A diatomite-derived silicon-carbon negative electrode material, a preparation method thereof and application thereof in lithium ion batteries

Abstract

The application discloses diatomite-derived silicon-carbon negative electrode material and a preparation method thereof and application in lithium ion batteries, and belongs to the technical field of lithium ion battery negative electrode materials. The method discloses the diatomite and the pitch as raw materials by adopting magnesium heat treatment, and the diatomite-derived silicon-carbon negative electrode material is obtained through specific composite process and calcination treatment. The method can uniformly coat the carbon material on the inner and outer surfaces of the porous micron-sized silicon negative electrode, solves the technical problems of the existing silicon-carbon negative electrode material nano-particle agglomeration and the carbon material coating only on the outer surface, and achieves the beneficial effects of further improving the conductivity and structural stability of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a diatomaceous earth-derived silicon-carbon anode material, its preparation method, and its application in lithium-ion batteries. Background Technology

[0002] With the rapid market penetration of electric vehicles (EVs) globally, the energy density of lithium-ion batteries (LIBs) used in EVs urgently needs further improvement. In this regard, silicon (Si) anodes, with a theoretical capacity (3579 mAh / g) nearly ten times higher than traditional graphite anodes (372 mAh / g), are considered one of the leading anode material candidates for improving the energy density of LIBs. However, the large-scale application of silicon anodes still faces several major challenges, including silicon particle crushing, continuous growth of the solid electrolyte interphase (SEI) layer during charging / discharging, and the significant damage to the electrode material structure caused by the volume expansion / contraction of silicon-based anodes.

[0003] Porous Si / C nanocomposites have been used as one of the most effective methods to accommodate the large volume changes in silicon-based anode materials and prevent side reactions between the electrolyte and Si. Representative designs of nanostructured Si include garnet-shaped Si / C anodes and Si nanoparticles embedded in graphite layers. However, as the size of primary silicon particles shrinks to the nanoscale, assembling nanostructured silicon into micrometer-scale materials presents certain challenges. Furthermore, carbon materials are typically coated on the surface of porous silicon-based anode materials, failing to affect the internal pore surfaces. Summary of the Invention

[0004] The purpose of this invention is to provide a diatomaceous earth-derived silicon-carbon anode material, its preparation method, and its application in lithium-ion batteries, in order to solve the technical problems of nanoparticle agglomeration in existing silicon-carbon anode materials and carbon materials only being coated on the outer surface.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a method for preparing diatomaceous earth-derived silicon-carbon anode materials, comprising the following steps:

[0007] After mixing magnesium-heat-treated diatomaceous earth and asphalt mixture, the mixture is filtered to obtain the filtered solid.

[0008] The filtered solid was calcined under an inert atmosphere to obtain a diatomaceous earth-derived silicon-carbon anode material.

[0009] The ratio of the magnesium-treated diatomaceous earth and asphalt mixture is (0.5-1) g : (10-20) mL;

[0010] The filtration process involves drawing the filtration device to a negative pressure state, with a pressure of -0.1 to -0.3 MPa, while simultaneously applying pressure from the upper part of the filtration head of the filtration device, with a pressure of 0.1 to 0.3 MPa.

[0011] Furthermore, before the magnesium-treated diatomaceous earth and the asphalt mixture are mixed, the magnesium-treated diatomaceous earth is washed sequentially with dilute hydrochloric acid and deionized water, and then dried under vacuum conditions.

[0012] Furthermore, the drying process is carried out at a temperature of 60–80°C for 10–12 hours.

[0013] Furthermore, the asphalt mixture is obtained by dissolving asphalt in a toluene solution and mixing.

[0014] Furthermore, the concentration of the asphalt mixture is 2–5 mg / mL.

[0015] Furthermore, the filtration device consists of a sealed filtration head and a glass filtration bottle connected to the lower part; the filtration head is a polytetrafluoroethylene cylindrical syringe.

[0016] The upper part of the filter head is connected to a polytetrafluoroethylene piston that can move up and down.

[0017] Furthermore, the calcination treatment is carried out at a temperature of 700–900°C for a time of 1–3 hours.

[0018] Furthermore, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder at a mass ratio of 1:1 to 3 and calcining it at 600°C under argon for 1 to 3 hours.

[0019] The present invention also discloses a diatomaceous earth-derived silicon-carbon anode material prepared by the above preparation method.

[0020] The present invention also discloses the application of the above-mentioned diatomite-derived silicon-carbon anode material, which is used as an anode material for lithium-ion batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention discloses a method for preparing diatomaceous earth-derived silicon-carbon anode materials. Using magnesium-treated diatomaceous earth and asphalt as raw materials, the method obtains the diatomaceous earth-derived silicon-carbon anode material through a composite process and calcination. This method employs a preparation process that simultaneously depressurizes the lower part of the filter head and pressurizes the upper part, enabling the asphalt liquid to be delivered simultaneously to the inner and outer surfaces of the porous diatomaceous earth structure. This allows for uniform coating of carbon material on both the inner and outer surfaces of the porous micron-sized silicon anode after calcination, solving the technical problems of nanoparticle agglomeration and carbon material coating only on the outer surface in existing silicon-carbon anode materials. This achieves the beneficial effect of further improving the conductivity and structural stability of the composite material.

[0023] Furthermore, the reaction raw materials used in this application are abundant, low-cost, and micron-sized, and have a natural nanoporous structure. The preparation method is simple, safe, and highly reproducible.

[0024] The present invention also discloses the application of the above-mentioned diatomite-derived silicon-carbon anode material in lithium-ion batteries. According to relevant experimental results, the material has an initial discharge specific capacity of nearly 1200 mAh / g and an initial coulombic efficiency of nearly 75% under 1C discharge conditions. After 100 cycles, the capacity retention rate is nearly 90%, which shows excellent electrochemical performance. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the diatomaceous earth-derived silicon-carbon anode material of this invention.

[0026] Figure 2 This is a SEM image of the diatomite-derived silicon-carbon anode material of this invention;

[0027] Figure 3 This is an enlarged SEM image of the diatomite-derived silicon-carbon anode material of this invention;

[0028] Figure 4 This is a charge-discharge curve of the diatomaceous earth-derived silicon-carbon anode material of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0030] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0031] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0032] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0033] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0034] This invention provides a method for preparing diatomaceous earth-derived silicon-carbon anode materials, comprising the following steps:

[0035] S1: The magnesium-heat-treated diatomaceous earth is washed sequentially with dilute hydrochloric acid and deionized water, and then vacuum-dried at 60-80℃ for 10-12 hours.

[0036] S2: Dissolve asphalt in toluene solution to a concentration of 2-5 mg / mL to obtain asphalt mixture;

[0037] S3: Mix 0.5-1g of magnesium-treated diatomaceous earth with 10-20mL of asphalt mixture, place it in an improved vacuum filter, filter, and collect the solid product;

[0038] S4: The solid product of S3 is calcined under an argon atmosphere to obtain the target product.

[0039] Preferably, the filtration process involves drawing the mixture into a negative pressure state in the filtration device, with a pressure of -0.1 to -0.3 MPa, while simultaneously pressurizing the filter head from the top using a peristaltic pump, with a pressure of 0.1 to 0.3 MPa.

[0040] The filtration device is a sealed filtration head with a glass filtration bottle connected to its lower part;

[0041] The filter head is a polytetrafluoroethylene cylindrical needle-shaped head;

[0042] The upper part of the filter head is connected to a polytetrafluoroethylene piston that can move up and down.

[0043] Preferably, the calcination temperature is 700–900℃ and the calcination time is 1–3 hours.

[0044] Preferably, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder at a mass ratio of 1:1 to 3 and calcining it at 600°C under argon for 1 to 3 hours.

[0045] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0046] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0047] Example 1

[0048] A method for preparing a diatomaceous earth-derived silicon-carbon anode material includes the following steps:

[0049] S1: The diatomaceous earth that has undergone magnesium heat treatment is washed sequentially with dilute hydrochloric acid and deionized water, and then vacuum dried at 80°C for 10 hours.

[0050] S2: Dissolve asphalt in toluene solution to obtain an asphalt mixture with a concentration of 4 mg / mL;

[0051] S3: Place 1g of magnesium-treated diatomaceous earth and 10mL of asphalt mixture in a vacuum filtration device, filter, and collect the solid after filtration; the pressure below the vacuum head is -0.1MP and the pressure above it is 0.3MP.

[0052] S4: The filtered solid was calcined at 900°C for 1 hour under an argon atmosphere to obtain diatomaceous earth-derived silicon-carbon anode material.

[0053] Among them, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder in a mass ratio of 1:1 and calcining it at 600℃ for 3 hours under argon.

[0054] Example 2

[0055] A method for preparing a diatomaceous earth-derived silicon-carbon anode material includes the following steps:

[0056] S1: The diatomaceous earth that has undergone magnesium heat treatment is washed sequentially with dilute hydrochloric acid and deionized water, and then vacuum dried at 60°C for 12 hours.

[0057] S2: Dissolve asphalt in toluene solution to obtain an asphalt mixture with a concentration of 2 mg / mL;

[0058] S3: Place 0.5g of magnesium-treated diatomaceous earth and 20mL of asphalt mixture in a vacuum filtration device, filter, and collect the solid after filtration; the pressure below the vacuum head is -0.3MP and the pressure above it is 0.1MP.

[0059] S4: The filtered solid was calcined at 700°C for 3 hours under an argon atmosphere to obtain diatomaceous earth-derived silicon-carbon anode material.

[0060] Among them, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder in a mass ratio of 1:1 and calcining it at 600℃ for 3 hours under argon.

[0061] Example 3

[0062] A method for preparing a diatomaceous earth-derived silicon-carbon anode material includes the following steps:

[0063] S1: The diatomaceous earth that has undergone magnesium heat treatment is washed sequentially with dilute hydrochloric acid and deionized water, and then vacuum dried at 70°C for 11 hours.

[0064] S2: Dissolve asphalt in toluene solution to obtain an asphalt mixture with a concentration of 5 mg / mL;

[0065] S3: Place 0.9g of magnesium-treated diatomaceous earth and 18mL of asphalt mixture in a vacuum filtration device, filter, and collect the solid after filtration; the pressure below the filter head is -0.2MP and the pressure above the filter head is 0.2MP.

[0066] S4: The filtered solid was calcined at 800°C for 2 hours under an argon atmosphere to obtain diatomaceous earth-derived silicon-carbon anode material.

[0067] Among them, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder at a mass ratio of 1:3 and calcining it at 600℃ for 1 hour under argon.

[0068] Example 4

[0069] A method for preparing a diatomaceous earth-derived silicon-carbon anode material includes the following steps:

[0070] S1: The diatomaceous earth that has undergone magnesium heat treatment is washed sequentially with dilute hydrochloric acid and deionized water, and then vacuum dried at 70°C for 10 hours.

[0071] S2: Dissolve asphalt in toluene solution to obtain an asphalt mixture with a concentration of 3 mg / mL;

[0072] S3: Place 0.8g of magnesium-treated diatomaceous earth and 17mL of asphalt mixture in a vacuum filtration device, filter, and collect the solid after filtration; the pressure below the filter head is -0.3MP and the pressure above the filter head is 0.1MP.

[0073] S4: The filtered solid was calcined at 900°C for 1 hour under an argon atmosphere to obtain diatomaceous earth-derived silicon-carbon anode material.

[0074] Among them, the magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder at a mass ratio of 1:3 and calcining it at 600℃ for 3 hours under argon.

[0075] Figure 1 The image shows the XRD pattern of the diatomaceous earth-derived silicon-carbon anode material of this invention. The image shows that the prepared composite material mainly consists of three components, with silicon exhibiting the best crystallinity and SiO2 having the lowest.

[0076] The nearby peaks correspond to amorphous carbon materials.

[0077] Figure 2 This is a SEM image of the diatomite-derived silicon-carbon anode material of the present invention. As can be seen from the image, the prepared composite material retains the disc-shaped morphology of the raw material diatomite and has a relatively complete structure.

[0078] Figure 3 This is a magnified SEM image of the diatomaceous earth-derived silicon-carbon anode material of the present invention. The image shows that the carbon material is uniformly covered on the inner and outer surfaces of the composite material pores.

[0079] Figure 4 The figure shows the charge-discharge curve of the diatomite-derived silicon-carbon anode material of the present invention. As can be seen from the figure, under 1C discharge conditions, the initial discharge specific capacity is close to 1200 mAh / g, the initial coulombic efficiency is close to 75%, and after 100 cycles, the capacity retention rate is close to 90%, which shows excellent electrochemical performance.

[0080] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a diatomaceous earth-derived silicon-carbon anode material, characterized in that, Includes the following steps: After mixing magnesium-heat-treated diatomaceous earth and asphalt mixture, the mixture is filtered to obtain the filtered solid. The filtered solid was calcined under an inert atmosphere to obtain a diatomaceous earth-derived silicon-carbon anode material. The ratio of the magnesium-treated diatomaceous earth and asphalt mixture is (0.5~1) g : (10~20) mL; The aforementioned filtration involves drawing the filtration device to a negative pressure state, with a pressure of -0.1 to -0.3 MPa, while simultaneously applying pressure from the upper part of the filtration head of the filtration device, with a pressure of 0.1 to 0.3 MPa. The filtration device consists of a sealed filtration head and a glass filtration bottle connected to the lower part; the filtration head is a polytetrafluoroethylene cylindrical syringe. The upper part of the filter head is connected to a polytetrafluoroethylene piston that can move up and down; The calcination treatment is carried out at a temperature of 700~900℃ for 1~3 hours. The magnesium-treated diatomaceous earth is obtained by mixing diatomaceous earth and magnesium powder at a mass ratio of 1:1~3 and calcining it at 600℃ under argon for 1~3 hours.

2. The method for preparing a diatomaceous earth-derived silicon-carbon anode material according to claim 1, characterized in that, Before the magnesium-treated diatomaceous earth and the asphalt mixture are mixed, the magnesium-treated diatomaceous earth is washed sequentially with dilute hydrochloric acid and deionized water, and then dried under vacuum conditions.

3. The method for preparing a diatomaceous earth-derived silicon-carbon anode material according to claim 2, characterized in that, The drying process is carried out at a temperature of 60-80℃ for 10-12 hours.

4. The method for preparing a diatomaceous earth-derived silicon-carbon anode material according to claim 1, characterized in that, The asphalt mixture is obtained by dissolving asphalt in a toluene solution and mixing.

5. The method for preparing a diatomaceous earth-derived silicon-carbon anode material according to claim 4, characterized in that, The concentration of the asphalt mixture is 2~5 mg / mL.

6. A diatomaceous earth-derived silicon-carbon anode material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5.

7. The application of the diatomaceous earth-derived silicon-carbon anode material according to claim 6, characterized in that, The diatomaceous earth-derived silicon-carbon anode material is used as the anode material for lithium-ion batteries.

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