A hard carbon negative electrode material, a preparation method and application thereof

Abstract

The application provides a hard carbon negative material, a preparation method and application thereof, and the preparation method comprises the following steps: S1: performing low-temperature heat treatment on pretreated waste clothes to obtain a first precursor; the temperature of the low-temperature heat treatment is 500 DEG C-800 DEG C; S2: activating and pore-forming the first precursor by using a crosslinking agent to obtain a second precursor; S3: performing carbonization treatment on the second precursor to obtain the hard carbon negative material; the carbonization treatment comprises first heat treatment and second heat treatment; the temperature of the first heat treatment is 500 DEG C-900 DEG C, the time of the first heat treatment is 1-6h; the temperature of the second heat treatment is 1200 DEG C-1500 DEG C, and the time of the second heat treatment is 1-6h. The lithium ion battery and the sodium ion battery prepared subsequently from the hard carbon negative material provided by the application both have excellent electrochemical performance, and the reversible specific capacity and the initial coulombic efficiency are both significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of hard carbon negative material, its preparation method and application. BACKGROUND

[0002] Secondary batteries have developed rapidly in just a few decades and have been widely used in the fields of electronic products, small electronic devices, electric vehicles and energy storage. The performance of secondary batteries is mainly affected by the positive electrode, negative electrode, electrolyte and separator, and the key to determining the performance of the battery is the positive electrode and negative electrode material. Among them, the important influence of negative electrode material on the battery includes the cycle life, energy density, power density and safety performance of the battery. Graphite is the most widely used negative material in lithium-ion batteries due to its low working point and excellent cycle stability, but the performance of graphite material has reached its theoretical specific capacity, and there is limited room for improvement. At the same time, due to the larger radius of sodium ions, it is difficult to embed inside the graphite, making it difficult to become a negative material for sodium-ion batteries. Today, hard carbon materials have a lot of applications in lithium battery fast charging due to their good rate performance and cycle stability, which helps to improve the performance of electric vehicles and digital products in terms of low temperature, fast charging and cycle stability. At the same time, due to the unique bulk structure of hard carbon, it can also store a large amount of sodium ions, thus becoming the preferred negative material for sodium-ion batteries.

[0003] The amount of waste and old clothes to be treated in China is about 26 million tons per year. According to the data of China Resource Utilization Association, about 26 million tons of old clothes are thrown into the garbage every year in China, and the recycling rate is less than 1%. It is estimated that by 2030, this amount will rise to 50 million tons, and an average of 16 pieces of waste clothes will be eliminated per year per person. If the waste clothes are treated as raw materials for the preparation of secondary battery hard carbon materials, and the waste clothes are recycled and reused, it has very high practical significance and market value. However, in the actual preparation process, the use of waste clothes to prepare hard carbon materials still has the disadvantages of low specific capacity and low first coulomb efficiency, which affect the overall performance of the battery. Although currently, in the prior art, when the hard carbon material prepared from waste clothes is applied to the negative electrode of the battery, the specific capacity and the first coulomb efficiency have been improved, but there is still a lot of room for improvement. SUMMARY

[0004] In order to solve the problems of low specific capacity and low first coulomb efficiency in the prior art when waste clothes are used to prepare hard carbon materials, the present application provides a kind of hard carbon negative material, its preparation method and application. The lithium-ion battery and sodium-ion battery prepared by the hard carbon negative material provided by the present application both have excellent electrochemical performance, and the reversible specific capacity and the first coulomb efficiency are significantly improved.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] The application provides a preparation method of a hard carbon negative material, which comprises the following steps:

[0007] S1: performing low-temperature heat treatment on the pretreated waste clothes to obtain a first precursor;

[0008] The low-temperature heat treatment is performed at a temperature of 500-800 DEG C.

[0009] S2: activating and forming pores on the first precursor by using a crosslinking agent to obtain a second precursor;

[0010] S3: performing carbonization treatment on the second precursor to obtain the hard carbon negative material;

[0011] The carbonization treatment comprises first heat treatment and second heat treatment; the first heat treatment is performed at a temperature of 500-900 DEG C and for 1-6 hours; and the second heat treatment is performed at a temperature of 1200-1500 DEG C and for 1-6 hours.

[0012] In the application, in step S1, the waste clothes can be one or more of cotton clothes, wool clothes, synthetic fiber clothes, leather clothes and animal fur clothes.

[0013] In some preferred embodiments, in step S1, the low-temperature heat treatment is performed in a coating kettle.

[0014] In some preferred embodiments, in step S1, the low-temperature heat treatment is performed in an inert atmosphere, for example, nitrogen and / or carbon dioxide.

[0015] In some preferred embodiments, in step S1, the low-temperature heat treatment is performed at a temperature of 500-700 DEG C.

[0016] In some preferred embodiments, in step S1, the low-temperature heat treatment is performed at a temperature increasing rate of 0.01-10 DEG C / min, preferably 0.1-4 DEG C / min, for example, 0.5 DEG C / min, 1 DEG C / min or 2 DEG C / min.

[0017] In some preferred embodiments, in step S1, the low-temperature heat treatment is performed for 1-10 hours, preferably 4-6 hours, for example, 4.5 hours. The time of the low-temperature heat treatment is the total time of heat preservation at the temperature of the low-temperature heat treatment.

[0018] In some more preferred embodiments, in step S1, the low-temperature heat treatment is performed by introducing nitrogen into the coating kettle with the waste clothes, increasing the temperature to 500 DEG C at a rate of 2 DEG C / min and heat preserving for 4 hours.

[0019] In some more preferred embodiments, in step S1, the low-temperature heat treatment is performed by introducing nitrogen gas into the jacketed kettle containing the waste clothes, and then heating to 500℃ at a rate of 0.5℃ / min and maintaining for 6h.

[0020] In some more preferred embodiments, in step S1, the low-temperature heat treatment is performed by first introducing carbon dioxide / nitrogen mixed gas into the jacketed kettle containing the waste clothes, and then heating to 500℃ at a rate of 1℃ / min and maintaining for 0.5h, and then introducing nitrogen gas, and then heating to 700℃ at a rate of 2℃ / min and maintaining for 4h.

[0021] In the present application, in step S1, the pretreatment can sequentially include the operations of crushing, demagnetization, washing and pulverization.

[0022] In some preferred embodiments, in step S1, the crushing is performed by crushing the waste clothes into waste cloth strips with a length of less than 100mm, preferably by using a shearing crusher.

[0023] In some preferred embodiments, in step S1, the demagnetization is performed by removing metal foreign matters from the waste clothes, preferably by using a wet demagnetizer.

[0024] In some preferred embodiments, in step S1, the washing is performed by using inorganic solvents and organic solvents sufficient to immerse the waste clothes.

[0025] In the above-mentioned scheme, the inorganic solvents are preferably one or both of clean water and deionized water.

[0026] In the above-mentioned scheme, the organic solvents are preferably one or more of methanol, ethanol, acetonitrile, petroleum ether, ethyl acetate, dichloromethane, N-methylpyrrolidone, N,N-dimethylformamide and dimethylacetamide.

[0027] In the above-mentioned scheme, the washing is preferably followed by a drying operation; the drying is preferably performed in a forced air drying oven; the drying is preferably performed in a nitrogen atmosphere; the temperature of the drying is preferably 70-90℃, for example 80℃; and the time of the drying is preferably ≥24h.

[0028] In some preferred embodiments, in step S1, the pulverization is performed by pulverizing the waste clothes into waste cloth powder with a particle size of 1-5μm. The clothes are first coarsely pulverized, and then finely pulverized until the D50 particle size of the clothes is 1 to 15 μm, and the clothes are more For example: 1.5 μm, 3 In the above-mentioned scheme, the coarse crushing is preferably performed by using a cutting-type pulverizer.

[0029] In the above-mentioned scheme, the coarse crushing is preferably performed by using a cutting-type pulverizer.

[0030] In the above scheme, the fine grinding is preferably performed using a freeze grinder and / or a wet sand mill.

[0031] In some preferred embodiments, in step S2, the first precursor and the crosslinking agent are used in a ratio of 1:(0.5-5), for example 1:1.2, 1:3 or 1:4.

[0032] In some preferred embodiments, in step S2, the crosslinking agent is one or more of oxygen, hydrogen peroxide, potassium permanganate, aqua regia, vinyl benzene, methyl methacrylate, vinyl acetate, diallyl phthalate, azobis isopropyl cyanide, ammonium persulfate, dicumyl peroxide, potassium persulfate, sodium persulfate, phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, acetic acid, formic acid, sodium hydroxide, potassium hydroxide, sodium bicarbonate, dimethylamine, triethylamine, aniline and diisopropyl ethylamine.

[0033] In some preferred embodiments, in step S2, the activation and pore forming operation is washing the first precursor with a crosslinking agent, and then washing the material to neutral with deionized water.

[0034] In some more preferred embodiments, in step S2, the activation and pore forming operation is first washing the first precursor with an acid solution, and then washing the material to neutral with deionized water.

[0035] In the above scheme, the acid solution is preferably a mixed solution of concentrated phosphoric acid / concentrated hydrochloric acid / hydrofluoric acid, and the volume ratio of the concentrated phosphoric acid, the concentrated hydrochloric acid and the hydrofluoric acid in the mixed solution is preferably 2:2:1.

[0036] In some more preferred embodiments, the activation and pore forming operation is first washing the first precursor with an acid solution, then washing the material to neutral with deionized water, and then washing the material with a base solution, and then washing the material to neutral with deionized water.

[0037] In the above scheme, the acid solution is preferably aqua regia or a mixed solution of concentrated sulfuric acid / concentrated nitric acid / concentrated hydrochloric acid, and the volume ratio of the concentrated sulfuric acid, the concentrated nitric acid and the concentrated hydrochloric acid in the mixed solution is preferably 1:2:2.

[0038] In the above scheme, the base solution is preferably a potassium hydroxide solution or a sodium hydroxide solution, and the concentration of the base solution is preferably 0.5-2 mol / L.

[0039] In the present application, the purpose of washing with a crosslinking agent (such as an acid solution) is mainly to etch and form pores on the surface of the material, and also to remove impurities, i.e. to form water-soluble compounds with part of the inorganic molecules, and then remove the impurities by washing with deionized water.

[0040] In some more preferable embodiments, after the activating pore-forming operation in step S2, a drying operation is further included.

[0041] In the above scheme, preferably, the drying is performed in a blast drying oven; the temperature of the drying is preferably 100-120℃, for example, 110℃; and the time of the drying is preferably ≥24h.

[0042] In the above scheme, preferably, the drying is first performed in a blast drying oven and then in a vacuum drying oven; the temperature of the drying is preferably 100-120℃, for example, 110℃; and the time of the drying is preferably ≥24h.

[0043] In the present application, in step S3, the time of the first heat treatment and the second heat treatment respectively refers to the time of holding at the corresponding temperature.

[0044] In some preferable embodiments, in step S3, the carbonization treatment is performed in a box-type atmosphere furnace or a tube furnace.

[0045] In some preferable embodiments, in step S3, the carbonization treatment is preferably performed under an inert atmosphere, for example, nitrogen and / or argon.

[0046] In some preferable embodiments, in step S3, the heating rate of the first heat treatment is 0.01-10℃ / min, preferably 1-6℃ / min, for example, 5℃ / min.

[0047] In some preferable embodiments, in step S3, the time of the first heat treatment is 1-4h.

[0048] In some preferable embodiments, in step S3, the temperature of the second heat treatment is 1300℃.

[0049] In some preferable embodiments, in step S3, the heating rate of the second heat treatment is 0.01-10℃ / min, preferably 1-4℃ / min, for example, 2℃ / min.

[0050] In some preferable embodiments, in step S3, the time of the second heat treatment is 1-4h.

[0051] The present application also provides a hard carbon negative electrode material prepared by the method for preparing a hard carbon negative electrode material as described above.

[0052] The D50 particle size of the hard carbon negative electrode material is 1-15μm.

[0053] In some preferable embodiments, the D50 particle size of the hard carbon negative electrode material is 1-5μm, μm, or 4 μm.Fig. 1

[0054] The application also provides application of the hard carbon negative material as described above in a lithium ion battery or a sodium ion battery.

[0055] On the basis of common general knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the application.

[0056] The reagents and raw materials used in the application are commercially available.

[0057] The positive progress effect of the application is that:

[0058] (1) The hard carbon negative material provided by the application has a good internal bulk structure, and the lithium ion battery and the sodium ion battery prepared therefrom both have excellent electrochemical performance, and the reversible specific capacity and the initial coulombic efficiency are both significantly improved.

[0059] (2) The preparation method of the hard carbon negative material provided by the application controls the step-by-step carbonization, so that molecules with different molecular weights and boiling points can be uniformly volatilized, and the surface of the material is not seriously etched, the etched surface is repaired after carbonization, and the two work together to achieve the purpose of regulating the particle size, the cross-linking degree and the internal pore structure of the hard carbon material.

[0060] (3) The preparation method of the hard carbon negative material provided by the application uses waste clothes as raw materials, and the synthesis process is simple, safe, reliable and green, compared with the traditional landfill, renovation recycling (with the risk of carrying bacteria), cracking and incineration and other methods, the application realizes harmless recycling of waste clothes, can save a lot of resources, reduce CO2 emission, and realizes sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0061] Fig. 2 The SEM image of the hard carbon negative material prepared in Example 1 of the application.

[0062] Fig. 3 The pore size distribution curve of the hard carbon negative material prepared in Example 1 of the application.

[0063] Fig. 4 The charge-discharge curve of the lithium ion battery prepared by using the hard carbon negative material prepared in Example 1 of the application.

[0064] Fig. 5 The charge-discharge curve of the sodium ion battery prepared by using the hard carbon negative material prepared in Example 1 of the application.

[0065] The pretreated product is finely pulverized by a freeze pulverizer and a wet sand mill until the D50 particle size is 3 μm. The SEM image of the hard carbon negative material prepared in Example 2 of the application. DETAILED DESCRIPTION

[0066] The present application is further illustrated by the following examples without thereby limiting the present application to the scope of the examples. The experimental methods in the following examples, for which no specific conditions are indicated, are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0067] Example 1

[0068] S1:

[0069] (1) The waste clothes were broken by a shearing-type crusher to obtain waste cloth strips with a length of less than 100 mm;

[0070] (2) The waste cloth strips were subjected to magnetic removal treatment by a wet magnetic separator;

[0071] (3) The waste cloth strips subjected to magnetic removal treatment were sequentially washed with water and deionized water sufficient to immerse the waste cloth strips, and then sequentially washed with ethanol, ethyl acetate, petroleum ether and dichloromethane sufficient to immerse the washed waste cloth strips, and then the material was placed in a nitrogen-protected air drying oven for drying treatment at 80℃ for 24h;

[0072] (4) The dried material was first coarsely crushed using a cutting-type crusher, and then finely crushed into a pretreated material with a D50 particle size of 4μm using a frozen crusher;

[0073] (5) The pretreated material was placed in a coating kettle and subjected to low-temperature heat treatment under nitrogen, wherein the final temperature treatment temperature of the coating kettle was 500℃, the heating rate was 2℃ / min, and the holding time was 4h, and after cooling, a first precursor was obtained;

[0074] S2:

[0075] (6) The first precursor was washed with aqua regia, and the mass ratio of the first precursor to aqua regia was 1:1.2, and then the filtered material was washed with deionized water until neutral, 2mol / L potassium hydroxide was added, and then the filtered material was washed with deionized water until neutral, and then transferred to an air drying oven, dried at 110℃ for 24h, and a second precursor was obtained;

[0076] S3:

[0077] (7) The second precursor was placed in a box-type atmosphere furnace and subjected to two-step carbonization under a nitrogen atmosphere, first step: heating to 500℃ at a rate of 5℃ / min, holding for 1h; second step: heating to 1300℃ at a rate of 2℃ / min, holding for 1h, and after natural cooling, the material was discharged to obtain a hard carbon negative electrode material.

[0078] Example 2

[0079] S1:

[0080] (1)-(3) are the same as in Example 1;

[0081] (4) The dried material was first coarsely crushed using a cutting-type crusher, and then finely crushed into a pretreated material with a D50 particle size of 1.5 μm using a wet sand mill;

[0082] (5) The pretreated material was put into a coating kettle, and low-temperature heat treatment was performed under nitrogen, wherein the final temperature of the coating kettle was 500℃, the heating rate was 0.5℃ / min, and the holding time was 6h, and the first precursor was obtained after cooling;

[0083] S2:

[0084] (6) A mixed solution of concentrated sulfuric acid / concentrated nitric acid / concentrated hydrochloric acid (volume ratio of 1:2:2) was added to the first precursor for washing, and the mass ratio of the first precursor to the mixed solution was 1:3, then the filtered material was washed with deionized water until neutral, 0.5 mol / L sodium hydroxide was added, and the filtered material was washed with deionized water until neutral, then it was transferred to a forced air drying oven, dried at 110℃ for 12h, and then vacuum dried at 100℃ for 12h, to obtain the second precursor;

[0085] S3:

[0086] (7) The second precursor was placed in a box-type atmosphere furnace and subjected to two-step carbonization under a nitrogen atmosphere, first step: heating to 900℃ at a rate of 5℃ / min and holding for 1h; second step: heating to 1200℃ at a rate of 2℃ / min and holding for 4h, and the material was discharged after natural cooling to obtain the hard carbon negative electrode material.

[0087] Example 3

[0088] S1:

[0089] (1)-(2) are the same as in Example 1;

[0090] (3) The waste cloth strips after magnetic treatment were washed with water and deionized water in turn until the waste cloth strips were immersed, then the washed waste cloth strips were washed with petroleum ether, acetonitrile, dichloromethane, N-methyl pyrrolidone and ethanol in turn until the waste cloth strips were immersed, and then the material was placed in a nitrogen-protected forced air drying oven and dried at 80℃ for 24h;

[0091] (4) The dried material was first coarsely crushed using a cutting-type crusher, and then finely crushed into a pretreated material with a D50 particle size of 1.5 μm using a wet sand mill; Fig. 1 Fig. 1

[0092] (5) The pretreated material is put into a coating kettle for low-temperature heat treatment. Carbon dioxide / nitrogen mixed gas is passed through the kettle, and the temperature is raised to 500°C at a rate of 1°C / min, and the temperature is kept for 0.5 h. Then nitrogen is passed through the kettle, and the temperature is raised to 700°C at a rate of 2°C / min, and the temperature is kept for 4 h. After cooling, the first precursor is obtained;

[0093] S2:

[0094] (6) A mixed solution of concentrated phosphoric acid / concentrated hydrochloric acid / hydrofluoric acid (volume ratio of 2:2:1) is added to the first precursor for washing. The mass ratio of the first precursor to the mixed solution is 1:4. Then the filtered material is washed with deionized water until it is neutral. Then the material is transferred to a forced air drying oven, dried at 120°C for 24 h, and then vacuum dried at 120°C for 12 h. The second precursor is obtained.

[0095] S3:

[0096] (7) The second precursor is placed in a tube furnace and subjected to two-step carbonization under a nitrogen atmosphere. In the first step, the temperature is raised to 900°C at a rate of 5°C / min, and the temperature is kept for 1 h. In the second step, the temperature is raised to 1500°C at a rate of 2°C / min, and the temperature is kept for 1 h. After natural cooling, the hard carbon negative electrode material is obtained.

[0097] Comparative Example 1

[0098] S1:

[0099] (1)-(3) are the same as in Example 1.

[0100] (4) The dried material is first coarsely crushed using a cutting-type crusher, and then finely crushed using a frozen crusher to obtain a pretreated material with a D50 particle size of 4 μm.

[0101] (5) The pretreated material is put into a coating kettle for low-temperature heat treatment. Nitrogen is passed through the kettle, and the final temperature of the coating kettle is 400°C. The temperature is raised at a rate of 2°C / min, and the temperature is kept for 4 h. After cooling, the first precursor is obtained.

[0102] S2:

[0103] (6) Aquafortis is added to the first precursor for washing. The mass ratio of the first precursor to the aquafortis is 1:1.2. Then the filtered material is washed with deionized water until it is neutral. Then the material is transferred to a forced air drying oven, dried at 110°C for 24 h, and the second precursor is obtained.

[0104] S3:

[0105] (7) The same as in Example 1.

[0106] Comparative Example 2

[0107] S1:

[0108] (1)-(4) are the same as in Example 2.

[0109] (5) The pretreated material is put into a coating kettle, and low-temperature heat treatment is carried out by passing nitrogen gas, wherein the final temperature of the coating kettle is 400℃, the heating rate is 0.5℃ / min, and the holding time is 4h, and the first precursor is obtained after cooling;

[0110] S2:

[0111] (6) The first precursor is washed with a mixed solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 1:2), and the mass ratio of the first precursor to the mixed solution is 1:3, then the filtered material is washed with deionized water until neutral, 2mol / L potassium hydroxide is added, and the filtered material is washed with deionized water until neutral, and then transferred to a forced air drying oven, dried at 110℃ for 24h to obtain the second precursor;

[0112] S3:

[0113] (7) The second precursor is placed in a box-type atmosphere furnace and subjected to two-step carbonization under a nitrogen atmosphere, the first step is to heat to 900℃ at a rate of 5℃ / min and hold for 1h, and the second step is to heat to 1100℃ at a rate of 2℃ / min and hold for 1h, and the hard carbon negative electrode material is obtained after natural cooling and discharging.

[0114] Comparative Example 3

[0115] S1:

[0116] (1)-(4) are the same as Example 3;

[0117] (5) The pretreated material is put into a coating kettle and subjected to low-temperature heat treatment, first passing a mixture of carbon dioxide and nitrogen gas, heating to 450℃ at a rate of 3℃ / min, holding for 4h, and obtaining the first precursor after cooling;

[0118] S2:

[0119] (6) The first precursor is washed with concentrated phosphoric acid, and the mass ratio of the first precursor to the mixed solution is 1:4, then the filtered material is washed with deionized water until neutral, transferred to a forced air drying oven, dried at 120℃ for 24h, and then vacuum dried at 180℃ for 12h to obtain the second precursor;

[0120] S3:

[0121] (7) The second precursor is placed in a tube furnace and subjected to one-step carbonization under a nitrogen atmosphere, the first step is to heat to 1500℃ at a rate of 5℃ / min and hold for 1h, and the hard carbon negative electrode material is obtained after natural cooling and discharging.

[0122] Example 1

[0123] Property characterization of hard carbon negative electrode material

[0124] (1) Test method

[0125] The surface morphology of the prepared hard carbon negative electrode material was characterized by a scanning electron microscope (phenome XL). The D50 particle size and pore size distribution curve of the prepared hard carbon negative electrode material were measured by a laser particle size analyzer (Mastersize 2000).

[0126] (2) Test results

[0127] The test results are shown in Tables Fig. 5 , 2 and 5. Fig. 1 Figure 1 is a SEM image of the hard carbon negative electrode material prepared in Example 1 of the present application. Fig. 2 Figure 2 is a SEM image of the hard carbon negative electrode material prepared in Example 2 of the present application. As shown in Figures Fig. 2 and 5 , the hard carbon negative electrode materials prepared in Examples 1 and 2 are both irregular black particles with uniform particles. ​ Figure 3 is a pore size distribution curve of the hard carbon negative electrode material prepared in Example 1 of the present application. As shown in Figure ​ , the hard carbon negative electrode material has both micropores and mesopores, and such a wide pore size distribution is beneficial to both lithium storage and sodium storage.

[0128] Effect Example 2

[0129] Electrochemical performance test of the battery prepared from the hard carbon negative electrode material

[0130] (1) Test method

[0131] a. Preparation of the electrode

[0132] The hard carbon negative electrode material prepared in Examples 1-3 and Comparative Examples 1-3, acetylene black conductive agent SP, and PVDF binder were mixed and prepared into a uniform slurry in a mass ratio of 8:1:1 with NMP as the solvent, and the slurry was uniformly coated on a copper foil with a coating density of about 5 mg / cm 2 . Subsequently, the copper foil was placed in a vacuum drying oven and dried at 90°C for 12 h. The dried copper foil was cut into a circular piece with an area of 2 cm 2 to prepare a working electrode.

[0133] b. Assembly of the half battery

[0134] In a vacuum glove box, a CR-2032 type button cell was assembled by using a lithium sheet as the counter electrode, the product obtained in step a as the working electrode, Celgard 2400 polypropylene porous membrane as the separator, and 1 mol / L LiPF6 in EC / DEC (the volume ratio of EC to DEC was 1:1) solution as the electrolyte.

[0135] In a vacuum glove box, a CR-2032 button cell was assembled with the product of step a as the working electrode, a piece of metallic sodium as the counter electrode, a glass fiber membrane as the separator, and 1 mol / L NaPF6 in EC / DEC (volume ratio of EC to DEC is 1:1) solution as the electrolyte at room temperature.

[0136] (2) Test results

[0137] Table 1

[0138]

[0139] As can be seen from Table 1, the reversible specific capacity and the first coulombic efficiency of the hard carbon negative electrode material prepared in Examples 1 and 3 of the present application are higher than those of Comparative Examples 1 and 3, respectively. This is because the preparation method of the hard carbon negative electrode material provided by the present application controls the step-by-step carbonization, so that molecules with different molecular weights and boiling points are uniformly volatilized, and the etching and pore forming are controlled, so as to realize the purpose of regulating the particle size, the cross-linking degree and the internal pore structure of the hard carbon material, and further improve the reversible specific capacity and the first coulombic efficiency of the hard carbon negative electrode material applied in the battery.

[0140] Meanwhile, the hard carbon negative electrode material prepared in Example 2 has smaller particle size, larger specific surface area, more oxygen-containing functional groups on the surface, more surface defects, more surface active sites, more developed pore distribution and stronger lithium storage capacity. Compared with Comparative Example 2, it can be seen that the battery prepared from the hard carbon negative electrode material prepared in Example 2 has higher reversible specific capacity, indicating that it has high lithium extraction capacity, and it can be inferred that it has higher lithium intercalation capacity, and has good application scenarios and high market value in the future.

[0141] The above only describes the preferred specific embodiments of the present application, and the present application includes but is not limited to the details in the above-described embodiments; in the case of avoiding unnecessary repetition, other combination modes are not described again, and any suitable combination mode within the technical solution range of the present application can be adopted; any simple modification and decoration made by those skilled in the art without departing from the technical essence of the present application is considered to be within the protection scope of the present application.

Claims

1. A method for producing a hard carbon negative electrode material, characterized by, It comprises the following steps: S1: the pretreated waste clothes are subjected to low-temperature heat treatment to obtain a first precursor; The temperature of the low-temperature heat treatment is 500-800℃; S2: the first precursor is activated and pore-formed by using a crosslinking agent to obtain a second precursor; S3: the second precursor is subjected to carbonization treatment to obtain a hard carbon negative electrode material; The carbonization treatment comprises first heat treatment and second heat treatment; the temperature of the first heat treatment is 500-900℃, the time of the first heat treatment is 1-6 h; the temperature of the second heat treatment is 1200-1500℃, and the time of the second heat treatment is 1-6 h; In step S2, the operation of activating and pore-forming is first washing the first precursor with acid solution, and then washing the material to neutral with deionized water; wherein the acid solution is a mixed solution of concentrated phosphoric acid, concentrated hydrochloric acid and hydrofluoric acid; Or, in step S2, the operation of activating and pore-forming is first washing the first precursor with acid solution, and then washing the material to neutral with deionized water, and then washing with alkali solution, and then washing the material to neutral with deionized water; wherein the acid solution is aqua regia, or the acid solution is a mixed solution of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid.

2. The method of producing a hard carbon negative material according to claim 1, wherein In step S1, the waste clothes are one or more of cotton clothes, wool clothes, synthetic fiber clothes, leather clothes and animal fur clothes.

3. The method of producing a hard carbon negative material according to claim 1, wherein It satisfies one or more of the following conditions: (1) In step S1, the low-temperature heat treatment is carried out in a coating kettle; (2) In step S1, the low-temperature heat treatment is carried out under an inert atmosphere; (3) In step S1, the temperature of the low-temperature heat treatment is 500-700℃; (4) In step S1, the heating rate of the low-temperature heat treatment is 0.01-10℃ / min; (5) In step S1, the time of the low-temperature heat treatment is 1-10 h; (6) In step S1, the operation of the low-temperature heat treatment is to introduce nitrogen into the coating kettle containing the waste clothes, to heat to 500℃ at a rate of 2℃ / min, and to keep the temperature for 4 h; (7) In step S1, the operation of the low-temperature heat treatment is to introduce nitrogen into the coating kettle containing the waste clothes, to heat to 500℃ at a rate of 0.5℃ / min, and to keep the temperature for 6 h; (8) In step S1, the operation of the low-temperature heat treatment is to first introduce carbon dioxide / nitrogen mixed gas into the coating kettle containing the waste clothes, to heat to 500℃ at a rate of 1℃ / min, to keep the temperature for 0.5 h, and then to introduce nitrogen, to heat to 700℃ at a rate of 2℃ / min, and to keep the temperature for 4 h.

4. The method of producing a hard carbon negative material according to claim 3, wherein In step S1, the low-temperature heat treatment is carried out under nitrogen and / or carbon dioxide.

5. The method of producing a hard carbon negative material according to claim 3, wherein In step S1, the heating rate of the low-temperature heat treatment is 0.1-4℃ / min.

6. The method of producing a hard carbon negative material according to claim 5, wherein In step S1, the heating rate of the low-temperature heat treatment is 0.5℃ / min, 1℃ / min or 2℃ / min.

7. The method of producing a hard carbon negative material according to claim 3, wherein In step S1, the time of the low-temperature heat treatment is 4-6 h.

8. The method of producing a hard carbon negative material according to claim 7, wherein In step S1, the time of the low-temperature heat treatment is 4.5 h.

9. The method of producing a hard carbon negative material according to claim 1, wherein The pretreatment comprises, in sequence, crushing, magnetic removal, cleaning and pulverization, and satisfies one or more of the following conditions: (1) In step S1, the crushing operation is to crush the used clothes into cloth strips with a length of less than 100 mm; (2) In step S1, the magnetic removal operation is to remove metal foreign matters in the used clothes; (3) In step S1, the cleaning operation is to clean the used clothes with inorganic and organic solvents sufficient to immerse the used clothes; (4) In step S1, the pulverization operation is to first coarsely crush and then finely pulverize the used clothes, so that the D50 particle size of the used clothes is 1-15 μm.

10. The method of producing a hard carbon negative material according to claim 9, wherein In step S1, the crushing operation is performed by using a shearing crusher.

11. The method of producing a hard carbon negative material according to claim 9, wherein In step S1, the magnetic removal operation is performed by using a wet magnetic separator.

12. The method of producing a hard carbon negative material according to claim 9, wherein The inorganic solvent is one or both of clean water and deionized water.

13. The method of producing a hard carbon negative material according to claim 9, wherein The organic solvent is one or more of methanol, ethanol, acetonitrile, petroleum ether, ethyl acetate, dichloromethane, N-methylpyrrolidone, N,N-dimethylformamide and dimethylacetamide.

14. The method of producing a hard carbon negative material according to claim 9, wherein The cleaning operation is followed by a drying operation.

15. The method of producing a hard carbon negative material according to claim 14, wherein It satisfies one or more of the following conditions: (1) The drying is performed in a blast drying oven; (2) The drying is performed in a nitrogen atmosphere; (3) The drying temperature is 70-90℃; (4) The drying time is ≥24 h.

16. The method of producing a hard carbon negative material according to claim 15, wherein The drying temperature is 80℃.

17. The method of producing a hard carbon negative material according to claim 9, wherein The D50 particle size of the used clothes is 1-5 μm.

18. The method of producing a hard carbon negative material according to claim 9, wherein The coarse crushing is performed by using a cutting crusher.

19. The method of producing a hard carbon negative material according to claim 9, wherein The fine pulverization is performed by using a frozen crusher and / or a wet sand mill.

20. The method of producing a hard carbon anode material according to claim 1, wherein It satisfies one or more of the following conditions: (1) In step S2, the use amount ratio of the first precursor to the crosslinking agent is 1:(0.5-5); (2) In step S2, the crosslinking agent is one or more of oxygen, hydrogen peroxide, potassium permanganate, aqua regia, vinyl benzene, methyl methacrylate, vinyl acetate, diallyl phthalate, azobis isopropyl cyanide, ammonium persulfate, dicumyl peroxide, potassium persulfate, sodium persulfate, phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, acetic acid, formic acid, sodium hydroxide, potassium hydroxide, sodium bicarbonate, dimethylamine, triethylamine, aniline and diisopropyl ethylamine.

21. The method of producing a hard carbon negative material according to claim 20, wherein In step S2, the use amount ratio of the first precursor to the crosslinking agent is 1:1.2, 1:3 or 1:

4.

22. The method of producing a hard carbon anode material according to claim 1, wherein It satisfies one or more of the following conditions: (1) In step S2, the volume ratio of concentrated phosphoric acid, concentrated hydrochloric acid and hydrofluoric acid in the mixed solution is 2:2:1; (2) In step S2, the volume ratio of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid in the mixed solution is 1:2:2; (3) In step S2, the alkali solution is a potassium hydroxide solution or a sodium hydroxide solution; (4) In step S2, the concentration of the alkali solution is 0.5-2 mol / L; (5) In step S2, the activation and pore forming operation is followed by a drying operation.

23. The method of producing a hard carbon negative material according to claim 22, wherein The drying is performed in a blast drying oven.

24. The method of producing a hard carbon negative material according to claim 23, wherein The drying temperature is 100-120℃.

25. The method of producing a hard carbon negative material according to claim 23, wherein The drying temperature is 110℃.

26. The method of producing a hard carbon negative material according to claim 23, wherein The drying time is ≥24 h.

27. The method of producing a hard carbon anode material according to claim 22, wherein The drying is first performed in a blast drying oven and then in a vacuum drying oven.

28. The method of producing a hard carbon negative material according to claim 27, wherein The drying temperature is 100-120℃.

29. The method of producing a hard carbon negative material according to claim 28, wherein The drying temperature is 110℃.

30. The method of producing a hard carbon negative material according to claim 27, wherein The drying time is ≥24 h.

31. The method of producing a hard carbon anode material according to claim 1, wherein It satisfies one or more of the following conditions: (1) In step S3, the carbonization treatment is performed in a box-type atmosphere furnace or a tube furnace; (2) In step S3, the carbonization treatment is performed under an inert atmosphere; (3) In step S3, the first heat treatment has a temperature increasing rate of 0.01-10℃ / min; (4) In step S3, the first heat treatment has a time of 1-4 h; (5) In step S3, the second heat treatment has a temperature of 1300℃; (6) In step S3, the second heat treatment has a temperature increasing rate of 0.01-10℃ / min; (7) In step S3, the second heat treatment has a time of 1-4 h.

32. The method of producing a hard carbon negative material according to claim 31, wherein In step S3, the carbonization treatment is performed under nitrogen and / or argon.

33. The method of producing a hard carbon anode material according to claim 31, wherein In step S3, the first heat treatment has a temperature increasing rate of 1-6℃ / min.

34. The method of producing a hard carbon negative material according to claim 33, wherein In step S3, the first heat treatment has a temperature increasing rate of 5℃ / min.

35. The method of producing a hard carbon anode material according to claim 31, wherein In step S3, the second heat treatment has a temperature increasing rate of 1-4℃ / min.

36. The method of producing a hard carbon negative material according to claim 35, wherein In step S3, the second heat treatment has a temperature increasing rate of 2℃ / min.

37. A hard carbon negative electrode material, characterized in that, It is prepared by the method of any one of claims 1-36; The D50 particle size of the hard carbon negative electrode material is 1-15 μm.

38. The hard carbon anode material of claim 37, wherein, The D50 particle size of the hard carbon negative electrode material is 1-5 μm.

39. The hard carbon anode material of claim 38, wherein, The D50 particle size of the hard carbon negative electrode material is 1.5 μm, 3 μm or 4 μm.

40. Use of the hard carbon negative electrode material of any one of claims 37-39 in a lithium ion battery or a sodium ion battery.

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