CN117069115A - Preparation method of silicon carbide doped silicon powder and silicon-carbon composite anode material of lithium battery - Google Patents
Preparation method of silicon carbide doped silicon powder and silicon-carbon composite anode material of lithium battery Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 174
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 127
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 126
- 239000011863 silicon-based powder Substances 0.000 title claims abstract description 108
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 44
- 239000011870 silicon-carbon composite anode material Substances 0.000 title claims description 22
- 238000002360 preparation method Methods 0.000 title claims description 8
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 64
- 239000010703 silicon Substances 0.000 claims abstract description 64
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 61
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 46
- 239000000463 material Substances 0.000 claims abstract description 42
- 239000002245 particle Substances 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims abstract description 6
- 239000002994 raw material Substances 0.000 claims abstract description 4
- 238000005204 segregation Methods 0.000 claims description 16
- 239000010410 layer Substances 0.000 claims description 15
- 239000011248 coating agent Substances 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 8
- 239000004215 Carbon black (E152) Substances 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 229930195733 hydrocarbon Natural products 0.000 claims description 6
- 150000002430 hydrocarbons Chemical class 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 238000006138 lithiation reaction Methods 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 4
- 230000000007 visual effect Effects 0.000 claims description 4
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 3
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 238000005229 chemical vapour deposition Methods 0.000 claims description 3
- 239000011247 coating layer Substances 0.000 claims description 3
- 238000013329 compounding Methods 0.000 claims description 3
- 238000005516 engineering process Methods 0.000 claims description 3
- -1 ethylene, propylene, acetylene Chemical group 0.000 claims description 3
- 238000003384 imaging method Methods 0.000 claims description 3
- MWWATHDPGQKSAR-UHFFFAOYSA-N propyne Chemical compound CC#C MWWATHDPGQKSAR-UHFFFAOYSA-N 0.000 claims description 3
- 239000006229 carbon black Substances 0.000 claims description 2
- 239000000843 powder Substances 0.000 claims description 2
- 239000012798 spherical particle Substances 0.000 claims description 2
- 239000010405 anode material Substances 0.000 abstract description 9
- 230000000694 effects Effects 0.000 abstract description 7
- 238000007599 discharging Methods 0.000 abstract description 3
- 230000015572 biosynthetic process Effects 0.000 abstract description 2
- 238000003786 synthesis reaction Methods 0.000 abstract description 2
- 239000012071 phase Substances 0.000 description 12
- 239000005543 nano-size silicon particle Substances 0.000 description 8
- 239000003575 carbonaceous material Substances 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 6
- 239000010439 graphite Substances 0.000 description 6
- 239000007773 negative electrode material Substances 0.000 description 6
- 239000002153 silicon-carbon composite material Substances 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 4
- 229910003481 amorphous carbon Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 238000003917 TEM image Methods 0.000 description 3
- 238000009830 intercalation Methods 0.000 description 3
- 238000001237 Raman spectrum Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 239000007833 carbon precursor Substances 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000011258 core-shell material Substances 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000011868 silicon-carbon composite negative electrode material Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 229910018540 Si C Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 239000011858 nanopowder Substances 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Classifications
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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
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
- C01B32/963—Preparation from compounds containing silicon
- C01B32/984—Preparation from elemental silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- C01B33/00—Silicon; Compounds thereof
- C01B33/02—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
- 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
- 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
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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
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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- C01P2004/00—Particle morphology
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- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01P2004/32—Spheres
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
A silicon carbide doped silicon powder is prepared by the following steps: a) Adding a silicon source material into a plasma arc located inside the reactor, causing it to evaporate and form silicon vapor; b) Feeding a carbon source material into the silicon vapor to react to obtain silicon carbide vapor; c) And mixing the silicon carbide vapor with excessive silicon vapor, and then introducing the mixture into a cooling section to enable particles to grow and form, thereby obtaining the silicon carbide doped silicon powder. The invention adopts a plasma gas phase synthesis process path, has lower requirements on raw materials and equipment, and the performance of the obtained product is controllable; the silicon carbide vapor and the silicon vapor are synchronously cooled, nucleated and grown to obtain single-particle silicon carbide doped silicon powder with a spheroid shape, so that the volume expansion effect of the silicon anode material in the charging and discharging process can be effectively relieved; (2) The first efficiency and the cycle performance of the prepared lithium battery are better improved compared with those of silicon carbide-doped silicon powder which is not used for preparing the lithium battery anode material after the silicon carbide-doped silicon powder is combined with a carbon source material.
Description
Technical Field
The invention relates to the technical field of nano powder, in particular to a preparation method of silicon carbide doped silicon powder and a silicon-carbon composite negative electrode material of a lithium battery.
Background
With the demands of new energy automobiles, communication, portable equipment and the like for high capacity and high endurance of lithium ion batteries, the development of the lithium ion batteries reaches a bottleneck. For the negative electrode, the currently adopted negative electrode material is various carbon materials mainly containing graphite, the theoretical capacity of the negative electrode material is only 372mAh/g, and the negative electrode material is close to the theoretical capacity in the practical application process and is difficult to reach higher capacity requirements. Therefore, research on high specific capacity anode active materials has been a trend, wherein the theoretical capacity of nano silicon powder is far higher than that of graphite carbon materials, 4200mAh/g can be achieved, and the resources are relatively rich, so that the nano silicon powder is a main choice of next-generation novel silicon carbon anode materials.
However, when silicon powder is used as a cathode material of a lithium battery, several important problems are faced with the urgent need to be solved: (1) In the process of inserting and extracting lithium or extracting lithium, huge volume change is accompanied, so that the silicon negative electrode is cracked, pulverized and separated, and the capacity is rapidly attenuated, thereby seriously affecting the cycle performance. (2) The conductivity of silicon is low and the high-rate discharge requirement of the battery cannot be met. (3) The silicon cathode reacts with the electrolyte to affect the initial effect of the battery, the interface of the silicon cathode is unstable, the silicon cathode is continuously broken in the circulating process, the interface film is also continuously broken, and fresh silicon is exposed in the electrolyte, so that active lithium is continuously consumed, and the capacity is continuously attenuated.
Therefore, the performance of the silicon-based anode material is improved mainly by the technologies of nanocrystallization, carbon coating, loading on a carrier with good electric conduction, pore-forming, prelithiation and the like in the industry.
For example, patent 2017109284430 provides a core-shell silicon-carbon material, wherein the core is a mixed and interwoven structure of nano silicon, carbon nanotubes and graphene, and the shell is coated with carbon. The structure has good conductivity, but the pore structure is limited, no graphite matrix support exists, the volume change of the material during charge and discharge is obvious, the gram volume of the silicon carbon material of the embodiment is high, the initial efficiency is between 1700 and 1800mAh/g, and the initial efficiency is not more than 85 percent.
The patent 2019107260394 discloses a porous carbon-containing silicon-carbon composite material, which is integrally in a core-shell structure, wherein the inner layer is composed of nano silicon, graphite and porous carbon, the outer layer is coated with carbon, a porous carbon precursor is added in a liquid phase form, the porous structure formed after carbonization is porous in the structure, and the space provided for the change of the silicon volume is limited.
The 2019106997897 patent provides a silicon-carbon composite material, wherein a carbon precursor is added in the process of ball milling silicon powder, the obtained slurry is mixed with a graphite matrix, spraying and carbonization are carried out, a structure of graphite, nano silicon and amorphous carbon are mixed with each other, and the amorphous carbon has a porous structure; and then carrying out secondary carbon coating. The porous structure of the internal amorphous carbon provides room for the volume expansion of silicon; and the carbon coating of the outer layer improves the stability of the material. However, amorphous carbon in the inner layer may have incomplete coating of nano silicon, and the conductive continuity between nano silicon is broken, and the outer layer carbon coating adopts solid phase coating, so that the risk of incomplete coating exists.
The characteristics of silicon directly influence the application of the carbon-coated nano-silicon composite material in the lithium battery anode material.
Disclosure of Invention
In order to exert the capacity advantage of the silicon powder applied to the lithium battery cathode material, aiming at the problems that silicon particles are pulverized and a conductive network in an electrode is damaged to cause sharp reduction of the capacity because silicon can show serious volume effect in the charging and discharging process, the inventor adopts silicon carbide to dope the silicon powder to obtain silicon carbide doped silicon powder; after the silicon carbide doped silicon powder is combined with a carbon material, a silicon-carbon material of a lithium battery cathode is formed.
The invention provides silicon carbide doped silicon powder, which is prepared by the following steps:
a) Adding a silicon source material into a plasma arc located inside the reactor, causing it to evaporate and form silicon vapor;
b) Feeding a carbon source material into the silicon vapor in the step a) to react to obtain silicon carbide vapor;
c) Mixing the silicon carbide vapor in the step b) with excessive silicon vapor, and then introducing the mixture into a cooling section to enable particles to grow and form to obtain silicon carbide doped silicon powder;
the silicon source material is granular or powdery pure silicon raw material, the carbon source material is graphite powder or carbon black powder, and the addition ratio of the silicon source material to the carbon source material in unit time is 1:0.05-0.3.
The average particle size of the silicon carbide doped silicon powder is 2-200 nm according to BET specific surface area conversion.
The silicon carbide doped silicon powder is of a polycrystalline structure.
The surface of the silicon carbide doped silicon powder is provided with an oxide layer, the oxygen content of the silicon carbide doped silicon powder is 0.25-10wt%, and the main component of the oxide layer is SiO 2 。
The carbon content of the silicon carbide doped silicon powder is 0.2-20wt%.
Furthermore, the silicon carbide doped silicon powder is spherical-like particles.
Furthermore, the silicon carbide doped silicon powder has segregation in the particles, and has a silicon carbide segregation phase, wherein the silicon carbide segregation phase accounts for not more than 70wt% of the silicon carbide doped silicon powder, and the Si/C molar ratio of the silicon carbide segregation phase is not more than 2.
Silicon carbide doped silicon powder is adopted, so that the cracking problem caused by the volume change of silicon in the process of lithium intercalation and deintercalation or lithium intercalation can be effectively buffered; meanwhile, the silicon carbide is doped, so that the conductivity of the silicon powder is improved; the existence of the surface oxide layer of the silicon carbide doped silicon powder delays and reduces the reaction of silicon and electrolyte. The above-mentioned special materials can effectively improve various bad characteristics when the silicon powder is used as negative electrode material.
The invention also provides a lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material.
The preparation technology which can be adopted by the silicon-carbon composite anode material of the lithium battery comprises the following steps: mechanically compounding silicon carbide doped silicon powder and graphite powder, or coating a carbon layer on the surface of the silicon carbide doped silicon powder by chemical vapor deposition; in the former method, either a carbon material of natural graphite or artificial graphite may be used as the carbon source material; in the latter method, the coated carbon layer can effectively inhibit electrolyte decomposition, improve first effect, reduce irreversible capacity loss, accelerate desolvation of lithium ions, ensure quick passing of lithium ions, avoid damage of co-intercalation of solvent molecules to graphite structures, and ensure stable multiplying power and cycle performance.
Further, the surface of the silicon carbide doped silicon powder is provided with a carbon coating layer after being cracked by hydrocarbon gas, and the hydrocarbon gas is one or more of methane, ethane, ethylene, propylene, acetylene or propyne.
Further, the silicon content of the silicon-carbon composite anode material of the lithium battery is 0.5-15wt%.
Further, after the silicon-carbon composite material is subjected to pre-lithiation treatment, the lithium content of the silicon-carbon composite material is 0.1-10wt%.
Further, the degree of dispersion of the observed particle diameter d1 of the silicon carbide doped silicon powder in the visual field of a preset scanning electron microscope imaging range is represented by an extremely poor R, and r=max (d 1) -Min (d 1), wherein R: d >1, d is the average particle diameter of the silicon carbide doped silicon powder.
The invention has the beneficial effects that:
(1) The preparation method adopts a plasma gas phase synthesis process path, has lower requirements on raw materials and equipment, has controllable performance of the obtained product, and is suitable for industrial production; according to the method, the silicon carbide vapor and the silicon vapor are synchronously cooled, nucleated and grown to obtain single-particle silicon carbide doped silicon powder with a similar spherical morphology, so that the volume expansion effect of the silicon anode material in the charging and discharging process can be effectively relieved, and the problems of damage of the anode structure and sharp reduction of the battery capacity are prevented;
(2) According to the invention, the lithium battery anode material prepared by combining the silicon carbide doped silicon powder with the carbon source material can effectively control the volume expansion of the lithium battery anode material during charge and discharge, and the first efficiency and the cycle performance of the prepared lithium battery are better improved compared with those of the lithium battery without the silicon carbide doped silicon powder.
Drawings
FIG. 1 is an SEM image of silicon carbide doped silicon powder produced in example 1.
Fig. 2 is a TEM image of silicon carbide doped silicon powder prepared in example 1.
Fig. 3 is an XRD pattern of the silicon carbide-doped silicon powder prepared in example 1.
FIG. 4 is a Raman spectrum of the silicon carbide doped silicon powder prepared in example 1.
Detailed Description
The following describes the embodiments of the present invention further with reference to the drawings. It should be noted that the description of these embodiments is for aiding in understanding the present invention, but is not to be construed as limiting the invention. In addition, the technical features described in the following embodiments of the present invention may be combined with each other as long as they do not collide with each other.
The silicon carbide doped silicon powder of the following embodiment is prepared by the following steps:
a) Adding a silicon source material into a plasma arc located inside the reactor, causing it to evaporate and form silicon vapor;
b) Feeding a carbon source material into the silicon vapor to react to obtain silicon carbide vapor;
c) Mixing the silicon carbide vapor with excessive silicon vapor, and then introducing the mixture into a cooling section to enable particles to grow and form to obtain silicon carbide doped silicon powder;
the silicon source material is silicon powder with the purity of 99.99 percent and the average grain diameter of 30 mu m, the carbon source material is graphite powder with the purity of 99.95 percent, and the adding mass ratio of the silicon source material to the carbon source material in unit time is 1:0.05-0.3;
the average grain diameter of the silicon carbide doped silicon powder is 2-200 nm according to BET specific surface area conversion;
the silicon carbide doped silicon powder is of a polycrystalline structure;
the surface of the silicon carbide doped silicon powderThe silicon carbide doped silicon powder has an oxide layer, wherein the oxygen content of the silicon carbide doped silicon powder is 0.25-10wt%, and the main component of the oxide layer is SiO 2 ；
The carbon content of the silicon carbide doped silicon powder is 0.2-20wt%.
The silicon carbide doped silicon powder is similar to spherical particles.
The silicon carbide doped silicon powder has segregation in the particles, and has a silicon carbide segregation phase, wherein the silicon carbide segregation phase accounts for not more than 70 weight percent of the silicon carbide doped silicon powder, and the Si/C molar ratio of the silicon carbide segregation phase is not more than 2.
The following embodiment also provides a lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material, specifically, the silicon carbide doped silicon powder and graphite powder are subjected to mechanical compounding, or hydrocarbon gas is cracked on the surface of the silicon carbide doped silicon powder by a chemical vapor deposition method to form a carbon coating layer.
The hydrocarbon gas is any one or more of methane, ethane, ethylene, propylene, acetylene or propyne.
The silicon content of the silicon-carbon composite anode material of the lithium battery is 0.5-15wt%.
After the silicon-carbon composite material is subjected to pre-lithiation treatment, the lithium content of the silicon-carbon composite material is 0.1-10wt%.
The dispersion degree of the observed particle diameter d1 of the silicon carbide doped silicon powder in the visual field of a preset scanning electron microscope imaging range is represented by an extremely poor R, and R=Max (d 1) -Min (d 1), wherein R: d >1, d is the average particle diameter of the silicon carbide doped silicon powder. :
example 1: the silicon carbide doped silicon powder of the embodiment is prepared by the following steps:
a) Adding a silicon source material into a plasma arc located inside the reactor, causing it to evaporate and form silicon vapor;
b) Feeding a carbon source material into the silicon vapor to react to obtain silicon carbide vapor;
c) Mixing the silicon carbide vapor with excessive silicon vapor, and then introducing the mixture into a cooling section to enable particles to grow and form to obtain silicon carbide doped silicon powder;
wherein, the mass ratio of the silicon source material to the carbon source material added in unit time is 1:0.3; the BET-converted average particle diameter of the obtained silicon carbide-doped silicon powder was 42nm, the oxygen content was 0.8wt%, and the carbon content was 17.4wt%. :
example 2: the silicon carbide doped silicon powder of the embodiment is prepared by the following steps:
a) Adding a silicon source material into a plasma arc torch positioned inside the reactor, allowing it to evaporate and form silicon vapor;
b) Feeding a carbon source material into the silicon vapor to react to obtain silicon carbide vapor;
c) Mixing the silicon carbide vapor with excessive silicon vapor, and carrying out cooling section through an air carrying belt to enable particles to grow and shape so as to obtain silicon carbide doped silicon powder;
wherein, the mass ratio of the silicon source material to the carbon source material added in unit time is 1:0.05; the BET-converted average particle diameter of the obtained silicon carbide-doped silicon powder was 200nm, the oxygen content was 9.8wt%, and the carbon content was 0.4wt%. Comprehensively calculating to obtain the silicon carbide segregation phase accounting for 1.6wt% of the silicon carbide doped silicon powder, wherein the C/Si molar ratio of the silicon carbide segregation phase is 0.65-0.84.
Example 3: in the embodiment, the silicon carbide doped silicon powder obtained in the embodiment 1 and argon are subjected to heat preservation for 6 hours in a tube furnace at 1000 ℃, and then the mixture of the silicon carbide doped silicon powder and graphite is calcined in a sintering furnace under a vacuum condition, so that the silicon-carbon composite negative electrode material of the lithium battery is prepared. The silicon content of the obtained lithium battery silicon-carbon composite anode material is 13.8 weight percent, and the lithium content of the lithium battery silicon-carbon composite anode material after the pre-lithiation treatment is 0.3 weight percent.
Example 4: in this example, the silicon carbide doped silicon powder obtained in example 2 was placed in a tube furnace while mixing the silicon carbide doped silicon powder with a silicon carbide powder at a ratio of 10: and (3) introducing mixed gas of argon and acetylene according to the flow ratio of 1, gradually heating to 1000 ℃, preserving heat for 18 hours, and then naturally cooling the product under the protection of argon atmosphere to prepare the silicon-carbon composite anode material of the lithium battery. The silicon content of the obtained lithium battery silicon-carbon composite anode material is 4.7 weight percent, and the lithium content of the lithium battery silicon-carbon composite anode material after pre-lithiation treatment is 1.4 weight percent. :
comparative example 1: this comparative example first employs the procedure of example 1, except that: the carbon source material is not added in the step b), the final product is silicon powder, the BET conversion average grain diameter of the silicon powder is 37nm, and the oxygen content is 2.1wt%; the silicon powder obtained was then used to prepare a silicon-based negative electrode material in the manner of example 3.
Effect example 1: fig. 1 and 2 are SEM images and TEM images of silicon carbide doped silicon powder obtained in example 1, respectively, and it can be seen from fig. 1 that the silicon carbide doped silicon powder particles are spherical or spheroid, the particle size of the particles in the visual range is not more than 100nm and the degree of dispersion is large, and R: d >2.7, and it can be seen from fig. 2 that silicon carbide is unevenly distributed in the silicon powder particles, and most of silicon carbide is located inside the silicon powder particles to form silicon carbide segregation phase, and a coating shell-like structure is partially formed, and a very small amount of silicon carbide particles are additionally present. And comprehensively measuring and calculating according to TEM image results under multiple views to obtain the silicon carbide segregation phase accounting for 46% of the silicon carbide doped silicon powder.
FIGS. 3 and 4 are respectively XRD patterns and Raman spectra of the silicon carbide doped silicon powder obtained in example 1, and as can be seen from FIG. 3, characteristic diffraction peaks of the faces of typical beta-SiC (111), (200), (220) and (311) appear at 35.7 degrees, 41.7 degrees, 60.2 degrees and 72 degrees respectively, and diffraction peaks of carbon are not found, so that the reaction is relatively complete, and the crystallinity of the obtained silicon carbide doped silicon powder is relatively good; also visible from FIG. 4 is 800cm -1 The silicon carbide doped silicon powder obtained in example 1 has a slightly weaker Si-C vibration absorption peak, and no characteristic peak other than Si is found. Based on the above electron microscopic results, the C/Si molar ratio of the segregated phase of silicon carbide in example 1 was estimated to be 0.81-0.96.
Effect example 2: the negative electrode materials obtained in example 3, example 4 and comparative example 1 were slurried with a conductive agent and a binder and coated on a copper foil current collector to prepare a negative electrode sheet, which was then assembled with a lithium sheet counter electrode and LiPF6/ec+dmc electrolyte to form a 2032 coin cell. Buckling test conditions: the blue battery test system is adopted, the charge and discharge cut-off voltage is 0.005-1.5V, the discharge multiplying power is that the discharge multiplying power is firstly put to 0.005V at 0.1C, then put to 0.005V at 0.01C, the charge multiplying power is that the charge is 0.1C and is charged to 1.5V, the first-circle discharge capacity and the charge capacity of the battery are recorded, and the first effect= (charge capacity/discharge capacity) ×100%. And (3) testing the cycle performance: the charge-discharge multiplying power is 1C/1C, the voltage range is 2.5V-4.2V, and the test environment temperature is 25+/-2 ℃. The test results are shown in Table 1.
| Gram volume (mAh/g) | First cycle efficiency (%) | Capacity retention of 100 cycles (%) | |
| Example 3 | 1434 | 92.6 | 88.3 |
| Example 4 | 1359 | 89.1 | 90.7 |
| Comparative example 1 | 1613 | 83.5 | 63.8 |
As can be seen from table 1, the silicon-carbon composite anode material prepared by the invention can effectively solve the problem of poor cycle performance of the silicon-based anode material, and can maintain higher capacitance.
Claims (10)
1. A preparation method of silicon carbide doped silicon powder is characterized by comprising the following steps: the preparation method comprises the following steps:
a) Adding a silicon source material into a plasma arc located inside the reactor, causing it to evaporate and form silicon vapor;
b) Feeding a carbon source material into the silicon vapor in the step a) to react to obtain silicon carbide vapor;
c) And b) mixing the silicon carbide vapor in the step b) with excessive silicon vapor, and then introducing the mixture into a cooling section to enable particles to grow and form, thereby obtaining the silicon carbide doped silicon powder.
2. A method for preparing silicon carbide doped silicon powder as defined in claim 1, wherein: the silicon source material is granular or powdery pure silicon raw material, the carbon source material is graphite powder or carbon black powder, and the adding amount ratio of the silicon source material to the carbon source material in unit time is 1:0.05-0.3.
3. A method for preparing silicon carbide doped silicon powder as defined in claim 1, wherein: the average particle size of the silicon carbide doped silicon powder is 2-200 nm according to BET specific surface area conversion.
4. A method for preparing silicon carbide doped silicon powder as defined in claim 1, wherein: the silicon carbide doped silicon powder is of a polycrystalline structure, an oxide layer is arranged on the surface of the silicon carbide doped silicon powder, the oxygen content of the silicon carbide doped silicon powder is 0.25-10wt%, the carbon content of the silicon carbide doped silicon powder is 0.2-20wt%, and the main component of the oxide layer is SiO 2 。
5. A method for preparing silicon carbide doped silicon powder as defined in claim 1, wherein: the silicon carbide doped silicon powder is similar to spherical particles, segregation exists in the particles of the silicon carbide doped silicon powder, the silicon carbide doped silicon powder has silicon carbide segregation phases, the silicon carbide segregation phases account for not more than 70wt% of the silicon carbide doped silicon powder, and the Si/C molar ratio of the silicon carbide segregation phases is not more than 2.
6. The lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material is characterized in that: the preparation technology which can be adopted by the silicon-carbon composite anode material of the lithium battery comprises the following steps: and mechanically compounding the silicon carbide doped silicon powder with graphite powder, or coating a carbon layer on the surface of the silicon carbide doped silicon powder by chemical vapor deposition.
7. The lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material as claimed in claim 6, wherein the silicon carbide doped silicon powder is characterized in that: the surface of the silicon carbide doped silicon powder is provided with a carbon coating layer after being cracked by hydrocarbon gas, and the hydrocarbon gas is one or more of methane, ethane, ethylene, propylene, acetylene or propyne.
8. The lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material as claimed in claim 6, wherein the silicon carbide doped silicon powder is characterized in that: the silicon content of the silicon-carbon composite anode material of the lithium battery is 0.5-15wt%.
9. The lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material as claimed in claim 6, wherein the silicon carbide doped silicon powder is characterized in that: after the lithium battery silicon-carbon composite anode material is subjected to pre-lithiation treatment, the lithium content of the lithium battery silicon-carbon composite anode material is 0.1-10wt%.
10. The lithium battery silicon-carbon composite anode material prepared by combining the silicon carbide doped silicon powder and a carbon source material as claimed in claim 6, wherein the silicon carbide doped silicon powder is characterized in that: the dispersion degree of the observed particle diameter d1 of the silicon carbide doped silicon powder in the visual field of a preset scanning electron microscope imaging range is represented by an extremely poor R, and R=Max (d 1) -Min (d 1), wherein R: d >1, d is the average particle diameter of the silicon carbide doped silicon powder.
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| CN1636870A (en) * | 2004-12-30 | 2005-07-13 | 清华大学 | Nanometer SiC powder preparing process |
| CN108649197A (en) * | 2018-02-07 | 2018-10-12 | 光宇材料股份有限公司 | Nitrogen-doped carbon-silicon composite material and manufacturing method thereof |
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