Powdered silicon oxide, preparation method and use thereof

Abstract

The present invention relates to a powdered silicon oxide, a preparation method and its use. The preparation method of the powdered silicon oxide comprises: mixing silicon and silicon dioxide powders in required amounts and putting them into a vacuum rotary kiln; under vacuum conditions, the vacuum rotary kiln drives a material lifting plate for disturbing mixing inside the kiln; at this time, the cooling zone is rotated and closed, and heating is performed while stirring and mixing. When the temperature is heated to the reaction temperature, the rotation is stopped, and heating and reaction are continued to obtain silicon oxide vapor; after the reaction is complete, the rotation control of the furnace body in the cooling zone is turned on, and an inert gas is introduced from the bottom of the furnace body (in the opposite direction of the condensation and sinking of the silicon oxide vapor), and the collected materials are cooled to obtain powdered silicon oxide; the vacuum rotary kiln comprises internal parts that can disturb mixing, and the high-temperature reaction zone and the cooling zone have independent rotation control, and there is a vent below the condensation section furnace body. The negative electrode material obtained by using the powdered silicon oxide of the present invention can reach a capacity of more than 1600 mAh / g after carbon coating, and the first efficiency is more than 78%. The silicon oxide negative electrode material can be used as a negative electrode active material in the field of lithium ion batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to powdered silicon oxide, a preparation method and use thereof. Background Art

[0002] Lithium-ion batteries have become the most promising chemical energy in the 21st century due to their advantages such as good cycle stability, high energy density, long cycle life, and environmental friendliness, and have gradually developed into the main body of the secondary battery market. Among them, electrode materials are one of the key factors that determine the performance of lithium-ion batteries. Because the reversible specific capacity of positive electrode materials has little room for improvement, and negative electrode materials have a huge impact on the cycle stability and capacity of batteries, improving the reversible specific capacity of negative electrode materials is currently the key to improving the energy density of lithium-ion batteries.

[0003] At present, graphite-based carbon materials are commonly used as negative electrode materials for commercial lithium-ion batteries. However, the theoretical lithium storage capacity of graphite electrodes is relatively low. Research and development of new negative electrode materials with high performance is extremely urgent and has become a hot topic in the field of lithium-ion battery research. Silicon negative electrode is considered to be one of the most promising negative electrode materials for lithium-ion batteries. However, silicon negative electrode materials have a high volume expansion rate and cannot form a stable SEI film, which ultimately affects battery performance.

[0004] Therefore, obtaining lithium-ion battery negative electrode materials with high capacity and / or high initial efficiency has become a technical problem that needs to be solved urgently.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] Purpose of the Invention

[0007] The object of the present invention is to provide a powdered silicon oxide, a preparation method and use thereof, so as to solve at least one of the above problems.

[0008] Solution

[0009] To achieve the purpose of the present invention, the embodiments of the present invention provide the following technical solutions.

[0010] The silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives the material lifting plate inside to disturb the mixing. At this time, the cooling zone is rotated and closed, and the mixture is heated while being stirred and mixed. When the mixture is heated to the reaction temperature, the rotation is stopped, and the heating and reaction are continued to obtain silicon oxide vapor. After the reaction is complete, the rotation control of the furnace body in the condensation zone is turned on, and an inert gas is introduced from the bottom of the furnace body (in the opposite direction of the condensation and sinking of the silicon oxide vapor), and the material is cooled and collected to obtain powdered silicon oxide.

[0011] The vacuum rotary kiln includes internal parts that can disturb mixing, a high-temperature reaction zone and a cooling zone. The cooling zone has independent rotation control, and a vent is provided below the furnace body of the cooling zone.

[0012] Preferably, the rotation frequency of the vacuum rotary kiln before being heated to the reaction temperature is 5-50 Hz, and the rotation frequency of the furnace body in the cooling zone during cooling is 20-60 Hz.

[0013] Preferably, the reaction temperature is 1000-1600° C., and the reaction time is 2-10 h.

[0014] Preferably, the cooling condition is that the condensation temperature is 500-900° C., and at the same time, the furnace body of the cooling zone is rotated and inert gas is introduced from under the furnace body to increase the disturbance of the solid.

[0015] Preferably, after the reaction is completed, the Dmax of the collected material is less than 150 μm.

[0016] Preferably, the particle size of the powdered silicon oxide satisfies the following conditions:

[0017] D10 is 1-6μm, D50 is 3-15μm, D90 is 6-30μm, and the D90 / D10 range is 2-5;

[0018] Preferably, the powdered silicon oxide has a D50 of 3-10 μm and a D90 / D10 range of 2-4.

[0019] Preferably, the method further comprises: the step of subjecting the collected material after the reaction to multiple stage-by-stage crushing and classification, specifically:

[0020] The collected materials after the reaction are screened according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 1-6μm, D50 of 3-15μm, D90 of 6-30μm, and D90 / D10 range of 2-5, including:

[0021] First, if the particle size of the material under the sieve meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the sieve will be directly crushed, and the crushed material will continue the above screening, classification, and crushing steps, and this will be repeated until the material is finished;

[0022] Preferably, the target particle size D50 is 3-10 μm, and the D90 / D10 range is 2-4;

[0023] Preferably, a screening machine is used for screening, and the screening machine is one of a straight screen, a rotary vibrating screen, and an ultrasonic vibrating screen, and the mesh number of the screen is 20-100 meshes.

[0024] A powdery silicon oxide obtained by the method as described above.

[0025] A method for preparing a silicon oxide negative electrode material, the method comprising:

[0026] The powdered silicon oxide as described above is subjected to carbon coating treatment to obtain a silicon oxide negative electrode material coated with a carbon coating layer;

[0027] Preferably, the proportion of the carbon coating layer is 2-10% of the mass of the powdered silicon oxide.

[0028] A silicon oxide negative electrode material, characterized in that it is obtained by the silicon oxide negative electrode material preparation method as described above, or,

[0029] A lithium ion battery comprises the silicon monoxide negative electrode material as described above.

[0030] Beneficial Effects

[0031] The capacity of the silicon monoxide negative electrode material provided by the present invention can reach more than 1600 mAh / g, and the initial efficiency can reach more than 78%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Example 1 charge and discharge curve of powdered silicon oxide negative electrode material. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0035] According to one aspect of the present invention, there is provided a method for preparing powdered silicon oxide, the method comprising:

[0036] The silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives the material lifting plate inside to disturb the mixing. At this time, the cooling zone is rotated and closed (that is, at this time, the rotation of the reaction zone of the vacuum rotary furnace is turned on, and the rotation of the cooling zone is turned off, and the rotation of the two can be independently controlled). Stirring and mixing are carried out while heating. When heated to the reaction temperature, the rotation is stopped (that is, the rotation of the reaction zone is turned off at this time), and heating and reaction are continued to obtain silicon oxide vapor; the rotation control of the furnace body in the condensation zone is turned on, and an inert gas is introduced from the bottom of the furnace body (the opposite direction of the condensation and sinking of the silicon oxide vapor), and the materials are cooled and collected to obtain powdered silicon oxide;

[0037] The vacuum rotary kiln includes internal parts that can disturb mixing, a high-temperature reaction zone and a cooling zone. The cooling zone has independent rotation control, and a vent is provided below the furnace body of the cooling zone.

[0038] The component that can disturb the mixing may be, for example, a lifting plate.

[0039] In the present invention, a vacuum rotary kiln is used, and the rotation of the kiln body and the physical disturbance of the internal lifting plate are utilized to make the solid material flow. The powdered silicon oxide is formed by the rotation of the vacuum rotary kiln itself and the physical disturbance of the lifting plate and the purge of inert gas during the condensation and collection process after the high-temperature solid phase reaction of the silicon-containing solid reactant. It is grown in situ during the preparation of silicon oxide, and its morphology is more regular and has relatively fewer surface defects. Such morphological characteristics make it possible to prepare silicon oxide negative electrode materials with a lower proportion of the coating carbon layer, and the capacity of the silicon oxide negative electrode material can reach more than 1600mAh / g, and the first efficiency can reach more than 78%.

[0040] In addition, in the vacuum rotary kiln, since the materials are still in a dynamic mixing state, the reaction is more complete, so the generated products are more uniform and the quality of silicon oxide is more stable.

[0041] In a preferred embodiment of the present invention, the molar ratio of the silicon powder to silicon dioxide is 1:1.

[0042] In a preferred embodiment of the present invention, the method comprises: mixing silicon and silicon dioxide powders in required amounts, crushing and grinding them, and then placing them in a vacuum rotary furnace for reaction.

[0043] In a preferred embodiment of the present invention, the rotation frequency of the vacuum rotary kiln before heating to the reaction temperature is 5-50 Hz, and the rotation frequency of the furnace body in the cooling zone during cooling is 20-60 Hz.

[0044] The rotation frequency is, for example, 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz or 50 Hz. If the rotation frequency is lower than 5 Hz, the mixing effect is weak and the reaction is incomplete. If the rotation frequency is higher than 50 Hz, the solid reactant has excessive fluidity, which blocks the cooling rate of the silicon-oxygen vapor generated by the high-temperature reaction.

[0045] The rotation frequency of the furnace in the cooling zone is 20-60 Hz, and the rotation frequency is, for example, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, 50 Hz, 55 Hz or 60 Hz. If the frequency is lower than 20 Hz, blocky or other granular silicon oxide is easily formed, and if the frequency is higher than 60 Hz, the rotation speed is too fast, and small particles in the powdered silicon oxide cannot be collected because they are too light, and the product yield is reduced.

[0046] In a preferred embodiment of the present invention, the heating temperature is 1000-1600° C., and the reaction time is 2-10 h.

[0047] If the high temperature solid phase reaction temperature is less than 1000℃, the high temperature solid phase reaction of silicon and silicon dioxide is a self-purification process in addition to generating silicon oxygen vapor, which can remove impurity elements in the raw materials. If the reaction temperature is less than 1000℃, the purification effect is not significant. In addition, the reaction rate of high temperature reaction is related to the reaction temperature. Therefore, the higher the reaction temperature, the faster the reaction rate and the higher the production capacity. If the high temperature solid phase reaction temperature is greater than 1600℃, the reaction rate is too fast and will be accompanied by the appearance of other trace elements, affecting the silicon oxygen ratio in silicon oxide.

[0048] If the reaction time is less than 2 hours, the reaction is incomplete. If the reaction time is more than 10 hours, the time is too long and the silicon oxygen vapor produced by the reaction will regenerate silicon dioxide, reducing the production yield.

[0049] In a preferred embodiment of the present invention, after a reaction time of 2-10 hours, the reaction is complete and the rotation control of the furnace body in the cooling zone is turned on.

[0050] In a preferred embodiment of the present invention, the cooling condition is that the condensation temperature is 500-900° C., and at the same time, the furnace body of the cooling zone is rotated and inert gas is introduced from under the furnace body to increase the disturbance of the solid.

[0051] In a preferred embodiment of the present invention, after the reaction is completed, the Dmax of the collected material is less than 150 μm.

[0052] In a preferred embodiment of the present invention, the particle size of the powdered silicon oxide meets the following conditions:

[0053] D10 is 1-6μm, D50 is 3-15μm, D90 is 6-30μm, and the D90 / D10 range is 2-5.

[0054] Selecting powdered silicon oxide that meets the above conditions has the following advantages:

[0055] The particle size and distribution width have a great influence on the material performance: for silicon-based materials, the smaller the particles, the smaller the volume expansion, and the better the conductivity after carbon coating (the fewer gaps between particles and the better the contact), so the cycle performance and rate performance are better, but if the particles are too small, the specific surface area will be larger, and the amount of carbon coating required will be more, which will also cause capacity loss. In addition, the processed particles are small, the material loss is more serious, the yield is lower, and the production cost of the material will also increase significantly; if the particles are too large, the silicon-based material will expand more, the cycle performance is poor, and the conductivity after carbon coating is general. The influence of particle size distribution: mainly the narrow particle size distribution has many advantages in terms of material performance, but the production cost is high and the process yield is very low; if the distribution is too wide, there will be ultrafine powder and large particles. Ultrafine powder improves the rate and cycle performance, but at the same time, due to its large specific surface area, it will require more carbon coating and there will be a loss of capacity. Large particles affect the processing performance of the material and may cause scratches on the coating. Based on the above analysis, the above particle size range is adopted to seek a balance between performance and actual production cost. Considering the optimal balance between material properties and production costs, the D50 of the powdered silicon oxide is preferably 3-10 μm, and the D90 / D10 is preferably in the range of 2-4.

[0056] Preferably, the method further comprises:

[0057] The step of subjecting the collected materials after the reaction to multiple stage-by-stage crushing and classification is specifically as follows:

[0058] The collected materials after the reaction are screened according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 1-6μm, D50 of 3-15μm, D90 of 6-30μm, and D90 / D10 range of 2-5, including:

[0059] First, if the particle size of the material under the sieve meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the sieve will be directly crushed, and the crushed material will continue the above screening, classification, and crushing steps, and this will be repeated until the material is finished;

[0060] Preferably, the target particle size D50 is 3-10 μm, and the D90 / D10 range is 2-4;

[0061] Preferably, a screening machine is used for screening, and the screening machine is one of a straight screen, a rotary vibrating screen, and an ultrasonic vibrating screen, and the mesh number of the screen is 20-100 meshes.

[0062] By adopting multiple step-by-step crushing and grading, the loss of raw materials caused by the coarse crushing process can be avoided. At the same time, the multiple step-by-step crushing and grading also greatly improves the overall processing yield of silicon oxide and reduces the production cost of silicon oxide negative electrode materials.

[0063] A powdery silicon oxide obtained by the method as described above.

[0064] A method for preparing a silicon oxide negative electrode material, the method comprising:

[0065] The powdered silicon oxide as described above is subjected to carbon coating treatment to obtain a silicon oxide negative electrode material coated with a carbon coating layer;

[0066] Preferably, the proportion of the carbon coating layer is 2-10% of the mass of the powdered silicon oxide.

[0067] Preferably, the carbon coating method comprises:

[0068] The powdered silicon oxide is solid-phase carbonized or gas-phase carbonized to complete the carbon coating process.

[0069] Preferably, the solid phase carbonization is carried out under the following reaction conditions:

[0070] Reaction temperature 1000-1400°C and protective atmosphere;

[0071] The gas phase carbonization is carried out under the following reaction conditions:

[0072] Protective atmosphere and reaction temperature 700~1000℃;

[0073] Preferably, the carbon source for solid phase carbonization comprises asphalt and / or resin;

[0074] Preferably, the carbon source for gas phase carbonization includes acetylene and / or methane.

[0075] Preferably, the protective atmosphere is nitrogen and / or argon.

[0076] Preferably, the gas phase carbonization can be carried out in a CVD rotary furnace.

[0077] Preferably, the carbon coating process further includes the steps of screening and demagnetization.

[0078] Screening and demagnetization are both routine operations in the negative electrode material industry.

[0079] A silicon oxide negative electrode material, characterized in that it is obtained by the silicon oxide negative electrode material preparation method as described above, or,

[0080] A lithium ion battery comprises the silicon monoxide negative electrode material as described above.

[0081] In the following examples, all the raw materials used are commercially available.

[0082] Example 1

[0083] A method for preparing a silicon oxide negative electrode material, comprising:

[0084] Silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives a lifting plate to stir, mix and heat at a rotation frequency of 10 Hz. When the reaction temperature is heated to 1400°C, the rotation of the high-temperature section (i.e., reaction zone) rotary furnace is stopped, and heating is continued for 6 hours to obtain silicon oxide vapor; the rotation control of the furnace body in the cooling zone is turned on, and an inert gas is introduced from the bottom of the furnace body (in the opposite direction of condensation and sinking of silicon oxide vapor); the material is cooled and collected; the cooling condition is that the condensation temperature is 700°C, and at the same time, the furnace body in the cooling zone is rotated and an inert gas is introduced from the bottom of the furnace body to increase the disturbance of the solid, and the inert gas is nitrogen.

[0085] The vacuum rotary kiln comprises a material lifting plate, and a vent is provided below the furnace body in the cooling zone.

[0086] The collected material Dmax is less than 150 μm, and the steps of crushing and classifying the collected material multiple times in stages include:

[0087] The collected materials after the reaction are sieved according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 2μm, D50 of 3μm, D90 of 6μm, and the range of D90 / D10 is 3, including:

[0088] First, if the particle size of the material under the screen meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the screen will be directly crushed, and the crushed material will continue the above screening, grading, and crushing steps. This will be repeated until the material is finished. Among them, a screening machine is used for screening, and the screening machine is a straight-discharge screen.

[0089] After physically mixing the above-mentioned powder materials after particle size adjustment, solid phase carbonization is carried out to complete carbon coating modification. The reaction conditions of the solidification carbonization include: carrying out in a nitrogen atmosphere, the reaction temperature is 1000°C, the reaction time is 4h, and the carbon source is asphalt.

[0090] The material obtained after the above coating is screened and demagnetized to obtain a carbonized modified silicon iodide negative electrode material.

[0091] The charge and discharge performance of the silicon oxide negative electrode material obtained in the embodiment was tested. At a current density of 0.1C, the discharge capacity in the first week was 1680.2mAh / g, and the charge and discharge efficiency in the first week was 80.9%. Figure 1 shown.

[0092] Example 2

[0093] A method for preparing a silicon oxide negative electrode material, comprising:

[0094] Silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives a lifting plate to stir, mix and heat at a rotation frequency of 50 Hz. When the reaction temperature is heated to 1600°C, the rotation of the high-temperature section (i.e., reaction zone) rotary furnace is stopped, and heating is continued for 10 hours to obtain silicon oxide vapor; the rotation control of the furnace body in the cooling zone is turned on, and an inert gas is introduced from the bottom of the furnace body (in the opposite direction of condensation and sinking of silicon oxide vapor); the material is cooled and collected; the cooling condition is that the condensation temperature is 900°C, and at the same time, the furnace body in the cooling zone is rotated and an inert gas is introduced from the bottom of the furnace body to increase the disturbance of the solid, and the inert gas is nitrogen.

[0095] The vacuum rotary kiln comprises a material lifting plate, and a vent is provided below the furnace body in the cooling zone.

[0096] The collected material Dmax is less than 150 μm, and the steps of crushing and classifying the collected material multiple times in stages include:

[0097] The collected materials after the reaction are screened according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 6μm, D50 of 15μm, D90 of 30μm, and the range of D90 / D10 is 5, including:

[0098] First, if the particle size of the material under the screen meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the screen will be directly crushed, and the crushed material will continue the above screening, grading, and crushing steps. This will be repeated until the material is finished. Among them, a screening machine is used for screening, and the screening machine is a straight-discharge screen.

[0099] After physically mixing the above-mentioned powder materials after particle size adjustment, solid phase carbonization is carried out to complete carbon coating modification. The reaction conditions of the solidification carbonization include: carrying out in a nitrogen atmosphere, the reaction temperature is 1400°C, the reaction time is 2h, and the carbon source is asphalt.

[0100] The material obtained after the above coating is screened and demagnetized to obtain a carbonized modified silicon iodide negative electrode material.

[0101] Example 3

[0102] A method for preparing a silicon oxide negative electrode material, comprising:

[0103] A method for preparing a silicon oxide negative electrode material, comprising:

[0104] Silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives a lifting plate to stir, mix and heat at a rotation frequency of 25 Hz. When the reaction temperature is heated to 1300°C, the rotation of the high-temperature section (i.e., reaction zone) rotary furnace is stopped, and heating is continued for 5 hours to obtain silicon oxide vapor; the rotation control of the furnace body in the cooling zone is turned on, and an inert gas is introduced from the bottom of the furnace body (in the opposite direction of condensation and sinking of silicon oxide vapor); the material is cooled and collected; the cooling condition is that the condensation temperature is 700°C, and at the same time, the furnace body in the cooling zone is rotated and an inert gas is introduced from the bottom of the furnace body to increase the disturbance of the solid, and the inert gas is nitrogen.

[0105] The vacuum rotary kiln comprises a material lifting plate, and a vent is provided below the furnace body in the cooling zone.

[0106] The collected material Dmax is less than 150 μm, and the steps of crushing and classifying the collected material multiple times in stages include:

[0107] The collected materials after the reaction are screened according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 4μm, D50 of 8μm, D90 of 12μm, and the D90 / D10 range is 3, including:

[0108] First, if the particle size of the material under the screen meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the screen will be directly crushed, and the crushed material will continue the above screening, grading, and crushing steps. This will be repeated until the material is finished. Among them, a screening machine is used for screening, and the screening machine is a straight-discharge screen.

[0109] After physically mixing the above-mentioned powder materials after particle size adjustment, solid phase carbonization is carried out to complete carbon coating modification. The reaction conditions of the solidification carbonization include: carrying out in a nitrogen atmosphere, the reaction temperature is 1200°C, the reaction time is 3 hours, and the carbon source is asphalt.

[0110] The material obtained after the above coating is screened and demagnetized to obtain a carbonized modified silicon iodide negative electrode material.

[0111] Example 4

[0112] The rest is the same as Example 1, except that the particle size distribution of the target product is D10 of 1 μm, D50 of 2 μm, D90 of 6 μm, and the range of D90 / D10 is 6.

[0113] Example 5

[0114] The rest is the same as Example 1, except that the particle size distribution of the target product is D10 of 6 μm, D50 of 15 μm, D90 of 30 μm, and the range of D90 / D10 is 5.

[0115] Example 6

[0116] The rest is the same as Example 1, except that there is no vent below the furnace body, and during cooling, inert gas cannot be introduced through the vent to increase solid disturbance.

[0117] Example 7

[0118] The rest is the same as Example 1, except that the rotation frequency of the high temperature zone of the vacuum rotary kiln is 2 Hz, and the rotation frequency of the furnace body in the cooling zone is 10 Hz.

[0119] Example 8

[0120] The rest is the same as Example 1, except that the rotation frequency of the high temperature section (reaction zone) of the vacuum rotary kiln is 60 Hz, and the rotation frequency of the furnace body in the cooling zone is 70 Hz.

[0121] Comparative Example 1

[0122] The rest is the same as Example 1, except that a high-temperature solid phase reaction occurs in a vacuum high-temperature kiln.

[0123] Comparative Example 2

[0124] The rest is the same as in Example 1, except that the vacuum rotary kiln does not include a lifting plate.

[0125] The performance of the silicon dioxide negative electrode materials of Example 1 and Comparative Examples 1-2 was tested, as shown in the following table:

[0126] Capacity mAh / g Initial efficiency % Example 1 1680.2 80.9 Example 2 1650.9 79.8 Example 3 1692.2 81.1 Example 4 1609.5 78.9 Example 5 1615.3 79.2 Example 6 1611.8 79.6 Example 7 1602.5 78.1 Example 8 1675.1 79.9 Comparative Example 1 1489.7 67.8 Comparative Example 2 1500.2 65.5

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon oxide negative electrode material, characterized in that: The method comprises: The powdered silicon oxide is subjected to carbon coating treatment to obtain a silicon oxide negative electrode material coated with a carbon coating layer; The mass of the carbon coating is 2-10% of the mass of the powdered silicon oxide; The method for preparing powdered silicon oxide comprises: Silicon and silicon dioxide powders are mixed evenly according to the required amount and put into a vacuum rotary furnace. Under vacuum conditions, the vacuum rotary furnace drives the material lifting plate inside to disturb the mixing. At this time, the cooling zone is rotated and closed, and the mixture is heated while being stirred and mixed. When the mixture is heated to the reaction temperature, the rotation is stopped, and the heating and reaction are continued to obtain silicon oxide vapor. After the reaction is complete, the rotation control of the furnace body in the cooling zone is turned on, and an inert gas is introduced from the bottom of the furnace body to cool and collect the materials to obtain powdered silicon oxide. The vacuum rotary furnace includes internal parts that can disturb mixing, a high-temperature reaction zone and a cooling zone, the cooling zone has independent rotation control, and a vent is provided below the furnace body of the cooling zone; The rotation frequency of the vacuum rotary kiln before heating to the reaction temperature is 5-50 Hz, and the rotation frequency of the furnace body in the cooling zone during cooling is 20-60 Hz; The particle size of the powdered silicon oxide meets the following conditions: D10 is 1-6μm, D50 is 3-15μm, D90 is 6-30μm, and the D90 / D10 range is 2-5; In the method for preparing powdered silicon oxide, the reaction temperature is 1000-1600° C. and the reaction time is 2-10 hours; The capacity of the silicon monoxide negative electrode material reaches more than 1600 mAh / g, and the first efficiency reaches more than 78%.

2. The preparation method according to claim 1, characterized in that In the preparation method of powdered silicon oxide, the cooling condition is that the condensation temperature is 500-900° C., and at the same time, the furnace body in the cooling zone is rotated and inert gas is introduced from under the furnace body to increase the disturbance of the solid.

3. The preparation method according to claim 1, characterized in that: In the method for preparing powdered silicon oxide, after the reaction is completed, the collected material has a Dmax of <150 μm.

4. The preparation method according to claim 1, characterized in that: The particle size of the powdered silicon oxide meets the following conditions: The powdered silicon oxide has a D50 of 3-10 μm and a D90 / D10 range of 2-4.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The method for preparing powdered silicon oxide further includes the step of subjecting the collected material after the reaction to multiple stage-by-stage crushing and grading, specifically: The collected materials after the reaction are screened according to the particle size to screen out the product with the target particle size. The particle size distribution of the target product is D10 of 1-6μm, D50 of 3-15μm, D90 of 6-30μm, and D90 / D10 range of 2-5, including: First, if the particle size of the material under the sieve meets the target, it will be directly collected. If the particle size is too small, it will be classified to the target particle size; the material on the sieve will be directly crushed, and the crushed material will continue the above screening, classification, and crushing steps, and this will be repeated until the material is finished; The screening is performed by a screening machine, which is one of a straight screen, a rotary vibrating screen, and an ultrasonic vibrating screen, and the mesh number of the screen is 20-100 meshes.

6. A silicon oxide negative electrode material, characterized in that: It is obtained by the method for preparing the silicon 2 oxide negative electrode material as claimed in claim 1.

7. A lithium ion battery, characterized in that: Comprising the silicon monoxide negative electrode material as described in claim 6.

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