CN113675362A - Method and system for preparing electrode slice by dry method and application - Google Patents
Method and system for preparing electrode slice by dry method and application Download PDFInfo
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- CN113675362A CN113675362A CN202110949805.0A CN202110949805A CN113675362A CN 113675362 A CN113675362 A CN 113675362A CN 202110949805 A CN202110949805 A CN 202110949805A CN 113675362 A CN113675362 A CN 113675362A
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Images
Classifications
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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
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
-
- 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
-
- 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
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
- Materials Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a method, a system and application for preparing an electrode plate by a dry method. The method comprises the following steps: mixing an electrode active material, a conductive agent and a dry-process binder to obtain a mixture; kneading the mixture by mechanical extrusion to preliminarily fibrillate the dry binder to obtain a lumpy and/or flocculent prefibrated product; crushing the pre-fibrosis product to obtain granular material; and (3) rolling and forming the granular material and the current collector so as to form a pole piece film on the surface of the current collector and obtain the dry electrode pole piece. The method is simple and feasible, the required equipment is simple, the problem that the electrode active substance structure is damaged in the material crushing treatment process can be effectively solved, the production efficiency is higher, the amplification is easy, the method is more suitable for large-scale mass production of the dry electrode technology, the development of new energy industry is facilitated, and the method has a wide application prospect.
Description
Technical Field
The invention belongs to the field of lithium batteries, and particularly relates to a method and a system for preparing an electrode plate by a dry method and application of the electrode plate.
Background
The processing technology of the pole pieces of the lithium ion battery and the super capacitor can be divided into a wet process and a dry process according to whether a solvent is used or not. The difference between the dry-process electrode plate and the wet-process battery electrode plate mainly focuses on whether a solvent is used in the preparation process of the electrode plate, and a large amount of solvent preparation slurry is needed to prepare the electrode plate into the wet-process electrode by coating. Correspondingly, the dry electrode plate is obtained by using no solvent or only adding a small amount of auxiliary agent, fiberizing through an adhesive, rolling the prepared electrode plate film through a roller press, and hot-pressing and compounding. The wet process, which is the most common coating process at present, is to uniformly mix an electrode active material, a conductive agent and a binder to prepare a battery slurry, and in order to ensure the fluidity of the battery slurry, the solvent content of the battery slurry is generally over 50%. The process of coating and preparing the pole piece is also a process of heating and drying a large amount of solvent, which means that the process of producing the pole piece by the mainstream wet coating needs to consume huge energy consumption, and meanwhile, the production efficiency is low. The corresponding dry process does not need to add any solvent, the electrode film can be prepared only by the fiberization of the dry binder under the solvent-free condition, and the dry electrode pole piece can be obtained by hot-pressing and compounding the electrode film and the current collector. The process for preparing the pole piece by the dry method does not need complex coating equipment, and can prepare the battery pole piece only by continuous heating and rolling.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a method, a system and an application for dry-process preparation of an electrode sheet, so as to solve the problem that the structure of an electrode active material is easily damaged when the electrode sheet is prepared by a dry process, and thus the electrochemical performance of a battery or a super capacitor is reduced.
The present application is primarily based on the following problems:
the development of the wet coating process in the last 30 years is a mature production process technology, and is also the mainstream production technology of most lithium ion batteries and partial super capacitor manufacturers at present. Although the dry process is greatly superior to the wet coating process in the aspects of cost, energy consumption, efficiency and the like, the maturity of the dry process technology is far behind the wet coating process at present, and a plurality of problems to be solved exist at the same time, for example, an electrode film is prepared by pulverizing and fibrosis of an active substance, a conductive agent and a dry adhesive through airflow pulverization equipment, but because the airflow pulverization equipment needs a strong shearing force in the material pulverization process, the structure of the active substance can be damaged while the dry adhesive is fiberized, such as graphite surface damage, ternary material spherical structure breakage and the like. The direct result of the active material structure damage is that the electrochemical performance of the prepared lithium ion battery or super capacitor is reduced. Although the problem that the surface of the active material is damaged can be solved by the supercritical carbon dioxide technology, the supercritical carbon dioxide needs professional equipment, the equipment investment is huge, and the industrial requirements are very difficult to adapt.
In view of the above, an object of the present invention is to provide a method for preparing an electrode sheet by a dry method, so as to solve the problem that the structure of an electrode active material is easily damaged during the dry preparation process. To achieve this object, according to a first aspect of the present invention, a method for dry-process preparation of an electrode sheet is provided. According to an embodiment of the invention, the method comprises:
(1) mixing an electrode active material, a conductive agent and a dry-process binder to obtain a mixture;
(2) kneading the mixture by mechanical pressing to preliminarily fibrillate the dry binder to obtain a lumpy and/or flocculent prefibrated product;
(3) crushing the pre-fibrosis product to obtain granular material;
(4) and rolling and forming the granular materials and the current collector so as to form a pole piece film on the surface of the current collector and obtain the dry electrode pole piece.
Further, in step (1), the mixing further comprises: incorporating an organic auxiliary agent to improve the fiberization effect of the dry binder; and/or the dry-process binder is a fluororesin.
Further, the step (1) satisfies at least one of the following conditions: the organic auxiliary agent comprises a solvent C selected from alkanes6-C20At least one of naphtha, toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1, 4-dioxane, N-methylpyrrolidone, acetone, butanone, N-dimethylacetamide, and dimethylsulfoxide; the addition amount of the organic auxiliary agent is 0.1-20 wt% based on the total mass of the electrode active material, the conductive agent and the dry-process binder; the fluororesin includes at least one selected from the group consisting of a polytetrafluoroethylene resin, a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a polychlorotrifluoroethylene resin.
Further, in the step (2), during the kneading treatment, the mechanical extrusion forces of the mixture at least in two different force-bearing directions are different; and/or the kneading treatment is carried out using a kneading device which is at least one selected from the group consisting of a kneader, an internal mixer, a single-screw extruder, a twin-screw extruder, and a hydraulic extruder.
Further, the kneading device is provided with at least two rotating blades which are mutually matched and arranged side by side in a tangent differential type manner, and the kneading treatment is realized by mechanically extruding the mixture by utilizing the differential rotation of the two rotating blades.
Further, the rotating blades are sigma-shaped.
Further, the step (3) satisfies at least one of the following conditions: screening the granular materials to obtain granular materials with expected particle size ranges; the particle size of the granular material is not less than 2 mm; the crushing treatment is carried out by a crusher, and the rotating speed of the crusher is not more than 1000 rpm.
Further, the step (4) satisfies at least one of the following conditions: the dry electrode pole piece is a positive pole piece and/or a negative pole piece; what is needed isThe pole piece film comprises 80-99.8 wt% of electrode active material, 0.1-10 wt% of conductive agent and 0.1-10 wt% of binder; the compacted density of the pole piece film is 1-5 mg/cm3(ii) a And respectively forming a layer of pole piece film on the upper surface and the lower surface of the current collector, wherein the thickness of each layer of pole piece film is 50-300 mu m, and the total thickness of the dry electrode pole piece is 100-600 mu m.
Further, the step (4) further comprises: (4-1) carrying out hot press molding on the granular materials so as to obtain a primary pole piece membrane; (4-2) performing at least one hot press molding on the primary pole piece film so as to obtain a pole piece film with a desired thickness; and (4-3) carrying out hot-press compounding on the pole piece film and the current collector so as to obtain the dry electrode pole piece.
Further, in the step (4-3), a conductive carbon coating is formed on the surface of the current collector in advance, and then the electrode sheet film and the current collector are subjected to hot-press compounding.
Further, the thickness of the conductive carbon coating is 1-5 μm;
further, conductive carbon powder and thermal sensitive adhesive are mixed and coated on the surface of the current collector so as to form the conductive carbon coating.
Compared with the prior art, the method for preparing the electrode plate by the dry method has the following advantages: 1. the dry electrode mixture is pre-fibrillated into a cluster shape by shearing force formed by mechanical extrusion in advance, and large-particle powder is formed by simple mechanical crushing, so that the rolling film forming of the electrode mixture can be directly carried out, and the damage of a strong shearing force device such as a strong crusher or a jet mill to the structure of an electrode active material can be avoided; 2. the method has the advantages that the airflow crushing step is not needed, the damage effect of the airflow crushing fiberization on the appearance of the anode and cathode material is solved, and the adverse effect of the preparation process of the pole piece on the electrical property of the battery or the capacitor is greatly reduced; 3. the method can continuously provide a pre-fibrosis mixture material by utilizing a continuously-fed mechanical extrusion device, and is subsequently combined with a multi-stage continuous rolling device to directly roll and prepare the double-sided pole piece, so that the production efficiency of the battery pole piece can be greatly improved compared with the conventional wet coating scheme; 4. a small amount of auxiliary agent can be added into the mixture to improve the fiberization effect of the binder, and the problem that the electrode active substance is difficult to directly form a cluster with the dry-process binder due to too high hardness is avoided, wherein the dosage of the adopted organic auxiliary agent is far lower than that of a wet-process preparation process, and the organic auxiliary agent can be removed by drying, so that the electrochemical performance of the pole piece is not adversely affected; 5. the pole piece film prepared by adding the organic auxiliary agent is softer and has better processing performance, meanwhile, under the participation of the organic auxiliary agent, the pole piece is not easy to be rolled excessively, the compaction density is easier to control, and the damage of the rolled excessively to the material appearance can be avoided; 6. the method is simple and feasible, the required equipment is simple, the production efficiency is higher, the amplification is easy, the method is more suitable for large-scale mass production of the dry electrode technology, the development of new energy industry is promoted, and the method has a wide application prospect.
The invention also aims to provide a system for preparing the electrode plate by a dry method, so as to implement the method for preparing the electrode plate by the dry method. To achieve this object, according to a second aspect of the present invention, there is provided a system for carrying out the above-described method for dry-process preparation of an electrode sheet. According to an embodiment of the invention, the system comprises:
a mixing device comprising a feedstock inlet and a mixture outlet;
a kneading device comprising a mixture inlet and a pre-fiberized product outlet, the mixture inlet being connected to the mixture outlet;
the crushing device comprises a pre-fibrosis product inlet and a granular material outlet, and the pre-fibrosis product inlet is connected with the pre-fibrosis product outlet;
the horizontal heating and pressing device comprises a first granular material inlet and a primary pole piece film outlet, wherein the first granular material inlet is connected with the granular material outlet;
the first vertical type heating and pressing device comprises a primary pole piece film inlet and a pole piece film outlet, wherein the primary pole piece film inlet is connected with the primary pole piece film outlet;
the second vertical type heating and pressing device comprises a pole piece film inlet, a current collector inlet and a dry electrode pole piece outlet, wherein the pole piece film inlet is connected with the pole piece film outlet.
Further, at least one of the following conditions is satisfied: at least two rotating blades which are arranged in parallel and tangent in a differential mode are arranged in the kneading device; the screening device comprises a second granular material inlet, an oversize material outlet and an undersize material outlet, wherein the second granular material inlet is connected with the granular material outlet, the oversize material outlet is connected with the first granular material inlet, and the undersize material outlet is connected with the mixture inlet; the crushing device is a crusher; the device comprises at least two first vertical heating and pressing devices which are connected end to end, wherein the first vertical heating and pressing devices comprise primary pole piece film inlets, and the tail end of the first vertical heating and pressing devices comprise pole piece film outlets.
Further, the rotating blades are sigma-shaped.
Further, the kneading device is a kneader, an internal mixer, a single-screw extruder, a twin-screw extruder or a hydraulic extruder.
Compared with the prior art, the system for preparing the electrode plate by the dry method has the following advantages: 1. the dry electrode mixture can be pre-fibrillated into a mass by adopting a shearing force formed by mechanical extrusion in a kneading device in advance, and then is subjected to simple mechanical crushing to form large-particle powder which can be directly rolled into a film, so that the rolling film forming of the electrode mixture is facilitated, and the damage to the electrode active material structure caused by the use of a strong shearing force device such as a strong crusher or a jet mill can be avoided; 2. the jet milling device is not arranged, so that the damage of jet milling fiberization to the appearance of the anode and cathode materials is avoided, and the adverse effect of the preparation process of the pole piece on the electrical property of the battery or the capacitor is greatly reduced; 3. the device can continuously provide a pre-fibrosis mixture material by utilizing a continuously-fed kneading device, and is subsequently combined with multi-stage continuous rolling equipment to directly roll and prepare the double-sided pole piece, so that the production efficiency of the battery pole piece can be greatly improved compared with the conventional wet coating scheme; 4. a small amount of auxiliary agent can be added into the mixture to improve the fiberization effect of the binder, and the problem that the electrode active substance is difficult to directly form a cluster with the dry-process binder due to too high hardness is avoided, wherein the dosage of the adopted organic auxiliary agent is far lower than that of a wet-process preparation process, and the organic auxiliary agent can be removed by drying, so that the electrochemical performance of the pole piece is not adversely affected; 5. the pole piece film prepared by adding the organic auxiliary agent is softer and has better processing performance, meanwhile, under the participation of the organic auxiliary agent, the pole piece is not easy to be rolled excessively, the compaction density is easier to control, and the damage of the rolled excessively to the material appearance can be avoided; 6. the system is simple in structure, high in production efficiency, easy to amplify, suitable for large-scale mass production of the dry electrode technology, beneficial to promoting development of new energy industry and wide in application prospect.
Another object of the present invention is to provide an energy storage device to improve the electrochemical performance of the energy storage device. To achieve the object, according to a third aspect of the present invention, an energy storage device is provided. According to an embodiment of the invention, the energy storage device comprises the electrode plate obtained by adopting the method for preparing the electrode plate by the dry method and/or the electrode plate obtained by adopting the system for preparing the electrode plate by the dry method. Compared with the prior art, the energy storage device has the following advantages: the electrochemical performance is more stable.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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 is a flowchart of a method for dry-process preparation of an electrode sheet according to an embodiment of the present invention.
Fig. 2 is a flowchart of a method for dry-process preparation of an electrode sheet according to still another embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a system for dry-process preparation of an electrode sheet according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a system for dry-process preparation of an electrode sheet according to still another embodiment of the present invention.
Fig. 5 is a flowchart of roll forming in dry process preparation of an electrode sheet according to an embodiment of the present invention.
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 drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "length", "width", "thickness", "upper", "lower", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral connections; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
According to a first aspect of the invention, the invention provides a method for preparing an electrode plate by a dry method. According to an embodiment of the invention, as shown with reference to fig. 1, the method comprises: mixing an electrode active material, a conductive agent and a dry-process binder to obtain a mixture; kneading the mixture by mechanical extrusion to preliminarily fibrillate the dry binder to obtain a lumpy and/or flocculent prefibrated product; crushing the pre-fibrosis product to obtain granular material; and (3) rolling and forming the granular material and the current collector so as to form a pole piece film on the surface of the current collector and obtain the dry electrode pole piece. The inventor finds that compared with the method of directly crushing the dry electrode raw material mixture by using a jet mill, the dry electrode raw material mixture is pre-pulverized into a mass by using the shearing force formed by mechanical extrusion in advance, and then is subjected to simple mechanical crushing to form large-particle powder, so that the rolling film forming of the electrode mixture can be directly carried out, and the damage to the electrode active material structure caused by using a strong shearing force device such as a strong crusher or a jet mill can be avoided. The method is simple and feasible, the required equipment is simple, the production efficiency is higher, the amplification is easy, the method is more suitable for large-scale mass production of the dry electrode technology, the development of new energy industry is promoted, and the method has a wide application prospect.
The method for preparing the electrode plate by the dry method according to the above embodiment of the present invention is described in detail with reference to fig. 1 to 2.
S100, mixing the electrode active substance, the conductive agent and the dry-process binder to obtain a mixture
According to the embodiment of the present invention, the kinds of the electrode active material, the conductive agent, and the dry-process binder are not particularly limited, and those skilled in the art may select them according to the actual situation, such as the application scenario of the electrode sheet and the performance requirements of the positive electrode sheet/the negative electrode sheet.
According to some embodiments of the present invention, when the electrode sheet is used in a supercapacitor, the electrode active material may include one or more selected from activated carbon, carbon aerogel, carbon nanotube, glassy carbon, graphene, carbon fiber, carbon/carbon composite, and the like; when the electrode tab is used in a lithium battery, the electrode active material for the negative electrode tab may include at least one selected from carbonaceous materials, silicon materials, lithium alloy materials, wherein the carbonaceous materials may include natural graphite, artificial graphite, mesocarbon microbeads, etc., and the silicon materials may include silicon monoxide, silicon nanowires, composite silicon carbon materials, etc.; the lithium and lithium alloy material may include at least one of titanium oxide, lithium, a lithium alloy, and a material capable of forming a lithium alloy; the electrode active material for the positive electrode sheet may include an electrode selected from the group consisting of LiNixCoyMnzL(1-x-y-z)O2、LiMxN1-xPO4、LiCoxM1-xO2、xLi2MnO3·(1-x)LiMO2、LiMxMn2-xO4-yFyWherein: LiNixCoyMnzL(1-x-y-z)O2In the formula, x is more than or equal to 0.2 and less than or equal to 0.8, y is more than or equal to 0 and less than or equal to 0.8, z is more than or equal to 0 and less than or equal to 0.8, and L is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe; LiMxN1-xPO4Wherein x is more than 0 and less than or equal to 1, and M, N are respectively and independently one or more selected from Fe, Co, Mn, Mg, Ti or V; LiCoxM1-xO2In the middle, x is more than 0 and less than or equal to 1,m is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe; xLi2MnO3·(1-x)LiMO2Wherein x is more than 0 and less than or equal to 1, and M is one or more selected from Mn, Ni, Co, Cr, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe; LiMxMn2-xO4-yFyIn the formula, M is a doping element, x is more than 0.5 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 0.5, and M is one or more selected from Fe, Ni, Co, Ti, V and Cr.
According to still some embodiments of the present invention, the conductive agent may be one or more selected from Carbon Nanotubes (CNTs), graphite-based conductive agents, conductive carbon black, ketjen black, acetylene black, graphene, and carbon fibers (VGCF), whereby the conductive performance of the pole piece may be further ensured.
According to still other embodiments of the present invention, the dry-process binder may be a fluororesin, wherein the fluororesin may include one or more selected from the group consisting of polytetrafluoroethylene resin (PTFE), tetrafluoroethylene and perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene and hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene resin (PCTFE), and further, the actual material state of the fluororesin includes, but is not limited to, suspension resin, dispersion resin, and dispersion emulsion, and those skilled in the art may select a suitable preparation process according to actual circumstances and obtain a fluororesin of a desired material state. The inventor finds that the fluororesin is used as the binder, so that the mixture can achieve a better fiberizing and agglomerating effect, and the fluororesin binder also has the advantages of good thermal stability, easiness in processing and the like.
According to still other embodiments of the present invention, the inventors found that there may be a problem that the binder fiberization of the kneading apparatus using a weak shearing force is not desirable during the subsequent kneading process, and a problem that the lithium ion battery positive electrode material (e.g., nickel-cobalt-manganese ternary material, lithium iron phosphate, lithium manganate, lithium cobaltate, etc. metal oxide positive electrode material) is difficult to prefibrate due to its relatively high hardness, and in order to solve the problem, the inventors found that, as shown in fig. 2, a small amount of organic auxiliary agent (i.e., semi-dry process) may be added to the mixture of the active material, the dry binder, and the conductive agent, thereby achieving an effect of effectively improving the fiberization effect of the binder, and the mechanism of the effect is to soften the dry binder through the interaction of the auxiliary agent and the dry binder, so that the electrode material and the dry binder are more easily fiberized into a mass, thereby effectively solving the problem that the binder is easily fiberized in the kneading apparatus due to a weak shearing force of the kneading apparatus or a relatively high hardness of the positive electrode material Difficult to pre-fibrosis. The amount of the organic auxiliary is 0.1-20 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 13 wt%, 15 wt%, 17 wt%, or 19 wt%, based on the total mass of the electrode active material, the conductive agent, and the dry-process binder, and the inventors found that the preparation efficiency is affected if the amount of the organic auxiliary is too large, and preferably, the amount of the organic auxiliary is 0.1-10 wt%, so that the fiberization effect of the dry-process binder can be significantly improved, the mixture can be more easily fiberized into lumps, and the use of the organic auxiliary can be further ensured not to adversely affect the efficiency of the dry-process preparation process. The organic auxiliary agent used in the present invention is a small-molecular organic auxiliary agent, and the amount of the organic auxiliary agent used in the present invention is much lower than the amount of the solvent used in the wet preparation process, and the form and action of the organic auxiliary agent in the present invention are different from the action of adding the solid polymer in the prior art when preparing the electrode sheet, and the solid polymer is substantially used as the binder, while the organic auxiliary agent in the present invention is liquid and used as the solvent, and the purpose of the present invention is to improve the fiberization effect of the dry binder.
According to further embodiments of the present invention, the kind of the organic auxiliary agent in the present invention is not particularly limited, and one skilled in the art can select the organic auxiliary agent according to actual needs as long as the effect of softening the dry-process binder and making the dry-process binder easier to fiberize is achieved, for example, the organic auxiliary agent may include, but is not limited to, alkane solvent C6-C20Naphtha, toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1, 4-dioxane, N-methylpyrrolidone, acetone, butanone, N-dimethylacetamide, and dimethyleneOne or more of a sulfone; for another example, the organic auxiliary agent can be preferably an auxiliary agent which is easily volatile or has a low melting point and the like and is easily removed by heating, so that the requirement for improving the fiberization effect of the dry-process binder can be met, and the organic auxiliary agent can be removed by drying or subsequent heating and rolling, so that the residue of the organic auxiliary agent in the pole piece can be greatly reduced.
S200, kneading the mixture through mechanical extrusion to preliminarily fiberize the dry-process binder to obtain blocky and/or flocculent pre-fiberization products
According to the embodiment of the present invention, the damage of the electrode active material structure using a strong shearing force device such as a strong pulverizer, a jet mill, or the like can be avoided by a method of pre-fibrillating and kneading the mixture into a mass using a shearing force formed by mechanical extrusion in advance, followed by re-crushing into large particle powder.
According to some embodiments of the present invention, the mechanical pressing force of the mixture in at least two different directions can be different during the kneading process, and the inventors have found that by kneading the mixture in a plurality of different directions with different mechanical pressing forces, the shearing rate of the mixture can be significantly increased, and the mixture can be rapidly sheared, thereby enabling rapid fiberization of the dry-process binder. For achieving a good fiberization effect, a kneading device may be used to carry out the kneading treatment. It should be noted that the kneading apparatus in the present invention refers to an apparatus capable of forming a shear force by mechanical extrusion, and includes, but is not limited to, a kneader, an internal mixer, a single screw extruder, a twin screw extruder, a hydraulic extruder, and the like. Preferably, the kneading device may be provided with at least two (for example, a pair of) rotating blades which are mutually matched and arranged in a side-by-side tangential differential type, and the differential rotation of the two rotating blades is used for mechanically extruding the mixture to generate a strong shearing action so as to enable the dry-process adhesive to be fiberized, namely, the fiberization action is achieved through different rotating speeds of the two rotating blades and a side-by-side tangential differential type arrangement is adopted, namely, one stirring paddle is high in speed and one stirring paddle is low in speed so as to generate shearing force, and the different paddle speeds enable the mixed materials to be rapidly sheared, so that the dry-process adhesive can be rapidly fiberized. Thus, the preliminary fiberization of the dry-process binder can be realized by the extrusion shearing force of the kneading device, and an uneven massive or flocculent mixture is formed after the preliminary fiberization. Further, the rotating blades arranged in the kneading device in a side-by-side tangential differential manner can also be sigma-shaped, so that the rapid shearing of the mixture can be further facilitated, the dry-process binder can be fiberized more rapidly, and a better fiberizing effect can be achieved.
S300, crushing the pre-fibrosis product to obtain granular material
According to the embodiment of the invention, the non-uniform block-shaped or flocculent pre-fibrosis product can be crushed into large-particle powder by adopting a low-speed crushing device, and then the electrode film and the dry electrode pole piece are prepared by heating a roller press, so that the damage to the electrode active material structure possibly generated in the crushing process can be further avoided.
According to some embodiments of the present invention, the crushing treatment may be performed using a crusher, wherein the rotation speed of the crusher may be not greater than 1000 rpm, and the inventors have found that if the rotation speed of the crusher is too high, not only may the mixture be crushed excessively, and the fiber structure formed by pre-fibrosis may be destroyed; and too garrulous granule still is unfavorable for going on of follow-up roll-in shaping, takes place the caking phenomenon easily, and the granule is too garrulous still can lead to pole piece compaction density too big simultaneously, is unfavorable for energy storage equipment electrochemical performance's promotion. According to the invention, the low-speed crushing is carried out on the kneaded and agglomerated pre-fibrosis product by controlling the rotating speed range, so that the fiber structure of the pre-fibrosis product can be prevented from being damaged, and the particle size can be prevented from being excessively crushed, thereby being more beneficial to the smooth subsequent roll forming and obtaining the pole piece with proper compaction density.
According to some embodiments of the present invention, the granular material obtained by the crushing process may be pre-screened and then subjected to a subsequent roll forming process, thereby further avoiding the occurrence of agglomeration during the roll forming process. Further, the particle size of the particulate material may be not less than 2mm, for example, 2 to 20mm, 3mm, 5mm, 8mm, 10mm, or 12mm, and the particulate material may be sieved by using an 8-mesh sieve, for example, the inventors found that the particulate material having the above particle size range does not have an obvious agglomeration phenomenon in the subsequent roll forming process. Preferably, the particle size of the granular material can be 2-10 mm, so that the smooth subsequent roll forming is facilitated, the pole piece film with the appropriate compaction density is obtained, and the problem that the feeding efficiency is influenced in the roll forming process due to the overlarge particle size of the granular material can be avoided.
S400, rolling and forming the granular materials and the current collector to form a pole piece film on the surface of the current collector to obtain a dry electrode pole piece
According to the embodiment of the invention, the large-particle dry electrode powder mixture obtained by crushing treatment is heated and rolled to obtain the electrode piece film, and then the electrode piece film and the current collector are heated and compounded into a whole to obtain the dry electrode pole piece.
As understood with reference to fig. 5, roll forming may further include, according to some embodiments of the present invention: carrying out hot-press molding on the granular materials so as to obtain a primary pole piece membrane; carrying out at least one-time hot press molding on the primary pole piece film so as to obtain a pole piece film with an expected thickness; and carrying out hot-pressing compounding on the pole piece film and the current collector so as to obtain the dry electrode pole piece. The inventor finds that when the granular material is subjected to hot press molding, the obtained primary pole piece film is generally thick, meanwhile, the edge shape of the primary pole piece film is irregular, the cut and shaped primary pole piece film can be subjected to at least one heating rolling shaping again to obtain a pole piece film with an expected thickness, and the specific times of the heating rolling shaping on the primary pole piece film can be selected according to the state of the primary pole piece film; and finally, carrying out hot-pressing compounding on the pole piece film with the expected thickness and the current collector to obtain a dry electrode pole piece, wherein preferably, two layers of pole piece films are respectively formed on the upper surface and the lower surface of the current collector to carry out hot-pressing compounding at the same time to obtain a double-sided dry electrode plate, so that the preparation efficiency can be further improved. The hot press forming of the granular materials can be carried out by adopting a horizontal heating roller press, the hot press forming of the primary pole piece film can be carried out by adopting at least one vertical heating roller press, for example, a plurality of vertical heating roller presses arranged from head to tail or a single multi-stage roller can be adopted, and the hot press compounding of the pole piece film and the current collector can also be finished by adopting a vertical heating roller press. The rolling forming can be carried out under a heating condition, the rolling temperature can be 50-180 ℃, for example, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 140 ℃ or 160 ℃ and the like, and the inventor finds that the heating rolling can further soften the diaphragm, improve the processing performance of the pole piece film, avoid the pole piece film from being too hard to influence the processing performance of the pole piece film and the pole piece, and simultaneously can avoid the service life of equipment from being influenced by too high temperature by controlling the rolling temperature not to be more than 180 ℃.
According to still other embodiments of the present invention, the current collector may include copper foil, aluminum foil, and other metal foils. The inventor finds that a conductive carbon coating can be formed on the surface of the current collector in advance, then the pole piece film and the current collector are subjected to hot-pressing compounding, and the conductive carbon coating is introduced, so that the laminating effect of the current collector and the pole piece film can be improved, and the interface impedance between the current collector and the pole piece film can be reduced, thereby being more beneficial to improving the stability and the electrochemical performance of the pole piece. The thickness of the conductive carbon coating can be 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, so that the energy density of the pole piece can be prevented from being affected by the excessively thick conductive coating on the basis of ensuring the good functionality of the conductive carbon coating. Preferably, conductive carbon powder and thermosensitive adhesive can be mixed and coated on the surface of the current collector so as to form a conductive carbon coating, and the thermosensitive adhesive is selected as a binder, so that the bonding effect between the conductive carbon coating and the current collector and between the conductive carbon coating and the pole piece membrane can be further improved, and the pole piece can be bonded firmly without foaming after the pole piece membrane and the current collector are subjected to high-temperature hot-pressing compounding. In the formation of the conductive carbon coating layer, the type of the conductive carbon to be selected is not limited to characteristics, and may be selected by those skilled in the art according to actual needs.
According to further embodiments of the present invention, the dry electrode tab may be a positive tab and/or a negative tab. Furthermore, the electrode sheet film can comprise 80-99.8 wt% of electrode active material, 0.1-10 wt% of conductive agent and 0.1-10 wt% of binder, so that the influence of too small amount of conductive agent on the conductivity of the electrode sheet and the influence of too small amount of binder on the binding performance with a current collector can be avoided, the influence of too large amount of conductive agent and/or binder on the energy density of the battery can be avoided, and the control of the component proportion of the electrode active material, the conductive agent and the dry binder can be specifically realized. Further, the compacted density of the pole piece film can be 1-5 mg/cm3. Moreover, the thickness of the pole piece films formed on the upper surface and the lower surface of the current collector can be respectively and independently 50-300 microns, and the total thickness of the dry electrode pole piece can be 100-600 microns, so that high energy density can be obtained, the structural stability of the pole piece can be ensured, and the influence of the excessive thickness of the pole piece film on the bonding property of the current collector is avoided.
According to the embodiment of the invention, the subsequent battery preparation process of the dry electrode is completely the same as the battery preparation step of coating the battery pole piece, and the dry electrode pole piece can be cut into a sheet shape or a strip shape. The positive and negative pole pieces can be separated by a diaphragm through welding lugs, and the battery cell is prepared by using a lamination or winding process. And after the battery core is baked to remove water, injecting electrolyte, and forming and grading to obtain the finished product lithium ion battery or the super capacitor.
Compared with the prior art, the method for preparing the electrode plate by the dry method has the following advantages: 1. the dry electrode mixture is pre-fibrillated into a cluster shape by shearing force formed by mechanical extrusion in advance, and large-particle powder is formed by simple mechanical crushing, so that the rolling film forming of the electrode mixture can be directly carried out, and the damage of a strong shearing force device such as a strong crusher or a jet mill to the structure of an electrode active material can be avoided; 2. the method has the advantages that the airflow crushing step is not needed, the damage effect of the airflow crushing fiberization on the appearance of the anode and cathode material is solved, and the adverse effect of the preparation process of the pole piece on the electrical property of the battery or the capacitor is greatly reduced; 3. the method can continuously provide a pre-fibrosis mixture material by utilizing a continuously-fed mechanical extrusion device, and is subsequently combined with a multi-stage continuous rolling device to directly roll and prepare the double-sided pole piece, so that the production efficiency of the battery pole piece can be greatly improved compared with the conventional wet coating scheme; 4. a small amount of auxiliary agent can be added into the mixture to improve the fiberization effect of the binder, and the problem that the electrode active substance is difficult to directly form a cluster with the dry-process binder due to too high hardness is avoided, wherein the dosage of the adopted organic auxiliary agent is far lower than that of a wet-process preparation process, and the organic auxiliary agent can be removed by drying, so that the electrochemical performance of the pole piece is not adversely affected; 5. the pole piece film prepared by adding the organic auxiliary agent is softer and has better processing performance, meanwhile, under the participation of the organic auxiliary agent, the pole piece is not easy to be rolled excessively, the compaction density is easier to control, and the damage of the rolled excessively to the material appearance can be avoided; 6. the method is simple and feasible, the required equipment is simple, the production efficiency is higher, the amplification is easy, the method is more suitable for large-scale mass production of the dry electrode technology, the development of new energy industry is promoted, and the method has a wide application prospect.
According to a second aspect of the invention, the invention proposes a system for implementing the above-mentioned method for dry-process preparation of an electrode sheet. According to an embodiment of the invention, as shown with reference to fig. 3, the system comprises: a mixing device 10, a kneading device 20, a crushing device 30, a horizontal heating and rolling device 40, a first vertical heating and rolling device 50, and a second vertical heating and rolling device 60.
Wherein the mixing device 10 comprises a raw material inlet 11 and a mixture outlet 12, the mixing device 10 is adapted to mix the electrode active material, the conductive agent, the dry-process binder (and preferably the added organic auxiliary agent) so as to obtain a mixture, wherein the electrode active material, the conductive agent, the dry-process binder and the organic auxiliary agent can be added from the raw material inlet; the kneading device 20 comprises a mixture inlet 21 and a pre-fiberized product outlet 22, the mixture inlet 21 being connected to the mixture outlet 12, the kneading device 20 being adapted to knead the mixture by mechanical pressing in order to preliminarily fiberize the dry binder to obtain a lumpy and/or fluffy pre-fiberized product; the crushing device 30 comprises a pre-fibrosis product inlet 31 and a granular material outlet 32, the pre-fibrosis product inlet 31 is connected with the pre-fibrosis product outlet 22, and the crushing device 30 is suitable for crushing the pre-fibrosis product so as to obtain the granular material; the horizontal heating and pressing device 40 comprises a first granular material inlet 41 and a primary pole piece film outlet 42, wherein the first granular material inlet 41 is connected with the granular material outlet 32; the first vertical type heating and rolling device 50 comprises a primary pole piece film inlet 51 and a pole piece film outlet 52, wherein the primary pole piece film inlet 51 is connected with the primary pole piece film outlet 42; the second vertical heating and rolling device 60 comprises a pole piece film inlet 61, a current collector inlet 62 and a dry electrode pole piece outlet 63, the pole piece film inlet 61 is connected with the pole piece film outlet 52, and the horizontal heating and rolling device 40, the first vertical heating and rolling device 50 and the second vertical heating and rolling device 60 are suitable for roll forming of granular materials and current collectors so as to form a pole piece film on the surface of the current collector and obtain the dry electrode pole piece.
The system is simple in structure, can continuously provide a pre-fibrosis mixture material by using a screw extrusion device with continuous feeding, can directly roll and prepare the double-sided pole piece by using a subsequent multistage continuous rolling device, greatly improves the production efficiency of the battery pole piece compared with the conventional wet coating process, is easy to amplify, is more suitable for large-scale mass production of a dry electrode technology, is beneficial to promoting the development of a new energy industry, and has a wide application prospect.
According to some specific embodiments of the present invention, the type of the kneading device 20 in the present invention is not particularly limited, and may be selected by those skilled in the art according to actual needs as long as it can pre-fibrillate the mixture by forming shear force through mechanical extrusion, for example, the kneading device may include, but is not limited to, a kneader, an internal mixer, a single screw extruder, a twin screw extruder, a hydraulic extruder, and the like. Preferably, at least two rotating blades arranged side by side tangentially and differentially may be provided in the kneading device 20, for example, to fiberize the dry binder by the intense shearing action produced by a pair of cooperating and rotating blades, wherein the rotating blades have different speeds, one blade has a high speed and one blade has a low speed, so as to generate shearing forces. More preferably, the rotating blades may be sigma shaped, thereby further facilitating rapid shearing of the mixture, allowing faster fiberization of the dry binder, while still achieving better fiberization.
According to still other embodiments of the present invention, referring to fig. 4, the system for dry-process electrode sheet preparation may further include a sieving device 70, the sieving device 70 includes a second granular material inlet 71, an oversize material outlet 72 and an undersize material outlet 73, the second granular material inlet 71 is connected to the granular material outlet 32, the oversize material outlet 72 is connected to the first granular material inlet 41, and the undersize material outlet 73 is connected to the mixture inlet 21, the sieving device is adapted to sieve the granular materials obtained by the crushing process, so as to ensure that the granular materials have larger particle sizes, thereby avoiding the problems that the rolling film forming effect is affected by the over-crushing of the granular materials, and the over-crushed materials may be returned to the kneading equipment for reprocessing.
According to further embodiments of the present invention, the type of the crushing device 30 is not particularly limited, and those skilled in the art can select the crushing device according to actual needs, for example, the crushing device may be a low-speed crusher, and the speed of the crusher may be not more than 1000 rpm, so that the over-crushing of the granular material can be avoided.
According to further embodiments of the present invention, roll-forming the electrode sheet film may include at least 3 heated roll-forming devices, i.e., a horizontal heating and rolling device 40 can be included for rolling the granular materials to prepare the primary pole piece film, which is generally thicker, meanwhile, the edge shape of the pole piece film is irregular, the cut and shaped primary pole piece film is transferred to a first vertical heating and rolling device 50 for shaping, the primary pole piece film is secondarily rolled and shaped by at least one vertical heating and rolling device 50 in the heating, rolling and shaping stage, the roll shaping work may be performed by a plurality of (or a single multi-stage roll) vertical roll devices depending on the state of the primary electrode sheet film, for example, at least two first vertically heated roll-off means 50 may be included, the first vertically heated roll-off means including a primary pole piece film inlet 51 and the first vertically heated roll-off means including a pole piece film outlet 52. After the electrode sheet film is rolled to a set film thickness, the electrode sheet film and a current collector can be subjected to hot-pressing compounding to prepare a dry electrode sheet, and the hot-pressing compounding is completed through a second vertical heating and pressing device 60.
According to further embodiments of the present invention, a first cutting device (not shown) for cutting the primary electrode sheet film may be disposed between the horizontally heated rolling device 40 and the first vertically heated rolling device 50, and/or a second cutting device (not shown) for cutting the dry electrode sheet may be disposed downstream of the second vertically heated rolling device 60, thereby further facilitating obtaining a dry electrode sheet of a desired shape and size.
It should be noted that the features and effects described in the method for preparing an electrode plate by a dry method are also applicable to the system for preparing an electrode plate by a dry method, and are not described in detail herein.
Compared with the prior art, the system for preparing the electrode plate by the dry method has the following advantages: 1. the dry electrode mixture can be pre-fibrillated into a mass by adopting a shearing force formed by mechanical extrusion in a kneading device in advance, and then is subjected to simple mechanical crushing to form large-particle powder which can be directly rolled into a film, so that the rolling film forming of the electrode mixture is facilitated, and the damage to the electrode active material structure caused by the use of a strong shearing force device such as a strong crusher or a jet mill can be avoided; 2. the jet milling device is not arranged, so that the damage of jet milling fiberization to the appearance of the anode and cathode materials is avoided, and the adverse effect of the preparation process of the pole piece on the electrical property of the battery or the capacitor is greatly reduced; 3. the device can continuously provide a pre-fibrosis mixture material by utilizing a continuously-fed kneading device, and is subsequently combined with multi-stage continuous rolling equipment to directly roll and prepare the double-sided pole piece, so that the production efficiency of the battery pole piece can be greatly improved compared with the conventional wet coating scheme; 4. a small amount of auxiliary agent can be added into the mixture to improve the fiberization effect of the binder, and the problem that the electrode active substance is difficult to directly form a cluster with the dry-process binder due to too high hardness is avoided, wherein the dosage of the adopted organic auxiliary agent is far lower than that of a wet-process preparation process, and the organic auxiliary agent can be removed by drying, so that the electrochemical performance of the pole piece is not adversely affected; 5. the pole piece film prepared by adding the organic auxiliary agent is softer and has better processing performance, meanwhile, under the participation of the organic auxiliary agent, the pole piece is not easy to be rolled excessively, the compaction density is easier to control, and the damage of the rolled excessively to the material appearance can be avoided; 6. the system is simple in structure, high in production efficiency, easy to amplify, suitable for large-scale mass production of the dry electrode technology, beneficial to promoting development of new energy industry and wide in application prospect.
According to a third aspect of the invention, an energy storage device is presented. According to an embodiment of the invention, the energy storage device comprises the electrode plate obtained by adopting the method for preparing the electrode plate by the dry method and/or the electrode plate obtained by adopting the system for preparing the electrode plate by the dry method. Compared with the prior art, the energy storage device has the following advantages: the electrochemical performance is more stable. It should be noted that the features and effects described for the method for preparing an electrode plate by a dry method and the system for preparing an electrode plate by a dry method are also applicable to the energy storage device, and are not repeated here. In addition, it should be noted that the type of the energy storage device in the present invention is not particularly limited, and those skilled in the art can select the type according to actual needs, for example, the type may be a lithium battery or a super capacitor. When the energy storage equipment is a battery, the positive and negative pole pieces of the battery are separated by a diaphragm to avoid short circuit. It should be noted that the type of the battery separator is not particularly limited, and can be selected by those skilled in the art according to actual needs, for example, the battery separator can be all types of separators used in lithium ion batteries, including but not limited to polyethylene, polypropylene, polyvinylidene fluoride, and other composite membranes. In addition, the battery electrolyte can comprise conventional carbonate electrolyte and solid electrolyte, and can also comprise a composite electrolyte system combining the carbonate electrolyte and the solid electrolyte, such as gel electrolyte, semi-solid electrolyte, quasi-solid electrolyte and the like; the carbonate electrolyte may include carbonate and carboxylate solvents, electrolyte lithium salts, and various functional additives; the solid electrolyte may include a polymer system, an oxide system, a sulfide system, and the like.
The following examples are illustrative only and are not to be construed as limiting 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. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1
(1) Mixing an electrode active substance, a conductive agent and a dry-process binder by using a mixing device to obtain a mixture, wherein the electrode active substance is an NCM523 positive electrode material, the conductive agent is SP (superconducting carbon black), the dry-process binder is PTFE, and the mass ratio of the three components is 97: 1: 2;
(2) the mixture is kneaded by a kneading device with a pair of sigma-shaped rotating blades which are mutually matched and arranged side by side in a tangent differential mode, so that the dry-method binder is subjected to preliminary fibrosis to obtain a pre-fibrosis product, and the rotating speeds of the two blades are 42 revolutions per minute and 28 revolutions per minute respectively.
(3) And (3) crushing the pre-fibrosis product by using a crusher to obtain granular materials, wherein the rotating speed of the crusher is 500 revolutions per minute, screening the granular materials by using an 8-mesh screen, and collecting undersize materials.
(4) Carrying out hot press molding on the sieved material at 100 ℃ by adopting a horizontal heating roller press to obtain a primary pole piece film; carrying out 3 batches of accumulated 9 times of hot roll forming on the primary pole piece film at 120 ℃ by adopting 1 continuous vertical three-roll heating roll press to obtain a pole piece film with the thickness of 180 mu m; the compacted density of the positive electrode sheet film reaches 3.4g/cm3And the pole piece film cannot be rolled into a thinner pole piece film continuously.
Example 2
The difference from example 1 is that: in the step (2), an organic auxiliary agent isomeric hexadecane (trade name Isopar M) is further added, and the proportion of the organic auxiliary agent in the mixture is 8 wt%. Step (4) carrying out hot-press molding on the sieved material at 100 ℃ by adopting a horizontal heating roller press to obtain a primary pole piece film; 1 continuous vertical three-roller heating roller press 1 is adoptedCarrying out 3 batches of accumulated 9 times of hot roll forming on the primary pole piece film at the temperature of 20 ℃ to obtain a pole piece film with the thickness of 80 mu m; the compacted density of the positive electrode sheet film reaches 2.9g/cm3. Drying by blowing at 150 ℃ for 4h, removing the assistant Isopar M, and performing hot-pressing compounding on the electrode sheet film and a double-sided carbon-coated aluminum foil current collector with the thickness of 17 mu M at 120 ℃ by using a vertical hot-rolling press, wherein the carbon-coated layer thickness is 2 mu M, so as to obtain a double-sided electrode sheet, the thickness of the electrode sheet is 159 mu M, and the compacted density of the electrode sheet is 3.3g/cm3。
Comparative example 1
The difference from example 1 is that: the mixture was crushed by jet mill in place of the steps (2) to (3) in example 1. Wherein the air pressure of the feeding hole is 0.5MPa, the air pressure of the air flow crushing is 0.3MPa, the vibration frequency of the vibration feeder is 15Hz, and the air flow crushing only collects the materials in the first-stage cyclone collector. Directly rolling and forming a film on the material subjected to jet milling at 100 ℃ by adopting a horizontal heating roller press to obtain a pole piece film with the thickness of 180 mu m and the compaction density of 3.6g/cm3。
The bonding strength and mechanical properties of the pole piece films prepared in examples 1-2 and comparative example 1 were tested, and the test results were as follows: the pole piece films prepared in example 1 and comparative example 1 are relatively thick and exhibit brittle mechanical properties, while the pole piece films have a compacted density of greater than 3.0g/cm3The pole piece is hard and is difficult to roll to less than 100 μm, but the brittleness and hardness of the pole piece film prepared in example 1 are obviously improved in comparison example 1. In addition, comparative example 1, since the positive electrode material was treated by jet milling, the compacted density was higher than that of example 1 due to the problem of crushing of particles of the positive electrode material during jet milling.
Example 2 very simple rolling of an extremely thin film to 80 μ M with a compacted density of 2.9g/cm, with effective softening of the binder PTFE by introduction of the auxiliary agent Isopar M3And the flexibility of the pole piece is good. The auxiliary agent can be removed by simple heating treatment, and the dry-process battery pole piece can be prepared by hot-pressing and compounding the pole piece film and the carbon-coated aluminum foil current collector.
In the above embodiment of the invention, the positive electrode material is taken as an example, and the negative electrode plate can also be prepared by using the method.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example 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.
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 for preparing an electrode plate by a dry method is characterized by comprising the following steps:
(1) mixing an electrode active material, a conductive agent and a dry-process binder to obtain a mixture;
(2) kneading the mixture by mechanical pressing to preliminarily fibrillate the dry binder to obtain a lumpy and/or flocculent prefibrated product;
(3) crushing the pre-fibrosis product to obtain granular material;
(4) and rolling and forming the granular materials and the current collector so as to form a pole piece film on the surface of the current collector and obtain the dry electrode pole piece.
2. The method of claim 1, wherein in step (1), the mixing further comprises: incorporating an organic auxiliary agent to improve the fiberization effect of the dry binder; and/or the presence of a gas in the gas,
the dry-process binder is fluororesin.
3. The method of claim 2, wherein step (1) satisfies at least one of the following conditions:
the organic auxiliary agent comprises a solvent C selected from alkanes6-C20At least one of naphtha, toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1, 4-dioxane, N-methylpyrrolidone, acetone, butanone, N-dimethylacetamide, and dimethylsulfoxide;
the addition amount of the organic auxiliary agent is 0.1-20 wt% based on the total mass of the electrode active material, the conductive agent and the dry-process binder;
the fluororesin includes at least one selected from the group consisting of a polytetrafluoroethylene resin, a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a polychlorotrifluoroethylene resin.
4. The method according to claim 1 or 3, wherein in the step (2), the mixture is subjected to different mechanical extrusion forces in at least two different force-receiving directions during the kneading treatment; and/or the presence of a gas in the gas,
the kneading treatment is carried out using a kneading apparatus which is at least one selected from the group consisting of a kneader, an internal mixer, a single-screw extruder, a twin-screw extruder and a hydraulic extruder.
5. A method according to claim 4, wherein the kneading device is provided with at least two rotating blades arranged tangentially side by side and cooperating with each other, the kneading being effected by mechanical pressing of the mixture by differential rotation of the two rotating blades,
optionally, the rotating blades are sigma shaped.
6. The method according to claim 1 or 5, wherein step (3) satisfies at least one of the following conditions:
screening the granular materials to obtain granular materials with expected particle size ranges;
the particle size of the granular material is not less than 2 mm;
the crushing treatment is carried out by a crusher, and the rotating speed of the crusher is not more than 1000 rpm.
7. The method of claim 1, wherein step (4) satisfies at least one of the following conditions:
the dry electrode pole piece is a positive pole piece and/or a negative pole piece;
the pole piece film comprises 80-99.8 wt% of electrode active material, 0.1-10 wt% of conductive agent and 0.1-10 wt% of binder;
the compacted density of the pole piece film is 1-5 mg/cm3；
Respectively forming a layer of pole piece film on the upper surface and the lower surface of the current collector, wherein the thickness of each layer of pole piece film is 50-300 mu m, and the total thickness of the dry electrode pole piece is 100-600 mu m;
the step (4) further comprises: (4-1) carrying out hot press molding on the granular materials so as to obtain a primary pole piece membrane; (4-2) performing at least one hot press molding on the primary pole piece film so as to obtain a pole piece film with a desired thickness; (4-3) carrying out hot-pressing compounding on the pole piece film and the current collector so as to obtain the dry electrode pole piece,
wherein the content of the first and second substances,
optionally, in the step (4-3), a conductive carbon coating is formed on the surface of the current collector in advance, and then the electrode sheet film and the current collector are subjected to hot-press compounding;
optionally, the thickness of the conductive carbon coating is 1-5 μm;
optionally, conductive carbon powder and thermal sensitive adhesive are mixed and coated on the surface of the current collector so as to form the conductive carbon coating.
8. A system for dry-process preparation of an electrode sheet for carrying out the method of any one of claims 1 to 7, comprising:
a mixing device comprising a feedstock inlet and a mixture outlet;
a kneading device comprising a mixture inlet and a pre-fiberized product outlet, the mixture inlet being connected to the mixture outlet;
the crushing device comprises a pre-fibrosis product inlet and a granular material outlet, and the pre-fibrosis product inlet is connected with the pre-fibrosis product outlet;
the horizontal heating and pressing device comprises a first granular material inlet and a primary pole piece film outlet, wherein the first granular material inlet is connected with the granular material outlet;
the first vertical type heating and pressing device comprises a primary pole piece film inlet and a pole piece film outlet, wherein the primary pole piece film inlet is connected with the primary pole piece film outlet;
the second vertical type heating and pressing device comprises a pole piece film inlet, a current collector inlet and a dry electrode pole piece outlet, wherein the pole piece film inlet is connected with the pole piece film outlet.
9. The system of claim 8, wherein at least one of the following conditions is satisfied:
at least two rotating blades which are arranged in parallel and tangent in a differential mode are arranged in the kneading device;
the screening device comprises a second granular material inlet, an oversize material outlet and an undersize material outlet, wherein the second granular material inlet is connected with the granular material outlet, the oversize material outlet is connected with the first granular material inlet, and the undersize material outlet is connected with the mixture inlet;
the crushing device is a crusher;
comprises at least two first vertical heating and pressing devices which are connected end to end, wherein the first vertical heating and pressing device comprises a primary pole piece film inlet, the first vertical heating and pressing device comprises a pole piece film outlet,
wherein the content of the first and second substances,
optionally, the rotating blades are sigma-shaped;
optionally, the kneading device is a kneader, internal mixer, single screw extruder, twin screw extruder or hydraulic extruder.
10. An energy storage device comprising an electrode sheet produced by the method of any one of claims 1 to 7 and/or an electrode sheet produced by the system of any one of claims 8 to 9.
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