Eutectic solid electrolyte coating diaphragm, solid-state battery and preparation method of solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, in particular to a eutectic solid-state electrolyte coating diaphragm, a solid-state battery and a preparation method of the solid-state battery. The preparation method of the eutectic solid electrolyte coated diaphragm comprises the following steps: coating a base membrane with slurry, and then drying; the slurry is mainly composed of oxygen-containing lithium tetrachloroaluminate and lithium bis (fluorosulfonyl) imide, the chemical formula of the oxygen-containing lithium tetrachloroaluminate is LiAlCl4-2xOx, and x < lt > is larger than or equal to 0.01; 2. The eutectic solid electrolyte coated diaphragm prepared by the invention contains the eutectic solid electrolyte, and the interface wettability between the eutectic solid electrolyte and the base membrane is good, so that the lithium ion transmission efficiency can be improved; and the eutectic solid electrolyte can uniformly permeate into the base membrane and the positive and negative electrode materials through a hot pressing process, so that the contact uniformity is improved, and the interface impedance between the electrode and the eutectic solid electrolyte is reduced, thereby improving the battery performance.

Description

Technical Field

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

[0002] Traditional lithium-ion batteries use liquid electrolytes and have safety problems such as electrolyte leakage, lithium dendrite growth, and thermal runaway. Solid-state batteries use solid electrolytes to replace liquid electrolytes and have significant safety advantages. By coating a solid electrolyte material on the surface of a traditional battery separator for the assembly of a solid-state battery, the lithium-ion transport path inside the battery can be optimized, the ion conduction efficiency can be improved, and the interfacial impedance can be reduced. At the same time, the coated solid electrolyte layer has high mechanical strength, can effectively inhibit the growth of lithium dendrites at high current densities, prevent them from penetrating the separator and causing short circuits, and improve the safety and cycle life of the battery.

[0003] However, when traditional separators (such as PP, PE) are combined with existing solid electrolytes (such as oxides, sulfides, halides), due to the poor interfacial wettability between the separator and the electrolyte material, it is easy to form a lithium-ion transport bottleneck. To solve this problem, it is usually necessary to add a liquid electrolyte or an ionic liquid to improve this interfacial wettability, which poses a challenge to the commercial application of all-solid-state batteries.

[0004] In addition, the existing solid electrolytes have the following problems: (1) The contact between the solid electrolyte and the electrode is usually not as good as that in a liquid electrolyte system, resulting in a higher interfacial impedance. (2) Although the solid electrolyte has high mechanical strength, it lacks sufficient toughness. In practical applications, it is easy to crack or break due to volume change or stress concentration during charge and discharge, and lithium dendrites may grow here, leading to battery short circuit and performance degradation.

[0005] When directly pressing a solid electrolyte into a separator, the amount of solid electrolyte required is large and the cost is high.

[0006] Therefore, a new type of solid electrolyte material needs to be used to address 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-coated separator. The eutectic solid electrolyte-coated separator prepared by this method contains a eutectic solid electrolyte, which has good interfacial wettability with the base film, and the eutectic solid electrolyte can uniformly penetrate into the base film and the positive and negative electrode materials through hot pressing, improving the contact uniformity, reducing the interfacial impedance between the electrode and the eutectic solid electrolyte. LiFSI will also react with the negative electrode to form a SEI film mainly composed of LiF, inhibiting the growth of lithium dendrites, avoiding short circuits and improving battery performance; in addition, the cost of this eutectic solid electrolyte-coated separator is low. It solves the problems of poor interfacial wettability, high impedance, lack of toughness, etc. of traditional solid electrolytes.

[0009] The second object of the present invention is to provide a eutectic solid electrolyte-coated separator, which can improve the lithium ion transport efficiency, reduce the interfacial impedance between the electrode and the eutectic solid electrolyte, and thus improve battery performance, such as cycle performance.

[0010] The third object of the present invention is to provide a solid-state battery with excellent cycle performance.

[0011] The fourth object of the present invention is to provide a preparation method of a solid-state battery. By assembling the solid-state battery through a hot pressing process, the molten eutectic solid electrolyte can improve the contact between the electrode and the eutectic solid electrolyte, and at the same time fill the internal pores of the electrode, reduce the interfacial impedance, and achieve the long cycle performance of the battery.

[0012] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0013] The present invention first provides a preparation method of a eutectic solid electrolyte-coated separator, including the following steps: coating a slurry on a base film, and after drying, the slurry forms a eutectic solid electrolyte layer to obtain the eutectic solid electrolyte-coated separator; wherein, the slurry is mainly composed of lithium tetrachloroaluminate oxide and lithium bis(fluorosulfonyl)imide; the chemical formula of the lithium tetrachloroaluminate oxide is LiAlCl 4-2x O x , where 0.01 ≤ x < 2.

[0014] Further, the thickness of the eutectic solid electrolyte layer is 5 - 50 μm.

[0015] Further, the mass ratio of the lithium tetrachloroaluminate oxide to the lithium bis(fluorosulfonyl)imide is 1:0.2 - 5.

[0016] Further, the slurry also contains a binder and a solvent.

[0017] Further, the binder includes at least one of PVDF and PVDF-HFP.

[0018] Further, the solvent includes at least one of NMP, DMF, and acetone.

[0019] Further, the mass ratio of the sum of the masses of the lithium tetrachloroaluminate and the lithium bis(fluorosulfonyl)imide to the mass of the binder is 90-99:1-10.

[0020] Further, the lithium 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.

[0021] The present invention further provides a eutectic solid electrolyte-coated separator, which is prepared by using the preparation method of the above eutectic solid electrolyte-coated separator; wherein, the eutectic solid electrolyte-coated separator includes a base film and a eutectic solid electrolyte layer provided on the surface of the base film.

[0022] Further, the eutectic point of the eutectic solid electrolyte layer ≤ 100 °C.

[0023] Further, the ionic conductivity of the eutectic solid electrolyte layer at room temperature ≥ 2 mS / cm.

[0024] Further, the electrochemical window of the eutectic solid electrolyte layer > 4.5 V vs. Li + / Li.

[0025] Further, the thermal decomposition temperature of the eutectic solid electrolyte layer > 250 °C.

[0026] Further, the base film includes at least one of a PP base film and a PE base film.

[0027] The present invention also provides a solid-state battery, which is mainly made of the above eutectic solid electrolyte-coated separator.

[0028] The present invention also provides a preparation method of the above solid-state battery, including the following steps: assembling a positive electrode sheet, the eutectic solid electrolyte-coated separator, and a negative electrode sheet; during the assembling process, a hot pressing process is used to make the molten eutectic solid electrolyte in the eutectic solid electrolyte-coated separator penetrate into the base film, the positive electrode sheet, and the negative electrode sheet and make full contact.

[0029] Further, the temperature of the hot pressing is 100-150 °C.

[0030] Further, the pressure of the hot pressing is 10-50 MPa.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) The preparation method of the eutectic solid electrolyte-coated separator provided by the present invention. The obtained eutectic solid electrolyte-coated separator contains a eutectic solid electrolyte. The interfacial wettability between the eutectic solid electrolyte and the base film is good, which can improve the lithium ion transport efficiency. And through the hot pressing process, the eutectic solid electrolyte can uniformly penetrate into the base film and the positive and negative electrode materials, improving the contact uniformity and reducing the interfacial impedance between the electrode and the eutectic solid electrolyte, thereby improving the battery performance; LiFSI will also react with the negative electrode to form a SEI film mainly composed of LiF, inhibiting the growth of lithium dendrites, avoiding short circuits and improving the battery performance.

[0033] (2) The preparation method of the eutectic solid electrolyte-coated separator provided by the present invention has low raw material costs.

[0034] (3) The present invention assembles a solid-state battery through a hot pressing process. The molten eutectic solid electrolyte can improve the contact between the electrode and the eutectic solid electrolyte, and at the same time fill the pores inside the electrode, reducing the interfacial impedance and realizing the long cycle performance of the battery. Description of the Drawings

[0035] 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.

[0036] Figure 1 It is a schematic diagram of the solid-state battery assembled with the eutectic solid electrolyte-coated separator provided by the present invention before and after hot pressing;

[0037] Figure 2 It is a cyclic performance test chart of the solid-state battery prepared in Example 1 of the present invention under the conditions of room temperature and 1C. Specific Embodiments

[0038] 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 creative work 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 the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0039] If there is no special indication, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood 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.

[0040] If there is no special indication, "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.

[0041] If there is no special indication, in the present invention, "one or more" or "at least one" refers to any one, any two or any two or more of the listed items. Among them, "several" refers to any two or any two or more.

[0042] In the first aspect, the present invention provides a preparation method of a eutectic solid electrolyte-coated separator, comprising the following steps:

[0043] Coat the slurry on the base film, and after drying, the slurry forms a eutectic solid electrolyte layer, thus obtaining the eutectic solid electrolyte-coated separator.

[0044] That is, after drying, the slurry forms a eutectic solid electrolyte layer, and the eutectic solid electrolyte layer is located on the surface of the base film.

[0045] It can be understood that the slurry can be coated on one surface of the base film, or can be coated on both surfaces of the base film at the same time.

[0046] Among them, the slurry mainly consists of lithium tetrachloroaluminate containing oxygen and lithium bis(fluorosulfonyl)imide.

[0047] Lithium oxytetrachloroaluminate and lithium bis(fluorosulfonyl)imide form a eutectic solid electrolyte. Among them, the eutectic solid electrolyte is a mixture formed by mixing two or more components in a specific ratio, and its eutectic point (the lowest melting point) is much lower than the melting point of a single component. In the battery manufacturing process, this material can reduce energy consumption, simplify equipment, and avoid material decomposition or interfacial side reactions caused by high temperatures. At the same time, the molten electrolyte can flow and fill the pores on the electrode surface, reducing the interfacial impedance between the electrode and the electrolyte and improving the ion transport efficiency.

[0048] The present invention uses a eutectic solid electrolyte composed of lithium oxytetrachloroaluminate and lithium bis(fluorosulfonyl)imide, which 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.

[0049] Among them, the chemical formula of the lithium oxytetrachloroaluminate is LiAlCl 4-2x O x , where 0.01 ≤ x < 2. Among them, x includes but is not limited to any one of the point values of 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, 1.9 or the range values between any two of them.

[0050] The eutectic solid electrolyte-coated separator prepared by the above preparation method contains a eutectic solid electrolyte, and the interfacial wettability between the eutectic solid electrolyte and the base film is good, which can improve the lithium ion transport efficiency.

[0051] Moreover, through the hot pressing process, the eutectic solid electrolyte can uniformly penetrate into the base film and the positive and negative electrode materials, improving the contact uniformity and reducing the interfacial impedance between the electrode and the eutectic solid electrolyte, thereby improving the battery performance. LiFSI will also react with the negative electrode to form a SEI film mainly composed of LiF, inhibiting the growth of lithium dendrites, avoiding short circuits and improving the battery performance.

[0052] In addition, the eutectic solid electrolyte-coated separator prepared by this method has obvious cost advantages compared with traditional oxide solid electrolytes (such as LLZO, LLZTO, LATP, etc.), sulfide solid electrolytes (Li6PS5Cl), and halide solid electrolytes (Li3InCl3, Li3YCl6, Li3ScCl6). At the same time, the eutectic solid electrolyte used in this method is less and the cost is low.

[0053] In some specific embodiments, the thickness (referring to the single-sided thickness) of the eutectic solid electrolyte layer is 5 - 50 μm, such as 10 μm, 20 μm, 30 μm or 40 μm.

[0054] In some specific embodiments, the mass ratio of the lithium oxytetrachloroaluminate and the lithium bis(fluorosulfonyl)imide used for preparing the eutectic solid electrolyte is 1:0.2 to 5, including but not limited to any one of the point values of 1:0.2, 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 values between any two of them. This is beneficial to improving the lithium ion transport efficiency and reducing the impedance.

[0055] Among them, the slurry containing the eutectic solid electrolyte is an oil-based slurry.

[0056] In some specific embodiments, the slurry further contains a binder and a solvent.

[0057] In some specific embodiments, the binder includes at least one of PVDF (polyvinylidene fluoride) and PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer).

[0058] In some specific embodiments, the solvent includes at least one of NMP (N-methylpyrrolidone), DMF (N,N-dimethylformamide) and acetone.

[0059] In some specific embodiments, the mass ratio of the sum of the masses of the lithium oxytetrachloroaluminate and the lithium bis(fluorosulfonyl)imide to the mass of the binder is 90 to 99:1 to 10, such as 90:10, 92:8, 93:7, 95:5 or 98:2.

[0060] In some specific embodiments, the lithium oxytetrachloroaluminate 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.

[0061] In a second aspect, the present invention provides a eutectic solid electrolyte-coated separator, which is prepared by using the preparation method of the above-mentioned eutectic solid electrolyte-coated separator. Among them, the eutectic solid electrolyte-coated separator includes a base film and a eutectic solid electrolyte layer provided on the surface of the base film.

[0062] The interfacial wettability between the eutectic solid electrolyte layer and the base film in the eutectic solid electrolyte-coated separator is good, which can improve the lithium ion transport efficiency.

[0063] When preparing a solid-state battery using the eutectic solid-state electrolyte-coated separator, the eutectic solid-state electrolyte can uniformly penetrate into the base film and the positive and negative electrode materials through a hot pressing process, improving the contact uniformity and reducing the interfacial impedance between the electrode and the eutectic solid-state electrolyte, thereby improving the battery performance, such as the cycling performance.

[0064] Meanwhile, the cost of the eutectic solid-state electrolyte-coated separator is low.

[0065] In some specific embodiments, the eutectic point of the eutectic solid-state electrolyte layer ≤ 100 °C, including but not limited to the point value of any one of 95 °C, 90 °C, 85 °C, 80 °C or the range value between any two of them; preferably 80 - 90 °C.

[0066] In some specific embodiments, the ionic conductivity of the eutectic solid-state electrolyte layer at room temperature ≥ 2 mS / cm, including but not limited to the point value of any one 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 or the range value between any two of them.

[0067] In some specific embodiments, the electrochemical window of the eutectic solid-state electrolyte layer > 4.5 V vs. Li + / Li, including but not limited to the point value of any one 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.

[0068] In some specific embodiments, the thermal decomposition temperature of the eutectic solid-state electrolyte layer > 250 °C.

[0069] In some specific embodiments, the base film includes at least one of a PP base film and a PE base film.

[0070] In some specific embodiments, the thickness of the base film is 10 micrometers.

[0071] In a third aspect, the present invention provides a solid-state battery mainly prepared from the above-mentioned eutectic solid-state electrolyte-coated separator.

[0072] The above-mentioned eutectic solid-state electrolyte-coated separator adopts the traditional liquid battery process, can be used in the fields of button batteries, soft-pack batteries and cylindrical batteries, has the characteristics of low energy consumption and simple operation, and can quickly realize industrial production.

[0073] It can be understood that in addition to the above-mentioned eutectic solid-state electrolyte-coated separator, a positive electrode sheet and a negative electrode sheet are also required for preparing a solid-state battery.

[0074] The eutectic solid-state electrolyte-coated separator is used for the assembly of solid-state batteries. During the assembly process, a hot pressing process is adopted to enable the molten eutectic solid-state electrolyte to penetrate into the base film, the positive electrode sheet, and the negative electrode sheet and make full contact, so as to reduce the interfacial impedance.

[0075] In a fourth aspect, the present invention provides a method for preparing the above-mentioned solid-state battery, which includes the following steps: assembling a positive electrode sheet, the eutectic solid-state electrolyte-coated separator, and a negative electrode sheet. Among them, during the assembly process, a hot pressing process is adopted to enable the molten eutectic solid-state electrolyte in the eutectic solid-state electrolyte-coated separator to penetrate into the base film, the positive electrode sheet, and the negative electrode sheet and make full contact.

[0076] Figure 1 It is a schematic diagram of a solid-state battery assembled with a eutectic solid-state electrolyte-coated separator before and after the hot pressing process.

[0077] It can be understood that during the hot pressing process, a eutectic solid-state electrolyte is formed.

[0078] The present invention assembles a solid-state battery through a hot pressing process. The molten eutectic solid-state electrolyte can improve the contact between the electrode and the eutectic solid-state electrolyte, and at the same time fill the pores inside the electrode, reduce the interfacial impedance, and achieve the long cycle performance of the battery.

[0079] Moreover, this process has the advantages of low energy consumption, simple operation, etc., is easy to realize large-scale production, and has good application prospects.

[0080] In some specific embodiments, the temperature of the hot pressing is 100-150 °C; including but not limited to any point value among 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C or the range value between any two of them.

[0081] In some specific embodiments, the pressure of the hot pressing is 10-50 MPa, including but not limited to any point value among 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa or the range value between any two of them.

[0082] In some specific embodiments, the time of the hot pressing is 5-10 min.

[0083] Using the hot pressing process to assemble the battery can enable the eutectic electrolyte to uniformly penetrate into the separator and the positive and negative electrode materials, realize the close contact between the electrode and the electrolyte, reduce the interfacial impedance, and further improve the battery performance. Using the above-mentioned hot pressing temperature and pressure can further optimize the interfacial contact between the electrode and the electrolyte, thereby further improving the battery performance.

[0084] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples 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 examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments not specified for the manufacturer can be obtained as conventional products through commercial purchase.

[0085] The preparation method of lithium tetrachloroaluminate oxide used in the following examples and comparative examples of the present invention is as follows: LiCl, AlCl3 and Sb2O3 are mixed evenly according to the ratio of the target chemical formula, and then annealed at 250 °C for 6 h (the formed SbCl3 will volatilize at about 200 °C).

[0086] Example 1

[0087] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this example includes the following steps: The eutectic solid-state electrolyte LiAlCl3O 0.5 -LiFSI (prepared from LiAlCl3O and LiFSI with a mass ratio of 1:0.5) 0.5 and the oil-based binder PVDF and the solvent NMP are mixed evenly to form an oil-based coating slurry; among them, the mass ratio of the eutectic solid-state electrolyte to the oil-based binder is 95:5. Subsequently, the coating slurry is uniformly coated on both surfaces of the PE base film by a coating process and dried to form a eutectic solid-state electrolyte layer with a thickness of 10 μm on one side, and a eutectic solid-state electrolyte-coated separator is obtained. That is, the eutectic solid-state electrolyte-coated separator includes a base film and eutectic solid-state electrolyte layers respectively provided on both surfaces of the base film, and the thickness of each eutectic solid-state electrolyte layer is 10 μm.

[0088] The preparation method of the solid-state battery provided in this example includes the following steps: The LiFePO4 positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this example, and the graphite negative electrode sheet are sequentially assembled in a CR2032 button case, encapsulated, and hot-pressed at 120 °C and 15 MPa for 5 minutes. 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 uniformly coated on the surface of 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. 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 uniformly coated on the surface of copper foil and dried at 110 °C.

[0089] Example 2

[0090] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this example is basically the same as that in Example 1, except that the oil-based binder is replaced with an equal mass of PVDF-HFP.

[0091] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the LiFePO4 positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this example, and the silicon-carbon negative electrode sheet in sequence. After welding the electrode tabs, the electrode assembly is placed into an aluminum-plastic film packaging shell and hot-pressed at 120 °C and 15 MPa for 10 minutes, and then vacuum-sealed. 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 basically the same as that in Example 1, except that graphite is replaced with an equal mass of silicon-carbon composite material.

[0092] Example 3

[0093] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this example is basically the same as that in Example 1, except that the eutectic solid-state electrolyte is replaced with an equal mass of LiAlCl 2.5 O 0.75 -LiFSI (prepared from LiAlCl with a mass ratio of 1:1 2.5 O 0.75 and LiFSI).

[0094] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this example, and the graphite negative electrode sheet in sequence. After welding the electrode tabs, the electrode assembly is placed into an aluminum-plastic film packaging shell and hot-pressed at 110 °C and 15 MPa for 10 minutes, and then vacuum-sealed. 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 NCM622 positive electrode material. The preparation method of the negative electrode sheet is the same as that in Example 1.

[0095] Example 4

[0096] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this example is basically the same as that in Example 3, except that the oil-based binder is replaced with an equal mass of PVDF-HFP.

[0097] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this example, and the graphite negative electrode sheet in sequence. After welding the electrode tabs, the electrode assembly is placed into an aluminum-plastic film packaging shell and hot-pressed at 110 °C and 50 MPa for 5 minutes, and then vacuum-sealed. Among them, the preparation methods of both the positive electrode sheet and the negative electrode sheet are the same as those in Example 3.

[0098] Example 5

[0099] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this embodiment is basically the same as that in Example 1, except that the eutectic solid-state electrolyte is replaced with an equal mass of LiAlCl 2.5 O 0.75 -LiFSI (prepared from LiAlCl 2.5 O 0.75 and LiFSI with a mass ratio of 1:2).

[0100] The preparation method of the solid-state battery provided in this embodiment includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this embodiment, and the lithium metal negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot press it at 100 °C and 40 MPa for 10 minutes, then vacuum package. Among them, the preparation method of the positive electrode sheet is the same as that in Example 3.

[0101] Example 6

[0102] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this embodiment is basically the same as that in Example 5, except that the oil-based binder is replaced with an equal mass of PVDF-HFP.

[0103] The preparation method of the solid-state battery provided in this embodiment includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this embodiment, and the lithium metal negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot press it at 100 °C and 30 MPa for 10 minutes, then vacuum package. Among them, the preparation method of the positive electrode sheet is the same as that in Example 5.

[0104] Example 7

[0105] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this embodiment is basically the same as that in Example 1, except that the eutectic solid-state electrolyte is replaced with an equal mass of LiAlCl₂O-LiFSI (prepared from LiAlCl₂O and LiFSI with a mass ratio of 1:2).

[0106] The preparation method of the solid-state battery provided in this embodiment includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid-state electrolyte-coated separator prepared in this embodiment, and the silicon-carbon negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot press it at 100 °C and 15 MPa for 10 minutes, then vacuum package. Among them, the preparation method of the positive electrode sheet is the same as that in Example 3. The preparation method of the negative electrode sheet is the same as that in Example 2.

[0107] Example 8

[0108] The preparation method of the eutectic solid electrolyte-coated separator provided in this example is basically the same as that in Example 7, except that the oil-based binder is replaced with an equal mass of PVDF-HFP.

[0109] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid electrolyte-coated separator prepared in this example, and the silicon-carbon negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot-press it at 100 °C and 15 MPa for 10 minutes, then vacuum package it. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 7.

[0110] Example 9

[0111] The preparation method of the eutectic solid electrolyte-coated separator provided in this example is basically the same as that in Example 1, except that the eutectic solid electrolyte is replaced with an equal mass of LiAlCl3O 0.5 -LiFSI (prepared from LiAlCl3O and LiFSI with a mass ratio of 1:3) 0.5 and LiFSI).

[0112] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid electrolyte-coated separator prepared in this example, and the silicon-carbon negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot-press it at 100 °C and 20 MPa for 5 minutes, then vacuum package it. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 8.

[0113] Example 10

[0114] The preparation method of the eutectic solid electrolyte-coated separator provided in this example is basically the same as that in Example 9, except that the oil-based binder is replaced with an equal mass of PVDF-HFP.

[0115] The preparation method of the solid-state battery provided in this example includes the following steps: Stack the NCM positive electrode sheet, the eutectic solid electrolyte-coated separator prepared in this example, and the silicon-carbon negative electrode sheet in sequence. After welding the tabs, place the electrode assembly into an aluminum-plastic film packaging shell, and hot-press it at 100 °C and 20 MPa for 5 minutes, then vacuum package it. Among them, the preparation methods of the positive electrode sheet and the negative electrode sheet are the same as those in Example 9.

[0116] Example 11

[0117] The preparation method of the eutectic solid electrolyte-coated separator provided in this example is basically the same as that in Example 1, except that the single-sided thickness of the eutectic solid electrolyte layer is replaced with 20 μm.

[0118] The eutectic solid-state electrolyte-coated separator prepared in this example was used to fabricate a solid-state battery according to the method of Example 1.

[0119] Example 12

[0120] The preparation method of the eutectic solid-state electrolyte-coated separator provided in this example is basically the same as that of Example 1, except that the mass ratio of the eutectic solid-state electrolyte to the oily binder is replaced with 90:10.

[0121] The eutectic solid-state electrolyte-coated separator prepared in this example was used to fabricate a solid-state battery according to the method of Example 1.

[0122] Comparative Example 1

[0123] The preparation method of the separator provided in this comparative example is basically the same as that of Example 1, except that the eutectic solid-state electrolyte was not added and replaced with an equal mass of LiAlCl3O 0.5 .

[0124] The separator prepared in this comparative example was used to fabricate a solid-state battery according to the method of Example 1.

[0125] Comparative Example 2

[0126] The preparation method of the separator provided in this comparative example is basically the same as that of Example 1, except that the eutectic solid-state electrolyte was not added and replaced with an equal mass of LiFSI.

[0127] The separator prepared in this comparative example was used to fabricate a solid-state battery according to the method of Example 1.

[0128] Comparative Example 3

[0129] The preparation method of the separator provided in this comparative example is basically the same as that of Example 1, except that the eutectic solid-state electrolyte LiAlCl3O 0.5 -LiFSI was prepared from LiAlCl3O with a mass ratio of 1:0.01 0.5 and LiFSI.

[0130] The separator prepared in this comparative example was used to fabricate a solid-state battery according to the method of Example 1.

[0131] Comparative Example 4

[0132] The preparation method of the separator provided in this comparative example is basically the same as that of Example 1, except that the eutectic solid-state electrolyte LiAlCl3O 0.5 -LiFSI was prepared from LiAlCl3O with a mass ratio of 1:8 0.5 and LiFSI.

[0133] The separator obtained in this comparative example was used to fabricate a solid-state battery according to the method of Example 1.

[0134] Comparative Example 5

[0135] The method for preparing the separator provided in this comparative example was basically the same as that of Example 1, except that the mass ratio of the eutectic solid electrolyte to the oily binder was replaced with 70:30.

[0136] The separator obtained in this comparative example was used to fabricate a solid-state battery according to the method of Example 1.

[0137] The eutectic points, ionic conductivities at room temperature, and electrochemical window results of the eutectic solid electrolyte layers of the eutectic solid electrolyte-coated separators obtained in the above examples and the solid electrolyte layers obtained in each comparative example are shown in Table 1.

[0138] Table 1 Physical and chemical property parameters of the eutectic solid electrolyte layer and the solid electrolyte layer

[0139]

[0140]

[0141] As can be seen from Table 1, the eutectic solid electrolyte layers obtained in each example have high ionic conductivity, wide electrochemical window, low melting point, and high stability at room temperature. While the ionic conductivities of each comparative example are relatively low, the electrochemical windows are relatively narrow, the melting points are relatively high, or the stabilities are relatively poor.

[0142] In addition, the cycle performance test chart of the solid-state battery prepared in Example 1 at room temperature under 1C condition is shown in Figure 2 , and it can be seen that the cycle stability of the solid-state battery prepared in Example 1 is good. This shows that by assembling the solid-state battery through the hot pressing process, the molten eutectic solid electrolyte can improve the contact between the electrode and the eutectic solid electrolyte, fill the pores inside the electrode at the same time, reduce the interfacial impedance, and achieve the long cycle performance of the battery.

[0143] Although the present invention has been illustrated and described with specific examples, it should be realized that the above examples are only used to illustrate the technical solutions of the present invention, rather than 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 examples can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications belonging to the scope of the present invention are included in the appended claims.

Claims

1. A preparation method of a eutectic solid electrolyte-coated separator, characterized in that, It includes the following steps: Coat the slurry on the base film. After drying, the slurry forms a eutectic solid electrolyte layer to obtain the eutectic solid electrolyte-coated separator; Among them, the slurry is mainly composed of lithium oxytetrachloroaluminate and lithium bis(fluorosulfonyl)imide; the chemical formula of the lithium oxytetrachloroaluminate is LiAlCl 4-2x O x , where 0.01 ≤ x < 2.

2. The preparation method of the eutectic solid electrolyte-coated separator according to claim 1, characterized in that, The thickness of the eutectic solid electrolyte layer is 5 - 50 μm.

3. The preparation method of the eutectic solid electrolyte-coated separator according to claim 1, wherein, The mass ratio of the lithium tetrachloroaluminate containing oxygen to the lithium bis(fluorosulfonyl)imide is 1:0.2 - 5.

4. The preparation method of the eutectic solid electrolyte-coated separator according to claim 1, characterized in that, The slurry also contains a binder and a solvent; Preferably, the binder includes at least one of PVDF and PVDF-HFP; Preferably, the solvent includes at least one of NMP, DMF, and acetone; Preferably, the mass ratio of the sum of the mass of the lithium tetrachloroaluminate containing oxygen and the lithium bis(fluorosulfonyl)imide to the mass of the binder is 90 - 99:1 - 10.

5. The preparation method of the eutectic solid electrolyte-coated separator 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.

6. A eutectic solid electrolyte-coated separator, characterized in that, It is prepared by using the preparation method of the eutectic solid electrolyte-coated separator according to any one of claims 1 - 5; Among them, the eutectic solid electrolyte-coated separator includes a base film and a eutectic solid electrolyte layer provided on the surface of the base film.

7. The eutectic solid electrolyte-coated separator according to claim 6, characterized in that, Meet at least one of the following conditions: (1) The eutectic point of the eutectic solid electrolyte layer ≤ 100 °C; (2) The ionic conductivity of the eutectic solid electrolyte layer at room temperature ≥ 2 mS / cm; (3) The electrochemical window of the eutectic solid electrolyte layer > 4.5V vs. Li + / Li; (4) The thermal decomposition temperature of the eutectic solid electrolyte layer > 250 °C.

8. The eutectic solid electrolyte-coated separator according to claim 6, characterized in that, The base film includes at least one of a PP base film and a PE base film.

9. A solid-state battery, characterized in that, It is mainly made of the eutectic solid electrolyte-coated separator according to any one of claims 6 - 8.

10. The preparation method of the solid-state battery according to claim 9, characterized in that, It includes the following steps: Assemble the positive electrode sheet, the eutectic solid electrolyte-coated separator, and the negative electrode sheet; During the assembly process, use a hot pressing process to make the molten eutectic solid electrolyte in the eutectic solid electrolyte-coated separator penetrate into the base film, the positive electrode sheet, and the negative electrode sheet and make full contact; Preferably, the temperature of the hot pressing is 100 - 150 °C; Preferably, the pressure of the hot pressing is 10 - 50 MPa.

Images