Lithium ion solid-state battery negative electrode material and preparation method thereof

Abstract

The application provides a lithium ion solid-state battery negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: placing a silicon source material in a vacuum drying box, adjusting the temperature to 120 DEG C, and performing a moisture removal operation for 6 hours; after the operation is completed, a passivation coating material is sprayed to obtain a modified silicon precursor; the porous graphite is placed in a grinding machine and ground for 30 minutes, then metal oxide doped carbon and a dispersing agent are added and mixed to obtain a conductive mixture; the conductive mixture and the modified silicon precursor are mixed, and a directional electromagnetic field is applied for orientation and rearrangement to obtain a negative electrode preform; and the negative electrode preform is placed in a mold, combined with a solid-state electrolyte through hot pressing, and cooled to obtain the lithium ion solid-state battery negative electrode material. The stability and energy density of the lithium ion solid-state battery negative electrode material are effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a lithium ion solid-state battery negative electrode material and a preparation method thereof. BACKGROUND

[0002] The traditional lithium ion solid-state battery negative electrode material mainly uses graphite and silicon as the negative electrode material. The graphite has good chemical stability and can maintain a stable structure during the charging and discharging process, and is not easy to cause severe volume expansion. However, the theoretical capacity of the graphite is relatively low, which is 372 mAh / g, and cannot meet the increasing demand for energy density. During high-rate charging and discharging, the capacity of the graphite negative electrode is easy to decay, resulting in a short cycle life of the battery.

[0003] Silicon is widely studied and applied as the negative electrode material due to its high capacity. The theoretical capacity of silicon is 3579 mAh / g, which is much higher than that of graphite. The theoretical capacity of silicon is much higher than that of graphite, and can provide greater energy density to meet the demand for high-energy batteries. However, silicon will undergo a huge volume expansion (about 300%) during the charging and discharging process, which will cause mechanical damage and structure collapse of the material, and further affect the cycle stability and life of the battery. It is also easy to cause the interface between the electrolyte and the negative electrode material to be unstable, thereby causing the internal resistance of the battery to increase and the capacity to decay. Therefore, the traditional lithium ion solid-state battery negative electrode material has the problems of low energy density and poor stability. SUMMARY

[0004] The technical problem to be solved by the application is to provide a lithium ion solid-state battery negative electrode material and a preparation method thereof, which aims to solve the problems of low energy density and poor stability of the negative electrode material.

[0005] To solve the above problems, the application provides a preparation method of a lithium ion solid-state battery negative electrode material, which comprises the following steps:

[0006] S1, placing a silicon source material in a vacuum drying box, adjusting the temperature to 120 DEG C for 6 hours of dehumidification operation, and then spraying a passivation coating material to obtain a modified silicon precursor; wherein the passivation coating material comprises at least one of a nitride coating material, an oxide coating material and a metal compound coating material;

[0007] S2, placing porous graphite in a grinding machine and grinding for 30 minutes, then adding metal oxide doped carbon and a dispersing agent for mixing to obtain a conductive mixture;

[0008] S3, mixing the conductive mixture and the modified silicon precursor, and then applying a directional electromagnetic field for orientation rearrangement to obtain a negative electrode preform;

[0009] S4. Put the negative electrode preform into a mold, combine with the solid-state electrolyte by hot pressing, and obtain a lithium ion solid-state battery negative electrode material after cooling.

[0010] In some embodiments, in step S1, the silicon source material includes at least one of micron-sized silicon powder with an average particle size of 1-5 µm, nano-sized silicon particles with an average particle size of 50-100 nm, and porous silicon, the nitride coating material includes at least one of boron nitride, aluminum nitride, and titanium nitride, the oxide coating material includes at least one of aluminum oxide, zirconium oxide, and silicon oxide, and the metal compound coating material includes at least one of titanium carbide, zirconium boride, and nickel phosphide.

[0011] In some embodiments, step S1 includes:

[0012] S1.1. First, place the silicon source material in a vacuum drying box, heat to 120°C, maintain a vacuum degree of -0.1 MPa to -0.09 MPa for 6 hours;

[0013] S1.2. Use a plasma reaction chamber to treat the dried silicon source material in an argon atmosphere or argon / hydrogen mixed gas for 1-5 minutes, set the plasma power to 10-50 W, and set the cavity pressure of the plasma reaction chamber to 100-300 Pa to obtain silicon source particles;

[0014] S1.3. Spray a passivation coating material on the silicon source particles, the spraying temperature is 200-300°C, the flow rate of the passivation coating material is controlled at 25 mL / min, the spraying process lasts for 10-30 minutes until the coating thickness reaches 10-50 nm;

[0015] S1.4. Heat the silicon source particles after spraying to 400-600°C for pyrolysis to obtain a modified silicon precursor.

[0016] In some embodiments, step S2 includes:

[0017] S2.1. Preheat the porous graphite to 120°C in a vacuum environment for drying;

[0018] S2.2. Add the dried porous graphite to a planetary ball mill, the grinding time is 30 minutes, the rotation speed is 300 rpm, the grinding medium is hard alumina ball or silicon carbide ball with a particle size of 5 mm;

[0019] S2.3. Add the metal oxide precursor and the organic carbon source to a stirring reaction kettle, add a solvent and stir at room temperature for 1 hour, then dry to remove the solvent residue and perform low-temperature sintering under an argon atmosphere for 3 hours, the low-temperature sintering temperature is 300-500°C, to obtain metal oxide-doped carbon;

[0020] S2.4, mix the metal oxide doped carbon and the porous graphite, and add a dispersant, the mixing time is controlled to be 20-30 minutes, after the mixing is completed, heat to 100-150 DEG C for 3-5 hours to obtain a conductive mixture.

[0021] In some embodiments, in step S2, the metal oxide precursor includes at least one of titanium dioxide, iron oxide, and manganese oxide, the organic carbon source includes at least one of glucose, citric acid, and polyvinyl alcohol, and the dispersant includes at least one of polyvinylpyrrolidone, polyacrylic acid, sodium dodecyl benzene sulfonate, and dimethyl sulfoxide.

[0022] In some embodiments, the mass ratio of the metal oxide doped carbon to the porous graphite is (1-3):(14-16).

[0023] In some embodiments, step S3 includes:

[0024] S3.1, uniformly mix the conductive mixture and the modified silicon precursor in an inert atmosphere using a planetary ball mill at a speed of 300-400 rpm for 30-45 minutes to obtain a negative electrode preform;

[0025] S3.2, place the negative electrode preform in a directional electromagnetic field treatment device for orientation and rearrangement, the electromagnetic field strength is 0.5-3 Tesla, the current frequency is 50-100 Hz, the electromagnetic field application time is 5-15 minutes, and the ambient temperature is 25-50 DEG C, the metal oxide and carbon in the negative electrode preform are arranged in the same direction as the magnetic field direction;

[0026] S3.3, after the orientation and rearrangement of the directional electromagnetic field are completed, vacuum dry the negative electrode preform, the vacuum drying temperature is 60-80 DEG C, the vacuum drying time is 2-4 hours, and the vacuum degree is 0.1 MPa.

[0027] In some embodiments, the mass ratio of the conductive mixture to the modified silicon precursor is (1-2):(3-5).

[0028] In some embodiments, step S4 includes:

[0029] S4.1, heat the negative electrode preform and the solid-state electrolyte in the mold to 120-160 DEG C, and apply a stress of 10-30 MPa, the heating and stress application time is controlled to be 10-30 minutes;

[0030] S4.2, cool the hot-pressed mold in a water cooling or air cooling system until room temperature, the cooling rate is controlled to be 2-5 DEG C / min to obtain a lithium ion solid-state battery negative electrode material.

[0031] The application provides a lithium ion solid-state battery negative electrode material prepared by the preparation method of the lithium ion solid-state battery negative electrode material, and the lithium ion solid-state battery negative electrode material comprises a silicon source material, a passivation coating material, porous graphite, metal oxide doped carbon and an organic carbon source.

[0032] The silicon source material is used for improving the energy density of the lithium ion solid-state battery negative electrode material.

[0033] The passivation coating material is used for coating the silicon source material and reducing the side reaction of the silicon source material and the solid-state electrolyte.

[0034] The porous graphite is used for forming a stable conductive network.

[0035] The metal oxide doped carbon is used for providing electrochemical activity.

[0036] The organic carbon source is used for relieving the stress caused by the volume expansion of the silicon source material.

[0037] Compared with the prior art, the preparation method of the lithium ion solid-state battery negative electrode material has the beneficial effects that:

[0038] The silicon source material is used as the basis of the negative electrode, which can significantly improve the energy density of the battery, and the use of the passivation coating can effectively reduce the volume expansion of the silicon during the charging and discharging process and enhance the mechanical stability. The passivation coating can prevent the silicon particles from breaking or pulverizing during the cycle process, prolong the service life of the battery, and thus enhance the long-term stability of the battery. The porous graphite, the metal oxide doped carbon and the dispersant are mixed to form a conductive mixture. Graphite is a material with excellent electrical conductivity, which can effectively improve the electronic conductivity of the negative electrode and form a stable conductive network, especially maintaining stable performance during high-rate discharge. The pore structure of the porous graphite not only provides a large specific surface area, but also helps to relieve the stress caused by the volume expansion of the silicon during the charging and discharging process, reduces the material rupture or interface failure caused by the volume change, and thus improves the stability and energy density of the lithium ion solid-state battery.

[0039] The conductive mixture is subjected to directional rearrangement by applying a directional electromagnetic field, so that the metal oxide and the carbon particles are arranged along the direction of the electromagnetic field. This directional arrangement helps to improve the electronic conductivity of the negative electrode material and enhance the overall electrical conductivity of the battery, especially during high-current charging and discharging, which can reduce the internal resistance of the battery and improve the rate performance. The directional arrangement of the particles can also optimize the microstructure of the material, reduce the non-uniformity, and improve the stability and reliability of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a flowchart of the preparation method of the lithium ion solid-state battery negative electrode material in an embodiment of the application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0042] Please refer to Figure 1 This invention proposes a method for preparing a negative electrode material for lithium-ion solid-state batteries, characterized by the following steps:

[0043] S1. Place the silicon source material in a vacuum drying oven, adjust the temperature to 120°C and perform a dehumidification operation for 6 hours. After completion, spray a passivation coating material to obtain a modified silicon precursor. The passivation coating material includes at least one of nitride coating material, oxide coating material, and metal compound coating material.

[0044] In step S1, the silicon source material includes at least one of micron-sized silicon powder with an average particle size of 1~5µm, nano-sized silicon particles with an average particle size of 50~100nm, and porous silicon; the nitride coating material includes at least one of boron nitride, aluminum nitride, and titanium nitride; the oxide coating material includes at least one of aluminum oxide, zirconium oxide, and silicon oxide; and the metal compound coating material includes at least one of titanium carbide, zirconium boride, and nickel phosphide.

[0045] Step S1 includes:

[0046] S1.1 First, place the silicon source material in a vacuum drying oven, heat it to 120℃, and maintain the vacuum degree between -0.1MPa and -0.09MPa for 6 hours.

[0047] A vacuum environment significantly lowers the boiling point of water, and at 120°C, it helps remove moisture, solvents, and volatile organic compounds from the surface or pores of silicon particles, ensuring uniform adhesion of the subsequent passivation coating material. The dehumidification process increases the surface energy of the silicon particles, which is beneficial for the uniform coating and adhesion of the passivation material, thereby improving the overall performance of the material.

[0048] S1.2. The dried silicon source material is treated in an argon atmosphere or an argon / hydrogen mixture for 1 to 5 minutes using a plasma reaction chamber. The plasma power is set to 10 to 50 W and the chamber pressure of the plasma reaction chamber is 100 to 300 Pa to obtain silicon source particles.

[0049] Plasma treatment can remove oxides or impurities on the surface of silicon particles and form a high-energy surface through plasma reaction, enhancing the activity of the material. By activating the surface of silicon particles, the adhesion of passivation coating material to silicon particles can be greatly improved, reducing the peeling or unevenness of the coating in subsequent operations. Plasma treatment can help improve the surface porosity of silicon particles, providing more surface area for the subsequent penetration of the passivation coating, ensuring more stable coating formation.

[0050] S1.3, spray a passivation coating material on the silicon source particles, the spraying temperature is 200-300°C, the flow rate of the passivation coating material is controlled at 25 mL / min, the spraying process lasts for 10-30 minutes until the coating thickness reaches 10-50 nm.

[0051] Through the spraying process, a uniform and dense passivation coating can be formed on the surface of silicon particles, reducing the side reaction between silicon and electrolyte and prolonging the service life of the battery. The passivation coating material can effectively alleviate the volume expansion of silicon during charging and discharging, avoid cracks and pulverization caused by expansion, and improve the cycle stability. The passivation coating material can improve the electrical conductivity and chemical stability of silicon, thereby improving the energy density and cycle life of the overall battery.

[0052] Specifically, in an embodiment, a layer of low-conductivity but highly stable oxide coating material or nitride layer coating material is first sprayed on the silicon source particles, and then a layer of metal compound coating material is sprayed, realizing a multi-layer protective structure. The multi-layer coating fully blocks the side reaction and reduces the chemical corrosion of silicon on the solid-state electrolyte. The outermost conductive coating can provide efficient electron transport, balancing mechanical protection and electrical performance.

[0053] S1.4, pyrolysis of the silicon source particles after spraying at a temperature of 400-600°C to obtain a modified silicon precursor.

[0054] The pyrolysis process can remove unreacted organic matter and solvents during the spraying process, ensuring the purity and stability of the modified silicon precursor. Pyrolysis helps to cure the passivation coating and promote its combination with the silicon particles, improving the mechanical strength and chemical stability of the coating. Through high-temperature pyrolysis, the combination between silicon particles and passivation coating is more firm, ensuring the stability of the material under high temperature, high rate and other working conditions.

[0055] S2, grind the porous graphite in a grinder for 30 minutes, then add metal oxide doped carbon and a dispersing agent for mixing to obtain a conductive mixture.

[0056] In step S2, the metal oxide precursor includes at least one of titanium dioxide, iron oxide, and manganese oxide, the organic carbon source includes at least one of glucose, citric acid, and polyvinyl alcohol, and the dispersant includes at least one of polyvinylpyrrolidone, polyacrylic acid, sodium dodecylbenzenesulfonate, and dimethyl sulfoxide. The mass ratio of the metal oxide doped carbon to the porous graphite is (1-3):(14-16).

[0057] Step S2 includes:

[0058] S2.1, preheat the porous graphite to 120°C in a vacuum environment for drying.

[0059] By drying in a vacuum environment, water and other volatile substances that may exist in the porous graphite can be removed. If these impurities are not removed, they may affect the performance of the subsequent material, leading to uneven contact or incomplete reaction of the doped material with the graphite. The drying process can increase the activity of the surface of the porous graphite, making it easier to mix uniformly with the metal oxide doped carbon and the organic carbon source in the subsequent steps, ensuring that the dispersion and adhesion of the material in the subsequent steps are more sufficient.

[0060] S2.2, add the dried porous graphite to a planetary ball mill, grind for 30 minutes at a speed of 300 rpm, and use hard alumina balls or silicon carbide balls with a particle size of 5 mm as the grinding medium.

[0061] By using a planetary ball mill, the particle size of the porous graphite can be reduced, increasing its surface area and further increasing its contact area with other materials such as metal oxide doped carbon and organic carbon source, which helps to improve the overall electrical conductivity and electrochemical performance of the composite material. The ball milling process can uniformly disperse the graphite particles, avoiding particle agglomeration, thereby improving the cycle stability and reliability of the negative electrode material in lithium-ion batteries.

[0062] S2.3, add the metal oxide precursor and the organic carbon source to a stirred reaction kettle, add a solvent and stir at room temperature for 1 hour, then dry to remove the solvent residue and perform low-temperature sintering under an argon atmosphere for 3 hours, with the low-temperature sintering temperature being 300-500°C, to obtain the metal oxide doped carbon.

[0063] By combining metal oxides with organic carbon sources, metal oxide-doped carbon is prepared. This composite not only provides better electronic conductivity, but also enhances the stability and electrochemical performance of the negative electrode material. During the low-temperature sintering process, the metal oxide precursor reacts with the organic carbon source to form a stable metal oxide-carbon composite structure. This process can effectively avoid the damage of high temperature to carbon materials, maintain the high conductivity and good chemical stability of metal oxide-doped carbon. Through the drying operation to remove the solvent, it ensures that the final product does not contain solvent residues, avoids the negative impact of the solvent on the performance of the material, and ensures the purity and performance stability of the composite material.

[0064] S2.4, mix the metal oxide-doped carbon with the porous graphite and add a dispersant, the mixing time is controlled at 20-30 minutes, after mixing, heat to 100-150℃ for 3-5 hours to obtain a conductive mixture. According to the mass ratio, conductive mixture: modified silicon precursor = (1-2):(3-5).

[0065] By mixing the metal oxide-doped carbon with the porous graphite, a more stable conductive network can be formed. The metal oxide-doped carbon not only enhances the electronic conductivity, but also provides better chemical stability, which helps to improve the cycle performance and high-rate charge-discharge performance of the negative electrode material. The addition of a dispersant helps to uniformly disperse the metal oxide-doped carbon and the porous graphite, avoiding agglomeration. Good dispersion ensures the uniformity of the composite material, which helps to improve the capacity, power density and cycle life of the battery. The heating process helps to further solidify and stabilize the composite material, promoting the structural stability of the material. The material after heat treatment has stronger mechanical strength and more stable electrochemical performance.

[0066] S3, mix the conductive mixture and the modified silicon precursor, and then apply a directional electromagnetic field for orientation and rearrangement to obtain a negative electrode preform. According to the mass ratio, conductive mixture: modified silicon precursor = (1-2):(3-5).

[0067] Step S3 includes:

[0068] S3.1, uniformly mix the conductive mixture and the modified silicon precursor under inert atmosphere using a planetary ball mill at a speed of 300-400 rpm for 30-45 minutes to obtain a negative electrode preform. The planetary ball mill can effectively uniformly mix the modified silicon precursor and the conductive mixture, avoiding agglomeration of the material and ensuring uniform distribution of each particle. Uniform dispersion is crucial for improving the conductivity and electrochemical performance of the battery. Inert atmosphere (such as argon or nitrogen) can prevent the silicon precursor and other components from reacting with oxygen in the air during mixing, ensuring the purity of the material and avoiding the impact of oxidation on the performance of the negative electrode.

[0069] S3.2, place the negative electrode preform in a directional electromagnetic field processing device for orientation and rearrangement, the electromagnetic field intensity is 0.5-3 Tesla, the current frequency is 50-100 Hz, the electromagnetic field application time is 5-15 minutes, the environmental temperature is 25-50℃, the metal oxide and carbon in the negative electrode preform are arranged in the same direction as the magnetic field.

[0070] By applying an electromagnetic field, especially the metal oxide doped carbon will arrange along the direction of the electromagnetic field, optimizing the electronic conductive network. This directional arrangement helps to provide a more efficient electron conduction path, reducing the electron transport impedance that may occur during the charging and discharging process of the battery. The metal oxide doped carbon and other carbon materials form an ordered arrangement under the guidance of the magnetic field, so that the electronic conductivity of the material is significantly enhanced. This structure helps to improve the high-rate charging and discharging performance of the battery, especially in the case of large current fast charging. Directional arrangement can reduce the interface defects inside the material, help to improve the capacity retention rate and cycle stability of the battery, and optimize the structural stability of the material, reduce the structural collapse and capacity decay caused by high-rate charging and discharging.

[0071] S3.3, after the orientation and rearrangement of the directional electromagnetic field is completed, the negative electrode preform is vacuum dried, the vacuum drying temperature is 60-80℃, the vacuum drying time is 2-4 hours, and the vacuum degree is 0.1 MPa. The vacuum drying process can effectively remove the water and solvent residues in the negative electrode preform. The removal of water and solvent helps to reduce the adverse reactions between the electrolyte and the material, and improves the stability of the battery. Drying in a low-temperature vacuum environment can avoid the negative effects of high temperature on the performance of the material, such as avoiding thermal expansion or deformation of the material, while further ensuring the structural integrity and electrochemical performance of the composite. The drying process in a vacuum environment helps to further optimize the combination of metal oxide and carbon materials, so that the negative electrode material is more stable in the application of solid-state batteries, and the performance decay caused by moisture is reduced.

[0072] S4, place the negative electrode preform in the mold and combine with the solid-state electrolyte by hot pressing, and obtain the lithium ion solid-state battery negative electrode material after cooling.

[0073] Step S4 includes:

[0074] S4.1, heat the negative electrode preform and solid-state electrolyte in the mold to 120-160℃, apply a stress of 10-30 MPa, and control the heating and stress application time to 10-30 minutes.

[0075] The heating makes the particles of the solid-state electrolyte become more softened and flow under the action of temperature. During the process of pressurization, the solid-state electrolyte can penetrate into the surface and pores of the negative electrode material, enhancing the contact area and binding force between the negative electrode material and the solid-state electrolyte. This process helps to reduce the interfacial impedance, improve the ionic conductivity and interface stability of the battery. By applying pressure, the close combination between the electrolyte and the negative electrode material is ensured, avoiding the presence of gaps or uneven areas. This helps to improve the energy density and cycle stability of the solid-state battery. Proper heating and pressurization can help the composite material to form a denser layer better, reduce the interface defects between the electrolyte and the negative electrode, and thus improve the capacity retention rate and rate performance of the battery.

[0076] To control the influence of stress on the negative electrode preform, the stress calculation equation applied to the negative electrode preform is:

[0077]

[0078] The final stress is the total stress borne by the negative electrode preform material after considering the volume change, which includes not only the initial mechanical or contact stress, but also the additional stress increment caused by the volume change. The original stress is the stress applied to the negative electrode preform, with the unit of MPa. The force applied to the negative electrode preform is applied by the hot press machine, with the unit of Newton (N), The stress cross-sectional area of the negative electrode preform is square meters (m 2 ), which is obtained by a pressure sensor or mechanical test. The relative volume change of the negative electrode preform is dimensionless, where, represents the average volume change of the negative electrode preform during the hot pressing process, which is determined by multiple cycle tests and is a fixed value when using the stress calculation equation, is the initial volume of the negative electrode preform; is the amplification degree of the stress increment caused by the volume change. The larger the value, the more significant the contribution of volume expansion to stress. Through multiple cycle tests, the stress increment caused by the volume change of the negative electrode preform at different and are fitted, which can be 0.1-1, dimensionless.

[0079] Therefore, through this equation, the final stress applied to the negative electrode preform can be determined by adjusting the force and hot pressing area of the negative electrode preform given by the hot press machine whether it reaches the threshold value of 10-30 MPa. If it exceeds the threshold value, cracks or interface separation are likely to occur; if it is less than the threshold value, the hot pressing combination is poor.

[0080] S4.2, the hot-pressed mold is placed in a water cooling or air cooling system for cooling until room temperature, with a cooling rate controlled at 2-5℃ / min, to obtain a lithium ion solid-state battery negative electrode material.

[0081] A slow cooling rate can effectively avoid thermal stress caused by a large temperature difference in the material during cooling, thereby reducing material cracking or stress concentration. During cooling, the electrolyte and negative electrode material can be stably solidified and crystallized, ensuring the structural stability of the battery material. This helps the negative electrode material maintain good mechanical strength and long-term cycle stability during battery operation. By controlling the cooling rate, the interface structure between the solid-state electrolyte and the negative electrode material can be ensured to be uniform, avoiding defects such as interface inhomogeneity or bubbles caused by rapid cooling, and improving the long service life and high efficiency of the battery.

[0082] In an embodiment, the solid-state electrolyte can be a sulfide-based solid-state electrolyte, such as lithium phosphorus sulfide, lithium selenide, etc., which has very high ionic conductivity and can form good interface contact with the negative electrode material. It can also be an oxide-based solid-state electrolyte, such as lithium-silicon oxide, lithium-phosphorus oxide-nitride, lithium-aluminum oxide, etc., which has excellent chemical stability, especially at high temperatures. It can also be a polymer-based solid-state electrolyte, such as polyvinyl alcohol lithium salt composite, polymethyl methacrylate composite, etc., which has good flexibility and processability and can adapt to the shape and size requirements in battery design. The polymer electrolyte can still maintain certain ionic conductivity at lower temperatures and is suitable for low-temperature applications.

[0083] The present application provides a lithium ion solid-state battery negative electrode material, which is prepared by a preparation method of a lithium ion solid-state battery negative electrode material. The lithium ion solid-state battery negative electrode material comprises a silicon source material, a passivation coating material, porous graphite, metal oxide doped carbon, and an organic carbon source.

[0084] The silicon source material is used to improve the energy density of the lithium ion solid-state battery negative electrode material.

[0085] The passivation coating material is used to coat the silicon source material to reduce the side reaction between the silicon source material and the solid-state electrolyte.

[0086] The porous graphite is used to form a stable conductive network.

[0087] The metal oxide doped carbon is used to provide electrochemical activity.

[0088] The organic carbon source is used to relieve the stress caused by the volume expansion of the silicon source material.

[0089] The above merely preferred embodiments of the present application are not used to limit the present application, any modification, equivalent replacement and improvement etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a lithium-ion solid-state battery negative electrode material, characterized by the steps of The method comprises the following steps: S1, place the silicon source material in a vacuum drying oven, adjust the temperature to 120°C for 6 hours of moisture removal operation, and then spray a passivation coating material to obtain a modified silicon precursor; wherein the passivation coating material comprises at least one of a nitride coating material, an oxide coating material, and a metal compound coating material; S2, place the porous graphite in a grinder and grind for 30 minutes, then add metal oxide doped carbon and a dispersing agent for mixing to obtain a conductive mixture, wherein the mass ratio of the metal oxide doped carbon to the porous graphite is (1-3):(14-16); S3 comprises: S3.1, uniformly mix the conductive mixture and the modified silicon precursor in an inert atmosphere using a planetary ball mill at a speed of 300-400 rpm for 30-45 minutes to obtain a negative electrode preform, wherein the mass ratio of the conductive mixture to the modified silicon precursor is (1-2):(3-5); S3.2, place the negative electrode preform in a directional electromagnetic field treatment device for orientation and rearrangement, wherein the electromagnetic field intensity is 0.5-3 Tesla, the current frequency is 50-100 Hz, the electromagnetic field application time is 5-15 minutes, the environmental temperature is 25-50°C, and the arrangement direction of the metal oxide and the carbon in the negative electrode preform is the same as the direction of the magnetic field; S3.3, after the orientation and rearrangement of the directional electromagnetic field are completed, vacuum dry the negative electrode preform at a temperature of 60-80°C for 2-4 hours under a vacuum degree of 0.1 MPa; S4, place the negative electrode preform in a mold and combine it with a solid-state electrolyte through hot pressing, and then cool to obtain a lithium ion solid-state battery negative electrode material; Step S4 comprises: S4.1, heat the negative electrode preform and the solid-state electrolyte in the mold to 120-160°C, and apply a stress of 10-30 MPa, and the heating and stress application time is controlled to be 10-30 minutes; S4.2, cool the hot-pressed mold in a water cooling or air cooling system until room temperature, and the cooling rate is controlled to be 2-5°C / min to obtain a lithium ion solid-state battery negative electrode material; The stress calculation equation applied to the negative electrode preform is: Final stress, unit: Mpa, refers to the total stress inside the anode preform material after considering the volume change, Original stress, unit: Mpa, refers to the stress applied to the anode preform, Force applied to the anode preform, applied by the hot press machine, unit: Newton (N), Cross-sectional area of the anode preform under stress, unit: square meter (m 2 ), obtained through pressure sensors or mechanical tests, Relative volume change of the anode preform, unit: dimensionless, where, represents the average volume change of the anode preform during the hot pressing process, determined by multiple cycle tests, and is a fixed value when using the stress calculation equation, is the initial volume of the anode preform, is the amplification factor representing the volume change stress increment, the larger the value, the more significant the volume expansion contribution to stress, is 0.1~1, unit: dimensionless; The final stress applied to the negative preform is determined by adjusting the force and hot press area of the hot press machine to the negative preform whether the threshold of 10-30 MPa is reached.

2. The method of claim 1, wherein the method is characterized by: In step S1, the silicon source material comprises at least one of micron-sized silicon powder with an average particle size of 1-5 µm, nano-sized silicon particles with an average particle size of 50-100 nm, and porous silicon, the nitride coating material comprises at least one of boron nitride, aluminum nitride, and titanium nitride, the oxide coating material comprises at least one of aluminum oxide, zirconium oxide, and silicon oxide, and the metal compound coating material comprises at least one of titanium carbide, zirconium boride, and nickel phosphide.

3. The method of claim 1, wherein the method is characterized by: Step S1 comprises: S1.1, first place the silicon source material in a vacuum drying oven, heat to 120°C, and maintain the vacuum degree between -0.1 MPa and -0.09 MPa for 6 hours; S1.2, using a plasma reaction cavity to treat the dried silicon source material in an argon atmosphere or argon / hydrogen mixed gas for 1-5 minutes, the plasma power is set to 10-50 W, the cavity pressure of the plasma reaction cavity is 100-300 Pa, to obtain silicon source particles; S1.3, spraying a passivation coating material on the silicon source particles, the spraying temperature is 200-300 DEG C, the flow rate of the passivation coating material is controlled at 25 mL / min, the spraying process lasts for 10-30 minutes until the coating thickness reaches 10-50 nm; S1.4, heating the sprayed silicon source particles to 400-600 DEG C for pyrolysis to obtain a modified silicon precursor.

4. The method of claim 1, wherein the method is characterized by: Step S2 comprises: S2.1, preheating the porous graphite to 120 DEG C in a vacuum environment for drying; S2.2, adding the dried porous graphite into a planetary ball mill, the grinding time is 30 minutes, the rotation speed is 300 rpm, the grinding medium is hard alumina ball or silicon carbide ball, and the particle size is 5 mm; S2.3, adding a metal oxide precursor and an organic carbon source into a stirring reaction kettle, adding a solvent and stirring at room temperature for 1 hour, then drying to no solvent residue and low temperature sintering under argon atmosphere for 3 hours, the low temperature sintering temperature is 300-500 DEG C, to obtain metal oxide doped carbon; S2.4, mixing the metal oxide doped carbon with the porous graphite and adding a dispersing agent, the mixing time is controlled at 20-30 minutes, after mixing, heating to 100-150 DEG C for 3-5 hours to obtain a conductive mixture.

5. The method of claim 4, wherein the method further comprises a step of adding a binder to the mixture of the step of mixing. In step S2, the metal oxide precursor includes at least one of iron oxide and manganese oxide, the organic carbon source includes at least one of glucose, citric acid and polyvinyl alcohol, and the dispersing agent includes at least one of polyvinylpyrrolidone, polyacrylic acid, sodium dodecylbenzenesulfonate and dimethyl sulfoxide.

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