Hard carbon composite material with uniformly dispersed nano-silica, preparation method and application thereof

Abstract

The invention discloses a hard carbon composite material with uniformly dispersed nano silicon dioxide, a preparation method and an application thereof. The preparation method comprises: dissolving a soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 30%; adding a high molecular polymer containing an exchange group to the solution, fully stirring at a rotation speed of 100 rpm to 900 rpm until ion exchange is completed, filtering and washing the solution, and drying the filtered product to obtain a high molecular polymer containing silicon groups; heating the high molecular polymer containing silicon groups to 800 to 1200°C at a heating rate of 0.5°C / min to 5°C / min in a protective atmosphere, and keeping the temperature for 5 to 20 hours to obtain a hard carbon composite material containing nano silicon dioxide.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and particularly relates to a hard carbon composite material with uniformly dispersed nano-silica, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of lithium batteries, currently widely used carbon anode materials mainly include artificial graphite, natural graphite, carbon nanotubes, hard carbon and other carbon materials. Among them, as an amorphous carbon, hard carbon materials have a relatively high reversible capacity, theoretically reaching 700 mAh / g to 1000 mAh / g, far exceeding the theoretical capacity of graphitized carbon of 372 mAh / g. At the same time, due to the irregular structure of hard carbon, the structural stability during charge and discharge can be guaranteed, enabling the lithium battery to have a long cycle life and good rate performance. And silica with a wide source has a theoretical capacity of 1965 mAh / g as an anode material, and can also be used as a potential lithium battery anode material.

[0003] However, at present, the reversible capacity of commercially available hard carbon materials is still relatively low (200 mAh / g to 400 mAh / g), and silica needs to be in an amorphous state to be active. For example, Won-Seok Chang et al. in the literature (Quartz SiO2 a new energy storage anode material for Li-ion batteries) prepared nano-silica by ball milling to obtain an active anode material. Therefore, there are many limitations in currently commercially available hard carbon materials.

[0004] Although some materials can already have the characteristics of large capacity and high capacity retention rate, the industry is still actively seeking better hard carbon materials with high capacity and capacity retention rate that can be commercially applied through simpler preparation methods. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies of the prior art and provide a hard carbon composite material with uniformly dispersed nano-silica, a preparation method thereof, and an application thereof. The preparation equipment of the hard carbon composite material with uniformly dispersed nano-silica of the present invention is simple, the raw material cost is low, the repeatability is good, and it is easy to operate. The prepared hard carbon composite material has uniform dispersion of nano-silica particles, presents an amorphous state, and has activity. This material can be used as a lithium battery anode material or other fields.

[0006] In view of this, an embodiment of the present invention provides a preparation method of a hard carbon composite material with uniformly dispersed nano-silica, including:

[0007] Dissolve a soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 30%.

[0008] Adding a high molecular polymer containing an exchange group to the solution, stirring the solution at a speed of 100 rpm to 900 rpm until the ion exchange is completed, filtering and washing the solution, and drying the filtered product to obtain a high molecular polymer containing a silicon group;

[0009] The high molecular polymer having silicon-containing groups is heated to 800°C to 1200°C at a heating rate of 0.5°C / min to 5°C / min in a protective atmosphere, and kept warm for 5 to 20 hours to obtain a hard carbon composite material containing nano-silicon dioxide.

[0010] Preferably, the exchange group includes one or more of a sulfonic acid group (-SO3H), a carboxyl group (-COOH), and a quaternary amine group (-NR3OH).

[0011] Preferably, the molar ratio of silicon in the soluble silicon-containing compound to the exchange groups in the high molecular polymer containing exchange groups is 0.1:1 to 1:1.

[0012] Preferably, the time for fully stirring to complete the ion exchange is 24 hours to 48 hours.

[0013] Preferably, the high molecular polymer includes: one or a combination of polystyrene, epoxy resin, urea-formaldehyde resin, acrylic resin, and polyethylene oxide;

[0014] The soluble silicon-containing compound includes sodium silicate and / or potassium silicate.

[0015] Preferably, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere, and the second protective atmosphere is an argon atmosphere.

[0016] In a second aspect, an embodiment of the present invention provides a hard carbon composite material prepared by the preparation method described in the first aspect, wherein nano-silicon dioxide particles are uniformly dispersed inside the hard carbon composite material;

[0017] The particle size of the hard carbon composite material is in the range of 0.1 nm to 100 nm, and the mass content of nano silicon dioxide in the hard carbon composite material is 1% to 80%.

[0018] Preferably, the hard carbon composite material is formed by carbonizing a polymer containing silicon groups formed by ion exchange between a polymer containing exchange groups and a soluble silicon-containing compound; the exchange groups include one or more of sulfonic acid groups (-SO3H), carboxyl groups (-COOH), and quaternary amine groups (-NR3OH).

[0019] In a third aspect, an embodiment of the present invention provides a negative electrode, wherein the negative electrode comprises the hard carbon composite material described in the first aspect.

[0020] In a fourth aspect, an embodiment of the present invention provides a lithium battery, which includes the negative electrode described in the third aspect above.

[0021] The preparation method of the hard carbon composite material with uniformly dispersed nano-silica provided by the present invention has simple preparation equipment, low raw material cost, good repeatability, and easy operation. The nano-silica particles in the prepared hard carbon composite material are uniformly dispersed, showing an amorphous state and having activity. This material can be used as a negative electrode material for lithium batteries or other fields. Description of the Drawings

[0022] The technical solutions of the embodiments of the present invention will be further described in detail below through the drawings and embodiments.

[0023] Figure 1 It is a flow chart of the preparation method of the hard carbon composite material with uniformly dispersed nano-silica provided by the embodiment of the present invention;

[0024] Figure 2 It is a scanning electron microscope (SEM) image of the hard carbon composite material with uniformly dispersed nano-silica provided by Embodiment 1 of the present invention;

[0025] Figure 3 It is an energy dispersive spectrum (EDS) image of the hard carbon composite material with uniformly dispersed nano-silica provided by Embodiment 1 of the present invention;

[0026] Figure 4 It is an X-ray diffraction (XRD) image of the hard carbon composite material with uniformly dispersed nano-silica provided by Embodiment 1 of the present invention;

[0027] Figure 5 It is a comparison chart of the charge-discharge curves of the button cells of Embodiment 1 and Embodiment 2 of the present invention. Detailed Embodiments

[0028] The technical solutions of the present invention will be further described in detail below through the drawings and embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several deformations and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

[0029] Figure 1 It is the hard carbon composite material with uniformly dispersed nano-silica provided by the embodiment of the present invention, which is prepared through the preparation process as Figure 1 shown. The preparation method includes:

[0030] Step 110, dissolving the soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 30%;

[0031] Specifically, the soluble silicon-containing compound includes sodium silicate and / or potassium silicate.

[0032] Step 120, adding a high molecular polymer containing an exchange group to the solution, stirring the solution at a speed of 100 rpm to 900 rpm until the ion exchange is completed, filtering and washing the solution, and drying the filtered product to obtain a high molecular polymer containing a silicon group;

[0033] Specifically, the exchange group includes one or more of sulfonic acid group (-SO3H), carboxyl group (-COOH), and quaternary amino group (-NR3OH). The high molecular polymer includes one or more of polystyrene, epoxy resin, urea-formaldehyde resin, acrylic resin, and polyethylene oxide.

[0034] The amount of the high molecular polymer containing exchange groups added is 0.1:1 to 1:1 according to the molar ratio of silicate in the soluble silicon-containing compound to the exchange groups in the high molecular polymer containing exchange groups.

[0035] The time required for sufficient stirring to complete the ion exchange is 24 to 48 hours.

[0036] The silicon-containing groups in the silicon-containing polymer in this embodiment include silicate. Of course, other silicon-containing groups that can form nano-silicon dioxide after a high temperature process known to those skilled in the art according to common knowledge are also within the scope of the present invention.

[0037] Step 130, heating the high molecular polymer having silicon-containing groups to 800°C to 1200°C at a heating rate of 0.5°C / min to 5°C / min in a protective atmosphere, and keeping the temperature for 5 to 20 hours to obtain a hard carbon composite material containing nano-silicon dioxide.

[0038] The protective atmosphere is a nitrogen atmosphere or an argon atmosphere; the reaction device can be selected from conventional equipment such as a high-temperature furnace, and is not particularly limited here.

[0039] The hard carbon composite material prepared by the present invention has nano silicon dioxide particles uniformly dispersed inside; the particle size of the hard carbon composite material ranges from 0.1nm to 100nm, and the mass content of the nano silicon dioxide in the hard carbon composite material accounts for 1% to 80%.

[0040] The hard carbon composite material with uniformly dispersed nano silicon dioxide prepared by the invention can be used as a negative electrode material of a lithium ion battery.

[0041] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process of preparing the hard carbon composite containing nano-silica by using the method provided in the above embodiments of the present invention, as well as the method of applying it to a lithium-ion secondary battery and the battery characteristics.

[0042] Example 1

[0043] The present embodiment provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0044] Step 1: Take 20 g of potassium silicate and dissolve it in 1980 ml of water to prepare a solution with a mass concentration of about 1%. Add 289 g of polystyrene containing a carboxyl (-COOH) exchange group (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to the exchange group in the polymer of 1:1. Stir well at a speed of 100 r / min for 24 hours until the ion exchange is completed. Then filter and wash the polymer 3 times, and dry it to obtain a polymer containing silicon groups.

[0045] Step 2: Put the dried sample into a reaction device, heat it to 1200 °C at a rate of 0.5 °C / min, and keep it at this temperature for 6 hours in a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0046] Perform SEM and EDS tests on the hard carbon composite containing nano-silica obtained in this embodiment. Figure 2 The SEM image of the hard carbon composite containing nano-silica provided in Example 1 of the present invention. Figure 3 The EDS image shows that the hard carbon particles contain silicon elements and are evenly distributed. Figure 4 The XRD image of the hard carbon composite containing nano-silica provided in Example 1 of the present invention. The characteristic peak of silica is not shown in the figure, indicating that the silica distributed inside the hard carbon composite reaches the nano level and presents an amorphous state.

[0047] Example 2

[0048] The present embodiment provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0049] Step 1: Take 200 g of potassium silicate and dissolve it in 6500 ml of water to prepare a solution with a mass concentration of about 3%. Add 2890 g of polystyrene containing a carboxyl (-COOH) exchange group (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to the exchange group in the polymer of 0.1:1. Stir well at a speed of 100 r / min for 24 hours until the ion exchange is completed. Then filter and wash the polymer 3 times, and dry it to obtain a polymer containing silicon groups.

[0050] Step 2: Place the dried sample into a reaction device, heat it to 800 °C at a rate of 5 °C / min, and keep it at this temperature for 20 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0051] Example 3

[0052] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0053] Step 1: Take 200 g of potassium silicate and dissolve it in 800 ml of water to prepare a solution with a mass concentration of about 20%. Add 1445 g of polystyrene containing carboxyl (-COOH) exchange groups (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to the exchange groups in the polymer of 0.5:1. Stir well at a speed of 100 r / min for 24 hours until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer containing silicon groups.

[0054] Step 2: Place the dried sample into a reaction device, heat it to 1000 °C at a rate of 2 °C / min, and keep it at this temperature for 10 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0055] Example 4

[0056] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0057] Step 1: Take 200 g of potassium silicate and dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 2890 g of polystyrene containing carboxyl (-COOH) exchange groups (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to the exchange groups in the polymer of 0.1:1. Stir well at a speed of 100 r / min for 24 hours until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer containing silicon groups.

[0058] Step 2: Place the dried sample into a reaction device, heat it to 1100 °C at a rate of 0.5 °C / min, and keep it at this temperature for 10 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0059] Example 5

[0060] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0061] Step 1: Take 200 g of sodium silicate, dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 364 g of polystyrene containing carboxyl (-COOH) exchange groups (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 1:1. Stir thoroughly at a speed of 100 r / min for 24 hours until ion exchange is completed. Then filter and wash the polymer 3 times, and dry it to obtain a silicon-containing group polymer.

[0062] Step 2: Put the dried sample into a reaction device, heat it to 1100 °C at a rate of 5 °C / min, and keep it at this temperature for 15 hours in a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0063] Example 6

[0064] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0065] Step 1: Take 200 g of sodium silicate, dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 936 g of polystyrene containing quaternary amino (-NR3OH) exchange groups (exchange capacity is about 3.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 0.5:1. Stir thoroughly at a speed of 100 r / min for 24 hours until ion exchange is completed. Then filter and wash the polymer 3 times, and dry it to obtain a silicon-containing group polymer.

[0066] Step 2: Put the dried sample into a reaction device, heat it to 1100 °C at a rate of 1 °C / min, and keep it at this temperature for 20 hours in a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0067] Example 7

[0068] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0069] Step 1: Take 200 g of sodium silicate, dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 1311 g of polystyrene containing quaternary amino (-NR3OH) exchange groups (exchange capacity is about 3.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 0.7:1. Stir thoroughly at a speed of 100 r / min for 24 hours until ion exchange is completed. Then filter and wash the polymer 3 times, and dry it to obtain a silicon-containing group polymer.

[0070] Step 2: Place the dried sample into a reaction device, heat it to 1050 °C at a rate of 5 °C / min, and keep it at this temperature for 10 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0071] Example 8

[0072] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0073] Step 1: Take 200 g of potassium silicate and dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 3715 g of polystyrene containing quaternary amine group (-NR3OH) exchange groups (exchange capacity is about 3.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 0.1:1. Stir well at a speed of 100 r / min for 24 hours until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer containing silicon groups.

[0074] Step 2: Place the dried sample into a reaction device, heat it to 950 °C at a rate of 5 °C / min, and keep it at this temperature for 10 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0075] Example 9

[0076] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0077] Step 1: Take 200 g of potassium silicate and dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 372 g of polystyrene containing quaternary amine group (-NR3OH) exchange groups (exchange capacity is about 3.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 1:1. Stir well at a speed of 200 r / min for 30 h until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer containing silicon groups.

[0078] Step 2: Place the dried sample into a reaction device, heat it to 900 °C at a rate of 5 °C / min, and keep it at this temperature for 15 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0079] Example 10

[0080] This example provides a method for preparing a hard carbon composite containing nano-silica, which includes:

[0081] Step 1: Take 200 g of potassium silicate and dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 743 g of a polymer containing quaternary ammonium group (-NR3OH) exchange groups (exchange capacity about 3.5 mmol / g) according to the molar ratio of silicon to the exchange groups in the polymer of 0.5:1. Stir thoroughly at a speed of 100 r / min for 28 h until ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a silicon-containing group polymer.

[0082] Step 2: Put the dried sample into a reaction device, heat it to 950 °C at a rate of 5 °C / min, and keep it at this temperature for 20 hours under a nitrogen atmosphere for carbonization to obtain a hard carbon composite containing nano-silica.

[0083] To test the electrochemical performance of the materials prepared in each example, the obtained hard carbon composite containing nano-silica is used as the negative electrode material and uniformly mixed with 2% carbon black, 2% sodium carboxymethyl cellulose, and 3% styrene-butadiene rubber (by total mass excluding solvent) in a polyvinylidene fluoride (PVDF) solvent to form a battery slurry. Coat it on a copper foil, dry it, cut it into circular pieces with a diameter of 14 mm, vacuum dry it at 100 °C for 12 hours, and then use metallic lithium as the counter electrode in a glove box containing a high-purity Ar atmosphere, and a solution of 1 mol of LiPF6 (ethylene carbonate (EC) / dimethyl carbonate (DMC) v:v = 1:1) as the electrolyte to assemble a button cell, and evaluate its structure and electrochemical performance through testing.

[0084] Use the constant current charge-discharge mode for testing. The discharge cut-off voltage is 0.005 V, and the charge cut-off voltage is 1.5 V. The charge-discharge test is carried out at a current density of C / 10. The results are recorded in Table 1. In addition, Figure 5 This is a comparison chart of the charge-discharge curves of the button cells in Example 1 and Example 2 of the present invention.

[0085]

[0086] Table 1

[0087] It can be seen from Table 1 and the charge-discharge curves that the hard carbon composite with uniformly dispersed nano-silica inside proposed by the present invention has a high first-cycle charge specific capacity and first-cycle cycling efficiency. By uniformly dispersing nano-silica particles inside, the reversible specific capacity of the material is improved compared with existing commercial hard carbon materials. The preparation method proposed by the present invention has the characteristics of simple equipment, low raw material cost, good repeatability, easy operation, etc., and the dispersion of nano-silica particles in the prepared hard carbon-based composite is uniform, which can effectively improve the specific capacity of the hard carbon negative electrode material.

[0088] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a hard carbon composite material with uniformly dispersed nano-silica, characterized in that, The preparation method comprises: Dissolving a soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 30%; Adding a high molecular polymer containing an exchange group to the solution, stirring the solution at a speed of 100 rpm to 900 rpm until the ion exchange is completed, filtering and washing the solution, and drying the filtered product to obtain a high molecular polymer containing a silicon group; The high molecular polymer having silicon-containing groups is heated to 800°C to 1200°C at a heating rate of 0.5°C / min to 5°C / min in a protective atmosphere, and kept warm for 5 to 20 hours to obtain a hard carbon composite material containing nano-silicon dioxide.

2. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The exchange group includes one or more of a sulfonic acid group (-SO3H), a carboxyl group (-COOH), and a quaternary amine group (-NR3OH).

3. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The molar ratio of silicon in the soluble silicon-containing compound to the exchange groups in the high molecular polymer containing exchange groups is 0.1:1 to 1:

1.

4. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The time for fully stirring to complete the ion exchange is 24 hours to 48 hours.

5. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The high molecular polymer includes: one or a combination of polystyrene, epoxy resin, urea-formaldehyde resin, acrylic resin, and polyoxyethylene; The soluble silicon-containing compound includes sodium silicate and / or potassium silicate.

6. The method for preparing a hard carbon composite material according to claim 1, characterized in that, The protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

7. A hard carbon composite material prepared by the preparation method according to any one of claims 1-6 above, characterized in that, Nano-silicon dioxide particles are uniformly dispersed inside the hard carbon composite material; The particle size of the hard carbon composite material ranges from 0.1 nm to 100 nm, and the mass content of nano silicon dioxide in the hard carbon composite material accounts for 1% to 80%.

8. The hard carbon composite material according to claim 7 above, characterized in that, The hard carbon composite material is formed by carbonizing a high molecular polymer containing silicon groups formed by ion exchange between a high molecular polymer containing exchange groups and a soluble silicon-containing compound; the exchange groups include one or more of sulfonic acid groups (-SO3H), carboxyl groups (-COOH), and quaternary amine groups (-NR3OH).

9. A negative electrode, characterized in that, The negative electrode comprises a hard carbon composite material prepared by the preparation method described in any one of claims 1 to 6 above.

10. A lithium battery, characterized in that, The lithium battery comprises the negative electrode as claimed in claim 9.

Images