System and process method for large-scale preparation of high-first-effect silicon-carbon material

Abstract

The invention discloses a system capable of preparing a high-first-effect silicon-carbon material on a large scale and a technological method.The system capable of preparing the high-first-effect silicon-carbon material on the large scale comprises a raw material bin, and a discharging port of the raw material bin is connected with feeding ports of a plurality of silicon deposition reactors through material conveying pipelines; discharge ports of the plurality of silicon deposition reactors are connected with a feed port of the mixing bin, a discharge port of the mixing bin is connected with a feed port of the carbon-coated reactor, the side part of the carbon-coated reactor is connected with a lithium source supply device, the carbon-coated reactor is provided with two discharge ports, and the two discharge ports discharge materials to a finished product bin and a standby bin respectively; the system further comprises a silane gas fan, a nitrogen fan, an acetylene gas fan and a PLC control system. According to the system and the process method capable of preparing the high-first-effect silicon-carbon material on a large scale, the technical problems that the existing silicon-carbon material is low in production efficiency, high in cost and low in first effect are solved.

Description

Technical Field

[0001] The present invention relates to a system and a process method for large-scale preparation of high-first-efficiency silicon-carbon materials, belonging to the technical field of preparation of anode materials for lithium-ion batteries. Background Art

[0002] With the accelerating development of frontier fields such as new energy vehicles, humanoid robots, and low-altitude aircraft, lithium-ion batteries are facing higher performance thresholds of energy density leap, safety and reliability enhancement, and long cycle life guarantee. Currently, the commercially available graphite anode is limited by the theoretical capacity ceiling of 372 mAh / g and is difficult to meet the iterative requirements. However, the silicon-based anode material with a theoretical capacity as high as 4200 mAh / g has always been difficult to break through the industrial application bottleneck because of the 300% severe volume deformation during the lithiation / delithiation process, resulting in the pulverization and failure of the electrode structure.

[0003] The industry has recently made key progress through process innovation: based on chemical vapor deposition (CVD) technology, the controllable deposition of nano-silicon particles is realized inside the porous carbon network, and a dense carbon coating structure is synchronously constructed on the outer layer. This composite system design of "three-dimensional carbon skeleton + gradient buffer protection layer" has increased the measured specific capacity of the silicon-carbon composite anode to 1800 mAh / g, and the cycle stability has exceeded 1500 cycles, significantly narrowing the gap between laboratory performance and engineering application.

[0004] However, at present, the production capacity of silicon-carbon is mainly realized by using decentralized single-batch production capacity of 20 kg or 50 kg of silicon deposition fluidized bed equipment combined with carbon coating rotary kiln equipment. The initial equipment investment and fixed plant investment costs are high, the degree of intelligence is low, the production efficiency is low, the batch stability is poor, which is not conducive to the application and promotion of silicon-carbon materials. In addition, most of the silicon-carbon materials have a low first efficiency, only at the level of 80-85%, while the first efficiency of lithium iron phosphate materials can reach more than 95%, and the first efficiency of graphite materials can reach more than 92%. When silicon-carbon materials / graphite are used in combination with lithium iron phosphate, the first efficiency drops to 87% or even lower, which will seriously affect the value of lithium iron phosphate materials.

[0005] Therefore, there is an urgent need to provide a system and a process method for large-scale preparation of high-first-efficiency silicon-carbon materials to solve the above problems. Summary of the Invention

[0006] Aiming at the deficiencies in the background art, the present invention provides a system and a process method for large-scale preparation of high-first-efficiency silicon-carbon materials to solve the technical problems of low production efficiency, high cost, and low first efficiency of current silicon-carbon materials.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions: A system for scalable preparation of high first-efficiency silicon-carbon materials, comprising a raw material bin, the discharge port of the raw material bin is connected to the feed ports of several silicon deposition reactors through a material conveying pipeline, the discharge ports of the several silicon deposition reactors are connected to the feed port of a mixing bin, the discharge port of the mixing bin is connected to the feed port of a carbon coating reactor, a lithium source supply device is connected to the side of the carbon coating reactor, and the carbon coating reactor is provided with two discharge ports, respectively discharging to a finished product bin and a spare bin; it also includes a silane gas blower, a nitrogen gas blower, an acetylene gas blower and a PLC control system.

[0008] Further, the silane gas blower is connected to the bottoms of several silicon deposition reactors through pipelines respectively, the nitrogen gas blower is connected to the bottoms of the several silicon deposition reactors, the mixing bin and the carbon coating reactor through pipelines, and the acetylene gas blower is connected to the bottom of the carbon coating reactor through a pipeline.

[0009] Further, the tail gases of the several silicon deposition reactors and the carbon coating reactor are connected to a tail gas treatment system through a tail gas conveying pipeline.

[0010] Further, the number of the silicon deposition reactors is two to twelve; the number of the mixing bins is one or two; the number of the carbon coating reactors is one to three.

[0011] Further, the lithium source supply device is one of a thermal evaporation device, a spraying device or a magnetron sputtering device.

[0012] A process method for scalable preparation of high first-efficiency silicon-carbon materials, applying the above system for scalable preparation of high first-efficiency silicon-carbon materials, comprising the following steps: S1. The porous carbon powder in the raw material bin enters several silicon deposition reactors through the material conveying pipeline respectively. First, it is heated, purged with nitrogen for fluidization, and after maintaining a certain temperature for a certain time, a nitrogen and silane mixture is introduced. After the silane is cracked for a certain time, the intermediate material is conveyed to the mixing bin. S2. The mixing bin is preheated to a certain temperature in advance, and the materials conveyed from several silicon deposition reactors are batch-mixed by physical methods. After maintaining a certain temperature for a certain time, the materials are conveyed to the carbon coating reactor. S3. The carbon coating reactor has been heated to the set temperature, the powder is fluidized by purging with nitrogen, the lithium source supply device conveys the lithium-containing material to the carbon coating reactor. After maintaining a certain temperature for a certain time, a nitrogen and acetylene mixture is introduced. After the acetylene is cracked for a certain time, the products analyzed to be qualified enter the finished product bin, and the products analyzed to be unqualified enter the spare bin.

[0013] Further, the shape of the reaction cavity of the silicon deposition reactor is cylindrical, and the ratio of the cavity height H to the inner diameter D of the cavity is 8:1 to 12:1.

[0014] Further, the inner diameter D of the reaction cavity of the silicon deposition reactor is 300 - 800 mm; the temperature inside the silicon deposition reactor is 450 - 500 °C, and the total silicon deposition reaction time is 2 - 10 h.

[0015] Further, the temperature inside the carbon coating reactor is 550 - 650 °C, and the total carbon coating time is 2 - 8 h.

[0016] Further, the lithium source raw material of the lithium source supply device is one or more of lithium block, lithium foil, lithium powder, lithium hydroxide, lithium carbonate, lithium oxalate, lithium squarate, lithium hydride, butyllithium, naphthyllithium, biphenylyllithium.

[0017] After the present invention adopts the above technical solutions, compared with the prior art, it has the following advantages: 1. It can realize the large-scale production of silicon-carbon materials, with high production efficiency, reduced energy consumption, and reduced manufacturing cost of silicon-carbon materials; 2. In the whole process, the processes of silicon deposition, prelithiation, and carbon coating are all carried out based on the fluidized state of the materials, with high heat transfer and mass transfer efficiency, good reaction uniformity, and no need for frequent cooling; 3. During the whole production process, it is controlled by the PLC system, with more precise control; sharing the feeding system, mixing system, gas pipeline system, and tail gas treatment system greatly reduces the equipment investment cost; 4. The prepared silicon-carbon materials have the characteristics of high capacity, long cycle life, and high initial efficiency.

[0018] The present invention will be described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a system for large-scale preparation of high-initial-efficiency silicon-carbon materials; Figure 2 is a summary diagram of the performance and annual production capacity estimation of the silicon-carbon materials prepared in Specific Examples 1 - 4.

[0020] In the figure, 1 - raw material bin, 2 - material conveying pipeline, 3 - silicon deposition reactor, 4 - mixing bin, 5 - carbon coating reactor, 6 - lithium source supply device, 7 - finished product bin, 8 - spare bin, 9 - tail gas conveying pipeline, 10 - tail gas treatment system, 11 - silane gas blower, 12 - nitrogen gas blower, 13 - acetylene gas blower, 14 - PLC control system. Detailed Embodiments

[0021] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described with reference to the drawings.

[0022] As Figure 1As shown in the figure, the present invention provides a system for large-scale preparation of high-first-efficiency silicon-carbon materials, including a raw material bin 1. The discharge port of the raw material bin 1 is connected to the feed ports of several silicon precipitation reactors 3 through a material conveying pipeline 2. The discharge ports of several silicon precipitation reactors 3 are connected to the feed port of a mixing bin 4. The discharge port of the mixing bin 4 is connected to the feed port of a carbon coating reactor 5. A lithium source supply device 6 is connected to the side of the carbon coating reactor 5. The carbon coating reactor 5 is provided with two discharge ports, which discharge materials to a finished product bin 7 and a spare bin 8 respectively; it also includes a silane gas blower 11, a nitrogen gas blower 12, an acetylene gas blower 13 and a PLC control system 14.

[0023] The silane gas blower 11 is connected to the bottoms of several silicon precipitation reactors 3 through pipelines respectively. The nitrogen gas blower 12 is connected to the bottoms of several silicon precipitation reactors 3, the mixing bin 4 and the carbon coating reactor 5 through pipelines. The acetylene gas blower 13 is connected to the bottom of the carbon coating reactor 5 through a pipeline.

[0024] The tail gases of several silicon precipitation reactors 3 and the carbon coating reactor 5 are connected to a tail gas treatment system 10 through a tail gas conveying pipeline 9.

[0025] The PLC control system 14 controls the feeding, reaction and discharging processes with a PLC and a human-machine interface as the core.

[0026] In the present invention, the number of silicon precipitation reactors 3 is two to twelve.

[0027] In the present invention, the number of mixing bins 4 is one or two.

[0028] In the present invention, the number of carbon coating reactors 5 is one to three.

[0029] In the present invention, the lithium source supply device 6 is one of a thermal evaporation device, a spraying device or a magnetron sputtering device.

[0030] A process method for preparing high-first-efficiency silicon-carbon materials by using the above system includes the following steps: Step 1: The porous carbon powder in the raw material bin 1 enters several silicon precipitation reactors 3 respectively through the material conveying pipeline 2. First, it is heated, purged with nitrogen and fluidized, and after maintaining a certain temperature for a certain time, a nitrogen and silane mixture gas is introduced. After the silane is cracked for a certain time, the intermediate material is conveyed to the mixing bin 4. Step 2: The mixing bin 4 is preheated to a certain temperature in advance, and the materials conveyed from several silicon precipitation reactors 3 are batch-mixed by physical methods (such as vibration, stirring, air flow dispersion, etc.). After maintaining a certain temperature for a certain time, the materials are conveyed to the carbon coating reactor 5. Step 3: The carbon coating reactor 5 has been heated to the set temperature. The powder is fluidized by nitrogen purging. The lithium source supply device 6 transports the lithium-containing material to the carbon coating reactor 5. After maintaining the temperature for a certain period of time, a mixture of nitrogen and acetylene is introduced. After the acetylene is cracked for a certain period of time, the qualified products are analyzed and enter the finished product bin 7, and the unqualified products are analyzed and enter the spare bin 8.

[0031] During the reaction process, the tail gases generated by several silicon deposition reactors 3 and carbon coating reactors 5 enter the tail gas treatment system 10 (such as alkali solution washing tank, spray combustion, etc.) through the tail gas transmission pipeline 9 for treatment.

[0032] In the present invention, the shape of the reaction cavity of the silicon deposition reactor 3 is cylindrical, and the ratio of the cavity height H to the inner diameter D of the cavity is 8:1 to 12:1.

[0033] In the present invention, the inner diameter D of the reaction cavity of the silicon deposition reactor 3 is 300 to 800 mm.

[0034] In the present invention, the temperature in the silicon deposition reactor 3 is 450 to 500 °C, and the total silicon deposition reaction time is 2 to 10 h.

[0035] In the present invention, the temperature in the carbon coating reactor 5 is 550 to 650 °C, and the total carbon coating time is 2 to 8 h.

[0036] In the present invention, the lithium source raw material of the lithium source supply device 6 is one or more of lithium blocks, lithium foils, lithium powders, lithium hydroxide, lithium carbonate, lithium oxalate, lithium squarate, lithium hydride, butyllithium, naphthyllithium, and biphenylyllithium. Example 1

[0037] A system for scalable preparation of high initial efficiency silicon-carbon materials, equipment parameters: the inner cavity of the silicon deposition reactor is cylindrical, with a diameter D of 300 mm, a height H of 3000 mm, and the number is twelve; the number of mixing bins is two; the number of carbon coating reactors is three; the lithium source supply device is a thermal evaporator device.

[0038] This example also provides a process method for preparing high initial efficiency silicon-carbon materials using the aforementioned system, specifically: Step 1: The porous carbon powder in the raw material bin enters twelve silicon deposition reactors respectively through the material conveying pipeline. First, it is heated and fluidized by nitrogen purging. After maintaining the temperature at 490 °C for 60 min, a mixture of nitrogen and silane is introduced. After the silane is cracked for 8 h, the intermediate material is transported to the mixing bin. Step 2: The two mixing bins are preheated to 590 °C in advance. By physical methods (such as vibration, stirring, air flow dispersion, etc.), the materials transported from six silicon deposition reactors are batch-mixed respectively. After maintaining the temperature for 60 min, the materials are transported to the carbon coating reactor. Step 3: The carbon coating reactor has been heated to 590°C. The powder is fluidized by purging with nitrogen. The lithium source supply device melts and boils lithium blocks at 1400°C to form lithium vapor, which is transported into the carbon coating reactor. After maintaining the temperature for 20 minutes, a mixture of nitrogen and acetylene is introduced. After 8 hours of acetylene cracking, the qualified products are analyzed and enter the finished product bin, while the unqualified products enter the spare bin.

[0039] The performance of the silicon-carbon materials prepared by this system and the estimated annual production capacity are summarized in Figure 2 as shown. Example 2

[0040] A system for large-scale preparation of high initial efficiency silicon-carbon materials, equipment parameters: The inner cavity of the silicon deposition reactor is cylindrical, with a diameter D of 800 mm, a height H of 7000 mm, and the number is two; the number of mixing bins is one; the number of carbon coating reactors is one; the lithium source supply device is a spraying device.

[0041] This example also provides a process method for preparing high initial efficiency silicon-carbon materials using the aforementioned system. The specific process parameters are as follows: The temperature of the silicon deposition reactor is 460°C, and the reaction duration is 10 hours; the temperature of the mixing bin is 620°C, and the heat preservation time is 1 hour; the lithium source supply device melts lithium blocks at 230°C to form lithium liquid, and the lithium liquid is transported into the carbon coating reactor through a nozzle and kept warm for 60 minutes; the temperature of the carbon coating reactor is 620°C, and the reaction duration is 6 hours.

[0042] The performance of the silicon-carbon materials prepared by this system and the estimated annual production capacity are summarized in Figure 2 as shown. Example 3

[0043] A system for large-scale preparation of high initial efficiency silicon-carbon materials, equipment parameters: The inner cavity of the silicon deposition reactor is cylindrical, with a diameter D of 450 mm, a height H of 5000 mm, and the number is ten; the number of mixing bins is two; the number of carbon coating reactors is three; the lithium source supply device is a spraying device.

[0044] This example also provides a process method for preparing high initial efficiency silicon-carbon materials using the aforementioned system. The specific process parameters are as follows: The temperature of the silicon deposition reactor is 490°C, and the reaction duration is 4 hours; the temperature of the mixing bin is 600°C, and the heat preservation time is 1 hour; the lithium source supply device melts lithium blocks at 230°C to form lithium liquid, and the lithium liquid is transported into the carbon coating reactor through a nozzle and kept warm for 60 minutes; the temperature of the carbon coating reactor is 600°C, and the reaction duration is 4 hours.

[0045] The performance of the silicon-carbon materials prepared by this system and the estimated annual production capacity are summarized in Figure 2 as shown. Example 4

[0046] A system for scalable preparation of high-first-efficiency silicon-carbon materials, equipment parameters: the inner cavity of the silicon deposition reactor is cylindrical, with a diameter D of 450 mm, a height H of 5000 mm, and the number is ten; the number of mixing bins is two; the number of carbon coating reactors is three; the lithium source supply device is a magnetron sputtering device.

[0047] This embodiment also provides a process method for preparing high-first-efficiency silicon-carbon materials using the aforementioned system. The specific process parameters are as follows: the temperature of the silicon deposition reactor is 490 °C, and the reaction duration is 4 h; the temperature of the mixing bin is 600 °C, and heat preservation is carried out for 1 h; the lithium source supply device uses lithium foil as the raw material, and lithium particles are transported into the carbon coating reactor by magnetron sputtering for heat preservation for 40 min; the temperature of the carbon coating reactor is 600 °C, and the reaction duration is 4 h.

[0048] The performance and annual production capacity estimation of the silicon-carbon materials prepared by this system are summarized in Figure 2 as shown.

[0049] The above is an example of the best implementation mode of the present invention. The parts not described in detail are all common general knowledge of those skilled in the art. The protection scope of the present invention shall be subject to the content of the claims, and any equivalent transformation based on the technical inspiration of the present invention is also within the protection scope of the present invention.

Claims

1. A system for scalable preparation of high initial efficiency silicon-carbon materials, characterized in that: The invention comprises a raw material bin (1), wherein the discharge port of the raw material bin (1) is respectively connected to the feed ports of a plurality of silicon precipitation reactors (3) through a material conveying pipeline (2), the discharge ports of the plurality of silicon precipitation reactors (3) are connected to the feed port of a mixing bin (4), the discharge port of the mixing bin (4) is connected to the feed port of a carbon coating reactor (5), the side of the carbon coating reactor (5) is connected to a lithium source supply device (6), and the carbon coating reactor (5) is provided with two discharge ports, which discharge materials to a finished product bin (7) and a spare bin (8) respectively; the invention also comprises a silane gas blower (11), a nitrogen gas blower (12), an acetylene gas blower (13) and a PLC control system (14).

2. A system for scalable preparation of high first-efficiency silicon-carbon materials as claimed in claim 1, characterized in that: The silane gas blower (11) is connected to the bottom of the plurality of silicon precipitation reactors (3) through pipelines, the nitrogen gas blower (12) is connected to the bottom of the plurality of silicon precipitation reactors (3), the mixing bin (4), and the carbon coating reactor (5) through pipelines, and the acetylene gas blower (13) is connected to the bottom of the carbon coating reactor (5) through pipelines.

3. A system for scalable preparation of high first-efficiency silicon-carbon materials as claimed in claim 1, characterized in that: The tail gas from the plurality of silicon precipitation reactors (3) and the carbon coating reactor (5) is connected to the tail gas treatment system (10) via the tail gas delivery pipeline (9).

4. A system for scalable preparation of high first-efficiency silicon-carbon materials as claimed in claim 1, characterized in that: The number of the silicon precipitation reactors (3) is two to twelve; the number of the mixing bins (4) is one or two; and the number of the carbon coating reactors (5) is one to three.

5. A system for scalable preparation of high first-efficiency silicon-carbon materials as claimed in claim 1, characterized in that: The lithium source supply device (6) is a thermal evaporation device, a spray device or a magnetron sputtering device.

6. A process for preparing high-initial-efficiency silicon-carbon materials on a large scale, using the system for preparing high-initial-efficiency silicon-carbon materials on a large scale as described in any one of claims 1 to 5, characterized in that: The following steps are involved: S1, the porous carbon powder in the raw material bin (1) enters several silicon precipitation reactors (3) through the material conveying pipeline (2), is first heated, purged with nitrogen to fluidize, and kept warm for a certain period of time, and then a nitrogen and silane mixed gas is introduced. After the silane is cracked for a certain period of time, the intermediate material is conveyed to the mixing bin (4); S2, the mixing bin (4) is preheated to a certain temperature in advance, and the materials delivered from the plurality of silicon precipitation reactors (3) are batch mixed by a physical method. After being kept warm for a certain period of time, the materials are delivered to the carbon coating reactor (5); S3, the carbon coating reactor (5) has been heated to a set temperature, and the powder is fluidized by nitrogen purging. The lithium source supply device (6) delivers lithium-containing materials to the carbon coating reactor (5). After a certain period of insulation, a nitrogen and acetylene mixed gas is introduced. After a certain period of acetylene cracking, qualified products are analyzed and enter the finished product bin (7), and unqualified products are analyzed and enter the spare bin (8).

7. A process for scalably preparing high initial efficiency silicon-carbon materials according to claim 6, characterized in that: The reaction chamber of the silicon precipitation reactor (3) is cylindrical in shape, wherein the ratio of the chamber height H to the chamber inner diameter D is between 8:1 and 12:

1.

8. A process for preparing high initial efficiency silicon-carbon materials on a large scale as claimed in claim 6, characterized in that: The inner diameter D of the reaction chamber of the silicon precipitation reactor (3) is 300 to 800 mm; the temperature in the silicon precipitation reactor (3) is 450 to 500° C., and the total silicon precipitation reaction time is 2 to 10 hours.

9. A process for preparing high initial efficiency silicon-carbon materials on a large scale as claimed in claim 6, characterized in that: The temperature in the carbon coating reactor (5) is between 550°C and 650°C, and the total carbon coating time is between 2 and 8 hours.

10. A process for preparing high initial efficiency silicon-carbon materials on a large scale as claimed in claim 6, characterized in that: The lithium source raw material of the lithium source supply device (6) is one or more of lithium block, lithium foil, lithium powder, lithium hydroxide, lithium carbonate, lithium oxalate, lithium squarate, lithium hydride, butyl lithium, naphthalene lithium, and biphenyl lithium.

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