WO2022166058A1 - High-energy-density low-temperature artificial graphite material for fast-charge and preparation method therefor - Google Patents

Abstract

Provided is a high-energy-density low-temperature artificial graphite material for fast-charge applied to the field of battery negative electrode materials, comprising the following steps: crushing, shaping and spheroidizing; ultrahigh-temperature graphitization; vapor deposition; cooling; and screening. Provided is a low-cost high-energy-density low-temperature artificial graphite material for fast-charge. Further provided is a preparation method for the high-energy-density low-temperature artificial graphite material for fast-charge with a simple process.

Description

A kind of high energy density low temperature fast charging artificial graphite material and preparation method thereof

CROSS-REFERENCE TO RELATED APPLICATIONS.

This application claims the priority of the Chinese patent application filed on February 2, 2021 with the application number 202110140814.5 and the invention title is "A high-energy-density low-temperature fast-charging artificial graphite material and its preparation method", all of which The contents are incorporated herein by reference.

technical field

The invention relates to the field of battery negative electrode materials, in particular to a high-energy-density low-temperature fast-charging artificial graphite material and a preparation method thereof.

Background technique

In recent years, the state has vigorously promoted new energy electric vehicles. However, electric vehicles have short cruising range and long charging time, and the battery performance is greatly reduced in cold weather in winter, which hinders the promotion of electric vehicles. Therefore, there is an urgent need for lithium-ion batteries. Fast charging performance has been improved. The improvement of lithium-ion battery performance mainly depends on the improvement of electrochemical performance of electrode materials. Therefore, it is of great significance to improve the energy density of anode materials while maintaining superior low-temperature fast charging performance.

technical problem

In the prior art, low-temperature fast-charging graphite negative electrode materials are basically formed by carbonization of secondary particles, but the carbonization of secondary particles has the disadvantages of requiring coating modification, complex process, and high cost. At the same time, if the coating layer is too thick, it will cause a certain degree of energy density loss; in addition, this technical solution is restricted by the large particle size of the secondary particles, which cannot further improve the low-temperature fast charging performance of the graphite anode material, and it is difficult to meet the requirements of lithium-ion batteries. Performance requirements for low temperature fast charging. In view of this, it is indeed necessary to develop a graphite anode material with both high energy density and low-temperature fast charging performance and its preparation method.

technical solutions

According to various embodiments of the present application, the present invention provides a low-cost high-energy density low-temperature fast-charging artificial graphite material; the present invention also provides a preparation method of a high-energy density low-temperature fast-charging artificial graphite material with a simple process.

A preparation method of high-energy-density low-temperature fast-charging artificial graphite material, comprising the following steps.

The raw materials are pulverized, shaped and spheroidized to obtain graphite precursor powder.

Put the above-mentioned graphite precursor powder into the graphitization furnace, heat up to 2800-3200°C at a heating rate of 5~20°C/min, and keep the temperature for 1~20°C. 96h, the graphite matrix was obtained after cooling.

Put the graphite matrix into the furnace chamber of the vapor deposition furnace, heat up at a rate of 3~15℃/min, and at the same time pass in an inert protective gas at a flow rate of 50~500L/h, when the temperature reaches 750~1150℃, adjust the inert protection The flow rate of the gas is 100~1000L/h, and the catalytic gas and the carbon source gas are introduced at the same time.

Stop feeding the catalytic gas and carbon source gas, adjust the flow rate of the inert protective gas to 50~500L/h, adopt the method of natural cooling in the furnace to 450~600℃, and keep the temperature for 0.5~2h; turn off the heating power, and use the natural cooling in the furnace When the temperature is below 80°C, the inert protective gas is stopped to obtain an artificial graphite material.

The artificial graphite material is sieved, and the mesh number of the ultrasonic vibrating screen is 325 meshes to obtain a low-temperature fast-charging artificial graphite material with an average particle size D50 of 3-8 μm.

In one embodiment, in the step of pulverizing and spheroidizing raw materials to obtain graphite precursor powder, the raw materials are petroleum coke, pitch coke, mesophase coke, isotropic coke with particle size less than 10 mm one or more of.

In one embodiment, in the step of pulverizing and spheroidizing the raw material to obtain the graphite precursor powder, the particle size D50 of the graphite precursor powder is 2-7 microns.

In one embodiment, the above-mentioned graphite precursor powder is put into a graphitization furnace, heated to 2800-3200°C at a heating rate of 5-20°C/min, kept for 1-96 hours, and cooled to obtain In the graphite matrix step, the graphitization furnace is one of a box-type high-temperature graphite furnace, a continuous high-temperature graphitization furnace, a series-connected graphitization furnace, and an Acheson graphitization furnace.

In one embodiment, the graphite substrate is put into the furnace chamber of the vapor deposition furnace, the temperature is increased at a rate of 3-15°C/min, and an inert protective gas is introduced at a flow rate of 50-500L/h at the same time. When reaching 750～1150 ℃, adjust the flow rate of inert protective gas to 100～1000L/h, feed into catalytic gas and carbon source gas step simultaneously, the flow ratio of described inert protective gas, carbon source gas, catalytic gas is 1: (0.1~1): (0.01~0.1), the access time is 1~10h.

In one embodiment, the graphite substrate is put into the furnace chamber of the vapor deposition furnace, the temperature is increased at a rate of 3-15°C/min, and an inert protective gas is introduced at a flow rate of 50-500L/h at the same time. When reaching 750~1150°C, adjust the flow rate of the inert protective gas to 100~1000L/h, and feed the catalytic gas and carbon source gas at the same time. The vapor deposition furnace is a rotary kiln, a tube furnace, and a fluidized bed. A sort of.

In one embodiment, the graphite substrate is put into the furnace chamber of the vapor deposition furnace, the temperature is increased at a rate of 3-15°C/min, and an inert protective gas is introduced at a flow rate of 50-500L/h at the same time. When the temperature reaches 750-1150°C, the flow rate of the inert protective gas is adjusted to 100-1000 L/h, and the catalytic gas and carbon source gas are introduced simultaneously. The inert protective gas is nitrogen or argon.

In one embodiment, the graphite substrate is put into the furnace chamber of the vapor deposition furnace, the temperature is increased at a rate of 3-15°C/min, and an inert protective gas is introduced at a flow rate of 50-500L/h at the same time. When the temperature reaches 750-1150°C, the flow rate of the inert protective gas is adjusted to 100-1000 L/h, and the catalytic gas and the carbon source gas are introduced at the same time, and the catalytic gas is hydrogen.

In one embodiment, the graphite substrate is put into the furnace chamber of the vapor deposition furnace, the temperature is increased at a rate of 3-15°C/min, and an inert protective gas is introduced at a flow rate of 50-500L/h at the same time. When reaching 750~1150°C, adjust the flow rate of the inert protective gas to 100~1000L/h, and simultaneously feed the catalytic gas and the carbon source gas in the step, the carbon source gas is methane, ethane, acetylene, ethylene, natural gas, liquefied gas, etc. One of petroleum gas, benzene or thiophene.

A high-energy-density low-temperature fast-charging artificial graphite material is prepared by using the above preparation method.

beneficial effect

The small-diameter graphite particles used in the present invention have more superior high-current charge-discharge performance than the large-diameter graphite particles. On the one hand, small particles can reduce the current loaded per unit area, which is beneficial to reduce overpotential; on the other hand, the edges of small carbon crystallites can provide more migration channels for lithium ions; at the same time, the migration path of lithium ions is short. , the diffusion resistance is small. The invention adopts the ultra-high temperature graphitization method to make the graphite have higher purity and crystallinity, thereby improving the energy density of the material. The invention adopts a two-step cooling CVD vapor deposition coating method to deposit amorphous carbon on the surface of the graphite base material. The two-step cooling method is beneficial to eliminate the internal stress generated in the material preparation process, so that the surface coating layer has better structural stability. In the present invention, CVD vapor deposition coating can reduce the amount of carbon coating so that the material has a higher specific capacity; the interlayer spacing of the amorphous carbon coating layer in the present invention is larger than that of graphite, which can improve the diffusion performance of lithium ions therein. , which is equivalent to forming a lithium ion buffer layer on the outer surface of graphite, thereby improving the high current charge-discharge performance of the material; the in-situ growth of amorphous carbon can improve the interaction with lithium ions, increase the desolvation speed, and improve the interface. The reaction speed is improved, and the low-temperature charge-discharge performance is improved. The carbon coating layer has a low degree of graphitization and a high lithium intercalation potential, thereby preventing the electrolyte from getting electrons on the graphite surface and being reduced, improving the charge-discharge efficiency, reducing the deposition of Li metal on the graphite surface, and improving the safety. Through the combination of the above advantages, when the graphite anode material prepared in the present invention is applied to a battery, a higher energy density and an excellent low-temperature fast charging performance can be achieved.

Description of drawings

In order to better describe and illustrate embodiments and/or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be construed as limiting the scope of any of the disclosed inventions, the presently described embodiments and/or examples, and the best mode presently understood of these inventions.

FIG. 1 is a SEM image of the high-energy-density low-temperature fast-charging artificial graphite material of the present invention.

Embodiments of the present invention

In order to facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure is provided.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

As shown in Figure 1, a method for preparing a high-energy-density, low-temperature fast-charging artificial graphite material includes the following steps: pulverizing and spheroidizing raw materials to obtain graphite precursor powder; placing the above-mentioned graphite precursor powder into graphitization In the furnace, the temperature is raised to 2800-3200°C at a heating rate of 5-20°C/min, and the temperature is kept for 1-96 hours. After cooling, a graphite matrix is obtained; At the same time, the inert protective gas was introduced at a flow rate of 50~500L/h. When the temperature reached 750~1150℃, the flow rate of the inert protective gas was adjusted to 100~1000L/h, and the catalytic gas and carbon source were introduced at the same time. gas; stop feeding the catalytic gas and carbon source gas, adjust the flow rate of the inert protective gas to 50~500L/h, adopt the method of natural cooling in the furnace to 450~600℃, and keep the temperature for 0.5~2h; The natural cooling method is below 80 °C, and the inert protective gas is stopped to obtain artificial graphite material; the artificial graphite material is sieved, and the mesh number of the ultrasonic vibrating screen is 325 meshes to obtain a low temperature with an average particle size D50 of 3~8 μm. Fast charging artificial graphite material.

In the step of pulverizing and spheroidizing the raw materials to obtain the graphite precursor powder, the raw materials are one or more of petroleum coke, pitch coke, mesophase coke, and isotropic coke with a particle size of less than 10 mm.

In the step of pulverizing, shaping and spheroidizing the raw materials to obtain the graphite precursor powder, the particle size D50 of the graphite precursor powder is 2-7 microns.

Putting the above-mentioned graphite precursor powder into the graphitization furnace, heating up to 2800-3200°C at a heating rate of 5～20°C/min, and keeping the temperature for 1～20°C 96h, in the step of obtaining a graphite matrix after cooling, the graphitization furnace is one of a box-type high-temperature graphite furnace, a continuous high-temperature graphitization furnace, a series-connected graphitization furnace, and an Acheson graphitization furnace.

Putting the graphite matrix into the furnace chamber of the vapor deposition furnace, heating up at a rate of 3~15°C/min, and feeding an inert protective gas at a flow rate of 50~500L/h at the same time, when the temperature reaches 750~1150°C, Adjust the flow of inert protective gas to 100～1000L/h, feed into catalytic gas and carbon source gas step simultaneously, the flow ratio of described inert protective gas, carbon source gas, catalytic gas is 1: (0.1~1): (0.01~0.1), the access time is 1~10h.

Putting the graphite matrix into the furnace chamber of the vapor deposition furnace, heating up at a rate of 3~15°C/min, and feeding an inert protective gas at a flow rate of 50~500L/h at the same time, when the temperature reaches 750~1150°C, The flow rate of the inert protective gas is adjusted to 100-1000 L/h, and the catalytic gas and the carbon source gas are introduced simultaneously. The vapor deposition furnace is one of a rotary kiln, a tube furnace, and a fluidized bed.

Putting the graphite matrix into the furnace chamber of the vapor deposition furnace, heating up at a rate of 3~15°C/min, and feeding an inert protective gas at a flow rate of 50~500L/h at the same time, when the temperature reaches 750~1150°C, The flow rate of the inert protective gas is adjusted to 100-1000 L/h, and in the step of feeding the catalytic gas and the carbon source gas at the same time, the inert protective gas is nitrogen or argon.

Putting the graphite matrix into the furnace chamber of the vapor deposition furnace, heating up at a rate of 3~15°C/min, and feeding an inert protective gas at a flow rate of 50~500L/h at the same time, when the temperature reaches 750~1150°C, The flow rate of the inert protective gas is adjusted to 100-1000 L/h, and the catalytic gas and the carbon source gas are simultaneously introduced in the step, and the catalytic gas is hydrogen.

Putting the graphite matrix into the furnace chamber of the vapor deposition furnace, heating up at a rate of 3~15°C/min, and feeding an inert protective gas at a flow rate of 50~500L/h at the same time, when the temperature reaches 750~1150°C, Adjust the flow rate of the inert protective gas to 100~1000L/h, and feed into the catalytic gas and the carbon source gas at the same time. The carbon source gas is methane, ethane, acetylene, ethylene, natural gas, liquefied petroleum gas, benzene or thiophene. a kind of.

A high-energy-density low-temperature fast-charging artificial graphite material is prepared by using the above preparation method.

Example 1.

A method for preparing a high-energy-density, low-temperature fast-charging artificial graphite material, comprising the following steps: pulverizing and spheroidizing raw materials to obtain graphite precursor powder; placing the graphite precursor powder in a graphitization furnace, and heating at 5° C. /min heating rate, heat up to 2800°C, keep for 20h, and cool to obtain a graphite matrix; put the graphite matrix into the furnace of the vapor deposition furnace, heat up at a rate of 5°C/min, and at the same time pass in a flow rate of 200L/h Inert protective gas, when the temperature reaches 750℃, adjust the flow rate of inert protective gas to 200L/h, and feed catalytic gas and carbon source gas at the same time; stop feeding catalytic gas and carbon source gas, and adjust the flow rate of inert protective gas to 100L /h, adopt the method of natural cooling in the furnace to 450 °C, and keep the temperature for 1 h; turn off the heating power, adopt the natural cooling method in the furnace to below 80 °C, stop feeding the inert protective gas, and obtain the artificial graphite material; sieve the artificial graphite material The mesh number of the ultrasonic vibrating screen is 325 meshes, and a low-temperature fast-charging artificial graphite material with an average particle size D50 of 3 μm is obtained.

Example 2.

A method for preparing a high-energy-density, low-temperature fast-charging artificial graphite material, comprising the following steps: pulverizing and spheroidizing raw materials to obtain graphite precursor powder; placing the graphite precursor powder in a graphitization furnace, and heating the powder at 10° C. /min heating rate, heat up to 3000°C, hold for 40h, and cool to obtain a graphite matrix; put the graphite matrix into the furnace chamber of the vapor deposition furnace, heat up at a rate of 10°C/min, and at the same time pass in a flow rate of 250L/h Inert protective gas, when the temperature reaches 1000℃, adjust the flow rate of inert protective gas to 600L/h, and feed catalytic gas and carbon source gas at the same time; stop feeding catalytic gas and carbon source gas, and adjust the flow rate of inert protective gas to 300L /h, adopt the method of natural cooling in the furnace to 500 °C, and keep the temperature for 1 h; turn off the heating power, adopt the natural cooling method in the furnace to below 80 °C, stop feeding the inert protective gas, and obtain the artificial graphite material; sieve the artificial graphite material The mesh number of the ultrasonic vibrating screen is 325 meshes, and a low-temperature fast-charging artificial graphite material with an average particle size D50 of 5 μm is obtained.

Example 3.

A preparation method of high-energy-density low-temperature fast-charging artificial graphite material, comprising the following steps: pulverizing raw materials, shaping and spheroidizing to obtain graphite precursor powder; placing the above-mentioned graphite precursor powder in a graphitization furnace at 20° C. /min heating rate, heat up to 3200°C, hold for 80h, and cool down to obtain a graphite matrix; put the graphite matrix into the furnace of the vapor deposition furnace, heat up at a rate of 15°C/min, and at the same time pass in a flow rate of 500L/h Inert protective gas, when the temperature reaches 1150℃, adjust the flow rate of inert protective gas to 1000L/h, and feed catalytic gas and carbon source gas at the same time; stop feeding catalytic gas and carbon source gas, and adjust the flow rate of inert protective gas to 500L /h, adopt the method of natural cooling in the furnace to 600 °C, and keep the temperature for 2 hours; turn off the heating power, adopt the natural cooling method in the furnace to below 80 °C, stop feeding the inert protective gas, and obtain the artificial graphite material; sieve the artificial graphite material The mesh number of the ultrasonic vibrating screen is 325 meshes, and a low-temperature fast-charging artificial graphite material with an average particle size D50 of 8 μm is obtained.

The small-diameter graphite particles used in the present invention have more superior high-current charge-discharge performance than the large-diameter graphite particles. On the one hand, small particles can reduce the current loaded per unit area, which is beneficial to reduce overpotential; on the other hand, the edges of small carbon crystallites can provide more migration channels for lithium ions; at the same time, the migration path of lithium ions is short. , the diffusion resistance is small.

The invention adopts the ultra-high temperature graphitization method to make the graphite have higher purity and crystallinity, thereby improving the energy density of the material.

The invention adopts a two-step cooling CVD vapor deposition coating method to deposit amorphous carbon on the surface of the graphite base material. The two-step cooling method is beneficial to eliminate the internal stress generated in the material preparation process, so that the surface coating layer has better structural stability.

In the present invention, CVD vapor deposition coating can reduce the amount of carbon coating so that the material has a higher specific capacity; the interlayer spacing of the amorphous carbon coating layer in the present invention is larger than that of graphite, which can improve the diffusion performance of lithium ions therein. , which is equivalent to forming a lithium ion buffer layer on the outer surface of graphite, thereby improving the high current charge-discharge performance of the material; the in-situ growth of amorphous carbon can improve the interaction with lithium ions, increase the desolvation speed, and improve the interface. The reaction speed is improved, and the low-temperature charge-discharge performance is improved. The carbon coating layer has a low degree of graphitization and a high lithium intercalation potential, thereby preventing the electrolyte from getting electrons on the graphite surface and being reduced, improving the charge-discharge efficiency, reducing the deposition of Li metal on the graphite surface, and improving the safety.

Through the combination of the above advantages, when the graphite anode material prepared in the present invention is applied to a battery, a higher energy density and an excellent low-temperature fast charging performance can be achieved.

The above-mentioned embodiments are only preferred embodiments of the present invention, and cannot be used to limit the scope of protection of the present invention. Any insubstantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of the present invention. Scope of protection claimed.

Claims (10)

1. A preparation method of high-energy-density low-temperature fast-charging artificial graphite material, characterized in that it comprises the following steps:

   The raw materials are pulverized, shaped and spheroidized to obtain graphite precursor powder;

   Put the above-mentioned graphite precursor powder into a graphitization furnace, heat up to 2800-3200°C at a heating rate of 5-20°C/min, keep the temperature for 1-96h, and cool to obtain a graphite matrix;

   Put the graphite matrix into the furnace chamber of the vapor deposition furnace, heat up at a rate of 3~15℃/min, and at the same time pass in an inert protective gas at a flow rate of 50~500L/h, when the temperature reaches 750~1150℃, adjust the inert protection The flow rate of the gas is 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time;

   Stop feeding the catalytic gas and carbon source gas, adjust the flow rate of the inert protective gas to 50~500L/h, adopt the method of natural cooling in the furnace to 450~600℃, and keep the temperature for 0.5~2h; turn off the heating power, and use the natural cooling in the furnace When the temperature is below 80 °C, the inert protective gas is stopped to obtain artificial graphite material;

   The artificial graphite material is sieved, and the mesh number of the ultrasonic vibrating screen is 325 meshes to obtain a low-temperature fast-charging artificial graphite material with an average particle size D50 of 3-8 μm.
2. The method for preparing a high-energy-density, low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, in the step of pulverizing and spheroidizing raw materials to obtain graphite precursor powder, the raw materials have a particle size smaller than One or more of 10mm petroleum coke, pitch coke, mesophase coke, and isotropic coke.
3. The method for preparing a high-energy-density, low-temperature fast-charging artificial graphite material according to claim 1, wherein, in the step of pulverizing and spheroidizing raw materials to obtain graphite precursor powder, the graphite precursor powder The particle size D50 is 2~7 microns.
4. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the above-mentioned graphite precursor powder into a graphitization furnace, and heating at a temperature of 5 to 20°C/min. speed, heat up to 2800 ~ 3200 ° C, heat preservation for 1 ~ 96h, and cooling to obtain a graphite matrix. In the step of obtaining a graphite matrix, the graphitization furnace is a box-type high-temperature graphite furnace, a continuous high-temperature graphitization furnace, a series-connected graphitization furnace, and an Acheson graphitization furnace. a kind of.
5. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the graphite matrix into the furnace chamber of the vapor deposition furnace, and heating at a speed of 3～15°C/min, At the same time, the inert protective gas is introduced at a flow rate of 50~500L/h. When the temperature reaches 750~1150℃, the flow rate of the inert protective gas is adjusted to 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time. The flow ratio of the inert protective gas, the carbon source gas, and the catalytic gas is 1: (0.1~1): (0.01~0.1), and the introduction time is 1~10h.
6. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the graphite matrix into the furnace chamber of the vapor deposition furnace, and heating at a speed of 3～15°C/min, At the same time, the inert protective gas is introduced at a flow rate of 50~500L/h. When the temperature reaches 750~1150℃, the flow rate of the inert protective gas is adjusted to 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time. The vapor deposition furnace is one of rotary kiln, tube furnace and fluidized bed.
7. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the graphite matrix into the furnace chamber of the vapor deposition furnace, and heating at a speed of 3～15°C/min, At the same time, the inert protective gas is introduced at a flow rate of 50~500L/h. When the temperature reaches 750~1150℃, the flow rate of the inert protective gas is adjusted to 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time. The inert protective gas is nitrogen or argon.
8. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the graphite matrix into the furnace chamber of the vapor deposition furnace, and heating at a speed of 3～15 ℃/min, At the same time, the inert protective gas is introduced at a flow rate of 50~500L/h. When the temperature reaches 750~1150℃, the flow rate of the inert protective gas is adjusted to 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time. The catalytic gas is hydrogen.
9. The preparation method of high-energy-density low-temperature fast-charging artificial graphite material according to claim 1, characterized in that, putting the graphite matrix into the furnace chamber of the vapor deposition furnace, and heating at a speed of 3～15°C/min, At the same time, the inert protective gas is introduced at a flow rate of 50~500L/h. When the temperature reaches 750~1150℃, the flow rate of the inert protective gas is adjusted to 100~1000L/h, and the catalytic gas and carbon source gas are introduced at the same time. The carbon source gas is one of methane, ethane, acetylene, ethylene, natural gas, liquefied petroleum gas, benzene or thiophene.
10. A high-energy-density low-temperature fast-charging artificial graphite material, characterized in that, it is prepared by using the preparation method according to any one of claims 1-9.