CN112661163A

CN112661163A - Silica-based composite anode material, preparation method thereof and lithium ion battery

Info

Publication number: CN112661163A
Application number: CN202011565055.9A
Authority: CN
Inventors: 张正裕; 付炳杰; 邓铭声; 黄新萍; 李军
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2021-04-16
Anticipated expiration: 2040-12-25
Also published as: CN112661163B

Abstract

The invention provides a silica-based composite negative electrode material, a preparation method thereof and a lithium ion battery. The preparation method of the silica-based composite anode material provided by the invention comprises the following steps: a) mixing micron-sized SiO, magnesium carbonate, polyvinylpyrrolidone and water to obtain a mixture; b) under the condition of stirring, subjecting the mixture toThe mixture is thermally treated to obtain SiO-MgCO₃-a PVP solid composite cluster; c) calcining the solid composite cluster in protective gas atmosphere to obtain three-dimensional honeycomb SiO_x‑MgSiO₃-C nanocomposites, wherein 0 < x < 2. The preparation method is simple and easy to implement, and can effectively improve the first coulombic efficiency, obtain high specific capacity and good cycle performance.

Description

Silica-based composite anode material, preparation method thereof and lithium ion battery

Technical Field

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

Background

The lithium ion battery is considered as a battery energy storage system with the best comprehensive performance in recent years, and is the most important in applications such as portable electronic products, electric automobiles, smart grid energy storage and the like. The performance of the electrode material significantly affects the performance of the lithium ion battery, and the development of the electrode material with high energy density is particularly important in order to meet the development requirements of high-tech devices.

Silicon-based anode materials are certainly the best candidates for anode materials with high energy density. The silicon-based anode material comprises simple substance silicon and silicon oxide; wherein, the simple substance silicon has obvious capacity advantage, and the theoretical specific capacity can reach 4200mAh g^-1Is a graphite negative electrode (372mAh g) commercially available at present^-1) More than 10 times. Silica (SiO) in contrast to elemental silicon_xX is more than 0 and less than 2), still keeps higher theoretical specific capacity, and has lower price and obvious commercial value. Therefore, the silicon oxide has a certain positive effect on accelerating the industrialization process of the silicon-based negative electrode material.

Present barrier SiO_xThe most critical problem for the application of the material is its low first coulombic efficiency, which is caused by SiO_xSiO present in the material₂The components react with lithium ions to generate Li in the first charge-discharge process₂O and Li₄SiO₄This irreversible reaction consumes large amounts of lithium, resulting in an irreversible loss of material capacity. At the same time, compared with simple substance silicon, SiO_xThe volume expansion of the material is caused by Li₂O and Li₄SiO₄Can be relieved to a certain extent, but the problem of volume expansion is still not completely solved, and the volume expansion can cause the structural collapse of the electrode material and influence the capacity and the service life of the battery. Furthermore, SiO_xThe low conductivity of the material can cause the rate capability of the electrode material to be poor, thereby influencingAnd (4) exerting the performance of the battery.

For SiO_xThe problem of low coulombic efficiency of the material for the first time is solved by the prior method, namely, the material is pre-lithiated, an external lithium source is added into the pre-lithiation, and the negative electrode reacts with the external lithium source firstly to avoid the large consumption of the positive electrode lithium source and reduce the loss of irreversible capacity. SiO 2_xThe first coulombic efficiency of the material is also influenced by the oxygen content, and the lower the oxygen content is, the higher the first coulombic efficiency is, so that the material can also be used in SiO_xThe first coulombic efficiency of the material is improved by regulating and controlling the oxygen content in the preparation of the material. For SiO_xThe problems of volume expansion and low conductivity of the material are solved by the prior methods, such as nano-crystallization and composite of the material, wherein the carbon-coated SiO with the nano-structure is prepared_xMaterials are currently the simplest and most efficient method.

In patent application CN110620223A, a pre-lithiation silicon oxide and a lithium-containing ionic liquid are mixed and sintered to realize pre-lithiation, then a graphene material is grown on the surface of the material through chemical vapor deposition, and finally the graphene material is homogeneously fused with a carbon source and subjected to heat treatment to obtain a pre-lithiation silicon-carbon multilayer composite negative electrode material. Patent application CN111342030A uses a multicomponent compounding method, in which a multicomponent conductive layer is used to coat a silicon oxide to form a multicomponent composite material, and the prelithiation is achieved by doping with a lithium salt. However, the above prior art has the following disadvantages: the preparation process is complex, the required raw materials are more, the cost is higher, and the like.

Disclosure of Invention

In view of the above, the present invention provides a silica-based composite anode material, a preparation method thereof, and a lithium ion battery. The preparation method is simple and easy to implement, and can effectively improve the first coulombic efficiency, obtain high specific capacity and good cycle performance.

The invention provides a preparation method of a silica-based composite anode material, which comprises the following steps:

a) mixing micron-sized SiO, magnesium carbonate, polyvinylpyrrolidone and water to obtain a mixture;

b) under the condition of stirring, carrying out heat treatment on the mixture to obtain SiO-MgCO₃-a PVP solid composite cluster;

c) calcining the solid composite cluster in protective gas atmosphere to obtain three-dimensional honeycomb SiO_x-MgSiO₃-C nanocomposites, wherein 0 < x < 2.

Preferably, in the step a), the mass ratio of the micron-sized SiO to the magnesium carbonate to the polyvinylpyrrolidone is 1 to (0.1-0.3) to (0.15-0.3);

the dosage ratio of the micron-sized SiO to the water is 1g to (25-100) mL;

the water is deionized water.

Preferably, in the step a), the mixing is stirring mixing;

the stirring speed is 100-400 r/min, and the stirring time is 1-2 h.

Preferably, in the step b), the temperature of the heat treatment is 70-85 ℃.

Preferably, in the step b), the stirring speed under the stirring condition is 100-400 r/min.

Preferably, in the step c), the calcining temperature is 800-1000 ℃, and the heat preservation time is 2-6 h.

Preferably, in the step c), the temperature rise rate of the calcination is 2-6 ℃/min.

Preferably, the micron-sized SiO is SiO subjected to ball milling;

the ball milling conditions are as follows: the rotating speed is 300-500 r/min, the time is 2-4 h, and the ball material ratio is (20-40) to 1;

before ball milling, the granularity of the micron-sized SiO is 5-10 mu m, and after ball milling, the granularity of the obtained SiO is 1-5 mu m.

The invention also provides the silica-based composite anode material prepared by the preparation method in the technical scheme.

The invention also provides a lithium ion battery, and the negative electrode material in the lithium ion battery is the silica-based composite negative electrode material in the technical scheme.

The invention provides a preparation method of a silica-based composite anode material, which is prepared by mixing micron-sized SiO and carbonMixing magnesium, polyvinylpyrrolidone and water, performing heat treatment on the mixture to remove water, and uniformly solidifying the material to obtain SiO-MgCO₃-a PVP solid composite cluster; then carrying out calcination treatment, wherein MgCO is generated in the calcination process₃Pyrolysis will produce CO₂The three-dimensional honeycomb structure can relieve the volume expansion problem of the silicon oxide, improve the circulation stability of the material, and the carbon honeycomb wall can also improve the multiplying power performance of the material. Simultaneously, SiO is subjected to disproportionation reaction at high temperature to generate Si and SiO₂，SiO₂Will react with MgO to generate MgSiO₃Thereby achieving the regulation and control of the oxygen content in the silicon monoxide and further improving the first coulombic efficiency of the material. Electrochemically inert MgSiO₃And the material is cooperated with a three-dimensional honeycomb structure to further improve the cycling stability of the material.

The nano-scale three-dimensional honeycomb structure silicon oxide composite negative electrode material is prepared by using simpler raw materials and adopting a simpler method; the content of the silica oxide is regulated and controlled through the chemical reaction among the raw materials, and the first coulombic efficiency of the material is improved; the electrochemical inert substance generated by the chemical reaction between the raw materials and the three-dimensional honeycomb structure have synergistic effect, so that the problem of volume expansion of the silicon monoxide is relieved, and the circulation stability of the material is improved.

Experimental results show that the silica-based composite negative electrode material prepared by the invention can enable the first coulombic efficiency of a battery to reach more than 84%, and the first charge specific capacity to be 1000 mAh.g^-1Above, the capacity retention rate after 50 cycles reaches 85% or more.

Detailed Description

b) under the stirring condition, carrying out heat treatment on the mixture to obtain SiO-MgCO₃-a PVP solid composite cluster;

The invention mixes micron SiO, magnesium carbonate, polyvinylpyrrolidone and water, and then carries out heat treatment on the obtained mixture to remove water, so that the material is uniformly solidified, and SiO-MgCO is obtained₃-a PVP solid composite cluster; then carrying out calcination treatment, wherein MgCO is generated in the calcination process₃Pyrolysis will produce CO₂The three-dimensional honeycomb structure can relieve the volume expansion problem of the silicon oxide, improve the circulation stability of the material, and the carbon honeycomb wall can also improve the multiplying power performance of the material. Simultaneously, SiO is subjected to disproportionation reaction at high temperature to generate Si and SiO₂，SiO₂Will react with MgO to generate MgSiO₃Thereby achieving the regulation and control of the oxygen content in the silicon monoxide and further improving the first coulombic efficiency of the material. Electrochemically inert MgSiO₃And the material is cooperated with a three-dimensional honeycomb structure to further improve the cycling stability of the material.

With respect to step a): mixing the micron-sized SiO, magnesium carbonate, polyvinylpyrrolidone and water to obtain a mixture.

In the invention, the granularity of the micron-sized SiO (namely, SiO) is preferably 1-5 μm. In the invention, the micron-sized SiO is preferably obtained by ball milling, and particularly, the micron-sized SiO raw material is ball milled to form the micron-sized SiO with smaller granularity. In the invention, before ball milling, the granularity of the micron-sized SiO raw material is preferably 5-10 μm. The conditions of the ball milling are preferably as follows: the ball milling speed is 300-500 r/min, in some embodiments of the invention, the ball milling speed is 450r/min and 500 r/min; the ball milling time is 2-4 h, and in some embodiments of the invention, the ball milling time is 2h or 4 h; the ball-material ratio of ball milling is (20-40) to 1; in some embodiments of the invention, the pellet to pellet ratio is 20: 1 or 40: 1. The SiO material has the advantages that the volume expansion phenomenon in the charging and discharging processes can cause the electrode structure to be seriously damaged, so that the capacity is sharply attenuated, and the cycle performance is poor; meanwhile, a larger specific surface area can be obtained, the absorption of electrolyte is promoted, and the charge transfer of the electrode is promoted.

In the present invention, magnesium carbonate is used, which decomposes to produce MgO, MgO and SiO₂React to form MgSiO₃The method realizes the regulation and control of the oxygen content in the silicon monoxide, further improves the first coulombic efficiency of the material, and simultaneously has the electrochemical inertia of MgSiO₃And the material is cooperated with a three-dimensional honeycomb structure to further improve the cycling stability of the material. When other carbonate is substituted, the above-mentioned effects are hardly obtained.

In the invention, polyvinylpyrrolidone (PVP) is also introduced, and is mixed with the other raw materials, so that composite agglomeration is more favorably formed after heat treatment, and then the mixture is carbonized in high-temperature calcination and matched with MgCO₃The gas generated by decomposition escapes, a honeycomb structure similar to a hexagon is formed, and a 3D conductive network is constructed.

In the invention, the mass ratio of the micron-sized SiO, the magnesium carbonate and the polyvinylpyrrolidone is preferably 1 to (0.1-0.3) to (0.15-0.3); if the mass ratio of the magnesium carbonate is too low, the first coulombic efficiency of the product is not facilitated, and if the mass ratio of the magnesium carbonate is too high, the specific capacity of the product is influenced; if the mass ratio of the polyvinylpyrrolidone is too low or too high, the carbon layer outside the product is too thin or too thick, which is not beneficial to forming a honeycomb structure, and in addition, the carbon layer is too thin and is also not beneficial to the cycling stability of the product, and the carbon layer is too thick, which can affect the specific capacity of the product. In some embodiments of the invention, the mass ratio is 1: 0.1: 0.2, 1: 0.2, 1: 0.3: 0.15, or 1: 0.3: 0.2.

In the invention, the water is preferably deionized water, and if other water such as common tap water is adopted, impurities in the water can influence the product performance. In the invention, the preferable dosage ratio of the water to the micron-sized SiO is (25-100) mL: 1 g.

In the present invention, the mixing is preferably stirring mixing; the stirring speed is 100-400 r/min, and the stirring and mixing time is 1-2 h. The temperature of the mixing is not particularly limited, and the mixing can be carried out at room temperature, and specifically can be 20-30 ℃. And mixing to obtain a mixture.

With respect to step b): under the condition of stirring, carrying out heat treatment on the mixture to obtain SiO-MgCO₃-PVP solid composite clusters.

In the invention, after the mixed material is obtained in the step a), the mixed material is heated to evaporate water, and stirring is continuously carried out in the process. In the invention, the stirring speed is preferably 100-400 r/min.

In the invention, the temperature of the heat treatment is preferably 70-85 ℃; in some embodiments of the invention, the temperature of the heat treatment is 80 ℃ or 85 ℃. In the present invention, the heat treatment is preferably performed for a time until moisture in the mixture is evaporated. After the stirring, heating and evaporation treatment, the mixture is uniformly mixed and solidified to form SiO-MgCO₃-PVP solid composite clusters.

With respect to step c): calcining the solid composite cluster in protective gas atmosphere to obtain three-dimensional honeycomb SiO_x-MgSiO₃-C nanocomposites, wherein 0 < x < 2.

In the present invention, the kind of the protective gas is not particularly limited, and may be a conventional inert gas known to those skilled in the art, such as nitrogen or argon.

In the invention, the calcination temperature is preferably 800-1000 ℃, if the temperature is too low, disproportionation reaction of SiO cannot be initiated, and the target product of the invention cannot be obtained, and if the temperature is too high, the material is damaged to a certain extent, the material performance is influenced, and energy consumption is wasted. In some embodiments of the invention, the temperature of the calcination is 800 ℃ or 1000 ℃. In the invention, the heating rate of the calcination is preferably 2-6 ℃/min; in some embodiments of the invention, the ramp rate is 2 ℃/min or 4 ℃/min. In the invention, the calcination heat preservation time is preferably 2-6 h; in some implementations of the inventionIn the examples, the calcination was carried out for 2 hours or 4 hours. After the calcination treatment, the three-dimensional honeycomb SiO is obtained_x-MgSiO₃-C nanocomposites, wherein 0 < x < 2.

During the calcination process, MgCO₃Pyrolysis will produce CO₂The three-dimensional honeycomb structure can relieve the volume expansion problem of the silicon oxide, improve the circulation stability of the material, and the carbon honeycomb wall can also improve the multiplying power performance of the material. Simultaneously, SiO is subjected to disproportionation reaction at high temperature to generate Si and SiO₂，SiO₂Will react with MgO to generate MgSiO₃Thereby achieving the regulation and control of the oxygen content in the silicon monoxide and further improving the first coulombic efficiency of the material. Electrochemically inert MgSiO₃And the material is cooperated with a three-dimensional honeycomb structure to further improve the cycling stability of the material. The particle size of the nano composite material particles obtained by the method is 100-500 nm, the nano composite material particles are of a honeycomb structure, the C honeycomb wall is used as a shell, and the generated MgSiO is₃With SiO_xMixing in the honeycomb, i.e. the walls of C honeycomb are wrapped with MgSiO₃With SiO_x. SiO 2_xWith amorphous Si phase and amorphous SiO phase inside₂Phase, x is passing through SiO₂The reaction with MgO.

According to the preparation method provided by the invention, the nano-scale three-dimensional honeycomb structure silicon oxide composite negative electrode material is prepared by using simpler raw materials and adopting a simpler mode; the content of the silica oxide is regulated and controlled through the chemical reaction among the raw materials, and the first coulombic efficiency of the material is improved; the electrochemical inert substance generated by the chemical reaction between the raw materials and the three-dimensional honeycomb structure have synergistic effect, so that the problem of volume expansion of the silicon monoxide is relieved, and the circulation stability of the material is improved.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

Example 1

S1, ball-milling SiO with the particle size of 5-10 mu m by using a planetary ball mill, wherein the ball-material ratio is 20: 1, the rotating speed is 450r/min, and the ball-milling time is 4h, so that refined SiO with the particle size of 1.5 mu m is obtained.

S2, ball-milled micron-sized SiO and MgCO₃Adding PVP and PVP into deionized water according to the mass ratio of 1: 0.1: 0.2 (the dosage ratio of the micron-sized SiO to the water is 1 g: 50mL), and continuously stirring (the speed is 300r/min), wherein the stirring time is 2 h; heating the mixture at 85 deg.C in oil bath to evaporate water, stirring continuously during evaporation (speed of 200r/min), mixing the mixture by evaporation, and solidifying to obtain SiO/MgCO₃the/PVP compound cluster.

S3, mixing SiO/MgCO₃Calcining the/PVP composite cluster in a tube furnace in argon atmosphere at 800 ℃ for 4h at the heating rate of 2 ℃/min to obtain the three-dimensional honeycomb nano SiO_x/MgSiO₃@ C composite material.

Example 2

The procedure is as in example 1, except that SiO, MgCO are present in micron size₃The mass ratio of the PVP to the PVP is adjusted to be 1: 0.2.

Example 3

The procedure is as in example 1, except that SiO, MgCO are present in micron size₃The mass ratio of the PVP to the PVP is adjusted to be 1: 0.3: 0.2.

Example 4

S1, ball-milling SiO with the particle size of 5-10 mu m by using a planetary ball mill, wherein the ball-material ratio is 40: 1, the rotating speed is 500r/min, and the ball-milling time is 2 hours, so that refined SiO with the particle size of 2.0 mu m is obtained.

S2, ball-milled micron-sized SiO and MgCO₃Adding PVP and PVP into deionized water according to the mass ratio of 1: 0.3: 0.15 (the dosage ratio of the micron-sized SiO to the water is 1 g: 50mL), and continuously stirring (the speed is 300r/min), wherein the stirring time is 2 h; heating the mixture in an oil bath at 80 deg.C to evaporate water, stirring continuously during evaporation (speed of 200r/min), mixing the mixture by evaporation, and solidifying to obtain SiO/MgCO₃the/PVP compound cluster.

S3, mixing SiO/MgCO₃Calcining the/PVP composite cluster in a tube furnace in argon atmosphere at 1000 ℃ for 2h at the heating rate of 4 ℃/min to obtain the three-dimensional honeycomb nano SiO_x/MgSiO₃@ C composite material.

Comparative example 1

The procedure of example 3 was followed except that PVP was not added.

Comparative example 2

The procedure is as in example 3, except that MgCO is not added₃。

Example 5

1.1 Battery Assembly

Preparing a negative pole piece: the prepared active material, acetylene black (conductive agent) and styrene butadiene rubber SBR (adhesive) are mixed and dissolved in deionized water according to the mass ratio of 80:10:10, and the mixture is magnetically stirred for more than 8 hours to prepare slurry. The slurry was uniformly coated on a battery-grade copper foil to a thickness of 10 μm, and then dried in a vacuum oven at 85 ℃ for 12 hours, taken out of the roll, and die-cut into a negative electrode sheet with a diameter of 14mm with a die cutter.

Assembling the battery: the prepared cathode pole piece is a working electrode, the lithium piece is a counter electrode, the Celgard 2400 polypropylene microporous membrane is a diaphragm, and 1M LiPF₆Dissolving EC/DMC/DEC in a volume ratio of 1:1:1 as an electrolyte, and assembling a CR2032 button half cell in a glove box filled with high-purity argonThe water content and the oxygen content of the manufacturing environment are both less than 0.1 ppm.

1.2 Performance testing

Electrochemical performance tests were performed on the batteries assembled with the negative electrode materials of examples 1 to 4 and comparative examples 1 to 2, respectively.

And (3) performing charge and discharge tests on the assembled CR2032 button half-cell by adopting a CT-4008T cell test system of New Wille electronics Limited, Shenzhen, at room temperature, wherein the test voltage range is 0.01-3.0V, and the current density is 150 mAh/g.

The test results are shown in table 1:

TABLE 1 electrochemical Properties of the materials obtained in examples 1-4 and comparative examples 1-2

According to the test results, the three-dimensional honeycomb nano SiO prepared by the invention_x/MgSiO₃The @ C composite material can effectively improve the first coulombic efficiency, specific capacity and cycle performance of the material. Comparison of the effects with comparative examples 1-2 demonstrates that the present invention employs both PVP and MgCO₃The method can generate a synergistic effect and obviously improve the electrochemical performance of the material.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the silica-based composite anode material is characterized by comprising the following steps of:

2. The preparation method of claim 1, wherein in the step a), the mass ratio of the micron-sized SiO to the magnesium carbonate to the polyvinylpyrrolidone is 1: 0.1-0.3: 0.15-0.3;

the dosage ratio of the micron-sized SiO to the water is 1g to (25-100) mL;

the water is deionized water.

3. The method according to claim 1, wherein in the step a), the mixing is stirring mixing;

the stirring speed is 100-400 r/min, and the stirring time is 1-2 h.

4. The method according to claim 1, wherein the heat treatment temperature in the step b) is 70 to 85 ℃.

5. The method according to claim 1 or 4, wherein the stirring conditions in step b) are performed at a stirring speed of 100 to 400 r/min.

6. The preparation method of claim 1, wherein in the step c), the calcining temperature is 800-1000 ℃ and the holding time is 2-6 h.

7. The method according to claim 1 or 6, wherein in the step c), the temperature increase rate of the calcination is 2 to 6 ℃/min.

8. The method of claim 1, wherein the micron-sized SiO is ball-milled SiO;

9. The silica-based composite anode material prepared by the preparation method of any one of claims 1 to 8.

10. A lithium ion battery, wherein the negative electrode material in the lithium ion battery is the silica-based composite negative electrode material according to claim 9.