A double-layer coated silicon oxide composite negative electrode material and preparation method thereof

Abstract

The present invention provides a double-layer coated silicon oxide composite negative electrode material and a preparation method thereof. The silicon oxide is a multi-layer composite coated network cross-linked structure, the innermost layer is silicon oxide SiOx, the middle layer is a silicon-doped titanium dioxide coating layer, and the outer layer is an amorphous carbon formed by polymerization and calcination of organic monomers. In the entire composite material, the middle layer is tightly connected to the surface of the micron-sized silicon oxide inner layer through the formed Si-O-Ti bond chemical skeleton, which effectively reduces the interface resistance and increases the bonding force between the coating layer and the silicon oxide. The middle layer is doped with silicon, which not only improves the overall capacity of the material, but also forms hydrogen bonds with the outer organic monomer, guides the directional and regular growth of the polymer, makes the polymer coating layer more uniform and dense, improves the contact between the electrolyte and the electrode surface, and inhibits volume expansion. The silicon oxide composite negative electrode material provided by the present invention has the advantages of high conductivity, good cycle performance, and stable interface, and the process is simple and suitable for industrialization.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a high-performance silicon-carbon negative electrode material for lithium batteries and a preparation method thereof. Background Art

[0002] With the rapid development of mobile electronic products and new energy vehicle industries, the market's requirements for the energy density of lithium-ion batteries are also increasing. As a key material for lithium-ion batteries, negative electrode materials play a decisive role in the energy of batteries. The theoretical specific capacity of traditional negative electrode material graphite is only 372 mAh / g, which can no longer meet the requirements of high energy density lithium-ion batteries. The theoretical capacity of silicon is as high as 4200 mAh / g, which is more than ten times the theoretical capacity of graphite. In order to achieve the goal of higher energy density, it is a consensus in the industry to develop silicon-based negative electrodes for use in lithium-ion battery systems.

[0003] Although silicon-based negative electrode materials have broad application prospects, there are still technical barriers to be overcome in the actual use of silicon-based materials. The main problems are: 1) The volume expansion reaches 320% after lithium insertion, and the volume expansion will further lead to material pulverization, changes in electrode structure and continuous formation of solid electrolyte (SEI) film; 2) It is an intrinsic semiconductor material with poor conductivity. Due to the limitations of the above bottleneck problems, silicon materials cannot be used alone as negative electrode materials. At present, the main practice of battery material companies is to combine silicon with graphite, conductive agents and other carbon materials. The introduction of carbon materials can improve the conductivity of silicon-carbon negative electrodes.

[0004] CN1014022257 B discloses a lithium-ion battery silicon oxide composite negative electrode material, a preparation method and its use. A carbon coating layer is formed on the surface of silicon oxide powder by a solid phase coating method. The carbon layer is difficult to evenly coat the surface of micron-sized particles, and some particle surfaces are still exposed and in contact with the electrolyte, resulting in more irreversible reactions during the charge and discharge process and low coulomb efficiency.

[0005] CN 107658455 A discloses a method for preparing a conductive polymer-carbon-coated silicon oxide composite material, in which carbon is directly coated on the surface of silicon oxide particles, and a conductive polymer is connected and coated on the carbon surface via a coupling agent, thereby reducing the volume expansion effect of the material. However, the battery capacity is affected and the initial efficiency is low. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a double-layer coated silicon oxide negative electrode material and a preparation method thereof. The silicon monoxide composite negative electrode material provided by the present invention has the advantages of high conductivity, good cycle performance, and stable interface, and the process is simple and suitable for industrialization.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A double-layer coated silicon oxide composite negative electrode material, the silicon oxide negative electrode material is a multi-layer composite coated cross-linked structure, the innermost layer is silicon oxide, the middle layer is a silicon-doped titanium dioxide coating layer (TiO2@Si), and the outermost layer is an amorphous carbon coating layer generated by polymer decomposition. Among them, TiO2 is closely connected to the micron-scale silicon oxide surface through the formed Si-O-Ti bond chemical skeleton to form a cross-linked structure, the silicon in the TiO2 coating layer can form a Si-O bond, and the Si-O bond forms a hydrogen bond with the organic monomer, so that the coating layer formed by the polymerization of the monomer is more orderly and dense, and finally a mixed double-layer coating effect is achieved.

[0009] Furthermore, the mass fraction of silicon oxide in the double-layer coated silicon oxide composite negative electrode material is 90-98%, the middle layer, i.e., the silicon-doped titanium dioxide coating layer, accounts for 1-8% of the mass of the silicon-oxygen composite negative electrode material, and the amorphous carbon coating layer accounts for 1-8% of the mass of the silicon-oxygen composite negative electrode material.

[0010] The preparation method of the double-layer coated silicon monoxide composite negative electrode material of the present invention comprises the following steps:

[0011] (1) mixing a titanium dioxide precursor, a silicon source material and a solvent to obtain a solution A, and stirring an acid, water and a solvent to obtain a solution B;

[0012] (2) adding solution B dropwise to solution A, stirring, and sintering at high temperature in a muffle furnace to obtain Si-doped titanium dioxide;

[0013] (3) adding silicon dioxide powder and Si-doped titanium dioxide into an ethanol solution, mixing the solid and liquid phases at high energy, drying, and calcining at high temperature to obtain titanium dioxide-coated silicon dioxide;

[0014] (4) Add the coated silicon dioxide and aniline monomer into dilute hydrochloric acid and stir to react, add ammonium persulfate dropwise, and filter and calcine the product at high temperature to obtain a silicon dioxide composite negative electrode material.

[0015] Furthermore, the titanium dioxide precursor in step (1) includes one of tetrabutyl titanate, butyl titanate, propyl titanate, and isopropyl titanate. The silicon source includes one of ethyl orthosilicate, propyl orthosilicate, and methyl orthosilicate. The solvent includes one of ethanol, methanol, isopropanol, and acetone.

[0016] Furthermore, in step (2), the stirring time is 0.5 to 2 hours, the muffle furnace sintering temperature is 400 to 600° C., the heating rate is 5 to 10° C. / min, and the sintering time is 2 to 6 hours.

[0017] Furthermore, in the step (3), the particle size of the silicon oxide powder is 3-6 μm, and the mixing method of the solid-liquid high-energy mixing includes one of magnetic stirring, ball milling, and ultrasonic oscillation; drying is performed in a blast drying oven at a temperature of 50-80°C; high-temperature calcination is performed in an inert gas in a tubular furnace, the inert gas is one of nitrogen and argon, the heating rate is 5°C / min, the sintering temperature is 700-900°C, the sintering time is 2-4h, and the temperature is naturally cooled.

[0018] Furthermore, in the step (4), the mass of aniline monomer accounts for 3% to 10% of silicon oxide, the concentration of hydrochloric acid is 1 to 3M, the mass ratio of aniline to ammonium persulfate is 1:(3 to 5), and a tubular furnace is used for high-temperature calcination in an inert gas, the inert gas is one of nitrogen and argon, the heating rate is 5°C / min, the sintering temperature is 700 to 900°C, the sintering time is 2 to 4 hours, and the temperature is naturally cooled.

[0019] Beneficial effects of the present invention:

[0020] (1) TiO2 and silicon dioxide form a Si-O-Ti bond chemical skeleton, which closely connects the inner layer and the middle layer, effectively reduces the interface resistance, increases the bonding force between the coating layer and silicon dioxide, and enhances the stability of the material. (2) Doping Si elements in TiO2 not only improves the overall capacity of the material, but also forms Si-O bonds. The Si-O bonds form hydrogen bonds with aniline monomers, guiding the directional and regular growth of the polymer, making the polymer coating more uniform and dense, and improving the contact between the electrolyte and the electrode surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of silicon dioxide negative electrode material, where 1 is silicon dioxide, 2 is the TiO2@Si coating layer, and 3 is the amorphous carbon layer formed by the polymer.

[0022] Figure 2 This is a diagram of the cyclability of the silicon monoxide composite negative electrode material prepared in Example 1. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention.

[0024] The silicon-oxygen negative electrode material prepared in the embodiment of the invention was assembled into a half-cell and the electrochemical performance was tested: the silicon-carbon negative electrode material: Super P: binder were homogenized and smeared in a mass ratio of 8:1:1. Among them, the binder is a solution of sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR): polyacrylic acid (PAA) in a mass ratio of 1:1:1, and the electrolyte is a conventional LiPF6 electrolyte. The lithium sheet was used as the counter electrode and assembled into a CR2025 button battery. Under normal temperature conditions, the charge and discharge test was carried out at a current density of 100 mA / g using the LANHE CT2001A blue electricity test system, and the voltage range was 0.005 ~ 2.0 V.

[0025] Example 1

[0026] The preparation method of the double-layer coated silicon oxide composite negative electrode material of this embodiment is as follows:

[0027] (1) Add 10 g of tetrabutyl titanate and 2 g of ethyl orthosilicate to 200 mL of anhydrous ethanol and stir for 30 min; add 10 g of pure hydrate to 200 mL of anhydrous ethanol in 1 M dilute hydrochloric acid and stir for 30 min. Add the latter dropwise to the latter, continue stirring, and sinter at 500 ° C in a muffle furnace for 2 h to obtain Si-doped TiO2.

[0028] (2) Add 10 g of silicon 2 oxide and 1 g of silicon-doped TiO2 into 200 mL of ethanol solution, stir for 30 min, sinter in a muffle furnace at 500 °C for 2 h, and then place it in a tubular furnace and calcine at 700 °C for 2 h. During calcination, protective gas N2 was introduced and the heating rate was 5 °C / min to obtain a composite material SiO2@TiO2.

[0029] (3) SiO2@TiO2 and aniline monomers were added to dilute hydrochloric acid, stirred and reacted for 4 h in an ice bath, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800 °C in a tubular furnace for 2 h. Protective gas N2 was introduced during calcination, and the heating rate was 5 °C / min to obtain the silicon-oxygen negative electrode material SiO2@TiO2@C.

[0030] Example 2

[0031] The preparation method of the double-layer coated silicon oxide composite negative electrode material of this embodiment is as follows:

[0032] (1) Add 10 g of tetrabutyl titanate and 2 g of propyl orthosilicate to 200 mL of anhydrous ethanol and stir for 30 min; add 10 g of pure hydrate to 200 mL of anhydrous ethanol in 1 M dilute hydrochloric acid and stir for 30 min. Add the latter dropwise to the latter, continue stirring, and sinter at 500 ° C in a muffle furnace for 2 h to obtain Si-doped TiO2.

[0033] (2) 10 g SiO2 and 1 g silicon-doped TiO2 were added to 200 mL of ethanol solution, stirred for 30 min, sintered at 500 °C in a muffle furnace for 2 h, and then calcined at 700 °C in a tube furnace for 2 h. During calcination, protective gas N2 was introduced at a heating rate of 5 °C / min to obtain a composite material SiO2@TiO2.

[0034] (3) SiO2@TiO2 and aniline monomers were added to dilute hydrochloric acid, stirred and reacted for 4 h in an ice bath, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800 °C in a tubular furnace for 2 h. Protective gas N2 was introduced during calcination, and the heating rate was 5 °C / min to obtain the silicon-oxygen negative electrode material SiO2@TiO2@C.

[0035] Example 3

[0036] The preparation method of the double-layer coated silicon oxide composite negative electrode material of this embodiment is as follows:

[0037] (1) Add 10 g of tetrabutyl titanate and 2 g of ethyl orthosilicate to 200 mL of anhydrous ethanol and stir for 30 min; add 10 g of pure hydrate to 200 mL of anhydrous ethanol in 1 M dilute hydrochloric acid and stir for 30 min. Add the latter dropwise to the latter, continue stirring, and sinter at 500 ° C in a muffle furnace for 2 h to obtain Si-doped TiO2.

[0038] (2) 10 g SiO2 and 1 g silicon-doped TiO2 were added to 200 mL of ethanol solution, stirred for 30 min, sintered at 500 °C in a muffle furnace for 2 h, and then calcined at 700 °C in a tube furnace for 2 h. During calcination, protective gas N2 was introduced at a heating rate of 5 °C / min to obtain a composite material SiO2@TiO2.

[0039] (3) SiO2@TiO2 and aniline monomers were added to dilute hydrochloric acid, stirred and reacted for 4 h in an ice bath, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800 °C in a tubular furnace for 2 h. Protective gas N2 was introduced during calcination, and the heating rate was 5 °C / min to obtain the silicon-oxygen negative electrode material SiO2@TiO2@C.

[0040] Comparative Example 1

[0041] (1) Add 10 g of tetrabutyl titanate and 2 g of ethyl orthosilicate to 200 mL of anhydrous ethanol and stir for 30 min; add 10 g of pure hydrate to 200 mL of anhydrous ethanol in 1 M dilute hydrochloric acid and stir for 30 min. Add the latter dropwise to the latter, continue stirring, and sinter at 500 ° C in a muffle furnace for 2 h to obtain Si-doped TiO2.

[0042] (2) 10 g SiO2 and 1 g silicon-doped TiO2 were added to 200 mL of ethanol solution, stirred for 30 min, sintered at 500 °C in a muffle furnace for 2 h, and then placed in a tubular furnace and calcined at 700 °C for 2 h. During calcination, protective gas N2 was introduced and the heating rate was 5 °C / min to obtain the composite material SiO2@TiO2Si.

[0043] Comparative Example 2

[0044] SiO2 and aniline monomers were added to dilute hydrochloric acid, stirred for reaction in an ice bath for 4 hours, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800°C in a tubular furnace for 2 hours. Protective gas N2 was introduced during calcination, and the heating rate was 5°C / min to obtain the silicon-oxygen negative electrode material SiO2@C.

[0045] Comparative Example 3 (Compared with Example 1, the intermediate layer of this comparative example is TiO2)

[0046] (1) Add 10 g of tetrabutyl titanate to 200 mL of anhydrous ethanol and stir for 30 min; add 10 g of pure hydrate to 200 mL of anhydrous ethanol in 1 M dilute hydrochloric acid and stir for 30 min. Add the latter dropwise to the latter, continue stirring, and sinter at 500 ° C in a muffle furnace for 2 h to obtain TiO2.

[0047] (2) 10 g SiO2 and 1 g TiO2 were added to 200 mL of ethanol solution, stirred for 30 min, sintered in a muffle furnace at 500 °C for 2 h, and then placed in a tube furnace and calcined at 700 °C for 2 h. During calcination, protective gas N2 was introduced at a heating rate of 5 °C / min to obtain a composite material SiO2@TiO 2。

[0048] (3) SiO2@TiO2 and aniline monomers were added to dilute hydrochloric acid, stirred and reacted for 4 h in an ice bath, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800 °C in a tubular furnace for 2 h. Protective gas N2 was introduced during calcination, and the heating rate was 5 °C / min to obtain the silicon-oxygen negative electrode material SiO2@TiO2@C.

[0049] Comparative Example 4

[0050] 10 g of silicon dioxide and 2 g of tetrabutyl titanate were added to ethanol, stirred for pretreatment, and then calcined at 800° C. for 4 h in a nitrogen atmosphere to obtain a SiO2@TiO2 composite material.

[0051] SiO2@TiO2 and aniline monomer were added to dilute hydrochloric acid, stirred for reaction in an ice bath for 4 hours, and ammonium persulfate was added dropwise. The solution was then filtered and dried, and calcined at 800°C in a tubular furnace for 2 hours. Protective gas N2 was introduced during calcination, and the heating rate was 5°C / min to obtain the silicon-oxygen negative electrode material SiO2@TiO2@C.

[0052] Table 1 is a table showing the electrochemical properties of silicon oxide negative electrode materials of Examples 1-3 and Comparative Examples 1-4

[0053]

[0054] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A double-layer coated silicon oxide composite negative electrode material, characterized in that: The silicon oxide negative electrode material is a multi-layer composite coating cross-linked structure, the innermost layer is silicon oxide, the middle layer is a silicon-doped titanium dioxide coating layer, and the outermost layer is an amorphous carbon coating layer generated by polymer decomposition; The method for preparing the double-layer coated silicon monoxide composite negative electrode material comprises the following steps: (1) mixing a titanium dioxide precursor, a silicon source material and a solvent to obtain a solution A, and mixing an acid, water and a solvent to obtain a solution B; (2) adding solution B dropwise into solution A and stirring evenly, and sintering at high temperature in a muffle furnace to obtain silicon-doped titanium dioxide; (3) adding silicon oxide powder and silicon-doped titanium dioxide into an ethanol solution, mixing the solid and liquid phases at high energy, drying, and calcining at high temperature to obtain silicon oxide coated with silicon-doped titanium dioxide; (4) Add silicon-doped titanium dioxide-coated silicon monoxide and aniline monomers into dilute hydrochloric acid and stir to react, add ammonium persulfate dropwise, and filter and calcine the product at high temperature to obtain a silicon-oxygen composite negative electrode material.

2. The double-layer coated silicon 2 O composite negative electrode material according to claim 1, characterized in that: The mass fraction of silicon oxide in the double-layer coated silicon oxide composite negative electrode material is 90-98%, the middle layer, i.e., the silicon-doped titanium dioxide coating layer, accounts for 1-8% of the mass of the double-layer coated silicon oxide composite negative electrode material, and the amorphous carbon coating layer accounts for 1-8% of the mass of the double-layer coated silicon oxide composite negative electrode material.

3. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 1, characterized in that The following steps are involved: (1) mixing a titanium dioxide precursor, a silicon source material and a solvent to obtain a solution A, and mixing an acid, water and a solvent to obtain a solution B; (2) adding solution B dropwise into solution A and stirring evenly, and sintering at high temperature in a muffle furnace to obtain silicon-doped titanium dioxide; (3) adding silicon oxide powder and silicon-doped titanium dioxide into an ethanol solution, mixing the solid and liquid phases at high energy, drying, and calcining at high temperature to obtain silicon oxide coated with silicon-doped titanium dioxide; (4) Add silicon-doped titanium dioxide-coated silicon monoxide and aniline monomers into dilute hydrochloric acid and stir to react, add ammonium persulfate dropwise, and filter and calcine the product at high temperature to obtain a silicon-oxygen composite negative electrode material.

4. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 3, characterized in that: In the step (1), the titanium dioxide precursor includes tetrabutyl titanate, propyl titanate or isopropyl titanate; the silicon source includes ethyl orthosilicate, propyl orthosilicate or methyl orthosilicate; and the solvent includes ethanol, methanol, isopropanol or acetone.

5. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 3, characterized in that: In the step (1), the mass ratio of titanium dioxide to silicon source is 10:(1-3).

6. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 3, characterized in that: In the step (2), the stirring time is 0.5 to 2 hours, the sintering temperature is 400 to 600° C., the heating rate is 5 to 10° C. / min, and the sintering time is 2 to 6 hours.

7. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 3, characterized in that: In the step (3), the particle size of the silicon oxide powder is 3-6 μm, and the mass ratio of the silicon oxide powder to silicon-doped titanium dioxide is 10:(0.5-2).

8. The method for preparing a double-layer coated silicon 2 O composite negative electrode material according to claim 3, characterized in that: The drying in step (3) is carried out in a blast drying oven at a drying temperature of 50-80°C, and a tubular furnace is used for high-temperature calcination in an inert gas, the inert gas is nitrogen or argon, the heating rate is 5°C / min, the sintering temperature is 700-900°C, the sintering time is 2-4h, and the temperature is naturally cooled.

9. The method for preparing a double-layer coated silicon 2 O composite negative electrode material according to claim 3, characterized in that: In the step (4), the aniline monomer accounts for 3% to 10% of the mass of the titanium dioxide-coated silicon oxide, the concentration of hydrochloric acid is 1 to 3M, and the mass ratio of the aniline monomer to ammonium persulfate is 1:(3 to 5).

10. The method for preparing a double-layer coated silicon oxide composite negative electrode material according to claim 3, characterized in that: In the step (4), a tubular furnace is used to carry out high-temperature calcination in an inert gas, the inert gas is nitrogen or argon, the heating rate is 5°C / min, the sintering temperature is 700-900°C, the sintering time is 2-4h, and the temperature is naturally cooled.

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