CN112510180B

CN112510180B - Silicon oxide-carbon filament active material and preparation method and application thereof

Info

Publication number: CN112510180B
Application number: CN202011403814.1A
Authority: CN
Inventors: 丁旭丽; 赵洪达; 梁道伟
Original assignee: Jiangsu University of Science and Technology
Current assignee: Jiangsu Saier Rubber Co ltd
Priority date: 2020-12-02
Filing date: 2020-12-02
Publication date: 2021-11-09
Anticipated expiration: 2040-12-02
Also published as: CN112510180A

Abstract

The invention discloses a silicon oxide-carbon filament active material. The material is composed of carbon filaments and silicon oxide, and the carbon filaments account for 10% to 30% of the total mass. Preparation method: high-energy ball milling of silicon oxide in an argon atmosphere for 10 to 30 hours, placing the obtained precursor in a corundum boat wrapped in copper foil, and then placing the corundum boat in a chemical vapor deposition device, and evacuating to ≤1.0× ^10-2 Torr, pass argon to normal pressure, then start to heat up, pass protective gas and reducing gas during the heating process, heat up to 1000-1200 ℃ and hold for 1-3 hours, and then drop to 900-1100 ℃, pass After the carbon source gas was introduced and kept for 1-3 hours, it was naturally cooled to room temperature. The invention grows carbon filaments on the surface of silicon oxide, improves the cycle stability of silicon oxide; and effectively suppresses the volume change of silicon oxide in the process of lithium insertion and delithiation, so that silicon oxide has high cycle stability, first coulomb efficiency and conductivity.

Description

Silicon oxide-carbon filament active material and preparation method and application thereof

Technical Field

The invention belongs to the field of lithium ion battery materials, and particularly relates to a silicon oxide-carbon filament active material as well as a preparation method and application thereof.

Background

The currently used lithium ion battery cathode material is mainly carbon-based cathode material, and the theoretical specific capacity of the cathode material is only 372mAh/g, which cannot meet the requirement of high specific energy lithium ion batteries required by world development. In various negative electrode materials researched at present, silicon-based negative electrode materials are widely concerned due to the fact that the theoretical specific capacity of silicon reaches 4200mAh/g and the storage capacity of silicon in the earth crust is the second place. However, the silicon-based material has its own disadvantages, which affect the commercial application and popularization of the silicon-based negative electrode material due to large volume deformation (about-300%) caused by intercalation and deintercalation of lithium ions during charge and discharge, and low conductivity of silicon. Compared with a silicon negative electrode, silicon oxide (silicon monoxide (2615mAh/g) and silicon dioxide (1965mAh/g)) generates smaller volume deformation in the charging and discharging processes, but the silicon oxide negative electrode material has low initial coulombic efficiency (ICE: 20-40%), is unstable in circulation and poor in conductivity, and the development of the silicon oxide negative electrode material is influenced by the problems.

In order to solve the problems, the patent CN111584855A adds silicon oxide particles into absolute ethyl alcohol, and ultrasonic dispersion is carried out to obtain dispersion liquid; adding resin into the dispersion liquid, heating to dissolve the resin, stirring and grinding to obtain a mixture; spray drying the mixture to obtain a dried product; and carrying out heat treatment on the dried product to foam the resin and then carbonize the resin, and carrying out carbon deposition on the surface by using a chemical vapor deposition method. The method has complex content, cannot play a good role in the volume change of the silicon monoxide, and cannot effectively improve the first coulombic efficiency and the conductivity of the silicon oxide.

Patent CN110890540A discloses a fluorine-containing silicon monoxide negative electrode material, and a preparation method and application thereof. Mixing and grinding silicon monoxide powder and ammonium fluoride powder to obtain silicon monoxide-ammonium fluoride composite powder; and sintering the silicon monoxide-ammonium fluoride composite powder under the protection of inert gas to obtain the fluorine-containing silicon monoxide negative electrode material. The method is difficult to uniformly distribute the fluorine element on the silicon monoxide surface, and the average grain diameter of the fluorine-containing silicon monoxide material is 10-70 mu m, so that the method is not beneficial to the rapid de-intercalation of lithium ions in the composite cathode material. And does not effectively solve the problem of volume expansion of SiO during the process of intercalation/deintercalation.

Disclosure of Invention

One object of the present invention is to provide a silica-carbon filament active material. The specific technical scheme is as follows:

the silicon oxide-carbon filament active material consists of carbon filaments and SiOx, wherein x is more than or equal to 0 and less than or equal to 2, the carbon filaments account for 10-30% of the total mass, and the particle size of the SiOx is 10nm-10 mu m.

The other purpose of the invention is to provide a preparation method of the silicon oxide-carbon filament active material. The specific technical scheme is as follows:

the preparation method of the silicon oxide-carbon filament active material comprises the following steps: carrying out high-energy ball milling on silicon oxide for 10-30 hours in an argon environment to obtain a precursor; placing the precursor in a chemical vapor deposition device (or placing the precursor in a corundum boat wrapped by copper foil, and then placing the corundum boat in the chemical vapor deposition device), and vacuumizing to less than or equal to 1.0 multiplied by 10^-2And (2) introducing argon to normal pressure, then starting heating, introducing 100-500 sccm of protective gas and 20-100 sccm of reducing gas in the heating process, heating to 1000-1200 ℃, keeping for 1-3 hours, then cooling to 900-1100 ℃, introducing 10-100 sccm of carbon source gas, keeping for 1-3 hours at 900-1000 ℃, closing the carbon source gas, and naturally cooling to room temperature to obtain the silicon oxide-carbon filament active material.

Preferably, the protective gas is nitrogen, argon or helium.

Preferably, the reducing gas is any one or a mixture of two or more of ammonia gas, hydrogen gas or hydrogen sulfide.

Preferably, the carbon source gas is CH₄、C₂H₄、C₂H₂、C₂H₆、C₃H₄、C₃H₆、C₃H₈、C₄H₆、C₄H₈、C₄H₁₀Or C₇H₈Any one or a mixture of two or more of them.

Preferably, the particle size of the silicon oxide is 10nm to 10 μm.

Preferably, the rate of temperature rise is as follows: the temperature rise rate is 8-10 ℃/min at 0-1000 ℃, and the temperature rise rate is 2-5 ℃/min at 1000-1100 ℃; the cooling rate is 2-5 ℃/min.

The invention also aims to provide application of the silicon oxide-carbon filament active material. The specific technical scheme is as follows:

the silicon oxide-carbon filament active material is applied to a lithium ion battery cathode material.

Preferably, the anode material further includes: conductive agents, binders; the conductive agent is at least one or a mixture of more than two of carbon black, acetylene black, natural graphite, carbon nanotubes, graphene and carbon fibers; the binder is one or a mixture of more than two of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylic acid, polyamide, polypropylene, polyvinyl ether, polyimide, styrene-butadiene copolymer, sodium carboxymethylcellulose and sodium alginate; in the negative electrode material, 50-99.5 wt% of active material, 0.1-40 wt% of conductive agent and 0.1-40 wt% of binder.

Preferably, the lithium ion battery further comprises a positive electrode, a diaphragm and electrolyte; wherein the positive electrode is lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate or lithium composite metal oxide; the diaphragm is any one of an aramid diaphragm, a non-woven fabric diaphragm, a polyethylene microporous film, a polypropylene-polyethylene double-layer or three-layer composite film and a ceramic coating diaphragm; the electrolyte comprises an electrolyte and a solvent, wherein the electrolyte is LiPF₆、LiBF₄、LiClO₄、LiAsF₆、LiCF₃SO₃、LiN(CF₃SO₂) Any one or a mixture of two or more of LiBOB, LiCl, LiBr and LiI; the solvent is one or more of Propylene Carbonate (PC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), 1, 2-Dimethoxyethane (DME), Ethylene Carbonate (EC), Butylene Carbonate (BC), diethyl carbonate (DEC), Ethyl Acetate (EA), and ethylene sulfite (GS).

The invention has the advantages of

Firstly, ball-milling silicon oxide for 10-30 hours by a high-energy ball mill until the ball-milling is in a nanometer level, wherein the ball-milled silicon oxide is in an argon environment during ball-milling, carrying out Chemical Vapor Deposition (CVD) treatment on the ball-milled silicon oxide, coating a layer of copper foil on the periphery of the silicon oxide before the CVD treatment, and realizing the growth of carbon filaments on the surface of the silicon oxide by controlling the flow of gas.

The preparation method has simple process, does not need some harmful chemical reagents, and firstly reduces the size of the silicon oxide particles so as to enable lithium ions to have more transportation paths. Before the chemical vapor deposition treatment, if a layer of copper foil is coated around the silicon oxide, the growth of carbon filaments is facilitated, and the first coulombic efficiency and the conductivity of the silicon oxide can be improved. The carbon filaments grow on the surface of the silicon oxide, so that the volume expansion of the silicon oxide can be effectively inhibited, the transmission path of lithium ions is increased, and the cycle stability of the silicon oxide is improved; and the volume change of the silicon oxide in the processes of lithium intercalation and lithium deintercalation is effectively inhibited, so that the silicon oxide has high cycle stability, and the first coulombic efficiency and the conductivity of the silicon oxide are improved.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of an active material obtained in example 1; FIG. 1a is a SEM of 1 μm unit length, FIGS. 1b and 1c are SEM of 200nm unit length, and FIG. 1d is SEM of 1nm unit length.

Fig. 2a is an electrochemical impedance spectrum of the active material obtained in example 1, and fig. 2b is an electrochemical impedance spectrum of the active material obtained in example 3.

Fig. 3a is a charge and discharge curve of the active material obtained in example 1, and fig. 3b is a charge and discharge curve of the active material obtained in example 2.

Fig. 4a is an electrochemical cycling test curve of the active material obtained in example 1, and fig. 4b is an electrochemical cycling test curve of the active material obtained in example 2.

Fig. 5 is a rate capability test curve of the active material obtained in example 1.

Detailed Description

Example 1

In a glove box filled with argon, silicon monoxide (ball powder ratio is 20:1, and the particle size of the silicon monoxide is more than 100 μm) is filled into a ball milling tank, the ball milling tank is sealed and then is subjected to high-energy ball milling for 10 hours, the ball milled silicon monoxide is uniformly placed into a corundum boat, a copper foil is placed between the corundum boat and the silicon monoxide, a CVD (chemical vapor deposition) device is placed, a vacuum system is opened, and the vacuum degree is reduced to 1.0 x 10^- ²And (5) closing the vacuum system when the pressure is Torr, introducing argon into the tube furnace until the air pressure in the tube furnace is recovered to the normal pressure, and opening an air outlet valve. Heating a tubular furnace, wherein the heating rate is 10 ℃/min between 0 and 1000 ℃, the heating rate is 5 ℃/min between 1000 and 1100 ℃, 200sccm of nitrogen and 40sccm of ammonia gas are introduced in the heating process, the temperature is increased to 1150 ℃ for 1h, then acetylene gas is introduced when the temperature is reduced to 1000 ℃ at the cooling rate of 5 ℃/min, the acetylene gas is introduced for 40sccm, the temperature is maintained for 1h at 1000 ℃, then the acetylene gas is closed, and the active material silicon oxide/carbon filament (SiOx/C, x is more than or equal to 0 and less than or equal to 2) is obtained by naturally cooling to room temperature, wherein the particle size is 20 nm-10 mu m.

Uniformly mixing 80 wt% of active material, 10 wt% of carbon nano tube conductive agent and 10 wt% of polyvinylidene fluoride (PVDF) adhesive, uniformly coating the mixture on copper foil by using 1-methyl-2-pyrrolidone as a solvent, and drying the copper foil for 12 hours in a drying oven at 100 ℃. Subsequently, the dried copper foil was cut into electrode pieces (lithium ion battery negative electrodes) having a diameter of 10 mm. The CR2032 button cell used in the electrochemical measurements was assembled in an argon filled glove box with less than 1ppm of water and oxygen. The assembled cell was allowed to stand for 12 hours and electrochemical measurements were taken.

As can be seen from fig. 1a, 1b, 1c, and 1d, the size of the silica particles reaches nanometer level, and at the same time, carbon filaments grow on the surface of the silica, which can inhibit the volume expansion degree of the silica during the lithium intercalation and de-intercalation processes, and provide more transmission paths for lithium ions, thereby improving the lithium ion conductivity of the composite material.

It can be seen from fig. 2a that the resistance of the negative electrode composite is small, indicating that the mobility of lithium ions in the negative electrode composite is high.

The charge-discharge curve in fig. 3a is the charge-discharge curve of the first three circles, and it can be seen that the negative electrode material has high first coulombic efficiency, and the defect of low first coulombic efficiency of oxide is effectively improved by growing carbon filaments on silicon oxide.

As can be seen from fig. 4a, the negative electrode material has high first coulombic efficiency, large specific capacity and good cycling stability.

Fig. 5 is a graph showing the rate capability test of the active material obtained in this example. The negative electrode material is charged and discharged at a current density of 0.05A/g-1.4A/g, and then at a current density of 1.4A/g-0.05A/g, and the negative electrode material has good rate capability as shown in figure 5.

Example 2

In a glove box filled with argon, silicon monoxide (ball powder ratio is 20:1, and the particle size of the silicon monoxide is more than 100 μm) is filled into a ball milling tank, high-energy ball milling is carried out for 30 hours after the ball milling tank is sealed, the ball-milled silicon monoxide is uniformly placed into a corundum boat, a copper foil is placed between the corundum boat and the silicon monoxide, a CVD (chemical vapor deposition) device is placed, a vacuum system is opened, and the vacuum degree is pumped to 1.0 x 10^- ²When the temperature is kept below the Torr, argon is introduced into the tubular furnace, the tubular furnace is started to be heated, the heating rate is 10 ℃/min between 0 ℃ and 1000 ℃, the heating rate is 5 ℃/min between 1000 ℃ and 1100 ℃, 100sccm of argon and 20sccm of hydrogen are introduced in the heating process, the temperature is raised to 1100 ℃ and kept for 1h, then when the temperature is reduced to 1000 ℃ at the cooling rate of 5 ℃/min, 20sccm of methane gas is introduced, the methane gas is closed after the temperature is kept for 1h at 1000 ℃, and the temperature is naturally cooled to room temperature, so that the prepared active material silicon oxide/carbon filament (SiOx/C, x is more than or equal to 0 and less than or equal to 2) (the particle size is 10nm-10 mu m) is obtained.

Uniformly mixing 70 wt% of active material, 15 wt% of conductive carbon (super-P) and 15 wt% of sodium alginate adhesive, uniformly coating the mixture on a copper foil by using deionized water as a solvent, and drying the copper foil for 12 hours at a temperature of 50 ℃ in a drying oven. Subsequently, the dried copper foil was cut into electrode pieces (lithium ion battery negative electrodes) having a diameter of 10 mm. The CR2032 button cell used in the electrochemical measurements was assembled in an argon filled glove box with less than 1ppm of water and oxygen. The assembled cell was allowed to stand for 12 hours and electrochemical measurements were taken.

The charge-discharge curve in fig. 3b is the charge-discharge curve of the first three circles, and it can be seen that the negative electrode material has high first coulombic efficiency, and the defect of low first coulombic efficiency of oxide is effectively improved by growing carbon filaments on silicon oxide.

As can be seen from fig. 4b, the negative electrode material has high first coulombic efficiency, large specific capacity, and good cycling stability.

Example 3

In a glove box filled with argon, silicon monoxide (ball powder ratio is 20:1, and the particle size of the silicon monoxide is more than 100 μm) is filled into a ball milling tank, high-energy ball milling is carried out for 30 hours after the ball milling tank is sealed, the ball-milled silicon monoxide is uniformly placed into a corundum boat, a copper foil is placed between the corundum boat and the silicon monoxide, a CVD (chemical vapor deposition) device is placed, a vacuum system is opened, and the vacuum degree is pumped to 1.0 x 10^- ²And (5) closing the vacuum system when the pressure is Torr, introducing argon into the tube furnace until the air pressure in the tube furnace is recovered to the normal pressure, and opening an air outlet valve. And (2) starting heating the tubular furnace, wherein the heating rate is 8 ℃/min between 0 and 1000 ℃, the heating rate is 5 ℃/min between 1000 and 1150 ℃, argon gas of 500sccm and ammonia gas of 100sccm are introduced during the heating process, the temperature is increased to 1150 ℃ for 2h, then when the temperature is reduced to 1000 ℃ at the cooling rate of 5 ℃/min, toluene gas of 40sccm is introduced, the temperature is maintained at 1050 ℃ for 1h, the toluene gas is closed, and the material is naturally cooled to room temperature to obtain the prepared active material silicon oxide/carbon filament (SiOx/C, x is more than or equal to 0 and less than or equal to 2) (the particle size is 20nm to 10 mu m).

Uniformly mixing 60 wt% of active material, 20 wt% of carbon nano tube conductive agent and 20 wt% of sodium alginate adhesive, uniformly coating the mixture on copper foil by using deionized water as a solvent, and drying the copper foil for 12 hours in a drying oven at 100 ℃. Subsequently, the dried copper foil was cut into electrode pieces (lithium ion battery negative electrodes) having a diameter of 10 mm. The CR2032 button cell used in the electrochemical measurements was assembled in an argon filled glove box with less than 1ppm of water and oxygen. The assembled cell was allowed to stand for 12 hours and electrochemical measurements were taken. It can be seen from fig. 2b that the resistance of the negative electrode material is small, indicating that the mobility of lithium ions in the negative electrode material is high.

Claims

1. A silicon oxide-carbon filament active material, characterized in that the active material is composed of carbon filament and SiOx, 0≤x≤2, wherein the carbon filament accounts for 10% to 30% of the total mass, and the particle size of SiOx 10nm-10μm; and prepared according to the following steps, high-energy ball milling silicon oxide in an argon atmosphere for 10-30 hours to obtain a precursor; placing the precursor in a chemical vapor deposition device, and vacuuming to ≤1.0× 10 ^-2 Torr, pass argon gas to normal pressure, then start to heat up, pass protective gas 100-500 sccm and reducing gas 20-100 sccm during the heating process, heat up to 1000-1200 ℃ and hold for 1-3 hours, and then drop to 900 When the temperature is ~1100°C, 10-100 sccm of carbon source gas is introduced, and after maintaining at 900-1000°C for 1-3 hours, the carbon source gas is turned off and cooled to room temperature naturally to obtain the silicon oxide-carbon filament active material.

2 . The method for preparing a silicon oxide-carbon filament active material according to claim 1 , comprising the following steps: high-energy ball milling silicon oxide in an argon atmosphere for 10 to 30 hours to obtain a precursor; The body was placed in a chemical vapor deposition apparatus, evacuated to ≤1.0×10 ^-2 Torr, passed argon to normal pressure, and then began to heat up. Keep it at 1000-1200℃ for 1-3 hours, then when it drops to 900-1100℃, feed the carbon source gas for 10-100sccm, keep it at 900-1000℃ for 1-3h, turn off the carbon source gas, and cool to room temperature naturally , the silicon oxide-carbon filament active material can be obtained.

3 . The method for preparing a silicon oxide-carbon filament active material according to claim 2 , wherein the protective gas is nitrogen, argon or helium. 4 .

4 . The method for preparing a silicon oxide-carbon filament active material according to claim 2 , wherein the reducing gas is any one or a mixture of two or more of ammonia, hydrogen or hydrogen sulfide. 5 .

_5. The preparation method of silicon oxide _- carbon filament active material according to claim ₂ , wherein the carbon source gas is _CH4 , _C2H4 , _C2H2 , _C2H6 , _C3H _4. Any one or a mixture of two or more of C ₃ H ₆ , C ₃ H ₈ , C ₄ H ₆ , C ₄ H ₈ , C ₄ H ₁₀ or C ₇ H ₈ .

6 . The method for preparing a silicon oxide-carbon filament active material according to claim 2 , wherein the particle size of the silicon oxide is 10 nm-10 μm. 7 .

7. The preparation method of the silicon oxide-carbon filament active material according to claim 2, characterized in that, the rate of temperature increase is as follows: The heating rate between ~1100°C is 2-5°C/min; the cooling rate is 2-5°C/min.

8. The silicon oxide-carbon filament active material according to claim 1 is applied to a negative electrode material of a lithium ion battery.

9 . The application according to claim 8 , wherein the negative electrode material further comprises: a conductive agent and a binder; wherein the conductive agent is carbon black, acetylene black, natural graphite, carbon nanotubes, graphite At least one or a mixture of two or more of olefin and carbon fiber; the binder is polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylic acid, polyamide, polypropylene, polyvinyl ether, polyamide Any one or a mixture of two or more of imine, styrene-butadiene copolymer, sodium carboxymethyl cellulose, and sodium alginate; in the negative electrode material, the active material accounts for 50-99.5 wt%, and the conductive material is conductive The agent accounts for 0.1-40wt%, and the binder accounts for 0.1-40wt%.

10. The application according to claim 8, wherein the lithium ion battery further comprises a positive electrode, a separator, and an electrolyte; wherein, the positive electrode is lithium iron phosphate or a composite metal oxide of lithium; the separator is Any one of aramid membrane, non-woven membrane, polyethylene microporous membrane, polypropylene membrane, polypropylene polyethylene double-layer or triple-layer composite membrane, and ceramic-coated membrane; the electrolyte contains electrolyte and solvent , the electrolyte is LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiN (CF3SO2), LiBOB, LiCl, LiBr, LiI in any one or a mixture of two or more; the solvent is propylene carbonate (PC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), 1,2-Dimethoxyethane (DME), Ethylene Carbonate (EC), Butylene Carbonate (BC), Diethyl Carbonate (DEC), Acetic Acid Any one or a mixture of two or more of ethyl ester (EA) and vinyl sulfite (GS).