A method and device for pre-magnesiumization of silicon dioxide lithium-ion battery negative electrode material

Abstract

The present invention discloses a method and device for pre-magnesiumization of negative electrode materials for silicon dioxide lithium-ion batteries. The method for pre-magnesiumization of negative electrode materials for silicon dioxide lithium-ion batteries of the present invention comprises the following steps: introducing solid silicon dioxide and magnesium vapor into a reactor in sequence, causing the solid silicon dioxide and the magnesium vapor to be vapor-deposited in a suspended state in the reactor, and collecting the sediment to achieve the pre-magnesiumization. The present invention prepares silicon dioxide composite negative electrode materials by vapor deposition, converting the reaction system from a solid-solid reaction to a gas-solid reaction, significantly improving the reaction efficiency and reaction uniformity, and avoiding excessive growth of silicon grains due to intense heat release from local reactions, which affects the cycle life of the battery; the prepared silicon dioxide composite negative electrode material has the advantages of low expansion and high initial efficiency; the reaction device has the advantages of controllable pre-magnesium degree and semi-continuous production.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a method and device for pre-magnesiumizing anode materials of silicon monoxide lithium-ion batteries. Background Art

[0002] With the increasing number of cars, exhaust pollution is impacting people's living environment. The emergence of new energy vehicles will transform our lives. As the core of new energy vehicles, power batteries must offer advantages such as long driving range, high power efficiency, safety, and low cost.

[0003] High-quality lithium-ion battery anode materials need to meet the advantages of low potential, stable structure, high conductivity, and cheap raw materials during the process of lithium insertion and extraction. Silicon dioxide (SiO) as a lithium-ion battery anode material has a high theoretical specific capacity (~2043mAh·g -1 ) and a suitable lithium delithiation potential (<0.5V), along with abundant raw material reserves, low preparation cost, and environmental friendliness, it is considered a promising candidate for the anode of next-generation high-energy-density lithium-ion batteries. However, SiO suffers from a severe volume effect (~200%) during the lithium deintercalation and insertion process, which can easily lead to material particle pulverization and shedding, severely affecting the interfacial stability and electrochemical performance of the SiO anode electrode.

[0004] Patent CN113241426A discloses a method for preparing a carbon-composite coated silicon oxide anode material. The method involves first coating the silicon oxide with CVD vapor at a temperature of 900-1100°C for 0.4-0.6 hours. The silicon oxide is then carbonized and sintered with a mixture of pitch and boric acid at a temperature of 900-1100°C for 1.2-1.8 hours. The resulting silicon oxide precursor consists of a core of silicon oxide particles, a CVD vapor-coated carbon layer in the middle, and an outermost layer of a solid-phase coated carbon layer formed by carbonization and sintering. Electrochemical testing revealed an initial reversible specific capacity of approximately 460 mAh / g and an initial coulombic efficiency of approximately 88.2%.

[0005] Patent CN113258051A discloses a uniformly modified silicon oxide negative electrode material, its preparation method and application. First, silicon and silicon dioxide powders are mixed evenly and placed in a furnace body, and heated under reduced pressure conditions at a heating temperature of 1000°C-1800°C; then, a solution of carbon-containing substance is passed into the furnace body to vaporize it to obtain mixed steam; the mixed steam is cooled and deposited on a water-cooled substrate, and the deposited material is crushed to obtain a silicon oxide material with carbon atoms uniformly dispersed at the atomic level.

[0006] Patent CN113410448A discloses a silicon oxide composite negative electrode material for lithium-ion batteries and a preparation method thereof. Silicon oxide is first mixed evenly with metallic magnesium powder and molten salt and treated at high temperature under a protective atmosphere, with the temperature controlled at 200-1000°C and the insulation time being 0.5-24 hours; it is then blended with a carbon-coated material, or carbonized under a protective atmosphere using gas-phase coating, with the temperature controlled at 500-1100°C and the insulation time being 2-8 hours. After cooling, a silicon oxide / carbon-coated composite material is obtained. The first reversible specific capacity of the buckled electrochemical test is approximately 1412.8 mAh / g, and the first coulombic efficiency is approximately 87.1%.

[0007] However, while carbon coating can reduce the volume expansion of silicon oxide and improve the battery's cycle life, the battery's first-cycle charge and discharge capacity shows a significant downward trend with increasing carbon content. Furthermore, silicon oxide undergoes a disproportionation reaction at 700°C, producing silicon and silicon dioxide. The rapid growth of silicon crystals reduces cycle life, while the resulting silicon dioxide reduces the material's conductivity. During the initial lithium insertion process, silicon oxide produces irreversible products such as lithium oxide and lithium silicate, resulting in a low initial coulombic efficiency for silicon oxide anode materials. Recent advances in technology have shown that while carbon coating silicon oxide can reduce volume expansion and increase cycle life, it is important to control the impact of carbon content on the battery's first-cycle charge and discharge capacity. Carbon treatment of silicon oxide requires controlling the reaction temperature to inhibit the disproportionation reaction and avoid further reductions in cycle life and conductivity. Furthermore, pre-lithiation can be used to replenish lithium in the anode to compensate for capacity loss caused by SEI film formation. This can achieve higher initial efficiency, but the amount of pre-lithiation must be carefully considered to avoid bubbles during the slurry mixing process, which can affect coating. Research has shown that magnesium thermal reaction can pre-bind oxygen in silicon oxide with magnesium, reducing lithium consumption during cycling and improving battery initial efficiency. However, current pre-magnesium technology is typically performed using a solid-phase reaction. The magnesium thermal reduction reaction releases a large amount of heat, which can easily lead to silicon grain growth and affect the battery's cycle life. Summary of the Invention

[0008] The purpose of the present invention is to provide a method and device for pre-magnesiumization of negative electrode materials for lithium-ion batteries using silicon monoxide. The negative electrode material obtained by pre-magnesiumization has the advantages of low expansion and high initial efficiency. Compared with the traditional solid-phase pre-magnesiumization method, the solid particles in the fluidized state show a violent turbulent state, the gas-solid two-phase contact area is large and continuously updated and changed, and the heat and mass transfer between the two phases are enhanced. The pre-magnesiumization process is more sufficient and safe. The gas-phase pre-magnesiumization technology improves the reaction efficiency and can achieve semi-continuous production.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for pre-magnesiumizing a negative electrode material of silicon dioxide lithium-ion battery, comprising the following steps:

[0011] The pre-magnesium process is achieved by introducing solid silicon oxide and magnesium vapor into a reactor in sequence, allowing the solid silicon oxide and magnesium vapor to be vapor-deposited in a suspended state in the reactor, and collecting the deposits.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] Preferably, the temperature of the vapor deposition is 700-800° C., and the pressure is 0.05-1.6 MPa.

[0014] Preferably, the particle size volume distribution of the silicon oxide is controlled to be D10≥6.0 μm, D50 is 10.0±1 μm, and Dmax≤15.0 μm.

[0015] Preferably, magnesium vapor is introduced from the bottom of the reactor upward, and the flow rate of the magnesium vapor is controlled to be 0.10-0.35 m / s, so that the silicon oxide is in a suspended state;

[0016] During the vapor deposition process, the sediment is collected by utilizing its own gravity.

[0017] In the above method, further, the method further comprises the following steps: separating excess magnesium vapor from the reaction system after the vapor deposition and condensing and recovering the excess magnesium vapor;

[0018] The condensation temperature is ≥180°C.

[0019] The present invention also provides a device for pre-magnesiumizing anode materials of silicon monoxide lithium-ion batteries, comprising a fluidized bed reactor, wherein the fluidized bed reactor comprises a cylinder, wherein a removable baffle is provided inside the cylinder to separate the internal space of the cylinder into upper and lower parts;

[0020] The bottom of the cylinder is provided with a magnesium vapor inlet, and the top is provided with a magnesium vapor outlet;

[0021] A solid silicon oxide inlet is provided on the side wall of the cylinder above the extractable baffle;

[0022] Below the extractable baffle, a sediment collecting device is provided inside the cylinder;

[0023] A temperature control device is provided on the outer wall of the cylinder.

[0024] In the above-mentioned device, the surface of the extractable baffle is provided with evenly distributed holes with a diameter of ≤6.0 μm;

[0025] An upper baffle is provided on the top of the cylinder;

[0026] The surface of the upper baffle is evenly distributed with holes having a diameter of ≤10.0 μm;

[0027] A magnesium vapor outlet is provided on the top of the upper baffle, and the magnesium vapor outlet is connected to the cyclone separation device and the condensation device in sequence.

[0028] In the above-mentioned device, the gas inlet pipeline of the magnesium vapor inlet leads to the gas distributor arranged at the bottom end of the cylinder;

[0029] The gas distributor is built with uniformly distributed gas inlet holes with a diameter of ≤2.0 μm;

[0030] The gas distributor is arranged around the side wall of the cylinder and the top thereof gradually slopes downward from the outside to the inside, forming a funnel-shaped cavity in the center of the cylinder;

[0031] The bottom end of the funnel-shaped cavity is sealed to form the sediment collecting device;

[0032] Along the vertical direction of the outer wall of the cylinder, the top of the gas distributor is tilted downward at an angle of 20 to 45 degrees.

[0033] In the above device, the solid silicon oxide inlet is inclined upward by 15 to 20 degrees along the vertical direction of the outer wall of the cylinder;

[0034] A closable baffle is provided at the inlet of the solid silicon oxide.

[0035] The present invention also provides a silicon oxide composite negative electrode material prepared by any of the above methods. The silicon oxide composite negative electrode material of the present invention is mainly composed of a mixture of silicon and magnesium silicates, mainly composed of carbon, oxygen, magnesium, and silicon.

[0036] The present invention has the following beneficial effects:

[0037] The present invention uses vapor deposition to prepare silicon dioxide composite anode materials, transforming the reaction system from a solid-solid reaction to a gas-solid reaction. This significantly improves reaction efficiency and uniformity, preventing the intense exothermic heat of localized reactions that can lead to excessive silicon grain growth and affect battery cycle life. The pre-magnesium-treated silicon dioxide material prepared by the present invention exhibits low expansion, high initial efficiency, and improved cycle performance. Furthermore, the reaction apparatus offers controllable pre-magnesium levels and allows for semi-continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of a device for pre-magnesiumizing anode materials of silicon dioxide lithium-ion batteries in a specific embodiment of the present invention.

[0039] Figure 1 The tags are as follows:

[0040] 100-Fluidized bed reactor; 101-Cylinder; 102-Upper baffle; 103-Removable baffle; 104-Temperature control device; 105-Inlet pipe; 106-Inlet valve; 107-Gas distributor; 108-Solid silicon oxide inlet; 109-Closable baffle; 110-Sediment collection device; 111-Outlet; 112-Outlet pipe; 113-Cyclone separator; 114-Outlet valve.

[0041] Figure 2 This is the XRD test result of the product in Comparative Example 1 of the present invention.

[0042] Figure 3 These are the XRD test results of the products in Examples 1 to 3 of the present invention.

[0043] Figure 4 This is the EDS test result of the product in Example 1 of the present invention.

[0044] Figure 5 is the content of each element in the product of Example 1 of the present invention.

[0045] Figure 6 The charge and discharge curves of the lithium-ion battery assembled with the silicon monoxide composite negative electrode materials of Comparative Example 1 and Examples 1-3 of the present invention are shown. DETAILED DESCRIPTION

[0046] In response to the technical problems described in the background technology, the present invention provides a method for pre-magnesiumization of silicon dioxide lithium-ion battery negative electrode materials, comprising the following steps: introducing solid silicon dioxide and magnesium vapor into a reactor in sequence, allowing solid silicon dioxide and magnesium vapor to be vapor-deposited in a suspended state in the reactor, and collecting the sediment to achieve pre-magnesiumization. The method of the present invention converts the reaction system from a solid-solid reaction to a gas-solid reaction, and magnesium vapor is deposited on the surface of the sediment for pre-magnesiumization, which significantly improves the reaction efficiency and reaction uniformity, avoids excessive growth of silicon grains caused by intense heat release from local reactions, and affects the cycle life of the battery. The prepared silicon dioxide material after pre-magnesiumization has the advantages of low grain size and high initial efficiency. At the same time, the reaction device has the advantages of controllable pre-magnesiumization degree and semi-continuous production.

[0047] According to the characteristics of the gas-solid reaction of the present invention, to achieve vapor deposition, the vapor deposition temperature is preferably 700-800°C, for example, 700°C, 750°C, or 800°C, and the pressure is preferably 0.05-1.6 MPa, for example, 0.3-1.5 MPa, 0.3-0.5 MPa, 0.3 MPa, 0.5 MPa, or 1.5 MPa. Further preferably, the particle size volume distribution of silicon oxide is controlled to be D10 ≥ 6.0 μm, D50 is 10.0 ± 1 μm, and Dmax ≤ 15.0 μm.

[0048] According to the present invention, magnesium vapor is introduced from the bottom of the reactor upward, with the flow rate controlled to be 0.10 to 0.35 m / s to suspend silicon dioxide. During the vapor deposition process, the sediment is collected by its own gravity. For example, the magnesium vapor flow rate is 0.15 to 0.3 m / s, 0.15 to 0.2 m / s, 0.2 to 0.3 m / s, 0.15 m / s, 0.2 m / s, or 0.3 m / s. Magnesium vapor, flowing from a gas distributor at the bottom of the fluidized bed, enters the fluidized bed and passes through the solid particles therein from bottom to top. The drag force exerted by the gas on the particle surface is adjusted by controlling the gas velocity. When the gas velocity reaches the critical fluidization velocity of the solid particles, the drag force exerted by the magnesium vapor on the particle surface balances the particle's own gravity, and the solid particles achieve a fluidized state. As the reaction proceeds, the weight of the pre-magnesium-treated silicon dioxide particles increases continuously. When the drag force cannot balance the gravity, the material enters a sediment collection device. Therefore, the present invention controls the pre-magnesium degree of the material by controlling the flow rate of magnesium vapor.

[0049] The present invention also provides a silicon monoxide composite negative electrode material prepared by the above method. The results show that the main component of the silicon monoxide composite negative electrode material prepared by the present invention is a mixture of silicon and magnesium silicates. The silicon grain size in the negative electrode material is smaller and the volume expansion is lower.

[0050] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0051] In the description of the present invention, it should be noted that the terms "upper" and "lower" and other terms indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the systems or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the use of terms such as "first" and "second" to define components is solely for the purpose of distinguishing those components. Unless otherwise stated, these terms have no special meanings and should not be construed as indicating or implying relative importance.

[0052] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "assembly," "disposition," and "connection" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0053] like Figure 1 As shown, the device for pre-magnesiumizing the negative electrode material of silicon dioxide lithium-ion battery of the present invention includes a fluidized bed reactor 100, which includes a cylinder 101, an upper baffle 102 is provided on the top of the cylinder, and holes with a diameter of ≤10.0 μm are uniformly distributed on the surface of the upper baffle 102, and a removable baffle 103 is provided inside the cylinder 101, which divides the internal space of the cylinder into two parts, the upper and lower parts, and the surface of the removable baffle 103 is provided with holes with a diameter of ≤6.0 μm; a temperature control device 104 is provided on the outer wall of the cylinder 101, such as a steam temperature control device, including but not limited to a steam jacket or a steam pipe, etc.; a magnesium vapor air inlet pipe 105 is provided at the bottom of the cylinder 101, and an air inlet valve 106 is provided on the air inlet pipe 105, and the air inlet pipe 105 leads to a gas distributor 107 arranged at the bottom of the cylinder, and the gas distributor 107 has a built-in uniformly distributed diameter. An air inlet hole of ≤2.0μm is only used to introduce magnesium vapor. The gas distributor 107 is arranged around the side wall of the cylinder 101 and the top gradually tilts downward from the outside to the inside (forming a cone). Along the vertical direction of the outer wall of the cylinder, the top of the gas distributor tilts downward at an angle of 20 to 45 degrees, forming a funnel-shaped cavity in the center of the cylinder. The bottom end of the funnel-shaped cavity is sealed to form a sediment collection device 110 located below the removable baffle 103; above the removable baffle 103, a solid silicon oxide inlet 108 is provided on the side wall of the cylinder 101, and the feed pipeline at the inlet 108 is tilted upward by 15 to 20 degrees. A closable baffle 109 is provided at the solid silicon oxide inlet 108; a magnesium vapor outlet, i.e., an air outlet 111, is provided on the top of the upper baffle 102, which is connected to the cyclone separator 113 and the condensing device in sequence through the air outlet pipeline 112, and an air outlet valve 114 is provided on the air outlet pipeline 112.

[0054] During use, solid silicon oxide material (the particle size volume distribution of silicon oxide is controlled to be D10 ≥ 6.0 μm, D50 is 10.0 ± 1 μm, and Dmax ≤ 15.0 μm) enters the cylinder 101 from the solid silicon oxide inlet 108 and accumulates on the removable baffle 103; magnesium vapor enters the gas distributor 107 along the air inlet pipe 105 and then enters the cylinder 101, and the air flow is transported upward in the cylinder 101 to fluidize the gas and form a fluidized bed in the cylinder; by controlling the air flow rate of the bed (controlling the air inlet valve 106), the material is suspended in the middle reaction zone of the fluidized bed. When the gas flow rate is low, the silicon oxide particles remain stationary and the bed is in a fixed bed state. When the gas velocity reaches the critical fluidization velocity of the solid particles (the gas flow rate is 0.10 to 0.35 m / s), the silicon oxide particles reach a fluidized state, and the baffle is then removed. Within cylinder 101, the temperature is controlled at 700-800°C and the pressure is controlled at 0.05-1.6 MPa by temperature control device 104. The material flow and the air flow fully contact each other to form a vapor deposition sediment. As the sediment is transported through the fluidized bed, it falls into material collection device 110 as its mass increases. After deposition is completed, the sediment is removed from material collection device 110 to obtain a silicon dioxide composite negative electrode material. Excess magnesium vapor, carrying fine particles, enters the cyclone separator through top outlet 111 through outlet pipe 112. The aperture of the upper baffle is set to prevent large particles from entering the magnesium vapor condensation recovery device. The magnesium vapor is condensed and recovered (condensation temperature ≥ 180°C), and the outlet flow rate is adjusted by outlet valve 114.

[0055] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0056] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0057] The particle size volume distribution of silicon oxide used in the following comparative examples and examples is shown in Table 1 below:

[0058] Table 1. Particle size volume distribution of silicon oxide

[0059] Dmin D10 D50 D90 D100 Particle size (μm) 4.05 6.64 10.88 12.29 15.35

[0060] Comparative Example 1

[0061] The traditional method for pre-forming silicon oxide into magnesium involves high-temperature solid-phase sintering. Silicon oxide and magnesium powder are uniformly mixed and then sintered at 800-900°C. Product characterization test results are shown in Table 2.

[0062] Table 2. Comparative Example Characterization Test Results

[0063]

[0064] XRD test results, see Figure 2 .like Figure 2 As shown, the product of a traditional solid-phase pre-magnesium reaction is a mixture of silicon and magnesium silicates. Calculation of the silicon peak reveals the silicon grain size within the material. During charge and discharge, silicon-carbon anode materials alloy to form a silicon-lithium alloy. This volume expansion during charge and discharge affects the battery's cycling performance. Therefore, the size of the silicon grains can be used to infer the battery's cycling performance. Smaller silicon grains reduce volume expansion during charge and discharge, resulting in better cycling performance.

[0065] Therefore, traditional solid-phase pre-magnesium methods typically require the use of molten salts. However, the use of molten salts requires a washing process, using strong acids to remove salt impurities from the material. Companies must pay attention to safety regulations and management, while also increasing process and equipment costs.

[0066] Example 1

[0067] In order to verify the effect of the present invention, the Figure 1 The apparatus shown here is used to pre-magnesiumize silicon dioxide (SiO) negative electrode materials for lithium-ion batteries. During the pre-magnesiumization process, the reaction temperature was controlled at 700°C, the pressure was 0.3 MPa, and the magnesium vapor flow rate was 0.15 m / s. Excess magnesium vapor was condensed and recovered at 180°C for future use.

[0068] Example 2

[0069] The experimental process was the same as that of Example 1, except that the conditions were adjusted to the following: the reaction temperature was 800° C., the pressure was adjusted to 1.5 MPa, and the flow rate of the magnesium vapor was 0.3 m / s.

[0070] Example 3

[0071] The experimental process was the same as that of Example 1, except that the conditions were adjusted to the following: the reaction temperature was 750° C., the pressure was adjusted to 0.5 MPa, and the flow rate of the magnesium vapor was 0.2 m / s.

[0072] The experiment was carried out under the conditions in the above embodiment, and the sediments obtained were tested respectively. The specific results are shown in Table 3.

[0073] Table 3. Characterization test results of the examples

[0074]

[0075] The XRD test results of Examples 1-3 are shown in Figure 3 .like Figure 3As shown, the sediment is primarily composed of a mixture of silicon and magnesium silicates. The silicon grain size was calculated using the Scherrer formula, with the calculated results shown in Table 1. The silicon grains in the sediment are relatively small, indicating low volume expansion.

[0076] The EDS test results of Example 1 are shown in Figure 4 .like Figure 4 As shown in Figure 2, the sediment is mainly composed of carbon, oxygen, magnesium and silicon. The content of each element is as follows: Figure 5 shown.

[0077] Performance Testing

[0078] The silicon oxide pre-magnesium anode materials from Examples 1-3 and the comparative example were thoroughly mixed at a mass ratio of 8:1:1. Deionized water was used as the solvent to prepare a slurry. After uniform dispersion, the slurry was coated with 8μm copper foil, vacuum-dried at 50°C for 12 hours, and then cut into 14mm diameter discs to produce the anode materials. After drying, the slices were packaged with lithium foil to form a button battery. The first cycle of charge and discharge testing was conducted at 0.05C.

[0079] The charge and discharge capacity and initial efficiency are shown in Table 4. The charge and discharge curves of Example 1 to Example 3 are shown in Table 4. Figure 6 shown.

[0080] Table 4. Electrochemical performance test results

[0081]

[0082] In Table 4, the charge capacity at 0.8V of Example 1 is approximately 40 mAh / g higher than that of the comparative example, and the charge capacity at 0.8V of Example 3 is approximately 30 mAh / g higher than that of the comparative example, with first-time efficiencies exceeding 76%. While the charge capacity of pure silicon dioxide anode material at 0.8V is comparable to that of the comparative example, the first-time coulombic efficiency is only 60%.

[0083] Expansion test

[0084] The negative electrode plates of Examples 1-3 and the comparative example were measured using a micrometer at the center, middle, and outer rings. After the first week of charge-discharge testing, the battery packs were disassembled and in-situ measurements were performed. The electrode plate thicknesses before and after the first week of charge-discharge testing are detailed in Table 5.

[0085] Table 5. Expansion test results

[0086]

[0087] As shown in Table 5, the expansion rates of the negative electrode sheets prepared in Examples 1-3 after the first cycle of charge and discharge are significantly improved compared with the control examples.

[0088] From Table 4, Table 5 and Figure 6 It can be seen that the pre-magnesium-treated silicon 2 oxide materials prepared in Examples 1-3 have the advantages of low expansion, high initial efficiency and high capacity.

[0089] Therefore, in summary, the purpose of the present invention is to provide a method and device for pre-magnesiumization of negative electrode materials for lithium-ion batteries using silicon dioxide. The negative electrode material obtained by pre-magnesiumization has the advantages of low expansion and high initial efficiency. Compared with the traditional solid-phase pre-magnesiumization method, the solid particles in the fluidized state show a violent turbulent state, and the contact area between the gas and solid phases is large and continuously updated. At the same time, the heat transfer and mass transfer between the two phases are enhanced, and the pre-magnesiumization process is more sufficient and safe. The gas-phase pre-magnesiumization technology improves the reaction efficiency and can achieve semi-continuous production.

[0090] The present invention has been described in detail above. It will be apparent to those skilled in the art that the present invention may be practiced over a wide range of parameters, concentrations, and conditions without departing from the spirit and scope of the present invention and without unnecessary experimentation. Although specific embodiments have been given herein, it should be understood that further modifications may be made to the present invention. In summary, this application is intended to encompass any variations, uses, or improvements to the present invention, including those made by conventional techniques known in the art that depart from the scope of the present invention. Applications of the essential features may be made within the scope of the following claims.

Claims

1. A method for pre-magnesiumizing a negative electrode material of silicon dioxide lithium-ion battery, comprising the following steps: The pre-magnesium process is achieved by introducing solid silicon oxide and magnesium vapor into a reactor in sequence, allowing the solid silicon oxide and magnesium vapor to be vapor-deposited in a suspended state in the reactor, and collecting the deposits; The pre-magnesium device includes a fluidized bed reactor, which includes a cylinder with a removable baffle inside the cylinder to divide the internal space of the cylinder into upper and lower parts; The surface of the extractable baffle is provided with evenly distributed holes with a diameter of ≤6.0 μm; The bottom of the cylinder is provided with a magnesium vapor inlet, and the top is provided with a magnesium vapor outlet; A solid silicon oxide inlet is provided on the side wall of the cylinder above the extractable baffle; Below the extractable baffle, a sediment collecting device is provided inside the cylinder; A temperature control device is provided on the outer wall of the cylinder; The temperature of the vapor deposition is 700-800°C and the pressure is 0.05-1.6MPa; introducing magnesium vapor from the bottom of the reactor upwards, controlling the flow rate of the magnesium vapor to be 0.10-0.35 m / s, so that the silicon oxide is in a suspended state; During the vapor deposition process, the sediment is collected by utilizing its own gravity.

2. The method for pre-magnesiumization of silicon dioxide lithium-ion battery negative electrode material according to claim 1, characterized in that: The particle size volume distribution of the silicon oxide is controlled to be D10≥6.0 μm, D50 is 10.0±1 μm, and Dmax≤15.0 μm.

3. The method for pre-magnesiumization of silicon monoxide lithium-ion battery negative electrode material according to claim 1 or 2, characterized in that: The method further comprises the following steps: separating excess magnesium vapor from the reaction system after the vapor deposition and condensing and recovering the excess magnesium vapor, wherein the condensation temperature is ≥180°C.

4. The method for pre-magnesiumization of silicon monoxide lithium-ion battery negative electrode material according to claim 1, characterized in that: The surface of the extractable baffle is provided with evenly distributed holes with a diameter of ≤6.0 μm; An upper baffle is provided on the top of the cylinder; The surface of the upper baffle is evenly distributed with holes having a diameter of ≤10.0 μm; A magnesium vapor outlet is provided on the top of the upper baffle, and the magnesium vapor outlet is connected to the cyclone separation device and the condensation device in sequence.

5. The method for pre-magnesiumization of silicon monoxide lithium-ion battery negative electrode material according to claim 1 or 4, characterized in that: The gas inlet pipeline of the magnesium vapor inlet leads to the gas distributor arranged at the bottom end of the cylinder; The gas distributor is built with uniformly distributed gas inlet holes with a diameter of ≤2.0 μm; The gas distributor is arranged around the side wall of the cylinder and the top thereof is gradually inclined downward from the outside to the inside, forming a funnel-shaped cavity in the center of the cylinder; The bottom end of the funnel-shaped cavity is sealed to form the sediment collecting device; Along the vertical direction of the outer wall of the cylinder, the top of the gas distributor is tilted downward at an angle of 20 to 45 degrees.

6. The method for pre-magnesiumization of silicon monoxide lithium-ion battery negative electrode material according to claim 1 or 4, characterized in that: Along the vertical direction of the outer wall of the cylinder, the feed pipeline of the solid silicon oxide inlet is inclined upward from the inside to the outside at 15 to 20 degrees; A closable baffle is provided at the inlet of the solid silicon oxide.

7. A silicon oxide composite negative electrode material, characterized in that: The method is prepared by the method according to any one of claims 1 to 3.

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