Electrode material film, method for preparing the same, electrode sheet, and battery

Abstract

An electrode material film, a method for manufacturing the same, an electrode sheet, and a battery, the electrode material film including a substrate and an electrode active material, the substrate including polymer fibers in a three-dimensional network; the electrode active material being located in the substrate, and at least part of the electrode active material connecting the polymer fibers. The structure of the electrode material film has stability, is easy to be once hot-pressed, and has high strength after multiple calendering and the electrode active material is not easily damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrode material film, a preparation method thereof, an electrode sheet and a battery. BACKGROUND

[0002] With the rapid development of electric vehicles, consumers have increasingly stringent requirements for the mileage of electric vehicles. The mileage requirements of electric vehicles are usually closely related to the built-in battery technology. Lithium ion batteries can be applied not only in electric vehicles but also in various electrical devices and equipment, and are relatively important basic energy components.

[0003] Most of the current preparation methods of lithium ion battery electrode sheets are wet electrode processes, in which mixed slurry is coated on a current collector, and then the electrode material is combined with the current collector by drying and curing. The disadvantage of this method is that the steps are numerous, and the recovery and discharge of solvents after drying also lead to an increase in the preparation cost of lithium ion batteries.

[0004] Dry electrode process is a new type of lithium ion battery manufacturing method, which has lower manufacturing cost and better battery performance. However, in order to ensure that the final obtained electrode sheet meets the use requirements of existing lithium ion batteries, it usually needs to be pressed twice or more times to reduce the thickness of the electrode sheet. However, the method of pressing twice or more times will cause the strength of the electrode sheet to decrease, the material to be damaged, and the stacking structure of the electrode sheet to change, thereby affecting the subsequent foil compounding process and the final electrochemical performance. SUMMARY

[0005] The purpose of the present application is to provide an electrode material film, a preparation method thereof, an electrode sheet and a battery. The structure of the electrode material film has stability, is easy to be hot-pressed into shape at one time, and has high strength after multiple pressings and is not easy to be damaged.

[0006] To achieve the purpose of the present application, the present application provides the following technical solutions:

[0007] In a first aspect, the present application provides an electrode material film, comprising a substrate and an electrode active material, wherein the substrate comprises a three-dimensional network of polymer fibers; the electrode active material is located in the substrate, and at least part of the electrode active material is connected to the polymer fibers.

[0008] In one embodiment, at least part of the electrode active material is embedded in the polymer fibers.

[0009] In one embodiment, the material for preparing the substrate comprises one or more of polytetrafluoroethylene and copolymers thereof, polyvinylidene fluoride and copolymers thereof, polyolefins and copolymers thereof, polyethers and copolymers thereof, polyphenylene ether and copolymers thereof, polysiloxane and copolymers thereof, polyesters and copolymers thereof, polyethylene oxide, polyethylene-polyethylene glycol block copolymer, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), nitrile rubber, polyvinyl acetate, polyvinyl acetate, polyacrylate.

[0010] In one embodiment, the mass ratio of the substrate in the electrode material film is 0.5% to 6%.

[0011] In one embodiment, the thickness of the electrode material film is 50 μm to 200 μm.

[0012] In one embodiment, the substrate is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by calendering the substrate.

[0013] In one embodiment, the electrode material film is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by calendering the electrode material film.

[0014] In one embodiment, the electrode active material is a positive electrode active material or a negative electrode active material.

[0015] In a second aspect, the present application provides a method for preparing an electrode material film, comprising: mixing an electrode active material and a binder, and fiberizing the binder by shear force to obtain a fiberized mixture; and performing hot-pressing treatment on the fiberized mixture to obtain an electrode material film, wherein the binder forms a substrate, the substrate comprises polymer fibers connected in a three-dimensional network, the electrode active material is located in the substrate, and at least part of the electrode active material is connected to the polymer fibers.

[0016] In one embodiment, the apparent bulk density of the binder ranges from 0.1 kg / L to 0.6 kg / L; and / or, the average particle size D50 of the binder ranges from 0.1 mm to 3 mm.

[0017] In a third aspect, the present application provides a pole piece, comprising a current collector and the electrode material film of any one of the embodiments of the first aspect, wherein the electrode material film is arranged on the current collector.

[0018] In a fourth aspect, the present application provides a battery, comprising a separator and the pole piece of the third aspect, wherein the pole piece comprises a positive pole piece and a negative pole piece, and the positive pole piece and the negative pole piece are arranged on opposite sides of the separator, respectively.

[0019] The electrode material membrane provided in the present application is provided with a substrate so that the electrode active material can be attached to the substrate to form a self-supporting structure, which is convenient for storage and transportation. The electrode material membrane does not require the process steps of drying and solvent recovery during the preparation process, which can greatly save the preparation cost of the battery while reducing environmental pollution; at the same time, the three-dimensional network of polymer fibers also provides more accommodation space for the electrode active material and more compressible space for the electrode material membrane, so that the stability of the electrode material membrane is higher. Even if the electrode material membrane after one molding cannot reach the required thickness, multiple calendering will not reduce the strength of the electrode material membrane or damage the electrode active material, and the electrochemical properties of the electrode material membrane can still be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the implementation methods or the description of the prior art. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 is a schematic diagram of a cross-sectional structure of an electrode material membrane according to an embodiment;

[0022] Figure 2 The present invention is a schematic diagram of the preparation process of an electrode material membrane according to an embodiment. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be an intermediate component. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be an intermediate component.

[0025] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used in this application includes any and all combinations of one or more of the relevant listed items.

[0026] Some embodiments of the present application will be described in detail with reference to the drawings, which are shown by way of illustration. The following embodiments and features of the embodiments can be combined with each other, without conflict.

[0027] The dry electrode process of lithium ion battery is generally to dry mix the binder with the positive and negative active materials; then to make the dry mixed powder into a self-supporting electrode sheet by hot pressing or extrusion; to thin the electrode sheet to the required area density by multiple calendering; to make a double-sided electrode sheet by compounding the self-supporting electrode sheet with a metal foil. However, due to the limitation of the materials used, the self-supporting electrode sheet prepared initially still needs to be thinned to the required area density by multiple calendering. The disadvantage of this method is that the self-supporting electrode sheet prepared initially has a large thickness and less internal compressible space, so that after multiple calendering, the strength of the electrode sheet is reduced, the material is damaged, and the electrode sheet stacking structure is changed, thereby affecting the subsequent foil compounding process and the final electrochemical performance.

[0028] Based on the above problems, the first aspect of the present application provides an electrode material film which has a relatively low thickness after one-time forming and can still retain at least part of the compressible space inside, which is beneficial to ensuring the structural stability under multiple compression.

[0029] Please refer to Figure 1 The electrode material film 100 includes a substrate 10 and an electrode active material 20, the substrate 10 includes polymer fibers in a three-dimensional network; the electrode active material 20 is located in the substrate 10, and at least part of the electrode active material 20 is connected to the polymer fibers.

[0030] In one embodiment, at least part of the electrode active material 20 is embedded in the polymer fibers. It can be understood that at least part of the electrode active material 20 is embedded in the three-dimensional network formed by the polymer fibers. It can be understood that the substrate can be composed of a plurality of polymer fibers, each fiber is connected to each other to form a three-dimensional network, at least part of the electrode active material 20 is connected to the outer surface of the polymer fibers, or at least part of the electrode active material 20 is embedded in the internal structure of the three-dimensional network formed by the polymer fibers.

[0031] Specifically, the electrode material film 100 can be prepared by a dry electrode process, the raw material of the substrate 10 can be a high polymer, and the high polymer has a low bulk density. The high polymer with a low bulk density is more likely to form a fluffy state, so that the electrode material film 100 with a suitable thickness can be obtained after one heat pressing. The high polymer can be treated into polymer fibers by shear force, and the polymer fibers are mixed with the electrode active material 20 to prepare the electrode material film 100 by heat pressing. Among them, the high molecular fibers form a three-dimensional network-like stacking connection under heat pressing, and finally form the substrate 10. Part of the electrode active material 20 can connect the polymer fibers, or be embedded in the polymer fibers. It can be understood that the electrode material film 100 prepared by the dry electrode process has a self-supporting characteristic, and the polymer fibers constitute the substrate 10 frame to support the electrode active material 20.

[0032] Moreover, using a polymer with a low bulk density as a raw material makes the substrate 10 more likely to form a three-dimensional network. The polymer fibers in the three-dimensional network have a larger compressible space, and when the electrode material film 100 after one heat pressing cannot reach a suitable thickness, it can be subjected to secondary or multiple calendering. Moreover, due to the existence of the compressible space during the calendering process, the mutual extrusion of materials can be avoided to prevent the materials from being damaged.

[0033] The structure of the electrode material film 100 provided in the present application is different from that of the existing electrode sheet in that the polymer fibers in the substrate 10 can form a three-dimensional network connection through the physical properties of the raw material itself, thereby having a higher compressible space. Further, in combination with the low bulk density of the material itself, the electrode material film 100 can have a lower thickness or area density after one film forming, and the electrode material film 100 in the present application is not easy to change after transportation and storage.

[0034] The electrode material film 100 provided in the present application is provided with the substrate 10, so that the electrode active material 20 can form a self-supporting structure attached to the substrate 10, which is convenient for storage and transportation. The electrode material film 100 does not need the process steps of drying and solvent recovery during preparation, which can greatly save the preparation cost of the battery and reduce environmental pollution; at the same time, the three-dimensional network of polymer fibers also provides more accommodation space for the electrode active material 20 and more compressible space for the electrode material film 100, so that the stability of the electrode material film 100 is higher. Even if the electrode material film 100 after one forming cannot reach the required thickness, multiple calendering will not reduce the strength of the electrode material film 100 and damage the electrode active material 20.

[0035] In one embodiment, the material of the substrate comprises one or more of polytetrafluoroethylene and copolymers thereof, polyvinylidene fluoride and copolymers thereof, polyolefins and copolymers thereof, polyethers and copolymers thereof, polyphenylene ether and copolymers thereof, polysiloxane and copolymers thereof, polyester and copolymers thereof, polyethylene oxide, polyethylene-polyethylene glycol block copolymer, polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), nitrile rubber, polyvinyl ester, polyvinyl acetate, polyacrylate.

[0036] Specifically, the polyolefins comprise one or more of polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / vinylidene fluoride copolymer, propylene / vinylidene fluoride copolymer; the polytetrafluoroethylene and copolymers thereof can be one or more of tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / ether copolymer, tetrafluoroethylene / siloxane copolymer, tetrafluoroethylene / branched polyether copolymer, tetrafluoroethylene / vinyl ether copolymer, tetrafluoroethylene / branched polyether / vinyl ether copolymer.

[0037] In one embodiment, the mass ratio of the substrate in the electrode material film is 0.5% to 6%. For example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%. It can be understood that the mass ratio of the substrate in the electrode material film can be the mass of the raw materials used in the preparation process. Controlling the mass ratio of the substrate in the electrode material film in the above range not only can control the thickness of the electrode material film, but also can ensure the electrochemical performance of the electrode material film. If the mass ratio of the substrate in the electrode material film is less than the above range, the substrate cannot effectively support the electrode active material, and the electrode material film is not stable enough; if the mass ratio of the substrate in the electrode material film is greater than the above range, the content of the substrate is too large, which reduces the proportion of the active material and affects the electrochemical performance of the electrode material film.

[0038] In one embodiment, the thickness of the electrode material film is 50 μm to 200 μm. For example, 50 μm, 75 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 200 μm.

[0039] In one embodiment, the substrate is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by calendering the substrate.

[0040] In one embodiment, the electrode material film is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by calendering the electrode material film. During the calendering process, the gap between each electrode active material is further reduced, thereby thinning the electrode material film. At this time, the support and adhesion of the substrate to the electrode active material enable the electrode active material to maintain structural integrity during compression, while the entire electrode material film remains intact.

[0041] In a second aspect, the present application provides a method for preparing an electrode material film, which comprises the following steps: Figure 2 The method is used for preparing the electrode material film provided in the first aspect, and the specific steps include:

[0042] In step S10, the electrode active material and the binder are mixed, and the binder is fiberized by shearing force to obtain a fiberized mixture.

[0043] Specifically, in step S10, the electrode active material can be a positive electrode active material or a negative electrode active material. It can be understood that when the positive electrode active material is used, the obtained electrode material film can be used to make a positive electrode sheet; when the negative electrode active material is used, the obtained electrode material film can be used to make a negative electrode sheet.

[0044] The positive electrode active material can be a compound capable of reversibly intercalating / deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.). Taking a lithium secondary battery as an example, the positive electrode active material can be, but is not limited to, one or more of lithium cobaltate (LiCoO2), lithium iron phosphate (LiFePO4), lithium manganate (LiMn2O4), LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.4 Co 0.2 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2. Optionally, a conductive agent can be added to the positive electrode material film to improve the conductivity of the positive electrode active material. The conductive agent can include one or more of acetylene black, Ketjen black, Super-P, carbon nanotubes, carbon nanofibers, activated carbon, and graphene. The areal density of the positive electrode material film is 100 g / m 2 ~300 g / m 2 .

[0045] The negative active material can include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, lithium titanate, iron oxide, lithium titanium phosphate, titanium dioxide, silicon, silicon monoxide, aluminum, tin, and antimony. Optionally, a conductive agent can also be added in the negative material film to improve the conductivity to the positive active material. The conductive agent can include one or more of acetylene black, ketjen black, Super-P, carbon nanotube, carbon nanofiber, activated carbon, and graphene. The areal density of the negative material film is 50 g / m2~150 g / m2. 2 ~150g / m 2 The binder is a precursor for making the substrate in the above embodiments, which can be referred to the above embodiments and will not be repeated here. The initial state of the binder can be a powder.

[0046] Optionally, the bulk density of the binder ranges from 0.1 kg / L to 0.6 kg / L. For example, 0.1 kg / L, 0.2 kg / L, 0.3 kg / L, 0.4 kg / L, 0.5 kg / L, or 0.6 kg / L. It can be understood that the bulk density of the binder is controlled in the above range to ensure that the fiberized mixture can have a sufficiently fluffy state. If the bulk density of the binder is less than the above range, the preparation of such material is more difficult, the production cost is higher, and commercialization is not easy to achieve. If the bulk density of the binder is greater than the above range, the substrate made of the binder is not fluffy enough, and it is difficult to achieve the required thickness and areal density by one-time hot pressing. Or after multiple hot pressing, the mechanical strength of the electrode material film is reduced.

[0047] Optionally, the average particle size Dv50 of the binder is 0.1 mm to 3 mm. For example, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.6 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm. The meaning of Dv50 is the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample, that is, it can be understood as the median particle size or median particle size. The particle size distribution of the binder in this particle size range is uniform, the degree of shear force acting on each binder during the preparation of the electrode sheet is comparable, the polymer fiber network formed is uniform, and the structural stability of the substrate is high.

[0048] Optionally, the molecular weight of the binder is 100 w to 1000 w. The binder with a molecular weight in this range has high adhesive strength and molecular toughness, and the electrode material film prepared therefrom has more optimal structural strength and better electrochemical performance.

[0049] The specific method of fiberizing the binder by shear force in step S10 includes a high-speed airflow shearing method or a high-speed dispersion method. The above method can not only fiberize the binder by providing shear force, but also can uniformly mix the fiberized binder and the electrode active material. Moreover, the equipment of the high-speed airflow shearing method includes but is not limited to an airflow mill pulverizer. The equipment of the high-speed dispersion method includes but is not limited to a high-speed stirring mixer.

[0050] Optionally, the high-speed airflow shearing method adopts an air pressure of 0.1 Mpa~1.2 Mpa. For example, 0.1 Mpa, 0.3 Mpa, 0.5 Mpa, 0.7 Mpa, 0.8 Mpa, 1 Mpa, or 1.2 Mpa. It can be understood that the binder is fiberized by high-speed airflow, and the effect of rapid fiberization can be achieved by controlling the size of the air pressure. If the air pressure is too low, the airflow is small, so the shear force is also small, which on the one hand will lead to too long mixing time, increasing the time cost, and on the other hand will lead to unsatisfactory fiberization effect; if the air pressure is too high, the airflow is large, so the shear force is also large, which on the one hand will cause large damage to the equipment, reducing the service life of the equipment, and on the other hand will easily lead to damage to the electrode active material, thereby reducing the performance of the final battery.

[0051] Optionally, the high-speed dispersion method adopts a blade linear speed of 2 m / s~80 m / s. For example, 2 m / s, 10 m / s, 30 m / s, 50 m / s, 70 m / s, or 80 m / s. It can be understood that the binder is stirred and sheared by high-speed blade, which on the one hand can realize uniform mixing of the materials, and on the other hand is more important, which is to realize fiberization of the fiberizable polymer under the action of super-high-speed dispersion to realize fiberization. If the speed is too low, the shear force is small, which on the one hand will lead to too long mixing time, increasing the time cost, and on the other hand will lead to unsatisfactory fiberization effect; if the speed is too high, the shear force is large, which on the one hand will cause large damage to the equipment, reducing the service life of the equipment, and on the other hand will possibly cause performance degradation of the temperature-sensitive raw materials due to heat production. The above range of preparation conditions is more conducive to making the binder play a greater role.

[0052] The fiberized mixture can be obtained by the above method, and the electrode active material can be connected or embedded in the fiberized binder. Because more loose raw materials are used, the binder can present a fluffy state when it is not processed; after fiberization by shear force, the fiberized binder can also maintain a fluffy state, and the binder can maintain the original loose density as much as possible due to the elasticity of the binder itself even if it is pressed when it is not heated. The influence of the material state in the process of material storage, transportation, and equipment conveying can be avoided.

[0053] Step S20, the fibrous mixture is subjected to hot-pressing to obtain an electrode material film, the binder forms a substrate, the substrate comprises polymer fibers connected in a three-dimensional network, and the electrode active material is located in the substrate and at least partially connects the polymer fibers.

[0054] Specifically, the specific manner of hot-pressing is not limited, for example, a roller press can be used for hot-rolling at a certain temperature. During the hot-pressing, the fibrous binder softens or melts due to heat, and the fibrous binder can be released from the fluffy state, and the fibers are connected in a three-dimensional network, and the fibers form the substrate of the electrode material film, which can accommodate the electrode active material and provide the self-supporting characteristics of the electrode material film.

[0055] Optionally, the temperature of the hot-pressing is 100℃-200℃, for example, 100℃, 110℃, 120℃, 150℃, 180℃, or 200℃. It can be understood that, since the types of the binder provided by the present application are various, and the heat-resistant temperatures of the various binders are different, the temperature of the hot-pressing can be set according to the type of the binder selected.

[0056] The preparation method of the electrode material film provided by the present application is different from the traditional wet tabletting process. The electrode active material and the binder are mixed, the binder is fibrousized by using the shearing force, and then the electrode material film is formed by hot-pressing. The electrode material film can be transported and stored alone, and then the battery pole piece is prepared by compounding with the current collector. In the preparation process, no organic solvent is added, the drying process is omitted, and the problems such as organic solvent post-treatment and recovery are avoided, thereby effectively saving the production cost and avoiding environmental pollution. At the same time, the low bulk density binder with fluffy microstructure is used, so that the fibrous mixture after treatment can have a more fluffy state compared with the traditional binder. Under the same conditions of the hot-rolling equipment, the fibrous mixture has more compressible space, so that the thickness of the first hot-pressed film is low, and the phenomenon of too thick first film and the subsequent multiple calendering process can be avoided.

[0057] In a third aspect, the present application also provides a pole piece, comprising a current collector and the electrode material film described in the first aspect. Specifically, the preparation method of the pole piece is not limited. For example, the electrode material film can be hot-pressed on the current collector to form a composite of the two. The electrode material film can also be prepared in advance, and then the electrode material film and the current collector are compounded by hot-pressing.

[0058] Optionally, when the active material is a positive active material, the electrode material film prepared is a positive material film, and the current collector can be an aluminum foil, and the positive material film is attached to the surface of the aluminum foil to form a positive pole piece.

[0059] Optionally, when the active material is a negative active material, the electrode material film prepared is a negative electrode material film, and the current collector can be a copper foil, and the negative electrode material film is attached to the surface of the copper foil to form a negative electrode sheet.

[0060] In a fourth aspect, the application also provides a battery comprising a separator and the above-mentioned electrode sheet, wherein the electrode sheet comprises a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are arranged on opposite sides of the separator. The application does not limit the specific type of the battery, and both the positive electrode sheet and the negative electrode sheet of the battery can be prepared by the above method.

[0061] The technical solutions of the application are described in detail below through specific examples.

[0062] Example 1

[0063] This example provides a positive electrode material film and a preparation method thereof, and the formula is 97% LiFePO4, 2% mixed adhesive and 1% carbon black. The adhesive contains 1% polytetrafluoroethylene (PTFE, bulk density of 0.55 kg / L, molecular weight of 5 million, Dv50 of 0.3 mm), 1% polyethylene (PE, bulk density of 0.2 kg / L, molecular weight of 3 million, Dv50 of 0.1 mm).

[0064] (1) The above materials are added to an Eirich EL5 laboratory stirrer and stirred at 200 rpm (linear speed of about 2 m / s) for 5 minutes; then increased to 1000 rpm (linear speed of about 10 m / s) for 10 minutes; again increased to 4000 rpm (linear speed of about 40 m / s) for 15 minutes; and then continuously stirred at 200 rpm for cooling to obtain a fibrous mixture.

[0065] (2) The fibrous mixture is added to a hot roller press at 150°C, the roller gap is set to 100 μm, the pressure is 5T, and the rotation speed is 10 rpm, and finally a positive electrode material film with a thickness of 150 μm is obtained.

[0066] Example 2

[0067] This example provides a negative electrode material film and a preparation method thereof, and the formula is 97% graphite, 2% mixed adhesive and 1% carbon black. The adhesive contains 1% polytetrafluoroethylene (PTFE, bulk density of 0.55 kg / L, molecular weight of 5 million, Dv50 of 0.3 mm), 1% polyethylene (PE, bulk density of 0.2 kg / L, molecular weight of 3 million, Dv50 of 0.1 mm).

[0068] (1) The above materials were added into an Eirich EL5 laboratory stirrer and stirred at 200 rpm (linear speed about 2 m / s) for 5 minutes, then raised to 1000 rpm (linear speed about 10 m / s) for 10 minutes, and then raised to 4000 rpm (linear speed about 40 m / s) for 15 minutes, and then continuously stirred at 200 rpm for cooling to obtain a fiberized mixture.

[0069] (2) The above fiberized mixture was added into a hot roller press at 150 °C, the roller gap was set to 100 μm, the pressure was 5 T, and the rotation speed was 10 rpm, and finally a positive electrode material film with a thickness of 120 μm was obtained.

[0070] Example 3

[0071] The difference from Example 1 is that the binder used in the formula of the positive electrode material film is a mixed binder with a total amount of 0.5%, wherein the binder comprises 0.25% polytetrafluoroethylene (PTFE, bulk density 0.55 kg / L, molecular weight 5 million, Dv50 0.3 mm), 0.25% polyethylene (PE, bulk density 0.2 kg / L, molecular weight 3 million, Dv50 0.1 mm); and the thickness of the positive electrode material film obtained is 140 μm.

[0072] Example 4

[0073] The difference from Example 1 is that the binder used in the formula of the positive electrode material film is a mixed binder with a total amount of 6%, wherein the binder comprises 3% polytetrafluoroethylene (PTFE, bulk density 0.55 kg / L, molecular weight 5 million, Dv50 0.3 mm), 3% polyethylene (PE, bulk density 0.2 kg / L, molecular weight 3 million, Dv50 0.1 mm); and the thickness of the positive electrode material film obtained is 200 μm.

[0074] Example 5

[0075] The difference from Example 2 is that the binder used in the formula of the negative electrode material film is a mixed binder with a total amount of 5.5%, wherein the binder comprises 2.75% polytetrafluoroethylene (PTFE, bulk density 0.55 kg / L, molecular weight 5 million, Dv50 0.3 mm), 2.75% polyethylene (PE, bulk density 0.2 kg / L, molecular weight 3 million, Dv50 0.1 mm); and the thickness of the negative electrode material film obtained is 180 μm.

[0076] Comparative Example 1

[0077] The comparative example provides a positive electrode material film and a preparation method thereof, and the formula is 97% LiFeP04, 1% polytetrafluoroethylene (PTFE, bulk density is 0.65 kg / L), 1% polyethylene (PE, bulk density is 0.7 kg / L), and 1% carbon black.

[0078] (1) The above materials are added to an Eirich EL5 laboratory stirrer and stirred at 200 rpm (linear speed is about 2 m / s) for 5 minutes; then increased to 1000 rpm (linear speed is about 10 m / s) for 10 minutes; then increased to 4000 rpm (linear speed is about 40 m / s) for 15 minutes; and then continuously stirred at 200 rpm for cooling to obtain a fiberized mixture.

[0079] (2) The above fiberized mixture is added to a hot roller press at 150°C, the roller gap is set to 100 pm, the pressure is 5T, and the rotation speed is 10 rpm, and finally a positive electrode material film with a thickness of 270 pm is obtained.

[0080] Comparative Example 2

[0081] The comparative example provides a negative electrode material film and a preparation method thereof, and the formula is 97% graphite, 1% polytetrafluoroethylene (PTFE, bulk density is 0.65 kg / L), 1% polyethylene (PE, bulk density is 0.7 kg / L), and 1% carbon black.

[0082] (1) The above materials are added to an Eirich EL5 laboratory stirrer and stirred at 200 rpm (linear speed is about 2 m / s) for 5 minutes; then increased to 1000 rpm (linear speed is about 10 m / s) for 10 minutes; then increased to 4000 rpm (linear speed is about 40 m / s) for 15 minutes; and then continuously stirred at 200 rpm for cooling to obtain a fiberized mixture.

[0083] (2) The above fiberized mixture is added to a hot roller press at 150°C, the roller gap is set to 100 pm, the pressure is 5T, and the rotation speed is 10 rpm, and finally a negative electrode material film with a thickness of 230 pm is obtained.

[0084] The electrode material films of the above-mentioned embodiments and comparative examples are respectively compounded with current collectors to form positive or negative electrodes; the positive and negative electrodes are cut into 15 mm round pieces. The positive electrodes provided in the embodiments and comparative examples are aligned with existing graphite negative electrodes and diaphragms of the same specifications, and the negative electrodes provided in the embodiments and comparative examples are aligned with existing lithium electrodes and diaphragms of the same specifications, and are respectively loaded into 2025 model button batteries, injected with sufficient electrolyte and sealed to assemble into lithium-ion batteries. Among them, the diaphragm is a PE film, and the electrolyte is LiPF6 (at a concentration of 1M in the electrolyte) dissolved in a mixture of ethylene carbonate (EC) / dimethyl carbonate (DEC) / ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1. Charge and discharge are performed at 0.1C. The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] From the test results of Example 1 and Comparative Example 1 in Table 1, it can be seen that the positive electrode material film produced using an adhesive with a lower apparent density not only has a smaller thickness, but also the resulting lithium-ion battery has superior electrochemical performance. This is because the adhesive with a lower apparent density can form the electrode material film in a single step through hot pressing, eliminating the need for repeated hot pressing to meet the battery's areal density. This can prevent the positive electrode active material in the electrode material film from being damaged and the electrode stacking structure from being altered, ultimately ensuring the electrochemical performance of the lithium-ion battery.

[0088] It can also be seen from the test results of Example 2 and Example 5 in Table 1 that the negative electrode material film made with an adhesive having a smaller bulk density can have a smaller thickness, and the lithium-ion battery produced can also have excellent electrochemical properties. Therefore, the preparation method of the electrode material film provided in the present application can be applied to both positive electrode material films and negative electrode material films. It can be seen from Examples 3 and 4 in Table 1 that if too little adhesive is added, the tensile strength of the electrode material film is low; if too much adhesive is added, the proportion of active materials will be greatly reduced, and the electrochemical performance of the battery will be reduced. However, compared with Comparative Example 1, Example 4 still has relatively excellent electrochemical properties, which also illustrates that the use of an adhesive with a smaller bulk density can improve the performance of the electrode material film.

[0089] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", and "outside" are based on the orientation or positional relationship described in the accompanying drawings. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present application.

[0090] The above-described is only a preferred embodiment of the present application, of course, cannot be limited by this to the scope of the claims of the present application, the person skilled in the art can understand that the implementation of all or part of the above-mentioned embodiments, and according to the equivalent changes made by the claims of the present application, still belong to the scope covered by the present application.

Claims

1. An electrode material film, characterized in that include: a substrate comprising polymer fibers in a three-dimensional network; an electrode active material disposed within the substrate, with at least a portion of the electrode active material attached to the polymer fibers; The substrate is formed by fiberizing an adhesive, and the bulk density of the adhesive is 0.1 kg / L to 0.6 kg / L.

2. The electrode material film according to claim 1, characterized in that At least a portion of the electrode active material is embedded in the polymer fibers.

3. The electrode material film according to claim 1, characterized in that The material for preparing the substrate includes one or more of polytetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and its copolymers, polyethers and its copolymers, polyphenylene ether and its copolymers, polyesters and its copolymers, nitrile rubber, polyvinyl ester, polyvinyl acetate, and polyacrylate.

4. The electrode material film according to claim 1, characterized in that The mass proportion of the substrate in the electrode material film is 0.5% to 6%.

5. The electrode material film according to claim 1, characterized in that The thickness of the electrode material film is 50 μm to 200 μm.

6. The electrode material film according to claim 1, characterized in that The substrate is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by rolling the substrate.

7. The electrode material film according to claim 1, characterized in that The electrode material film is a deformable structure in the thickness direction of the electrode material film, and the electrode material film is thinned by rolling the electrode material film.

8. The electrode material film according to claim 1, characterized in that The electrode active material is a positive electrode active material or a negative electrode active material.

9. A method for preparing an electrode material film, characterized in that: include: mixing an electrode active material and a binder, and fiberizing the binder by shearing force to obtain a fiberized mixture; The fiberized mixture is subjected to hot pressing to obtain an electrode material film, wherein the adhesive forms a substrate, the substrate includes polymer fibers connected in a three-dimensional network, the electrode active material is located within the substrate, and at least a portion of the electrode active material is connected to the polymer fibers; the bulk density of the adhesive is 0.1 kg / L~0.6 kg / L.

10. The method for preparing an electrode material film according to claim 9, wherein: The average particle size Dv50 of the adhesive is 0.1 mm to 3 mm.

11. A pole piece, characterized in that: The invention comprises a current collector and the electrode material film according to any one of claims 1 to 8, wherein the electrode material film is arranged on the current collector.

12. A battery, characterized in that: The device comprises a diaphragm and the electrode sheet as claimed in claim 11, wherein the electrode sheet comprises a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are respectively arranged on two opposite sides of the diaphragm.

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