Preparation Method of High-Capacity Hard Carbon Composite Material, Hard Carbon Composite Material and Application

Abstract

The present invention discloses a preparation method of a high-capacity hard carbon composite material, the hard carbon composite material and an application thereof. The preparation method includes: dissolving a soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 20%; adding a high-molecular polymer containing exchange groups into the solution, stirring sufficiently at 100 rpm to 900 rpm until ion exchange is completed, then filtering and washing, and drying the filtered product to obtain a high-molecular polymer with silicon-containing groups. The high-molecular polymer with 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 first protective atmosphere environment, and kept warm for 5 hours to 20 hours to obtain a hard carbon composite material containing nano-silica; the material is placed in a reaction device, heated to 1450°C to 1600°C in a second protective atmosphere, and kept warm for 0.5 hours to 10 hours. During the heat preservation process, the nano-silica in the material reacts with carbon to obtain a hard carbon composite material with uniformly dispersed nano-SiOx particles and nano-pores inside; the nano-pores exist around the nano-SiOx particles.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and particularly relates to a preparation method of a high-capacity hard carbon composite material, the hard carbon composite material and applications thereof. Background Art

[0002] Currently, with the vigorous development of lithium-ion batteries, the existing main anode material, graphite, has been difficult to meet the requirements of people for battery capacity. Developing high-capacity anode materials has become a top priority.

[0003] The theoretical specific capacity of silicon materials reaches 4200 mAh / g, and the sources are extensive. However, silicon materials have a huge volume effect during the process of lithium insertion and extraction, expanding and pulverizing during charge and discharge, resulting in a decline in the battery cycle performance. Currently, continuous modification work on silicon-based materials is being carried out. It has been found that, as in the literature (X.H. Liu, L. Zhong, S.H. Huang, S.X. Mao, T. Zhu, J.Y. Huang, Size-Dependent Fracture of Silicon Nanoparticles During Lithiation, ACS Nano, 6(2012)1522 - 1531), Liu et al. proved through in-situ TEM that silicon materials have a critical size. When the silicon particles exceed the critical size (about 150 nm), crack generation can be observed during the lithium insertion process. After that, nano-sized silicon materials have become an important development direction for silicon-based anode materials. However, due to the agglomeration of nanoparticles, the first-cycle Coulomb efficiency of nano-silicon materials will be reduced.

[0004] Silicon monoxide SiOx, further developed on the basis of pure silicon materials, although it has a smaller volume expansion and also has a relatively high theoretical capacity, also has problems commonly existing in silicon-based materials, such as poor conductivity and a large volume effect during the process of lithium insertion and extraction.

[0005] Therefore, improving silicon-based composite materials and enhancing the cycle stability have become an important development direction for the anode materials of lithium-ion batteries at present. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and provide a preparation method of a high-capacity hard carbon composite material, with simple preparation equipment, low raw material costs, good repeatability, and easy operation. In the prepared hard carbon composite material, the dispersion of nano-SiOx particles and nano-pores is uniform; moreover, the sintering temperature of the preparation process of the present invention is relatively low, reducing the raw material and production costs. At the same time, the pores existing around the nano-silicon particles can provide a buffer space for the volume expansion of SiOx particles, ensuring the structural stability during the process of lithium insertion and extraction and ensuring a relatively high cycle stability. This material can be used as the anode material of lithium batteries or other fields.

[0007] In view of this, in a first aspect, an embodiment of the present invention provides a method for preparing a high-capacity hard carbon composite material, comprising:

[0008] Dissolving a soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 20%;

[0009] 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;

[0010] 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 first protective atmosphere, and kept at this temperature for 5 to 20 hours to obtain a hard carbon composite material containing nano-silicon dioxide;

[0011] The hard carbon composite material containing nano-silicon dioxide is placed in a reaction device, heated to 1450°C to 1600°C under a second protective atmosphere, and then kept warm for 0.5 to 10 hours. During the warming process, the nano-silicon dioxide in the material reacts with carbon to obtain a hard carbon composite material with nano-SiOx particles and nano-pores uniformly dispersed inside; wherein the nano-pores exist around the nano-SiOx particles; 0<X<2.

[0012] Preferably, the exchange groups include sulfonic acid groups (—SO 3 H) and / or carboxyl groups (—COOH).

[0013] 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.

[0014] Preferably, the time for fully stirring to complete the ion exchange is 24 hours to 48 hours.

[0015] Preferably, the high molecular polymer includes: one or a combination of polystyrene, epoxy resin, urea-formaldehyde resin, acrylic resin, and polyethylene oxide;

[0016] The soluble silicon-containing compound includes sodium silicate and / or potassium silicate.

[0017] Preferably, the first protective atmosphere is a nitrogen atmosphere or an argon atmosphere, and the second protective atmosphere is an argon atmosphere.

[0018] Second aspect, an embodiment of the present invention provides a high-capacity hard carbon composite material prepared by the preparation method described in the first aspect above. The high-capacity hard carbon composite material is a hard carbon material with uniformly dispersed nano-SiOx particles and nano-pores inside; the nano-pores exist around the nano-SiOx particles; 0 < X < 2;

[0019] The particle size range of the high-capacity hard carbon composite material is 0.1 nm to 100 nm. In the high-capacity hard carbon composite material, the mass content ratio of SiOx is 1% to 40%.

[0020] Preferably, the hard carbon composite material is carbonized from a silicon-containing group polymer formed by ion exchange between a polymer with exchange groups and a soluble silicon-containing compound; the exchange groups include sulfonic acid group (-SO3H) and / or carboxyl group (-COOH).

[0021] Third aspect, an embodiment of the present invention provides a negative electrode, which includes the high-capacity hard carbon composite material described in the first aspect above.

[0022] Fourth aspect, an embodiment of the present invention provides a lithium battery, which includes the negative electrode described in the third aspect above.

[0023] The preparation method of the high-capacity hard carbon composite material provided by the present invention has simple preparation equipment, low raw material cost, good repeatability, and easy operation. In the prepared hard carbon composite material, the dispersion of nano-SiOx particles and nano-pores is uniform; and the sintering temperature of the preparation process of the present invention is relatively low, reducing the raw material and production costs. At the same time, the pores existing around the nano-silicon particles can provide a buffer space for the volume expansion of the SiOx particles, ensuring the structural stability during the lithium insertion and extraction process and ensuring a high cycle stability. This material can be used as a negative electrode material for lithium batteries or other fields. Description of the Drawings

[0024] The technical solutions of the embodiments of the present invention will be further described in detail below through the drawings and embodiments.

[0025] Figure 1 It is a flowchart of the preparation method of the high-capacity hard carbon composite material provided by the embodiment of the present invention;

[0026] Figure 2 It is a scanning electron microscope (SEM) image of the high-capacity hard carbon composite material provided by Embodiment 1 of the present invention;

[0027] Figure 3 It is a scanning electron microscope (SEM) image of the cross-section of the high-capacity hard carbon composite material provided by Embodiment 1 of the present invention;

[0028] Figure 4EDS spectrum diagram of the high-capacity hard carbon composite material provided in Embodiment 1 of the present invention;

[0029] Figure 5 Comparison diagram of charge-discharge curves of button cells for Embodiment 1, Embodiment 2 and Comparative Example 1 of the present invention. Detailed implementation manners

[0030] The technical solution of the present invention will be further described in detail below through the accompanying 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 for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

[0031] Figure 1 The high-capacity hard carbon composite material provided in the embodiment of the present invention is prepared through the preparation process as Figure 1 shown. The preparation method includes:

[0032] Step 110, dissolving the soluble silicon-containing compound in water to prepare a solution with a mass concentration of 1% to 20%;

[0033] Specifically, the soluble silicon-containing compound includes: sodium silicate and / or potassium silicate.

[0034] Step 120, adding a high molecular polymer containing an exchange group into the solution, stirring sufficiently at a speed of 100 rpm to 600 rpm until ion exchange is completed, filtering and washing the solution, and drying the filtered product to obtain a high molecular polymer with a silicon-containing group;

[0035] Specifically, the exchange group includes a sulfonic acid group (-SO3H) and / or a carboxyl group (-COOH). The high molecular polymer includes: one or a combination of several of polystyrene, epoxy resin, urea-formaldehyde resin, acrylic resin, and polyethylene oxide.

[0036] The addition amount of the high molecular polymer containing an exchange group is based on the molar ratio of the silicate radical in the soluble silicon-containing compound to the exchange group in the high molecular polymer containing an exchange group of 0.1:1 to 1:1.

[0037] The time for sufficient stirring until ion exchange is completed is 24 hours to 48 hours.

[0038] The silicon-containing group in the high molecular polymer with a silicon-containing group includes a silicate radical in this embodiment. 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.

[0039] Step 130: Heat the polymer with a silicon-containing group to 800°C to 1200°C at a heating rate of 0.5°C / min to 5°C / min in a protective atmosphere environment, and hold for 5 hours to 20 hours to obtain a hard carbon composite containing nano-silica;

[0040] The protective atmosphere is a nitrogen atmosphere or an argon atmosphere; Conventional equipment such as a high-temperature furnace can be specifically selected for the reaction device, and no special limitation is made here.

[0041] Step 140: Place the hard carbon composite containing nano-silica in a reaction device, heat it to 1450°C to 1600°C under a second protective atmosphere, and hold for 0.5 hours to 10 hours. During the holding process, the nano-silica in the material reacts with carbon to obtain a hard carbon composite with uniformly dispersed nano-SiOx particles and nano-pores inside;

[0042] Among them, nano-pores exist around the nano-SiOx particles; 0 < X < 2.

[0043] During the holding process, a redox reaction occurs between nano-silica and carbon. The nano-silica particles consume the surrounding carbon and are reduced to form SiOx particles, and nano-pores are left after the surrounding carbon is consumed.

[0044] Among them, the high-capacity hard carbon composite has uniformly dispersed nano-SiOx particles and nano-pores inside; nano-pores exist around the nano-SiOx particles; 0 < X < 2.

[0045] The particle size range of the high-capacity hard carbon composite prepared by the present invention is 0.1nm to 100nm. In the high-capacity hard carbon composite, the mass content ratio of SiOx is 1% to 40%.

[0046] The high-capacity hard carbon composite prepared by the present invention can be used as the negative electrode material of a lithium-ion battery.

[0047] 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 a high-capacity hard carbon composite by using the method provided in the above embodiments of the present invention, as well as the method and battery characteristics of applying it to a lithium-ion secondary battery.

[0048] Example 1

[0049] This example provides a method for preparing a high-capacity hard carbon composite, including:

[0050] 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 289 g of polystyrene with a carboxyl group (-COOH) exchange group (exchange capacity of 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 48 hours until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer with silicon.

[0051] 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 for 5 hours in a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0052] Step 3: Put the sample obtained in Step 2 into a reaction device, introduce argon, heat it to 1450 °C at a rate of 1 °C / min, and keep it for 1 hour to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1) and nano-pores inside.

[0053] Perform SEM and EDS tests on the high-capacity hard carbon composite material obtained in this example. Figure 2 This is the SEM image of the high-capacity hard carbon composite material provided in Example 1 of the present invention. Figure 3 This is the SEM image of the cross-section of the high-capacity hard carbon composite material; it can be seen that the dispersion of nano-SiOx particles and nano-pores in the hard carbon composite material is uniform. The present invention solves the problems of uneven dispersion and nano-agglomeration existing in the preparation process of the current carbon-based composite material containing nano-silicon; there are pores constructed around the nano-SiOx particles, which can provide a buffer space for the volume expansion of silicon particles and ensure the structural stability during the process of lithium deintercalation and intercalation. Figure 4 This is the EDS image of the cross-section. It can be seen that the silicon element is uniformly distributed in the material, indicating that SiOx itself is uniformly dispersed.

[0054] Example 2

[0055] The present example provides a preparation method of a high-capacity hard carbon composite material, including:

[0056] 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 with a carboxyl group (-COOH) exchange group (exchange capacity of 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 three times, and dry it to obtain a polymer with silicon.

[0057] Step 2: Put 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 carbonized polymer material containing nano-silica.

[0058] Step 3: Put the sample obtained in Step 2 into a reaction device, introduce argon, heat it to 1600 °C, and keep it at this temperature for 10 hours to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1) and nano-pores inside.

[0059] Example 3

[0060] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0061] 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 with silicon.

[0062] Step 2: Put 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 carbonized polymer material containing nano-silica.

[0063] Step 3: Put the sample obtained in Step 2 into a reaction device, introduce argon, heat it to 1500 °C, and keep it at this temperature for 2 hours to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1.7) and nano-pores inside.

[0064] Example 4

[0065] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0066] 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 with silicon.

[0067] Step 2: Put the dried sample into the reaction device, heat it up to 900 °C at a rate of 5 °C / min, and keep it for 15 hours under a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0068] Step 3: Put the sample obtained in Step 2 into the reaction device, introduce argon, heat it up to 1600 °C, and keep it for 0.5 hour to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1.5) and nano-pores inside.

[0069] Example 5

[0070] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0071] 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 sulfonic acid group (-SO3H) 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 it at a speed of 100 r / min for 24 hours until the ion exchange is completed, filter and wash the polymer 3 times, and dry it to obtain a polymer with silicon.

[0072] Step 2: Put the dried sample into the reaction device, heat it up to 1000 °C at a rate of 5 °C / min, and keep it for 15 hours under a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0073] Step 3: Put the sample obtained in Step 2 into the reaction device, introduce argon, heat it up to 1550 °C, and keep it for 1 hour to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 0.3) and nano-pores inside.

[0074] Example 6

[0075] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0076] 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 728 g of polystyrene containing sulfonic acid group (-SO3H) exchange groups (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 0.5:1, stir it at a speed of 100 r / min for 24 hours until the ion exchange is completed, filter and wash the polymer 3 times, and dry it to obtain a polymer with silicon.

[0077] Step 2: Put the dried sample into the reaction device, heat it to 1000 °C at a rate of 5 °C / min, and keep it at this temperature for 12 hours under a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0078] Step 3: Put the sample obtained in Step 2 into the reaction device, introduce argon, heat it to 1550 °C, and keep it at this temperature for 1 hour to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1.5) and nano-pores inside.

[0079] Example 7

[0080] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0081] Step 1: Take 200 g of sodium silicate and dissolve it in 1800 ml of water to prepare a solution with a mass concentration of about 10%. Add 1020 g of polystyrene containing sulfonic acid group (-SO3H) 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 0.7:1. 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 with silicon.

[0082] Step 2: Put the dried sample into the reaction device, heat it to 1000 °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 carbonized polymer material containing nano-silica.

[0083] Step 3: Put the sample obtained in Step 2 into the reaction device, introduce argon, heat it to 1550 °C, and keep it at this temperature for 1 hour to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1.5) and nano-pores inside.

[0084] Example 8

[0085] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0086] 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 sulfonic acid group (-SO3H) 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 with silicon.

[0087] 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 10 hours under a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0088] Step 3: Put the sample obtained in Step 2 into a reaction device, introduce argon, heat it to 1600 °C, and keep it at this temperature for 0.5 hours to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 1.8) and nano-pores inside.

[0089] Example 9

[0090] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0091] 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 289 g of polystyrene containing sulfonic acid group (-SO3H) 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 at a speed of 200 r / min for 30 hours until the ion exchange is completed. Then filter and wash the polymer three times, and dry it to obtain a polymer with silicon.

[0092] Step 2: Put 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 carbonized polymer material containing nano-silica.

[0093] Step 3: Put the sample obtained in Step 2 into a reaction device, replace the gas with argon, evacuate to -30 KPa, heat it to 1500 °C, and keep it at this temperature for 0.5 hours to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 0.7) and nano-pores inside.

[0094] Example 10

[0095] This example provides a method for preparing a high-capacity hard carbon composite material, which includes:

[0096] 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 578 g of polystyrene containing sulfonic acid group (-SO3H) exchange groups (exchange capacity is about 4.5 mmol / g) according to the molar ratio of silicon to exchange groups in the polymer of 0.5:1. Stir 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 with silicon.

[0097] Step 2: Put the dried sample into the reaction device, heat it up to 950 °C at a rate of 3 °C / min, and keep it at this temperature for 12 hours in a nitrogen atmosphere for carbonization to obtain a carbonized polymer material containing nano-silica.

[0098] Step 3: Put the sample obtained in Step 2 into the reaction device, introduce argon, heat it up to 1500 °C, and keep it at this temperature for 0.5 hours to obtain a hard carbon composite material with uniformly distributed nano-SiOx (X = 0.5) and nano-pores inside.

[0099] To better illustrate the properties of the high-capacity hard carbon composite material of the present invention, Comparative Example 1 is used for comparison.

[0100] Comparative Example 1

[0101] This comparative example provides a preparation method of a common nano-silicon-containing carbon composite material, which includes:

[0102] Step 1: Take 200 g of nano-SiOx (X = 1) and 500 g of polystyrene powder, mix them and put them into the reaction device, heat it up to 1200 °C at a rate of 0.5 °C / min, and keep it at this temperature for 5 hours in a nitrogen atmosphere for carbonization.

[0103] Step 2: Put the sample obtained above into the reaction device, introduce argon, heat it up to 1450 °C at a rate of 1 °C / min, and keep it at this temperature for 1 hour to obtain a comparative sample of the high-capacity hard carbon composite material.

[0104] To test the electrochemical performance of the materials prepared in each example, the obtained hard carbon composite material is used as the negative electrode material and uniformly mixed with 2% carbon black, 2% sodium carboxymethyl cellulose, and 3% styrene-butadiene rubber based on the total mass (excluding the solvent) in a polyvinylidene fluoride (PVDF) solvent to form a battery slurry. The slurry is coated on a copper foil, dried and cut into circular pieces with a diameter of 14 mm, vacuum dried at 100 °C for 12 hours, and then in a glove box containing a high-purity Ar atmosphere, a metal lithium is used as the counter electrode, and a solution of 1 mol of LiPF6 (ethylene carbonate (EC) / dimethyl carbonate (DMC) v:v = 1:1) is used as the electrolyte to assemble a button cell, and its structure and electrochemical performance are evaluated through testing.

[0105] The constant current charge-discharge mode is used 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.

[0106]

[0107] Table 1

[0108] As can be seen from Table 1, the high-capacity hard carbon composite material proposed by the present invention has a relatively high first-cycle charge specific capacity and first-cycle cycling efficiency. The reversible specific capacity of the material is improved compared with that of the existing commercial hard carbon materials by uniformly dispersing nano-SiOx particles and nano-pores inside. The preparation method proposed by the present invention has the characteristics of simple equipment, low raw material cost, good repeatability, easy operation, etc.

[0109] Figure 5 This is a comparison chart of the charge-discharge curves of the coin cells for Example 1, Example 2 and Comparative Example 1 of the present invention. It can be seen that compared with Comparative Example 1, the high-capacity hard carbon composite materials of Example 1 and Example 2 can improve the cycling stability.

[0110] The specific embodiments described above further elaborate on the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-capacity hard carbon composite material, 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 20%; 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 first protective atmosphere, and kept at this temperature for 5 to 20 hours to obtain a hard carbon composite material containing nano-silicon dioxide; The hard carbon composite material containing nano-silicon dioxide is placed in a reaction device, heated to 1450°C to 1600°C under a second protective atmosphere, and then kept warm for 0.5 to 10 hours. During the warming process, the nano-silicon dioxide in the material reacts with carbon to obtain a hard carbon composite material with nano-SiOx particles and nano-pores uniformly dispersed inside; wherein the nano-pores exist around the nano-SiOx particles; 0<X<2.

2. The method for preparing a high-capacity hard carbon composite material according to claim 1, characterized in that, The exchange groups include sulfonic acid groups (-SO3H) and / or carboxyl groups (-COOH).

3. The method for preparing a high-capacity 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 high-capacity 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 high-capacity 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 high-capacity hard carbon composite material according to claim 1, characterized in that, The first protective atmosphere is a nitrogen atmosphere or an argon atmosphere, and the second protective atmosphere is an argon atmosphere.

7. A high-capacity hard carbon composite material prepared by the preparation method according to any one of claims 1-6, characterized in that, The high-capacity hard carbon composite material is a hard carbon material in which nano-SiOx particles and nano-pores are uniformly dispersed; wherein the nano-pores exist around the nano-SiOx particles; 0<X<2; The particle size of the high-capacity hard carbon composite material is in the range of 0.1 nm to 100 nm, and the mass content of SiOx in the high-capacity hard carbon composite material is 1% to 40%.

8. The high-capacity hard carbon composite material according to claim 7, 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 sulfonic acid groups (-SO3H) and / or carboxyl groups (-COOH).

9. A negative electrode, characterized in that, The negative electrode comprises a high-capacity 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.

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