Eutectic solid electrolyte diaphragm, preparation method thereof and solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, in particular to a eutectic solid-state electrolyte diaphragm, a preparation method thereof and a solid-state battery. The preparation method of the eutectic solid electrolyte diaphragm comprises the following steps: mixing oxygen-containing lithium tetrachloroaluminate and imide lithium salt, melting and quenching, and pressing; wherein the chemical formula of the oxygen-containing lithium aluminum tetrachloride is LiAlCl < 4-2x > O < x >, and x < lt > is greater than or equal to 0.01; 2; the imide lithium salt comprises lithium bis (fluorosulfonyl) imide and / or lithium bis (trifluoromethylsulfonyl) imide. The preparation method is simple and low in cost, is similar to a traditional liquid battery process, and can quickly realize batch production; and the eutectic solid electrolyte diaphragm prepared by the method has high ionic conductivity, wide electrochemical window, good thermal stability and good interface compatibility.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and more particularly, to a eutectic solid electrolyte separator, a preparation method thereof, and a solid-state battery. Background Art

[0002] With the increasingly severe global energy problem, as a new type of energy storage device, lithium-ion batteries have been widely used in fields such as electronic devices and electric vehicles due to their advantages such as high energy density, long cycle life, and environmental friendliness. With continuous breakthroughs in material innovation and process optimization, the energy density of commercially mass-produced lithium-ion batteries has exceeded the technical threshold of 300 Wh / kg. However, in the face of the rapid development of emerging fields such as artificial intelligence, electric vehicles, and renewable energy storage, the market has put forward more stringent requirements for core indicators such as the energy density, intrinsic safety, and cycle stability of battery systems.

[0003] Traditional liquid electrolytes are widely used in lithium-ion batteries. However, their flammability, volatility, and corrosiveness lead to the risk of thermal runaway in batteries under high temperature or external impact, and may even cause fires or explosions in severe cases. To address these safety hazards, solid electrolytes have emerged as an alternative solution. Solid electrolytes (such as oxides, sulfides, halides) have the advantages of being non-flammable, non-corrosive, and non-volatile, significantly improving the safety of batteries. However, the processing technology of some solid electrolytes (such as sulfides, halides) is complex and the manufacturing cost is high, which limits their large-scale production and application.

[0004] Lithium tetrachloroaluminate oxide (LACO) solid electrolyte has attracted much attention in recent years due to its high lithium-ion conductivity and excellent mechanical properties. However, its grain boundary impedance is relatively high, and there are significant differences in battery processes compared to traditional liquid electrolyte systems.

[0005] Eutectic solid electrolytes combine the advantages of solid and liquid electrolytes and have broad application prospects. However, existing systems (such as LiTFSI-succinonitrile) generally suffer from problems such as insufficient ionic conductivity (<1 mS / cm) and narrow electrochemical window (<4 V), and it is also difficult to balance their thermal stability and interfacial compatibility in solid-state battery systems.

[0006] Therefore, there is an urgent need to develop a new eutectic solid electrolyte based on LACO to solve the above problems.

[0007] In view of this, the present invention is specifically proposed. Summary of the Invention

[0008] The first object of the present invention is to provide a preparation method of a eutectic solid electrolyte separator, which has a simple preparation method, low cost, is similar to the traditional liquid battery process, and can achieve large-scale production quickly; moreover, the eutectic solid electrolyte separator prepared by this method has high ionic conductivity, a wide electrochemical window, good thermal stability and good interfacial compatibility. It solves the problem that it is difficult to balance thermal stability and interfacial compatibility of traditional solid electrolytes in solid battery systems.

[0009] The second object of the present invention is to provide a eutectic solid electrolyte separator, which has high ionic conductivity, a wide electrochemical window, a low melting point and high stability at room temperature, and at the same time exhibits good interfacial compatibility.

[0010] The third object of the present invention is to provide a solid battery.

[0011] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0012] The present invention first provides a preparation method of a eutectic solid electrolyte separator, including the following steps: mixing lithium oxytetrachloroaluminate and imide lithium salts and then performing melt quenching, and then pressing to obtain the eutectic solid electrolyte separator; wherein, the chemical formula of the lithium oxytetrachloroaluminate is LiAlCl 4-2x O x , where 0.01 ≤ x < 2; the imide lithium salts include at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

[0013] Furthermore, the mass ratio of the lithium oxytetrachloroaluminate to the imide lithium salts is 1:0.1 - 5.

[0014] Furthermore, the thickness of the eutectic solid electrolyte separator is 10 - 100 μm.

[0015] Furthermore, the lithium oxytetrachloroaluminate includes at least one of LiAlCl3O 0.5 , LiAlCl 2.8 O 0.6 , LiAlCl 2.6 O 0.7 , LiAlCl 2.5 O 0.75 , LiAlCl 2.4 O 0.8 , LiAlCl 2.2 O 0.9 and LiAlCl2O.

[0016] Furthermore, the mixing method includes ball milling.

[0017] Further, the rotation speed of the ball milling is 100 - 500 rpm, and the time of the ball milling is 1 - 6 h.

[0018] Further, the ball milling is carried out under a protective atmosphere.

[0019] Further, the protective atmosphere includes at least one of an argon atmosphere, a nitrogen atmosphere, a helium atmosphere, a hydrogen atmosphere, and a carbon dioxide atmosphere.

[0020] Further, the temperature of the melt quenching is 100 - 150 °C.

[0021] Further, the pressure of the pressing is 10 - 30 MPa.

[0022] The present invention further provides a eutectic solid electrolyte separator, which is prepared by using the preparation method of the above eutectic solid electrolyte separator.

[0023] Further, the eutectic point of the eutectic solid electrolyte separator is 70 - 120 °C.

[0024] Further, the ionic conductivity of the eutectic solid electrolyte separator at room temperature is ≥2 mS / cm, the electrochemical window is ≥4.5 V vs. Li + / Li, and the thermal decomposition temperature is ≥200 °C.

[0025] The present invention also provides a solid-state battery, which includes the above eutectic solid electrolyte separator.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The preparation method of the eutectic solid electrolyte separator provided by the present invention is similar to the traditional liquid battery process, has the advantages of simplicity and low cost, can quickly realize mass production, and can achieve long cycle performance of the solid-state battery at room temperature.

[0028] (2) The preparation method of the eutectic solid electrolyte separator provided by the present invention combines the advantages of solid electrolytes and liquid electrolytes, specifically as follows: First, it has a high ionic conductivity: The anionic radii of LiFSI and LiTFSI are relatively large, which is conducive to the dissociation and migration of lithium ions. With the LACO fast lithium ion migration channels, after the formation of a eutectic between lithium tetrachloroaluminate and imide lithium salts, the ion conduction path in the eutectic solid electrolyte is further optimized, thereby improving the overall ionic conductivity and reducing the internal resistance of the battery. Second, it has a wide electrochemical window: The eutectic solid electrolyte separator prepared by this method can remain stable within a wide voltage range, can adapt to various battery material systems, reduce side reactions during the charge and discharge process of the battery, and thus improve the energy efficiency and cycle life of the battery. Third, it has good thermal stability: LiFSI and LiTFSI themselves have relatively high decomposition temperatures, and the eutectic solid electrolyte formed with LACO can also remain stable at high temperatures, enabling the battery to still operate normally in a high-temperature environment and reducing safety risks such as thermal runaway. Fourth, it has good interfacial compatibility: A SEI film rich in LiF / LiCl is formed on the surface of the lithium metal, which helps to inhibit the growth of lithium dendrites.

[0029] (3) The eutectic solid electrolyte separator provided by the present invention has a high ionic conductivity, a wide electrochemical window, a low melting point, and high stability at room temperature, and at the same time exhibits good interfacial compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is the DSC curve graph of the eutectic solid electrolyte separator prepared in Example 1 provided by the present invention;

[0032] Figure 2 It is the CV curve graph of the eutectic solid electrolyte separator prepared in Example 1 provided by the present invention;

[0033] Figure 3 It is the ionic conductivity performance curve graph of the eutectic solid electrolyte separator prepared in Example 1 provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0035] If there is no special description, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes, and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive listing and description, and it should be understood that they do not constitute a closed limitation on the quantity.

[0036] If there is no special description, "including" and "comprising" mentioned in the present invention mean open-ended, and can also be closed-ended. For example, the said "including" and "comprising" can mean that other components not listed can also be included or comprised, or it can only include or comprise the listed components.

[0037] If there is no special description, in the present invention, "one or more" or "at least one" means any one, any two or any two or more of the listed items. Among them, "several" means any two or any two or more.

[0038] In a first aspect, the present invention provides a method for preparing a eutectic solid electrolyte separator for a solid-state battery, comprising the following steps:

[0039] Mix lithium tetrachloroaluminate containing oxygen (abbreviated as LACO) and imide lithium salt, then perform melt quenching, and after cooling, press at room temperature to obtain the eutectic solid electrolyte separator.

[0040] That is, the eutectic solid electrolyte separator is composed of a eutectic solid electrolyte, and the eutectic solid electrolyte is prepared from lithium tetrachloroaluminate containing oxygen and imide lithium salt.

[0041] Among them, melt quenching refers to the quenching of a molten crystal, specifically heating the crystal above its melting point and then rapidly cooling it to make it solidify quickly.

[0042] Among them, the chemical formula of the lithium tetrachloroaluminate containing oxygen is LiAlCl 4-2x O x, where 0.01 ≤ x < 2, such as 0.01, 0.03, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1, 1.2, 1.3, 1.5, 1.8 or 1.9, preferably x is 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.

[0043] The imide lithium salt includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0044] This preparation method is similar to the traditional liquid battery process, with the advantages of simplicity and low cost, can quickly realize industrial production, and can achieve long cycle performance of solid-state batteries at room temperature.

[0045] Moreover, the eutectic solid electrolyte separator prepared by this method combines the advantages of solid electrolytes and liquid electrolytes, as follows: (1) It has a high ionic conductivity: The anionic radius of LiFSI and LiTFSI is relatively large, which is conducive to the dissociation and migration of lithium ions. With the rapid lithium ion migration channels of LACO, after lithium tetrachloroaluminate containing oxygen and imide lithium salt form a eutectic, the ionic conduction path in the eutectic solid electrolyte is further optimized, thereby improving the overall ionic conductivity and reducing the internal resistance of the battery. (2) It has a wide electrochemical window: The eutectic solid electrolyte separator prepared by this method can remain stable within a wide voltage range, can adapt to a variety of battery material systems, reduce side reactions during the charge and discharge process of the battery, and thus improve the energy efficiency and cycle life of the battery. (3) It has good thermal stability: The decomposition temperature of LiFSI and LiTFSI themselves is relatively high, and the eutectic solid electrolyte formed with LACO can also remain stable at high temperatures, enabling the battery to still work normally in a high-temperature environment and reducing safety risks such as thermal runaway. (4) It has good interfacial compatibility: It forms a LiF / LiCl-rich SEI film on the surface of lithium metal, which helps to inhibit the growth of lithium dendrites.

[0046] In some specific embodiments, the mass ratio of the lithium tetrachloroaluminate containing oxygen to the imide lithium salt is 1:0.1 to 5, including but not limited to any point value of 1:0.1, 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or the range value between any two of them. This is beneficial to improving the ionic conductivity of the eutectic solid electrolyte separator, broadening its electrochemical window, and improving its thermal stability and interfacial compatibility.

[0047] In some specific embodiments, the thickness of the eutectic solid electrolyte separator is 10-100 μm, such as 20 μm, 30 μm, 50 μm, 60 μm or 80 μm.

[0048] In some specific embodiments, the lithium aluminum tetrachloroaluminate containing oxygen includes LiAlCl3O 0.5 , LiAlCl 2.8 O 0.6 , LiAlCl 2.6 O 0.7 , LiAlCl 2.5 O 0.75 , LiAlCl 2.4 O 0.8 , LiAlCl 2.2 O 0.9 and at least one of LiAlCl2O.

[0049] In some specific embodiments, the preparation method of the lithium aluminum tetrachloroaluminate containing oxygen includes: mixing LiCl, AlCl3 and AlCl3·6H2O uniformly according to the ratio of the target chemical formula, and then annealing at 180-260 °C (such as 200 °C, 220 °C or 250 °C) for 4-48 h (such as 8 h, 12 h, 18 h, 24 h or 36 h).

[0050] In some specific embodiments, the mixing method includes ball milling (mechanical ball milling). Ball milling is beneficial to the uniform mixing and dispersion of materials.

[0051] In some specific embodiments, the rotation speed of the ball milling is 100-500 rpm, including but not limited to any point value of 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm or the range value between any two of them.

[0052] In some specific embodiments, the ball milling time is 1-6 h; including but not limited to any point value of 1 h, 2 h, 3 h, 4 h, 5 h, 6 h or the range value between any two of them.

[0053] In some specific embodiments, the ball milling is carried out in a protective atmosphere.

[0054] In some specific embodiments, the protective atmosphere includes at least one of argon atmosphere, nitrogen atmosphere, helium atmosphere, hydrogen atmosphere and carbon dioxide atmosphere.

[0055] In some specific embodiments, the temperature of the melt quenching is 100-150 °C, including but not limited to any point value of 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C or the range value between any two of them.

[0056] In some specific embodiments, the time of the melt quenching is 5 to 60 minutes, such as 10 minutes, 20 minutes, 30 minutes or 40 minutes.

[0057] In some specific embodiments, the pressure of the pressing is 10 to 30 MPa, including but not limited to any point value of 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa or the range value between any two of them.

[0058] In a second aspect, the present invention provides a eutectic solid electrolyte separator, which is prepared by using the preparation method of the eutectic solid electrolyte separator.

[0059] The eutectic solid electrolyte separator has a high ionic conductivity, a wide electrochemical window, a low melting point and high stability at room temperature, and at the same time exhibits good interfacial compatibility.

[0060] Specifically, the eutectic solid electrolyte separator prepared by the present invention has a low melting point. In some specific embodiments, the eutectic point of the eutectic solid electrolyte separator is 70 to 120 °C, including but not limited to any point value of 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C or the range value between any two of them.

[0061] The eutectic solid electrolyte separator prepared by the present invention has a high ionic conductivity at room temperature. In some specific embodiments, the ionic conductivity of the eutectic solid electrolyte separator at room temperature is ≥2 mS / cm, including but not limited to any point value of 2.1 mS / cm, 2.2 mS / cm, 2.3 mS / cm, 2.4 mS / cm, 2.5 mS / cm, 2.6 mS / cm, 2.7 mS / cm, 2.8 mS / cm, 2.9 mS / cm, 3 mS / cm or the range value between any two of them.

[0062] The eutectic solid electrolyte separator prepared by the present invention has a wide electrochemical window. In some specific embodiments, the electrochemical window of the eutectic solid electrolyte separator is ≥4.5 V vs. Li + / Li, including but not limited to any point value of 4.5 V, 4.6 V, 4.7 V, 4.8 V, 4.9 V, 5.0 V or the range value between any two of them.

[0063] The eutectic solid electrolyte separator prepared by the present invention has high stability. In some specific embodiments, the thermal decomposition temperature of the eutectic solid electrolyte separator is ≥200 °C, preferably 200 to 300 °C.

[0064] In a third aspect, the present invention provides a solid-state battery, including the eutectic solid electrolyte separator.

[0065] Among them, the solid-state battery includes a lithium solid-state battery.

[0066] In some specific embodiments, the solid-state battery further includes a positive electrode plate and a negative electrode plate.

[0067] Among them, the positive electrode plate contains a positive electrode active material, and the positive electrode active material can adopt any positive electrode material commonly used in the art, such as lithium iron phosphate or ternary NCM. The present invention does not limit this.

[0068] The negative electrode plate includes any negative electrode plate commonly used in the art, such as a lithium metal negative electrode plate, a graphite negative electrode plate, a silicon-carbon negative electrode plate, a hard carbon negative electrode plate, etc. The present invention does not limit this.

[0069] For the solid-state battery assembled with the above eutectic solid electrolyte separator, during low-temperature packaging, the eutectic solid electrolyte can quickly penetrate into the electrode material, thereby reducing the solid-solid interface impedance between the positive and negative electrode materials and the eutectic solid electrolyte, and further improving the electrochemical performance of the battery (such as charge-discharge efficiency and cycle life), solving the problem of high interface impedance between the traditional solid electrolyte and the electrode material.

[0070] The above eutectic solid electrolyte separator can be applied in coin cells and soft-pack batteries. After long-term cycling, the interface impedance problem caused by the volume expansion of the materials inside the battery can be treated by a hot pressing process, thereby improving the cycling performance of the battery.

[0071] In some specific embodiments, the preparation method of the solid-state battery includes: packaging the positive electrode plate, the eutectic solid electrolyte separator, and the negative electrode plate, where the packaging temperature is 70-90°C. Among them, if the packaging temperature is too high and completely melts, it will cause a short circuit. If the packaging temperature is too low, the surface does not melt and the interface problem between the positive and negative electrodes and the solid electrolyte cannot be improved.

[0072] The following will describe the implementation schemes of the present invention in detail with reference to the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0073] The preparation method of lithium tetrachloroaluminate containing oxygen used in the following embodiments and comparative examples of the present invention is as follows: Mix LiCl, AlCl3, and AlCl3·6H2O evenly according to the ratio of the target chemical formula, and then anneal at 200°C for 24 hours.

[0074] Example 1

[0075] The preparation method of the eutectic solid electrolyte separator provided by this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl 2.5 O 0.75 and LiFSI being 1:1, where the rotation speed of ball milling is 200 rpm and the ball milling time is 3 h. Then, the ball-milled mixed material is melted and quenched at 120 °C to synthesize LiAlCl 2.5 O 0.75 -LiFSI eutectic solid electrolyte. After that, in a pressure mold, it is pressurized to 30 MPa to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0076] The LiFePO4 positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the lithium metal negative electrode sheet are sequentially assembled in a CR2032 button cell case, heated to 80 °C, and held for 10 minutes to complete the encapsulation, obtaining a button cell. Among them, the preparation method of the positive electrode sheet is: Lithium iron phosphate, conductive carbon black, and binder PVDF (polyvinylidene fluoride) with a mass ratio of 95:2:3 are dispersed in NMP (N-methylpyrrolidone) and stirred to make a positive electrode slurry, and then the positive electrode slurry is evenly coated on the surface of an aluminum foil (with a thickness of 9 μm) and dried at 110 °C to obtain a single-sided coated positive electrode sheet with a positive electrode active material layer thickness of 100 μm.

[0077] Example 2

[0078] The preparation method of the eutectic solid electrolyte separator provided by this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl3O 0.5 and LiFSI being 1:1, where the rotation speed of ball milling is 250 rpm and the ball milling time is 5 h. Then, the ball-milled mixed material is melted and quenched at 120 °C to synthesize LiAlCl3O 0.5 -LiFSI eutectic solid electrolyte. After that, in a pressure mold, it is pressurized to 10 MPa to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0079] The LiFePO4 positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the graphite negative electrode sheet are sequentially assembled in a CR2032 button cell case, heated to 80 °C, and held for 10 minutes to complete the encapsulation, obtaining a button cell. Among them, the preparation method of the positive electrode sheet is the same as that in Example 1. The preparation method of the negative electrode sheet is: Graphite, conductive carbon black, and binder CMC-SBR with a mass ratio of 95:2:3 are dispersed in deionized water and stirred to make a negative electrode slurry, and then the negative electrode slurry is evenly coated on the surface of a copper foil and dried at 110 °C.

[0080] Example 3

[0081] The preparation method of the eutectic solid electrolyte separator provided by this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl3O 0.5 and LiFSI of 1:2, where the rotation speed of ball milling is 250 rpm and the ball milling time is 4 h. Then, the ball-milled mixed material is subjected to melt quenching at 110 °C to synthesize LiAlCl3O 0.5 -LiFSI eutectic solid electrolyte. After that, in a pressure mold, a pressure of 20 MPa is applied to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0082] The LiFePO4 positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the silicon-carbon negative electrode sheet are successively assembled in a CR2032 button cell case, heated to 80 °C, and held for 10 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation method of the positive electrode sheet is the same as that in Example 1. The preparation method of the negative electrode sheet is as follows: A silicon-carbon composite material, conductive carbon black, and a binder CMC-SBR with a mass ratio of 95:2:3 are dispersed in deionized water and stirred to make a slurry to obtain a negative electrode slurry, and then the negative electrode slurry is uniformly coated on the surface of a copper foil and dried at 110 °C.

[0083] Example 4

[0084] The preparation method of the eutectic solid electrolyte separator provided by this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl3O 0.5 and LiFSI of 1:3, where the rotation speed of ball milling is 250 rpm and the ball milling time is 3 h. Then, the ball-milled mixed material is subjected to melt quenching at 100 °C to synthesize LiAlCl3O 0.5 -LiFSI eutectic solid electrolyte. After that, in a pressure mold, a pressure of 25 MPa is applied to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0085] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the hard carbon negative electrode sheet are successively assembled in a CR2032 button cell case, heated to 75 °C, and held for 5 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation method of the positive electrode sheet is basically the same as that in Example 1, except that lithium iron phosphate is replaced with an equal mass of NCM811 positive electrode material. The preparation method of the negative electrode sheet is as follows: A hard carbon material, conductive carbon black, and a binder CMC-SBR with a mass ratio of 95:2:3 are dispersed in deionized water and stirred to make a slurry to obtain a negative electrode slurry, and then the negative electrode slurry is uniformly coated on the surface of a copper foil and dried at 110 °C.

[0086] Example 5

[0087] The preparation method of the eutectic solid electrolyte separator provided in this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl3O 0.5 and LiTFSI of 1:0.5, where the rotation speed of the ball milling is 300 rpm and the ball milling time is 4 h. Then, the ball-milled mixed material is melted and quenched at 150 °C to synthesize LiAlCl3O 0.5 -LiTFSI eutectic solid electrolyte. After that, in a pressure mold, a pressure of 10 MPa is applied to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0088] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the silicon-carbon negative electrode sheet are sequentially assembled in a CR2032 button cell case, heated to 90 °C, and held for 15 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation method of the positive electrode sheet is the same as that in Example 4. The preparation method of the negative electrode sheet is the same as that in Example 3.

[0089] Example 6

[0090] The preparation method of the eutectic solid electrolyte separator provided in this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl 2.5 O 0.75 and LiTFSI of 1:0.5, where the rotation speed of the ball milling is 350 rpm and the ball milling time is 2 h. Then, the ball-milled mixed material is melted and quenched at 150 °C to synthesize LiAlCl 2.5 O 0.75 -LiTFSI eutectic solid electrolyte. After that, in a pressure mold, a pressure of 20 MPa is applied to make a eutectic solid electrolyte separator with a thickness of 50 μm.

[0091] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this embodiment, and the silicon-carbon negative electrode sheet are sequentially assembled in a CR2032 button cell case, heated to 90 °C, and held for 20 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 5.

[0092] Example 7

[0093] The preparation method of the eutectic solid electrolyte separator provided in this embodiment includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl 2.8 O 0.6 and LiFSI of 1:1, where the rotation speed of the ball milling is 250 rpm and the ball milling time is 4 h. Then, the ball-milled mixed material is melted and quenched at 100 °C to synthesize LiAlCl 2.8 O 0.6-LiFSI eutectic solid electrolyte. Then, in a pressure mold, it was pressurized to 10 MPa to form a eutectic solid electrolyte separator with a thickness of 50 μm.

[0094] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this example, and the silicon-carbon negative electrode sheet were sequentially assembled in a CR2032 button cell case, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 5.

[0095] Example 8

[0096] The preparation method of the eutectic solid electrolyte separator provided in this example includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing were carried out according to the mass ratio of LiAlCl 2.6 O 0.7 and LiFSI of 1:1, where the rotation speed of the ball milling was 300 rpm and the ball milling time was 3 h. Then, the ball-milled mixed material was melted and quenched at 120 °C to synthesize LiAlCl 2.6 O 0.7 -LiFSI eutectic solid electrolyte. Then, in a pressure mold, it was pressurized to 15 MPa to form a eutectic solid electrolyte separator with a thickness of 50 μm.

[0097] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this example, and the silicon-carbon negative electrode sheet were sequentially assembled in a CR2032 button cell case, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 5.

[0098] Example 9

[0099] The preparation method of the eutectic solid electrolyte separator provided in this example includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing were carried out according to the mass ratio of LiAlCl 2.4 O 0.8 and LiFSI of 1:1, where the rotation speed of the ball milling was 250 rpm and the ball milling time was 5 h. Then, the ball-milled mixed material was melted and quenched at 120 °C to synthesize LiAlCl 2.4 O 0.8 -LiFSI eutectic solid electrolyte. Then, in a pressure mold, it was pressurized to 20 MPa to form a eutectic solid electrolyte separator with a thickness of 50 μm.

[0100] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this example, and the silicon-carbon negative electrode sheet were sequentially assembled in a CR2032 button cell case, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 5.

[0101] Example 10

[0102] The preparation method of the eutectic solid-state electrolyte diaphragm provided in this example includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl 2.2 O 0.9 and LiFSI being 1:1, where the rotation speed of the ball milling is 250 rpm and the ball milling time is 4 h. Then the ball-milled mixed material is melt quenched at 120 °C to synthesize LiAlCl 2.2 O 0.9 -LiFSI eutectic solid-state electrolyte. Then, in a pressure mold, a pressure of 20 MPa is applied to make a eutectic solid-state electrolyte diaphragm with a thickness of 50 μm.

[0103] The LiFePO4 positive electrode sheet, the eutectic solid-state electrolyte diaphragm prepared in this example, and the lithium metal negative electrode sheet are sequentially assembled in a CR2032 button cell case, heated to 80 °C, and kept for 10 minutes to complete the encapsulation, obtaining a button battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 1.

[0104] Example 11

[0105] The preparation method of the eutectic solid-state electrolyte diaphragm provided in this example includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl3O 05 and LiFSI being 1:2, where the rotation speed of the ball milling is 300 rpm and the ball milling time is 3 h. Then the ball-milled mixed material is melt quenched at 120 °C to synthesize LiAlCl3O 0.5 -LiFSI eutectic solid-state electrolyte. Then, in a pressure mold, a pressure of 20 MPa is applied to make a eutectic solid-state electrolyte diaphragm with a thickness of 50 μm.

[0106] The LiFePO4 positive electrode sheet, the eutectic solid-state electrolyte diaphragm prepared in this example, and the graphite negative electrode sheet are sequentially stacked. After welding the electrode tabs, the electrode assembly is placed in an aluminum-plastic film packaging case, heated to 80 °C, and kept for 15 minutes to complete the encapsulation, obtaining a soft-pack battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 2.

[0107] Example 12

[0108] The preparation method of the eutectic solid-state electrolyte diaphragm provided in this example includes the following steps: Under an argon atmosphere, mechanical ball milling and mixing are carried out according to the mass ratio of LiAlCl 2.5 O 0.75 and LiFSI being 1:1, where the rotation speed of the ball milling is 250 rpm and the ball milling time is 4 h. Then the ball-milled mixed material is melt quenched at 110 °C to synthesize LiAlCl 2.5O 0.75 -LiFSI eutectic solid electrolyte. Then, in a pressure mold, it was pressed at 25 MPa to form a eutectic solid electrolyte separator with a thickness of 50 μm.

[0109] The NCM positive electrode sheet, the eutectic solid electrolyte separator prepared in this example, and the silicon-carbon negative electrode sheet were stacked in sequence. After welding the electrode tabs, the electrode assembly was placed into an aluminum-plastic film packaging shell, heated to 80 °C, and maintained for 15 minutes to complete the encapsulation, obtaining a soft-pack battery. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 5.

[0110] Comparative Example 1

[0111] The preparation method of the solid electrolyte separator provided in this comparative example includes the following steps: Using LiAlCl 2.5 O 0.75 , adding it to a pressure mold, and pressing it at 30 MPa to form a solid electrolyte separator with a thickness of 50 μm.

[0112] The LiFePO4 positive electrode sheet, the solid electrolyte separator prepared in this comparative example, and the lithium metal negative electrode sheet were assembled in a CR2032 button cell in sequence, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 1.

[0113] Comparative Example 2

[0114] The preparation method of the solid electrolyte separator provided in this comparative example is basically the same as that in Example 1, except that LiFSI is replaced with an equal mass of LiBF4.

[0115] The LiFePO4 positive electrode sheet, the solid electrolyte separator prepared in this comparative example, and the lithium metal negative electrode sheet were assembled in a CR2032 button cell in sequence, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 1.

[0116] Comparative Example 3

[0117] The preparation method of the solid electrolyte separator provided in this comparative example is basically the same as that in Example 1, except that the mass ratio of LiAlCl 2.5 O 0.75 and LiFSI is replaced with 1:0.01.

[0118] The LiFePO4 positive electrode sheet, the solid electrolyte separator prepared in this comparative example, and the lithium metal negative electrode sheet were assembled in a CR2032 button cell in sequence, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet were the same as those in Example 1.

[0119] Comparative Example 4

[0120] The preparation method of the solid electrolyte separator provided in this comparative example is basically the same as that in Example 1, except that the mass ratio of LiAlCl 2.5 O 0.75 and LiFSI is replaced with 1:7.

[0121] The LiFePO4 positive electrode sheet, the solid electrolyte separator prepared in this comparative example, and the lithium metal negative electrode sheet are sequentially assembled in a CR2032 button cell, heated to 80 °C, and maintained for 10 minutes to complete the encapsulation. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 1.

[0122] The eutectic points, ionic conductivities at room temperature, and electrochemical window results of the eutectic solid electrolytes prepared in the above examples and the solid electrolytes prepared in the comparative examples are shown in Table 1.

[0123] Table 1 Physical and chemical property parameters of each eutectic solid electrolyte and solid electrolyte

[0124]

[0125]

[0126] Among them, the DSC curve of the eutectic solid electrolyte separator prepared in Example 1 is shown in Figure 1 , and it can be seen through Figure 1 that the eutectic point of this eutectic solid electrolyte separator is 84.8 °C. The CV curve of the eutectic solid electrolyte separator prepared in Example 1 is shown in Figure 2 , and it can be seen through Figure 2 that the electrochemical window of this eutectic solid electrolyte separator is 4.8 V. The ionic conductivity performance curve of the eutectic solid electrolyte separator prepared in Example 1 is shown in Figure 3 , and it can be seen through Figure 3 that the ionic conductivity of this eutectic solid electrolyte separator is 2.5 mS / cm.

[0127] It can be seen from Table 1 that the eutectic solid electrolyte separators prepared in the examples have high ionic conductivity, wide electrochemical window, low melting point, and high stability at room temperature.

[0128] However, the solid electrolyte separators prepared in the comparative examples have low ionic conductivity, narrow electrochemical window, high melting point, or poor stability.

[0129] It can be seen that the preparation method provided by the present invention can improve the ionic conductivity of the eutectic solid electrolyte separator, broaden its electrochemical window, and has good thermal stability and interfacial compatibility.

[0130] Although the present invention has been illustrated and described with reference to specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A preparation method of a eutectic solid electrolyte separator, characterized in that, It includes the following steps: Mix lithium tetrachloroaluminate containing oxygen and lithium imide salt, then perform melt quenching, and then press to obtain the eutectic solid electrolyte separator; Among them, the chemical formula of the lithium oxytetrachloroaluminate is LiAlCl 4-2x O x , where 0.01 ≤ x < 2; The lithium imide salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

2. The preparation method of the eutectic solid electrolyte separator according to claim 1, characterized in that, The mass ratio of the lithium tetrachloroaluminate containing oxygen to the lithium imide salt is 1:0.1 - 5; And / or, the thickness of the eutectic solid electrolyte separator is 10 - 100 μm.

3. The preparation method of the eutectic solid electrolyte diaphragm according to claim 1, characterized in that, The lithium aluminum oxytetrachloride includes LiAlCl3O 0.5 , LiAlCl 2.8 O 0.6 , LiAlCl 2.6 O 0.7 , LiAlCl 2.5 O 0.75 , LiAlCl 2.4 O 0.8 , LiAlCl 2.2 O 0.9 and at least one of LiAlCl2O.

4. The preparation method of the eutectic solid electrolyte diaphragm according to claim 1, characterized in that, The method of mixing includes ball milling; Preferably, the rotation speed of the ball milling is 100 - 500 rpm, and the time of the ball milling is 1 - 6 h; Preferably, the ball milling is carried out in a protective atmosphere; more preferably, the protective atmosphere includes at least one of argon atmosphere, nitrogen atmosphere, helium atmosphere, hydrogen atmosphere and carbon dioxide atmosphere.

5. The preparation method of the eutectic solid electrolyte separator according to claim 1, characterized in that, The temperature of the melt quenching is 100 - 150 °C.

6. The preparation method of the eutectic solid electrolyte diaphragm according to claim 1, characterized in that, The pressure of the pressing is 10 - 30 MPa.

7. A eutectic solid electrolyte separator, characterized in that It is prepared by using the preparation method of the eutectic solid electrolyte separator according to any one of claims 1 - 6.

8. The eutectic solid electrolyte separator according to claim 7, characterized in that, The eutectic point of the eutectic solid electrolyte separator is 70 - 120 °C.

9. The eutectic solid electrolyte separator according to claim 7, wherein, The ionic conductivity of the eutectic solid electrolyte separator at room temperature is ≥2 mS / cm, the electrochemical window is ≥4.5 V vs. Li+ / Li, and the thermal decomposition temperature is ≥200 °C.

10. A solid-state battery, characterized in that, It includes the eutectic solid electrolyte separator according to any one of claims 7 - 9.

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