CN110911643B - A kind of diatomite-based lithium-ion battery negative electrode material and preparation method thereof - Google Patents

Abstract

The invention discloses a diatomite-based lithium ion battery anode material and a preparation method thereof, wherein the anode material is M-SiO formed by filling or coating metal with a porous silicon oxide material by a high-temperature solid-phase self-assembly synthesis method _x Composite material, M is one of Sn and Al, siO _x Wherein x is more than or equal to 0 and less than or equal to 2, and the lithium ion battery assembled by the negative plate prepared by the negative electrode material has excellent lithium storage performance, cycle life and good rate capability.

Description

A kind of diatomite-based lithium-ion battery negative electrode material and preparation method thereof

technical field

The invention relates to the technical field of battery preparation, in particular to a diatomite-based lithium ion battery negative electrode material and a preparation method thereof.

Background technique

At present, the commercially produced lithium-ion battery anode materials on the market are mainly carbon-based anode materials, including graphite and mesocarbon microsphere anode materials. The theoretical capacity of this type of negative electrode material is about 372 mAh/g, but it has actually reached 370 mAh/g. There is almost no room for improvement in the capacity of graphite-based negative electrode materials. At the same time, the preparation process of carbon anode materials is also slightly complicated. Therefore, it is extremely necessary to develop a lithium-ion battery anode material with large theoretical capacity, commercialization, and mass production.

In recent years, a variety of new high-capacity and high-rate anode materials have been successively developed and put into production. Among them, silicon oxide anode materials have become a research hotspot because of their high theoretical capacity and abundant reserves. Among them, the theoretical capacity of SiO is as high as 2800 mAh/g, and the theoretical capacity of _SiO2 is as high as 1965 mAh/g. The abundant reserves make this type of material a wide source and low price. Therefore, silicon oxide material has become a very ideal lithium-ion battery anode material.

Some metal elements also have high theoretical specific capacity, for example, Sn can reach 994 mAh/g, and Al can reach 2978 mAh/g, and their metallicity determines that they have very good electrical conductivity. However, both silicon oxide materials and metal materials have their own shortcomings when used as anode materials for lithium-ion batteries. For example, large volume deformation caused by the intercalation and extraction of lithium ions during charging and discharging, and the low conductivity of silicon oxide materials restrict their commercial applications.

Patent CN 108075110 A discloses the preparation of a lithium-ion battery negative electrode material with carbon-coated nano-silicon composite negative electrode. The preparation steps of this compound are cumbersome, and the obtained target product particles are relatively large, which is not suitable for large-scale commercial production.

Patent CN110165177 A discloses a method for preparing a silicon-based composite negative electrode material for a lithium-ion battery. The method involves ball milling silicon and copper oxide to prepare a silicon-based composite negative electrode material. The purity of the material prepared by this method cannot be guaranteed, and the yield is low, and there are also disadvantages such as poor shape controllability.

Patent CN108598442 A discloses a method for preparing a silicon-based lithium-ion battery negative electrode material. The method is to wrap graphene oxide with silicon nanoparticles to form a silicon-based lithium-ion battery negative electrode material. The aniline used in this method is toxic, and the production cost is high. The steps are cumbersome, which is not conducive to large-scale commercial production.

Patent CN102437318 A discloses a silicon-carbon composite lithium-ion battery negative electrode material and its preparation method. First, silicon particles are coated with phenolic resin, and then the phenolic resin is transformed into a hard carbon coating through high-temperature pyrolysis, thereby obtaining a carbon-coated silicon-carbon negative electrode material with a core-shell structure. However, the synthesis process of phenolic resin has disadvantages such as high toxicity and high cost. At the same time, the carbon obtained by pyrolyzing the resin has high hardness and cannot adapt well to the volume change of silicon. Therefore, the cycle stability of this composite material is relatively poor.

Patent CN102983317 A discloses a silicon-carbon composite lithium-ion battery negative electrode material and its preparation method. By blending silicon particles and carbon precursors, a mixed slurry of the two is obtained, and then a silicon-carbon composite is obtained through high-temperature carbonization. However, there are disadvantages such as uneven silicon distribution and easy agglomeration in the compound obtained by this production process. At the same time, the carbonization temperature is high, the process is difficult, and the production cost is high.

So far, there has been no research on the use of metal-filled porous diatomite as a whole composite system for lithium-ion battery anode materials.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention discloses a porous silicon oxide negative electrode material formed by uniformly embedding nanoscale metal particles inside silicon oxide or covering the surface of silicon oxide, and preparing negative electrode sheets and lithium-ion batteries based on this. For the first time, the present invention puts silicon oxide and metal, two anode materials that have been independently researched before, in a composite system for research, fully exerts the advantages of both, and solves the defects when the two independently constitute anode materials.

The technical solution of the present invention is: a diatomite-based negative electrode material for lithium ion batteries, the negative electrode material is an M- _SiOx composite material formed by filling or coating a porous silicon oxide material with a metal by a high-temperature solid-phase self-assembly synthesis method, wherein M is one of Sn and Al, and in _SiOx , 0≤x≤2.

A preparation method based on a diatomite-based negative electrode material for lithium ion batteries, specifically comprising the steps of:

1) Mix the metal source M with the porous silicon oxide SiO _x and ultrasonically disperse it for 0.5-1 h, then dry it in an oven at 50-80°C to obtain the mixture A;

2) Grind the mixture A obtained in step 1 for 10-30 min, so that M in the mixture is in full contact with SiO _x to obtain mixture B;

3) The mixture B obtained in step 2 is heated up to 400-1500°C at a rate of 2-20°C/min under the condition of nitrogen, argon or argon-hydrogen mixed gas, and kept for 3-10 hours, and cooled naturally to obtain the metal-coated silicon oxide negative electrode material C;

In step 1, the metal source is a single substance of Sn and Al, a hydroxide, a halide or a nitrate compound;

In step 1, the SiO _x refers to a porous silicon oxide material with a particle size of 100 nm-40 um;

In step 1, the mixing molar ratio of the metal source M to the porous silicon oxide SiO _x is 1:1 to 10:1.

In step 2, the grinding time is preferably 20 min;

In step 3, the volume content of hydrogen in the argon-hydrogen mixture is 5%-15%, preferably 5%.

A negative electrode sheet prepared from the above negative electrode material, further comprising a conductive agent and a binder, the weight percentage range of the negative electrode material is 50-99.5 wt%, the weight percentage range of the conductive agent is 0.1-40 wt%, and the weight percentage range of the binder is 0.1-40 wt%.

The conductive agent is at least one of carbon black, acetylene black, natural graphite, carbon nanotubes, graphene, and carbon fiber; the binder is at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylic acid, polyamide, polypropylene, polyvinyl ether, polyimide, styrene-butadiene copolymer, and sodium carboxymethylcellulose.

A lithium ion battery prepared by using the above-mentioned negative electrode sheet also includes a positive electrode, a separator and an electrolyte.

The positive electrode is a commonly used lithium battery positive electrode, specifically comprising one of lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium titanate, nickel-cobalt-manganese ternary system, or lithium composite metal oxide; the separator includes one of aramid separator, non-woven fabric separator, polyethylene microporous membrane, polypropylene membrane, polypropylene polyethylene double-layer or three-layer composite membrane and ceramic coating membrane; the electrolyte contains electrolyte and solvent, and the electrolyte is LiPF₆、LiBF₄, LiClO₄, LiAsF₆、LiCF₃SO₃, LiN(CF₃SO₂), LiBOB, LiCl, LiBr, LiI at least one; Solvent includes at least one in propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (DME), ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, methylpropyl carbonate, acetonitrile, ethyl acetate, vinyl sulfite.

The beneficial effects of the present invention are:

1. The invention creatively fills or coats diatomite (porous silicon oxide) with Sn or Al to form a negative electrode active material. Using porous diatomite as a skeleton can effectively suppress the volume expansion of active materials such as Sn and Al in the process of charging and discharging lithium. At the same time, the addition of metal substances can improve the conductivity of silicon oxide. The lithium-ion battery assembled with the negative electrode sheet prepared on the basis of it shows superior lithium storage performance, cycle life and good rate performance;

2. The present invention uses a high-temperature solid-phase self-assembly synthesis method to complete the preparation of the negative electrode material. The reaction method is simple and controllable, and can be scaled up for large-scale production. This synthesis process is conducive to cost control and commercial popularization and application.

Description of drawings

Fig. 1 is the electrochemical impedance comparison figure of the electrode prepared by embodiment 1 and comparative example 1;

Fig. 2 is the charge-discharge curve diagram of the electrode prepared in embodiment 1;

3 is a schematic diagram of a negative electrode material formed by metal-coated porous silicon oxide;

Figure 4 is a graph showing the comparison of tin-filled silicon oxide and silicon oxide rate performance;

Fig. 5 is a graph showing the cycle performance comparison between tin-filled silicon oxide and silicon oxide.

Detailed ways

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, the modifications and substitutions made to the methods, steps or conditions of the present invention all belong to the scope of the present invention.

Example 1

Take 6 mmol of diatomaceous earth (the component of diatomite is porous silicon oxide) and 4 mmol of tin powder into ethanol for 30 minutes of ultrasonication, and then dry in a 50°C oven to obtain a mixture of silicon oxide and tin powder. Afterwards, the mixture was ground in the grinding body for 20 minutes to make it fully contact, and the ground product was transferred to a tube furnace. The tube furnace was filled with argon-hydrogen mixed gas (95% argon, 5% hydrogen), and then the temperature was raised to 500°C at a rate of 10°C/min.

The present invention uses a high-temperature solid-phase self-assembly synthesis method to prepare metal-filled or coated porous silicon oxide composite materials (M-SiO _x ). The solid-phase synthesis method has the advantages of simplicity and large-scale production, which is conducive to the effective promotion of the diatomite-based silicon oxide negative electrode material prepared by the present invention in future commercial applications.

At the same time, metals can spontaneously self-assemble in high-temperature solid-state reactions, and can be effectively filled in porous diatomite. Using porous diatomite as a skeleton can effectively suppress the volume expansion of Sn during lithium charging and discharging. At the same time, the addition of metal substances can improve the conductivity of silicon oxide, thereby forming a synergy between metal and silicon oxide to improve the electrochemical energy storage characteristics of the composite system.

The prepared tin-coated silicon oxide active material, conductive carbon black, and binder polyvinylidene fluoride were uniformly mixed at a mass ratio of 8:1:1, and a negative electrode slurry was prepared with 1-methyl-2-pyrrolidone as a solvent, which was coated on a copper foil to make a negative electrode sheet, and dried overnight at 50°C. The electrochemical test was carried out using a CR2025 button cell. The counter electrode was an analytically pure metal lithium sheet. The electrolyte was 1M LiPF ₆ ethylene carbonate (EC)/methyl ethyl carbonate (DEC) (volume ratio 1:1) solution, and the battery separator was Celgard-2320 (microporous polypropylene membrane). Cell assembly was performed in an argon-filled glove box.

Comparative example 1

In order to compare with the product in Example 1, a comparative test was carried out. In this experiment, the diatomaceous earth used in Example 1 was ultrasonicated in ethanol for 30 minutes, and dried in an oven at 50°C to obtain a silicon oxide powder. After grinding it in the grinding body for 20 minutes, the ground product was transferred to a tube furnace. The tube furnace was filled with an argon-hydrogen mixed gas (95% argon, 5% hydrogen), raised to 500°C at a heating rate of 10°C/min, and then kept at a temperature of 3 hours. After natural cooling, a silicon oxide negative electrode material was obtained, and then battery assembly was performed under the same conditions as in Example 1.

Example 2: Characterization of negative electrode materials

Electrochemical impedance tests were performed on the electrodes prepared in Example 1 and Comparative Example 1. The results are shown in Figure 1. The results in the figure show that the resistance of silicon oxide coated with tin is significantly improved. Compared with the resistance of the original silicon oxide of 400Ω, the resistance of the compounded material is reduced to about 200Ω, and the resistance is greatly improved.

Figure 2 is the charge-discharge cycle diagram of the electrode prepared in Example 1. It can be seen from the figure that the first discharge of porous silicon dioxide after metal tin coating can reach about 380 mAh/g, while the first charge and discharge of silicon dioxide is only 150 mAh/g, compared with a single silicon dioxide electrode, the performance is improved.

The basic principles, main features and advantages of the present invention have been shown and described above. However, the above descriptions are only specific embodiments of the present invention, and the technical features of the present invention are not limited thereto. Any other implementations obtained by those skilled in the art without departing from the technical solutions of the present invention should be covered by the patent scope of the present invention.

Claims (6)

1. A preparation method of a diatomite-based lithium ion battery anode material is characterized in that the anode material is M-SiO formed by filling or coating metal with a porous diatomite material by a high-temperature solid-phase self-assembly synthesis method _x Composite material, wherein M is Sn, siO _x X is more than or equal to 0 and less than or equal to 2;

the preparation process comprises the following steps:

1) Combining a metal source M with porous silicon oxide SiO _x Ultrasonic treatment is carried out for 0.5 to 1 h after mixing, so that the mixture is dispersed, and then the mixture is dried in a baking oven at 50 to 80 ℃ to obtain a mixture A;

2) Grinding the mixture A obtained in the step 1) for 10-30 min to ensure that M and SiO in the mixture _x Fully contacting to obtain a mixture B;

3) Heating the mixture B obtained in the step 2) to 500 ℃ at a speed of 10 ℃/min under the condition of argon-hydrogen mixed gas, preserving heat for 3 h, and naturally cooling to obtain a metal-coated silicon oxide anode material C;

the porous silica SiO _x Is diatomite;

the porous silica SiO _x The particle size of (2) is 100 nm-40 um;

metal source M and porous silicon oxide SiO _x The mixed molar ratio of (2) to (3);

the metal source is Sn powder.

2. The preparation method of the diatomite-based lithium ion battery anode material as claimed in claim 1, wherein in the step 3, the hydrogen gas volume content in the argon-hydrogen mixture is 5% -15%.

3. The negative plate prepared from the diatomite-based lithium ion battery negative material is characterized by being prepared from the preparation method of the diatomite-based lithium ion battery negative material according to any one of claims 1-2, and further comprises a conductive agent and a binder, wherein the weight percentage of the negative plate is 50-99.5 wt%, the weight percentage of the conductive agent is 0.1-40 wt%, and the weight percentage of the binder is 0.1-40 wt%.

4. The negative electrode sheet prepared from the diatomite-based lithium ion battery negative electrode material according to claim 3, wherein the conductive agent is at least one of carbon black, acetylene black, natural graphite, carbon nanotubes, graphene, and carbon fibers; the binder is at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylic acid, polyamide, polypropylene, polyvinyl ether, polyimide, styrene-butadiene copolymer and sodium carboxymethyl cellulose.

5. A lithium ion battery is characterized in that the lithium ion battery is prepared based on the negative electrode sheet according to claim 4, and further comprises a positive electrode, a separator and electrolyte.

6. The lithium ion of claim 5A sub-battery characterized in that the positive electrode material comprises one of lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium titanate, a nickel-cobalt-manganese ternary system, or a composite metal oxide of lithium; the membrane comprises one of an aramid membrane, a non-woven membrane, a polyethylene microporous membrane, a polypropylene-polyethylene double-layer or three-layer composite membrane and a ceramic coating membrane; the electrolyte comprises electrolyte and solvent, wherein the electrolyte is LiPF ₆ 、LiBF ₄ 、LiClO ₄ 、LiAsF ₆ 、LiCF ₃ SO ₃ 、LiN(CF ₃ SO ₂ ) At least one of LiBOB, liCl, liBr, liI; the solvent comprises at least one of propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, 1, 2-dimethoxyethane, ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, methyl propyl carbonate, acetonitrile, ethyl acetate and ethylene sulfite.