Novel structure lithium manganate, positive electrode sheet with the lithium manganate and preparation method

Abstract

The application discloses a novel structure lithium manganate, a positive electrode sheet with the lithium manganate and a preparation method, relates to the technical field of lithium ion battery electrode materials and preparation thereof, and the structure comprises a lithium manganate matrix of a core structure; a lithiated polymer coated on the surface of the lithium manganate matrix to form a gel film; and a lithium supplementing agent uniformly dispersed in the gel film. The application improves the performance of the positive electrode sheet by adopting the novel structure lithium manganate, overcomes the defects of the prior art, and meets the actual production and application requirements.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery electrode materials and their preparation technology, specifically to a novel structure of lithium manganese oxide, a positive electrode sheet having the lithium manganese oxide, and a preparation method thereof. Background Technology

[0002] At present, the field of lithium-ion battery electrode materials and their preparation technology faces numerous problems at the material, process, and electrode levels, such as: Existing conductive polymers (polyaniline, polypyrrole) dissolve and fail in NMP, and non-conductive polymers hinder lithium-ion transport; lithium replenishment agents are unstable and unevenly dispersed in air, resulting in poor interfacial contact with the cathode material.

[0003] Existing heat treatment processes cannot control the degree of polymerization, resulting in coatings that are too thick (hindering ion transport) or too thin (insufficient protection); lithium supplements are prone to agglomeration or interfacial debonding during heat treatment.

[0004] In current electrode preparation, particles are only physically bonded by PVDF, resulting in high interfacial resistance and failure of interparticle contact during cycling; the rapid reaction of lithium replenishment agent in the early stage of cycling leads to local stress concentration and structural damage.

[0005] Therefore, to meet practical needs, a novel structure of lithium manganese oxide and its related technologies are now provided. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a novel structure of lithium manganese oxide, a positive electrode sheet having the lithium manganese oxide, and a preparation method thereof. By adopting a novel structure of lithium manganese oxide, the performance of the positive electrode sheet is improved, the deficiencies of existing technologies are overcome, and the needs of practical production applications are met.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: In a first aspect, this application discloses a novel structural lithium manganese oxide, which comprises: A lithium manganese oxide matrix with a core structure; A lithium-ionized polymer that forms a gel film on the surface of the lithium manganese oxide matrix; A lithium supplement agent uniformly dispersed in the gel membrane.

[0008] Based on the above technical solution, the lithium polymer is insoluble in NMP and is at least one of lithium polyacrylate, lithium polyvinyl chloride, and lithium polystyrene.

[0009] Based on the above technical solution, the lithium replenishing agent is Li3FeO3, Li5FeO4 or Li3NiO3.

[0010] Based on the above technical solution, the particle size of the lithium manganese oxide matrix ranges from 5 to 15 μm; The thickness of the gel film ranges from 10 to 100 nm; The particle size of the lithium supplement has a range of 0.5-2 μm.

[0011] Secondly, this application discloses a positive electrode sheet of lithium manganese oxide with the novel structure mentioned in the first aspect: The positive electrode slurry for fabricating the positive electrode sheet includes the novel structured lithium manganese oxide and a curing agent; wherein, The curing agent is poly(adipitic anhydride), tetrahydrophthalic anhydride, phthalic anhydride, diaminodiphenylmethane, diethylaminopropylamine, diacid anhydride curing agent, or a custom-mixed curing agent; wherein... The diacid anhydride curing agent is a mixture of oxalic acid and polyadipic anhydride; The custom-mixed curing agent is a mixture of polyazelic anhydride and tetrahydrophthalic anhydride.

[0012] Thirdly, this application discloses a method for preparing the novel lithium manganese oxide structure mentioned in the first aspect, the method comprising the following steps: According to the preset mass ratio, polyethylene ester, sodium polyvinyl acetate, ethanol and polyethylene glycol are mixed and stirred at the preset temperature for the preset duration to obtain an organic polymer solution. According to the preset corresponding mass ratio, the organic polymer solution, lithium supplement and lithium manganese oxide matrix are added to a high-speed mixer and mixed for the corresponding preset duration to obtain an intermediate product; The intermediate product is placed in an oven and subjected to pre-crosslinking treatment according to the type of lithium supplement, followed by deep curing treatment to obtain a novel structured lithium manganese oxide.

[0013] Based on the above technical solution, the lithium replenishing agent is Li3FeO3, Li2SiO3, Li3CoO3, Li3NiO3, LiFeO2, Li5FeO4 or Li3(FeO3)2.

[0014] Fourthly, this application discloses a method for preparing the positive electrode sheet mentioned in the second aspect, the method comprising the following steps: According to the preset mass ratio, the novel structure lithium manganese oxide, conductive carbon black, PVDF and curing agent are mixed, NMP is added to adjust the viscosity to the preset viscosity value, and vacuum stirring is performed for the preset duration to obtain the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, and the areal density is controlled at the corresponding preset areal density value. Vacuum drying is carried out at the corresponding preset drying temperature for the corresponding preset duration to obtain an unrolled electrode sheet. Using a hot roller press, the unrolled electrode sheet is processed at a corresponding preset working pressure, a corresponding preset working temperature, and a corresponding preset rolling speed to obtain a positive electrode sheet.

[0015] Compared with the prior art, the advantages of this application are: This application improves the performance of the positive electrode by adopting a novel lithium manganese oxide structure, overcomes the shortcomings of existing technologies, and meets the needs of practical production applications. Attached Figure Description

[0016] Terminology Explanation: In-situ confined polymerization: refers to the process in which organic polymer monomers undergo polymerization reactions in specific areas on the surface of lithium manganese oxide particles, forming a coating layer of controllable thickness, and physically confining the lithium supplement within it.

[0017] Pre-crosslinking degree: The degree of crosslinking reaction that occurs in the organic polymer during the heat treatment stage, expressed as the percentage of gel content that is insoluble in NMP, with a critical control point in the range of 30-60%.

[0018] Three-dimensional network between particles: In the positive electrode sheet, the organic polymer coating layers on the surface of adjacent lithium manganese oxide particles undergo chemical cross-linking through a curing agent, forming a continuous network structure across particles.

[0019] Electron-ion dual conduction channel: The lithium supplement provides electronic conductivity, and the lithium polymer (such as lithium polyacrylate) provides lithium-ion conductivity, together forming a composite conduction system.

[0020] Lithium-containing polymers: polymers whose molecular chains contain lithium carboxylic acid groups (-COOLi), including lithium polyacrylate, lithium polyvinyl chloride, lithium polystyrene, etc.

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the novel lithium manganese oxide according to an embodiment of this application. Detailed Implementation

[0023] Terminology Explanation: To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0025] This application provides a novel structure of lithium manganese oxide, a positive electrode sheet having the lithium manganese oxide, and a preparation method thereof. By adopting a novel structure of lithium manganese oxide, the performance of the positive electrode sheet is improved, the shortcomings of the prior art are overcome, and the needs of actual production applications are met.

[0026] To achieve the aforementioned technical effects, the overall concept of this application is as follows: A novel structured lithium manganese oxide, comprising: A lithium manganese oxide matrix with a core structure; A lithium-ionized polymer that forms a gel film on the surface of the lithium manganese oxide matrix; A lithium supplement agent uniformly dispersed in the gel membrane.

[0027] The embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0028] Firstly, see [the following] Figure 1 As shown in the embodiments of this application, a novel structural lithium manganese oxide is provided, the novel structural lithium manganese oxide comprising: A lithium manganese oxide matrix with a core structure; A lithium-ionized polymer that forms a gel film on the surface of the lithium manganese oxide matrix; A lithium supplement agent uniformly dispersed in the gel membrane.

[0029] In this embodiment, a novel lithium manganese oxide structure is adopted to improve the performance of the positive electrode, overcome the shortcomings of the prior art, and meet the needs of actual production applications.

[0030] Furthermore, the lithium polymer is insoluble in NMP and is at least one of lithium polyacrylate, lithium polyvinyl chloride, and lithium polystyrene.

[0031] Furthermore, the lithium replenishing agent is Li3FeO3, Li5FeO4, or Li3NiO3.

[0032] Furthermore, the particle size of the lithium manganese oxide matrix ranges from 5 to 15 μm; The thickness of the gel film ranges from 10 to 100 nm; The particle size of the lithium supplement has a range of 0.5-2 μm.

[0033] Currently, spinel lithium manganese oxide (LiMn2O4) cathode materials possess advantages such as stable crystal structure, high discharge voltage (3.9V vs Li / Li⁺), and low cost, making them suitable for power batteries. However, they also have the following problems: Dissolution of manganese (Mn) 3+ Disproportionation reaction and HF corrosion in the electrolyte lead to deterioration of cycle performance; The formation of an SEI film during the first charge results in irreversible lithium loss (approximately 15-20%). Under high temperature conditions (>50℃), manganese dissolution intensifies and capacity decays rapidly.

[0034] The technical solutions and shortcomings of several existing technologies are as follows: Prior art 1, patent publication number CN201410778368.0, entitled "A method for coating lithium nickel cobalt manganese oxide cathode material with conductive polymer": Technical solution

[0035] Add polyaniline or polypyrrole solution to the precursor, spray dry, and then calcine at 500-700℃.

[0036] Defect Analysis: Polyaniline / polypyrrole decomposes into carbon at temperatures above 500°C, losing its polymer properties. NMP solvent can dissolve polyaniline / polypyrrole, damaging the coating layer during slurry preparation; The design without lithium replenishment cannot solve the problem of initial irreversible lithium loss.

[0037] Prior art 2, patent publication number CN202311275361.2, titled "A composite cathode material and its preparation method and secondary battery"; Technical solution

[0038] The surface of lithium manganese oxide is coated with cyanuric chloride polymer.

[0039] Defect Analysis: Cyanobenyl chloride is hydrophobic but has no ionic conductivity, thus increasing polarization resistance; It readily decomposes in water and alkalis, producing HCl, which corrodes battery components; It contains no lithium supplement and has no chemical bond between the coating layer and the substrate, making it easy to peel off.

[0040] In summary, the common shortcomings of existing technologies are: Solvent compatibility issues: Existing conductive polymers dissolve or swell in NMP, causing coating layer failure during positive electrode slurry preparation (60-70% solid content, NMP solvent); Ion transport obstruction: Non-conductive polymer coating layer hinders Li + Poor transmission speed and rate capability; Lithium supplement stability: Lithium supplements (such as Li5FeO4) decompose upon contact with water / CO2 and cannot be stably stored and dispersed in air; The interface structure is fragile: the particles are only bonded by van der Waals forces or physical bonds of PVDF, and particle slippage during cycling leads to contact failure.

[0041] It should be noted that, based on the technical solutions of the embodiments of this application, in specific implementation, Case 1, when the lithium replenishing agent is Li3FeO3: Pre-crosslinking treatment stage: The intermediate product was placed in an oven and heat-treated at 150℃ for 1 hour. The degree of pre-crosslinking was controlled at 45±5% (determined by measuring the NMP insoluble content). Deep curing stage: Heat to 200℃, keep warm for 2 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0042] Case 2, when the lithium replenishing agent is Li2SiO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 180℃ for 1.5h, with the degree of pre-crosslinking controlled at 40%; Deep curing stage: Heat to 300℃, keep warm for 4 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0043] Case 3, when the lithium replenishing agent is Li3CoO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 250℃ for 2 hours, with the degree of pre-crosslinking controlled at 55%; Deep curing stage: Heat to 250℃, keep warm for 4 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0044] Case 4, when the lithium replenishing agent is Li3NiO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 120℃ for 1 hour, with the degree of pre-crosslinking controlled at 35%; Deep curing stage: Heat to 200℃, keep warm for 3 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0045] Case 5, when the lithium replenishing agent is Li3FeO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 160℃ for 1 hour, with the degree of pre-crosslinking controlled at 50%; Deep curing stage: Heat to 180℃, keep warm for 3.5h, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0046] Case 6, when the lithium replenishing agent is LiFeO2: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 300℃ for 0.5h. The degree of pre-crosslinking is controlled at 60%, which is the upper limit. Deep curing stage: Heat to 360℃, keep warm for 3.5h, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0047] Case 7, when the lithium replenishing agent is Li3FeO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 200℃ for 1 hour, with the degree of pre-crosslinking controlled at 45%; Deep curing stage: Heat to 380℃, keep warm for 1.5h, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0048] Case 8, when the lithium replenishing agent is Li5FeO4: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 140℃ for 0.5h. The degree of pre-crosslinking is controlled at 30%, which is the lower limit value. Deep curing stage: Heat to 180℃, keep warm for 1 hour, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0049] Case 9, when the lithium replenishing agent is Li3NiO3: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 280℃ for 1.5 hours, with the degree of pre-crosslinking controlled at 50%; Deep curing stage: Heat to 350℃, keep warm for 3 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0050] Case 10, when the lithium replenishing agent is Li3(FeO3)2: Pre-crosslinking treatment stage: The intermediate product is placed in an oven and heat-treated at 220℃ for 1 hour, with the degree of pre-crosslinking controlled at 42%; Deep curing stage: heat to 300℃, keep warm for 2.5h, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer, namely, novel structured lithium manganese oxide.

[0051] Secondly, embodiments of this application provide a positive electrode sheet having the novel structure of lithium manganese oxide mentioned in the first aspect: The positive electrode slurry for fabricating the positive electrode sheet includes the novel structured lithium manganese oxide and a curing agent; wherein, The curing agent is poly(adipitic anhydride), tetrahydrophthalic anhydride, phthalic anhydride, diaminodiphenylmethane, diethylaminopropylamine, diacid anhydride curing agent, or a custom-mixed curing agent; wherein... The diacid anhydride curing agent is a mixture of oxalic acid and polyadipic anhydride; The custom-mixed curing agent is a mixture of polyazelic anhydride and tetrahydrophthalic anhydride.

[0052] In this embodiment, a novel lithium manganese oxide structure is adopted to improve the performance of the positive electrode, overcome the shortcomings of the prior art, and meet the needs of actual production applications.

[0053] Thirdly, this application discloses a method for preparing the novel lithium manganese oxide structure mentioned in the first aspect, the method comprising the following steps: According to the preset mass ratio, polyethylene ester, sodium polyvinyl acetate, ethanol and polyethylene glycol are mixed and stirred at the preset temperature for the preset duration to obtain an organic polymer solution. According to the preset corresponding mass ratio, the organic polymer solution, lithium supplement and lithium manganese oxide matrix are added to a high-speed mixer and mixed for the corresponding preset duration to obtain an intermediate product; The intermediate product is placed in an oven and subjected to pre-crosslinking treatment according to the type of lithium supplement, followed by deep curing treatment to obtain a novel structured lithium manganese oxide.

[0054] In this embodiment, a novel lithium manganese oxide structure is adopted to improve the performance of the positive electrode, overcome the shortcomings of the prior art, and meet the needs of actual production applications.

[0055] Furthermore, the lithium replenishing agent is Li3FeO3, Li2SiO3, Li3CoO3, Li3NiO3, LiFeO2, Li5FeO4 or Li3(FeO3)2.

[0056] Fourthly, this application discloses a method for preparing the positive electrode sheet mentioned in the second aspect, the method comprising the following steps: According to the preset mass ratio, the novel structure lithium manganese oxide, conductive carbon black, PVDF and curing agent are mixed, NMP is added to adjust the viscosity to the preset viscosity value, and vacuum stirring is performed for the preset duration to obtain the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, and the areal density is controlled at the corresponding preset areal density value. Vacuum drying is carried out at the corresponding preset drying temperature for the corresponding preset duration to obtain an unrolled electrode sheet. Using a hot roller press, the unrolled electrode sheet is processed at a corresponding preset working pressure, a corresponding preset working temperature, and a corresponding preset rolling speed to obtain a positive electrode sheet.

[0057] In this embodiment, a novel lithium manganese oxide structure is adopted to improve the performance of the positive electrode, overcome the shortcomings of the prior art, and meet the needs of actual production applications.

[0058] Fifthly, this application discloses an implementation process for preparing a novel structured lithium manganese oxide and the corresponding positive electrode sheet, the details of which are as follows: Raw material source: Lithium manganese oxide matrix: commercially available LiMn2O4 (D50=8μm, specific capacity 115mAh / g) Lithium polyacrylate (PAA-Li): self-made, 90% neutralization, molecular weight 50,000 Lithium polyvinyl chloride (PVA-Li): self-made, saponification degree 88%, molecular weight 80,000 Lithium supplements: Li3FeO3, Li5FeO4, Li3NiO3, Li2SiO3 (commercially available, battery grade) Curing agents: Poly(adipitic anhydride) (PAPA), Phthalic anhydride (PA), Diaminodiphenylmethane (DDM, commercially available analytical grade).

[0059] Implementation Plan 1: S1. Preparation of organic polymer solution: Polyvinyl ester, sodium polyvinyl acetate, ethanol, and polyethylene glycol were mixed in a mass ratio of 0.5:0.5:4.5:4.5 and stirred at 60°C for 2 hours to obtain a transparent and viscous organic polymer solution (solid content 10wt%).

[0060] S2. Mixing and Coating: The organic polymer solution, Li3FeO3 (lithium supplement), and lithium manganese oxide matrix were added to a high-speed mixer (2000 rpm) at a mass ratio of 0.05:0.01:0.98 and mixed for 30 min to obtain intermediate product I. At this point, the lithium supplement is uniformly coated by the polymer solution and adheres to the surface of the lithium manganese oxide.

[0061] S3. Step-by-step heat treatment (key step): Pre-crosslinking stage: Intermediate product I was placed in an oven and heat-treated at 150°C for 1 hour. The degree of pre-crosslinking was controlled at 45±5% (determined by measuring the NMP insoluble content). Deep curing stage: Heat to 200℃, keep warm for 2 hours, cool naturally to room temperature, and pass through a 200-mesh sieve to obtain lithium manganese oxide cathode material coated with lithium supplement and organic polymer.

[0062] Structural characterization: SEM showed that the coating layer was about 30 nm thick, and the lithium supplement particles were uniformly dispersed in the coating layer, with no exposed lithium manganese oxide surface.

[0063] S4. Preparation of positive electrode slurry: The above-mentioned lithium manganese oxide cathode material, conductive carbon black (Super P), PVDF (molecular weight 500,000), and polyadipin anhydride (curing agent) were mixed at a mass ratio of 0.97:0.015:0.015:0.005. NMP was added to adjust the viscosity to 6500 mPa·s, and the mixture was stirred under vacuum for 2 hours. Observation showed that the coating layer was intact and there was no dissolution.

[0064] S5. Coating and Drying: The slurry was coated onto aluminum foil (20 μm thick) with an areal density of 25 mg / cm², and vacuum dried at 80 °C for 12 h to obtain an unrolled electrode sheet.

[0065] S6. Hot-press polymerization (key step): Using a hot roller press with a pressure of 100 kN, a temperature of 80 °C, and a roller speed of 2 m / s, the residual carboxyl groups in the organic polymer undergo a cross-linking reaction with the polyadipic anhydride. Simultaneously, the coating layers of adjacent particles fuse together to form a three-dimensional network. A positive electrode sheet with a compaction density of 3.21 g / cm³ is obtained.

[0066] S7. Battery Assembly and Testing: A CR2025 coin cell was assembled using lithium metal as the negative electrode, Celgard 2400 as the separator, and 1M LiPF6 / EC+DMC (1:1) as the electrolyte. Test conditions: 0.2C charge / discharge (1C=120mA / g), voltage range 3.0-4.3V.

[0067] Implementation Plan 2: S1: Prepare an organic polymer solution by mixing polyethylene ester, lithium polyvinyl chloride, water, and polyethylene glycol in a mass ratio of 0.5:0.5:4.5:4.5.

[0068] S2: A mixture of organic polymer solution, Li₂SiO₃, and lithium manganese oxide matrix in a mass ratio of 0.025:0.01:0.985 is used. Li₂SiO₃ was chosen because its ionic conductivity is superior to its electronic conductivity, and it synergistically forms ion channels with lithium polyacrylate.

[0069] S3: Pre-crosslink at 180℃ for 1.5h (pre-crosslinking degree 40%), then deep cure at 300℃ for 4h.

[0070] S4: Mix lithium manganese oxide, carbon black, PVDF, and polyadipic anhydride in a mass ratio of 0.96:0.02:0.02:0.0025, and adjust the viscosity to 5500 mPa·s.

[0071] S5-S6: After coating and drying, hot pressing at 120kN, 85℃, and 2.5m / s results in a compaction density of 3.18 g / cm³.

[0072] Implementation Plan 3: S1: Mix polypropylene, lithium polystyrene, and polyethylene glycol in a mass ratio of 0.5:1.5:8.

[0073] S2: A mixture of organic polymer solution, Li3CoO3 and lithium manganese oxide matrix in a mass ratio of 0.2:0.016:0.98.

[0074] S3: Pre-crosslink at 250℃ for 2 hours (pre-crosslinking degree 55%), then deep cure at 250℃ for 4 hours. High pre-crosslinking degree retains more active groups for electrode crosslinking.

[0075] S4: A mixture of lithium manganese oxide, carbon black, PVDF, diethylaminopropylamine, and diaminodiphenylmethane (dual curing agent system) in a mass ratio of 0.955:0.02:0.025:0.002:0.002, with a viscosity of 7000 mPa·s.

[0076] S5-S6: After coating and drying, hot pressing at 130kN, 110℃, and 2m / s results in a compacted density of 3.19 g / cm³.

[0077] Implementation Plan 4: S1: Mix lithium polyacrylate and polyethylene glycol at a mass ratio of 2:8.

[0078] S2: Mix organic polymer solution, Li3NiO3 and lithium manganese oxide matrix in a mass ratio of 0.1:0.005:0.975.

[0079] S3: Pre-crosslink at 120℃ for 1 hour (pre-crosslinking degree 35%), then deep cure at 200℃ for 3 hours.

[0080] S4: A mixture of lithium manganese oxide, carbon black, PVDF, and phthalic anhydride in a mass ratio of 0.96:0.02:0.02:0.0025, with a viscosity of 10000 mPa·s.

[0081] S5-S6: After coating and drying, hot pressing at 90kN, 90℃, and 1.5m / s results in a compaction density of 3.22 g / cm³.

[0082] Implementation Plan 5: S1: Mix polyacrylic acid, polyvinylidene fluoride, ethanol, and polyethylene glycol in a mass ratio of 2:1:2:5 (polyacrylic acid provides crosslinking sites).

[0083] S2: A mixture of organic polymer solution, Li3FeO3 and lithium manganese oxide matrix in a mass ratio of 0.05:0.001:0.983 (low lithium supplement content).

[0084] S3: Pre-crosslink at 160℃ for 1 hour (pre-crosslinking degree 50%), then deep cure at 180℃ for 3.5 hours.

[0085] S4: A mixture of lithium manganese oxide, carbon black, PVDF, and tetrahydrophthalic anhydride with a mass ratio of 0.97:0.015:0.015:0.002 is prepared, with a viscosity of 6000 mPa·s.

[0086] S5-S6: After coating and drying, hot pressing at 110kN, 105℃, and 1.2m / s results in a compacted density of 3.17 g / cm³.

[0087] Implementation Plan 6: S1: Mix sodium polyacrylate, polystyrene, and polyethylene glycol in a mass ratio of 1:1.5:7.5.

[0088] S2: A mixture of organic polymer solution, LiFeO2 and lithium manganese oxide matrix in a mass ratio of 0.2:0.01:0.94 (high lithium supplement content).

[0089] S3: Pre-crosslink at 300℃ for 0.5h (pre-crosslinking degree 60%, upper limit), then deep cure at 360℃ for 3.5h.

[0090] S4: A mass ratio of 0.975:0.01:0.015:0.025:0.025 is used to mix lithium manganese oxide, carbon black, PVDF, oxalic acid, and polyadipic anhydride (di-anhydride curing agent), with a viscosity of 7500 mPa·s.

[0091] S5-S6: After coating and drying, hot pressing at 80kN, 70℃, and 2.5m / s results in a compacted density of 3.15 g / cm³.

[0092] Implementation Plan 7: S1: Mix polystyrene acid, sodium polyacrylate, ethanol and polyethylene glycol in a mass ratio of 1:1:2:2:4.

[0093] S2: A mixture of organic polymer solution, Li3FeO3 and lithium manganese oxide matrix in a mass ratio of 0.2:0.005:0.945.

[0094] S3: Pre-crosslink at 200℃ for 1 hour (pre-crosslinking degree 45%), then deep cure at 380℃ for 1.5 hours.

[0095] S4: A mixture of lithium manganese oxide, carbon black, PVDF, and phthalic anhydride (high curing agent content) with a mass ratio of 0.975:0.01:0.015:0.04, with a viscosity of 4500 mPa·s.

[0096] S5-S6: After coating and drying, hot pressing at 120kN, 45℃ (low temperature hot pressing, testing the lower limit of the crosslinking reaction temperature), and 1.8m / s resulted in a compaction density of 3.19 g / cm³.

[0097] Implementation Plan 8: S1: Mix lithium polyvinyl chloride, water, and polyethylene glycol in a mass ratio of 5:4:1 (high water content, environmentally friendly process).

[0098] S2: A mixture of organic polymer solution, Li5FeO4 and lithium manganese oxide matrix in a mass ratio of 0.05:0.008:0.967.

[0099] S3: Pre-crosslink at 140℃ for 0.5h (pre-crosslinking degree 30%, lower limit), then deep cure at 180℃ for 1h.

[0100] S4: A mixture of lithium manganese oxide, carbon black, PVDF, and methyltetrahydrophthalic anhydride in a mass ratio of 0.96:0.02:0.02:0.03, with a viscosity of 5000 mPa·s.

[0101] S5-S6: After coating and drying, hot pressing at 100kN, 50℃, and 1m / s results in a compaction density of 3.08 g / cm³.

[0102] Implementation Plan 9: S1: Mix lithium polyacrylate, polystyrene acid, and water in a mass ratio of 4.5:0.5:5.

[0103] S2: A mixture of organic polymer solution, Li3NiO3 and lithium manganese oxide matrix in a mass ratio of 0.02:0.08:0.91 (with an ultra-high lithium supplement content of 8%).

[0104] S3: Pre-crosslink at 280℃ for 1.5h (pre-crosslinking degree 50%), then deep cure at 350℃ for 3h.

[0105] S4: A mass ratio of 0.97:0.015:0.015:0.02:0.005 is used to mix lithium manganese oxide, carbon black, PVDF, polyazelic anhydride, and tetrahydrophthalic anhydride, with a viscosity of 6500 mPa·s.

[0106] S5-S6: After coating and drying, hot pressing at 90kN, 100℃, and 1.5m / s results in a compaction density of 3.12 g / cm³.

[0107] Implementation Plan 10: S1: Mix lithium polyacrylate, polyacrylic acid, water, and ethanol in a mass ratio of 1.5:0.5:3:5 (mixed lithium polymer).

[0108] S2: Mix the organic polymer solution, Li3(FeO3)2 and lithium manganese oxide matrix in a mass ratio of 0.1:0.005:0.97.

[0109] S3: Pre-crosslink at 220℃ for 1 hour (pre-crosslinking degree 42%), then deep cure at 300℃ for 2.5 hours.

[0110] S4: A mixture of lithium manganese oxide, carbon black, PVDF, oxalic acid, and polyadipic anhydride with a mass ratio of 0.96:0.02:0.02:0.005:0.015 is prepared by mixing these components at a viscosity of 6000 mPa·s.

[0111] S5-S6: After coating and drying, hot pressing at 110kN, 105℃, and 1.2m / s results in a compacted density of 3.20 g / cm³.

[0112] The innovation of the technical solution in this application is as follows: Innovation Point 1: Electron-ion dual-conduction core-shell-lithium replenisher structure design, details of which are as follows: Technical solution: Constructing a core-shell structure of "lithium manganese oxide matrix @ lithium-ion polymer gel film / conductive lithium supplement": Core: Lithium manganese oxide matrix (LiMn2O4 or its doped and modified form, particle size D50=5-15μm).

[0113] Shell: A lithium polymer insoluble in NMP (at least one of lithium polyacrylate, lithium polyvinyl chloride, and lithium polystyrene) forms a gel film with a thickness of 10-100 nm, providing lithium-ion conduction channels (ionic conductivity 10). -4 ~10 -3 S / cm).

[0114] Functional fillers: Electron-conductive lithium supplements (Li3FeO3, Li5FeO4, Li3NiO3, etc., particle size D50=0.5-2μm) are uniformly dispersed in the gel film, forming an "island-sea" structure to provide electron conduction channels (conductivity 10). -3 ~10 -2 S / cm).

[0115] Key features: NMP solvent resistance: Lithium-based polymers (such as lithium polyacrylate) have a swelling degree of <5wt% in NMP, while polyaniline has a solubility of >30wt%, ensuring the integrity of the coating layer during slurry preparation.

[0116] Dual conduction mechanism: The lithium polymer provides Li⁺ conduction (lithium carboxylate group), while the lithium supplement provides e⁻ conduction, synergistically reducing polarization.

[0117] Lithium replenisher confinement protection: The hydrophobic polymer network isolates water vapor, and the decomposition rate of the lithium replenisher after 7 days of exposure to air is <2% (>50% for uncoated).

[0118] Innovation Point 2: Stepwise in-situ confined polymerization preparation process, details of which are as follows: Technical solution: A two-step heat treatment process of "low temperature pre-crosslinking - high temperature deep curing" is adopted, combined with a specific solvent system.

[0119] S1 solvent system design: Solvent: Water / ethanol / polyethylene glycol (mass ratio 1:4:4.5) mixed solvent.

[0120] Solubility parameter matching: Lithium polyacrylate has a solubility of >20wt% in mixed solvents and a swelling degree of <5wt% in NMP.

[0121] The evaporation gradient is: water (100℃) < ethanol (78℃) < polyethylene glycol (>200℃), achieving progressive curing.

[0122] S2 step-by-step heat treatment: First stage (110-180℃, 0.5-2h): Remove low-boiling-point solvents, and the polymer undergoes pre-crosslinking, with the degree of pre-crosslinking controlled at 30-60%. At this time, the polymer still has a certain fluidity, which can coat the edges of the lithium supplement and avoid stress concentration, while retaining the uncrosslinked active groups (-COOH, -OH) for subsequent electrode crosslinking.

[0123] The second stage (250-400℃, 1-4h): deep cross-linking forms a three-dimensional network, the pre-cross-linking degree is increased to 80-95%, and a stable gel film is formed.

[0124] Key control parameters: Pre-crosslinking degree control is the core innovation. If the pre-crosslinking degree is too low (<30%), the coating layer will have excessive fluidity during subsequent electrode hot pressing, leading to lithium supplement agglomeration; if the pre-crosslinking degree is too high (>60%), the electrode will not be able to form effective crosslinks with adjacent particles during electrode hot pressing.

[0125] Innovation Point 3: Construction of a three-dimensional cross-linked network between particles induced by hot pressing, as detailed below: Technical solution: Add a multifunctional curing agent (anhydride such as polyadipic anhydride, or an amine such as diaminodiphenylmethane, dosage 0.2-4wt%) to the positive electrode slurry. During the hot pressing process (80-110℃, pressure 80-150kN, speed 0.5-5m / s), the following reaction is triggered: Particle surface crosslinking: The -COOLi / -COOH groups on the surface of lithium manganese oxide A are the same groups on the surface of lithium manganese oxide B, and are bridged by a curing agent (such as the reaction of acid anhydride and carboxyl group to form ester bond).

[0126] Lithium replenishment agent anchoring: The -OH / -COOH on the surface of the lithium replenishment agent reacts with the polymer network, fixing the lithium replenishment agent at the three-dimensional network nodes, thus achieving slow and controllable lithium replenishment.

[0127] Interface optimization: The formed cross-linked network fills the gaps between particles, realizing the transformation from "point contact" to "surface contact" and constructing a continuous electron-ion transport channel.

[0128] Technical effects: Chemical bonds are formed between particles, increasing the peel strength to 1.5-2.0 N / cm (compared to only 0.8-1.0 N / cm for traditional PVDF bonding).

[0129] The lithium replenisher is confined to the network nodes, and lithium ions are released slowly during the first charge to avoid local stress concentration.

[0130] A three-dimensional network blocks electrolyte penetration and inhibits manganese leaching.

[0131] In summary, the advantages of the technical solution in this application are as follows: 1. Resolving the contradiction between solvent compatibility and ion conduction (Innovation Point 1): By selecting lithium polymers (such as lithium polyacrylate) as the coating layer, it not only avoids dissolution in NMP (the polyaniline in comparative document 1 is dissolved), but also provides lithium ion conduction channels through the lithium carboxylic acid groups (the cyanochloride in comparative document 2 has no ion conduction), thus achieving a synergistic effect of "solvent resistance + high ion conduction".

[0132] 2. Achieve precise positioning and controllable release of lithium supplements (Innovation Point 2): The stepwise heat treatment process controls the pre-crosslinking degree to 30-60%, ensuring that the lithium replenisher is firmly coated (avoiding gas generation caused by direct mixing in Comparative Example 6) while preserving the subsequent crosslinking activity. The lithium replenisher is dispersed in the polymer network and slowly releases lithium ions during charging, avoiding local stress concentration, and the initial coulombic efficiency is improved to over 94% (compared to only 88.5% in Comparative Example 1).

[0133] 3. Constructing a stable three-dimensional interparticle network (Innovation Point 3): During hot pressing, the curing agent and the polymer coating undergo chemical cross-linking to form a three-dimensional network across particles, increasing the peel strength by more than 100% (1.82 vs 0.85 N / cm) and the compaction density by 16.7% (3.21 vs 2.75 g / cm³). At the same time, it effectively blocks electrolyte penetration and reduces manganese leaching by 85% (75 vs 511 ppm).

[0134] 4. The process is simple, environmentally friendly, and suitable for large-scale production: Using a water / ethanol / polyethylene glycol mixed solvent (Example 8) avoids organic solvent contamination; the step-by-step heat treatment can be completed in a conventional oven; the hot pressing process is compatible with existing electrode production processes and requires no additional equipment.

[0135] Based on the technical solution of the embodiments of this application, the following alternative solutions also exist: Alternative Option 1 (Changing the polymer composition): Lithium polyacrylate can be blended with polyethylene oxide (PEO) (mass ratio 1:1). PEO provides flexible segments, which improves the toughness of the coating layer and is suitable for high-density electrodes (>3.3 g / cm³).

[0136] Alternative Option 2 (Changing the Lithium Supplement Combination): When Li3FeO3 and Li2SiO3 are combined (mass ratio 1:1), Li3FeO3 provides electronic conduction, while Li2SiO3 provides ionic conduction, and Li2SiO3 has better stability in air.

[0137] Alternative Solution 3 (Changing the Crosslinking Method): Using gamma-ray irradiation crosslinking to replace hot-press chemical crosslinking is suitable for heat-sensitive cathode materials. The irradiation dose is 50-200 kGy, and interparticle crosslinking can be achieved at room temperature.

[0138] Alternative Option 4 (Multi-layer Coating): First, a layer of lithium-based polymer is coated (inner layer, 20nm thick), and then a layer of hydrophobic polymer is coated (outer layer, such as polyvinylidene fluoride, 10nm thick) to further improve the waterproof performance.

[0139] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0140] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0141] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A novel structure of lithium manganese oxide, characterized in that, The novel structural lithium manganese oxide includes: A lithium manganese oxide matrix with a core structure; A lithium-ionized polymer that forms a gel film on the surface of the lithium manganese oxide matrix; A lithium supplement agent uniformly dispersed in the gel membrane.

2. The novel lithium manganese oxide structure as described in claim 1, characterized in that: The lithium polymer is insoluble in NMP and is at least one of lithium polyacrylate, lithium polyvinyl chloride, and lithium polystyrene.

3. The novel lithium manganese oxide structure as described in claim 1, characterized in that: The lithium replenishing agent is Li3FeO3, Li2SiO3, Li3CoO3, Li3NiO3, LiFeO2, Li5FeO4 or Li3(FeO3)2.

4. The novel lithium manganese oxide structure as described in claim 1, characterized in that: The particle size of the lithium manganese oxide matrix ranges from 5 to 15 μm. The thickness of the gel film ranges from 10 to 100 nm; The particle size of the lithium supplement has a range of 0.5-2 μm.

5. A positive electrode sheet having the novel structure of lithium manganese oxide as described in any one of claims 1 to 4, characterized in that: The positive electrode slurry for fabricating the positive electrode sheet includes the novel structured lithium manganese oxide and a curing agent; wherein, The curing agent is poly(adipitic anhydride), tetrahydrophthalic anhydride, phthalic anhydride, diaminodiphenylmethane, diethylaminopropylamine, diacid anhydride curing agent, or a custom-mixed curing agent; wherein... The diacid anhydride curing agent is a mixture of oxalic acid and polyadipic anhydride; The custom-mixed curing agent is a mixture of polyazelic anhydride and tetrahydrophthalic anhydride.

6. A method for preparing a novel lithium manganese oxide structure as described in any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: According to the preset mass ratio, polyethylene ester, sodium polyvinyl acetate, ethanol and polyethylene glycol are mixed and stirred at the preset temperature for the preset duration to obtain an organic polymer solution. According to the preset corresponding mass ratio, the organic polymer solution, lithium supplement and lithium manganese oxide matrix are added to a high-speed mixer and mixed for the corresponding preset duration to obtain an intermediate product; The intermediate product is placed in an oven and subjected to pre-crosslinking treatment according to the type of lithium supplement, followed by deep curing treatment to obtain a novel structured lithium manganese oxide.

7. A method for preparing a positive electrode sheet as described in claim 5, characterized in that, The preparation method includes the following steps: According to the preset mass ratio, the novel structure lithium manganese oxide, conductive carbon black, PVDF and curing agent are mixed, NMP is added to adjust the viscosity to the preset viscosity value, and vacuum stirring is performed for the preset duration to obtain the positive electrode slurry. The positive electrode slurry is coated on aluminum foil, and the areal density is controlled at the corresponding preset areal density value. Vacuum drying is carried out at the corresponding preset drying temperature for the corresponding preset duration to obtain an unrolled electrode sheet. Using a hot roller press, the unrolled electrode sheet is processed at a corresponding preset working pressure, a corresponding preset working temperature, and a corresponding preset rolling speed to obtain a positive electrode sheet.

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