Novel graphite negative electrode material and preparation method and application thereof

Abstract

The invention discloses a novel graphite negative electrode material as well as a preparation method and application thereof. The novel graphite negative electrode material comprises a three-dimensional porous material with micropores, mesopores and macropores; wherein the aperture of the novel graphite negative electrode material is between 0.1 nm and 80 nm, the micropore rate is between 30% and 80%, the mesopore rate is between 20% and 50%, and the macropore rate is between 10% and 40%; the total pore volume of the novel graphite negative electrode material is between 0.5 cm < 3 > / g and 8 cm < 3 > / g, and the specific surface area is between 500 m < 2 > / g and 3500 m < 2 > / g; the novel graphite negative electrode material is obtained by carrying out oxidation and high-temperature expansion treatment on graphite to form mesopores and macropores and then forming micropores by using a pore-forming agent; the novel graphite negative electrode material disclosed by the invention is applied to a secondary battery, so that the polarization effect of the battery is effectively reduced, rapid transmission and storage of ions are facilitated, and the specific capacity and rate capability of the battery are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a novel graphite anode material, a preparation method thereof, and an application thereof. Background Art

[0002] Graphite is a substance composed of single carbon atoms. On the layer plane, carbon atoms are combined by σ bonds formed by SP2 hybrid orbitals and delocalized π bonds formed by Pz orbitals to form a firm hexagonal grid-like plane. Graphite materials are rich in sources and low in price. When applied to battery anode materials, they exhibit advantages such as high reversible capacity, low charge and discharge voltage platform, no voltage hysteresis, and good electrical conductivity, and have been widely studied.

[0003] However, current graphite anodes have problems such as low power density and low rate performance, which severely limit the fast charging of power lithium batteries. To improve the fast insertion and extraction performance of graphite anodes, the porosity of graphite materials can be increased to alleviate this problem.

[0004] Chinese Patent CN114068885A (publication date: February 18, 2022) provides a graphite material with a porous carbon layer. The graphite material includes a graphite matrix and a porous carbon layer coated on the surface of the graphite matrix. The thickness of the porous carbon layer is 1nm - 20nm. However, the material protected by this patent has a relatively low specific surface area after pore formation, and the formation of porous carbon is limited to the surface.

[0005] Chinese Patent CN107305949A (publication date: October 31, 2017) etches metal or metal compounds on the layered surface and end faces of graphite to obtain more pores, increasing the specific surface area of graphite without significantly reducing its electrical conductivity. However, the specific surface area of this porous graphite is 1m 3 / g - 8m 3 / g, and the pore-forming effect is limited. Therefore, porous graphite with moderate pore size and relatively high specific surface area is needed to improve the rate performance of the material. Summary of the Invention

[0006] Embodiments of the present invention provide a novel graphite anode material, a preparation method thereof, and an application thereof. By forming a three-dimensional porous graphite material with micropores, mesopores, and macropores in raw graphite, a novel graphite anode material with a high specific surface area and a low expansion rate is obtained. Among them, micropores can store lithium ions to improve the capacity of the material; mesopores are beneficial to the diffusion of ions, thereby improving the rate performance; macropores can increase the contact area between the material and the electrolyte, thereby reducing the distance of ion diffusion and increasing the diffusion rate. When the novel graphite anode material of the present invention is used in secondary batteries, the specific capacity and rate performance of the battery can be improved.

[0007] To this end, in a first aspect, embodiments of the present invention provide a novel graphite anode material, which is a three-dimensional porous material including micropores, mesopores, and macropores;

[0008] The microporosity of the novel graphite anode material is between 30% and 80%, the mesoporosity is between 20% and 50%, and the macroporosity is between 10% and 40%;

[0009] The total pore volume of the novel graphite anode material is between 0.5 cm 3 / g and 8 cm 3 / g;

[0010] The specific surface area of the novel graphite anode material is between 500 m 2 / g and 3500 m 2 / g;

[0011] The pore diameter of the novel graphite anode material is between 0.1 nm and 80 nm;

[0012] The novel graphite anode material is obtained by oxidizing graphite, performing high-temperature expansion treatment to form mesopores and macropores, and then using a pore-forming agent to form micropores.

[0013] Preferably, the particle size D 50 of the novel graphite anode material is between 7 μm and 28 μm.

[0014] Preferably, the graphite includes one or more of dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite.

[0015] In a second aspect, embodiments of the present invention provide a preparation method of the novel graphite anode material described in the first aspect, and the preparation method includes:

[0016] Step S1: Add an oxidant to the graphite, stir at a certain temperature to cause an oxidation reaction between the graphite and the oxidant, and obtain a mixed solution containing precipitates;

[0017] Step S2: Filter the mixed solution containing precipitates, wash the precipitates with water until neutral after obtaining the precipitates, and perform drying treatment to obtain a solid substance;

[0018] Step S3: Perform high-temperature expansion treatment on the solid substance to obtain an expanded product containing mesopores and macropores;

[0019] Step S4: Mix the expanded product with a pore-forming agent, and obtain a precursor material after mixing evenly;

[0020] Step S5: Subject the precursor material to high-temperature activation treatment. After cooling to room temperature and discharging, use hydrochloric acid pickling to remove the residual pore-forming agent to form a microporous structure, and obtain a novel graphite anode material after drying.

[0021] Preferably, the graphite includes one or more of the following: dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite;

[0022] The oxidant is a solution with a concentration of 5wt% - 30wt%; the solute of the solution includes KMnO 4 , K 2 CrO 7 , NaNO 3 , KClO 4 , (NH 4 ) 2 S 2 , HClO 4 , H 2 O 2 , HNO 3 or one or more of them; the solvent of the solution is deionized water;

[0023] The mass ratio of the graphite to the solute of the oxidant is [5:1] to [1:2];

[0024] The pore-forming agent includes one or more of the following: potassium hydroxide, potassium oxide, potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium oxide, sodium carbonate, sodium bicarbonate, metal nickel particles, metal iron particles, metal cobalt particles, and metal copper particles;

[0025] The mass ratio of the swelling agent to the pore-forming agent is [4 - 19]:1.

[0026] Preferably, the certain temperature is 25°C to 60°C; the stirring time in step S1 is 0.5 hours to 3 hours, and the rotation speed is 30 rpm to 200 rpm;

[0027] The drying temperature in step S2 is 80°C to 120°C, and the time is 2 hours to 6 hours;

[0028] The temperature of the high-temperature swelling treatment is 400°C to 1000°C, and the time of the high-temperature swelling treatment is 30 seconds to 90 seconds.

[0029] Preferably, the mixing method in step S4 includes solid-phase mixing or liquid-phase mixing; among them, the solid-phase mixing includes grinding mixing and / or ball milling mixing; the specific method of liquid-phase mixing is: dissolve the swelling agent and the pore-forming agent in deionized water, fully mix them evenly, and obtain the precursor material after drying;

[0030] The temperature range of the high-temperature activation treatment is from 500°C to 900°C, and the time of the high-temperature activation treatment is from 0.5 hours to 5 hours.

[0031] In a third aspect, an embodiment of the present invention provides a negative electrode sheet, which includes the novel graphite negative electrode material described in the first aspect above.

[0032] Preferably, the negative electrode sheet includes a silicon-carbon material formed by compounding the novel graphite negative electrode material with silicon by chemical vapor deposition, or a sulfur-carbon material formed by compounding the novel graphite negative electrode material with sulfur by chemical vapor deposition.

[0033] In a fourth aspect, an embodiment of the present invention provides a secondary battery, which includes the negative electrode sheet described in the third aspect above.

[0034] The present invention provides a novel graphite negative electrode material, its preparation method and application. First, an oxidant is added to the graphite raw material to undergo an oxidation reaction to obtain a precipitate. The precipitate is subjected to high-temperature expansion treatment to form mesopores and macropores. Then, the expanded product is mixed with a pore-forming agent and subjected to high-temperature activation treatment. After washing the pore-forming agent with hydrochloric acid, micropores are formed, and finally a novel graphite negative electrode material with micropores, mesopores and macropores is obtained. The novel graphite negative electrode material has the characteristic of a high specific surface area, wherein the specific surface area is between 500 m 2 / g and 3500 m 2 / g, and the total pore volume is between 0.5 cm 3 / g and 8 cm 3 / g.

[0035] For the novel graphite negative electrode material provided by the present invention, the micropores can store lithium ions to improve the capacity of the material; the mesopores are beneficial to the diffusion of ions, thereby improving the rate performance; the macropores can increase the contact area between the material and the electrolyte, thereby reducing the distance of ion diffusion and increasing the diffusion rate. Therefore, using the novel graphite negative electrode material of the present invention in a secondary battery can improve the specific capacity and rate performance of the battery.

[0036] The present invention provides a preparation method of a novel graphite negative electrode material, which has simple operation, low production cost and is easy to realize large-scale production. Description of the Drawings

[0037] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0038] Figure 1 is a flowchart of the preparation method of the novel graphite negative electrode material provided by the embodiment of the present invention. Detailed Embodiments

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0040] An embodiment of the present invention provides a novel graphite anode material, which is a three-dimensional porous material including micropores, mesopores and macropores; the particle size D of the novel graphite anode material 50 is between 7 μm and 28 μm, preferably between 7 μm and 14 μm; the specific surface area of the novel graphite anode material is between 500 m 2 / g and 3500 m 2 / g, preferably between 800 m 2 / g and 1800 m 2 / g; the total pore volume of the novel graphite anode material is between 0.5 cm 3 / g and 8 cm 3 / g, preferably between 2 cm 3 / g and 5 cm 3 / g.

[0041] The pore diameter of the pores in the novel graphite anode material is between 0.1 nm and 80 nm. Among them, the pore diameter of the micropores is greater than or equal to 0.1 nm and less than or equal to 2 nm, and the porosity is between 30% and 80%; the pore diameter of the mesopores is greater than 2 nm and less than or equal to 50 nm, and the porosity is between 20% and 50%; the pore diameter of the macropores is greater than 50 nm and less than or equal to 80 nm, and the porosity is between 10% and 40%.

[0042] The novel graphite anode material of the present invention is obtained by oxidizing and high-temperature expanding graphite to form mesopores and macropores, and then using a pore-forming agent to form micropores. Among them, the graphite includes one or more of dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite.

[0043] An embodiment of the present invention provides a preparation method of the above novel graphite anode material, as Figure 1 shown, which specifically includes the following steps:

[0044] Step S1, adding an oxidant to the graphite and stirring at a certain temperature to make the graphite react with the oxidant to obtain a mixed solution containing precipitates;

[0045] Among them, the graphite includes one or more of dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite;

[0046] The oxidant is a solution with a concentration of 5 wt%-30 wt%; the solute of the solution includes KMnO 4 、K2 CrO 7 、NaNO 3 、KClO 4 、(NH 4 ) 2 S 2 、HClO 4 、H 2 O 2 、HNO 3 One or more of them; the solvent of the solution is deionized water;

[0047] The mass ratio of graphite to the solute of the oxidant is [5:1] to [1:2];

[0048] In this step, the specific conditions for stirring at a certain temperature are: the temperature is 25°C to 60°C, the stirring time is 0.5 hour to 3 hours, and the rotation speed is 30 rpm to 200 rpm.

[0049] Step S2, filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then obtain the solid substance after drying treatment;

[0050] Among them, the temperature of the drying treatment is 80°C to 120°C, and the time is 2 hours to 6 hours.

[0051] Step S3, perform high-temperature expansion treatment on the solid substance to obtain an expanded product containing mesopores and macropores;

[0052] Among them, the temperature of the high-temperature expansion treatment is 400°C to 1000°C, and the time of the high-temperature expansion treatment is 30 seconds to 90 seconds.

[0053] Step S4, mix the expanded product with the pore-forming agent, and obtain the precursor material after mixing evenly;

[0054] Among them, the mass ratio of the expanded product to the pore-forming agent is [4 - 19]:1;

[0055] The pore-forming agent includes: one or more of potassium hydroxide, potassium oxide, potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium oxide, sodium carbonate, sodium bicarbonate, metal nickel particles, metal iron particles, metal cobalt particles, and metal copper particles; among them, the particle size D 50 of metal nickel particles, metal iron particles, metal cobalt particles, and metal copper particles ranges from 2 nm to 50 nm, preferably 2 nm to 10 nm; since potassium hydroxide, potassium oxide, potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium oxide, sodium carbonate, and sodium bicarbonate are easily dispersed into molecular levels in water, the particle sizes of these pore-forming agents are not required.

[0056] The mixing methods include solid-phase mixing or liquid-phase mixing; among them, solid-phase mixing includes grinding mixing and / or ball milling mixing; specifically, the liquid-phase mixing method is: dissolving the bulking agent and the pore-forming agent in deionized water, fully mixing and drying to obtain a precursor material.

[0057] Step S5: Perform high-temperature activation treatment on the precursor material. After cooling to room temperature and discharging, use hydrochloric acid pickling to remove the residual pore-forming agent to form a microporous structure, and dry to obtain a novel graphite anode material.

[0058] Among them, the temperature range of the high-temperature activation treatment is 500°C to 900°C, and the time of the high-temperature activation treatment is 0.5 hour to 5 hours.

[0059] The novel graphite anode material obtained by the above preparation method in the embodiments of the present invention can be used as an anode active material to directly prepare an anode electrode sheet.

[0060] In an alternative solution, the novel graphite anode material of the present invention can be compounded with silicon by chemical vapor deposition to form a silicon-carbon material for preparing an anode electrode sheet, wherein silicon is deposited in the pores of the novel graphite anode material. Or, the novel graphite anode material of the present invention can be compounded with sulfur by chemical vapor deposition to form a sulfur-carbon material for preparing an anode electrode sheet, wherein sulfur is deposited in the pores of the novel graphite anode material.

[0061] The anode electrode sheet containing the novel graphite anode material of the present invention can be used to assemble a secondary battery, and the secondary battery includes but is not limited to a lithium-ion battery or a sodium-ion battery, which can significantly improve the specific capacity and rate performance of the secondary battery.

[0062] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the preparation process and characteristics of the novel graphite anode material of the present invention.

[0063] Example 1

[0064] This example provides a preparation process and performance test of a novel graphite anode material, and the specific process is as follows:

[0065] (1) Place 10 g of flake graphite with a particle size of 8 μm in a beaker, add H 2 O 2 , stir and react at 60°C for 3 hours, and the stirring speed is 100 rpm to cause the graphite to undergo an oxidation reaction with the oxidant to obtain a mixed solution containing precipitates; among them, the added H 2 O 2 is an aqueous solution with a concentration of 5 wt%, and the mass ratio of flake graphite to H 2 O 2 is [5:1].

[0066] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 100 °C for 4 hours to obtain a solid substance.

[0067] (3) Subject the solid substance to high-temperature expansion treatment at 600 °C for 30 seconds to obtain an expanded product containing mesopores and macropores.

[0068] (4) Mix the expanded product, the pore-forming agent potassium hydroxide, and metal iron particles evenly by grinding to obtain a precursor material; the mass ratio of the expanded product to the pore-forming agent is 7:1, the mass ratio of potassium hydroxide to metal iron particles is 1:1, and the particle size D of the metal iron particles 50 is 5 nm.

[0069] (5) Place the precursor material in a box furnace and perform high-temperature activation treatment at 900 °C for 3 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid to pickle and remove the residual pore-forming agent to form a microporous structure, and then dry it at 100 °C to obtain a novel graphite anode material.

[0070] The specific surface area of the novel graphite anode material prepared in this example is 1854 m 2 / g, the total pore volume is 3.175 cm 3 / g, the microporosity is 55.68%, the mesoporosity is 23.77%, the macroporosity is 20.55%, and the pore size range is between 0.43 nm and 58.7 nm.

[0071] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific process is as follows.

[0072] Battery assembly process: Weigh the novel graphite anode material, the conductive additive carbon black, and the binder (where the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber with a mass ratio of 1:0.8) according to a mass ratio of 95:2:3, and prepare a slurry using a pulper at room temperature. Coat the prepared slurry evenly on the copper foil with a coating thickness of 220 μm, place it in a blast drying oven and dry it at 55 °C for 2 hours, cut it into circular electrode sheets with a diameter of 14 mm, and then vacuum dry it at 100 °C for 8 hours in a vacuum drying oven. Immediately transfer the dried electrode sheets into a glove box for standby to assemble the battery.

[0073] The assembly of the simulated battery is carried out in a glove box containing a high-purity Ar atmosphere. Use metallic lithium as the counter electrode, and a solution of 1 mol / L LiPF 6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) / diethyl carbonate (DEC) (where the volume ratio of EC, DMC, and DEC is 1:1:1) as the electrolyte, and a polyethylene (PE) diaphragm as the separator to assemble the battery.

[0074] Test process: The constant current charge-discharge mode test was carried out using a charge-discharge instrument. The discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 2 V, and the regular charge test was carried out at a current density of C / 10; the charge rate test was carried out at current densities of 1C / 2C / 3C / 4C / 5C. The test results are shown in Table 1.

[0075] To better illustrate the effects of the embodiments of the present invention, Comparative Examples 1-2 were compared with Example 1 above.

[0076] Comparative Example 1

[0077] This comparative example provides a preparation process of a graphite negative electrode material. The difference from Example 1 is that step (4) was not carried out and the pore-forming agent was not added, and the other steps are the same as those in Example 1.

[0078] The specific surface area of the graphite negative electrode material prepared in this comparative example is 47 m 2 / g, the total pore volume is 2.681 cm 3 / g, the microporosity is 5.91%, the mesoporosity is 42.12%, the macroporosity is 51.97%, and the pore size range is between 5.12 nm and 57.9 nm.

[0079] Using the graphite negative electrode material of this comparative example as the negative electrode active material to prepare a negative electrode sheet and assemble it into a battery for testing. The specific assembly process and test process are the same as those in Example 1. The test data are shown in Table 1 for details.

[0080] Comparative Example 2

[0081] This comparative example provides a preparation process of a porous graphite negative electrode material. The specific process is as follows:

[0082] (1) Place 10 g of flake graphite with a particle size of 8 μm in a beaker, and mix the pore-forming agent potassium hydroxide and metal iron particles evenly by grinding. After mixing evenly, a precursor material is obtained; the mass ratio of the swelling agent to the pore-forming agent is 7:1, and the mass ratio of potassium hydroxide to metal iron particles is 1:1.

[0083] (2) Place the precursor material in a box furnace and perform high-temperature activation treatment at 900 °C for 3 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid to pickle to remove the residual pore-forming agent to form a microporous structure, and dry it at 100 °C to obtain a new graphite negative electrode material.

[0084] The specific surface area of the porous graphite negative electrode material prepared in this comparative example is 23 m 2 / g, the total pore volume is 0.13 cm 3 / g, and the pore size range is between 0.42 nm and 4.52 nm.

[0085] The porous graphite negative electrode material of this comparative example was used as the negative electrode active material to prepare a negative electrode sheet and assembled into a battery for testing. The specific assembly process and testing process were the same as those in Example 1. The test data are shown in Table 1 in detail.

[0086] Example 2

[0087] This example provides a preparation process and performance test of a novel graphite negative electrode material. The specific process is as follows:

[0088] (1) 10 g of cryptocrystalline graphite with a particle size of 10 μm was placed in a beaker, and an aqueous solution of KMnO with a concentration of 3 wt% was added. Stirring reaction was carried out at 25 °C for 0.5 hours, and the stirring speed was 100 rpm to cause an oxidation reaction between the graphite and the oxidant, obtaining a mixed solution containing precipitates, where the mass ratio of cryptocrystalline graphite to KMnO was [3:1]. 4 aqueous solution, stirred at 25 °C for 0.5 h, stirring speed was 100 rpm, to make the graphite react with the oxidant to obtain a mixed solution containing precipitates, where the mass ratio of cryptocrystalline graphite to KMnO 4 is [3:1].

[0089] (2) The mixed solution containing precipitates was filtered. After obtaining the precipitates, the precipitates were washed with water until neutral and dried at 110 °C for 2 hours to obtain a solid substance.

[0090] (3) The solid substance was subjected to high-temperature expansion treatment at 400 °C for 90 seconds to obtain an expanded product containing mesopores and macropores.

[0091] (4) The expanded product was mixed evenly with the pore-forming agent potassium hydroxide and metal nickel particles by grinding to obtain a precursor material; where the mass ratio of the expanded product to the pore-forming agent was 5:1, the mass ratio of potassium hydroxide to metal iron particles was 1:1, and the particle size D 50 of the metal nickel particles was 5 nm.

[0092] (5) The precursor material was placed in a box furnace and subjected to high-temperature activation treatment at 900 °C for 0.5 hours. After cooling to room temperature and discharging, it was pickled with 1 mol / L hydrochloric acid to remove the residual pore-forming agent to form a microporous structure, and then dried at 80 °C to obtain a novel graphite negative electrode material.

[0093] The specific surface area of the novel graphite negative electrode material prepared in this example was 783.97 m 2 / g, the total pore volume was 7.621 cm 3 / g, the microporosity was 33.27%, the mesoporosity was 33.52%, the macroporosity was 33.21%, and the pore size range was between 0.52 nm and 63.91 nm.

[0094] The novel graphite negative electrode material of this example was used as the negative electrode active material to prepare a negative electrode sheet and assembled into a battery for testing. The specific assembly process and testing process were the same as those in Example 1. The test data are shown in Table 1 in detail.

[0095] Example 3

[0096] This embodiment provides a preparation process and performance test of a novel graphite negative electrode material, and the specific process is as follows:

[0097] (1) Place 10 g of 15 μm flake graphite in a beaker and add 20 wt% HNO 3 The aqueous solution was stirred at 45°C for 2 hours at a stirring speed of 100 rpm to cause an oxidation reaction between graphite and the oxidant to obtain a mixed solution containing a precipitate, in which flake graphite and HNO 3 The mass ratio is [1:1].

[0098] (2) The mixed solution containing the precipitate was filtered to obtain the precipitate, which was then washed with water until neutralized and dried at 90° C. for 3 hours to obtain a solid substance.

[0099] (3) The solid material is subjected to a high-temperature puffing treatment at 800°C for 60 seconds to obtain a puffed material containing mesopores and macropores.

[0100] (4) The expanded material, the pore-forming agent potassium hydroxide, and the metal cobalt particles are mixed uniformly by grinding to obtain a precursor material; wherein the mass ratio of the expanded material to the pore-forming agent is 8:1, the mass ratio of potassium hydroxide to the metal iron particles is 1:1, and the particle size D of the metal cobalt particles is 50 It is 5nm.

[0101] (5) The precursor material was placed in a box furnace for high-temperature activation treatment at 500°C for 5 hours. After cooling to room temperature, the material was pickled with 1 mol / L hydrochloric acid to remove the residual pore-forming agent to form a microporous structure. After drying at 100°C, a new graphite negative electrode material was obtained.

[0102] The specific surface area of ​​the new graphite negative electrode material prepared in this example is 892 m 2 / g, and the total pore volume is 3.611cm 3 / g, the microporosity is 39.21%, the mesoporosity is 41.65%, the macroporosity is 19.14%, and the pore size ranges from 0.48nm to 66.31nm.

[0103] The novel graphite negative electrode material of this embodiment is used as the negative electrode active material to prepare the negative electrode plate and assemble it into a battery for testing. The specific assembly process and test process are the same as those in Example 1. The test data are detailed in Table 1.

[0104] Example 4

[0105] This embodiment provides a preparation process and performance test of a novel graphite negative electrode material, and the specific process is as follows:

[0106] (1) Place 10 g of dense crystalline graphite with a particle size of 18 μm in a beaker, add an aqueous solution of K 2 CrO 7 with a concentration of 30 wt%, and stir and react at 40 °C for 1.5 hours at a stirring speed of 150 rpm to cause an oxidation reaction between the graphite and the oxidant, obtaining a mixed solution containing a precipitate. The mass ratio of the dense crystalline graphite to K 2 CrO 7 is [3:1].

[0107] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 100 °C for 2 hours to obtain a solid substance.

[0108] (3) Subject the solid substance to high-temperature expansion treatment at 400 °C for 45 seconds to obtain an expanded product containing mesopores and macropores.

[0109] (4) Mix the expanded product, the pore-forming agent potassium carbonate, and metal iron particles evenly by grinding to obtain a precursor material. The mass ratio of the expanded product to the pore-forming agent is 11:1, the mass ratio of potassium hydroxide to metal iron particles is 1:1, and the particle size D 50 of the metal iron particles is 6 nm.

[0110] (5) Place the precursor material in a box furnace and perform high-temperature activation treatment at 600 °C for 1 hour. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid for pickling to remove the residual pore-forming agent to form a microporous structure, and then dry it at 80 °C to obtain a novel graphite anode material.

[0111] The specific surface area of the novel graphite anode material prepared in this example is 839 m 2 / g, the total pore volume is 6.943 cm 3 / g, the microporosity is 37.13%, the mesoporosity is 33.14%, the macroporosity is 29.73%, and the pore size range is between 0.51 nm and 71.56 nm.

[0112] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1 for details.

[0113] Example 5

[0114] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0115] (1) Place 10 g of needle coke artificial graphite with a particle size of 13 μm in a beaker, add an aqueous NaOH solution with a concentration of 10 wt%, and stir and react at 50 °C for 1 hour with a stirring speed of 100 rpm to cause the graphite to undergo an oxidation reaction with the oxidant, obtaining a mixed solution containing precipitates, where the mass ratio of the needle coke artificial graphite to NaOH is [2:1].

[0116] (2) Filter the mixed solution containing precipitates. After obtaining the precipitates, wash the precipitates with water until neutral, and then dry them at 110 °C for 3 hours to obtain a solid substance.

[0117] (3) Subject the solid substance to high-temperature expansion treatment at 900 °C for 30 seconds to obtain an expanded product containing mesopores and macropores.

[0118] (4) Mix the expanded product, the pore-forming agent potassium hydroxide, and metal nickel particles evenly by grinding to obtain a precursor material; where the mass ratio of the expanded product to the pore-forming agent is 6:1, the mass ratio of potassium hydroxide to metal iron particles is 1:1, and the particle size D 50 of the metal nickel particles is 5 nm.

[0119] (5) Place the precursor material in a box furnace and conduct high-temperature activation treatment at 800 °C for 3 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid to pickling to remove the residual pore-forming agent to form a microporous structure, and then dry it at 100 °C to obtain a novel graphite anode material.

[0120] The specific surface area of the novel graphite anode material prepared in this example is 1331.8 m 2 / g, the total pore volume is 6.201 cm 3 / g, the microporosity is 44.81%, the mesoporosity is 28.29%, the macroporosity is 26.90%, and the pore size range is between 0.54 nm and 77.02 nm.

[0121] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1 for details.

[0122] Example 6

[0123] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0124] (1) Place 10 g of petroleum coke artificial graphite with a particle size of 28 μm in a beaker, add HClO with a concentration of 5 wt% 4An aqueous solution was stirred and reacted at 60 °C for 3 hours at a stirring speed of 100 rpm to cause an oxidation reaction between graphite and an oxidant, obtaining a mixed solution containing a precipitate, where the mass ratio of petroleum coke artificial graphite to HClO 4 was [3:1].

[0125] (2) The mixed solution containing the precipitate was filtered. After obtaining the precipitate, the precipitate was washed with water until neutral and dried at 110 °C for 2 hours to obtain a solid substance.

[0126] (3) The solid substance was subjected to high-temperature expansion treatment at 1000 °C for 60 seconds to obtain an expanded product containing mesopores and macropores.

[0127] (4) The expanded product was mixed uniformly with the pore-forming agent potassium hydroxide and metal nickel particles by grinding to obtain a precursor material; where the mass ratio of the expanded product to the pore-forming agent was 6:1, the mass ratio of potassium hydroxide to metal iron particles was 1:1, and the particle size D 50 of the metal nickel particles was 5 nm.

[0128] (5) The precursor material was placed in a box furnace and subjected to high-temperature activation treatment at 700 °C for 3 hours. After cooling to room temperature and discharging, it was pickled with 1 mol / L hydrochloric acid to remove the residual pore-forming agent to form a microporous structure, and then dried at 80 °C to obtain a novel graphite anode material.

[0129] The specific surface area of the novel graphite anode material prepared in this example was 1283 m 2 / g, the total pore volume was 5.439 cm 3 / g, the microporosity was 41.62%, the mesoporosity was 32.17%, the macroporosity was 26.21%, and the pore size range was between 0.55 nm and 63.88 nm.

[0130] The novel graphite anode material of this example was used as the anode active material to prepare an anode electrode sheet and assembled into a battery for testing. The specific assembly process and testing process were the same as those in Example 1. The test data are shown in Table 1.

[0131] Example 7

[0132] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0133] (1) 10 g of flake graphite with a particle size of 14 μm was placed in a beaker, and an aqueous solution of KClO with a concentration of 15 wt% 4 was added. It was stirred and reacted at 25 °C for 2 hours at a stirring speed of 100 rpm to cause an oxidation reaction between graphite and an oxidant, obtaining a mixed solution containing a precipitate, where the mass ratio of flake graphite to KClO 4 was [1:2].

[0134] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 100 °C for 5 hours to obtain a solid substance.

[0135] (3) Subject the solid substance to high-temperature expansion treatment at 1000 °C for 90 seconds to obtain an expanded product containing mesopores and macropores.

[0136] (4) Mix the expanded product, the pore-forming agent sodium hydroxide, and the metal nickel particles evenly by grinding to obtain a precursor material; the mass ratio of the expanded product to the pore-forming agent is 19:1, the mass ratio of potassium hydroxide to the metal iron particles is 1:1, and the particle size D of the metal nickel particles 50 is 4 nm.

[0137] (5) Place the precursor material in a box furnace and perform high-temperature activation treatment at 800 °C for 5 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid for pickling to remove the residual pore-forming agent to form a microporous structure, and then dry it at 100 °C to obtain a novel graphite anode material.

[0138] The specific surface area of the novel graphite anode material prepared in this example is 983.12 m 2 / g, the total pore volume is 3.981 cm 3 / g, the microporosity is 37.68%, the mesoporosity is 41.12%, the macroporosity is 21.20%, and the pore size range is between 0.41 nm and 77.31 nm.

[0139] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1.

[0140] Example 8

[0141] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0142] (1) Place 10 g of flake graphite with a particle size of 7 μm in a beaker, add an aqueous solution of (NH 4 ) 2 S 2 with a concentration of 20 wt%, and stir and react at 35 °C for 2 hours with a stirring speed of 100 rpm to cause the graphite to undergo an oxidation reaction with the oxidant to obtain a mixed solution containing a precipitate, where the mass ratio of the flake graphite to (NH 4 ) 2 S 2 is [3:1].

[0143] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 100 °C for 3 hours to obtain a solid substance.

[0144] (3) Subject the solid substance to high-temperature expansion treatment at 800 °C for 90 seconds to obtain an expanded product containing mesopores and macropores.

[0145] (4) Mix the expanded product, the pore-forming agent sodium hydroxide, and the metal iron particles evenly by grinding to obtain a precursor material; the mass ratio of the expanded product to the pore-forming agent is 4:1, the mass ratio of potassium hydroxide to the metal iron particles is 1:1, and the particle size D 50 of the metal iron particles is 7 nm.

[0146] (5) Place the precursor material in a box furnace and perform high-temperature activation treatment at 500 °C for 2.5 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid to pickle and remove the residual pore-forming agent to form a microporous structure, and then dry it at 100 °C to obtain a novel graphite anode material.

[0147] The specific surface area of the novel graphite anode material prepared in this example is 1642 m 2 / g, the total pore volume is 4.505 cm 3 / g, the microporosity is 49.61%, the mesoporosity is 31.65%, the macroporosity is 18.74%, and the pore size range is between 0.52 nm and 79.67 nm.

[0148] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1.

[0149] Example 9

[0150] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0151] (1) Place 10 g of flake graphite with a particle size of 8 μm in a beaker, add an aqueous solution of K 2 CrO 7 with a concentration of 10 wt%, and stir and react at 25 °C for 2 hours. The stirring speed is 200 rpm to cause the graphite to undergo an oxidation reaction with the oxidant to obtain a mixed solution containing a precipitate, where the mass ratio of the flake graphite to K 2 CrO 7 is [4:1].

[0152] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 110 °C for 2 hours to obtain a solid substance.

[0153] (3) The solid material is subjected to high-temperature puffing treatment at 700 °C for 90 seconds to obtain a puffed product containing mesopores and macropores.

[0154] (4) The puffed product, the pore-forming agent sodium hydroxide, and the metal iron particles are uniformly mixed by grinding to obtain a precursor material; the mass ratio of the puffed product to the pore-forming agent is 8:1, the mass ratio of potassium hydroxide to the metal iron particles is 1:1, and the particle size D of the metal iron particles 50 is 8 nm.

[0155] (5) The precursor material is placed in a box furnace and subjected to high-temperature activation treatment at 750 °C for 2.5 hours. After cooling to room temperature and discharging, it is pickled with 1 mol / L hydrochloric acid to remove the residual pore-forming agent to form a microporous structure, and then dried at 100 °C to obtain a novel graphite anode material.

[0156] The specific surface area of the novel graphite anode material prepared in this example is 1488 m 2 / g, the total pore volume is 4.521 cm 3 / g, the microporosity is 47.13%, the mesoporosity is 33.12%, the macroporosity is 19.75%, and the pore size range is between 0.61 nm and 74.83 nm.

[0157] Using the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1 for details.

[0158] Example 10

[0159] This example provides a preparation process and performance test of a novel graphite anode material. The specific process is as follows:

[0160] (1) Place 10 g of flake graphite with a particle size of 13 μm in a beaker, add an aqueous solution of H 2 O 2 with a concentration of 30 wt%, stir and react at 25 °C for 2 hours, and the stirring speed is 100 rpm to cause the graphite to undergo an oxidation reaction with the oxidant to obtain a mixed solution containing a precipitate. The mass ratio of the flake graphite to H 2 O 2 is [3:1].

[0161] (2) Filter the mixed solution containing the precipitate. After obtaining the precipitate, wash the precipitate with water until it is neutral, and then dry it at 110 °C for 2 hours to obtain a solid material.

[0162] (3) The solid material is subjected to high-temperature puffing treatment at 750 °C for 90 seconds to obtain a puffed product containing mesopores and macropores.

[0163] (4) Mix the expanded material, the pore-forming agent sodium hydroxide, and the metallic iron particles evenly by grinding to obtain a precursor material after uniform mixing. The mass ratio of the expanded material to the pore-forming agent is 5:1, the mass ratio of potassium hydroxide to the metallic iron particles is 1:1, and the particle size D 50 of the metallic iron particles is 10 nm.

[0164] (5) Place the precursor material in a box furnace for high-temperature activation treatment at 850 °C for 5 hours. After cooling to room temperature and discharging, use 1 mol / L hydrochloric acid for pickling to remove the residual pore-forming agent to form a microporous structure, and dry it at 100 °C to obtain a novel graphite anode material.

[0165] The specific surface area of the novel graphite anode material prepared in this example is 1102 m 2 / g, the total pore volume is 6.101 cm 3 / g, the microporosity is 41.19%, the mesoporosity is 25.14%, the macroporosity is 33.67%, and the pore size range is between 0.56 nm and 77.8 nm.

[0166] Use the novel graphite anode material of this example as the anode active material to prepare an anode electrode sheet and assemble it into a battery for testing. The specific assembly process and testing process are the same as those in Example 1. The test data are shown in Table 1 for details.

[0167] Table 1 is a summary of the test data for Examples 1-10 and Comparative Examples 1-2:

[0168]

[0169] Table 1

[0170] From the test data in Table 1, it can be seen that the charge specific capacity and rate performance of Example 1 are better than those of Comparative Example 1 and Comparative Example 2. This is because the novel graphite anode material in Example 1 is a three-dimensional porous graphite material with micropores, mesopores, and macropores. Among them, the micropores can store lithium ions to improve the capacity of the material, the mesopores are beneficial to the diffusion of ions, thereby improving the rate performance, and the macropores can increase the contact area between the material and the electrolyte, thereby reducing the distance of ion diffusion and increasing the diffusion rate. Therefore, the novel graphite anode material in Example 1 has the characteristic of a high specific surface area. Assembling it into a lithium-ion battery can improve the specific capacity and rate performance of the lithium-ion battery.

[0171] The above-mentioned specific embodiments have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only the 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 principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A novel graphite anode material, characterized in that, the novel graphite anode material is a three-dimensional porous material including micropores, mesopores and macropores; the microporosity of the novel graphite anode material is between 30% and 80%, the mesoporosity is between 20% and 50%, and the macroporosity is between 10% and 40%; The total pore volume of the novel graphite anode material is between 0.5 cm 3 / g and 8 cm 3 / g; The specific surface area of the novel graphite anode material is between 500 m 2 / g and 3500 m 2 / g; the pore diameter of the novel graphite anode material is between 0.1 nm and 80 nm; the novel graphite anode material is obtained by oxidizing graphite, performing high-temperature expansion treatment to form mesopores and macropores, and then using a pore-forming agent to form micropores.

2. The novel graphite anode material according to claim 1, characterized in that, The particle size D of the novel graphite anode material 50 is between 7 μm and 28 μm.

3. The novel graphite anode material according to claim 1, characterized in that, the graphite includes one or more of dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite.

4. A preparation method of the novel graphite anode material according to any one of claims 1-3, characterized in that, the preparation method includes: Step S1, adding an oxidant to graphite, stirring at a certain temperature to cause an oxidation reaction between the graphite and the oxidant to obtain a mixed solution containing precipitates; Step S2, filtering the mixed solution containing precipitates, washing the precipitates with water until neutral after obtaining the precipitates, and drying to obtain a solid substance; Step S3, performing high-temperature expansion treatment on the solid substance to obtain an expanded product containing mesopores and macropores; Step S4, mixing the expanded product with a pore-forming agent, and obtaining a precursor material after mixing evenly; Step S5, performing high-temperature activation treatment on the precursor material, discharging after cooling to room temperature, pickling with hydrochloric acid to remove the residual pore-forming agent to form a microporous structure, and drying to obtain the novel graphite anode material.

5. The preparation method according to claim 4, characterized in that, the graphite includes one or more of dense crystalline graphite, flake graphite, cryptocrystalline graphite, petroleum coke artificial graphite, and needle coke artificial graphite; The oxidizing agent is a solution with a concentration of 5 wt% - 30 wt%; the solute of the solution includes KMnO 4 , K 2 CrO 7 , NaNO 3 , KClO 4 , (NH 4 ) 2 S 2 , HClO 4 , H 2 O 2 , HNO 3 or more of them; the solvent of the solution is deionized water; the mass ratio of the graphite to the solute of the oxidant is [5:1] to [1:2]; the pore-forming agent includes one or more of potassium hydroxide, potassium oxide, potassium carbonate, potassium bicarbonate, sodium hydroxide, sodium oxide, sodium carbonate, sodium bicarbonate, metal nickel particles, metal iron particles, metal cobalt particles, and metal copper particles; the mass ratio of the expanded product to the pore-forming agent is [4-19]:

1.

6. The preparation method according to claim 4, characterized in that, the certain temperature is 25°C to 60°C; the stirring time in Step S1 is 0.5 hours to 3 hours, and the rotation speed is 30 rpm to 200 rpm; the drying temperature in Step S2 is 80°C to 120°C, and the time is 2 hours to 6 hours; the temperature of the high-temperature expansion treatment is 400°C to 1000°C, and the time of the high-temperature expansion treatment is 30 seconds to 90 seconds.

7. The preparation method according to claim 4, characterized in that, The mixing method in the step S4 includes solid-phase mixing or liquid-phase mixing; wherein, the solid-phase mixing includes grinding mixing and / or ball-milling mixing; the specific method of the liquid-phase mixing is: dissolving the expanded material and the pore-forming agent in deionized water, fully mixing evenly and then drying to obtain a precursor material; The temperature range of the high-temperature activation treatment is 500°C to 900°C, and the time of the high-temperature activation treatment is 0.5 hours to 5 hours.

8. A negative electrode sheet, characterized in that, the negative electrode sheet includes the novel graphite negative electrode material according to any one of claims 1-3 above.

9. The negative electrode sheet according to claim 8, characterized in that, the negative electrode sheet includes a silicon-carbon material formed by compounding the novel graphite negative electrode material and silicon by chemical vapor deposition, or a sulfur-carbon material formed by compounding the novel graphite negative electrode material and sulfur by chemical vapor deposition.

10. A secondary battery, characterized in that, the secondary battery includes the negative electrode sheet according to claim 8 above.

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