A coated silicon monoxide composite material, a preparation method and application thereof

Abstract

The application discloses a coated silicon monoxide composite material and a preparation method and application thereof. The method is as follows: micron-sized silicon monoxide, nano-sized titanium dioxide or a nano-sized titanium dioxide precursor and a surface modifier are mixed, and then heat treatment is performed to obtain titanium dioxide@silicon monoxide; the surface of the titanium dioxide@silicon monoxide is coated with a carbon coating layer through gas phase deposition, and then depolymerization treatment is performed, so as to obtain a carbon@titanium dioxide@silicon monoxide composite material. The composite material can be used as a lithium ion battery negative electrode material, can reduce migration resistance of lithium ions in a charging and discharging process, greatly reduces polarization, and makes the battery have good initial discharge coulomb efficiency. The preparation method is simple, the production cost is low, and the method is beneficial to large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to a modified silicon monoxide composite material, in particular to a silicon monoxide composite material with double coating layers of carbon and titanium dioxide, and a preparation method thereof, and application of the coated silicon monoxide composite material in lithium ion batteries, belonging to the technical field of lithium battery materials. BACKGROUND

[0002] At present, silicon monoxide negative electrode material has become the first choice for high-capacity negative electrodes due to its reversible capacity of 1965-4200 mAh / g, and has a broad market prospect. Compared with graphite materials, silicon monoxide materials have the problem of large volume expansion, which on the one hand causes stress accumulation in the electrode, resulting in electrode pulverization and reducing the cycle performance, and on the other hand, the volume change also causes repeated consumption of the SEI film at the negative electrode, resulting in consumption of active lithium and reducing the first coulombic efficiency, which to some extent hinders the wide application of silicon-based negative electrodes.

[0003] In lithium batteries, an appropriate amount of nano-titanium dioxide can reduce the stress between particles, relieve the micro-strain of the structure and volume caused by the material during the cycle process, increase the stability of the battery, and improve the cycle performance of the battery. At the same time, nano-titanium dioxide has the effect of improving the polarization problem of the material during the charge and discharge process, and slightly improving the first coulombic efficiency of the battery.

[0004] In the existing technology, there are many modification methods for silicon monoxide negative electrode materials, such as a Chinese patent with publication number CN115295775A, which discloses a multifunctional titanium oxynitride layer modified silicon monoxide negative electrode material and its preparation method and application. The material is fully mixed and uniform under ball milling conditions, and high electrochemical activity and high stability of the composite negative electrode material are formed by partial nitridation of calcined titanium dioxide, which can relieve the volume expansion problem of silicon-based negative electrode materials, stabilize the electrode / electrolyte interface, enhance the ion / electron conductivity of the material surface interface, and improve the cycle stability of the silicon-based negative electrode. However, this method introduces mechanical ball milling, which will cause an uncontrollable proportion of nanoscale powder in micrometer-sized silicon monoxide material to some extent, which will increase the side reaction of the electrode / electrolyte and affect the cycle performance.

[0005] A Chinese patent with publication number CN111170364A discloses a carbon-coated silicon-based titanium-niobium composite material, its preparation method and a lithium ion battery. Deionized water is used as a solvent, and a titanium source and a niobium source are added, and then wet grinding, spray drying and high-temperature calcination are performed to obtain titanium-niobium oxide. Then, in the solvent of anhydrous ethanol, the titanium-niobium oxide, a silicon source and a carbon source are sequentially added, and then wet grinding, spray drying and high-temperature calcination are performed to obtain the carbon-coated silicon-based titanium-niobium composite material. However, anhydrous ethanol is introduced in the preparation process, the preparation process conditions are harsh, the requirements for equipment and environment are high, and the application is limited. SUMMARY

[0006] In view of the above problems in the prior art, a first object of the present application is to provide a coated silicon monoxide composite material having a core-shell structure, with micron-sized silicon monoxide as the core and a double-layered coating structure of a nanometer-sized titanium dioxide coating layer and a carbon coating layer as the shell, the nanometer-sized titanium dioxide distributed on the surface of the silicon monoxide can reduce the inter-particle stress and relieve the slight strain in structure and volume caused by the material cycling process, thereby increasing the stability of the battery, while the nanometer-sized titanium dioxide coating layer and the carbon coating layer can synergistically improve the contact effect between the composite material and the electrolyte, reduce the migration resistance of lithium ions during the charging and discharging process, greatly reduce the polarization phenomenon, and improve the first discharge coulombic efficiency of the battery, and the composite material has good first coulombic efficiency and cycling performance when used in a lithium ion battery.

[0007] A second object of the present application is to provide a preparation method of the coated silicon monoxide composite material, which has simple process and low production cost, and the product obtained by the method has good consistency.

[0008] A third object of the present application is to provide an application of the coated silicon monoxide composite material, which is used as a negative electrode material of a lithium ion battery, can increase the stability of the battery and improve the cycling performance of the battery.

[0009] In order to achieve the above technical objects, the present application provides a preparation method of a coated silicon monoxide composite material, which comprises the following steps: mixing micron-sized silicon monoxide with nanometer-sized titanium dioxide and / or nanometer-sized titanium dioxide precursor and a surface modifier, and then performing heat treatment to obtain titanium dioxide@silicon monoxide; performing gas-phase deposition of a carbon coating layer on the surface of the titanium dioxide@silicon monoxide, and then performing depolymerization treatment to obtain a carbon@titanium dioxide@silicon monoxide composite material.

[0010] The micron-sized silicon monoxide used in the present application is obtained by rough breaking, crushing and grading of silicon monoxide bulk in amorphous state without silicon peak. The micron-sized silicon monoxide is beneficial to full contact with the nanometer-sized titanium dioxide in the mixing process, so that the nanometer-sized titanium dioxide is distributed on the surface of the silicon monoxide, laying a foundation for subsequent uniform coating. Meanwhile, the poor flowability of the silicon monoxide can be improved by introducing a surface modifier, which is beneficial to the smooth progress of the coating process. High-temperature treatment can remove most of the impurities in the silicon monoxide, the titanium source and the modifier, ensuring the quality of the product and improving the bonding stability of the nanometer-sized titanium dioxide on the surface of the silicon monoxide. When a nanometer-sized titanium dioxide precursor is used, the nanometer-sized titanium dioxide can be generated in situ on the surface of the silicon monoxide by using the heat treatment process, which is beneficial to obtaining a more stable titanium dioxide coating layer. Subsequently, a pyrolytic carbon layer can be uniformly and controllably coated on the outer surface of the titanium dioxide@silicon monoxide by gas phase deposition. Finally, the partially agglomerated coated silicon monoxide particles are dissociated into individual particles by mechanical action.

[0011] As a preferred scheme, the median particle size of the micron-sized silicon monoxide is 3.0-8.0 μm; further preferably 4.0-6.0 μm. If the particle size is too small, the contact area between the material particles and the electrolyte is large, which is easy to cause side reactions and affect the cycle performance. If the particle size is too large, the conductivity of the material is poor, resulting in low reversible capacity of the battery.

[0012] As a preferred scheme, the nanometer-sized titanium dioxide is anatase titanium dioxide and / or rutile titanium dioxide. The selected two types of titanium dioxide are relatively stable during high-temperature treatment.

[0013] As a preferred scheme, the surface modifier is at least one of glucose, sucrose and starch; further preferably glucose. The selected surface modifier increases the flowability of the silicon monoxide in the mixing process, promotes uniform mixing and is beneficial to the coating process. Meanwhile, the selected modifier is composed of only carbon, hydrogen and oxygen, and does not introduce impurities into the system.

[0014] As a preferred scheme, the nanometer-sized titanium dioxide precursor is a substance that generates nanometer-sized titanium dioxide by pyrolysis, such as titanium oxalate.

[0015] As a preferred scheme, the particle size of the nanometer-sized titanium dioxide is 20-50 nm.

[0016] As a preferred scheme, the mass ratio of the micro-sized silicon monoxide, the nano-sized titanium dioxide and / or the nano-sized titanium dioxide precursor and the modifier is 100:0.25-1:0.5-2. If the nano-sized titanium dioxide or the nano-sized titanium dioxide precursor is added in a small amount, the performance is poor when applied to the battery; if the nano-sized titanium dioxide or the nano-sized titanium dioxide precursor is added in a large amount, the coating layer is too thick, which is not conducive to the release of the reversible capacity of the battery. The amount of the modifier also directly affects the performance of the battery. If the amount of the modifier is too small, the dispersion effect of the nano-sized titanium dioxide or the nano-sized titanium dioxide precursor is not obvious; if the amount of the modifier is too large, the carbon coating layer is too thick, which is not conducive to the release of the reversible capacity of the battery.

[0017] As a preferred scheme, the mixing condition is that the stirring speed is 1000-3000 rpm and the time is 60-180 min. Through high-speed stirring, the silicon monoxide and the nano-sized titanium dioxide or the nano-sized titanium dioxide precursor can be uniformly mixed.

[0018] As a preferred scheme, the heat treatment condition is that the temperature is 400-600°C and the time is 30-120 min, and further preferably the temperature is 450-550°C. If the heat treatment temperature is too low, the carbon source is not cracked sufficiently; if the heat treatment temperature is too high, the particle size of the silicon particles in the silicon monoxide is affected, which leads to the expansion of the composite material.

[0019] As a preferred scheme, the vapor deposition condition is that the temperature rising rate is 1.0-10.0°C / min, the deposition temperature is 700-1000°C, the deposition time is 60-300 min, and the flow rate of the cracking gas is 0.1-1.0 L / min. Further preferably, the deposition time is 120-180 min; by controlling the deposition condition, the deposition thickness can be controlled to be 20-150 nm, and the preferred deposition thickness is 50-100 nm.

[0020] As a preferred scheme, the cracking gas is at least one of methane, acetylene and ethylene.

[0021] As a preferred scheme, the carbon coating amount is 1.0-6.5 wt.%. If the carbon coating amount is too low, the effective coating of the silicon monoxide and the nano-sized titanium dioxide or the nano-sized titanium dioxide precursor cannot be achieved, and if the carbon coating amount is too high, the electrochemical performance of the silicon monoxide composite material is affected.

[0022] As a preferred scheme, the depolymerization adopts mechanical depolymerization, and the depolymerization condition is that the mechanical stirring depolymerization treatment is performed at a speed of 100-300 rpm for 30-120 min. Under the preferred depolymerization condition, the agglomerated particles can be dissociated into individual particles without damaging the structure of the coating layer. If the stirring speed is too fast or the depolymerization time is too long, the structure of the coating layer is easily damaged.

[0023] The application further provides the coated silicon monoxide composite material prepared by the preparation method.

[0024] The application further provides application of the coated silicon monoxide composite material as a negative electrode material of a lithium ion battery, and the application is as follows:

[0025] The coated silicon monoxide composite material, carbon nanotubes, carbon black, carboxymethyl cellulose and butadiene styrene rubber are uniformly mixed according to a mass ratio of 90:4.8:0.2:3.5:1.5, deionized water with a solid content of 45% is added to prepare a slurry, the slurry is uniformly coated on a copper foil on a coating machine, and then the working electrode is prepared after baking at 120 DEG C in a vacuum box for 2 hours. A lithium sheet is used as a counter electrode, a 25um PP separator is used, 1mol / l LiPF6 (a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) is used as an electrolyte, and a button cell is assembled in a glove box under the protection of argon to complete the button cell.

[0026] Compared with the prior art, the technical scheme of the application has the beneficial technical effects:

[0027] The coated silicon monoxide composite material provided by the application can reduce inter-particle stress, relieve the slight strain of structure and volume caused in the material cycle process, increase the stability of the battery, improve the cycle performance of the battery, and improve the contact effect between the composite material and the electrolyte, reduce the migration resistance of lithium ions in the charge and discharge process, greatly reduce the polarization phenomenon, and improve the first discharge coulomb efficiency of the battery (the reversible capacity of the button cell at 0.1C-1.5V is 1580.84-1606.68mAh / g, and the first discharge efficiency is 76.33-77.68%).

[0028] The preparation method of the metal oxide coated silicon monoxide composite material is simple, the production cost is low, and the material is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The application further provides the coated silicon monoxide composite material prepared by the preparation method.

[0030] Figure 2The capacity-voltage curves of the coated silicon monoxide composite material prepared in Example 1 and the silicon monoxide powder of Comparative Example 1 are prepared. The test results show that, using the coated silicon monoxide composite material, the 0.1C-1.5V reversible capacity of the button cell is 1580.84 mAh / g, and the first discharge efficiency is 77.13%, which is obviously higher than that of the pure silicon monoxide powder of Comparative Example 1: the 0.1C-1.5V reversible capacity of the button cell is 1600.64 mAh / g, and the first discharge efficiency is 68.24%.

[0031] Figure 3 The XRD pattern of the coated silicon monoxide composite material prepared in Example 1 is prepared. The results show that, for the composite material coated with titanium dioxide, the main phase is silicon monoxide, and no peak of titanium dioxide is found, which indicates that the appropriate amount of titanium dioxide does not affect the structure of silicon monoxide.

[0032] Figure 4 The cycle performance diagram of the coated silicon monoxide composite material prepared in Example 1 and the silicon monoxide composite material 1 prepared in Comparative Example 2 is prepared. The test results show that, under the test conditions of 0.5C charging / 1C discharging at room temperature, the capacity retention rate after 600 cycles is 89.48%, which is obviously higher than that of Comparative Example 2 (the capacity retention rate after 600 cycles is 86.86%). DETAILED DESCRIPTION

[0033] In order to further understand the present application, the following specific embodiments are used to elaborate the present application in detail, so as to help the technical workers in the relevant field to better understand the concept and technical scheme of the present application.

[0034] The micron-sized silicon monoxide powder used in the present application is prepared from amorphous silicon monoxide bulk by coarse crushing, pulverization and classification, and the particle size median of the silicon monoxide powder is 5.5 μm.

[0035] Example 1

[0036] The silicon monoxide powder, the rutile-type titanium dioxide powder with a particle size median of 30 nm, and the glucose are sequentially added into a mixer at a mass ratio of 100:0.5:1, and after stirring at a speed of 1500 rpm for 120 min, a uniform mixture is obtained; the mixture is placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, and then continuously introduced with methane at a flow rate of 0.5 L / min for 120 min at a constant temperature of 1000 ℃ to perform high-temperature vapor deposition, and finally naturally cooled to room temperature. Then, mechanical stirring is performed at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material is obtained.

[0037] Example 2

[0038] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:0.5:1, stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 180 min by continuously introducing methane at a flow rate of 0.5 L / min, finally naturally cooled to room temperature, then mechanically stirred at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0039] Example 3

[0040] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:0.5:1, stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 240 min by continuously introducing methane at a flow rate of 0.5 L / min, finally naturally cooled to room temperature, then mechanically stirred at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0041] Example 4

[0042] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:0.5:1, stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 360 min by continuously introducing methane at a flow rate of 0.5 L / min, finally naturally cooled to room temperature, then mechanically stirred at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0043] Example 5

[0044] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:0.25:1, and stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 120 min by continuously introducing methane at a flow rate of 0.5 L / min, and finally naturally cooled to room temperature. Mechanical stirring was performed at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0045] Example 6

[0046] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:0.75:1, and stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 120 min by continuously introducing methane at a flow rate of 0.5 L / min, and finally naturally cooled to room temperature. Mechanical stirring was performed at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0047] Example 7

[0048] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added into a mixer in a mass ratio of 100:1.00:1, and stirred at a speed of 1500 rpm for 120 min to obtain a uniform mixture; the mixture was placed in a nitrogen atmosphere, first treated at a high temperature of 500 ℃ for 60 min, then heated to 1000 ℃ at a heating rate of 5 ℃ / min, then treated at 1000 ℃ for 120 min by continuously introducing a cracking gas at a flow rate of 0.5 L / min, and finally naturally cooled to room temperature. Mechanical stirring was performed at 200 rpm for 60 min to complete depolymerization, and finally a coated silicon monoxide composite material was obtained.

[0049] Comparative Example 1

[0050] The silicon monoxide powder was obtained by coarse crushing, pulverization, and grading of an amorphous silicon monoxide bulk, and had a median particle size of 5.5 μm. The test method was the same as that of Example 1.

[0051] Comparative Example 2

[0052] The silicon monoxide powder was placed in a nitrogen atmosphere, first high-temperature treated at 500°C for 60 min, then heated to 1000°C at a heating rate of 5°C / min, and then high-temperature vapor deposition was performed at 1000°C for 120 min by continuously introducing methane at 0.5 L / min, and finally naturally cooled to room temperature. Mechanical stirring was then performed at 200 rpm for 60 min to complete depolymerization, and finally the silicon monoxide composite material 1 was obtained. The other steps and test methods were the same as in Example 1.

[0053] Comparative Example 3

[0054] The silicon monoxide powder, the rutile titanium dioxide powder with a median particle size of 30 nm, and the glucose were sequentially added to a mixer in a mass ratio of 100:0.5:1, and stirred at a speed of 1500 rpm for 120 min to obtain the silicon monoxide composite material 2. The other steps and test methods were the same as in Example 1.

[0055] Application Examples 1-10

[0056] The silicon monoxide composite materials prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to performance testing of button cells, and the button cell manufacturing steps were as follows:

[0057] The coated silicon monoxide composite material, carbon nanotubes, carbon black, carboxymethyl cellulose, and butadiene styrene rubber prepared under the above conditions were mixed uniformly in a mass ratio of 90:4.8:0.2:3.5:1.5, deionized water with a solid content of 45% was added to form a slurry, and then the slurry was uniformly coated on a copper foil on a coating machine. After baking at 120°C in a vacuum oven for 2 h, a working electrode was prepared. A lithium sheet was used as a counter electrode, a 25-μm PP separator was used, 1 mol / L LiPF6 (a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) was used as an electrolyte, and a button cell was assembled in a glove box under an argon atmosphere.

[0058] Table 1: 0.1C-1.5V reversible capacity and first discharge efficiency data of button cells

[0059]

[0060]

Claims

1. A method for producing a coated silicon monoxide composite material, characterized by: The micron-sized silicon monoxide is mixed with nano-sized titanium dioxide and / or nano-sized titanium dioxide precursor and a surface modifier, and then heat-treated to obtain titanium dioxide@silicon monoxide; the surface of the titanium dioxide@silicon monoxide is coated with a carbon layer by gas phase deposition, and then subjected to depolymerization treatment to obtain a carbon@titanium dioxide@silicon monoxide composite material. The surface modifier is at least one of glucose, sucrose and starch. The mass ratio of the micron-sized silicon monoxide, nano-sized titanium dioxide and / or nano-sized titanium dioxide precursor and the surface modifier is 100:0.25-1:0.5-2, wherein the nano-sized titanium dioxide precursor is measured by the mass of the nano-sized titanium dioxide generated by pyrolysis thereof.

2. The preparation method of the coated silicon monoxide composite material according to claim 1, characterized in that: The median particle size of the micron-sized silicon monoxide is 3.0-8.0 μm. The nano-sized titanium dioxide is anatase titanium dioxide and / or rutile titanium dioxide. The nano-sized titanium dioxide precursor is a substance that generates nano-sized titanium dioxide by pyrolysis. The particle size of the nano-sized titanium dioxide is 20-50 nm.

3. The method of claim 1 or 2, wherein the method is characterized by: The mixing conditions are: stirring speed of 1000-3000 rpm and mixing time of 60-180 min.

4. The method for preparing a coated silica-substrate composite material according to claim 1, characterized in that: The heat treatment conditions are: temperature of 400-600 ℃ and time of 30-120 min.

5. The method for preparing a coated silica-substrate composite material according to claim 1, characterized in that: The gas phase deposition conditions are: temperature rising rate of 1.0-10.0 ℃ / min, deposition temperature of 700-1000 ℃, deposition time of 60-300 min and flow rate of the cracking gas of 0.1-1.0 L / min. The cracking gas is at least one of methane, acetylene and ethylene.

6. The method of claim 5, wherein the coating is applied by a method selected from the group consisting of: spray coating, dip coating, and spin coating. The depolymerization is mechanical depolymerization, and the depolymerization conditions are: mechanical stirring at a speed of 100-300 rpm for 30-120 min.

7. The method for preparing a coated silica-substrate composite material according to claim 1, characterized in that: The preparation method is prepared by any one of claims 1-7.

8. A coated silicon monoxide composite material, characterized by: It is used as a negative electrode material for lithium ion batteries.

9. Use of a coated silicon monoxide composite according to claim 8, characterized in that: ​

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