Semi-solid battery and preparation method thereof

Abstract

The invention relates to a semi-solid-state battery and a preparation method in the technical field of lithium battery production, the semi-solid-state battery comprises a positive electrode, a negative electrode and an electrolyte, and a solid-state electrolyte layer is arranged on the surface of one side, close to the electrolyte, of the positive electrode; the electrolyte comprises a film-forming agent ethylene carbonate and a film-forming agent methylene methyldisulfonate. Vinyl carbonate (VC) and methylene methyldisulfonate (MMDS) can form a stable and compact SEI film on the negative electrode side, and the storage performance and the cycle performance of the battery taking lithium manganate as the positive electrode at a high temperature can be effectively improved through the synergistic matching of the solid electrolyte layer on the positive electrode side and the stable SEI film on the negative electrode side. The CEI film formed on the positive electrode by using the solid electrolyte layer instead of an additive is beneficial to improving the stability of the solid electrolyte film on the positive electrode side.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery production, and in particular to a semi-solid battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in electronics and new energy vehicles due to their environmental friendliness, high energy density, and long cycle life. The main components of a lithium-ion battery include a positive electrode, a negative electrode, an electrolyte, and a separator. The electrolyte, a key component of a lithium-ion battery, conducts ions within the battery.

[0003] Lithium manganate (LiMn2O4) cathode materials have three-dimensional channels that are conducive to lithium ion diffusion, resulting in outstanding rate performance. However, lithium manganate cathode materials are prone to manganese ion dissolution and dissolution, causing battery performance degradation. When working at room temperature, additives can be added to the electrolyte to form a CEI film on the cathode side to prevent the dissolution and migration of manganese ions. However, when the battery is operated at high temperatures, the dissolution of manganese ions at the cathode is aggravated, and the CEI film and SEI film also become unstable, causing rapid deterioration of battery performance. Therefore, how to solve the high-temperature storage and cycling stability of lithium manganate has become an urgent problem to be solved in this field. Summary of the Invention

[0004] In order to solve the above problems, the present invention discloses a semi-solid battery and a preparation method. The technical solution of the present invention is implemented as follows:

[0005] The first aspect of the present invention discloses a semi-solid-state battery; the semi-solid-state battery comprises a positive electrode, a negative electrode and an electrolyte, wherein a solid electrolyte layer is provided on a surface of the positive electrode close to the electrolyte;

[0006] The electrolyte includes a film-forming agent ethylene carbonate and a film-forming agent methylene disulfonate.

[0007] Preferably, in the electrolyte, the sum of the mass proportions of the ethylene carbonate and the methylene disulfonate is 3% to 8%.

[0008] Preferably, in the electrolyte, the mass proportion of the methylene disulfonate is 0.01% to 1%.

[0009] Preferably, the thickness of the solid electrolyte layer is 8 μm to 12 μm.

[0010] Preferably, the solid electrolyte layer includes an oxide solid electrolyte.

[0011] Preferably, the oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, and lithium aluminum titanium phosphate.

[0012] A second aspect of the present invention discloses a method for preparing a semi-solid battery, which is used to prepare the semi-solid battery disclosed in the first aspect of the present invention, and comprises the following steps:

[0013] S1. Preparing a composite positive electrode: preparing a positive electrode layer and a solid electrolyte layer respectively, and thermally combining the positive electrode layer and the solid electrolyte layer to form a composite positive electrode;

[0014] S2, preparing the negative electrode;

[0015] S3, forming a dry battery cell by combining the composite positive electrode, separator, and negative electrode;

[0016] S4. Inject electrolyte:

[0017] S4.1. Primary injection: inject ml g of a first electrolyte into the dry cell; the first electrolyte comprises a first solvent and a first film-forming agent;

[0018] The first film-forming agent includes ethylene carbonate and methylene disulfonate;

[0019] S4.2. After the first injection, the battery cell is sequentially soaked, formed, and aged;

[0020] S4.3, Secondary electrolyte injection: Inject m2g of the second electrolyte into the aged cell; the first electrolyte includes a second film-forming agent and a second solvent;

[0021] The second film-forming agent includes ethylene carbonate and methylene disulfonate;

[0022] S4.4. After the second injection is completed, let it stand and separate the volume to obtain a semi-solid-state battery.

[0023] Preferably, the mass of the first film-forming agent is m 11 ;

[0024] The mass of the second film-forming agent is m 21 ;

[0025] And satisfied,

[0026]

[0027] Preferably, m1>m2.

[0028] Preferably, the first solvent comprises ethylene carbonate, ethyl methyl carbonate and ethyl acetate;

[0029] Preferably, the second solvent is the same as the first solvent.

[0030] The advantages of the present invention are as follows:

[0031] The present invention adds ethylene carbonate (VC) and methylene disulfonate (MMDS) to the electrolyte. VC and MMDS form a stable and dense SEI film on the negative electrode side. The synergistic effect of the solid electrolyte layer on the positive electrode side and the stable SEI film on the negative electrode side effectively improves the storage performance and cycle performance of batteries using lithium manganese oxide as the positive electrode at high temperatures. Replacing the CEI film formed by additives on the positive electrode with the solid electrolyte layer helps improve the stability of the solid electrolyte film on the positive electrode side.

[0032] In addition, the present invention also improves the injection process of the semi-solid-state battery, divides the electrolyte into a first electrolyte and a second electrolyte and injects them in sequence, controls the different mass proportions of the additives VC and MMDS in the first electrolyte and the second electrolyte, and adds them in batches, which is conducive to the formation of a dense and stable SEI film on the negative electrode side. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0035] In the description of the specific embodiments of the present invention, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present invention, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0036] References to "embodiments" in this disclosure mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0037] In the description of the embodiments of the present invention, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exists simultaneously, and B exists alone. In addition, the character " / " in this invention generally indicates that the associated objects are in an "or" relationship.

[0038] Throughout this disclosure, numerical values ​​represent approximate measures or limits of ranges to encompass minor deviations from a given value, as well as embodiments having approximately the stated value and embodiments having the exact value stated. Except for the working examples provided at the end of the detailed description, all numerical values ​​for parameters (e.g., amounts, or conditions) in this specification (including the appended claims) should be understood as being modified in all instances 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 imprecision (some degree of closeness to the exact value of the stated value; approximately or reasonably close to the stated value; nearly). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about," as used herein, at least indicates the variation that can occur due to ordinary methods of measuring and using such parameters. For example, "about" can encompass variations of 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 certain aspects, optionally less than or equal to 0.1%.

[0039] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges stated for such ranges.

[0040] Lithium manganate (LiMn2O4) system cathode materials have three-dimensional channels that are conducive to the diffusion of lithium ions, so the rate performance is outstanding. However, lithium manganate system cathode materials are prone to the dissolution and migration of manganese ions, causing battery performance degradation. When working at room temperature, additives can be added to the electrolyte to form a CEI film on the positive electrode side to prevent the dissolution and migration of manganese ions. However, when the battery is working at high temperature, the dissolution of manganese ions in the positive electrode is intensified, and the CEI film and SEI film also become unstable, causing rapid deterioration of battery performance.

[0041] In order to improve the high-temperature storage performance and cycle stability of lithium manganese oxide, the first aspect of the present invention discloses a semi-solid-state battery; the semi-solid-state battery includes a positive electrode, a negative electrode and an electrolyte, and a solid electrolyte layer is provided on the surface of the positive electrode on the side close to the electrolyte;

[0042] The electrolyte includes a film-forming agent ethylene carbonate and a film-forming agent methylene disulfonate.

[0043] Ethylene carbonate (VC) and methylene disulfonate (MMDS) form a stable and dense SEI film on the negative electrode side. The synergistic effect of the solid electrolyte layer on the positive electrode side and the stable SEI film on the negative electrode side can effectively improve the storage performance and cycling performance of batteries with lithium manganese oxide as the positive electrode at high temperatures. Replacing the CEI film formed by additives on the positive electrode with a solid electrolyte layer is beneficial to improving the stability of the solid electrolyte film on the positive electrode side.

[0044] In addition, since a solid electrolyte layer is provided on the surface of the positive electrode facing the electrolyte, MMDS cannot directly contact the positive electrode, which can effectively reduce the formation of additive film on the positive electrode and reduce battery impedance.

[0045] In some embodiments, in the electrolyte, the sum of the mass proportions of the ethylene carbonate and the methylene disulfonate is 3% to 8%.

[0046] In specific applications, the sum of the mass of the ethylene carbonate and the methylene disulfonate in the electrolyte can be selected to account for 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, etc. The percentage values ​​listed above are only examples and are not limiting. The present invention can be freely implemented with any percentage value within the range of 3% to 8% without exceeding the scope of understanding of those skilled in the art.

[0047] In some preferred embodiments, in the electrolyte, the mass proportion of methylene disulfonate is 0.01% to 1%.

[0048] In specific applications, the mass percentage of the methylene disulfonate can be selected as: 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc. The percentage values ​​listed above are only examples and are not limiting. Under the premise of not exceeding the scope of understanding of those skilled in the art, the present invention can freely implement any percentage value within the range of 0.01% to 1%.

[0049] In some embodiments, the solid electrolyte layer has a thickness of 8 μm to 12 μm.

[0050] In specific applications, the thickness of the solid electrolyte layer can be selected as: 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, etc. The above values ​​are only examples and are not limiting. Without exceeding the scope of understanding of those skilled in the art, the present invention can be freely implemented with any value within the range of 8 μm to 12 μm.

[0051] In some embodiments, the solid electrolyte layer includes an oxide solid electrolyte.

[0052] In specific applications, the oxide solid electrolyte can be selected from: perovskite type, garnet type, LISICON type, NASICON type, wherein the perovskite type solid electrolyte material is preferably LLTO (lithium lanthanum titanate / lithium lanthanum titanate, Li 0.33 La 0.56 TiO3), the garnet-type solid electrolyte material is preferably LLZO (lithium zirconium oxide / lithium lanthanum zirconate, Li7La3Zr2O 12 ), NASICON (sodium super ion conductor) type solid electrolyte material is preferably lithium titanium aluminum phosphate

[0053] LATPLi 1.3 Al 0.3 Ti 1.7 (PO4)3) at least one.

[0054] The term "at least one" as used in the present invention means that any one element can be selected from the listed elements as a technical solution, or a combination of two or more elements can be used as a technical solution. Such a combination will not exceed the understanding of those skilled in the art, and therefore the form of combination can be freely selected as needed, up to a maximum of all combinations of the listed elements.

[0055] In some preferred embodiments, the oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, and lithium aluminum titanium phosphate.

[0056] When the oxide solid electrolyte is at least one or a combination of two or three of the above materials, the oxide solid electrolyte has the best performance in the semi-solid battery disclosed in the present invention.

[0057] A second aspect of the present invention discloses a method for preparing a semi-solid battery, the method comprising the following steps:

[0058] S1. Preparing a composite positive electrode: preparing a positive electrode layer and a solid electrolyte layer respectively, and thermally combining the positive electrode layer and the solid electrolyte layer to form a composite positive electrode;

[0059] S2, preparing the negative electrode;

[0060] S3, forming a dry battery cell by combining the composite positive electrode, separator, and negative electrode;

[0061] S4. Inject electrolyte:

[0062] S4.1. Primary injection: inject ml g of a first electrolyte into the dry cell; the first electrolyte comprises a first solvent and a first film-forming agent;

[0063] The first film-forming agent includes ethylene carbonate and methylene disulfonate;

[0064] S4.2. After the first injection, the battery cell is sequentially soaked, formed, and aged;

[0065] S4.3, Secondary electrolyte injection: Inject m2g of the second electrolyte into the aged cell; the first electrolyte includes a second film-forming agent and a second solvent;

[0066] The second film-forming agent includes ethylene carbonate and methylene disulfonate;

[0067] After the second injection, allow the solution to stand for 12 to 36 hours and allow the solution to separate into smaller volumes to form a semi-solid-state battery.

[0068] In specific applications, in step S4.4, the standing time can be 12 hours, 14 hours, 15 hours, 18 hours, 20 hours, 22 hours, 24 hours, 25 hours, 28 hours, 30 hours, 32 hours, 34 hours, 35 hours, 36 hours, etc. The times listed above are only examples, and those skilled in the art can freely implement any time within 12 hours to 36 hours without exceeding the scope of understanding of those skilled in the art.

[0069] In specific applications, the specific steps for preparing the composite positive electrode are as follows:

[0070] Lithium manganate, binder PVDF, and conductive agent Super-P are mixed in a mass ratio of 95:3:2, and solvent NMP is added to form a slurry, which is then coated and dried to form a positive electrode sheet;

[0071] Li 1.3 Al 0.3 Ti 1.7 Preparation of (PO4)3(LATP): LiOH·H2O, Al2O3, TiO2, and NH4H2PO4 were mixed in a stoichiometric ratio and ball-milled for 6–12 h. The resulting powder was heated at 800°C in a muffle furnace for 8–15 h to obtain the desired product.

[0072] The ball milling time can be specifically selected from 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.; the heating time can be specifically selected from 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc. The above times are only examples and are not limiting.

[0073] According to a certain ratio, Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) was mixed with PVDF and deionized water to form a slurry, which was then coated on the surface of the PP film and dried;

[0074] The positive electrode sheet is brought into close contact with LATP under a certain pressure, and the two are thermally composited while maintaining a certain temperature of 60°C-150°C, and the PP film is removed; the thickness of the resulting composite positive electrode sheet is 130μm-180μm, of which the thickness of the solid electrolyte layer is 8μm-12μm.

[0075] The thickness of the composite positive electrode sheet can be specifically selected to be 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, etc. The thickness of the solid electrolyte layer can be specifically selected to be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc. The thickness values ​​listed above are only examples and are not limiting.

[0076] In specific applications, the preparation steps of the negative electrode sheet are: mixing graphite, binder CMC, and conductive agent Super-P in a mass ratio of 95:3:2, adding solvent deionized water to form a slurry, and then coating and drying to form a negative electrode sheet.

[0077] After the second injection, the cell was left to stand at room temperature for 24 hours (12 to 36 hours) before volume separation to obtain finished battery A1. Batteries A2 to A10 were prepared in the same manner.

[0078] For comparison, the battery without the positive electrode solid electrolyte layer was named Battery B (the other processes were the same as Battery A1), the battery without the secondary injection was named Battery C (the total injection was the same as Battery A1), and the battery without the positive electrode solid electrolyte layer and the secondary injection strategy was named Battery D.

[0079] In some embodiments, the mass of the first film-forming agent is m 11 ;

[0080] The mass of the second film-forming agent is m 21 ;

[0081] And satisfied,

[0082]

[0083] In some preferred embodiments, m1>m2.

[0084] In a specific application, the percentage of the mass of the first electrolyte to the total electrolyte can be selected as 0.5, 0.6, 0.7, 0.8, etc. The above values ​​are only examples and are not limiting.

[0085] In a specific application, taking the total mass of the first film-forming agent and the second film-forming agent as 1, the mass of the second film-forming agent can be selected to be 0.6, 0.7, 0.8, 0.9, etc.

[0086] The advantage of such a setting is to prevent the negative electrode SEI film from being too thick, resulting in an increase in the internal resistance of the battery.

[0087] In some preferred embodiments, the first solvent includes ethylene carbonate, ethyl methyl carbonate, and ethyl acetate;

[0088] In some preferred embodiments, the second solvent is the same as the first solvent.

[0089] In some embodiments, the solid electrolyte layer includes at least one of halide solid electrolytes, sulfide solid electrolytes, and oxide solid electrolytes.

[0090] In some embodiments, the halide solid electrolyte includes at least one of chloride, bromide, and iodide solid electrolytes;

[0091] In some embodiments, the sulfide solid electrolyte includes at least one of vitreous sulfides, glass-ceramic sulfides, and crystalline sulfide solid electrolytes;

[0092] In some embodiments, the oxide solid electrolyte includes at least one of fluorite-type oxides, perovskite-structured oxides, lithium lanthanum zirconium oxides, lithium lanthanum titanium oxides, and lithium aluminum titanium phosphorus oxides;

[0093] In specific applications, the halide solid electrolyte can be selected from: Li2CdC l4 , Li2MgC l4 , Li2Cd I4 , Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Br x (where 0 < x < 1) and the like.

[0094] In specific applications, the sulfide solid electrolyte can be selected from: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li(Ge 0.5 Sn 0.5 )P2S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP2S 12 (LGPS), Li6PS5X (wherein X is Cl, Br or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 、Li 10 SiP2S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 、 (1-x) P2S 5-x At least one of Li2S (wherein 0.5≤x≤0.7).

[0095] In specific applications, the oxide solid electrolyte can be selected from: perovskite type, garnet type, LISICON type, NASICON type, wherein the perovskite type solid electrolyte material is preferably LLTO (lithium lanthanum titanate / lithium lanthanum titanate, Li 0.33 La 0.56 TiO3), the garnet-type solid electrolyte material is preferably LLZO (lithium zirconium oxide / lithium lanthanum zirconate, Li7La3Zr2O 12 ), NASICON (sodium super ion conductor) type solid electrolyte material is preferably lithium titanium aluminum phosphate

[0096] LATPLi 1.3 Al 0.3 Ti 1.7 (PO4)3) at least one.

[0097] In some embodiments, the composite positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material, a positive electrode conductor, and a positive electrode binder.

[0098] In specific applications, the positive electrode active material can include any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron manganese phosphate, or a lithium-rich manganese-based material. The above are all common positive electrode active materials in the field and are only examples and not limitations.

[0099] In specific applications, the positive electrode conductive agent may include any conductive material as long as it does not cause chemical changes. Conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. The above are all common conductive agents in the art, which are only examples and not limitations.

[0100] In specific applications, the positive electrode binder may include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), polyvinyl alcohol, polyacrylic acid, polyethylene glycol, polyethylene oxide, poly(p-phenylene oxide), poly(methyl methacrylate), polyacrylonitrile, or polyvinyl chloride (PVC). The above are all common binders in the art and are only examples and not limitations.

[0101] The separator includes one or more of a polyolefin separator, a coated polyester film, a cellulose film, a polyimide film and a polyamide film, a spandex or aramid film, a non-woven fabric separator, and an inorganic nano solid electrolyte layer.

[0102] In some embodiments, the negative electrode includes a negative electrode active material, a negative electrode conductor, and a negative electrode binder.

[0103] In some embodiments, the negative electrode active material includes at least one of graphite, a composite material of single crystal silicon and graphite, soft carbon, and hard carbon.

[0104] In specific applications, the negative electrode conductive agent may include any conductive material as long as it does not cause chemical changes. Conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. The above are all common conductive agents in the art and are only examples and not limitations.

[0105] In specific applications, non-limiting examples of negative electrode binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0106] The positive electrode binder can improve the bonding between the positive electrode active material particles and also improve the bonding between the positive electrode material layer and the positive electrode current collector; the negative electrode binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector.

[0107] The embodiments of the present invention will be described in detail below through examples and comparative examples. All examples and comparative examples are groups of semi-solid-state battery samples prepared using the same process, with 20 samples in each group.

[0108] Example 1:

[0109] 1. Preparation of composite positive electrode:

[0110] Preparation of the positive electrode layer: lithium manganese oxide, binder PVDF, and conductive agent Super-P were mixed in a mass ratio of 95:3:2, and solvent NMP was added to form a slurry. After coating and drying, a positive electrode sheet was formed;

[0111] Preparation of solid electrolyte layer: LiOH·H2O, Al2O3, TiO2, and NH4H2PO4 were mixed and ball-milled according to the stoichiometric ratio for 10 h, and the obtained powder was heated at 800℃ in a muffle furnace for 12 h to obtain the target product Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP);

[0112] According to a certain ratio, Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) was mixed with PVDF and deionized water to form a slurry, which was then coated on the surface of the PP film and dried;

[0113] The positive electrode sheet was brought into close contact with LATP under a certain pressure, and the temperature was maintained at 120°C to thermally composite the two, and remove the PP film; the resulting composite positive electrode sheet had a thickness of 150 μm, of which the solid electrolyte layer had a thickness of 10 μm.

[0114] Preparation of negative electrode:

[0115] Graphite, binder CMC, and conductive agent Super-P are mixed in a mass ratio of 95:3:2, and deionized water is added as a solvent to form a slurry, which is then coated and dried to form a negative electrode sheet.

[0116] Assembling dry cells:

[0117] The composite positive electrode, separator and negative electrode are combined to form a dry battery cell;

[0118] Inject electrolyte:

[0119] One injection: inject m1 g of the first electrolyte into the dry cell; the first electrolyte includes a first solvent and a first film-forming agent; the first film-forming agent includes ethylene carbonate VC and methylene disulfonate MMDS; the mass of the first film-forming agent is m 11 In the first film-forming agent, the mass ratio of ethylene carbonate VC and methylene disulfonate MMDS is 6:1; the first solvent is a product obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) in a mass ratio of EC:EMC:EA=30:60:10;

[0120] After the first injection, the battery cell is sequentially soaked, formed and aged;

[0121] S4.3, Secondary electrolyte injection: Inject m2g of the second electrolyte into the aged cell; the first electrolyte includes a second film-forming agent and a second solvent;

[0122] The second film-forming agent includes ethylene carbonate VC and methylene disulfonate MMDS; the mass of the second film-forming agent is m 21 In the second film-forming agent, the mass ratio of ethylene carbonate VC and methylene disulfonate MMDS is 5:1; the second solvent is a product obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) in a mass ratio of EC:EMC:EA=30:60:10;

[0123] Preparation of semi-solid batteries:

[0124] After the secondary liquid injection, the battery cell was left to stand at room temperature for 24 hours and then the capacity was divided to obtain a semi-solid-state battery, numbered A1.

[0125] In this embodiment, the mass ratio of the first electrolyte to the total electrolyte is 70%, and the mass ratio of the second electrolyte to the total electrolyte is 30%.

[0126] In this embodiment, the mass proportion of the first film-forming agent in the first film-forming agent and the second film-forming agent is 50%.

[0127] Example 2: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the mass ratio of the first electrolyte to the total electrolyte is 60%. In this example, the semi-solid-state battery is numbered A2.

[0128] Example 3: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the mass ratio of the first electrolyte to the total electrolyte is 80%. In this example, the semi-solid-state battery is numbered A3.

[0129] Example 4: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the first film-forming agent accounts for 40% of the total mass of the first and second film-forming agents. In this example, the semi-solid-state battery is numbered A4.

[0130] Example 5: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the first film-forming agent accounts for 60% of the total mass of the first and second film-forming agents. In this example, the semi-solid-state battery is numbered A5.

[0131] Example 6: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the first film-forming agent accounts for 70% of the total mass of the first and second film-forming agents. In this example, the semi-solid-state battery is numbered A6.

[0132] Example 7: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that the thickness of the solid electrolyte layer is 8 μm. In this example, the semi-solid-state battery is numbered A7.

[0133] Example 8: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that in this example, the thickness of the solid electrolyte layer is 12 μm. In this example, the semi-solid-state battery is numbered A8.

[0134] Example 9: The process for preparing a semi-solid-state battery in this example is substantially the same as that in Example 1, with the only difference being that the thickness of the solid electrolyte layer in this example is 14 μm. In this example, the semi-solid-state battery is numbered A9.

[0135] Example 10: The process for preparing a semi-solid-state battery in this example is basically the same as that in Example 1, except that in this example, the solid electrolyte layer in the composite positive electrode is Li7La3Zr2O 12 (LLZO). In this embodiment, the semi-solid-state battery is numbered A10.

[0136] Comparative Example 1: The process for preparing the semi-solid-state battery in this comparative example is basically the same as that in Example 1, with the only difference being the positive electrode preparation method.

[0137] In this comparative example, the specific steps for preparing the positive electrode are as follows:

[0138] Lithium manganate, binder PVDF, and conductive agent Super-P were mixed in a mass ratio of 95:3:2, and solvent NMP was added to form a slurry, which was then coated and dried to form a positive electrode.

[0139] In this comparative example, the semi-solid-state battery is numbered B.

[0140] Comparative Example 2: The process for preparing a semi-solid-state battery in this comparative example is basically the same as that in Example 1, with the only difference being the injection method. This comparative example uses a single injection. The specific injection steps are:

[0141] Injecting m1 g of a first electrolyte and m2 g of a second electrolyte into the dry cell; the first electrolyte includes a first solvent and a first film-forming agent; the first film-forming agent includes ethylene carbonate VC and methylene disulfonate MMDS; the first electrolyte includes a second film-forming agent and a second solvent;

[0142] The mass of the first film-forming agent is m 11 In the first film-forming agent, the mass ratio of ethylene carbonate VC and methylene disulfonate MMDS is 6:1; the first solvent is a product obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) in a mass ratio of EC:EMC:EA=30:60:10;

[0143] The second film-forming agent includes ethylene carbonate VC and methylene disulfonate MMDS; the mass of the second film-forming agent is m 21 ; In the second film-forming agent, the mass ratio of ethylene carbonate VC and methylene disulfonate MMDS is 5:1; the second solvent is the product obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) in a mass ratio of EC:EMC:EA=30:60:10.

[0144] In this comparative example, the semi-solid-state battery is numbered C.

[0145] Comparative Example 3: The process for preparing the semi-solid-state battery in this comparative example is basically the same as that in Example 1, except that: in this comparative example, the liquid injection method is the same as that in Comparative Example 3, and the positive electrode preparation method is the same as that in Comparative Example 2.

[0146] In this comparative example, the semi-solid-state battery is numbered D.

[0147] The main parameters of the semi-solid-state batteries of Examples 1-10 and Comparative Examples 1-3 are shown in the following table:

[0148]

[0149] A total of 13 groups of samples, including Example 1 to Example 10 and Comparative Example 1 to Comparative Example 3, were tested as follows. All test results were averaged, and some results were rounded off.

[0150] DCR test;

[0151] Discharge DCR test: At room temperature of 25℃±2℃, pre-discharge the battery to 50% SOC. While the battery is in the discharged state, draw a DC current from the test object at a test current of 3C for 10s, and measure the voltage drop at this current.

[0152] The voltage value V1 at the start of discharge and the voltage value V2 at the end of discharge are recorded.

[0153] Calculate discharge DCR = (V1-V2) / I.

[0154] Charging DCR test:

[0155] At room temperature (25°C ± 2°C), precharge the battery to 50% SOC. While the battery is charging, apply a DC current to the device under test at a test current of 3C for 10 seconds, and measure the voltage drop at this current. Calculate the DC resistance of the device under test using Ohm's law: R = U / I (where R is resistance, U is voltage drop, and I is test current).

[0156] First discharge capacity test:

[0157] At room temperature (25°C), the fully charged battery was discharged at a constant current of 1 / 3C to a cut-off voltage of 3.0V to obtain the initial discharge capacity.

[0158] 45℃, 1C cycle 200 times capacity retention test:

[0159] At 45°C, charge at 1C to a cutoff voltage of 4.25V. Switch to constant voltage charging to a cutoff current of 0.05C, let stand for 0.5h, then discharge at 1C to a cutoff voltage of 3.0V. Let stand for 0.5h before entering the next charge-discharge cycle. Repeat this cycle for a total of 200 charge-discharge cycles. Capacity retention = discharge capacity after 200 cycles / initial discharge capacity.

[0160] Capacity retention test after 7 days storage at 55°C:

[0161] ① Fully charge the battery at room temperature using a standard charging method; discharge at 1C to the final discharge voltage, and calculate the remaining capacity, which is the initial capacity C0; Fully charge the battery at room temperature using a standard charging method;

[0162] ②Store at 55±2℃ for 7 days;

[0163] ③ After standing at room temperature for 5 hours, discharge at 1C to the final discharge voltage and calculate the remaining capacity C1;

[0164] Standard: 55°C 7-day high-temperature storage capacity recovery rate (%) = C1*100% / C0.

[0165] Capacity recovery rate test after 7 days storage at 55°C:

[0166] ① Fully charge the battery at room temperature using a standard charging method; discharge at 1C to the final discharge voltage, and calculate the remaining capacity, which is the initial capacity C0; Fully charge the battery at room temperature using a standard charging method;

[0167] ②Store at 55±2℃ for 7 days;

[0168] ③ After standing at room temperature for 5 hours, discharge at 1C to the final discharge voltage and calculate the remaining capacity C1;

[0169] ④ Then charge the battery using the standard charging method until it is fully charged, and then perform a discharge test, recording the discharge capacity, which is recorded as C2;

[0170] Standard: 55°C 7-day high-temperature storage capacity recovery rate (%) = (C2-C1)*100% / (C0-C1).

[0171] 55℃ storage for 7 days discharge DCR growth rate test:

[0172] ① Test the battery's discharge DCR at 25°C, recorded as R0; fully charged using the standard charging method at room temperature

[0173] ②Store at 55±2℃ for 7 days;

[0174] ③After standing at room temperature for 5 hours, test the battery’s discharge DCR, which is recorded as R1;

[0175] Standard: Discharge DCR growth rate = (R1-R0)*100% / R0.

[0176] The comparative test results are shown in the following table:

[0177]

[0178]

[0179] According to the above table, compared with comparative example 1, embodiment 1 of the present invention has a capacity retention rate of more than 90.0% after 200 cycles at 1C at 45°C; the capacity retention rate of 1 / 3C high-temperature discharge at 55°C is as high as 98.2%; after 7 days of high-temperature storage at 55°C, it also has an ideal capacity retention rate (89.2%), capacity recovery rate (93.3%) and discharge DCR growth rate (19.0%). The reason is that both the first electrolyte and the second electrolyte contain VC and MMDS. First, it is beneficial for VC and MMDS to cooperate to form a more stable, more uniform and dense SEI film. To prevent it from being destroyed in a high-temperature environment, the film layer formed by the decomposition products of MMDS and VC is intertwined, which reduces the porosity of the film, better prevents the electrolyte from contacting the electrode, and inhibits side reactions. Secondly, it is conducive to the continuous formation of an SEI film with the same or similar composition. The SEI film can effectively prevent the Mn ions dissolved at high temperature from being adsorbed on the negative electrode surface, inhibit the impedance increase, and improve the cycle performance.

[0180] Compare Example 1 with Comparative Examples 2, 3, and 4:

[0181] The DCRs of batteries B and C during charge and discharge are both lower than those of battery D, indicating that the addition of the solid electrolyte layer and secondary film formation do not increase the battery's internal resistance. Battery A also exhibits the lowest DCR, demonstrating the effectiveness of the synergistic effect of the positive electrode solid electrolyte layer and secondary injection in reducing the battery's internal resistance. This is because the solid electrolyte membrane acts as a bridge between the positive and negative electrode active materials and the electrolyte (promoting lithium ion transport). Furthermore, the presence of a solid electrolyte layer on the positive electrode prevents direct contact between the MMDS and the positive electrode, effectively reducing additive film formation at the positive electrode and lowering battery impedance.

[0182] At 45°C and 1C rate, semi-solid-state battery A has the best capacity retention rate (capacity retention rate is as high as 90.0% after 200 cycles). Under the same conditions, the capacity retention rates of battery B and battery C are 87.6% and 87.3%, respectively, both higher than battery D (81.9%). At this time, the positive electrode solid electrolyte layer can effectively improve the cycle interface stability. At the same time, the secondary film-forming additives continuously modify the damaged negative electrode SEI film during the cycle process, ensuring the stable operation of the battery at high temperature.

[0183] Battery A has the best high-temperature discharge capacity retention rate (98.2%), while the corresponding capacity retention rates of Battery B and Battery C are 97.8% and 97.6% respectively, while the capacity retention rate of Battery D, which is not installed with a solid electrolyte layer and has not undergone secondary film formation, is only 96.3%.

[0184] After high-temperature storage, battery A has the most ideal capacity retention rate (89.2%), capacity recovery rate (93.3%) and discharge DCR growth rate (19.0%). The reason is that the positive electrode solid electrolyte layer has a good modification of the solid-liquid interface, which can reduce the occurrence of interfacial side reactions and improve high-temperature storage performance. At the same time, the secondary formed negative electrode SEI film has better film formation quality, which greatly improves its stability in high-temperature environments.

[0185] It should be pointed out that the above 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 in the scope of protection of the present invention.

Claims

1. A semi-solid-state battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: A solid electrolyte layer is provided on the surface of the positive electrode close to the electrolyte; The electrolyte includes a film-forming agent ethylene carbonate and a film-forming agent methylene disulfonate.

2. The semi-solid-state battery according to claim 1, characterized in that In the electrolyte, the total mass proportion of the ethylene carbonate and the methylene disulfonate is 3% to 8%.

3. The semi-solid-state battery according to any one of claims 1 or 2, characterized in that: In the electrolyte, the mass proportion of the methylene disulfonate is 0.01% to 1%.

4. The semi-solid-state battery according to claim 1, characterized in that The thickness of the solid electrolyte layer is 8 μm to 12 μm.

5. The semi-solid-state battery according to claim 1, characterized in that The solid electrolyte layer includes an oxide solid electrolyte.

6. The semi-solid-state battery according to claim 5, characterized in that The oxide solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, and lithium aluminum titanium phosphate.

7. A method for preparing a semi-solid-state battery according to claim 1, characterized in that: The steps include: S1. Preparing a composite positive electrode: preparing a positive electrode layer and a solid electrolyte layer respectively, and thermally combining the positive electrode layer and the solid electrolyte layer to form a composite positive electrode; S2, preparing the negative electrode; S3, forming a dry battery cell by combining the composite positive electrode, separator, and negative electrode; S4. Inject electrolyte: S4.

1. Primary injection: inject ml g of a first electrolyte into the dry cell; the first electrolyte comprises a first solvent and a first film-forming agent; The first film-forming agent includes ethylene carbonate and methylene disulfonate; S4.

2. After the first injection, the battery cell is sequentially soaked, formed, and aged; S4.3, Secondary electrolyte injection: Inject m2g of the second electrolyte into the aged cell; the first electrolyte includes a second film-forming agent and a second solvent; The second film-forming agent includes ethylene carbonate and methylene disulfonate; S4.

4. After the second injection is completed, let it stand and separate the volume to obtain a semi-solid-state battery.

8. The preparation method according to claim 7, characterized in that The mass of the first film-forming agent is m 11 ; The mass of the second film-forming agent is m 21 ; And satisfied, 9. The preparation method according to claim 7, characterized in that m1>m2.

10. The method according to claim 7, characterized in that The first solvent includes ethylene carbonate, ethyl methyl carbonate and ethyl acetate; The second solvent is the same as the first solvent.

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