CN103996835A - Silicon-base negative material with silane coupling agent cladding layer structure as well as preparation method and application of material - Google Patents

Abstract

The invention discloses a silicon-based negative electrode material with a coating layer structure of a silane coupling agent, a preparation method and application thereof. The silicon-based negative electrode material is based on elemental silicon, and the substrate is coated with a silane coupling agent modification layer. The preparation method is: ultrasonically blending the silane coupling agent and silicon powder, and then heating the mixture at a certain temperature in a protective atmosphere. Reflux to modify the silicon powder; wash the mixed solution, filter it with suction, and dry it in vacuum. The silicon-based negative electrode material with a silane coupling agent coating layer structure prepared by the above method can be used to prepare a negative electrode material for a lithium ion battery when doped in graphite. The present invention uses a silane coupling agent to modify the silicon powder to form a coating modification layer on the surface of the silicon substrate. Due to the bridge effect of the silane coupling agent, the silicon substrate and the outermost conductive polymer are closely combined, which can effectively prevent the silicon material from Due to the expansion pulverization effect, the silicon-based negative electrode material has a high initial Coulombic efficiency and good cycle stability, so as to meet the requirements of power batteries.

Description

A silicon-based negative electrode material with a silane coupling agent coating layer structure and its preparation method and application

technical field

The invention belongs to the technical field of lithium-ion battery negative electrode materials and electrochemistry, and relates to a silicon-based negative electrode material with a coating layer structure of a silane coupling agent, a preparation method and an application thereof.

Background technique

In recent years, compared with traditional secondary batteries such as lead-acid batteries, iron batteries, and nickel-metal hydride batteries, lithium-ion batteries have the advantages of high energy density, high output voltage, low self-discharge, small memory effect, and environmental friendliness, and have gained a lot of attention. Extensive application and research. The performance of key materials for lithium-ion batteries is an important determinant of battery performance, and the development and improvement of negative electrode materials is a global research hotspot. Negative electrode materials such as silicon materials, carbon materials, tin materials, lithium titanate, and metal oxides have been extensively studied. However, the lithium-ion battery system assembled with these negative electrode materials has defects such as poor cycle performance, low specific energy density, high cost, poor safety, and consistency problems, which make it difficult to meet the requirements of power storage batteries.

Silicon-based anode materials have always been the anode materials for lithium-ion batteries due to their theoretical specific capacity exceeding 4200 mAh/g, low lithium intercalation potential, actual specific capacity greater than 3000 mAh/g, rich content in nature, and relatively low raw material prices. Research hotspots. However, the disadvantages of silicon materials such as low initial Coulombic efficiency, poor rate performance, and poor cycle performance severely inhibit the large-scale application of silicon-based anode materials in lithium-ion batteries.

In order to develop silicon-based anode materials with excellent cycle performance, researchers have developed a variety of technical means to modify and improve silicon materials. Graphite, hard carbon, pitch, carbon nanotubes, nanocarbon fibers, metal nanotubes, etc. have been used to coat silicon-based anode materials. For example, Si ₂ C ₅₂ H ₁₈ with a regular structure was prepared by N. Kurita et al. Compared with C ₅₄ H ₁₈ , this material can intercalate a large number of lithium ions, and its structure will also reduce the irreversible reaction of lithium ion extraction, which has a good cycle performance. N. Dimov et al. used hot gas deposition method to coat a layer of carbon material on the surface of simple silicon, and obtained particles with an average size of 18 μm. The specific capacity was above 600 mAh/g, which was higher than the theoretical specific capacity of carbon material (372 mAh/g). , the cycle performance is equivalent to that of carbon materials, and it is greatly improved compared with elemental silicon. Z. S. Wen et al. obtained a silicon-carbon composite by pyrolyzing a resin filled with graphite and simple silicon, and its specific capacity reached 800-900 mAh/g. After 20 cycles, its specific capacity was stable at 600 mAh/g. BJ Neudecker et al. prepared SiSn _0.87 O _1.20 N _1.72 , the specific capacity is close to 800 mAh/g, and it can still maintain at 600 mAh/g after 10,000 charge and discharge cycles, the discharge voltage is 4.1-2.7V, and the irreversible capacity loss per cycle is 0.002 %, but the high cost hinders its commercialization process.

Silane coupling agent is the earliest researched and applied coupling agent, which has the advantages of less dosage and low cost. Since the silane coupling agent has two types of chemical groups X and R in the molecule, R is an organic functional group that can be combined with a polymer; X is a hydrolyzable group that can react with the hydroxyl group in the silicon surface oxide layer. Therefore, the interaction between the silane coupling agent between the polymer and the inorganic system plays the role of coupling.

Therefore, there is an urgent need to find a simple and feasible modification method and preparation method of silicon-based negative electrode materials, so that silicon-based negative electrode materials have both high first-time Coulombic efficiency and good cycle stability, so as to meet the power requirements. battery requirements.

Contents of the invention

The purpose of the present invention is to provide a silicon-based negative electrode material with a silane coupling agent coating layer structure and its preparation method and application, using a silane coupling agent to modify the silicon powder, the silane coupling agent can improve the silicon-based negative electrode in the Expansion and pulverization in charge and discharge cycles, the method is simple and easy, has low manufacturing cost, good reproducibility, and is convenient for large-scale industrial production.

The purpose of the present invention is achieved through the following technical solutions:

The invention relates to a silicon-based negative electrode material with a silane coupling agent coating layer structure, which uses simple silicon as a base and is coated with a silane coupling agent modification layer outside the base.

A method for preparing the above-mentioned silicon-based negative electrode material with a silane coupling agent coating layer structure, the steps are as follows:

(1) Ultrasonic blending of silane coupling agent and silicon powder in an ethanol-water system, reflux at a certain temperature in a protective atmosphere, and modification of silicon powder; wherein: the preparation method of silicon powder is gas phase method, sol — One of the gel method, precipitation method, microemulsion method, and ball milling method; the particle size range of silicon powder is between 20 and 8000 nm; the silane coupling agent is γ-aminopropyltriethoxysilane, γ ―(2,3-Glycidoxy) Propyltrimethoxysilane, γ-(Methacryloyloxy)propyltrimethoxysilane, Octyltriethoxysilane, Dimethyldimethoxysilane , one of methyl tributylketoxime silane and isocyanate propyltriethoxysilane; the amount of silane coupling agent added is 0.01-10% of the mass fraction of silicon powder; the reflux temperature is 40-120°C, The reflow time is 5-10 h;

(2) Wash the mixed solution, suction filter, and vacuum-dry to obtain a silicon-based negative electrode material with a silane coupling agent coating layer structure; wherein: the vacuum drying temperature is 45-55°C, and the vacuum drying time is 10-12 h.

The silicon-based negative electrode material with the coating layer structure of the silane coupling agent prepared by the above method can be used to prepare the negative electrode material of the lithium-ion battery when doped in graphite, wherein the silicon-based negative electrode material with the coating layer structure of the silane coupling agent accounts for 1~98% of the content.

The present invention modifies silicon powder with a silane coupling agent to form a coating modification layer on the surface of the silicon substrate. Due to the bridging effect of the silane coupling agent, the silicon substrate and the outermost conductive polymer are closely combined, which can effectively prevent silicon materials from Due to the expansion pulverization effect, the silicon-based negative electrode material has a high initial Coulombic efficiency and good cycle stability, so as to meet the requirements of power batteries.

The advantages of the present invention are as follows:

(1) Modification of elemental silicon with silane coupling agent to form a coating layer improves the first Coulombic efficiency and cycle stability of silicon-based anode materials, which can meet the requirements of power batteries.

(2) The modification process is applicable to all silicon-based anode materials, and is simple and easy to operate, with low manufacturing cost and good reproducibility, and is convenient for large-scale industrial production.

(3) Compared with the silicon-based negative electrode of the prior art, the silicon-based negative electrode of the present invention has a higher specific capacity, especially the cycle performance of the existing silicon negative electrode has been greatly improved, and the doped graphite After middle and high temperature, the performance of graphite anode material has been greatly improved.

(4) The silicon-based negative electrode material prepared in the present invention has an infrared spectrum as shown in Figure 5, and its characteristic peaks are 2972cm ^-1 , 2926cm ^-1 and 1735cm ^-1 .

Description of drawings

Fig. 1 is the schematic diagram of the reaction between silane coupling agent and elemental silicon substrate;

Fig. 2 is the infrared spectrogram of the silicon-based negative electrode material with silane coupling agent coating layer;

Fig. 3 is the SEM picture of the silicon-based negative electrode material before silane coupling agent modification;

Fig. 4 is the SEM picture of the silicon-based negative electrode material (embodiment 1) of silane coupling agent coating layer structure;

Fig. 5 is a cycle performance curve of a silicon-based negative electrode material with a coating layer structure of a silane coupling agent.

Detailed ways

The present invention is further described below through examples and comparative examples. These examples are only used to illustrate the present invention, and the present invention is not limited to the following examples. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention.

Example 1:

1. Mix 0.1g of γ-(methacryloyloxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-neck flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the condition of protective gas flow rate of 200mL/min, temperature of 80°C and magnetic stirring, and vacuum dried at 55°C for 12h to finally obtain γ—(methacryloyloxy) A silicon-based anode material surface-modified by propyltrimethoxysilane.

Figure 1 explains the principle of the reaction between the silane coupling agent and the elemental silicon substrate. After the silane coupling agent is hydrolyzed, a water molecule is removed, and the silicon atoms are connected to each other to form a network structure.

Fig. 2 is an infrared spectrum of a silicon-based negative electrode material with a coating layer of a silane coupling agent. The silane coupling agent γ-(methacryloyloxy)propyltrimethoxysilane contains alkoxy groups and carbon-carbon unsaturated double bonds in the molecule. It can be seen from Figure 2 that the modified material modified by γ-(methacryloyloxy)propyltrimethoxysilane has absorption peaks at 2972 and 2926 cm ^-1 , which correspond to the CH bond stretching vibration.

In the comparative example, the agglomeration of silicon powder is more serious (see Figure 3), while the prepared silicon-based negative electrode material with a coating layer of silane coupling agent is a sphere with complete particles (see Figure 4), the agglomeration situation has been alleviated, and the particle size About 20-8000 nm.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that the initial charge capacity of the material is 2839 mAh/g, the initial charge-discharge efficiency is 72%, and the charge capacity after 200 cycles is 1801.84mAh/g , the capacity is maintained at about 1800 mAh/g, which has excellent performance.

Example 2:

1. Mix 0.25g of γ-(2,3-glycidyloxypropoxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-neck flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the conditions of protective gas flow rate of 200mL/min, temperature of 60°C and magnetic stirring, and vacuum drying for 12h at a temperature of 55°C to finally obtain γ―(2,3― Glycidoxy) Propyltrimethoxysilane Surface Modified Silicon-Based Anode Material.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that the first charge capacity of the material is 2687 mAh/g, the first charge and discharge efficiency is 71.8%, and the charge capacity after 200 cycles is 1898.95 mAh/g , the capacity is maintained at about 1900 mAh/g, which has excellent performance.

Example 3:

1. Mix 0.25g of γ-(methacryloyloxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-necked flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the conditions of protective gas flow rate of 200 mL/min, temperature of 80 °C, magnetic stirring, and vacuum drying at 55 °C for 12 h to finally obtain γ—(methacryloyloxy ) Surface-modified silicon-based anode material with propyltrimethoxysilane.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that the initial charge capacity of the material is 2695.17 mAh/g, the initial charge and discharge efficiency is 72.7%, and the charge capacity after 200 cycles is 1941.59 mAh/g , the capacity is maintained at about 1940 mAh/g, which has excellent performance.

Example 4:

1. Mix 0.5g of γ-(2,3-glycidyloxypropoxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-necked flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the conditions of protective gas flow rate of 200mL/min, temperature of 60°C and magnetic stirring, and vacuum drying for 12h at a temperature of 55°C to finally obtain γ―(2,3― Glycidoxy) Propyltrimethoxysilane Surface Modified Silicon-Based Anode Material.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that the initial charge capacity of the material is 2417.28 mAh/g, the initial charge-discharge efficiency is 72.1%, and the charge capacity after 200 cycles is 1718.21 mAh/g , the capacity is maintained at about 1700 mAh/g, which has excellent performance.

Example 5:

1. Mix 0.25g of γ-(methacryloyloxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-necked flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the conditions of protective gas flow rate of 200 mL/min, temperature of 80 °C, magnetic stirring, and vacuum drying at 55 °C for 12 h to finally obtain γ—(methacryloyloxy ) Surface-modified silicon-based anode material with propyltrimethoxysilane.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that after adding 20% by mass to graphite, the composite material has good cycle performance, and the initial charge capacity of the material is 836.64 mAh /g, the first charge and discharge efficiency is 85.7%, the charge capacity after 200 cycles is 764.19mAh/g, and the capacity remains at about 760 mAh/g, which has excellent performance.

Embodiment 6:

1. Mix 0.25g of γ-(methacryloyloxy)propyltrimethoxysilane with 45mL of ethanol and 5mL of water in a three-necked flask for hydrolysis, add 5g of silicon powder, and mix ultrasonically for 0.5h;

2. The material mixed uniformly in step 1 was refluxed for 10 h under the conditions of protective gas flow rate of 200 mL/min, temperature of 80 °C, magnetic stirring, and vacuum drying at 55 °C for 12 h to finally obtain γ—(methacryloyloxy ) Surface-modified silicon-based anode material with propyltrimethoxysilane.

3. After mixing the γ-(methacryloyloxy)propyltrimethoxysilane surface-modified silicon-based negative electrode material prepared in step 2 with graphite at a ratio of 50%, it can be used as a new type of lithium ion Battery anode materials, replacing traditional lithium-ion battery anode materials.

It can be seen from the cycle performance curve of the silicon-based negative electrode material with the silane coupling agent coating layer structure in Figure 5 that after adding 50% by mass to graphite, the composite material has good cycle performance, and the initial charge capacity of the material is 1533.59 mAh /g, the first charge and discharge efficiency is 79.32%, the charge capacity after 200 cycles is 1411.02 mAh/g, and the capacity remains at about 1411.02 mAh/g, which has excellent performance.

Comparative example: untreated elemental silicon.

The test conditions of each embodiment and comparative example are compared as shown in Table 1.

Table 1

Claims (9)

1. A silicon-based negative electrode material with a silane coupling agent coating layer structure, characterized in that the silicon-based negative electrode material is based on simple silicon, and is coated with a silane coupling agent modification layer outside the substrate. 2. a preparation method of the silicon-based negative electrode material with silane coupling agent coating layer structure according to claim 1, is characterized in that described method step is as follows: (1) Ultrasonic blending of silane coupling agent and silicon powder, reflux at 40-120°C in a protective atmosphere to modify silicon powder; where: the amount of silane coupling agent added is the mass fraction of silicon powder 0.01-10%; (2) The mixed solution is washed, suction filtered, and vacuum-dried to obtain a silicon-based negative electrode material having a coating layer structure of a silane coupling agent. 3. the preparation method of the silicon-based negative electrode material with silane coupling agent coating layer structure according to claim 2, it is characterized in that the preparation method of described silicon powder is gas phase method, sol-gel method, precipitation method, A kind of microemulsion method and ball milling method. 4. The method for preparing a silicon-based negative electrode material having a silane coupling agent coating layer structure according to claim 2 or 3, characterized in that the particle size range of the silicon powder is between 20 and 8000 nm. 5. The preparation method of a silicon-based negative electrode material having a silane coupling agent coating layer structure according to claim 2, wherein the silane coupling agent is γ-aminopropyltriethoxysilane, γ- (2,3-Glycidoxy) Propyltrimethoxysilane, γ-(Methacryloyloxy)propyltrimethoxysilane, Octyltriethoxysilane, Dimethyldimethoxysilane, One of methyl tributylketoxime silane and isocyanate propyltriethoxysilane. 6. the preparation method of the silicon-based negative electrode material with silane coupling agent coating layer structure according to claim 2, is characterized in that described reflux time is 5-10 h. 7. The method for preparing a silicon-based negative electrode material having a coating layer structure of a silane coupling agent according to claim 2, wherein the vacuum drying temperature is 45-55° C., and the vacuum drying time is 10-12 h. 8. The application of the silicon-based negative electrode material with silane coupling agent cladding layer structure doped in graphite as lithium ion battery negative electrode material according to claim 1. 9. the silicon-based negative electrode material with silane coupling agent coating layer structure according to claim 8 is doped in graphite as the application of lithium-ion battery negative electrode material, it is characterized in that described silicon-based negative electrode material accounts for graphite content 1~98%.