Graphite negative electrode material, preparation method and application thereof, negative electrode and battery containing same

Abstract

The application discloses a graphite negative electrode material and a preparation method and application thereof, a negative electrode and a battery containing the same, and relates to the technical field of batteries. The graphite negative electrode material comprises a core and a coating layer covering the surface of the core. The core comprises a graphite matrix, and the coating layer is an amorphous carbon layer. A phosphate functional group is connected to the surface of the amorphous carbon layer. The graphite negative electrode material can improve the low-temperature stability of a lithium ion battery and has good rate performance.

Description

Technical Field

[0001] This invention relates to graphite anode materials, their preparation methods and applications, and anodes and batteries containing the same. Background Technology

[0002] Lithium-ion batteries are being used in increasingly diverse applications, such as in cold weather where there is a growing demand for improved battery performance. The improvement of low-temperature performance in lithium batteries largely depends on the anode material, and artificial graphite, as the mainstream anode material, plays a crucial role in achieving good low-temperature performance.

[0003] Currently, the industry's development of low-temperature graphite anode materials mainly focuses on coating amorphous carbon materials. Introducing elements into the amorphous coating layer can alter the surface charge state and enhance surface activity. For example, existing technologies use elemental phosphorus (P) for doping modification, which can improve the material's fast-charging performance. However, in practical applications, elemental phosphorus itself has poor chemical stability and requires inert storage after doping with graphite, making mass production extremely difficult. Selecting P compounds with stable chemical properties under normal conditions can improve the overall low-temperature performance of the material, but may adversely affect the material's capacity. Furthermore, existing preparation processes typically require multiple raw materials and solvents, making the process complex. Summary of the Invention

[0004] The main technical problem addressed by this invention is to overcome the poor low-temperature stability of existing graphite anode materials, and to provide graphite anode materials, their preparation methods and applications, anodes containing these materials, and batteries. When the graphite anode material of this invention is used to make anode sheets in lithium-ion batteries, it exhibits excellent low-temperature stability.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: The present invention provides a graphite anode material comprising a core and a coating layer covering the surface of the core. The core comprises a graphite matrix, and the coating layer is an amorphous carbon layer with phosphate ester functional groups attached to the surface of the amorphous carbon layer.

[0006] In this invention, the phosphate ester functional group is connected to the amorphous carbon by a chemical bond.

[0007] In this invention, the Dv50 particle size of the graphite anode material can be 4-20 μm, preferably 10-14 μm, such as 12.2 μm, 12.8 μm, 13.5 μm, 13.2 μm or 11.6 μm.

[0008] In this invention, the specific surface area of ​​the graphite anode material can be 0.7-2 m². 2 / g, preferably 1-2m 2 / g, for example 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.4m 2 / g or 1.7m 2 / g.

[0009] In this invention, the mass ratio of phosphorus to graphite anode material in the graphite anode material can be 0-1000ppm, but not 0, preferably 300-950ppm, such as 345ppm, 845ppm, 929ppm, 785ppm or 616ppm.

[0010] In this invention, the mass ratio of the coating layer to the core can be (0.001-0.05):1, preferably (0.002-0.04):1, for example 0.003:1, 0.01:1 or 0.03:1.

[0011] This invention also provides a method for preparing a graphite anode material, comprising the following steps: The graphite anode material precursor is carbonized to obtain the graphite anode material; the graphite anode material precursor includes a liquid phase coating agent and a graphite matrix; the liquid phase coating agent includes a phosphate ester and a carbon source.

[0012] In this invention, the phosphate ester may be an alkyl phosphate ester and / or an aromatic phosphate ester.

[0013] The alkyl phosphate is preferably one or more of trimethyl phosphate, tributyl phosphate, and trioctyl phosphate.

[0014] The aromatic phosphate ester is preferably triphenyl phosphate and / or binaphthol phosphate ester.

[0015] In this invention, the carbon source can be a liquid carbon source that can form amorphous carbon on the surface of graphite material and is miscible with phosphate esters, preferably ethylene tar and / or pitch.

[0016] The coking value of the ethylene tar is preferably 10% to 25%, for example, 20%.

[0017] The coking value of the asphalt is preferably 40% to 85%, for example, 60%; the softening point of the asphalt is preferably 100 to 300℃, for example, 210℃.

[0018] In this invention, the mass ratio of the phosphate ester to the carbon source can be (0.01-5):1, preferably (0.5-2):1, for example 0.5:1, 1:1 or 2:1.

[0019] In this invention, the mass ratio of the liquid phase coating agent to the graphite matrix can be (0.005-0.15):1, preferably (0.02-0.15):1, for example 0.05:1, 0.075:1, 0.1:1 or 0.15:1.

[0020] In this invention, the preparation method of the liquid-phase coating agent can be conventional in the art, as long as the phosphate ester and the carbon source are miscible. Preferably, the preparation method of the liquid-phase coating agent includes the following steps: mixing the phosphate ester and the carbon source to obtain the coating agent.

[0021] The mixing is preferably carried out under heating conditions; the heating temperature is preferably 70-90°C, for example 80°C.

[0022] The mixing is preferably carried out under stirring conditions; the stirring time is preferably 20-40 minutes, for example 30 minutes.

[0023] Preferably, the mixing process further includes a step of cooling to room temperature.

[0024] In this invention, room temperature refers to 20-40℃.

[0025] In this invention, the preparation method of the graphite anode material precursor is conventional in the art, which involves mixing the liquid-phase coating agent with the graphite matrix. The mixing is preferably carried out under stirring conditions. The stirring rate is preferably 600-1000 r / min, for example, 800 r / min. The stirring time is preferably 3-10 min, for example, 5 min.

[0026] In this invention, the carbonization temperature can be 1150-1600℃, preferably 1250-1400℃, for example 1350℃.

[0027] In this invention, the heating rate of carbonization can be 2-5℃ / min, for example 3℃ / min.

[0028] In this invention, the carbonization time can be 5-15 hours, for example, 8 hours.

[0029] In this invention, the carbonization atmosphere can be an inert atmosphere; the inert atmosphere may optionally be nitrogen.

[0030] In this invention, the carbonization process may further include a cooling step. The target cooling temperature is preferably ≤50°C, for example, 50°C.

[0031] In this invention, the carbonization process preferably further includes a sieving step.

[0032] In some specific implementations, the phosphate ester is triphenyl phosphate, and the carbon source is ethylene tar.

[0033] In some specific implementations, the phosphate ester is triphenyl phosphate, and the carbon source is pitch.

[0034] The present invention also provides a graphite anode material, which is prepared by the above-described method for preparing graphite anode materials.

[0035] The present invention also provides an application of the above-mentioned graphite anode material in a battery.

[0036] The battery is a lithium-ion battery.

[0037] The present invention also provides a negative electrode comprising the graphite negative electrode material as described above.

[0038] The present invention also provides a battery comprising a negative electrode as described above. The battery is a lithium-ion battery.

[0039] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0040] The reagents and raw materials used in this invention are all commercially available.

[0041] The positive and progressive effects of this invention are as follows: (1) The amorphous carbon on the surface of the graphite anode material provided by the present invention is modified with phosphate ester functional groups. Some of the phosphate ester functional groups decompose to produce phosphoric acid, which has an etching effect on the amorphous carbon layer, so that the material has a higher specific surface area. The higher specific surface area provides more reactive interfaces. In addition, the phosphate ester functional groups have a high affinity for lithium ions. In the lithium intercalation process of the lithium-ion battery anode, they can effectively reduce the electrochemical impedance in the desolvation process of the lithium-ion battery anode, improve the low temperature performance of the material, and have good rate performance.

[0042] (2) The method for preparing graphite anode material provided by the present invention uses a liquid phase coating agent, which ensures the uniformity of the coating process and the doping effect. The process is simple and has good repeatability. Moreover, the preparation method does not require complex pretreatment or special equipment, which is convenient for large-scale production. Attached Figure Description

[0043] Figure 1 The image shows a SEM image of the graphite anode material prepared in Example 1.

[0044] Figure 2 The image shows a SEM image of the graphite anode material prepared in Example 2.

[0045] Figure 3 This is a SEM image of the graphite anode material prepared in Example 3.

[0046] Figure 4 This is a SEM image of the graphite anode material prepared in Example 4.

[0047] Figure 5 This is a SEM image of the graphite anode material prepared in Example 5.

[0048] Figure 6 SEM image of the graphite anode material prepared for Comparative Example 1.

[0049] Figure 7 SEM image of the graphite anode material prepared for Comparative Example 2. Detailed Implementation

[0050] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0051] Example 1

[0052] (1) Triphenyl phosphate and ethylene tar (coking value 20%) were mixed at a mass ratio of 0.5:1, heated to 80°C, mechanically stirred for 30 min to dissolve, and cooled to room temperature to obtain a liquid phase coating agent; the liquid phase coating agent and graphite matrix were mixed at a mass ratio of 7.5:100, put into a fusion machine, and stirred for 5 min (rate 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0053] Example 2

[0054] (1) Triphenyl phosphate and ethylene tar (coking value 20%) were mixed at a mass ratio of 1:1, heated to 80°C, mechanically stirred for 30 min to dissolve, and cooled to room temperature to obtain a liquid phase coating agent; the liquid phase coating agent and graphite matrix were mixed at a mass ratio of 10:100, put into a fusion machine, and stirred for 5 min (rate 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0055] Example 3

[0056] (1) Triphenyl phosphate and ethylene tar (coking value 20%) were mixed at a mass ratio of 2:1, heated to 80°C, mechanically stirred for 30 min to dissolve, and cooled to room temperature to obtain a liquid phase coating agent; the liquid phase coating agent was mixed with graphite matrix at a mass ratio of 15:100, put into a fusion machine, and stirred for 5 min (rate 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0057] Example 4

[0058] (1) Triphenyl phosphate and asphalt (coking value of 60% and softening point of 210℃) were mixed at a mass ratio of 2:1 using a VC machine at 80℃ for 30 min to obtain a liquid phase coating agent; the liquid phase coating agent was mixed with graphite matrix at a mass ratio of 15:100, put into a fusion machine, and stirred for 5 min (speed of 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0059] Example 5

[0060] (1) Tributyl phosphate and ethylene tar (coking value 20%) were mixed at a mass ratio of 2:1, heated to 80°C, mechanically stirred for 30 min to dissolve, and cooled to room temperature to obtain a liquid phase coating agent; the liquid phase coating agent was mixed with graphite matrix at a mass ratio of 15:100, put into a fusion machine, and stirred for 5 min (rate 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0061] Comparative Example 1

[0062] (1) Ethylene tar (coking value 20%) was used as a liquid phase coating agent and mixed with graphite matrix at a mass ratio of 5:100. The mixture was put into a fusion machine and stirred for 5 min (at a rate of 800 r / min) to obtain a graphite anode material precursor. (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0063] Comparative Example 2

[0064] (1) Phosphoric acid and ethylene tar (coking value 20%) were mixed at a mass ratio of 2:1, heated to 80°C, mechanically stirred for 30 min to dissolve, and cooled to room temperature to obtain a liquid phase coating agent; the liquid phase coating agent was mixed with graphite matrix at a mass ratio of 15:100, put into a fusion machine, and stirred for 5 min (rate 800 r / min) to obtain a graphite anode material precursor; (2) The graphite anode material precursor is fed into a high-temperature carbonization device with a high-purity nitrogen atmosphere for carbonization. The carbonization process is as follows: heating from room temperature to 1350℃ at a heating rate of 3℃ / min, holding at a constant temperature for 8 hours, and then naturally cooling to 50℃ for 48 hours before discharging. The material is then sieved with a sieve mesh of 350 mesh to obtain the graphite anode material.

[0065] Example 1

[0066] 1. Microscopic morphological observation

[0067] SEM images of the graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2 were taken using a scanning electron microscope. The test conditions were: HV=10kV; Mag.=3000 X; FW=173μm; Pres.=0.1Pa.

[0068] Figure 1 This is a SEM image of the graphite anode material prepared in Example 1. Figure 2 This is a SEM image of the graphite anode material prepared in Example 2. Figure 3 This is a SEM image of the graphite anode material prepared in Example 3. Figure 4 This is a SEM image of the graphite anode material prepared in Example 4. Figure 5 This is a SEM image of the graphite anode material prepared in Example 5. Figure 6 This is a SEM image of the graphite anode material prepared in Comparative Example 1. Figure 7The image shows a SEM image of the graphite anode material prepared in Comparative Example 2. As can be seen from the image, in Examples 1-5, the graphite anode materials all formed a relatively uniform coating layer with a certain degree of roughness, exhibiting a loose surface structure. In contrast, the graphite anode material in Comparative Example 1 had a denser surface with fewer pores. The graphite anode material in Comparative Example 2 had an uneven coating layer and a poor coating effect.

[0069] 2. Particle size Dv50 test

[0070] The particle size distribution of the graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2 was measured by laser diffraction using a Malvern MS3000 laser particle size analyzer, and the median particle size Dv50 was calculated. The results are shown in Table 1.

[0071] 3. Specific surface area test

[0072] The specific surface area of ​​the graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2 was determined by the BET nitrogen adsorption method using a specific surface area and pore size analyzer. The results are shown in Table 1.

[0073] 4. Phosphorus content test

[0074] The phosphorus content of the graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2 was determined by inductively coupled plasma spectrometry after appropriate digestion treatment. The results are shown in Table 1.

[0075] 5. Mass ratio test of coating layer to core (graphite matrix)

[0076] This invention employs thermogravimetric analysis (TGA) to determine the mass of the coating layer in graphite anode materials. The method involves taking appropriate amounts of dried graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2, placing them in a thermogravimetric analyzer, and heating them under a flowing inert atmosphere. During this process, the coating layer undergoes thermal decomposition and escapes, resulting in a decrease in sample mass, while the graphite matrix mass remains unchanged. The thermogravimetric curves are recorded and analyzed. The mass loss within the temperature range where the coating layer completely decomposes and the substrate does not undergo oxidation weight loss is considered the mass of the coating layer. The mass fraction of the coating layer is directly determined by this percentage of weight loss, and the mass fraction of the graphite matrix is ​​the difference between the total mass and the mass of the coating layer; the ratio of the two is the mass ratio of the coating layer to the core (graphite matrix).

[0077] Example 2

[0078] Preparation method of CR-2430 coin cell lithium-ion half-cell

[0079] The graphite anode materials prepared in Examples 1-5 and Comparative Examples 1-2 were mixed with carboxymethyl cellulose (CMC2200, purchased from Dassault), styrene-butadiene rubber (SN307, purchased from A&L), and conductive agent (Super-P, purchased from Yirui Stone) at a mass ratio of 95.5:1.5:1.5:1.5 respectively. The mixture was then coated onto copper foil and vacuum dried to obtain the anode material. The resulting anode surface density was 10 mg / cm³. 2 The compacted density is 1.50 g / cm³. 3 Using lithium metal as the counter electrode, the electrolyte is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 1:1:1 using 1M LiPF6, and the separator is a PE / PP / PE composite membrane. The resulting coin cell lithium-ion half-cell can be assembled into a battery.

[0080] The coin-type lithium-ion half-cells assembled in the above manner were subjected to the following electrochemical performance tests: 1. Reversible capacity test At 25°C, the battery was discharged at a constant current of 0.1C to 5 mV, and then discharged at a constant voltage of 5 mV until the current dropped to 0.01C and cutoff was achieved. The resulting capacity was recorded as the discharge capacity. Then, the battery was charged at a constant current of 0.1C to 2 V, and the resulting capacity was recorded as the charging capacity, which is the reversible capacity. The results are recorded in Table 2.

[0081] 2. Low-temperature capacity retention test

[0082] At 25℃, the battery was discharged at a constant current of 0.1C to 5 mV, then discharged at a constant voltage of 5 mV until the current cutoff was 0.01C; subsequently, it was charged at a constant current of 0.1C to 2 V, and its charging capacity was recorded as C1. The same battery was placed in a constant temperature environment at -10℃ for 24 hours, then discharged at a constant current of 0.1C to 5 mV, left to stand for 5 minutes, and then charged at a constant current of 0.1C to 2 V, and its charging capacity was recorded as C2.

[0083] The low-temperature capacity retention rate was calculated using the formula (C2 / C1) × 100%, and the results are recorded in Table 2.

[0084] 3. Low-temperature DC internal resistance (DCIR) test

[0085] At 25°C, the battery was discharged at a constant current of 0.1C to 5 mV, then discharged at a constant voltage of 5 mV to 0.01C cutoff, and subsequently charged at a constant current of 0.1C to 2 V, completing one charge-discharge cycle. Afterward, it was discharged at a constant current of 0.1C for 300 min. The discharged battery was then placed in a constant temperature environment of -10°C for 24 h, and its stable open-circuit voltage U0 was recorded. Subsequently, it was pulsed discharged at a constant current of 0.1C (current I1) for 2 seconds, and the voltage U1 at the end of the discharge was recorded.

[0086] The calculation was performed using the formula DCIR = (U0 - U1) / I1. The results are recorded in Table 2.

[0087] 4. Ratio Performance Test

[0088] At 25°C, the battery was discharged at a constant current of 0.1C to 5 mV, then discharged at a constant voltage of 5 mV until the current cutoff was 0.01C; subsequently, it was charged at a constant current of 0.1C to 2 V, completing one charge-discharge cycle. It was then charged again at a constant current of 0.1C to 2V, then discharged at a constant current of 0.2C to 5 mV, and finally discharged at a constant voltage of 5 mV until the current cutoff was 0.01C. The total discharge capacity D was recorded. 0.2C .

[0089] Then, the same battery was charged to 2V at a constant current of 0.1C, discharged to 5mV at a constant current of 2.0C, and then discharged at a constant voltage of 5mV until the current cutoff was 0.01C. The capacity D of the constant current discharge segment was recorded. 2C .

[0090] Rate performance is evaluated by the ratio of the constant current capacity under 2.0C and 0.2C discharge conditions, and the calculation formula is: (D 2C / D 0.2C () × 100%. The results are recorded in Table 2.

[0091] Table 1. Characterization test results of graphite materials

[0092] Table 2 Electrochemical performance test results

[0093] As can be seen from Table 2, when the graphite anode material provided by the present invention is applied to lithium-ion batteries, the lithium-ion batteries have good low-temperature capacity retention (the low-temperature capacity retention at -10℃ is more than 70%), as well as low low-temperature DCIR (DCIR at -10℃ is less than 255Ω) and good rate performance (2C / 0.2C is more than 21%).

[0094] The results of Examples 1-3 show that when the mass ratio of phosphate ester to carbon source increases from 0.5:1 to 2:1, the phosphorus content in the graphite anode material increases accordingly (from 345 ppm to 929 ppm), and the specific surface area also increases (from 1.3 to 1.5 m² / g). Correspondingly, the rate performance (2C / 0.2C ratio increases from 21.1% to 24.9%), low-temperature DCIR (decreases from 251 Ω to 207 Ω), and low-temperature capacity retention (increases from 71% to 77%) are all improved. This indicates that the introduction of phosphate ester effectively improves the low-temperature stability of the graphite anode material.

[0095] Compared to Example 3 (using ethylene tar as the carbon source), Example 4 uses pitch as the carbon source. Under the same phosphate ester content, Example 3 exhibits superior rate performance, low-temperature DCIR, and low-temperature capacity retention compared to Example 4. This demonstrates that using ethylene tar as the carbon source is more beneficial for improving the performance of graphite anode materials in this invention.

[0096] Compared with Example 3, Example 5 uses tributyl phosphate instead of triphenyl phosphate. Under the same preparation conditions, the rate performance, low-temperature DCIR and low-temperature capacity retention of Example 3 are all better than those of Example 5. This shows that in the present invention, aromatic phosphates (such as triphenyl phosphate) are more conducive to improving the performance of graphite anode materials.

[0097] Compared with the embodiments, Comparative Example 1 used only ethylene tar as a liquid phase coating agent, and the phosphorus content in the graphite anode material was only 89 ppm (which is the phosphorus element naturally present in the graphite matrix). It had the lowest specific surface area and the worst electrochemical performance.

[0098] Compared with Example 3, Comparative Example 2 used phosphoric acid instead of phosphate ester. The electrochemical performance of Example 3 (especially low-temperature DCIR and low-temperature capacity retention) was significantly better than that of Comparative Example 2, indicating that phosphate ester can better improve the low-temperature stability of materials than phosphoric acid.

[0099] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A graphite anode material, characterized in that, It includes the kernel and a covering layer that covers the surface of the kernel; The core comprises a graphite matrix, and the coating layer is an amorphous carbon layer; phosphate ester functional groups are attached to the surface of the amorphous carbon layer.

2. The graphite anode material as described in claim 1, characterized in that, It satisfies one or more of the following conditions: a. The Dv50 particle size of the graphite anode material is 4-20 μm, preferably 10-14 μm, such as 12.2 μm, 12.8 μm, 13.5 μm, 13.2 μm or 11.6 μm; b. The specific surface area of ​​the graphite anode material is 0.7-2 m². 2 / g, preferably 1-2m 2 / g, for example 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.4m 2 / g or 1.7m 2 / g; c. The mass ratio of phosphorus to graphite anode material in the graphite anode material is 0-1000ppm, but not 0, preferably 300-950ppm, such as 345ppm, 845ppm, 929ppm, 785ppm or 616ppm. d. The mass ratio of the coating layer to the core is (0.001-0.05):1, preferably (0.002-0.04):1, for example 0.003:1, 0.01:1 or 0.03:

1.

3. A method for preparing a graphite anode material, characterized in that, It includes the following steps: The graphite anode material precursor is carbonized to obtain the graphite anode material. The graphite anode material precursor includes a liquid phase coating agent and a graphite matrix; the liquid phase coating agent contains a phosphate ester and a carbon source.

4. The method for preparing the graphite anode material as described in claim 3, characterized in that, It satisfies one or more of the following conditions: a. The phosphate ester is an alkyl phosphate ester and / or an aromatic phosphate ester; the alkyl phosphate ester is preferably one or more of trimethyl phosphate, tributyl phosphate and trioctyl phosphate; the aromatic phosphate ester is preferably triphenyl phosphate and / or binaphthol phosphate; b. The carbon source is ethylene tar and / or pitch; the coking value of the ethylene tar is preferably 10% to 25%, for example 20%; the coking value of the pitch is preferably 40% to 85%, for example 60%; the softening point of the pitch is preferably 100 to 300°C, for example 210°C. c. The mass ratio of the phosphate ester to the carbon source is (0.01-5):1, preferably (0.5-2):1, for example 0.5:1, 1:1 or 2:1; d. The mass ratio of the liquid coating agent to the graphite matrix is ​​(0.005-0.15):1, preferably (0.02-0.15):1, for example 0.05:1, 0.075:1, 0.1:1 or 0.15:

1.

5. The method for preparing the graphite anode material as described in claim 3, characterized in that, It satisfies one or more of the following conditions ah: a. The preparation method of the liquid phase coating agent includes the following steps: mixing phosphate ester and carbon source to obtain the liquid phase coating agent; b. The preparation method of the graphite anode material precursor includes the following steps: mixing the liquid phase coating agent with the graphite matrix to obtain the graphite anode material precursor; the mixing is preferably carried out under stirring conditions; the stirring rate is preferably 600-1000 r / min, for example 800 r / min; the stirring time is preferably 3-10 min, for example 5 min; c. The carbonization temperature is 1150-1600℃, preferably 1250-1400℃, for example 1350℃; d. The heating rate for carbonization is 2-5℃ / min, for example, 3℃ / min; e. The carbonization time is 5-15 hours, for example, 8 hours; f. The carbonization atmosphere is an inert atmosphere; the inert atmosphere is preferably nitrogen. g. The carbonization process further includes a cooling step; the target cooling temperature is preferably ≤50℃, for example, 50℃; h. Preferably, the carbonization process also includes a sieving step.

6. The method for preparing the graphite anode material as described in claim 5, characterized in that, It satisfies one or more of the following conditions ac: a. In the preparation method of the liquid phase coating agent, the mixing is carried out under heating conditions; the heating temperature is preferably 70-90℃, for example 80℃; b. In the preparation method of the liquid phase coating agent, the mixing is carried out under stirring conditions; the stirring time is preferably 20-40 min, for example 30 min; c. In the preparation method of the liquid phase coating agent, the mixing process further includes a step of cooling to room temperature.

7. A graphite anode material, characterized in that, It is prepared by the method of preparing graphite anode material as described in any one of claims 3-6.

8. The application of a graphite anode material as described in any one of claims 1, 2 and 7 in a battery.

9. A negative electrode, characterized in that, It includes the graphite anode material as described in any one of claims 1, 2 and 7.

10. A battery, characterized in that, It includes the negative electrode as described in claim 9, and the battery is a lithium-ion battery.

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