A method for preparing a pole piece, a positive pole piece, and a lithium-ion battery
By coating and hot pressing to form two solid electrolyte layers on the diaphragm substrate, the problem of curling and bending of the pole piece during the coating process is solved, and the safety and performance of the lithium-ion battery are improved.
Patent Information
- Application Number
- CN202211464018.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-23
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2042-11-23
AI Technical Summary
During the solid electrolyte coating process, the electrode is prone to curling and bending, affecting the safety and performance of the lithium-ion battery.
Using two-layer solid electrolyte slurry coating and hot pressing technology, the first solid electrolyte layer is first coated on the diaphragm substrate and then dried, and then the second solid electrolyte layer is coated and cross-linked and cured during the rolling process. Finally, the composite diaphragm is transferred to the surface of the electrode to form the third solid electrolyte layer.
Effectively remove the solvent to prevent the electrode from curling and bending during the transfer process, improve the flatness and safety of the electrode, and enhance the safety performance of the lithium-ion battery.
Smart Images
Figure CN115799453B_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of battery technology, and more specifically, to a method for preparing a pole piece, a positive pole piece, and a lithium-ion battery. Background Art
[0002] Lithium-ion batteries are widely used in portable electronic devices, smart grids, and new energy vehicles due to their light weight, high energy density, and long life. Traditional lithium-ion batteries use liquid electrolytes, but liquid electrolytes have a low flash point. Under abnormal conditions such as high-current discharge, overcharging, and internal short circuits, the electrolytes may heat up and spontaneously combust, or even cause safety issues such as explosions. Solid-state lithium-ion batteries use non-flammable or non-combustible solid electrolytes instead of the flammable organic electrolytes in traditional lithium-ion batteries. This can fundamentally solve the safety issues of lithium-ion batteries and further improve the operating temperature range, cycle life, and energy density of lithium-ion batteries.
[0003] For solid-state lithium-ion batteries, coating a solid electrolyte layer on the surface of the positive electrode active material layer helps improve the safety of the solid-state lithium-ion battery. However, in the traditional coating process, the volatilization of the solvent of the coated solid electrolyte layer can cause the electrode to curl and bend.
[0004] Therefore, how to prevent the electrode from curling and bending during the coating process of the solid electrolyte becomes a technical problem that needs to be solved by those skilled in the art. Summary of the Invention
[0005] The present application provides a method for preparing a pole piece, a positive pole piece and a lithium-ion battery, which can solve the problem of curling and bending of the pole piece during the process of coating with a solid electrolyte.
[0006] To solve one or more of the above technical problems, the technical solutions adopted in this application are:
[0007] In a first aspect, the present application provides a method for preparing a pole piece, the method comprising:
[0008] Applying the first solid electrolyte slurry onto the separator substrate and drying it to form a first solid electrolyte layer;
[0009] Applying a second solid electrolyte slurry onto the first solid electrolyte layer to form a second solid electrolyte layer to prepare a composite separator;
[0010] The composite diaphragm and the electrode to be processed are hot-pressed to transfer the first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm to the surface of the electrode to be processed to form a third solid electrolyte layer, so as to prepare a target electrode.
[0011] Furthermore, both sides of the electrode to be processed are covered with the third solid electrolyte layer.
[0012] Furthermore, the electrode to be processed includes a current collector and an active material layer coated on the surface of the current collector.
[0013] Furthermore, the first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm are transferred to both sides of the electrode to be processed by rolling.
[0014] Furthermore, the first solid electrolyte slurry includes ceramic solid electrolyte slurry, and the second solid electrolyte slurry includes polymer solid electrolyte slurry.
[0015] Furthermore, the polymer solid electrolyte slurry includes a polymer monomer, an initiator, a cross-linking agent, and a lithium salt. During the rolling process, the polymer monomer is cross-linked and solidified under the action of the cross-linking agent and the initiator.
[0016] Furthermore, the polymer monomer includes at least one of 1,3-dioxolane, ethylene glycol, butoxide, tetrahydrofuran, tetrahydropyran, ethylene oxide, dioxane, trioxane, dioxepane, dioxocane, and propylene oxide.
[0017] Furthermore, the initiator includes at least one of stannous trifluoromethanesulfonate, azobisisobutyronitrile, didodecanoyl peroxide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorooxalatoborate, aluminum trifluoromethanesulfonate, lithium trifluoride, and polyethylene glycol diamine.
[0018] Furthermore, the cross-linking agent includes at least one of an epoxy cross-linking agent and an olefin cross-linking agent.
[0019] Furthermore, the volume ratio of the cross-linking agent to the polymer monomer is 1:2-50.
[0020] Preferably, the cross-linking agent accounts for 0.1-10% of the total weight of the polymer monomers.
[0021] Furthermore, the lithium salt includes lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiBF2(C2O4))(LiODFB), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2)(LiBOB), lithium tetrafluorooxalatophosphate (LiPF4(C2O4))(LiFOP), lithium nitrate (LiNO3), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl imide) (LITFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2)(LIFSI) and combinations thereof. In certain variations, the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2)(LiFSI), lithium fluoroalkylphosphonate (LiFAP), lithium phosphate (Li3PO4), and combinations thereof.
[0022] Furthermore, the ceramic solid electrolyte slurry includes a fast ion conductor and a binder.
[0023] Furthermore, the fast ion conductor includes at least one of LiNbO3, Li4Ti5O4 or Li3PO4.
[0024] Furthermore, the binder includes at least one of polyvinylidene fluoride and polytetrafluoroethylene.
[0025] Furthermore, the thickness of the first solid electrolyte layer is 1-3 microns.
[0026] Furthermore, the thickness of the third solid electrolyte layer is 1-20 microns.
[0027] Preferably, the thickness of the third solid electrolyte layer is 1-5 microns.
[0028] Furthermore, the hot pressing temperature is 80-110°C.
[0029] Furthermore, the coating speed is 5-30 m / min.
[0030] In a second aspect, the present application also provides a positive electrode plate, which is prepared by the above-mentioned preparation method of the plate.
[0031] Furthermore, the positive electrode plate includes a positive electrode current collector, a positive electrode active material layer covering the surface of the positive electrode current collector, and a third solid electrolyte layer covering the surface of the positive electrode active material layer.
[0032] Furthermore, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes a plurality of positive electrode active particles of one or more transition metal cations, and the transition metal includes manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V) and combinations thereof.
[0033] Furthermore, the positive electrode active material may be one of layered oxides, spinels and polyanions.
[0034] In a third aspect, the present application further provides a lithium-ion battery, which includes the above-mentioned positive electrode sheet, negative electrode sheet and separator, and the separator is arranged between the positive electrode sheet and the negative electrode sheet.
[0035] Furthermore, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode current collector includes, but is not limited to, aluminum, copper, nickel, or zinc. The negative electrode active material layer includes a negative electrode binder, a negative electrode active material, and a negative electrode conductive agent.
[0036] According to the specific embodiments provided in this application, this application discloses the following technical effects:
[0037] In this application, a first solid electrolyte slurry is first applied to a diaphragm substrate and dried to form a first solid electrolyte layer. A second solid electrolyte slurry composed of a polymer monomer, an initiator, a crosslinker, and a lithium salt is then applied to the first solid electrolyte layer to form a second solid electrolyte layer, thereby preparing a composite diaphragm. Finally, the composite diaphragm and the electrode to be processed are hot-pressed to transfer the first and second solid electrolyte layers on the composite diaphragm to the surface of the electrode to be processed, forming a third solid electrolyte layer. On the one hand, drying the first solid electrolyte slurry after application to the surface of the diaphragm substrate effectively removes the solvent in the first solid electrolyte layer. On the other hand, during the hot-pressing process, the polymer monomer in the second solid electrolyte slurry undergoes crosslinking and curing under the action of the crosslinker and initiator, further removing some of the solvent from the second solid electrolyte layer. Since the solvent in the first and second solid electrolyte layers is partially removed, curling and bending of the electrode can be avoided during the transfer of the first and second solid electrolyte layers from the composite diaphragm to the electrode to be processed.
[0038] In addition, since the peeling force between the first solid electrolyte layer and the second solid electrolyte layer and the diaphragm substrate is moderate, the peeling force between the first solid electrolyte layer and the second solid electrolyte layer and the diaphragm substrate will not be too large, which will cause difficulty in peeling the first solid electrolyte layer and the second solid electrolyte layer from the diaphragm substrate, thereby affecting the composite effect between the first solid electrolyte layer and the second solid electrolyte layer and the electrode; nor will the peeling force between the first solid electrolyte layer and the second solid electrolyte layer and the diaphragm substrate be too small, which will cause the first solid electrolyte layer and the second solid electrolyte layer to be unable to composite with the diaphragm substrate in the early stage, thereby affecting the hot pressing effect during the hot pressing process.
[0039] Of course, any product implementing the present application does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0041] Figure 1 Flowchart of the method for preparing the electrode provided in the embodiment of the present application.
[0042] Figure 2 A schematic diagram of the structure of the electrode preparation equipment provided in an embodiment of the present application.
[0043] Figure 3 Schematic diagram of the structure of the intermediate product during the hot pressing process.
[0044] Figure 4 It is a schematic diagram of the structure of the pole piece coated with the third solid electrolyte layer. DETAILED DESCRIPTION
[0045] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the embodiments described are only part of the embodiments of the present application, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present application are within the scope of protection of this application.
[0046] As described in the background, for solid-state lithium-ion batteries, coating a solid electrolyte layer on the surface of the positive electrode active material layer helps improve the safety of solid-state lithium-ion batteries. However, during the traditional coating process, the volatilization of the solvent in the coated solid electrolyte layer can cause the electrode to curl or bend. To address this issue, the present application provides a method for preparing an electrode, a positive electrode, and a lithium-ion battery that can address the problem of electrode curling and bending during the solid electrolyte coating process.
[0047] Figure 1 The flow chart of the method for preparing the electrode provided in the embodiment of the present application is as follows: Figure 1 As shown, a method for preparing a pole piece includes:
[0048] S1: coating a first solid electrolyte slurry onto a diaphragm substrate, and drying the slurry to form a first solid electrolyte layer.
[0049] The first solid electrolyte slurry includes a ceramic solid electrolyte slurry, and the ceramic solid electrolyte slurry includes a fast ion conductor and a binder. The fast ion conductor is also called a lithium ion conductive material, which generally refers to a material with good ion conductivity. The fast ion conductor in this application includes inorganic substances, including but not limited to LiNbO3, Li4Ti5O4, Li3PO4 and other solid electrolyte materials. The binder includes but is not limited to polyvinylidene fluoride and polytetrafluoroethylene. Users can choose according to actual needs and are not specifically limited here.
[0050] The first solid electrolyte slurry is coated onto the separator substrate and dried to form a first solid electrolyte layer. In the embodiment of the present application, the thickness of the first solid electrolyte layer is 1-3 microns. Specifically, the thickness of the first solid electrolyte layer can be 1, 1.2, 1.5, 2, 2.5, or 3 microns, as well as specific values between the above values, preferably 1.2-2.5 microns. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific values within the above range.
[0051] The type of diaphragm substrate in this application is not subject to specific restrictions. Without violating the inventive concept of this application, it can be any material used in existing diaphragm substrates, such as PP film, PE film, PE / PP double-layer film, PE / PP / PE three-layer film, PP / PE / PP three-layer film, etc.
[0052] S2: coating a second solid electrolyte slurry onto the first solid electrolyte layer to form a second solid electrolyte layer to prepare a composite separator.
[0053] The second solid electrolyte slurry includes a polymer solid electrolyte slurry, which includes a polymer monomer, an initiator, a crosslinking agent, and a lithium salt. During the rolling process, the polymer monomer undergoes a polymerization reaction under the action of the initiator. The polymer monomer includes at least one of 1,3-dioxolane, ethylene glycol, butoxycyclic ring, tetrahydrofuran, tetrahydropyran, ethylene oxide, dioxane, trioxane, dioxepin, dioxoctan, and propylene oxide. The initiator includes at least one of stannous trifluoromethanesulfonate, azobisisobutyronitrile, didodecanoyl peroxide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorooxalatoborate, aluminum trifluoromethanesulfonate, lithium trifluoride, and polyethylene glycol diamine. The crosslinking agent includes at least one of an epoxy crosslinking agent and an olefin crosslinking agent. During the rolling process, the polymer monomer undergoes crosslinking and curing under the action of the crosslinking agent and initiator. In the embodiment of the present application, the crosslinking agent and initiator can also be used to adjust the crosslinking polymerization rate of the polymer monomer. Preferably, the crosslinking agent accounts for 0.1-10% of the total weight of the polymer monomer.
[0054] The lithium salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiBF2(C2O4))(LiODFB), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2)(LiBOB), lithium tetrafluorooxalatophosphate (LiPF4(C2O4))(LiFOP), lithium nitrate (LiNO3), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl imide) (LITFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2)(LIFSI) and combinations thereof. In certain variations, the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2)(LiFSI), lithium fluoroalkylphosphonate (LiFAP), lithium phosphate (Li3PO4), and combinations thereof.
[0055] S3: hot pressing the composite diaphragm and the electrode to be processed so that the first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm are transferred to the surface of the electrode to be processed to form a third solid electrolyte layer, so as to prepare a target electrode.
[0056] Furthermore, both sides of the electrode to be processed are covered with the third solid electrolyte layer. The electrode to be processed includes a current collector and an active material layer coated on the surface of the current collector.
[0057] The first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm are transferred to both sides of the electrode to be processed by rolling. The rolling process referred to in the embodiment of the present application is achieved by the electrode preparation equipment. Figure 2 This is a schematic diagram of the structure of the electrode preparation equipment provided in the embodiment of the present application. Figure 2 As shown, the electrode preparation equipment includes a first unwinding shaft 11, a second unwinding shaft 12, a third unwinding shaft 13, a first hot pressing roller 21, a second hot pressing roller 22, a first winding shaft 31, a second winding shaft 32, and a third winding shaft 33. The first unwinding shaft 11 and the third unwinding shaft 13 are respectively used to wind and pull two composite diaphragms. The second unwinding shaft 12 is arranged between the first unwinding shaft 11 and the third unwinding shaft 13. The second unwinding shaft 12 is used to wind and pull the electrode to be processed 10. The composite diaphragm is composed of a diaphragm substrate 20 and a first solid electrolyte layer 30 covering the surface of the diaphragm substrate 20, and a second solid electrolyte layer 40 covering the surface of the first solid electrolyte layer 30. The first hot pressing roller 21 and the second hot pressing roller 22 are used to transfer the first solid electrolyte layer 30 and the second solid electrolyte layer 40 on the two composite diaphragms to the surface of the electrode to be processed 10 to form a third solid electrolyte layer 50, so as to prepare the target electrode. The first winding shaft 31 and the third winding shaft 33 are used to recycle the two composite diaphragms. The second winding shaft 32 is arranged between the first winding shaft 31 and the third winding shaft 33. The second winding shaft 32 is used to wind up the target electrode coated with the third solid electrolyte layer 50.
[0058] During specific implementation, the two composite diaphragms and the electrode sheet to be processed 10 are pulled to between the first hot pressing roller 21 and the second hot pressing roller 22 for hot pressing by the first unwinding shaft 11, the second unwinding shaft 12 and the third unwinding shaft 13 respectively. Specifically, the electrode sheet to be processed 10 is arranged between the two composite diaphragms. During the hot pressing process, the two composite diaphragms and the electrode sheet to be processed 10 are bonded together. Furthermore, a gap is provided between the first hot pressing roller 21 and the second hot pressing roller 22 for the two composite diaphragms and the electrode sheet to be processed 10 to pass through. The gap between the first hot pressing roller 21 and the second hot pressing roller 22 is less than the sum of the thicknesses of the two composite diaphragms and the electrode sheet to be processed 10, so as to ensure that the pressure of the first hot pressing roller 21 and the second hot pressing roller 22 can be applied to the two composite diaphragms and the electrode sheet to be processed 10. The gap between the first hot pressing roller 21 and the second hot pressing roller 22 is smaller than the sum of the thicknesses of the two composite diaphragms and the electrode 10 to be processed. On the one hand, the first solid electrolyte layer 30 and the second solid electrolyte layer 40 on the two composite diaphragms can be coated on the electrode 10 to be processed. On the other hand, the warped edges and collapsed edges on the electrode 10 to be processed can be gradually leveled, making the electrode 10 to be processed more flat. In addition, the first hot pressing roller 21 and the second hot pressing roller 22 also have a heating function. During the rolling process, the two composite diaphragms and the electrode 10 to be processed can be heated. In the embodiment of the present application, the hot pressing temperature is 80-110°C. Specifically, the hot pressing temperature can be 80, 90, 100 or 110°C, as well as specific point values between the above point values, preferably 90°C. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range. Heating within the above temperature range is conducive to the full volatilization of the solvent and avoids bending and deformation of the electrode. Furthermore, the coating speed is 5-30 m / min. Specifically, the coating speed can be 5, 10, 15, 20, 25 or 30 m / min, as well as specific point values between the above point values, preferably 15 m / min. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.
[0059] Figure 3 It is a structural diagram of the intermediate product during the hot pressing process, such as Figure 3As shown, during the hot pressing process, the separator substrate 20, the first solid electrolyte layer 30, the second solid electrolyte layer 40, the electrode 10 to be processed, the second solid electrolyte layer 40, the first solid electrolyte layer 30, and the separator substrate 20 are sequentially combined. The intermediate product is pulled by the first winding shaft 31, the second winding shaft 32, and the third winding shaft 33 and passes between the first hot pressing roller 21 and the second hot pressing roller 22. Due to the moderate peeling force between the separator substrate 20 and the first solid electrolyte layer 30 and the second solid electrolyte layer 40 of the composite separator, the separator substrate 20 and the first solid electrolyte layer 30 and the second solid electrolyte layer 40 of the composite separator are peeled off during the movement, and the first solid electrolyte layer 30 and the second solid electrolyte layer 40 of the composite separator are transferred to the electrode 10 to be processed.
[0060] Figure 4 is a schematic structural diagram of a target electrode coated with a third solid electrolyte layer 50, as shown in FIG. Figure 4 As shown, the target electrode includes a to-be-processed electrode 10 and a third solid electrolyte layer 50 coated on the surface of the to-be-processed electrode 10. Generally speaking, a thicker solid electrolyte layer helps to improve the safety performance of the battery, and when coating the solid electrolyte, the coating process is simple, but a thicker solid electrolyte layer will affect the energy density of the battery, which does not meet the current requirements for lightweight and thin batteries. In the embodiment of the present application, the thickness of the third solid electrolyte layer 50 is 1-20 microns. Specifically, the thickness of the third solid electrolyte layer 50 can be 1, 1.5, 2, 2.5, 3, 2.5, 4, 4.5, 5, 7, 10, 13, 16 or 20 microns, as well as specific point values between the above point values, preferably 1.5-5 microns. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.
[0061] The present application also provides a positive electrode sheet, produced using the above-described electrode sheet preparation method. Furthermore, the positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer covering the surface of the positive electrode current collector, and a solid electrolyte layer covering the surface of the positive electrode active material layer. The relevant details of the solid electrolyte layer can be found in the above description and will not be elaborated here.
[0062] The positive electrode active material layer includes a positive electrode active material, which can be formed by a plurality of positive electrode active particles containing one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V) and combinations thereof. In some embodiments, the positive electrode active material layer further includes an electrolyte, such as a plurality of electrolyte particles.
[0063] The positive electrode active material may also be one of a layered oxide, a spinel, and a polyanion. For example, the layered oxide (e.g., a rock salt layered oxide) comprises one or more lithium-based positive electrode active materials selected from the group consisting of LiCoO2, LiNi x Mn y Co 1-x-y O2 (where 0≤x≤1 and 0≤y≤1), LiNi 1-x-y Co x Al y O2 (where 0≤x≤1 and 0≤y≤1), LiNi x Mn 1-x O2 (where 0≤x≤1) and Li 1+x MO2 (wherein M is one of Mn, Ni, Co and Al and 0≤x≤1).
[0064] In one embodiment, one or more lithium-based positive active materials may be optionally coated and / or may be doped. In addition, in certain embodiments, one or more lithium-based positive active materials may be optionally mixed with one or more conductive materials that provide an electron conduction path and / or at least one polymer binder material that improves the structural integrity of the positive electrode. For example, the positive active material layer may include greater than or equal to about 30 wt% to less than or equal to about 98 wt% of one or more lithium-based positive active materials; greater than or equal to about 0 wt% to less than or equal to about 30 wt% of a conductive material; and greater than or equal to about 0 wt% to less than or equal to about 20 wt% of a binder, and in some aspects, optionally greater than or equal to about 1 wt% to less than or equal to about 20 wt% of a binder.
[0065] As a preferred embodiment, in the embodiment of the present application, the positive electrode active material layer may be optionally mixed with the following binder: such as polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), acrylonitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate and combinations thereof. The conductive material may include a carbon-based material, powdered nickel or other metal particles, or a conductive polymer. Carbon-based materials may include, for example, carbon black, graphite, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like.
[0066] The present application also provides a lithium-ion battery, comprising the aforementioned positive electrode sheet, negative electrode sheet, and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet. The relevant contents of the positive electrode sheet can be referred to above and will not be elaborated here.
[0067] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode current collector is not particularly limited, as long as it is conductive and does not cause chemical changes in the battery. Specifically, the negative electrode current collector includes, but is not limited to, aluminum, copper, nickel, or zinc. For example, the negative electrode current collector can be copper, such as copper foil.
[0068] Furthermore, the negative electrode active material layer includes a negative electrode binder, a negative electrode active material, and a negative electrode conductive agent. The negative electrode binder includes, but is not limited to, polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, etc. The negative electrode active material includes at least one of graphite, soft carbon, hard carbon, silicon oxide, or silicon carbon. The negative electrode conductive agent includes at least one of conductive carbon black, carbon nanotubes, vapor-grown carbon nanotubes, or nanofibers.
[0069] Hereinafter, the embodiments of the present invention will be described in more detail by way of examples. However, the embodiments of the present invention are not limited only to these examples.
[0070] Example 1
[0071] The ceramic solid electrolyte slurry is coated on the PP diaphragm substrate and dried to form a first solid electrolyte layer, wherein the ceramic solid electrolyte slurry is a slurry formed by dissolving LiNbO3 in a solvent NMP;
[0072] Applying a polymer solid electrolyte slurry onto the first solid electrolyte layer to form a composite diaphragm, wherein the polymer solid electrolyte slurry is a slurry formed by mixing 1,3-dioxolane, stannous trifluoromethanesulfonate and acrylic acid;
[0073] The composite diaphragm coated with the first and second solid electrolyte layers prepared above passes through the first and third unwinding reels and then, along with the unprocessed positive electrode sheet from the second unwinding reel, enters the space between the first and second hot pressing rollers for lamination. The lamination of the positive electrode sheet passes through the second take-up reel for rewinding. At this point, the first and second solid electrolyte layers in the original composite diaphragm are laminated to the sides of the unprocessed positive electrode sheet to form the third solid electrolyte layer, and the PP diaphragm substrate in the composite diaphragm is recovered from the first and third take-up reels.
[0074] The current collector of the positive electrode sheet to be processed is aluminum foil, the positive electrode active material layer is 96wt% NCM622, the positive electrode conductive agent is 2wt% super-P, and the positive electrode binder is 2wt% PTFE.
[0075] In this embodiment, the coating speed is 10 m / min and the hot pressing temperature is 90°C.
[0076] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared was 2.5 microns, without curling or bending.
[0077] Example 2
[0078] The difference between Example 2 and Example 1 is that the ceramic solid electrolyte slurry is a slurry formed by dissolving LiNbO3 and PTFE binder in NMP solvent. The polymer solid electrolyte slurry is a slurry formed by mixing ethylene glycol, azobisisobutyronitrile, and acrylic acid. Furthermore, the coating speed in this example is 15 m / min, and the hot pressing temperature is 100°C.
[0079] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared is 3 microns, without curling or bending.
[0080] Example 3
[0081] The difference between Example 3 and Example 1 lies in that the solid electrolyte slurry is a slurry formed by dissolving Li₄Ti₅O₄ and PTFE binder in NMP. The polymer solid electrolyte slurry is a mixture of 1,3-dioxolane, didodecanoyl peroxide, and acrylic acid. Furthermore, the coating speed in this example is 15 m / min, and the hot pressing temperature is 95°C.
[0082] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared is 3 microns, without curling or bending.
[0083] As can be seen from the above, the embodiments of the present application provide a method for preparing a pole piece, a positive pole piece, and a lithium-ion battery. On the one hand, the first solid electrolyte slurry is applied to the surface of the diaphragm substrate and then dried to effectively remove the solvent in the first solid electrolyte layer. On the other hand, during the hot pressing process, the polymer monomers in the second solid electrolyte slurry undergo cross-linking and curing under the action of the cross-linking agent and initiator, further removing some of the solvent in the second solid electrolyte layer. Since the solvent in the first and second solid electrolyte layers is partially removed, the pole piece can be prevented from curling or bending during the process of transferring the first and second solid electrolyte layers on the composite diaphragm to the pole piece to be processed.
[0084] The above is a detailed introduction to the electrode preparation method, positive electrode sheet, and lithium-ion battery provided by this application. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting this application.
Claims
1. A method for preparing a pole piece, characterized in that: The method for preparing the pole piece includes: Applying the first solid electrolyte slurry onto the separator substrate and drying it to form a first solid electrolyte layer; Applying a second solid electrolyte slurry onto the first solid electrolyte layer to form a second solid electrolyte layer to prepare a composite separator; The first solid electrolyte slurry includes a ceramic solid electrolyte slurry, and the second solid electrolyte slurry includes a polymer solid electrolyte slurry; Hot pressing the composite diaphragm and the electrode to be processed so that the first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm are transferred to the surface of the electrode to be processed to form a third solid electrolyte layer, thereby preparing a target electrode; The polymer solid electrolyte slurry includes a polymer monomer, an initiator, a cross-linking agent, and a lithium salt. During the hot pressing process, the polymer monomer is cross-linked and solidified under the action of the cross-linking agent and the initiator.
2. The method for preparing a pole piece according to claim 1, characterized in that: Both sides of the electrode to be processed are covered with the third solid electrolyte layer.
3. The method for preparing a pole piece according to claim 1, characterized in that: The first solid electrolyte layer and the second solid electrolyte layer on the composite diaphragm are transferred to both sides of the electrode to be processed by rolling.
4. The method for preparing a pole piece according to claim 1, characterized in that: The polymer monomer includes at least one of 1,3-dioxolane, ethylene glycol, butoxide, tetrahydrofuran, tetrahydropyran, ethylene oxide, dioxane, trioxane, dioxepane, dioxocane, and propylene oxide.
5. The method for preparing a pole piece according to claim 1, characterized in that: The initiator includes at least one of stannous trifluoromethanesulfonate, azobisisobutyronitrile, didodecanoyl peroxide, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorooxalatoborate, aluminum trifluoromethanesulfonate, lithium trifluoride, and polyethylene glycol diamine.
6. The method for preparing a pole piece according to claim 1, characterized in that: The cross-linking agent includes at least one of an epoxy cross-linking agent and an olefin cross-linking agent.
7. A positive electrode plate, characterized in that: The positive electrode plate is prepared according to the method for preparing the plate according to any one of claims 1 to 6.
8. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the positive electrode sheet, the negative electrode sheet, and a separator as claimed in claim 7, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet.