Graphite material and preparation method thereof, pole piece and battery

Abstract

The invention discloses a graphite material and a preparation method thereof, a pole piece and a battery. The specific surface area (BET), roundness, solid density and tap density of the graphite material meet the following conditions: (1.4-BET) * (1-roundness * solid density) is greater than or equal to 0 and less than or equal to 5; and 5.9 < 25 / (tap density + 5 * roundness * solid density) < 8.3. When the graphite material is applied to a battery, the graphite material has excellent high-temperature storage performance and high-temperature cycle performance.

Description

Technical Field

[0001] The invention relates to a graphite material and a preparation method thereof, a pole piece and a battery. Background Art

[0002] In recent years, with the dramatic increase in CO2 emissions and the continued rise in global temperatures, global warming has led to a growing number of problems that are becoming increasingly acute. To address this global warming, we must accelerate the transition of human activities to a green, low-carbon future. Achieving low carbon is the minimum action we can take to protect our planet.

[0003] Lithium-ion batteries (LIBs) dominate the electrochemical energy storage sector, accounting for 92% of the market. Their development will significantly contribute to the global goal of achieving low-carbon emissions, attracting widespread attention. In the first half of 2024, China's LIB shipments are projected to reach 115GWh, a 41% increase from the first half of 2023, demonstrating a thriving market. Graphite, a key material for negative electrodes in lithium-ion batteries, has seen a sharp increase in demand, driven by the explosive growth of the electric vehicle and energy storage markets. The negative electrode industry is currently undergoing a technological revolution, with high-energy-density, long-life graphite materials becoming a key research and development priority and a pressing task for contemporary materials scientists.

[0004] Prior art CN115477301A discloses a method for preparing a long-cycle graphite anode material for energy storage. The method involves sequentially crushing, shaping, and grading raw coke, followed by low-temperature carbonization and graphitization to produce the long-cycle graphite anode material. However, this material's high-temperature performance is limited, resulting in poor high-temperature storage and high-temperature cycling performance. Summary of the Invention

[0005] To overcome the shortcomings of prior art graphite materials, which suffer from poor high-temperature storage and cycling performance, the present invention provides a graphite material, a preparation method thereof, a pole piece, and a battery. When used in batteries, the graphite material exhibits excellent high-temperature storage and cycling performance.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a graphite material, wherein the specific surface area (BET), roundness, solid density and tap density of the graphite material satisfy the following conditions:

[0008] 0≤(1.4-BET)×(1-roundness×actual density)≤5; 5.9<25 / (tapped density+5×roundness×actual density)<8.3.

[0009] In the present invention, the actual density can reflect the similarity between the projected shape of the graphite material and a circle, and is defined as the ratio of the equivalent area diameter to the maximum Feret diameter (particle length), with the average value taken.

[0010] In the present invention, the roundness can reflect the degree of similarity between the projected area of ​​the graphite material and a circle, taking into account the smoothness of the perimeter, and is defined as the ratio of the equivalent area diameter to the equivalent perimeter diameter, with the average value taken.

[0011] In the present invention, preferably, the specific surface area of ​​the graphite material is 0.5-1.5 m 2 / g, more preferably 0.8-1.2m 2 / g, for example, 0.86 m 2 / g, 0.92 m 2 / g, 0.98 m 2 / g or 1.12 m 2 / g.

[0012] In the present invention, preferably, the roundness of the graphite material is 0.4-0.6, more preferably 0.45-0.55, for example, 0.481, 0.486, 0.499 or 0.514.

[0013] In the present invention, preferably, the actual density of the graphite material is 0.5-0.8, more preferably 0.6-0.75, for example, 0.682, 0.685, 0.694 or 0.706.

[0014] In the present invention, preferably, the tap density of the graphite material is 1.2-1.5 g / cm 3 , more preferably 1.3-1.4 g / cm 3 , for example, 1.32 g / cm 3 , 1.35 g / cm 3 , 1.37 g / cm 3 or 1.38 g / cm 3 .

[0015] In the present invention, preferably, the specific surface area (BET), roundness, actual density and tap density of the graphite material satisfy the following relationship:

[0016] 0≤(1.4-BET)×(1-roundness×actual density)≤1;

[0017] 7.5≤25 / (tapped density+5×roundness×tapped density)≤8.3.

[0018] In a specific embodiment of the present invention, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.184, and 25 / (tap density + 5×circularity×actual density) is 8.18.

[0019] In a specific embodiment of the present invention, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.281, and 25 / (tap density + 5×circularity×actual density) is 8.23.

[0020] In a specific embodiment of the present invention, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.306, and 25 / (tap density + 5×circularity×actual density) is 7.9.

[0021] In a specific embodiment of the present invention, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.353, and 25 / (tap density + 5×circularity×actual density) is 8.06.

[0022] In the present invention, preferably, the graphitization degree of the graphite material is 91%-95%, for example, 92%, 92.8%, 93.5% or 94.6%.

[0023] In the present invention, preferably, the Raman median of the graphite material is 0.8-0.15, for example, 0.082, 0.104, 0.112 or 0.125.

[0024] In the present invention, preferably, the particle size distribution range of the graphite material is 0.5-55 μm.

[0025] In a specific embodiment of the present invention, the particle size distribution range of the graphite material is 0.8-45.72 μm.

[0026] In a specific embodiment of the present invention, the particle size distribution range of the graphite material is 0.88-45.35 μm.

[0027] In a specific embodiment of the present invention, the particle size distribution range of the graphite material is 0.9-46.9 μm.

[0028] In a specific embodiment of the present invention, the particle size distribution range of the graphite material is 1.1-52.39 μm.

[0029] In the present invention, preferably, the D50 particle size of the graphite material is 10-15 μm, for example, 10.33 μm, 11.57 μm, 12.49 μm or 14.58 μm.

[0030] The present invention also provides a method for preparing a graphite material, comprising the following steps: shaping a raw material to obtain a carbon precursor; sequentially subjecting the carbon precursor to heat treatment and graphitization to obtain the graphite material; the heat treatment temperature is 600-1500°C; the graphitization temperature is 2700-3200°C;

[0031] The Hardgrove Grindability Index (HGI) of the raw material is greater than 65;

[0032] The Hardgrove grindability coefficient of the raw material, the roundness and the solid density of the carbon precursor satisfy the following conditions:

[0033] 0<(Harrington grindability coefficient - 66) / Harrington grindability coefficient + (roundness - 0.46) × 32<2;

[0034] 4<actual density×Hargrove grindability coefficient / 10<10.

[0035] In this invention, the Hardgrove Grindability Index (HGI) reflects the relative ease of grinding a raw material into powder. A higher HGI indicates that the same amount of raw material of a specified particle size can be ground into a finer powder with a given amount of energy. Alternatively, the lower the energy consumption, the lower the amount of raw material of a specified particle size can be ground into the same fineness.

[0036] In the present invention, the actual density reflects the degree of similarity between the projected shape of the carbon precursor and a circle and is defined as the average value of the ratio of the equivalent area diameter to the maximum Feret diameter (particle length). The actual density can be measured using a particle size and shape analyzer.

[0037] In the present invention, the roundness reflects the degree to which the projected area of ​​the carbon precursor resembles a circle, taking into account the smoothness of the perimeter. It is defined as the ratio of the equivalent area diameter to the equivalent perimeter diameter, taking the average value. The roundness can be measured using a particle size and shape analyzer.

[0038] In the present invention, preferably, the type of the raw material is one or more of petroleum coke, pitch coke and needle coke.

[0039] In the present invention, preferably, the mass content of the volatile matter of the raw material is 5%-20%, for example, 6.6%, 8.6% or 11.5%, wherein the mass content means the mass percentage of the volatile matter to the mass percentage of the raw material.

[0040] In the present invention, preferably, the ash content of the raw material is less than 1% by mass, for example, 0.22%, 0.35% or 0.41%, wherein the mass content means the mass percentage of the ash to the mass percentage of the raw material.

[0041] In the present invention, preferably, the mass content of sulfur in the raw material is 1.5% or less, for example, 0.13%, 0.18% or 0.58%, wherein the mass content refers to the mass percentage of sulfur in the raw material.

[0042] In the present invention, preferably, the moisture content of the raw material is less than 10%, more preferably less than 9.3%, for example, 6.5%, 8% or 8.7%. Wherein, the moisture content means the mass percentage of water to the mass percentage of the raw material.

[0043] In the present invention, preferably, the Hardgrove Grindability Index (HGI) of the raw material is greater than 85, for example, 96, 103 or 114.

[0044] In the present invention, preferably, the roundness of the carbon precursor is 0.4-0.5, for example, 0.461, 0.463, 0.48 or 0.481.

[0045] In the present invention, preferably, the actual density of the carbon precursor is 0.6-0.7, for example, 0.665, 0.667, 0.68 or 0.681.

[0046] In the present invention, preferably, the Hardgrove grindability coefficient of the raw material, the roundness and the solid density of the carbon precursor satisfy the following relationship:

[0047] 0.2≤(Harrington grindability coefficient -66) / Harrington grindability coefficient + (roundness -0.46)×32≤1.5;

[0048] 5≤actual density×Hargrove grindability coefficient / 10≤8.

[0049] In a specific embodiment of the present invention, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following conditions: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 1, and the actual density × Hardgrove grindability coefficient / 10 is 7.

[0050] In a specific embodiment of the present invention, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.52, and the actual density × Hardgrove grindability coefficient / 10 is 7.6.

[0051] In a specific embodiment of the present invention, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.98, and the actual density × Hardgrove grindability coefficient / 10 is 6.54.

[0052] In a specific embodiment of the present invention, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.26, and the actual density × Hardgrove grindability coefficient / 10 is 5.65.

[0053] In the present invention, preferably, the shaping includes pulverization and fine shaping in sequence.

[0054] The equipment used for the crushing can be conventional equipment in the art, such as a mechanical mill.

[0055] The equipment used for the fine shaping can be conventional equipment in the art, such as a shaping machine.

[0056] Preferably, the shaping machine is of intermittent type.

[0057] Preferably, the frequency of the shaping machine is 5-50 Hz.

[0058] Preferably, the time for the fine shaping is 1-60 minutes, for example, 30 minutes.

[0059] In the present invention, preferably, the temperature of the heat treatment is 1000-1500°C, for example 1100°C.

[0060] In the present invention, preferably, the heat treatment time is 10-60 hours, for example, 30 hours.

[0061] In the present invention, preferably, the temperature of the graphitization treatment is 2800-3200°C, for example, 3000°C.

[0062] In the present invention, preferably, the graphitization treatment time is 30-50 hours, for example, 40 hours.

[0063] The present invention also provides a graphite material prepared by the method for preparing the graphite material.

[0064] The present invention also provides a pole piece, which comprises the above-mentioned graphite material.

[0065] The present invention also provides a battery comprising the above-mentioned electrode piece.

[0066] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0067] The reagents and raw materials used in the present invention are commercially available.

[0068] The positive progress effect of the present invention is:

[0069] The graphite material of the present invention controls its specific surface area, roundness, actual density and tap density to satisfy the above-mentioned relationship, so that the particles of the graphite material tend to be spherical, the surface is round and smooth, there are fewer tips, and there are fewer side reactions, so that when it is used in a battery, it can have excellent high-temperature storage performance and high-temperature cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 This is the SEM image of the graphite material of Example 1. DETAILED DESCRIPTION

[0071] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0072] The parameters of the raw materials used in the following examples and comparative examples are listed in Table 1:

[0073] Table 1

[0074] ; Among them, the testing methods of the above parameters of raw materials are as follows:

[0075] 1. Moisture content test: Use a coulometric moisture meter to test the moisture content of the raw materials.

[0076] 2. Ash mass content test: Calcine the raw material sample in a muffle furnace at 850°C for 5-6 hours, and calculate the ash mass content based on the mass difference of the sample before and after calcination.

[0077] 3. Volatile matter mass content test: Heat the raw material sample to 850℃ without air introduction and keep the temperature constant for 7 minutes. Determine the volatile matter based on the difference between the total weight loss and the evaporation water loss.

[0078] 4. Test of sulfur content: Use infrared sulfur meter to test the sulfur content in raw materials.

[0079] 5. Hardgrove grindability coefficient test: Use Hardgrove grindability tester to test the Hardgrove grindability coefficient of raw materials.

[0080] Example 1

[0081] Raw materials: Select raw material A mentioned above.

[0082] The preparation method of graphite material is as follows:

[0083] Preparation of carbon precursor: The above raw materials were mechanically ground and then finely shaped by a shaping machine to obtain a carbon precursor; the shaping machine frequency was 50 Hz, and the fine shaping time was 30 min.

[0084] Preparation of graphite material: The above carbon precursor was placed in a tunnel kiln, heat treated at 1100°C for 30 hours, and then graphitized in an Acheson crucible furnace at 3000°C for 40 hours to obtain a graphite material.

[0085] Example 2

[0086] Raw materials: Select raw material B mentioned above.

[0087] The preparation conditions of the graphite material are the same as those in Example 1.

[0088] Example 3

[0089] Raw materials: The above raw materials B and C were selected, and the mass ratio of raw materials B and C was 3:7. The Hardgrove grindability coefficient of the raw materials in Example 3 was 96.

[0090] The preparation conditions of the graphite material are the same as those in Example 1.

[0091] Example 4

[0092] Raw materials: Select raw material C mentioned above.

[0093] The preparation conditions of the graphite material are the same as those in Example 1.

[0094] Comparative Example 1

[0095] Raw materials: Select raw material D mentioned above.

[0096] The preparation conditions of the graphite material are the same as those in Example 1.

[0097] Comparative Example 2

[0098] Raw materials: Select raw material D mentioned above.

[0099] The preparation conditions of the graphite material are the same as those in Example 1.

[0100] Comparative Example 3

[0101] Raw materials: The above raw materials E and C were selected, and the mass ratio of raw materials E and C was 7:3. The Hardgrove grindability coefficient of the raw materials in Comparative Example 3 was 64.

[0102] The preparation conditions of the graphite material are the same as those in Example 1.

[0103] Effect Example 1

[0104] The carbon precursors prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to the following tests:

[0105] 1. Use R-3000 particle size and shape analyzer to test the actual density and roundness of the carbon precursor;

[0106] The above test results are listed in Table 2:

[0107] Table 2

[0108] ; The graphite materials prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to the following tests:

[0109] 1. Use laser particle size analyzer MS3000 to test the D50 median particle size and particle size distribution range of graphite materials;

[0110] 2. Use R-3000 particle size and shape analyzer to test the actual density and roundness of graphite materials;

[0111] 3. Use the specific surface area meter NOVA Touch2000 to test the specific surface area of ​​graphite material;

[0112] 4. The tap density of graphite material tested by tap density meter BT-312;

[0113] 5. Use Bruker equipment to test the graphitization degree of graphite materials;

[0114] 6. Using Raman equipment (Renishaw), the confocal Raman spectrum of graphite material was tested (Renishaw). The G peak ("Graphite" band) is located at about 1580 cm -1 The D peak (“Defect” band) is located at about 1360 cm-1, corresponding to the E2g vibration mode. -1 , corresponding to the disordered carbon ring structure; thus obtaining the Raman median.

[0115] 7. SEM test: The graphite material was characterized by scanning electron microscopy. The SEM image of the graphite material of Example 1 is as follows: Figure 1 shown.

[0116] The above test results are listed in Table 3:

[0117] Table 3

[0118] ; The Hardgrove grindability index (HGI) of the raw materials of Examples 1-4 is greater than 65, and the Hardgrove grindability index, the roundness and the actual density of the carbon precursor satisfy the following conditions: 0<(Haugh grindability index-66) / Haugh grindability index+(roundness-0.46)×32<2; 4<actual density×Haugh grindability index / 10<10; so that the specific surface area (BET), roundness, actual density and tap density of the prepared graphite material satisfy the following conditions: 0≤(1.4-BET)×(1-roundness×actual density)≤5; 5.9<25 / (tap density+5×roundness×actual density)<8.3.

[0119] The tap density of the graphite material particles of Examples 1-4 is higher than 1.3 g / cm 3 ;Specific surface area is 0.8-1.2 m 2 / g; moderate size and relatively even distribution.

[0120] Effect Example 2

[0121] Preparation of half-cell:

[0122] The graphite material, conductive carbon black SP, CMC, and SBR from Examples 1-4 and Comparative Example 1 were weighed in a mass ratio of 95:1:2:2, mixed evenly in water to form a negative electrode slurry. This was evenly coated onto copper foil using an applicator. The coated electrode was vacuum-dried in a 110°C vacuum drying oven for 4 hours and then pressed into a sheet to form the negative electrode. The compacted density is calculated as the electrode mass / (thickness of the electrode after rolling - current collector thickness). CR-2430 button cells were assembled in an argon-filled Braun glove box in Germany. The electrolyte consisted of 1M LiPF6 + EC:EMC:DMC in a 1:1:1 ratio (volume ratio). A lithium metal sheet served as the counter electrode.

[0123] Preparation of full battery:

[0124] The graphite materials prepared in Examples 1-4 and Comparative Example 1 were respectively used to prepare full battery tests according to the following method:

[0125] The negative electrode materials, conductive carbon black SP, CMC, and SBR of Examples 1-4 and Comparative Example 1 were weighed in a mass ratio of 96:1.2:1:1.8. The negative electrode materials, conductive carbon black SP, CMC, and SBR were mixed in water to form a negative electrode slurry. The slurry was evenly applied to copper foil using an applicator. The coated electrode was vacuum-dried in a 90°C vacuum drying oven for 48 hours, and then pressed into a negative electrode. The compaction density was calculated as: electrode mass / (thickness of the electrode after rolling - thickness of the current collector). The electrolyte solution was 1M LiPF6, and the main additives were EC, EMC, DMC, and FEC. The negative and positive electrode sheets were stacked into a soft-pack cell with a capacity of 1000mAh.

[0126] The following tests were performed on the half-cells prepared above:

[0127] 1. Discharge capacity and first discharge efficiency test: The prepared half-cell was subjected to discharge capacity and first discharge efficiency tests on an American Arbin BT2000 battery tester. The battery was subjected to the first long cycle charge and discharge, and its charge capacity and discharge capacity were measured. The operating voltage range of the battery test was 2.8V (discharge cut-off voltage) to 4.35V (charge cut-off voltage), and the test rate was 0.3C; first discharge efficiency = first discharge capacity / first charge capacity × 100%.

[0128] The following tests were performed on the full battery prepared above:

[0129] 2. 0.25P / 0.25P 35℃ 1000-cycle capacity retention rate: The battery is charged at 0.25P power and discharged at 0.25P power for 1000 cycles. Calculate the ratio of the discharge capacity after 1000 cycles to the initial discharge capacity of the battery.

[0130] 3. 58-day 60°C capacity retention rate: Measure the initial discharge capacity of the battery, place it at 60°C for 58 days, and then test the discharge capacity after 58 days. Calculate the ratio of the discharge capacity after 58 days to the initial discharge capacity.

[0131] The above test results are listed in Table 4:

[0132] Table 4

[0133] ; According to the results in the above table, after the graphite materials prepared in Examples 1-4 were used to prepare batteries, the first discharge efficiency of the batteries was above 94%, and the capacity retention rate at 0.25P / 0.25P at 35°C for 1000 cycles was above 91%, indicating that the high-temperature cycle performance at low rates was excellent, and the capacity retention rate at 60°C for 58 days was above 94%, indicating that the high-temperature storage performance was excellent; at the same time, the discharge capacity was above 342 mAh / g.

[0134] The raw materials of Comparative Examples 1-3 are not within the scope of the present invention, so that the specific surface area (BET), roundness, solid density and tap density of the graphite materials prepared from the raw materials cannot meet the relationship of the present invention, resulting in the first discharge efficiency, 1000-cycle capacity retention rate and 58-day 60°C capacity retention rate all being deteriorated when used in batteries.

Claims

1. A graphite material, characterized in that: The BET, roundness, solid density and tap density of the graphite material satisfy the following conditions: 0≤(1.4-BET)×(1-roundness×actual density)≤5; 5.9<25 / (tapped density+5×roundness×actual density)<8.

3.

2. The graphite material according to claim 1, wherein The specific surface area of ​​the graphite material is 0.5-1.5 m 2 / g, preferably 0.8-1.2 m 2 / g, for example, 0.86 m 2 / g, 0.92 m 2 / g, 0.98 m 2 / g or 1.12 m 2 / g; And / or, the roundness of the graphite material is 0.4-0.6, preferably 0.45-0.55, for example 0.481, 0.486, 0.499 or 0.514; And / or, the actual density of the graphite material is 0.5-0.8, preferably 0.6-0.75, for example 0.682, 0.685, 0.694 or 0.706; And / or, the specific surface area (BET), roundness, actual density and tap density of the graphite material satisfy the following conditions: 0≤(1.4-BET)×(1-roundness×actual density)≤1; 7.5≤25 / (tap density+5×roundness×actual density)≤8.3; And / or, the graphite material has a degree of graphitization of 91%-95%, for example, 92%, 92.8%, 93.5% or 94.6%; And / or, the Raman median of the graphite material is 0.8-0.15, for example, 0.082, 0.104, 0.112 or 0.125; And / or, the particle size distribution range of the graphite material is 0.5-55 μm; And / or, the D50 particle size of the graphite material is 10-15 μm, for example, 10.33 μm, 11.57 μm, 12.49 μm or 14.58 μm.

3. The graphite material according to claim 1, wherein The specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.184, and 25 / (tap density+5×circularity×actual density) is 8.18; Alternatively, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.281, and 25 / (tap density+5×circularity×actual density) is 8.23; Alternatively, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following conditions: (1.4-BET)×(1-circularity×actual density) is 0.306, and 25 / (tap density+5×circularity×actual density) is 7.9; Alternatively, the specific surface area (BET), circularity, actual density and tap density of the graphite material satisfy the following relationship: (1.4-BET)×(1-circularity×actual density) is 0.353, and 25 / (tap density+5×circularity×actual density) is 8.

06.

4. A method for preparing a graphite material, characterized in that: The preparation method of the graphite material comprises the following steps: shaping the raw material to obtain a carbon precursor; sequentially subjecting the carbon precursor to heat treatment and graphitization treatment to obtain the graphite material; the heat treatment temperature is 600-1500° C.; the graphitization temperature is 2700-3200° C.; The Hardgrove Grindability Index (HGI) of the raw material is greater than 65; The Hardgrove grindability coefficient of the raw material, the roundness and the solid density of the carbon precursor satisfy the following conditions: 0<(Harrington grindability coefficient - 66) / Harrington grindability coefficient + (roundness - 0.46) × 32<2; 4<actual density×Hargrove grindability coefficient / 10<10.

5. The method for preparing a graphite material according to claim 4, wherein: The raw materials are one or more of petroleum coke, pitch coke and needle coke; And / or, the mass content of volatile matter in the raw material is 5%-20%, for example, 6.6%, 8.6% or 11.5%; wherein the mass content means the mass percentage of the volatile matter to the mass percentage of the raw material; And / or, the ash content of the raw material is less than 1% by mass, for example, 0.22%, 0.35% or 0.41%; wherein the mass content means the mass percentage of the ash to the mass percentage of the raw material; And / or, the mass content of sulfur in the raw material is less than 1.5%, for example, 0.13%, 0.18% or 0.58%; wherein the mass content means the mass percentage of sulfur in the raw material; And / or, the moisture content of the raw material is less than 10%, more preferably less than 9.3%, for example 6.5%, 8% or 8.7%; wherein the moisture content means the mass percentage of water to the mass percentage of the raw material; and / or the Hardgrove grindability coefficient of the raw material is greater than 85, for example, 96, 103 or 114; and / or, the carbon precursor has a roundness of 0.4-0.5, for example, 0.461, 0.463, 0.48 or 0.481; and / or, the carbon precursor has a solid density of 0.6-0.7, for example, 0.665, 0.667, 0.68 or 0.681; And / or, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: 0.2≤(Hattgrove grindability coefficient-66) / Hattgrove grindability coefficient+(roundness-0.46)×32≤1.5; 5≤actual density×Hattgrove grindability coefficient / 10≤8.

6. The method for preparing a graphite material according to claim 4, wherein: The Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following conditions: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 1, and the actual density × Hardgrove grindability coefficient / 10 is 7; Alternatively, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.52, and the actual density × Hardgrove grindability coefficient / 10 is 7.6; Alternatively, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.98, and the actual density × Hardgrove grindability coefficient / 10 is 6.54; Alternatively, the Hardgrove grindability coefficient of the raw material, the roundness and the actual density of the carbon precursor satisfy the following relationship: (Hattgrove grindability coefficient - 66) / Hardgrove grindability coefficient + (roundness - 0.46) × 32 is 0.26, and the actual density × Hardgrove grindability coefficient / 10 is 5.

65.

7. The method for preparing a graphite material according to claim 4, wherein: The shaping includes crushing and fine shaping in sequence; And / or, the temperature of the heat treatment is 1000-1500° C., for example, 1100° C.; And / or, the heat treatment time is 10-60h, for example, 30h; And / or, the temperature of the graphitization treatment is 2800-3200° C., for example, 3000° C.; And / or, the graphitization treatment time is 30-50 hours, for example, 40 hours.

8. A graphite material obtained by the method for preparing a graphite material according to any one of claims 4 to 7.

9. A pole piece, characterized in that: It comprises the graphite material according to any one of claims 1 to 3 and 8.

10. A battery, characterized in that: It comprises the pole piece as claimed in claim 9.

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