Coated pre-lithiated silicon-oxygen negative electrode material, preparation method and application thereof

Abstract

The application provides a coated pre-lithiated silicon-oxygen negative electrode material and a preparation method and application thereof, and relates to the technical field of silicon negative electrode material preparation. The coated pre-lithiated silicon-oxygen negative electrode material comprises a pre-lithiated silicon-oxygen material, an interface stabilizing layer coated on the outer surface of the pre-lithiated silicon-oxygen material, and a hydrophobic layer coated on the outer surface of the interface stabilizing layer. The coated pre-lithiated silicon-oxygen negative electrode material can isolate the silicon from water and electrolyte, avoid the reaction of the silicon and hydroxyl ions to produce gas in the pulping process, and improve the cycle performance of the battery cell.

Description

Technical Field

[0001] This invention relates to the field of silicon anode material preparation technology, specifically to a coated pre-lithium silicon-oxygen anode material, its preparation method, and its application. Background Technology

[0002] In recent years, people have placed increasingly higher demands on battery performance, including battery life, safety, and fast charging. Silicon-based anode materials, due to their advantages such as high specific capacity, good safety, and abundant sources, are considered a novel high-performance lithium-ion battery anode material. With the development of high-capacity silicon-based anode materials, surface modification and element doping techniques have been widely applied to improve material performance. Among these, pre-lithiation technology has shown significant improvement in initial efficiency and battery energy density.

[0003] However, the instability associated with the pre-lithiation process of silicon-oxygen materials leads to the exposure of nano-silicon, which in turn makes the pre-lithiated silicon-oxygen materials prone to reacting with hydroxide ions during slurry preparation, generating gas and affecting the quality of subsequent coating processes. To reduce silicon exposure, surface coating methods are commonly used to modify the surface of pre-lithiated silicon-oxygen materials. However, existing coating methods often require sintering at 700℃ to 900℃, which leads to excessive growth of silicon grains and a significant volume expansion effect, which is detrimental to the long-term cycling of pre-lithiated silicon-oxygen anode materials. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a coated pre-lithium silicon-oxygen anode material, its preparation method, and its application, solving the technical problem that existing coating methods require high-temperature sintering.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a coated pre-lithium silicon-oxygen anode material, comprising:

[0009] Pre-lithium silicon oxide materials;

[0010] An interface stabilizing layer is applied to the outer surface of the pre-lithium silicon oxide material.

[0011] A hydrophobic layer is formed on the outer surface of the interface stabilizing layer.

[0012] The pre-lithium silicon-oxygen anode material of this invention includes an interface stabilizing layer and a hydrophobic layer. The interface stabilizing layer and the hydrophobic layer isolate the silicon in the pre-lithium silicon-oxygen material from contact with water and electrolyte, avoiding the reaction of silicon with hydroxide ions to generate gas during the slurry preparation process, and improving the cycle performance of the battery cell.

[0013] Preferably, the coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions:

[0014] The interface stabilizing layer is obtained by calcining a water-soluble polymer, thereby achieving liquid-phase low-temperature carbon coating. The coating effect is uniform and does not cause excessive growth of silicon grains, which is beneficial to the size control of silicon grains.

[0015] The hydrophobic layer is obtained by coating hydrophobic materials using a supercritical fluid method. The supercritical fluid acts as a solvent, and the hydrophobic materials exhibit varying solubility within it. When the pressure decreases sharply, the hydrophobic materials, in a supersaturated state, rapidly nucleate and precipitate, forming hydrophobic micronuclei. An expanding gas flow carries these hydrophobic micronuclei, which collide with silicon oxide particles in a fluidized bed, creating uniform contact and forming a uniform hydrophobic layer on the surface of the fine silicon oxide particles. This supercritical fluid coating method does not contaminate the product and offers advantages such as high purity, uniform geometry, narrow particle size distribution, simple manufacturing process, and moderate operation. It is particularly advantageous for handling heat-sensitive and structurally unstable materials. This coating method can achieve high-quality hydrophobic coating at low temperatures (100℃~200℃), avoiding the problem of continuous silicon grain growth under multiple coating methods.

[0016] The hydrophobic material of this application forms a supercritical fluid under high pressure. When the supercritical fluid passes through the nozzle, it expands rapidly and the temperature drops sharply. The solvent and solute particles after the rapid expansion of the fluid are easily and completely separated, with no solvent residue in the particles. This process does not cause any pollution to the product and is a green process.

[0017] Preferably, the coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions:

[0018] The water-soluble polymer is selected from at least one of polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polymaleic anhydride, polyquaternary ammonium salt, and polyethylene glycol. The polyvinylpyrrolidone (PVP) contains nitrogen element. The resulting interface stabilizing layer includes nitrogen-doped carbon. The nitrogen-doped carbon connects the dispersed materials (dispersed conductive agent materials) to form a 2D and 3D conductive network in the interface stabilizing layer, thereby improving the conductivity of the negative electrode material.

[0019] The thickness of the interface stabilizing layer is 1–20 nm.

[0020] The water-soluble polymer accounts for 1 wt% to 6 wt% of the mass of the pre-lithium silicon oxide material;

[0021] The calcination temperature is 400–650°C.

[0022] Preferably, the coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions:

[0023] The hydrophobic material is selected from at least one of polystyrene, polyimide, aluminophosphate, fluoride, and oxide;

[0024] The particle size D of the hydrophobic material 50 It is 0.2–0.5 μm;

[0025] The amount of hydrophobic material added is 0.1 wt% to 1 wt% of the mass of the pre-lithium silicon oxide material.

[0026] Preferably, the coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions:

[0027] The fluoride is selected from lithium fluoride and conductive adhesive;

[0028] The oxide is selected from aluminum oxide.

[0029] Preferably, the interface stabilizing layer further includes a crosslinking agent obtained by calcination. The use of the crosslinking agent greatly enhances the coating strength, making the interface stabilizing layer more firmly bonded to the surface of the pre-lithium silicon oxide material. This avoids excessive shear force during slurry mixing, which could damage or peel off the structure of the interface stabilizing layer and the hydrophobic layer. It maintains the structural integrity of the coated pre-lithium silicon oxide anode material and prevents silicon particles from being exposed during the slurry mixing process and reacting with water to generate gas. Therefore, it has a good gas generation suppression effect and excellent battery cycle performance.

[0030] Preferably, the gas production test method of the coated pre-lithium silicon-oxygen anode material is as follows: the coated pre-lithium silicon-oxygen anode material is mixed with a conductive agent and a binder to form a slurry. About 30g of the homogenized slurry is sealed in an aluminum-plastic film bag and left to stand at room temperature for 24-168h. The gas production volume is tested by the water displacement method. The slurry formula is that the mass ratio of silicon, conductive agent and binder is (60-80):(10-20):(10-20), and the slurry mixing method is semi-dry.

[0031] Preferably, the method for testing the electrical performance of the coated pre-lithium silicon-oxygen anode material is as follows: the coated pre-lithium silicon-oxygen anode material is coated onto the current collector to form an electrode sheet, and then a full cell is formed together with a separator and an electrolyte, and the battery performance is tested.

[0032] In a second aspect, the present invention provides a method for preparing a coated pre-lithium silicon-oxygen anode material as described in the first aspect, comprising the following steps:

[0033] S1. Dissolve the pre-lithium silicon oxide material, water-soluble polymer, and crosslinking agent in a solvent, evaporate the solvent, and calcine at 400-650°C under a protective atmosphere to obtain carbon-coated silicon oxide material.

[0034] S2. Mix carbon-coated silicon-oxygen materials and hydrophobic materials, and then coat them using a supercritical fluid method to obtain coated pre-lithium silicon-oxygen anode materials.

[0035] Preferably, the preparation method satisfies at least one of the following conditions:

[0036] The crosslinking agent is selected from at least one of dicumyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, polyurethane, styrene, and butadiene;

[0037] The crosslinking agent is added at a volume mass percentage of 3% to 10% of the pre-lithium silicate material;

[0038] The solvent is selected from either alcohol or water;

[0039] The protective atmosphere is selected from either argon or helium.

[0040] Preferably, the specific process of the supercritical fluid coating method is as follows:

[0041] The hydrophobic material is dissolved in a solvent and fed into a high-pressure tank to form a supercritical fluid. Then, it is rapidly expanded in a fluidized bed through a nozzle via a controlled heating pipeline. The particles in the fluidized bed are coated by the combined action of the expanding jet and the fluidizing gas. The coating time is 60 min to 300 min. The temperature before expansion is controlled at 100℃ to 200℃, and the micro-nucleus particle size formed by the hydrophobic material is controlled at 20 to 50 nm.

[0042] Thirdly, the present invention provides an application of the coated pre-lithium silicon-oxygen anode material as described in the first aspect in the preparation of a battery, the battery comprising the coated pre-lithium silicon-oxygen anode material, a current collector, a separator, and an electrolyte. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 These are the gas generation curves of silicon anode slurry in Example 1 and Comparative Example 1;

[0045] Figure 2 These are cycle curves of the pouch cells in Example 2 and Comparative Example 2. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] This application provides a coated pre-lithium silicon-oxygen anode material, its preparation method, and its application, solving the technical problem that existing coating methods require high-temperature sintering.

[0048] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0049] This invention discloses a coated pre-lithium silicon-oxygen anode material. The interface stabilization layer constructs an electrochemically stable interface between silicon and water, electrolyte, etc., while also exhibiting good conductivity. To increase the coating strength and the adhesion between the interface stabilization layer and silicon, a crosslinking agent is added during coating, making the interface stabilization layer more firmly bonded to the silicon anode surface. This prevents excessive shear force on the dispersion disk during slurry mixing, which could damage or peel off the interface stabilization layer structure, thus maintaining the structural integrity and stability of the interface stabilization layer. Next, a hydrophobic layer is coated using a supercritical fluid method to achieve uniform low-temperature ultrafine particle coating of hydrophobic materials such as oxides and fluorides. The coated pre-lithium silicon-oxygen anode material prepared by this invention exhibits good structural stability, uniform and controllable coating, low coating temperature, and facilitates control of silicon grain growth. The interface stabilizing layer and the hydrophobic layer work together to effectively prevent silicon particles from being exposed, thereby avoiding the gas generation caused by the reaction of coated pre-lithium silicon-oxygen anode material with hydroxide ions during the slurry preparation process. This solves the problem of gas generation in the pre-lithium silicon-oxygen material slurry, ensures the quality of the coating process, and improves the cycle performance of the battery cell.

[0050] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0051] Example 1

[0052] This embodiment provides a method for preparing a coated pre-lithium silicon-oxygen anode material, including the following steps:

[0053] S1. The pre-lithiated silicon oxide material is sequentially washed by acetic acid filtration and water filtration, and finally dried at low temperature for later use.

[0054] S2. Add 30g of washed pre-lithium silicon oxide material, 5g of PVP material, and 1mL of diisopropylbenzene hydrogen peroxide to 100mL of alcohol. After complete dissolution, evaporate the alcohol completely and then calcine at 600℃ for 6h under an argon protective atmosphere to obtain carbon-coated silicon oxide material SiO / C composite material.

[0055] S3. The SiO / C composite material is mixed with 0.1% wt alumina material and coated by supercritical fluid method for 60 min. The temperature before expansion is controlled at 100℃ and the solute (hydrophobic material) micro-nucleus particle size is controlled at 20 nm to obtain the coated pre-lithium silicon-oxygen anode material.

[0056] The prepared coated pre-lithium silicon-oxygen anode material, along with a conductive agent and binder, was added to a mixing tank. The mixture was prepared according to a ratio of silicon: ultrafine carbon powder (SP): single-walled carbon nanotubes (SWCNT): polyacrylic acid (PAA) = 60:10:10:20. The mixture was first dry-mixed, then kneaded, and finally the viscosity was adjusted. The solid content was controlled at 15%, and the viscosity at 8000 mPa. The mixture was stirred to obtain a uniformly dispersed silicon anode slurry. Approximately 30g of the homogenized silicon anode slurry was sealed in an aluminum-plastic film bag and allowed to stand at room temperature for 7 days. The gas production volume was tested using the water displacement method, and the gas production curve is shown in the figure. Figure 1 .

[0057] Example 2

[0058] This embodiment provides a coated pre-lithium silicon-oxygen anode material, including the following steps:

[0059] S1. The pre-lithiated silicon oxide material is filtered and washed with trifluoroacetic acid, and then dried at low temperature for later use.

[0060] S2. Dissolve 30g of washed pre-lithium silica material, 10g of polyacrylamide material, and 3mL of crosslinking agent di-tert-butyl peroxide in deionized water. After the water is completely evaporated, calcine at 500℃ for 8h under an argon protective atmosphere to obtain carbon-coated silica material SiO / C composite material.

[0061] S3. The SiO / C composite material is mixed with 0.5 wt% lithium fluoride material and coated by supercritical fluid method to obtain coated pre-lithium silicon-oxygen anode material.

[0062] The coated pre-lithium silicon-oxygen anode material, conductive agent, binder, etc., are added to a mixing tank and mixed in a ratio of silicon:graphite:SP:SWCNT:PAA = 5:88:2:0.1:4.9. The mixture is first dry-mixed, then kneaded, and then the viscosity is adjusted. The solid content is controlled at 50%, and the viscosity at 3500 mPa. The mixture is stirred to obtain a uniformly dispersed silicon anode slurry, which is then coated onto the current collector, with the areal density controlled at 100 g / m². 2It was paired with a ternary cathode to form a pouch cell, and its cycle performance was tested. The results are shown in […]. Figure 2 .

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that steps S2 and S3 are omitted. Instead of the coated pre-lithium silicon oxide anode material, the washed pre-lithium silicon oxide material is used to prepare the silicon anode slurry by mixing it with the conductive agent and binder. Otherwise, the process is the same as in Example 1. The gas generation curve is shown in [Figure number missing]. Figure 1 .

[0065] Figure 1 It can be seen that the gas production of the pre-lithium silicon-oxygen anode material of the present invention after 7 days is only 1.5 mL, while the gas production of the pre-lithium silicon-oxygen material of Comparative Example 1 is 36.8 mL after 7 days. The pre-lithium silicon-oxygen anode material of the present invention can significantly reduce the gas production.

[0066] Comparative Example 2

[0067] The difference from Example 2 is that steps S2 and S3 are omitted. Instead of the coated pre-lithium silicon oxide anode material, washed pre-lithium silicon oxide material is used, along with conductive agents and binders, to prepare the silicon anode slurry in the mixing tank. Otherwise, the process is the same as in Example 2. The cycle performance results of the pouch cell are shown below. Figure 2 .

[0068] Depend on Figure 2 It can be seen that the cycle life of the pouch battery in Example 2 is >1200 cycles, while the cycle life of the pouch battery in Comparative Example 2 is only 650 cycles. This shows that the coated pre-lithium silicon-oxygen anode material of the present invention can significantly improve the cycle performance of the battery.

[0069] Comparative Example 3

[0070] The only difference between this comparative example and Example 1 is that S2 is not included. Instead of carbon-coated silicon oxide material SiO / C composite material, washed pre-lithiated silicon oxide material is used to prepare coated pre-lithiated silicon oxide anode material. Otherwise, it is the same as Example 1. The gas production of silicon anode slurry is 10.5 mL after 7 days.

[0071] Comparative Example 4

[0072] The only difference between this comparative example and Example 1 is that S3 is not included. The silicon anode slurry is prepared using carbon-coated silicon oxide material SiO / C composite material. Otherwise, it is the same as Example 1, and its gas production in 7 days is 15.5 mL.

[0073] In summary, the coated pre-lithium silicon-oxygen anode material prepared by this invention has a low coating temperature, which is beneficial for controlling the growth of silicon grains. The interface stabilizing layer and the hydrophobic layer form an effective synergistic effect, effectively preventing the exposure of silicon particles, solving the problem of gas generation in the pre-lithium silicon-oxygen material slurry, and significantly improving the cell cycle performance.

[0074] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coated pre-lithium silicon-oxygen anode material, characterized in that, include, Pre-lithium silicon oxide materials; An interface stabilizing layer is formed by coating the outer surface of the pre-lithium silicon oxide material. A hydrophobic layer, which covers the outer surface of the interface stabilizing layer; The interface stabilizing layer is obtained by dissolving pre-lithium silicon oxide material, water-soluble polymer, and crosslinking agent in a solvent, evaporating the solvent, and calcining under a protective atmosphere. The crosslinking agent is selected from at least one of dicumyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, polyurethane, styrene, and butadiene; The crosslinking agent is added at a volume mass percentage of 3% to 10% of the pre-lithium silicon oxide material.

2. The coated pre-lithium silicon-oxygen anode material according to claim 1, characterized in that, The hydrophobic layer is obtained by coating a hydrophobic material with a supercritical fluid method.

3. The coated pre-lithium silicon-oxygen anode material according to claim 1, characterized in that, The coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions: The water-soluble polymer is selected from at least one of polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polymaleic anhydride, polyquaternium salt, and polyethylene glycol; The water-soluble polymer accounts for 1 / 6 and 1 / 3 of the mass of the pre-lithium silicon oxide material; The calcination temperature is 400–650°C.

4. The coated pre-lithium silicon-oxygen anode material according to claim 2, characterized in that, The coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions: The hydrophobic material is selected from at least one of polystyrene, polyimide, aluminophosphate, fluoride, and oxide; The particle size D of the hydrophobic material 50 It is 0.2–0.5 μm; The amount of hydrophobic material added is 0.1 wt% to 1 wt% of the mass of the pre-lithium silicon oxide material.

5. The coated pre-lithium silicon-oxygen anode material according to claim 4, characterized in that, The coated pre-lithium silicon-oxygen anode material satisfies at least one of the following conditions: The fluoride is selected from lithium fluoride; The oxide is selected from aluminum oxide.

6. A method for preparing a coated pre-lithium silicon-oxygen anode material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Dissolve the pre-lithium silicon oxide material, water-soluble polymer, and crosslinking agent in a solvent, evaporate the solvent, and calcine at 400-650°C under a protective atmosphere to obtain carbon-coated silicon oxide material. S2. The carbon-coated silicon-oxygen material and the hydrophobic material are mixed and then coated by supercritical fluid method to obtain a coated pre-lithium silicon-oxygen anode material.

7. The preparation method according to claim 6, characterized in that, The preparation method satisfies at least one of the following conditions: The solvent is selected from either alcohol or water; The protective atmosphere is selected from either argon or helium.

8. The preparation method according to claim 6, characterized in that, The supercritical fluid coating process includes: The carbon-coated silicon oxide material and the hydrophobic material are dissolved in a solvent and pressurized to form a supercritical fluid, and then rapidly expanded to achieve coating. The coating time is 60 min to 300 min. The temperature before expansion is 100℃ to 200℃, and the micro-nucleus particle size formed by the hydrophobic material is 20 to 50 nm.

9. The application of the coated pre-lithium silicon-oxygen anode material as described in any one of claims 1 to 5 in the fabrication of batteries, characterized in that, The battery includes a pre-lithium silicon-oxygen anode material, a current collector, a separator, and an electrolyte.

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