A method for preparing a pole piece, a positive pole piece, and a lithium-ion battery

Abstract

This application discloses a method for preparing a pole piece, a positive pole piece, and a lithium-ion battery. The pole piece preparation method comprises: applying a solid electrolyte slurry to a separator to form a composite separator; placing the side of the composite separator coated with the solid electrolyte slurry opposite the pole piece to be processed, and hot pressing to transfer the solid electrolyte on the composite separator to the surface of the pole piece to be processed to form a solid electrolyte layer, thereby preparing the target pole piece. The pole piece preparation method, positive pole piece, and lithium-ion battery provided in this application can solve the problem of pole piece curling and bending during the solid electrolyte coating process.

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 to improve the safety of solid-state lithium-ion batteries. The current methods for coating the solid electrolyte membrane on the positive electrode surface are: 1. directly coating the solid electrolyte on the surface of the positive electrode active material layer; 2. first preparing the solid electrolyte membrane on a release film and then separating it at a later stage; however, the above methods all have many disadvantages. For example, when the solid electrolyte slurry is coated on the surface of the positive electrode active material layer, the pole piece may easily curl and bend due to solvent volatilization during the drying process; and the bonding strength between the release film and the solid electrolyte membrane is low and the support is poor, making it impossible to coat an ultra-thin, stable, and non-breakable solid electrolyte layer (<5 microns) on the positive electrode surface, and it also faces the problem of curling.

[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] coating the solid electrolyte slurry on the separator to form a composite separator;

[0009] The side of the composite diaphragm coated with the solid electrolyte slurry is placed opposite to the electrode to be processed, and hot pressing is performed to transfer the solid electrolyte on the composite diaphragm to the surface of the electrode to be processed to form a solid electrolyte layer, so as to prepare the target electrode.

[0010] Furthermore, both sides of the electrode to be processed are covered with a solid electrolyte layer.

[0011] Furthermore, the electrode to be processed includes a current collector and an active material layer coated on the surface of the current collector.

[0012] Furthermore, the solid electrolyte on the composite diaphragm is transferred to both sides of the electrode to be processed by rolling.

[0013] Furthermore, the solid electrolyte slurry includes a solid electrolyte, and the solid electrolyte includes an inorganic solid electrolyte.

[0014] The inorganic solid electrolyte may include one or more solid electrolyte particles. Preferably, the solid electrolyte particles may include one or more oxide particles, sulfide particles, halide particles, borate particles, nitride particles or hydride particles.

[0015] As an embodiment, the oxide particles may comprise one or more garnet ceramics, LISICON type oxides, NASICON type oxides and perovskite type ceramics. For example, the one or more garnet ceramics may be selected from the group consisting of: Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li7La3Zr2O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12And combinations thereof. The one or more LISICON type oxides may be selected from the group consisting of: Li 14 Zn(GeO4)4、Li 3+x (P 1-x Si x )O4 (where 0<x<1), Li 3+x Ge x V 1-x O4 (where 0 < x < 1) and combinations thereof. One or more NASICON-type oxides may be defined by LiMM'(PO4)3, where M and M' are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, one or more NASICON-type oxides may be selected from the group consisting of: Li 1+x Al x Ge 2-x (PO4)3(LAGP)(where 0≤x≤2), Li 1+x Al x Ti 2-x (PO4)3(LATP)(where 0≤x≤2), Li 1+x Y x Zr 2-x (PO4)3(LYZP)(where 0≤x≤2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3 and combinations thereof. One or more perovskite ceramics may be selected from the group consisting of: Li 3.3 La 0.53 TiO3、LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x=0.75y and 0.60<y<0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3、Li 3x La (2 / 3-x) TiO3 (where 0 < x < 0.25) and combinations thereof. In one variation, one or more oxide-based materials may have a thickness greater than or equal to about 10 -5 S / cm to less than or equal to about 10 - 1 S / cm ionic conductivity.

[0016] In various aspects, the sulfide-based particles may include one or more sulfide-based materials selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0≤x≤2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li(Ge 0.5 Sn 0.5 )P2S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (wherein X is Cl, Br or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 、Li 10 SiP2S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C 10.3 、 (1-x) P2S 5-x Li2S (where 0.5≤x≤0.7) and combinations thereof. In one variation, one or more sulfide-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to an ionic conductivity of less than or equal to about 1 S / cm.

[0017] In various aspects, the halide-based particles may include one or more halide-based materials selected from the group consisting of: Li2CdC 14 、Li2MgC 14 、Li2Cd I4 , Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Br x (where 0 < x < 1) and combinations thereof. In one variation, one or more halide-based materials may have a -8 S / cm to less than or equal to about 10 -1 S / cm ionic conductivity.

[0018] In various aspects, the borate-based particles may include one or more borate-based materials selected from the group consisting of Li2B4O7, Li2O-(B2O3)-(P2O5), and combinations thereof. In one variation, the one or more borate-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to less than or equal to about 10 -2 S / cm ionic conductivity.

[0019] In various aspects, the nitride-based particles may include one or more nitride-based materials selected from the group consisting of Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof. In one variation, the one or more nitride-based materials may have a carbon content greater than or equal to about 10 -9 S / cm to an ionic conductivity of less than or equal to about 1 S / cm.

[0020] In various aspects, the hydride-based particles may include one or more hydride-based materials from the group consisting of Li3AlH6, LiBH4, LiBH4-LiX (wherein X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2, and combinations thereof. In one variation, the one or more hydride-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to less than or equal to about 10 -2 S / cm ionic conductivity.

[0021] In other variations, the solid electrolyte particles may be one or more metal oxide particles or lithium-containing compounds, including but not limited to Al2O3, SiO2, TiO2, LiNbO3, Li4Ti5O4, Li3PO4.

[0022] Furthermore, the solid electrolyte also includes a polymer solid electrolyte. Preferably, the solid electrolyte is a composite solid electrolyte composed of a polymer solid electrolyte and an inorganic solid electrolyte.

[0023] Furthermore, the polymer solid electrolyte includes at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0024] Furthermore, the solid electrolyte slurry also includes at least one of a binder and a lithium salt.

[0025] Furthermore, the binder includes polyethylene glycol, polyethylene oxide (PEO), poly(p-phenylene ether) (PPO), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC) and combinations thereof. Without violating the inventive concept of the present application, it can be selected according to actual needs and is not specifically limited here.

[0026] 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 (LiA s F6), 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 fluoroalkyl phosphonate (LiFAP), lithium phosphate (Li3PO4), and combinations thereof.

[0027] Furthermore, the thickness of the solid electrolyte layer is 1-20 microns.

[0028] Preferably, the thickness of the solid electrolyte layer is 2-6 microns.

[0029] Furthermore, the hot pressing temperature is 80-110°C.

[0030] Furthermore, the coating speed is 5-30 m / min.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Furthermore, the positive electrode active material may be one of layered oxides, spinels and polyanions.

[0035] 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.

[0036] 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.

[0037] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0038] In this application, the solid electrolyte slurry is first applied to the diaphragm. Because the peeling force between the solid electrolyte slurry and the diaphragm is moderate, the peeling force between the solid electrolyte layer and the diaphragm is neither too strong, which would cause difficulty in peeling the solid electrolyte layer from the diaphragm and affect the composite effect between the solid electrolyte layer and the electrode. Nor is the peeling force too weak, which would prevent the solid electrolyte layer from being composited with the diaphragm in the early stages and affect the hot pressing effect during the hot pressing process. Furthermore, during the hot pressing process, the electrode is in a taut state and heated to fully volatilize the solvent, thereby preventing the electrode from curling or bending when the solid electrolyte is applied.

[0039] At the same time, in this application, the coating process of the solid electrolyte and the diaphragm is well integrated with the rolling process of the composite diaphragm and the electrode. When the solid electrolyte is not dried, it is compounded with the electrode, thereby improving the interface bonding ability and interface performance between the electrode and the solid electrolyte membrane on the diaphragm.

[0040] This application makes up for the problem of weak adhesion of current release films by wet rolling and specific bonding force with the diaphragm.

[0041] 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

[0042] 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 any creative work.

[0043] Figure 1 Flowchart of the method for preparing the electrode provided in the embodiment of the present application.

[0044] Figure 2 A schematic diagram of the structure of the electrode preparation equipment provided in an embodiment of the present application.

[0045] Figure 3 Schematic diagram of the structure of the intermediate product during the hot pressing process.

[0046] Figure 4 Schematic diagram of the structure of the electrode coated with a solid electrolyte layer. DETAILED DESCRIPTION

[0047] 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.

[0048] 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 sheet to curl and bend. To address this issue, the present application provides a method for preparing an electrode sheet, a positive electrode sheet, and a lithium-ion battery that can address the problem of electrode sheet curling and bending during solid electrolyte coating.

[0049] 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:

[0050] S1: coating the solid electrolyte slurry onto the separator to prepare a composite separator.

[0051] The solid electrolyte slurry includes a solid electrolyte, and the solid electrolyte has good chemical inertness to the electrolyte or liquid additives in the battery, so that the safety performance of the battery is greatly improved. The solid electrolyte here can be a fast ion conductor or a metal oxide, wherein the fast ion conductor is also called a lithium ion conductive material, which generally refers to a material with good ion conductive properties. The fast ion conductor in this application includes an inorganic solid electrolyte, and the inorganic solid electrolyte may include one or more solid electrolyte particles. Preferably, the solid electrolyte particles may include one or more oxide particles, sulfide particles, halide particles, borate particles, nitride particles or hydride particles.

[0052] As an embodiment, the oxide particles may comprise one or more garnet ceramics, LISICON type oxides, NASICON type oxides and perovskite type ceramics. For example, the one or more garnet ceramics may be selected from the group consisting of: Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li7La3Zr2O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 And combinations thereof. The one or more LISICON type oxides may be selected from the group consisting of: Li 14 Zn(GeO4)4、Li 3+x (P 1-x Si x )O4 (where 0<x<1), Li3+x Ge x V 1-x O4 (where 0 < x < 1) and combinations thereof. One or more NASICON-type oxides may be defined by LiMM'(PO4)3, where M and M' are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, one or more NASICON-type oxides may be selected from the group consisting of: Li 1+x Al x Ge 2-x (PO4)3(LAGP)(where 0≤x≤2), Li 1+x Al x Ti 2-x (PO4)3(LATP)(where 0≤x≤2), Li 1+x Y x Zr 2-x (PO4)3(LYZP)(where 0≤x≤2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3 and combinations thereof. One or more perovskite ceramics may be selected from the group consisting of: Li 3.3 La 0.53 TiO3、LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x=0.75y and 0.60<y<0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4 Zr 1 / 4 O3、Li 3x La (2 / 3-x) TiO3 (where 0 < x < 0.25) and combinations thereof. In one variation, one or more oxide-based materials may have a thickness greater than or equal to about 10 -5 S / cm to less than or equal to about 10 - 1 S / cm ionic conductivity.

[0053] In various aspects, the sulfide-based particles may include one or more sulfide-based materials selected from the group consisting of: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0≤x≤2), Li3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 、Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li(Ge 0.5 Sn 0.5 )P2S 12 、Li(Si 0.5 Sn 05 )PsS 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (wherein X is Cl, Br or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 、Li 10 SiP2S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C 10.3 、 (1-x) P2S 5-x Li2S (where 0.5≤x≤0.7) and combinations thereof. In one variation, one or more sulfide-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to an ionic conductivity of less than or equal to about 1 S / cm.

[0054] In various aspects, the halide-based particles may include one or more halide-based materials selected from the group consisting of: Li2CdC l4 、Li2MgC 14 、Li2Cd I4, Li2ZnI4, Li3OCl, LiI, Li5ZuI4, Li3OCl 1-x Br x (where 0 < x < 1) and combinations thereof. In one variation, one or more halide-based materials may have a -8 S / cm to less than or equal to about 10 -1 S / cm ionic conductivity.

[0055] In various aspects, the borate-based particles may include one or more borate-based materials selected from the group consisting of Li2B4O7, Li2O-(B2O3)-(P2O5), and combinations thereof. In one variation, the one or more borate-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to less than or equal to about 10 -2 S / cm ionic conductivity.

[0056] In various aspects, the nitride-based particles may include one or more nitride-based materials selected from the group consisting of Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof. In one variation, the one or more nitride-based materials may have a carbon content greater than or equal to about 10 -9 S / cm to an ionic conductivity of less than or equal to about 1 S / cm.

[0057] In various aspects, the hydride-based particles may include one or more hydride-based materials from the group consisting of Li3AlH6, LiBH4, LiBH4-LiX (wherein X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2, and combinations thereof. In one variation, the one or more hydride-based materials may have a carbon content greater than or equal to about 10 -7 S / cm to less than or equal to about 10 -2 S / cm ionic conductivity.

[0058] In other variations, the solid electrolyte particles may be one or more metal oxide particles or lithium-containing compounds, including but not limited to Al2O3, SiO2, TiO2, LiNbO3, Li4Ti5O4, Li3PO4.

[0059] In one embodiment, the solid electrolyte further comprises a polymer solid electrolyte, and the polymer solid electrolyte and the inorganic solid electrolyte constitute a composite solid electrolyte. In the embodiment of the present application, there is no special requirement for the mass ratio of the inorganic solid electrolyte and the polymer solid electrolyte in the composite solid electrolyte, and the user can design it according to actual needs. Among them, the polymer solid electrolyte can be at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyethylene oxide (PEO).

[0060] In another embodiment, the solid electrolyte slurry includes at least one of a binder and a lithium salt. The binder includes but is not limited to polyethylene glycol, polyethylene oxide (PEO), poly(p-phenylene oxide) (PPO), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof. Without violating the inventive concept of the present application, it can be selected according to actual needs and is not specifically limited here.

[0061] 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.

[0062] The type of diaphragm 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 diaphragms, such as PP film, PE film, PE / PP double-layer film, PE / PP / PE three-layer film, PP / PE / PP three-layer film, etc.

[0063] S2: Place the side of the composite diaphragm coated with the solid electrolyte slurry opposite to the electrode to be processed, and roll the composite diaphragm to transfer the solid electrolyte on the composite diaphragm to the surface of the electrode to be processed to form a solid electrolyte layer, so as to prepare the target electrode.

[0064] Furthermore, both sides of the electrode to be processed are covered with a 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.

[0065] The solid electrolyte on the composite diaphragm is transferred to both sides of the electrode to be processed by rolling. The rolling process referred to in the embodiments of the present application is achieved by electrode preparation equipment. This electrode preparation equipment is used to prepare electrode sheets containing solid electrolyte layers.

[0066] 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 used to wind and pull the first composite diaphragm and the second composite diaphragm. The second unwinding shaft 12 is arranged between the first unwinding shaft 11 and the third unwinding shaft 13 and is used to wind and pull the electrode to be processed. The first composite diaphragm is composed of a first diaphragm 40 and a first solid electrolyte layer 20 covering the surface of the first diaphragm 40. The second composite diaphragm is composed of a second diaphragm 50 and a second solid electrolyte layer 30 covering the surface of the second diaphragm 50. The first hot pressing roller 21 and the second hot pressing roller 22 are used to transfer the solid electrolyte layers on the first composite diaphragm and the second composite diaphragm to the electrode to be processed. The first and third reels 31 and 33 are used to recycle the first and second composite diaphragms. The second reel 32 is located between the first and third reels 31 and 33 and is used to wind up the target electrode coated with the solid electrolyte layer. In the embodiment of the present application, the solid electrolyte layers on the first and second composite diaphragms can be the same or different, without limitation.

[0067] During specific implementation, the first composite diaphragm, the electrode to be processed and the second composite diaphragm are respectively pulled to the first hot pressing roller 21 and the second hot pressing roller 22 by the first unwinding shaft 11, the second unwinding shaft 12 and the third unwinding shaft 13 for rolling. Specifically, the electrode to be processed is arranged between the first composite diaphragm and the second composite diaphragm. During the hot pressing process, the first composite diaphragm, the second composite diaphragm and the electrode to be processed 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 to be processed to pass through. The gap between the first hot pressing roller 21 and the second hot pressing roller 22 is smaller than the total thickness of the composite diaphragm and the electrode to be processed, 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 composite diaphragm and the electrode to be processed. 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 composite diaphragm and the electrode to be processed. On the one hand, the solid electrolyte layer on the composite diaphragm can be coated on the electrode to be processed. On the other hand, the warped and collapsed edges on the electrode to be processed can be gradually leveled, making the electrode to be processed more flat. Preferably, the first hot pressing roller 21 and the second hot pressing roller 22 also have a heating function, and the composite diaphragm and the electrode to be processed can be heated during the rolling process. 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 90-100°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. 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.

[0068] Figure 3 It is a structural diagram of the intermediate product during the hot pressing process, such as Figure 3 As shown, during the hot pressing process, the first separator 40, the first solid electrolyte layer 20, the electrode 10 to be processed, the second solid electrolyte layer 30, and the second separator 50 are sequentially combined. The intermediate product is pulled between the first hot pressing roller 21 and the second hot pressing roller 22 by the first winding shaft 31, the second winding shaft 32, and the third winding shaft 33. Due to the moderate peeling force between the separator layer and the solid electrolyte layer of the composite separator, the separator layer and the solid electrolyte layer of the composite separator are peeled off during the movement, and the solid electrolyte layer of the composite separator is transferred to the electrode 10 to be processed.

[0069] Figure 4 is a schematic diagram of the structure of the target electrode coated with a solid electrolyte layer, such as Figure 4As shown, the target electrode includes a to-be-processed electrode 10 and a first solid electrolyte layer 20 and a second solid electrolyte layer 30 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 solid electrolyte layer is 1-20 microns. Specifically, the thickness of the solid electrolyte layer can be 1, 2, 3, 4, 5, 7, 10, 13, 16 or 20 microns, as well as specific point values ​​between the above point values, preferably 2-6 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.

[0070] A thinner solid electrolyte layer is beneficial for improving the energy density of the battery and making the battery lighter and thinner.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Example 1

[0081] The solid electrolyte slurry is coated on the PP diaphragm to prepare a composite diaphragm, wherein the solid electrolyte slurry is a slurry formed by dissolving LLZO solid electrolyte in solvent NMP;

[0082] After passing through the first and third unwinding reels, the composite diaphragm coated with the solid electrolyte layer is passed between the first and second hot-pressing rollers along with the unprocessed positive electrode sheet from the second unwinding reel for lamination. The lamination is then reeled up by the second reel. At this point, the solid electrolyte layer in the composite diaphragm is laminated to both sides of the unprocessed positive electrode sheet, and the diaphragm in the composite diaphragm is recovered from the first and third reels.

[0083] 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.

[0084] The coating speed in this embodiment is 15 m / min and the hot pressing temperature is 90°C.

[0085] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared is 3 microns, without curling or bending.

[0086] Example 2

[0087] The difference between Example 2 and Example 1 is that the solid electrolyte slurry is a slurry formed by dissolving SiO2 inorganic particles and PTFE binder in NMP solvent, wherein the mass ratio of PTFE to LiNbO3 is 9:1. In addition, the hot pressing temperature in this example is 100°C.

[0088] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared is 2 microns, without curling or bending.

[0089] Example 3

[0090] The difference between Example 3 and Example 1 is that the solid electrolyte slurry is a slurry formed by dissolving LiNbO3 inorganic solid electrolyte particles, PTFE binder, PEO polymer solid electrolyte, and lithium hexafluorophosphate (LiPF6) in NMP solvent. The mass ratio of PTFE, LiNbO3, PEO, and LiPF6 is 5:0.5:3.5:1. In addition, the hot pressing temperature in this example is 110°C.

[0091] The thickness of the solid electrolyte layer on the surface of the positive electrode plate finally prepared is 2.5 microns, without curling or bending.

[0092] 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. First, a solid electrolyte slurry is applied to the surface of a diaphragm to form a composite diaphragm. Then, the composite diaphragm coated with the solid electrolyte layer is hot-pressed with the pole piece to be processed, thereby transferring the solid electrolyte layer on the composite diaphragm to the surface of the pole piece to be processed. During the hot-pressing process, the pole piece is in a taut state and is heated to fully volatilize the solvent, thereby preventing the pole piece from curling or bending during the application of the solid electrolyte.

[0093] 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: coating the solid electrolyte slurry on the separator to form a composite separator; The side of the composite diaphragm coated with the solid electrolyte slurry is opposite to the electrode to be processed. When the solid electrolyte is not dried, the solid electrolyte on the composite diaphragm is transferred to the surface of the electrode to be processed by hot pressing to form a solid electrolyte layer, so as to prepare a target electrode; wherein, Both sides of the electrode to be processed are covered with a solid electrolyte layer; the solid electrolyte on the composite diaphragm is transferred to both sides of the electrode to be processed in a rolling manner.

2. The method for preparing a pole piece according to claim 1, characterized in that: The solid electrolyte slurry includes a solid electrolyte, and the solid electrolyte includes an inorganic solid electrolyte.

3. The method for preparing a pole piece according to claim 2, characterized in that: The solid electrolyte also includes a polymer solid electrolyte.

4. The method for preparing a pole piece according to claim 2, characterized in that: The solid electrolyte slurry further includes at least one of a binder and a lithium salt.

5. The method for preparing a pole piece according to claim 1, characterized in that: The thickness of the solid electrolyte layer is 1-20 microns.

6. The method for preparing a pole piece according to claim 1, characterized in that: The hot pressing temperature is 80-110°C.

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.

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