Composite positive electrode slurry, positive electrode sheet, preparation method thereof, and all-solid-state battery

Abstract

The application relates to the field of all-solid-state lithium ion batteries, and particularly discloses a composite positive electrode slurry, a positive electrode sheet, a preparation method of the positive electrode sheet and an all-solid-state battery. The slurry comprises a positive electrode active material, a first solid-state electrolyte, a conductive agent, a binder and a low-surface-energy substance, the low-surface-energy substance is a substance with a contact angle greater than 90 degrees, and the low-surface-energy substance is one or more of fluorinated polysiloxane, polysiloxane, octadecanoic acid and stearic acid. The low-surface-energy substance provided by the application belongs to a polymer with excellent hydrophobicity. Mixing the polymer in the slurry can block the contact between the sulfide electrolyte and moisture in the air, reduce the generation of toxic H2S gas, reduce the structural damage of the sulfide, and thus improve the stability of the battery. In addition, the polymer is directly mixed in the slurry, and the operation is simple, which is beneficial to large-scale tests.

Description

Technical Field

[0001] This application relates to the field of all-solid-state lithium-ion battery material preparation, specifically to a composite positive electrode slurry, a positive electrode sheet and its preparation method, and an all-solid-state battery. Background Technology

[0002] Sulfide solid electrolytes have attracted much attention due to their high ionic conductivity and good mechanical properties (facilitating the elimination of grain boundary impedance), and are currently commonly used electrolyte materials in solid-state batteries. However, sulfide solid electrolytes are very sensitive to air and have poor electrochemical stability. In particular, sulfide electrolytes containing phosphorus are extremely sensitive to moisture in the air, and exposure to air easily generates hydrogen sulfide, leading to solid electrolyte failure. At the same time, the composition, crystal structure, and morphology of sulfide electrolytes change, resulting in a significant decrease in electrochemical properties such as ionic conductivity; this also increases the cost of material synthesis, processing, transportation, and battery fabrication.

[0003] Currently, some researchers in the industry are using metal elements to partially or completely replace phosphorus (P) to obtain electrolytes with higher air stability and higher ion mobility. Others are constructing coatings on the surface of sulfide particles, using air-stable or even hydrophobic materials as modification methods for these coatings. However, the ionic conductivity of the prepared coatings is far lower than that of the sulfide electrolyte materials themselves. Furthermore, the lithium-free hydrophobic molecular layer used as a coating lacks lithium-ion transport capability, significantly limiting the utilization of the high lithium-ion conductivity of sulfides. In particular, the coating of solid electrolytes with fluorinated polysiloxane materials hinders the transport of lithium ions. + The conduction of fluorinated polysiloxanes slows down the reaction kinetics, and the process of coating solid electrolytes with fluorinated polysiloxanes is complex and costly, which is not conducive to scale-up experiments.

[0004] Therefore, improving the stability of all-solid-state batteries while ensuring battery performance remains a pressing problem for researchers. Summary of the Invention

[0005] To address the poor stability problem of existing all-solid-state batteries, this invention provides a composite cathode slurry, a cathode sheet, a method for preparing the same, and an all-solid-state battery. The cathode sheet prepared using the composite cathode slurry can produce an all-solid-state battery with superior performance and better stability. The technical solution of this invention is implemented as follows:

[0006] The first aspect of the present invention provides a composite positive electrode slurry, the composite positive electrode slurry comprising a positive electrode active material, a first solid electrolyte, a conductive agent, a binder, and a low surface energy material; the low surface energy material is a material with a contact angle greater than 90°.

[0007] In one embodiment, the mass of the low surface energy material is set as W1, and the total mass of the positive electrode active material, the first solid electrolyte, the conductive agent, the binder, and the low surface energy material is set as W2, wherein the mass percentage of W1 to W2 is 0.1% to 1%.

[0008] In one embodiment, the positive electrode active material is one or more of lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt aluminum oxide (NCA), and lithium-rich manganese-based oxide (LRMO).

[0009] In one embodiment, the first solid electrolyte material is a type of sulfide solid electrolyte.

[0010] Li6PS5Cl(LPSC) and Li are preferred. 10 GeP2S 12 One or more of (LGPS);

[0011] In one embodiment, the conductive agent material is one or more of conductive carbon black, conductive graphite, carbon nanotubes, carbon nanofibers, and graphene.

[0012] In one embodiment, the adhesive material is one or more selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nitrile rubber (NBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA).

[0013] In one embodiment, the low surface energy material is one or more of fluorinated polysiloxane, polysiloxane, octadecanoic acid, and stearic acid.

[0014] A second aspect of the present invention provides a composite positive electrode sheet, the composite positive electrode sheet being made of the composite positive electrode slurry described in the first aspect; the composite positive electrode sheet further includes a positive current collector.

[0015] A third aspect of the present invention provides a method for preparing a composite positive electrode sheet, the method comprising the following steps:

[0016] S1, the positive electrode active material, the first solid electrolyte, the conductive agent, the binder and the low surface energy material are mixed and added to the solvent;

[0017] S2, Repeat high-speed stirring and mixing, defoaming, to form a mixed slurry;

[0018] S3, the above-mentioned mixed slurry is coated onto the positive electrode current collector and then dried;

[0019] S4, then rolled and slit to obtain the positive electrode sheet.

[0020] In one embodiment, the solvent is one or more of toluene, isobutyl isobutyrate, butyl butyrate, hexyl butyrate, diisobutyl ketone, and anisole.

[0021] In one embodiment, in the method for preparing the composite positive electrode sheet, the composite positive electrode slurry and solvent are mixed, and the solid content is 50% to 70%.

[0022] In one embodiment, the positive current collector is an aluminum foil with a thickness of 12 μm, and the thickness of the positive electrode sheet is 0.1 μm to 200 μm.

[0023] In the preparation method of the composite positive electrode sheet, the composite positive electrode slurry and solvent are mixed under high-speed stirring in a drying room, followed by defoaming under stirring, and the mixing is repeated to form a slurry.

[0024] In one embodiment, the method for preparing the composite positive electrode sheet involves mixing the material in a drying room at -50°C to -30°C using a high-speed mixer at a speed of 1500 rpm to 3000 rpm for 5 min to 30 min, followed by defoaming at a speed of 400 rpm to 1000 rpm for 3 min to 10 min, and repeating the mixing process twice to form a uniform slurry.

[0025] In one embodiment, in the method for preparing the composite positive electrode sheet, a mixed slurry is coated on the positive current collector, dried at 60°C to 120°C for 8 to 16 hours, and then rolled and slit to obtain the positive electrode sheet.

[0026] The fourth aspect of the present invention provides an all-solid-state battery, which includes a positive electrode, a negative electrode, and a second solid electrolyte as proposed in the second and third aspects of the present invention.

[0027] The beneficial effects of this invention are:

[0028] This invention provides a composite positive electrode slurry for all-solid-state batteries, in which a low surface energy material is added—a polymer with excellent hydrophobic properties. When this polymer is mixed into the slurry, it can block the contact between the sulfide electrolyte and moisture in the air, reducing the generation of toxic H2S gas and minimizing structural damage to the sulfide, thereby improving battery stability. Furthermore, directly mixing it into the slurry is simple and beneficial for large-scale testing. Specifically, the resulting positive electrode exhibits a higher initial discharge specific capacity and a higher capacity retention rate after 100 cycles. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Identical parts are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific part, respectively.

[0031] Figure 1 This is a static contact angle image with water in Embodiment 1 of the present invention; as the only accompanying drawing of the present invention, this image is also designated as the abstract drawing. Specific Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in the detailed description is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0034] In the description of specific embodiments of the present invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, "multiple" means two or more, unless otherwise explicitly defined.

[0035] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0036] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this invention, the character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0037] Throughout this invention, numerical values ​​represent approximate measurements or limits of a range to cover minute deviations from a given value, as well as embodiments with approximately the mentioned value and embodiments with the exact mentioned value. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term “about,” regardless of whether “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows for some minor inaccuracy (approaching the exact value in some way; approximately or reasonably approaching the value; almost). If the inaccuracy provided by “about” is not otherwise understood in this general sense in the art, then “about” as used in this invention at least indicates a variation that can be produced by common methods of measuring and using such a parameter. For example, “about” may include a variation less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some respects, optionally less than or equal to 0.1%.

[0038] Additionally, the disclosure of the range includes the disclosure of all values ​​across the entire range and the disclosure of further subdivided ranges, including the endpoints and subranges given for these ranges.

[0039] Sulfide solid electrolytes are highly sensitive to air and exhibit poor electrochemical stability. In particular, sulfide electrolytes containing phosphorus (P) are extremely sensitive to moisture in the air; exposure to air easily generates hydrogen sulfide, leading to solid electrolyte failure. Simultaneously, the composition, crystal structure, and morphology of the sulfide electrolyte change, resulting in a significant decline in electrochemical properties such as ionic conductivity. This increases the costs associated with material synthesis, processing, transportation, and battery fabrication.

[0040] Currently, some researchers in the industry are using metal elements to partially or completely replace phosphorus (P) to obtain electrolytes with higher air stability and higher ion mobility. Others are constructing coatings on the surface of sulfide particles, using air-stable or even hydrophobic materials as modification methods for these coatings. However, the ionic conductivity of the prepared coatings is far lower than that of the sulfide electrolyte materials themselves. Furthermore, the lithium-free hydrophobic molecular layer used as a coating lacks lithium-ion transport capability, significantly limiting the utilization of the high lithium-ion conductivity of sulfides. In particular, the coating of solid electrolytes with fluorinated polysiloxane materials hinders the transport of lithium ions. + The conduction of fluorinated polysiloxanes slows down the reaction kinetics, and the process of coating solid electrolytes with fluorinated polysiloxanes is complex and costly, which is not conducive to scale-up experiments.

[0041] To address the aforementioned problems, this invention proposes a technical solution: adding a low surface energy material, a polymer with excellent hydrophobic properties, to the composite cathode slurry. This polymer, when mixed into the slurry, can block the contact between the sulfide electrolyte and moisture in the air, reducing the generation of toxic H2S gas and minimizing structural damage to the sulfide, thereby improving battery stability. Furthermore, its direct mixing into the slurry is simple and beneficial for large-scale testing.

[0042] The first aspect of the present invention provides a composite positive electrode slurry, the composite positive electrode slurry comprising a positive electrode active material, a first solid electrolyte, a conductive agent, a binder, and a low surface energy material; the low surface energy material is a material with a contact angle greater than 90°.

[0043] In one embodiment, the mass of the low surface energy material is set as W1, and the total mass of the positive electrode active material, the first solid electrolyte, the conductive agent, the binder, and the low surface energy material is set as W2, wherein the mass percentage of W1 to W2 is 0.1% to 1%.

[0044] In one embodiment, the mass percentage of W1 to W2 can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc. The values ​​listed above are merely examples, and the present invention does not impose any limitations on them.

[0045] In one embodiment, the positive electrode active material is one or more of lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt aluminum oxide (NCA), and lithium-rich manganese-based oxide (LRMO).

[0046] In one embodiment, the first solid electrolyte material is a type of sulfide solid electrolyte.

[0047] Li6PS5Cl(LPSC) and Li are preferred. 10 GeP2S 12 One or more of (LGPS);

[0048] The main advantages of sulfide solid electrolytes include high ionic conductivity, high energy density, good safety performance, long cycle life, and fast charging capability.

[0049] In one embodiment, the conductive agent material is one or more of conductive carbon black, conductive graphite, carbon nanotubes, carbon nanofibers, and graphene.

[0050] In one embodiment, the adhesive material is one or more selected from polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nitrile rubber (NBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA).

[0051] In one embodiment, the low surface energy material is one or more selected from fluorinated polysiloxane, polysiloxane, octadecanoic acid, and stearic acid. The present invention selects fluorinated polysiloxane as the low surface energy material.

[0052] A small amount of low surface energy material—fluorinated polysiloxane—is introduced into the composite cathode slurry. By introducing perfluoroalkyl groups into the side chains or branches of the polysiloxane, the advantages of organosilicon and organofluorine compounds can be organically combined, so that the fluorinated polysiloxane has both the low surface energy similar to fluorine and the flexibility of organosilicon, thus obtaining a polymer with excellent hydrophobic properties.

[0053] A second aspect of the present invention provides a composite positive electrode sheet, the composite positive electrode sheet being made of the composite positive electrode slurry described in the first aspect; the composite positive electrode sheet further includes a positive current collector.

[0054] A third aspect of the present invention provides a method for preparing a composite positive electrode sheet, the method comprising the following steps:

[0055] S1, the positive electrode active material, the first solid electrolyte, the conductive agent, the binder and the low surface energy material are mixed and added to the solvent;

[0056] S2, Repeat high-speed stirring and mixing, defoaming, to form a mixed slurry;

[0057] S3, the above-mentioned mixed slurry is coated onto the positive electrode current collector and then dried;

[0058] S4, then rolled and slit to obtain the positive electrode sheet.

[0059] In one embodiment, the solvent is one or more of toluene, isobutyl isobutyrate, butyl butyrate, hexyl butyrate, diisobutyl ketone, and anisole.

[0060] In one embodiment, in the method for preparing the composite positive electrode sheet, the composite positive electrode slurry and solvent are mixed, and the solid content is 50% to 70%.

[0061] Solid content, or solid content, refers to the percentage of solid components in a slurry.

[0062] In one embodiment, the solid content of the positive electrode active material, the first solid electrolyte, the conductive agent, the binder, the low surface energy material, and the solvent after mixing can be selected as 50%, 55%, 60%, 65%, 70%, etc. The values ​​listed above are merely examples, and the present invention does not impose any limitations on them.

[0063] In one embodiment, the positive current collector is an aluminum foil with a thickness of 12 μm, and the thickness of the positive electrode sheet is 0.1 μm to 200 μm.

[0064] In one embodiment, the thickness of the positive electrode sheet can be selected as 0.1μm, 5μm, 10μm, 25μm, 50μm, 75μm, 100μm, 125μm, 150μm, 175μm, or 200μm. The values ​​listed above are merely examples, and the present invention does not impose any limitations on them.

[0065] In the preparation method of the composite positive electrode sheet, the composite positive electrode slurry and solvent are mixed under high-speed stirring in a drying room, followed by defoaming under stirring, and the mixing is repeated to form a slurry.

[0066] In one embodiment, the method for preparing the composite positive electrode slurry involves mixing the material in a drying room at -50°C to -30°C using a high-speed mixer at 1500 rpm to 3000 rpm for 5 to 30 minutes, followed by defoaming at 400 rpm to 1000 rpm for 3 to 10 minutes. This mixing process is repeated twice to form a uniform slurry.

[0067] In one embodiment, the temperature in the drying chamber can be selected as -50℃, -45℃, -40℃, -35℃, -30℃, etc., the speed of the high-speed mixer can be selected as 1500rpm, 2000rpm, 2500rpm, 3000rpm, etc., and the mixing time can be selected as 5min, 10min, 15min, 20min, 25min, 30min, etc.; subsequently, the defoaming speed can be selected as 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc., and the defoaming time can be selected as 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, etc. The values ​​listed above are merely examples, and the present invention does not impose any limitations on them.

[0068] In one embodiment, in the preparation method of the composite positive electrode sheet, a mixed slurry is coated onto the positive current collector and dried at 60℃~120℃ for 8h~16h. After drying, the positive electrode sheet is obtained by rolling and slitting. In one embodiment, the drying temperature of the composite positive electrode sheet can be selected as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, etc., and the drying time can be selected as 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, etc. The values ​​listed above are only examples, and the present invention does not impose any limitations on them.

[0069] The fourth aspect of the present invention provides an all-solid-state battery, which includes a positive electrode, a negative electrode, and a second solid electrolyte as proposed in the second and third aspects of the present invention.

[0070] The method for preparing the negative electrode sheet of the present invention is as follows: 95% (mass percentage) of negative electrode active material (graphite:silicon oxide mass percentage of 80%:20%), 2% of solid electrolyte, 2% of conductive agent and 1% of binder are mixed to form a negative electrode slurry. The negative electrode slurry is coated on a negative electrode current collector (copper foil), dried and then rolled and cut to obtain a negative electrode sheet.

[0071] The solid electrolyte layer preparation method of the present invention: the solid electrolyte layer is composed of a second solid electrolyte and a binder (PTFE); the mass ratio of the two is 99:1, and the film thickness is 200μm.

[0072] In one embodiment, the second solid electrolyte material is a type of sulfide solid electrolyte.

[0073] Li6PS5Cl(LPSC) and Li are preferred. 10 GeP2S 12 One or more of (LGPS);

[0074] The present invention discloses a method for preparing an all-solid-state battery: A positive electrode, a solid electrolyte layer, and a negative electrode are sequentially stacked and encapsulated in an aluminum-plastic film. After applying a vacuum to the aluminum-plastic film and sealing it, the battery is subjected to isostatic pressure at 460 MPa to obtain an all-solid-state lithium-ion battery.

[0075] The embodiments of the present invention will be described in more detail below through examples and comparative examples. All examples and comparative examples are lithium-ion battery sample groups prepared using the same process.

[0076] To demonstrate the advantages of the present invention in a clear and comprehensive manner, all embodiments and comparative examples have been recorded or subjected to the following tests: contact angle test, 0.1C first discharge specific capacity test, and capacity retention rate test after 100 cycles at 0.33C.

[0077] It should be noted that the embodiments of the present invention are not limited to these examples.

[0078] Example 1

[0079] I. Preparation of positive electrode sheet

[0080] 1) Using LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), sulfide solid electrolyte Li6PS5Cl, conductive agent carbon nanofiber, binder NBR, and low surface energy material fluorinated polysiloxane are mixed. The mass of the low surface energy material is set as W1, and the total mass of the positive electrode active material, the first solid electrolyte, the conductive agent, the binder, and the low surface energy material is set as W2. The mass percentage of W1 to W2 is 0.5%. The mixture is added to the solvent isobutyl isobutyrate, and the solid content is 60%.

[0081] 2) In a drying room (-40℃), mix the above raw materials with a high-speed mixer at 2000 rpm for 10 minutes, then defoam at 500 rpm for 5 minutes. Repeat the above mixing operation twice to form a uniform slurry.

[0082] 3) Next, the above slurry is coated onto the positive electrode current collector using a scraper in a drying room, then transferred to a vacuum oven and dried at 80°C for 12 hours. After drying, it is rolled and slit to obtain the positive electrode sheet. The positive electrode current collector is aluminum foil with a thickness of 12 μm; the positive electrode sheet has a thickness of 100 μm.

[0083] II. Negative Electrode Preparation

[0084] A negative electrode slurry is prepared by mixing 95% of the negative electrode active material (graphite:silicon oxide = 80%:20%), 2% of the solid electrolyte Li6PS5Cl, 2% of the conductive agent conductive carbon black, and 1% of the binder PAA. The negative electrode slurry is coated on the negative electrode current collector (copper foil), dried, rolled, and slit to obtain the negative electrode sheet.

[0085] III. Preparation of Solid Electrolyte Layer

[0086] The solid electrolyte layer consists of a second solid electrolyte, Li6PS5Cl, and a binder, PTFE; the mass ratio of the two is 99:1, and the film thickness is 200 μm.

[0087] IV. Preparation of All-Solid-State Batteries

[0088] The positive electrode, solid electrolyte layer, and negative electrode are stacked sequentially and encapsulated in an aluminum-plastic film. After applying a vacuum to the aluminum-plastic film, it is sealed, and the battery is subjected to isostatic pressure at 460 MPa to obtain an all-solid-state lithium-ion battery.

[0089] After measuring the contact angle of the above positive electrode (e.g.) Figure 1 As shown in Table 1, the composite positive electrode sheet was then used in an all-solid-state battery, and its performance was tested.

[0090] Example 2

[0091] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.1%.

[0092] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0093] Example 3

[0094] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.2%.

[0095] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0096] Example 4

[0097] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.3%.

[0098] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0099] Example 5

[0100] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.4%.

[0101] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0102] Example 6

[0103] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.6%.

[0104] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0105] Example 7

[0106] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used in Example 1 are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.7%.

[0107] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0108] Example 8

[0109] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used in Example 1 are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.8%.

[0110] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0111] Example 9

[0112] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 0.9%.

[0113] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0114] Example 10

[0115] Example 1 provides a composite cathode slurry, a cathode electrode preparation method, and an all-solid-state battery. The low surface energy material and preparation method used are the same as those in Example 1. The only difference from Example 1 is that the mass percentage of W1 and W2 is 1%.

[0116] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0117] Comparative Example 1

[0118] The preparation method of the positive electrode sheet is the same as that used in Example 1. The difference from Example 1 is that the low surface energy material fluorinated polysiloxane is not added.

[0119] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0120] Comparative Example 2

[0121] The preparation method of the positive electrode sheet is the same as that used in Example 1, except that the mass percentage of W1 and W2 is 0.02%.

[0122] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0123] Comparative Example 3

[0124] The preparation method of the positive electrode sheet is the same as that used in Example 1. The difference from Example 1 is that the mass percentage of W1 and W2 is 1.2%.

[0125] After measuring the contact angle of the above positive electrode sheet, the composite positive electrode sheet was used in an all-solid-state battery, and its performance was tested. The test results are shown in Table 1.

[0126] The positive electrode sheets prepared in Examples 1-10 and Comparative Examples 1-3 were used to prepare all-solid-state batteries. The performance of the all-solid-state batteries was tested, and the test results are shown in Table 1 below:

[0127] Methods for measuring contact angle:

[0128] The contact angle was measured using the static contact angle method. A certain amount of water was placed on a solid surface, and the shape of the droplet was observed under a microscope. The angle between the edge of the droplet and the solid interface was then measured.

[0129] First discharge capacity test:

[0130] At room temperature (25℃), a fully charged battery is discharged at a constant current of 0.1C until the cutoff voltage of 2.5V to obtain the initial discharge capacity.

[0131] Cycle battery capacity retention:

[0132] At a temperature of 45℃, charge at a current of 0.33C to the charging cutoff voltage of 4.2V, then switch to constant voltage charging to the cutoff current of 0.05C, let stand for 0.5h, then discharge at a current of 0.33C to the cutoff voltage of 2.5V, let stand for 0.5h, and then enter the next charge-discharge cycle. This process is repeated for a total of 100 charge-discharge cycles.

[0133] Table 1. Performance test results of all-solid-state batteries

[0134]

[0135] As shown in the table above, compared with Comparative Examples 1-10 and Comparative Examples 1-3, this invention provides a composite cathode slurry for all-solid-state batteries, wherein the added low surface energy material is a polymer with excellent hydrophobic properties. The mixing of this polymer into the slurry can block the contact between the sulfide electrolyte and moisture in the air, reduce the generation of toxic H2S gas, and reduce structural damage to sulfides, thereby improving battery stability. Furthermore, its direct mixing into the slurry is simple and beneficial for large-scale testing.

[0136] Examples 1-10 show that by adding low surface energy materials to the positive electrode material, the contact angle continuously increases with the increase of the amount of low surface energy material added. The specific capacity at the first discharge at 0.1C and the capacity retention rate after 100 cycles at 0.33C both show a trend of first increasing and then decreasing, reaching a peak at an addition amount of 0.5%. When the contact angle increases, it indicates that the wettability of the liquid on the solid surface deteriorates, that is, the hydrophobicity increases and the hydrophilicity decreases. Therefore, low surface energy materials can enhance the hydrophobicity of the battery and improve both cycle performance and rate performance.

[0137] Compared with Example 1 and Comparative Examples 1-3, when no low surface energy material is added, the hydrophobicity is significantly weakened, and the rate performance and cycle performance reach their lowest levels. Comparative Example 2 shows that when the addition amount is 0.02%, the overall battery performance is slightly improved, while when the addition amount is excessive, the battery performance will decrease.

[0138] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite cathode slurry, characterized by, The low surface energy substance is one or more of fluorinated polysiloxane, polysiloxane, octadecanoic acid, and stearic acid. The mass of the low surface energy substance is set as W1, and the total mass of the positive electrode active material, the first solid-state electrolyte, the conductive agent, the binder, and the low surface energy substance is set as W2, and the mass percentage of W1 to W2 is 0.1% to 1%. The low surface energy substance is one or more of fluorinated polysiloxane, polysiloxane, octadecanoic acid, and stearic acid. The low surface energy substance is directly mixed in the slurry.

2. The composite cathode slurry of claim 1, wherein, The positive electrode active material is one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich manganese-based oxide.

3. A composite cathode electrode sheet, characterized by, The composite positive electrode plate is made of the composite positive electrode slurry of claim 1 or 2.

4. The composite cathode electrode sheet according to claim 3, wherein The composite positive electrode plate further comprises a positive electrode current collector.

5. A method for producing a composite positive electrode sheet for producing the composite positive electrode sheet according to claim 4, characterized by, The method comprises the following steps: S1, mixing the positive electrode active material, the first solid-state electrolyte, the conductive agent, the binder, and the low surface energy substance and adding them to the solvent; S2, repeating the high-speed stirring mixing and bubble removal to form a mixed slurry; S3, coating the above-mentioned mixed slurry on the positive electrode current collector and performing drying; S4, then rolling and slitting to obtain the composite positive electrode plate.

6. The method of claim 5, wherein the method further comprises, After the composite positive electrode slurry and the solvent are mixed, the solid content is 50% to 70%.

7. The method for preparing the composite positive electrode sheet as described in claim 5, characterized in that, The thickness of the composite positive electrode plate is 0.1 μm to 200 μm.

8. An all-solid battery, characterized by, The composite positive electrode plate, the negative electrode plate, and the second solid-state electrolyte as claimed in claim 3 or 4.

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