Rotary furnace, method for preparing silicon-based negative electrode material by using rotary furnace, obtained material and application

Abstract

The embodiment of the invention relates to a rotary furnace which comprises a furnace shell, a cavity, a first air inlet pipe, two second air inlet pipes, a plurality of protruding air pipes, a motor and a hydraulic device. Wherein the cavity is arranged in the furnace shell; the gas inlet end of the first gas inlet pipe is arranged outside the furnace shell, and two gas outlet ends are arranged in the furnace shell; the two second air inlet pipes are arranged on the two sides of the cavity and communicate with the two air outlet ends of the first air inlet pipe correspondingly. The multiple protruding air pipes are arranged on the side wall of the cavity at intervals, the air inlet ends communicate with the second air inlet pipe, and the air outlet ends communicate with the cavity. When the rotary furnace works, an air source is introduced into the first air inlet pipe and conveyed into the multiple protruding air pipes through the second air inlet pipe, and therefore the air source is conveyed into the cavity; the motor is used for controlling the cavity to rotate through the rotating shaft and the balls; the hydraulic device is arranged at the feeding port of the cavity and used for lifting the feeding port, and therefore discharging is conducted.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery materials, and in particular to a rotary kiln and a method for preparing a silicon-based negative electrode material using the rotary kiln, the obtained material and application thereof. Background Art

[0002] Energy is the driving force for the development of the entire world and the foundation for human survival. With the serious conflict between the growing demand for energy and the limited global supply of fossil fuels, it is imperative to develop sustainable energy to help achieve the dual carbon goals.

[0003] Silicon is a typical negative electrode material for lithium-ion batteries, with its high theoretical capacity, suitable operating voltage and high natural abundance. However, due to the large volume expansion rate caused by the insertion and extraction of lithium ions, the negative electrode conductivity will deteriorate, affecting the cycle performance of lithium-ion batteries. Introducing carbon sources to modify silicon-based negative electrodes is an effective method that has been proven to improve the conductivity and stability of materials.

[0004] The air intake device of the traditional rotary kiln mostly adopts a straight tube with an opening extending into the furnace cavity. The coated carbon source gas is concentratedly ejected from the aperture of the straight tube, which will cause the gas carbon source to gather, resulting in uneven coating of the material surface and the gas cannot be fully utilized. Summary of the invention

[0005] The purpose of the present invention is to provide a rotary kiln and a method for preparing silicon-based negative electrode materials using the rotary kiln, the obtained materials and applications thereof, in view of the defects of the prior art. Compared with the prior art, the improved rotary kiln coating is used to change the gas source from a single inlet to a porous and dispersed inlet, which can not only make the coating gas source and the negative electrode material more fully mixed and contacted in the furnace cavity, but also make the surface coating distribution of the negative electrode material more uniform, the carbon content distribution of the material more uniform and concentrated, the coating effect is better, and the number of cycles is increased; in addition, the amount of coating gas source can be effectively reduced and the utilization rate of the gas source can be increased. Therefore, the present invention can not only reduce costs, but also obtain high-performance negative electrode materials with more uniform distribution and better cycle performance.

[0006] In view of this, in a first aspect, an embodiment of the present invention provides a rotary kiln, comprising: a furnace shell, a cavity, a first air inlet pipe, two second air inlet pipes, a plurality of protruding air pipes, a motor and a hydraulic device; wherein,

[0007] The cavity is arranged inside the furnace shell; the first air inlet pipe has an air inlet end arranged outside the furnace shell and two air outlet ends arranged inside the furnace shell;

[0008] Two second air inlet pipes are arranged on both sides of the cavity and are respectively connected to two air outlet ends of the first air inlet pipe;

[0009] A plurality of protruding air pipes are arranged at intervals on the side wall of the cavity, the air inlet end is connected to the second air inlet pipe, and the air outlet end is connected to the cavity; when the rotary kiln is working, the gas source is passed into the first air inlet pipe, and is transported to the plurality of protruding air pipes through the second air inlet pipe, thereby sending the gas source into the cavity;

[0010] The motor is used to control the rotation of the cavity through the ball and the shaft;

[0011] The hydraulic device is arranged at the feed port of the cavity and is used to raise the feed port so as to discharge the material.

[0012] Preferably, there are multiple air inlets on the cavity, the distance between the multiple protruding air tubes is 20-100 cm, the length of the protruding air tube protruding from the cavity is 2-5 cm, the diameter of the protruding air tube is 1-3 cm, and the air outlet end of the protruding air tube is provided with multiple openings, the number of openings is 2-12 holes, and the diameter of a single hole is 0.2-3 mm.

[0013] Preferably, the first air inlet pipe, the two second air inlet pipes, and the plurality of protruding air pipes are all made of heat-resistant stainless steel.

[0014] Preferably, the rotary kiln further comprises a conversion device, which is arranged at the connection between the first air inlet pipe and the second air inlet pipe.

[0015] In a second aspect, an embodiment of the present invention provides a method for preparing a silicon-based negative electrode material using the rotary kiln of the first aspect, characterized in that the method comprises:

[0016] The silicon-based raw material is placed in the furnace cavity through the feed port of the rotary furnace, the feed port is closed, and an inert gas is introduced;

[0017] When the oxygen content in the cavity is reduced to a preset oxygen content, the motor is turned on to control the cavity to rotate and heat it. When the temperature is heated to a preset temperature, an air source is introduced and kept warm. The air source is transported to a plurality of protruding air pipes through a first air inlet pipe and a second air inlet pipe, and then enters the cavity from a plurality of openings of the protruding air pipes, fully contacts with the silicon-based raw material in the cavity, and is coated;

[0018] After the preset insulation time, stop introducing the gas source, and stop introducing the inert gas after the temperature drops to room temperature; open the hydraulic device to raise the feed port of the rotary kiln, and open the discharge port to discharge the material;

[0019] After the material is discharged, it is crushed, demagnetized and sieved to obtain a silicon-based negative electrode material with a uniform carbon coating layer.

[0020] Preferably, the silicon-based raw material includes silicon monoxide, pre-magnesium silicon oxide, pre-lithium silicon oxide, silicon carbon or doped modified silicon-based raw material; the gas source includes one or more of methane, ethylene, acetylene, ethane, propyne and propane, the preset oxygen content is 3000ppm, the gas source flow rate is 2-20L / min, the preset temperature is 700-1000℃, and the insulation time is 1-10h.

[0021] Preferably, the particle size Dv50 of the silicon-based negative electrode material is 0.5nm-10μm, and the tap density is 0.8-1.3g / cm 3 .

[0022] In a third aspect, an embodiment of the present invention provides a silicon-based negative electrode material, wherein the silicon-based negative electrode material includes the silicon-based negative electrode material prepared by the preparation method described in the second aspect above.

[0023] In a fourth aspect, an embodiment of the present invention provides a negative electrode plate, wherein the negative electrode plate comprises the silicon-based negative electrode material described in the third aspect above.

[0024] In a fifth aspect, an embodiment of the present invention provides a lithium battery, wherein the lithium battery comprises the negative electrode plate described in the fourth aspect.

[0025] The embodiment of the present invention provides a rotary kiln and a method for preparing silicon-based negative electrode materials using the same, the obtained materials and applications. The rotary kiln is used for coating, and the gas source is changed from a single inlet to a porous and dispersed inlet, which can not only make the coating gas source and the negative electrode material more fully mixed and contacted in the furnace cavity, so that the surface coating distribution of the negative electrode material is more uniform, the carbon content distribution of the material is more uniform and concentrated, the coating effect is better, and the number of cycles is increased; in addition, the amount of coating gas source can be effectively reduced and the utilization rate of the gas source can be increased. Therefore, the present invention can not only reduce costs, but also obtain high-performance negative electrode materials with more uniform distribution and better cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a rotary kiln provided in an embodiment of the present invention;

[0027] Figure 2 A flow chart of a method for preparing silicon-based negative electrode materials using a rotary kiln provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0029] Figure 1 A schematic diagram of the structure of a rotary kiln provided in an embodiment of the present invention is shown in FIG. Figure 1As shown, the rotary kiln specifically includes a furnace shell 1, a cavity 2, a first air inlet pipe 3, two second air inlet pipes 4, a plurality of protruding air pipes 5, a motor 6 and a hydraulic device 7. Figure 1 The structures of various parts of the rotary kiln provided in this embodiment are introduced.

[0030] The furnace shell 1 is the shell of the rotary furnace.

[0031] The cavity 2 is arranged inside the furnace shell 1 and serves as a reaction zone for materials. A feed port and a discharge port are respectively provided at both ends. Furthermore, there are multiple air inlets on the cavity 2 for accommodating the protruding air pipe 5.

[0032] The first air inlet pipe 3 is used for inputting an air source. The air inlet end of the first air inlet pipe 3 is arranged outside the furnace shell 1 , and the two air outlet ends are arranged inside the furnace shell 1 .

[0033] The second air inlet pipe 4 is used to transmit the air source. There are two second air inlet pipes 4 , which are respectively arranged on both sides of the cavity 2 and are respectively connected to the two air outlet ends of the first air inlet pipe 3 .

[0034] The protruding air pipe 5 is used to transmit the gas source to the cavity 2. There are multiple protruding air pipes 5, which are evenly spaced on the side walls of the cavity 2. The air inlet end of the protruding air pipe 5 is connected to the second air inlet pipe 4, and the air outlet end is connected to the cavity 2. Preferably, the multiple protruding air pipes 5 are spaced apart by 20-100cm, the length of the protruding air pipe 5 protruding from the cavity 2 is 2-5cm, and the diameter of the protruding air pipe 5 is 1-3cm. Further preferably, the air outlet end of the protruding air pipe 5 is provided with multiple openings, the number of openings is 2-12 holes, and the diameter of a single hole is 0.2-3mm. Therefore, when the rotary kiln is working, the gas source is passed into the first air inlet pipe 3, and the gas source is transported to the multiple protruding air pipes 5 through the second air inlet pipe 4, and then enters the cavity 2 from the multiple openings of the protruding air pipe 5, so that the gas source is in full and uniform contact with the material in the cavity 2, and the material is evenly wrapped. Preferably, the first air inlet pipe 3, the two second air inlet pipes 4, and the plurality of protruding air pipes 5 are all made of heat-resistant stainless steel.

[0035] The motor 6 is used to control the rotation of the cavity through the rotating shaft 61 and the ball 62. Specifically, the rotation of the motor 6 drives the rotating shaft 61 to rotate, and then drives the ball 62 to rotate, thereby driving the cavity 2 and the furnace tube and the air inlet pipe inside the cavity 2 to rotate, so that the gas source and the material in the cavity 2 are fully and evenly contacted and coated under high temperature conditions.

[0036] The hydraulic device 7 is arranged at the feed port of the cavity 2. When the hydraulic device 7 is in the open state, the feed port is controlled to rise. At this time, the cavity 2 is tilted, and the discharge port is located lower than the feed port, thereby discharging the material.

[0037] Preferably, the rotary kiln also includes a conversion device 8, which is arranged at the connection between the first air inlet pipe 3 and the second air inlet pipe 4, and plays a connecting role. When the internal second air inlet pipe 4 rotates, it does not affect the air intake of the external first air inlet pipe 3. Specifically, the conversion device 8 is a rotatable air pipe joint, which can be a compression sleeve pipe joint.

[0038] Based on the understanding of the structure of the rotary kiln provided in this embodiment, the method for preparing silicon-based negative electrode materials using the rotary kiln is introduced below, specifically, the method for preparing high-performance negative electrode materials for secondary lithium-ion batteries using the new rotary kiln. Figure 2 A flow chart of a method for preparing silicon-based negative electrode materials using a rotary kiln according to an embodiment of the present invention, combined with Figure 2 As shown, the method for preparing the silicon-based negative electrode material specifically includes the following steps.

[0039] Step 101, placing silicon-based raw materials into a furnace chamber from a feed port of a rotary furnace, closing the feed port, and introducing an inert gas.

[0040] The silicon-based raw materials include but are not limited to silicon monoxide, pre-magnesium silicon oxide, pre-lithium silicon oxide, silicon carbon or doped and modified silicon-based raw materials.

[0041] Step 102, when the oxygen content in the cavity is reduced to a preset oxygen content, the motor is turned on to control the cavity to rotate and heat it. When the cavity temperature is heated to a preset temperature, an air source is introduced and kept warm. The air source is transported to a plurality of protruding air pipes through a first air inlet pipe and a second air inlet pipe, and then enters the cavity from a plurality of openings of the protruding air pipes, fully contacts with the silicon-based raw material in the cavity, and is coated.

[0042] Specifically, the preset oxygen content here is preferably 3000ppm, the preset temperature is 700-1000°C, the gas source includes but is not limited to one or more of methane, ethylene, acetylene, ethane, propyne, propane, and can also be a material with a vapor deposition effect, etc. The gas source flow rate is preferably 2-20L / min; further, the insulation time is preferably 1-10h.

[0043] Step 103, after the preset insulation time, stop introducing the gas source, and after the temperature drops to room temperature, stop introducing the inert gas; open the hydraulic device, raise the feed port of the rotary kiln, and open the discharge port for discharge.

[0044] The insulation time here is preferably 1-10h.

[0045] Step 104, after the material is discharged, it is crushed, demagnetized, and sieved to obtain a silicon-based negative electrode material with a uniform carbon coating layer.

[0046] The particle size Dv50 of the silicon-based negative electrode material finally obtained is 0.5nm-10μm, and the tap density is 0.8-1.3g / cm3 , which is beneficial to the processing technology of lithium batteries.

[0047] In a specific example, the carbon source material in the negative electrode material prepared by the above method accounts for 4%-6% of the mass of silicon oxide.

[0048] The embodiment of the present invention further provides a silicon-based negative electrode material, which is prepared by the above-mentioned preparation method.

[0049] Furthermore, an embodiment of the present invention also provides a negative electrode plate, using the silicon-based negative electrode material in the above embodiment.

[0050] Furthermore, an embodiment of the present invention also provides a lithium battery, including the negative electrode plate in the above embodiment.

[0051] In order to better understand the technical solution provided by the present invention, the following specific examples are used to illustrate the specific process of preparing high-performance negative electrode materials for secondary lithium-ion batteries using the method provided by the above embodiment of the present invention, as well as the method and battery characteristics of applying it to lithium-ion batteries.

[0052] Example 1

[0053] This embodiment provides a method for preparing a high-performance negative electrode material for a secondary lithium-ion battery using a novel rotary kiln, comprising:

[0054] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0055] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 3L / min, and keep warm for 10H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0056] Step 3, finally, the material is crushed, demagnetized and sieved to obtain a silicon oxide material containing a uniform carbon coating layer;

[0057] The negative electrode plate was prepared using the silicon oxide material containing a uniform carbon coating layer prepared in this embodiment, and a button half-cell was assembled for testing. Under the 1C state, the number of cycles when the first efficiency was not less than 80%, the expansion rate of the plate after the first cycle, the carbon content, and the coating gas consumption were tested. The specific test preparation method and test method are as follows.

[0058] Preparation and testing of button half-cell: The silicon-oxygen composite material containing a carbon coating layer, the conductive additive carbon black, and the adhesive (sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:1) are weighed in a mass ratio of 95%:2%:3%, and the slurry is prepared with a beater, and then coated, dried, cut, and assembled into a button half-cell in a glove box. The test process includes: using a charge and discharge instrument to test the prepared button half-cell in a constant current charge and discharge mode, with a discharge cut-off voltage of 0.005V and a charge cut-off voltage of 2V, and recording the number of cycles under 1C state when the first efficiency is not less than 80%. The test data is shown in Table 1.

[0059] Pole piece expansion rate test: At 1C, after the first cycle, 5 groups of batteries were dismantled, and their negative pole pieces were taken. The thickness of 3 different areas of each group of pole pieces was measured with a thickness gauge, and the average value was taken. Under the same test conditions, the average thickness of the pole piece in the initial state was obtained. The calculation formula is: Pole piece full charge expansion rate = (average thickness of the pole piece when fully charged for different cycles - initial average thickness of the pole piece) / initial average thickness of the pole piece; the expansion rate of the tested negative pole piece can be obtained. The test results of the pole piece expansion rate after the first cycle prepared in this embodiment are detailed in Table 1.

[0060] Carbon content test: The carbon content data measured by high-frequency infrared carbon-sulfur analyzer is shown in Table 1.

[0061] Example 2

[0062] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0063] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 4L / min, and keep warm for 7H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0064] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0065] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0066] Example 3

[0067] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0068] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 3L / min, and keep warm for 9H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0069] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0070] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0071] Example 4

[0072] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0073] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 4L / min, and keep warm for 6.5H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0074] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0075] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0076] Example 5

[0077] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0078] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 5L / min, and keep warm for 5H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0079] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0080] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0081] Example 6

[0082] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0083] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 4L / min, and keep warm for 6H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0084] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0085] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0086] Example 7

[0087] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0088] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 6L / min, and keep warm for 4H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0089] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0090] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0091] Example 8

[0092] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0093] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 9L / min, and keep warm for 3H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0094] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0095] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0096] Example 9

[0097] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0098] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 7L / min, and keep warm for 4H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0099] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0100] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0101] Example 10

[0102] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0103] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900°C, introduce acetylene at a gas flow rate of 10L / min, and keep warm for 3H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0104] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0105] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0106] Comparative Example 1

[0107] This comparative example provides a preparation process and performance test of a traditional silicon-based negative electrode material. The specific preparation process is as follows.

[0108] Step 1, placing 5 kg of silicon dioxide raw material into the furnace chamber from the feed inlet, closing the feed inlet, and introducing inert gas nitrogen;

[0109] Step 2, after the oxygen content is less than 3000ppm, start the motor, set the cavity speed to 0.3r / min, arrange to heat up to 900℃, introduce acetylene at a gas flow rate of 3L / min, and keep warm for 10H. After the insulation is completed, stop introducing the coating gas source acetylene, and turn off the inert gas after cooling to room temperature; turn on the hydraulic device, raise the feed end, and open the discharge port;

[0110] Step 3: Finally, the material is crushed, demagnetized and sieved to obtain silicon dioxide material containing a uniform carbon coating layer.

[0111] The silicon oxide material with a uniform carbon coating layer prepared in this embodiment was used to prepare a negative electrode plate and assembled into a battery for testing, and the specific process was the same as that in embodiment 1. The test data is shown in Table 1.

[0112] The negative electrode materials in Examples 1-10 and the comparative example were subjected to a charge-off test, and the number of cycles when the first efficiency was not less than 80% under 1C state, the expansion rate test of the electrode after the first cycle, the carbon content test, and the coating gas consumption were tested. The results are shown in Table 1:

[0113] Table 1

[0114]

[0115] From the comparison of the test data in Table 1, it can be seen that under the same test conditions, the expansion rate of the negative electrode plates of Examples 1-10 is less than that of the negative electrode plates of the comparative example, and the amount of coating gas is significantly reduced. This is because in Examples 1-10, an improved new rotary kiln is used, the gas and the material are in more complete contact, the carbon shell coated on the surface of silicon oxide is uniform, and the volume expansion is buffered during the charge and discharge process. From the test data of Example 1 and Comparative Example 1, with the same amount of coating gas, the carbon content of Comparative Example 1 is lower than that of Example 1. After the first cycle, the expansion rate of the plate of Comparative Example 1 is significantly lower than that of Example 1; the number of cycles with the first effect not less than 80% is higher in Example 1 than in Comparative Example 1. The improved rotary kiln is better than traditional equipment in application.

[0116] The present invention provides a preparation method and application of silicon-based materials coated with a rotary kiln, the purpose of which is to introduce a carbon source during the coating process, reduce the amount of coating gas used, and rationally utilize the carbon source modification to solve the problems of large volume expansion rate of silicon-based materials and poor battery cycle performance. The volume expansion of silicon can be effectively suppressed, and the structural stability of the material can be maintained, thereby achieving a low volume expansion rate and high cycle performance of the battery.

[0117] In the present invention, the term "plurality" refers to two or more than two, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0118] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0119] In the descriptions in this specification, the terms "a specific embodiment", "some embodiments", "an embodiment", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0120] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rotary kiln, characterized in that: The rotary furnace comprises a furnace shell, a cavity, a first air inlet pipe, two second air inlet pipes, a plurality of protruding air pipes, a motor and a hydraulic device; wherein, The cavity is arranged inside the furnace shell; the first air inlet pipe has an air inlet end arranged outside the furnace shell and two air outlet ends arranged inside the furnace shell; Two second air inlet pipes are arranged on both sides of the cavity and are respectively connected to two air outlet ends of the first air inlet pipe; A plurality of protruding air pipes are arranged at intervals on the side wall of the cavity, the air inlet end is connected to the second air inlet pipe, and the air outlet end is connected to the cavity; when the rotary kiln is working, the gas source is passed into the first air inlet pipe, and is transported to the plurality of protruding air pipes through the second air inlet pipe, thereby sending the gas source into the cavity; The motor is used to control the rotation of the cavity through the ball and the shaft; The hydraulic device is arranged at the feed port of the cavity and is used to raise the feed port so as to discharge the material.

2. The rotary kiln according to claim 1, characterized in that: There are multiple air inlets on the cavity, the distance between the multiple protruding air tubes is 20-100cm, the length of the protruding air tube protruding from the cavity is 2-5cm, the diameter of the protruding air tube is 1-3cm, and the air outlet end of the protruding air tube is provided with multiple openings, the number of openings is 2-12 holes, and the diameter of a single hole is 0.2-3mm.

3. The rotary kiln according to claim 1, characterized in that: The first air inlet pipe, the two second air inlet pipes, and the plurality of protruding air pipes are all made of heat-resistant stainless steel.

4. The rotary kiln according to claim 1, characterized in that: The rotary kiln also includes a conversion device, which is arranged at the connection between the first air inlet pipe and the second air inlet pipe.

5. A method for preparing silicon-based negative electrode materials using a rotary kiln according to any one of claims 1 to 4, characterized in that: The method comprises: The silicon-based raw material is placed in the furnace cavity through the feed port of the rotary furnace, the feed port is closed, and an inert gas is introduced; When the oxygen content in the cavity is reduced to a preset oxygen content, the motor is turned on to control the cavity to rotate and heat it. When the temperature is heated to a preset temperature, an air source is introduced and kept warm. The air source is transported to a plurality of protruding air pipes through a first air inlet pipe and a second air inlet pipe, and then enters the cavity from a plurality of openings of the protruding air pipes, fully contacts with the silicon-based raw material in the cavity, and is coated; After the preset insulation time, stop introducing the gas source, and stop introducing the inert gas after the temperature drops to room temperature; open the hydraulic device to raise the feed port of the rotary kiln, and open the discharge port to discharge the material; After the material is discharged, it is crushed, demagnetized and sieved to obtain a silicon-based negative electrode material with a uniform carbon coating layer.

6. The method for preparing silicon-based negative electrode materials by rotary kiln according to claim 5, characterized in that: The silicon-based raw material includes silicon monoxide, pre-magnesium silicon oxide, pre-lithium silicon oxide, silicon carbon or doped modified silicon-based raw material; the gas source includes one or more of methane, ethylene, acetylene, ethane, propyne and propane, the preset oxygen content is 3000ppm, the gas source flow rate is 2-20L / min, the preset temperature is 700-1000℃, and the insulation time is 1-10h.

7. The method for preparing silicon-based negative electrode materials by rotary kiln according to claim 5, characterized in that: The particle size Dv50 of the silicon-based negative electrode material is 0.5nm-10μm, and the tap density is 0.8-1.3g / cm 3 .

8. A silicon-based negative electrode material, characterized in that: The silicon-based negative electrode material includes the silicon-based negative electrode material prepared by the preparation method described in any one of claims 5-7 above.

9. A negative electrode plate, characterized in that: The negative electrode plate comprises the silicon-based negative electrode material as described in claim 8 above.

10. A lithium battery, characterized in that: The lithium battery comprises the negative electrode sheet as described in claim 9 above.

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