CN116425166A - Method for removing oxide layer on surface of porous silicon - Google Patents
Method for removing oxide layer on surface of porous silicon Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/037—Purification
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application provides a method for removing an oxide layer on the surface of porous silicon, which comprises the following steps: mixing the reducing metal powder with the porous silicon to obtain a mixture 1, calcining the mixture 1, and then adding SiCl 4 Preparing a mixture 2 in the atmosphere, and cleaning, separating and drying the mixture 2 to remove the oxide layer on the surface of the porous silicon; the calcination temperature of the calcination is 700-800 ℃; the calcination time is 1.5h to 2.5h. The method provided by the application does not generate magnesium silicate, does not influence gram capacity of materials, does not damage a porous silicon structure, does not introduce new impurity phases, and does not use acids such as hydrochloric acid hydrofluoric acid and the like. The method can effectively avoid the conditions of agglomeration and sintering and damaging the matrix material, and the prepared silicon material has the advantages of good surface uniformity, stable performance, simple process, convenient operation, safety and reliability, large-scale production and easy realizationAnd (5) subsequent processing.
Description
Technical Field
This document relates to, but is not limited to, the field of inorganic materials, to, but is not limited to, a method of removing oxide layers from a porous silicon surface, and in particular to, but is not limited to, a method of first-turn coulombic efficiency of porous silicon.
Background
With the increasing energy crisis and the increasing demand for high specific energy storages, lithium ion batteries are becoming hot spots in the scientific research and industry as a medium with high energy density, high cycling stability, high safety and portability. Compared with the current situation that the energy density of the anode material cannot be broken through in a short time, the anode material is a key break-through for realizing the high-energy-density battery. The existing graphite anode material has low working voltage, rich reserve and strong structural stability, but the limited theoretical specific capacity (372 mAh/g) of the existing graphite anode material cannot meet the energy density and power density requirements required by modern electronic products, and particularly cannot meet the endurance requirements of new energy automobiles. Therefore, there is an urgent need to find new high-performance electrode materials to replace graphite. In recent years, silicon materials have been found to be novel electrode materials that are most promising alternatives to graphite anodes, and have attracted considerable attention from researchers, due to their high theoretical specific capacity (4200 mAh/g), low operating potential (< 0.5v vs. Li/li+), abundant reserves, and environmental friendliness. However, silicon anodes have significant drawbacks, poor intrinsic conductivity, and large volume effects of over 300% during charge and discharge, especially their low first-turn coulombic efficiency (ICE), have hindered their further development.
The silicon negative electrode ICE is lower because of two main reasons, namely, the silicon negative electrode is pulverized due to the volume change in the charge-discharge process, so that a plurality of silicon with poor conductivity cannot participate in subsequent reactions; in addition, the silicon dioxide on the surface, the non-metering silicon oxide compound and other various substances adsorbed by dangling bonds are irreversible after lithium intercalation reaction, so that the first effect is low. For the first reason, the silicon negative electrode is nanocrystallized or porous, and then a layer of conductive carbon is deposited by vapor deposition, so that the effect can be alleviated. However, the low ICE caused by the second reason is a difficult problem in industry and scientific research, and the pre-lithiation technology is commonly used at present to perform pre-supplement side reaction to consume lithium, so as to improve the first-circle coulombic efficiency. Common prelithiation technologies comprise in-situ doping, contact reaction, an electrochemical method, a chemical method and the like, expensive and explosive lithium powder, lithium foil and the like are used as lithium sources, prelithiation of a silicon negative electrode is realized in an electrochemical structure or a high-temperature and high-pressure environment, lithium is reacted with a silicon oxygen compound to generate lithium silicate, so that the coulombic efficiency of the lithium silicate is improved, but the technology is extremely complex, the safety is poor, the alkalinity of materials is improved, the industrialization is difficult to realize, and the cost of the silicon negative electrode material is greatly improved.
Disclosure of Invention
The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.
The silicon oxide on the surface of silicon is difficult to remove by a simple method, and the method provided by the application can effectively break the oxide layer, does not generate agglomeration and sintering, does not damage the structure of a matrix material, and does not influence subsequent processing.
The application provides a method for removing an oxide layer on the surface of porous silicon, which comprises the following steps:
mixing the reducing metal powder with the porous silicon to obtain a mixture 1, calcining the mixture 1, and then adding SiCl 4 Preparing a mixture 2 in an atmosphere, andthe mixture 2 is cleaned, separated and dried, and then the oxide layer on the surface of the porous silicon can be removed; the calcination temperature of the calcination is 700-800 ℃; the calcination time is 1.5h to 2.5h.
In one embodiment provided herein, the reducing metal powder is selected from any one or more of sodium powder, potassium powder, magnesium powder, and aluminum powder.
In one embodiment provided herein, the reducing metal powder is 300 mesh sieved reducing metal powder.
In one embodiment provided herein, the weight ratio of the reducing metal powder to the porous silicon is (2 to 15): 100.
In one embodiment provided herein, the porous silicon has a surface oxide layer thickness of 5nm to 20nm.
In one embodiment provided herein, the porous silicon has a D50 particle size of 0.5 μm to 15 μm.
In one embodiment provided herein, mixture 1 is calcined after SiCl 4 Maintaining the temperature at 300-500 ℃ for 1.5-5 h in the atmosphere;
in one embodiment provided herein, the SiCl 4 The weight ratio of the metal powder to the reducing metal powder is (3.5 to 4.5) 1.
In one embodiment provided herein, the mixing is ball milling for a period of 1 to 5 hours; the mixing is performed under an inert atmosphere.
In one embodiment provided herein, the inert atmosphere gas is selected from any one or more of helium, neon, and argon.
In one embodiment provided herein, the wash is an alcohol wash, and the alcohol used in the alcohol wash is any one or more of methanol, ethanol, and glycerol.
In one embodiment provided herein, the alcohol used in the alcohol wash is methanol and ethanol mixed in any ratio.
In yet another aspect, the present application provides a method for improving the initial coulombic efficiency of porous silicon, the method comprising removing the oxide layer on the surface of the porous silicon using the method described above.
In yet another aspect, the present application provides a porous silicon made according to the above method of improving the initial coulombic efficiency of porous silicon.
In yet another aspect, the present application provides an electrochemical cell comprising the porous silicon described above.
In one embodiment provided herein, the electrochemical cell is a lithium ion cell.
In yet another aspect, the present application provides an apparatus comprising an apparatus housing, and a motor and/or circuit board located inside the apparatus housing, the apparatus housing further comprising a battery electrically connected to the motor and/or circuit board for powering the motor and/or circuit board, the battery comprising the electrochemical cell described above.
The beneficial effects of this application include:
1. the amorphous silicon generated at a lower temperature by the method is attached to the surface of the porous silicon, so that the electrochemical performance of the material can be improved. Meanwhile, the catalyst can react with the unreacted completely reduced metal powder, so that the alkalinity and the unsafe property of the material are eliminated.
2. The method provided by the application can remove the silicon oxide on the surface of the porous silicon, the reaction is easy to occur, and the reaction is more uniform, so that the lithium removal and intercalation efficiency of the porous silicon is improved, the first-ring coulomb efficiency (ICE) of the silicon anode material is greatly improved, and the first-ring discharge specific capacity is also improved. Avoiding the defects of more silicon generation and uneven reaction.
3. The method provided by the application does not generate silicate, does not affect gram capacity of materials, does not damage a porous silicon structure, does not introduce new impurity phases, and does not use acids such as hydrochloric acid hydrofluoric acid and the like. The method can effectively avoid the conditions of agglomeration and sintering and damaging the matrix material, and the prepared silicon material has the advantages of good surface uniformity, stable performance, simple process, convenient operation, safety and reliability, large-scale production and easy subsequent processing and use.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application. Other advantages of the present application may be realized and attained by the structure particularly pointed out in the written description.
Drawings
The accompanying drawings are included to provide an understanding of the technical aspects of the present application, and are incorporated in and constitute a part of this specification, illustrate the technical aspects of the present application and together with the examples of the present application, and not constitute a limitation of the technical aspects of the present application.
FIG. 1 is an SEM image of example 1 without alcohol washing.
Fig. 2 is an SEM image after the alcohol washing in example 1.
FIG. 3 is a graph showing electrochemical properties before and after modification in example 1.
FIG. 4 is a graph showing the electrochemical performance of the modified polymer of example 2.
FIG. 5 is a graph showing the electrochemical performance of the modified polymer of example 3.
FIG. 6 is a graph showing the electrochemical performance of comparative example 1 after modification.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application are described in detail below. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be arbitrarily combined with each other.
In the examples and the comparative examples of the application, the purity of the metal magnesium is more than or equal to 99.5 percent; the purity of the porous silicon is more than or equal to 95%; the purity of the methanol is more than or equal to 99.5%; the purity of the ethanol is more than or equal to 95 percent.
Example 1
Taking 5kg of porous silicon material (D50=6μm, the thickness of the surface oxide layer is 5nm to 20 nm), ball milling and mixing 0.5kg of metal magnesium powder (300 meshes) in a ball mill under the protection of argon gas for 2 hours, and rotary calcining in a batch argon gas rotary furnace at 750 ℃ for 1.5 hours; the temperature of the electric furnace is reduced to 450 ℃, and after the electric furnace is stabilized, 2kg of SiCl is introduced at a rate of 15ml/min 4 Gas is reacted for 2 hours, and then cooled and discharged after the reaction is finished. The obtained raw materials are washed in ethanol for 2 hours according to the volume ratio of ethanol=1:4, and are dried in a vacuum drying oven at 80 ℃ after being filtered and separated, and meanwhile, the solvent is recycled. The obtained dry yellow powder is porous silicon with high first circle coulombic efficiency.
As shown in fig. 1, the porous silicon material without alcohol washing can also see magnesium chloride grains, and as shown in fig. 2, magnesium chloride is effectively removed after alcohol washing. The prepared modified and unmodified porous silicon materials are respectively assembled and tested to form a button type lithium ion half battery, as shown in figure 3, under the current density of 100mA/g, the discharge specific capacity of an unmodified group is 3122.8mAh/g, the charge specific capacity is 2653.0mAh/g, the initial circle coulomb efficiency is 84.95%, the discharge specific capacity of the modified porous silicon material is 3353.2mAh/g, the charge specific capacity is 3100.2mAh/g, the initial circle coulomb efficiency is 92.46%, the excellent initial circle high coulomb efficiency characteristic is shown, and the charge and discharge specific capacity is also improved.
Example 2
Taking 5kg of the same porous silicon material as in example 1, ball-milling and mixing 0.25kg of metal magnesium powder (300 meshes) in a ball mill under the protection of argon for 2 hours, and rotary calcining in a batch argon rotary furnace at 730 ℃ for 2 hours; the temperature of the electric furnace was lowered to 380 ℃, after the electric furnace was stabilized, 0.875kg of SiCl4 gas was introduced at a rate of 15ml/min, the reaction was then carried out for 2 hours, and after the reaction was completed, the discharge was cooled. The obtained raw materials are washed in methanol for 2 hours according to the volume ratio of the materials of methanol=1:4, and are dried in a vacuum drying oven at 80 ℃ after being filtered and separated, and meanwhile, the solvent is recycled. The obtained dry yellow powder is porous silicon with high first circle coulombic efficiency.
The prepared porous silicon material is assembled and buckled into a lithium ion half battery by the same method as in the embodiment 1, and as shown in fig. 4, the modified porous silicon has a specific discharge capacity of 3179.4mAh/g, a specific charge capacity of 2871.4mAh/g and a first-ring coulomb efficiency of 90.31% at a current density of 100mA/g, and excellent first-ring high-coulomb efficiency characteristics are shown.
Example 3
5kg of the same porous silicon material as in example 1 was taken, and 0.75kg of metal magnesium powder (300 mesh) was ball-milled in a ball mill under an argon atmosphereGrinding and mixing for 2 hours, and rotating and calcining for 2 hours at 800 ℃ in an intermittent argon rotary furnace; the temperature of the electric furnace is reduced to 500 ℃, after the electric furnace is stabilized, 3.375kg of SiCl is introduced at a rate of 15ml/min 4 And (3) reacting for 2 hours, and cooling and discharging after the reaction is finished. The obtained raw materials are washed in ethanol for 2 hours according to the volume ratio of ethanol=1:4, and are dried in a vacuum drying oven at 80 ℃ after being filtered and separated, and meanwhile, the solvent is recycled. The obtained dry yellow powder is porous silicon with high first circle coulombic efficiency.
The prepared porous silicon material is assembled and buckled into a lithium ion half battery by the same method as in the embodiment 1, and as shown in fig. 5, the modified porous silicon has a specific discharge capacity of 3247.4mAh/g, a specific charge capacity of 2968.1mAh/g and a first-ring coulomb efficiency of 91.40% at a current density of 100mA/g, and excellent first-ring high-coulomb efficiency characteristics are shown.
Comparative example 1
Comparative example 1 a porous silicon material was prelithiated according to the conventional prelithiation method:
a negative electrode sheet was prepared from the same porous silicon material as in example 1 in the same manner as in example 1, using a lithium foil in a special anhydrous and anaerobic battery glove box (water oxygen < 0.1 ppm), uniformly passing through a roller at 200 ℃ in an electric twin roller machine, and then testing a button type lithium ion half cell in the same manner as in example 1. As shown in fig. 6. At a current density of 100mA/g, the specific discharge capacity is 3137.8mAh/g, the specific charge capacity is 2820.5mAh/g, and the initial coulomb efficiency is 89.89%. It can be seen that the pre-lithiation method is effective but the cost of the pre-lithiation raw material is extremely high, the pre-lithiation process is low in efficiency and limited to an ultra-pure environment, cannot be applied to mass production, and is easy to cause the material to be alkaline to influence the subsequent use of the whole battery.
Comparative examples 2 to 5
The difference between comparative examples 2 to 5 and example 1 and the electrical properties of comparative examples 2 to 5 are detailed in the following table.
Table 1: tables of electrical properties statistics of example 1 and comparative examples 2 to 5
| The treatment conditions differ from those of example 1 only in that | First-turn discharge specific capacity mAh/g | First circle coulombic efficiency/% | |
| Example 1 | - | 3353.2 | 92.46 |
| Comparative example 2 | The calcination temperature is 900 DEG C | 2447.3 | 90.12 |
| Comparative example 3 | The calcination temperature is 600 DEG C | 2996.5 | 85.56 |
| Comparative example 4 | Calcination time was 0.5h | 3015.4 | 86.62 |
| Comparative example 5 | Calcination time was 3.5h | 2673.1 | 89.75 |
Claims (11)
1. A method of removing an oxide layer from a porous silicon surface, the method comprising:
mixing the reducing metal powder with the porous silicon to obtain a mixture 1, calcining the mixture 1, and then adding SiCl 4 Preparing a mixture 2 in the atmosphere, and cleaning, separating and drying the mixture 2 to remove the oxide layer on the surface of the porous silicon;
the calcination temperature of the calcination is 700-800 ℃; the calcination time is 1.5h to 2.5h.
2. The method of claim 1, wherein the reducing metal powder is selected from any one or more of sodium powder, potassium powder, magnesium powder, and aluminum powder;
optionally, the reducing metal powder is 300 mesh screened reducing metal powder.
3. The method of claim 1, wherein the weight ratio of the reducing metal powder to the porous silicon is (2 to 15) 100.
4. The method of claim 1, wherein the porous silicon has a surface oxide layer thickness of 5nm to 20nm; alternatively, the porous silicon has a D50 particle size of 0.5 μm to 15 μm.
5. The method according to claim 1, characterized in that the mixture 1 is calcined after SiCl 4 Maintaining the temperature at 300-500 ℃ for 1.5-5 h in the atmosphere;
optionally, the SiCl 4 The weight ratio of the metal powder to the reducing metal powder is (3.5 to 4.5) 1.
6. The method of any one of claims 1 to 5, wherein the mixing is ball milling for a time of 1 to 5 hours;
the mixing is performed under an inert atmosphere gas, optionally selected from any one or more of helium, neon and argon.
7. The method according to any one of claims 1 to 5, wherein the washing is an alcohol washing, and the alcohol used in the alcohol washing is any one or more of methanol, ethanol and glycerol;
optionally, the alcohol used in the alcohol washing is methanol and ethanol mixed in any proportion.
8. A method of increasing the initial coulombic efficiency of porous silicon, comprising removing the surface oxide layer of porous silicon using the method of any one of claims 1 to 7.
9. The porous silicon made by the method for improving the initial coulombic efficiency of porous silicon according to claim 8.
10. An electrochemical cell comprising the porous silicon of claim 9;
optionally, the electrochemical cell is a lithium ion cell.
11. An apparatus comprising an apparatus housing, and a motor and/or circuit board located within the apparatus housing, the apparatus housing further comprising a battery within the apparatus housing, the battery being electrically connected to the motor and/or circuit board for powering the motor and/or circuit board, the battery comprising the electrochemical cell of claim 10.
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| CN102942184A (en) * | 2012-12-06 | 2013-02-27 | 安徽工业大学 | Method for preparing silicon nanotube by taking porous silicon as substrate |
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| CN102942184A (en) * | 2012-12-06 | 2013-02-27 | 安徽工业大学 | Method for preparing silicon nanotube by taking porous silicon as substrate |
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