Negative electrode sheet and preparation method therefor, battery and electric device

Abstract

The present invention relates to the technical field of lithium batteries. Particularly disclosed are a negative electrode sheet and a preparation method therefor, a battery and an electric device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a carbon-based material, and the value of the orientation index (OI) of the negative electrode active material layer satisfies: OI is greater than 0 and less than 30; grooves are formed in the surface of the negative electrode active material layer far away from the negative electrode current collector; and the OI value is the ratio of the intensity of a (004) diffraction peak in an XRD diffraction pattern of the negative electrode active material layer to the intensity of a (110) diffraction peak therein. The negative electrode sheet has a higher charging rate and also a longer fast-charging cycle life.

Description

Negative electrode sheet, preparation method thereof, battery, and electric device

[0001] Priority information

[0002] The present disclosure claims priority to and the benefit of the patent application with the patent application number 2024113514492 filed on September 25, 2024 with the China National Intellectual Property Bureau, and incorporates it herein in its entirety by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of lithium batteries, and in particular to a negative electrode sheet, a preparation method thereof, a battery, and an electric device. BACKGROUND

[0004] With the rapid development and intensifying competition of the new energy automobile industry, higher requirements are put forward for the performance of power batteries, i.e. higher energy density and shorter charging time. For the performance requirement of high energy density, the current common way is to increase the electrode area density and compaction. With the increase of the area density and compaction, for the same capacity design, the number of layers of the electrode sheet can be reduced, and then the proportion of non-active substances such as current collectors and separators can be reduced, so as to realize the increase of energy density. For the performance requirement of shorter charging time, the common way is to reduce the electrode area density and compaction. With the reduction of the area density and compaction, the thickness of the electrode sheet is reduced, the porosity is increased, and the lithium ion transmission capacity is enhanced, so as to realize fast charging. That is, increasing the electrode area density and compaction can realize the performance requirement of high energy density, and reducing the electrode area density and compaction can realize fast charging. However, these two ways are contradictory, and high energy density and shorter charging time cannot be realized at the same time by these ways, because with the increase of the area density and compaction, the thickness of the electrode is increased, which leads to the lengthening of the transmission path of lithium ions. With the increase of the compaction, the porosity is reduced, and under high compaction, the graphite particles of the negative electrode tend to arrange in parallel to the direction of the current collector. The ion passage formed by the porosity between the electrode material particles from the electrode surface to the bottom of the electrode has a large tortuosity, the transmission path of lithium ions is lengthened, the transmission rate of lithium ions is reduced, a large polarization resistance is generated in the process of large current charging, and thus poor fast charging performance is caused. At the same time, high compaction also leads to the densification of the surface layer of the electrode, and the wettability of the electrolyte to the electrode is reduced, so that the fast charging cycle life is shortened. Therefore, an electrode capable of realizing high energy density and shorter charging time needs to be provided. SUMMARY

[0005] The present disclosure aims to at least partly solve one of the technical problems in the related art. To this end, the present disclosure provides a negative electrode sheet, a preparation method thereof, a battery, and an electric device. The negative electrode sheet has a faster charging rate, and also has a longer fast charging cycle life.

[0006] To this end, the first aspect of the present disclosure provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector;

[0007] The negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a carbon-based material, and the OI value of the negative electrode active material layer satisfies: 0

[0008] The negative electrode active material layer is provided with a groove away from the surface of the negative electrode current collector.

[0009] The orientation degree OI value is the intensity ratio of the (004) diffraction peak to the (110) diffraction peak in the XRD diffraction pattern of the negative electrode active material layer.

[0010] The present disclosure finds that when the orientation degree OI value of the negative electrode active material layer satisfies 0

[0011] According to the embodiments of the present disclosure, the OI value of the negative electrode active material layer satisfies: 0.1

[0012] According to the embodiments of the present disclosure, the depth d of the groove, the compaction density V of the negative electrode sheet, and the orientation degree OI value of the carbon-based material satisfy:

[0013] According to the embodiments of the present disclosure, the depth of the groove is 10

[0014] And / or, the width of the groove is 20

[0015] According to the embodiments of the present disclosure, the compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9 g / cm 3 .

[0016] According to the embodiments of the present disclosure, the compaction density of the negative electrode sheet is 1.5 g / cm 3 -1.7 g / cm 3 .

[0017] According to an embodiment of the present disclosure, the grooves include a plurality of first grooves and a plurality of second grooves, the first grooves extending along a length direction of the negative current collector, the second grooves extending along a width direction of the negative current collector, the first grooves intersecting with the second grooves;

[0018] wherein a distance between adjacent second grooves is g1, a distance between adjacent first grooves is g2, the g1 and the g2 satisfy: 0.1≤g1 / g2≤50.

[0019] According to an embodiment of the present disclosure, the g1 is 100μm-5000μm, and the g2 is 100μm-1000μm.

[0020] According to an embodiment of the present disclosure, the areal density of the negative tab is 150g / m 2 -500g / m 2 .

[0021] According to an embodiment of the present disclosure, the areal density of the negative tab is 200g / m 2 -300g / m 2 .

[0022] According to an embodiment of the present disclosure, the tortuosity of the negative active material layer is 2.2-3.5.

[0023] The second aspect of the present disclosure provides a preparation method of the negative tab of the first aspect, the preparation method comprising:

[0024] preparing a negative active slurry, the negative active slurry comprising a carbon-based material, coating the negative active slurry on at least one side surface of a negative current collector;

[0025] processing the negative active slurry by a magnetic induction orientation device, drying and rolling to obtain a negative active material layer;

[0026] slotting the surface of the negative active material layer away from the negative current collector to obtain the negative tab.

[0027] Thus, the negative tab is obtained, in which the carbon-based material particles are arranged according to a certain orientation and the surface of the tab has grooves. When the negative tab is used in a battery, the transmission rate of lithium ions can be improved, the wetting ability of electrolyte to the electrode can be improved, and thus the fast charging ability can be improved, realizing a longer fast charging cycle life.

[0028] The third aspect of the present disclosure provides a battery, comprising the negative tab of the first aspect.

[0029] Thus, the battery has good fast charging performance.

[0030] The fourth aspect of the present disclosure provides a power consuming device comprising the battery of the third aspect.

[0031] Thus, the power consuming device has all the advantages of the battery, which are not repeated here.

[0032] Additional aspects and advantages of the present disclosure will be in part apparent and in part pointed out thereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and / or additional aspects and advantages of the present disclosure will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0034] FIG. 1 shows a structural schematic diagram of a negative electrode sheet provided by the present disclosure;

[0035] FIG. 2 shows a structural schematic diagram of a negative electrode sheet surface provided by the present disclosure. DETAILED DESCRIPTION

[0036] Embodiments of the present disclosure are described in detail below. The embodiments described below are examples only and are not intended to limit the present disclosure, which can be embodied in various forms.

[0037] It should be noted that the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. Further, in the description of the present disclosure, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0038] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be approximations that allow for significant variation. Within each range, other points are included, and the endpoints are not included unless otherwise specified. Other ranges not explicitly delineated are also contemplated.

[0039] For the purpose of the present disclosure, certain technical and scientific terms are specifically defined below. Unless otherwise clearly indicated, all other technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0040] In the present disclosure, the term "comprising" or "including" is an open-ended expression, i.e. including the indicated content of the present disclosure, but not excluding other aspects.

[0041] According to an embodiment of the present disclosure, the first aspect of the present disclosure provides a negative electrode sheet, as shown in FIG. 1, comprising a negative electrode current collector and a negative electrode active material layer arranged on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a carbon-based material, and the orientation degree (OI) value of the negative electrode active material layer satisfies 0 < OI < 30; and a groove is arranged on the surface of the negative electrode active material layer away from the negative electrode current collector.

[0042] wherein the orientation degree (OI) value is the intensity ratio of the (004) diffraction peak to the (110) diffraction peak in the XRD diffraction pattern of the negative electrode active material layer.

[0043] To solve the problem that high energy density and short charging time cannot be simultaneously achieved in the prior art, the present disclosure provides an electrode structure in which electrode material particles are arranged in an orientation and the electrode surface has a groove. Specifically, in the prior art, after the prepared electrode sheet is rolled, the electrode material particles tend to be arranged in a direction parallel to the current collector. This arrangement orientation will result in a large tortuosity of the pores formed between the electrode material particles, a long path for lithium ions to reach the bottom of the electrode from the electrode surface, a low transmission efficiency of lithium ions, and thus a large diffusion impedance, which affects the fast charging performance of the battery. The present disclosure adjusts the arrangement orientation of the carbon-based material in the electrode, so that the carbon-based material particles of the negative electrode are more likely to be arranged in a direction perpendicular to the current collector. This arrangement greatly reduces the tortuosity of the ion path formed by the pores between the electrode material particles from the electrode surface to the bottom of the electrode, thereby shortening the transmission path of lithium ions, enhancing the diffusion ability of lithium ions, reducing the polarization resistance during large current charging, and improving the fast charging performance. At the same time, the groove on the electrode surface has a capillary effect, which can greatly improve the wettability of the electrolyte to the electrode, and also has a certain liquid storage effect, avoiding the occurrence of lithium precipitation due to local electrolyte concentration being too low or being consumed too quickly, thereby realizing a longer fast charging cycle life.

[0044] Specifically, the orientation degree OI value of the negative electrode active material layer is related to the degree of arrangement orientation of the carbon-based material particles in the electrode, and the OI value of the high surface density and high compaction negative electrode sheet prepared conventionally is usually above 30, and the OI value of the negative electrode active material layer in the negative electrode sheet provided by the present disclosure satisfies 0 < OI < 30, and as some specific examples, the OI value of the negative electrode active material layer can be 0.1, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, etc., preferably 0.1 ≤ OI ≤ 5, indicating that the carbon-based material particles in the negative electrode sheet are more inclined to arrange in the direction perpendicular to the current collector.

[0045] Specifically, the orientation degree OI value of the negative electrode active material layer can be obtained by XRD measurement of the electrode sheet, and the scanning range is 50°-80°, and the intensity of the (004) diffraction peak (54°-55° position) and the (110) diffraction peak (77°-78° position) is obtained from the obtained XRD spectrum, and the OI value is calculated according to the formula OI = I(004) / I(110).

[0046] Specifically, the type of the carbon-based material is not particularly limited, and those skilled in the art can select according to actual needs, and as some specific examples, the carbon-based material can be selected from graphite, soft carbon, hard carbon, etc.

[0047] Specifically, the shape of the groove of the negative electrode active material layer away from the surface of the negative electrode current collector is not particularly limited, and those skilled in the art can select according to actual needs, and as some specific examples, the groove can be a strip-shaped groove. The cross-sectional shape of the groove is also not particularly limited, and those skilled in the art can select according to actual needs, and as some specific examples, the cross-sectional shape can be rectangular, trapezoidal, triangular, and other geometric shapes, preferably triangular.

[0048] According to a specific embodiment of the present disclosure, the depth d (μm) of the groove, the compaction density V (g / cm 3 The orientation degree OI value of the carbon-based material, i.e., the OI value of the negative electrode active coating layer, satisfies: wherein each physical quantity in the formula is divided by the respective unit to convert into dimensionless form. The depth d of the groove is affected by the compaction degree of the pole piece and the particle arrangement orientation of the carbon-based material (i.e., the OI value of the negative active material layer), and for a pole piece with low compaction degree, since the porosity of the pole piece itself is already relatively large, the internal porosity is sufficient to satisfy the diffusion infiltration of the electrolyte, and the area with low surface layer porosity of the pole piece is relatively thin, so the depth of the groove can be set shallow; for a pole piece with high compaction degree, a deeper groove is required, and the OI value also has a similar effect.

[0049] According to a specific embodiment of the present disclosure, the depth of the groove refers to the vertical distance from the bottom of the groove to the edge of its opening, which can be measured using confocal microscopy measurement. Specifically, the depth of the groove is 10-70 μm. The depth of the groove can be selected according to actual needs, and as some specific examples, the depth of the groove can be selected to be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, etc.

[0050] According to a specific embodiment of the present disclosure, the compaction density V of the negative pole piece refers to the mass per unit volume of the pole piece material after compaction in the battery manufacturing process. Specifically, the compaction density of the negative pole piece is 1.2-1.9 g / cm 3 -1.9g / cm 3 , which can be selected according to actual needs, and as some specific examples, the compaction density of the negative pole piece can be selected to be 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , etc., and preferably the compaction density is 1.5-1.7 g / cm 3 -1.7g / cm 3 , so as to meet the design requirements of battery energy density or power performance.

[0051] According to a specific embodiment of the present disclosure, the width of the groove refers to the width at the opening of the groove on the surface of the negative active material layer. The width can be measured using a confocal microscope measurement. Specifically, the width of the groove is 20-150 μm, which can be selected according to actual needs. As some specific examples, the width of the groove can be selected to be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, etc.

[0052] According to a specific embodiment of the present disclosure, the groove includes a plurality of first grooves and a plurality of second grooves, the first grooves extend along the length direction of the negative current collector, the second grooves extend along the width direction of the negative current collector, and the first grooves intersect the second grooves. Specifically, the number of the first grooves and the plurality of second grooves is not particularly limited, and can be selected according to actual needs by those skilled in the art.

[0053] According to a specific embodiment of the present disclosure, the distance between adjacent second grooves is g1, and the distance between adjacent first grooves is g2, as shown in FIG. 2, the g1 and g2 satisfy: 0.1≤g1 / g2≤50. Thus, the wettability of the electrolyte to the electrode is ensured, i.e., when the distance of the grooves in two directions satisfies the above condition, the electrolyte can be uniformly diffused in each region of the electrode sheet, thereby improving the problem of uneven distribution of electrolyte concentration in each region of the electrode sheet during the cycle, avoiding the occurrence of lithium precipitation due to local electrolyte concentration being too low or being consumed too quickly, thereby improving the fast-charging cycle life.

[0054] Specifically, the distance between adjacent grooves is understood as the distance between the centers of two adjacent grooves.

[0055] Specifically, the value of g1 / g2 can be selected from 0.1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc. The value of g1 is not particularly limited, and can be selected by those skilled in the art according to actual needs. As some specific examples, g1 can be selected from 100 μm to 5000 μm, for example, 100 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, 2500 μm, 3000 μm, 3500 μm, 4000 μm, 4500 μm, 5000 μm, etc. The value of g2 is not particularly limited, and can be selected by those skilled in the art according to actual needs. As some specific examples, g2 can be selected from 100 μm to 1000 μm, for example, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, etc. The distance between adjacent grooves can be measured by a confocal microscope.

[0056] According to a specific embodiment of the present disclosure, the area density of the negative electrode sheet refers to the mass per unit area of the battery electrode sheet. Specifically, the area density of the negative electrode sheet is 150 g / m2 to 500 g / m2. 2 -500g / m 2 The area density of the negative electrode sheet can be selected according to actual needs. As some specific examples, the area density of the negative electrode sheet can be selected from 150 g / m2 to 500 g / m2, preferably 200 g / m2 to 300 g / m2. 2 、200g / m 2 、250g / m 2 、300g / m 2 、350g / m 2 、400g / m 2 、450g / m 2 、500g / m 2 , etc. Preferably, the area density is 200 g / m2 to 300 g / m2, so as to meet the design requirements of the energy density or power performance of the battery. 2 -300g / m 2

[0057] According to a specific embodiment of the present disclosure, the tortuosity of the negative electrode active material layer is 2.2 to 3.5. Compared with a conventional electrode sheet (the tortuosity of which is 3.9), the tortuosity is reduced, indicating that the path of lithium ion transmission from the electrode surface to the bottom of the electrode is shortened.

[0058] ​Wherein, the tortuosity refers to that the transport of lithium ions in the electrolyte in the negative active material layer does not proceed along a straight line, but moves in a tortuous manner, and the tortuosity is the degree of reflecting such tortuous movement, and the tortuosity is equal to the ratio of the actual path length of the transport of lithium ions in the internal pores of the negative active coating to the apparent length (macroscopic distance, i.e. the thickness of the negative active coating) passing through the negative active material layer, i.e. the real length of the movement track in the internal pores when the lithium ions pass through the negative active material layer per unit distance.

[0059] The tortuosity of the negative active material layer can be determined by instruments and methods known in the art. For example, it can be obtained by the following method:

[0060] 1. Two identical electrode sheets and separators are assembled into a symmetrical battery;

[0061] 2. After injecting the electrolyte, it is infiltrated;

[0062] 3. Electrochemical impedance test is performed, and the electrode ion impedance Rion is fitted;

[0063] 4. The thickness of the electrode sheet is L, the porosity is τ, and the area is A; the conductivity of the electrolyte is σ;

[0064] Wherein, the thickness L of the electrode sheet can be measured by using a micrometer to measure the thickness, and the average value of 10 points taken in the transverse and longitudinal directions of the electrode sheet is taken as the thickness of the electrode sheet;

[0065] The porosity τ of the electrode sheet can be determined by instruments and methods known in the art. For example, the mercury intrusion method, the specific test method: place the dried sample into a suitable dilatometer, place the dilatometer into a low-pressure test interval, first vacuumize the dilatometer, then press in mercury, and test the mercury intrusion volume from 0 to 30 psi by using nitrogen compression; after the test is completed, place the dilatometer into a high-pressure test interval, test the mercury intrusion volume from 30 to 33000 psi by using oil pressure, and the porosity τ = Vt / V0*100%, wherein Vt is the total volume of the pressed-in mercury, and V0 is the volume of the sample. t

[0066] The conductivity σ of the electrolyte can be determined by instruments and methods known in the art. For example, it can be tested according to the industry standard HG / T4067-2015 "Lithium hexafluorophosphate electrolyte", the measurement temperature of the density instrument is set to 20℃, the sample is injected into the measurement cell of the instrument, and the data is read after measurement.

[0067] 5. The tortuosity is calculated by the formula: ε = (Rion x A x τ x σ) / L.

[0068] The second aspect of the present disclosure provides a preparation method of the negative electrode sheet of the first aspect, comprising the following steps:

[0069] ​(1) preparing a negative active slurry including a carbon-based material, and coating the negative active slurry on at least one side surface of a negative current collector.

[0070] According to a specific embodiment of the present disclosure, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0071] According to a specific embodiment of the present disclosure, the raw material composition of the negative active slurry is not particularly limited, and can be selected by a person skilled in the art according to actual needs. As some specific examples, the negative active slurry can include a negative active material, which can include graphite, and can further include other commonly used negative active materials, such as soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can include at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include at least one of elemental tin, tin oxide compound, and tin alloy.

[0072] Specifically, the negative active slurry can further optionally include a binder. The binder can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0073] Specifically, the negative active material layer can further optionally include a conductive agent. The conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0074] Specifically, the negative active material layer can further optionally include other additives, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC)), etc.

[0075] Specifically, the components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is coated on the surface of the negative current collector.

[0076] (2) treating the negative active slurry by a magnetic induction orientation device, drying, and rolling to obtain a negative active material layer.

[0077] According to a specific embodiment of the present disclosure, the magnetic induction orientation device can be used to orient and arrange the carbon-based material particles in the negative active slurry. The magnetic induction orientation device is not particularly limited, and can specifically be a magnetic block with a uniform magnetic field (magnetic field strength of 0.5-2 T), which is placed on the side of the current collector that is not coated with the negative active slurry during the coating process. The orientation degree of the carbon-based material particles in the negative active coating (i.e., the OI value of the negative active material layer) can be controlled by adjusting the distance between the magnetic block and the copper foil (0-3 mm) and the time for the current collector to pass through the magnetic block (5-60 s).

[0078] According to a specific embodiment of the present disclosure, the drying and rolling methods in this step are not particularly limited, and the drying temperature and time are also not particularly limited, which can be selected according to actual needs by those skilled in the art.

[0079] (3) Slotting the surface of the negative active material layer away from the negative current collector to obtain the negative sheet.

[0080] According to a specific embodiment of the present disclosure, the slotting method is not particularly limited, which can be selected according to actual needs by those skilled in the art. As some specific examples, the slotting can be performed by laser etching, ion beam etching, mechanical indentation, etc., and laser etching is preferred.

[0081] The third aspect of the present disclosure provides a battery comprising the negative sheet of the first aspect.

[0082] According to a specific embodiment of the present disclosure, the battery is a secondary battery. Typically, the battery comprises a positive sheet, a negative sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are inserted and extracted between the positive sheet and the negative sheet. The electrolyte conducts ions between the positive sheet and the negative sheet. The separator is arranged between the positive sheet and the negative sheet to prevent short circuiting of the positive and negative electrodes, while allowing ions to pass through.

[0083] According to a specific embodiment of the present disclosure, the battery is a lithium ion battery.

[0084] According to a specific embodiment of the present disclosure, the positive sheet comprises a positive current collector and a positive active coating arranged on at least one surface of the positive current collector, and the positive active coating comprises a positive active material.

[0085] According to a specific embodiment of the present disclosure, the positive current collector can include a metal foil or a composite positive current collector. For example, the metal foil can employ an aluminum foil. The composite positive current collector can include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer. For example, the composite negative current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material base material (e.g., a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0086] According to a specific embodiment of the present disclosure, the positive active coating layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] According to a specific embodiment of the present disclosure, the positive active coating layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0088] According to a specific embodiment of the present disclosure, the positive electrode sheet can be prepared by dispersing the above-described components for preparing the positive electrode sheet, e.g., the positive active material, the conductive agent, the binder, in a solvent (e.g., N-methylpyrrolidone, NMP) to form a positive electrode slurry; coating the positive electrode slurry on the positive current collector, and then performing processes such as drying, cold pressing, etc., to obtain the positive electrode sheet.

[0089] According to a specific embodiment of the present disclosure, the composition and preparation of the negative electrode sheet are described above.

[0090] According to a specific embodiment of the present disclosure, the type of the separator film is not particularly limited, and any publicly known porous structure separator film having good chemical stability and mechanical stability can be used. In some embodiments of the present disclosure, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0091] According to a specific embodiment of the present disclosure, the positive electrode sheet, the negative electrode sheet, and the separator film can be prepared into an electrode assembly through a winding process or a stacking process.

[0092] According to a specific embodiment of the present disclosure, the above-described battery can include an outer package. The outer package can be used to package the above-described electrode assembly and the electrolyte.

[0093] According to a specific embodiment of the present disclosure, the outer package of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0094] The fourth aspect of the present disclosure provides a power consuming device comprising the battery of the third aspect.

[0095] According to a specific embodiment of the present disclosure, the battery can be used as a power source of the power consuming device, and can also be used as an energy storage unit of the power consuming device. The power consuming device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric car, an electric vehicle, a ship, a spacecraft, etc. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0096] The solutions of the present disclosure will be explained below in combination with examples. Those skilled in the art will understand that the examples below are only for illustrating the present disclosure, and should not be considered as limiting the scope of the present disclosure. If a specific technology or condition is not specified in the examples, it is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase in the market.

[0097] Example 1

[0098] (1) Preparation of electrolyte: mix lithium salt (LiPF6), solvent (EC, EMC, DMC), additive (VC) in a mass ratio of 12.6:29.2:32.6:23.2:1.9 uniformly, and make the lithium salt fully dissolved;

[0099] (2) Preparation of positive electrode sheet: mix positive electrode material lithium iron phosphate (LiFePO4), binder PVDF, conductive agent (carbon black, carbon nanotube), and solvent NMP (mass ratio is 100:1.8:0.8:55) uniformly to form a slurry, and get a positive electrode sheet with a surface density of 440 g / m 2 , and a compactness of 2.65 g / cm 3 after coating, baking, and rolling;

[0100] (3) Preparation of the negative electrode sheet: the negative electrode material graphite, conductive agent carbon black, thickening agent CMC, binder SBR and solvent water (mass ratio 100:1:1.6:1.35:110) are mixed uniformly to form a slurry, and a layer of slurry with uniform thickness is coated on the front and back of the current collector respectively, the graphite particles are oriented and arranged by the magnetic induction orientation device, the distance between the magnetic block and the copper foil and the time of the current collector passing through the magnetic block are adjusted so that the OI value of the electrode sheet is close to 0.1, and then the electrode sheet with a surface density of 200 g / m 2 and a compacted density of 1.6 g / cm 3 is obtained by baking and rolling. Then the laser is used to etch a groove with a minimum unit of square and a width of 20 μm, a depth of 10 μm and a transverse and longitudinal interval of 100 μm;

[0101] (4) Separator: the selected separator is a polypropylene (PP) separator;

[0102] (5) Assembly of the battery: the above positive electrode sheet, separator and negative electrode sheet are stacked in order so that the separator is between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then the bare cell is wound; after welding the tab, the bare cell is placed in the outer packaging shell, dried and then injected with the above electrolyte, and finally the battery with a design capacity of 900 mAh is obtained after vacuum packaging, standing, formation, shaping and the like.

[0103] Example 2

[0104] The difference between Example 2 and Example 1 is only that:

[0105] The laser is used to etch a groove with a minimum unit of square and a width of 20 μm, a depth of 10 μm, a transverse interval (g1) of 2500 μm and a longitudinal interval (g2) of 100 μm.

[0106] Example 3

[0107] The difference between Example 3 and Example 1 is only that:

[0108] The compacted density of the electrode sheet is 1.7 g / cm 3 .

[0109] The laser is used to etch a groove with a minimum unit of square and a width of 20 μm, a depth of 10 μm, a transverse interval (g1) of 2500 μm and a longitudinal interval (g2) of 550 μm.

[0110] Example 4

[0111] The difference between Example 4 and Example 1 is only that:

[0112] The orientation degree of the graphite particles is changed to make the OI value of the pole piece close to 2.5.

[0113] The areal density of the pole piece is 250 g / m 2 , and the compacted density is 1.5 g / cm 3 .

[0114] The laser is used to etch grooves on the surface layer of the pole piece, and the minimum unit is a square groove with a width of 85 μm, a depth of 40 μm, a lateral interval (gl) of 100 μm, and a longitudinal interval (g2) of 1000 μm.

[0115] Example 5

[0116] The difference between Example 5 and Example 1 is only that:

[0117] The orientation degree of the graphite particles is changed to make the OI value of the pole piece close to 5.

[0118] The areal density of the pole piece is 300 g / m 2 , and the compacted density is 1.5 g / cm 3 .

[0119] The laser is used to etch grooves on the surface layer of the pole piece, and the minimum unit is a square groove with a width of 150 μm, a depth of 70 μm, a lateral interval (gl) of 5000 μm, and a longitudinal interval (g2) of 100 μm.

[0120] Example 6

[0121] The difference between Example 6 and Example 1 is only that:

[0122] The compacted density of the pole piece is 1.2 g / cm 3 .

[0123] Example 7

[0124] The difference between Example 7 and Example 1 is only that:

[0125] The compacted density of the pole piece is 1.9 g / cm 3 .

[0126] Example 8

[0127] The difference between Example 8 and Example 1 is only that:

[0128] The orientation degree of the graphite particles is changed to make the OI value of the pole piece close to 10.

[0129] Example 9

[0130] The difference between Example 9 and Example 1 is only that:

[0131] The degree of orientation of the graphite particles is changed so that the OI value of the electrode sheet approaches 20.

[0132] Example 10

[0133] Example 10 differs from Example 1 only in that:

[0134] The degree of orientation of the graphite particles is changed so that the OI value of the electrode sheet approaches 29.

[0135] Comparative Example 1

[0136] Comparative Example 1 differs from Example 1 only in that:

[0137] A groove is not formed on the surface of the electrode.

[0138] Comparative Example 2

[0139] Comparative Example 2 differs from Example 1 only in that:

[0140] A magnetic field orientation is not applied and a groove is not formed on the surface of the electrode.

[0141] Comparative Example 3

[0142] Comparative Example 3 differs from Example 1 only in that:

[0143] A magnetic field orientation is not applied.

[0144] Test Example

[0145] (1) Groove depth d, width w, second groove distance gl, first groove distance g2 test

[0146] The depth d, width w, second groove distance gl, and first groove distance g2 of the groove formed on the surface of each electrode sheet in the examples and comparative examples were measured using a confocal microscope.

[0147] (2) Negative electrode sheet compactness V, area density A test

[0148] The thickness d of the negative electrode sheet and the current collector copper foil after rolling was measured using a micrometer N , d Cu (unit: μm), a 15 mm negative electrode sheet and copper foil were cut using a circular cutter with a diameter of 15 mm, and weighed using an electronic balance to obtain m N , m Cu (unit: mg), then the negative electrode sheet compactness V = 4 x (m N -m Cu ) ÷ (15 x 15 x 3.14 x (d N -d Cu )) x 1000, and the area density A = 4 x (m N -m Cu(15 x 15 x 3.14) x 1000;

[0149] (3) Pole piece OI value test

[0150] Place the negative pole piece on the sample table of the XRD diffractometer for testing, the scanning range is 50°-80°, obtain the intensity of the (004) diffraction peak (54°-55° position) and the intensity of the (110) diffraction peak (77°-78° position) from the obtained XRD spectrum, and calculate the OI value of the pole piece according to the formula OI = I(004) / I(110);

[0151] (4) Liquid phase diffusion impedance test

[0152] Assemble two same negative pole pieces and separators in order to form a pole core; place the pole core in an outer packaging shell, inject electrolyte, and go through processes such as packaging and infiltration to obtain a liquid phase diffusion impedance battery. Use an electrochemical workstation to perform liquid phase diffusion impedance test in a frequency range of 100000 Hz-0.05 Hz, plot the obtained data of Z'(X axis) and -Z"(Y axis), take the second derivative of all data in the curve, find the point where the absolute value of the second inverse between the 25th and 60th data is the maximum, which is the inflection point, and linearly fit the data from the third point to the thirteenth point after the inflection point to obtain the fitted intercept a and slope b. Use Zview software to fit the impedance data to obtain Rs, and the fitted equivalent circuit is Subsequently, calculate the liquid phase diffusion impedance Rion according to the following formula:

[0153] (5) Tortuosity test of negative active coating

[0154] 1) Assemble two same pole pieces and separators to form a symmetrical battery;

[0155] 2) Infiltrate after injecting electrolyte;

[0156] 3) Perform electrochemical impedance test to obtain the electrode ion impedance Rion;

[0157] 4) The thickness of the pole piece is L, the porosity is τ, and the area is A; the conductivity of the electrolyte is σ;

[0158] The thickness L of the pole piece is measured using a micrometer, and 10 points are taken in the transverse and longitudinal directions of the pole piece using the micrometer, and the average value is taken as the thickness of the pole piece;

[0159] The porosity τ of the pole piece can be measured by using the instruments and methods known in the art. For example, the mercury intrusion method, the specific test method: the dried sample is placed into a suitable dilatometer, the dilatometer is placed into a low-pressure test interval, the dilatometer is first vacuumed, then the mercury is pressed in, and the mercury intrusion amount from 0 to 30 psi is tested by using the nitrogen compression method; after the test is completed, the dilatometer is placed into a high-pressure test interval, the mercury intrusion amount from 30 to 33,000 psi is tested by using the oil pressure method, and the porosity τ = V t / V0*100%, wherein V t is the total volume of the mercury pressed in, and V0 is the sample volume.

[0160] The conductivity σ of the electrolyte can be measured by using the instruments and methods known in the art. For example, the industry standard HG / T 4067-2015 “Lithium Hexafluorophosphate Electrolyte” can be referred to, the measurement temperature of the density instrument is set to 20°C, the sample is injected into the measurement cell of the instrument, the measurement is performed, and the data is read.

[0161] 5) The tortuosity is calculated by using the formula: ε = (Rion x A x τ x σ) / L.

[0162] (6) Energy density test

[0163] At room temperature, the weight W (kg) of the battery prepared in the examples and the comparative examples is measured by using an electronic balance, and then the battery is tested according to the following steps:

[0164] 1) 1 / 3C constant current discharge to 2.0V, and stand for 30 min;

[0165] 2) 1 / 3C constant current constant voltage charging to 3.8V, and the cutoff current is 0.05C;

[0166] 3) 1 / 3C constant current discharge to 2.0V, and stand for 30 min;

[0167] 4) Cycle steps 2)-3) three times, and record the last discharge energy E (Wh);

[0168] Then the energy density ED = E / W.

[0169] (7) Fast charging capacity test

[0170] At room temperature, the battery prepared in the examples and the comparative examples is tested according to the following steps:

[0171] 1) 0.2C constant current discharge to 2.0V, and stand for 30 min;

[0172] 2) 0.2C constant current charging to 3.8V, and stand for 30 min (#0.2C charging#);

[0173] 3) 0.2C constant current discharge to 2.0V, and stand for 30 min;

[0174] 4) 3.0C constant current charge to 3.8V, rest for 30min (#3C charge #);

[0175] The capacity charged by 3C / capacity charged by 0.2C is the 3C / 0.2C charge ratio.

[0176] (8) fast charge cycle test

[0177] At room temperature, the batteries prepared from the examples and comparative examples were tested according to the following steps:

[0178] 1) 1 / 3C constant current discharge to 2.0V, rest for 30min;

[0179] 2) 4C constant current charge for 4.05min, cut-off voltage 3.8V;

[0180] 3) 3.5C constant current charge for 1.03min, cut-off voltage 3.8V;

[0181] 4) 3C constant current charge for 2.2min, cut-off voltage 3.8V;

[0182] 5) 2.5C constant current charge for 1.92min, cut-off voltage 3.8V;

[0183] 6) 2C constant current charge for 2.1min, cut-off voltage 3.8V;

[0184] 7) 1.5C constant current charge for 8.4min, cut-off voltage 3.8V;

[0185] 8) 1 / 3C constant current charge to 3.8V, rest for 10min;

[0186] 9) 1C constant current discharge to 2.0V, rest for 10min, 1 / 3C constant current discharge to 2.0V, record the discharge capacity, stand for 30min;

[0187] 10) according to steps 2)-9), cycle to the capacity attenuation reaches 80%, record the corresponding cycle number.

[0188] The test results are shown in the following table.

[0189] Table 1

[0190] Table 1 continued

[0191] In Table 1, " / " means that there is no.

[0192] The results show that, compared with Comparative Examples 1-3, the graphite particles of Examples 1-10 have a certain orientation arrangement, the battery corresponding to the electrode with a groove structure on the surface of the electrode has a lower liquid-phase diffusion impedance, a smaller tortuosity, a stronger lithium ion diffusion capacity, a better fast-charging performance, and a longer fast-charging cycle life.

[0193] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in an appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0194] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present disclosure, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present disclosure.

Claims

1. A negative electrode sheet, wherein, The negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a carbon-based material. The orientation degree OI value of the negative electrode active material layer satisfies 0 The negative electrode active material layer is provided with grooves away from the surface of the negative electrode current collector. The orientation degree OI value is the intensity ratio of the (004) diffraction peak to the (110) diffraction peak in the XRD diffraction pattern of the negative electrode active material layer.

2. The negative electrode sheet according to claim 1, wherein The OI value of the negative electrode active material layer satisfies 0.1≤OI≤5.

3. The negative electrode sheet according to claim 1 or 2, wherein The depth d of the recess, the compaction density V of the negative electrode sheet, and the degree of orientation of the carbon-based material, i.e., the OI value of the negative electrode active material layer satisfy:

4. The negative electrode sheet according to any one of claims 1 to 3, wherein The depth of the grooves is 10μm-70μm. The width of the grooves is 20μm-150μm.

5. The negative electrode sheet according to any one of claims 1 to 4, wherein The compacted density of the negative electrode sheet is 1.2 g / cm 3 -1.9 g / cm 3 .

6. The negative electrode sheet according to any one of claims 1 to 5, wherein The compacted density of the negative electrode sheet is 1.5 g / cm 3 -1.7 g / cm 3 .

7. The negative electrode sheet according to any one of claims 1-6, wherein The grooves comprise a plurality of first grooves and a plurality of second grooves, the first grooves extend along the length direction of the negative electrode current collector, the second grooves extend along the width direction of the negative electrode current collector, and the first grooves intersect with the second grooves. The distance between adjacent second grooves is g1, and the distance between adjacent first grooves is g2, and the g1 and g2 satisfy 0.1≤g1 / g2≤50.

8. The negative electrode sheet according to claim 7, wherein The g1 is 100μm-5000μm, and the g2 is 100μm-1000μm.

9. The negative electrode sheet according to any one of claims 1-8, wherein, The face density of the negative electrode sheet is 150 g / m 2 - 500 g / m 2 .

10. The negative electrode sheet according to any one of claims 1 to 9, wherein The face density of the negative electrode sheet is 200 g / m 2 -300 g / m 2 .

11. The negative electrode sheet according to any one of claims 1 to 10, wherein The tortuosity of the negative electrode active material layer is 2.2-3.

5.

12. A method for producing the negative electrode sheet according to any one of claims 1 to 11, wherein The negative electrode active material layer is prepared by the following steps: Preparation of a negative electrode active slurry comprising a carbon-based material, coating the negative electrode active slurry on at least one side surface of a negative electrode current collector; Treatment of the negative electrode active slurry by a magnetic induction orientation device, drying and rolling to obtain a negative electrode active material layer; Grooving treatment is performed on the surface of the negative electrode active material layer away from the negative electrode current collector to obtain the negative electrode sheet.

13. A battery, wherein, The battery comprises the negative electrode sheet of any one of claims 1-11.

14. An electrical device, comprising: The battery comprises the negative electrode sheet of claim 13.

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