Graphite, precursor thereof, preparation method of precursor, negative electrode and battery

Abstract

The invention relates to the technical field of battery materials, and discloses graphite, a precursor thereof, a preparation method of the precursor, a negative electrode and a battery. The preparation method of the graphite precursor comprises the following steps: uniformly mixing green coke powder with a polar organic solvent, and fully dissolving soluble substances in the green coke powder into the polar organic solvent to obtain a mixture; volatilizing the polar organic solvent in the mixture to obtain a graphite precursor; the graphite precursor disclosed by the invention is prepared by adopting the preparation method. The graphite disclosed by the invention is obtained by graphitizing the graphite precursor. The precursor prepared by the preparation method provided by the invention is used for preparing graphite, and small molecules loaded outside green coke particles are carbonized at high temperature to form a disordered carbon coating layer, so that the surface of the prepared graphite has more pores, sufficient channels are provided for embedding of lithium ions, and the fast charging performance of the graphite can be effectively improved. In addition, the material of the coating layer in the method is taken from the green coke and is self-sufficiency, so that the cost of the coating agent is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to graphite, a precursor thereof, a preparation method thereof, a negative electrode and a battery. Background Art

[0002] Lithium-ion batteries, due to their high energy density and excellent cycle performance, are widely used in various fields, including new energy. Graphite anode materials are widely used in lithium batteries due to their high specific capacity, low price, and environmental friendliness. However, the lithium intercalation mechanism at the end faces of graphite anodes has limited their development in the field of fast charging.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide graphite, its precursor and preparation method thereof, negative electrode and battery, so as to improve at least one problem mentioned in the background art.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for preparing a graphite precursor, comprising:

[0007] uniformly mixing green coke powder and a polar organic solvent so that soluble matter in the green coke powder is fully dissolved in the polar organic solvent to obtain a mixture;

[0008] The polar organic solvent in the mixture is volatilized to obtain a graphite precursor.

[0009] In an optional embodiment, the F value of the green coke is ≥ 0.1%;

[0010] Optionally, the green coke is petroleum coke, needle coke or pitch coke;

[0011] Optionally, the particle size of the green coke powder is 1 to 100 μm.

[0012] In an optional embodiment, the method of fully dissolving the soluble matter in the green coke powder into the polar organic solvent to obtain a mixture includes:

[0013] The raw coke powder is mixed with a polar organic solvent and then stirred. The stirring time is not particularly limited, as long as the soluble matter in the raw coke powder is fully dissolved in the polar organic solvent. Optionally, the stirring time is 2 to 6 hours.

[0014] In an optional embodiment, the polar organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloromethane, chloroform and ethyl acetate;

[0015] Optionally, the ratio of green coke powder to polar organic solvent is 1 kg: 1-5 L. Specifically, the ratio of green coke powder to organic solvent is 1 Kg: 1 L, 2 L, 3 L, 4 L, 5 L. It is only necessary to uniformly disperse the green coke powder in the organic solvent, and there is no special limitation.

[0016] In an alternative embodiment, the method of volatilizing the polar organic solvent in the mixture includes:

[0017] The mixture is dried at 80-120 °C, and a suitable temperature is selected according to the boiling point of the organic solvent used, and there is no special limitation. For example, when using tetrahydrofuran or dichloromethane with a lower boiling point as the solvent, it can be dried at 80 °C; when using toluene with a higher boiling point as the solvent, it is dried at 120 °C.

[0018] Alternatively, the mixture is first subjected to rotary evaporation to recover the polar organic solvent, and then dried at 80-120 °C.

[0019] ]>In a second aspect, the present invention provides a graphite precursor prepared by the preparation method according to any one of the foregoing embodiments.

[0020] In a third aspect, the present invention provides a method for preparing graphite, which graphitizes the graphite precursor according to the foregoing embodiment; optionally, the graphitization temperature is 2900-3100 °C.

[0021] In a fourth aspect, the present invention provides a method for preparing graphite, including:

[0022] Mix the green coke powder and the polar organic solvent evenly, and dissolve the soluble substances in the green coke powder into the polar organic solvent to obtain a mixture;

[0023] Volatilize the polar organic solvent in the mixture to obtain a graphite precursor;

[0024] Perform graphitization treatment on the graphite precursor. Optionally, the graphitization temperature is 2900-3100 °C.

[0025] Before graphitization, it can also be treated by methods such as classification, modification or granulation, and after graphitization, it can also be treated by methods such as modification, coating or granulation.

[0026] In a fifth aspect, the present invention provides a graphite prepared by the preparation method according to the foregoing embodiment.

[0027] In a sixth aspect, the present invention provides a negative electrode prepared from the graphite according to the foregoing embodiment.

[0028] In a seventh aspect, the present invention provides a battery including the negative electrode according to the foregoing embodiment.

[0029] The present invention has the following beneficial effects:

[0030] A method for preparing a graphite precursor. By treating green coke powder with a polar organic solvent, some small molecules that can dissolve in the polar organic solvent inside the green coke are extracted. After the organic solvent volatilizes, these small molecules are loaded on the outside of the green coke particles. When this precursor is used to prepare graphite, the small molecules on the surface layer of the precursor are carbonized at high temperature to form a hard carbon thin layer that is non-oriented and contains more pores, making the surface of the prepared graphite have more pores, providing sufficient channels for the insertion of lithium ions, and effectively improving the fast charging performance of graphite. In addition, the coating material in this method is taken from the green coke itself, which is "self-sufficient" and saves the cost of the coating agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a process flow chart of the technical solution provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0034] The graphite, its precursor, the preparation method thereof, the negative electrode, and the battery provided by the embodiments of the present invention will be specifically described below.

[0035] As Figure 1 shown, a method for preparing a graphite precursor provided by an embodiment of the present invention includes:

[0036] Mix the green coke powder evenly with a polar organic solvent so that the soluble substances in the green coke powder are fully dissolved in the polar organic solvent to obtain a mixture;

[0037] Volatilize the polar organic solvent in the mixture to obtain a graphite precursor.

[0038] The preparation method of the graphite precursor provided by the embodiment of the present invention treats the green coke powder with a polar organic solvent, so that some small molecules that can be dissolved in the polar organic solvent inside the green coke are extracted. After the organic solvent volatilizes, these small molecules are loaded on the outside of the green coke particles. When this precursor is used to prepare graphite, the small molecules on the surface layer of the precursor are carbonized at high temperature to form a hard carbon thin layer that is non-oriented and contains more pores, making the surface of the prepared graphite have more pores, providing sufficient channels for the insertion of lithium ions, and effectively improving the fast charging performance of the graphite. In addition, the coating material in this method is taken from the green coke itself, which is "self-sufficient" and saves the cost of the coating agent.

[0039] Therefore, compared with the untreated green coke powder, the graphite precursor prepared by the preparation method of the graphite precursor provided by the embodiment of the present invention has better fast charging performance when used to prepare graphite.

[0040] Optionally, the method for fully dissolving the soluble substances in the green coke powder into the polar organic solvent to obtain a mixture includes: mixing the green coke powder and the polar organic solvent and then stirring; optionally, the stirring time is 2 to 6 h (such as 2 h, 4 h or 6 h).

[0041] By stirring and mixing for a sufficient time, it can be ensured that the small molecules in the green coke particles that are soluble in the polar organic solvent are dissolved in the polar organic solvent.

[0042] Optionally, the particle size of the green coke powder is 1 to 100 μm (such as 1 μm, 10 μm, 20 μm, 50 μm, 80 μm or 100 μm).

[0043] The graphite prepared from the green coke powder within this particle size range has good performance after being made into a negative electrode, and the small molecules in the green coke powder within this particle size range can be fully dissolved in the polar organic solvent.

[0044] Optionally, the polar organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloromethane, chloroform and ethyl acetate.

[0045] Optionally, to ensure that the small molecules in the green coke powder are fully dissolved, the ratio of the green coke powder to the polar organic solvent is 1 kg: 1 to 5 L (such as 1 kg: 1 L, 1 kg: 2 L or 1 kg: 5 L).

[0046] Optionally, the method for volatilizing the polar organic solvent in the mixture includes:

[0047] Placing the mixture in an oven at 80 to 120 °C (such as 80 °C, 90 °C, 100 °C or 120 °C) for drying;

[0048] Or, first subjecting the mixture to rotary evaporation to recover the polar organic solvent, and then drying it at 80 to 120 °C (such as 80 °C, 90 °C, 100 °C or 120 °C).

[0049] Preferably, the mixture is first subjected to rotary evaporation to recover the polar organic solvent, and then dried at 80-120 °C. The recovered polar organic solvent can be reused, which can save costs.

[0050] Optionally, to obtain a graphite precursor with better performance, the F value of the green coke used is ≥ 0.10%, F = M1 / M c × 100%, where M c is the mass of the green coke, M1 is the mass of the residue obtained by heat-treating the substance dissolved in the solvent after solvent extraction of the green coke in an air atmosphere at 500-600 °C, and the polarity parameter of the solvent used is 4.0-4.5. The solvent is selected from at least one of chloroform, ethyl acetate, and tetrahydrofuran.

[0051] The F value can to some extent represent the content of small molecules inside the green coke. When the F value is too small, too few organic small molecules are extracted, making it difficult to achieve the expected coating effect and having a poor improvement effect on the fast charging performance of the graphite anode. It should be noted that for the same green coke, as long as a solvent with any polarity within the range of 4.0-4.5 is selected for extraction and heat treatment is carried out at any temperature within the range of 500-600 °C, the measured F value is basically the same.

[0052] The graphite precursor provided by the embodiment of the present invention is prepared by the preparation method provided by the embodiment of the present invention.

[0053] The preparation method of graphite provided by the embodiment of the present invention graphitizes the graphite precursor provided by the embodiment of the present invention at 2900-3100 °C (for example, 2900 °C, 3000 °C, or 3100 °C).

[0054] In this preparation method, since the graphite is prepared using the graphite precursor provided by the embodiment of the present invention, the prepared graphite has better fast charging performance.

[0055] Optionally, after graphitization, it further includes dispersing the obtained graphitized product and sieving it through a 325-mesh sieve, and the material passing through the sieve is the final product.

[0056] The graphite provided by the embodiment of the present invention is prepared by the preparation method provided by the embodiment of the present invention. It has better fast charging performance.

[0057] The anode provided by the embodiment of the present invention is prepared using the graphite provided by the embodiment of the present invention.

[0058] The battery provided by the embodiment of the present invention includes the anode provided by the embodiment of the present invention.

[0059] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0060] Example 1

[0061] Mix 1 Kg of petroleum coke powder with a particle size of 1 - 50 μm and F = 0.5% with 3 L of tetrahydrofuran, and stir for 4 h to obtain a mixture;

[0062] First, perform rotary evaporation under reduced pressure on the mixture. After the solvent is basically volatilized, place the obtained substance in a drying oven and dry it at a temperature of 80 °C for 8 h to fully volatilize the solvent to obtain a graphite precursor;

[0063] Graphitize the graphite precursor at 3000 °C for 2 h to obtain graphite.

[0064] Comparative Example 1

[0065] This comparative example is basically the same as Example 1, except that: the petroleum coke powder is not treated and is directly graphitized.

[0066] Example 2

[0067] Mix 1 Kg of needle coke powder with a particle size of 1 - 60 μm and F = 0.1% with 1 L of dichloromethane, and stir for 2 h to obtain a mixture;

[0068] First, perform rotary evaporation under reduced pressure on the mixture. After the solvent is basically volatilized, place the obtained substance in a drying oven and dry it at a temperature of 80 °C for 8 h to fully volatilize the solvent to obtain a graphite precursor;

[0069] Graphitize the graphite precursor at 2900 °C for 2 h to obtain graphite.

[0070] Comparative Example 2

[0071] This comparative example is basically the same as Example 3, except that: the needle coke powder is not treated and is directly graphitized.

[0072] Example 3

[0073] Mix 1 Kg of pitch coke powder with a particle size of 1 - 80 μm and F = 0.05% with 5 L of toluene, and stir for 6 h to obtain a mixture;

[0074] First, perform rotary evaporation under reduced pressure on the mixture. After the solvent is basically volatilized, place the obtained substance in a drying oven and dry it at a temperature of 120 °C for 8 h to fully volatilize the solvent to obtain a graphite precursor;

[0075] Graphitize the graphite precursor at 3100 °C for 2 h to obtain graphite.

[0076] Comparative Example 3

[0077] This comparative example is basically the same as Example 3, except that: the pitch coke is not treated and is directly graphitized.

[0078] Experimental Example

[0079] The specific surface area, graphitization degree, and Raman of the graphite obtained in each example and comparative example were tested:

[0080] Specific surface area test method: Using the static method, the BET specific surface area of the sample was calculated according to the nitrogen adsorption and desorption curve.

[0081] Graphitization degree test method: The 002 crystal plane spacing was tested by X-ray diffraction and denoted as d 002 , and the graphitization degree was calculated according to the formula graphitization degree = (0.344 - d 002 ) / (0.344 - 0.3354).

[0082] Raman test method: The Raman signal of the sample was tested by a Raman spectrometer, and I D / I G is the ratio of the peak intensities of the D peak and G peak after baseline correction.

[0083] The graphite obtained in each example and comparative example was assembled into a battery to measure the electrochemical performance:

[0084] 1. The method for making a battery with graphite is as follows: Graphite is mixed evenly with SBR, CMC, and SP in a ratio of 95.5:2:1.5:1, coated on a copper foil, and made into a pole piece through drying and rolling, and then assembled with a lithium metal sheet into a button battery.

[0085] 2. The specific method for testing the electrochemical performance is as follows: Under the conditions of constant current charge and discharge at 0.1C and a charge and discharge voltage of 0.05 - 2.0V, the capacity and first Coulomb efficiency of the button battery were tested; the rate performance is the ratio of the capacities at 1.2C and 0.05C currents.

[0086] The test results were recorded in Table 1.

[0087] Table 1 Performance tests of the graphite obtained in each example and comparative example

[0088]

[0089]

[0090] From the test results in Table 1, it can be seen that the graphite precursor prepared by the preparation method of the graphite precursor provided in the examples of the present invention has a slightly increased specific surface area compared with the graphite prepared from the untreated raw coke powder, while the graphitization degree is slightly reduced. This may be attributed to the successful extraction of small molecules inside the coke and their carbonization during the subsequent graphitization process, forming a disordered carbon coating layer containing more defects and pores. The modified graphite shows a significantly improved 1.2C charging capacity and capacity retention rate, indicating that the formed disordered carbon coating layer effectively improves the fast charging performance of the graphite.

[0091] In summary, in the preparation method of the graphite precursor provided by the embodiment of the present invention, by treating the green coke powder with a polar organic solvent, some small molecules that can be dissolved in the polar organic solvent inside the green coke are extracted. After the organic solvent volatilizes, these small molecules are loaded on the outside of the green coke particles; when this precursor is used to prepare graphite, the small molecules on the surface layer of the precursor are carbonized at high temperature to form a hard carbon thin layer that is non-oriented and contains more pores, so that the surface of the prepared graphite has more pores, providing sufficient channels for the insertion of lithium ions and effectively improving the fast charging performance of the graphite. In addition, the coating material in this method is taken from the green coke itself, "self-sufficient", saving the cost of the coating agent.

[0092] Compared with the untreated green coke powder, the graphite precursor provided by the embodiment of the present invention has better fast charging performance when used to prepare graphite.

[0093] The graphite provided by the embodiment of the present invention has better fast charging performance.

[0094] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a graphite precursor, characterized in that, Comprising: Mixing green coke powder evenly with a polar organic solvent to fully dissolve the soluble substances in the green coke powder into the polar organic solvent to obtain a mixture; Volatilizing the polar organic solvent in the mixture to obtain a graphite precursor.

2. The preparation method according to claim 1, characterized in that, The F value of the green coke ≥ 0.1%; Optionally, the green coke is petroleum coke, needle coke or pitch coke; Optionally, the particle size of the green coke powder is 1 - 100 μm.

3. The preparation method according to claim 1, wherein The method of fully dissolving the soluble substances in the green coke powder into the polar organic solvent to obtain a mixture includes: Mixing the green coke powder with the polar organic solvent and stirring for 2 - 6 h.

4. The preparation method according to claim 1, characterized in that, The polar organic solvent is selected from at least one of tetrahydrofuran, toluene, dichloromethane, chloroform and ethyl acetate; Optionally, the ratio of the green coke powder to the polar organic solvent is 1 kg: 1 - 5 L.

5. The preparation method according to claim 1, characterized in that, The method of volatilizing the polar organic solvent in the mixture includes: Placing the mixture in an oven at 80 - 120 °C for drying; Alternatively, first subjecting the mixture to rotary evaporation to recover the polar organic solvent, and then drying at 80 - 120 °C.

6. A graphite precursor, characterized in that, Prepared by using the preparation method according to any one of claims 1 - 5.

7. A method for preparing graphite, characterized in that, Graphitizing the graphite precursor according to claim 6; Preferably, the graphitization temperature is 2900 - 3100 °C.

8. A method for preparing graphite, characterized in that, Comprising: Mixing green coke powder evenly with a polar organic solvent to fully dissolve the soluble substances in the green coke powder into the polar organic solvent to obtain a mixture; Volatilizing the polar organic solvent in the mixture to obtain a graphite precursor; Performing graphitization treatment on the graphite precursor.

9. A kind of graphite, characterized in that, Prepared by using the preparation method according to claim 7 or 8.

10. A negative electrode, characterized in that, Prepared by using the graphite according to claim 9.

11. A battery, characterized in that, Comprising a negative electrode according to claim 10.

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