A separator for lithium ion batteries and a method for manufacturing the same, and a lithium ion battery

Abstract

This application provides a method for preparing a separator membrane for lithium-ion batteries, as well as the separator membrane and the lithium-ion battery. The method includes micro-pressuring a substrate layer and a polymer support layer together using an adhesive layer to obtain an intermediate. A solid electrolyte slurry is then coated onto the side of the substrate layer of the intermediate away from the adhesive layer. After drying, a first solid electrolyte layer is formed. The intermediate after forming the first solid electrolyte layer is then released and wound up to obtain a separator membrane for lithium-ion batteries and a release layer. The separator membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer. By combining the substrate layer and the polymer support layer during the preparation process, this application provides support for the thin substrate layer, facilitating the coating of the solid electrolyte layer on the substrate layer, and avoiding problems such as shrinkage and wrinkling of the substrate layer during the coating process.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method for preparing a separator for lithium-ion batteries, the separator for lithium-ion batteries, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles and other fields due to their high energy density and good rate performance. A lithium-ion battery typically consists of a positive electrode, a negative electrode, and a separator membrane. The separator membrane is located between the positive and negative electrodes, and its main function is to separate the active materials of the two electrodes, preventing short circuits caused by contact. For systems using non-aqueous electrolytes or solid-liquid mixtures, the separator membrane can retain necessary electrolytes or liquid additives, forming channels for ion movement. Different types of batteries use different separator membranes. In the structure of a lithium-ion battery, the separator membrane is one of the key internal components. The performance of the separator membrane determines the battery's interface structure, internal resistance, etc., directly affecting the battery's capacity, cycle life, and safety performance. A high-performance separator membrane plays a crucial role in improving the overall performance of the battery.

[0003] Conventional lithium-ion battery separators include traditional lithium-ion battery separators and composite lithium-ion battery separators. Traditional lithium-ion battery separators are mainly polymer-based, such as polypropylene (PP) or polyethylene (PE) lithium-ion battery separators. Composite lithium-ion battery separators typically rely on a base membrane (the lithium-ion battery separator layer) to maintain structural stability, with a functional slurry coated on the surface of the base membrane to form a functional layer (such as a ceramic layer). However, on the one hand, because the base membrane is usually quite thin (typically a few micrometers) and has poor mechanical strength, directly coating a solid electrolyte layer onto its surface is difficult, requiring highly sophisticated coating processes, and the resulting film exhibits poor product support and is prone to detachment.

[0004] Therefore, there is an urgent need to propose a new method for preparing separation membranes for lithium-ion batteries to solve the above problems. Summary of the Invention

[0005] In order to solve one or more of the technical problems existing in the prior art, this application provides a new method for preparing a separator membrane for lithium-ion batteries, as well as a separator membrane and a lithium-ion battery, which can solve the problem of coating the solid electrolyte layer under the current trend of thinner and lighter separators.

[0006] To achieve the above objectives, the technical solution adopted by this application to solve its technical problem is as follows:

[0007] In a first aspect, this application provides a method for preparing a separation membrane for lithium-ion batteries, the method comprising:

[0008] An intermediate is obtained by micro-compressing the substrate layer and the polymer support layer using an adhesive layer;

[0009] A solid electrolyte slurry is coated on the side of the substrate layer of the intermediate away from the adhesive layer, and after drying, a first solid electrolyte layer is formed.

[0010] The intermediate after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer. The separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer.

[0011] In one specific embodiment, the intermediate obtained by micro-compressing the substrate layer and the polymer support layer using an adhesive layer comprises:

[0012] An adhesive is coated on the surface of the polymer support layer to form an adhesive layer on the surface of the polymer support layer;

[0013] The substrate layer and the side of the polymer support layer coated with the adhesive layer are bonded together by an adhesive, and micro-pressure lamination is performed to obtain an intermediate. In one specific embodiment, the bond strength between the substrate layer and the adhesive is less than the bond strength between the polymer support layer and the adhesive.

[0014] In one specific embodiment, the adhesive includes at least one of electrostatic silicone or fluorinated adhesive.

[0015] In one specific embodiment, the substrate layer comprises at least one of polyethylene, polypropylene, or nonwoven fabric; and / or,

[0016] The polymer support layer includes at least one of polypropylene, polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, comonomer-modified polyvinylidene fluoride, cellulose, hemicellulose, and lignin.

[0017] In one specific embodiment, the first solid electrolyte layer includes at least one solid electrolyte, which includes at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, polymer solid electrolyte, borate solid electrolyte, nitride solid electrolyte or hydride solid electrolyte.

[0018] In one specific embodiment, the thickness of the substrate layer is 2-7 μm, preferably 3 μm.

[0019] In one specific embodiment, the thickness of the polymer support layer is 30-100 μm, preferably 50 μm.

[0020] In one specific embodiment, the thickness of the first solid electrolyte layer is 1-5 μm.

[0021] Secondly, corresponding to the above-mentioned method for preparing a separation membrane for lithium-ion batteries, this application also provides a separation membrane for lithium-ion batteries, wherein the separation membrane for lithium-ion batteries is prepared by the method described above, and the separation membrane for lithium-ion batteries includes a substrate layer and a first solid electrolyte layer disposed on the surface of the substrate layer.

[0022] Thirdly, corresponding to the separation membrane for lithium-ion batteries described above, this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, and a separation membrane for lithium-ion batteries as described above disposed between the positive electrode and the negative electrode.

[0023] In one specific embodiment, the negative electrode sheet includes a negative current collector and a layer of negative active material disposed on the negative current collector.

[0024] In one specific embodiment, the positive electrode sheet includes a positive current collector and a layer of positive active material disposed on the positive current collector.

[0025] The beneficial effects of the technical solutions provided in this application are:

[0026] The present application provides a method for preparing a separation membrane for lithium-ion batteries, as well as the separation membrane and the lithium-ion battery. The method includes micro-pressing a substrate layer and a polymer support layer together using an adhesive layer to obtain an intermediate. A solid electrolyte slurry is coated on the side of the substrate layer of the intermediate away from the adhesive layer. After drying, a first solid electrolyte layer is formed. The intermediate after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer. The separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer. By combining the substrate layer and the polymer support layer during the preparation process, the present application provides support for the thin substrate layer, which facilitates the coating of the solid electrolyte layer on the substrate layer. At the same time, it can avoid problems such as shrinkage and wrinkling of the substrate layer during the coating process.

[0027] The products in this application do not need to have all of the above effects. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating the preparation method of a separation membrane for lithium-ion batteries provided in this application embodiment. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] In response to one or more technical problems raised in the background art, this application creatively proposes a new method for preparing a separation membrane for lithium-ion batteries. In the process of preparing the separation membrane for lithium-ion batteries, a thick polymer support layer is used to provide support for a thin substrate layer, thereby facilitating the coating of a solid electrolyte layer on the substrate layer and avoiding problems such as shrinkage and wrinkling of the substrate layer during the coating process.

[0032] Reference Figure 1 As shown in the embodiments of this application, the method for preparing the separation membrane for lithium-ion batteries includes the following steps:

[0033] S100: The substrate layer and the polymer support layer are micro-pressurized together using an adhesive layer to obtain an intermediate.

[0034] Specifically, the substrate layer of the separator used in composite lithium-ion batteries is typically thin and has poor mechanical strength, making it prone to cracking during the actual fabrication process. Furthermore, its thinness makes bonding with the functional layer difficult, leading to shrinkage and wrinkling during bonding, resulting in product defects. To address these issues, this application proposes providing a thicker support layer for the substrate layer. Specifically, before coating the substrate layer with a solid electrolyte slurry, the substrate layer is first composited with a thick polymer support layer to form an intermediate, thus providing support for the substrate layer. The composite of the substrate layer and the polymer support layer can be achieved through an adhesive layer, which can be a micro-adhesive adhesive.

[0035] In one specific embodiment, the intermediate obtained by micro-compressing the substrate layer and the polymer support layer using an adhesive layer comprises:

[0036] An adhesive is coated on the surface of the polymer support layer to form an adhesive layer on the surface of the polymer support layer;

[0037] The substrate layer and the side of the polymer support layer coated with the adhesive layer are bonded together by the adhesive, and the substrate layer and the polymer support layer are bonded together by the adhesive, and the intermediate is obtained by micro-pressure composite.

[0038] In a preferred embodiment of this application, the bonding strength between the substrate layer and the adhesive is less than or equal to the bonding strength between the polymer support layer and the adhesive.

[0039] The micro-pressure composite refers to the process where the substrate layer and the polymer support layer are initially bonded together by applying only slight pressure using an adhesive. If the micro-pressure is too high, the bonding force between the substrate layer and the adhesive layer will be too great, which may easily damage the substrate layer during the subsequent release process.

[0040] It is understood that this application does not specifically limit the pressure for micro-pressure composite. As long as the adhesive layer loaded on the polymer support layer can be separated from the substrate layer without damage, it is acceptable without violating the inventive concept of this application.

[0041] S200: A solid electrolyte slurry is coated on the side of the substrate layer of the intermediate away from the adhesive layer, and after drying, a first solid electrolyte layer is formed.

[0042] Specifically, in the composite intermediate, one side of the substrate layer is connected to the polymer support layer through an adhesive layer. In this embodiment, a solid electrolyte slurry is coated on the other side of the substrate layer. After drying, a first solid electrolyte layer is formed on the surface of the substrate layer. The solid electrolyte slurry is mainly composed of solid electrolyte. In this embodiment, the specific composition of the solid electrolyte slurry is not limited, and users can configure it according to actual needs.

[0043] It is understood that the above-described method of forming the first solid electrolyte layer is exemplary and not restrictive. That is, the method of forming the first solid electrolyte layer is not specifically limited in the embodiments of this application, and any known coating or attachment method can be used in this application. For example, the coating method may be to first mix electrolyte particles (i.e., the above-described solid electrolyte) with a binder and dissolve them in a solvent to form an electrolyte slurry, and then coat the electrolyte slurry onto the surface of the substrate layer, dry it, and then roll it. The attachment method may be to first form an electrolyte layer on the substrate film, and then transfer the electrolyte layer on the substrate film to the substrate layer by means of rolling or other methods, etc., and so on. These are not exhaustive examples here.

[0044] It is understandable that there are no special requirements for the types of solvents used to dissolve the solid electrolyte and binder, as long as they can form a stable slurry with the solid electrolyte and binder and are chemically stable with the solid electrolyte, binder and other related materials.

[0045] S300: The intermediate body after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer, wherein the separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer, and the release layer includes the polymer support layer and the adhesive layer.

[0046] Specifically, since the adhesive layer in this embodiment is achieved using a micro-adhesive adhesive, the substrate layer can be separated under force during release winding to form a lithium-ion battery separation membrane including a substrate layer and a first solid electrolyte layer disposed on the substrate layer, as well as an adhesive layer including a polymer support layer and an adhesive layer disposed on the polymer support layer.

[0047] As a preferred embodiment, in this application embodiment, the adhesive layer can be pre-set on the surface of the polymer support layer. In specific implementation, an adhesive can be coated on the surface of the polymer support layer to form an adhesive layer, and then the whole formed by the two can be combined with the substrate layer by a rolling device to form an intermediate.

[0048] In the embodiments of this application, the adhesive layer preferably contains a micro-adhesive adhesive so that the subsequent substrate layer can be peeled off from the adhesive layer during release winding. As an exemplary and not limiting illustration, the adhesive includes at least one of electrostatic silicone or fluorinated adhesive. Fluorinated adhesives can be poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVDF), etc., which will not be listed here.

[0049] The first solid electrolyte layer in this embodiment can be a single layer or a composite of multiple layers; no specific limitation is imposed here, and users can set it according to actual needs. As an illustrative rather than restrictive illustration, in this embodiment, the first solid electrolyte layer can be formed by a composite of multiple electrolyte layers. It should be noted that in this embodiment, the multiple electrolyte layers can be identical or different, and can be set according to actual needs; no limitation is imposed here. It is understood that identical multiple electrolyte layers mean identical structure and composition, that is, their physical, chemical, and electrochemical properties have industrial manufacturing consistency, and they have the same capacity, areal density, and other related parameters.

[0050] In this application embodiment, the substrate layer and polymer support layer are preferably made of polymer materials. Polymer materials are chemically inert, easy to mold, flexible, easy to form films, have good liquid retention, and are low in cost. In this application embodiment, the specific materials of the substrate layer and polymer support layer are not limited. Without departing from the inventive concept of this application, any known polymer material can be used as the substrate layer or polymer support layer. The polymer material includes at least one of polymer fibers and polymer particles. For example, the polymer material used as the substrate layer can be polyethylene, polypropylene, or nonwoven fabric, and the polymer material used as the polymer support layer can be polypropylene, polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, comonomer-modified polyvinylidene fluoride, cellulose, hemicellulose, and lignin. Preferably, the polymer material in this application embodiment is polyethylene or polypropylene.

[0051] It should be noted that the materials of the substrate layer and the polymer support layer in the embodiments of this application can be the same or different, but the adhesion between the substrate layer and the adhesive must be less than or equal to the adhesion between the polymer support layer and the adhesive, so that the adhesive layer separates from the substrate layer along with the polymer support layer during release winding.

[0052] In a preferred embodiment, the first solid electrolyte layer in this application includes at least a solid electrolyte. This application does not specifically limit the type of solid electrolyte; any known type of solid electrolyte can be used in this application, and is merely an illustrative example rather than a limitation on the scope of protection. The solid electrolyte includes one or a combination of several of the following: oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, polymer solid electrolyte, borate solid electrolyte, nitride solid electrolyte, or hydride solid electrolyte.

[0053] In one embodiment, the polymer solid electrolyte may comprise one or more polymeric materials selected from the group consisting of: polyethylene glycol, polyethylene oxide (PEO), poly(p-phenylene ether) (PPO), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride cohexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof. In one variation, one or more polymeric materials may have a content equal to about 10 - 4 Ionic conductivity in S / cm.

[0054] As one implementation, the oxide solid electrolyte consists of oxide solid electrolyte particles and may include one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and perovskite ceramics. For example, 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 Ga0.3La 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. 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-type 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 variant, one or more oxide-based materials may have an ionic conductivity greater than or equal to about 10 -5 S / cm to less than or equal to about 10 -1 S / cm.

[0055] As one embodiment, the sulfide solid electrolyte consists of sulfide solid electrolyte particles and 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 9.8 1Sn 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 (where 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 Cl 0.3 , (1 - x)P2S 5-x Li2S (where 0.5 ≤ x ≤ 0.7) and combinations thereof. In one variant, one or more sulfide-based materials may have an ionic conductivity greater than or equal to about 10 -7 S / cm to less than or equal to about 1 S / cm.

[0056] As one embodiment, the halide solid electrolyte may be composed of halide solid electrolyte particles, including Li2CdCl4, Li2MgCl4, Li2Cdl4, Li2Znl4, Li3OCl, Lil, Li5Znl4, Li3OCl 1-x Br x (where 0 < x < 1) and combinations thereof. In one variant, one or more halide-based materials may have an ionic conductivity greater than or equal to about 10 -8 S / cm to less than or equal to about 10 -1 S / cm.

[0057] As one embodiment, the borate solid electrolyte is composed of borate solid electrolyte particles, including one or more borate-based materials of the group consisting of: Li2B4O7, Li2O-(B2O3)-(P2O5) and combinations thereof. In one variant, one or more borate-based materials may have an ionic conductivity greater than or equal to about 10 -7 S / cm to less than or equal to about 10 -2 S / cm.

[0058] In one embodiment, the nitride solid electrolyte comprises nitride solid electrolyte particles, including Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof. In one variation, one or more nitride-based materials may have a density greater than or equal to about 10. -9 Ionic conductivity from S / cm to less than or equal to about 1 S / cm.

[0059] In one embodiment, the hydride solid electrolyte comprises hydride solid electrolyte particles, and the hydride-based particles may include one or more hydride-based materials selected from the group consisting of: Li3AlH6, LiBH4, LiBH4-Li X (where X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2, and combinations thereof. In one variant, one or more hydride-based materials may have a content greater than or equal to about 10. -7 S / cm to less than or equal to approximately 10 - 2 Ionic conductivity in S / cm.

[0060] In one of the variant embodiments, the solid electrolyte may be a quasi-solid electrolyte comprising a mixture of the non-aqueous liquid electrolyte solution and the solid electrolyte system detailed above, for example, comprising one or more ionic liquids and one or more metal oxide particles (such as alumina (Al2O3) and / or silicon dioxide (SiO2)).

[0061] In a preferred embodiment of this application, the first solid electrolyte layer further includes a binder. This is merely an example and not a limitation on the scope of protection; in this embodiment, the binder in the solid electrolyte layer may be poly(tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof.

[0062] This application does not have any particular requirements on the ratio of binder to solid electrolyte in the first solid electrolyte layer. Preferably, the proportion of solid electrolyte in the first solid electrolyte layer is more than 70%, such as 71%, 72%, 75%, 80%, etc., which will not be listed here.

[0063] In a preferred embodiment of this application, the thickness of the substrate layer is any value between 2 and 7 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc. Preferably, the thickness of the substrate layer is 3 μm.

[0064] As a preferred embodiment, in this application embodiment, the thickness of the polymer support layer is any value between 30-100 μm, preferably, the thickness of the polymer support layer is 50 μm.

[0065] As a preferred implementation, in this embodiment of the application, the thickness of the first solid electrolyte layer is any value between 1 and 5 μm, such as 1 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc., which will not be listed here.

[0066] In a preferred embodiment, the preparation method further includes step S400:

[0067] A second solid electrolyte layer is coated on the side of the separator membrane for lithium-ion batteries that is not coated with the first solid electrolyte layer.

[0068] Preferably, step S400 further includes coating a second solid electrolyte layer on the side of the separator membrane for lithium-ion batteries that is not coated with the first solid electrolyte layer, and then drying it to obtain the separator membrane for lithium-ion batteries.

[0069] Compared to existing solid electrolyte layer coating technologies, coating both sides of the substrate layer simultaneously places excessive demands on the coating equipment, requiring it to have a highly precise structure. If the solid electrolyte layer is coated on one side first and then on the other, the substrate layer is relatively thin, and it is prone to cracking due to stress when coating the first side. Furthermore, during solvent evaporation, the substrate layer curls due to solvent volatilization, which greatly reduces the yield and the performance of the separation membrane.

[0070] In this application, when the first solid electrolyte layer is coated, the mechanical properties of the intermediate membrane are improved because the substrate layer is supported by the polymer support layer. At the same time, because the polymer support layer has high mechanical strength and thick thickness, even if stress occurs due to solvent evaporation during the coating process, it is not enough to cause deformation of the separation membrane.

[0071] Meanwhile, after separating the polymer support layer and the substrate layer, the stress on the solid electrolyte layer coated on the other side has been largely released, and the size and shape of the separation membrane will not change or deform.

[0072] In a preferred embodiment, the separator for lithium-ion batteries may further include a flame retardant. In this application, there are no limitations on the method of adding the flame retardant to the separator for lithium-ion batteries. Any known method of adding a flame retardant to the substrate layer can be used in this invention without departing from the inventive concept, including but not limited to directly mixing the components of the substrate layer with the flame retardant.

[0073] Corresponding to the above-described method for preparing a separation membrane for lithium-ion batteries, this application also provides a separation membrane for lithium-ion batteries. The separation membrane for lithium-ion batteries includes a substrate layer and a first solid electrolyte layer disposed on the surface of the substrate layer. The specific details of the separation membrane for lithium-ion batteries can be referred to the foregoing description, and will not be repeated here.

[0074] Corresponding to the above-described method for preparing a separator for lithium-ion batteries and the separator for lithium-ion batteries, this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, and a separator for lithium-ion batteries disposed between the positive electrode and the negative electrode.

[0075] In a preferred embodiment of this application, the negative electrode includes a negative current collector and a negative active material layer disposed on the negative current collector, and the positive electrode includes a positive current collector and a positive active material layer disposed on the positive current collector.

[0076] The lithium-ion battery in this application embodiment can adopt a stacked or wound design inside the battery. It can be understood that, due to the stacked or wound design inside the battery, the current collectors (including positive electrode current collectors and negative electrode current collectors) can be coated on both sides, that is, active material layers are formed on both sides of the current collector.

[0077] When the lithium-ion battery is a liquid battery system, the battery also includes an electrolyte, which includes at least a non-aqueous liquid electrolyte solution. In a preferred embodiment, the electrolyte consists only of a non-aqueous electrolyte solution, which includes an organic solvent and a lithium salt dissolved in the organic solvent. This application does not impose any particular limitation on the types of lithium salts and solvents for dissolving lithium salts. Any known lithium salt and solvent can be used in this application without departing from the inventive concept of this application.

[0078] As illustrative examples, usable lithium salts include: lithium hexafluorophosphate (LiPF6); lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (Lil), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiBF2(C2O4))(LiODFB), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalate)borate (LiB(C2O4)2)(LiBOB), lithium tetrafluorooxalate phosphate (LiPF4(C2O4))(LiFOP), lithium nitrate (LiNO3), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonylimide) (LITFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonylimide) (LiN(FSO2)2)(LIFSI), and combinations thereof. In some variations, the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonylimide) (LiTFSI)(LiN(CF3SO2)2), lithium bis(fluorosulfonylimide) (LiN(FSO2)2)(LiFSI), lithium fluoroalkylphosphonate (LiFAP), lithium phosphate (Li3PO4), and combinations thereof. Solvents that may be used include, but are not limited to, various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC)), aliphatic carboxylic acid esters (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain ethers (e.g., 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane (DOL), sulfur compounds (e.g., sulfolane), and combinations thereof. In a completely non-aqueous electrolyte system, the electrolyte may include one or more lithium salts with a concentration greater than or equal to 1 M to less than or equal to about 2 M. In some embodiments, such as when the electrolyte has a lithium concentration greater than about 2M or has an ionic liquid, the electrolyte may include one or more diluents, such as fluoroethylene carbonate (FEC) and / or hydrofluoroether (HFE).

[0079] Particularly preferred is that the electrolyte is a solid electrolyte or a combination of a non-aqueous liquid electrolyte solution and a solid electrolyte.

[0080] This application does not have any special requirements on the composition or structure of the positive electrode and the negative electrode. Without departing from the inventive concept of this application, any known positive electrode active material, negative electrode active material, current collector, and corresponding auxiliary structure and composition can be used in this application.

[0081] The following is a brief explanation of the positive and negative electrode materials and structures, provided merely as an illustrative example and not to limit the scope of protection.

[0082] The negative electrode is formed from a lithium-based material that can be used as the negative electrode in a lithium-ion battery. For example, the negative electrode may contain a negative electrode active material that can be used as the negative electrode in a battery. The negative electrode active material layer may be composed of a variety of negative electrode active materials. In some embodiments, the negative electrode may also include an electrolyte, such as oxide, sulfide, or halide electrolyte particles (not shown) as previously mentioned.

[0083] This application does not specifically limit the type of negative electrode active material. Any known negative electrode active material can be used in this application without departing from the inventive concept. In one embodiment, the negative electrode active material comprises lithium metal and / or lithium alloy. In other embodiments, the negative electrode is a silicon-based negative electrode active material comprising silicon, such as silicon alloys, silicon oxide, or combinations thereof, and in some cases may be mixed with graphite. In other embodiments, the negative electrode may comprise a carbon-based negative electrode active material comprising one or more of graphite, graphene, carbon nanotubes (CNTs), and combinations thereof. In yet another embodiment, the negative electrode comprises one or more lithium-accepting negative electrode active materials, such as lithium titanium oxide (Li4Ti5O). 12 One or more transition metals (e.g., tin (Sn)), one or more metal oxides (e.g., vanadium oxide (V2O5), tin oxide (SnO), titanium dioxide (TiO2)), titanium niobium oxide (TixNbyOz, where 0≤x≤2, 0≤y≤24 and 0≤z≤64), metal alloys (e.g., copper-tin alloy (Cu6Sn5)), and one or more metal sulfides (e.g., iron sulfide (FeS)).

[0084] Optionally, the negative electrode active material in the negative electrode sheet may be doped with one or more conductive agents that provide an electron conduction path and / or at least one polymer binder material that improves the structural integrity of the negative electrode. For example, the binder may optionally be: poly(tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), acrylonitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof. The conductive agent may include carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, superP, acetylene black (e.g., KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene)polysulfonated styrene, etc.

[0085] The negative electrode may include more than or equal to about 50 wt% to less than or equal to about 97 wt% of a negative electrode active material, optionally more than or equal to about 0 wt% to less than or equal to about 60 wt% of a solid electrolyte, optionally more than or equal to about 0 wt% to less than or equal to about 15 wt% of a conductive material, and optionally more than or equal to about 0 wt% to less than or equal to about 10 wt% of a binder.

[0086] The positive electrode is formed of a plurality of positive electrode active particles comprising 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 comprises an electrolyte, such as a plurality of electrolyte particles. The positive electrode active material layer has a thickness greater than or equal to about 1 μm to less than or equal to about 1,000 μm.

[0087] The positive electrode active material layer is one of layered oxide cathodes, spinel cathodes, and polyanion cathodes. For example, a layered oxide cathode (e.g., rock salt layered oxide) contains one or more lithium-based positive electrode active materials selected from: LiCoO2 (LCO), 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+xMO2 (where M is one of Mn, Ni, Co, and Al and 0 ≤ x ≤ 1). The spinel cathode contains one or more lithium-based positive electrode active materials selected from the following: LiMn2O4 (LMO) and LiNi. x Mn 1.5 O4. The olivine-type cathode comprises one or more lithium-based positive electrode active materials, LiMPO4 (where M is at least one of Fe, Ni, Co, and Mn). The polyanionic cation comprises, for example, phosphates such as LiV2(PO4)3 and / or silicates such as LiFeSiO4.

[0088] In one embodiment, one or more lithium-based positive electrode active materials may optionally be coated (e.g., by LiNbO3 and / or Al2O3) and / or may be doped (e.g., by magnesium (Mg)). Furthermore, in some embodiments, one or more lithium-based positive electrode active materials may optionally be mixed with one or more conductive materials that provide an electronic conduction path and / or at least one polymeric binder material that improves the structural integrity of the positive electrode. For example, the positive electrode active material layer may comprise more than or equal to about 30 wt% to less than or equal to about 98 wt% of one or more lithium-based positive electrode active materials; more than or equal to about 0 wt% to less than or equal to about 30 wt% of a conductive agent; and more than or equal to about 0 wt% to less than or equal to about 20 wt% of a binder, and in some aspects, optionally more than or equal to about 1 wt% to less than or equal to about 20 wt% of a binder.

[0089] The positive electrode active material layer may optionally be mixed with binders such as polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof. The conductive agent may include carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, acetylene black (e.g., KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, etc.

[0090] The positive current collector (including first and second positive current collectors) facilitates the flow of electrons between the positive electrode and an external circuit. The positive current collector may comprise a metal, such as a metal foil, metal grid or screen, or metal mesh. For example, the positive current collector may be formed from aluminum, stainless steel, and / or nickel, or any other suitable conductive agent known to those skilled in the art.

[0091] Example 1

[0092] An adhesive with electrostatic silicone as the bonding layer, a PP layer as the polymer support layer with a thickness of 50 μm, and a PE / PP layer as the substrate layer with a thickness of 5 μm are used.

[0093] An intermediate is obtained by coating an electrostatic silicone layer onto a PP layer and then micro-pressing it with a substrate layer. The micro-pressing process involves placing the PP layer coated with electrostatic silicone into a molding die and applying pressure to the die to fuse the PP layer and the adhesive layer into a whole.

[0094] A solid electrolyte slurry is coated on the side of the substrate layer of the intermediate away from the adhesive layer. The solid electrolyte in the slurry is LLZO and the adhesive is PVDF. The coating thickness is 3μm. After coating, the substrate layer is dried to form the first solid electrolyte layer.

[0095] The intermediate after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer. The separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer.

[0096] Ultimately, the prepared lithium battery separator membrane has a thickness of 7 μm. This separator membrane exhibits good mechanical strength and shows no damage during subsequent stacking processes. Example 2

[0097] An adhesive with electrostatic silicone as the bonding layer, a PP layer as the polymer support layer with a thickness of 50 μm, and a PE / PP layer as the substrate layer with a thickness of 5 μm are used.

[0098] An intermediate is obtained by coating an electrostatic silicone layer onto a PP layer and then micro-pressing it with a substrate layer. The micro-pressing process involves placing the PP layer coated with electrostatic silicone into a molding die and applying pressure to the die to fuse the PP layer and the adhesive layer into a whole.

[0099] A first solid electrolyte layer is coated on the side of the substrate layer of the intermediate away from the adhesive layer. The solid electrolyte in the first solid electrolyte layer is LLZO, the adhesive is PVDF, the coating thickness is 3μm, and the coating is dried after coating.

[0100] The intermediate after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer. The separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer.

[0101] A second solid electrolyte layer is coated on the side of the lithium battery separator membrane that is not coated with the first solid electrolyte layer. The solid electrolyte in the second solid electrolyte layer is LLTO, the binder is PVDF, the coating thickness is 4μm, and the membrane is dried after coating.

[0102] Ultimately, the prepared lithium battery separator membrane has a thickness of 10 μm. This separator membrane has good mechanical strength and is not damaged in subsequent stacking processes.

[0103] As can be seen from the above embodiments, the embodiments prepared in this application overcome the problems of coating difficulties and curling deformation caused by insufficient mechanical properties of the solid electrolyte layer coated with ultrathin diaphragm, and realize the ultrathin composite of solid electrolyte layer and diaphragm layer.

[0104] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0105] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0106] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing a separator film for a lithium ion battery, characterized by, The method includes: An intermediate is obtained by micro-compressing the substrate layer and the polymer support layer using an adhesive layer; A solid electrolyte slurry is coated on the side of the substrate layer of the intermediate away from the adhesive layer, and after drying, a first solid electrolyte layer is formed. The intermediate after forming the first solid electrolyte layer is released and wound up to obtain a separation membrane for lithium-ion batteries and a release layer. The separation membrane for lithium-ion batteries includes the substrate layer and the first solid electrolyte layer disposed on the substrate layer. The release layer includes the polymer support layer and the adhesive layer.

2. The method for producing a separator film for a lithium-ion battery according to claim 1, characterized by, The intermediate obtained by micro-compressing the substrate layer and the polymer support layer using an adhesive layer includes: An adhesive is coated on the surface of the polymer support layer to form an adhesive layer on the surface of the polymer support layer; The substrate layer and the side of the polymer support layer coated with the adhesive layer are bonded together by the adhesive, and the substrate layer and the polymer support layer are bonded together by the adhesive, and the intermediate is obtained by micro-pressure composite.

3. The method for preparing the separation membrane for lithium-ion batteries according to claim 2, characterized in that, The bond strength between the substrate layer and the adhesive is less than the bond strength between the polymer support layer and the adhesive.

4. The method for preparing the separation membrane for lithium-ion batteries according to claim 2, characterized in that, The adhesive includes at least one of electrostatic silicone or fluorinated adhesive.

5. The method for preparing a separation membrane for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The substrate layer comprises at least one of polyethylene, polypropylene, or nonwoven fabric; and / or, The polymer support layer includes at least one of polypropylene, polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, comonomer-modified polyvinylidene fluoride, cellulose, hemicellulose, and lignin.

6. The method for preparing a separation membrane for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The first solid electrolyte layer includes at least one solid electrolyte, which includes at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, polymer solid electrolyte, borate solid electrolyte, nitride solid electrolyte or hydride solid electrolyte.

7. The method for preparing a separation membrane for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The thickness of the substrate layer is 2-7 μm; and / or, The thickness of the polymer support layer is 30-100 μm.

8. The method for preparing a separation membrane for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The thickness of the first solid electrolyte layer is 1-5 μm.

9. A separator membrane for lithium-ion batteries, characterized in that, The separation membrane for lithium-ion batteries is prepared by the method for preparing a separation membrane for lithium-ion batteries as described in any one of claims 1 to 8, and the separation membrane for lithium-ion batteries includes a substrate layer and a first solid electrolyte layer disposed on the surface of the substrate layer.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and a separator membrane for lithium-ion batteries as described in claim 9, disposed between the positive electrode and the negative electrode.

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