CN111725507B - High-compaction silicon-carbon negative electrode material for lithium ion battery and preparation method thereof - Google Patents
High-compaction silicon-carbon negative electrode material for lithium ion battery and preparation method thereof Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
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- H01M4/02—Electrodes composed of, or comprising, active material
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- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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Abstract
The invention discloses a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery, which is characterized in that the furnace pressure of a nitrogen atmosphere protective furnace is simply controlled, so that smoke volatilized from asphalt forms a gas-solid two-phase interface on the surface of a silicon-carbon negative electrode, the innermost layer is coated by the solid phase of the asphalt, the outer layer is coated by the gas phase of smoke components volatilized from the asphalt, and the gas phase is used as a supplementary secondary coating method of the solid phase coating. Meanwhile, the consumption of the asphalt can be further reduced, and the residual carbon rate is further reduced by using the asphalt with the consumption less than 5 percent, so that the silicon-carbon negative electrode material prepared by the method has high compaction density and excellent cycle performance.
Description
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to a high-compaction silicon-carbon negative electrode material for a lithium ion battery and a preparation method thereof.
Background
With the wide application and rapid development of various portable electronic devices and electric vehicles, people have higher and higher requirements on power sources and performance of various electric products, and lithium ion secondary batteries have been successfully and widely applied to the field of mobile electronic terminal devices in recent decades due to superior comprehensive properties such as high power characteristics.
The improvement of the performance of lithium ion batteries depends mainly on the performance of the intercalation and deintercalation lithium electrode materials. At present, the intermediate-phase carbon microspheres and the modified graphite are widely used as negative electrode materials for commercial lithium ion batteries, but the defects of low theoretical lithium storage capacity (372 mAh/g graphite), easy organic solvent co-intercalation and the like exist, so that the research and application of the negative electrode materials of the high-capacity lithium ion batteries become the key for improving the performance of the batteries. Among the known lithium storage materials, silicon has the highest theoretical capacity (about 4200mAh/g excluding the mass of intercalated lithium) and relatively moderate intercalation/deintercalation potential (about 0.1-0.5V.v.Li/Li +), very suitable as a negative electrode material for lithium ion batteries. However, under the condition of high-degree lithium intercalation and deintercalation, the silicon-based material has a serious volume effect, so that the structural collapse of the material and the peeling of the electrode material are easily caused to cause the loss of the electric contact of the electrode material, thereby causing the rapid reduction of the electrode cycle performance.
Patent document CN 107408681A discloses a silicon negative electrode active material and a method for producing the same, in which silicon is subjected to nano-sizing and pre-oxidation, and carbon coating is performed on a silicon outer layer to suppress silicon expansion and enhance conductivity between silicon particles. However, the solution containing the organic carbon source is used for liquid-phase secondary coating, so that the outer carbon coating layer is not uniform, meanwhile, the residual carbon content of the organic carbon source is low, the specific surface area of the material after thermal decomposition is large, and the nano silicon is easy to contact with electrolyte, so that the cycle performance is poor.
Disclosure of Invention
In view of the above, the present invention provides a high-compaction silicon-carbon negative electrode material for a lithium ion battery and a preparation method thereof, which aims at overcoming the defects of uneven carbon coating and difficulty in integrity on the surface of the existing silicon-carbon material and improving the compaction density; the negative electrode material prepared by the invention has the advantages of large reversible capacity for the first time, excellent cycle performance, simple preparation method, large-scale preparation and low cost.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery comprises the following steps:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and treating for 5-20min to obtain a silicon-carbon anode material precursor;
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon anode material precursor obtained in the step (1) into a nitrogen atmosphere protective furnace for carbonization, raising the temperature to 400-1000 ℃ at the heating rate of 2-25 ℃/min, keeping the temperature for 4-18 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 100-150Pa, and crushing and screening to obtain the high-compaction silicon-carbon anode material for the lithium ion battery after the carbonization is finished.
As a preferable scheme, the graphite precursor in the step (1) is one or a mixture of several of artificial graphite or natural graphite, and the average particle size D50 is 5-10 μm.
As a preferable scheme, in the step (1), the binder is one or a mixture of more of coal-series or oil-series asphalt, and the softening point is 200-300 ℃.
Preferably, the average particle diameter D50 of the nano silicon in the step (1) is 10 to 100 nm.
In a preferable embodiment, the rotation speed of the mechanical fusion machine in the step (1) is 600 to 1000 rpm.
As a preferable scheme, the mass ratio of the graphite precursor, the binder and the nano-silicon in the step (1) is 1.
A high-compaction silicon-carbon negative electrode material for a lithium ion battery is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery.
Compared with the prior art, the invention has obvious advantages and beneficial effects, and specifically, the technical scheme shows that:
the furnace pressure of the furnace is protected by simply controlling the nitrogen atmosphere, so that smoke volatilized from asphalt forms a gas-solid two-phase interface on the surface of the silicon-carbon cathode, the innermost layer is coated by the solid phase of the asphalt, the outer layer is coated by the gas phase of the smoke components volatilized from the asphalt, and the gas phase coating is used as a supplementary secondary coating method of the solid phase coating. Meanwhile, the consumption of the asphalt can be further reduced, and the residual carbon rate is further reduced by using the asphalt with the consumption less than 5 percent, so that the silicon-carbon anode material prepared by the method has high compaction density and excellent cycle performance. The preparation method has simple process and convenient operation, realizes functions by controlling the process under the condition of not changing equipment, further reduces the cost, is convenient for popularization and application, and is suitable for large-scale production.
Drawings
Fig. 1 is an SEM image of the anode material prepared according to the present invention.
Detailed Description
The invention discloses a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery, which comprises the following steps of:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and treating for 5-20min to obtain the silicon-carbon anode material precursor. The graphite precursor is one or a mixture of more of artificial graphite or natural graphite, and the average particle size D50 is 5-10 mu m; the binder is one or a mixture of coal-series or oil-series asphalt, and the softening point is 200-300 ℃; the average grain diameter D50 of the nano silicon is 10-100 nm; the mass ratio of the graphite precursor to the binder to the nano-silicon is 1.005-0.03; and the rotation speed of the mechanical fusion machine during treatment is 600-1000 rpm.
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon negative electrode material precursor obtained in the step (1) into a nitrogen atmosphere protective furnace for carbonization, raising the temperature to 400-1000 ℃ at a heating rate of 2-25 ℃/min, keeping the temperature for 4-18 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 100-150Pa, enabling smoke volatilized by asphalt to form a gas-solid two-phase interface on the surface of the silicon-carbon negative electrode, wherein the innermost layer is coated by the solid phase of the asphalt, and the outer layer is coated by the gas phase of the smoke component volatilized by the asphalt, and the gas-phase coating is adopted as a supplementary secondary coating method of the solid-phase coating.
The invention also discloses a high-compaction silicon-carbon negative electrode material for the lithium ion battery, which is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery.
The invention is illustrated in more detail below in the following examples:
example 1:
a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery comprises the following steps:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and processing for 5-20min to obtain the silicon-carbon anode material precursor. The graphite precursor is artificial graphite, and the average particle size D50 is 10 mu m; the binder is coal-series asphalt, and the softening point is 200 ℃; the average grain diameter D50 of the nano silicon is 10nm; the mass ratio of the graphite precursor to the binder to the nano-silicon is 1:0.005: 0.1; and the rotation speed at the time of the mechanical fusion machine treatment was 1000 rpm.
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon anode material precursor obtained in the step (1) into a nitrogen atmosphere protection furnace for carbonization, raising the temperature to 1000 ℃ at the heating rate of 25 ℃/min, preserving the temperature for 4 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 100Pa, and crushing and screening to obtain the high-compaction silicon-carbon anode material for the lithium ion battery after the carbonization is finished.
A high-compaction silicon-carbon negative electrode material for a lithium ion battery is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery.
Example 2:
a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery comprises the following steps:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and treating for 5-20min to obtain the silicon-carbon anode material precursor. The graphite precursor is natural graphite, and the average particle size D50 is 5 micrometers; the binder is oil-based asphalt, and the softening point is 300 ℃; the average grain diameter D50 of the nano silicon is 100 nm; the mass ratio of the graphite precursor to the binder to the nano-silicon is 1: 0.03; and the rotation speed at the time of the mechanical fusion machine treatment was 600rpm.
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon anode material precursor obtained in the step (1) into a nitrogen atmosphere protection furnace for carbonization, raising the temperature to 400 ℃ at a heating rate of 2 ℃/min, preserving the temperature for 18 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 150Pa, and crushing and screening to obtain the high-compaction silicon-carbon anode material for the lithium ion battery after the carbonization is finished.
A high-compaction silicon-carbon negative electrode material for a lithium ion battery is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery.
Example 3:
a preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery comprises the following steps:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and treating for 5-20min to obtain the silicon-carbon anode material precursor. The graphite precursor is a mixture of artificial graphite and natural graphite, and the average particle size D50 is 8 mu m; the binder is the mixture of coal-series asphalt and oil-series asphalt, and the softening point is 250 ℃; the average grain diameter D50 of the nano silicon is 50 nm; the mass ratio of the graphite precursor to the binder to the nano-silicon is 1; and the rotation speed at the time of the mechanical fusion machine treatment was 800 rpm.
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon anode material precursor obtained in the step (1) into a nitrogen atmosphere protection furnace for carbonization, raising the temperature to 800 ℃ at a heating rate of 15 ℃/min, keeping the temperature for 8 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 120Pa, and crushing and screening to obtain the high-compaction silicon-carbon anode material for the lithium ion battery after the carbonization is finished.
A high-compaction silicon-carbon negative electrode material for a lithium ion battery is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery.
Comparative example 1:
the silicon surface is directly coated with the nano silicon material of carbon without furnace pressure control.
The following performance tests were performed for each of the above examples and comparative examples:
1. the specific surface area of the negative electrode material was measured using a Micromeritics TriStar II 3020 specific surface area meter from Mach instruments, USA.
2. And testing the surface appearance and the like of the cathode material by adopting a scanning electron microscope.
3. And (3) electrochemical performance testing:
in order to test the performance of the lithium ion battery cathode material, a half-cell test method is used for testing, the cathode material of the above embodiment and the comparative example, SBR (solid content is 50 percent), CMC: super-p = 95.5: 2: 1.5: 1 (weight ratio), a proper amount of deionized water is added to be blended into slurry, the slurry is coated on copper foil and dried in a vacuum drying oven for 12 hours to prepare a cathode piece, the electrolyte is 1M LiPF6/EC + DEC + DMC = 1: 1, the polypropylene microporous membrane is a diaphragm, the counter electrode is a lithium piece, and the battery is assembled. And carrying out a constant-current charge and discharge experiment in the LAND battery test system, limiting the charge and discharge voltage to be 0.01-3.0V, and collecting and controlling data by using a charge and discharge cabinet controlled by a computer. The roller machine is tested for pole piece compaction performance by adopting the Shore Yang Dai force DYG-703 BH-phi 600 multiplied by 600/300T oil pressure.
The test results are shown in table 1 below:
TABLE 1 comparison of performances of anode materials in different examples and comparative examples
| Examples/comparative examples | Specific surface area (m) 2 / g） | Pole piece compaction density (g/cm) 3 ） | 0.1C first specific capacity (mAh/g) | 0.1C Primary efficiency (%) | 0.1 Retention ratio of C300 cycle Capacity (%) |
| Example 1 | 3.5 | 1.65 | 600 | 90.5 | 85.9 |
| Example 2 | 1.8 | 1.68 | 562 | 91.1 | 83.7 |
| Example 3 | 2.3 | 1.75 | 700 | 91.2 | 89.8 |
| Comparative example 1 | 5.7 | 1.50 | 478 | 84 | 76 |
As can be seen from table 1, the prepared high-compaction silicon carbon negative electrode material for the lithium ion battery has a smaller specific surface area, which indicates that the outer layer carbon is uniformly and compactly coated, and direct contact between silicon and electrolyte is isolated, so that the material has a better cycle performance, and also has high compaction density, excellent capacity performance, and first charge-discharge efficiency. The two-phase coating of the bitumen and its volatiles plays a very critical role: the uniform coating structure can effectively relieve the volume expansion effect of silicon in the lithium extraction process, isolate electrolyte and inhibit pulverization of active substances.
In addition, the SEM image of the high-compaction silicon carbon negative electrode material for the lithium ion battery prepared in example 1 is shown in fig. 1, and it can be seen that the material is a secondary particle composed of graphite and silicon, the surface is uniformly coated, and no nano-silicon is exposed, which proves that the present invention can realize uniform and complete coating of nano-silicon, thereby reducing the specific surface area of the material and avoiding the contact of silicon with the electrolyte. Meanwhile, it can be seen that the surfaces of the secondary particles prepared by the method are irregular in pore shape, and the expansion space can be reserved for silicon, so that the influence caused by the expansion of the silicon particles is reduced, and the influence is remained under the action of certain nitrogen pressure and the limitation of asphalt volatilization.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.
Claims (5)
1. A preparation method of a high-compaction silicon-carbon negative electrode material for a lithium ion battery is characterized by comprising the following steps: the method comprises the following steps:
(1) Mixing materials:
adding the graphite precursor, the binder and the nano-silicon into a mechanical fusion machine according to a certain proportion, and treating for 5-20min to obtain a silicon-carbon anode material precursor; the mass ratio of the graphite precursor to the binder to the nano-silicon is 1.005-0.03; the binder is one or a mixture of coal-series or oil-series asphalt, and the softening point is 200-300 ℃;
(2) Two-phase coating carbonization:
and (2) putting the silicon-carbon anode material precursor obtained in the step (1) into a nitrogen atmosphere protective furnace for carbonization, raising the temperature to 400-1000 ℃ at the heating rate of 2-25 ℃/min, keeping the temperature for 4-18 hours, continuously introducing nitrogen in the process, controlling the furnace pressure to be 100-150Pa, and crushing and screening to obtain the high-compaction silicon-carbon anode material for the lithium ion battery after the carbonization is finished.
2. The preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery according to claim 1 is characterized by comprising the following steps: the graphite precursor in the step (1) is one or a mixture of more of artificial graphite or natural graphite, and the average particle size D50 is 5-10 μm.
3. The method for preparing the high-compaction silicon-carbon negative electrode material for the lithium ion battery according to claim 1, wherein the method comprises the following steps: the average grain diameter D50 of the nano silicon in the step (1) is 10-100 nm.
4. The preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery according to claim 1 is characterized by comprising the following steps: the rotation speed of the mechanical fusion machine in the step (1) during treatment is 600-1000 rpm.
5. A high compaction silicon carbon negative electrode material for a lithium ion battery is characterized in that: the high-compaction silicon-carbon negative electrode material for the lithium ion battery is prepared by the preparation method of the high-compaction silicon-carbon negative electrode material for the lithium ion battery as claimed in any one of claims 1 to 4.
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