Novel granular negative electrode material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a novel granular negative electrode material and a preparation method and application thereof. The preparation method comprises the following steps: by taking NH3.H2O as a catalyst, carrying out condensation polymerization on phenol and formaldehyde to prepare a phenolic resin solution; adding a polymer and stirring to obtain a mixed solution; adding hydrochloric acid to neutralize the mixed solution, and drying to remove the solvent to obtain a solid resin mixture; after curing the solid resin mixture, crushing the solid resin mixture into small particles of 7-18 microns, then putting the small particles into an activation furnace, and introducing water vapor for activation; placing the activated product in a mixed solution of NaOH and a carbon source to generate carbon dots in situ in a pore structure of the three-dimensional pore structure particulate matter, and standing to obtain the carbon dot modified three-dimensional pore structure particulate matter; calcining the carbon dot modified three-dimensional pore structure particulate matter to obtain a three-dimensional pore structure particulate matter with a cross-linked network structure inside; and carrying out acid pickling and water washing on the three-dimensional pore structure particles with the cross-linked network structure inside, and drying to obtain the novel granular negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a novel granular negative electrode material and a preparation method and application thereof. Background Art

[0002] With the successful application of safe, reliable and low-cost lithium-ion batteries, research on similar sodium-ion batteries has emerged in an endless stream. + Larger radius (than Li + The application efficiency of the developed lithium-ion battery electrode materials in sodium-ion batteries is low. For example, when the commercial graphite anode of lithium-ion batteries is used as the anode of sodium-ion batteries, it only provides 31 mAh·g -1 capacity.

[0003] A large number of materials have been explored for use as negative electrodes for sodium-ion batteries, among which carbon materials have the advantages of abundant resources, low cost, non-toxicity, and high safety, and their feasibility of sodium storage has been confirmed. Hard carbon is currently the most promising negative electrode material for sodium-ion batteries, but its specific conductivity and physical stability need to be improved. Carbon dots (CDs), as a member of carbon nanomaterials, can theoretically also be used as carbon-based electrode materials. However, the complex synthesis of carbon dots themselves, high equipment precision requirements, and high synthesis costs limit their application. At the same time, it is also difficult to synthesize carbon dots with excellent performance. Summary of the invention

[0004] The purpose of the present invention is to provide a new type of granular negative electrode material and its preparation method and application. Compared with the prior art, the network cross-linked structure composed of carbon dots has a larger specific surface area and rich oxygen-containing functional groups, and has a higher sodium storage capacity when used as a negative electrode material. The modification of carbon dots improves the sodium storage performance on the one hand, and the network cross-linked structure in the pores formed by the cross-linking has a good supporting effect on the hard carbon, thereby extending the cycle life.

[0005] To this end, in a first aspect, an embodiment of the present invention provides a method for preparing a novel granular negative electrode material, the preparation method comprising:

[0006] The phenolic resin solution was prepared by polycondensation reaction of phenol and formaldehyde using NH3·H2O as catalyst.

[0007] Adding a polymer to the phenolic resin solution and stirring the mixture to uniformly mix the polymer and the phenolic resin to obtain a mixed solution;

[0008] adding hydrochloric acid to the mixed solution to neutralize the mixed solution, and drying the neutralized solution to remove the solvent to obtain a solid resin mixture;

[0009] After the solid resin mixture is cured, it is broken into small particles of 7-18 microns, and then placed in an activation furnace and activated by passing water vapor to obtain an activated product with a three-dimensional pore structure;

[0010] The activated product is placed in a mixture of NaOH and a carbon source to generate carbon dots in situ in the pore structure of the three-dimensional pore structure particles, and the three-dimensional pore structure particles are allowed to stand to obtain carbon dot-modified particles;

[0011] calcining the carbon dot-modified three-dimensional pore structure particles to obtain three-dimensional pore structure particles having a cross-linked network structure inside;

[0012] The three-dimensional pore structure particles with a cross-linked network structure inside are acid-washed and water-washed, and then dried to obtain the novel granular negative electrode material.

[0013] Preferably, the mass ratio of phenol to formaldehyde is 1:1-1:1.5;

[0014] The reaction temperature of the polycondensation reaction is 60° C.-80° C., and the reaction time is 3-8 hours.

[0015] Preferably, the polymer includes any one of polyethylene glycol, polypropylene ether, methyl methacrylate or benzoyl peroxide;

[0016] The mass fraction of the polymer accounts for 5%-15% of the phenolic resin solution;

[0017] The stirring temperature for adding the polymer into the phenolic resin solution and stirring is 60° C.-80° C., and the stirring time is 1-3 hours.

[0018] Preferably, the curing temperature is 130°C-180°C and the curing time is 3-8 hours;

[0019] The activation temperature is 800° C.-900° C., and the activation time is 1-3 hours.

[0020] Preferably, the carbon source comprises: any one of methanol, ethanol, formaldehyde, acetaldehyde or glucose;

[0021] The activated product is placed in a mixture of NaOH and a carbon source and stirred for more than 1 hour. Hydroxyl ions (OH) are generated in the three-dimensional pore structure of the activated product. - ) adsorption, which enhances the surface activity and at the same time - ) mediates the reduction reaction of the carbonyl group (C=O) in the carbon source to form carbon dots;

[0022] The standing time is 100-200 hours.

[0023] Preferably, the porosity of the activated product is greater than 70%, the average pore size is greater than 10 nm, and there are macropores or mesopores with a pore size of 30-200 nm.

[0024] Preferably, the calcination atmosphere is argon or nitrogen or a combination of the two, with a flow rate of 2-10 L / min; the heating rate is 5-10°C / min; the calcination temperature is 400-800°C, and the calcination time is 2-8 hours, so that the carbon dots are solidified and form a cross-linked structure.

[0025] Preferably, the acid washing is washing with a hydrochloric acid solution; the water washing is washing with pure water; and the drying is drying at 70-100° C. for 3-12 hours.

[0026] In a second aspect, an embodiment of the present invention provides a new type of granular negative electrode material prepared by the preparation method described in the first aspect above; the new type of granular negative electrode material is a granular material composed of a three-dimensional pore structure and a cross-linked network structure within the pores.

[0027] In a third aspect, an embodiment of the present invention provides a sodium ion battery, wherein the sodium ion battery comprises the novel granular negative electrode material described in the second aspect.

[0028] The preparation method of the novel granular negative electrode material provided in the embodiment of the present invention forms carbon dots in the pores of the cross-linked network structure under alkaline conditions, and forms the cross-linked network structure in the pores by calcination. This structure can not only adjust the morphology and structure of the electrode material, thereby providing better sodium storage performance, but also alleviate the volume change of the negative electrode material during the sodium ion insertion and extraction process, thereby extending the cycle life. The synthesis method is simple, and the synthesized material has a large specific surface area, and the rich oxygen-containing functional groups on the surface also contribute to the storage of sodium. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart of a method for preparing a novel granular negative electrode material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0031] The present invention provides a novel granular negative electrode material, and the preparation method thereof is as follows: Figure 1 As shown, it mainly includes the following steps:

[0032] Step 110, using NH3·H2O as a catalyst, using phenol and formaldehyde to perform a polycondensation reaction to prepare a phenolic resin solution;

[0033] Specifically, the mass ratio of phenol to formaldehyde is 1:1-1:1.5;

[0034] The reaction temperature of the polycondensation reaction is 60°C-80°C, and the reaction time is 3-8 hours.

[0035] This step utilizes the condensation reaction of formaldehyde and phenol to form a resin structure, and NH3·H2O as an alkaline catalyst helps to accelerate the polycondensation reaction.

[0036] Step 120, adding a polymer to the phenolic resin solution and stirring the mixture so that the polymer and the phenolic resin are evenly mixed to obtain a mixed solution;

[0037] The polymer includes any one of polyethylene glycol, polypropylene ether, methyl methacrylate or benzoyl peroxide; the mass fraction of the polymer accounts for 5%-15% of the phenolic resin solution; the stirring temperature of adding the polymer into the phenolic resin solution and stirring is 60°C-80°C, and the stirring time is 1-3 hours.

[0038] Adding polymers can improve the processability of the resin and enhance its flexibility.

[0039] Step 130, adding hydrochloric acid to the mixed solution to neutralize the mixed solution, and drying the neutralized solution to remove the solvent to obtain a solid resin mixture;

[0040] The mixed solution is neutralized with hydrochloric acid, and the alkaline catalyst that may remain in the reaction is neutralized with hydrochloric acid to remove the solvent to obtain a solid resin mixture.

[0041] Step 140, after solidifying the solid resin mixture, breaking it into small particles of 7-18 microns, and then placing it in an activation furnace and introducing water vapor for activation to obtain an activated product with a three-dimensional pore structure;

[0042] The curing temperature is 130℃-180℃ and the curing time is 3-8 hours;

[0043] The activation temperature is 800°C-900°C and the activation time is 1-3 hours.

[0044] The activated product with a three-dimensional pore structure has a porosity greater than 70%, an average pore diameter greater than 10 nm, and has macropores or mesopores with a pore diameter of 30-200 nm.

[0045] Step 150, placing the activated product in a mixture of NaOH and a carbon source to in-situ generate carbon dots in the pore structure of the three-dimensional porous structure particles, and allowing to stand to obtain three-dimensional porous structure particles modified with carbon dots;

[0046] Specifically, the carbon source includes any one of methanol, ethanol, formaldehyde, acetaldehyde or glucose;

[0047] The activated product is placed in a mixture of NaOH and a carbon source and stirred for more than 1 hour. Hydroxyl ions (OH - ) adsorption, which enhances the surface activity and at the same time - ) mediates the reduction reaction of the carbonyl group (C=O) in the carbon source to form carbon dots;

[0048] The standing time is preferably 100-200 hours.

[0049] Step 160, calcining the carbon dot-modified three-dimensional porous structure particles to obtain three-dimensional porous structure particles having a cross-linked network structure inside;

[0050] Specifically, the calcination atmosphere is argon or nitrogen or a combination of the two, with a flow rate of 2-10 L / min; the heating rate is 5-10°C / min; the calcination temperature is 400-800°C, and the calcination time is 2-8 hours, so that the carbon dots solidify and form a cross-linked structure.

[0051] Step 170, the three-dimensional pore structure particles with a cross-linked network structure inside are acid-washed and water-washed, and then dried to obtain a new type of granular negative electrode material.

[0052] The pickling process includes washing with a hydrochloric acid solution; the water washing process includes washing with pure water; and the drying process includes drying at 70-100° C. for 3-12 hours.

[0053] The novel granular negative electrode material prepared by the preparation method of the present invention is a granular material composed of a three-dimensional pore structure and a cross-linked network structure in the pores. The material can be used as a negative electrode material for a sodium ion battery.

[0054] The present invention forms carbon dots in the pores of a cross-linked network structure under alkaline conditions, and forms a cross-linked network structure in the pores through calcination. This structure can not only adjust the morphology and structure of the electrode material, thereby providing better sodium storage performance, but also alleviate the volume change of the negative electrode material during the sodium ion insertion and extraction process, thereby extending the cycle life. The synthesis method is simple, and the network cross-linked structure formed by the carbon dots has a large specific surface area and rich oxygen-containing functional groups, and has a high sodium storage capacity when used as a negative electrode material. This scheme utilizes the modification of carbon dots to improve the sodium storage performance on the one hand, and on the other hand, the network cross-linked structure in the pores formed by the cross-linking has a good supporting effect on the hard carbon, thereby extending the cycle life.

[0055] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention is further described below in conjunction with the embodiments. In addition, the embodiments described in the present invention are only partial embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention. In addition, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0056] Example 1

[0057] This embodiment provides a method for preparing a novel granular negative electrode material, comprising:

[0058] Step 1, preparing an activated product with a three-dimensional pore structure;

[0059] Step 2: Prepare a new type of granular negative electrode material using the activated product with a three-dimensional pore structure.

[0060] Wherein, the preparation method of step 1 is as follows:

[0061] Phenol:formaldehyde is polymerized at a ratio of 1:1.3 at 70°C for 5 hours, and NH3·H2O is used as a catalyst to obtain a phenolic resin solution; polyethylene glycol with a mass fraction of 10% of the phenolic resin solution is added, and stirring is continued at 70°C for 2 hours to uniformly mix the polymer and the phenolic resin; after the polymerization reaction is completed, the mixed solution is neutralized with hydrochloric acid, and the solvent is dried to obtain a solid resin mixture; the solid resin mixture is cured at 150°C for 5 hours, and then crushed into small particles of 7-18 microns; the crushed small particles of 7-18 microns are placed in an activation furnace, water vapor is introduced, and activated at 850°C for 1.5 hours to obtain an activated product with a three-dimensional pore structure.

[0062] The preparation method of step 2 is as follows:

[0063] Step 21: Add 10 g of NaOH into 45 mL of acetone solution and stir at 60 r / min for 1 hour;

[0064] Step 22: placing the activated small particles with a diameter of 7 μm in a mixture of NaOH and acetone and leaving it to stand for 100 hours;

[0065] Step 23: calcining the dark brown mixture obtained by standing at 800° C. for 6 hours to obtain carbon point modified particles;

[0066] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 100°C for 10 hours to obtain a new granular negative electrode material.

[0067] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 88%, and the mass fraction of the three-dimensional network structure in the pore accounts for 12%.

[0068] The obtained material is used as the negative electrode material. The obtained negative electrode material, conductive additive carbon black, and adhesive (sodium carboxymethyl cellulose and styrene-butadiene rubber with a mass ratio of 1:0.8) are weighed in a ratio of 95:2.5:2.5, and the slurry is prepared in a pulping machine at room temperature. The prepared slurry is evenly applied on the copper foil, placed in a blast drying oven at 55°C for 2 hours, cut into circular pole pieces with a diameter of 14 mm, and vacuum dried in a vacuum drying oven at 100°C for 8 hours. The dried pole pieces are then transferred to the glove box for standby use for battery assembly.

[0069] The assembly of the simulated battery was carried out in a glove box containing a high-purity Ar atmosphere, using metallic lithium as the counter electrode and a 1 mol / L Li PF6 solution in ethylene carbonate (EC) / dimethyl carbonate (DMC) / diethyl carbonate (DEC) (volume ratio 1:1:1) as the electrolyte to assemble the battery. The constant current charge and discharge mode test was carried out using a charge and discharge instrument, with a discharge cut-off voltage of 0.005V and a charge cut-off voltage of 1.5V. The charge and discharge test was carried out at a current density of C / 10. The test results are recorded in Table 1.

[0070] Comparative Example 1

[0071] Step 21: Add 10 g of NaOH into 45 mL of acetone solution and stir at 60 r / min for 1 hour;

[0072] Step 22: Let stand for 100 hours;

[0073] Step 23: calcining the dark brown mixture obtained by standing at 800° C. for 6 hours to obtain carbon point modified particles;

[0074] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 100°C for 10 hours to obtain comparative material 1.

[0075] Comparative Example 2

[0076] Step 1 is the same as in Example 1, and the preparation method of step 2 is as follows:

[0077] Step 21: Add 10 g of NaOH to 45 mL of acetone solution, add the activated 7-micron particles, and mix and stir at 60 r / min for 1 hour;

[0078] Step 22: Filter out the 7-micron particles and calcine them at 800°C for 6 hours;

[0079] Step 23: Wash the particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 100°C for 10 hours to obtain comparative material 2.

[0080] Example 2

[0081] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0082] Step 21: Add 15 g of NaOH into 45 mL of acetone solution and stir at 60 r / min for 1 hour;

[0083] Step 22: placing the activated 10-micron particles in a mixture of NaOH and acetone and leaving it to stand for 120 hours;

[0084] Step 23: calcining the dark brown mixture obtained by standing at 800° C. for 8 hours to obtain carbon point modified particles;

[0085] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 70°C for 12 hours to obtain a new granular negative electrode material.

[0086] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 85%, and the mass fraction of the three-dimensional network structure in the pore accounts for 15%.

[0087] Example 3

[0088] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0089] Step 21: Add 8 g of NaOH into 40 mL of acetone solution and stir at 60 r / min for 1 hour;

[0090] Step 22: placing the activated 18-micron particles in a mixture of NaOH and acetone and leaving it to stand for 200 hours;

[0091] Step 23: calcining the dark brown mixture obtained by standing at 400° C. for 5 hours to obtain carbon point modified particles;

[0092] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 80°C for 12 hours to obtain a new granular negative electrode material.

[0093] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 85%, and the mass fraction of the three-dimensional network structure in the pore accounts for 15%.

[0094] Example 4

[0095] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0096] Step 21: Add 16 g of NaOH into 40 mL of acetone solution and stir at 60 r / min for 1 hour;

[0097] Step 22: placing the activated 14-micron particles in a mixture of NaOH and acetone and leaving it to stand for 160 hours;

[0098] Step 23: calcining the dark brown mixture obtained by standing at 600° C. for 6 hours to obtain carbon point modified particles;

[0099] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 90°C for 8 hours to obtain a new granular negative electrode material.

[0100] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 80%, and the mass fraction of the three-dimensional network structure in the pores accounts for 20%.

[0101] Example 5

[0102] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0103] Step 21: Add 8 g of NaOH into 45 mL of acetone solution and stir at 60 r / min for 1 hour;

[0104] Step 22: placing the activated 12-micron particles in a mixture of NaOH and acetone and leaving it to stand for 180 hours;

[0105] Step 23: calcining the dark brown mixture obtained by standing at 800° C. for 5 hours to obtain carbon point modified particles;

[0106] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 80°C for 12 hours to obtain a new granular negative electrode material.

[0107] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 87%, and the mass fraction of the three-dimensional network structure in the pore accounts for 13%.

[0108] Example 6

[0109] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0110] Step 21: Add 10 g of NaOH to 38 mL of acetone solution and stir at 60 r / min for 1 hour;

[0111] Step 22: placing the activated 9-micron particles in a mixture of NaOH and acetone and leaving it to stand for 150 hours;

[0112] Step 23: calcining the dark brown mixture obtained by standing at 500° C. for 8 hours to obtain carbon point modified particles;

[0113] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 70°C for 12 hours to obtain a new granular negative electrode material.

[0114] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 83%, and the mass fraction of the three-dimensional network structure in the pore accounts for 17%.

[0115] Example 7

[0116] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0117] Step 21: Add 7 g of NaOH to 39 mL of acetone solution and stir at 60 r / min for 1 hour;

[0118] Step 22: placing the activated 11-micron particles in a mixture of NaOH and acetone and leaving it to stand for 120 hours;

[0119] Step 23: calcining the dark brown mixture obtained by standing at 800° C. for 8 hours to obtain carbon point modified particles;

[0120] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 70°C for 12 hours to obtain a new granular negative electrode material.

[0121] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 83%, and the mass fraction of the three-dimensional network structure in the pore accounts for 17%.

[0122] Example 8

[0123] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0124] Step 21: Add 8 g of NaOH into 40 mL of acetone solution and stir at 60 r / min for 1 hour;

[0125] Step 22: placing the activated 13-micron particles in a mixture of NaOH and acetone and leaving it to stand for 160 hours;

[0126] Step 23: calcining the dark brown mixture obtained by standing at 600° C. for 4 hours to obtain carbon point modified particles;

[0127] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 90°C for 3 hours to obtain a new granular negative electrode material.

[0128] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 89%, and the mass fraction of the three-dimensional network structure in the pore accounts for 11%.

[0129] Example 9

[0130] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0131] Step 21: Add 8 g of NaOH into 40 mL of acetone solution and stir at 60 r / min for 1 hour;

[0132] Step 22: placing the activated 10-micron particles in a mixture of NaOH and acetone and leaving it to stand for 200 hours;

[0133] Step 23: calcining the dark brown mixture obtained by standing at 600° C. for 8 hours to obtain carbon point modified particles;

[0134] Step 24: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 80°C for 12 hours to obtain a new granular negative electrode material.

[0135] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 85%, and the mass fraction of the three-dimensional network structure in the pore accounts for 15%.

[0136] Example 10

[0137] This embodiment provides a method for preparing a novel granular negative electrode material. Step 1 is the same as that of Embodiment 1, and the preparation method of step 2 is as follows:

[0138] Step 1: Add 11 g NaOH into 45 mL acetone solution and stir at 60 r / min for 1 hour;

[0139] Step 2: Place the activated 8-micron particles in a mixture of NaOH and acetone and leave it for 200 hours;

[0140] Step 3: calcining the dark brown mixture obtained by standing at 800° C. for 3 hours to obtain carbon point modified particles;

[0141] Step 4: Wash the carbon dot modified particles with 1 mol / L hydrochloric acid solution, then wash with pure water, and finally dry at 80°C for 6 hours to obtain a new granular negative electrode material.

[0142] In the obtained samples, the mass fraction of the three-dimensional pore structure accounts for 84%, and the mass fraction of the three-dimensional network structure in the pore accounts for 16%.

[0143] For each embodiment and comparative example, button cells were assembled according to the method of the above embodiment 1, and their electrochemical properties were evaluated by testing and recorded in Table 1.

[0144]

[0145] Table 1

[0146] From the data comparison in Table 1, it can be seen that the granular negative electrode material with a three-dimensional pore structure modified with carbon dots and a cross-linked network structure in the pores provided in the embodiment of the present invention has a higher specific capacity and cycle capacity retention rate than that of Comparative Example 1 and Comparative Example 2. The present invention is modified by constructing a carbon dot cross-linked network structure inside the three-dimensional pore structure. The network cross-linked structure composed of carbon dots has a large specific surface area and rich oxygen-containing functional groups, which improves the sodium storage capacity of the negative electrode material. Its support for the inside of the three-dimensional pore structure also prolongs the cycle life of the negative electrode material.

[0147] The specific embodiments of the present invention described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a novel granular negative electrode material, characterized in that: The preparation method comprises: The phenolic resin solution was prepared by polycondensation reaction of phenol and formaldehyde using NH3·H2O as catalyst. Adding a polymer to the phenolic resin solution and stirring the mixture to uniformly mix the polymer and the phenolic resin to obtain a mixed solution; adding hydrochloric acid to the mixed solution to neutralize the mixed solution, and drying the neutralized solution to remove the solvent to obtain a solid resin mixture; After the solid resin mixture is cured, it is broken into small particles of 7-18 microns, and then placed in an activation furnace and activated by passing water vapor to obtain an activated product with a three-dimensional pore structure; The activated product is placed in a mixture of NaOH and a carbon source to generate carbon dots in situ in the pore structure of the three-dimensional pore structure particles, and the three-dimensional pore structure particles are allowed to stand to obtain carbon dot-modified particles; calcining the carbon dot-modified three-dimensional pore structure particles to obtain three-dimensional pore structure particles having a cross-linked network structure inside; The three-dimensional pore structure particles with a cross-linked network structure inside are acid-washed and water-washed, and then dried to obtain the novel granular negative electrode material.

2. The preparation method according to claim 1, characterized in that: The mass ratio of phenol to formaldehyde is 1:1-1:1.5; The reaction temperature of the polycondensation reaction is 60° C.-80° C., and the reaction time is 3-8 hours.

3. The preparation method according to claim 1, characterized in that: The polymer includes any one of polyethylene glycol, polypropylene ether, methyl methacrylate or benzoyl peroxide; The mass fraction of the polymer accounts for 5%-15% of the phenolic resin solution; The stirring temperature for adding the polymer into the phenolic resin solution and stirring is 60° C.-80° C., and the stirring time is 1-3 hours.

4. The preparation method according to claim 1, characterized in that: The curing temperature is 130°C-180°C and the curing time is 3-8 hours; The activation temperature is 800° C.-900° C., and the activation time is 1-3 hours.

5. The preparation method according to claim 1, characterized in that: The carbon source includes any one of methanol, ethanol, formaldehyde, acetaldehyde or glucose; The activated product is placed in a mixture of NaOH and a carbon source and stirred for more than 1 hour. Hydroxyl ions (OH) are generated in the three-dimensional pore structure of the activated product. - ) adsorption, which enhances the surface activity and at the same time - ) mediates the reduction reaction of the carbonyl group (C=O) in the carbon source to form carbon dots; The standing time is 100-200 hours.

6. The preparation method according to claim 1, characterized in that: The porosity of the activated product is greater than 70%, the average pore size is greater than 10 nm, and there are macropores or mesopores with a pore size of 30-200 nm.

7. The preparation method according to claim 1, characterized in that: The calcination atmosphere is argon or nitrogen or a combination of the two, with a flow rate of 2-10 L / min; the heating rate is 5-10°C / min; the calcination temperature is 400-800°C, and the calcination time is 2-8 hours, so that the carbon dots are solidified and form a cross-linked structure.

8. The preparation method according to claim 1, characterized in that: The acid washing specifically includes washing with a hydrochloric acid solution; the water washing specifically includes washing with pure water; and the drying specifically includes drying at 70-100° C. for 3-12 hours.

9. A novel granular negative electrode material prepared by the preparation method according to any one of claims 1 to 8; The novel granular negative electrode material is a granular material composed of a three-dimensional pore structure and a cross-linked network structure within the pores.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the novel granular negative electrode material as described in claim 9 above.

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