Lithium manganate battery and preparation method thereof

Abstract

The invention discloses a lithium manganate battery and a preparation method thereof. The lithium manganate battery comprises a positive plate, a diaphragm, a negative plate and a functional diaphragm, the functional diaphragm comprises CaO2 and a multi-dimensional conductive carbon material; the functional diaphragm is arranged between the positive plate and the diaphragm, and / or the functional diaphragm is arranged between the negative plate and the diaphragm, HF in an electrolyte is consumed through alkaline compounds in the functional diaphragm, dissolution of manganese in the positive electrode is reduced, but interface impedance can be increased through an interface layer composed of the independent alkaline compounds, so that the performance of the lithium ion battery is improved, and the service life of the lithium ion battery is prolonged. Therefore, in combination with the multi-dimensional conductive material, the porous structure of the multi-dimensional conductive material can adsorb and intercept the dissolved manganese, and meanwhile, the alkaline compound material can be uniformly distributed in a conductive pore channel, so that the damage to the negative electrode is reduced, and the high-temperature cycle and high-temperature storage performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium-ion battery technology, and in particular to a lithium manganese oxide battery and its preparation method. Background Technology

[0002] With the development and advancement of technology, lithium-ion batteries are increasingly widely used in power, energy storage, and 3C (computers, communications, and consumer electronics) fields. The market demand for higher energy density in lithium-ion batteries is growing, making the adoption of high-energy-density positive and negative electrodes, reducing the proportion of inactive materials, and using thicker electrodes the main development directions in this field. Lithium manganese oxide batteries have attracted industry attention due to their cost and safety advantages, but their poor high-temperature cycle performance and storage performance limit their large-scale commercial application. The main reason is the gradual dissolution of manganese in lithium manganese oxide materials, especially under high-temperature conditions, where the negative effects of dissolution are more pronounced. Therefore, effective suppression of manganese is a necessary condition for the widespread application of lithium manganese oxide batteries.

[0003] Therefore, the industry urgently needs a better way to solve the above problems. Summary of the Invention

[0004] In view of this, the present invention designs a functional membrane of CaO2 composite multidimensional conductive carbon material. The alkaline compound in the functional membrane can consume HF in the electrolyte and reduce the dissolution of manganese from the positive electrode. However, the interface layer composed of alkaline compound alone will increase the interface impedance. Therefore, by combining it with multidimensional conductive material, its porous structure can also adsorb and retain the dissolved manganese. At the same time, the alkaline compound material can be evenly distributed in the conductive channels, thereby reducing the damage to the negative electrode and improving the high-temperature cycling and high-temperature storage performance of the battery.

[0005] The technical solution of the present invention is as follows: The first aspect of this invention discloses a lithium manganese oxide battery, which includes a positive electrode, a separator, a negative electrode, and a functional separator. The functional membrane comprises CaO2 and multidimensional conductive carbon material; The functional diaphragm is disposed between the positive electrode plate and the diaphragm, and / or, The functional diaphragm is disposed between the negative electrode and the diaphragm.

[0006] Preferably, in the functional diaphragm, the mass ratio of CaO2 to the multidimensional conductive carbon material is (5~30):(70~95).

[0007] Preferably, the multidimensional conductive carbon material includes at least one of carbon nanofiber membrane, graphene carbon membrane, and porous carbon paper.

[0008] Preferably, the thickness of the functional diaphragm is 100μm~150μm.

[0009] Preferably, the functional diaphragm includes a first pore with a pore size of 5μm to 10μm.

[0010] Preferably, the functional diaphragm further includes a second pore, the pore size of which is 100nm~500nm.

[0011] A second aspect of this invention discloses a method for preparing a lithium manganese oxide battery, including the step of preparing a functional separator, wherein the preparation of the functional separator includes: S1. Dissolve the film-forming agent and CaO2 in the solvent and stir to form a homogeneous solution; S2. Add the multidimensional conductive carbon material to the homogeneous solution obtained in S1 in two batches, and then place it in a constant temperature oil bath for stirring and cooling before taking it out. S3. The mixed material prepared in S2 is coated onto the substrate to form a liquid film and placed in a water bath. After curing and stabilizing the film, it is removed. S4, Drying; S5, pre-oxidation and calcination, to obtain a functional diaphragm.

[0012] Preferably, in step S1, the mass ratio of film-forming agent, CaO2, and solvent is (1~5):(1~5):(30~35). Preferably, step S5 includes: The product dried in step S4 is pre-oxidized in air at 200℃~300℃ for 1h~3h; then the pre-oxidized product is calcined in an inert atmosphere at 600℃~800℃ for 0.5h~3h.

[0013] A third aspect of the present invention discloses a battery device, including a lithium manganese oxide battery as described in claims 1 to 6.

[0014] The advantages of this invention are as follows: This invention reduces manganese dissolution from the positive electrode by consuming HF in the electrolyte through an alkaline compound in the functional separator. However, the interfacial layer composed solely of alkaline compounds increases interfacial impedance. Therefore, combining it with a multidimensional conductive material, whose porous structure can also adsorb and retain the dissolved manganese, while the alkaline compound material can be uniformly distributed in the conductive channels, thereby reducing damage to the negative electrode and improving the battery's high-temperature cycling and high-temperature storage performance. The functional separator of this invention is simple to prepare and has mass production feasibility; it can be applied to existing mature lithium-ion battery production processes and has the potential for large-scale production. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a split view of the battery cell structure according to Embodiment 1 of the present invention; Figure 2 This is a split view of the battery cell structure according to Embodiment 2 of the present invention; Figure 3 This is a microstructure diagram of the functional diaphragm in embodiments 1-2 of the present invention, wherein, Figure 3 The left image (a) is a screenshot of the functional diaphragm. Figure 3 The right figure (b) in the figure is a skeletal structure diagram of the functional diaphragm. Detailed Implementation

[0017] 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.

[0018] 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 and claims of this invention are intended to cover non-exclusive inclusion.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] It should be noted that, for ease of description, all identical technical features are labeled with the same symbols in the following embodiments.

[0023] Lithium manganese oxide batteries have attracted attention in the lithium-ion battery industry due to their cost and safety advantages, but their poor high-temperature cycle performance and storage performance limit their large-scale commercial application. The main reason is the gradual dissolution of manganese from the lithium manganese oxide material, especially under high-temperature conditions where the negative effects of dissolution are more pronounced. Therefore, effective suppression of manganese is a necessary condition for the widespread application of lithium manganese oxide batteries.

[0024] To address the above problems, this invention proposes a technical solution.

[0025] The first aspect of this invention discloses a lithium manganese oxide battery, comprising a positive electrode, a separator, a negative electrode, and a functional separator; Functional membranes include CaO2 and multidimensional conductive carbon materials; A functional separator is disposed between the positive electrode and the separator, and / or, A functional diaphragm is disposed between the negative electrode plate and the diaphragm.

[0026] This invention reduces the dissolution of manganese from the positive electrode by consuming HF in the electrolyte through alkaline compounds in the functional membrane. However, the interfacial layer composed of alkaline compounds alone will increase the interfacial impedance. Therefore, by combining it with multidimensional conductive materials, the porous structure of which can also adsorb and retain the dissolved manganese, and the alkaline compound materials can be evenly distributed in the conductive channels, thereby reducing damage to the negative electrode and improving the high-temperature cycling and high-temperature storage performance of the battery.

[0027] In practical applications, the functional separator can be disposed only between the positive electrode and the separator, or only between the negative electrode and the separator. As a third option, functional separators can be disposed between both the positive electrode and the separator, and between both the negative electrode and the separator. Those skilled in the art can implement this freely according to actual needs.

[0028] In some embodiments, in the functional diaphragm, with the total mass of CaO2 and multidimensional conductive carbon material as 100, the mass of CaO2 accounts for 5% to 30% of the total mass, and the mass of multidimensional conductive carbon material accounts for 70% to 95% of the total mass.

[0029] In specific applications, the mass percentage of CaO2 in the functional diaphragm can be selected as 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, etc., and the mass percentage of the multidimensional conductive carbon material can be selected as 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, etc. The values ​​listed above are examples and not limitations. Within the above ranges, as long as the sum of the ratios of the mass percentage of CaO2 to the mass percentage of the multidimensional conductive carbon material equals 100%, those skilled in the art can freely implement the design.

[0030] In some embodiments, the mass ratio of CaO2 to multidimensional conductive carbon material in the functional diaphragm is (5~30):(70~95).

[0031] In specific applications, the mass ratio of CaO2 to the multidimensional conductive carbon material can be selected as 1:19, 2:23, 1:9, 3:17, 1:4, 3:7, etc.; the numerical ratios listed above are merely examples and are not limitations. Within the scope of understanding of those skilled in the art, any ratio within the range of (5~30):(70~95) can be freely implemented, as long as the sum of the ratios of the mass percentage of CaO2 to the mass percentage of the multidimensional conductive carbon material equals 100%.

[0032] In some embodiments, the multidimensional conductive carbon material includes at least one of carbon nanofiber membranes, graphene carbon membranes, and porous carbon paper.

[0033] The term "at least one" in this invention means that one of the elements listed above can be selected as the technical solution, or a mixture of two or more elements can be selected as the technical solution. Without exceeding the understanding of those skilled in the art, those skilled in the art can select appropriate elements based on the actual situation.

[0034] In some embodiments, the thickness of the functional diaphragm is 100 μm to 150 μm.

[0035] In practical applications, the thickness of the functional diaphragm can be selected from 100μm, 102μm, 105μm, 108μm, 110μm, 112μm, 115μm, 118μm, 120μm, 125μm, 128μm, 130μm, 135μm, 138μm, 140μm, 142μm, 145μm, 148μm, 150μm, etc. The numerical ratios listed above are merely examples and not limitations. Those skilled in the art can freely implement any value within the range of 100μm to 150μm without exceeding their understanding.

[0036] In some embodiments, the functional diaphragm includes a first pore with a pore size of 5 μm to 10 μm.

[0037] In practical applications, the pore size of the first aperture can be selected as 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, etc. The numerical ratios listed above are merely examples and not limitations. Within the scope of understanding of those skilled in the art, any value within the range of 5μm to 10μm can be freely implemented.

[0038] In some embodiments, the functional diaphragm further includes a second pore with a pore size of 100 nm to 500 nm.

[0039] In practical applications, the aperture of the second hole can be selected as 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc. The numerical ratios listed above are merely examples and are not limitations. Without exceeding the understanding of those skilled in the art, they are free to implement any value within the range of 100nm to 500nm.

[0040] A second aspect of this invention discloses a method for preparing a lithium manganese oxide battery, including the step of preparing a functional separator, wherein the preparation of the functional separator includes: S1. Dissolve the film-forming agent and CaO2 in the solvent and stir for 10 min to 60 min to form a homogeneous solution; the mass ratio of film-forming agent, CaO2 and solvent is (1~5):(1~5):(30~35); the stirring time and the mass ratio of film-forming agent, CaO2 and solvent in this step can be selected according to the actual situation, as long as they do not exceed the above range.

[0041] S2. Add the multidimensional conductive carbon material to the homogeneous solution obtained in S1 in two batches, and place it in a constant temperature oil bath at 60℃~100℃ and stir for 8h~16h. Then cool it to room temperature and remove it. In specific applications, the multidimensional conductive carbon material can be divided into two equal parts and added to the homogeneous solution sequentially. In this step, the temperature of the constant temperature oil bath and the stirring time can be selected according to the actual situation, as long as they do not exceed the above range.

[0042] S3. The mixed material prepared in S2 is coated onto a substrate glass plate to form a liquid film of 100μm-150μm and placed in a water bath. After curing and stabilizing for 20h-30h, it is removed. In this step, the thickness of the liquid film can be arbitrarily selected within the range of 100μm-150μm, and the stabilization time after curing can be arbitrarily selected from 20h to 30h.

[0043] S4. First dry in air for 12h~48h, then vacuum dry at 70℃~100℃ for 2h~6h. This step includes two drying processes. The drying time for the first drying can be arbitrarily selected within the range of 12h~48h, and the drying temperature and duration for the second drying can be arbitrarily selected within the range of 70℃~100℃ and arbitrarily selected within the range of 2h~6h.

[0044] S5. The functional diaphragm is successfully prepared by pre-oxidation at 200℃~300℃ for 1h~3h in a muffle furnace at a heating rate of 2℃ / min~5℃ / min, followed by calcination at 600℃~800℃ for 0.5h~3h in an inert atmosphere at a heating rate of 3℃ / min~5℃ / min. In this step, the heating rate in the muffle furnace can be freely selected within the range of 2℃ / min~5℃ / min, and the pre-oxidation temperature and time can be freely selected based on actual conditions, as long as they do not exceed the above ranges. The heating rate in the tube furnace can be freely selected within the range of 3℃ / min~5℃ / min, the calcination temperature can be arbitrarily selected within the range of 600℃~800℃, and the calcination time can be arbitrarily selected within the range of 0.5h~3h. In this invention, the inert atmosphere refers to any one of argon, nitrogen, or helium selected to provide the calcination atmosphere for the functional diaphragm.

[0045] In some embodiments, step S2 involves adding the multidimensional conductive carbon material to the homogeneous solution obtained in step S1 in two separate steps to make it more uniformly dispersed in the mixed solution; ultimately, it can also be uniformly distributed in the finished carbon film.

[0046] In some embodiments, the substrate in step S3 is a glass plate.

[0047] In some embodiments, step S3 further includes coating the mixed material prepared in step S2 onto a glass plate to form a liquid film, and then placing it in water for 5 to 10 minutes; then covering the other side of the liquid film with another glass plate to clamp the formed liquid film and then curing it to stabilize it for 20 to 30 hours. In this step, the time for placing the liquid film in water can be arbitrarily selected within the range of 5 to 10 minutes, and the stabilization time after curing can be arbitrarily selected from 20 to 30 hours.

[0048] In some implementations, the water bath temperature in step S3 is room temperature; specifically, any temperature value can be selected within the range of 20°C to 30°C.

[0049] In some implementations, step S4 involves two drying processes: First, air drying removes free solvent from the surface through natural evaporation, preventing solvent residue from causing structural collapse during subsequent processing. Direct high-temperature or vacuum drying may cause stress concentration due to rapid solvent evaporation, leading to membrane cracking or curling. Second, vacuum drying lowers the boiling point of the solvent, thoroughly removing residual solvent and moisture from the membrane and preventing solvent leakage and contamination during subsequent applications (such as solvent residue in electrolyte batteries causing side reactions). Furthermore, by reducing the gas phase pressure, the capillary force on the pore walls during solvent evaporation is reduced, thereby maintaining the integrity of the porous structure (especially crucial for nanoscale pores).

[0050] In some embodiments, step S5 involves two calcinations. The pre-oxidation calcination is the "shaping" stage, where chemical cross-linking fixes the macroscopic morphology, transforming its linear molecular chains into a stable structure and preventing melting and decomposition during carbonization, which could lead to the collapse of the pore structure. Carbonization is the "carbonization" stage, where non-carbon elements are removed, and the functional properties of the carbon material (conductivity, adsorption, etc.) are obtained through high-temperature pyrolysis.

[0051] In practical applications, the functional separator can be disposed only between the positive electrode and the separator, or only between the negative electrode and the separator. As a third option, functional separators can be disposed between both the positive electrode and the separator, and between both the negative electrode and the separator. Those skilled in the art can implement this freely according to actual needs.

[0052] In some embodiments, the lithium manganese oxide battery prepared by the present invention further includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector. The positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes lithium manganese oxide.

[0053] In some embodiments, the positive current collector may be aluminum (Al) foil, but is not limited thereto.

[0054] In some embodiments, the positive electrode active layer includes a positive electrode binder. The positive electrode binder can improve the bonding between the positive electrode active material particles and also improve the bonding between the positive electrode active layer and the positive electrode current collector.

[0055] In some embodiments, non-limiting examples of positive electrode binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0056] In some embodiments, the positive electrode active layer includes a positive electrode conductive agent, thereby imparting conductivity to the electrode. The positive electrode conductive agent may include any conductive material, as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0057] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, wherein the negative electrode active layer includes a negative electrode active material.

[0058] In this invention, the specific type of negative electrode active material is not specifically limited and can be selected according to requirements. Specifically, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. Crystalline carbon can be amorphous or flake-shaped, small flake-shaped, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, etc.

[0059] In some embodiments, elemental metals and metal compounds may also be selected as negative electrode active materials, such as compounds containing metals or metalloids such as Li, Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, and Zn.

[0060] In some embodiments, the negative electrode active layer may include a negative electrode binder; 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.

[0061] In some embodiments, non-limiting examples of negative electrode binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0062] In some embodiments, the negative electrode active layer can be obtained by coating a negative electrode slurry onto a negative electrode current collector and then performing operations such as drying. The negative electrode slurry includes at least a negative electrode active material and a negative electrode binder. When an aqueous solvent is used as the liquid medium for forming the negative electrode slurry, a thickener is preferably used for slurry formation. The thickener is typically used to adjust the viscosity of the slurry.

[0063] In some embodiments, the aforementioned thickener may be one or more of the following: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and their salts, etc.

[0064] In some embodiments, the mass percentage of the thickener in the negative electrode slurry can be 0.1%-5%, for example, 0.1%, 0.2%, 0.5%, 0.6%, 1%, 2%, 3%, 4%, 5%, etc., preferably 0.5%-3%, and more preferably 0.6%-2%.

[0065] In some embodiments, the negative electrode active layer comprises a negative electrode conductive material, thereby making the electrode conductive. The conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of negative electrode conductive materials include carbon-based materials (e.g., natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0066] In some embodiments, the negative current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0067] In this invention, the separator provides insulation protection for the positive and negative electrodes, preventing short circuits caused by contact between the positive and negative electrodes. The material and shape of the separator used in the lithium-ion battery of this invention are not particularly limited and can be any technology disclosed in the prior art.

[0068] In some embodiments, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide.

[0069] The present invention and its technical effects will be clearly and completely described below with reference to embodiments and comparative examples, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0070] It should be noted that, in order to reduce the influence of variables on the experiment, the steps for preparing the positive and negative electrode sheets in the embodiments and comparative examples of this invention are exactly the same, and the separators and electrolytes used are also exactly the same. Specifically, as follows: Step 1: Prepare the positive electrode: The positive electrode binder polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone solvent and mixed evenly to form the first positive electrode mixing system. The mixing time was 4 hours. The first positive electrode mixture system was mixed evenly with the positive electrode conductive agent superconducting carbon (Super-P) to form the second positive electrode mixture system, and the mixing time was 3 hours. The second mixing system of the positive electrode is mixed evenly with the positive electrode active material lithium manganese oxide to form a mixed positive electrode slurry, and the mixing time is 3 hours. The mixed positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil using a coating equipment. After rolling and die cutting, the positive electrode sheet is obtained; the thickness of the aluminum foil is 12 micrometers.

[0071] In step one, the mass ratio of the positive electrode active material lithium manganese oxide, the positive electrode binder polyvinylidene fluoride (PVDF), and the positive electrode conductive agent superconducting carbon (Super-P) is 96.2:1.8:2.

[0072] Step 2: Preparation of the negative electrode: The negative electrode binder polytetrafluoroethylene was added to deionized water and mixed evenly to form the first negative electrode mixing system. The mixing time was 4 hours. The first negative electrode mixing system is mixed evenly with the negative electrode conductive agent carbon black to form the second negative electrode mixing system, and the mixing time is 3 hours.

[0073] The negative electrode mixing system and the negative electrode active material graphite and the second negative electrode mixing system are mixed evenly to form a mixed negative electrode slurry, and the mixing time is 3 hours.

[0074] The mixed negative electrode slurry is coated evenly on both sides of the negative electrode current collector copper foil using a coating equipment. After rolling and die cutting, the negative electrode sheet is obtained; the copper foil thickness is 6 micrometers.

[0075] In step two, the mass ratio of the negative electrode active material graphite, the negative electrode binder polytetrafluoroethylene, and the negative electrode conductive agent conductive carbon black is 95:3:2.

[0076] Step 3, Separator Selection: In the embodiments and comparative examples of this invention, the separator is a composite ceramic separator. The base membrane is a PE separator, and a 2-micron-thick nano-alumina coating is applied to the surface of the base membrane using a coating process to form the composite ceramic separator.

[0077] Step 4, Electrolyte selection: In the embodiments and comparative examples of the present invention, the electrolyte is 1.0 M LiPF6 dissolved in a mixed solvent of EC / EMC / DEC (volume ratio 1:1:1). Example

[0078] A lithium manganese oxide battery is prepared by the following method: Preparation of functional membranes: Dissolve 1g of polyacrylonitrile and 1g of CaO2 in 30g of N,N-dimethylformamide solution and stir for 30min to form a homogeneous solution. Add 9g (4.5g each time) of multidimensional conductive carbon material graphene carbon film to the above solution twice every half hour, then place it in a 100℃ constant temperature oil bath and stir for 10 h, then cool it to room temperature. The above product was scraped into a liquid film with a thickness of 100 μm using an automatic film coating machine, and then placed in a water bath to solidify into a film after a phase inversion process.

[0079] After stabilization for 20 hours, the membrane was removed and dried in air for 30 hours, followed by vacuum drying at 100°C for 4 hours. Finally, it was pre-oxidized in a muffle furnace at 300°C with a heating rate of 5°C / min for 1.5 hours, and then calcined in a tube furnace at 800°C with Ar2 at a heating rate of 5°C / min for 1 hour, successfully producing a functional membrane. The microstructure of the prepared functional membrane is as follows: Figure 3 As shown.

[0080] In the functional membrane prepared in this embodiment, the mass percentage of CaO2 is 10%, and the mass percentage of multidimensional conductive carbon material is 90%.

[0081] Preparation of lithium manganese oxide batteries: The positive electrode sheet prepared in step one, the functional separator prepared in this embodiment, the separator selected in step three, and the negative electrode sheet prepared in step two are assembled into a bare cell using a stacking method, as shown in the figure. Figure 1 As shown. After the bare cell is tab-welded, it is placed in an aluminum-plastic film casing and packaged into a cell; after baking, it undergoes electrolyte injection, formation, and capacity testing to form a battery. Electrolyte injection involves injecting the electrolyte selected in step four into the cell.

[0082] Example 2: The process of preparing the functional separator in this embodiment is exactly the same as in Example 1. The only difference is that in this embodiment, when assembling the bare cell, the functional separator is not placed between the positive electrode and the separator, but between the negative electrode and the separator. The specific structure is as follows: Figure 2 As shown.

[0083] Example 3: The process of preparing the functional diaphragm in this embodiment is basically the same as that in Example 1. The only difference is that in the functional diaphragm of this embodiment, the mass ratio of CaO2 to multidimensional conductive carbon material is 5%:95%=1:19, and the amount of CaO2 used is 0.5g, while the amount of multidimensional conductive carbon material used is 9.5g.

[0084] The process of preparing lithium manganese oxide batteries in this embodiment is exactly the same as that in the previous embodiment.

[0085] Example 4: The process of preparing the functional membrane in this embodiment is basically the same as that in Example 1. The only difference is that in the functional membrane of this embodiment, the mass ratio of CaO2 to multidimensional conductive carbon material is 20%:80%=1:4. At this time, the amount of CaO2 used is 2g and the amount of multidimensional conductive carbon material used is 8g.

[0086] The process of preparing lithium manganese oxide batteries in this embodiment is exactly the same as that in Example 1.

[0087] Example 5: The process of preparing the functional membrane in this embodiment is basically the same as that in Example 1. The only difference is that in the functional membrane of this embodiment, the mass ratio of CaO2 to multidimensional conductive carbon material is 30%:70%=3:7. At this time, the amount of CaO2 used is 3g and the amount of multidimensional conductive carbon material used is 7g.

[0088] The process of preparing lithium manganese oxide batteries in this embodiment is exactly the same as that in Example 1.

[0089] Example 6: The process of preparing the functional diaphragm in this embodiment is basically the same as that in Example 1. The only difference is that in the functional diaphragm of this embodiment, the mass ratio of CaO2 to multidimensional conductive carbon material is 2%:98%=1:49, and the amount of CaO2 used is 0.2g, while the amount of multidimensional conductive carbon material used is 9.8g.

[0090] The process of preparing lithium manganese oxide batteries in this embodiment is exactly the same as that in Example 1.

[0091] Example 7: The process of preparing the functional membrane in this embodiment is basically the same as that in Example 1. The only difference is that in the functional membrane of this embodiment, the mass ratio of CaO2 to multidimensional conductive carbon material is 40%:60%=2:3, and the amount of CaO2 used is 4g and the amount of multidimensional conductive carbon material used is 6g.

[0092] The process of preparing lithium manganese oxide batteries in this embodiment is exactly the same as that in Example 1.

[0093] Comparative Example 1: The difference between this comparative example and Example 1 is that this example does not add a functional separator. Instead, the positive electrode sheet prepared in step one, the separator selected in step three, and the negative electrode sheet prepared in step two are directly assembled into a bare cell using a stacking method, as shown in the figure. Figure 1As shown. After the bare cell is tab-welded, it is placed in an aluminum-plastic film casing and packaged into a cell; after baking, it undergoes electrolyte injection, formation, and capacity testing to form a battery. Electrolyte injection involves injecting the electrolyte selected in step four into the cell.

[0094] Comparative Example 2: Preparation of functional diaphragms, Dissolve 1g of polyacrylonitrile and 10g of CaO2 in 30g of N,N-dimethylformamide solution and stir for 30min to form a homogeneous solution. The above product was scraped into a liquid film with a thickness of 100 μm using an automatic film coating machine, and then placed in a water bath to solidify into a film after a phase inversion process.

[0095] After stabilization for 20 hours, the membrane was removed and dried in air for 30 hours, followed by vacuum drying at 100°C for 4 hours. Finally, it was pre-oxidized in a muffle furnace at 300°C with a heating rate of 5°C / min for 1.5 hours, and then calcined in a tube furnace at 800°C with Ar2 at a heating rate of 5°C / min for 1 hour, successfully producing a functional membrane.

[0096] In the functional diaphragm of this embodiment, CaO2 accounts for 100% by mass.

[0097] Preparation of lithium manganese oxide batteries: The positive electrode sheet prepared in step one, the functional separator prepared in this embodiment, the separator selected in step three, and the negative electrode sheet prepared in step two are assembled into a bare cell using a stacking method, as shown in the figure. Figure 1 As shown. After the bare cell is tab-welded, it is placed in an aluminum-plastic film casing and packaged into a cell; after baking, it undergoes electrolyte injection, formation, and capacity testing to form a battery. Electrolyte injection involves injecting the electrolyte selected in step four into the cell.

[0098] Comparative Example 3: Preparation of functional diaphragms, Dissolve 1g of polyacrylonitrile in 30g of N,N-dimethylformamide solution and stir for 30min to form a homogeneous solution; Add 10g (5g each time) of multidimensional conductive carbon material graphene carbon film to the above solution twice every half hour, then place it in a 100℃ constant temperature oil bath and stir for 10 h, then cool to room temperature. The above product was scraped into a liquid film with a thickness of 100 μm using an automatic film coating machine, and then placed in a water bath to solidify into a film after a phase inversion process.

[0099] After stabilization for 20 hours, the membrane was removed and dried in air for 30 hours, followed by vacuum drying at 100°C for 4 hours. Finally, it was pre-oxidized in a muffle furnace at 300°C with a heating rate of 5°C / min for 1.5 hours, and then calcined in a tube furnace at 800°C with Ar2 at a heating rate of 5°C / min for 1 hour, successfully producing a functional membrane.

[0100] In the functional diaphragm of this embodiment, the multidimensional conductive carbon material graphene carbon film accounts for 100% of the mass.

[0101] Preparation of lithium manganese oxide batteries: The positive electrode sheet prepared in step one, the functional separator prepared in this embodiment, the separator selected in step three, and the negative electrode sheet prepared in step two are assembled into a bare cell using a stacking method, as shown in the figure. Figure 1 As shown. After the bare cell is tab-welded, it is placed in an aluminum-plastic film casing and packaged into a cell; after baking, it undergoes electrolyte injection, formation, and capacity testing to form a battery. Electrolyte injection involves injecting the electrolyte selected in step four into the cell.

[0102] Comparative experiment: Eleven groups of samples were taken from Examples 1-7 and Comparative Examples 1-3, with 30 samples in each group. Cyclic testing and storage testing were performed on each group, and the average of all test data was taken.

[0103] The cyclic testing (capacity retention) process is as follows: 1. Place the manganese-ion battery sample at an ambient temperature of 45±2℃ and let it stand for 5 hours. Then discharge it at a constant current of 1C to 3.0V and let it stand for 1 hour. 2. At an ambient temperature of 45±2℃, charge at 1C constant current and constant voltage until the upper limit voltage is 4.2V, cut off the current to 0.05C, and let stand for 1 hour; 3. At an ambient temperature of 45±2℃, discharge at a constant current of 1C to the lower limit voltage of 3.0V, and let stand for 1 hour; 4. Repeat steps 2-3 for 500 cycles and calculate the capacity retention rate; Capacity retention rate = discharge capacity in the nth cycle / discharge capacity in the first cycle.

[0104] The storage testing (capacity recovery rate test) process is as follows: 1. Place the manganese-ion battery sample in an ambient temperature of 25±2℃, charge it at 1 / 3C constant current and constant voltage to the upper limit voltage of 4.2V, cut off the current to 0.05C, and let it stand for 3 hours; The measured voltage is recorded as OCV0; Store at an ambient temperature of 55±2℃ for 7 days; The measured voltage is denoted as OCV1; At an ambient temperature of 25±2℃, discharge at a constant current of 1 / 3C to the lower limit voltage of 3.0V, and let stand for 30 minutes; Measuring charge retention capacity (Ah); Under ambient temperature of 25±2℃, charge at 1 / 3C constant current and constant voltage to the upper limit voltage of 4.2V, cut off current to 0.05C, and let stand for 30 minutes; At an ambient temperature of 25±2℃, discharge at a constant current of 1 / 3C to the lower limit voltage of 3.0V, and let stand for 30 minutes; Repeat steps 7-8 three times, and take the average capacity of the three cycles as C (capacity recovery rate).

[0105] The test results are shown in the table below:

[0106] As shown in the table above, compared to lithium manganese oxide batteries without a functional separator, batteries equipped with a functional separator exhibit improved capacity retention at 45℃ and storage capacity recovery at 55℃. This indicates that the functional separator effectively inhibits manganese dissolution and improves the performance of lithium manganese oxide batteries. Increasing the content of alkaline oxides in the functional layer significantly inhibits manganese dissolution within a certain range, but the effect becomes less pronounced beyond that range.

[0107] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A lithium manganese oxide battery, comprising a positive electrode, a separator, and a negative electrode, characterized in that, It also includes functional diaphragms; The functional membrane comprises CaO2 and multidimensional conductive carbon material; The functional diaphragm is disposed between the positive electrode plate and the diaphragm, and / or, The functional diaphragm is disposed between the negative electrode and the diaphragm.

2. The lithium manganese oxide battery according to claim 1, characterized in that, In the functional membrane, the mass ratio of CaO2 to the multidimensional conductive carbon material is (5-30):(70-95).

3. The lithium manganese oxide battery according to claim 2, characterized in that, The multidimensional conductive carbon material includes at least one of carbon nanofiber membrane, graphene carbon membrane, and porous carbon paper.

4. The lithium manganese oxide battery according to claim 1, characterized in that, The thickness of the functional diaphragm is 100μm to 150μm.

5. The lithium manganese oxide battery according to claim 1, characterized in that, The functional diaphragm includes a first pore with a pore size of 5 μm to 10 μm.

6. The lithium manganese oxide battery according to claim 1, characterized in that, The functional diaphragm also includes a second pore, the pore size of which is 100nm to 500nm.

7. A method for preparing a lithium manganese oxide battery, characterized in that, The process includes the step of preparing a functional membrane, wherein the preparation of the functional membrane includes: S1. Dissolve the film-forming agent and CaO2 in the solvent and stir to form a homogeneous solution; S2. Add the multidimensional conductive carbon material to the homogeneous solution obtained in S1 in two batches, and then place it in a constant temperature oil bath for stirring and cooling before taking it out. S3. The mixed material prepared in S2 is coated onto the substrate to form a liquid film and placed in a water bath. After curing and stabilizing the film, it is removed. S4, dry; S5, pre-oxidation and calcination, to obtain a functional diaphragm.

8. The method according to claim 7, characterized in that, In step S1, the mass ratio of film-forming agent, CaO2, and solvent is (1-5):(1-5):(30-35).

9. The method according to claim 7, characterized in that, Step S5 includes: The product dried in step S4 is pre-oxidized in air at 200℃~300℃ for 1h~3h; then the pre-oxidized product is calcined in an inert atmosphere at 600℃~800℃ for 0.5h~3h.

10. A battery device comprising a lithium manganese oxide battery as described in claims 1 to 6.

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