CN111430671A - Bipolar pole piece and preparation method thereof, lithium ion battery and preparation method thereof - Google Patents

Bipolar pole piece and preparation method thereof, lithium ion battery and preparation method thereof Download PDF

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Publication number
CN111430671A
CN111430671A CN201911368947.7A CN201911368947A CN111430671A CN 111430671 A CN111430671 A CN 111430671A CN 201911368947 A CN201911368947 A CN 201911368947A CN 111430671 A CN111430671 A CN 111430671A
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material layer
electrode material
current collector
positive electrode
pole piece
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CN111430671B (en
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王亚州
谢涛
于奥
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Svolt Energy Technology Co Ltd
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Svolt Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/029—Bipolar electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The invention discloses a bipolar pole piece and a preparation method thereof, and a lithium ion battery and a preparation method thereof. The method comprises the following steps: arranging a positive electrode material on one surface of a current collector to form a positive electrode material layer rough blank, and performing first rolling treatment on the positive electrode material layer rough blank; arranging a negative electrode material on the other surface of the current collector to form a negative electrode material layer rough blankSimultaneously performing second rolling treatment on the rough blank and the rough blank of the positive electrode material layer subjected to the first rolling treatment to obtain a compact density of 3.40-3.70g/cm3And the compacted density of the positive electrode material layer is 1.40-1.70g/cm3The anode material layer to obtain the bipolar pole piece, wherein the anode material comprises a ternary anode material, and the cathode material comprises graphite. Thus, the positive electrode material layer and the negative electrode material layer obtained by the method can simultaneously satisfy the respective required compaction densities.

Description

Bipolar pole piece and preparation method thereof, lithium ion battery and preparation method thereof
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a bipolar pole piece and a preparation method thereof, and a lithium ion battery and a preparation method thereof.
Background
The lithium ion battery is used as an energy storage device with high voltage, high energy density and long cycle life, and is widely applied to the fields of digital products, electric tools, new energy automobiles, energy storage and the like. In recent years, with the popularization of new energy automobiles, as the most important part of the new energy automobiles, the technology of the lithium ion power battery also enters a rapid development stage, and a lot of research results are obtained in research directions and fields such as high energy density, rapid charging, high safety application and the like. In order to meet the requirements of electric vehicles, a plurality of lithium ion power batteries need to be connected in series to ensure output power, however, the requirement of the series connection on the consistency of the batteries is very high, and the consistency of the batteries applied in series connection is difficult to guarantee according to the current battery manufacturing technology. Meanwhile, the use of the structural member increases the weight of the whole module and reduces the energy density of the whole module, thereby affecting the use of the lithium ion battery.
The bipolar battery is an energy storage device formed by serially overlapping bipolar pole pieces, wherein the positive pole and the negative pole of the bipolar pole pieces share one current collector, namely one side of the current collector is coated with a positive pole material, and the other side of the current collector is coated with a negative pole material.
However, the existing bipolar pole piece and preparation method thereof, lithium ion battery and preparation method thereof still need to be improved.
Disclosure of Invention
The present invention is based on the discovery and recognition by the inventors of the following facts and problems:
the inventor finds that the positive electrode material layer and the negative electrode material layer of the current bipolar pole piece are difficult to simultaneously meet the required compaction densities, so that the lithium ion battery applying the bipolar pole piece has poor service performance or is difficult to obtain higher energy density. Specifically, because the positive electrode material layer and the negative electrode material layer share one current collector, and the compaction density of the positive electrode material and the negative electrode material has a certain difference, when the positive electrode material layer reaches the required compaction density, the compaction density of the negative electrode material layer can exceed the required compaction density, so that the negative electrode material layer is easy to crack and fall off, the use of a pole piece is influenced, when the negative electrode material layer reaches the required compaction density, the positive electrode material layer often cannot reach the required compaction density, and the energy density of the whole battery is influenced.
The present invention aims to alleviate or solve at least to some extent at least one of the above mentioned problems.
In one aspect of the invention, a method of making a bipolar plate is provided. The method comprises the following steps: arranging a positive electrode material on one surface of a current collector to form a positive electrode material layer rough blank, and performing first rolling treatment on the positive electrode material layer rough blank; arranging a negative electrode material on the other surface of the current collector to form a negative electrode material layer rough blank, and simultaneously performing second rolling treatment on the negative electrode material layer rough blank and the positive electrode material layer rough blank subjected to the first rolling treatment to obtain a compact density of 3.40-3.70g/cm3And the compacted density of the positive electrode material layer is 1.40-1.70g/cm3The bipolar pole piece is obtained, wherein the positive electrode material comprises a ternary positive electrode material, and the negative electrode material comprises graphite. Therefore, the positive electrode material layer and the negative electrode material layer of the bipolar pole piece obtained by the method can simultaneously meet the required compaction density, so that the lithium ion battery applying the bipolar pole piece has higher energy density, and the adverse phenomena of cracking, powder falling and the like of the material layers can be effectively avoided, so that the bipolar pole piece has good use performance.
According to an embodiment of the present invention, the first roll nip of the roll press treatment increases with the increase of the thickness of the current collector and the cathode material layer rough blank, the second roll nip of the roll press treatment increases with the increase of the thickness of the current collector, the cathode material layer rough blank and the anode material layer rough blank, and the second roll nip of the roll press treatment is larger than the first roll nip of the roll press treatment. Therefore, the positive electrode material layer and the negative electrode material layer of the bipolar pole piece can meet the required compaction density at the same time.
According to an embodiment of the present invention, the current collector has a thickness of 18 to 24 μm, the cathode material layer blank has a thickness of 48 to 51 μm, the first roll-processed roll gap is 18 to 20 μm, the anode material layer blank has a thickness of 69 to 71 μm, the second roll-processed roll gap is 36 to 40 μm, and the second roll-processed roll gap is 1.8 to 2.2 times the first roll-processed roll gap. Therefore, the positive electrode material layer and the negative electrode material layer of the bipolar pole piece can simultaneously meet the required compaction densities.
According to the embodiment of the invention, the setting of the positive electrode material is realized by performing blade coating on the basis of a first template, the first template is provided with a first hollow part, and the orthographic projection of the first hollow part on the current collector is matched with the orthographic projection of the positive electrode material layer rough blank on the current collector. This enables the positive electrode material layer blank to be easily formed on the current collector.
According to the embodiment of the invention, the negative electrode material is arranged by performing blade coating based on a second template, the second template is provided with a second hollow part, the orthographic projection of the second hollow part on the current collector is matched with the orthographic projection of the negative electrode material layer rough blank on the current collector, the opening area of the second hollow part is larger than that of the first hollow part, and the orthographic projection of the second hollow part on the current collector covers the orthographic projection of the positive electrode material layer rough blank on the current collector. This enables the anode material layer blank to be easily formed on the current collector.
According to the embodiment of the invention, an orthographic projection of the center of the second hollow part on the current collector coincides with an orthographic projection of the center of the rough blank of the positive electrode material layer on the current collector. This can further reduce the number of lithium ion transfer paths and improve the transfer efficiency of lithium ions.
In another aspect of the invention, a bipolar pole piece is provided. According to an embodiment of the invention, the bipolar pole piece comprises: the current collector, set up positive electrode material layer on a surface of the said current collector and set up the negative pole material layer on another surface of the said current collector, the compaction density of the said positive electrode material layer is 3.40-3.70g/cm3And the compacted density of the anode material layer is 1.40-1.70g/cm3Wherein the cathode material comprises a ternary cathode material and the anode material comprises graphite. Therefore, the positive electrode material layer and the negative electrode material layer of the bipolar pole piece can simultaneously meet the required compaction density, so that the lithium ion battery applying the bipolar pole piece has higher energy density, and the adverse phenomena of breakage, powder falling and the like of the material layers can be effectively avoided, so that the bipolar pole piece has good use performance.
According to an embodiment of the present invention, an orthographic projection of the negative electrode material layer on the current collector covers an orthographic projection of the positive electrode material layer on the current collector, and an orthographic projection area of the negative electrode material layer on the current collector is larger than an orthographic projection area of the positive electrode material layer on the current collector. The orthographic projection of the negative electrode material layer on the current collector covers the orthographic projection of the positive electrode material layer on the current collector, therefore, the path for lithium ion migration can be reduced, the migration efficiency of lithium ions is improved, the area of the negative electrode material layer is larger than that of the positive electrode material layer, therefore, the negative electrode material layer can provide enough space for the embedding of the lithium ions, the bad phenomenon that lithium is separated out on the negative electrode material layer can be effectively relieved, and the use safety of the lithium ion battery is improved.
According to an embodiment of the present invention, an orthographic projection of the center of the negative electrode material layer on the current collector coincides with an orthographic projection of the center of the positive electrode material layer on the current collector. This can further reduce the number of lithium ion transfer paths and improve the transfer efficiency of lithium ions.
In another aspect of the invention, a method of making a lithium ion battery is provided. According to an embodiment of the invention, the method comprises: providing a positive pole piece, a negative pole piece and at least one bipolar pole piece, wherein the bipolar pole piece is prepared by the method, or the bipolar pole piece is the bipolar pole piece; a sealing structure and a diaphragm are sequentially arranged between two adjacent pole pieces, the bipolar pole pieces are positioned between the positive pole piece and the negative pole piece, a positive pole material layer of the bipolar pole pieces is arranged close to the negative pole piece, and a negative pole material layer of the bipolar pole pieces is arranged close to the positive pole piece; and sealing a part of the sealing structure, wherein the part of the sealing structure which is not sealed forms an opening, injecting electrolyte between two adjacent pole pieces through the opening, and sealing the part of the sealing structure which is not sealed. Therefore, the lithium ion battery with higher energy density, higher output working voltage and good service performance can be obtained by using the method.
According to an embodiment of the present invention, the sealing structure includes a sealing rubber strip formed by rolling and cutting a resin. Therefore, the sealing rubber strip with uniform thickness is convenient to obtain, and the reliability of the sealing structure is improved.
According to the embodiment of the invention, the sealing is realized by heating the sealing structure, the sealing temperature is 150 ℃ and 170 ℃, and the sealing time is 5-10 s. Thus, sealing can be easily achieved.
In another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery is prepared using the method described above. Therefore, the lithium ion battery has higher energy density, higher output working voltage and good service performance.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 shows a schematic flow diagram of a method for making a bipolar pole piece according to one embodiment of the invention;
fig. 2 shows a schematic flow chart of coating a positive electrode material on a current collector according to an embodiment of the present invention;
fig. 3 shows a schematic flow chart of coating a negative electrode material on a current collector according to an embodiment of the present invention;
FIG. 4 shows a schematic structural diagram of a bipolar pole piece according to an embodiment of the invention;
FIG. 5 shows a schematic structural diagram of a bipolar pole piece according to another embodiment of the present invention;
fig. 6 shows a schematic flow diagram of a method of making a lithium ion battery according to one embodiment of the invention;
FIG. 7 shows a schematic flow diagram for providing a seal and a diaphragm on a pole piece according to one embodiment of the present invention;
fig. 8 shows a schematic diagram of a lithium ion battery according to an embodiment of the invention.
Description of reference numerals:
100: a current collector motherboard; 110: a current collector; 111: an aluminum layer; 112: a copper layer; 200: a positive electrode material layer; 210: a rough blank of the positive electrode material layer; 300: a negative electrode material layer; 310: rough blank of the negative electrode material layer; 400: a positive electrode plate; 410: a positive current collector; 420: a positive electrode material layer of the positive electrode plate; 500: a negative pole piece; 510: a negative current collector; 520: a negative electrode material layer of the negative electrode plate; 600: a diaphragm; 700: a sealing structure; 800: and (3) an electrolyte.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In one aspect of the invention, a method of making a bipolar plate is provided. For ease of understanding, the method according to an embodiment of the invention is first briefly described below:
the inventor finds that the rolling gap has a large influence on the compaction density of the positive electrode material layer and the negative electrode material layer, and the negative electrode material layer can more easily reach the required compaction density compared with the positive electrode material layer under the same rolling gap, so that the obtained positive electrode material layer and the negative electrode material layer can simultaneously reach the respective required compaction density by designing the sequence and the times of rolling treatment and the rolling gap in the preparation process, so as to improve the energy density of the lithium ion battery applying the bipolar pole piece and ensure that the lithium ion battery obtains good service performance.
In the present invention, the "compaction density required by the positive electrode material layer in the bipolar electrode plate" refers to the compaction density actually achieved by the positive electrode material layer in the conventional positive electrode plate (i.e., the positive electrode material is coated on both sides of the current collector), and the "compaction density required by the negative electrode material layer in the bipolar electrode plate" refers to the compaction density actually achieved by the negative electrode material layer in the conventional negative electrode plate (i.e., the negative electrode material is coated on both sides of the current collector).
The following is a detailed description of the various steps of the method according to an embodiment of the invention:
according to an embodiment of the invention, with reference to fig. 1, the method comprises:
s100: arranging a positive electrode material on one surface of a current collector to form a positive electrode material layer rough blank, and performing first rolling treatment on the positive electrode material layer rough blank
According to an embodiment of the present invention, in this step, a cathode material forming cathode material layer rough blank is provided on one surface of the current collector, and the cathode material layer rough blank is subjected to the first rolling process. Therefore, the positive electrode material layer rough blank is rolled in advance, namely, the positive electrode material layer rough blank is preliminarily compacted, and the positive electrode material layer with the required compaction density can be obtained through the second rolling treatment conveniently.
According to the embodiment of the invention, the positive electrode material is arranged on one surface of the current collector by performing blade coating based on the first template, the first template is provided with the first hollow-out part, and the orthographic projection of the first hollow-out part on the current collector is matched with the orthographic projection of the positive electrode material layer rough blank on the current collector. This enables the positive electrode material layer blank to be easily formed on the current collector.
According to an embodiment of the present invention, referring to fig. 2 (a), the first template 10 has a plurality of first hollowed portions 11, thereby forming a plurality of positive electrode material layer blanks arranged at intervals on the current collector mother plate simultaneously. The specific opening area and the opening shape of the first hollow-out portion are not particularly limited as long as the opening area of the first hollow-out portion matches with the cross-sectional dimension of the rough blank of the positive electrode material layer, and the opening shape of the first hollow-out portion matches with the cross-sectional shape of the rough blank of the positive electrode material layer, and those skilled in the art can design the opening area and the opening shape according to specific situations. For example, the opening area of the first hollow portion may be 30mm · 30mm, and the opening shape of the first hollow portion may be square.
The material of the first template is not particularly limited, and may be, for example, plastic, polyethylene terephthalate (PET), or metal, and the metal may be copper.
According to a specific embodiment of the present invention, forming the rough blank of the positive electrode material layer on one surface of the current collector may be achieved by: first, a current collector mother plate 100 is provided, and the current collector mother plate 100 is tiled on a coater station. Subsequently, the side to be coated (the surface of the aluminum layer) of the current collector mother plate 100 is wiped with ethanol, and the first template 10 is placed on the surface of the current collector mother plate 100, and the first template 10 is aligned with the current collector mother plate 100 (fig. 2 (b) is a schematic cross-sectional view of the first template and the current collector mother plate, and fig. 2 (c) is a schematic top view of the first template and the current collector mother plate), and corners of the first template are fixed with an adhesive tape. And then, injecting the slurry of the positive electrode material into one side of the first template, which is far away from the current collector mother board, adjusting the coating height of a scraper, and scraping the slurry of the positive electrode material on the current collector mother board uniformly by using the scraper. Finally, a drying process is performed, and the first mold is removed, so as to form a plurality of cathode material layer blanks 210 arranged at intervals on the current collector mother plate 100 (as shown in (d) of fig. 2). The temperature and time of the drying treatment in this step are not particularly limited, and can be designed by those skilled in the art as the case may be. For example, in this step, the temperature of the drying treatment may be 110 ℃ and the time may be 2 hours.
According to the embodiment of the invention, after the cathode material layer rough blank is formed, the cathode material layer rough blank is subjected to the first rolling treatment so as to realize the preliminary compaction of the cathode material layer rough blank.
According to the embodiment of the invention, the rolling gap of the first rolling treatment is increased along with the increase of the thicknesses of the current collector and the rough blank of the positive electrode material layer, namely, after the thicknesses of the current collector and the rough blank of the positive electrode material layer are changed, the rolling gap of the first rolling treatment is correspondingly changed, and the rolling gap of the second rolling treatment is larger than the rolling gap of the first rolling treatment, so as to realize the preliminary compaction of the rough blank of the positive electrode material layer, and the rolling gap of the first rolling treatment is matched with the rolling gap of the subsequent second rolling treatment, so that the positive electrode material layer obtained after two rolling treatments can reach the required compaction density.
According to an embodiment of the present invention, the thickness of the current collector may be 18 to 24 μm, such as 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, and the thickness of the green sheet of the positive electrode material layer may be 48 to 51 μm, such as 48 μm, 49 μm, 50 μm, 51 μm, and at this time, the roll gap of the first roll process may be 18 to 20 μm, such as 18 μm, 19 μm, 20 μm. Therefore, the initial compaction density of the rough blank of the positive electrode material layer can be obtained, and the rolling gap of the first rolling treatment is matched with the rolling gap of the subsequent second rolling treatment, so that the positive electrode material layer obtained after the two rolling treatments can reach the required compaction density.
The material of the current collector is not particularly limited, and those skilled in the art can design the current collector according to the materials commonly used in bipolar pole pieces. For example, according to an embodiment of the present invention, the current collector may include an aluminum layer and a copper layer stacked together, wherein the aluminum layer is disposed adjacent to the positive electrode material layer, and the copper layer is disposed adjacent to the negative electrode material layer, so that the aluminum layer may be matched with the positive electrode material layer, and the copper layer may be matched with the negative electrode material layer, thereby preventing the current collector from being corroded.
According to an embodiment of the present invention, the ternary positive electrode material may include at least one of a nickel cobalt manganese ternary material and a nickel cobalt aluminum ternary material. Therefore, the bipolar pole piece can obtain better service performance.
S200: arranging a negative electrode material on the other surface of the current collector to form a negative electrode material layer rough blank, performing first rolling treatment on the negative electrode material layer rough blank and the positive electrode material layer rough blank, and performing second rolling treatment to obtain a positive electrode material layer and a negative electrode material layer
According to an embodiment of the present invention, in this step, an anode material is disposed on the other surface of the current collector to form an anode material layer rough blank, and the anode material layer rough blank and the cathode material layer rough blank after the first rolling treatment are simultaneously subjected to the second rolling treatment to obtain a cathode material layer and an anode material layer. Therefore, through the second rolling treatment, the cathode material layer and the anode material layer can be synchronously formed, and the cathode material layer and the anode material layer can simultaneously meet the respective required compaction densities.
According to an embodiment of the present invention, the disposing of the negative electrode material on the other surface of the current collector may be performed by performing doctor blade coating based on a second template, where the second template has a second hollow portion, and an orthographic projection of the second hollow portion on the current collector matches an orthographic projection of the negative electrode material layer rough blank on the current collector. This enables the anode material layer blank to be easily formed on the current collector.
And the orthographic projection of the second hollow part on the current collector covers the orthographic projection of the rough blank of the positive electrode material layer on the current collector. Therefore, the formed orthographic projection of the rough blank of the negative electrode material layer on the current collector covers the orthographic projection of the rough blank of the positive electrode material layer on the current collector, namely, the orthographic projection of the finally formed negative electrode material layer on the current collector covers the orthographic projection of the finally formed positive electrode material layer on the current collector, so that the lithium ion migration path can be reduced, and the lithium ion migration efficiency is improved.
Moreover, the opening area of the second hollow-out portion is larger than that of the first hollow-out portion, that is, the cross-sectional area of the rough blank of the negative electrode material layer is larger than that of the rough blank of the positive electrode material layer, that is, the cross-sectional area of the finally formed negative electrode material layer is larger than that of the positive electrode material layer, so that the negative electrode material layer can provide enough space for the insertion of lithium ions, the bad phenomenon of lithium precipitation of the negative electrode material layer can be effectively relieved, and the use safety of the lithium ion battery is improved.
According to an embodiment of the present invention, referring to fig. 3 (a), the second template 20 has a plurality of second cutouts 21, thereby forming a plurality of anode material layer blanks arranged at intervals on the current collector mother plate simultaneously. The specific opening area and the opening shape of the second hollow-out portion are not particularly limited as long as the opening area of the second hollow-out portion is matched with the cross-sectional area of the rough blank of the negative electrode material layer, the opening shape of the second hollow-out portion is matched with the cross-sectional shape of the rough blank of the negative electrode material layer, and the opening area of the second hollow-out portion is larger than the opening area of the first hollow-out portion, and those skilled in the art can design the opening area and the opening shape according to specific situations. For example, the opening area of the second hollow portion may be 35mm · 35mm, and the opening shape of the second hollow portion may be square.
The material of the second template is not particularly limited, and may be, for example, plastic, polyethylene terephthalate (PET), or metal, and the metal may be copper.
According to a specific embodiment of the present invention, forming the anode material layer rough blank on the other surface of the current collector may be achieved by: first, the other surface (copper layer surface) of the current collector mother plate obtained in S100 is taken as a surface to be coated. Subsequently, the surface to be coated (the surface of the copper layer) of the current collector mother plate 100 is wiped with ethanol, and a second template 20 is placed on the surface of the current collector mother plate 100, and the second template 20 is aligned with the current collector mother plate 100 (fig. 3 (b) is a schematic cross-sectional view of the second template and the current collector mother plate, and a schematic top view of the second template and the current collector mother plate), and corners of the second template are fixed with an adhesive tape. And then injecting the slurry of the negative electrode material into one side of the second template, which is far away from the current collector mother board, adjusting the coating height of a scraper, and utilizing the scraper to scrape the slurry of the negative electrode material to be uniformly coated on the current collector mother board. Finally, a drying process is performed, and the second mold is removed to form a plurality of anode material layer blanks 310 arranged at intervals on the current collector mother plate 100 (see (d) in fig. 3). The temperature and time of the drying treatment in this step are not particularly limited, and can be designed by those skilled in the art as the case may be. For example, in this step, the temperature of the drying treatment may be 100 ℃ and the time may be 2 hours.
The current collector mother plate obtained in S100 is a current collector mother plate provided with a cathode material layer rough blank, and the cathode material layer rough blank is subjected to a first rolling process.
According to the embodiment of the invention, the orthographic projection of the center of the second hollow part on the current collector is overlapped with the orthographic projection of the center of the rough blank of the positive electrode material layer on the current collector. That is, the orthographic projection of the center of the formed rough blank of the negative electrode material layer on the current collector coincides with the orthographic projection of the center of the rough blank of the positive electrode material layer on the current collector (or the orthographic projection of the center of the finally formed negative electrode material layer on the current collector coincides with the orthographic projection of the center of the positive electrode material layer on the current collector). This can further reduce the number of lithium ion transfer paths and improve the transfer efficiency of lithium ions.
According to the embodiment of the invention, after the anode material layer rough blank is formed, the anode material layer rough blank and the cathode material layer rough blank after the first rolling treatment are simultaneously subjected to the second rolling treatment, so that the cathode material layer and the anode material layer are synchronously obtained.
According to the embodiment of the invention, the rolling gap of the second rolling treatment is increased along with the increase of the thicknesses of the current collector, the rough blank of the positive electrode material layer and the rough blank of the negative electrode material layer, and the rolling gap of the second rolling treatment is larger than that of the first rolling treatment, namely when the thickness of the current collector, the thickness of the rough blank of the positive electrode material layer and the thickness of the rough blank of the negative electrode material layer are changed, the rolling gap of the second rolling treatment is correspondingly changed. Since the negative electrode material layer and the positive electrode material layer share one current collector, the rolling gap of the second rolling treatment increases as the thickness of the negative electrode material layer blank increases after the first rolling treatment. Therefore, after the second rolling treatment, the positive electrode material layer and the negative electrode material layer can be synchronously obtained, and the positive electrode material layer and the negative electrode material layer can simultaneously meet the respective required compaction densities.
According to an embodiment of the present invention, when the thickness of the current collector is 18 to 24 μm, the thickness of the cathode material layer blank is 48 to 51 μm, the roll gap of the first roll treatment is 18 to 20 μm, and the thickness of the anode material layer blank is 69 to 71 μm, the roll gap of the second roll treatment may be 36 to 40 μm, and the roll gap of the second roll treatment is 1.8 to 2.2 times, such as 1.8 times, 1.9 times, 2.0 times, 2.1 times, 2.2 times, the roll gap of the first roll treatment. Therefore, the rolling gap of the second rolling treatment is matched with the rolling gap of the first rolling treatment, so that the obtained positive electrode material layer can reach the required compacted density, and meanwhile, the obtained negative electrode material layer can also reach the required compacted density.
According to an embodiment of the present invention, the anode material may include graphite. Therefore, the bipolar pole piece can obtain better service performance.
According to the embodiment of the invention, after the second rolling treatment, the positive electrode material layer and the negative electrode material layer can be dried and cut to obtain the final bipolar pole piece. The temperature and time of the drying treatment in this step are not particularly limited, and can be designed by those skilled in the art as the case may be. For example, the drying temperature in this step may be 100 ℃ and the time may be 24 hours. Regarding the specification of the cutting, the cutting can be performed according to the size required for the actual product. For example, the cutting specification is 60 mm.
According to the embodiment of the invention, the compaction density of the positive electrode material layer in the bipolar pole piece obtained by the method is 3.40-3.70g/cm3The compacted density of the negative electrode material layer is 1.40-1.70g/cm3. Therefore, the positive electrode material layer and the negative electrode material layer in the bipolar pole piece obtained by the method can reach higher compaction density, in other words, the positive electrode material layer and the negative electrode material layer can simultaneously reach the required pressuresThe density is real, so that the energy density of the lithium ion battery applying the bipolar pole piece can be effectively improved, and the adverse phenomena of cracking, powder falling and the like of the material layer can be effectively avoided under the compaction density, so that the bipolar pole piece has good use performance, and the method also has the advantages of simple process and low cost.
In another aspect of the invention, a bipolar pole piece is provided. According to an embodiment of the invention, referring to fig. 4, the bipolar pole piece comprises: the positive electrode comprises a current collector 110, a positive electrode material layer 200 and a negative electrode material layer 300, wherein the positive electrode material layer 200 is arranged on one surface of the current collector 110, the negative electrode material layer 300 is arranged on the other surface of the current collector 110, and the compaction density of the positive electrode material layer 200 is 3.40-3.70g/cm3And the compacted density of the anode material layer 300 is 1.40 to 1.70g/cm3And the cathode material comprises a ternary cathode material, and the anode material comprises graphite. Therefore, the positive electrode material layer and the negative electrode material layer of the bipolar pole piece can simultaneously meet the required compaction density, so that the lithium ion battery applying the bipolar pole piece has higher energy density, and the adverse phenomena of breakage, powder falling and the like of the material layers can be effectively avoided, so that the bipolar pole piece has good use performance.
According to an embodiment of the present invention, the bipolar pole piece may be formed using the methods described above. Therefore, the bipolar pole piece also has the advantages of simple preparation process, low cost and the like.
The specific components of the ternary cathode material have been described in detail above, and are not described in detail herein.
According to an embodiment of the present invention, referring to fig. 4, an orthographic projection of the negative electrode material layer 300 on the current collector 110 covers an orthographic projection of the positive electrode material layer 200 on the current collector 110, and an orthographic area of the negative electrode material layer 300 on the current collector 110 is larger than an orthographic area of the positive electrode material layer 200 on the current collector 110. Therefore, the lithium ion migration path can be reduced, the lithium ion migration efficiency is improved, the negative electrode material layer can provide enough space for the insertion of lithium ions, the bad phenomenon of lithium precipitation of the negative electrode material layer can be effectively relieved, and the use safety of the lithium ion battery is improved.
According to the specific embodiment of the present invention, on the basis of the above, the orthographic projection of the center of the negative electrode material layer 300 on the current collector 110 coincides with the orthographic projection of the center of the positive electrode material layer 200 on the current collector 110. This can further reduce the number of lithium ion transfer paths and improve the transfer efficiency of lithium ions.
According to an embodiment of the present invention, referring to fig. 5, the current collector 110 may include an aluminum layer 110 and a copper layer 120 that are stacked, the positive electrode material layer 200 being disposed on a side of the aluminum layer 110 away from the copper layer 120, and the negative electrode material layer 300 being disposed on a side of the copper layer 120 away from the aluminum layer 110. Therefore, the aluminum layer can be matched with the anode material layer, and the copper layer can be matched with the cathode material layer, so that the phenomenon that the current collector is corroded is avoided.
In another aspect of the invention, a method of making a lithium ion battery is provided. According to an embodiment of the invention, referring to fig. 6, the method comprises:
s300: providing a positive electrode plate, a negative electrode plate and at least one bipolar plate
According to an embodiment of the invention, in this step, a positive pole piece, a negative pole piece and at least one bipolar pole piece are provided. According to an embodiment of the present invention, the bipolar pole piece may be prepared by the method described above, or the bipolar pole piece may be the bipolar pole piece described above. Therefore, the bipolar pole piece can enable the lithium ion battery to obtain higher energy density and higher safety.
As can be understood by those skilled in the art, the positive electrode tab includes a positive electrode current collector and a positive electrode material layer disposed on one side of the positive electrode current collector, and the negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on one side of the negative electrode current collector.
S400: a sealing structure and a diaphragm are sequentially arranged between two adjacent pole pieces
According to an embodiment of the present invention, in this step, a sealing structure and a diaphragm are sequentially disposed between two adjacent pole pieces. According to the embodiment of the invention, the bipolar pole piece is positioned between the positive pole piece and the negative pole piece, the positive pole material layer of the bipolar pole piece is arranged close to the negative pole piece, and the negative pole material layer of the bipolar pole piece is arranged close to the positive pole piece. Thereby, a bipolar battery is constructed.
According to an embodiment of the present invention, the sealing structure may include a sealing strip, which may be formed by rolling and cutting a resin. The inventor finds that the bipolar battery needs to be sealed by a special battery shell at present, the operation is difficult and the cost is high. Compared with the sealing structure formed by a coating method, the sealing structure formed by the method has uniform thickness, so that each area of the sealing structure has good sealing effect, the reliability of the sealing structure is improved, and the sealing rubber strips with uniform thickness can avoid the current collectors of two adjacent pole pieces from contacting during sealing, thereby avoiding the bad phenomena of short circuit and the like.
Specific components of the resin are not particularly limited as long as they do not react with the electrolytic solution and do not have conductivity. For example, according to embodiments of the present invention, the material comprising the bead may be a modified acrylate.
According to an embodiment of the invention, the bead of sealant may be formed by: first, two metal foils (e.g., aluminum foils) having the same size are prepared, an appropriate amount of resin is added to one of the metal foils, and the other metal foil is covered with the resin. Subsequently, the above structure is rolled and left for a certain time, and the resin film is taken out after the resin is solidified. Finally, the resin film is cut out to obtain the joint strip. The gap for rolling can be designed according to the specific material of the resin used, the thickness of the metal foil and the thickness of the finally required bead. For example, the metal foil has a thickness of 20 μm, the resin is a modified acrylate, the bead has a thickness of 135 μm, and the roll gap is 150 μm. The time for the standing may be designed according to the specific material of the resin used until the resin is solidified. For example, the resin is modified acrylate, and the standing time can be 1 h. The cutting specification is not particularly limited as long as the sealing rubber strip can form a sealing space with two adjacent pole pieces and is convenient for storing electrolyte. For example, the size of the pole piece is 60mm, and the size of the sealing rubber strip can be 60mm 3mm (length) and 54mm 3mm (width).
According to an embodiment of the present invention, the sequentially disposing the sealing structure and the diaphragm between two adjacent pole pieces may include: (1) the sealing tape 700 is disposed on the side of the positive electrode sheet 400 on which the positive electrode material layer 420 is disposed, and is fixed to the positive electrode collector 410 of the positive electrode sheet (refer to fig. 7 (a)). (2) The diaphragm 600 is arranged on the side of the positive pole piece provided with the sealing rubber strip 700 and fixed on the positive current collector 410 of the positive pole piece, and the orthographic projection of the diaphragm 600 on the positive pole piece is matched with the orthographic projection of the area enclosed by the inner side of the sealing rubber strip 700 on the positive pole piece (refer to (b) in fig. 7). (3) And arranging the side of the bipolar pole piece, which is provided with the negative electrode material layer, on the side of the diaphragm, which is far away from the positive pole piece. (4) And arranging a sealing rubber strip on one side of the bipolar pole piece, which is provided with the positive pole material layer, and fixing the sealing rubber strip. (5) And arranging a diaphragm on one side of the bipolar pole piece, which is provided with the positive electrode material layer, and fixing the diaphragm on a current collector of the bipolar pole piece, wherein the orthographic projection of the diaphragm on the bipolar pole piece is matched with the orthographic projection of an area, which is enclosed by the inner side of the sealing rubber strip, on the bipolar pole piece. (6) And arranging the side of the negative pole piece provided with the negative pole material layer on the side of the diaphragm far away from the bipolar pole piece provided with the positive pole material layer. In the above process, only one bipolar pole piece is provided, and a plurality of bipolar pole pieces can be provided, which is not described herein again.
It should be noted that the fixing of the sealing rubber strip and the fixing of the diaphragm in the above process can be realized by double-sided adhesive tape.
S500: sealing the sealing structure and injecting electrolyte between two adjacent pole pieces
According to an embodiment of the invention, in this step, the sealing structure is sealed and an electrolyte is injected between two adjacent pole pieces. Specifically, a part of the sealing structure is sealed, an opening is formed in the unsealed part of the sealing structure, electrolyte is injected between two adjacent pole pieces through the opening, and the unsealed part of the sealing structure is sealed, so that the lithium ion battery is obtained (see fig. 8).
According to an embodiment of the invention, the sealing may be achieved by heating the sealing structure. Thus, sealing can be easily achieved. Specifically, the stacked structure obtained in S400 is placed on a vacuum sealing machine for sealing, the sealing temperature can be 150 ℃ and 170 ℃, and the sealing time can be 5-10S. Therefore, a sealing space can be formed between the sealing rubber strip and two adjacent pole pieces, and electrolyte can be stored conveniently.
According to the embodiment of the invention, the sealing rubber strip can enclose a quadrilateral area, three sides of the sealing rubber strip are sealed firstly, electrolyte is injected into the fourth side which is not sealed, and finally the fourth side is sealed to obtain the lithium ion battery.
According to an embodiment of the present invention, the method further comprises vacuum sealing the lithium ion battery with an aluminum plastic film to obtain a final lithium ion battery.
In another aspect of the present invention, a lithium ion battery is provided. According to the embodiment of the invention, the lithium ion battery is prepared by the method described above, so that the lithium ion battery has higher energy density, higher output working voltage and good use performance.
According to an embodiment of the present invention, referring to fig. 8, the lithium ion battery includes: the lithium ion battery comprises a positive pole piece 400, a negative pole piece 500, at least one bipolar pole piece, a diaphragm 600, a sealing structure 700 and an electrolyte 800, wherein the bipolar pole pieces are the bipolar pole pieces described above, the bipolar pole pieces are located between the positive pole piece 400 and the negative pole piece 500, a positive material layer 200 of the bipolar pole pieces is located close to the negative pole piece 500, a negative material layer 300 of the bipolar pole pieces is located close to the positive pole piece 400, the diaphragm 600 is located between two adjacent pole pieces, for example, the diaphragm 600 is located between the positive pole piece 400 and the bipolar pole pieces, between the bipolar pole piece and the negative pole piece 500, and between two adjacent bipolar pole pieces (fig. 8 shows that the lithium ion battery includes one bipolar pole piece), the sealing structure 700 and the two adjacent pole pieces form a sealing space, and the electrolyte. Therefore, the lithium ion battery has higher energy density, higher output working voltage and good service performance.
According to an embodiment of the present invention, referring to fig. 8, the positive electrode tab 400 includes a positive electrode current collector 410 and a positive electrode material layer 420 disposed on one surface of the positive electrode current collector 410, the positive electrode material layer 420 of the positive electrode tab 400 is disposed adjacent to the negative electrode material layer 300 of the bipolar tab, the negative electrode tab 500 includes a negative electrode current collector 510 and a negative electrode material layer 520 disposed on one surface of the negative electrode current collector 510, and the negative electrode material layer 520 of the negative electrode tab 500 is disposed adjacent to the positive electrode material layer 200 of the bipolar tab. Therefore, the lithium ion battery has good use performance.
According to the embodiment of the invention, the lithium ion battery has a larger output working voltage compared with the conventional lithium ion battery, namely, the output working voltage of the lithium ion battery is equivalent to the total output working voltage after the conventional lithium ion batteries are connected in series, so that the lithium ion battery can omit the aluminum shells of the conventional lithium ion batteries compared with the conventional lithium ion batteries connected in series, saves the internal space, can be filled with more electrode materials in the same volume, and simultaneously reduces the manufacturing cost of a battery module.
The invention will now be illustrated by means of specific examples, which are provided for illustration only and should not be construed as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications.
Example 1
The preparation process of the bipolar pole piece is as follows:
(1) an aluminum-copper composite current collector is selected, and the thickness of the current collector is 24 micrometers (the thickness of an aluminum layer is 8 micrometers, and the thickness of a copper layer is 16 micrometers). And coating a nickel-cobalt-manganese ternary material on one side of the aluminum layer to form a rough blank of the positive electrode material layer, wherein the thickness of the rough blank of the positive electrode material layer is 51 mu m. Carrying out first rolling treatment on the anode material layer rough blank, wherein the rolling gap of the first rolling treatment is 20 mu m, and the compacted density of the anode material layer rough blank subjected to the first rolling treatment is 3.32g/cm3。
(2) Graphite was applied to the copper layer side to form a negative electrode material layer blank, and the thickness of the negative electrode material layer blank was 71 μm. And simultaneously carrying out second rolling treatment on the anode material layer rough blank and the anode material layer rough blank subjected to the first rolling treatment, wherein the rolling gap of the second rolling treatment is 40 mu m, so as to obtain an anode material layer and an anode material layer.
The compacted density of the positive electrode material layer was 3.63g/cm3The compacted density of the negative electrode material layer is 1.63g/cm3。
Example 2
The procedure for manufacturing the bipolar electrode sheet of this example was substantially the same as in example 1, except that the current collector had a thickness of 18 μm (the aluminum layer had a thickness of 6 μm and the copper layer had a thickness of 12 μm), the positive electrode material layer blank had a thickness of 48 μm, the first roll treatment had a roll gap of 18 μm, and the green positive electrode material layer had a compact density of 3.20g/cm3The thickness of the anode material layer blank was 69 μm, and the rolling gap of the second rolling treatment was 36 μm.
The compacted density of the positive electrode material layer was 3.56g/cm3The compacted density of the negative electrode material layer is 1.58g/cm3。
Comparative example 1
The preparation process of the bipolar pole piece is as follows:
(1) an aluminum-copper composite current collector is selected, and the thickness of the current collector is 24 micrometers (the thickness of an aluminum layer is 8 micrometers, and the thickness of a copper layer is 16 micrometers). And coating a nickel-cobalt-manganese ternary material on one side of the aluminum layer to form a rough blank of the positive electrode material layer, wherein the thickness of the rough blank of the positive electrode material layer is 51 mu m.
(2) Graphite was applied to the copper layer side to form a negative electrode material layer blank, and the thickness of the negative electrode material layer blank was 71 μm. And simultaneously carrying out rolling treatment on the anode material layer rough blank and the cathode material layer rough blank, wherein the rolling gap of the rolling treatment is 20 mu m, so as to obtain the anode material layer and the cathode material layer.
The compacted density of the positive electrode material layer was 3.37g/cm3The compacted density of the negative electrode material layer is 1.80g/cm3。
Comparative example 2
The procedure for preparing the bipolar electrode sheet of this comparative example was substantially the same as in example 1, except that the rolling gap of the first rolling treatment was 40 μm and the rolling gap of the second rolling treatment was 40 μm.
The compacted density of the positive electrode material layer was 3.21g/cm3The compacted density of the negative electrode material layer is 1.45g/cm3。
In the description of the present invention, the terms "upper", "lower", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention but do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. In addition, it should be noted that the terms "first" and "second" in this specification are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. A method of making a bipolar pole piece, comprising:
arranging a positive electrode material on one surface of a current collector to form a positive electrode material layer rough blank, and performing first rolling treatment on the positive electrode material layer rough blank;
arranging a negative electrode material on the other surface of the current collector to form a negative electrode material layer rough blank, and simultaneously performing second rolling treatment on the negative electrode material layer rough blank and the positive electrode material layer rough blank subjected to the first rolling treatment to obtain a compact density of 3.40-3.70g/cm3And the compacted density of the positive electrode material layer is 1.40-1.70g/cm3To obtain the bipolar pole piece,
wherein the cathode material comprises a ternary cathode material and the anode material comprises graphite.
2. The method according to claim 1, wherein the first roll nip is increased with increasing thickness of the current collector and the cathode material layer blank, the second roll nip is increased with increasing thickness of the current collector, the cathode material layer blank and the anode material layer blank, and the second roll nip is larger than the first roll nip.
3. The method according to claim 2, wherein the current collector has a thickness of 18 to 24 μm, the positive electrode material layer blank has a thickness of 48 to 51 μm, the first roll treatment has a roll gap of 18 to 20 μm,
the thickness of the anode material layer rough blank is 69-71 μm, the rolling gap of the second rolling treatment is 36-40 μm, and the rolling gap of the second rolling treatment is 1.8-2.2 times of the rolling gap of the first rolling treatment.
4. The method according to claim 1, wherein the disposing of the positive electrode material is performed by blade coating based on a first template, the first template having a first hollowed-out portion, and an orthographic projection of the first hollowed-out portion on the current collector matches an orthographic projection of the rough blank of the positive electrode material layer on the current collector.
5. The method according to claim 4, wherein the negative electrode material is arranged by blade coating based on a second template, the second template is provided with a second hollow-out part, the orthographic projection of the second hollow-out part on the current collector is matched with the orthographic projection of the negative electrode material layer rough blank on the current collector, the opening area of the second hollow-out part is larger than that of the first hollow-out part, and the orthographic projection of the second hollow-out part on the current collector covers the orthographic projection of the positive electrode material layer rough blank on the current collector;
optionally, an orthographic projection of the center of the second hollow part on the current collector coincides with an orthographic projection of the center of the rough blank of the positive electrode material layer on the current collector.
6. A bipolar pole piece, comprising:
the current collector, set up positive electrode material layer on a surface of the said current collector and set up the negative pole material layer on another surface of the said current collector, the compaction density of the said positive electrode material layer is 3.40-3.70g/cm3And the compacted density of the anode material layer is 1.40-1.70g/cm3Wherein the cathode material comprises a ternary cathode material and the anode material comprises graphite.
7. The bipolar pole piece of claim 6, wherein an orthographic projection of the negative electrode material layer on the current collector covers an orthographic projection of the positive electrode material layer on the current collector, and an orthographic projection area of the negative electrode material layer on the current collector is larger than an orthographic projection area of the positive electrode material layer on the current collector;
optionally, an orthographic projection of the center of the negative electrode material layer on the current collector coincides with an orthographic projection of the center of the positive electrode material layer on the current collector.
8. A method of making a lithium ion battery, comprising:
providing a positive pole piece, a negative pole piece and at least one bipolar pole piece, wherein the bipolar pole piece is prepared by the method of any one of claims 1 to 5, or the bipolar pole piece is the one of claims 6 or 7;
a sealing structure and a diaphragm are sequentially arranged between two adjacent pole pieces, the bipolar pole pieces are positioned between the positive pole piece and the negative pole piece, a positive pole material layer of the bipolar pole pieces is arranged close to the negative pole piece, and a negative pole material layer of the bipolar pole pieces is arranged close to the positive pole piece;
and sealing a part of the sealing structure, wherein the part of the sealing structure which is not sealed forms an opening, injecting electrolyte between two adjacent pole pieces through the opening, and sealing the part of the sealing structure which is not sealed.
9. The method of claim 8, wherein the sealing structure comprises a bead of sealant formed by rolling and cutting a resin;
optionally, the sealing is performed by heating the sealing structure, the sealing temperature is 150 ℃ and 170 ℃, and the sealing time is 5-10 s.
10. A lithium ion battery, characterized in that it is prepared by the process of claim 8 or 9.
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