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

Abstract

The present disclosure relates to the technical field of lithium batteries, and relates to a negative electrode sheet, a preparation method therefor, a battery, and an electrical device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer disposed on the surface of at least one side of the negative electrode current collector. The negative electrode active layer comprises a negative electrode active substance, and the negative electrode active substance comprises a carbon-based material. The negative electrode active layer has an orientation index (OI) value of 0.1-30, and the surface of the negative electrode active layer away from the negative electrode current collector is provided with channels. The OI value is an intensity ratio of a (004) diffraction peak to a (110) diffraction peak of the negative electrode active layer in an XRD diffraction pattern.

Description

Negative plate, preparation method thereof, battery, and electric device

[0001] Priority information

[0002] This application claims priority to and the benefit of the filing date of Chinese Patent Application No. 2024113482415, filed September 25, 2024, and is incorporated herein by reference in its entirety. TECHNICAL FIELD

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

[0004] The fast charging capability of a lithium ion battery is an important indicator for measuring the performance of a product. When the battery is charging, lithium ions diffusing from the positive electrode need to diffuse from the surface of the negative electrode to each negative electrode particle along the pore channel inside the negative electrode to be embedded. The electrode pore structure of the negative electrode and the diffusion capability of lithium ions in the negative electrode will directly affect the charging capability of the battery. Therefore, for the improvement of the fast charging capability, it is particularly important to optimize the design of the negative electrode structure to reduce the tortuosity of the electrode and shorten the transmission path of lithium ions so as to improve the diffusion capability of lithium ions. At present, the fast charging capability is mainly improved by reducing the coating amount and compaction of the negative plate. However, this only increases the porosity of the electrode and reduces the thickness of the plate, and does not realize the optimal design of the electrode pore structure.

[0005] DISCLOSURE

[0006] 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 plate, a preparation method thereof, a battery, and an electric device. The negative plate increases the channel for the transmission of lithium ions from the surface of the electrode to the bottom of the plate, and also shortens the path for the transmission of lithium ions from the surface of the electrode to the bottom of the electrode, thereby significantly improving the charging capability of the battery.

[0007] To this end, the first aspect of the present disclosure provides a negative plate, comprising a negative current collector and a negative active layer arranged on at least one side surface of the negative current collector, the negative active layer comprising a negative active material, the negative active material comprising a carbon-based material, the orientation degree (OI) value of the negative active layer being 0.1-30, and the surface of the negative active layer away from the negative current collector being provided with a pore channel.

[0008] 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 active layer.

[0009] The present disclosure finds that when the OI value of the negative active layer is 0.1-30, the arrangement orientation of the carbon-based material particles in the electrode is perpendicular or close to perpendicular to the direction of the current collector, at this time the bending degree of the pore structure formed between the particles is reduced, the path experienced by lithium ions from the surface of the electrode to the bottom of the electrode is shortened, the transmission rate of lithium ions can be improved, and the charging capacity can be improved. At the same time, the channels arranged on the surface of the negative active layer away from the negative current collector can increase the number of channels for lithium ions to enter the inside of the electrode from the surface of the electrode, further improving the diffusion capacity of lithium ions and improving the charging capacity.

[0010] According to an embodiment of the present disclosure, the OI value of the negative active layer is 0.1-10;

[0011] And / or, the angle between the arrangement orientation direction of the carbon-based material particles in the negative plate and the negative current collector is 45°-90°.

[0012] According to an embodiment of the present disclosure, the channel penetrates at least part of the negative active layer in the thickness direction;

[0013] And / or, the depth of the channel is less than the thickness of the negative active layer;

[0014] And / or, the ratio of the depth of the channel to the thickness of the negative active layer is 0.1-0.8;

[0015] And / or, the depth of the channel is 10 μm-50 μm;

[0016] And / or, the thickness of the negative active layer is 62 μm-95 μm.

[0017] According to an embodiment of the present disclosure, the percentage of the total area of the channel to the area of the surface of the negative active layer away from the negative current collector is 0.20%-78%.

[0018] According to an embodiment of the present disclosure, the pore size of the channel is 5 μm-40 μm.

[0019] According to an embodiment of the present disclosure, the surface of the negative active layer away from the negative current collector has at least two channels, and the spacing between any two adjacent channels is 20 μm-100 μm.

[0020] According to an embodiment of the present disclosure, the tortuosity of the negative active layer is 2.2-3.5.

[0021] The second aspect of the present disclosure provides a preparation method of the negative plate of the first aspect, the preparation method comprising:

[0022] Preparation of a negative active paste, the negative active paste comprising a carbon-based material, coating the negative active paste on at least one side surface of the negative current collector;

[0023] The negative active paste coating process is processed by a magnetic induction orientation device, and a negative active layer is obtained by drying and rolling.

[0024] The surface of the negative active layer away from the negative current collector is treated by opening holes to obtain the negative sheet.

[0025] Thus, the negative sheet is obtained, in which the carbon-based material particles are arranged in a certain orientation and the surface of the sheet has a pore structure. The negative sheet used in the battery can improve the transmission rate of lithium ions and improve the charging capacity.

[0026] The third aspect of the present disclosure provides a battery, which comprises the negative sheet of the first aspect.

[0027] Thus, the battery has good fast charging performance.

[0028] The fourth aspect of the present disclosure provides a power-using device, which comprises the battery of the third aspect.

[0029] Thus, the power-using device has all the advantages of the battery, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and / or additional aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0031] FIG. 1 shows a structural schematic diagram of the negative sheet provided by the present disclosure;

[0032] FIG. 2 shows a structural schematic diagram of the negative sheet in the prior art. DETAILED DESCRIPTION

[0033] The embodiments of the present disclosure are described in detail below. The embodiments described below are exemplary and are only used to explain the present disclosure, and cannot be understood as a limitation of the present disclosure.

[0034] It should be noted that the terms "first", "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features limited by "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.

[0035] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the practice of the application. Any numerical range recited herein is intended to include all sub-ranges of the same exact number of increments subsumed therein. For example, a range of 1 to 10 is intended to include all sub-ranges between and including the values 1 and 10, e.g., 1 to 6.1, 1 to 6.9, 1 to 6, 1 to 4, 4 to 10, 5.5 to 10, etc.

[0036] For the purposes of the present disclosure, certain technical and scientific terms are specifically defined below. Unless explicitly described otherwise, 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.

[0037] In this document, the terms "comprising" or "including" or "containing" are open-ended, that is, they mean including, but not limited to, what is specifically recited.

[0038] In this document, the terms "optionally", "optional" or "may" generally mean that the subsequently described event or circumstance can or can not occur, and the description includes instances where the event or circumstance occurs and instances where it does not.

[0039] According to the embodiments 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 layer arranged on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising a carbon-based material, the orientation degree OI value of the negative electrode active layer being 0.1-30, and the negative electrode active layer being provided with a pore away from the surface of the negative electrode current collector.

[0040] 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 layer.

[0041] The negative active material commonly used in lithium ion batteries is graphite. The shape of graphite particles is generally lamellar and ellipsoidal. After rolling, the graphite particles tend to be arranged parallel to the current collector (see FIG. 2). The inventors found that this arrangement orientation will lead to a large tortuosity of the pores formed between the graphite particles, the path of lithium ions from the electrode surface to the bottom of the electrode becomes longer, the transport efficiency of lithium ions becomes lower, and a large diffusion impedance is generated, which affects the fast charging performance of the battery. In addition, during the rolling process, the surface of the negative electrode directly contacts the rollers of the rolling machine, and the surface after rolling is more likely to form a dense structure, reducing the number of channels for lithium ions to enter the interior of the electrode from the surface of the electrode, limiting the transport capacity of lithium ions, and affecting the fast charging performance of the battery. To solve the above problems, the present disclosure controls the arrangement orientation of carbon-based materials in the electrode, changes the pore structure between the particles of the electrode, and makes the particles of the carbon-based material more inclined to be arranged perpendicular to the current collector. The degree of curvature of the pore structure formed between the particles is reduced, the path of lithium ions to the bottom of the electrode is shortened, thereby improving the transport rate of lithium ions and the charging capacity of the battery. At the same time, the channels are provided on the surface of the electrode, increasing the number of channels for lithium ions to enter the interior of the electrode from the surface of the electrode, further improving the diffusion capacity of lithium ions and the charging capacity of the battery.

[0042] Specifically, the degree of arrangement orientation of carbon-based material particles in the electrode in the electrode sheet is related to the orientation degree OI value of the negative active layer. The arrangement orientation of carbon-based material particles in the electrode refers to the state that the carbon-based material lamella in the cross section of the electrode sheet is perpendicular or close to perpendicular to the current collector. In this case, the angle between the center line of the carbon-based material lamella and the current collector is quantified. According to the experimental verification results, when the angle between the carbon-based material lamella and the current collector is 45°-90°, the preferred orientation arrangement effect is considered to be achieved, and the orientation degree OI value of the carbon-based material in the electrode sheet is 10-0.1.

[0043] Specifically, the angle test between the carbon-based material lamella and the current collector can be specifically as follows: the oriented electrode sheet is exposed to a flat cross section by ion beam grinding and cutting, and a scanning electron microscope (SEM) is used for shooting. The angle between the carbon-based material lamella and the current collector is measured using a picture processing tool.

[0044] Specifically, the orientation degree OI value of the negative active layer in the electrode sheet is the intensity ratio of the (004) diffraction peak to the (110) diffraction peak in the XRD diffraction pattern of the negative active layer, which can be obtained by XRD measurement of the rolled electrode sheet.

[0045] Specifically, the type of carbon-based material is not particularly limited, and those skilled in the art can select according to actual needs. As some specific examples, the carbon-based material can be selected from graphite, soft carbon, hard carbon, etc.

[0046] Specifically, the number of the pores away from the surface of the negative current collector of the negative active layer is not particularly limited, and can be selected by those skilled in the art according to actual needs. As some specific examples, one, two or more can be provided.

[0047] According to a specific embodiment of the present disclosure, the pores penetrate at least part of the negative active layer in the thickness direction, and can be non-penetrating pores, i.e., the depth of the pores is less than the thickness of the negative active layer, and the ratio of the depth of the pores to the thickness of the negative active layer is 0.1-0.8. As some specific examples, the ratio of the depth of the pores to the thickness of the negative active layer is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc. Thus, additional vertical transmission channels can be provided for lithium ion transmission, the transmission distance of lithium ions is shortened, the tortuosity is reduced, the transmission rate of lithium ions is improved, the polarization during high-rate charging and discharging is reduced, and thus the fast charging capability is improved.

[0048] Specifically, the depth of the pores refers to the shortest vertical distance from the starting surface of the pores to the bottom of the pores, i.e., the distance is perpendicular to the plane in which the pores are located, i.e., the surface of the negative active layer away from the surface of the negative current collector, without considering the inclination or bending of the pores.

[0049] According to a specific embodiment of the present disclosure, the depth of the pores is 10-50 μm. Since the surface of the pole piece is relatively dense and has fewer pores after rolling, mainly due to the fact that the surface layer particles tend to be parallel under the action of the rolling force, the depth of the pores is limited to be greater than the thickness of a single graphite particle (the size of a graphite particle is usually between ten and several tens of microns). Specifically, the depth of the pores can be selected according to actual needs. As some specific examples, the depth of the pores can be selected to be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., which can be measured by a confocal microscope. The thickness of the negative active layer is 62-95 μm. As some specific examples, the thickness of the negative active layer is 62 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, etc.

[0050] Specifically, the orientation of the pores can be parallel to the thickness direction of the current collector, i.e., the pores are vertical pores. The shape of the pores in the top view perpendicular to the current collector direction is not particularly limited, and can be selected by those skilled in the art according to actual needs. As some specific examples, a circular shape, a square shape or other regular geometric shapes can be selected, preferably a circular shape. The cross-sectional shape of the pores is also not particularly limited, and can be selected by those skilled in the art according to actual needs. As some specific examples, a rectangular shape, a triangular shape, a trapezoidal shape and other geometric shapes can be selected, preferably a triangular shape.

[0051] According to a specific embodiment of the present disclosure, the total area of the pores accounts for 0.20%-78% of the area of the surface of the negative active layer away from the negative current collector, which can be selected by those skilled in the art according to actual needs. As some specific examples, the total area of the pores accounts for 0.20%, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 78%, etc. of the area of the surface of the negative active layer away from the negative current collector.

[0052] Specifically, the pore area refers to the projected pore profile area of the surface of the pole piece, and the adjustment of the pore area ratio can be achieved by adjusting the pore size and the pore spacing.

[0053] According to a specific embodiment of the present disclosure, the pore size of the pores is 5-40 μm, which can be selected by those skilled in the art according to actual needs. As some specific examples, the pore size of the pores can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc.

[0054] Specifically, the pore size of the pores refers to its size on the surface of the negative active layer, which has different representations for different shapes of the pores. For example, when the pores are circular in the top view shape perpendicular to the direction of the current collector, the pore size is the diameter; when the top view shape is square and rectangular, the pore size can be represented by the side length (for square) or the length and width (for rectangular); when the top view shape is elliptical, the pore size can be represented by the length of the major axis and the minor axis, etc. The pore size of the pores can be specifically measured by a confocal microscope.

[0055] Specifically, the size of the pores and the size of the gap between the negative active materials are close to each other, and too large pores will cause excessive loss of carbon-based materials.

[0056] According to a specific embodiment of the present disclosure, the surface of the negative active layer away from the negative current collector has at least two pores, and the spacing between any two adjacent pores is 20-100 μm.

[0057] Specifically, the surface of the negative active layer away from the negative current collector can be provided with two or more pores, which are preferably arrayed, and the spacing between any two adjacent pores is 20-100 μm, which can be selected by those skilled in the art according to actual needs. As some specific examples, the spacing between any two adjacent pores 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, etc.

[0058] In particular, the distance between the channels is understood as the distance between the centers of the channels.

[0059] According to a specific embodiment of the present disclosure, the tortuosity of the negative active layer is 2.2-3.5. 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.

[0060] wherein the tortuosity refers to the fact that the transmission of lithium ions in the electrolyte in the negative active layer does not proceed along a straight line, but rather meanders, and the tortuosity is a measure of the degree of meandering, the meandering degree being equal to the ratio of the actual path length of lithium ion transmission in the internal pores of the negative active layer to the apparent length of the negative active material layer (macroscopic distance, i.e. the thickness of the negative active layer), i.e. the true length of the trajectory in the internal pores when lithium ion crosses a unit distance of the negative active layer.

[0061] The tortuosity of the negative active layer can be determined by means and methods known in the art. For example, it can be obtained by the following method:

[0062] 1. Two identical electrode sheets and a separator are assembled into a symmetrical battery;

[0063] 2. After injection of the electrolyte, the sample is immersed;

[0064] 3. Electrochemical impedance testing is performed, and the electrode ion impedance Rion is fitted;

[0065] 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;

[0066] wherein the thickness L of the electrode sheet can be measured using a micrometer, 10 points are taken in the transverse and longitudinal directions of the electrode sheet using a micrometer, and the average value is taken as the thickness of the electrode sheet;

[0067] The porosity τ of the electrode sheet can be determined by means 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 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 33,000 psi by oil pressure, and the porosity τ = Vt / V0*100%, wherein Vt is the total volume of the mercury pressed in, and V0 is the volume of the sample. t

[0068] The conductivity σ of the electrolyte can be determined by means and methods known in the art. For example, refer to the industry standard HG / T 4067-2015 "Lithium hexafluorophosphate electrolyte", set the measurement temperature of the density meter to 20℃, inject the sample into the measurement cell of the instrument, and measure and read the data.​

[0069] 5. The tortuosity calculation employs the formula: ε = (Rion x A x τ x σ) / L.

[0070] The second aspect of the present disclosure provides a method for preparing the negative electrode sheet of the first aspect, comprising the following steps:

[0071] (1) preparing a negative electrode active paste comprising a carbon-based material, and coating the negative electrode active paste on at least one side surface of a negative electrode current collector.

[0072] According to a specific embodiment of the present disclosure, the negative electrode 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 substrate and a metal layer formed on at least one side surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0073] According to a specific embodiment of the present disclosure, the raw material composition of the negative electrode active paste is not particularly limited, and a person skilled in the art can select it according to actual needs. As some specific examples, the negative electrode active paste can include a negative electrode active material, which includes graphite, and can also include other commonly used negative electrode 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.

[0074] Specifically, the negative electrode active paste can also 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).

[0075] Specifically, the negative electrode active material layer can also optionally include a conductive agent. The conductive agent can include at least one of super-conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] Specifically, the negative electrode active material layer can also optionally include other auxiliary agents, such as thickening agents (such as sodium carboxymethyl cellulose (CMC)), etc.

[0077] Specifically, the components used for preparing the negative electrode sheet, such as the negative electrode 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 electrode current collector.

[0078] (2) The negative electrode active slurry is treated by a magnetic induction orientation device, and is dried and rolled to obtain a negative electrode active layer.

[0079] According to a specific embodiment of the present disclosure, the magnetic induction orientation device can realize the orientation arrangement of the carbon-based material particles in the negative electrode active slurry. The magnetic induction orientation device is not particularly limited, and specifically can adopt a magnetic block with a uniform magnetic field (magnetic field strength 0.5 T-2 T), which is placed on the side of the current collector that is not coated with the negative electrode active slurry during the coating process, and the orientation degree of the carbon-based material particles in the negative electrode active layer (i.e., the OI value of the electrode sheet) is realized by adjusting the distance between the magnetic block and the copper foil (0 mm-3 mm) and the time for the current collector to pass through the magnetic block (5 s-60 s).

[0080] 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, and can be selected according to actual needs by those skilled in the art.

[0081] (3) The surface of the negative electrode active layer away from the negative electrode current collector is subjected to a hole opening treatment to obtain the negative electrode sheet.

[0082] According to a specific embodiment of the present disclosure, the hole opening method is not particularly limited, and can be selected according to actual needs by those skilled in the art. As some specific examples, the hole opening can be realized by laser etching, ion beam etching, mechanical pore making and template pore making, and preferably laser etching and roller pin rolling pore making.

[0083] The third aspect of the present disclosure provides a battery comprising the negative electrode sheet of the first aspect.

[0084] According to a specific embodiment of the present disclosure, the battery is a secondary battery. Generally, the battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte conducts ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet to prevent short circuiting of the positive and negative electrodes, while allowing the ions to pass through.

[0085] According to a specific embodiment of the present disclosure, the battery is a lithium ion battery.

[0086] According to a specific embodiment of the present disclosure, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side surface of the positive electrode current collector, and the positive electrode active layer comprises a positive electrode active material.

[0087] 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 substrate and a metal layer formed on at least one side surface of the polymer material substrate, 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 substrate (e.g., a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. substrate).

[0088] According to a specific embodiment of the present disclosure, the positive active 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.

[0089] According to a specific embodiment of the present disclosure, the positive active 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.

[0090] According to a specific embodiment of the present disclosure, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive active material, the conductive agent, and 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 drying, cold pressing, etc. to obtain the positive electrode tab.

[0091] According to a specific embodiment of the present disclosure, the composition and preparation of the negative electrode tab are described above.

[0092] According to a specific embodiment of the present disclosure, the type of the separator film is not particularly limited, and any 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.

[0093] According to a specific embodiment of the present disclosure, the positive electrode tab, the negative electrode tab, and the separator film can be prepared into an electrode assembly by a winding process or a stacking process.

[0094] According to a specific embodiment of the present disclosure, the above-mentioned battery can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and the electrolyte.

[0095] 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.

[0096] The fourth aspect of the present disclosure provides a power consuming device comprising the battery of the third aspect.

[0097] 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.

[0098] 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 the specific technology or condition is not specified in the examples, it is carried out 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.

[0099] Example 1

[0100] (1) Preparation of electrolyte: lithium salt (LiPF6), solvent (EC, EMC, DMC), additive (VC) were mixed uniformly according to the mass ratio of 12.6:29.2:32.6:23.2:1.9, and the lithium salt was fully dissolved.

[0101] (2) Preparation of positive electrode sheet: the positive electrode material lithium iron phosphate (LiFePO4), the binder PVDF, the conductive agent (carbon black, carbon nanotube) (mass ratio of 100:1.8:0.8:55) and the solvent NMP were mixed uniformly to form a slurry, and the positive electrode sheet with a surface density of 500 g / m 2 and a compactness of 2.65 g / cm 3 was obtained by coating, baking and rolling.

[0102] (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, a layer of slurry with uniform thickness is coated on the current collector, 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 to realize the control of the OI value of the electrode sheet. Then, the electrode sheet with a surface density of 230 g / m 2 , 1.6 g / cm 3 is obtained after baking and rolling. Then, the laser etching or the needle roller is used to produce vertical pore channels with a pore diameter of 20 μm, a pore depth of 15 μm and a pore spacing of 50 μm in an array distribution on the surface of the electrode sheet;

[0103] (4) Separator: the selected separator is a polypropylene (PP) separator;

[0104] (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, and after drying, the above electrolyte is injected, and after vacuum packaging, standing, formation and shaping, etc., the battery with a design capacity of 900 mAh is finally obtained.

[0105] Example 2

[0106] The difference between Example 2 and Example 1 is only that:

[0107] The orientation degree of the graphite particles is changed, so that the OI value of the electrode sheet is close to 0.1.

[0108] Example 3

[0109] The difference between Example 3 and Example 1 is only that:

[0110] The orientation degree of the graphite particles is changed, so that the OI value of the electrode sheet is close to 10.

[0111] Example 4

[0112] The difference between Example 4 and Example 1 is only that:

[0113] The orientation degree of the graphite particles is changed, so that the OI value of the electrode sheet is close to 15.

[0114] Example 5

[0115] The difference between Example 5 and Example 1 is only that:

[0116] The orientation degree of the graphite particles is changed, so that the OI value of the electrode sheet is close to 30.

[0117] Example 6

[0118] Example 6 differs from Example 1 only in that:

[0119] Laser etching or roller pin pressing is used to produce vertical pores with a pore diameter of 5 μm, a pore depth of 10 μm, and a pore spacing of 20 μm, in an array, on the surface of the pole piece.

[0120] Example 7

[0121] Example 7 differs from Example 1 only in that:

[0122] Laser etching or roller pin pressing is used to produce vertical pores with a pore diameter of 40 μm, a pore depth of 50 μm, and a pore spacing of 100 μm, in an array, on the surface of the pole piece.

[0123] Comparative Example 1

[0124] Comparative Example 1 differs from Example 1 only in that:

[0125] No vertical pores arranged in an array are constructed on the surface of the electrode.

[0126] Comparative Example 2

[0127] Comparative Example 2 differs from Example 1 only in that:

[0128] No magnetic field orientation is applied and no vertical pores arranged in an array are constructed on the surface of the electrode.

[0129] Comparative Example 3

[0130] Comparative Example 3 differs from Example 1 only in that:

[0131] The degree of orientation of the graphite particles is changed so that the OI value of the pole piece is close to 35.

[0132] Test Example

[0133] (1) Pore diameter, pore depth, and pore spacing test

[0134] The pore diameter, pore depth, and pore spacing of the array of openings constructed on the surface of each pole piece in the examples and comparative examples are measured using a confocal microscope;

[0135] (2) Test of the angle between the graphite particles and the current collector

[0136] The pole piece after orientation is exposed by ion beam milling and cutting to a flat cross section, and is photographed under an electron microscope, and the angle between the graphite sheet and the current collector is measured using a picture processing tool;

[0137] (3) Negative active layer OI value test

[0138] The negative electrode sheet is placed on the sample stage of the XRD diffractometer for testing, the scanning range is 50-80°, the intensity of the (004) diffraction peak (54-55° position) and the intensity of the (110) diffraction peak (77-78° position) are obtained from the obtained XRD spectrum, and the OI value of the negative electrode active layer is calculated according to the formula OI = I(004) / I(110);

[0139] (4) Liquid phase diffusion impedance test

[0140] The same two negative electrode sheets and separators are assembled into a core in sequence; the core is placed in an outer packaging shell, and electrolyte is injected and baked, and then subjected to packaging, infiltration and other processes to obtain a liquid phase diffusion impedance battery. The liquid phase diffusion impedance test is carried out using an electrochemical workstation in a frequency range of 100000 Hz-0.05 Hz, the obtained data Z'(X axis) and -Z"(Y axis) are plotted, the second derivative of all data in the curve is calculated, the point where the absolute value of the second inverse between the 25th and 60th data is the maximum is found, which is the inflection point, and the data from the third point to the thirteenth point after the inflection point are linearly fitted to obtain the fitted intercept a and slope b. The Rs is obtained by fitting the impedance data using Zview software, and the fitted equivalent circuit is The liquid phase diffusion impedance Rion is then calculated according to the following formula:

[0141] (5) Tortuosity test of negative electrode active layer

[0142] 1) The same two electrode sheets and separators are assembled into a symmetrical battery;

[0143] 2) After injecting electrolyte, infiltration is carried out;

[0144] 3) Electrochemical impedance test is carried out, and the electrode ion impedance Rion is fitted;

[0145] 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;

[0146] The thickness L of the electrode sheet is measured using a micrometer, 10 points are taken in the transverse and longitudinal directions of the electrode sheet using a micrometer, and the average value is taken as the thickness of the electrode sheet;

[0147] The porosity τ of the electrode sheet can be measured by instruments and methods known in the art. For example, mercury intrusion method, the specific test method is as follows: 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 mercury is pressed in, and the mercury intrusion amount from 0 to 30 psi is tested by using 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 33000 psi is tested by using oil pressure method, 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 ​

[0148] The conductivity σ of the electrolyte can be determined by using an instrument and method known in the art. For example, the determination temperature of the density meter can be set to 20°C according to the industry standard HG / T 4067-2015 "Lithium Hexafluorophosphate Electrolyte", the sample is injected into the determination cell of the instrument, and the data is read.

[0149] 5) The tortuosity is calculated by the formula: ε = (Rion x A x τ x σ) / L.

[0150] (6) Fast charging capacity test

[0151] At room temperature, the batteries prepared from the examples and the comparative examples are tested according to the following test procedures:

[0152] 1) 0.2C constant current discharge to 2.0V, and stand for 30min;

[0153] 2) 0.2C constant current charge to 3.8V, and stand for 30min (#0.2C charge#);

[0154] 3) 0.2C constant current discharge to 2.0V, and stand for 30min;

[0155] 4) 3.0C constant current charge to 3.8V, and stand for 30min (#3C charge#);

[0156] The capacity charged by 3C / the capacity charged by 0.2C is the 3C / 0.2C charge ratio.

[0157] The test results are shown in the following table.

[0158] Table 1

[0159] In Table 1, " / " means that there is no.

[0160] The results show that, compared with the comparative examples, the battery corresponding to the electrode with graphite particles having a certain orientation arrangement and a pore structure on the surface of the electrode has a lower liquid phase diffusion impedance, a smaller tortuosity, a stronger lithium ion diffusion capacity, and a better fast charging performance.

[0161] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any 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 specification and the features of the different embodiments or examples without contradiction.

[0162] 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 skilled 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, comprising a negative electrode current collector and a negative electrode active layer disposed on at least one side surface of the negative electrode current collector, wherein the negative electrode active layer comprises a negative electrode active material, the negative electrode active material comprises a carbon-based material, the negative electrode active layer has an orientation degree (OI) value of 0.1-30, and the negative electrode active layer has a plurality of pores on a surface thereof away from the negative electrode current collector. wherein The orientation degree (OI) value is a ratio of intensity of a (004) diffraction peak to intensity of a (110) diffraction peak in an XRD diffraction pattern of the negative electrode active layer.

2. The negative electrode sheet according to claim 1, wherein The negative electrode active layer has an orientation degree (OI) value of 0.1-10.

3. The negative electrode sheet according to claim 1 or 2, wherein An angle between the carbon-based material sheet and the negative electrode current collector is 45°-90°.

4. The negative electrode sheet according to any one of claims 1 to 3, wherein The pores penetrate at least part of the negative electrode active layer in a thickness direction.

5. The negative electrode sheet according to any one of claims 1 to 4, wherein A depth of the pores is less than a thickness of the negative electrode active layer.

6. The negative electrode sheet according to any one of claims 1 to 5, wherein A ratio of the depth of the pores to the thickness of the negative electrode active layer is 0.1-0.

8.

7. The negative electrode sheet according to any one of claims 1 to 6, wherein The depth of the pores is 10 μm-50 μm.

8. The negative electrode sheet according to any one of claims 1 to 7, wherein The thickness of the negative electrode active layer is 62 μm-95 μm.

9. The negative electrode sheet according to any one of claims 1 to 8, wherein A total area of the pores accounts for 0.20%-78% of an area of the surface of the negative electrode active layer away from the negative electrode current collector.

10. The negative electrode sheet according to any one of claims 1 to 9, wherein A pore size of the pores is 5 μm-40 μm.

11. The negative electrode sheet according to any one of claims 1 to 10, wherein The surface of the negative electrode active layer away from the negative electrode current collector has at least two pores, and a distance between any two adjacent pores is 20 μm-100 μm.

12. The negative electrode sheet according to any one of claims 1 to 11, wherein The negative electrode active layer has a tortuosity of 2.2-3.

5. 13.A method for preparing the negative electrode sheet according to any one of claims 1-12, comprising: preparing a negative electrode active slurry, the negative electrode active slurry comprising a carbon-based material, and coating the negative electrode active slurry on at least one side surface of a negative electrode current collector; processing the negative electrode active slurry coating process by a magnetic induction orientation device, drying, and rolling to obtain a negative electrode active layer; performing a pore opening treatment on a surface of the negative electrode active layer away from the negative electrode current collector to obtain the negative electrode sheet.

14. A battery, wherein, The negative electrode sheet according to any one of claims 1-12.

15. An electrical device, comprising: The battery according to claim 14.

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