CN112289985B - C @ MgAl2O4Composite coating modified silicon-based negative electrode material and preparation method thereof - Google Patents

Abstract

The invention discloses a C@MgAl ₂ O ₄ composite coating modified silicon-based negative electrode material and a preparation method thereof, and relates to the technical field of electrochemical energy storage. The material comprises a silicon-based negative electrode material and a silicon-based negative electrode sequentially coated on MgAl ₂ O ₄ coating layer and carbon coating layer on the surface of the material; the preparation process is as follows: prepare an aqueous solution of Al(NO ₃ ) ₃ ·9H ₂ O and Mg(NO ₃ ) ₂ ·6H ₂ O, mix, and add cross-linking monolayer body, cross-linking agent, initiator, heating and reaction to obtain gel; ball-milling silicon-based negative electrode material to obtain slurry, adding gel to it, stirring and dispersing in vacuum, and spray-drying to obtain silicon-based negative electrode material precursor ; The silicon-based negative electrode material precursor is calcined at high temperature in an air atmosphere to obtain a MgAl ₂ O ₄ -coated and modified silicon-based negative electrode material, which is then calcined in a mixed atmosphere containing acetylene. The C@MgAl ₂ O ₄ composite-coated and modified silicon-based negative electrode material prepared by the invention has stable structure, small volume expansion during charging and discharging, and improves the first Coulomb efficiency and cycle stability performance of the material.

Description

A kind of C@MgAl2O4 composite coating modified silicon-based negative electrode material and preparation method thereof

technical field

The invention relates to the technical field of electrochemical energy storage, in particular to a C@MgAl ₂ O ₄ composite coating modified silicon-based negative electrode material and a preparation method thereof.

Background technique

With the rapid development of electric vehicles, energy storage power stations and portable electronic devices, high specific energy lithium-ion batteries have received more and more attention. Because the reversible specific capacity of the positive electrode material has little room for improvement, currently improving the reversible specific capacity of the negative electrode material is the key to improving the energy density of lithium-ion batteries. However, the current commercial lithium-ion battery anode materials are mainly graphite-based carbon anode materials, and the theoretical specific capacity is only 372mAh/g (LiC ₆ ), which seriously limits the further development of lithium-ion batteries. The silicon-based material is a research system with a high theoretical specific capacity in the negative electrode material. The alloy formed by it is Li _x Si (x=0~4.4), and the theoretical specific capacity is as high as 4200mAh/g. Atomic mass, high energy density, and high Li mole fraction in Li-Si alloys are considered ideal alternatives to carbon anode materials. However, due to the severe volume expansion and contraction of the silicon anode during the intercalation and delithiation cycle, the material structure is destroyed and mechanically pulverized, resulting in the poor cycle performance of the electrode. The conductivity of SiO is poor, and its properties are close to that of an insulator, resulting in poor kinetic performance of its electrochemical reaction, and the SiO ₂ contained in the SiO material is transformed into Li ₄ SiO ₄ and Li ₂ Si ₂ O ₅ in the first lithium intercalation reaction. In other phases, more lithium ions are consumed, resulting in lower first charge-discharge efficiency. The mainstream commercial silicon oxide composite anode materials are generally carbon-coated, which improves the conductivity of the material, and also avoids the direct contact of the silicon oxide material with the electrolyte, which improves the cycle performance of the material. However, the large-scale application of silicon-based anode materials still faces many challenges. To further improve the cycle performance of the material, improve the first Coulomb efficiency of the material, and reduce the production cost, the majority of researchers and manufacturers still have a long way to go.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background technology, the present invention proposes a C@MgAl ₂ O ₄ composite coating modified silicon-based negative electrode material and a preparation method thereof. The negative electrode material has a stable structure and small volume expansion during charging and discharging. The first coulombic efficiency and cycle stability performance of silicon-based anode materials are improved.

A silicon-based negative electrode material modified by C@MgAl ₂ O ₄ composite coating proposed by the present invention includes a silicon-based negative electrode material, a MgAl ₂ O ₄ coating layer and a carbon coating that are sequentially coated on the surface of the silicon-based negative electrode material. Floor.

Preferably, in the C@MgAl ₂ O ₄ composite modified silicon-based negative electrode material, the mass percentage content of the MgAl ₂ O ₄ coating layer is 0.5-5%, and the mass percentage content of the carbon coating layer is 0.5% ~5%.

Preferably, the silicon-based negative electrode material is a commercial pure silicon oxide negative electrode material or a nano-silicon negative electrode material.

The present invention also proposes a method for preparing the above-mentioned C@MgAl ₂ O ₄ composite coating modified silicon-based negative electrode material, comprising the following steps:

S1. Prepare an aqueous solution of Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ .6H ₂ O, mix them, add a cross-linking monomer, a cross-linking agent and an initiator, and heat up the reaction to obtain a condensate. glue;

S2, performing ball milling on the silicon-based negative electrode material to obtain a slurry, adding gel to it, stirring and dispersing in a vacuum, and spray-drying to obtain a silicon-based negative electrode material precursor;

S3, calcining the silicon-based negative electrode material precursor at a high temperature in an air atmosphere to obtain a silicon-based negative electrode material modified by MgAl ₂ O ₄ coating;

S4. Using acetylene as the carbon source, the MgAl ₂ O ₄ -coated and modified silicon-based negative electrode material is calcined in a mixed atmosphere containing acetylene to obtain a C@MgAl ₂ O ₄ composite-coated and modified silicon-based negative electrode material .

Preferably, in S1, the crosslinking monomer is acrylamide, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is ammonium persulfate; 6h.

Preferably, in S2, the spray drying temperature is 120-200°C.

Preferably, in S3, the calcination temperature is 700-900°C, the heating rate is 3-10°C/min, and the calcination time is 2-5h.

Preferably, in S4, the mixed atmosphere is a nitrogen-acetylene mixed atmosphere, wherein the volume percentage of acetylene is 40-50%.

Preferably, in S4, the calcination temperature is 750-950°C, the heating rate is 3-10°C/min, and the calcination time is 1-3h.

Compared with the prior art, the beneficial effects of the present invention are embodied in the following aspects:

1. The present invention first coats a layer of MgAl ₂ O ₄ on the silicon-based negative electrode material, which is prepared by calcination through the polymer network gel method. The obtained coating material has good chemical stability, and has a porous structure, which is compatible with The good matching performance of silicon can effectively alleviate the volume expansion problem of Si and SiO in the process of lithium deintercalation; and then carbon coating can effectively improve its conductivity.

2. The C@MgAl ₂ O ₄ composite-coated and modified silicon-based negative electrode material prepared by the present invention has stable structure, small volume expansion during charging and discharging, and improves the first Coulomb efficiency and cycle stability performance of the material.

3. The preparation method of the present invention is simple, feasible, low in cost, environmentally friendly, and easy to realize industrialized production.

Description of drawings

Fig. 1 is the first charge-discharge curve diagram of the silicon-based negative electrode material prepared in Example 1 of the present invention; wherein, the curve a is SiO _x @MgAl ₂ O ₄ @C silicon-based negative electrode material, and the curve b is the uncoated modified negative electrode material. SiO _x silicon-based negative electrode material.

Detailed ways

Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments.

Example 1

Preparation of a C@MgAl ₂ O ₄ composite modified silicon-based anode material:

(1) Using Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ .6H ₂ O as raw materials to prepare an aqueous solution, wherein Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ The molar ratio of 6H ₂ O is 2:1 (wherein the masses of Al(NO ₃ ) ₃ 9H ₂ O and Mg(NO ₃ ) ₂ 6H ₂ O are 10.7586g and 3.6768g, respectively), respectively add to the aqueous solution 4g of acrylamide monomer, 4g of cross-linking agent N,N'-methylenebisacrylamide, 1g of initiator ammonium persulfate were polymerized at 80°C for 5h to obtain gel.

(2) take 100g of commercial SiO _x powder and place it in a ball mill to ball-mill to obtain a slurry, then add gel for vacuum stirring and dispersion, and spray-dry to obtain a silicon-based negative electrode material precursor at a drying temperature of 180°C;

(3) The spray-dried mixture is placed in a tube furnace for high temperature calcination, the calcination atmosphere is air, the calcination temperature is 800°C, the heating rate is 5°C/min, and the calcination time is 3h to obtain 2% MgAl ₂ O ₄ Modified silicon-based anode material; then continue to carry out C coating in a tube furnace, the tube furnace is a nitrogen-acetylene mixed atmosphere, the coating temperature is 800 °C, the heating rate is 5 °C/min, and the flow rate of the mixed gas is 200L /h, the coating time was 2h, and the volume of acetylene in the mixed atmosphere was 50%. After coating, it was naturally cooled to room temperature to obtain a C@MgAl ₂ O ₄ composite coating modified silicon-based anode material (SiO _x @ MgAl ₂ O ₄ @C).

The electrochemical performance of the SiO _x @MgAl ₂ O ₄ @C silicon-based negative electrode material obtained in Example 1 was tested. Figure 1 shows the SiO _x @MgAl ₂ O ₄ @C silicon-based negative electrode material of Example 1 and the The first charge-discharge curve of the coated commercial SiO _x at a rate of 0.05C (1C=1300mA/g) and a voltage range of 0.05-1.5V. Among them, the first discharge specific capacity of commercial SiO _x is 1649.43 mAh/g, the charging specific capacity is 703.58 mAh/g, and the first coulombic efficiency is only 42.66%. The SiO _x @MgAl ₂ O ₄ @C material has a first discharge specific capacity of 2020.42mAh/g, a charge specific capacity of 1495.62mAh/g, and a first Coulomb efficiency of 74.03%, showing higher first effect and first charge specific capacity. This is of great significance for improving the capacity and first efficiency of the full battery. Meanwhile, the discharge plateau of the _SiOx @ _MgAl2O4 @C material is significantly lower _than that of commercial _SiOx , showing a smaller polarization. Therefore, compared with the untreated commercial _SiOx material, the _SiOx @ _{MgAl2O4 @} C material exhibits higher specific capacity and first effect, and the material has small polarization and better electrochemical performance.

Example 2

Preparation of a C@MgAl ₂ O ₄ composite modified silicon-based anode material:

(1) Using Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ .6H ₂ O as raw materials to prepare an aqueous solution, wherein Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ The molar ratio of 6H ₂ O is 2:1 (wherein the masses of Al(NO ₃ ) ₃ 9H ₂ O and Mg(NO ₃ ) ₂ 6H ₂ O are 10.7586g and 3.6768g, respectively), respectively add to the aqueous solution 4g of acrylamide monomer, 4g of cross-linking agent N,N'-methylenebisacrylamide, 1g of initiator ammonium persulfate were polymerized at 60°C for 6h to obtain gel.

(2) take 40g of commercial SiO _x powder and place it in a ball mill to ball mill to obtain a slurry, then add gel for vacuum stirring and dispersion, and spray-dry to obtain a silicon-based negative electrode material precursor, and the drying temperature is 130 ° C;

(3) The spray-dried mixture was placed in a tube furnace for high temperature calcination, the calcination atmosphere was air, the calcination temperature was 700°C, the heating rate was 3°C/min, and the calcination time was 5h to obtain 5% MgAl ₂ O ₄ Modified silicon-based anode material; then continue to carry out C coating in a tube furnace, the tube furnace is a nitrogen-acetylene mixed atmosphere, the coating temperature is 850 °C, the heating rate is 5 °C/min, and the flow rate of the mixed gas is 200L /h, the coating time was 2.5h, and the volume of acetylene in the mixed atmosphere was 40%. After coating, it was naturally cooled to room temperature to obtain a C@MgAl ₂ O ₄ composite coating modified silicon-based anode material (SiO _x @MgAl ₂ O ₄ @C).

Example 3

Preparation of a C@MgAl ₂ O ₄ composite modified silicon-based anode material:

(1) Using Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ .6H ₂ O as raw materials to prepare an aqueous solution, wherein Al(NO ₃ ) ₃ .9H ₂ O and Mg(NO ₃ ) ₂ The molar ratio of 6H ₂ O is 2:1 (wherein the masses of Al(NO ₃ ) ₃ 9H ₂ O and Mg(NO ₃ ) ₂ 6H ₂ O are 10.7586g and 3.6768g, respectively), respectively add to the aqueous solution 4g of acrylamide monomer, 4g of cross-linking agent N,N'-methylenebisacrylamide, and 1g of initiator ammonium persulfate were polymerized at 100°C for 3h to obtain gel.

(2) take 400g of commercial _SiOx powder and place it in a ball-milling tank for ball milling to obtain a slurry, then add gel for vacuum stirring and dispersion, and spray-dry to obtain a silicon-based negative electrode material precursor at a drying temperature of 200°C;

(3) The spray-dried mixture was placed in a tube furnace for high temperature calcination, the calcination atmosphere was air, the calcination temperature was 900°C, the heating rate was 10°C/min, and the calcination time was 2h to obtain 0.5% MgAl ₂ O ₄ Modified silicon-based anode material; then continue to carry out C coating in a tube furnace, the tube furnace is a nitrogen-acetylene mixed atmosphere, the coating temperature is 950 °C, the heating rate is 10 °C/min, and the flow rate of the mixed gas is 200L /h, the coating time was 1h, and the volume of acetylene in the mixed atmosphere was 45%. After coating, it was naturally cooled to room temperature to obtain a C@MgAl ₂ O ₄ composite coating modified silicon-based anode material (SiO _x @ MgAl ₂ O ₄ @C).

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (5)

1. C @ MgAl₂O₄The preparation method of the composite coated and modified silicon-based negative electrode material is characterized by comprising the silicon-based negative electrode material and MgAl coated on the surface of the silicon-based negative electrode material in sequence₂O₄A coating layer and a carbon coating layer;

the method specifically comprises the following steps:

s1, preparation of Al (NO)₃)₃·9H₂O and Mg (NO)₃)₂·6H₂Mixing the water solution of O, adding a crosslinking monomer, a crosslinking agent and an initiator, and heating to react to prepare gel; the crosslinking monomer is acrylamide, the crosslinking agent is N, N' -methylene bisacrylamide, and the initiator is ammonium persulfate; the temperature rise reaction temperature is 60-100 ℃, and the reaction time is 3-6 h;

s2, performing ball milling treatment on the silicon-based negative electrode material to obtain slurry, adding gel into the slurry, stirring and dispersing in vacuum, and performing spray drying to obtain a precursor of the silicon-based negative electrode material; the spray drying temperature is 120-200 ℃;

s3, calcining the silicon-based anode material precursor at high temperature in the air atmosphere to obtain MgAl₂O₄Coating the modified silicon-based negative electrode material; the calcination temperature is 700-900 ℃, the heating rate is 3-10 ℃/min, and the calcination time is 2-5 h;

s4, using acetylene as carbon source and MgAl₂O₄Calcining the coated and modified silicon-based negative electrode material in a mixed atmosphere containing acetylene to obtain C @ MgAl₂O₄And compounding and coating the modified silicon-based negative electrode material.

2. C @ MgAl of claim 1₂O₄The preparation method of the composite coating modified silicon-based anode material is characterized in that C @ MgAl₂O₄In the composite modified silicon-based negative electrode material, MgAl₂O₄The mass percentage of the coating layer is 0.5-5%, and the mass percentage of the carbon coating layer is 0.5-5%.

3. C @ MgAl of claim 1₂O₄The preparation method of the composite coating modified silicon-based negative electrode material is characterized in that the silicon-based negative electrode material is a commercial pure silicon oxide negative electrode material or a nano silicon negative electrode material.

4. C @ MgAl of claim 1₂O₄The preparation method of the composite coating modified silicon-based negative electrode material is characterized in that in S4, the mixed atmosphere is a nitrogen-acetylene mixed atmosphere, wherein the volume percentage of acetylene is 40-50%.

5. C @ MgAl of claim 1₂O₄The preparation method of the composite coating modified silicon-based negative electrode material is characterized in that in S4, the calcining temperature is 750-950 ℃, the heating rate is 3-10 ℃/min, and the calcining time is 1-3 h.

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