Silicon-carbon negative electrode material based on instantaneous joule heat method and preparation method and application thereof

Abstract

The application provides a silicon-carbon negative electrode material based on a transient Joule heat method and a preparation method and application thereof, relates to the technical field of silicon-carbon negative electrode material preparation, and the preparation method comprises the following steps: obtaining a silicon sol and porous carbon, and stirring and mixing the porous carbon in the silicon sol; placing the uniformly mixed slurry in a drying box for drying to obtain a dried precursor; loosely packing the precursor in a graphite tube or wrapping the precursor with graphite paper, and then clamping the precursor between two electrodes of a transient Joule furnace for heat treatment, and then cooling the furnace to room temperature, to obtain a silicon-carbon negative electrode sample. The silicon-carbon negative electrode material obtained by uniformly mixing the silicon sol and the porous carbon and then performing high-temperature treatment through the transient Joule heat method has high specific capacity and high stability.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon anode material preparation technology, and particularly to a silicon-carbon anode material based on the instantaneous Joule heating method, its preparation method and application. Background Technology

[0002] With the increasing popularity and development of electric vehicles, people have higher and higher requirements for the driving range of electric vehicles. Traditional graphite anode materials are almost at their limit in terms of improving the driving range of lithium batteries due to the limitation of their theoretical specific capacity (372mAh / g). Against this background, silicon anodes have received widespread attention due to their high theoretical specific capacity (4200mAh / g) and are currently the most effective anode material for solving the problem of long driving range of electric vehicles.

[0003] However, pure silicon has two major problems as a negative electrode material for lithium-ion batteries: First, its volume expands by up to 300% during the charging and discharging process, causing the silicon negative electrode to pulverize and fall off, reducing the battery's cycle stability; second, the interface is unstable. During the charging and discharging process, the solid electrolyte interphase (SEI) layer on the surface of the silicon negative electrode is prone to breakage, causing the exposed silicon to repeatedly react with the electrolyte to form an SEI film, resulting in electrolyte consumption and affecting the battery's performance and lifespan. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a silicon-carbon anode material based on the instantaneous Joule heating method, its preparation method and application, to solve the technical problems of low battery cycle stability and interface instability that easily occur when pure silicon is used as an anode material for lithium-ion batteries in the prior art.

[0005] This invention provides a method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method, comprising: Obtain silica sol and porous carbon, and place the porous carbon in the silica sol and stir to mix; The well-mixed slurry is placed in a drying oven and dried to obtain a well-dried precursor. The precursor is loosely packed in a graphite tube or wrapped in graphite paper, then sandwiched between the two electrodes of a transient Joule furnace for heat treatment, and then cooled to room temperature with the furnace to obtain a silicon-carbon anode sample.

[0006] The aforementioned method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method involves uniformly mixing silica sol with porous carbon, followed by high-temperature treatment using the instantaneous Joule heating method to obtain the silicon-carbon anode material, thus avoiding the use of pure silicon as the anode material. Secondly, the silicon-carbon composite approach can utilize both the high specific capacity of silicon and the stability of carbon, enabling the silicon-carbon anode to improve both specific capacity and stability. Furthermore, the instantaneous Joule heating process is simple and quick, making the silicon-carbon anode material preparation method provided in this application highly efficient.

[0007] In addition, the silicon-carbon anode material preparation method based on the instantaneous Joule heating method according to the present invention may also have the following additional technical features: Furthermore, the heat treatment steps include: evacuating the furnace cavity of the instantaneous Joule furnace; then filling the furnace cavity with high-purity inert gas to atmospheric pressure to achieve the evacuation-filling operation, repeating the evacuation-filling operation three times, and then flowing high-purity inert gas at a rate of 50 ml / min; performing Joule heating to 1500℃-1800℃ and holding at that temperature for 30s-100s.

[0008] Furthermore, the step of evacuating the furnace cavity of the instantaneous joule furnace includes: evacuating the furnace cavity of the instantaneous joule furnace to -0.1 MPa.

[0009] Further, the steps for obtaining silica sol and porous carbon include: obtaining silica sol and porous carbon according to the concentration of silica sol and the ratio of silica mass to porous carbon mass = 1:(5-10).

[0010] Further, the step of drying the uniformly mixed slurry in a drying oven includes: Place the well-mixed slurry in a drying oven and dry at 80°C for 10 hours.

[0011] Furthermore, the silica sol can be an acidic silica sol, an alkaline silica sol, or a neutral silica sol.

[0012] Furthermore, the inert gas is an inert gas that does not react with silicon dioxide and carbon, including argon and helium.

[0013] In another aspect, the present invention provides a silicon-carbon anode material, which is prepared by the above-mentioned silicon-carbon anode material preparation method based on the instantaneous Joule heating method.

[0014] Another aspect of the present invention provides an application of silicon-carbon anode material in coin cells, wherein the above-mentioned silicon-carbon anode material is used, and the application is as follows: Silicon-carbon anode material, carbon black conductive agent, and binder are mixed in a mass ratio of 95:3:2 to form a slurry. The slurry is then coated, dried, and cut into sheets to form a negative electrode. The counter electrode is a lithium metal sheet with Celgard 2400 as the separator. A 1 mol / L lithium hexafluorophosphate is dissolved in a 1:1 volume ratio of ethylene carbonate and dimethyl carbonate to obtain an electrolyte. Finally, a coin cell is assembled. Attached Figure Description

[0015] Figure 1 The XRD pattern of the silicon-carbon anode prepared in Example 1; Figure 2 SEM image of the silicon-carbon anode prepared in Example 1; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] To address the technical issues of low cycle stability and interface instability that arise when using pure silicon as an anode material in lithium-ion batteries, silicon-carbon composites are commonly used. This approach leverages both silicon's high specific capacity and carbon's stability, resulting in silicon-carbon anodes that improve both specific capacity and stability. This is a prevalent method for overcoming the shortcomings of silicon as an anode material. Silicon-carbon composites involve various methods (such as mechanical mixing and chemical vapor deposition) to organically combine silicon and carbon. This process can, to some extent, suppress silicon particle pulverization, thereby inhibiting the repeated formation of the SEI film and improving the specific capacity of the anode.

[0019] The present invention provides a method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method. The method involves uniformly mixing silica sol with porous carbon and then treating it at high temperature using the instantaneous Joule heating method to obtain silicon-carbon anode materials, thus avoiding the use of pure silicon as anode materials. Furthermore, the instantaneous Joule heating process is simple and quick, making the silicon-carbon anode material preparation method provided in this application highly efficient.

[0020] To facilitate understanding of the present invention, several embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0021] Example 1 The method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method provided in this embodiment includes: Based on the silica sol concentration, and with a silica mass to porous carbon mass ratio of 1:5, weigh out the two substances. Add the weighed porous carbon to the weighed silica sol and stir for 5 hours. Place the uniformly mixed slurry in a drying oven at 80 degrees Celsius for 10 hours and store the dried precursor for later use. Loosely pack the obtained precursor into a graphite tube and clamp it between the two electrodes of a transient Joule furnace. Evacuate the furnace cavity to -0.1 MPa, then fill it with high-purity inert gas to atmospheric pressure. Perform two more evacuation-filling operations, then flow high-purity inert gas at a rate of 50 ml / min. Perform Joule heating to 1600 degrees Celsius and hold for 30 seconds. Then cool the furnace to room temperature and remove the sample for later use.

[0022] Example 2 The method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method provided in this embodiment includes: Based on the silica sol concentration, and with a silica mass: porous carbon mass ratio of 1:10, weigh out the two substances. Add the weighed porous carbon to the weighed silica sol and stir for 5 hours. Place the uniformly mixed slurry in a drying oven at 80 degrees Celsius for 10 hours and store the dried precursor for later use. Loosely wrap the obtained precursor in graphite paper and then clamp it between the two electrodes of a transient Joule furnace. Evacuate the furnace cavity to -0.1 MPa, then fill it with high-purity inert gas to atmospheric pressure. Perform two more evacuation-filling operations, then flow high-purity inert gas at a rate of 10-50 ml / min. Perform Joule heating to 1600 degrees Celsius and hold for 30 seconds. Then cool the furnace to room temperature and remove the sample for later use.

[0023] Example 3 The method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method provided in this embodiment includes: Based on the silica sol concentration, and with a silica mass: porous carbon mass ratio of 1:5, weigh out the two substances. Add the weighed porous carbon to the weighed silica sol and stir for 5 hours. Place the uniformly mixed slurry in a drying oven at 80 degrees Celsius for 10 hours and store the dried precursor for later use. Loosely pack the obtained precursor into a graphite tube and clamp it between the two electrodes of a transient Joule furnace. Evacuate the furnace cavity to -0.1 MPa, then fill it with high-purity inert gas to atmospheric pressure. Perform two more evacuation-filling operations, then flow high-purity inert gas at a rate of 50 ml / min. Perform Joule heating to 1800 degrees Celsius and hold for 30 seconds. Then cool the furnace to room temperature and remove the sample for later use.

[0024] Example 4 The method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method provided in this embodiment includes: Based on the silica sol concentration, and with a silica mass: porous carbon mass ratio of 1:5, weigh out the two substances. Add the weighed porous carbon to the weighed silica sol and stir for 5 hours. Place the uniformly mixed slurry in a drying oven at 80 degrees Celsius for 10 hours, and store the dried precursor for later use. Loosely pack the obtained precursor into a graphite tube and clamp it between the two electrodes of a transient Joule furnace. Evacuate the furnace cavity to -0.1 MPa, then fill it with high-purity inert gas to atmospheric pressure. Perform two more evacuation-filling operations, then flow high-purity inert gas at a rate of 50 ml / min. Perform Joule heating to 1800 degrees Celsius and hold for 100 seconds. Then cool the furnace to room temperature and remove the sample for later use.

[0025] The silicon-carbon anode materials from Examples 1 to 4 were mixed in a mass ratio of silicon-carbon anode material: carbon black conductive agent: binder of 95:3:2 to form a slurry. This slurry was then coated, dried, cut into sheets, and assembled into anode plates. A lithium metal sheet was used as the counter electrode, with Celgard 2400 as the separator. A 1 mol / L lithium hexafluorophosphate solution was dissolved in a 1:1 volume ratio mixture of ethylene carbonate and dimethyl carbonate to obtain the electrolyte. The resulting coin cells were assembled and electrochemically tested at a 0.1C discharge rate using a Land electrochemical analyzer. To highlight the effectiveness of the silicon-carbon composite anode in the examples, pure carbon and pure silicon were used as anodes, respectively, following the battery preparation and testing methods described above, resulting in Comparative Example 1 and Comparative Example 2.

[0026] Specifically, the battery test results are shown in Table 1: Table 1:

[0027] As shown in Table 1, the silicon-carbon composite anode material prepared by Joule heating of porous carbon and silica sol has a significantly improved lithium insertion / extraction capacity compared to carbon anodes, and its first coulombic efficiency and cycle stability are also greatly improved compared to silicon anodes.

[0028] In summary, the silicon-carbon anode material preparation method based on the instantaneous Joule heating method in the above embodiments of the present invention obtains the silicon-carbon anode material by uniformly mixing silica sol with porous carbon and then treating it at high temperature using the instantaneous Joule heating method, thus avoiding the use of pure silicon as the anode material. Secondly, the silicon-carbon composite method can utilize both the high specific capacity of silicon and the stability of carbon, so that the silicon-carbon anode can improve its specific capacity while taking into account its stability. Furthermore, the instantaneous Joule heating method is simple and quick, making the silicon-carbon anode material preparation method provided by this application highly efficient.

[0029] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing silicon-carbon anode materials based on the instantaneous Joule heating method, characterized in that, include: Obtain silica sol and porous carbon, and place the porous carbon in the silica sol and stir to mix; The well-mixed slurry is placed in a drying oven and dried to obtain a well-dried precursor. The precursor is loosely packed in a graphite tube or wrapped in graphite paper, then sandwiched between the two electrodes of a transient Joule furnace for heat treatment, and then cooled to room temperature with the furnace to obtain a silicon-carbon anode sample.

2. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 1, characterized in that, The heat treatment process includes: Vacuum the furnace chamber of the instantaneous Joule furnace; Then, high-purity inert gas is introduced into the furnace cavity to atmospheric pressure to achieve the vacuum-filling operation. After repeating the vacuum-filling operation three times, high-purity inert gas is flowed at a rate of 50 ml / min. Perform Joule heating to 1500℃-1800℃ and hold for 30s-100s.

3. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 2, characterized in that, The steps for evacuating the furnace cavity of a transient Joule furnace include: The furnace cavity of the instantaneous Joule furnace was evacuated to -0.1 MPa.

4. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 1, characterized in that, The steps for obtaining silica sol and porous carbon include: Based on the concentration of the silica sol, the silica sol and porous carbon are obtained according to the ratio of silica mass to porous carbon mass of 1:(5-10).

5. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 1, characterized in that, The steps of drying the well-mixed slurry in a drying oven include: Place the well-mixed slurry in a drying oven and dry at 80°C for 10 hours.

6. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 1, characterized in that, Silica sol can be acidic, alkaline, or neutral.

7. The method for preparing silicon-carbon anode material based on instantaneous Joule heating according to claim 2, characterized in that, Inert gases are inert gases that do not react with silicon dioxide and carbon, including argon and helium.

8. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material was prepared using the instantaneous Joule heating method as described in any one of claims 1-7.

9. An application of a silicon-carbon anode material in a coin cell, characterized in that, The applications of the silicon-carbon anode material described in claim 8 are as follows: Silicon-carbon anode material, carbon black conductive agent, and binder are mixed in a mass ratio of 95:3:2 to form a slurry. The slurry is then coated, dried, and cut into sheets to form a negative electrode. The counter electrode is a lithium metal sheet with Celgard 2400 as the separator. A 1 mol / L lithium hexafluorophosphate is dissolved in a 1:1 volume ratio of ethylene carbonate and dimethyl carbonate to obtain an electrolyte. Finally, a coin cell is assembled.

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