance of the battery.

[0008] According to an embodiment of the present invention, the relationship is satisfied: Z n >Z n-1 .

[0009] According to an embodiment of the present invention, the relationship: 0.08≤Z n ≤4.81.

[0010] According to an embodiment of the present invention, the relationship is satisfied: n-1 ≥p n ; and / or, satisfy the relationship: 0.15≤p n ≤0.40.

[0011] According to an embodiment of the present invention, the relationship is satisfied: n-1 ≥c n ; and / or, satisfying the relationship: 1.3g / cm 3 ≤c n ≤1.7g / cm 3 .

[0012] According to an embodiment of the present invention, the relationship is satisfied: (D50) n-1 ≥(D50) n ; and / or, satisfy the relationship: 3μm≤(D50) n ≤20μm.

[0013] According to an embodiment of the present invention, the sub-active material layer includes a binder, and the binder content of the plurality of sub-active material layers decreases from close to the current collector to far away from the current collector.

[0014] According to the embodiment of the present invention, the relationship: 2≤N≤6 is satisfied.

[0015] A battery according to an embodiment of the present invention includes an electrode assembly, which includes: a first pole piece, a second pole piece and a diaphragm, the first pole piece and / or the second pole piece are the above-mentioned pole pieces, and the first pole piece, the diaphragm and the second pole piece are assembled together to form the electrode assembly.

[0016] An electric device according to an embodiment of the present invention includes the above-mentioned battery.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 Schematic diagram of a pole piece according to an embodiment of the present invention.

[0020] Reference numerals:

[0021] Current collector 1; active material layer 2; sub-active material layer 3; first sub-active material layer 31; second sub-active material layer 32; third sub-active material layer 33; fourth sub-active material layer 34; fifth sub-active material layer 35; sixth sub-active material layer 36;

[0022] Pole piece 100. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0024] Reference below Figure 1 The electrode piece 100, a battery and an electric device according to an embodiment of the present invention are described.

[0025] like Figure 1 As shown, the pole piece 100 according to the embodiment of the present invention includes: a current collector 1 and an active material layer 2 .

[0026] Among them, along the thickness direction of the pole piece 100 (ie Figure 1 The current collector 1 and the active material layer 2 are stacked. The current collector 1 can be copper foil, aluminum foil, composite current collector, etc. The current collector 1 can be used to collect and conduct current to ensure that the electrons in the battery or electrochemical device can flow smoothly. Figure 1 In the Z direction shown in the figure), at least one side of the current collector 1 is provided with an active material layer 2, that is, one side of the current collector 1 can be provided with an active material layer 2, or both sides of the current collector 1 can be provided with an active material layer 2. The active material layer 2 includes N layers of sub-active material layers 3, N is a positive integer greater than 1, and the active material layer 2 includes but is not limited to two layers of sub-active material layers 3, three layers of sub-active material layers 3, four layers of sub-active material layers 3, five layers of sub-active material layers 3, six layers of sub-active material layers 3, etc. For example Figure 1As shown, the active material layer 2 includes a first sub-active material layer 31, a second sub-active material layer 32, a third sub-active material layer 33, a fourth sub-active material layer 34, a fifth sub-active material layer 35, and a sixth sub-active material layer 36, along the thickness direction of the electrode 100 (i.e. Figure 1 In the Z direction shown in the figure, from the direction close to the current collector 1 to the direction away from the current collector 1, the first sub-active material layer 31, the second sub-active material layer 32, the third sub-active material layer 33, the fourth sub-active material layer 34, the fifth sub-active material layer 35, and the sixth sub-active material layer 36 are stacked in sequence, the first sub-active material layer 31 is the sub-active material layer 3 closest to the current collector 1, and the sixth sub-active material layer 36 is the sub-active material layer 3 farthest from the current collector 1.

[0027] The performance parameters of the sub-active material layer 3 are Z, Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 (N represents the layer number), according to the formula Z n =(1-p n )×c n ×100 / (π×(D 50 ) n 2 ) determines the performance parameter Z of the corresponding active material layer 3, where p n is the porosity of the nth active material layer 3, c n is the compaction density of the nth active material layer 3, (D50) n It is the particle size corresponding to the point where the cumulative particle size distribution of the active material in the n-th sub-active material layer 3 reaches 50%.

[0028] The performance parameters of the sub-active material layer 3 are Z, Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 , the following description is made by taking the active material layer 2 including six sub-active material layers 3 as an example, wherein the six sub-active material layers 3 are respectively a first sub-active material layer 31, a second sub-active material layer 32, a third sub-active material layer 33, a fourth sub-active material layer 34, a fifth sub-active material layer 35, and a sixth sub-active material layer 36, along the thickness direction of the electrode 100 (i.e. Figure 1In the Z direction shown in the figure, from the direction close to the current collector 1 to the direction away from the current collector 1, the first sub-active material layer 31, the second sub-active material layer 32, the third sub-active material layer 33, the fourth sub-active material layer 34, the fifth sub-active material layer 35, and the sixth sub-active material layer 36 are stacked in sequence, the first sub-active material layer 31 is the sub-active material layer 3 closest to the current collector 1, and the sixth sub-active material layer 36 is the sub-active material layer 3 farthest from the current collector 1. The performance parameters of the first sub-active material layer 31, the second sub-active material layer 32, the third sub-active material layer 33, the fourth sub-active material layer 34, the fifth sub-active material layer 35, and the sixth sub-active material layer 36 are Z1, Z2, Z3, Z4, Z5, and Z6, respectively.

[0029] Z1, Z2, Z3, Z4, Z5, and Z6 can be 1, 2, 3, 4, 5, and 6 respectively, so that Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 Alternatively, Z1, Z2, Z3, Z4, Z5, and Z6 can be 1, 1, 1, 2, 2, and 3, respectively, so that Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 .

[0030] Such a setting can make the performance parameter Z of the multi-layer sub-active material layer 3 reasonably matched, so that the porosity, compaction density and D50 of the multi-layer sub-active material layer 3 can be reasonably matched, which is beneficial to the infiltration of electrolyte and helps the transmission of lithium ions in each layer of sub-active material layer 3, so that the battery using the electrode 100 proposed in this application can have both high-rate fast charging and stable cycling capabilities.

[0031] Thus, by making the performance parameter Z of the N-layer active material layer 3 satisfy Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 The compaction density, porosity and D50 of each sub-active material layer 3 can be reasonably configured, which is beneficial to the infiltration of the electrolyte and can improve the fast charging performance and stable cycle performance of the battery.

[0032] As some embodiments of the present application, the pole piece 100 proposed in the present application may be a positive pole piece, and the pole piece 100 proposed in the present application may also be a negative pole piece. The present application is described by taking the pole piece 100 as a negative pole piece as an example.

[0033] As some embodiments of the present application, each sub-active material layer 3 includes: active material, adhesive, and conductive agent. Among them, the conductive agent may include at least one of conductive carbon black, KS-6, acetylene black, Ketjen black, conductive fiber, graphene, conductive graphite, graphene oxide, and carbon nanotubes. For example, the conductive agent may include conductive carbon black, KS-6, and acetylene black. The conductive agent may also include conductive carbon black, Ketjen black, conductive fiber, and graphene. The conductive agent may also include acetylene black, conductive graphite, graphene oxide, and carbon nanotubes. In this way, the materials included in the conductive agent can be selected according to the needs of the product, which is conducive to improving the selectivity of the conductive agent. In addition, by making the conductive agent include multiple materials at the same time, the charge and discharge performance can be improved.

[0034] The binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyethyleneimine, polyaniline, polyacrylic acid, sodium alginate, styrene-butadiene rubber, sodium carboxymethyl cellulose, phenolic resin, and epoxy resin. For example, the binder may include polyvinylidene fluoride, polytetrafluoroethylene, and polyethyleneimine. The binder may also include polyaniline, polyacrylic acid, and sodium alginate. In this way, the materials included in the binder can be selected according to the requirements of the product, which is beneficial to improving the selectivity of the binder. In addition, by making the binder include multiple materials at the same time, the bonding performance can be improved.

[0035] The active material may include at least one of graphite, silicon, hard carbon, soft carbon, silicon carbon, tin, lithium titanate, and mesophase carbon microspheres, wherein the graphite includes artificial graphite and / or natural graphite. For example: the active materials all include graphite, silicon, and hard carbon, or the active materials all include soft carbon, silicon carbon, tin, and lithium titanate, or the active materials all include graphite, tin, and lithium titanate. The materials included in the active materials can be selected according to the requirements of the product to improve the selectivity of the active materials, and by making the active materials include a variety of materials, it is beneficial to improve the charge and discharge performance of the battery.

[0036] In some embodiments of the present invention, the relationship is satisfied: n >Z n-1 The following description takes the example that the active material layer 2 includes six sub-active material layers 3. The six sub-active material layers 3 are respectively a first sub-active material layer 31, a second sub-active material layer 32, a third sub-active material layer 33, a fourth sub-active material layer 34, a fifth sub-active material layer 35, and a sixth sub-active material layer 36. The performance parameters of the first sub-active material layer 31, the second sub-active material layer 32, the third sub-active material layer 33, the fourth sub-active material layer 34, the fifth sub-active material layer 35, and the sixth sub-active material layer 36 are respectively Z1, Z2, Z3, Z4, Z5, and Z6.

[0037] Z1, Z2, Z3, Z4, Z5, and Z6 can be 1, 2, 3, 4, 5, and 6 respectively, so that Zn >Z n-1 , or, Z1, Z2, Z3, Z4, Z5, and Z6 can be 1, 2, 4, 5, 8, and 10 respectively, so that Z n >Z n-1 Such an arrangement can make the performance parameter Z of the multi-layer active material layer 3 match reasonably, and can form a gradient of the performance parameter Z of the multi-layer active material layer 3, which is more conducive to the transmission of lithium ions in each layer of the active material layer 3, and can significantly improve the fast charging performance and stable cycle performance of the battery.

[0038] In some embodiments of the present invention, the relationship is satisfied: 0.08≤Z n ≤4.81, that is, the performance parameter Z of each sub-active material layer 3 can be any value between 0.08 and 4.81, for example, the performance parameter Z of each sub-active material layer 3 can be but not limited to 0.08, 1.08, 2.08, 3.08, 3.81, 4.81, etc. Such a setting can make the performance parameter Z of each layer of sub-active material layer 3 reasonable, and can make the porosity, compaction density and D50 of each layer of sub-active material layer 3 reasonably matched, which is conducive to the transmission of lithium ions in each layer of sub-active material layer 3, and can improve the fast charging performance and stable cycle performance of the battery.

[0039] As some embodiments of the present application, the relationship is satisfied: 0.12≤Z n ≤1.43, that is, the performance parameter Z of each sub-active material layer 3 can be any value between 0.12 and 1.43, for example, the performance parameter Z of each sub-active material layer 3 can be but not limited to 0.12, 0.33, 0.73, 1.13, 1.43, etc. Such a setting can make the performance parameter Z of each sub-active material layer 3 more reasonable, and can make the porosity, compaction density, and D50 of each layer of sub-active material layer 3 reasonably matched, which is more conducive to the transmission of lithium ions in each layer of sub-active material layer 3, and can significantly improve the fast charging performance and stable cycle performance of the battery.

[0040] As some embodiments of the present application, the relationship is satisfied: 0.20≤Z n ≤0.63, that is, the performance parameter Z of each sub-active material layer 3 can be any value between 0.20 and 0.63, for example, the performance parameter Z of each sub-active material layer 3 can be but not limited to 0.20, 0.33, 0.43, 0.53, 0.63, etc. Such a setting can make the performance parameter Z of each sub-active material layer 3 reasonable, and can make the porosity, compaction density, and D50 of each layer of sub-active material layer 3 reasonably matched, which is more conducive to the transmission of lithium ions in each layer of sub-active material layer 3, and can more significantly improve the fast charging performance and stable cycle performance of the battery.

[0041] In some embodiments of the present invention, the relationship is satisfied: n-1 ≥p n , and / or, satisfy the relationship: 0.15≤p n ≤0.40.

[0042] Specifically, for p n-1 ≥p n It can be understood that, in each of two adjacent sub-active material layers 3, the porosity of the sub-active material layer 3 close to the current collector 1 is greater than or equal to the porosity of the sub-active material layer 3 away from the current collector 1. Such a setting can make the porosity of the multiple layers of sub-active material layers 3 reasonably matched, can reduce the internal resistance of the battery, can increase the infiltration rate, is beneficial to improve the battery output power, and is beneficial to improve the capacity and charge and discharge performance of the battery.

[0043] As some embodiments of the present application, the relationship is satisfied: n-1 >p n This can be understood as that in each of two adjacent sub-active material layers 3, the porosity of the sub-active material layer 3 close to the current collector 1 is greater than the porosity of the sub-active material layer 3 away from the current collector 1. This arrangement can form a porosity gradient for the multiple layers of sub-active material layers 3, which can significantly reduce the internal resistance of the battery, significantly increase the infiltration rate, and is more conducive to improving the battery output power, and is more conducive to improving the battery capacity and charge and discharge performance.

[0044] Satisfy the relationship: 0.15≤p n ≤0.40, that is, the porosity of each sub-active material layer 3 can be any value between 0.15 and 0.40. For example, the porosity of each sub-active material layer 3 can be but not limited to 0.15, 0.25, 0.35, 0.40, etc. Such a setting can make the porosity of each sub-active material layer 3 reasonable, and can make the battery have excellent capacity and charge and discharge performance.

[0045] As some embodiments of the present application, the relationship is satisfied: 0.20≤p n ≤0.35, that is, the porosity of each sub-active material layer 3 can be any value between 0.20 and 0.35. For example, the porosity of each sub-active material layer 3 can be but not limited to 0.20, 0.25, 0.35, etc. Such a setting can make the porosity of each sub-active material layer 3 more reasonable, and can make the battery have better capacity and charge and discharge performance.

[0046] As some embodiments of the present application, the relationship is satisfied: 0.25≤p n≤0.35, that is, the porosity of each sub-active material layer 3 can be any value between 0.25 and 0.35. For example, the porosity of each sub-active material layer 3 can be but not limited to 0.25, 0.30, 0.35, etc. Such a setting can make the porosity of each sub-active material layer 3 more reasonable, and can make the battery have better capacity and charge and discharge performance.

[0047] In some embodiments of the present invention, the relationship is satisfied: n-1 ≥c n , and / or, satisfy the relationship: 1.3g / cm 3 ≤c n ≤1.7g / cm 3 .

[0048] Specifically, for c n-1 ≥c n It can be understood that, in each of two adjacent sub-active material layers 3, the compaction density of the sub-active material layer 3 close to the current collector 1 is greater than or equal to the compaction density of the sub-active material layer 3 away from the current collector 1. This arrangement can make the compaction density of the multiple layers of sub-active material layers 3 reasonably matched, and can make the electrolyte infiltration effect good, which is beneficial to improving the fast charging performance of the battery, and is beneficial to improving the capacity of the battery.

[0049] As some embodiments of the present application, the relationship is satisfied: n-1 >c n This can be understood as that in each of two adjacent sub-active material layers 3, the compaction density of the sub-active material layer 3 close to the current collector 1 is greater than the compaction density of the sub-active material layer 3 far away from the current collector 1. This arrangement can form a gradient in the compaction density of the multiple layers of sub-active material layers 3, so that the compaction density of the sub-active material layer 3 farther away from the current collector 1 can be lower, thereby making the electrolyte infiltration effect better, significantly improving the fast charging performance of the battery, and significantly improving the battery capacity.

[0050] Satisfy the relationship: 1.3g / cm 3 ≤c n ≤1.7g / cm 3 That is to say, the compaction density of each sub-active material layer 3 can be 1.3 g / cm 3 Up to 1.7g / cm 3 For example, the compaction density of each sub-active material layer 3 can be, but is not limited to, 1.3 g / cm 3 , 1.5g / cm 3 , 1.7g / cm 3 Etc., such an arrangement can make the compaction density of each layer of the active material layer 3 reasonable, and can make the battery have a larger capacity and excellent fast charging performance.

[0051] As some embodiments of the present application, the relationship is satisfied: 1.5 g / cm 3 ≤c n ≤1.65g / cm 3 That is to say, the compaction density of each sub-active material layer 3 can be 1.5 g / cm 3 Up to 1.65g / cm 3 For example, the compaction density of each sub-active material layer 3 can be, but is not limited to, 1.5 g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 Etc., such an arrangement can make the compaction density of each sub-active material layer 3 more reasonable, and can make the battery have a larger capacity and a better fast charging performance.

[0052] As some embodiments of the present application, the relationship is satisfied: 1.6 g / cm 3 ≤c n ≤1.65g / cm 3 That is to say, the compaction density of each sub-active material layer 3 can be 1.6 g / cm 3 Up to 1.65g / cm 3 For example, the compaction density of each sub-active material layer 3 can be, but is not limited to, 1.6 g / cm 3 、1.62g / cm 3 , 1.65g / cm 3 Etc., such an arrangement can make the compaction density of each sub-active material layer 3 more reasonable, and can make the battery have a larger capacity and a better fast charging performance.

[0053] In some embodiments of the present invention, the relationship is satisfied: (D50) n-1 ≥(D50) n , and / or, satisfying the relationship: 3μm≤(D50)n≤20μm.

[0054] Specifically, for (D50) n-1 ≥(D50) n It can be understood that, in each of two adjacent sub-active material layers 3, the D50 of the sub-active material layer 3 close to the current collector 1 is greater than or equal to the D50 of the sub-active material layer 3 far away from the current collector 1. Such a setting can make the D50 of the multiple layers of sub-active material layers 3 reasonably matched, can make the electrolyte infiltration effect good, and can make the electrode 100 have excellent processing performance and electrochemical performance.

[0055] As some embodiments of the present application, the relationship is satisfied: (D50) n-1>(D50) n It can be understood that in each of two adjacent sub-active material layers 3, the D50 of the sub-active material layer 3 close to the current collector 1 is greater than the D50 of the sub-active material layer 3 far away from the current collector 1. Such an arrangement can form a gradient of D50 of the multiple layers of sub-active material layers 3, which can make the electrolyte infiltration effect better, and can make the electrode 100 have more excellent processing performance and electrochemical performance.

[0056] Satisfy the relationship: 3μm≤(D50) n ≤20μm, that is, the D50 of each layer of the sub-active material layer 3 can be any value between 3μm and 20μm. For example, the D50 of each layer of the sub-active material layer 3 can be but not limited to 3μm, 8μm, 13μm, 20μm, etc. Such a setting can make the D50 of each layer of the sub-active material layer 3 reasonable, can take into account the processing performance and electrochemical performance of the electrode sheet 100, and can improve the performance of the battery.

[0057] As some embodiments of the present application, the relationship is satisfied: 5μm≤(D50) n ≤13μm, that is, the D50 of each sub-active material layer 3 can be any value between 5μm and 13μm. For example, the D50 of each sub-active material layer 3 can be but not limited to 5μm, 8μm, 13μm, etc. Such a setting can make the D50 of each sub-active material layer 3 more reasonable, can make the electrode 100 have excellent processing performance and electrochemical performance, and can significantly improve the performance of the battery.

[0058] As some embodiments of the present application, the relationship is satisfied: 8μm≤(D50) n ≤13μm, that is, the D50 of each sub-active material layer 3 can be any value between 8μm and 13μm. For example, the D50 of each sub-active material layer 3 can be but not limited to 8μm, 11μm, 13μm, etc. Such a setting can make the D50 of each sub-active material layer 3 more reasonable, can make the electrode 100 have more excellent processing performance and electrochemical performance, and can more significantly improve the performance of the battery.

[0059] In some embodiments of the present invention, the sub-active material layer 3 includes a binder, and the binder content of multiple sub-active material layers 3 decreases from close to the current collector 1 to away from the current collector 1. Such a configuration can make the content of the conductive agent and active material in multiple sub-active material layers 3 increase from close to the current collector 1 to away from the current collector 1, which is beneficial to improving the conductive performance of the electrode 100 and the fast charging performance of the battery.

[0060] In some embodiments of the present invention, the relationship is satisfied: 2≤N≤6, that is, the sub-active material layer 3 included in the active material layer 2 is any value between 2 and 6 layers. For example, the number of layers of the sub-active material layer 3 can be but not limited to 2, 3, 4, 5, 6, etc. Such a setting can make the number of layers of the sub-active material layer 3 reasonable, can improve the fast charging performance and stable cycle performance of the battery, and can also make the processing of the active material layer 2 easier (compared with the active material layer 2 with too many sub-active material layers 3).

[0061] The pole piece 100 proposed in the present application is verified by comparing the embodiments and comparative examples.

[0062] Embodiment 1:

[0063] First coating slurry: Add 840g of deionized water to a beaker, then add 8g of binder CMC (0.8%), stir magnetically until dissolved, then add 967g of negative electrode active material artificial graphite (96.7%), 5g of conductive agent SuperP (0.5%), 22g of binder SBR (1%) and 166g of PAA (1%) to the beaker and stir to form a stable and uniform negative electrode slurry.

[0064] Second coating slurry: Add 840g of deionized water to a beaker, then add 15g of binder CMC (1.5%), stir magnetically until dissolved, then add 960g of negative electrode active material artificial graphite (96%), 5g of conductive agent SuperP (0.5%) and 45g of binder SBR (2%) to the beaker and stir to form a stable and uniform negative electrode slurry.

[0065] The third coating slurry: add 840g of deionized water into a beaker, add 15g of binder CMC (1.6%), stir magnetically until dissolved, then add 960g of negative electrode active material artificial graphite (96.1%), 5g of conductive agent SuperP (0.5%) and 45g of binder SBR (1.8%) into the beaker and stir to form a stable and uniform negative electrode slurry.

[0066] Fourth coating slurry: Add 17g of deionized water to a beaker, then add 15g of binder CMC (1.6%), stir magnetically until dissolved, then add 960g of negative electrode active material artificial graphite (96.4%), 5g of conductive agent SuperP (0.5%) and 45g of binder SBR (1.5%) to the beaker and stir to form a stable and uniform negative electrode slurry.

[0067] The coating slurry is uniformly coated on the copper foil of the current collector 1, and a single-sided electrode sheet 100 is obtained after a drying process. The coating process is repeated on the other side of the copper foil, and the double-sided coated electrode sheet 100 is dried to obtain the first sub-active material layer 31; the second coating slurry is coated on the surface of the first sub-active material layer 31 and then dried to obtain the second sub-active material layer 32; similarly, the third sub-active material layer 33 and the fourth sub-active material layer 34 can be obtained by coating in sequence, and a negative electrode sheet 100 with four sub-active material layers 3 is obtained after a rolling process.

[0068] In the prepared negative electrode sheet 100, the thickness of the current collector 1 is 6 μm, and the total thickness of the active coating is 22.5 μm, 30 μm, 45 μm, and 90 μm, respectively.

[0069] Lithium-ion battery: The negative electrode sheet 100 prepared above is assembled with a separator, a lithium sheet, and an electrolyte to obtain a lithium-ion button battery, wherein the separator is a PE-based film; and the main components of the electrolyte are LiPF6 and EC / DMC.

[0070] Examples 2 to 12 and comparative examples 1 to 3 adopt the same method as Example 1, select negative electrode active materials with different particle sizes, and adjust the process parameters during coating, drying and rolling so that the relevant parameters of the porosity, compaction density and D50 value of the four-layer active material layer 3 are as shown in Table 1, and different negative electrode sheets 100 are prepared respectively. The data are summarized as shown in the following table, where A is an example and DA is a comparative example.

[0071]

[0072] Experimental example:

[0073] (1) Room temperature 3C rate discharge performance test:

[0074] The lithium ion button cells provided in the embodiments and comparative examples were charged at 0.33C to the termination voltage at room temperature, with a cut-off current of 0.05C, and allowed to stand for 30 minutes. They were discharged at 1C and 3C to the termination voltage, respectively, and the discharge capacities were recorded. The 3C discharge capacity was compared with the 1C discharge capacity to obtain the room temperature 3C rate discharge performance.

[0075] (2) Test of capacity retention rate after 200 cycles at room temperature:

[0076] The lithium ion button cells provided in the embodiments and comparative examples were charged at room temperature at 1C to the final voltage, with a cut-off current of 0.05C, and left to stand for 30 minutes; discharged at 1C to the final discharge voltage, the discharge capacity was recorded, and left to stand for 30 minutes;

[0077] The charge and discharge cycle was repeated for 200 cls and the capacity retention rate data was recorded. The capacity retention rate was the ratio of the discharge capacity in each cycle to the discharge capacity in the first cycle, in %.

[0078] The data of Examples 1 to 12 and Comparative Examples 1 to 3 are summarized in the following table.

[0079]

[0080] Combining the data in the above two tables, it can be seen that when the first active material sub-layer 31 , the second active material sub-layer 32 , the third active material sub-layer 33 and the fourth active material sub-layer 34 all meet the conditions defined in the present application, the performance is excellent.

[0081] The battery according to the embodiment of the present invention includes an electrode assembly, the electrode assembly includes: a first electrode sheet, a second electrode sheet and a diaphragm, the first electrode sheet and / or the second electrode sheet is the above-mentioned electrode sheet 100, the first electrode sheet, the diaphragm and the second electrode sheet are assembled to form an electrode assembly, and the performance parameter Z of the N-layer sub-active material layer 3 satisfies Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 The compaction density, porosity and D50 of each sub-active material layer 3 can be reasonably configured, which is beneficial to the infiltration of the electrolyte and can improve the fast charging performance and stable cycle performance of the battery.

[0082] According to an embodiment of the present invention, the electric device includes the above-mentioned battery, by making the performance parameter Z of the N-layer sub-active material layer 3 satisfy Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 The compaction density, porosity and D50 of each sub-active material layer 3 can be reasonably configured, which is beneficial to the infiltration of the electrolyte and can improve the fast charging performance and stable cycle performance of the battery.

[0083] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0084] In the description of the present invention, "first feature" or "second feature" may include one or more of the features.

[0085] In the description of the present invention, "plurality" means two or more.

[0086] In the description of the present invention, a first feature being “on” or “under” a second feature may include that the first and second features are directly in contact with each other, or may include that the first and second features are not in direct contact with each other but are in contact with each other via another feature therebetween.

[0087] In the description of the present invention, “on”, “over” and “above” a first feature from a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0089] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A pole piece (100), characterized in that: include: A current collector (1) and an active material layer (2), wherein the active material layer (2) is provided on at least one side of the current collector (1) along the thickness direction of the current collector (1); The active material layer (2) comprises N sub-active material layers (3), N being a positive integer greater than 1, and the performance parameter of the sub-active material layer (3) being Z, Z n Not less than Z n-1 And at least one Z n Greater than Z n-1 , according to the formula Z n =(1-p n )×c n ×100 / (π×(D 50 ) n 2 ) determines the performance parameter Z corresponding to the sub-active material layer (3), wherein p n is the porosity of the nth active material layer (3), c n is the compaction density of the nth active material layer (3), (D50) n It is the particle size corresponding to the cumulative particle size distribution number of the active material in the n-th active material layer (3) reaching 50%.

2. The pole piece (100) according to claim 1, characterized in that: Satisfy the relationship: Z n >Z n-1 .

3. The pole piece (100) according to claim 1, characterized in that: Satisfy the relationship: 0.08≤Z n ≤4.

81.

4. The pole piece (100) according to claim 1, characterized in that: Satisfies the relationship: p n-1 ≥p n ; And / or, satisfy the relationship: 0.15≤p n ≤0.

40.

5. The pole piece (100) according to claim 1, characterized in that: Satisfies the relationship: c n-1 ≥c n ; And / or, satisfy the relationship: 1.3g / cm 3 ≤c n ≤1.7g / cm 3 .

6. The pole piece (100) according to claim 1, characterized in that: Satisfies the relationship: (D50) n-1 ≥(D50) n ; And / or, satisfy the relationship: 3μm≤(D50) n ≤20μm.

7. The pole piece (100) according to claim 1, characterized in that: The sub-active material layer (3) comprises a binder, and the binder content of the plurality of sub-active material layers (3) decreases gradually from the direction close to the current collector (1) to the direction away from the current collector (1).

8. The pole piece (100) according to any one of claims 1 to 7, characterized in that: The relationship is satisfied: 2≤N≤6.

9. A battery, characterized in that: The invention comprises an electrode assembly, wherein the electrode assembly comprises: a first pole piece, a second pole piece and a diaphragm, wherein the first pole piece and / or the second pole piece is a pole piece (100) according to any one of claims 1 to 8, and the first pole piece, the diaphragm and the second pole piece are assembled together to form the electrode assembly.

10. An electrical device, characterized in that: Comprising a battery according to claim 9.

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