JP7384829B2 - Silicon fine particles and their manufacturing method - Google Patents
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 141
- 229910052710 silicon Inorganic materials 0.000 title claims description 133
- 239000010703 silicon Substances 0.000 title claims description 133
- 239000010419 fine particle Substances 0.000 title claims description 111
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 239000002245 particle Substances 0.000 claims description 42
- 239000007789 gas Substances 0.000 claims description 39
- 239000002243 precursor Substances 0.000 claims description 34
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 27
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 27
- 239000000460 chlorine Substances 0.000 claims description 27
- 229910052801 chlorine Inorganic materials 0.000 claims description 27
- 239000001301 oxygen Substances 0.000 claims description 27
- 229910052760 oxygen Inorganic materials 0.000 claims description 27
- 239000011164 primary particle Substances 0.000 claims description 24
- 239000012535 impurity Substances 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 5
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 4
- FDNAPBUWERUEDA-UHFFFAOYSA-N silicon tetrachloride Chemical compound Cl[Si](Cl)(Cl)Cl FDNAPBUWERUEDA-UHFFFAOYSA-N 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 description 31
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 28
- 238000010438 heat treatment Methods 0.000 description 27
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 description 26
- 239000005052 trichlorosilane Substances 0.000 description 26
- 238000000034 method Methods 0.000 description 21
- 238000006298 dechlorination reaction Methods 0.000 description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 13
- 229910052757 nitrogen Inorganic materials 0.000 description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 11
- 238000001816 cooling Methods 0.000 description 11
- 229910052744 lithium Inorganic materials 0.000 description 10
- 239000011856 silicon-based particle Substances 0.000 description 10
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 9
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 9
- 239000005049 silicon tetrachloride Substances 0.000 description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 229910002804 graphite Inorganic materials 0.000 description 7
- 239000010439 graphite Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 239000007773 negative electrode material Substances 0.000 description 7
- 239000011863 silicon-based powder Substances 0.000 description 7
- 238000005979 thermal decomposition reaction Methods 0.000 description 7
- 239000011859 microparticle Substances 0.000 description 6
- 229910021426 porous silicon Inorganic materials 0.000 description 6
- 239000011163 secondary particle Substances 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000011149 active material Substances 0.000 description 5
- 125000001309 chloro group Chemical group Cl* 0.000 description 5
- 230000008602 contraction Effects 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 description 4
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 229910000077 silane Inorganic materials 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000005046 Chlorosilane Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002401 inhibitory effect Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000005169 Debye-Scherrer Methods 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910000676 Si alloy Inorganic materials 0.000 description 2
- 229910003902 SiCl 4 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- 229910018077 Li 15 Si 4 Inorganic materials 0.000 description 1
- 229910013458 LiC6 Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- OLBVUFHMDRJKTK-UHFFFAOYSA-N [N].[O] Chemical compound [N].[O] OLBVUFHMDRJKTK-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 239000012717 electrostatic precipitator Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000005543 nano-size silicon particle Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000004756 silanes Chemical class 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- 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
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、新規なシリコン微粒子とその製造方法に関する。詳しくは、リチウムイオン二次電池の負極材料に好適なシリコン微粒子および、該微粒子の製造方法を提供するものである。 The present invention relates to novel silicon fine particles and a method for manufacturing the same. Specifically, the present invention provides silicon fine particles suitable for negative electrode materials of lithium ion secondary batteries and a method for producing the fine particles.
現在、シリコンは、リチウムイオン二次電池の電極材（負極材）をはじめとして種々の用途に使用され或いはその使用が提案されている。
従来、リチウムイオン二次電池の負極材にはグラファイト、黒鉛などのカーボン系材料が一般的に使用されているが、理論容量が３７２ｍＡｈ／ｇ（ＬｉＣ6までリチウム化した場合）と低く、より高容量の負極材料が望まれている。シリコンは、カーボン材料に比べて単位質量あたりのリチウムの吸蔵量が大きく、理論容量が３，５７９ｍＡｈ／ｇ（Ｌｉ15Ｓｉ4までリチウム化した場合）と非常に高容量であり、次世代の負極材として検討されている。Currently, silicon is used or proposed for various uses, including as an electrode material (negative electrode material) for lithium ion secondary batteries.
Conventionally, carbon-based materials such as graphite and graphite have been commonly used as negative electrode materials for lithium-ion secondary batteries, but their theoretical capacity is as low as 372 mAh/g (when lithiated up to LiC6 ), and higher Capacitive negative electrode materials are desired. Silicon has a larger lithium storage capacity per unit mass than carbon materials, and has an extremely high theoretical capacity of 3,579 mAh/g (when Li 15 Si 4 is lithiated), making it an ideal material for next-generation negative electrodes. It is being considered as a material.
シリコンをリチウムイオン二次電池の負極材として使用する場合の課題として、シリコンとリチウムが合金を形成してリチウムを吸蔵する際の体積膨張が大きく、充放電による膨張収縮の繰り返しによって、歪エネルギーが内部に蓄積して、シリコンが粉々に破断して空隙が発生し、電気伝導性やイオン伝導性を喪失することで負極の充電容量が低下することが挙げられる。 When using silicon as a negative electrode material for lithium-ion secondary batteries, the problem is that when silicon and lithium form an alloy and absorb lithium, the volumetric expansion is large, and repeated expansion and contraction due to charging and discharging causes strain energy to increase. When it accumulates inside, the silicon breaks into pieces, creating voids and losing electrical conductivity and ionic conductivity, resulting in a decrease in the charging capacity of the negative electrode.
そこで本発明者らは、結晶子径の小さい多結晶型であり、かつ体積膨張を緩和する空隙を有するシリコン微粒子を使用することに着目した。
シリコン微粒子として、特許第５６１８１１３号公報（特許文献１）には、２０ｎｍ乃至２００ｎｍの平均一次粒子径を有するシリコン粉末であって、前記粉末は０＜ｘ＜２のＳｉＯｘ表面層を有し、前記表面層は０．５ｎｍ乃至１０ｎｍの平均厚さを有し、かつ前記粉末は室温で３質量％以下の全酸素含量を有する、シリコン粉末が開示されている。Therefore, the present inventors focused on using silicon microparticles that are polycrystalline with a small crystallite diameter and have voids that alleviate volume expansion.
As silicon fine particles, Japanese Patent No. 5618113 (Patent Document 1) describes a silicon powder having an average primary particle diameter of 20 nm to 200 nm, the powder having a SiOx surface layer of 0<x<2, A silicon powder is disclosed in which the surface layer has an average thickness of 0.5 nm to 10 nm and the powder has a total oxygen content of 3% by weight or less at room temperature.
また、特許第５３３８６７６号公報（特許文献２）には、多結晶珪素の結晶子の粒子径が、Ｘ線回折パターンの分析において２θ＝２８．４°付近のＳｉ（１１１）に帰属される回折線の半値全幅よりシェラー法（Ｓｃｈｅｒｒｅｒ法）で求められる該結晶子サイズで２０ｎｍ以上１００ｎｍ以下であり、真比重が２．３００～２．３２０であるシリコン粒子が開示されている。特許文献２では、前記多結晶ケイ素粒子を、クロロシランガスを原料として１，０００℃以下の熱分解により製造することが開示されている。 Furthermore, in Japanese Patent No. 5338676 (Patent Document 2), it is disclosed that the particle size of polycrystalline silicon crystallites is attributed to Si(111) near 2θ=28.4° in the analysis of an X-ray diffraction pattern. Silicon particles are disclosed that have a crystallite size of 20 nm or more and 100 nm or less as determined by the Scherrer method from the full width at half maximum of a line, and a true specific gravity of 2.300 to 2.320. Patent Document 2 discloses that the polycrystalline silicon particles are produced by thermal decomposition at 1,000° C. or lower using chlorosilane gas as a raw material.
さらには、特許第４６０７１２２号公報および特表２００７－５１１４６０号公報（特許文献３および４）には、凝集した結晶質シリコン粉末において、２０～１５０ｍ2／ｇのＢＥＴ表面積を有し、リン、ヒ素、（中略）、銅、銀、金又は亜鉛によりドープされていることを特徴とする凝集した結晶質シリコン粉末が開示されており、その製造方法として蒸気もしくは気体状のシラン（シランにはクロロシランも含む）と蒸気もしくは気体状の前記ドープ材料、不活性ガスおよび、水素をホットウォール反応器中で加熱し反応させる方法が開示されている。Furthermore, in Japanese Patent No. 4607122 and Japanese Translated Patent Publication No. 2007-511460 (Patent Documents 3 and 4), agglomerated crystalline silicon powder has a BET surface area of 20 to 150 m 2 /g, and contains phosphorus, arsenic, etc. (omitted), discloses an agglomerated crystalline silicon powder characterized in that it is doped with copper, silver, gold or zinc, and a method for its production using vapor or gaseous silane (silane also includes chlorosilane). Disclosed is a method of heating and reacting the dope material in vapor or gaseous form, an inert gas, and hydrogen in a hot wall reactor.
しかし、これらの特許文献においては、シリコン微粒子の結晶子径を有効に制御する方法、特にクロロシランを原料とした場合に塩素含有量を調整する意義および方法、またシリコンの膨張を緩和する空隙を保持する方法等について全く示唆がない。 However, these patent documents describe a method for effectively controlling the crystallite size of silicon fine particles, the significance and method of adjusting the chlorine content when chlorosilane is used as a raw material, and the retention of voids to alleviate the expansion of silicon. There is no suggestion whatsoever as to how to do so.
一方、空隙を有する多孔質シリコン粒子としては、特許第５５９８８６１号公報（特許文献５）では、複数のシリコン微粒子が接合してなる多孔質シリコン粒子であって、シリコン微粒子の平均粒径または平均支柱径が１０ｎｍ～５００ｎｍであり、多孔質シリコン粒子の平均粒径が０．１μｍ～１０００μｍであり、多孔質シリコン粒子は連続した空隙を有する三次元網目構造を有し、かつ多孔質シリコン粒子の平均空隙率が１５～９３％のものが開示されている。なお、この三次元網目構造を有する多孔質シリコン粒子は、シリコンと他の中間合金元素との合金を作製し、シリコン微粒子と第２相とを分離させたのち、第２相を除去することで、製造できる旨が開示されている。 On the other hand, as a porous silicon particle having voids, Japanese Patent No. 5598861 (Patent Document 5) describes a porous silicon particle formed by bonding a plurality of silicon fine particles, which has an average particle diameter or an average support column of the silicon fine particles. The diameter is 10 nm to 500 nm, the average particle size of the porous silicon particles is 0.1 μm to 1000 μm, the porous silicon particles have a three-dimensional network structure with continuous voids, and the average particle size of the porous silicon particles is 0.1 μm to 1000 μm. A material having a porosity of 15 to 93% is disclosed. In addition, porous silicon particles having this three-dimensional network structure can be obtained by preparing an alloy of silicon and other intermediate alloying elements, separating the silicon fine particles from the second phase, and then removing the second phase. , it is disclosed that it can be manufactured.
また、特許第３８２７６４２号公報（特許文献６）には、Ｓｉのみからなる多孔質粒子の集合体からなり、前記多孔質粒子の内部に平均孔径が１０ｎｍ以上１０μｍ以下の範囲である多数のボイドが形成され、前記集合体の平均粒径が１μｍ以上１００μｍ以下の範囲であり、前記多孔質粒子の組織の一部がＳｉの非晶質相であり、残部がＳｉの結晶質相であることが開示されている。特許文献６では、この多孔質粒子を、シリコンを含む合金から他の元素を酸またはアルカリによって、溶出除去することで、多孔質粒子を製造する旨が開示されている。 Furthermore, Japanese Patent No. 3827642 (Patent Document 6) discloses that the porous particles are composed of an aggregate of porous particles made only of Si, and inside the porous particles there are many voids with an average pore diameter in the range of 10 nm or more and 10 μm or less. formed, the average particle size of the aggregate is in the range of 1 μm or more and 100 μm or less, and the structure of the porous particles is partially an amorphous phase of Si and the remainder is a crystalline phase of Si. Disclosed. Patent Document 6 discloses that porous particles are manufactured by eluting and removing other elements from an alloy containing silicon using acid or alkali.
しかし、これらの特許文献に開示の方法、すなわち多孔質粒子の製造方法としてシリコン合金を相分離させ、分離した第２相を除去するものは製造方法が煩雑であるため、工業的かつ安価に空隙を有する多結晶シリコン微粒子を大量製造することは困難である。 However, the methods disclosed in these patent documents, that is, the methods for producing porous particles in which a silicon alloy is phase-separated and the separated second phase is removed, are complicated, and therefore voids can be produced industrially and inexpensively. It is difficult to mass-produce polycrystalline silicon fine particles having .
以上のように、結晶子径の小さい多結晶型であり、かつ体積膨張を緩和する空隙を有するシリコン微粒子を工業的に生産する有効な方法はこれまで見出されていない。 As described above, an effective method for industrially producing silicon microparticles that are polycrystalline with a small crystallite diameter and have voids that alleviate volume expansion has not been found so far.
従って、本発明の目的は、リチウムと合金化する際の膨張収縮による破壊・変形が少なく、膨張収縮を緩和する空隙を有し、安全性（耐酸化性）にも優れるシリコン微粒子およびその製造方法を提供することにある。 Therefore, an object of the present invention is to provide silicon fine particles that are less likely to be destroyed or deformed due to expansion and contraction when alloyed with lithium, have voids that alleviate expansion and contraction, and have excellent safety (oxidation resistance), and a method for producing the same. Our goal is to provide the following.
本発明者らは、上記課題を解決するために、多結晶一次粒子の平均結晶子径および平均直径とともに、塩素含有濃度が、所定の範囲にあるシリコン微粒子は、上記課題をいずれも解決できることを見出し、本発明を完成するに至った。 In order to solve the above problems, the present inventors have found that silicon fine particles in which the average crystallite diameter and average diameter of polycrystalline primary particles as well as the chlorine content concentration are within a predetermined range can solve all of the above problems. This discovery led to the completion of the present invention.
本発明にかかるシリコン微粒子は、平均結晶子径が２０～４０ｎｍ、平均直径が８０～９００ｎｍの範囲にある多結晶一次粒子が部分融着した不定形の凝集粒子よりなり、且つ、塩素濃度が粒子重量に対し０．１～１．０質量％であることを特徴とする。 The silicon fine particles according to the present invention are composed of amorphous aggregated particles in which polycrystalline primary particles having an average crystallite size in the range of 20 to 40 nm and an average diameter in the range of 80 to 900 nm are partially fused, and the chlorine concentration is in the particle size. It is characterized by being 0.1 to 1.0% by mass based on weight.
前記多結晶一次粒子の平均直径は、１３０～８５０ｎｍであることが好ましい態様である。 前記シリコン微粒子は、１０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度が１．３ｇ／ｃｍ3以下であることが好ましい態様である。また、５０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度が１．８ｇ／ｃｍ3以下であることが好ましい態様である。In a preferred embodiment, the average diameter of the polycrystalline primary particles is 130 to 850 nm. In a preferred embodiment, the silicon fine particles have a bulk density of 1.3 g/cm 3 or less when a load of 10 kN/cm 2 is applied. Further, it is a preferred embodiment that the bulk density is 1.8 g/cm 3 or less when a load of 50 kN/cm 2 is applied.
また、粒子中に不純物として含まれる酸素の濃度Ｃｏ［質量％］と比表面積Ｓ［ｍ2／ｇ］の比Ｃｏ／Ｓが０．０５未満であることが好ましい態様である。
前記特性のシリコン微粒子は、塩化珪素ガスを６００～９００℃の温度で熱分解して得られたシリコン微粒子前駆体を、組成に酸素原子を含まないガスの流通下、または減圧下で９００℃を超えて１２００℃以下に加熱することで製造することができる。Further, it is a preferred embodiment that the ratio Co/S between the concentration Co [mass %] of oxygen contained as an impurity in the particles and the specific surface area S [m 2 /g] is less than 0.05.
Silicon fine particles having the above characteristics are produced by heating a silicon fine particle precursor obtained by thermally decomposing silicon chloride gas at a temperature of 600 to 900°C at 900°C under flowing a gas that does not contain oxygen atoms in its composition or under reduced pressure. It can be produced by heating above 1200°C or below.
本発明のシリコン微粒子は、塩素が低量ながら所定の割合で含まれており、平均結晶子径が所定の範囲にある多結晶一次粒子が部分融着した不定形の凝集粒子よりなり、充放電の際に、リチウムとの合金化による体積変化が少なく、しかも表面酸化物の影響も少ない。
また、酸素量を比表面積との比率を特定の範囲に調整されたものは、酸素の影響を極めて少なくすることができ、充電容量の低下を防止することができるので好ましい。The silicon fine particles of the present invention contain a low amount of chlorine in a predetermined proportion, and are composed of irregularly shaped aggregated particles in which polycrystalline primary particles with an average crystallite diameter within a predetermined range are partially fused, and are chargeable and dischargeable. At this time, there is little change in volume due to alloying with lithium, and there is also little influence from surface oxides.
Further, a battery in which the ratio of the amount of oxygen to the specific surface area is adjusted within a specific range is preferable because the influence of oxygen can be extremely reduced and a decrease in charging capacity can be prevented.
本発明の製造方法では、トリクロロシランの熱分解工程と、得られたシリコン微粒子前駆体の脱塩素工程とからなる２段階の加熱工程を所定の温度で採用することで上記の特徴を有するシリコン微粒子を効率的に生産できる。 In the manufacturing method of the present invention, silicon fine particles having the above-mentioned characteristics are obtained by employing a two-step heating process consisting of a thermal decomposition process of trichlorosilane and a dechlorination process of the obtained silicon fine particle precursor at a predetermined temperature. can be produced efficiently.
このような本発明のシリコン微粒子は、荷重をかけた際の嵩密度が小さく、プレス成型してもその空隙を保持できるので、充電時の電極の体積膨張を空隙が吸収することで体積変化を抑制できる。 The silicon fine particles of the present invention have a low bulk density when a load is applied, and can retain their voids even when press-molded, so the voids absorb volumetric expansion of the electrode during charging, thereby reducing volume change. It can be suppressed.
本発明のシリコン微粒子は、グラファイト、黒鉛などのカーボン材料や、酸化ケイ素、スズ、アンチモン、マグネシウム、ビスマスなどの既知の負極材料と混合した複合物の形態、またはシリコン単体で、全固体電池やゲル状の電解質を用いた電池を含むリチウムイオン二次電池の負極の活物質として使用することが可能である。 The silicon fine particles of the present invention can be in the form of a composite mixed with a carbon material such as graphite or graphite, or a known negative electrode material such as silicon oxide, tin, antimony, magnesium, or bismuth, or in the form of a single silicon, used in all-solid-state batteries or gels. It can be used as an active material for the negative electrode of lithium ion secondary batteries, including batteries using such electrolytes.
以下、本発明の実施の形態を説明するが本発明はこれらの記載に何ら限定されるものではない。
＜シリコン微粒子＞
本発明にかかるシリコン微粒子は、多結晶一次粒子が部分融着した不定形の凝集粒子からなる。Embodiments of the present invention will be described below, but the present invention is not limited to these descriptions.
<Silicon fine particles>
The silicon fine particles according to the present invention are composed of amorphous aggregated particles in which polycrystalline primary particles are partially fused.
結晶子径の大きい、単結晶に近いシリコン微粒子はリチウムイオン電池の負極材として用いられた場合、リチウムと反応して合金を形成する際の相変化が大きいために、負極の膨張率が大きくなることが知られている。本発明のシリコン微粒子は、アモルファスまたは多結晶型またはその混合物であり、好ましくは多結晶型であり、多結晶一次粒子の平均結晶子径は、２０～４０ｎｍ、好ましくは２５～３５ｎｍの範囲にある。なお平均結晶子径は、Ｘ線回折パターンからＳｃｈｅｒｒｅｒ法、Ｗｉｌｌａｍｓｏｎ－Ｈａｌｌ法、Ｈａｌｄｅｒ－Ｗａｇｎｅｒ法などの方法で解析できる。 When fine silicon particles with a large crystallite diameter and close to a single crystal are used as a negative electrode material in a lithium-ion battery, the expansion rate of the negative electrode increases due to the large phase change when reacting with lithium to form an alloy. It is known. The silicon fine particles of the present invention are amorphous or polycrystalline, or a mixture thereof, preferably polycrystalline, and the average crystallite diameter of the polycrystalline primary particles is in the range of 20 to 40 nm, preferably 25 to 35 nm. . Note that the average crystallite diameter can be analyzed from the X-ray diffraction pattern by a method such as the Scherrer method, the Williamson-Hall method, or the Halder-Wagner method.
シリコン微粒子の結晶性をシリコン単体で制御することは困難であり、第二成分の存在が重要となるが、本発明のシリコン微粒子ではこの役割を塩素原子が担っている。一般に、シリコン原子と結合した塩素基は反応活性が高く、空気中などの水分と速やかに反応して塩化水素ガスを放出して酸化するため、塩素の残存したシリコン微粒子を安全に取り扱うことは難しいと考えられている。しかし、本発明者らの研究によれば、シリコン微粒子中に残存する塩素は、粒子表面近傍に露出する塩素基のみが高活性であり、粒子内部に存在する塩素はほとんど反応性を有しない。さらに、シリコン微粒子内に所定量の塩素を含有させておくと、シリコンの結晶化を阻害して結晶子径を小さく保つことができる。本発明のシリコン微粒子中の塩素濃度は、粒子重量に対し０．１～１．０質量％であり、好ましくは０．３～０．８質量％の範囲にある。塩素を所定の範囲で含んでいると、シリコンの結晶化を妨げることで結晶子径の増大を抑制し、リチウムとシリコンが合金化する際の膨張を抑制する効果がある。塩素が少なすぎると、塩素を含む効果が薄くなり膨張抑制の効果は得られず、塩素が多すぎると粒子表面に残存した反応性の高い塩素基が空気中の水分と反応して酸素不純物が増えたり、その他の電池材料と反応して塩化物を生成したりする場合があり好ましくない。 It is difficult to control the crystallinity of silicon fine particles using silicon alone, and the presence of a second component is important, and in the silicon fine particles of the present invention, chlorine atoms play this role. In general, chlorine groups bonded to silicon atoms have high reactivity and quickly react with moisture in the air, releasing hydrogen chloride gas and oxidizing, making it difficult to safely handle silicon particles with residual chlorine. It is believed that. However, according to research by the present inventors, of the chlorine remaining in silicon fine particles, only the chlorine groups exposed near the particle surface are highly active, and the chlorine present inside the particles has almost no reactivity. Furthermore, if a predetermined amount of chlorine is contained in the silicon fine particles, crystallization of silicon can be inhibited and the crystallite size can be kept small. The chlorine concentration in the silicon fine particles of the present invention is in the range of 0.1 to 1.0% by mass, preferably 0.3 to 0.8% by mass based on the particle weight. When chlorine is contained within a predetermined range, it has the effect of inhibiting crystallization of silicon, thereby inhibiting an increase in crystallite diameter, and inhibiting expansion when lithium and silicon are alloyed. If there is too little chlorine, the effect of containing chlorine will be diluted and the expansion suppression effect will not be obtained, and if there is too much chlorine, the highly reactive chlorine groups remaining on the particle surface will react with moisture in the air, creating oxygen impurities. This is undesirable because it may increase in amount or react with other battery materials to produce chlorides.
また、シリコン微粒子を負極として用いる場合、一次粒子の直径も重要である。一次粒子の直径が大きすぎる場合、リチウムとの反応に伴う膨張収縮によってシリコン微粒子が破断することで導電性を喪失し、電池性能におけるサイクル特性が悪化することが知られている。逆に、一次粒子の直径が小さすぎる場合、比表面積が増大することによってシリコン微粒子表面に生成される電解液の分解生成物（ＳＥＩ）の量が多くなり、電池性能における初期充放電効率が低下することが知られている。本発明のシリコン微粒子における一次粒子の平均直径は８０～９００ｎｍ、好ましくは１３０～８５０ｎｍ、より好ましくは１５０～３００ｎｍの範囲にある。上記シリコン微粒子における一次粒子の平均直径は、比表面積より求めたものである。 Furthermore, when using silicon fine particles as a negative electrode, the diameter of the primary particles is also important. It is known that when the diameter of the primary particles is too large, the silicon fine particles break due to expansion and contraction due to reaction with lithium, resulting in loss of conductivity and deterioration of cycle characteristics in battery performance. On the other hand, if the diameter of the primary particles is too small, the specific surface area increases, which increases the amount of electrolyte decomposition products (SEI) generated on the surface of the silicon fine particles, reducing the initial charge and discharge efficiency in battery performance. It is known to do. The average diameter of primary particles in the silicon fine particles of the present invention is in the range of 80 to 900 nm, preferably 130 to 850 nm, more preferably 150 to 300 nm. The average diameter of the primary particles in the silicon fine particles was determined from the specific surface area.
このような一次粒子の平均直径を有するものは、充放電に伴う粒子の膨張収縮によって粒子が破断することもなく、また、粒子表面におけるＳＥＩ層の形成が過度に生じることもない。 If the primary particles have such an average diameter, the particles will not be broken due to expansion and contraction of the particles due to charging and discharging, and the formation of an SEI layer on the particle surface will not occur excessively.
二次粒子は、多結晶一次粒子が部分融着した凝集粒子から構成される。部分融着は、一次粒子が数珠状や網目状に連結し、連結部が狭窄したネック部を構成する。凝集粒子である二次粒子自体は不定形であるため粒子径や形状を特定できないが、電池の負極として用いる際には二次粒子の大きさが形成する負極の厚みを越えないことが重要であり、平均直径（不定形粒子においては最長径）を２０μｍ以下、好ましくは１０μｍ以下、さらに好ましくは５μｍ以下にすることが望ましい。 The secondary particles are composed of aggregated particles in which polycrystalline primary particles are partially fused. In partial fusion, primary particles are connected in a bead-like or mesh-like manner, and the connected portion forms a narrow neck portion. The particle size and shape cannot be determined because the secondary particles themselves, which are aggregated particles, are amorphous, but when used as a negative electrode for a battery, it is important that the size of the secondary particles does not exceed the thickness of the negative electrode formed. It is desirable that the average diameter (the longest diameter for irregularly shaped particles) be 20 μm or less, preferably 10 μm or less, and more preferably 5 μm or less.
本発明のシリコン微粒子は二次粒子内に空隙を有するとともに、また他の二次粒子との間にも他の粒子が入ることができない空隙を有する。かかる空隙は電極作成時に加圧成型する際にも維持される。通常、リチウムイオン電池の負極として用いられる場合、シリコンとリチウムの反応によってシリコンが合金化する際に大きく体積膨張するが、本発明では、空隙を含む凝集粒子を使用するため、シリコンの体積膨張を凝集粒子の空隙が緩和することで負極の体積膨張を効果的に抑制することができる。 The silicon fine particles of the present invention have voids within the secondary particles, and also have voids between them and other secondary particles that prevent other particles from entering. Such voids are maintained even during pressure molding during electrode production. Normally, when used as the negative electrode of a lithium-ion battery, the volume expands significantly when silicon is alloyed by the reaction between silicon and lithium. However, in the present invention, since agglomerated particles containing voids are used, the volume expansion of silicon is reduced. By relaxing the voids of the aggregated particles, volumetric expansion of the negative electrode can be effectively suppressed.
本発明のシリコン微粒子は特に高い荷重をかけたときの嵩密度が小さく、空隙を保持する特性を有する。電池の電極作製時には電極と集電体との密着性の向上、電極の電気伝導性の向上のため一般的に強い荷重をかけて成形されるが、電池の高性能化に伴ってこの荷重は近年増加する傾向にある。従来の製造方法で得られたシリコン微粒子は、より強い荷重をかけたときに空隙が詰まって微粒子が充填されるために嵩密度が大きくなるが、本発明のシリコン微粒子では空隙が保持されるため、嵩密度は小さく保たれる。本発明のシリコン微粒子は、１０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度が１．３ｇ／ｃｍ3以下、好ましくは１．１ｇ／ｃｍ3以下であることが好ましい態様である。また、５０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度が１．８ｇ／ｃｍ3以下、好ましくは１．５ｇ／ｃｍ3以下であることが好ましい態様である。なお、本発明における嵩密度は、１０ｋＮ／ｃｍ2の荷重、５０ｋＮ／ｃｍ2の荷重の嵩密度が前記範囲にあればいいが、同一試料の場合、５０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度が、１０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度よりも低くなることはない。The silicon fine particles of the present invention have a low bulk density especially when a high load is applied, and have the property of retaining voids. When manufacturing battery electrodes, a strong load is generally applied to improve the adhesion between the electrode and the current collector and the electrical conductivity of the electrode, but as the performance of batteries improves, this load increases. There has been a tendency to increase in recent years. Silicon microparticles obtained by conventional manufacturing methods have a large bulk density because the voids become clogged and filled with microparticles when a stronger load is applied, but the silicon microparticles of the present invention retain the voids. , the bulk density is kept small. In a preferred embodiment, the silicon fine particles of the present invention have a bulk density of 1.3 g/cm 3 or less, preferably 1.1 g/cm 3 or less when a load of 10 kN/cm 2 is applied. Further, in a preferred embodiment, the bulk density when a load of 50 kN/cm 2 is applied is 1.8 g/cm 3 or less, preferably 1.5 g/cm 3 or less. In addition, the bulk density in the present invention is sufficient if the bulk density under a load of 10 kN/cm 2 and a load of 50 kN/cm 2 is within the above range, but in the case of the same sample, when a load of 50 kN/cm 2 is applied, the bulk density is within the above range. The bulk density never becomes lower than the bulk density when a load of 10 kN/cm 2 is applied.
また、５０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度（ＢＤ50）と、１０ｋＮ／ｃｍ2の荷重をかけたときの嵩密度（ＢＤ10）との間に、（ＢＤ50－ＢＤ10）／（５０－１０）＜０．０１３０の関係があることが好ましい。Also, between the bulk density (BD 50 ) when a load of 50 kN/cm 2 is applied and the bulk density (BD 10 ) when a load of 10 kN/cm 2 is applied, (BD 50 - BD 10 ) It is preferable that there is a relationship of /(50-10)<0.0130.
シリコン微粒子中に不純物として含まれる酸素の濃度（Ｃo：質量％）と、比表面積（Ｓ：ｍ2／ｇ）との比（Ｃo／Ｓ）は０．０５未満、好ましくは０．０３未満である。シリコンの酸素濃度はシリコン微粒子表面の表面酸化層に起因するものが主体であるため、シリコン微粒子の粒子径が小さくなれば比表面積が増え、酸素濃度は高くなる。このため比表面積と酸素濃度をそれぞれ定義することが難しい。そこで本発明では、比（Ｃo／Ｓ）によって、シリコン中の酸素不純物の影響が少ない範囲を定義している。シリコン中の酸素不純物は、リチウムと不可逆的に結合することで、電池性能における充電容量低下の原因となるが、本発明の所定の比率に比（Ｃo／Ｓ）を調整することで、酸素の影響を極めて少なく抑制することができる。The ratio (C o /S) between the concentration of oxygen contained as an impurity in the silicon fine particles (C o : % by mass) and the specific surface area (S: m 2 /g) is less than 0.05, preferably 0.03. less than Since the oxygen concentration of silicon is mainly caused by the surface oxidation layer on the surface of the silicon fine particles, as the particle size of the silicon fine particles becomes smaller, the specific surface area increases and the oxygen concentration becomes higher. For this reason, it is difficult to define the specific surface area and oxygen concentration, respectively. Therefore, in the present invention, a range in which the influence of oxygen impurities in silicon is small is defined by the ratio (C o /S). Oxygen impurities in silicon irreversibly combine with lithium, causing a decrease in charging capacity in battery performance. However, by adjusting the ratio (C o /S) to a predetermined ratio according to the present invention, oxygen impurities The effects of this can be suppressed to an extremely low level.
このような本発明のシリコン微粒子の走査型電子顕微鏡写真を図１に示す。
図１では、５０～３００ｎｍ程度の球状の微粒子が複数、数珠つなぎ状に連なった凝集粒子を構成するが、二次粒子の形状としては特に限定されない。A scanning electron micrograph of such silicon fine particles of the present invention is shown in FIG.
In FIG. 1, a plurality of spherical fine particles of about 50 to 300 nm form aggregated particles connected in a chain, but the shape of the secondary particles is not particularly limited.
＜シリコン微粒子の製造方法＞
本発明は、前記シリコン微粒子を製造するための好適な製造方法も提供する。
即ち、本発明にかかる製造方法によれば、
反応器内で、トリクロロシランを熱分解させてシリコン微粒子前駆体を生成させる熱分解工程と、捕集したシリコン微粒子前駆体を加熱して脱塩素を行う脱塩素工程を含む。<Method for producing silicon fine particles>
The present invention also provides a suitable manufacturing method for manufacturing the silicon fine particles.
That is, according to the manufacturing method according to the present invention,
The method includes a thermal decomposition step in which trichlorosilane is thermally decomposed to generate silicon fine particle precursors in a reactor, and a dechlorination step in which the collected silicon fine particle precursors are heated and dechlorinated.
・熱分解工程
本発明では、Ｓｉ源として、塩化珪素ガスが使用され、トリクロロシランが主成分として使用される。またトリクロロシラン以外のＳｉ源として、ジクロロシラン、四塩化珪素などが含まれていてもよく、これらを含む場合、Ｓｉ源中の全モル中に３０モル％以下の量で使用されることが望ましい。- Thermal decomposition step In the present invention, silicon chloride gas is used as the Si source, and trichlorosilane is used as the main component. In addition, dichlorosilane, silicon tetrachloride, etc. may be included as a Si source other than trichlorosilane, and when these are included, it is desirable to use them in an amount of 30 mol% or less based on the total moles of the Si source. .
反応容器に、Ｓｉ源とともに、窒素やアルゴン、ヘリウム等の本発明の製造方法の反応に対して本質的に不活性なガスを同伴ガスとして混合することができる。主要なＳｉ源であるトリクロロシランは沸点が約３２℃と高く液化しやすいが、同伴ガスを混合することでガス状態を保ち容易に定量供給することができる。同伴ガスの量は特に制限されず、トリクロロシランに対して、５～８０体積％の範囲で使用されることが、トリクロロシランの気化安定化のために望ましい。また、気化条件およびガス配管の加温を適切に実施することで、工業的には同伴ガスは使用しなくともよい。 In the reaction vessel, a gas essentially inert to the reaction of the production method of the present invention, such as nitrogen, argon, helium, etc., can be mixed as an accompanying gas together with the Si source. Trichlorosilane, which is the main source of Si, has a high boiling point of about 32° C. and is easily liquefied, but by mixing it with an accompanying gas, it can be maintained in a gaseous state and easily supplied in a fixed amount. The amount of the entrained gas is not particularly limited, and it is desirable to use it in a range of 5 to 80% by volume based on trichlorosilane in order to stabilize the vaporization of trichlorosilane. Further, by appropriately implementing vaporization conditions and heating of gas piping, it is not necessary to use entrained gas industrially.
本発明における熱分解工程では、下記のようにトリクロロシランが熱分解して、中間生成物であるＳｉＣｌx（ｘは一般的に０．１～０．３である）をシリコン微粒子前駆体として生成する。この熱分解工程での代表的な反応は、下記式（２）で表される。In the thermal decomposition step of the present invention, trichlorosilane is thermally decomposed as described below to produce intermediate product SiCl x (x is generally 0.1 to 0.3) as a silicon fine particle precursor. do. A typical reaction in this thermal decomposition step is represented by the following formula (2).
ＳｉＨＣｌ3 →（1-n）ＳｉＣｌ4＋ｎＳｉＣｌx＋（1/2）Ｈ2 （２）
なお、副生物には、四塩化珪素の他に、ジクロロシランやポリマー状のシランも含まれる。SiHCl 3 → (1-n)SiCl 4 +nSiCl x + (1/2)H 2 (2)
In addition to silicon tetrachloride, the by-products also include dichlorosilane and polymeric silane.
熱分解工程では、Ｓｉ源を６００～９００℃、好ましくは６５０～９００℃、より好ましくは７００～８５０℃の温度に加熱する。シリコン微粒子前駆体を生成するには、加熱温度が重要となり、加熱温度が所定の温度より高い場合、反応物が反応器の内壁に融着して反応器を閉塞し、また、所定の温度より低い場合、目的とするシリコン微粒子前駆体が得られない。反応容器としては、通常、内壁がカーボン等の材質よりなる管型反応容器が使用され、所定の温度に内壁を加熱しうる加熱装置が設けられている。 In the pyrolysis step, the Si source is heated to a temperature of 600 to 900°C, preferably 650 to 900°C, more preferably 700 to 850°C. In order to generate silicon fine particle precursors, the heating temperature is important; if the heating temperature is higher than a predetermined temperature, the reactants will fuse to the inner wall of the reactor, clogging the reactor, and if the heating temperature is higher than the predetermined temperature. If it is low, the desired silicon fine particle precursor cannot be obtained. A tubular reaction vessel whose inner wall is made of a material such as carbon is usually used as the reaction vessel, and is equipped with a heating device that can heat the inner wall to a predetermined temperature.
前記式（２）で表されるシリコン微粒子前駆体を生成する反応を経由することで、前記したような従来になかった結晶子径が小さく、酸素量、塩素量が所定の範囲に調整されたシリコン微粒子を得ることができる。 By going through the reaction that generates the silicon fine particle precursor represented by the above formula (2), the crystallite diameter as described above is small, which has not been seen before, and the amount of oxygen and chlorine are adjusted to a predetermined range. Silicon fine particles can be obtained.
反応容器内部の温度は前記の範囲に加熱できれば特に制限なく、段階的に温度を変えてもよい。またＳｉ源のガス流速や滞留時間も、反応容器の大きさや伝熱面積（効率）に応じて適宜選択される。 The temperature inside the reaction vessel is not particularly limited as long as it can be heated within the above range, and the temperature may be changed stepwise. Further, the gas flow rate and residence time of the Si source are also appropriately selected depending on the size and heat transfer area (efficiency) of the reaction vessel.
Ｓｉ源は反応容器に導入する前にあらかじめ４０℃以上、６００℃未満の温度に予熱しておくことが好ましく、次いで、前記温度に上昇することが望ましい。反応容器内で低温のＳｉ源を前記温度まで速やかに加熱しようとする場合、反応容器の内壁（加熱体）温度が前記温度を越えて高温になり、反応容器の内壁近傍で局所的にＳｉ源の温度が前記温度範囲を越えることで反応容器壁面に反応物の融着が発生する原因となりやすい。予熱をすることで前記温度までの加熱を緩やかに行うことができ、反応容器内壁の温度を前記Ｓｉ源の熱分解温度の範囲に適切に保つことができる。また、反応容器内のＳｉ源の予熱に必要な領域を小さくすることができる。さらには、Ｓｉ源の温度を均一に保ちやすいため得られるシリコン微粒子の粒子径のばらつきを抑制できる。 It is preferable that the Si source be preheated to a temperature of 40° C. or more and less than 600° C. before being introduced into the reaction vessel, and then preferably raised to the above temperature. When trying to quickly heat a low-temperature Si source to the above temperature in a reaction vessel, the temperature of the inner wall of the reaction vessel (heating body) becomes high enough to exceed the above temperature, and the Si source is locally heated near the inner wall of the reaction vessel. If the temperature exceeds the above-mentioned temperature range, it tends to cause fusion of reactants on the wall surface of the reaction vessel. By preheating, heating to the above temperature can be performed slowly, and the temperature of the inner wall of the reaction vessel can be appropriately maintained within the range of the thermal decomposition temperature of the Si source. Furthermore, the area required for preheating the Si source in the reaction vessel can be reduced. Furthermore, since it is easy to keep the temperature of the Si source uniform, it is possible to suppress variations in the particle diameter of the obtained silicon fine particles.
反応生成物のシリコン微粒子前駆体は捕集され、水素や四塩化珪素、窒素、未反応トリクロロシラン、副生物のジクロロシラン、ポリマー状のシランなどと分離される。捕集方法は特に制限なく、たとえば、サイクロン式の捕集手段や、バグフィルター、電気集塵などの既知の方法を使用できる。 The reaction product, silicon fine particle precursor, is collected and separated from hydrogen, silicon tetrachloride, nitrogen, unreacted trichlorosilane, by-product dichlorosilane, polymeric silane, and the like. The collection method is not particularly limited, and for example, known methods such as a cyclone type collection means, a bag filter, and an electrostatic precipitator can be used.
シリコン微粒子前駆体が分離された反応排ガスから、未反応トリクロロシランおよび四塩化珪素、窒素ガスを回収し、四塩化珪素は、金属シリコンおよび水素と反応させてトリクロロシランに転化させて、再度反応原料として用いることも可能である。 Unreacted trichlorosilane, silicon tetrachloride, and nitrogen gas are recovered from the reaction exhaust gas from which the silicon fine particle precursor has been separated, and the silicon tetrachloride is reacted with metal silicon and hydrogen to be converted into trichlorosilane and used as a reaction raw material again. It is also possible to use it as
反応排ガスから、シラン類とその他のガス成分との分離は、深冷などによって行うことができる。深冷は、加圧下、一般的には、５００乃至８００ｋＰａＧ程度の圧力下で、熱交換器などにより－３０乃至－５０℃程度に冷却して行われる。このような深冷により、トリクロロシランおよび四塩化珪素が凝縮して、窒素ガス、水素ガスや塩化水素ガスなどのガス成分と分離される。一方、ガス成分は、活性炭等の吸着剤を充填した吸着塔で塩化水素ガスを除去した後、分離回収された水素を含む窒素ガスは同伴ガスとして再利用してもよい。 Silanes and other gas components can be separated from the reaction exhaust gas by deep cooling or the like. Deep cooling is performed under pressure, generally about 500 to 800 kPaG, by cooling to about -30 to -50°C using a heat exchanger or the like. By such deep cooling, trichlorosilane and silicon tetrachloride are condensed and separated from gas components such as nitrogen gas, hydrogen gas, and hydrogen chloride gas. On the other hand, after hydrogen chloride gas is removed from the gas component in an adsorption tower filled with an adsorbent such as activated carbon, the separated and recovered nitrogen gas containing hydrogen may be reused as an accompanying gas.
凝縮液から、蒸留等によってトリクロロシランを回収し、上記反応に再利用することができる。
分離された四塩化珪素は、水素と金属シリコンと反応させて（式（３））、トリクロロシランに転化して、Ｓｉ源として再利用することが好ましい。Trichlorosilane can be recovered from the condensate by distillation or the like and reused in the above reaction.
It is preferable that the separated silicon tetrachloride is reacted with hydrogen and metal silicon (formula (3)) to be converted into trichlorosilane and reused as a Si source.
Ｓｉ ＋ ２Ｈ2 ＋ ３ＳｉＣｌ4 → ４ＳｉＨＣｌ3 （３）
得られたトリクロロシランを含む反応生成物を蒸留してトリクロロシランを回収し、反応原料として再利用する。前記深冷によって回収された凝縮液と、上記反応の反応生成物とを混合してトリクロロシランを回収してもよい。式（３）の反応式で、未反応の四塩化珪素は、再度上記反応によるトリクロロシランに転化することも可能であり、このループを繰り返して、副生物の排出ロスを抑制し、原料を有効活用することができる。なお、蒸留工程を多段にして、さらにトリクロロシランを精製してもよい。Si + 2H 2 + 3SiCl 4 → 4SiHCl 3 (3)
The obtained reaction product containing trichlorosilane is distilled to recover trichlorosilane and reused as a reaction raw material. Trichlorosilane may be recovered by mixing the condensate recovered by the deep cooling and the reaction product of the reaction. In the reaction formula (3), unreacted silicon tetrachloride can be converted to trichlorosilane again by the above reaction, and by repeating this loop, the emission loss of by-products can be suppressed and the raw material can be used effectively. It can be utilized. Note that trichlorosilane may be further purified by performing the distillation process in multiple stages.
一方、捕集されたシリコン微粒子前駆体は、脱塩素工程に送られる。移送手段は、酸素および水分に触れず、かつ容器からのコンタミがない限り、特に制限されない。
たとえば、シリコン微粒子前駆体を、カーボン製、アルミニウム製、ニッケル被覆されたＳＵＳ製などの容器に窒素置換後、充填し、脱塩素工程に移送してもよい。カーボン製容器は特に電池材料として使用する際に問題となる金属系コンタミの影響が少なく、高温の粒子を充填しても変性することがないため好ましい。あるいは、前記既知の捕集手段で捕集されたシリコン微粒子前駆体をホッパー等に蓄積し、これを窒素などの酸素および水を含まないガスに同伴させて配管で空送することもできる。On the other hand, the collected silicon fine particle precursors are sent to a dechlorination step. The transfer means is not particularly limited as long as it does not come into contact with oxygen and moisture and is free from contamination from the container.
For example, the silicon fine particle precursor may be filled into a container made of carbon, aluminum, nickel-coated SUS, etc. after being replaced with nitrogen, and the container may be transferred to the dechlorination step. Carbon containers are particularly preferred because they are less affected by metal contamination, which is a problem when used as a battery material, and do not denature even when filled with high-temperature particles. Alternatively, it is also possible to accumulate the silicon fine particle precursors collected by the known collection means in a hopper or the like, and transport them air through piping while being entrained with a gas such as nitrogen that does not contain oxygen and water.
・脱塩素工程
次いで、捕集したシリコン微粒子前駆体を、脱塩素反応容器に装入し、９００℃を超える温度で、１２００℃までの温度、好ましくは１０５０℃を超える温度から１１８０℃までの温度に加熱して脱塩素処理を行う。脱塩素処理は、脱塩素反応容器中で、酸素原子を含まないガスの流通下に行うか、減圧下で行われる。上記脱塩素反応容器に供給し、酸素原子を含まないガスは、シリコン微粒子前駆体と反応しないものであれば特に限定されない。前記ガスは、酸素原子を含まない限り制限はなく、窒素、アルゴン、ヘリウム等のガスが好適に使用される。上記ガスは、水分を可及的に減少せしめたガスが好ましく、露点が－５０℃以下のものが特に好ましい。また、前記減圧下に行う場合、その圧力が、１ｋＰａ以下となるように脱塩素反応容器よりガスを排気することが好ましい。・Dechlorination step Next, the collected silicon fine particle precursor is charged into a dechlorination reaction vessel and heated at a temperature of over 900°C to 1200°C, preferably from a temperature of over 1050°C to 1180°C. Dechlorination treatment is performed by heating to . The dechlorination treatment is performed in a dechlorination reaction vessel under the flow of a gas that does not contain oxygen atoms or under reduced pressure. The oxygen-free gas supplied to the dechlorination reaction vessel is not particularly limited as long as it does not react with the silicon fine particle precursor. The gas is not limited as long as it does not contain oxygen atoms, and gases such as nitrogen, argon, and helium are preferably used. The above-mentioned gas is preferably a gas whose moisture content is reduced as much as possible, and a gas having a dew point of −50° C. or lower is particularly preferable. Further, when performing the dechlorination under reduced pressure, it is preferable to exhaust the gas from the dechlorination reaction vessel so that the pressure becomes 1 kPa or less.
脱塩素処理によって、式（４）の反応が進み、シリコン微粒子が得られる。
ＳｉＣｌx → （１－ｘ／４）Ｓｉ ＋ （ｘ／４）ＳｉＣｌ4 （４）
前記脱塩素処理の加熱においては、シリコン微粒子前駆体を均一に加熱するため、前駆体を撹拌しながら加熱することが好ましい。撹拌は、反応器が転動するもの、反応器に撹拌翼を設けたもの、気流で撹拌するものなどの既知のいずれの方法であってもよく、さらに、邪魔板を設けて撹拌効率を向上させてもよい。By the dechlorination treatment, the reaction of formula (4) progresses, and silicon fine particles are obtained.
SiCl x → (1-x/4)Si + (x/4)SiCl 4 (4)
In the heating for the dechlorination treatment, in order to uniformly heat the silicon fine particle precursor, it is preferable to heat the precursor while stirring. Stirring may be done by any known method, such as a rolling reactor, a reactor equipped with stirring blades, or an air current stirrer, and a baffle plate may be provided to improve stirring efficiency. You may let them.
前記シリコン微粒子前駆体を前記所定の加熱温度で加熱する時間（保持時間）は、前記目的とする塩素濃度となる時間であれば特に制限されないが、５～６０分程度が一般的である。 The time (holding time) for heating the silicon fine particle precursor at the predetermined heating temperature is not particularly limited as long as the desired chlorine concentration is achieved, but it is generally about 5 to 60 minutes.
前記脱塩素処理には、加熱温度が重要であり、前記温度範囲で加熱することで、微粒子表面近傍の反応性の高い塩素が除去されて、所定の塩素含有量で、かつ、多結晶一次粒子が部分融着した、所定の比表面積を有する不定形の凝集粒子から構成されるシリコン微粒子が製造される。 The heating temperature is important for the dechlorination treatment, and by heating in the above temperature range, highly reactive chlorine near the surface of the fine particles is removed, and the polycrystalline primary particles have a predetermined chlorine content. Silicon microparticles are produced which are composed of amorphous agglomerated particles having a predetermined specific surface area and which are partially fused together.
加熱温度が高めにあると塩素濃度は低く、結晶子径が大きく、比表面積は小さくなる傾向にある。
本発明のシリコン微粒子は、所定の酸素量、塩素量に調整されており、結晶子径が小さく、空隙を保持した二次凝集構造を有しているため、リチウムイオンの吸蔵時の体積変化が少なく、また体積変化によって粒子が破断することもなく、高い充放電容量を長期間持続可能な負極を構成することが可能である。また、本発明のシリコン微粒子は、高活性な塩素基による急激な酸化が有効に抑制されているため、極めて安全に取り扱うことができる。When the heating temperature is high, the chlorine concentration tends to be low, the crystallite size is large, and the specific surface area is small.
The silicon fine particles of the present invention are adjusted to a predetermined amount of oxygen and chlorine, have a small crystallite diameter, and have a secondary agglomerated structure with voids, so that the volume change during occlusion of lithium ions is reduced. It is possible to construct a negative electrode that can maintain a high charge/discharge capacity for a long period of time without causing particles to break due to changes in volume. Further, the silicon fine particles of the present invention can be handled extremely safely because rapid oxidation by highly active chlorine groups is effectively suppressed.
本発明を、次の実施例および比較例で説明する。・物性の評価方法
（１）トリクロロシランの反応率
トリクロロシランの反応率は、反応後の排出ガスの組成をガスクロマトグラフで分析し、検出されるトリクロロシラン、四塩化ケイ素、ジクロロシランの比率から算出した。The invention is illustrated by the following examples and comparative examples.・Evaluation method for physical properties (1) Reaction rate of trichlorosilane The reaction rate of trichlorosilane is calculated from the ratio of trichlorosilane, silicon tetrachloride, and dichlorosilane detected by analyzing the composition of the exhaust gas after the reaction using a gas chromatograph. did.
（２）シリコン微粒子前駆体およびシリコン微粒子中の塩素濃度
試料を蛍光Ｘ線分析によって計測して求めた。
（３）シリコン微粒子前駆体およびシリコン微粒子中の酸素濃度と比表面積との比（ＣO／Ｓ）
試料を窒素ガスＢＥＴ吸着法を用いた比表面積測定装置で計測することで比表面積（Ｓ[ｍ2／ｇ]）を求め、試料を酸素窒素濃度分析計（ＬＥＣＯ社製ＴＣ－６００）で計測して酸素濃度（ＣO[質量％]）を求めた。酸素濃度を比表面積で割ることで酸素濃度と比表面積との比（Ｃo／Ｓ）を算出した。(2) Chlorine concentration in silicon fine particle precursor and silicon fine particles This was determined by measuring the sample by fluorescent X-ray analysis.
(3) Ratio of oxygen concentration to specific surface area in silicon fine particle precursor and silicon fine particles (C O /S)
The specific surface area (S [m 2 /g]) was determined by measuring the sample with a specific surface area measuring device using the nitrogen gas BET adsorption method, and the sample was measured with an oxygen nitrogen concentration analyzer (LECO TC-600). The oxygen concentration (C O [mass %]) was determined. The ratio of oxygen concentration to specific surface area (C o /S) was calculated by dividing the oxygen concentration by the specific surface area.
（４）シリコン微粒子の平均直径
試料を窒素ガスＢＥＴ吸着法を用いた比表面積測定装置で計測することで比表面積を求め、
ｄ＝６／ρ・Ｓ
により平均直径を求めた。なお、ｄは平均直径、ρはシリコンの密度、Ｓは比表面積を表す。(4) Average diameter of silicon fine particles The specific surface area is determined by measuring the sample with a specific surface area measuring device using the nitrogen gas BET adsorption method.
d=6/ρ・S
The average diameter was determined by Note that d represents the average diameter, ρ represents the density of silicon, and S represents the specific surface area.
（５）シリコン微粒子の平均結晶子径
試料のＸ線回折によって得られる回折プロファイルを、Ｈａｌｄｅｒ－Ｗａｇｎｅｒ法で解析することにより求めた。(5) Average crystallite diameter of silicon fine particles The diffraction profile obtained by X-ray diffraction of the sample was determined by analyzing it using the Halder-Wagner method.
（６）シリコン微粒子の嵩密度
規定重量の試料を超鋼製の粉末プレス成型用ダイスに充填し、これを精密万能試験機（島津製作所製 オートグラフ）を用いて圧縮し、圧縮荷重と圧縮ヘッドの変位の相関を測定した。ダイスの内径、ヘッドの変位から圧粉体の体積を算出し、試料重量と圧粉体の体積から嵩密度を算出した。(6) Bulk density of silicon fine particles Fill a specified weight of sample into a powder press molding die made of super steel, compress it using a precision universal testing machine (Autograph manufactured by Shimadzu Corporation), and compare the compression load and compression head. The correlation of displacement was measured. The volume of the compact was calculated from the inner diameter of the die and the displacement of the head, and the bulk density was calculated from the sample weight and the volume of the compact.
実施例１
・シリコン微粒子前駆体の合成
内径８０ｍｍ、長さ２５００ｍｍのグラファイト製反応筒を７５０℃に加熱し、ここにトリクロロシランを９００ｇ／ｍｉｎ、同伴窒素を３７ＮＬ（Ｌはリットル）／ｍｉｎの速度で供給してシリコン微粒子前駆体を合成し、バグフィルターで未反応ガスと分離・捕集した。トリクロロシランの反応率は約４０％であり、生成したシリコン微粒子前駆体の約７０％がバグフィルターで捕集された。捕集したシリコン微粒子前駆体は雰囲気を窒素で置換された貯蔵容器に蓄積した。 Example 1
・Synthesis of silicon fine particle precursor A graphite reaction tube with an inner diameter of 80 mm and a length of 2500 mm was heated to 750°C, and trichlorosilane was supplied thereto at a rate of 900 g/min and entrained nitrogen at a rate of 37 NL (L is liter)/min. A silicon fine particle precursor was synthesized using a bag filter and separated from unreacted gas and collected. The reaction rate of trichlorosilane was about 40%, and about 70% of the generated silicon fine particle precursors were collected by the bag filter. The collected silicon fine particle precursors were accumulated in a storage container whose atmosphere was purged with nitrogen.
捕集されたシリコン微粒子前駆体の一部を大気開放したところ、空気中の水分と反応し、塩化水素からなる白煙を生じて酸化した。大気開放後のシリコン微粒子前駆体を分析したところ、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．１９２となった。また、平均結晶子径は３ｎｍであった。When some of the collected silicon fine particle precursors were exposed to the atmosphere, they reacted with moisture in the air, producing white smoke consisting of hydrogen chloride and oxidizing. When the silicon fine particle precursor was analyzed after being exposed to the atmosphere, the ratio of oxygen concentration to specific surface area (C o /S) was 0.192. Moreover, the average crystallite diameter was 3 nm.
・シリコン微粒子前駆体の脱塩素
前記、貯蔵容器に蓄積されたシリコン微粒子前駆体（大気開放されていないもの）を、大気に触れないよう注意しながら窒素置換されたグラファイト製の加熱坩堝に供給した。坩堝内のシリコン微粒子前駆体をグラファイト製の撹拌羽根で撹拌しながら、加熱坩堝内部に適量の窒素を供給し、流通させながら１１５０℃まで加熱した。１１５０℃に到達後、すぐに加熱を停止し、自然冷却を行った。・Dechlorination of silicon fine particle precursor The silicon fine particle precursor accumulated in the storage container (not exposed to the atmosphere) was supplied to a heated crucible made of graphite that had been purged with nitrogen while being careful not to come into contact with the atmosphere. . While stirring the silicon fine particle precursor in the crucible with a graphite stirring blade, an appropriate amount of nitrogen was supplied into the heating crucible, and the mixture was heated to 1150° C. while being circulated. Immediately after reaching 1150°C, heating was stopped and natural cooling was performed.
冷却後、加熱坩堝を大気開放し、内部よりシリコン微粒子を取り出した。得られたシリコン微粒子は大気に曝されても塩化水素ガスに起因する臭気などは感じられなかった。得られたシリコン微粒子の塩素濃度は０．７質量％、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．０４３となった。また、一次粒子の平均直径は１５９ｎｍ、平均結晶子径は３０ｎｍの多結晶であった。After cooling, the heating crucible was opened to the atmosphere, and the silicon fine particles were taken out from inside. Even when the obtained silicon fine particles were exposed to the atmosphere, no odor caused by hydrogen chloride gas was detected. The obtained silicon fine particles had a chlorine concentration of 0.7% by mass and a ratio of oxygen concentration to specific surface area (C o /S) of 0.043. Further, the primary particles were polycrystalline with an average diameter of 159 nm and an average crystallite diameter of 30 nm.
実施例２
実施例１において、トリクロロシランを５４０ｇ／ｍｉｎ、同伴窒素を２２ＮＬ（Ｌはリットル）／ｍｉｎの速度で供給してシリコン微粒子前駆体を合成し、脱塩素を行ってシリコン微粒子を得た。得られたシリコン微粒子は大気に曝されても塩化水素ガスに起因する臭気などは感じられなかった。得られたシリコン微粒子の塩素濃度は０．８質量％、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．０３８となった。また、一次粒子の平均直径は４８６ｎｍ、平均結晶子径は３６ｎｍの多結晶であった。 Example 2
In Example 1, a silicon fine particle precursor was synthesized by supplying trichlorosilane at a rate of 540 g/min and entrained nitrogen at a rate of 22 NL (L: liter)/min, and dechlorination was performed to obtain silicon fine particles. Even when the obtained silicon fine particles were exposed to the atmosphere, no odor caused by hydrogen chloride gas was detected. The obtained silicon fine particles had a chlorine concentration of 0.8% by mass and a ratio of oxygen concentration to specific surface area (C o /S) of 0.038. Further, the primary particles were polycrystalline with an average diameter of 486 nm and an average crystallite diameter of 36 nm.
実施例３
実施例１において、トリクロロシランを５４０ｇ／ｍｉｎ、同伴窒素を８３ＮＬ（Ｌはリットル）／ｍｉｎの速度で供給してシリコン微粒子前駆体を合成し、脱塩素を行ってシリコン微粒子を得た。得られたシリコン微粒子は大気に曝されても塩化水素ガスに起因する臭気などは感じられなかった。得られたシリコン微粒子の塩素濃度は０．４質量％、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．０４９となった。また、一次粒子の平均直径は８４ｎｍ、平均結晶子径は３０ｎｍの多結晶であった。 Example 3
In Example 1, a silicon fine particle precursor was synthesized by supplying trichlorosilane at a rate of 540 g/min and entrained nitrogen at a rate of 83 NL (L: liter)/min, and dechlorination was performed to obtain silicon fine particles. Even when the obtained silicon fine particles were exposed to the atmosphere, no odor caused by hydrogen chloride gas was detected. The obtained silicon fine particles had a chlorine concentration of 0.4% by mass and a ratio of oxygen concentration to specific surface area (C o /S) of 0.049. Further, the primary particles were polycrystalline with an average diameter of 84 nm and an average crystallite diameter of 30 nm.
実施例４
実施例１においてシリコン微粒子前駆体の脱塩素を、１０５０℃まで加熱した。１０５０℃に到達後、すぐに加熱を停止し、自然冷却を行った。 Example 4
In Example 1, the silicon fine particle precursor was dechlorinated by heating to 1050°C. Immediately after reaching 1050°C, heating was stopped and natural cooling was performed.
冷却後、加熱坩堝を大気開放し、内部よりシリコン微粒子を取り出した。得られたシリコン微粒子は大気に曝されても塩化水素ガスに起因する臭気などは感じられなかった。得られたシリコン微粒子の塩素濃度は１．０質量％、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．０３８となった。また、一次粒子の平均直径は１４１ｎｍ、平均結晶子径は２０ｎｍの多結晶であった。After cooling, the heating crucible was opened to the atmosphere, and the silicon fine particles were taken out from inside. Even when the obtained silicon fine particles were exposed to the atmosphere, no odor caused by hydrogen chloride gas was detected. The obtained silicon fine particles had a chlorine concentration of 1.0% by mass and a ratio of oxygen concentration to specific surface area (C o /S) of 0.038. Further, the primary particles were polycrystalline with an average diameter of 141 nm and an average crystallite diameter of 20 nm.
参考例１
実施例１においてシリコン微粒子前駆体の脱塩素を、８００℃まで加熱した。８００℃に到達後、すぐに加熱を停止し、自然冷却を行った。 Reference example 1
In Example 1, the silicon fine particle precursor was dechlorinated by heating to 800°C. Immediately after reaching 800°C, heating was stopped and natural cooling was performed.
冷却後、加熱坩堝を大気開放し、内部よりシリコン微粒子を取り出した。得られたシリコン微粒子は大気に曝されても塩化水素ガスに起因する臭気などは感じられなかった。得られたシリコン微粒子の塩素濃度は４．８質量％、酸素濃度と比表面積との比（Ｃo／Ｓ）は０．０２９となった。また、一次粒子の平均直径は１２３ｎｍ、平均結晶子径は７ｎｍの多結晶であった。After cooling, the heating crucible was opened to the atmosphere, and the silicon fine particles were taken out from inside. Even when the obtained silicon fine particles were exposed to the atmosphere, no odor caused by hydrogen chloride gas was detected. The obtained silicon fine particles had a chlorine concentration of 4.8% by mass and a ratio of oxygen concentration to specific surface area (C o /S) of 0.029. Further, the primary particles were polycrystalline with an average diameter of 123 nm and an average crystallite diameter of 7 nm.
比較例１
多結晶シリコンを破砕した粉末（高純度化学研究所製試薬 平均直径５μｍ）を使用した。 Comparative example 1
A powder obtained by crushing polycrystalline silicon (reagent manufactured by Kojundo Kagaku Kenkyusho, average diameter 5 μm) was used.
比較例２
比較例１のシリコン粉末を、ビーズミルを用いて平均直径２００ｎｍ程度の板状に粉砕したものを使用した。 Comparative example 2
The silicon powder of Comparative Example 1 was pulverized into a plate shape with an average diameter of about 200 nm using a bead mill.
比較例３
プラズマ法で合成した平均直径１００ｎｍのシリコンナノ粒子（Ａｌｄｒｉｃｈ製試薬）を使用した。 Comparative example 3
Silicon nanoparticles (reagent manufactured by Aldrich) with an average diameter of 100 nm synthesized by a plasma method were used.
以上の実施例、参考例および比較例で調製したシリコン微粒子について、荷重をかけたときの嵩密度の変化を図３に、１０ｋＮ／ｃｍ2および５０ｋＮ／ｃｍ2の荷重をかけた際の嵩密度（ＢＤ10，ＢＤ50）を表１に示す。Figure 3 shows the change in bulk density when a load is applied to the silicon fine particles prepared in the above Examples, Reference Examples, and Comparative Examples . (BD 10 , BD 50 ) are shown in Table 1.
実験例１
実施例１で得られたシリコン微粒子を活物質として用いて、活物質、導電助剤（アセチレンブラック）およびバインダー（ポリイミド）を７：１：２の重量比となるように混練し、ＮＭＰ溶媒を加えて粘度０．８～１．５Ｐａ・Ｓのペーストを得た。このペーストを集電体（銅箔）上に塗布し、乾燥、プレスした後、窒素流通下、３５０度の温度で０．５時間加熱して負極シートを得た。 Experimental example 1
Using the silicon fine particles obtained in Example 1 as an active material, the active material, conductive agent (acetylene black), and binder (polyimide) were kneaded at a weight ratio of 7:1:2, and an NMP solvent was mixed. In addition, a paste with a viscosity of 0.8 to 1.5 Pa·S was obtained. This paste was applied onto a current collector (copper foil), dried and pressed, and then heated at a temperature of 350 degrees for 0.5 hour under nitrogen flow to obtain a negative electrode sheet.
この負極シートを負極とし、リチウム箔を対極とし、ビニレンカーボネートとフルオロエチレンカーボネートをそれぞれ１０ｖｏｌ％添加した電解液を用いてハーフセルを作成し、０．０５Ｃの充放電レートでサイクル試験を実施した。
その結果、５０サイクル後においても２，１００ｍＡｈ／ｇの高い充電容量を示した。This negative electrode sheet was used as a negative electrode, lithium foil was used as a counter electrode, a half cell was created using an electrolytic solution containing 10 vol % of each of vinylene carbonate and fluoroethylene carbonate, and a cycle test was conducted at a charge/discharge rate of 0.05C.
As a result, even after 50 cycles, a high charging capacity of 2,100 mAh/g was shown.
実験例２
比較例１のシリコン粉末を活物質として用いて、実験例１と同様の方法でハーフセルを作成してサイクル試験を実施した。その結果、５０サイクル後の充電容量は２３０ｍＡｈ／ｇとなり、充電容量は大きく低下した。 Experimental example 2
Using the silicon powder of Comparative Example 1 as an active material, a half cell was created in the same manner as in Experimental Example 1, and a cycle test was conducted. As a result, the charging capacity after 50 cycles was 230 mAh/g, which was a significant decrease.
実験例３
比較例２のビーズミルで粉砕したシリコン粉末を活物質として用いて、実験例１と同様の方法でハーフセルを作成してサイクル試験を実施した。その結果、５０サイクル後の充電容量は約１，５６０ｍＡｈ／ｇとなり、実験例１に対して充電容量は劣る結果となった。 Experimental example 3
Using the silicon powder ground with the bead mill of Comparative Example 2 as an active material, a half cell was created in the same manner as in Experimental Example 1, and a cycle test was conducted. As a result, the charging capacity after 50 cycles was approximately 1,560 mAh/g, which was inferior to Experimental Example 1.
Claims (6)
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018239572 | 2018-12-21 | ||
| JP2018239572 | 2018-12-21 | ||
| PCT/JP2019/044903 WO2020129499A1 (en) | 2018-12-21 | 2019-11-15 | Silicon fine particles and production method thereof |
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