Pole piece, preparation method thereof and lithium ion battery

Abstract

The invention relates to a pole piece, a preparation method thereof and a lithium ion battery in the technical field of lithium batteries, and the preparation method of the pole piece comprises the following steps: S1, coating a base material with second functional layer slurry, and drying to form the base material containing a second functional layer; s2, coating the second functional layer of the base material prepared in the step S1 with the first functional layer slurry, and drying to form the base material containing the first functional layer and the second functional layer; and S3, compounding the base material prepared in the step S2 with a to-be-treated pole piece, and transferring the first functional layer and the second functional layer on the base material to the surface of the to-be-treated pole piece to form a target pole piece. According to the invention, the pole piece is prepared by adopting a dry-method transfer printing method, so that the problems that materials in functional layer slurry possibly permeate into pores in the active substance layer in a wet-method preparation process to wrap the active substance materials, so that the electronic insulation among the active substance materials is caused, and the electrical property is influenced are solved; and meanwhile, the conditions of curling, bending and the like of the pole piece are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a pole piece and a preparation method thereof, and a lithium ion battery. Background Art

[0002] As a new generation of energy storage devices, lithium-ion batteries are widely used in portable electronic devices, grid energy storage systems, and new energy vehicles due to their high energy density, long cycle life, and no memory effect. As the demand for lithium-ion batteries increases, the cycle performance and safety performance of batteries are receiving more and more attention.

[0003] Setting a solid electrolyte layer or functional coating on the surface of lithium-ion battery electrodes can be used to improve the battery's cycle performance and safety performance, but the preparation process of the solid electrolyte layer or functional coating of traditional lithium-ion batteries often uses a wet coating method to compound it with the electrode pole piece. The material in the solid electrolyte layer or functional coating may penetrate into the pores inside the active material layer to form a wrap around the active material material, resulting in electronic insulation between the active material materials, affecting the electrical performance, and the volatilization of the solvent in the coated solid electrolyte layer will cause the pole piece to curl and bend.

[0004] Therefore, the present invention proposes a technical solution to prepare the electrode in the lithium-ion battery by a dry transfer method, thereby preventing the material in the slurry of the solid electrolyte layer or functional coating of the electrode from penetrating into the pores of the active material layer. At the same time, the preparation method of the present invention also avoids curling and bending of the electrode. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses a pole piece and a preparation method thereof, and a lithium-ion battery. The technical solution of the present invention is implemented as follows:

[0006] The first aspect of the present invention discloses a method for preparing a pole piece, the method comprising the following steps:

[0007] S1, coating the second functional layer slurry on a substrate, and drying to form a substrate containing the second functional layer;

[0008] S2, coating the first functional layer slurry on the second functional layer of the substrate prepared in step S1, and drying to form a substrate containing the first functional layer and the second functional layer;

[0009] S3, compounding the substrate prepared in step S2 and the electrode to be processed, so that the first functional layer and the second functional layer on the substrate are transferred to the surface of the electrode to be processed to form a target electrode.

[0010] In the step S1, the coating speed is 5 m / min-30 m / min.

[0011] Preferably, in the step S1, the coating speed is 15 m / min.

[0012] Preferably, in step S3, the compounding method is roller pressing; after the roller pressing compounding is completed, the substrate is recovered.

[0013] Preferably, in step S3, the rolling method is hot pressing, and the hot pressing temperature is 80°C-110°C;

[0014] Preferably, in step S3, the rolling method is hot pressing, and the hot pressing temperature is 90°C.

[0015] Preferably, the electrode to be processed comprises a current collector and an active material layer at least arranged on one side of the current collector, and the active material layer comprises an active material material, an active material conductive agent and a binder.

[0016] Preferably, the first functional layer includes a first inorganic solid electrolyte, a first polymer solid electrolyte and a first conductive agent.

[0017] Preferably, the mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the first functional layer is (5%-99%): (1%-95%): (0.01%-10%);

[0018] Preferably, the mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the first functional layer is (5%-99%): (50%-90%): (0.01%-10%).

[0019] Preferably, the second functional layer includes a second inorganic solid electrolyte and a second polymer solid electrolyte.

[0020] Preferably, the mass ratio of the second inorganic solid electrolyte to the second polymer solid electrolyte of the second functional layer is (5%-99%): (1%-95%);

[0021] Preferably, the mass ratio of the second inorganic solid electrolyte to the second polymer solid electrolyte is (5%-99%): (1%-10%).

[0022] Preferably, the bonding force between the electrode to be processed and the first functional layer is F1, and the bonding force between the substrate and the second functional layer is F2, wherein F1>F2.

[0023] The second aspect of the present invention is to provide a pole piece, which is prepared by the method provided by the first aspect of the present invention.

[0024] The third aspect of the present invention is to propose a lithium-ion battery, which includes a positive electrode plate, a separator and a negative electrode plate arranged in sequence, wherein the positive electrode plate is the plate proposed in the second aspect of the present invention and / or the negative electrode plate is the plate proposed in the second aspect of the present invention.

[0025] The present invention prepares the pole piece in the lithium-ion battery by a dry transfer method, avoiding the problem that under the traditional wet coating preparation process, the material in the functional layer slurry of the pole piece may penetrate into the pores inside the active material layer, forming a wrapping of the active material material, resulting in electronic insulation between the active material materials and affecting the electrical performance. At the same time, the preparation method of the present invention also avoids the problem of curling and bending of the pole piece. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific implementation methods are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0028] In the description of the specific implementation methods of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0029] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0030] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0031] Throughout the present invention, numerical values ​​represent approximate measures or limits of ranges to cover minor deviations from given values ​​as well as embodiments with about the values ​​mentioned and embodiments with the exact values ​​mentioned. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., amounts or conditions) in this specification (including the appended claims) should be understood to be modified by the term "about" in all cases, regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows some minor imprecision (close to the exact value of the value to some extent; approximately or reasonably close to the value; almost). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about" as used in the present invention at least indicates the variation that can be produced by the ordinary methods of measuring and using such parameters. For example, "about" may include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0032] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges given for such ranges.

[0033] In the traditional preparation process of lithium-ion battery electrodes, the materials in the functional layer slurry of the electrode may penetrate into the pores inside the active material layer, forming a wrapping of the active material, resulting in electronic insulation between the active material materials and affecting the electrical performance.

[0034] The present invention prepares the pole piece in the lithium-ion battery through a dry transfer method, thereby preventing the material in the functional layer slurry of the pole piece from penetrating into the pores inside the active material layer, forming a wrapping of the active material, resulting in electronic insulation between the active material materials and affecting the electrical performance. At the same time, the preparation method of the present invention also avoids the pole piece from curling and bending.

[0035] The first aspect of the present invention discloses a method for preparing a pole piece, the method comprising the following steps:

[0036] S1, coating the second functional layer slurry on a substrate, and drying to form a substrate containing the second functional layer;

[0037] S2, coating the first functional layer slurry on the second functional layer of the substrate prepared in step S1, and drying to form a substrate containing the first functional layer and the second functional layer;

[0038] S3, compounding the substrate prepared in step S2 and the electrode to be processed, so that the first functional layer and the second functional layer on the substrate are transferred to the surface of the electrode to be processed to form a target electrode.

[0039] In this application, a dry transfer method is adopted to avoid the problem that under the traditional preparation process, the material in the functional layer slurry may penetrate into the pores inside the active material layer, forming a wrapping of the active material, resulting in electronic insulation between the active material materials and affecting the electrical performance. At the same time, the preparation method of this application avoids the curling and bending of the electrode.

[0040] In some embodiments, in the step S1, the coating speed is 5m / min-30m / min. In practical applications, the coating speed can be specifically selected from 5m / min, 6m / min, 7m / min, 8m / min, 9m / min, 10m / min, 11m / min, 12m / min, 13m / min, 14m / min, 15m / min, 16m / min, 17m / min, 18m / min, 19m / min, 20m / min, 21m / min, 22m / min, 23m / min, 24m / min, 25m / min, 26m / min, 27m / min, 28m / min, 29m / min, 30m / min. The above values ​​are only examples and are not limited.

[0041] In some preferred embodiments, in the step S1, the coating speed is 15 m / min.

[0042] In specific applications, without violating the inventive concept of the present application, the substrate can be any material currently used, such as PP substrate, PE substrate, PE / PP double-layer substrate, PE / PP / PE three-layer substrate, PP / PE / PP three-layer substrate, etc.

[0043] In some embodiments, in step S3, the compounding method is roller pressing; after the roller pressing compounding is completed, the substrate is recovered.

[0044] In some preferred embodiments, in step S3, the rolling method is hot pressing, and the hot pressing temperature is 80°C-110°C. In practical applications, the hot pressing temperature can be specifically selected from 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, and 110°C. The above values ​​are only examples and are not limited.

[0045] In some more preferred embodiments, the hot pressing temperature is 90°C.

[0046] In some embodiments, the electrode to be processed includes a current collector and an active material layer disposed at least on one side of the current collector, and the active material layer includes an active material, an active material conductive agent, and a binder.

[0047] In specific applications, when the active material is a positive electrode active material, any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate or lithium-rich manganese-based materials can be selected. The above are all common positive electrode active materials in the field, which are only examples and not limitations.

[0048] In specific applications, when the active material is a negative electrode active material, it can be selected from any one or a combination of at least two of artificial graphite, natural graphite, microcrystalline graphite, soft carbon and hard carbon. The above are common negative electrode active materials in the art, which are only examples and not limitations.

[0049] In specific applications, the active material conductive agent includes any one or a combination of at least two of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers. The above are all common conductive agents in the art, which are only examples and not limitations.

[0050] In specific applications, the binder includes any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polystyrene, polyoxymethylene, polycarbonate, polyamide, acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene ether or carboxymethyl cellulose, preferably polytetrafluoroethylene or polyvinyl chloride. The above are all common binders in the art, which are only examples and not limitations.

[0051] The first functional layer includes a first inorganic solid electrolyte, a first polymer solid electrolyte and a first conductive agent.

[0052] The first functional layer can improve the interface stability and electrochemical working window between the diaphragm and the active material layer. The combined effect of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the functional layer can reduce the internal resistance of the battery, improve the lithium ion cycle performance, and thereby improve the fast charging and high-rate discharge performance of the battery.

[0053] Polymer solid electrolytes can be used as both electrolytes and binders. Compared with traditional binders, they can form a more complete mixed conductive network. At the same time, inorganic solid electrolytes make up for the poor ionic conductivity of polymer solid electrolytes themselves. Compared with the case of using only polymer solid electrolytes, they can better improve the performance of the battery.

[0054] In some embodiments, the mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte, and the first conductive agent in the first functional layer is (5%-99%): (1%-95%): (0.01%-10%).

[0055] In some preferred embodiments, the mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the first functional layer is (5%-99%): (50%-90%): (0.01%-10%)

[0056] In a specific application, the first conductive agent includes any one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers, or a combination of at least two thereof. Nano-scale single-walled CNTs are preferred, which can take into account the conductive effect while reducing the cost. The above are all common conductive agents in the art, which are only examples and not limitations.

[0057] In some embodiments, the second functional layer includes a second inorganic solid electrolyte and a second polymer solid electrolyte.

[0058] The second functional layer includes inorganic solid electrolytes and polymer electrolytes, which can effectively block direct contact between the positive and negative electrodes when the high-temperature diaphragm shrinks, avoiding safety problems such as internal short circuits and cell loss of control.

[0059] In some embodiments, the mass ratio of the second inorganic solid electrolyte to the second polymer solid electrolyte is (5%-99%): (1%-95%).

[0060] In some preferred embodiments, the mass ratio of the second inorganic solid electrolyte to the second polymer solid electrolyte is (5%-99%): (1%-10%).

[0061] In this application, the inorganic solid electrolyte and the polymer solid electrolyte in the first functional layer and the second functional layer can be the same or different, and can be a single type or multiple types, without limitation.

[0062] In specific applications, the inorganic solid electrolyte includes at least one of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0063] In specific applications, the halide solid electrolyte can be selected from: Li 2 CdC l4 、Li 2 MgC l4 、Li 2 Cd I4 、Li 2 ZnI 4 、Li 3 OCl、LiI、Li 5 ZnI 4 、Li 3 OCl 1-x Br x (where 0 < x < 1) and their combinations.

[0064] In specific applications, the sulfide solid electrolyte can be selected from: Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S 4 、Li 10 GeP 2 S 11.7 O 0.3 、Li 9.6 P 3 S 12 、Li 7 P 3 S 11 、Li 9 P 3 S 9 O 3 、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li10 (Si 0.5 Ge 0.5 ) 2 S 12 、Li(Ge 0.5 Sn 0.5 ) 2 S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 , Li 10 G 2 S 12 (LGPS), Li 6 PS 5 X (wherein X is Cl, Br or I), Li 7 P 2 S 8 I. Li 10.35 Ge 1.35 P 1.65 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 10 SnP 2 S 12 , Li 10 SiP 2 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 , (1-x) P 2 S 5-x Li 2 S (where 0.5≤x≤0.7) and their combinations.

[0065] In specific applications, oxide solid electrolytes include: perovskite type, garnet type, LISICON type, NASICON type. Among them, the perovskite type solid electrolyte material is preferably LLTO (Li 0.33 La 0.56 TiO 3 , lithium lanthanum titanate / lithium lanthanum titanate), the garnet-type solid electrolyte material is preferably LLZO (lithium lanthanum zirconium oxide / lithium lanthanum zirconate, Li 7 La 3 Zr 2 O 12 ); NASICON (sodium super ion conductor) type solid electrolyte material is preferably lithium aluminum titanium phosphate LATP (Li 1.3 Al 0.3 Ti1.7 (PO 4 ) 3 ).

[0066] In a specific application, the polymer solid electrolyte is selected from at least one of polyacrylic acid, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride and polymethylethylene carbonate, and the above is only an example and not a limitation.

[0067] In some embodiments, the bonding force between the electrode to be processed and the first functional layer is F1, and the bonding force between the substrate and the second functional layer is F2, wherein F1>F2.

[0068] In the present application, the bonding force between the electrode to be processed and the first functional layer is greater than the bonding force between the substrate and the second functional layer, which can ensure that the functional layer is better peeled off from the substrate and can be composited onto the electrode to be processed.

[0069] The second aspect of the present invention is to provide a pole piece, which is prepared by the method provided by the first aspect of the present invention.

[0070] The electrode may be a positive electrode and / or a negative electrode.

[0071] The third aspect of the present invention is to propose a lithium-ion battery, which includes a positive electrode plate, a separator and a negative electrode plate arranged in sequence, wherein the positive electrode plate is the plate proposed in the second aspect of the present invention and / or the negative electrode plate is the plate proposed in the second aspect of the present invention.

[0072] The embodiments of the present invention will be described in more detail below through examples and comparative examples. It should be noted that the embodiments of the present invention are not limited to these examples.

[0073] The following examples and comparative examples are all preparation processes of lithium-ion batteries, wherein the comparative examples are control groups of the examples, used to assist in illustrating the effects of the examples.

[0074] Example 1

[0075] Lithium-ion battery preparation process:

[0076] 1. Preparation of positive electrode sheet containing composite first functional layer and second functional layer:

[0077] 1. The positive electrode active material lithium manganese oxide, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 90:7:3 to form a positive electrode slurry, the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, and dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0078] 2. The LLZO inorganic solid electrolyte and the PVDF polymer solid electrolyte were mixed uniformly at a mass ratio of 70:30 to prepare a second functional layer slurry, the second functional layer slurry was coated on a PET substrate, and the PET substrate containing the second functional layer was prepared after drying;

[0079] 3. LLZO inorganic solid electrolyte, PVDF polymer solid electrolyte and conductive agent superconducting carbon (Super-P) were mixed uniformly in a mass ratio of 70:20:10 to prepare a first functional layer slurry, and the first functional layer slurry was coated on the surface of the second functional layer in step 2, and a PET substrate containing the first functional layer and the second functional layer was prepared after drying, wherein the coating speed was 10 m / min;

[0080] 4. The PET substrate containing the first functional layer and the second functional layer prepared in step 3, after passing through the first unwinding shaft, enters between the first hot pressing roller and the second hot pressing roller together with the positive electrode sheet containing the active material layer to be processed from the second unwinding shaft for compounding, and the compounded positive electrode sheet is wound up by the first winding shaft. At this time, the first functional layer and the second functional layer are formed on the active material layer of the positive electrode sheet in sequence, and the PET substrate is recovered from the second winding shaft, wherein the hot pressing temperature is 90°C.

[0081] 5. The positive electrode sheet containing the composite functional layer obtained in step 4 is trimmed, cut into pieces, and stripped. After stripping, it is used as a positive electrode sheet for a lithium-ion battery, and the surface of the positive electrode sheet has no curling or bending.

[0082] 2. Preparation of negative electrode sheet:

[0083] 1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then cold pressed to obtain a negative electrode sheet;

[0084] 2. Perform trimming, cutting and stripping in step 1, and make negative electrode sheets of lithium-ion batteries after stripping.

[0085] 3. Preparation of electrolyte

[0086] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0087] 4. Preparation of batteries

[0088] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0089] Comparative Example 1

[0090] 1. Preparation of positive electrode sheet containing composite first functional layer and second functional layer (wet coating):

[0091] 1.1. The positive electrode active material lithium manganese oxide, the conductive agent superconducting carbon (Super-P), and the binder polyvinylidene fluoride (PVDF) are mixed uniformly in a mass ratio of 90:7:3 to form a positive electrode slurry, and the positive electrode slurry is coated on both surfaces of the current collector aluminum foil, dried at 100°C to form a positive electrode active material layer, and then cold pressed to obtain a positive electrode sheet containing an active material layer;

[0092] 1.2. Dissolve LLZO inorganic solid electrolyte, PVDF polymer solid electrolyte and conductive agent superconducting carbon (Super-P) in an organic solvent N, N-dimethylacetamide (DMAC) at a mass ratio of 70:20:10, mix them evenly to form a first functional layer slurry, apply the first functional layer slurry on the surface of the positive electrode active material layer in step 1.1, and dry it at 60° C. to obtain a positive electrode sheet containing a first functional layer with a thickness of 5 μm;

[0093] 1.3, rolling the positive electrode sheet containing the first coating obtained in step 1.2;

[0094] 1.4. Dissolve LLZO inorganic solid electrolyte and PVDF polymer solid electrolyte in an organic solvent N,N-dimethylpyrrolidone at a mass ratio of 70:30, mix them evenly to form a second functional layer slurry, apply the second functional layer slurry on the surface of the first functional layer in step 1.3, and dry them at 80° C. to obtain a second functional layer with a thickness of 10 μm, that is, to obtain a positive electrode sheet containing a composite first functional layer and a second functional layer;

[0095] 1.5. The positive electrode sheet containing the composite functional layer obtained in step 1.4 is trimmed, cut into pieces, and divided into strips. After the strips are divided, they are used as positive electrode sheets for lithium-ion batteries.

[0096] 2. Preparation of negative electrode sheet:

[0097] 2.1. The negative electrode active material graphite, the conductive agent superconducting carbon (Super-P), the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are prepared into a negative electrode slurry at a mass ratio of 96.5:1.0:1.0:1.5, coated on the current collector copper foil and dried at 90°C to form a negative electrode active material layer, and then cold pressed to obtain a negative electrode sheet;

[0098] 2.2. The negative electrode sheet prepared in step 2.1 is trimmed, cut into pieces, and slit into strips to produce negative electrode sheets for lithium-ion batteries.

[0099] 3. Preparation of electrolyte

[0100] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0101] 4. Preparation of batteries

[0102] The positive electrode sheet and the negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets to obtain a bare cell. The bare cell is placed in an outer packaging shell, and an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0103] The positive electrode sheet and negative electrode sheet prepared above are stacked in order with the separator so that the separator is between the positive and negative electrode sheets, and then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0104] In order to further demonstrate the technical effect of the present invention, a total of two groups of samples, Example 1 and Comparative Example 1, are used for comparative experiments, with 20 samples in each group, and the experimental results are averaged. The test method is as follows:

[0105] 1. Internal resistance test: obtained through DCR test, 25℃, 3C discharge for 10 seconds.

[0106] 2. Fast charging test:

[0107] ① At room temperature: discharge at 1C current to the discharge end voltage (2.75V), and let stand for 1h;

[0108] ② Then charge it in the standard charging mode, discharge it at 1C current to the discharge end voltage (2.75V), and let it stand for 1 hour;

[0109] ③ Charge at 2C constant current to the charge end voltage, let stand for 1h; then discharge at 1C to the discharge end voltage (2.75V);

[0110] Charge at 2C constant current and constant voltage to the charge end voltage, then discharge at 1C to the discharge end voltage (2.75V), repeat 10 times, no lithium deposition after fully charged dissection

[0111] standard:

[0112] 3. High rate discharge performance test:

[0113] ①At room temperature: charge with standard charging method, let stand for 0.5h, discharge at 1C and 3C respectively to the end voltage (2.75V);

[0114] ②Standards:

[0115] 4. Cycle performance test: 1C constant current and constant voltage charge to the upper voltage limit, stand for 1 hour, 1C constant current discharge to the lower voltage limit, stand for 1 hour, cycle 500 times, and calculate the discharge capacity retention rate;

[0116] The test results are shown in the following table:

[0117] sheet:

[0118]

[0119]

[0120] According to the above table, when the above-mentioned electrode is prepared by the dry method, the battery's fast charging performance, high-rate charging and discharging performance, and cycle performance are better.

[0121] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a pole piece, characterized in that: The steps include: S1, coating the second functional layer slurry on a substrate, and drying to form a substrate containing the second functional layer; S2, coating the first functional layer slurry on the second functional layer of the substrate prepared in step S1, and drying to form a substrate containing the first functional layer and the second functional layer; S3, compounding the substrate prepared in step S2 and the electrode to be processed, so that the first functional layer and the second functional layer on the substrate are transferred to the surface of the electrode to be processed to form a target electrode.

2. The method for preparing a pole piece according to claim 1, characterized in that: In the step S3, the compounding method is roller pressing, and after the roller pressing compounding is completed, the substrate is recovered.

3. The method for preparing a pole piece according to claim 1, characterized in that: The electrode to be processed comprises a current collector and an active material layer at least arranged on one side of the current collector, wherein the active material layer comprises an active material, an active material conductive agent and a binder.

4. The method for preparing a pole piece according to claim 1, characterized in that: The first functional layer includes a first inorganic solid electrolyte, a first polymer solid electrolyte and a first conductive agent.

5. The method for preparing a pole piece according to claim 4, characterized in that: The mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the first functional layer is (5%-99%): (1%-94%): (0.01%-10%); Preferably, the mass ratio of the first inorganic solid electrolyte, the first polymer solid electrolyte and the first conductive agent in the first functional layer is (5%-99%): (50%-94%): (0.01%-10%).

6. The method for preparing a pole piece according to claim 1, characterized in that: The second functional layer includes a second inorganic solid electrolyte and a second polymer solid electrolyte.

7. The method for preparing a pole piece according to claim 6, characterized in that: The mass ratio of the second inorganic solid electrolyte and the second polymer solid electrolyte of the second functional layer is (5%-99%): (1%-95%); Preferably, the mass ratio of the second inorganic solid electrolyte to the second polymer solid electrolyte is (5%-99%): (1%-10%).

8. The method for preparing a pole piece according to claim 7, characterized in that: The bonding force between the electrode to be processed and the first functional layer is F1, and the bonding force between the substrate and the second functional layer is F2, wherein F1>F2.

9. A pole piece, characterized in that: The method is prepared by any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: The battery comprises a positive electrode sheet, a separator and a negative electrode sheet which are arranged in sequence, wherein the positive electrode sheet is the sheet according to claim 9 and / or the negative electrode sheet is the sheet according to claim 9.

Images