Composite separators and their applications

Abstract

This application provides a composite separator and its applications. The composite separator comprises a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate, wherein the electrolyte layer contains at least inorganic nanotubes and solid electrolyte particles, and the porosity of the inorganic nanotubes in the electrolyte layer is 0.2-5%. When used in a battery, the composite separator not only has excellent heat resistance and electrolyte permeability, but also excellent lithium-ion transmission performance, which can reduce the internal resistance of the lithium-ion battery and improve the multiplier performance and cycle performance of the lithium-ion battery.

Description

Technical Field

[0001] The embodiments of the present application relate to a composite separator and its applications, belonging to the field of energy technology.

Background Art

[0002] A separator is provided between the positive electrode and the negative electrode of a lithium-ion battery to prevent the occurrence of a short-circuit problem caused by direct contact between the positive electrode and the negative electrode. The performance of the separator directly affects the performance of the lithium-ion battery. However, the commonly used polyolefin separator currently has problems such as a low melting point and poor wettability of the electrolyte. During the use process of the lithium-ion battery, the separator is prone to shrinkage, causing the positive electrode and the negative electrode to contact and cause a short circuit, which is not only disadvantageous to the service life of the battery but also causes safety risks.

[0003] To solve this problem, connection techniques improve the heat resistance performance and electrolyte wettability of the polyolefin separator by providing a common ceramic coating such as alumina and boehmite, or a thermoplastic resin coating such as PVDF (Polyvinylidene Fluoride) , polyimide, and aramid on the surface of the polyolefin separator. However, this method is likely to reduce the lithium-ion transmission performance and improve the internal resistance of the lithium-ion battery.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present application provides a composite separator, which, when used in a battery, not only has excellent heat resistance performance and electrolyte wettability but also has excellent lithium-ion transmission performance, reduces the internal resistance of the lithium-ion battery, and can improve the rate performance and cycle performance of the lithium-ion battery.

[0005] The present application provides a battery, which has excellent safety performance, rate performance, and cycle performance because it includes the above composite separator. [Means for solving the problem]

[0006] This application provides a composite separator comprising a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate. The electrolyte layer comprises at least inorganic nanotubes and solid electrolyte particles. In the electrolyte layer, the porosity of the inorganic nanotubes is 0.2-5%.

[0007] According to the composite separator described above, the mass percentage content of the inorganic nanotubes is 5-60% based on the total mass of the electrolyte layer.

[0008] According to the composite separator described above, the inner diameter of the inorganic nanotube is 3-150 nm.

[0009] With the composite separator described above, the ratio of the outer diameter of the inorganic nanotube to the inner diameter of the inorganic nanotube is (1.5-20):1.

[0010] According to the composite separator described above, the length of the inorganic nanotube is 0.3-5 μm.

[0011] According to the composite separator described above, the ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte particle is greater than 0 and less than or equal to 30.

[0012] According to the composite separator described above, the particle size distribution of the solid electrolyte particles is ≤ 1.5.

[0013] According to the composite separator described above, the composite separator comprises at least, a. The thickness of the separator substrate shall be 5-30 μm. The following conditions must be met: b) the thickness of the electrolyte layer is 0.5-4 μm.

[0014] According to the composite separator described above, the electrolyte layer further comprises at least one of a dispersant, a wetting agent, a binder, and a thickening agent.

[0015] According to the composite separator described above, the composite separator comprises at least, a. Based on the total mass of the electrolyte layer, the mass percentage content of the binder is 3-10%. b. Based on the total mass of the electrolyte layer, the mass percentage content of the dispersant is 0.1-1.5%. c. Based on the total mass of the electrolyte layer, the mass percentage content of the thickener is 0.1-3%. d) The mass percentage content of the wetting agent is 0.1-1.5% based on the total mass of the electrolyte layer, and one of these conditions is met.

[0016] This invention provides a battery equipped with the composite separator described above. [Effects of the Invention]

[0017] The composite separator of the present invention comprises a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate, wherein the electrolyte layer contains at least inorganic nanotubes and solid electrolyte particles, and the porosity of the inorganic nanotubes in the electrolyte layer is 0.2 to 5%. When used in a battery, the composite separator not only has excellent heat resistance and electrolyte permeability, but also excellent lithium-ion transmission performance, which can reduce the internal resistance of the lithium-ion battery and improve the multiplier performance and cycle performance of the lithium-ion battery.

[0018] Because the battery according to this invention is equipped with the above-mentioned separator, it has excellent electrochemical performance and can be widely used and applied. [Brief explanation of the drawing]

[0019] [Figure 1] This is a surface SEM image (magnification 10K) of the composite separator in Example 2 of the present invention. [Figure 2]It is a cross-sectional SEM image (magnification 10K) of the composite separator in Example 2 of the present application.

Embodiments for Carrying out the Invention

[0020] To make the purpose, technical solution and advantages of the embodiments of the present application clearer, hereinafter, referring to the drawings in the embodiments of the present application, the technical solutions in the embodiments of the present invention will be clearly and completely described. Of course, the described embodiments are some of the embodiments of the present application, not all of its embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor shall fall within the scope protected by the present application.

[0021] The first aspect of the present application provides a composite separator, and the composite separator includes a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate. The electrolyte layer includes at least inorganic nanotubes and solid electrolyte particles. In the electrolyte layer, the through-hole rate of the inorganic nanotubes is 0.2 - 5%.

[0022] In the present application, the surface of the separator substrate means the two surfaces with the largest area and arranged opposite to each other among the separator substrates. The present application may form a composite separator by providing an electrolyte layer on one surface of the separator substrate, or may also form a composite separator by providing electrolyte layers on two surfaces of the separator substrate.

[0023] The present application does not particularly limit the separator substrate. The separator substrate may be a porous membrane commonly used in this field. Exemplarily, the separator substrate may be a polyolefin porous membrane, or may be a polyolefin porous membrane provided with a coating layer.

[0024] The polyolefin porous membrane may be a polyethylene porous membrane, a polypropylene porous membrane, or a polyethylene-polypropylene multilayer composite separator. A polyethylene-polypropylene multilayer composite separator refers to a multilayer composite porous membrane formed by stacking polypropylene (PP) and polyethylene (PE) in any order, and examples include a PP-PE-PP three-layer composite separator, a PP-PE two-layer composite separator, and a PP-PP-PE-PP four-layer composite separator.

[0025] A polyolefin porous membrane having a coating layer refers to a polyolefin porous membrane having a coating layer on at least one surface. The coating layer is not particularly limited, and a coating layer commonly used in this field can be selected as needed, such as alumina, boehmite, nanofiber, polyimide, or PMMA. (Polymethyl methacrylate) The PVDF may contain at least one coating layer. For example, the polyolefin porous membrane to which the coating layer is provided may be an alumina-coated polyolefin porous membrane, a boehmite-coated polyolefin porous membrane, a nanofiber-coated polyolefin porous membrane, a polyimide-coated polyolefin porous membrane, a PMMA-coated polyolefin porous membrane, or a PVDF-coated polyolefin porous membrane. The polyolefin porous membrane to which the coating layer is provided may be a polyolefin porous membrane coated with a mixture of nanofibers and alumina, a polyolefin porous membrane coated after mixing PVDF and alumina, or a porous membrane coated after mixing PMMA and alumina.

[0026] The electrolyte layer of the present application comprises at least inorganic nanotubes and solid electrolyte particles, and the present application does not particularly limit the material of the inorganic nanotubes, and the inorganic nanotubes may be tubular inorganic nanomaterials commonly used in the art, and exemplary the inorganic nanotubes may be at least one of titanium dioxide nanotubes, silicon nanotubes, halloysite nanotubes, alumina nanotubes, zinc oxide nanotubes, boron nitride nanotubes and silicon carbide nanotubes, and the present application does not particularly limit the solid electrolyte particles, and the solid electrolyte may be solid electrolytes commonly used in the art, and exemplary the solid electrolyte may be LATP (Lithium aluminum titanium phosphate) LAGP (Lithium aluminum germanium phosphate) , LLZO (lithium zirconium lanthanum oxide) and LLZTO (lithium lanthanum zirconium tantalum oxide) It may be at least one of the following: In some embodiments The solid electrolyte may be LATP.

[0027] In this application, the porosity of inorganic nanotubes refers to the ratio of the pore volume provided by the pores of inorganic nanotubes to the total volume of the electrolyte layer. In some embodiments, the porosity of inorganic nanotubes can be obtained by formula 1.

number

[0028] The inner and outer diameters of inorganic nanotubes are determined by known prior art in this field, for example, by field emission transmission electron microscopy (TEM). Specifically, in accordance with GB / T 18907-2013 "Microbeam Analysis - Analytical Electron Microscopy - Selective Region Electron Diffraction Analysis by Transmission Electron Microscopy," a TEM image of the electrolyte layer is obtained, the hollow structure of the inorganic nanotubes can be clearly observed from the TEM image of the electrolyte layer, and the inner and outer diameters of the inorganic nanotubes are measured using a scale bar.

[0029] The tap density of inorganic nanotubes is determined by known prior art in this field, and is obtained by measurement according to, for example, GBT21354-2008 "General Rules for Measurement of Tap Density in Powder Products".

[0030] The mass per unit area of ​​the separator substrate is determined by known prior art in this field, such as gravimetric methods. Specifically, the separator substrate is cut into 5cm x 5cm pieces, the weight of the sample is measured, and the mass per unit area of ​​the separator substrate is obtained by calculation.

[0031] The mass per unit area of ​​the composite separator is determined by known prior art in this field, such as gravimetric methods. Specifically, each composite separator is cut into 5cm x 5cm pieces, the weight of the sample is measured, and the mass per unit area of ​​the composite separator is obtained by calculation.

[0032] The thickness of the electrolyte layer is determined by known prior art in this field, for example, by obtaining the thickness of the electrolyte layer using the measurement method specified in national standard GB / T 36363-2018, or by scanning electron microscopy. Note that the thickness of the electrolyte layer refers to the thickness of a single-layer electrolyte layer; that is, if an electrolyte layer is provided on both sides of the separator substrate, the thickness of the electrolyte layer refers to the thickness of the electrolyte layer provided on one of the surfaces of the separator substrate.

[0033] For example, the porosity of inorganic nanotubes may be in the range of one or two of the following: 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.5%, 1.8%, 2%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3%, 3.5%, 4%, 4.5%, and 5%. In several other forms The porosity of inorganic nanotubes is 0.2-3%.

[0034] In this invention, both the solid electrolyte particles and the inorganic nanotubes have excellent heat resistance, which can improve the heat resistance of the composite separator, allowing the composite separator to maintain its complete shape during the charging and discharging process of the battery, and preventing short circuits between the positive and negative electrodes due to the composite separator contracting under heat during the charging and discharging process of the battery. In particular, because the inorganic nanotubes have a one-dimensional nanostructure, the heat resistance of the composite separator can be further improved after adhesion to the separator substrate, and at the same time, the solid electrolyte particles and inorganic nanotubes can further improve the electrolyte permeability of the composite separator.

[0035] Furthermore, the solid electrolyte in the composite separator can enhance lithium ion transmission performance, and during the battery's charge-discharge process, the solid electrolyte undergoes an oxidation-reduction reaction with the battery's electrodes, forming a dense interfacial film on the surface of the composite separator. This improves the battery's cycle performance. However, the formation of a dense interfacial film significantly increases the battery's internal resistance, affecting the complete release of battery performance (e.g., energy density, multiplier performance). On the other hand, inorganic nanotubes not only provide more channels for lithium ion transmission, but also, during the process of solid electrolyte particles forming an interfacial film, the inorganic nanotubes form nanochannels on the surface of the interfacial film, allowing lithium ions to be transmitted and avoiding a decrease in battery performance during the interfacial film formation process. Therefore, composite separators containing inorganic nanotubes and solid electrolyte particles have excellent lithium ion transmission performance and heat shrinkage resistance, and when used in batteries, they can significantly improve the safety performance, multiplier performance, cycle performance, and energy density of lithium-ion batteries.

[0036] The inventors, In some embodiments, We have discovered that when the porosity of inorganic nanotubes in the electrolyte layer is 0.2 to 5%, it improves the ion transfer efficiency of the composite separator, reduces the internal resistance of the battery, and is advantageous in improving the electrochemical performance of the battery. Furthermore, it exhibits excellent adhesion between the electrolyte layer and the separator substrate, preventing the separator substrate from detaching from the electrolyte layer during the battery's charge and discharge process, and effectively improving the battery's safety performance. Therefore, when the composite separator of this invention is used in a battery, the battery's safety performance, multiplier performance, cycle performance, and energy density can be significantly improved.

[0037] This application does not particularly limit the method for controlling the porosity of inorganic nanotubes in the electrolyte layer, and any control method can be freely selected according to the purpose, as long as it satisfies the various characteristics described above.

[0038] This application Several embodimentsTo further improve the integrated performance of the composite separator, the present invention allows for the adjustment of parameters such as the amount of inorganic nanotubes used, the inner diameter of the inorganic nanotubes, and the outer diameter of the inorganic nanotubes. In some embodiments of the present invention, the mass percentage content of inorganic nanotubes is 5-60% based on the total mass of the electrolyte layer.

[0039] For example, based on the total mass of the electrolyte layer, the mass percentage content of inorganic nanotubes may be in the range of one or two of the following: 5%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 55%, and 60%. In some embodiments Based on the total mass of the electrolyte layer, the mass percentage content of inorganic nanotubes is 10%-50%. In several other forms Based on the total mass of the electrolyte layer, the mass percentage content of inorganic nanotubes is 13%-50%.

[0040] When the mass percentage content of inorganic nanotubes satisfies the above range, the inorganic nanotubes and solid electrolyte particles can better form a "point-linear" nanonetwork structure in which particles and nanotubes are uniformly distributed. This results in good adhesion between the solid electrolyte composite coating layer and the separator substrate, improves the lithium ion transmission performance of the composite separator, and allows for the creation of a composite separator with excellent overall performance.

[0041] In some embodiments of the present application, the inner diameter of the inorganic nanotube is 3–150 nm. Exemplarily, the inner diameter of the inorganic nanotube may be in the range of one or two of the following: 3 nm, 10 nm, 20 nm, 40 nm, 60 nm, 100 nm, 130 nm, and 150 nm.

[0042] In several other forms The inner diameter of inorganic nanotubes is 5-150 nm.

[0043] When the inner diameter of the inorganic nanotube meets the above range, it can provide more transmission channels for lithium ions, enabling rapid transmission of lithium ions in the composite separator. This further reduces the internal resistance of the battery when the composite separator is used in a battery, improving the battery's multiplier performance and energy density.

[0044] In some embodiments of the present application, the ratio of the outer diameter to the inner diameter of the inorganic nanotube is (1.5-20):1.

[0045] The ratio of the outer diameter to the inner diameter of an inorganic nanotube may be within the range of one or two of the following: 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1. In several other forms The ratio of the outer diameter to the inner diameter of an inorganic nanotube is (2-15):1.

[0046] When the ratio of the outer diameter to the inner diameter of the inorganic nanotube satisfies the above range, rapid transmission of lithium ions in the composite separator is ensured, while at the same time, the bonding of the inorganic nanotubes becomes tighter, they adhere better to each other, and the resulting network structure becomes stronger.

[0047] The inventors also found that when the length of the inorganic nanotubes is 0.3-5 μm, the bonding between the inorganic nanotubes becomes tighter, resulting in a more uniform and dense distribution of pores in the inorganic nanotubes within the electrolyte layer, which is advantageous for lithium ion transmission. Furthermore, the network structure formed by the tight deposition of inorganic nanotubes is advantageous for improving the heat resistance of the composite separator. Exemplarily, the length of the inorganic nanotubes may be in the range of one or two of the following: 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2 μm, 2.3 μm, 2.5 μm, 2.7 μm, 2.9 μm, 3 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 4.8 μm, and 5 μm. In addition, the length of the inorganic nanotubes is 0.3-2 μm.

[0048] In some embodiments, the length of inorganic nanotubes is obtained according to the industry standard JY / T 0584-2020 "General Rules for Scanning Electron Microscopy Analysis Methods".

[0049] In some embodiments of the present application, the ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte particle is greater than 0 and less than or equal to 30.

[0050] For example, the ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte particle may be in the range of one or two of the following: 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. In several other forms The ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte is ≤20.

[0051] Length of inorganic nanotubes and D50 of solid electrolyte particles Ratio When the above relationship is satisfied, inorganic nanotubes can better bond with the solid electrolyte, resulting in a tighter electrolyte layer, thereby improving the overall performance of the composite separator.

[0052] In some embodiments of the present application, the particle size distribution (SPAN) of the solid electrolyte particles is ≤ 1.5.

[0053] For example, the particle size distribution of the solid electrolyte particles may be in the range of one or two of the following: 1.5, 1.4, 1.3, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.3, and 0.1. In several other forms The particle size distribution of the solid electrolyte particles is 0.8 to 1.5.

[0054] In some embodiments, the D10, D50, and D90 of the solid electrolyte particles are measured using a laser particle size analyzer, and then the particle size distribution SPAN of the solid electrolyte particles is calculated according to Equation 2.

number

[0055] When the particle size distribution of the solid electrolyte particles satisfies the above range, the inorganic nanotubes can better adhere to the solid electrolyte particles, resulting in a denser electrolyte layer, thereby improving the overall performance of the composite separator.

[0056] In some embodiments, the particle size of the solid electrolyte particles is determined by known prior art in the art. For example, the D50, D90, and D10 of the solid electrolyte particles can be characterized using a laser scattering particle size analyzer (Malvern ZEN3690 particle size analyzer), specifically involving dispersing the solid electrolyte particles in pure water and obtaining the D50, D90, and D10 of the solid electrolyte particles. Alternatively, the electrolyte layer can be scanned with a scanning electron microscope (SEM), and the D50, D90, and D10 of the solid electrolyte can be determined by statistical analysis calculations (e.g., ImageJ software analysis calculations) of the scanning results. The particle size corresponding to when the cumulative particle size distribution percentage reaches 10% is the D10 of the solid electrolyte particles, the particle size corresponding to when the cumulative particle size distribution percentage reaches 50% is the D50 of the solid electrolyte particles, and the particle size corresponding to when the cumulative particle size distribution percentage reaches 90% is the D90 of the solid electrolyte particles.

[0057] In some embodiments of the present application, the composite separator is at least: a. The thickness of the separator substrate shall be 5-30 μm. If one of the following conditions is met, b) the electrolyte layer thickness is 0.5 to 4 μm, then using the resulting composite separator in a battery can further improve the electrochemical performance of the battery. The electrolyte layer thickness refers to the thickness of the single-layer electrolyte layer.

[0058] This application Some embodiments In order to improve the adhesion between the electrolyte layer and the separator substrate and to adhere the electrolyte layer more tightly to the surface of the separator substrate, the electrolyte layer further comprises at least one of a dispersant, a wetting agent, a binder, and a thickening agent.

[0059] The present application is not particularly limited to the binder, and exemplifies that the binder may be at least one of the following: polyacrylate copolymers, polyacrylamide copolymers, polyurethane copolymers, polyimide copolymers, polyetherimide copolymers, polyurea copolymers, and styrene-butadiene rubber copolymers.

[0060] This application is not particularly limited to the dispersant, but exemplary the dispersant may be at least one of the following: a sodium salt of a polyacrylate copolymer, an ammonium salt of a polyacrylate copolymer, and an ammonium salt of an acidic group-containing alcohol.

[0061] This application is not particularly limited to thickeners, but exemplary, the thickener may be at least one of carboxymethylcellulose sodium, gas-phase silica, modified urea polymer, organic modified silicate, organic modified montmorillonite, and organic bentonite.

[0062] The present invention is not particularly limited to wetting agents, and exemplarily, the wetting agent may be at least one of a polyethersiloxane copolymer, an organosilicon bilayer copolymer, a polyacrylate copolymer, a polyether-modified silicone oil copolymer, and a polyoxyethylene alkylamine copolymer.

[0063] This application does not particularly limit the mass percentage content of binders, dispersants, thickeners, and wetting agents, and the amount added can be freely selected according to the purpose.

[0064] This application Several embodiments As such, the composite separator is at least, a. Based on the total mass of the electrolyte layer, the mass percentage content of the binder should be 3-10%. b. Based on the total mass of the electrolyte layer, the mass percentage content of the dispersant should be 0.1-1.5%. c. Based on the total mass of the electrolyte layer, the mass percentage content of the thickener should be 0.1-3%. d) The composite separator has better integrated performance when it satisfies one of the following conditions: the mass percentage content of the wetting agent is 0.1-1.5% based on the total mass of the electrolyte layer. When used in a battery, it can improve the electrochemical performance of the battery and broaden the range of battery applications.

[0065] For example, based on the total mass of the electrolyte layer, the mass percentage content of the binder may be in the range of one or two of the following: 3%, 4%, 5%, 7%, 9%, 10%. Based on the total mass of the electrolyte layer, the mass percentage content of the dispersant is within the range of one or two of the following: 0.1%, 0.5%, 0.8%, 1%, 1.3%, and 1.5%. Based on the total mass of the electrolyte layer, the mass percentage content of the thickener is within the range of one or two of the following: 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2.5%, and 3%. Based on the total mass of the electrolyte layer, the mass percentage content of the wetting agent is in the range of one or two of the following: 0.1%, 0.5%, 0.7%, 0.9%, 1.2%, and 1.5%.

[0066] This application does not particularly limit the method for preparing the composite separator, and any preparation method can be freely selected according to the purpose, as long as a composite separator that satisfies the above-mentioned range of characteristics can be prepared.

[0067] In some embodiments, the composite separator according to the present application is Step 1) involves dispersing inorganic nanotubes and solid electrolyte particles in a solvent to obtain a coating slurry, It can be prepared by a method comprising step 2) applying a coating slurry to at least one surface of a separator substrate, drying it, and then obtaining a composite separator. The solvent in step 1) may be at least one of water, ethanol, acetone, and N-methylpyrrolidone.

[0068] In some embodiments, at least one of a dispersant, wetting agent, binder, and thickener may be added to the solvent in step 1) to form a coating slurry.

[0069] In some embodiments, step 1) further involves adding a dispersant to the solvent and stirring and dispersing for 10-60 minutes, then adding inorganic nanotubes and solid electrolyte particles respectively and stirring and dispersing continuously for 10-240 minutes, then adding an adhesive and stirring and dispersing for 10-180 minutes, further adding a thickener and stirring and dispersing for 10-60 minutes, and finally adding a wetting agent and stirring and dispersing for 10-60 minutes to obtain a coating slurry. The rotation speed for stirring and dispersing may be 1000-5000 r / min, and the solid content of the coating slurry may be ≤45%.

[0070] A second aspect of the present application provides a battery comprising a composite separator according to the first aspect.

[0071] To make it easier to understand, the battery of this application further comprises a positive electrode plate, a negative electrode plate, and an outer casing. In this application, an electrode assembly can be obtained by stacking the positive electrode plate, a composite separator, and a negative electrode plate, and a battery can be obtained by placing the electrode assembly in an outer casing, injecting electrolyte into the outer casing, and sealing it.

[0072] Because the battery of this invention is equipped with the above-mentioned composite separator, it has excellent electrochemical performance and service life, provides a superior user experience, and is suitable for widespread use and application.

[0073] The technical solution of this application will be described in detail below through specific examples.

[0074] Example 1

[0075] The battery of this embodiment is prepared by a method comprising the following steps: 1) Preparation of composite separators A dispersant is added to deionized water and stirred and dispersed for 30 minutes. Inorganic nanotubes and solid electrolyte particles are added separately and stirred and dispersed continuously for 60 minutes. Next, a binder is added and stirred and dispersed for 30 minutes. Then, a thickener is added and stirred and dispersed for 30 minutes. Finally, a wetting agent is added and stirred and dispersed for 30 minutes to prepare the coating slurry. The coating slurry is applied to two surfaces of the separator substrate using a microgravure roll coating method, and then dried at 80°C to obtain a composite separator containing an electrolyte layer. The stirring and dispersion rotation speed was 2000 r / min, the solid content of the coated slurry was 35%, the dispersant was a modified polyamide polymer (Kemet KMT-3604, Foshan Techno New Materials Co., Ltd.), the binder was a polyacrylate-based binder (LIS-S104, Shanghai Sanrui Polymer Materials Co., Ltd.), the thickener was an organically modified bentonite (BP-188L, Shanghai Yan Titanium Industry Co., Ltd.), and the wetting agent was a polyether-modified organic silicone polymer (Kemet KMT-5514, Foshan Techno New Materials Co., Ltd.). The inorganic nanotube is a halloysite nanotube, with an inner diameter d2 of 20 nm, a ratio of the outer diameter to the inner diameter (d1:d2) of 3.5:1, and a length (L) of 1 μm. The solid electrolyte particles are LATP, the particle size distribution (SPAN) of the solid electrolyte particles is 0.9, and the ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte particles (L:D50) is 1.67. In the electrolyte layer, the porosity (P) of inorganic nanotubes is 1.22%, and based on the total mass of the electrolyte layer, the mass percentage content of the dispersant is 0.3%, the mass percentage content of the binder is 5%, the mass percentage content of the thickener is 0.3%, the mass percentage content of the wetting agent is 0.3%, the mass percentage content of inorganic nanotubes (W1) is 30%, and the mass percentage content of solid electrolyte particles (W2) is 64.1%. The separator substrate is a PE separator, with a thickness of 9 μm (h1) and a thickness of 2 μm on one side of the electrolyte layer (h2).

[0076] 2) Battery preparation An electrode assembly is obtained by laminating a positive electrode plate, a composite separator, and a negative electrode plate. The electrode assembly is then placed on an aluminum plastic film and sealed to obtain a battery. The positive electrode plate includes an aluminum foil and a positive electrode active layer provided on the surface of the aluminum foil. The positive electrode active layer contains lithium cobalt oxide, a conductive agent Super P, and a binder PVDF. The mass ratio of lithium cobalt oxide, conductive agent, and binder is 96:2:2. The negative electrode plate includes a copper foil and a negative electrode active layer provided on the surface of the copper foil. The negative electrode active layer consists of silicon-doped graphite, a conductive agent Super P, and a binder PAA. (Polyacrylic acid) It contains silicon-doped graphite, and the mass ratio of the conductive agent and binder is 95:2:3. The electrolyte is lithium hexafluoride phosphate (LiPF6), EC (Ethylene carbonate) DEC (Diethyl carbonate) and DMC (dimethyl carbonate) The electrolyte contains , the concentration of lithium hexafluoride phosphate is 1M, and the volume ratio of EC, DEC, and DMC is 1:1:1.

[0077] Examples 2-12, Comparative Examples 1-4 Examples 2-12 and Comparative Examples 1-4 use almost the same battery preparation method as Example 1. The only difference is that some parameters in the preparation process of the composite separator differ from those in Example 1. See Table 1 for details.

[0078] Performance Test The following performance tests were performed on the composite separators and batteries in the examples and comparative examples, and the results are shown in Table 2. 1. Morphological Characterization SEM images of the composite separator were obtained according to the method specified in industry standard JY / T 0584-2020 "General Rules for Scanning Electron Microscopy Analysis."

[0079] Figure 1 is a surface SEM view of the composite separator in Example 2 of the present invention, and Figure 2 is a cross-sectional SEM view of the composite separator in Example 2 of the present invention. As can be seen from Figure 1, the surface of the composite separator has particulate and tubular structures, which demonstrates that the electrolyte layer of the composite separator contains inorganic nanotubes and solid electrolyte particles, and as can be seen from Figure 2, both layers are prominent at the interface of the composite separator, which demonstrates that the composite separator includes a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate.

[0080] 2. Thermal shrinkage rate The thermal shrinkage rate of the composite separator was obtained by referring to the method specified in the national standard GB / T 36363-2018 "Lithium-ion battery separator performance test". The oven heat treatment temperature was 130°C and the heat treatment time was 1 hour.

[0081] 3, Magnification performance The battery's multiplier performance, including the battery's capacity retention rate at 1C and 3C, was obtained in accordance with the methods specified in the national standard GB / T31486-2015, "Electrical performance requirements and test methods for power storage batteries for electric vehicles."

[0082] 4. Cycle performance The battery's cycle performance, i.e., the capacity retention rate after 1000 cycles at a multiplier of 1C, was obtained in accordance with the method specified in the national standard GB / T31486-2015 "Electrical performance requirements and test methods for power storage batteries for electric vehicles".

[0083] 5. Hotbox performance test The hot box safety performance of the batteries was tested according to the methods specified in national standards GB / T 31485-2015 "Electrical performance requirements and test methods for power storage batteries for electric vehicles" and GB / T 31241-2014 "Safety requirements for lithium-ion batteries and battery packs for portable electronic products," with the test conditions being the safety performance when the batteries are stored in a hot box at 150°C for 10 minutes.

[0084] 6. Thickness Composite imaging using a scanning electron microscope (Hitachi Japan, model number: HITACHI SU8010) Separator The cross-section was scanned, 10 locations were randomly selected, and the thickness of a single layer of the electrolyte layer was measured. The average value of these measurements was then calculated as the thickness of a single layer of the electrolyte layer.

[0085] 7. Peel strength The peel strength of the electrolyte layer in the composite separator was tested according to the method specified in the national standard GBT 2792-2014, "Test method for peel strength of adhesive tapes."

[0086] 8. Low-temperature performance The ambient temperature for the battery test was adjusted to -20°C through a high / low temperature control box. Then, the low-temperature discharge performance of the battery, i.e., the discharge performance of the battery at -20°C with a multiplier of 1C, was tested according to the method specified in the national standard GB / T31486-2015 "Electrical performance requirements and test methods for power storage batteries for electric vehicles".

[0087] [Table 1]

[0088] [Table 2]

[0089] As can be seen from Table 1, when the composite separator in the embodiment of the present invention is used in a battery compared to the comparative example, the battery's multiplication performance, cycle performance, low-temperature performance, and safety performance can be significantly improved. In particular, by further selecting the relevant parameters of the composite separator, the peel strength and thermal shrinkage performance of the composite separator can be further improved, thereby further improving the overall performance of the battery. This demonstrates that the electrochemical performance of a battery can be improved by preparing a composite separator by adding inorganic nanotubes to the electrolyte layer and controlling the porosity of the inorganic nanotubes within the electrolyte layer.

[0090] Furthermore, as can be seen from Examples 1 and 3, by further selecting the porosity of the inorganic nanotubes in the electrolyte layer, the peel strength and thermal shrinkage performance of the composite separator can be further improved, resulting in improved multiplier performance, cycle performance, and low-temperature performance of the battery.

[0091] As can be seen from Examples 1-2 and 6, by further selecting the mass percentage content of inorganic nanotubes, the peel strength and thermal shrinkage performance of the composite separator can be improved, resulting in improved battery magnification performance, cycle performance, and low-temperature performance.

[0092] As can be seen from Examples 1 and 7, by further selecting the inner diameter of the inorganic nanotube, the peel strength and thermal shrinkage performance of the composite separator can be improved, and as a result, the multiplier performance, cycle performance and low-temperature performance of the battery can be improved.

[0093] As can be seen from Examples 1 and 8, the length of inorganic nanotubes Further selection This improves the overall performance of the composite separator, and as a result, improves the electrochemical performance of the battery.

[0094] As can be seen from Examples 1 and 9, the ratio of the length of inorganic nanotubes to the D50 of solid electrolyte particles affects the integrated performance of the composite separator, and consequently affects the integrated performance of the battery.

[0095] As can be seen from Examples 1 and 10, when the particle size distribution of the solid electrolyte meets a specific range, the composite separator has superior peel strength and thermal shrinkage performance, and when the composite separator is used in a battery, the electrochemical performance of the battery can be improved.

[0096] As can be seen from Examples 1 and 12, the overall performance of the composite separator can be further improved by further selecting the thickness of the electrolyte layer, and as a result, the overall performance of the battery can be improved.

[0097] Finally, it should be noted that the above embodiments are merely for illustrating and not limiting the technical means of the present application. While the present application has been described in detail with reference to the embodiments described above, those skilled in the art should understand that they may still modify the technical means described in the embodiments described above, or substitute some or all of the technical features therein, and that such modifications or substitutions will not cause the essence of the corresponding technical means to deviate from the scope of the technical means of the embodiments of the present application.

Claims

1. A composite separator comprising a separator substrate and an electrolyte layer provided on at least one surface of the separator substrate, The electrolyte layer comprises at least inorganic nanotubes and solid electrolyte particles. A composite separator in which the porosity of the inorganic nanotubes in the electrolyte layer is 0.2-5%.

2. The composite separator according to claim 1, wherein the mass percentage content of the inorganic nanotubes is 5-60% based on the total mass of the electrolyte layer.

3. The composite separator according to claim 1 or 2, wherein the inner diameter of the inorganic nanotube is 3-150 nm.

4. The composite separator according to any one of claims 1 to 3, wherein the ratio of the outer diameter to the inner diameter of the inorganic nanotube is (1.5-20):

1.

5. The composite separator according to any one of claims 1 to 4, wherein the length of the inorganic nanotube is 0.3 to 5 μm.

6. The composite separator according to any one of claims 1 to 5, wherein the ratio of the length of the inorganic nanotube to the D50 of the solid electrolyte particle is greater than 0 and 30 or less.

7. The composite separator according to any one of claims 1 to 6, wherein the particle size distribution of the solid electrolyte particles is ≤ 1.

5.

8. The composite separator comprises at least, a. The thickness of the separator substrate shall be 5-30 μm. The composite separator according to any one of claims 1 to 7, which satisfies one of the following: b, the thickness of the electrolyte layer is 0.5 to 4 μm.

9. The composite separator according to any one of claims 1 to 8, wherein the electrolyte layer further comprises at least one of a dispersant, a wetting agent, a binder, and a thickening agent.

10. The composite separator comprises at least, a. Based on the total mass of the electrolyte layer, the mass percentage content of the binder is 3-10%. b. Based on the total mass of the electrolyte layer, the mass percentage content of the dispersant is 0.1–1.5%. c. Based on the total mass of the electrolyte layer, the mass percentage content of the thickener is 0.1-3%. The composite separator according to claim 9, satisfying one of the following: d, the mass percentage content of the wetting agent is 0.1-1.5% based on the total mass of the electrolyte layer.

11. A battery comprising a composite separator according to any one of claims 1 to 10.

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