Method for preparing negative electrode material and application thereof

Abstract

The application provides a preparation method of a negative electrode material and application thereof, and comprises the following steps: calculating m according to the formula: n=a*(m) 2 +b*m+c, wherein a is -0.0077, b is 0.9108, c is 326.8, n is the preset specific capacity of the prepared negative electrode material, and the unit is mAh / g; and selecting petroleum coke with a mass percentage of m% of meso-aromatic hydrocarbons, and obtaining the negative electrode material after graphitization treatment. According to the preparation method, the raw material can be prepared according to a specific relationship, and the negative electrode material close to the preset specific capacity can be prepared. The preparation method is novel, the preparation process is simple, the controllability is high, and the industrialized production of the negative electrode material is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a preparation method of a negative electrode material and application thereof. BACKGROUND

[0002] At present, lithium ion batteries have been widely applied in many fields such as electronic devices and vehicles due to their high energy density and excellent cycle performance. Artificial graphite is a commonly used negative electrode material for lithium ion batteries. Different application scenarios have different requirements for the gram capacity of graphite negative electrode materials. In the prior art, it is difficult to directly prepare graphite negative electrode materials that are highly adapted to the gram capacity required by different application scenarios, which is not conducive to promoting the commercial application of graphite negative electrode materials. Therefore, it is necessary to provide a preparation method of a negative electrode material, which can adjust the preparation process according to the required gram capacity to obtain a negative electrode material as close as possible to the required gram capacity, thereby improving the adaptation degree of multi-scene application. SUMMARY

[0003] In view of this, the present application provides a preparation method of a negative electrode material and application thereof. The preparation method can prepare a negative electrode material close to a preset gram capacity by adjusting the preparation raw materials according to a specific relationship, and has the advantages of novel preparation method, simple preparation process and high controllability, which is beneficial to the industrial production of negative electrode materials.

[0004] In a first aspect, the present application provides a preparation method of a negative electrode material, comprising:

[0005] m is calculated according to the formula: n=a×(m) 2 +b×m+c, wherein a is -0.0077, b is 0.9108, c is 326.8, and n is a preset gram capacity of the prepared negative electrode material, with the unit of mAh / g;

[0006] The petroleum coke with a mass percentage of meso-aromatic hydrocarbons of m% is selected, and the negative electrode material is obtained after graphitization treatment, wherein the meso-aromatic hydrocarbons include polycyclic aromatic hydrocarbons and naphthenes with 2-4 benzene rings.

[0007] Optionally, n is 340 mAh / g-355 mAh / g, and the mass percentage of the meso-aromatic hydrocarbons is 20%-75%.

[0008] Optionally, the temperature of the graphitization treatment is 2800°C-3100°C.

[0009] Optionally, the particle size D50 of the petroleum coke is 9 μm-17 μm.

[0010] Optionally, the sulfur content of the petroleum coke is less than or equal to 3%, and the volatile matter of the petroleum coke is less than or equal to 14%.

[0011] The preparation method provided in the application can prepare the negative electrode material with the preset gram capacity by adjusting the composition of the preparation raw material through a specific relationship between the preparation raw material and the gram capacity of the prepared negative electrode material, and the preparation process is simple, the controllability is better, and the commercial application of the negative electrode material is facilitated.

[0012] In a second aspect, the application provides a method for predicting the gram capacity of a negative electrode material, comprising: obtaining the mass percentage content m of meso-aromatic hydrocarbons in petroleum coke; and calculating n according to the formula: n = a x (m) 2 +b x m + c, wherein a is -0.0077, b is 0.9108, and c is 326.8, and the n is the predicted gram capacity of the negative electrode material, in mAh / g.

[0013] In a third aspect, the application provides a method for selecting petroleum coke based on the preset gram capacity of a negative electrode material, comprising: determining the preset gram capacity n of the prepared negative electrode material, in mAh / g; and calculating m according to the formula: n = a x (m) 2 +b x m + c, wherein a is -0.0077, b is 0.9108, and c is 326.8, and the m is the mass percentage content of meso-aromatic hydrocarbons in the petroleum coke.

[0014] The method for selecting petroleum coke based on the preset gram capacity of a negative electrode material provided in the application can select the petroleum coke based on the preset gram capacity of the negative electrode material, and is beneficial to obtaining the negative electrode material with the ideal gram capacity.

[0015] In a fourth aspect, the application provides a negative electrode material, which is prepared by the preparation method in the first aspect.

[0016] In a fifth aspect, the application provides a negative electrode sheet, which comprises the negative electrode material prepared by the preparation method in the first aspect or the negative electrode material in the fourth aspect.

[0017] In a sixth aspect, the application provides a battery, which comprises the positive electrode sheet and the negative electrode sheet in the fifth aspect.

[0018] In a seventh aspect, the application provides an electric device, which comprises the battery in the sixth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0020] Figure 1 A flow chart of extracting aromatics from petroleum coke is provided for an embodiment of the present application.

[0021] Figure 2 A distribution diagram of aromatics after three times of expansion is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0023] The present application provides a preparation method of a negative electrode material, comprising: calculating m according to the formula: n = a x (m) 2 +b x m + c; wherein a is -0.0077, b is 0.9108, c is 326.8, n is a preset gram capacity of the prepared negative electrode material, and the unit is mAh / g; selecting petroleum coke with a mass percentage of meso-aromatic hydrocarbons of m%, and obtaining the negative electrode material after graphitization treatment. The preparation method provided by the present application selects the petroleum coke meeting the specific relationship formula according to the specific relationship formula constituted by the mass percentage of meso-aromatic hydrocarbons in the petroleum coke and the preset gram capacity of the prepared negative electrode material, and obtains the negative electrode material as close as possible to the preset gram capacity after graphitization treatment. The present application adjusts the preparation raw material through the specific relationship formula constituted by the preset gram capacity of the preparation raw material and the negative electrode material, and the prepared negative electrode material has a test gram capacity very close to the preset gram capacity, which improves the adaptation degree of the negative electrode material to different application scenarios, and the preparation method is novel, the preparation process is simple, the controllability is high, and it is conducive to the wide application of the negative electrode material.

[0024] In an embodiment of the present application, the preset gram capacity of the prepared negative electrode material is n mAh / g, the mass percentage of the required meso-aromatic hydrocarbons in the petroleum coke is calculated through the above formula, and the petroleum coke meeting the mass percentage requirement of meso-aromatic hydrocarbons is selected according to the calculated mass percentage of meso-aromatic hydrocarbons. After graphitization treatment, the negative electrode material as close as possible to the preset gram capacity can be obtained. In an embodiment of the present application, the preset gram capacity of the prepared negative electrode material is 348.1 mAh / g, and the specific formula: n = a x (m) 2+ b x m + c, a is -0.0077, b is 0.9108, and c is 326.8, the mass percentage of the required medium aromatic hydrocarbon in the petroleum coke is calculated to be 29.94% (m%), the petroleum coke containing the medium aromatic hydrocarbon with the mass percentage of 29.94% is selected, and after graphitization treatment, the negative electrode material is obtained, and the gram capacity of the negative electrode material is tested to be 345 mAh / g. The gram capacity of the prepared negative electrode material is close to the preset gram capacity of the negative electrode material. In some embodiments, the preset gram capacity of the prepared negative electrode material is n mAh / g, the mass percentage of the required medium aromatic hydrocarbon in the petroleum coke is calculated by the above formula, two different mass percentages of the medium aromatic hydrocarbon can be obtained, and any petroleum coke meeting the mass percentage requirement of the medium aromatic hydrocarbon can be selected to obtain the negative electrode material as close as possible to the preset gram capacity after graphitization treatment.

[0025] In an embodiment of the present application, the preset gram capacity (n) of the negative electrode material is 340 mAh / g-355 mAh / g. Specifically, the preset gram capacity of the negative electrode material can be, but is not limited to, 340 mAh / g, 342 mA h / g, 344 mA h / g, 346 mA h / g, 348 mA h / g, 350 mA h / g, 352 mA h / g, or 355 mA h / g, etc. In an embodiment of the present application, the preset gram capacity (n) of the negative electrode material can be 340 mA h / g-350 mA h / g. In another embodiment of the present application, the preset gram capacity (n) of the negative electrode material can be 347 mA h / g-355 mAh / g.

[0026] In the present application, the petroleum coke contains medium aromatic hydrocarbon, the medium aromatic hydrocarbon mainly contains polycyclic aromatic hydrocarbon with 2-4 benzene rings, and a small amount of naphthene, the mass percentage (m) of the medium aromatic hydrocarbon is 20%-75%, and the appropriate content of the medium aromatic hydrocarbon can improve the intermediate phase fusion kinetics in the graphitization process of the petroleum coke, improve the crystallinity of the negative electrode material, and further improve the gram capacity of the negative electrode material. If the content of the medium aromatic hydrocarbon is too low, the aromaticity is low, the carbonization rate is low in the graphitization process, the intermediate phase cannot be well fused, and it is not easy to form a good streamline structure, and if the content of the medium aromatic hydrocarbon is too high, the aromaticity is improved, the carbonization rate is increased, the intermediate phase cannot be fused, and a good streamline structure cannot be obtained, which further affects the gram capacity of the negative electrode material. Specifically, the mass percentage of the medium aromatic hydrocarbon can be, but is not limited to, 20%, 30%, 40%, 50%, 60%, 70%, or 75%, etc. In an embodiment of the present application, the mass content of the medium aromatic hydrocarbon can be 20%-55%. In another embodiment of the present application, the mass content of the medium aromatic hydrocarbon can be 50%-75%.

[0027] In an embodiment of the present application, the test gram capacity of the negative electrode material is the preset gram capacity of the negative electrode material ± 3 mAh / g. Due to the gram capacity testing instrument, method, etc., there is a certain error between the preset gram capacity and the test gram capacity, and the error between the test gram capacity of the negative electrode material and the preset gram capacity of the negative electrode material can be within ± 3 mA h / g. The gram capacity of the negative electrode material can be accurately predicted by the preparation method provided in the present application, and the adaptation degree of multiple scene applications can be improved.

[0028] Referring to Figure 1 The petroleum coke aromatic extraction flowchart provided in an embodiment of the present application includes:

[0029] The petroleum coke is mixed with n-heptane, and after filtration, insoluble matter is obtained.

[0030] The insoluble matter is mixed with toluene, and after filtration and concentration, concentrated aromatics are obtained.

[0031] The concentrated aromatics are separated by development, and medium-quality aromatics are obtained. In an embodiment of the present application, 3 g of petroleum coke powder is mixed with 30 ml of n-heptane, stirred and extracted for 1 h, and the filter residue is collected by filtration to obtain insoluble matter. The insoluble matter is mixed with 30 ml of toluene, stirred and extracted for 2 h, and the filtrate is collected by filtration and concentrated by rotary evaporation to obtain concentrated aromatics. The concentrated aromatics are placed on a silica gel column of a four-component analyzer, separated by development, and then placed in a hydrogen flame ionization detector (FID) to obtain the mass percentage content of medium-quality aromatics.

[0032] In an embodiment of the present application, the development and separation process includes one-time development, two-time development, and three-time development. According to the principle of similar solubility, that is, the solubility or adsorption force of each component in the concentrated aromatics is different on the silica gel column and in different solvents. After three-time development, the concentrated aromatics are separated into light aromatics, medium-quality aromatics, and heavy aromatics. As shown in Figure 2 the aromatic distribution diagram after three-time development in an embodiment of the present application.

[0033] In an embodiment of the present application, a first development liquid is used for one-time development, the first development liquid is a mixed solution of n-heptane and toluene with a volume ratio of 95:5, the time for one-time development is 35 min-45 min, and one-time development can separate out light aromatics in the concentrated aromatics. Specifically, the time for one-time development can be, but is not limited to, 35 min, 37 min, 39 min, 40 min, 42 min, or 45 min, etc. In an embodiment of the present application, the time for one-time development can be 35 min-40 min. In another embodiment of the present application, the time for one-time development can be 40 min-45 min.

[0034] In an embodiment of the present application, the second developing liquid is used for secondary development, the second developing liquid is a mixed solution of n-heptane and toluene with a volume ratio of 80:20, the time for secondary development is 12 min-17 min, and the secondary development can separate the medium-quality aromatic hydrocarbons in the concentrated aromatic hydrocarbons. Specifically, the time for secondary development can be, but is not limited to, 12 min, 13 min, 14 min, 15 min, 16 min, or 17 min, etc. In an embodiment of the present application, the time for secondary development can be 12 min-15 min. In another embodiment of the present application, the time for secondary development can be 14 min-17 min.

[0035] In an embodiment of the present application, the third developing liquid is used for tertiary development, the third developing liquid is a mixed solution of n-heptane and toluene with a volume ratio of 50:50, the time for tertiary development is 3 min-5 min, and the tertiary development can separate the heavy aromatic hydrocarbons in the concentrated aromatic hydrocarbons. Specifically, the time for tertiary development can be, but is not limited to, 3 min, 3.5 min, 4 min, 4.5 min, or 5 min, etc. In an embodiment of the present application, the time for tertiary development can be 3 min-4.5 min. In another embodiment of the present application, the time for tertiary development can be 4 min-5 min.

[0036] In an embodiment of the present application, the particle size D50 of the petroleum coke is 9 μm-17 μm, the prepared negative electrode material has a test gram capacity very close to a preset gram capacity, and the adaptation degree of the negative electrode material to different application scenarios is improved. Specifically, the particle size D50 of the petroleum coke can be, but is not limited to, 9 μm, 10 μm, 11 μm, 13 μm, 15 μm, or 17 μm, etc. In an embodiment of the present application, the particle size D50 of the petroleum coke can be 9 μm-15 μm. In another embodiment of the present application, the particle size D50 of the petroleum coke can be 13 μm-17 μm.

[0037] In an embodiment of the present application, the sulfur content of the petroleum coke is less than or equal to 3%, the prepared negative electrode material has a test gram capacity very close to a preset gram capacity, and the adaptation degree of the negative electrode material to different application scenarios is improved. Specifically, the sulfur content of the petroleum coke can be, but is not limited to, less than or equal to 3%, less than or equal to 2.5%, less than or equal to 2%, less than or equal to 1.5%, or less than or equal to 1%, etc. In an embodiment of the present application, the sulfur content of the petroleum coke can be less than or equal to 2.5%. In another embodiment of the present application, the sulfur content of the petroleum coke can be less than or equal to 2%.

[0038] In an embodiment of the present application, the volatile matter of the petroleum coke is less than or equal to 14%, and the prepared negative electrode material has a test gram capacity close to the preset gram capacity, thereby improving the adaptability of the negative electrode material to different application scenarios. Specifically, the volatile matter of the petroleum coke can be, but is not limited to, less than or equal to 14%, less than or equal to 12%, less than or equal to 10%, less than or equal to 8%, less than or equal to 6%, or less than or equal to 4%, etc. In an embodiment of the present application, the volatile matter of the petroleum coke can be less than or equal to 8%. In another embodiment of the present application, the volatile matter of the petroleum coke can be less than or equal to 6%. In some embodiments, the test national standard of the volatile matter in the petroleum coke is SH / T0026-90.

[0039] The present application also provides a method for predicting the gram capacity of a negative electrode material, comprising: obtaining the mass percentage content m of meso-aromatic hydrocarbons in petroleum coke; and calculating n according to the formula: n = a x (m) 2 +b x m + c, wherein a is -0.0077, b is 0.9108, and c is 326.8, and n is the predicted gram capacity of the negative electrode material, in mAh / g. Through this method, the gram capacity of the prepared negative electrode material can be predicted from the petroleum coke, thereby avoiding the complex process of obtaining the gram capacity of the negative electrode material after preparation and detection, and simplifying the process flow.

[0040] The present application also provides a method for selecting petroleum coke based on the preset gram capacity of a negative electrode material, comprising: determining the preset gram capacity n of the prepared negative electrode material, in mAh / g; and calculating m according to the formula: n = a x (m) 2 +b x m + c, wherein a is -0.0077, b is 0.9108, and c is 326.8, and m is the mass percentage content of meso-aromatic hydrocarbons in the petroleum coke (%). Through this method, the gram capacity of the negative electrode material can be directly preset, and the petroleum coke for preparing the negative electrode material with the preset gram capacity can be selected through the formula.

[0041] The present application also provides a negative electrode material prepared by the preparation method of any one of the above embodiments. The negative electrode material has low preparation cost, excellent gram capacity performance, and is conducive to the multi-scenario application of the negative electrode material.

[0042] The present application also provides a negative electrode sheet comprising the negative electrode material of any one of the above embodiments.

[0043] In an embodiment of the present application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, and the negative electrode active material layer comprises the negative electrode material of any one of the above embodiments. The negative electrode sheet provided by the present application has high capacity and good cycle stability.

[0044] In an embodiment of the present application, the negative current collector can include, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel. In an embodiment of the present application, the negative current collector can be a copper foil.

[0045] In an embodiment of the present application, the negative active material layer further includes a negative conductive agent. The negative conductive agent can increase the conductivity of the negative active material and improve the electronic conductivity. Specifically, the negative conductive agent can include, but is not limited to, at least one of graphite, carbon black, acetylene black, and graphene. In an embodiment of the present application, the negative conductive agent can be graphite. In another embodiment of the present application, the negative conductive agent can be carbon black.

[0046] In an embodiment of the present application, the negative active material layer further includes a negative binder. The negative binder can improve the binding ability of the components in the negative active material layer and improve the binding ability between the negative active material layer and the current collector. Specifically, the negative binder can include, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and butadiene-styrene latex. In an embodiment of the present application, the negative binder can be polyvinylidene fluoride. In another embodiment of the present application, the negative binder can be sodium carboxymethyl cellulose. The present application also provides a battery including the negative electrode sheet provided by any one of the above embodiments.

[0047] In an embodiment of the present application, the battery further includes a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector, and the positive active material layer includes a positive active material.

[0048] In an embodiment of the present application, the positive current collector can include, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel. In an embodiment of the present application, the positive current collector can be an aluminum foil.

[0049] In an embodiment of the present application, the positive active material can improve the conductivity, the specific capacity, and the cycle stability of the positive electrode sheet. Specifically, the positive active material can include, but is not limited to, at least one of lithium iron phosphate material, lithium iron manganese phosphate, lithium cobaltate material, lithium manganate material, nickel-cobalt-manganese material, and nickel-cobalt-aluminum material. In an embodiment of the present application, the positive active material can be lithium cobaltate material.

[0050] In an embodiment of the present application, the positive active material layer further includes a positive conductive agent. The positive conductive agent can increase the conductivity between the active materials and improve the electronic conductivity. Specifically, the positive conductive agent can include, but is not limited to, at least one of graphite, carbon black, acetylene black, and graphene. In an embodiment of the present application, the positive conductive agent can be graphite. In another embodiment of the present application, the positive conductive agent can be carbon black.

[0051] In an embodiment of the present application, the positive active material layer further comprises a positive electrode binder. The positive electrode binder can improve the binding ability of the components in the positive active material layer and the binding ability between the positive active material layer and the positive current collector. Specifically, the positive electrode binder can be, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and butadiene-styrene latex. In an embodiment of the present application, the positive electrode binder can be polyvinylidene fluoride.

[0052] In an embodiment of the present application, the battery further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet. Specifically, the separator can be, but is not limited to, a woven film, a non-woven fabric, a microporous film, a composite film, a calendered film, or a separator paper, etc. In an embodiment of the present application, the battery further comprises an electrolyte. At least part of the positive electrode sheet and at least part of the negative electrode sheet are soaked in the electrolyte. The electrolyte of the present application is not particularly limited and can be, but is not limited to, a substance capable of being used as a battery electrolyte in the art.

[0053] The present application also provides a power consuming device comprising the battery provided by any one of the embodiments described above. The power consuming device of the present application can be a vehicle, an electronic device, an energy storage system, etc.

[0054] The effects of the technical solutions of the present application are further described below through specific examples.

[0055] Embodiment 1

[0056] The preset gram capacity of the pre-prepared negative electrode material is 352.5 mAh / g. According to n = a x (m) 2 +b x m + c, a is -0.0077, b is 0.9108, and c is 326.8. The calculated m is 46.65. Petroleum coke with a mass percentage of 46.65% of mesitylene is selected. After graphitization treatment at 3000°C, the negative electrode material is obtained by grinding and sieving.

[0057] Embodiments 2-20

[0058] Embodiments 2-20 and Embodiment 1 differ only in that the preset gram capacity of the pre-prepared negative electrode material and the mass percentage of mesitylene in the selected petroleum coke are different.

[0059] Performance detection

[0060] The negative electrode material prepared in the above-mentioned embodiments 1-20 was mixed with styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and conductive carbon black (SP) to prepare a negative electrode slurry, wherein the mass ratio of the negative electrode material, styrene-butadiene rubber, carboxymethyl cellulose and conductive carbon black was 95.5:2:1.5:1; the negative electrode slurry was coated on a negative electrode current collector (copper foil), and then dried and rolled to prepare a negative electrode sheet, which was assembled with a lithium metal sheet to form a button cell.

[0061] The batteries prepared in the above-mentioned embodiments 1-20 were subjected to electrochemical performance testing, and the testing process was as follows: 0.1C constant current charging and discharging, and the capacity of the button cell was tested under the condition that the charging and discharging voltage was 0.05-2.0V. The test results are shown in Table 1.

[0062] Table 1: Performance test results of the negative electrode material

[0063]

[0064]

[0065] As can be seen from the embodiments 1-20 of the present application, the preparation method of the negative electrode material provided by the present application can calculate the mass percentage of the meso-aromatic hydrocarbon in the petroleum coke required by the preset capacity, select the petroleum coke according to the calculated value, prepare the negative electrode material, and the test capacity of the prepared negative electrode material is close to the preset capacity. That is, the preparation method of the negative electrode material provided by the present application can prepare a negative electrode material with ideal capacity, or the relationship can be used to achieve the purpose of selecting raw materials by presetting the capacity, or the mass content of meso-aromatic hydrocarbon in the petroleum coke can be controlled to prepare a negative electrode material with a preset capacity.

[0066] The above-mentioned preferred embodiments of the present application can not be interpreted as limiting the scope of the present application. It should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered within the scope of protection of the present application.

Claims

1. A method for producing a negative electrode material, characterized by, The method comprises the following steps: According to the formula: n=a x (m) 2 +b x m+c, m is calculated; wherein, a is -0.0077, b is 0.9108, c is 326.8, n is the preset specific capacity of the prepared negative electrode material, unit: mAh / g, n is 340 mA h / g-355 mA h / g; The petroleum coke with the mass percentage of medium aromatic hydrocarbon of m% is selected, and the negative electrode material is obtained after graphitization treatment.

2. The production method according to claim 1, wherein The mass percentage of the medium aromatic hydrocarbon is 20%-75%.

3. The production method according to claim 1, wherein The temperature of the graphitization treatment is 2800°C-3100°C.

4. The production method according to claim 1, wherein The particle size D50 of the petroleum coke is 9μm-17μm; the sulfur content of the petroleum coke is less than or equal to 3%, and the volatile content of the petroleum coke is less than or equal to 14%.

5. A method of predicting the gravimetric capacity of a negative electrode material, characterized by, The method comprises the following steps: The mass percentage m% of medium aromatic hydrocarbon in the petroleum coke is obtained. According to the formula: n = a x (m) 2 +b x m + c, the n is calculated; wherein a is -0.0077, b is 0.9108, c is 326.8, the n is the predicted specific capacity of the negative material, unit: mAh / g.

6. A method for selecting petroleum coke based on preset specific capacity of negative electrode material, characterized in that, The method comprises the following steps: The preset gram capacity n of the pre-prepared negative electrode material is determined, and the unit is mAh / g, n is 340 mA h / g-355 mA h / g; According to the formula: n=a x (m) 2 +b x m+c, m is calculated; wherein, a is -0.0077, b is 0.9108, c is 326.8; the m is the mass percentage content of the medium aromatic hydrocarbon in the petroleum coke.

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