A composite precursor for a negative electrode material, a negative electrode material, and a preparation method thereof

Abstract

The present invention aims to provide a composite precursor for a negative electrode material, a negative electrode material and a preparation method thereof, belonging to the technical field of lithium-ion batteries. The present invention adopts the following technological steps: petroleum residue, catalytic cracking slurry or coal tar are mixed uniformly with a lipophilic thermoplastic resin in a certain proportion to obtain a mixed oil mass. By using the internal components of petroleum residue, catalytic cracking slurry or coal tar and the method of variable temperature and variable pressure reaction, first the lipophilic thermoplastic resin in the mixed oil mass is cured and formed, and then the mixed oil mass is converted through dehydrogenation polycondensation to obtain an intermediate product of a composite carbon material precursor; the intermediate product of the composite carbon material precursor is crushed, spheroidized and shaped, and heat-treated to obtain a composite carbon material precursor suitable for a negative electrode material of a lithium-ion battery. The present invention combines the characteristics of graphite materials and hard carbon materials, has good conductivity and high crystallinity, and the rate performance, cycle performance and low-temperature performance of the material are all improved well.

Description

Technical Field:

[0001] The present invention relates to the technical field of lithium-ion batteries, and specifically to a composite precursor for a negative electrode material, a negative electrode material, and a preparation method thereof. Background Art:

[0002] Lithium-ion batteries have become the main carrier of green and environmentally friendly energy due to their advantages such as high specific energy, high working voltage, fast charge and discharge speed, long cycle life, safety and pollution-free. A good lithium-ion battery negative electrode material needs to have several characteristics such as a relatively high discharge voltage, a flat discharge platform, a spatial structure that can provide rapid lithium-ion insertion and extraction and is stable, good thermodynamic stability, and good compatibility with the electrolyte. Among the commercially produced negative electrode materials, carbon-based materials are mainly used. At present, the carbon-based negative electrode materials of lithium-ion batteries are mainly graphite, soft carbon materials, and hard carbon materials. Graphite, with artificial graphite as the mainstream, has advantages such as good electrical conductivity and high crystallinity, but still has problems such as poor rate performance, poor low-temperature performance, and easy lithium precipitation during charging due to crystal anisotropy; soft carbon materials have excellent low-temperature performance and good rate performance, but due to their relatively high irreversible capacity, low output voltage, and no obvious charge and discharge platform, they are generally only used as a coating agent for negative electrode materials; hard carbon materials have advantages such as high specific capacity, long service life, and good rate performance, but at the same time, they also have disadvantages such as large first irreversible capacity, obvious voltage hysteresis effect, and low tap density.

[0003] For example, in the invention titled "Negative Electrode Material Precursor, Negative Electrode Material and Its Preparation Method, Negative Electrode Sheet and Lithium-Ion Battery" in Patent CN115771893A, the negative electrode material precursor of this invention includes a carbon source, a binder, and an auxiliary agent, and the auxiliary agent includes an antifoaming agent or a desulfurizing agent that can dissolve the binder. The negative electrode material is obtained by graphitizing the negative electrode material precursor after granulation. The tap density of the negative electrode material is 1.8 g / cc to 2.2 g / cc, and the D50 of the negative electrode material is 13 μm to 18 μm. This invention is still a production process of an artificial graphite precursor, and the method of using an organic antifoaming agent is used to increase the granularity. In addition to problems such as high cost and large pollution, it also limits the preparation conditions of the negative electrode material, which makes the lithium battery negative electrode material prepared by this solution have a certain gap in high-rate and high-low temperature cycle performance.

[0004] For example, Patent CN101887966A discloses "Lithium-Ion Battery Composite Hard Carbon Negative Electrode Material and Its Preparation Method", which uses a thermoplastic resin as the hard carbon matrix and is coated with an organic hard carbon carbon source, and has excellent high-rate and high-low temperature cycle performance, but the first Coulombic efficiency still has a gap compared with graphite-based negative electrode materials.

[0005] And the present invention combines the characteristics of carbon-based materials such as graphite and hard carbon, and has good electrical conductivity, high crystallinity, and characteristics such as the rate performance, cycle performance, and low-temperature performance of the material. Summary of the Invention:

[0006] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0007] To enable those skilled in the art of this technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0008] The present invention aims to provide a method for preparing a composite precursor of a negative electrode material, which adopts the following process steps:

[0009] 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly in a certain proportion to obtain a mixed slurry; the slurry raw material is a refined product oil from which inorganic component impurities and primary quinoline insoluble matter have been removed, with a sulfur content ≤ 0.5% and an ash content ≤ 0.1%; the resin raw material is a lipophilic thermoplastic resin.

[0010] 2) Green coke reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with an inert gas, and then carry out a curing reaction on the mixed slurry under certain conditions to obtain a shaped resin slurry; continue to carry out a dehydrogenation polycondensation reaction on the obtained shaped resin slurry in the reaction kettle to obtain a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle, with a pressure range of 0.1 MPa - 5 MPa.

[0011] 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize the precursor intermediate product obtained in step 2) to obtain precursor micropowder.

[0012] 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln and carry out heat treatment under an inert atmosphere to obtain a composite carbon-based precursor for the negative electrode material of a lithium-ion battery.

[0013] The certain proportion in step 1) is that the mass ratio of the slurry raw material to the resin raw material is 70% - 80%: 30% - 20%, and the aromatic hydrocarbon content of the mixed slurry ≥ 40%.

[0014] The lipophilic thermoplastic resin in step 1) is one or more of PVDF, modified phenolic resin, polyparaphenylene, and benzoxazine.

[0015] Step 1): Mixing the slurry raw material and the resin raw material evenly means that at room temperature, after mixing the slurry raw material and the resin raw material, stir at 40 - 50 rpm for 10 - 30 min.

[0016] In Step 2), curing the mixed slurry under certain conditions means that under atmospheric pressure, raise the temperature of the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 0.5 - 1 °C / min, and maintain it at the curing reaction temperature for 15 - 25 h to cure and form the resin component inside the mixed slurry, obtaining a formed resin slurry; the curing reaction temperature is 90 - 110 °C.

[0017] In Step 2), continuing the dehydrogenation polycondensation reaction of the obtained formed resin slurry in the reaction kettle means adjusting the pressure of the reaction kettle to 0.3 - 0.5 Mpa, raising the temperature of the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 4 - 6 °C / min, and maintaining it at the dehydrogenation polycondensation reaction temperature for 10 - 12 h. After the reaction, cool to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 450 - 550 °C.

[0018] In Step 3), crush, pulverize, and spheroidize the obtained precursor intermediate product, and control the D50 of the precursor intermediate product fine powder to be 10.5 - 11.5 μm.

[0019] In Step 4), heat - treating the precursor fine powder under an inert atmosphere specifically means that under atmospheric pressure, raise the temperature of the rotary kiln from room temperature to the heat - treatment temperature at a heating rate of 0 - 20 °C / min, and maintain it at the heat - treatment temperature for 5 - 20 h; the inert atmosphere is that the rotary kiln is filled with nitrogen; the heat - treatment temperature is 800 - 1150 °C.

[0020] A negative electrode material composite precursor, including the negative electrode material composite precursor prepared by the preparation method of the negative electrode material composite precursor described in any one of the above.

[0021] A negative electrode material, including the described negative electrode material composite precursor.

[0022] The present invention has the following beneficial effects:

[0023] The precursor of the carbon - based negative electrode material for lithium - ion batteries is prepared by the method of the present invention. Its internal components are mainly composed of an easily graphitizable soft - carbon structure, with a part of a hard - carbon structure that is difficult to graphitize, and the two are evenly distributed. After graphitization, the prepared negative electrode material for lithium - ion batteries has the characteristics of good conductivity and high crystallinity of graphite materials; due to a certain proportion of carbon that is difficult to graphitize existing inside the material, after graphitization, it has a considerable number of nanopore structures and good isotropy. The rate performance, cycle performance, and low - temperature performance of the material have all been improved well. Brief Description of the Drawings:

[0024] In order to more clearly illustrate the solutions in the present application, the following will give a brief introduction to the drawings required to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a process flow chart of a negative electrode material composite precursor, a negative electrode material and a preparation method thereof described in the embodiments of the present invention.

[0026] Figure 2 It is a SEM electron micrograph of a composite precursor prepared by the preparation method of a negative electrode material composite precursor described in Embodiment 1 of the present invention.

[0027] Figure 3 It is a test diagram of a half-cell of a negative electrode material prepared from a composite precursor prepared by the preparation method of a negative electrode material composite precursor described in Embodiment 1 of the present invention.

[0028] Figure 4 It is a test diagram of the capacity cycling performance of a negative electrode material prepared from a composite precursor prepared by the preparation method of a negative electrode material composite precursor described in Embodiment 1 of the present invention, where the straight line is the performance of Embodiment 1 and the dotted line is the performance of Embodiment 2. Detailed Embodiments:

[0029] The following further illustrates the present invention with specific examples; unless otherwise stated, all raw materials used in the present invention can be obtained commercially, and the unstated parts below are in terms of mass ratio, mass or weight.

[0030] Embodiment 1:

[0031] In this embodiment, a preparation method of a negative electrode material composite precursor is provided, and the following process steps are adopted:

[0032] 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly at a ratio of 80%:20%, and stir for 10 min at 45 rpm to obtain a mixed slurry, and the aromatic hydrocarbon content of the mixed slurry ≥ 40; the slurry raw material is a cracked pyrolysis slurry raw material, removing inorganic component impurities and primary quinoline insoluble matters, with a sulfur content of 0.30% and an ash content of 0.05%; the resin raw material is poly(p-phenylene).

[0033] 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with nitrogen, and then heat the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 0.5 °C / min under atmospheric pressure, and keep it at the curing reaction temperature for 18 h to cure and form the resin components inside the mixed slurry, obtaining a formed resin slurry; the curing reaction temperature is 100 °C; continue to place the obtained formed resin slurry in this reaction kettle, adjust the pressure of the reaction kettle to 0.4 Mpa, heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 6 °C / min, and keep it at the dehydrogenation polycondensation reaction temperature for 12 h. After the reaction is completed, cool it to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 500 °C, obtaining a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle, and the pressure range is 0.1 MPa - 5 MPa;

[0034] 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize the precursor intermediate product obtained in step 2) to obtain precursor micropowder;

[0035] In step 3), the obtained precursor intermediate product is crushed, pulverized, and spheroidized, and the D50 of the precursor intermediate product micropowder is controlled to be 10.5 - 11.5 μm.

[0036] 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln, heat the rotary kiln from room temperature to the heat treatment temperature at a heating rate of 5 °C / min under a nitrogen atmosphere, and keep it at the heat treatment temperature for 10 h to obtain a composite carbon-based precursor of the lithium-ion battery anode material; the heat treatment temperature is 1100 °C.

[0037] A composite precursor of the anode material includes a composite precursor of the anode material prepared by the preparation method of a composite precursor of the anode material described in any one of the above.

[0038] An anode material includes the composite precursor of the anode material described above.

[0039] Example 2:

[0040] In this example, a preparation method of a composite precursor of the anode material is provided, and the following technological steps are adopted:

[0041] 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly at a ratio of 75%:25%, and stir for 20 min at 45 rpm to obtain a mixed slurry, and the aromatic hydrocarbon content of the mixed slurry ≥ 40; the slurry raw material is petroleum residue, removing inorganic component impurities and primary quinoline insoluble matter, with a sulfur content of 0.42% and an ash content of 0.08%; the resin raw material is modified phenolic resin;

[0042] 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with nitrogen, and then heat the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 1 °C / min under atmospheric pressure, and maintain it at the curing reaction temperature for 20 h to cure and form the resin component inside the mixed slurry, obtaining a shaped resin slurry; the curing reaction temperature is 90 °C; Place the obtained shaped resin slurry in the reaction kettle, adjust the pressure of the reaction kettle to 0.4 Mpa, heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 4 °C / min, and maintain it at the dehydrogenation polycondensation reaction temperature for 10 h. After the reaction, cool it to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 500 °C, obtaining a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle, and the pressure range is 0.1 MPa - 5 MPa;

[0043] 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize the precursor intermediate product obtained in step 2) to obtain precursor micropowder;

[0044] In step 3), the obtained precursor intermediate product is crushed, pulverized, and spheroidized, and the D50 of the precursor intermediate product micropowder is controlled to be 8.5 - 9.5 μm.

[0045] 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln, heat the rotary kiln from room temperature to the heat treatment temperature at a heating rate of 5 °C / min under a nitrogen atmosphere, and maintain it at the heat treatment temperature for 10 h to obtain a composite carbon-based precursor of the anode material for lithium-ion batteries; the heat treatment temperature is 1100 °C.

[0046] A composite precursor for anode material, comprising a composite precursor for anode material prepared by the preparation method of a composite precursor for anode material as described in any one of the above.

[0047] An anode material, comprising the composite precursor for anode material as described above.

[0048] Example 3:

[0049] In this example, a preparation method of a composite precursor for anode material is provided, and the following process steps are adopted:

[0050] 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly at a ratio of 80%:20%, and stir for 20 min at 40 rpm to obtain a mixed slurry, and the aromatic hydrocarbon content of the mixed slurry ≥ 40; the slurry raw material is high-temperature coal tar, the inorganic component impurities and primary quinoline insoluble matter are removed, the sulfur content is 0.45%, and the ash content is 0.06%; the resin raw material is benzoxazine;

[0051] 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with nitrogen, and then heat the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 0.5 °C / min under atmospheric pressure, and maintain it at the curing reaction temperature for 20 h to cure and form the resin component inside the mixed slurry, obtaining a formed resin slurry; the curing reaction temperature is 100 °C; continue to place the obtained formed resin slurry in this reaction kettle, adjust the pressure of the reaction kettle to 0.5 Mpa, heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 4 °C / min, and maintain it at the dehydrogenation polycondensation reaction temperature for 10 h. After the reaction, cool it to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 480 °C, obtaining a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle with a pressure range of 0.1 MPa - 5 MPa;

[0052] 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize the precursor intermediate product obtained in step 2) to obtain precursor micropowder;

[0053] In step 3), the obtained precursor intermediate product is crushed, pulverized, and spheroidized, and the D50 of the precursor intermediate product micropowder is controlled to be 14.5 - 15.5 μm.

[0054] 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln, heat the rotary kiln from room temperature to the heat treatment temperature at a heating rate of 8 °C / min under a nitrogen atmosphere, and maintain it at the heat treatment temperature for 12 h to obtain a composite carbon-based precursor of the anode material for lithium-ion batteries; the heat treatment temperature is 1100 °C.

[0055] A composite precursor for anode material, comprising a composite precursor for anode material prepared by the preparation method of a composite precursor for anode material described in any one of the above.

[0056] An anode material, comprising the composite precursor for anode material described above.

[0057] Example 4:

[0058] In this example, a preparation method of a composite precursor for anode material is provided, and the following process steps are adopted:

[0059] 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly at a ratio of 70%:30% and stir for 20 min at 40 rpm to obtain a mixed slurry, and the aromatic hydrocarbon content of the mixed slurry ≥ 40; the slurry raw material is cracked and pyrolyzed oil, with inorganic component impurities and primary quinoline insoluble matter removed, a sulfur content of 0.30%, and an ash content of 0.05%; the resin raw material is PVDF;

[0060] 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with nitrogen, and then heat the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 1.0 °C / min under atmospheric pressure, and maintain it at the curing reaction temperature for 24 h to cure and form the resin component inside the mixed slurry, obtaining a formed resin slurry; the curing reaction temperature is 100 °C; continue to place the obtained formed resin slurry in the reaction kettle, adjust the pressure of the reaction kettle to 0.4 Mpa, and heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 6 °C / min, and maintain it at the dehydrogenation polycondensation reaction temperature for 12 h. After the reaction is completed, cool it to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 500 °C, obtaining a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle, and the pressure range is 0.1 MPa - 5 MPa;

[0061] 3) Preparation of precursor fine powder: Crush, pulverize, and spheroidize and shape the precursor intermediate product obtained in step 2) to obtain a precursor fine powder;

[0062] In step 3), the obtained precursor intermediate product is crushed, pulverized, spheroidized and shaped, and the D50 of the precursor intermediate product fine powder is controlled to be 17.5 - 18.5 μm.

[0063] 4) Heat treatment: Place the precursor fine powder obtained in step 3) in a rotary kiln, heat the rotary kiln from room temperature to the heat treatment temperature at a heating rate of 5 °C / min under a nitrogen atmosphere, and maintain it at the heat treatment temperature for 10 h to obtain a composite carbon-based precursor of the lithium-ion battery anode material; the heat treatment temperature is 1100 °C.

[0064] A composite precursor of the anode material, including the composite precursor of the anode material prepared by the preparation method of the composite precursor of the anode material described in any one of the above.

[0065] An anode material, including the composite precursor of the anode material described above.

[0066] Comparative Example 1:

[0067] Compared with Example 1, in the preparation stage of the mixed slurry, instead of adding a resin raw material, a cracked and pyrolyzed slurry raw material of the same quality and equal amount is used to replace it. A preparation method of a composite precursor of an anode material adopts the following technological steps:

[0068] 1) Slurry preparation: Stir the slurry raw material at 45 rpm for 10 min to obtain a mixed slurry, and the aromatic hydrocarbon content of the mixed slurry ≥ 40; the slurry raw material is a cracked and pyrolyzed slurry raw material, removing inorganic component impurities and native quinoline insoluble matter, with a sulfur content of 0.30% and an ash content of 0.05%;

[0069] 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with nitrogen, and then heat the reaction kettle from room temperature to the curing reaction temperature at a heating rate of 0.5 °C / min under atmospheric pressure, and maintain it at the curing reaction temperature for 18 h to cure and form the resin components inside the mixed slurry, obtaining a formed resin slurry; the curing reaction temperature is 100 °C; continue to place the obtained formed resin slurry in the reaction kettle, adjust the pressure of the reaction kettle to 0.4 Mpa, and heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 6 °C / min, and maintain it at the dehydrogenation polycondensation reaction temperature for 12 h. After the reaction is completed, cool it to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 500 °C, obtaining a precursor intermediate product; the reaction kettle is a high-pressure reaction kettle, and the pressure range is 0.1 MPa - 5 MPa;

[0070] 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize and shape the precursor intermediate product obtained in step 2) to obtain precursor micropowder;

[0071] In step 3), the obtained precursor intermediate product is crushed, pulverized, spheroidized and shaped, and the D50 of the precursor intermediate product micropowder is controlled to be 10.5 - 11.5 μm.

[0072] 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln, heat the rotary kiln from room temperature to the heat treatment temperature at a heating rate of 5 °C / min under a nitrogen atmosphere, and maintain it at the heat treatment temperature for 10 h to obtain a composite carbon-based precursor for the negative electrode material of a lithium-ion battery; the heat treatment temperature is 1100 °C.

[0073] A composite precursor for a negative electrode material, including a composite precursor for a negative electrode material prepared by the preparation method of a composite precursor for a negative electrode material as described in any one of the above.

[0074] A negative electrode material, including the composite precursor for a negative electrode material as described above.

[0075] Comparative Example 2:

[0076] Compared with Example 1, in this example, low-sulfur petroleum coke is selected, and a conventional asphalt coating process is used. A preparation method for a composite precursor for a negative electrode material is adopted with the following process steps within the range of controlling the particle size D50 = 11 ± 0.5 um:

[0077] 1) Slurry preparation: Stir the slurry raw materials at 45 rpm for 10 min to obtain a mixed slurry; the slurry raw materials are sulfur petroleum coke;

[0078] 2) Use a conventional asphalt coating process to obtain a precursor intermediate product;

[0079] 3) Preparation of precursor micropowder: The precursor intermediate product obtained in step 2) is crushed, pulverized, and spheroidally shaped to obtain precursor micropowder;

[0080] In step 3), the obtained precursor intermediate product is crushed, pulverized, and spheroidally shaped, and the D50 of the precursor intermediate product micropowder is controlled to be 10.5 - 11.5 μm.

[0081] 4) Heat treatment: The precursor micropowder obtained in step 3) is placed in a rotary kiln, and the rotary kiln is heated from room temperature to the heat treatment temperature at a heating rate of 5 °C / min under a nitrogen atmosphere and maintained at the heat treatment temperature for 10 h to obtain a composite carbon-based precursor of the negative electrode material for lithium-ion batteries; the heat treatment temperature is 1100 °C.

[0082] A composite precursor for negative electrode material, including a composite precursor for negative electrode material prepared by the preparation method of a composite precursor for negative electrode material described in any one of the above.

[0083] A negative electrode material, including the composite precursor for negative electrode material described above.

[0084] The above embodiments are partial preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

[0085] The physical properties of the composite carbon-based precursors prepared in Examples 1 - 4 and the two types of different precursor materials for negative electrodes prepared in Comparative Examples 1 - 2 are shown in Table 1

[0086] Table 1: Precursors Prepared by Different Processes

[0087]

[0088] Table 2 shows the performance tests of the composite carbon material precursors prepared in Examples 1 - 4 and the two types of precursors prepared in Comparative Examples 1 - 2 after being made into negative electrode materials respectively.

[0089] Table 2: Performance of Precursors Prepared by Different Processes

[0090]

[0091]

[0092] As can be seen from the above table, the O / I value of the composite carbon material prepared by the method of the present invention is much lower than that of the negative electrode material prepared by the traditional method, and it has better isotropy and is more conducive to the insertion and extraction of lithium ions.

[0093] The lithium-ion anode material precursor prepared by this method, after being graphitized, is used as a lithium-ion anode material, having a higher Coulombic efficiency and more excellent rate cycling performance.

Claims

1. A method for preparing a composite precursor of a negative electrode material, characterized in that, The following process steps are adopted: 1) Slurry preparation: Mix the slurry raw material and the resin raw material evenly in a certain proportion to obtain a mixed slurry; the slurry raw material is a refined product oil from which inorganic component impurities and primary quinoline insoluble substances are removed, with a sulfur content ≤ 0.5% and an ash content ≤ 0.1%; the resin raw material is a lipophilic thermoplastic resin; 2) Coke formation reaction: Place the mixed slurry obtained in step 1) in a reaction kettle, replace the air in the reaction kettle with an inert gas, and then carry out a curing reaction on the mixed slurry under certain conditions to obtain a shaped resin slurry; continue to carry out a dehydrogenation polycondensation reaction on the obtained shaped resin slurry in the reaction kettle to obtain a precursor intermediate product; The reaction kettle is a high-pressure reaction kettle with a pressure range of 0.1 MPa - 5 MPa; 3) Preparation of precursor micropowder: Crush, pulverize, and spheroidize the precursor intermediate product obtained in step 2) to obtain precursor micropowder; 4) Heat treatment: Place the precursor micropowder obtained in step 3) in a rotary kiln and carry out heat treatment under an inert atmosphere to obtain a composite carbon-based precursor for the negative electrode material of a lithium-ion battery; The certain proportion described in step 1) is that the mass ratio of the slurry raw material to the resin raw material is 70% - 80%: 30% - 20%, and the aromatic hydrocarbon content of the mixed slurry ≥ 40%; The mixing of the slurry raw material and the resin raw material evenly described in step 1) is carried out at room temperature. After mixing the slurry raw material and the resin raw material, stir at 40 - 50 rpm for 10 - 30 min; The lipophilic thermoplastic resin described in step 1) is one or several of PVDF, modified phenolic resin, polyparaphenylene, and benzoxazine; The curing reaction of the mixed slurry under certain conditions described in step 2) is that under normal pressure conditions, the reaction kettle is heated from room temperature to the curing reaction temperature at a heating rate of 0.5 - 1 °C / min, and maintained at the curing reaction temperature for 15 - 25 h to solidify and form the resin component inside the mixed slurry to obtain a shaped resin slurry; the curing reaction temperature is 90 - 110 °C.

2. The preparation method of a composite precursor for a negative electrode material according to claim 1, characterized in that, The dehydrogenation polycondensation reaction of the obtained shaped resin slurry continued in the reaction kettle described in step 2) is to adjust the pressure of the reaction kettle to 0.3 - 0.5 Mpa, heat the reaction kettle from the curing reaction temperature to the dehydrogenation polycondensation reaction temperature at a heating rate of 4 - 6 °C / min, and maintain at the dehydrogenation polycondensation reaction temperature for 10 - 12 h. After the reaction, cool to room temperature to obtain a precursor intermediate product; the dehydrogenation polycondensation reaction temperature is 450 - 550 °C.

3. The preparation method of a composite precursor for a negative electrode material according to claim 1, characterized in that, In step 3), the precursor intermediate product obtained is crushed, pulverized, and spheroidized, and the D50 of the precursor intermediate product micropowder is controlled to be 10.5 - 11.5 μm.

4. The preparation method of a composite precursor for a negative electrode material according to claim 1, characterized in that, The heat treatment of the precursor micropowder under an inert atmosphere described in step 4) is specifically that under normal pressure conditions, the rotary kiln is heated from room temperature to the heat treatment temperature at a heating rate of 0 - 20 °C / min, and maintained at the heat treatment temperature for 5 - 20 h; the inert atmosphere is that the rotary kiln is filled with nitrogen; the heat treatment temperature is 800 - 1150 °C.

5. A composite precursor for a negative electrode material, characterized in that, The negative electrode material composite precursor includes a negative electrode material composite precursor prepared by the preparation method of any one of claims 1-4.

6. A negative electrode material, characterized in that, The negative electrode material includes a negative electrode material composite precursor as claimed in claim 5.

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