Polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material, positive electrode plate and lithium ion battery
By modifying lithium iron phosphate cathode materials with polyethylene oxide nanofibers, the problem of low lithium-ion transport efficiency in lithium-ion batteries has been solved, achieving high-efficiency lithium-ion transport and conductivity, and improving battery energy efficiency and cycle stability.
Patent Information
- Application Number
- CN202511644600.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-02-17
AI Technical Summary
The low lithium-ion transport efficiency in lithium-ion batteries leads to low battery energy efficiency. Existing improvement methods, such as the addition of carbon materials, particle nano-sizing, and conventional polymer modification, have limitations that affect battery performance.
Lithium iron phosphate cathode material is modified with polyethylene oxide nanofibers. Polyethylene oxide nanofibers are prepared by electrospinning and combined with conductive agents and binders to form an excellent cathode electrode structure, thereby improving lithium-ion transport performance.
It significantly improves the lithium-ion transport efficiency and conductivity of lithium-ion batteries, shortens the electrolyte immersion time, and enhances battery energy efficiency and cycle stability.
Smart Images
Figure CN121546012A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, specifically to a polyethylene oxide nanofiber modified lithium iron phosphate cathode material, cathode sheet, and lithium-ion battery. Background Technology
[0002] Among lithium-ion battery cathode materials, lithium iron phosphate (LiFePO4) has attracted widespread attention due to its advantages such as high safety, long cycle life and low cost.
[0003] However, its practical application still faces the following key technical bottlenecks: 1. Insufficient ion diffusion rate: The material itself has a low lithium-ion diffusion coefficient (approximately 10). -14 cm 2 1. **Severe polarization during high-rate charging and discharging ( / s), limiting its application in fast charging scenarios.** 2. **Electrode structure design defects:** The stacking of active particles in traditional electrodes leads to tortuous ion transport paths, and the electrolyte has difficulty effectively penetrating into the electrode interior, further exacerbating kinetic limitations.
[0004] Current methods for addressing the above problems still have significant limitations: 1. Excessive addition of carbon materials: While improving conductivity, it sacrifices volumetric energy density; 2. Particle nano-sizing: While shortening the ion diffusion path, it increases the specific surface area, exacerbates electrode-electrolyte side reactions, and leads to decreased cycle stability; 3. Conventional polymer modification: It easily clogs electrode pores, hinders ion transport, and increases interfacial impedance. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of low lithium-ion transport efficiency and low battery energy efficiency in existing lithium-ion batteries.
[0006] To achieve the above objectives, the first aspect of the present invention provides a lithium iron phosphate cathode material modified with polyethylene oxide nanofibers, the cathode material comprising lithium iron phosphate and polyethylene oxide nanofibers in a mass ratio of 90-98:1. The polyethylene oxide nanofibers are obtained by electrospinning from a spinning solution containing polyethylene oxide. The polyethylene oxide nanofibers have an average diameter of 50-500 nm and a specific surface area of 30-50 m². 2 / g, lithium-ion conductivity ≥1.2×10 -5 S / cm.
[0007] A second aspect of the present invention provides a lithium iron phosphate positive electrode sheet modified with polyethylene oxide nanofibers, the positive electrode sheet comprising a positive current collector and a positive active material coating disposed on at least one surface of the positive current collector; The positive electrode active material coating includes a conductive agent, a binder, and the polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material described in the first aspect.
[0008] A third aspect of the present invention provides a lithium-ion battery comprising a negative electrode, an electrolyte, a separator, and a positive electrode as described in the second aspect.
[0009] The polyethylene oxide nanofiber modified lithium iron phosphate cathode material provided by this invention has excellent structural stability and can shorten the electrolyte wetting time; the lithium-ion battery prepared using the cathode sheet of the polyethylene oxide nanofiber modified lithium iron phosphate cathode material provided by this invention has excellent lithium-ion transport efficiency and conductivity. Attached Figure Description
[0010] Figure 1 This is a SEM image of the polyethylene oxide nanofiber positive electrode sheet in Example 1 of the present invention.
[0011] Figure 2 This is an optical microscope image of the polyoxyethylene nanofibers prepared in Preparation Example 1 of the present invention.
[0012] Figure 3 This is a lithium-ion conductivity test chart using a single polyethylene oxide nanofiber as described in this invention. Detailed Implementation
[0013] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0014] As mentioned above, the first aspect of the present invention provides a lithium iron phosphate cathode material modified with polyethylene oxide nanofibers, the cathode material comprising lithium iron phosphate and polyethylene oxide nanofibers in a mass ratio of 90-98:1. The polyethylene oxide nanofibers are obtained by electrospinning from a spinning solution containing polyethylene oxide. The polyethylene oxide nanofibers have an average diameter of 50-500 nm and a specific surface area of 30-50 m². 2 / g, lithium-ion conductivity ≥1.2×10 -5 S / cm.
[0015] The polyoxyethylene nanofiber modified lithium iron phosphate cathode material of the present invention uses specific polyoxyethylene nanofibers obtained by electrospinning, which can improve its ion transport performance through nano-sizing, thereby significantly improving the lithium-ion transport efficiency of lithium-ion batteries.
[0016] Preferably, the polyoxyethylene has a weight-average molecular weight of 1000-10000 kg / mol. The inventors have found that under these preferred conditions, the prepared cathode material exhibits higher lithium-ion transport efficiency when applied to lithium-ion batteries.
[0017] In a preferred embodiment, the content of the polyethylene oxide in the spinning solution is 2-10 wt%. The inventors have discovered that under these preferred conditions, the prepared cathode material exhibits higher lithium-ion transport efficiency and rate performance when applied to lithium-ion batteries.
[0018] Preferably, the spinning solution further contains a solvent, and the solvent content is 90-98 wt% based on the total mass of the spinning solution.
[0019] This invention does not impose any particular requirements on the preparation method of the spinning solution; those skilled in the art can prepare it according to methods known in the art. Exemplarily, the polyethylene oxide and the solvent are first mixed at a speed of 450-550 rpm for 2-4 hours; wherein the solvent is selected from at least one of anhydrous ethanol, ethylene glycol, and deionized water. This invention will not be described in detail here, and those skilled in the art should not construe it as a limitation of the invention.
[0020] This invention does not impose special requirements on the specific operational steps of the electrospinning process; those skilled in the art can operate according to methods known in the art. This invention will not be described in detail here, and should not be construed as a limitation thereof.
[0021] This invention does not impose any particular requirements on the preparation method of the polyoxyethylene nanofiber modified lithium iron phosphate cathode material; those skilled in the art can prepare it according to methods known in the art. Exemplarily, the lithium iron phosphate and the polyoxyethylene nanofibers are mixed for a second time at a rotation speed of 450-550 rpm for 20-40 minutes. This invention will not be described in detail here, and those skilled in the art should not construe this as a limitation of the invention.
[0022] Preferably, the conditions for the electrospinning process include: voltage of 10-50kV, temperature of 20-50℃, relative humidity of 30-50%, and receiving distance of the spinning plate of 5-20cm.
[0023] A second aspect of the present invention provides a lithium iron phosphate positive electrode sheet modified with polyethylene oxide nanofibers, the positive electrode sheet comprising a positive current collector and a positive active material coating disposed on at least one surface of the positive current collector; The positive electrode active material coating includes a conductive agent, a binder, and the polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material described in the first aspect.
[0024] In a preferred embodiment, the positive current collector is aluminum foil.
[0025] Preferably, the conductive agent is selected from at least one of conductive carbon black (Super P), carbon nanotubes, graphene, and graphite.
[0026] Preferably, the adhesive is selected from at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber, and carboxymethyl cellulose.
[0027] The present invention does not particularly limit the preparation method of the positive electrode sheet; it can be prepared by a dry electrode sheet process or by a wet electrode sheet process.
[0028] To improve the performance of the positive electrode, preferably, the method for preparing the positive electrode includes: (1) The polyethylene oxide nanofiber modified lithium iron phosphate cathode material, the conductive agent, and the binder are mixed to obtain mixture I; (2) Mix the mixture I with N-methyl-2-pyrrolidone (NMP) to form a slurry, thereby obtaining a positive electrode active material coating material; (3) The positive electrode active material coating material is coated on at least one surface of the positive electrode current collector and dried to obtain the positive electrode sheet.
[0029] In a preferred embodiment, in step (2), the slurry is stirred in a planetary mixer to obtain a positive electrode active material coating material.
[0030] Preferably, the stirring conditions include: a rotation speed of 500-600 rpm and a stirring time of 8-12 min.
[0031] Preferably, the mass ratio of the mixture I to the N-methyl-2-pyrrolidone is 1-3:1.
[0032] Preferably, in step (1), the mixing conditions include: a rotation speed of 500-600 rpm and a time of 8-12 min.
[0033] Preferably, the coating thickness is 100-200 μm.
[0034] This invention does not impose any particular restrictions on the order or specific method of adding the substances in the mixture; those skilled in the art can make selections based on known techniques. This invention will not be described in detail here, and should not be construed as a limitation thereof.
[0035] According to a preferred embodiment, the mass ratio of the polyethylene oxide nanofiber modified lithium iron phosphate cathode material, the conductive agent, and the binder is 93-95:4-6:1.
[0036] According to another preferred embodiment, in step (3), the drying temperature is 90-140°C and the time is 8-12 min.
[0037] In a preferred embodiment, the electrolyte contact angle of the positive electrode is ≤10°.
[0038] As previously described, a third aspect of the present invention provides a lithium-ion battery comprising a negative electrode, an electrolyte, a separator, and the positive electrode described in the second aspect.
[0039] In a preferred embodiment, the lithium-ion battery has an energy efficiency of ≥95% at 1.0P.
[0040] This invention does not impose any particular requirements on the preparation method of lithium-ion batteries; those skilled in the art can prepare them using known techniques. The invention will not be described in detail here, and should not be construed as a limitation thereof.
[0041] The present invention will be described in detail below through examples. Unless otherwise specified, specific experimental steps or conditions in the following examples can be performed according to known experimental steps or conditions described in the literature in this field. Unless otherwise specified, the raw materials or instruments used are commercially available. Unless otherwise specified, the reaction temperature in the following examples is at room temperature, which refers to 22±2℃.
[0042] Polyethylene oxide A: weight average molecular weight of 2000 kg / mol, purchased from Aladdin Biochemical Technology Co., Ltd.
[0043] Polyethylene oxide B: weight average molecular weight of 600 kg / mol, purchased from Aladdin Biochemical Technology Co., Ltd.
[0044] Solvent A: A mixture of anhydrous ethanol and deionized water in a mass ratio of 4:1.
[0045] The specific surface area of polyethylene oxide nanofibers was determined by the BET specific surface area tester (manufacturer: Bestech, model: 3H-2000PS4).
[0046] Scanning electron microscope (SEM), manufacturer: Hitachi, Japan, model: Regulus 8100.
[0047] Preparation Example 1 S1: Polyethylene oxide A (100g) and solvent A are mixed for 3 hours at a speed of 500 rpm to obtain spinning solution I; Specifically, based on the total mass of the spinning solution I, the content of polyethylene oxide A is 6 wt%, and the content of solvent A is 94 wt%. S2: Electrospinning the spinning solution I to prepare polyethylene oxide nanofibers; The conditions for electrospinning are: voltage 20kV, temperature 25℃, relative humidity 35%, and receiving distance of the spinning plate 12cm. S3: The polyethylene oxide nanofibers and lithium iron phosphate are mixed for 30 minutes at a mass ratio of 1:95 at 500 rpm to obtain polyethylene oxide nanofiber modified lithium iron phosphate cathode material A. The polyethylene oxide nanofibers have an average diameter of 200 nm and a specific surface area of 40 m². 2 / g.
[0048] Preparation Example 2 S1: Polyethylene oxide A (100g) and solvent A are mixed for 3 hours at a speed of 500 rpm to obtain spinning solution I; Specifically, based on the total mass of the spinning solution, the content of polyethylene oxide A is 8 wt%, and the content of solvent A is 92 wt%. S2: Electrospinning the spinning solution I to prepare polyethylene oxide nanofibers; The conditions for electrospinning are: voltage 30kV, temperature 35℃, relative humidity 45%, and receiving distance of the spinning plate 15cm. S3: The polyethylene oxide nanofibers and lithium iron phosphate are mixed for 30 minutes at a mass ratio of 1:95 at 500 rpm to obtain polyethylene oxide nanofiber modified lithium iron phosphate cathode material B. The polyethylene oxide nanofibers have an average diameter of 290 nm and a specific surface area of 31 m². 2 / g.
[0049] Preparation Example 3 The same method as in Preparation Example 1 was used, except that polyethylene oxide A in step S1 was replaced with an equal mass of polyethylene oxide B to obtain polyethylene oxide nanofiber modified lithium iron phosphate cathode material C. The polyethylene oxide nanofibers have an average diameter of 429 nm and a specific surface area of 31 m². 2 / g.
[0050] Comparative Preparation Example 1 S1: Polyethylene oxide A (100g) and solvent A are mixed for 3 hours at a speed of 500 rpm to obtain spinning solution I; Based on the total mass of the spinning solution I, the content of polyethylene oxide A is 18 wt%, and the content of solvent A is 82 wt%. S2: Electrospinning the spinning solution I to prepare polyethylene oxide nanofibers; The conditions for electrospinning are: voltage of 8kV, temperature of 25℃, relative humidity of 35%, and receiving distance of the spinning plate of 5cm. S3: The polyethylene oxide nanofibers and lithium iron phosphate are mixed for 30 minutes at a mass ratio of 1:95 at 500 rpm to obtain polyethylene oxide nanofiber modified lithium iron phosphate cathode material D. The polyethylene oxide nanofibers have an average diameter of 959 nm and a specific surface area of 13 m². 2 / g.
[0051] Comparative Preparation Example 2 The same method as in Preparation Example 1 was used, except that the polyethylene oxide A in step S1 was replaced with an equal mass of polypropylene to obtain polypropylene nanofiber modified lithium iron phosphate cathode material. The polypropylene nanofibers have an average diameter of 400 nm and a specific surface area of 23 m². 2 / g.
[0052] Example 1 (1) Polyethylene oxide nanofiber modified lithium iron phosphate cathode material A (100g) was mixed with Super P and PVDF at a mass ratio of 95:4:1 at a speed of 500rpm for 10min to obtain mixture I; (2) Mix the mixture I and NMP at a mass ratio of 2:1 using a planetary mixer at 500 rpm for 10 min to prepare a slurry, thereby obtaining the positive electrode active material coating material; (3) The positive electrode active material coating material is uniformly coated on one surface of an aluminum foil to form a coating with a thickness of 150 μm, and dried at 120°C for 10 min to obtain a positive electrode sheet.
[0053] Example 2 The same method as in Example 1 was used, except that the polyethylene oxide nanofiber modified lithium iron phosphate cathode material A in step (1) was replaced with an equal mass of polyethylene oxide nanofiber modified lithium iron phosphate cathode material B to obtain the cathode sheet.
[0054] Example 3 The same method as in Example 1 was used, except that the polyethylene oxide nanofiber modified lithium iron phosphate cathode material A in step (1) was replaced with an equal mass of polyethylene oxide nanofiber modified lithium iron phosphate cathode material C to obtain the cathode sheet.
[0055] Comparative Example 1 The same method as in Example 1 was used, except that the polyethylene oxide nanofiber modified lithium iron phosphate cathode material A in step (1) was replaced with an equal mass of polyethylene oxide nanofiber modified lithium iron phosphate cathode material D to obtain the cathode sheet.
[0056] Comparative Example 2 The same method as in Example 1 was used, except that the polyethylene oxide nanofiber modified lithium iron phosphate cathode material A in step (1) was replaced with an equal mass of lithium iron phosphate to obtain the cathode sheet.
[0057] Comparative Example 3 The same method as in Example 1 was used, except that the polyethylene oxide nanofiber modified lithium iron phosphate cathode material A in step (1) was replaced with an equal mass of polypropylene nanofiber modified lithium iron phosphate cathode material to obtain the cathode sheet.
[0058] Test Example 1 The polyethylene oxide nanofiber modified lithium iron phosphate cathode sheet in Example 1 of this invention was tested using scanning electron microscopy, and SEM morphology images were obtained. Figure 1 ).Depend on Figure 1 It is known that the presence of electrospun nanofibers on the surface of lithium iron phosphate can improve the ionic conductivity of lithium iron phosphate and reduce the polarization of the electrode.
[0059] Test Example 2 The polyoxyethylene nanofibers prepared in Example 1 of this invention were tested using an optical microscope, and the optical microscope images were obtained ( Figure 2 ).Depend on Figure 2 It is known that the average diameter of the polyethylene oxide nanofibers is 200 nm.
[0060] Test Example 3 The polyoxyethylene nanofibers prepared in the above preparation example were placed in a lithium-ion battery electrolyte (a 1 mol / L lithium hexafluorophosphate solution) and allowed to stand for a while. Then, one fiber was taken out and dried. The lithium-ion conductivity of the polyoxyethylene nanofibers was measured using an electrochemical workstation (manufacturer: Shanghai Chenhua Instrument Co., Ltd., model: CHI660e). The results are shown in Table 1. Figure 3 An exemplary lithium-ion conductivity test diagram of polyethylene oxide nanofibers is provided, by... Figure 3 It can be seen that polyoxyethylene nanofibers were successfully prepared and distributed between two electrodes for measuring the lithium-ion conductivity of the nanofibers.
[0061] Test Example 4 The positive electrode sheet prepared in the above example is used as the positive electrode, graphite is used as the negative electrode, Celgard2400 polypropylene porous membrane is used as the separator, and LiPF6, EC, DMC and EMC (where EC is ethylene carbonate, EMC is ethyl methyl carbonate and DMC is dimethyl carbonate) in a volume ratio of 7:1:1:1 are used as the electrolyte. The manufacturing method of lithium-ion batteries is as follows: the positive electrode, lithium battery separator, and negative electrode are wound sequentially into a cell; then, one cell is assembled into a battery by welding, casing, and top cover welding, baked at 85°C for 24 hours, electrolyte is injected, high-temperature standing is performed, and formation is carried out to obtain a lithium battery with a designed capacity of 280Ah and a total electrolyte injection volume of 1203g; thus, a lithium-ion battery is prepared.
[0062] The lithium-ion battery prepared in the above embodiments was placed in a constant temperature chamber at 25°C and charged to 3.65V with a constant power of 1P (448W). Then it was discharged to 2.5V with a constant power of 1P (448W). This cycle was repeated 200 times. The discharge input energy and charging output energy were recorded. The energy efficiency of the battery at 1.0P was calculated as = discharge input energy / charging output energy × 100%. The results are shown in Table 1.
[0063] Test Example 5 The contact angle between the positive electrode sheet prepared in the above embodiments and the electrolyte was tested using a contact angle measuring instrument (manufacturer: Shanghai Zhongchen Digital Technology Equipment Co., Ltd., model: JC2000D2). The results are shown in Table 1.
[0064] Table 1
[0065] As can be seen from the results in Table 1, the cathode sheet and lithium-ion battery containing the polyethylene oxide-modified lithium iron phosphate cathode material provided by the present invention can significantly improve the lithium-ion transport efficiency and battery energy efficiency, and have excellent electrochemical performance.
[0066] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A polyethylene oxide nanofiber modified lithium iron phosphate cathode material, characterized in that, The positive electrode material comprises lithium iron phosphate and polyethylene oxide nanofiber in a mass ratio of 90-98:1; The polyethylene oxide nanofiber is obtained by electrospinning of a spinning solution containing polyethylene oxide; The average diameter of the polyethylene oxide nanofiber is 50-500 nm, and the specific surface area is 30-50 m 2 / g, and lithium ion conductivity ≥ 1.2 x 10 -5 S / cm.
2. The poly(ethylene oxide) nanofiber modified lithium iron phosphate cathode material of claim 1, wherein, The weight average molecular weight of the polyethylene oxide is 1000-10000 kg / mol.
3. The poly(ethylene oxide) nanofiber modified lithium iron phosphate cathode material of claim 1, wherein, In the spinning solution, the content of the polyethylene oxide is 2-10 wt%.
4. The poly(ethylene oxide) nanofiber modified lithium iron phosphate cathode material of any one of claims 1-3, wherein the lithium iron phosphate has a composition of Li1+xFexPO4, wherein x is between 0 and 0.
1. The electrospinning conditions include: voltage of 10-50 kV, temperature of 20-50℃, relative humidity of 30-50%, and spinning plate receiving distance of 5-20 cm.
5. A polyethylene oxide nanofiber modified lithium iron phosphate cathode electrode sheet, characterized in that, The positive electrode tab comprises a positive electrode current collector and a positive electrode active material coating layer arranged on at least one surface of the positive electrode current collector; The positive electrode active material coating layer comprises a conductive agent, a binder, and the polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material according to any one of claims 1-4.
6. The cathode electrode of claim 5, wherein, The preparation method of the positive electrode tab comprises: (1) mixing the polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material, the conductive agent, and the binder to obtain a mixture I; (2) sizing the mixture I with N-methyl-2-pyrrolidone to obtain a positive electrode active material coating material; (3) coating the positive electrode active material coating material on at least one surface of the positive electrode current collector, drying to obtain the positive electrode tab.
7. The cathode electrode of claim 6, wherein, The mass ratio of the polyethylene oxide nanofiber modified lithium iron phosphate positive electrode material, the conductive agent, and the binder is 93-95:4-6:
1.
8. The cathode electrode of claim 6, wherein, In step (3), the drying temperature is 90-140℃, and the time is 8-12 min.
9. The positive electrode sheet according to any one of claims 5 to 8, characterized by, The electrolyte contact angle of the positive electrode tab is ≤10°.
10. A lithium-ion battery, characterized by, The lithium ion battery comprises a negative electrode tab, an electrolyte, a separator, and the positive electrode tab according to any one of claims 5-9. Preferably, the energy efficiency of the lithium ion battery at 1.0P is ≥95%.