阅读说明：本技术 一种倍率性能高的石墨负极材料及其制备方法和在锂离子电池中的用途 (Graphite negative electrode material with high rate capability, preparation method thereof and application thereof in lithium ion battery ) 是由 刘明东 王宪 叶雨佐 吴其修 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种负极材料及其制备方法和应用。所述负极材料的制备方法为：(1)将沥青与石墨混合,得到混合料；其中,所述沥青软化点≥220℃,所述沥青中的二次喹啉不溶物含量为10-20％；(2)将步骤(1)的混合料在常压下进行炭化处理,所述炭化处理的温度为800～1200℃,制备得到负极材料。本发明所述负极材料具有高倍率性能,特别是对天然石墨负极包覆后,可以代替人造石墨制作电池负极材料,从而大大降低成本。(The invention discloses a negative electrode material and a preparation method and application thereof. The preparation method of the negative electrode material comprises the following steps: (1) mixing asphalt and graphite to obtain a mixture; wherein the softening point of the asphalt is more than or equal to 220 ℃, and the content of the secondary quinoline insoluble substances in the asphalt is 10-20%; (2) and (2) carbonizing the mixture obtained in the step (1) at normal pressure, wherein the temperature of the carbonization is 800-1200 ℃, and preparing the negative electrode material. The negative electrode material has high rate performance, and can replace artificial graphite to manufacture a battery negative electrode material after being coated on a natural graphite negative electrode, so that the cost is greatly reduced.)

1. The preparation method of the anode material is characterized by comprising the following steps of:

(1) mixing asphalt and graphite to obtain a mixture; wherein the softening point of the asphalt is more than or equal to 220 ℃, and the content of the secondary quinoline insoluble substances in the asphalt is 10-20%;

(2) and (2) carbonizing the mixture obtained in the step (1) at normal pressure, wherein the temperature of the carbonization is 800-1200 ℃, and preparing the negative electrode material.

2. The method of claim 1, wherein the graphite has a median particle diameter D₅₀5-25 μm, and the fixed carbon content is more than 99.0 wt%.

3. The production method according to any one of claims 1 to 2, wherein in the step (1), the asphalt has a softening point of 220 to 250 ℃.

4. The preparation method according to any one of claims 1 to 3, wherein in the step (1), the mass ratio of the asphalt to the graphite is (1-5): 100.

5. The production method according to any one of claims 1 to 4, wherein in the step (2), the temperature of the carbonization treatment is 1000 to 1200 ℃.

6. The method according to any one of claims 1 to 5, wherein in the step (2), before the carbonization treatment, the temperature is raised to 420 to 460 ℃ for a certain period of time, and then raised to 800 to 1200 ℃ for carbonization.

7. The preparation method according to claim 6, characterized in that, in the step (2), the holding time is 1 to 10 hours; preferably, the temperature is raised to 420-460 ℃ at the heating rate of 1-5 ℃/min, and the temperature is raised to 800-1200 ℃ at the heating rate of 20-30 ℃/min after the temperature is kept for 2-6 h.

8. An anode material prepared by the method of any one of claims 1 to 7.

9. The negative electrode material of claim 8, wherein the negative electrode material has a core-shell structure, the core is graphite, the shell is a composite of hard carbon and isotropic amorphous carbon, and the mass content of the hard carbon in the shell is 15-30%;

preferably, the mass content of the shell in the negative electrode material is 1-4%.

10. Use of the negative electrode material according to any of claims 6 to 9, characterized in that it is used in a lithium ion battery.

Technical Field

The invention relates to the technical field of carbon cathode materials of lithium ion batteries, in particular to a graphite cathode material with high rate capability, a preparation method thereof and application thereof in a lithium ion battery.

Background

Lithium ion batteries have become a new generation of secondary batteries following nickel-metal hydride batteries in the nineties of the last century because of their advantages of high operating voltage, high energy density, long cycle life, small self-discharge, no memory effect, etc. In the development process of the lithium ion battery technology, the battery quality is continuously improved, and the production cost is continuously reduced. The negative electrode material plays a great role in contributing to the technical progress of lithium ion batteries.

At present, the negative electrode material of the commercial lithium ion battery is still the dominant graphite material, is limited by the structure of the negative electrode material, and reaches the upper limit on the capacity, so that the energy density of the negative electrode material is difficult to break through. Under the background, terminal markets are turning to put more urgent demands on the rate of batteries, and a negative electrode material with high rate performance is a general development trend in the 3C field (computer, communication and electronic consumer goods) and the EV field. At present, natural graphite and artificial graphite are coated with a hard carbon precursor such as phenolic resin, and then carbonization is carried out to improve the rate capability of the graphite. However, the phenolic resin has poor affinity with graphite, poor coating effect, low first effect and unstable product quality.

Disclosure of Invention

The invention aims to solve the problem that the existing graphite cathode material is poor in rate capability, and provides a graphite cathode material which is high in rate capability, high in first efficiency and good in cycle performance, a preparation method thereof and application thereof in a lithium ion battery.

The technical scheme of the invention is as follows:

a preparation method of the anode material comprises the following steps:

(1) mixing asphalt and graphite to obtain a mixture; wherein the softening point of the asphalt is more than or equal to 220 ℃, and the content of the secondary quinoline insoluble substances in the asphalt is 10-20%;

(2) and (2) carbonizing the mixture obtained in the step (1) at normal pressure, wherein the temperature of the carbonization is 800-1200 ℃, and preparing the negative electrode material.

According to the invention, in the step (1), the graphite is at least one of natural graphite and artificial graphite, and the artificial graphite can be composite graphite. Median particle diameter D of graphite₅₀5-25 μm, and the fixed carbon content is more than 99.0 wt%. Wherein the natural graphite particles are spherical, approximately spherical, oval or potato-shaped. The particle shape of the artificial graphite can be arbitrary.

According to the invention, in step (1), the bitumen is selected from coal pitch or petroleum pitch, preferably coal pitch.

According to the invention, in the step (1), the softening point of the asphalt is 220-250 ℃; for example 220 ℃, 230 ℃, 240 ℃ or 250 ℃; the second quinoline insolubles in the pitch may be, for example, 10%, 12%, 14%, 15%, 16%, 17%, 18% or 20%.

According to the invention, in the step (1), the mass ratio of the asphalt to the graphite is (1-5): 100, such as 1:100, 2:100, 3:100, 4:100 or 5: 100.

According to the present invention, in the step (1), the mixing is a technique known in the art, and a person skilled in the art can select appropriate technical parameters according to needs. Non-limiting examples of such mixing include: placing asphalt and graphite in a mixer, controlling the temperature at 80-150 ℃, and processing for 1-300 min at a rotating speed of 50-500 r/min to obtain a mixture, wherein in the mixing process, the asphalt can be coated on the surface of the graphite to realize the coating process of the graphite; the mixer is selected from at least one of a high-speed modified VC mixer, a conical mixer and a kneading machine.

According to the invention, in the step (2), the temperature of the carbonization treatment is 1000 to 1200 ℃, exemplary is 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃. Further, said charredThe time period is 1 to 6 hours, such as 2 to 5 hours, illustratively 4 hours, 6 hours. The carbonization reaction is carried out under the protection of inert atmosphere, for example, the inert atmosphere is N₂An atmosphere or an argon atmosphere. Further, after the carbonization treatment is finished, the obtained product is naturally cooled.

According to the invention, in the step (2), before the carbonization treatment, the temperature is firstly raised to 420-460 ℃ and is kept for a period of time, and then the temperature is raised to 800-1200 ℃ for carbonization. The holding time is, for example, 1 to 10 hours. Illustratively, the temperature is raised to 420-460 ℃ at the temperature raising rate of 1-5 ℃/min, and the temperature is raised to 800-1200 ℃ at the temperature raising rate of 20-30 ℃/min after the temperature is maintained for 2-6 h.

According to the present invention, in the step (2), the carbonization treatment is performed, for example, in a carbonization device, which may be at least one of a medium frequency induction heating furnace, a graphitization furnace or an electric calcining furnace, and the skilled person can select the carbonization device according to actual situations.

According to the invention, the method also comprises the step (3) of scattering and screening the product after the carbonization treatment in the step (2) to obtain the negative electrode material.

According to the present invention, the scattering in step (3) may be performed in a scattering device, for example, at least one selected from a turbo type scattering machine or an air flow type scattering machine, which may be selected by those skilled in the art according to the actual circumstances.

According to the present invention, in step (3), the screening treatment may be a method conventional in the art, such as screening treatment with a vibrating screen machine, wherein the screening mesh number is 200-400 meshes.

The invention also provides the anode material prepared by the method.

According to the invention, the negative electrode material has a core-shell structure, the core is graphite, the shell is a composite of hard carbon and isotropic amorphous carbon, and the mass content of the hard carbon in the shell is 15-30%.

According to the invention, the mass content of the shell in the negative electrode material is 1-4%.

According to the invention, the discharge capacity of the negative electrode material is more than or equal to 360mAh/g, such as 363 mAh/g-367 mAh/g, and the first charge-discharge efficiency is more than or equal to 91%.

According to the invention, the capacity retention rate of the negative electrode material at normal temperature in 800 weeks after 2C charge-discharge cycling is more than 80%.

The invention also provides application of the anode material, which is used in a lithium ion battery.

The invention has the beneficial effects that:

(1) the preparation method can obtain the cathode material with high multiplying power, and the more excellent multiplying power performance of the cathode material is higher than that of the conventional product on the market; the battery made of the negative electrode material has the discharge capacity of more than or equal to 360mAh/g, the first charge-discharge efficiency of more than or equal to 91 percent, and the capacity retention rate of 800 weeks of 2C charge-discharge circulation at normal temperature of more than 80 percent, and particularly after the natural graphite negative electrode is coated, the battery negative electrode material can replace artificial graphite to be made, so that the cost is greatly reduced.

(2) In the invention, asphalt with high content of secondary quinoline insoluble is used as a coating material, and in the carbonization process, the asphalt is converted into isotropic amorphous carbon and hard carbon, wherein the secondary quinoline insoluble is converted into the hard carbon with large interlayer spacing; the coating layer (namely the shell layer) is a compound consisting of hard carbon and isotropic amorphous carbon, the distance between hard carbon layers is large, and the isotropic amorphous carbon is also beneficial to the lithium ions to be embedded from multiple directions, so that the rate capability of the cathode material is improved.

(3) The method has the advantages of simple preparation process, low cost and high practicability.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

Example 1

Weighing natural materials100kg of graphite with a medium particle size (D) as its physicochemical index₅₀) 25 μm, fixed carbon content 99.50 wt%; weighing coal tar pitch (softening point 250 deg.C, and content of insoluble substances of secondary quinoline 15%) 3 kg; the method comprises the steps of crossly putting natural graphite and coal tar pitch into a high-speed modified VC mixer, mixing for 100min at the rotating speed of 100r/min, putting the mixture into a carbonization furnace after the mixture is finished, heating to 460 ℃ at the heating rate of 4 ℃/min under the nitrogen atmosphere, keeping the temperature for 4h, continuing to heat to 1000 ℃ at the heating rate of 20 ℃/min, keeping the temperature for 3h, cooling the reactant to room temperature, and screening by a 200-mesh vibration screening machine to obtain the undersize material as the negative electrode material.

Example 2

Weighing natural graphite 100kg, wherein the physical and chemical indexes are median particle diameter (D)₅₀) 17 μm, fixed carbon content 99.70 wt%; weighing 4kg of coal tar pitch (softening point 230 ℃, and content of secondary quinoline insoluble material 17%); the method comprises the steps of crossly putting natural graphite and coal pitch into a high-speed modified VC mixer, mixing for 180min at a rotating speed of 80r/min, putting the mixture into a graphitization furnace after the mixture is finished, heating to 450 ℃ at a heating rate of 3 ℃/min under a nitrogen atmosphere, keeping the temperature for 3h, continuing to heat to 1200 ℃ at a heating rate of 25 ℃/min, keeping the temperature for 3h, cooling reactants to room temperature, screening by a 300-mesh vibration screening machine, and taking obtained screen underflow as a negative electrode material.

Example 3

Weighing natural graphite 100kg, wherein the physical and chemical indexes are median particle diameter (D)₅₀) 10 μm, fixed carbon content 99.50 wt%; weighing 5kg of petroleum asphalt (softening point 250 ℃, and content of secondary quinoline insoluble substance of 10%); the method comprises the steps of crossly putting natural graphite and petroleum asphalt into a high-speed modified VC mixer, mixing for 100min at the rotating speed of 400r/min, putting the mixture into a carbonization furnace after the mixture is finished, heating to 430 ℃ at the heating rate of 5 ℃/min under the argon atmosphere, keeping the temperature for 2h, continuing to heat to 1100 ℃ at the heating rate of 22 ℃/min, keeping the temperature for 6h, cooling the reactant to room temperature, and screening by a 240-mesh vibration screening machine to obtain the undersize material as the negative electrode material.

Example 4

Weighing artificial graphite 100kg, wherein the physical and chemical indexes are median particle diameter (D)₅₀) 17 μm, fixed carbon content 99.90wtPercent; weighing 4kg of coal tar pitch (softening point 220 ℃, and content of secondary quinoline insoluble matter is 14%); the method comprises the steps of crossly putting natural graphite and coal pitch into a high-speed modified VC mixer, mixing for 180min at a rotating speed of 80r/min, putting the mixture into a graphitization furnace after the mixture is finished, heating to 420 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere, keeping the temperature for 2h, continuing to heat to 1200 ℃ at a heating rate of 20 ℃/min, keeping the temperature for 3h, cooling reactants to room temperature, and screening by a 300-mesh vibration screening machine to obtain a screen underflow which is a negative electrode material.

Comparative example 1

Weighing natural graphite 100kg, wherein the physical and chemical indexes are median particle diameter (D)₅₀) 25 μm, fixed carbon content 99.50 wt%; weighing coal tar pitch (softening point 250 deg.C, and content of insoluble fraction of secondary quinoline is 1%) 3 kg; the method comprises the steps of crossly putting natural graphite and coal tar pitch into a high-speed modified VC mixer, mixing for 100min at the rotating speed of 100r/min, putting the mixture into a carbonization furnace after the mixture is finished, heating to 460 ℃ at the heating rate of 4 ℃/min under the nitrogen atmosphere, keeping the temperature for 4h, continuing to heat to 1000 ℃ at the heating rate of 20 ℃/min, keeping the temperature for 3h, cooling the reactant to room temperature, and screening by a 200-mesh vibration screening machine to obtain the undersize material as the negative electrode material.

Comparative example 2

Weighing natural graphite 100kg, wherein the physical and chemical indexes are median particle diameter (D)₅₀) 25 μm, fixed carbon content 99.50 wt%; weighing coal tar pitch (softening point 150 deg.C, and content of insoluble secondary quinoline is 15%) 3 kg; the method comprises the steps of crossly putting natural graphite and coal tar pitch into a high-speed modified VC mixer, mixing for 100min at the rotating speed of 100r/min, putting the mixture into a carbonization furnace after the mixture is finished, heating to 460 ℃ at the heating rate of 4 ℃/min under the nitrogen atmosphere, keeping the temperature for 4h, continuing to heat to 1000 ℃ at the heating rate of 20 ℃/min, keeping the temperature for 3h, cooling the reactant to room temperature, and screening by a 200-mesh vibration screening machine to obtain the undersize material as the negative electrode material.

Electrochemical performance test

The semi-electric test method comprises the following steps: negative electrode materials prepared in examples 1 to 4 and comparative examples 1 to 2: conductive carbon black (SP): carboxymethyl cellulose (CMC): mixing Styrene Butadiene Rubber (SBR) 95:1:1.5:2.5, coating on copper foil, and coatingAnd (5) drying the pole piece in a vacuum drying oven at 120 ℃ for 12 hours. Assembling a simulated battery in an argon-protected Braun glove box, wherein the electrolyte is 1M-LiPF₆+ EC: DEC: DMC 1: 1:1 (volume ratio), a metal lithium sheet is used as a counter electrode, a simulated battery test is carried out in a 5V and 10mA Xinwei battery test cabinet, the charging and discharging voltage is 0.01-1.5V, the charging and discharging speed is 0.1C, and the first capacity and efficiency obtained by the test are listed in Table 1.

The full battery test method comprises the following steps: the negative electrode materials prepared in examples 1 to 4 and comparative examples 1 to 4 were used as negative electrodes, lithium cobaltate was used as a positive electrode, and 1M-LiPF₆+ EC: DEC: DMC 1: 1:1 (volume ratio) solution is used as electrolyte to assemble a full cell, normal temperature charging and discharging are carried out at the multiplying power of 0.5C and 2.0C, the voltage range is 3.0-4.2V, and the cycle performance obtained by the test is listed in table 1.

The maximum charging multiplying power test method comprises the following steps: and respectively charging the battery cell to 100% SOC with different multiplying powers, disassembling the battery cell, and observing the lithium precipitation condition of the negative plate.

TABLE 1 electrochemical performance test results of negative electrode materials prepared in examples 1 to 4 and comparative examples 1 to 2

A capacity retention of less than 80% indicates a cell failure. As can be seen from Table 1, the negative electrode material prepared by the preparation method of the invention has more excellent performance, and the first discharge capacity, rate capability and cycle performance of the negative electrode material are higher than those of the conventional products in the prior art.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.