Preparation method of modified lithium iron phosphate material containing fumed silica

Abstract

The invention discloses a preparation method of a modified lithium iron phosphate material containing fumed silica, and relates to the technical field of lithium ion batteries, and the method comprises the following steps: firstly, dispersing fumed silica in dry inert gas to ensure that the fumed silica is not agglomerated; by adopting an ultrasonic dispersion or mechanical dispersion technology in an inert gas environment, fumed silica is uniformly loaded on the surface of lithium iron phosphate in the form of monodisperse nanoparticles, the agglomeration phenomenon is eliminated, the contact area of a modifier is increased by more than 40% by the process, and the consistency of electrochemical performance is ensured; the modified material shows excellent rate capability and low-temperature performance, and a novel solution is provided for application of a power battery in a high-energy density scene; the process not only can effectively solve the agglomeration problem of the lithium iron phosphate material in practical application, but also can remarkably improve the processability and electrochemical performance of the lithium iron phosphate material, and has wide application prospects and market value.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for preparing a fumed silica-containing modified lithium iron phosphate material. Background Art

[0002] With the transformation of the global energy structure and the rapid development of emerging industries such as electric vehicles and energy storage systems, lithium-ion batteries, as efficient and clean energy storage devices, have become a vital component of modern science and industry. Due to their high energy density, long cycle life, and low self-discharge rate, lithium-ion batteries are widely used in consumer electronics, electric vehicles, energy storage power stations, and other fields. In recent years, with the continuous advancement of technology, the research and application of lithium-ion battery cathode materials have also made significant progress. Among them, lithium iron phosphate (LiFePO4) has gradually become one of the mainstream cathode materials due to its high safety, low cost, and environmental friendliness.

[0003] Lithium iron phosphate material has an olivine crystal structure, a theoretical specific capacity of 170 mAh / g, and excellent thermal stability and cycle performance. However, despite the significant advantages of lithium iron phosphate materials in terms of safety, cost and environmental protection, they still face some technical challenges in practical applications. First, the particle size of lithium iron phosphate materials is small, usually at the nanometer or submicron level. Although this small particle characteristic is conducive to improving the specific surface area and electrochemical properties of the material, it is also prone to particle agglomeration. Particle agglomeration not only affects the uniform dispersion of the material, but also makes it difficult to homogenize the slurry during the battery preparation process, thereby affecting the coating quality of the electrode and the consistency of the battery.

[0004] Based on this, a method for preparing a lithium iron phosphate material modified with fumed silica is now provided, which can eliminate the disadvantages of the existing methods. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a fumed silica-containing modified lithium iron phosphate material to solve the problems in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a fumed silica-modified lithium iron phosphate material comprises the following steps:

[0008] Step 1: Disperse the fumed silica in a dry inert gas to ensure that the fumed silica is free of agglomerates;

[0009] Step 2: Drying the lithium iron phosphate powder in a high temperature vacuum environment until the moisture content drops below 0.1%;

[0010] Step 3: Adding fumed silica to lithium iron phosphate;

[0011] Step 4: Mixing lithium iron phosphate and fumed silicon dioxide.

[0012] Preferably, in step 1, the inert gas is nitrogen or argon, and the moisture content is ≤0.1%.

[0013] Preferably, in step 1, the fumed silica is dispersed by ultrasonic dispersion or mechanical dispersion.

[0014] Preferably, in step 2, the deep drying of the lithium iron phosphate powder adopts a vacuum heat treatment process, the drying temperature is 80-120° C., the vacuum degree is ≤100 Pa, the drying time is 24 hours, and the final moisture content is ≤0.1%.

[0015] Preferably, in step three, the amount of the added fumed silicon dioxide is 0.5% to 1.5% of the mass of the lithium iron phosphate.

[0016] Preferably, in step 4, the lithium iron phosphate and the fumed silica are mixed for 10 to 30 minutes using dry ball milling or high-speed shear mixing equipment, so that the fumed silica is evenly coated on the surface of the lithium iron phosphate particles.

[0017] Preferably, the thickness of the silicon dioxide coating layer is 220 nm, and the coating integrity is controlled by adjusting the mixing time, and the coating uniformity is ≥95%.

[0018] Preferably, the vacuum drying process adopts a gradient temperature rising process: the temperature is raised from room temperature to the target temperature at a heating rate of 5°C / min, and the holding time is not less than 2 hours.

[0019] Preferably, the fumed silica model is 200, specific surface area 200m 2 / g.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention adopts ultrasonic dispersion or mechanical dispersion technology under an inert gas environment to uniformly load the fumed silica on the surface of lithium iron phosphate in the form of monodisperse nanoparticles, eliminating agglomeration. This process increases the contact area of the modifier by more than 40%, ensuring the consistency of electrochemical performance; and the modified material exhibits excellent rate performance and low-temperature performance, providing a new solution for the application of power batteries in high-energy density scenarios; this process can not only effectively solve the agglomeration problem of lithium iron phosphate materials in practical applications, but also significantly improve their processing performance and electrochemical performance, and has broad application prospects and market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process of the present invention.

[0023] Figure 2 Schematic diagram of the comparison of particle size distribution test of fumed silica modified LFP and carbon-coated modified LFP of the present invention.

[0024] Figure 3 This is a comparison chart of the stability test of the fumed silica modified LFP and the carbon-coated modified LFP of the present invention.

[0025] Figure 4 This is a comparison chart of the particle size distribution test of fumed silica modified LFP and carbon-coated modified LFP. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0027] In one embodiment, Figures 1-4 As shown, the following steps:

[0028] Step 1: Disperse the fumed silica in a dry inert gas to ensure that the fumed silica is free of agglomerates;

[0029] Step 2: Drying the lithium iron phosphate powder in a high temperature vacuum environment until the moisture content drops below 0.1%;

[0030] Step 3: Adding fumed silica to lithium iron phosphate;

[0031] Step 4: Mixing lithium iron phosphate and fumed silicon dioxide.

[0032] The present invention is described in detail below with reference to the following examples. The examples provide detailed implementation methods and specific operating procedures based on the technical solutions of the present invention. However, the protection scope of the present invention is not limited to the following examples.

[0033] Example:

[0034] First, in a nitrogen environment, ultrasonic dispersion is used to break up the agglomerations of fumed silica to form monodisperse nanoparticles, with nitrogen humidity ≤0.1%. Then, 1 kg of lithium iron phosphate is dried in a vacuum environment at 100°C for 12 hours. After that, 1% fumed silica by mass of lithium iron phosphate is added, and the two are then mixed in a ball mill for 30 minutes.

[0035] Comparative Example:

[0036] 1 kg of lithium iron phosphate was dried under vacuum at 100° C. for 12 hours and then treated using conventional carbon coating modification technology in the art.

[0037] 1. Particle size distribution test comparison:

[0038] The particle size distribution of the fumed silica-modified LFP (Example) and the carbon-coated modified LFP (Comparative Example) was measured using a laser particle size analyzer (Mastersizer-3000). The particle refractive index was 1.55. The dispersion medium was water. The pretreatment was ultrasonication for 3 minutes without using a dispersant.

[0039] Comparison table:

[0040]

[0041] The comparison results are as follows Figure 2 shown.

[0042] Result analysis: Both fumed silica modified LFP and carbon-coated modified LFP were ultrasonically tested without using a dispersant. The particle size data of fumed silica modified LFP were smaller than that of carbon-coated modified LFP, and no large peak appeared at the end of the particle size distribution graph, indicating that the LFP modified with fumed silica was evenly dispersed without agglomeration.

[0043] 2. Stability comparison:

[0044] The slurry stability test of the fumed silica modified LFP (Example) and the carbon-coated modified LFP (Comparative Example) was conducted using a multiple light scattering instrument (Model Fromulaction); the backscattering scanning frequency was 1 time / 1 min, and the scanning time was 1 h;

[0045] The comparison results are as follows Figure 3 shown.

[0046] Result analysis: The TSI values of the slurries prepared by fumed silica modified LFP were lower than those of carbon-coated modified LFP, indicating that the slurries prepared by fumed silica modified LFP had better stability.

[0047] 3. Comparison of electrical properties:

[0048] Batteries were made using fumed silica-modified LFP (Example) and carbon-coated modified LFP (Comparative Example) and subjected to cycling performance tests at a temperature of 25°C and a rate of 1C.

[0049] The comparison results are as follows Figure 4 shown.

[0050] Result analysis: The capacity retention rate of the battery made of fumed silica modified LFP after 2500 cycles is 90.6%, while the capacity retention rate of the battery made of carbon-coated modified LFP after 2500 cycles is 88.2%, indicating that fumed silica modified LFP has a better effect on improving the battery cycle performance.

[0051] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a fumed silica-modified lithium iron phosphate material, characterized in that: The following steps are involved: Step 1: Disperse the fumed silica in a dry inert gas to ensure that the fumed silica is free of agglomerates; Step 2: Drying the lithium iron phosphate powder in a high temperature vacuum environment until the moisture content drops below 0.1%; Step 3: Adding fumed silica to lithium iron phosphate; Step 4: Mixing lithium iron phosphate and fumed silicon dioxide.

2. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, characterized in that: In step 1, the inert gas is nitrogen or argon, and the moisture content is ≤0.1%.

3. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, characterized in that: In step 1, the fumed silica is dispersed by ultrasonic dispersion or mechanical dispersion.

4. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, wherein: In step 2, the lithium iron phosphate powder is deeply dried using a vacuum heat treatment process, with a drying temperature of 80-120° C., a vacuum degree of ≤100 Pa, a drying time of 2-4 hours, and a final moisture content of ≤0.1%.

5. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, characterized in that: In step three, the amount of added fumed silicon dioxide is 0.5%-1.5% of the mass of the lithium iron phosphate.

6. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, characterized in that: In step 4, the lithium iron phosphate and fumed silica are mixed for 10-30 minutes using dry ball milling or high-speed shear mixing equipment to uniformly coat the surface of the lithium iron phosphate particles with the fumed silica.

7. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, wherein: The thickness of the silicon dioxide coating layer is 2-20 nm, and the coating integrity is controlled by adjusting the mixing time, and the coating uniformity is ≥95%.

8. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 4, characterized in that: The vacuum drying process adopts a gradient temperature rising process: the temperature is raised from room temperature to the target temperature at a heating rate of 5°C / min, and the holding time is not less than 2 hours.

9. The method for preparing a fumed silica-modified lithium iron phosphate material according to claim 1, characterized in that: The fumed silica model is 200, specific surface area 200m 2 / g.

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