WO2022166059A1 - Boron-doped resin-coated artificial graphite material - Google Patents

Abstract

The present invention relates to the field of battery materials, and particularly relates to a boron-doped resin-coated artificial graphite material. The material is of a core-shell structure, wherein the core is artificial graphite, and the shell is a boron-doped hard-carbon coating layer with a coating amount of 0.5%-2%. In the boron-doped resin-coated artificial graphite material provided in the present invention, a graphite surface is coated with a boron-containing complex of lithium salt and hard carbon, such that the first round-trip efficiency of the material can be improved while the electronic and ionic conductivity of the material is also improved, thereby improving the power performance, cycle performance and energy density of a battery.

Description

A boron-doped resin-coated artificial graphite material

CROSS-REFERENCE TO RELATED APPLICATIONS.

This application claims the priority of the Chinese patent application filed on February 2, 2021 with the application number 202110140851.6 and the invention title is "A boron-doped resin-coated artificial graphite material", the entire contents of which are incorporated by reference in this application.

technical field

The invention relates to the field of battery materials, in particular to a boron-doped resin-coated artificial graphite material.

Background technique

At present, with the increasing market requirements for battery energy density and rate performance, graphite anode materials are required to have high rate performance and first efficiency while having high energy density. One of the current methods to increase the energy density and rate of negative electrode materials is to perform surface coating, such as coating with soft carbon or hard carbon.

technical problem

For example, patent CN110797513A discloses a graphite-hard carbon coated material and a preparation method thereof. After mixing graphite and oligophenolic resin, curing and pyrolysis are performed, and the hard carbon is coated on the surface of the graphite material. A high-capacity negative electrode material was obtained. However, the negative electrode material coated with soft carbon or hard carbon can only improve the transport rate of lithium ions in the surface layer of the material, but does not improve the transport rate of lithium ions in the material itself; at the same time, due to the electronic conductivity of the hard carbon or soft carbon coating itself The rate difference will also affect the voltage platform of the battery, and the soft carbon/hard carbon coating will also reduce the first efficiency of the material.

technical solutions

According to various embodiments of the present application, the present invention provides a boron-doped resin-coated artificial graphite material. By coating a boron-containing lithium salt and a hard carbon composite on the surface of the graphite, it can improve the electronic and ionic conductivity of the material. At the same time, the first efficiency of the material can also be improved, thereby improving the power performance, cycling performance and energy density of the battery.

A boron-doped resin-coated artificial graphite material has a core-shell structure, the inner core is artificial graphite, and the outer shell is a boron-doped hard carbon coating layer, and the coating amount is 0.5-2%.

The further improvement to above-mentioned technical scheme is, its preparation method is:

Preparation of aminated boron doped phenolic resin: the phenolic resin is placed in a lithium difluorooxalate borate solution, then added to a graphene oxide solution, and then subjected to a hydrothermal reaction and reacted at a temperature of 120 to 200 ° C for 1 to 12 hours. Then, low temperature vacuum drying and pulverization are carried out, and then a mixed gas is introduced, and the reaction is carried out at a temperature of 500 to 800 ° C for 1 to 12 hours to obtain a boron amide doped phenolic resin;

Preparation of composite materials: Dissolve the amide doped phenolic resin in the ethyl acetate flux solution of the titanate coupling agent, stir evenly, add artificial graphite, mix evenly, transfer it to a high-speed mixer, and rotate at a speed of 100～1000r/min, temperature is 100～300℃, stirring time is 1～6h for coating, drying, pulverizing, then transferring to tube furnace and carbonizing in inert atmosphere to obtain boron-doped hard carbon coated artificial Graphite composite.

A further improvement to the above technical solution is that in the step of preparing the boron amide doped phenolic resin, the concentration of the lithium difluorooxalate borate solution is 0.5-5 wt %.

A further improvement to the above technical solution is that in the step of preparing the boron amide-doped phenolic resin, the concentration of the graphene oxide solution is 0.1-1 wt%.

A further improvement to the above technical solution is that in the step of preparing the boron amide-doped phenolic resin, the mixed gas is a mixture of ammonia and argon.

A further improvement to the above technical solution is that the volume ratio of the ammonia gas to the argon gas is 1:1.

A further improvement to the above technical solution is that, in the step of preparing the boron amide-doped phenolic resin, the mass ratio of the phenolic resin, difluorooxalic acid boric acid, and graphene oxide is 100:1-5:0.5-2.

A further improvement to the above technical solution is that in the step of preparing the composite material, the concentration of the titanate coupling agent is 1-5wt%.

A further improvement to the above technical scheme is that the titanate coupling agent is isopropyl triisostearate titanate, isopropyl triisostearate titanate, isopropyl dioleic acid acyloxy ( Dioctyl phosphoric acid acyloxy) titanate, isopropyl trioleic acid acyloxy titanate, propyl tris(dioctyl pyrophosphate acyloxy) titanate, bis(dioctyloxy pyrophosphate) Ester group) one of ethylene titanate.

A further improvement to the above technical solution is that in the step of preparing the composite material, the mass ratio of the boron amide-doped phenolic resin, the coupling agent, and the artificial graphite is 10-30:1-5:100.

beneficial effect

The boron-doped resin-coated artificial graphite material provided by the present invention utilizes the characteristic of strong electron-carrying ability of boron itself and the characteristic of high electrical conductivity of graphene to improve the electronic conductivity of the material. At the same time, the use of lithium difluorooxalate borate to dope lithium salt in the outer shell layer reduces the irreversible loss of SEI formed during the charge and discharge process of the material, and improves the first efficiency and ionic conductivity of the material. At the same time, the use of titanate coupling agent can form a network structure after carbonization of boron amide doped with phenolic aldehyde, which can improve the coating quality of the material, and improve its power and cycle performance.

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 boron-doped resin-coated artificial graphite material of Example 1 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.

Example 1

Preparation of boron amide-doped phenolic resin: 100 g of phenolic resin was placed in 300 ml of a 1wt% lithium difluorooxalate borate solution, and then added to 200 ml of a 0.5wt% graphene oxide solution, followed by a hydrothermal reaction , and reacted at a temperature of 150 °C for 6 hours, then vacuum-dried at a low temperature of 50 °C for 48 hours, pulverized, and then introduced into a mixture of ammonia gas (volume ratio: ammonia gas: argon = 1:1), and at a temperature of 600 The reaction was carried out at ℃ for 6 h to obtain boron amide doped phenolic resin;

Preparation of composite materials: Dissolve 20 g of boron amide doped phenolic resin in 100 ml of ethyl acetate flux solution of titanate coupling agent with a concentration of 3 wt%, stir evenly, add 100 g of artificial graphite, mix evenly and transfer to a high-speed In the mixing machine, the speed is 500r/min, the temperature is 200 °C, and the stirring time is 3h for coating, drying, pulverizing, and then transferring to a tube furnace for carbonization in an inert atmosphere for 12h to obtain boron-doped hard materials. Carbon-coated artificial graphite composites.

Example 2

Preparation of boron amide-doped phenolic resin: 100 g of phenolic resin was placed in 200 ml of a 0.5 wt% lithium difluorooxalate borate solution, and then added to 500 ml of a 0.1 wt % graphene oxide solution, and then heated by hydrothermal The reaction was carried out at a temperature of 120°C for 12h, then at a temperature of 50°C for 48h under low-temperature vacuum drying, pulverized, and then a mixture of ammonia gas (volume ratio: ammonia: argon = 1:1) was introduced, and in The temperature is 500℃ for 12h to obtain boron amide doped phenolic resin;

Preparation of composite material: Dissolve 10 g of boron amide doped phenolic resin in 100 ml of ethyl acetate flux solution of titanate coupling agent with a concentration of 1 wt%, stir evenly, add 100 g of artificial graphite, mix evenly and transfer to a high-speed In the mixing machine, the speed is 100r/min, the temperature is 100℃, and the stirring time is 6h. Carbon-coated artificial graphite composites.

Example 2

Preparation of boron amide doped phenolic resin: put 100g of phenolic resin in 100ml of 5wt% lithium difluorooxalate borate solution, then add 200ml of 1wt% graphene oxide solution, and then by hydrothermal reaction, And reacted at 200°C for 1 hour, then vacuum-dried at 50°C for 48 hours, pulverized, and then introduced a mixture of ammonia gas (volume ratio: ammonia gas: argon gas = 1:1), and at a temperature of The reaction was carried out at 800 °C for 1 h to obtain a boron amide doped phenolic resin;

Preparation of composite material: Dissolve 30 g of boron amide doped phenolic resin in 100 ml of ethyl acetate flux solution of titanate coupling agent with a concentration of 5 wt%, stir evenly, add 100 g of artificial graphite, mix evenly and transfer to a high-speed In the mixing machine, under the conditions of rotating speed of 1000r/min, temperature of 300℃, and stirring time of 1h, coating, drying and pulverizing are carried out, and then transferred to a tube furnace and carbonized for 48h in an inert atmosphere to obtain boron-doped hard materials. Carbon-coated artificial graphite composites.

Comparative ratio

Add 20g of phenolic resin to 100ml of N-methylpyrrolidone and mix it evenly, add 100g of artificial graphite, mix it evenly and transfer it to a high-speed mixer, and the speed is 1000r/min, the temperature is 300℃, and the stirring time is 6h After coating, drying and pulverizing, the coated material was transferred to a tube furnace, and in a nitrogen inert atmosphere, the temperature was raised to 700 °C at a heating rate of 10 °C/min, kept for 1 hour, and then cooled to room temperature naturally. , and pulverized to obtain hard carbon-coated graphite composites.

Physical and chemical performance test:

1.1SEM test

The artificial graphite composite material prepared in Example 1 was tested by SEM, and the test results are shown in FIG. 1 . It can be seen from FIG. 1 that the artificial graphite composite material prepared in Example 1 is granular, with uniform size distribution, and its particle size is between (10-20) μm.

1.2 Powder conductivity test:

The powder was pressed into a block structure, and then the electrical conductivity of the powder was tested with a four-point probe tester. The test results are shown in Table 1.

1.3 Powder compaction density test

The powder compaction density test was carried out on the artificial graphite composite materials in Examples 1-3 and Comparative Examples. Using a powder compaction density meter, 1g of powder was placed in a fixed kettle and then pressed at 2T pressure and kept at rest for 10S. After that, the volume size under compaction was calculated, and the compacted density was calculated to calculate the compacted density of the powder. The test results are shown in Table 1.

The physical and chemical properties of the graphite materials in the examples and comparative examples of Table 1

project	Example 1	Example 2	Example 3	Comparative Example 1
Powder resistivity (Ω·m))	8*10-6	5*10-6	6*10-6	8*10-5
Powder compacted density (g/cm3)	1.67	1.64	1.63	1.51

As can be seen from Table 1, the powder resistivity of the artificial graphite composite material prepared by the present invention is obviously lower than that of the comparative example, and the reason is that the surface of the negative electrode material is doped with boron and titanium element doped hard carbon with high electronic conductivity, Reduce its electronic conductivity; at the same time, the graphene doped on the surface of the material has a lubricating effect to increase the powder compaction density of the material.

Button battery test

The artificial graphite composite materials in Examples 1-3 and Comparative Examples were assembled into button batteries A1, A2, A3, and B1, respectively. The assembling method is as follows: adding a binder, a conductive agent and a solvent to the negative electrode material, stirring to make a slurry, coating it on a copper foil, drying and rolling to obtain a negative electrode sheet. The binder used is LA132 binder, the conductive agent is SP, the negative electrode material is the graphite composite material in Examples 1-3 and the comparative example, and the solvent is double distilled water. The ratio of each component is: negative electrode material: SP: LA132: double distilled water = 95g: 1g: 4g: 220mL; the electrolyte is LiPF6/EC+DEC (the concentration of LiPF6 is 1.2mol/L, and the volume ratio of EC and DEC is 1:1), the metal lithium sheet is the counter electrode, and the separator is made of polyethylene (PE), polypropylene (PP) or polyethylene propylene (PEP) composite membrane. The assembly of the button battery was carried out in an argon-filled glove box, and the electrochemical performance test was carried out on a Wuhan Landian CT2001A battery tester, with a charge-discharge voltage range of 0.005V to 2.0V, and a charge-discharge rate of 0.1C. The test results are shown in Table 2.

At the same time, the above-mentioned negative electrode pieces were taken to test the liquid absorption and liquid retention capacity of the electrode pieces.

Table 2 Performance comparison of lithium ion batteries prepared by the artificial graphite composite materials of Examples 1-3 and Comparative Examples

project	Example 1/A1	Example 2/A2	Example 3/A3	Comparative Example 1/B1
First discharge capacity (mAh/g)	358.3	357.4	358.5	350.4
First time efficiency (%)	95.1	94.8	94.7	91.9
Absorption capacity (mL/min)	7.8	7.3	7.8	2.4

It can be seen from Table 2 that the initial discharge capacity and initial charge-discharge efficiency of the lithium-ion battery using the graphite composite negative electrode material obtained in Examples 1-3 are significantly higher than those of the comparative example. The reason is that the boron-doped hard carbon coating layer is used. , which is conducive to the transmission of lithium ions, improves the gram capacity of its materials, and further improves the first efficiency; at the same time, the shell is coated with lithium salts to reduce the irreversible capacity during the charge and discharge process and improve its first efficiency. At the same time, the coating layer of the embodiment has the nano-micron pores left by the gas generated in the carbonization process of hard carbon, and the porosity is high, which is beneficial to the liquid absorption of the material.

Soft pack battery test

Using the artificial graphite composite materials in Examples 1-3 and Comparative Examples as the negative electrode material, a negative electrode pole piece was prepared. Using ternary material (LiNi1/3Co1/3Mn1/3O2) as positive electrode, using LiPF6 solution (solvent as EC+DEC, volume ratio 1:1, LiPF6 concentration 1.3mol/L) as electrolyte, celegard2400 as diaphragm, prepared 2Ah Soft pack batteries D1, D2, D3 and E1. Then, the cycle performance and rate performance of the soft pack battery were tested.

Cyclic performance test conditions: charge and discharge current 1C/1C, voltage range 2.8-4.2V, 500 cycles.

Rate performance test conditions: charging rate: 1C/2C/3C/5C, discharge rate 1C; voltage range: 2.8-4.2V.

The test results are shown in Table 3 and Table 4.

The cycle performance comparison of table 3 embodiment and comparative example

As can be seen from Table 3, the cycle performance of the pouch battery prepared by the artificial graphite composite material of the present invention is better than that of the comparative example. The characteristic of high ion transmission rate. In addition, the artificial graphite composite material of the embodiment has good structural stability, and the cycle process has little damage to the structure of the material, and the structure is stable, thereby improving its cycle performance.

Table 4 Comparison of rate charging performance between the embodiment and the comparative example

As can be seen from Table 4, the soft pack battery prepared by the artificial graphite composite material of the present invention has a better constant current ratio, and the reason is that the surface of the material in the embodiment is covered with boron-doped hard carbon material, which increases the The fast charging performance of the material is improved, and the lithium salt contained in the shell improves the lithium ion transmission rate during the charging and discharging process of the material, thereby improving its rate performance.

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 boron-doped resin-coated artificial graphite material is characterized in that the material presents a core-shell structure, the inner core is artificial graphite, and the outer shell is a boron-doped hard carbon coating layer, and the coating amount is 0.5-2%.
2. The boron-doped resin-coated artificial graphite material according to claim 1, wherein the preparation method is:

   Preparation of aminated boron doped phenolic resin: the phenolic resin is placed in a lithium difluorooxalate borate solution, then added to a graphene oxide solution, and then subjected to a hydrothermal reaction and reacted at a temperature of 120 to 200 ° C for 1 to 12 hours. Then, low temperature vacuum drying and pulverization are carried out, and then a mixed gas is introduced, and the reaction is carried out at a temperature of 500 to 800 ° C for 1 to 12 hours to obtain a boron amide doped phenolic resin;

   Preparation of composite materials: Dissolve the amide doped phenolic resin in the ethyl acetate flux solution of the titanate coupling agent, stir evenly, add artificial graphite, mix evenly, transfer it to a high-speed mixer, and rotate at a speed of 100～1000r/min, temperature is 100～300℃, stirring time is 1～6h for coating, drying, pulverizing, then transferring to tube furnace and carbonizing in inert atmosphere to obtain boron-doped hard carbon coated artificial Graphite composite.
3. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the boron amide-doped phenolic resin, the concentration of the lithium difluorooxalate borate solution is 0.5-5wt%.
4. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the boron amide-doped phenolic resin, the concentration of the graphene oxide solution is 0.1-1 wt%.
5. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the boron amide-doped phenolic resin, the mixed gas is a mixture of ammonia gas and argon gas.
6. The boron-doped resin-coated artificial graphite material according to claim 5, wherein the volume ratio of the ammonia gas to the argon gas is 1:1.
7. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the boron amide-doped phenolic resin, the quality of the phenolic resin, difluorooxalic acid boric acid, and graphene oxide is The ratio is 100:1 to 5:0.5 to 2.
8. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the composite material, the concentration of the titanate coupling agent is 1-5 wt%.
9. The boron-doped resin-coated artificial graphite material according to claim 8, wherein the titanate coupling agent is isopropyl triisostearate titanate, isopropyl triisostearate titanate Esters, isopropyl dioleic acid acyloxy (dioctyl phosphoric acid acyloxy) titanate, isopropyl trioleic acid acyloxy titanate, propyl tris (dioctyl pyrophosphate acyloxy) One of titanate and bis(dioctyloxypyrophosphate) ethylene titanate.
10. The boron-doped resin-coated artificial graphite material according to claim 1, wherein in the step of preparing the composite material, the mass ratio of the boron amide-doped phenolic resin, the coupling agent, and the artificial graphite is: 10～30:1～5:100.

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