Continuous preparation method and production equipment of spherical negative electrode active material

Abstract

The present application provides a continuous preparation method and production equipment for spherical negative electrode active materials, the preparation method comprising: providing a first mixture including elemental silicon and metal silicate; continuously feeding the first mixture into the plasma device from the top of the plasma device, melting the first mixture to form a second mixture; allowing the second mixture to enter an evaporation device and gasify to form a gas mixture; transferring the gas mixture to a carbon deposition device, and introducing a carbon source gas into the carbon deposition device, wherein the gas mixture condenses to form a spherical core body, and the carbon source gas is adsorbed to the surface of the spherical core body and undergoes a chemical reaction to form a carbon coating layer. The continuous preparation method and production equipment can improve the sphericity of the spherical negative electrode active material without the need for secondary pulverization.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion batteries, and in particular to a continuous preparation method and production equipment for spherical negative electrode active materials. Background Art

[0002] With the development of modern electronic products such as smart phones, wearables, and new energy vehicles, the requirements for the energy density, safety, and cost of the core power module - battery pack are getting higher and higher, and the market urgently calls for innovation in the material system. Silicon-based materials have significant advantages in energy density, but the proportion of them that can be scaled up and successfully introduced for use in battery consumption is still very low.

[0003] The negative electrode of the pure silicon system expands too much and the number of cycles is generally low; because the silicon-oxygen material forms a buffer structure between silicon atoms, it greatly enhances the structural stability, thus having a certain degree of improvement in the bottleneck issues that limit the application of silicon materials, such as cycle life and expansion. However, the first coulomb efficiency of ordinary silicon-oxygen materials is generally only about 75%, and although the first coulomb efficiency can be improved by pre-embedded lithium and other materials, the cycle performance is degraded and the cost is high, so it is still difficult to obtain large-scale use.

[0004] Therefore, the promotion of silicon-oxygen materials needs to strike a balance between circulation, initial effect, and cost. Studies have shown that compared with ordinary angular silicon-oxygen materials, spherical silicon-oxygen materials are expected to cover carbon more evenly on the surface of the substrate powder, and can also inhibit particle breakage and defects caused by repeated expansion and contraction, thereby improving the cycle characteristics of lithium batteries. However, there is currently no method suitable for the industrial production of spherical silicon-oxygen materials. Summary of the invention

[0005] The technical problem solved by the present application is to provide a continuous preparation method and production equipment for spherical negative electrode active materials, which can improve the sphericity of the spherical negative electrode active materials and do not require secondary crushing.

[0006] On the one hand, the present application provides a continuous preparation method for spherical negative electrode active materials, comprising: providing a first mixture comprising elemental silicon and metal silicate; continuously feeding the first mixture into a plasma device from the top of the plasma device to melt the first mixture to form a second mixture; allowing the second mixture to enter an evaporation device to gasify to form a gas mixture; transferring the gas mixture to a carbon deposition device, and introducing a carbon source gas into the carbon deposition device, wherein the gas mixture condenses to form a spherical core body, and the carbon source gas is adsorbed onto the surface of the spherical core body and undergoes a chemical reaction to form a carbon coating layer.

[0007] In some embodiments of the present application, the feed rate of the plasma device is 40m / s~100m / s, the flow rate of the feed carrier gas is 15L / min~40L / min, the flow rate of the plasma gas source is 15L / min~30L / min, the plasma power is 30kW~120kW, and the pressure is 10kPa~20kPa.

[0008] In some embodiments of the present application, the gas mixture is discharged from the bottom of the evaporation device and fed from the bottom of the carbon deposition device, wherein the temperature at the discharge point is 1470K~2000K, and the temperature at the feed point is 850K~1220K.

[0009] In some embodiments of the present application, the second mixture is vaporized in an evaporation chamber of the evaporation device, and the temperature of the evaporation chamber is above 6100K, and the pressure is 10 kPa to 60 kPa.

[0010] In some embodiments of the present application, an auxiliary cooling gas is also introduced into the carbon deposition device, and the flow ratio of the carbon source gas and the auxiliary cooling gas is 0.1 to 1; the gas mixture is condensed in the carbon deposition chamber of the carbon deposition device, and the temperature of the carbon deposition chamber is 1050K to 1370K.

[0011] In some embodiments of the present application, the molar ratio of the elemental silicon to the metal silicate is 8-15.

[0012] In some embodiments of the present application, the metal silicate includes at least one of Li2SiO3, Li2Si2O5, LiOH, MgSiO3 and Mg2SiO4.

[0013] In some embodiments of the present application, the carbon source gas includes at least one of methane, melamine, aniline, ethylene, acetylene, propane, propyne, methanol and fluorocarbon gas.

[0014] In some embodiments of the present application, the carbon coating layer includes at least one of elemental carbon, hydrocarbons, carbonitrides and fluorocarbons.

[0015] In some embodiments of the present application, the thickness of the carbon coating layer does not exceed 40 nm, and the mass of the carbon element accounts for no less than 0.5% to 10% of the total mass of the spherical negative electrode active material.

[0016] In some embodiments of the present application, the carbon source gas is introduced into the carbon sedimentation device from the bottom, and the spherical porous core body is also transported into the carbon sedimentation device from the top of the carbon sedimentation device, wherein the gas mixture is adsorbed in the pores of the spherical porous core body and condensed to fill the pores of the spherical porous core body, and the carbon source gas is adsorbed onto the surface of the spherical porous core body and undergoes a chemical reaction to form a carbon coating layer.

[0017] In some embodiments of the present application, the particle size of the spherical negative electrode active material is 100 nm to 50 μm, and the sphericity of the spherical negative electrode active material is not less than 0.9.

[0018] Another aspect of the present application also provides a continuous production equipment for spherical negative electrode active materials, including: a plasma device, used to melt a first mixture including elemental silicon and metal silicate to form a second mixture, and the first mixture is continuously fed into the plasma device from the top of the plasma device; an evaporation device, connected to the bottom of the plasma device, used to gasify the second mixture to form a gas mixture; a carbon precipitation device, connected to the evaporation device, used to condense the gas mixture to form a spherical core body, and form a carbon coating layer on the surface of the spherical core body.

[0019] In some embodiments of the present application, the plasma device includes: a plasma chamber, which is a place for forming the second mixture, and the plasma power of the plasma chamber when working is 30kW~120kW, and the pressure is 10kPa~20kPa; a first mixture feed port, located at the top of the plasma chamber; at least one plasma gas inlet, located on the side wall of the plasma chamber, for providing a plasma gas source, and when the plasma gas inlet is working, the flow rate of the plasma gas source is 15L / min~30L / min.

[0020] In some embodiments of the present application, the evaporation device includes: an evaporation chamber, which is the place where the second mixture is vaporized, and the temperature of the evaporation chamber when working is 1250K~2000K, and the pressure is 10kPa~60kPa; a second mixture feed port, located at the top of the evaporation chamber and connected to the bottom of the plasma device; a gas guide port, located at the bottom of the evaporation chamber and connected to the carbon deposition device, for exporting the gas mixture, and when the gas guide port is working, the temperature at the gas guide port is 1470K~2000K.

[0021] In some embodiments of the present application, the carbon deposition device includes: a carbon deposition chamber, which is the place for forming the spherical core body and the carbon coating layer, and the temperature of the carbon deposition chamber when working is 800℃~1100℃; a feed port, located at the bottom of the carbon deposition chamber and connected to the gas guide port, used to input the gas mixture, and when the feed port is working, the temperature at the feed port is 850K~1220K; an air inlet, located at the bottom of the carbon deposition chamber, used to input carbon source gas; a discharge port, located at the bottom of the carbon deposition chamber, used to output the spherical negative electrode active material.

[0022] In some embodiments of the present application, the continuous production equipment further includes a first delivery pipeline for delivering the carbon source gas, and the first delivery pipeline is connected to the gas inlet.

[0023] In some embodiments of the present application, the continuous production equipment also includes: a first conveying pipeline for conveying the carbon source gas; a second conveying pipeline for conveying auxiliary cooling gas; a gas mixing device for mixing the carbon source gas and the auxiliary cooling gas, wherein the first conveying pipeline and the second conveying pipeline are respectively connected to the gas mixing device, and the gas mixing device is connected to the air inlet.

[0024] In some embodiments of the present application, the carbon deposition device also includes a crystal nucleus feed inlet located at the top of the carbon deposition chamber and used to input the spherical porous core body; when the carbon deposition chamber is working, the input gas mixture is adsorbed in the pores of the spherical porous core body and condensed to fill the pores of the spherical porous core body, and the carbon source gas is adsorbed to the surface of the spherical porous core body and a chemical reaction occurs to form a carbon coating layer.

[0025] In some embodiments of the present application, the angle between the axis where the air inlet and the feed port are located is 60° to 180°.

[0026] Compared with the prior art, the continuous preparation method and production equipment of the spherical negative electrode active material of the technical solution of the present application has the following beneficial effects:

[0027] The continuous preparation method of the technical solution of the present application is carried out by melting a first mixture of silicon and metal silicate through plasma high temperature to form a second mixture, and gasifying the second mixture to form a gas mixture, and then condensing the gas mixture into a spherical core body, and allowing the carbon source gas to adsorb onto the surface of the spherical core body and react chemically to form a carbon coating layer. There is no need for scraper-type physical grinding treatment and secondary crushing, which can greatly improve the yield and save preparation costs. The spherical negative electrode active material finally formed has a narrow particle size distribution, the sphericity can reach more than 0.9, and the effective utilization rate of the material exceeds 95%.

[0028] The spherical negative electrode active material obtained by the continuous preparation method of the technical solution of the present application has a carbon coating layer. When the spherical negative electrode active material is used as an electrode material, the carbon coating layer can isolate the spherical core and the electrolyte to prevent the reaction between the two, thereby significantly improving the cycle stability of the battery.

[0029] The continuous preparation method of the technical solution of the present application can obtain a spherical negative electrode active material with high capacity and high first coulomb efficiency by controlling the molar ratio of elemental silicon and metal silicate to a suitable value, and the capacity of the spherical negative electrode active material of the technical solution of the present application can reach 1400mAh / g, and the first coulomb efficiency can reach 90%, eliminating the additional doping process in the silicon-oxygen material manufacturing process in the prior art, reducing production costs. The continuous preparation method of the technical solution of the present application can realize continuous production in the industry, which is very suitable for industrial promotion.

[0030] The production equipment of the technical solution of the present application can continuously obtain spherical negative electrode active materials with high sphericity and high production efficiency. At the same time, it can realize the particle size adjustment and performance adjustment of the spherical negative electrode active materials. It has a simple structure and is easy for industrial operation, and can be widely used in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals represent similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting, exemplary embodiments, and the drawings are only used for the purpose of illustration and description, and are not intended to limit the scope of this application. Other embodiments may also accomplish the inventive intent in this application. It should be understood that the drawings are not drawn to scale. Among them:

[0032] Figure 1 A schematic diagram of a continuous preparation method of a spherical negative electrode active material according to an embodiment of the present application;

[0033] Figure 2 This is a schematic structural diagram of a continuous production device for spherical negative electrode active materials according to an embodiment of the present application;

[0034] Figure 3 A schematic diagram of the structure of a plasma device and a feeding device in an embodiment of the present application;

[0035] Figure 4 Another structural schematic diagram of a plasma device and a feeding device in an embodiment of the present application;

[0036] Figure 5 It is another structural schematic diagram of the plasma device and the feeding device in the embodiment of the present application;

[0037] Figure 6This is a SEM image of the spherical negative electrode active material prepared in Example 1 of the present application;

[0038] Figure 7 This is a TEM image of the spherical negative electrode active material prepared in Example 1 of the present application;

[0039] Figure 8 This is a diffraction ring analysis diagram of the carbon coating layer of the spherical negative electrode active material prepared in Example 1 of the present application;

[0040] Fig. 9 This is a SEM image of the spherical negative electrode active material prepared in Example 3 of the present application;

[0041] Fig.10 This is a SEM image of the spherical negative electrode active material prepared in Example 15 of the present application. DETAILED DESCRIPTION

[0042] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content in the present application. It will be apparent to those skilled in the art that various local modifications to the disclosed embodiments are apparent, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments shown, but to the widest scope consistent with the claims.

[0043] At present, it is still difficult to industrially produce spherical granular silicon oxide powder without edges and corners. One method is to first heat a mixture of silicon dioxide and elemental silicon to produce silicon oxide gas, then cool it to form silicon oxide solid, and then crush the silicon oxide solid to obtain silicon oxide powder. However, the silicon oxide powder formed by crushing contains a large number of non-spherical particles with edges and corners, so it is necessary to add a process of screening spherical particles, which will also lead to serious material loss and greatly reduce the yield rate.

[0044] There are also some methods that use a blade to scrape the silicon oxide precipitates on the substrate, turn the silicon oxide precipitates into powder and recover them. This method has the following disadvantages: the overall sphericity of the obtained material is not high; the size of the silicon oxide powder is controlled by the distance between the scraper and the substrate, so the particle size of the silicon oxide powder is 0.1mm~3mm, so it cannot be used directly as an electrode material. The silicon oxide powder needs to be crushed for the second time to obtain micron-sized particles, and the secondary crushing will form edges and corners again, reducing the sphericity of the material, which not only increases the cost, but also has no essential difference from the crushing of ordinary silicon oxide deposits.

[0045] Although the preparation method of spherical silicon oxide materials has been explored, the existing preparation method still grinds and removes edges and corners from a physical perspective to improve the sphericity. Not only is the sphericity limited, but it also requires secondary crushing, which makes the material utilization rate low and cannot be promoted industrially. The technical solution of this application can directly prepare spherical silicon oxide materials with a sphericity of not less than 0.9 through the melting-condensation nucleation and carbon precipitation of raw materials, without the need for secondary mechanical crushing; at the same time, the entire preparation process can be continuously produced, and the material utilization rate is high; the prepared spherical silicon oxide materials are directly doped with metal elements, without the need to add additional doping processes; the surface of the prepared spherical silicon oxide materials is covered with a carbon coating layer, which realizes the surface modification of nanoscale materials and avoids the reaction of silicon oxide materials with electrolytes during the charge and discharge process when used as electrode materials, so it has good cycle stability.

[0046] refer to Figure 1 The present application provides a continuous preparation method of a spherical negative electrode active material, comprising:

[0047] Step S1: providing a first mixture including elemental silicon and metal silicate;

[0048] Step S2: continuously feeding the first mixture into the plasma device from the top of the plasma device to melt the first mixture to form a second mixture;

[0049] Step S3: allowing the second mixture to enter an evaporation device to be vaporized to form a gas mixture;

[0050] Step S4: transferring the gas mixture to a carbon deposition device, and introducing a carbon source gas into the carbon deposition device, wherein the gas mixture is condensed to form a spherical core body, and the carbon source gas is adsorbed onto the surface of the spherical core body and chemically reacts to form a carbon coating layer.

[0051] In step S1, the first mixture may be a mixture of particles having a particle size of 1 μm to 40 μm, and the metal silicate may include at least one of Li2SiO3, Li2Si2O5, LiOH, MgSiO3 and Mg2SiO4. Adding the metal silicate can reduce the irreversible substances in the spherical negative electrode active material during the charge and discharge process. Specifically, the existing negative electrode active material contains a large amount of silicon oxide compounds, and when the battery is charged, the silicon oxide compounds will react with the lithium ions in the electrolyte to form lithium silicate. This reaction is an irreversible reaction, which causes the lithium ions charged in to be unable to be released, resulting in the "dead lithium" phenomenon.

[0052] The relative proportions of the metal silicate and elemental silicon in the embodiment of the present application affect the performance of the negative electrode active material. The mass of the metal silicate should not be too much, which will easily lead to low capacity of the negative electrode active material. At the same time, the mass of the metal silicate should not be too much, which will affect the first coulombic efficiency of the negative electrode active material. Therefore, by controlling the masses of the elemental silicon and the metal silicate in a reasonable ratio, a base core with both high capacity and high first coulombic efficiency can be obtained, thereby effectively reducing costs. In the embodiment of the present application, the molar ratio of the elemental silicon to the metal silicate is 8 to 15. In addition, since silicon dioxide is not present in the raw materials of the embodiment of the present application, the problem of low first efficiency of the battery caused by silicon dioxide in the prior art can be avoided.

[0053] The first mixture first enters the plasma device and is melted by the plasma flame to form a second mixture, and the second mixture is in the form of molten droplets. The first mixture is continuously fed from the top of the plasma device. The continuous feeding described in the embodiment of the present application refers to a feeding method that continuously feeds within a certain period of time. The time period of continuous feeding is determined according to the specific production situation, such as production volume, whether the production line is operating normally, etc. Compared with feeding at the bottom of the plasma device, top feeding can be assisted by gravity, so a lower carrier gas flow rate can be used to bring in the first mixture powder, which has less effect on the temperature distribution of the equipment, and can obtain a higher material flight speed and a better gasification rate. At the same time, it can also avoid excessive gas flow affecting the reaction in the carbon deposition device.

[0054] The phase change process of the first mixture entering the plasma device is a complex heat and mass transfer process, which takes about tens of milliseconds and involves the interaction between the thermal fluid field, the induced electromagnetic field and the particle concentration field, and the plasma processing parameters are very important for the stable operation of the plasma device. In some embodiments, the feed rate of the plasma device is 40m / s to 100m / s, the feed carrier gas and the plasma gas source can be an inert gas, such as argon, and the flow rate of the feed carrier gas can be 15L / min to 40L / min, the flow rate of the plasma gas source can be 15L / min to 30L / min, the plasma power is 30kW to 120kW, and the pressure is 10kPa to 20kPa, wherein the flow rate of the plasma gas source determines the stability and heat of the plasma chamber, and cooperates with the plasma power and pressure so that the first mixture can be melted to form a second mixture and enter the evaporation device.

[0055] The second mixture formed by melting the first mixture enters the evaporation device, and after reaching the vaporization temperature point, a gas mixture is formed. The place where the second mixture is vaporized is the evaporation chamber of the evaporation device, and the temperature of the evaporation chamber is above 6100K, and the pressure is 10kPa~60kPa. Then, the gas mixture is transferred to the carbon deposition device. Specifically, the gas mixture is discharged from the bottom of the evaporation device and fed from the bottom of the carbon deposition device, wherein the temperature at the discharge is 1470K~2000K, and the temperature at the feed is 850K~1220K. The temperature at the discharge should not be too low to ensure that the gas mixture will not condense in advance, thereby blocking the channel. The temperature at the feed is related to the carbon deposition effect. If the temperature at the feed is too low, the carbon deposition is insufficient; if the temperature at the feed is too high, the silicon grains will be too large and the cycle performance will be reduced.

[0056] A carbon source gas is also introduced into the carbon deposition device, and the gas mixture enters the carbon deposition chamber of the carbon deposition device and condenses to form a spherical core body, and the carbon source gas is adsorbed to the surface of the spherical core body and undergoes a chemical reaction to form a carbon coating layer. The temperature of the carbon deposition chamber is 1050K~1370K. In some embodiments, an auxiliary cooling gas is also introduced into the carbon deposition device to quickly cool the gas mixture, wherein the flow ratio of the carbon source gas and the auxiliary cooling gas can be 0.1~1. If the flow ratio is too low, the carbon deposition time will be too long and the carbon deposition efficiency will be low; if the flow ratio is too high, the product generated by the reaction will be high and the carbon deposition effect will be poor.

[0057] The carbon source gas may include at least one of methane, melamine, aniline, ethylene, acetylene, propane, propyne, methanol and fluorocarbon gas. When the carbon source gas includes at least one of methane, ethylene, acetylene, propane and propyne, the carbon source gas is adsorbed to the surface of the spherical core body and undergoes a chemical reaction to generate elemental carbon and hydrogen; when the carbon source gas includes at least one of melamine and aniline, the carbon source gas is adsorbed to the surface of the spherical core body and the product of the chemical reaction mainly includes elemental carbon, carbon nitrogen compounds and hydrogen; when the carbon source gas includes methanol, the carbon source gas is adsorbed to the surface of the spherical core body and undergoes a chemical reaction to generate elemental carbon and water. When the carbon source gas includes fluorocarbon gas, the formed carbon coating layer will include fluorocarbon compounds. Therefore, the carbon coating layer of the embodiment of the present application may include at least one of elemental carbon, hydrocarbons, carbon nitrogen compounds and fluorocarbon compounds. The thickness of the carbon coating layer does not exceed 40 nm, and the mass of the carbon element accounts for no less than 0.5% to 10% of the total mass of the spherical negative electrode active material.

[0058] In some embodiments, the carbon source gas is introduced from the bottom of the carbon sink device, and a spherical porous core is also transported from the top of the carbon sink device into the carbon sink device, wherein the gas mixture is adsorbed in the pores of the spherical porous core and condensed to fill the pores of the spherical porous core, and the carbon source gas is adsorbed to the surface of the spherical porous core and chemically reacts to form a carbon coating. The particle size of the spherical porous core can be 0.5 μm to 30 μm, and the specific surface area can be 20 m 2 / g~1500m 2 / g.

[0059] The preparation method of the embodiment of the present application can realize industrial continuous production, and the particle size of the prepared spherical negative electrode active material can be 100nm to 50μm, and the sphericity can reach above 0.9.

[0060] refer to Figure 2 The embodiment of the present application also provides a continuous production device for spherical negative electrode active materials, including a plasma device 1, an evaporation device 2 and a carbon deposition device 3, wherein the plasma device 1 is used to melt a first mixture including elemental silicon and metal silicate to form a second mixture, and the first mixture is continuously fed into the plasma device 1 from the top of the plasma device 1.

[0061] refer to Figure 3 The plasma device 1 includes a plasma chamber 11, a first mixture feed port 12 and a plasma gas inlet 13. The plasma chamber 11 is a place for forming the second mixture, and the plasma power of the plasma chamber when working is 30kW to 120kW, and the pressure is 10kPa to 20kPa. The first mixture feed port 12 is located at the top of the plasma chamber 11 and is used for feeding the first mixture. The plasma gas inlet 13 is located on the side wall of the plasma chamber 11 and is used to provide a plasma gas source. The plasma gas source is transported to the plasma chamber 11 through a plasma conduit 14. The number of the plasma gas inlets 13 can be more than one Figure 3 The case with one plasma inlet 13 is shown. As an example, Figure 4 and Figure 5 The schematic diagrams of the structures when the number of the plasma inlets 13 is two and three are shown in turn. When the plasma inlets are working, the flow rate of the plasma gas source is 15L / min to 30L / min. The plasma device 1 can be, for example, a DC plasma device or a high-frequency induction thermal plasma device.

[0062] The top of the plasma device 1 is also connected to a feeding device 4. The feeding device 4 includes a feeding controller 41, a feeding pipe 42, and a feeding control valve 43. The feeding controller 41 is used to control the feeding rate of the first mixture. The feeding pipe 42 is connected to the first mixture feed port 12, and is used to transport the first mixture and the feeding carrier gas, and the feeding carrier gas is used to assist the feeding of the first mixture. In the embodiment of the present application, the feeding rate of the first mixture is 40m / s to 100m / s, and the flow rate of the feeding carrier gas is 15L / min to 40L / min.

[0063] The evaporation device 2 is connected to the bottom of the plasma device 1, and is used to gasify the second mixture to form a gas mixture. The evaporation device 2 includes an evaporation chamber 21, a second mixture feed port 22 and a gas guide port 23, wherein the evaporation chamber 21 is a place for gasification of the second mixture, and the temperature of the evaporation chamber 21 when working is 1250K~2000K, and the pressure is 10kPa~60kPa. The second mixture feed port 22 is located at the top of the evaporation chamber 21 and is connected to the bottom of the plasma device 1, and is used to input the second mixture. The gas guide port 23 is located at the bottom of the evaporation chamber 21 and is connected to the carbon deposition device 3, and is used to guide the gas mixture, and when the gas guide port 23 is working, the temperature at the gas guide port 23 is 1470K~2000K. The evaporation device 2 can be, for example, a graphite heating furnace or a high-frequency induction heating furnace. The embodiment of the present application can control the nucleation size by controlling the feed rate of the first mixture, the plasma power and pressure of the plasma device 1, and the temperature of the evaporation chamber 21, thereby achieving the regulation of the product particle size, and then completing the carbon coating process for particles with a particle size of 5nm to 10μm, and is particularly suitable for the carbon coating process for particles with a particle size of 5nm to 100nm.

[0064] The carbon deposition device 3 includes a carbon deposition chamber 31, a feed port (not shown), an air inlet (not shown) and a discharge port 32. The carbon deposition chamber 31 is a place for forming the spherical core body and the carbon coating layer, and the temperature of the carbon deposition chamber 31 when working is 800°C to 1100°C. The feed port is located at the bottom of the carbon deposition chamber 31 and is connected to the air guide port 23, and is used to input the gas mixture. When the feed port is working, the temperature at the feed port is 850K to 1220K. The air inlet is located at the bottom of the carbon deposition chamber and is used to input the carbon source gas. The angle between the air inlet and the axis of the feed port is 60° to 180°. The carbon source gas and the gas mixture are in contact within the angle range, and a better carbon deposition effect can be obtained. The discharge port 32 is located at the bottom of the carbon deposition chamber 31. The discharge port 32 can be connected to a discharge pipe, and the discharge pipe transports the product to the receiving bin 321. The embodiment of the present application can control the amount of carbon deposition by controlling the temperature of the carbon deposition chamber 31 and the flow rate of the carbon source gas, thereby achieving regulation of product performance.

[0065] In an embodiment of the present application, the carbon deposition device 3 also includes a crystal nucleus feed inlet 31 located at the top of the carbon deposition chamber 3 and used to input the spherical porous core body; when the carbon deposition chamber 31 is working, the input gas mixture is adsorbed in the pores of the spherical porous core body and condensed to fill the pores of the spherical porous core body, and the carbon source gas is adsorbed to the surface of the spherical porous core body and a chemical reaction occurs to form a carbon coating layer.

[0066] In the embodiment of the present application, the continuous production equipment further includes: a first delivery pipeline 51 for delivering the carbon source gas; a second delivery pipeline 52 for delivering auxiliary cooling gas; a gas mixing device 53 for mixing the carbon source gas and the auxiliary cooling gas, wherein the first delivery pipeline 51 and the second delivery pipeline 52 are respectively connected to the gas mixing device 53, and the gas mixing device 53 is connected to the air inlet. In some embodiments, only the first delivery pipeline 51 may be provided, and the first delivery pipeline 51 is connected to the air inlet, and the second delivery pipeline 52 and the gas mixing device 53 are omitted.

[0067] The continuous production equipment also includes a gas processing device, which includes: a separator 6, a dust removal chamber 7, a tail gas chamber 8, a separation chamber 9, a collection chamber 10, and a gas compression device 11. The working principle is as follows: Under normal circumstances, the gas generated in the carbon deposition device 3 enters the separator 6, and the separator 6 adopts the distillation principle to separate the inert gas from the hydrogen and most of the particulate matter, wherein the inert gas enters the separation chamber 9 for dust removal and separation again, and the obtained particulate matter enters the collection chamber 10, and the remaining inert gas is compressed and collected by the gas compression device 11, and then returned to the carbon deposition chamber 3 for recycling, while the hydrogen and most of the particulate matter enter the dust removal chamber 7, the particulate matter is separated, and the hydrogen enters the tail gas chamber 8 for gas incineration treatment; in special circumstances (maintenance, parking, etc.), the separation chamber 9, the collection chamber 10, and the gas compression device 11 are all closed, and only the separator 6, the dust removal chamber 7 and the tail gas chamber 8 are kept to work normally.

[0068] In some embodiments, the gas compression device 11 may include a power device 111, a first storage tank 112, a compression device 113 and a second storage tank 114 connected in sequence. The power device may be a fan as a power source for gas transportation, and the compression device 113 may be a compressor to condense the gas.

[0069] Example 1

[0070] The present application provides a continuous preparation method of a spherical negative electrode active material, comprising:

[0071] Providing a first mixture including elemental silicon and Li2SiO3, wherein the particle size of Li2SiO3 is 10 μm, and the molar ratio (A / B) of the elemental silicon to Li2SiO3 is 10;

[0072] The first mixture is continuously fed into the plasma device from the top of the plasma device, and the feeding speed of the plasma device is 50 m / s, the flow rate of the feed carrier gas (Ar) is 30 L / min, the flow rate of the plasma gas source (Ar) is 20 L / min, the plasma power is 50 kW, the pressure is 15 kPa, and the first mixture is melted to form a second mixture;

[0073] Allowing the second mixture to enter an evaporation device to vaporize and form a gas mixture, wherein the temperature of the evaporation chamber is 1800K and the pressure is 12 kPa;

[0074] Step S4: Transfer the gas mixture to a carbon deposition device, and introduce a carbon source gas into the carbon deposition device, wherein the gas mixture condenses to form a spherical core body, and the carbon source gas is adsorbed onto the surface of the spherical core body and undergoes a chemical reaction to form a carbon coating layer, wherein the temperature of the carbon deposition chamber is 1050K, the carbon source gas is C2H2, and the mass of the carbon element is 4% of the total mass of the spherical negative electrode active material (also referred to as "carbon content").

[0075] Embodiments 2 to 26

[0076] For the specific process description, please refer to Example 1, and for the process parameters, please refer to Table 1.

[0077] Comparative Example 1

[0078] Compared with Example 1, the first mixture contains only elemental silicon. For other process descriptions, please refer to Example 1. For specific process parameters, please refer to Table 1.

[0079] The spherical negative electrode active materials prepared in Example 1, Example 3 and Example 15 were characterized. Figure 6 This is a SEM image of the spherical negative electrode active material prepared in Example 1. Figure 7 This is a transmission electron microscope image of Example 1. It can be seen that a carbon coating layer of about 5 nm to 10 nm is formed on the surface of the spherical negative electrode active material prepared in Example 1. Figure 8 This is the diffraction ring analysis diagram of the carbon coating layer of Example 1. It can be seen that the fringe spacing is 0.34nm, which is consistent with the characteristics of the carbon layer. Fig. 9 This is the SEM image of the spherical negative electrode active material prepared in Example 3. Fig.10 This is the SEM image of the spherical negative electrode active material prepared in Example 15.

[0080] The negative electrode active materials of Examples 1 to 26 and Comparative Example 1, PAA (polyacrylic acid binder) and SP (conductive carbon black) were mixed at a mass ratio of 80:10:10, and 1 mol / L LiPF6 was used as an electrolyte. The mixture was applied to a button cell system (model CR2430), and the following electrochemical performance tests were performed at 25°C:

[0081] (1) First lithium removal capacity and coulombic efficiency test: discharge to 10 mV at a constant current of 0.1 C, let stand for 10 minutes, then continue to discharge to 5 mV at a constant current of 0.02 C; let stand for 10 minutes, then charge to 1.5 V at a constant current of 0.1 C. The results are shown in Table 1.

[0082] (2) Cyclic performance test: Discharge to 10 mV at a constant current of 0.1 C, let stand for 10 minutes, then continue to discharge to 5 mV at a constant current of 0.02 C; let stand for 10 minutes, then charge to 1.5 V at a constant current of 0.1 C, and repeat the subsequent cycles. The lithium desorption capacity corresponding to the number of cycles / lithium desorption capacity in the second cycle is regarded as the capacity retention rate. The results are shown in Table 1.

[0083]

[0084]

[0085] It can be seen that by using the continuous preparation method and production equipment of the embodiments of the present application, spherical negative electrode active materials with high sphericity can be obtained without secondary crushing, and the obtained spherical negative electrode active materials, when used as negative electrode materials, have higher first lithium desorption capacity and coulombic efficiency as well as better cycle performance.

[0086] Finally, it should be understood that the embodiments of the application disclosed herein are explanations of the principles of the embodiments of the present application. Other modified embodiments are also within the scope of the present application. Therefore, the embodiments disclosed in the present application are merely examples and not limitations. Those skilled in the art can adopt alternative configurations according to the embodiments in the present application to realize the application in the present application. Therefore, the embodiments of the present application are not limited to those embodiments that have been accurately described in the application.

Claims

1. A continuous preparation method of a spherical negative electrode active material, characterized in that: include: providing a first mixture including elemental silicon and a metal silicate; continuously feeding the first mixture into the plasma device from the top of the plasma device to melt the first mixture and cause a phase change to form a molten second mixture; Allowing the molten second mixture to enter an evaporation device to vaporize and form a gas mixture; The gas mixture is transferred to a carbon precipitation device, and a carbon source gas is introduced into the carbon precipitation device. The gas mixture is condensed in the carbon precipitation device to form a spherical core body, and the carbon source gas is adsorbed onto the surface of the spherical core body and chemically reacts to form a carbon coating layer. The sphericity of the spherical negative electrode active material is not less than 0.

9.

2. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The feed rate of the plasma device is 40m / s-100m / s, the flow rate of the feed carrier gas is 15L / min-40L / min, the flow rate of the plasma gas source is 15L / min-30L / min, the plasma power is 30kW-120kW, and the pressure is 10kPa-20kPa.

3. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The gas mixture is discharged from the bottom of the evaporation device and fed from the bottom of the carbon deposition device, wherein the temperature at the discharge point is 1470K-2000K, and the temperature at the feed point is 850K-1220K.

4. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The second mixture is vaporized in the evaporation chamber of the evaporation device, and the temperature of the evaporation chamber is above 6100K and the pressure is between 10 kPa and 60 kPa.

5. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: Auxiliary cooling gas is also introduced into the carbon deposition device, and the flow ratio of the carbon source gas to the auxiliary cooling gas is 0.1-1; the gas mixture is condensed in the carbon deposition chamber of the carbon deposition device, and the temperature of the carbon deposition chamber is 1050K-1370K.

6. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The molar ratio of the elemental silicon to the metal silicate is 8-15.

7. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The metal silicate includes at least one of Li2SiO3, Li2Si2O5, MgSiO3 and Mg2SiO4.

8. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The carbon source gas includes at least one of methane, melamine, aniline, ethylene, acetylene, propane, propyne, methanol and fluorocarbon gas.

9. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The carbon coating layer includes at least one of elemental carbon, hydrocarbons, carbonitrides and fluorocarbons.

10. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The thickness of the carbon coating layer does not exceed 40 nm, and the mass of the carbon element accounts for 0.5% to 10% of the total mass of the spherical negative electrode active material.

11. The continuous preparation method of spherical negative electrode active materials according to any one of claims 1 to 10, characterized in that: The carbon source gas is introduced into the carbon settling device from the bottom, and a spherical porous core body is also transported into the carbon settling device from the top, wherein the gas mixture is adsorbed in the pores of the spherical porous core body and condensed to fill the pores of the spherical porous core body, and the carbon source gas is adsorbed onto the surface of the spherical porous core body and undergoes a chemical reaction to form a carbon coating layer.

12. The continuous preparation method of spherical negative electrode active material according to claim 1, characterized in that: The particle size of the spherical negative electrode active material is 100nm-50μm.

13. A continuous production device for spherical negative electrode active materials, characterized in that: include: A plasma device, used for melting a first mixture including elemental silicon and metal silicate to undergo phase change to form a molten second mixture, wherein the first mixture is continuously fed into the plasma device from the top of the plasma device; an evaporation device, connected to the bottom of the plasma device, for vaporizing the molten second mixture to form a gas mixture; The carbon precipitation device is connected to the evaporation device and is used to condense the gas mixture to form a spherical core body and form a carbon coating layer on the surface of the spherical core body. The sphericity of the spherical negative electrode active material is not less than 0.

9.

14. The continuous production equipment of spherical negative electrode active materials according to claim 13, characterized in that: The plasma device comprises: A plasma chamber is a place for forming the second mixture, and the plasma power of the plasma chamber is 30 kW to 120 kW and the pressure is 10 kPa to 20 kPa when the plasma chamber is in operation; a first mixture feed port, located at the top of the plasma chamber; At least one plasma gas inlet is located on the side wall of the plasma chamber and is used to provide a plasma gas source. When the plasma gas inlet is working, the flow rate of the plasma gas source is 15L / min to 30L / min.

15. The continuous production equipment of spherical negative electrode active materials according to claim 13, characterized in that: The evaporation device comprises: An evaporation chamber is a place where the second mixture is vaporized, and the temperature of the evaporation chamber is 1250K to 2000K and the pressure is 10kPa to 60kPa when the evaporation chamber is in operation; a second mixture feed port, located at the top of the evaporation chamber and connected to the bottom of the plasma device; The gas guide port is located at the bottom of the evaporation chamber and is connected to the carbon deposition device, and is used to guide the gas mixture. When the gas guide port is working, the temperature at the gas guide port is 1470K to 2000K.

16. The continuous production equipment of spherical negative electrode active materials according to claim 15, characterized in that: The carbon precipitation device comprises: The carbon deposition chamber is a place where the spherical core and the carbon coating layer are formed, and the temperature of the carbon deposition chamber during operation is 800° C. to 1100° C.; A feed port, located at the bottom of the carbon deposition chamber and connected to the gas guide port, is used to input the gas mixture, and when the feed port is working, the temperature at the feed port is 850K to 1220K; An air inlet, located at the bottom of the carbon deposition chamber, for inputting carbon source gas; The discharge port is located at the bottom of the carbon deposition chamber and is used to discharge the spherical negative electrode active material.

17. The continuous production equipment of spherical negative electrode active materials according to claim 16, characterized in that: The continuous production equipment further includes a first delivery pipeline for delivering the carbon source gas, and the first delivery pipeline is communicated with the gas inlet.

18. The continuous production equipment of spherical negative electrode active materials according to claim 16, characterized in that: The continuous production equipment also includes: A first delivery pipeline, used for delivering the carbon source gas; A second delivery pipeline, used for delivering auxiliary cooling gas; A gas mixing device is used to mix the carbon source gas and the auxiliary cooling gas, wherein the first delivery pipeline and the second delivery pipeline are respectively connected to the gas mixing device, and the gas mixing device is connected to the gas inlet.

19. The continuous production equipment of spherical negative electrode active materials according to claim 17 or 18, characterized in that: The carbon deposition device also includes a crystal nucleus feed port located at the top of the carbon deposition chamber and used to input the spherical porous core body; when the carbon deposition chamber is working, the input gas mixture is adsorbed in the pores of the spherical porous core body and condensed to fill the pores of the spherical porous core body, and the carbon source gas is adsorbed to the surface of the spherical porous core body and undergoes a chemical reaction to form a carbon coating layer.

20. The continuous production equipment of spherical negative electrode active materials according to claim 16, characterized in that: The angle between the axis where the air inlet and the feed inlet are located is 60° to 180°.

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