CN114050247A - Modified silicon-based material, preparation method thereof and lithium battery negative electrode material - Google Patents

Modified silicon-based material, preparation method thereof and lithium battery negative electrode material Download PDF

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CN114050247A
CN114050247A CN202111357740.7A CN202111357740A CN114050247A CN 114050247 A CN114050247 A CN 114050247A CN 202111357740 A CN202111357740 A CN 202111357740A CN 114050247 A CN114050247 A CN 114050247A
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silicon
based material
conductive polymer
modified
preparation
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汪杨
何�轩
陈鹏
褚春波
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Sunwoda Electric Vehicle Battery Co Ltd
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Sunwoda Electric Vehicle Battery Co Ltd
Sunwoda Electronic Co Ltd
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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • 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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
    • 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 invention provides a modified silicon-based material, a preparation method thereof and a lithium battery negative electrode material. The preparation method comprises the following steps: step S1, doping the silicon-based material with a dopant by a hydrothermal method to obtain a doped silicon-based material; wherein the weight ratio of the dopant to the silicon-based material is (0.01-0.1): 1; and step S2, dispersing the doped silicon-based material in water to form a dispersion liquid, adding an oxidant and a conductive polymer monomer into the dispersion liquid, and then carrying out in-situ polymerization reaction to obtain the modified silicon-based material. The silicon-based material modified by the preparation method can better give consideration to the rate capability, the cycle performance, the first coulombic efficiency and the like of the silicon-based material on the basis of simpler working procedures, so that the negative electrode material has better comprehensive performance.

Description

Modified silicon-based material, preparation method thereof and lithium battery negative electrode material
Technical Field
The invention relates to the technical field of lithium battery materials, in particular to a modified silicon-based material, a preparation method thereof and a lithium battery cathode material.
Background
With the vigorous development of electric automobiles, the endurance mileage of lithium ion batteries becomes a key for restricting the improvement of the quality of travel life of people. In a lithium ion battery, the capacities of a positive electrode and a negative electrode determine the capacity of the entire battery. The positive electrode capacity reaches a bottleneck and is difficult to break through further. The capacity of the graphite cathode material adopted at present is low, and the lifting space is large. Therefore, in order to further increase the capacity of the lithium ion battery, it is a feasible way to find a high-capacity negative electrode material to replace the conventional graphite material.
Among the many cathode candidates, silicon-based materials have received much attention and research because of their ultra-high theoretical lithium storage capacity. However, silicon anodes still have many problems that prevent the material from further development and large-scale application: 1) silicon-based materials have extremely poor electronic conductivity and serious polarization in the charging and discharging processes, so that the problems of poor capacity performance, lithium precipitation and the like can be caused; 2) the volume change of the de-intercalated lithium is large, the de-intercalated lithium repeatedly expands and contracts in the charging and discharging process, so that the active material is pulverized and falls off from the current collector, and the capacity is greatly attenuated; 3) in the process of lithium intercalation, an SEI film is generated on the surface of the silicon negative electrode, and the SEI film is repeatedly expanded and contracted to be continuously broken and regenerated, so that a large amount of lithium ions are consumed, and the internal resistance of the battery is increased.
In view of the problems of silicon-based materials, researchers have proposed some improvements: 1) the porous silicon-based material is prepared, so that the diffusion path of lithium ions is reduced, and the negative influence of expansion on the electrode is relieved; 2) the composite carbon material is blended with the carbon material with better conductivity, or the carbon material is coated on the surface of the silicon-based material, so that the conductivity among material particles is improved, and the polarization is reduced to a certain extent. 3) The silicon-based material is nanocrystallized, the particle size of the material is reduced, and the diffusion path of lithium ions can be shortened. However, these improved methods do not improve the intrinsic conductivity of the silicon-based material, and the active silicon material still has large polarization during the charging and discharging processes, which seriously affects the performance of the battery. In order to further improve the performance of the silicon negative electrode, promote the development and large-scale commercial application of the silicon negative electrode, attempts to improve the conductivity of the silicon negative electrode by doping with hetero atoms, such as:
patent CN107195893A describes a boron-doped silicon-based negative electrode material for lithium ion batteries, which is prepared by baking a silicon-based material and boron trioxide at high temperature to make boron atoms replace part of silicon atoms. Boron doping improves the concentration of vacancy carriers in the silicon material, so that the intrinsic conductivity of the material is improved, and the performance of the battery is improved to a certain extent.
Patent CN107240693A describes a phosphorus-doped silicon-graphite composite material, and a negative electrode material and a lithium ion battery containing the same, and the phosphorus-doped silicon-graphite composite material is prepared by a two-step ball milling method, wherein in the first step, silicon and phosphorus are blended and ball-milled, and in the second step, the product of the first step and graphite are blended and ball-milled. The material prepared by the method has better capacity and cycle performance.
Patent CN110071272A describes a boron-doped silicon-based composite negative electrode material, and a preparation method and application thereof, wherein the boron-doped silicon negative electrode material is obtained by mixing a silicon negative electrode with boric acid, freeze-drying, and then pyrolyzing. The boron-doped silicon negative electrode material prepared by the method improves the first-week coulombic efficiency and shows better cycle performance.
Patent CN110838584A describes a boron-phosphorus co-doped porous silicon negative electrode material and a preparation method thereof, wherein a liquid silicon source, a boron-containing compound and a phosphorus-containing compound are dispersed in a solvent, and are subjected to liquid phase reaction and then calcined to obtain a precursor. And then grinding the precursor, a metal reducing agent and a metal chloride, carrying out thermal reduction reaction in an inert atmosphere, and finally removing by-products to obtain the boron-phosphorus co-doped porous silicon negative electrode material.
However, the above doping method or process is complicated, or the prepared silicon negative electrode material still has the problem that the rate performance, the cycle performance, the first coulombic efficiency and the like cannot be considered at the same time.
Disclosure of Invention
The invention mainly aims to provide a modified silicon-based material, a preparation method thereof and a lithium battery negative electrode material, and aims to solve the problems that the modified silicon-based material is doped or the process is complex in the prior art, or the prepared silicon negative electrode material cannot give consideration to good rate capability, cycle performance, first coulombic efficiency and the like.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a modified silicon-based material, comprising the steps of: step S1, doping the silicon-based material with a dopant by a hydrothermal method to obtain a doped silicon-based material; wherein the weight ratio of the dopant to the silicon-based material is (0.01-0.1): 1; and step S2, dispersing the doped silicon-based material in water to form a dispersion liquid, adding an oxidant and a conductive polymer monomer into the dispersion liquid, and then carrying out in-situ polymerization reaction to obtain the modified silicon-based material.
Further, step S1 includes: dispersing a silicon-based material in water, and then adding a dopant under the stirring condition to obtain a pre-dispersion liquid; and carrying out hydrothermal reaction on the pre-dispersion liquid to obtain the doped silicon-based material.
Furthermore, the temperature of the hydrothermal reaction is 100-160 ℃, and the time of the hydrothermal reaction is 12-36 h.
Further, the dopant is one or more of compounds containing N, B, P, Ni, Co or Mn; preferably, the dopant is H3BO3、H3PO4、HNO3、Ni(NO3)3、Co(NO3)2、Mn(NO3)2One or more of; preferably, the silicon-based material is one or more of silicon, silicon dioxide, silicon monoxide, silicon carbon composite material and silicon alloy; more preferably, the silicon-based material is particles with the particle size of 3-20 mu m.
Further, the oxidant is one or more of dichromate, persulfate and ferric chloride; preferably, the dichromate is potassium dichromate and the persulfate is sodium persulfate.
Further, the conductive polymer monomer is one or more of aniline, pyrrole and thiophene; preferably, the weight ratio of the conductive polymer monomer to the silicon-based material is (0.25-0.75): 1; preferably, the weight ratio of the oxidant to the conductive polymer monomer is (1-5): 1.
Further, in the in-situ polymerization reaction process, the reaction temperature is 20-40 ℃, and the reaction time is 1-3 h; preferably, after the in-situ polymerization reaction is finished, centrifuging and washing the reaction system to obtain the modified silicon-based material.
According to another aspect of the invention, the modified silicon-based material is prepared by the preparation method, and is of a core-shell structure, wherein the core layer is a doped silicon-based material, and the shell layer is a conductive polymer layer.
Further, the thickness of the conductive polymer layer is 0.02-0.05 μm.
According to another aspect of the invention, the invention also provides a lithium battery anode material which comprises the modified silicon-based material.
The invention provides a preparation method of a modified silicon-based material, which comprises the following steps: step S1, doping the silicon-based material with a dopant by a hydrothermal method to obtain a doped silicon-based material; wherein the weight ratio of the dopant to the silicon-based material is (0.01-0.1): 1; and step S2, dispersing the doped silicon-based material in water to form a dispersion liquid, adding an oxidant and a conductive polymer monomer into the dispersion liquid, and then carrying out in-situ polymerization reaction to obtain the modified silicon-based material.
In the preparation method, a hydrothermal method is adopted to dope the silicon-based material. Different from the traditional doping methods such as calcination and the like, the doping process of the silicon-based material can be effectively controlled by the hydrothermal method, so that the doping elements in the doping agent are uniformly doped in phase. Then, by adding an oxidant and a conductive polymer monomer into the dispersion liquid of the doped silicon-based material, in-situ polymerization can be carried out on the surface of the doped silicon-based material, so as to coat the conductive polymer. Compared with the direct blending coating, the in-situ polymerization coating can form a more complete conductive polymer shell layer with more compact coating and uniform thickness on the surface of the doped silicon-based material. Based on the two reasons, the obtained modified silicon-based material has better conductivity, so that the rate capability of the material is effectively improved, and the first coulombic efficiency is higher. Meanwhile, the invention effectively relieves the volume expansion of the silicon-based material, and avoids the silicon-based material from directly contacting the electrolyte by using the complete and uniform conductive polymer shell layer, so the invention can effectively improve the cycle performance of the battery when being applied to the lithium ion battery. In addition, the preparation method has simple process and mild modification conditions, and is very suitable for industrial large-scale use.
In a word, the silicon-based material modified by the preparation method can better give consideration to the rate capability, the cycle performance, the first coulombic efficiency and the like of the silicon-based material on the basis of simpler working procedures, so that the negative electrode material has better comprehensive performance.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the doping of the modified silicon-based material in the prior art is complicated, or the prepared silicon negative electrode material cannot achieve good rate performance, cycle performance, first coulombic efficiency, and the like. In order to solve the above problems, the present invention provides a method for preparing a modified silicon-based material, comprising the steps of: step S1, doping the silicon-based material with a dopant by a hydrothermal method to obtain a doped silicon-based material; wherein the weight ratio of the dopant to the silicon-based material is (0.01-0.1): 1; and step S2, dispersing the doped silicon-based material in water to form a dispersion liquid, adding an oxidant and a conductive polymer monomer into the dispersion liquid, and then carrying out in-situ polymerization reaction to obtain the modified silicon-based material.
In the preparation method, a hydrothermal method is adopted to dope the silicon-based material. Different from the traditional doping methods such as calcination and the like, the doping process of the silicon-based material can be effectively controlled by the hydrothermal method, so that the doping elements in the doping agent are uniformly doped in phase. Then, by adding an oxidant and a conductive polymer monomer into the dispersion liquid of the doped silicon-based material, in-situ polymerization can be carried out on the surface of the doped silicon-based material, so as to coat the conductive polymer. Compared with the direct blending coating, the in-situ polymerization coating can form a more complete conductive polymer shell layer with more compact coating and uniform thickness on the surface of the doped silicon-based material. Based on the two reasons, the obtained modified silicon-based material has better conductivity, so that the rate capability of the material is effectively improved, the first coulombic efficiency is higher, and the electrochemical capacity of the material is higher. Meanwhile, the invention effectively relieves the volume expansion of the silicon-based material, and avoids the silicon-based material from directly contacting the electrolyte by using the complete and uniform conductive polymer shell layer, so the invention can effectively improve the cycle performance of the battery when being applied to the lithium ion battery. In addition, the preparation method has simple process and mild modification conditions, and is very suitable for industrial large-scale use.
In a word, the silicon-based material modified by the preparation method can better give consideration to the rate capability, the cycle performance, the first coulombic efficiency and the like of the silicon-based material on the basis of simpler working procedures, so that the negative electrode material has better comprehensive performance.
In order to stabilize the doping process and further improve the uniformity of doping, in a preferred embodiment, the step S1 includes: dispersing a silicon-based material in water, and then adding a dopant under the stirring condition to obtain a pre-dispersion liquid; and carrying out hydrothermal reaction on the pre-dispersion liquid to obtain the doped silicon-based material. More preferably, the temperature of the hydrothermal reaction is 100-160 ℃, and the time of the hydrothermal reaction is 12-36 h. The reaction temperature and time are controlled at the temperature, so that the uniformity of doping is better facilitated, the generation of a mixed phase possibly caused by overhigh temperature is avoided, the doping effect is better improved, and the performance improvement of the modified silicon-based material is further facilitated.
In the specific reaction process, preferably, after the pre-dispersion liquid is obtained, the pre-dispersion liquid is transferred to a hydrothermal kettle for hydrothermal reaction, and the volume of the pre-dispersion liquid in the hydrothermal kettle is controlled to be 40-80% of the volume of the kettle, so that the reaction is safer. In addition, after the doping agent is added under the stirring condition, the stirring is preferably continued for 2-4 hours, and then the transfer is performed.
In a preferred embodiment, the dopant is one or more of compounds containing N, B, P, Ni, Co or Mn. The doping agent of the elements can better complete the in-phase doping of the silicon-based material, and the conductivity of the doped silicon-based material is further improved, thereby being beneficial to the materialThe rate capability and the first coulombic efficiency are better improved. More preferably, the dopant is H3BO3、H3PO4、HNO3、Ni(NO3)3、Co(NO3)2、Mn(NO3)2One or more of;
the silicon-based material may be of a type commonly used in the art, and preferably, the silicon-based material is silicon (Si), silicon dioxide (SiO)2) Silicon monoxide (SiO), silicon carbon composite materials and silicon alloys (such as silicon-aluminum alloys). The silicon-based material is applied to hydrothermal doping and polymerization coating, and the modified material has better comprehensive performance. More preferably, the silicon-based material is particles with the particle size of 3-20 mu m.
The oxidant is added for in-situ polymerization of the conductive polymer monomer, and in order to promote the in-situ polymerization reaction to be more stable and form a more uniform and complete conductive polymer shell layer, in a preferred embodiment, the oxidant is one or more of dichromate, persulfate and ferric chloride; preferably, the dichromate is potassium dichromate and the persulfate is sodium persulfate.
In order to achieve better compatibility between the conductivity and the coating effect of the modified silicon-based material, in a preferred embodiment, the conductive polymer monomer is one or more of aniline, pyrrole and thiophene. By adopting the conductive polymer monomers, the doped silicon-based material can be better coated, the conductivity is good, the barrier effect on the electrolyte is better, and the improvement of the comprehensive performance of the cathode material is facilitated.
Preferably, the weight ratio of the conductive polymer monomer to the silicon-based material is (0.25-0.75): 1. Therefore, the formed conductive polymer shell layer is more appropriate in thickness, the better balance cycle performance, rate capability and first coulombic efficiency are facilitated, and the electrochemical capacity of the material is also better. Preferably, the weight ratio of the oxidant to the conductive polymer monomer is (1-5): 1, so that the conductive polymer monomer is promoted to be fully polymerized, the polymerization reaction speed is more suitable, the complete coating of the doped silicon-based material is gradually completed in the polymerization process, and the improvement on the service performance of the material is more favorable. Preferably, in the in-situ polymerization reaction process, the reaction temperature is 20-40 ℃, and the reaction time is 1-3 h.
And after the in-situ polymerization reaction is finished, centrifuging and washing the reaction system to obtain the modified silicon-based material. The specific washing mode can adopt deionized water and ethanol for washing. Similarly, after the hydrothermal reaction is finished, the doped silicon-based material can also be obtained by centrifugation and washing, and the specific washing mode can be washing by using deionized water and ethanol.
According to another aspect of the invention, the modified silicon-based material is prepared by the preparation method, and is of a core-shell structure, wherein the core layer is a doped silicon-based material, and the shell layer is a conductive polymer layer. In the preparation method, a hydrothermal method is adopted to dope the silicon-based material. Different from the traditional doping methods such as calcination and the like, the doping process of the silicon-based material can be effectively controlled by the hydrothermal method, so that the doping elements in the doping agent are uniformly doped in phase. Then, by adding an oxidant and a conductive polymer monomer into the dispersion liquid of the doped silicon-based material, in-situ polymerization can be carried out on the surface of the doped silicon-based material, so as to coat the conductive polymer. Compared with the direct blending coating, the in-situ polymerization coating can form a more complete conductive polymer shell layer with more compact coating and uniform thickness on the surface of the doped silicon-based material. Based on the two reasons, the obtained modified silicon-based material has better conductivity, so that the rate capability of the material is effectively improved, the first coulombic efficiency is higher, and the electrochemical capacity of the material is higher. Meanwhile, the invention effectively relieves the volume expansion of the silicon-based material, and avoids the silicon-based material from directly contacting the electrolyte by using the complete and uniform conductive polymer shell layer, so the invention can effectively improve the cycle performance of the battery when being applied to the lithium ion battery.
In a word, the modified silicon-based material can better give consideration to the rate capability, the cycle performance, the first coulombic efficiency and the like of the silicon-based material, so that the negative electrode material has better comprehensive performance. The first coulombic efficiency of the modified silicon-based material can reach 85%, the discharge capacity after 6 weeks of charge and discharge can also reach 1223mAh/g, the capacity retention rate is 75.4% after 100 weeks of circulation and compared with the discharge capacity at the 6 th week, and the modified silicon-based material has high electrochemical capacity and good circulation stability. Meanwhile, when the modified silicon-based material is used as a lithium ion battery cathode, the modified silicon-based material has better rate capability. The discharge capacity can reach 1223, 1061, 812 and 648mAh/g at current densities of 0.1, 0.2, 0.5 and 1.0A/g.
More preferably, the conductive polymer layer has a thickness of 0.02 to 0.05 μm. The thickness of the conductive polymer layer is controlled within the range, so that the balance among cycle performance, rate performance and first coulombic efficiency is facilitated, and the electrochemical capacity of the material is better.
According to another aspect of the invention, the invention also provides a lithium battery anode material which comprises the modified silicon-based material. The cathode material has better comprehensive performance, high electrochemical capacity, rate capability, cycle performance and first coulombic efficiency.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 2
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.01g of H was slowly added with stirring3BO3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifugating and using water in turnAnd washing with ethanol to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 3
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.001g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 4
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 160 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 5
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring for 3 hours continuously, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60% of the volume of the kettle, and reacting for 24 hours at 100 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon substrateAnd (5) feeding. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 6
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 36 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with constant stirring and polymerized in situ at 20 ℃ for 4h (the thickness of the shell of the conductive polymer formed was about 0.32 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 7
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 12 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by addition of 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and in situ polymerization at 40 ℃ for 1h (resulting in a conductive polymer shell thickness of about 0.27 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 8
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. Adding doped silicon-based material for desorption0.025g of ferric chloride followed by 0.025g of pyrrole were added to the water with constant stirring and polymerized in situ at 25 ℃ for 2h (the shell thickness of the conductive polymer formed was about 0.18 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 9
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water and polymerized in situ for 2h at 25 deg.C (resulting in a conductive polymer shell thickness of about 0.36 μm) with continuous stirring with 0.375g ferric chloride followed by 0.075g pyrrole. And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 10
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water and 0.08g ferric chloride, followed by 0.09g pyrrole, with constant stirring, and polymerized in situ at 25 ℃ for 2h (resulting in a conductive polymer shell thickness of about 0.39 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 11
0.1g of Si material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3PO4(added in the form of aqueous solution with the mass concentration of 85%) and continuously stirred for 3 hours, and after stirring uniformly, the mixture is transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60% of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. Adding doped silicon-based materialTo deionized water, 0.12g of potassium dichromate, followed by 0.05g of aniline, were added with continuous stirring and polymerized in situ at 25 ℃ for 2h (the shell thickness of the conductive polymer formed was about 0.33 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 12
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride and 0.05g thiophene with continuous stirring, and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.32 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 13
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of Ni (NO) was slowly added with stirring3)3And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 14
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of Co (NO) was slowly added with stirring3)2And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. Adding the doped silicon-based material into deionized water, and continuously stirring0.12g of ferric chloride followed by 0.05g of pyrrole were added and polymerized in situ at 25 ℃ for 2h (the shell thickness of the conductive polymer formed was about 0.3. mu.m). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Example 15
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of Mn (NO) was slowly added with stirring3)2And continuously stirring for 3 hours, transferring the mixture into a 150mL hydrothermal kettle after stirring uniformly, wherein the volume of the solution accounts for 60 percent of the volume of the kettle, and reacting for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Comparative example 1
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.02g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. The doped silica-based material was added to deionized water, followed by 0.12g ferric chloride, 0.05g pyrrole with continuous stirring and polymerized in situ at 25 ℃ for 2h (the thickness of the shell of the conductive polymer formed was about 0.3 μm). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Comparative example 2
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.0002g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. Then centrifuging and washing by water and ethanol in sequence to obtain the doped silicon-based material. Adding the doped silicon-based material into deionized water, and adding 0.12g of ferric chloride and 0.05g of pyrrole successively under continuous stirringAnd polymerizing in situ for 2h at 25 ℃ (the shell layer of the formed conductive polymer is about 0.3 μm thick). And finally, centrifugally washing to obtain the modified silicon-based material with the core-shell structure.
Comparative example 3
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, followed by 0.12g of ferric chloride, 0.05g of pyrrole under continuous stirring and polymerization in situ at 25 ℃ for 2h (resulting in a shell of conductive polymer of about 0.3 μm thickness). And finally, centrifugally washing to obtain the silicon-based material with the surface coated with the conductive polymer shell.
Comparative example 4
0.1g of SiO material (average particle size about 6 μm) was added to deionized water, and 0.005g of H was slowly added with stirring3BO3Stirring is continuously carried out for 3 hours, the mixture is uniformly stirred and then transferred into a 150mL hydrothermal kettle, the volume of the solution accounts for 60 percent of the volume of the kettle, and the mixture is reacted for 24 hours at 140 ℃. And then centrifuging and washing with water and ethanol to obtain the doped silicon-based material.
And (3) performance testing:
the materials prepared in examples 1-9 and comparative examples 1-4 were tested for electrochemical performance using CR2032 button cell, one of which was a mixture of the modified silicon-based material prepared, acetylene black and polyvinylidene fluoride (mass ratio 70:15:15), and the other was a metal lithium plate, electrolyte was 1mol/L LiPF6Dissolved in a solvent of EC/DMC/EMC (volume ratio 1:1: 1). The constant-current charging and discharging voltage range is 0.01-3V.
1) Testing the first discharge capacity and the first coulombic efficiency:
after the button cell is assembled, discharging: discharging at constant current of 0.1A/g to 0.01V, and recording the discharge specific capacity as Q1; charging: charging to 3V at a constant current of 0.1A/g, and recording the charging specific capacity as Q2; the first coulombic efficiency is abbreviated ICE, ICE Q2/Q1.
2) And (3) testing the cycle performance:
discharging: constant current of 0.1A/g is released to 0.01V, and the interval is 10 min; charging: charging to 3V at constant current of 0.1A/g, and keeping the interval of 10 min; thirdly, repeating the first step and the second step for 100 circles. The discharge capacity at week 100 was Q100.
3) And (3) rate performance test:
discharging a constant current of 0.1A/g to 0.01V, and charging the constant current of 0.1A/g to 3V after 10min interval; ② repeating 'first' for 10 circles; thirdly, the current density in the 'first, second' is increased to 0.2, 0.5 and 1A/g, wherein the discharge capacities corresponding to 0.1, 0.2, 0.5 and 1A/g are Q6, Q16, Q26 and Q36 respectively.
TABLE 1 test of the properties of the examples and comparative examples
Figure BDA0003357991000000101
Figure BDA0003357991000000111
From the data in table 1, the modified silicon-based material prepared by the preparation method provided by the invention can better give consideration to rate capability, cycle performance, first coulombic efficiency and the like. In particular, it can be seen from comparative examples 1 and 2 and examples 1 to 3 that the doping can effectively improve the electrochemical performance of the silicon negative electrode, and when the doping amount is increased to 0.05, the battery cycle and rate performance are better. However, further increasing the doping amount generates impurities that hinder the transport of lithium ions and electrons, resulting in a decrease in battery performance. From examples 1, 4 to 7, the suitable hydrothermal temperature and time help to improve the electrochemical performance of the doped sample, mainly because the better reaction temperature and time can promote the elements to be uniformly doped in the bulk phase, and the temperature is too high to generate a hetero phase.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The preparation method of the modified silicon-based material is characterized by comprising the following steps of:
step S1, doping the silicon-based material with a dopant by a hydrothermal method to obtain a doped silicon-based material; wherein the weight ratio of the dopant to the silicon-based material is (0.01-0.1): 1;
and step S2, dispersing the doped silicon-based material in water to form a dispersion liquid, adding an oxidant and a conductive polymer monomer into the dispersion liquid, and then carrying out in-situ polymerization reaction to obtain the modified silicon-based material.
2. The method for preparing a composite material according to claim 1, wherein the step S1 includes:
dispersing the silicon-based material in water, and then adding the dopant under the stirring condition to obtain a pre-dispersion liquid;
and carrying out hydrothermal reaction on the pre-dispersion liquid to obtain the doped silicon-based material.
3. The preparation method according to claim 2, wherein the temperature of the hydrothermal reaction is 100 to 160 ℃ and the time of the hydrothermal reaction is 12 to 36 hours.
4. The production method according to any one of claims 1 to 3, wherein the dopant is one or more of compounds containing N, B, P, Ni, Co, or Mn; preferably, the dopant is H3BO3、H3PO4、HNO3、Ni(NO3)3、Co(NO3)2、Mn(NO3)2One or more of;
preferably, the silicon-based material is one or more of silicon, silicon dioxide, silicon monoxide, a silicon-carbon composite material and a silicon alloy; more preferably, the silicon-based material is particles with the particle size of 3-20 mu m.
5. The production method according to any one of claims 1 to 3, characterized in that the oxidizing agent is one or more of dichromate, persulfate, and ferric chloride; preferably, the dichromate is potassium dichromate and the persulfate is sodium persulfate.
6. The production method according to claim 4, wherein the conductive polymer monomer is one or more of aniline, pyrrole, and thiophene;
preferably, the weight ratio of the conductive polymer monomer to the silicon-based material is (0.25-0.75): 1;
preferably, the weight ratio of the oxidant to the conductive polymer monomer is (1-5): 1.
7. The preparation method according to any one of claims 1 to 3, wherein in the in-situ polymerization reaction process, the reaction temperature is 20-40 ℃, and the reaction time is 1-3 h;
preferably, after the in-situ polymerization reaction is finished, centrifuging and washing a reaction system to obtain the modified silicon-based material.
8. The modified silicon-based material is characterized by being prepared by the preparation method of any one of claims 1 to 7, and the modified silicon-based material is of a core-shell structure, wherein a core layer is a doped silicon-based material, and a shell layer is a conductive polymer layer.
9. The modified silicon-based material according to claim 8, wherein the conductive polymer layer has a thickness of 0.02 to 0.05 μm.
10. A negative electrode material for a lithium battery, comprising the modified silicon-based material according to claim 8 or 9.
CN202111357740.7A 2021-11-16 2021-11-16 Modified silicon-based material, preparation method thereof and lithium battery negative electrode material Pending CN114050247A (en)

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