A mechanically fused coated lithium-ion battery anode material and its preparation method

Abstract

This invention discloses a mechanically fused coated lithium-ion battery anode material and its preparation method. The anode material comprises a silicon-based material with a core structure, and a conductive nano-passivation layer coated on the outer layer of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized metal nitride or metal boride. The particle size ratio of the silicon-based material to the conductive material is R / r ≥ 100; the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1. The silicon-based material and the coating material are mechanically fused and coated under a protective atmosphere. The preparation method of the mechanically fused coated lithium-ion battery anode material of this invention has the characteristics of high stability, good processability, and excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a mechanically fused lithium-ion battery anode material and its preparation method. Background Technology

[0002] Silicon-based materials possess extremely high theoretical specific capacity (3579 mAh / g), nearly 10 times that of graphite anodes, and are considered the most promising next-generation lithium-ion battery anode materials. However, silicon-based materials exhibit a significant volume expansion effect during charge and discharge, making them prone to pulverization and failure. Furthermore, the exposed silicon material reacts with the electrolyte to form a new solid electrolyte interphase (SEI), leading to rapid capacity decay, poor cycle performance, and significant initial irreversible capacity loss.

[0003] Carbon coating of amorphous / nano-silicon is an effective strategy for addressing the aforementioned problems of silicon-based materials and achieving large-scale application of silicon. Coating silicon-based materials with carbon can effectively alleviate volume expansion during charge and discharge, suppress excessive SEI growth, and improve cycle stability. Furthermore, carbon materials possess excellent electrical conductivity, enabling the construction of a continuous conductive network on the silicon surface, reducing battery internal resistance, and thus improving battery performance. Commonly used carbon coating methods include vapor deposition, hydrothermal methods, and pyrolysis methods, as detailed in Table 1.

[0004]

[0005] Table 1 summarizes the advantages and disadvantages of several commonly used carbon coating technologies from five aspects: the required temperature, impurity phases, the orderliness, uniformity, and integrity of the coated carbon, and equipment requirements. Currently, commercial carbon coating requires temperatures above 800°C. However, at temperatures above 600°C, amorphous silicon crystallizes, and nano-silicon recrystallizes and grows, ultimately reducing the stability of lithium storage cycles. Besides the impact of high temperatures on silicon substrates, carbon coating processes are quite complex, and byproducts such as low-value pyrolysis gas and tar may be generated during pyrolysis. The disposal of these byproducts increases process costs and may also lead to environmental problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a mechanically fused coated lithium-ion battery anode material, which has the characteristics of high stability, good processability and excellent electrochemical performance.

[0007] This invention can be achieved through the following technical solutions:

[0008] This invention discloses a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material comprises a silicon-based material with a core structure, and a nano-conductive passivation layer coated on the outer layer of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized titanium powder. The ratio of the particle size of the silicon-based material to the particle size of the conductive material, i.e., R / r ≥ 100, is specified. The ratio of the number of conductive material particles to the number of silicon-based material particles is greater than 80,000:1 and less than 120,000:1. This is because the nano-conductive passivation material at least completely coats the silicon-based core material. It is assumed that the projected area of ​​n nano-conductive spheres is equal to the specific surface area of ​​one silicon-based core material sphere. nr 2 ≥4 R 2 We obtain n≥40000. For the silicon-based core material to be completely encapsulated without any gaps, at least two layers of nanospheres (n≥80000) are required; more than three layers (n≤120000) are not recommended because the encapsulating material is an inactive substance, and adding too much will reduce the capacity of the electrode material. The silicon-based material and the encapsulating material are mechanically fused and ground under a protective atmosphere to form the core material.

[0009] Furthermore, the control parameters for the mechanical fusion method are as follows: the distance between the crushing hammer and the tank wall is 0.5-10mm; the distance between the scraper and the tank wall is 0.2-5mm. If the distance between the crushing hammer and the tank wall is too small or too large, the extrusion effect between the silicon-based materials will not be achieved, resulting in an unsatisfactory coating effect; if the distance between the scraper and the pipe wall is too small, there is a risk of introducing impurities from the pipe wall; if the distance is too large, it will not effectively scrape off the conductive material.

[0010] Furthermore, the silicon-based material is one or more of pure silicon, silicon alloy, and silicon suboxide.

[0011] Furthermore, the coating material is a metal nitride or boride, including but not limited to one or more of Li3N, TiN, AlN, TaN, TiB2, and ZrB2, with a particle size r ranging from 5 to 50 nm. These materials possess excellent electrical conductivity, are resistant to acids and alkalis, and can withstand corrosion from electrolytes.

[0012] Furthermore, the protective atmosphere is one or more of argon, nitrogen, helium, and neon.

[0013] Furthermore, the particle size range of silicon-based materials is 1-30 μm, which facilitates subsequent coating processing as a negative electrode material.

[0014] Furthermore, the ratio of silicon-based material particle size to conductive material particle size, i.e., R / r, is ≥100; the ratio of conductive material particle number to silicon-based material particle number is 80000:1-120000:1. This is because the nano-conductive material at least completely covers the silicon-based core material. Assuming the projected area of ​​n nano-conductive spheres is equal to the specific surface area of ​​one silicon-based core material sphere, i.e. nr 2 ≥4 R 2 Therefore, n ≥ 40000. For the silicon-based core material to be completely encapsulated without any gaps, at least two layers of nanospheres (n ≥ 80000) are required; more than three layers (n ≤ 120000) are not recommended because conductive materials are inactive substances, and adding too many will reduce the capacity of the electrode material. Specifically, to ensure the operability of the particle number ratio, it is generally achieved by controlling the mass ratio, and the specific mass ratio is calculated in combination with the particle number ratio and volume.

[0015] Furthermore, the distance between the crushing hammer and the tank wall is adjusted according to the particle size of the conductive material and the silicon-based material, and the distance between the scraper and the tank wall is adjusted by the particle size of the conductive material.

[0016] Another aspect of the present invention is to protect a lithium-ion battery anode material, which is prepared by the above-described preparation method.

[0017] This invention discloses a mechanically fused coated lithium-ion battery anode material and its preparation method, which has the following beneficial effects:

[0018] The lithium-ion battery anode material of the present invention effectively solves the problem of silicon grain size growth caused by high-temperature coating, consolidates the stability of silicon-based materials, enhances the conductivity of the material, and avoids the corrosion of silicon materials by HF generated by side reactions of electrolyte.

[0019] The silicon-based anode material for lithium-ion batteries prepared by the method of this invention has good electrochemical performance. Attached Figure Description

[0020] Figure 1 This refers to the morphological changes before and after coating;

[0021] Figure 2 For Si 75 Ti 20 Voltage-specific capacitance comparison chart before and after Co5 coating of TiN. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0023] This invention discloses a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized nitride or boride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0024] Furthermore, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 0.5-10mm; the distance between the scraper and the tank wall is 0.2-5mm.

[0025] Furthermore, the silicon-based material is one or more of pure silicon, silicon alloy, and silicon suboxide.

[0026] Furthermore, the nano-conductive coating material is one or more of Li3N, TiN, AlN, TaN, TiB2 and ZrB2, and its particle size r ranges from 5 to 50 nm.

[0027] Furthermore, the protective atmosphere is one or more of argon, nitrogen, helium, and neon.

[0028] Furthermore, the particle size R of the silicon-based material ranges from 1 to 30 μm.

[0029] Furthermore, the ratio of silicon-based material particle size to coating material particle size R / r is ≥100; the ratio of coating material particle number to silicon-based material particle number is 80000:1-120000:1.

[0030] Furthermore, the silicon-based material undergoes spheroidization before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion.

[0031] Another aspect of the present invention is to protect a lithium-ion battery anode material, which is prepared by the above-described preparation method.

[0032] During the mechanical fusion process, changes in various parameters directly affect the material's properties, specifically in the following ways:

[0033] At the material properties level, selecting materials with good compatibility for bonding can improve the bonding strength and stability. The shape of the particles (such as spherical, plate-like, or irregular shapes) affects the packing density and contact conditions, thus affecting the bonding effect.

[0034] At the environmental level, humidity and atmosphere: The humidity and atmosphere of the environment can affect the chemical reactions and bonding effects of materials, especially in the processing of certain sensitive materials. Example 1

[0035] This embodiment relates to a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized nitride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0036] In this embodiment, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 10 mm; the distance between the scraper and the tank wall is 3 mm. The protective atmosphere is argon.

[0037] In this embodiment, regarding the selection of material type, the silicon-based material is pure silicon, and the particle size R of the silicon-based material ranges from 1 to 30 μm; the nano-conductive coating material is Li3N, and its particle size r ranges from 5 to 50 nm; the ratio of the particle size of the silicon-based material to the particle size of the coating material is R / r ≥ 100; and the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1.

[0038] In this embodiment, the silicon-based material is spheroidized before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion. Example 2

[0039] This embodiment relates to a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized nitride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0040] In this embodiment, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 5 mm; the distance between the scraper and the tank wall is 0.2 mm. The protective atmosphere is nitrogen and helium.

[0041] In this embodiment, regarding the selection of material type, the silicon-based material is a silicon alloy, and the particle size R of the silicon-based material ranges from 1 to 30 μm; the nano-conductive coating material is TiN or AlN, and its particle size r ranges from 5 to 50 nm; the ratio of the particle size of the silicon-based material to the particle size of the coating material is R / r ≥ 100; and the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1.

[0042] In this embodiment, the silicon-based material is spheroidized before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion. Example 3

[0043] This embodiment relates to a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized nitride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0044] In this embodiment, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 0.5 mm; the distance between the scraper and the tank wall is 5 mm. The protective atmosphere is helium or neon.

[0045] In this embodiment, regarding the selection of material type, the silicon-based material is silicon suboxide, and the particle size R of the silicon-based material ranges from 1 to 30 μm; the nano-conductive coating material is AlN or TaN, and its particle size r ranges from 5 to 50 nm; the ratio of the particle size of the silicon-based material to the particle size of the coating material is R / r ≥ 100; and the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1.

[0046] In this embodiment, the silicon-based material is spheroidized before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion. Example 4

[0047] This embodiment relates to a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized boride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0048] In this embodiment, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 30 mm; the distance between the scraper and the tank wall is 4 mm. The protective atmosphere is argon or neon.

[0049] In this embodiment, regarding the selection of material types, the silicon-based material is silicon alloy or silicon suboxide, and the particle size R of the silicon-based material ranges from 1 to 30 μm; the nano-conductive coating material is TiB2 and ZrB2, and its particle size r ranges from 5 to 50 nm; the ratio of the particle size of the silicon-based material to the particle size of the coating material is R / r ≥ 100; and the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1.

[0050] In this embodiment, the silicon-based material is spheroidized before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion. Example 5

[0051] This embodiment relates to a method for preparing a mechanically fused coated lithium-ion battery anode material. The anode material includes a silicon-based material with a core structure and a conductive nano-passivation layer coated on the outside of the silicon-based material. The silicon-based material is a micron-sized powder, and the coating material is a nano-sized boride. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method.

[0052] In this embodiment, the control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 8 mm; the distance between the scraper and the tank wall is 2 mm. The protective atmosphere is neon.

[0053] In this embodiment, regarding the selection of material types, the silicon-based material is pure silicon, silicon alloy, or silicon suboxide, and the particle size R of the silicon-based material ranges from 1 to 30 μm; the nano-conductive coating material is ZrB2, and its particle size r ranges from 5 to 50 nm; the ratio of the particle size of the silicon-based material to the particle size of the coating material is R / r ≥ 100; and the ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:1.

[0054] In this embodiment, the silicon-based material is spheroidized before mechanical fusion. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion.

[0055] Application Example 1

[0056] This embodiment relates to a mechanically fused coated lithium-ion battery anode material, the preparation process of which is as follows: 10 Si with a D50 of 25 μm is coated... 75 Ti 20Co5 alloy material was coated with 4wt% TiN powder with a size of 20 nm using a mechanical solid-phase fusion machine. The mechanical hammer spacing was 5 mm, the scraper spacing was 0.5 mm, the coating time was 4 h, and the ratio of the number of coated material particles to the number of silicon-based material particles was 80000:1-120000:1.

[0057] Application Example 2

[0058] This embodiment relates to a mechanically fused coated lithium-ion battery anode material, the preparation process of which is as follows: Si with a D50 of 25 μm is coated with a mechanically fused coated lithium-ion battery anode material. 75 Ti 20 Co5 alloy material was coated with 4wt% Li3N powder with a size of 20 nm using a mechanical solid-phase fusion machine. The mechanical hammer spacing was 5 mm, the scraper spacing was 0.5 mm, the coating time was 4 h, and the ratio of the number of coated material particles to the number of silicon-based material particles was 80000:1-120000:1.

[0059] Application Example 3

[0060] This embodiment relates to a mechanically fused coated lithium-ion battery anode material, the preparation process of which is as follows: Si with a D50 of 25 μm is coated with a mechanically fused coated lithium-ion battery anode material. 75 Ti 20 Co5 alloy material was coated with 4wt% TaN powder with a size of 20 nm using a mechanical solid-phase fusion machine. The mechanical hammer spacing was 5 mm, the scraper spacing was 0.5 mm, the coating time was 4 h, and the ratio of the number of coated material particles to the number of silicon-based material particles was 80000:1-120000:1.

[0061] Application Example 4

[0062] This embodiment relates to a mechanically fused coated lithium-ion battery anode material, the preparation process of which is as follows: Si with a D50 of 25 μm is coated with a mechanically fused coated lithium-ion battery anode material. 75 Ti 20 Co5 alloy material was coated with 4wt% TiB2 powder with a size of 20 nm using a mechanical solid-phase fusion machine. The mechanical hammer spacing was 5 mm, the scraper spacing was 0.5 mm, the coating time was 4 h, and the ratio of the number of coated material particles to the number of silicon-based material particles was 80000:1-120000:1.

[0063] Application Example 5

[0064] This embodiment relates to a mechanically fused coated lithium-ion battery anode material, the preparation process of which is as follows: Si with a D50 of 25 μm is coated with a mechanically fused coated lithium-ion battery anode material. 75 Ti 20Co5 alloy material was coated with 4wt% ZrB2 powder with a size of 20 nm using a mechanical solid-phase fusion machine. The mechanical hammer spacing was 5 mm, the scraper spacing was 0.5 mm, the coating time was 4 h, and the ratio of the number of coated material particles to the number of silicon-based material particles was 80000:1-120000:1.

[0065] Comparative Example 1

[0066] The main difference between Comparative Example 1 and Application Example 1 is that it does not have a nano-passivation layer.

[0067] To effectively evaluate the technical effects of the present invention, the electrochemical performance of lithium-ion batteries was tested using Examples 1-5 and the comparative examples. The test results are shown in Table 2.

[0068] Table 2 Comparison of electrochemical performance of Examples 1-5 and Comparative Example 1

[0069]

[0070] like Figure 1 As shown, (a, b, c) are SEM images of Comparative Example 1, where it can be observed that the alloy particles are spherical with relatively smooth surfaces. (d, e, f) are SEM images of Example 1, where it can be observed that the coated particles are slightly larger than the uncoated material, and a coating is clearly visible on the particle surface, which preliminarily indicates that conductive material is coated on silicon-based spherical particles.

[0071] like Figure 2 As shown, the blank portion before the previous curve is subtracted from the reversible capacity comparison. Both Comparative Example 1 and Example 1 exhibit the lithiation / delithiation characteristic curves of amorphous silicon, which further verifies that the silicon material did not crystallize and grow due to temperature during the coating process. It can be observed that the initial lithiation potential of Example 1 increased from 0.10 V to 0.22 V, indicating that TiN coating constructed a better conductive network and reduced polarization.

[0072] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for preparing a mechanically fused coated lithium-ion battery anode material, the anode material comprising a silicon-based material with a core structure and a conductive nano-passivation layer coated on the surface of the silicon-based material, characterized in that: The silicon-based material is a micron-sized powder, and the conductive nano-passivation layer uses a nano-sized nitride or boride as the coating material. The nano-sized nitride or boride is one or more of Li3N, TiN, AlN, TaN, TiB2, and ZrB2, and its particle size r ranges from 5 to 50 nm. The silicon-based material and the coating material are ground and coated under a protective atmosphere using a mechanical fusion method. The ratio of the particle size of the silicon-based material to the particle size of the coating material, R / r, is ≥100. The ratio of the number of coating material particles to the number of silicon-based material particles is 80000:1-120000:

1.

2. The method for preparing the mechanically fused coated lithium-ion battery anode material according to claim 1, characterized in that: The control parameters for the mechanical fusion method are: the distance between the crushing hammer and the tank wall is 0.5-10mm; the distance between the scraper and the tank wall is 0.2-5mm.

3. The method for preparing the mechanically fused coated lithium-ion battery anode material according to claim 2, characterized in that: The silicon-based material is one or more of pure silicon, silicon alloy, and silicon suboxide.

4. The method for preparing the mechanically fused coated lithium-ion battery anode material according to claim 1, characterized in that: The protective atmosphere is one or more of argon, nitrogen, helium, and neon.

5. The method for preparing the mechanically fused coated lithium-ion battery anode material according to claim 4, characterized in that: The particle size R of the silicon-based material ranges from 1 to 30 μm.

6. The method for preparing the mechanically fused coated lithium-ion battery anode material according to claim 5, characterized in that: Before mechanical fusion, the silicon-based material undergoes a spheroidization process. The spheroidization process involves using high-speed centrifugal force to evenly throw the silicon-based powder onto the tank wall, a mechanical hammer to compress the material, and a scraper to scrape the material off the tank wall. This method spheroidizes the silicon-based material and makes the material surface smoother, which is beneficial for subsequent mechanical fusion.

7. A lithium-ion battery anode material, characterized in that: It is prepared by any one of the preparation methods in claims 1-6.

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