Super-capacity and overpressure graphite negative electrode material and preparation method thereof

Abstract

The invention relates to the field of negative electrode materials, and provides a super-capacity and overpressure graphite negative electrode material which is prepared by modifying graphite through organic amine hydrochloride, so that the surface of the graphite carries a certain amount of active groups, and the active groups are chemically bonded with resin which is subsequently coated on the surface of the graphite, so that the super-capacity and overpressure graphite negative electrode material is obtained. The chemical bonding greatly enhances the interface bonding strength of the resin and the graphite, the resin forms a coating layer with a stable structure on the surface of the graphite, and the negative electrode material obtained after graphitization treatment has the characteristics of high capacity, high compaction, good rate capability, strong electrolyte compatibility and the like.

Description

Technical Field

[0001] This invention relates to the field of anode materials, and more particularly to a supercapacitive and superpressure graphite anode material and its preparation method. Background Technology

[0002] In the field of batteries, especially lithium-ion and sodium-ion batteries, the anode material has a significant impact on battery performance. Graphite is the primary anode material for these two types of batteries, but graphite anodes often have some unavoidable defects, as follows: (1) Natural graphite is widely found in nature and has the characteristics of high capacity and high compaction. Its price is lower than that of artificial graphite. However, the large surface defects of natural graphite and its poor compatibility with electrolytes result in poor cycle performance and rate performance of pure natural graphite. (2) Artificial graphite is prepared by crushing, pulverizing, granulating, shaping and graphitizing processes. However, the capacity of artificial graphite has almost reached a bottleneck. It is difficult for conventional needle coke graphite to reach a capacity of 360mAh / g. Increasing the specific capacity requires increasing the power consumption during graphitization, which will greatly increase the cost. (3) At present, the modification of graphite is limited to acid oxidation or resin coating, which has a limited effect on improving the performance of graphite.

[0003] Therefore, there is an urgent need for a method to modify graphite to greatly improve the electrochemical performance of graphite anode materials. Summary of the Invention

[0004] To address the technical problems existing in the background art, this invention proposes a method for preparing supercapacitive and superpressure graphite anode materials, comprising the following steps: S1. After mixing natural graphite with an organic amine hydrochloride solution, solid-liquid separation is performed to obtain modified natural graphite. S2. Mix the modified natural graphite and artificial graphite to obtain a modified natural graphite-artificial graphite composite material. S3. The modified natural graphite-artificial graphite composite material is granulated with resin to obtain a graphite-resin composite material. S4. Graphitize the graphite-resin composite material to obtain a supercapacitive and superpressure graphite anode material.

[0005] In this invention, modification can increase the affinity of graphite surface for resin. The naphthalene ring in the modifier molecule is adsorbed on the surface of natural graphite through π-π conjugation, while the active groups at the other end, such as amino groups, are chemically bonded to the resin, enhancing the interfacial bonding force between the resin and graphite. Graphitization forms a structurally stable coating structure, significantly improving the rate performance of the negative electrode material.

[0006] In step S1, the mass-to-volume ratio of the natural graphite to the organic amine hydrochloride solution is 100-300 g / L; Preferably, the mass-to-volume ratio of the natural graphite to the organic amine hydrochloride solution is 200 g / L.

[0007] In step S1, the concentration of the organic amine hydrochloride solution is ≥1 wt%.

[0008] In step S1, the organic amine hydrochloride is naphthylethylenediamine hydrochloride or 5-[(2-aminoethyl)amino]-1-naphthoic acid dihydrochloride.

[0009] In step S2, the mass ratio of modified natural graphite to artificial graphite is 1:5-10; Preferably, the mass ratio of the modified natural graphite to the artificial graphite is 1:9.

[0010] In this invention, the modified natural graphite is mixed with artificial graphite, which combines the advantages of both in terms of high capacity and stability.

[0011] In step S3, the mass ratio of the modified natural graphite-artificial graphite composite material to the resin during granulation is 1:0.1-0.14; the resin is melamine-formaldehyde resin.

[0012] In step S3, the granulation temperature is 120-200℃ and the granulation time is 6-8h.

[0013] In step S4, the graphitization temperature is ≥3000℃ and the graphitization time is 24-36h.

[0014] In this invention, when the modifier is selected as 5-[(2-aminoethyl)amino]-1-naphthoic acid dihydrochloride, the modifier simultaneously contains both amino and carboxyl active groups, which can participate in the curing reaction of melamine-formaldehyde resin. First, the carboxyl group can act as a catalyst, activating the hydroxymethyl group in melamine-formaldehyde resin and promoting the chemical bonding between the resin and the modifier. Secondly, as an acidic group, the carboxyl group reduces the protonation degree of the amino group on the modifier molecule through intramolecular acid-base balance, effectively increasing the reactivity of the amino group and promoting the curing and crosslinking of the amino group with melamine-formaldehyde resin on the graphite surface.

[0015] In step S4, before obtaining the supercapacitive and superpressure graphite anode material, demagnetization sieving is also included; Preferably, the screening is achieved through a double-layer screen; More preferably, the mesh counts of the double-layer screen are 325 mesh and 200 mesh, respectively.

[0016] In this invention, the magnetic material removed by sieving is ≤0.3ppm.

[0017] The present invention also proposes a supercapacitive and superpressure graphite anode material, which is prepared by the preparation method described in any one of claims 1-9.

[0018] The beneficial effects of this invention are as follows: by modifying natural graphite with organic amine hydrochloride, optimizing the ratio of natural graphite to artificial graphite, and then granulating and graphitizing graphite and resin, the resulting negative electrode material has the characteristics of high capacity and high compaction, good rate performance, and strong electrolyte compatibility. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0022] Example 1 This embodiment proposes a supercapacitive and superpressure graphite anode material, the preparation method of which is shown below: (1) Take the finished natural graphite (specific gravity 1.8 ± 0.2 m) 2 The modified natural graphite was mixed with an aqueous solution of naphthylethylenediamine hydrochloride (1wt%) at a mass-volume ratio of 200 g / L, stirred for 30 min, and then quickly rinsed once with deionized water. The washed natural graphite was then dried at 50 °C for 1 h to obtain the modified natural graphite. (2) The modified natural graphite and artificial graphite (1.5±0.3m) were mixed. 2 The modified natural graphite-artificial graphite composite material was obtained by mixing the particles (1.2±0.1 g / cc, 9.0±1 μm) in a mixer at a mass ratio of 1:9. (3) The modified natural graphite-artificial graphite composite material and melamine-formaldehyde resin were mixed at a mass ratio of 1:0.1 and then added to a small horizontal granulation kettle for granulation to obtain graphite-resin composite material. The granulation temperature was 150℃ and the granulation time was 7h.

[0023] (4) The graphite-resin composite material is placed in a vacuum graphitization furnace for high-temperature graphitization to obtain the precursor of the negative electrode material. The graphitization temperature is 3000℃ and the graphitization time is 24h.

[0024] (5) The precursor of the negative electrode material is demagnetized by double-layer sieve (325 mesh + 200 mesh) to obtain the supercapacitive and superpressure graphite negative electrode material.

[0025] Example 2 This embodiment proposes a supercapacitive and superpressure graphite anode material, the preparation method of which is shown below: (1) Take the finished natural graphite (specific gravity 1.8 ± 0.2 m) 2 The modified natural graphite was mixed with an aqueous solution of naphthylethylenediamine hydrochloride (1wt%) at a mass-volume ratio of 200 g / L, stirred for 40 min, and then quickly rinsed once with deionized water. The washed natural graphite was dried at 50 °C for 1 h to obtain the modified natural graphite. (2) The modified natural graphite and artificial graphite (1.5±0.3m) were mixed. 2 The modified natural graphite-artificial graphite composite material was obtained by mixing the particles (1.2±0.1 g / cc, 9.0±1 μm) in a mixer at a mass ratio of 1:7. (3) The modified natural graphite-artificial graphite composite material and melamine-formaldehyde resin were mixed at a mass ratio of 1:0.12 and then added to a small horizontal granulation kettle for granulation to obtain graphite-resin composite material. The granulation temperature was 160℃ and the granulation time was 7h.

[0026] (4) The graphite-resin composite material is placed in a vacuum graphitization furnace for high-temperature graphitization to obtain the precursor of the negative electrode material. The graphitization temperature is 3000℃ and the graphitization time is 24h.

[0027] (5) The precursor of the negative electrode material is demagnetized by double-layer sieve (325 mesh + 200 mesh) to obtain the supercapacitive and superpressure graphite negative electrode material.

[0028] Example 3 This embodiment proposes a supercapacitive and superpressure graphite anode material, the preparation method of which is shown below: The finished natural graphite (specific gravity 1.8 ± 0.2 m) 2 The modified natural graphite was mixed with an aqueous solution of 5-[(2-aminoethyl)amino]-1-naphthoic acid dihydrochloride (1wt%) at a mass-volume ratio of 200 g / L. After stirring for 30 min, the mixture was quickly rinsed once with deionized water. The washed natural graphite was then dried at 50 °C for 1 h to obtain the modified natural graphite. The preparation method of 5-[(2-aminoethyl)amino]-1-naphthoic acid dihydrochloride is shown below: 5-Amino-1-naphthoic acid and anhydrous potassium carbonate were added to a round-bottom flask at a mass ratio of 1:1. Then, 20 times the mass of DMF of 5-amino-1-naphthoic acid was added. After stirring, 0.7 times the mass of bromoacetonitrile of 5-amino-1-naphthoic acid was slowly added dropwise. The mixture was stirred at 60°C for 8 hours and then filtered and washed to obtain 5-(cyanomethylamino)-1-naphthoic acid. 5-(cyanomethylamino)-1-naphthoic acid, methanol solution, and Raney nickel were then stirred evenly at a mass ratio of 1:15:0.2. After hydrogenation for 8 hours, 5-(2-aminoethylamino)-1-naphthoic acid was obtained. Finally, 5-(2-aminoethylamino)-1-naphthoic acid was acidified in a 4 mol / L hydrochloric acid aqueous solution to obtain 5-[(2-aminoethyl)amino]-1-naphthoic acid dihydrochloride. (2) The modified natural graphite and artificial graphite (1.5±0.3m) were mixed. 2 The modified natural graphite-artificial graphite composite material was obtained by mixing the particles (1.2±0.1 g / cc, 9.0±1 μm) in a mixer at a mass ratio of 1:9. (3) The modified natural graphite-artificial graphite composite material and melamine-formaldehyde resin were mixed at a mass ratio of 1:0.1 and then added to a small horizontal granulation kettle for granulation to obtain graphite-resin composite material. The granulation temperature was 150℃ and the granulation time was 7h.

[0029] (4) The graphite-resin composite material is placed in a vacuum graphitization furnace for high-temperature graphitization to obtain the precursor of the negative electrode material. The graphitization temperature is 3000℃ and the graphitization time is 24h.

[0030] (5) The precursor of the negative electrode material is demagnetized by double-layer sieve (325 mesh + 200 mesh) to obtain the supercapacitive and superpressure graphite negative electrode material.

[0031] Comparative Example 1 This comparative example presents a supercapacitive and superpressure graphite anode material, the preparation method of which is the same as that of Example 1, except that step (1) is omitted.

[0032] In Comparative Example 1, the natural graphite was mixed with artificial graphite without modification. When the resin coated the graphite surface, the coating was not tight enough and it was easy to fall off during the subsequent graphitization process. The rate performance of the battery decreased by 13.8% compared with Example 1.

[0033] Comparative Example 2 This comparative example proposes a supercapacitive and superpressure graphite anode material, the preparation method of which is the same as that of Example 1, except that the melamine-formaldehyde resin in step (3) is omitted.

[0034] In Comparative Example 2, the granulation of the modified natural graphite and artificial graphite mixture was not coated with resin, resulting in a significantly reduced yield of the final product.

[0035] Comparative Example 3 This comparative example proposes a supercapacitive and superpressure graphite anode material, the preparation method of which is the same as that of Example 1, except that the melamine-formaldehyde resin in steps (1) and (3) is omitted.

[0036] In Comparative Example 3, the graphite was neither modified with organic amine hydrochloride nor encapsulated with resin during granulation, resulting in the worst performance of the final graphite anode material.

[0037] Five batches of negative electrode materials were prepared for each of the above embodiments and comparative examples. That is, five batches of negative electrode materials were prepared by the preparation method of each embodiment, and five batches of negative electrode materials were also prepared by the preparation method of the comparative examples. The negative electrodes and materials prepared above were used as negative electrodes to make coin cells (half cells). The electrode sheet coated with the above hard carbon was used as the negative electrode, the sodium sheet was used as the positive electrode, the polyethylene PE separator was used, and 1 mol / L NaPF6 was used as the electrolyte to make sodium ion half cells. The first discharge capacity and the first charge capacity of each batch of coin sodium ion half cells were measured, as detailed in Table 1. Table 1. Electrical performance test data of the negative electrode materials in each embodiment and comparative example.

[0038] As shown in Table 1, the negative electrode materials obtained in the above embodiments achieve the following performance: the average first charge capacity is greater than 362 mAh / g, which is close to the theoretical upper limit, and the diffusion coefficient is optimal (i.e., the rate performance is optimal).

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A preparation method of a graphite negative electrode material with super-capacity and super-pressure, characterized in that, The method comprises the following steps: S1, mixing natural graphite with an organic amine hydrochloride solution, and then performing solid-liquid separation to obtain modified natural graphite; S2, mixing the modified natural graphite with artificial graphite to obtain a modified natural graphite-artificial graphite composite material; S3, granulating the modified natural graphite-artificial graphite composite material with resin to obtain a graphite-resin composite material; S4, graphitizing the graphite-resin composite material to obtain an ultra-capacity and ultra-pressure graphite negative electrode material.

2. The method of claim 1, wherein the graphite negative electrode material having an ultra-high capacity and an ultra-high pressure is prepared by the steps of: In step S1, the mass-volume ratio of the natural graphite to the organic amine hydrochloride solution is 100-300 g / L. ​ Preferably, the mass-volume ratio of the natural graphite to the organic amine hydrochloride solution is 200 g / L.

3. The method for preparing the supercapacitive and superpressure graphite anode material according to claim 1 or 2, characterized in that, In step S1, the concentration of the organic amine hydrochloride solution is ≥1 wt%.

4. The method of claim 1-3, wherein the method is characterized by, In step S1, the organic amine hydrochloride is naphthyl ethylenediamine hydrochloride or 5-[(2-aminoethyl)amino]-1-naphthalene carboxylic acid dihydrochloride.

5. The method of claim 1-4, wherein the method is characterized by, In step S2, the mass ratio of the modified natural graphite to the artificial graphite is 1:5-10. Preferably, the mass ratio of the modified natural graphite to the artificial graphite is 1:

9.

6. The method of claim 1-5, wherein the method is characterized by, In step S3, the mass ratio of the modified natural graphite-artificial graphite composite material to the resin during granulation is 1:0.1-0.14; and the resin is melamine formaldehyde resin.

7. The method of claim 1-6, wherein the method is characterized by, In step S3, the granulation temperature is 120-200°C, and the granulation time is 6-8 h.

8. The method of claim 1-7, wherein the method is characterized by, In step S4, the graphitization temperature is ≥3000°C, and the graphitization time is 24-36 h.

9. The method for preparing the supercapacitive and superpressure graphite anode material according to claim 8, characterized in that, In step S4, the ultra-capacity and ultra-pressure graphite negative electrode material is obtained by further performing magnetic screening and screening. Preferably, the screening is realized by a double-layer screen. Further preferably, the mesh numbers of the double-layer screen are 325 mesh and 200 mesh, respectively.

10. A graphite negative electrode material with super-capacitive super-pressures, characterized in that, The ultra-capacity and ultra-pressure graphite negative electrode material is prepared by the method of any one of claims 1-9.

Images