Preparation method and application of silicon-carbon composite material with core-shell structure
The silicon-carbon composite material with core-shell structure is prepared by microwave-assisted method, which solves the problems of silicon material volume expansion and poor cycle stability, and achieves a lithium-ion battery negative electrode material with high specific capacity and good conductivity.
Patent Information
- Application Number
- CN202510494623.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-18
- Publication Date
- 2025-07-29
AI Technical Summary
In the prior art, silicon material, as the negative electrode of lithium-ion battery, has problems such as large volume expansion and poor cycle stability, and the traditional process of preparing silicon-carbon composite materials is complex and costly.
Using microwave-assisted method, a composite precursor solution was formed by an aminosilane coupling agent and organic carboxylic acid, and a silicon layer was dispersed in a gradient manner on the graphite surface and a nano-silicon layer was constructed by microwave radiation-assisted chemical deposition method, and finally a silicon-carbon composite material with a core-shell structure was calcined under a protective atmosphere.
The good interface combination between the silicon layer and the graphite matrix is achieved, the specific capacity and cycle stability of the lithium-ion battery are improved, the preparation process is simplified and the cost is reduced.
Smart Images
Figure HDA0005366632250000011 
Figure HDA0005366632250000012 
Figure HDA0005366632250000013
Abstract
Description
Technical Field
[0001] The present invention relates to a method for preparing a silicon-carbon composite material with a silicon layer-loaded core-shell structure by a microwave-assisted method and its application as an anode of a lithium-ion battery, belonging to the technical field of new energy materials. Background Art
[0002] With the increasing demand for the energy density of energy storage devices, silicon active materials with high theoretical capacity (about 4200 mAh / g), low lithium deintercalation / insertion potential, and rich raw material reserves are considered candidates for the next-generation anode materials of lithium-ion batteries. However, their practical applications have been hindered by electrochemical performance, including a huge volume expansion (about 300%) during charge and discharge processes, resulting in the destruction of the electrode structure and rapid capacity decay, which limits their practical applications in lithium battery anode materials. Graphite materials have good electrical conductivity and structural stability, but their specific capacity is relatively low (about 372 mAh / g).
[0003] Silicon-carbon composite materials are a new type of material, and their excellent properties are expected to be used as anodes in lithium-ion batteries. However, there are problems such as complex processes, high costs, and uneven silicon layer distribution in the traditional methods for preparing silicon-carbon composite materials. Summary of the Invention
[0004] The present invention provides a simple and low-cost preparation method. Using an amino-silane coupling agent and an organic carboxylic acid as raw materials, a silicon layer is uniformly loaded on the surface of graphite by a microwave method to prepare a silicon-carbon composite material with a silicon layer-loaded core-shell structure, which is used as a composite anode material for lithium-ion batteries to solve the problems of large volume expansion of silicon materials, poor cycle stability, and complex processes of traditional preparation methods in the prior art.
[0005] The technical object of the present invention is achieved by the following technical solutions:
[0006] A method for preparing a silicon-carbon composite material with a silicon layer-loaded core-shell structure by a microwave-assisted method. Mix an amino-silane coupling agent and an organic carboxylic acid in a certain molar ratio to form a composite precursor solution, then add a graphite matrix material, perform gradient dispersion treatment to form a uniform suspension, and then construct a nano-silicon layer on the surface of graphite by a microwave irradiation-assisted chemical deposition method. Preferably, a calcination treatment is carried out under a protective atmosphere to finally obtain a silicon-carbon composite material with a core-shell structure, including the following specific steps:
[0007] (1) Dissolve the amino-silane coupling agent and the organic carboxylic acid in a certain amount of deionized water, and perform ultrasonic mixing treatment to form a uniform and clear solution to obtain a composite precursor solution;
[0008] (2) Add the graphite substrate to the composite precursor solution in step (1) in three portions, and perform gradient dispersion treatment to form a uniform suspension;
[0009] (3) Place the suspension in a microwave reactor, completely evaporate the water, and construct a nanosilicon layer on the graphite surface through microwave irradiation-assisted chemical deposition method;
[0010] (4) Calcinate the microwave irradiation product in a heating furnace, then take it out for grinding and sieving, and finally obtain a silicon-carbon composite material with a core-shell structure.
[0011] The amino silane coupling agent includes but is not limited to APTES.
[0012] The organic carboxylic acid is selected from C4-C6 polycarboxylic acids, such as organic carboxylic acids like citric acid, formic acid, acetic acid, oxalic acid, oleic acid, etc.
[0013] The molar ratio of the amino silane coupling agent to the organic carboxylic acid is 85-115:1.
[0014] The graphite matrix material is modified graphite with an interlayer spacing of 0.335-0.340 nm and a tapped density of 1.0-1.2 g / cm3.
[0015] The mass ratio of silicon element to graphite in the composite precursor solution is 0.2-0.5:1.
[0016] The ultrasonic power of the ultrasonic mixing is 20-40 kHz, and the time is 3-8 min.
[0017] The gradient dispersion treatment is to first perform magnetic stirring for 20-50 min, and then perform ultrasonic treatment for 8-15 min.
[0018] The microwave irradiation-assisted chemical deposition method irradiates with a microwave irradiation power of 600-1000 W / 500 mL for 6-10 min; an inert gas with a flow rate of 10-300 mL / min is introduced during the microwave irradiation stage.
[0019] The calcination treatment is carried out in a protective gas, heating at a rate of 3-8 °C / min to 600-1000 °C, and holding for 3-5 h for calcination.
[0020] In the overall morphology of the core-shell structure silicon-carbon composite material prepared by the present invention, the silicon layer shows a relatively uniform coverage, the thickness of the silicon layer is less than 1 micron, and the coverage rate is close to 100%.
[0021] The core-shell structure silicon-carbon composite material prepared by the present invention is used as a negative electrode in a lithium-ion battery. Compared with traditional graphite, the discharge specific capacity is increased by 70.18%, and the capacity retention rate reaches 80.5% after 100 cycles at a 1C rate.
[0022] The present invention uniformly loads a silicon layer on the surface of graphite by a microwave-assisted method, achieving good interfacial bonding between the silicon layer and the graphite matrix. The prepared silicon-carbon composite material, used as the anode of a lithium-ion battery, has a high specific capacity and good electrical conductivity, effectively alleviating the volume expansion problem of silicon materials and improving the cycle stability of lithium-ion batteries, with broad application prospects.
[0023] The preparation method of the present invention is simple, efficient, and low-cost, and is easy to realize industrial production. Brief Description of the Drawings
[0024] Figure 1 is the SEM photograph of the silicon-carbon composite material;
[0025] Figure 2 is the EDS energy spectrum diagram of the silicon-carbon composite material;
[0026] Figure 3 is the first charge-discharge curve of the silicon-carbon composite material;
[0027] Figure 4 is the rate curve of the silicon-carbon composite material. Detailed Embodiments
[0028] In order to make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the drawings and embodiments.
[0029] Example 1
[0030] 1) Prepare a composite precursor solution: Mix an amino silane coupling agent (APTES) and citric acid at a molar ratio of 100:1, dissolve them in 200 mL of deionized water, and perform ultrasonic treatment at 30 kHz for 5 minutes to form a clear and uniform composite precursor solution;
[0031] 2) Disperse the graphite matrix: Add 1.6 g of modified graphite (interlayer spacing of 0.336 nm and tapped density of 1.1 g / cm3) to the above composite precursor solution, such that the mass ratio of silicon element to modified graphite is 0.2:1. Add the graphite substrate in 3 portions at intervals of 5 minutes. First, stir magnetically for 30 minutes, and then perform ultrasonic treatment for 10 minutes to ensure the uniformity of the suspension;
[0032] 3) Microwave irradiation-assisted deposition: Transfer the suspension to a microwave reactor, irradiate it at a power of 800 W / 500 mL for 8 minutes (the flow rate of the inert gas nitrogen during the microwave irradiation stage is 10 mL / min) until the water is completely evaporated to obtain a dry composite powder;
[0033] 4) Calcination: Place the composite powder in a tube furnace, heat it to 800 °C at a rate of 5 °C / min under nitrogen protection, hold for 4 hours, naturally cool and then grind and sieve to obtain a silicon-carbon composite material covered with a silicon nanolayer (Si / C mass ratio 0.2).
[0034] Example 2
[0035] 1) Preparation of composite precursor solution: Mix the amino-silane coupling agent (APTES) and citric acid at a molar ratio of 100:1, dissolve them in 200 mL of deionized water, and treat with 30 kHz ultrasonic waves for 5 minutes to form a clear and uniform composite precursor solution;
[0036] 2) Dispersion of graphite matrix: Add 2.2 g of modified graphite (interlayer spacing 0.336 nm, tapped density 1.1 g / cm3) to the above composite precursor solution so that the mass ratio of silicon element to modified graphite is 0.3:1. Add the graphite substrate in 3 portions at 5-minute intervals, first stir magnetically for 30 minutes, and then treat with ultrasonic waves for 10 minutes to ensure the suspension is uniform;
[0037] 3) Microwave irradiation-assisted deposition: Transfer the suspension to a microwave reactor and irradiate it at a power of 800 W / 500 mL for 8 minutes (nitrogen flow rate of inert gas nitrogen is 10 mL / min during the microwave irradiation stage) until the water is completely evaporated to obtain a dry composite powder;
[0038] 4) Calcination: Place the composite powder in a tube furnace, heat it to 800 °C at a rate of 5 °C / min under nitrogen protection, hold for 4 hours, naturally cool and then grind and sieve to obtain a silicon-carbon composite material covered with a silicon nanolayer (Si / C mass ratio 0.3).
[0039] Example 3
[0040] 1) Preparation of composite precursor solution: Mix the amino-silane coupling agent (APTES) and citric acid at a molar ratio of 100:1, dissolve them in 200 mL of deionized water, and treat with 30 kHz ultrasonic waves for 5 minutes to form a clear and uniform composite precursor solution;
[0041] 2) Dispersion of graphite matrix: Add 3.2 g of modified graphite (interlayer spacing 0.336 nm, tapped density 1.1 g / cm3) to the above composite precursor solution so that the mass ratio of silicon element to modified graphite is 0.4:1. Add the graphite substrate in 3 portions at 5-minute intervals, first stir magnetically for 30 minutes, and then treat with ultrasonic waves for 10 minutes to ensure the suspension is uniform;
[0042] 3) Microwave irradiation-assisted deposition: Transfer the suspension to a microwave reactor and irradiate it at a power of 800 W / 500 mL for 8 minutes (the flow rate of inert gas nitrogen during the microwave irradiation stage is 10 mL / min) until the water is completely evaporated to obtain dry composite powder;
[0043] 4) Calcination: Place the composite powder in a tube furnace, heat it to 800 °C at a rate of 5 °C / min under nitrogen protection, hold for 4 hours, naturally cool and then grind and sieve to obtain a silicon-carbon composite material covered with a silicon nanolayer (Si / C mass ratio 0.4).
[0044] As Figure 1 shown in
[0045] As Figure 2 shown, the EDS image of the silicon-carbon composite material with Si / C of 0.4 prepared in Example 3 is presented. It can be seen from the figure that the material is mainly composed of carbon (C), oxygen (O) and silicon (Si). In the EDS image, the distribution of carbon should be consistent with that of graphite, showing a uniform or aggregated morphology. O may come from the oxygen elements in APTES and citric acid, as well as the oxides formed during the reaction. Si comes from APTES and is loaded on the graphite surface through the microwave reaction. The distribution of silicon should be consistent with the coverage of the silicon layer, presenting a uniform distribution. It can be confirmed that the silicon layer is successfully and uniformly loaded on the graphite surface. And by inferring from the penetration depth of the electron beam, the thickness of the silicon coating on the graphite substrate surface is about within 1 micron.
[0046] The silicon-graphite composite materials and the raw material modified graphite (interlayer spacing of 0.336 nm and tapped density of 1.1 g / cm3) prepared in each example were used as the negative electrode active materials for lithium-ion batteries. The specific method was as follows: The active material powder, acetylene black, and PVDF900 were weighed according to a mass ratio of 8:1:1, and mixed evenly on a magnetic stirrer. The obtained slurry was coated on a copper foil and dried at 80 °C for 12 h to obtain an electrode sheet. Coin cell assembly was carried out in a glove box filled with argon, with a lithium sheet as the counter electrode, a glass microfiber as the separator, and a lithium-ion secondary electrolyte of LB-014 (1 M LiPF6 in DEC:DMC:EC = 1:1:1 Vol%). The assembled battery was subjected to electrochemical performance testing.
[0047] As Figure 3 shown in the first charge-discharge curves of the lithium-ion battery. It can be seen from the figure that the composite materials prepared in Examples 1-3 have similar charge-discharge curves. When Si / C = 0.2, due to the low silicon content and the strong leading role of graphite, it may result in higher conductivity and better mechanical stability, and better cycle stability; when Si / C = 0.3, the increase in silicon content improves the specific capacity; when Si / C = 0.4, the increase in silicon content significantly improves the specific capacity, but may also lead to volume expansion and structural instability. The specific capacity of pure graphite is relatively low. By adjusting the Si / C ratio, the specific capacity and cycle stability of the material can be optimized.
[0048] As Figure 4 shown in the rate curves of the lithium-ion battery. It can be seen from the figure that when Si / C = 0.2, it shows good capacity retention at lower rates (such as 0.1C and 0.2C). As the rate increases (such as 0.5C and 1C), the capacity retention may decrease, but it is still better than pure graphite; while when Si / C = 0.3, it shows good capacity retention at medium rates. As the rate increases, the capacity retention may decrease to some extent, but it is still better than pure graphite. The increase in silicon content improves the specific capacity but affects the cycle stability; when Si / C = 0.4, it shows the highest specific capacity at lower rates.
[0049] Through the charge-discharge performance test, it can be seen that under the condition of a current density of 40 mA / g, the initial discharge specific capacity of the graphite negative electrode is 368.22 mAh / g, the initial charge specific capacity is 256.88 mAh / g, and the capacity retention rate after 70 cycles is 92.11%. In contrast, the electrochemical performance of the silicon-carbon composite material prepared by the microwave method has been significantly improved: the initial discharge specific capacity of the silicon-carbon composite material with a Si / C mass ratio of 0.4 reaches 861.52 mAh / g, and the initial charge specific capacity is 611.27 mAh / g. It is worth noting that under the condition of a significant increase in the silicon content, the sample prepared by the microwave method can still maintain good cycle stability, indicating that the microwave method can not only significantly improve the specific capacity of the silicon-carbon composite material, but also has the advantage of a simple preparation process, providing an effective way for the development of high-performance anode materials for lithium-ion batteries.
[0050] Example 4
[0051] 1) Prepare the composite precursor solution: Mix the amino silane coupling agent (APTES) and formic acid at a molar ratio of 85:1, dissolve them in 200 mL of deionized water, and treat them with 20 kHz ultrasonic waves for 8 minutes to form a clear and uniform composite precursor solution;
[0052] 2) Disperse the graphite matrix: Add 1.6 g of modified graphite (the layer spacing is 0.336 nm, and the tapped density is 1.1 g / cm3) to the above composite precursor solution so that the mass ratio of silicon element to modified graphite is 0.2:1. Add the graphite substrate in 3 portions at intervals of 5 minutes. First, stir magnetically for 20 minutes, and then treat with ultrasonic waves for 15 minutes to ensure the uniformity of the suspension;
[0053] 3) Microwave irradiation-assisted deposition: Transfer the suspension to a microwave reactor and irradiate it at a power of 600 W / 500 mL for 10 minutes (the flow rate of the inert gas nitrogen during the microwave irradiation stage is 300 mL / min) until the water is completely evaporated to obtain a dry composite powder;
[0054] 4) Calcination: Place the composite powder in a tubular furnace, heat it to 600 °C at a rate of 3 °C / min under nitrogen protection, hold for 5 hours, cool naturally, and then grind and sieve to obtain a silicon-carbon composite material covered with a silicon nano-layer.
[0055] Example 5
[0056] 1) Prepare the composite precursor solution: Mix the amino silane coupling agent (APTES) and acetic acid at a molar ratio of 115:1, dissolve them in 200 mL of deionized water, and treat them with 40 kHz ultrasonic waves for 3 minutes to form a clear and uniform composite precursor solution;
[0057] 2) Dispersed graphite matrix: Add 1.6 g of modified graphite (interlayer spacing is 0.336 nm, tap density is 1.1 g / cm3) to the above composite precursor solution, so that the mass ratio of silicon element to modified graphite is 0.5:1. Add the graphite substrate in 3 portions with an interval of 5 minutes each. First, magnetically stir for 50 minutes, and then ultrasonically treat for 8 minutes to ensure the uniformity of the suspension;
[0058] 3) Microwave irradiation-assisted deposition: Transfer the suspension to a microwave reactor and irradiate it at a power of 1000 W / 500 mL for 6 minutes (the flow rate of inert gas nitrogen during the microwave irradiation stage is 100 mL / min) until the water is completely evaporated to obtain a dry composite powder;
[0059] 4) Calcination: Place the composite powder in a tubular furnace, heat it to 1000 °C at a rate of 8 °C / min under nitrogen protection, hold for 3 hours, naturally cool and then grind and sieve to obtain a silicon-carbon composite material covered with a silicon nanolayer.
[0060] The uniqueness of the present invention lies in the preparation of a silicon-carbon composite material with a microwave-loaded silicon layer by the microwave method, optimizing the ratio of silicon to carbon (Si / C), significantly improving the electrochemical performance and capacity of the material. The present invention is not only applicable to the anode material of lithium-ion batteries, but also can be widely used in other energy storage fields that require high specific capacity and high stability.
[0061] The scope of protection claimed by the present invention includes, but is not limited to, the specific steps, material compositions, process parameters and their combinations described in the above embodiments. Any modification, substitution or improvement based on the core idea and technical solution of the present invention shall be regarded as falling within the protection scope of the present invention.
Claims
1. A preparation method of a core-shell structured silicon-carbon composite material, characterized in that, It includes the following steps: Mix an amino-silane coupling agent and an organic carboxylic acid with water by ultrasonic treatment to form a composite precursor solution. Then add a graphite matrix material and perform gradient dispersion treatment to form a uniform suspension. Construct a nano-silicon layer on the graphite surface by microwave irradiation-assisted chemical deposition method, and then perform calcination treatment to finally obtain a silicon-carbon composite material with a core-shell structure.
2. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, wherein The amino-silane coupling agent includes but is not limited to APTES. The organic carboxylic acid is selected from C4-C6 polycarboxylic acids. The molar ratio of the amino-silane coupling agent to the organic carboxylic acid is 85-115:
1.
3. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, characterized in that The graphite matrix material is modified graphite with an interlayer spacing of 0.335-0.340 nm and a tapped density of 1.0-1.2 g / cm3.
4. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, characterized in that, The mass ratio of silicon element to the graphite matrix material is 0.2-0.5:
1.
5. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, wherein The ultrasonic power for the ultrasonic mixing is 20-40 kHz, and the time is 3-8 min.
6. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, characterized in that The gradient dispersion treatment is to first perform magnetic stirring for 20-50 min and then ultrasonic treatment for 8-15 min.
7. The preparation method of the core-shell structured silicon-carbon composite material according to claim 1, wherein The microwave irradiation-assisted chemical deposition method is to irradiate with a microwave irradiation power of 600-1000 W / 500 mL for 6-10 min; an inert gas with a flow rate of 10-300 mL / min is introduced during the microwave irradiation stage.
8. The preparation method of the core-shell structured silicon-carbon composite material as claimed in claim 1, wherein, The calcination treatment is to heat up to 600-1000 °C at a rate of 3-8 °C / min in a protective gas and hold for 3-5 h.
9. The silicon-carbon composite material with a core-shell structure prepared by the preparation method of the silicon-carbon composite material with a core-shell structure as claimed in claim 1 is used as a negative electrode in a lithium-ion battery.