JP5520538B2 - Negative electrode material for lithium ion secondary battery containing nano-sized particles, negative electrode for lithium ion secondary battery, lithium ion secondary battery - Google Patents
Negative electrode material for lithium ion secondary battery containing nano-sized particles, negative electrode for lithium ion secondary battery, lithium ion secondary battery Download PDFInfo
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- JP5520538B2 JP5520538B2 JP2009180733A JP2009180733A JP5520538B2 JP 5520538 B2 JP5520538 B2 JP 5520538B2 JP 2009180733 A JP2009180733 A JP 2009180733A JP 2009180733 A JP2009180733 A JP 2009180733A JP 5520538 B2 JP5520538 B2 JP 5520538B2
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- negative electrode
- lithium ion
- ion secondary
- secondary battery
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- 150000002642 lithium compounds Chemical class 0.000 description 1
- IDBFBDSKYCUNPW-UHFFFAOYSA-N lithium nitride Chemical compound [Li]N([Li])[Li] IDBFBDSKYCUNPW-UHFFFAOYSA-N 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002082 metal nanoparticle Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000002070 nanowire Substances 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001451 polypropylene glycol Polymers 0.000 description 1
- 229920001282 polysaccharide Polymers 0.000 description 1
- 239000005017 polysaccharide Substances 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- VQMWBBYLQSCNPO-UHFFFAOYSA-N promethium atom Chemical compound [Pm] VQMWBBYLQSCNPO-UHFFFAOYSA-N 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000002409 silicon-based active material Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- GKLVYJBZJHMRIY-UHFFFAOYSA-N technetium atom Chemical compound [Tc] GKLVYJBZJHMRIY-UHFFFAOYSA-N 0.000 description 1
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- Silicon Compounds (AREA)
- Carbon And Carbon Compounds (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Powder Metallurgy (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、リチウムイオン二次電池用の負極などに関するものであり、特に、高容量かつ長寿命のリチウムイオン二次電池用の負極に関する。 The present invention relates to a negative electrode for a lithium ion secondary battery, and more particularly to a negative electrode for a lithium ion secondary battery having a high capacity and a long life.
従来、負極活物質としてグラファイトを用いたリチウムイオン二次電池が実用化されている。また、負極活物質と、カーボンブラック等の導電助剤と、樹脂の結着剤とを混練してスラリーを調製し、銅箔上に塗布・乾燥して、負極を形成することが行われている。 Conventionally, lithium ion secondary batteries using graphite as a negative electrode active material have been put into practical use. Also, a negative electrode is formed by kneading a negative electrode active material, a conductive aid such as carbon black, and a resin binder to prepare a slurry, and applying and drying on a copper foil. Yes.
一方、高容量化を目指し、リチウム化合物として理論容量の大きな金属や合金、特にシリコンおよびその合金を負極活物質として用いるリチウムイオン二次電池用の負極が開発されている。しかし、リチウムイオンを吸蔵したシリコンは、吸蔵前のシリコンに対して約４倍まで体積が膨張するため、シリコンを負極活物質として用いた負極は、充放電サイクル時に膨張と収縮を繰り返す。そのため、負極活物質の剥離などが発生し、従来のグラファイト負極と比較して、寿命が極めて短いという問題があった。 On the other hand, negative electrodes for lithium ion secondary batteries using metals and alloys having a large theoretical capacity as lithium compounds, particularly silicon and its alloys as negative electrode active materials, have been developed with the aim of increasing the capacity. However, since the volume of silicon that occludes lithium ions expands to about 4 times that of silicon before occlusion, a negative electrode using silicon as a negative electrode active material repeats expansion and contraction during a charge / discharge cycle. For this reason, the negative electrode active material is peeled off, and there is a problem that the life is extremely short as compared with the conventional graphite negative electrode.
そこで、シリコン系活物質の表面にカーボンナノファイバーを成長させ、その弾性作用により負極活物質粒子の膨張と収縮による歪みを緩和し、サイクル特性を向上させるという非水電解液二次電池用負極が開示されている(例えば、特許文献１を参照)。 Therefore, a negative electrode for a non-aqueous electrolyte secondary battery that grows carbon nanofibers on the surface of a silicon-based active material, relaxes strain due to expansion and contraction of negative electrode active material particles by its elastic action, and improves cycle characteristics. It is disclosed (see, for example, Patent Document 1).
また、ＳｉやＳｎなどのＬｉを吸蔵可能な成分Ａと、ＣｕやＦｅなどの成分Ｂとをメカノケミカル法により混合することによって得られる、成分Ａと成分Ｂの化合物の粉末からなるリチウム二次電池用負極材料が開示されている（特許文献２を参照）。 Moreover, the lithium secondary which consists of the powder of the compound of the component A and the component B obtained by mixing the component A which can occlude Li, such as Si and Sn, and the component B, such as Cu and Fe, by a mechanochemical method A negative electrode material for a battery is disclosed (see Patent Document 2).
しかしながら、負極活物質と導電助剤と結着剤とのスラリーを塗布・乾燥して、負極を形成する従来の負極は、負極活物質と集電体とを導電性の低い樹脂の結着剤で結着しており、樹脂の使用量は内部抵抗が大きくならないように最小限に抑える必要があり、結合力が弱い。そのため、体積膨張を抑制できていないと、負極活物質は、充放電時に、負極活物質の微粉化と負極活物質の剥離、負極の亀裂の発生、負極活物質間の導電性の低下などが発生して容量が低下する。それゆえ、サイクル特性が悪く、二次電池の寿命が短いという問題点があった。 However, a conventional negative electrode in which a negative electrode is formed by applying and drying a slurry of a negative electrode active material, a conductive additive, and a binder, and the negative electrode active material and the current collector are bonded to a resin having low conductivity. The amount of resin used must be kept to a minimum so that the internal resistance does not increase, and the bonding force is weak. For this reason, if the volume expansion is not suppressed, the negative electrode active material may have a negative electrode active material pulverization and a negative electrode active material peeling, a crack of the negative electrode, a decrease in conductivity between the negative electrode active materials, and the like. Occurs and the capacity decreases. Therefore, there are problems that the cycle characteristics are poor and the life of the secondary battery is short.
また、特許文献１に記載の発明は、シリコン自体の体積膨張を抑制することが不十分であり、負極活物質と集電体とを結合力の不十分な樹脂で結着するものであり、サイクル特性の劣化は十分には防げなかった。さらに、カーボンナノファイバーの形成工程があるため、生産性が悪かった。また、特許文献２に記載の発明も、ナノサイズのレベルで各成分を均質に分散させることが困難であり、サイクル特性の劣化は十分には防げなかった。 In addition, the invention described in Patent Document 1 is insufficient to suppress the volume expansion of silicon itself, and binds the negative electrode active material and the current collector with a resin having insufficient bonding force, The deterioration of cycle characteristics could not be prevented sufficiently. Furthermore, the productivity was poor due to the formation process of carbon nanofibers. In the invention described in Patent Document 2, it is difficult to uniformly disperse each component at the nano-size level, and deterioration of cycle characteristics cannot be prevented sufficiently.
特に、負極材料としての実用化が期待されているシリコンは、充放電時の体積変化が大きいため、シリコンを含む活物質粒子は割れが発生しやすく、粒子内の集電性劣化を生じ、充放電サイクル特性が悪いという問題点があった。 In particular, silicon, which is expected to be put to practical use as a negative electrode material, has a large volume change during charge and discharge, and therefore active material particles containing silicon are liable to crack, causing deterioration of current collection in the particles, and charging and discharging. There was a problem that the discharge cycle characteristics were poor.
本発明は、前述した問題点に鑑みてなされたもので、その目的とすることは、高容量と良好なサイクル特性を実現するリチウムイオン二次電池用の負極材料を得ることである。 The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a negative electrode material for a lithium ion secondary battery that realizes high capacity and good cycle characteristics.
本発明者は、上記目的を達成するために鋭意検討した結果、リチウムを吸蔵しやすい第１の相中に、リチウムを吸蔵しにくい第２の相を設けると、第１の相がリチウムを吸蔵して膨張する際に、第２の相が膨張しないため、第２の相がくさびやピンのような効果を発揮し、第１の相の膨張を抑制するとともにナノサイズ粒子の充放電時の微細化を防止することができることを見出した。本発明は、この知見に基づきなされたものである。 As a result of intensive studies to achieve the above object, the present inventor has provided a second phase in which lithium is not occluded in the first phase in which lithium is occluded, and the first phase occludes lithium. When the second phase does not expand, the second phase exhibits an effect like a wedge or a pin, suppresses the expansion of the first phase, and at the time of charging / discharging of the nano-sized particles. It has been found that miniaturization can be prevented. The present invention has been made based on this finding.
すなわち本発明は、以下のナノサイズ粒子を負極活物質として含むリチウムイオン二次電池用負極材料などを提供するものである。
（１）種類の異なる元素Ａと元素Ｄとを含み、前記元素ＡがＳｉ（シリコン）であり、前記元素ＤがＦｅ（鉄）、Ｃｏ（コバルト）、Ｎｉ（ニッケル）、Ｃａ（カルシウム）、Ｓｃ（スカンジウム）、Ｔｉ（チタン）、Ｖ（バナジウム）、Ｃｒ（クロム）、Ｍｎ（マンガン）、Ｓｒ（ストロンチウム）、Ｙ（イットリウム）、Ｚｒ（ジルコニウム）、Ｎｂ（ニオブ）、Ｍｏ（モリブデン）、Ｔｃ（テクネチウム）、Ｒｕ（ルテニウム）、Ｒｈ（ロジウム）、Ｂａ（バリウム）、ランタノイド元素（Ｃｅ（セリウム）、およびＰｍ（プロメチウム）を除く）、Ｈｆ（ハフニウム）、Ｔａ（タンタル）、Ｗ（タングステン）、Ｒｅ（レニウム）、Ｏｓ（オスミウム）およびＩｒ（イリジウム）からなる群より選ばれた少なくとも１種の元素であり、前記元素Ａの単体または固溶体である、球形状の第１の相と、前記元素Ａと前記元素Ｄとの化合物である第２の相を少なくとも有し、前記第２の相が前記第１の相の中にあり、前記第２の相の一部または全部が、前記第１の相に覆われており、平均粒径が２〜３００ｎｍであることを特徴とするナノサイズ粒子を負極活物質として含むリチウムイオン二次電池用負極材料。なお、ランタノイド元素（ＣｅおよびＰｍを除く）とは、Ｌａ（ランタン）、Ｐｒ（プラセオジム）、Ｎｄ（ネオジム）、Ｓｍ（サマリウム）、Ｅｕ（ユウロピウム）、Ｇｄ（ガドリニウム）、Ｔｂ（テルビウム）、Ｄｙ（ジスプロシウム）、Ｈｏ（ホルミウム）、Ｅｒ（エルビウム）、Ｔｍ（ツリウム）、Ｙｂ（イッテルビウム）、Ｌｕ（ルテチウム）である。
（２）前記第２の相がＤＡｘ（１＜ｘ≦３)なる化合物であることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（３）前記第１の相が主としてアモルファスシリコンであり、前記第２の相が結晶質シリサイドであることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（４）前記第１の相がリンまたはホウ素を添加したシリコンであることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（５）前記ナノサイズ粒子において、前記元素Ａと前記元素Ｄの合計に占める前記元素Ｄの原子比率が０．０１〜３０％であることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（６）前記ナノサイズ粒子が、Ｆｅ、Ｃｏ、Ｎｉ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｓｒ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｔｃ、Ｒｕ、Ｒｈ、Ｂａ、ランタノイド元素（ＣｅおよびＰｍを除く）、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、ＯｓおよびＩｒからなる群より選ばれた少なくとも１種の元素である元素Ｄ´をさらに含み、前記元素Ｄ´が、前記第２の相を構成する前記元素Ｄとは種類の異なる元素であり、前記ナノサイズ粒子が、前記元素Ａと前記元素Ｄ´との化合物である他の第２の相をさらに有し、前記他の第２の相が前記第１の相の中にあり、前記他の第２の相の一部または全部が、前記第１の相に覆われていることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（７）導電助剤をさらに有し、前記導電助剤がＣ（炭素）、Ｃｕ（銅）、Ｓｎ（スズ）、Ｚｎ（亜鉛）、Ｎｉ（ニッケル）およびＡｇ（銀）からなる群より選ばれた少なくとも１種の粉末であることを特徴とする（１）に記載のリチウムイオン二次電池用負極材料。
（８）前記導電助剤がカーボンナノホーンを含むことを特徴とする（７）に記載のリチウムイオン二次電池用負極材料。
（９）（１）ないし（８）のいずれかに記載のリチウムイオン二次電池用負極材料を用いたリチウムイオン二次電池用負極。
（１０）リチウムイオンを吸蔵および放出可能な正極と、（９）に記載の負極と、前記正極と前記負極との間に配置されたセパレータとを有し、リチウムイオン伝導性を有する電解質中に、前記正極と前記負極と前記セパレータとを設けたことを特徴とするリチウムイオン二次電池。
That is, this invention provides the negative electrode material for lithium ion secondary batteries etc. which contain the following nanosize particles as a negative electrode active material .
(1) Including different types of elements A and D, the element A is Si (silicon ), and the element D is Fe (iron), Co (cobalt), Ni (nickel), Ca (calcium), Sc (scandium), Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Sr (strontium), Y (yttrium), Zr (zirconium), Nb (niobium), Mo (molybdenum), Tc (technetium), Ru (ruthenium), Rh (rhodium), Ba (barium), lanthanoid elements (excluding Ce (cerium) and Pm (promethium)), Hf (hafnium), Ta (tantalum), W (tungsten) ), Re (rhenium), Os (osmium) and Ir (iridium). The element is a simple substance or solid solution of A, and spherical first phase has at least a second phase which is a compound of the element D and the element A, the second phase is the first A nano-sized particle having a negative particle active material , wherein the second phase is partly or entirely covered with the first phase and has an average particle diameter of 2 to 300 nm A negative electrode material for lithium ion secondary batteries . The lanthanoid elements (excluding Ce and Pm) are La (lanthanum), Pr (praseodymium), Nd (neodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy. (Dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).
(2) The negative electrode material for a lithium ion secondary battery according to (1) the second phase is a DA x (1 <x ≦ 3 ) becomes compound.
( 3 ) The negative electrode material for a lithium ion secondary battery according to (1), wherein the first phase is mainly amorphous silicon and the second phase is crystalline silicide.
( 4 ) The negative electrode material for a lithium ion secondary battery according to (1), wherein the first phase is silicon to which phosphorus or boron is added.
( 5 ) The lithium ion secondary according to (1), wherein in the nano-sized particles, the atomic ratio of the element D in the total of the element A and the element D is 0.01 to 30%. Negative electrode material for batteries .
( 6 ) The nano-sized particles are Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (Ce and Further including an element D ′ which is at least one element selected from the group consisting of Hf, Ta, W, Re, Os and Ir, and the element D ′ constitutes the second phase The element D is a different type of element, and the nano-sized particles further include another second phase that is a compound of the element A and the element D ′, and the other second phase. In the first phase, and a part or all of the other second phase is covered with the first phase. The lithium ion secondary according to (1) Negative electrode material for batteries .
( 7 ) It further has a conductive assistant, and the conductive assistant is selected from the group consisting of C (carbon), Cu (copper), Sn (tin), Zn (zinc), Ni (nickel) and Ag (silver). The negative electrode material for a lithium ion secondary battery according to ( 1 ), wherein the negative electrode material is at least one kind of powder.
( 8 ) The negative electrode material for a lithium ion secondary battery according to ( 7 ), wherein the conductive additive contains carbon nanohorn.
( 9 ) A negative electrode for a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery according to any one of ( 1 ) to ( 8 ).
( 10 ) In an electrolyte having lithium ion conductivity, comprising a positive electrode capable of inserting and extracting lithium ions, a negative electrode according to ( 9 ), and a separator disposed between the positive electrode and the negative electrode. A lithium ion secondary battery comprising the positive electrode, the negative electrode, and the separator.
本発明により、高容量と良好なサイクル特性を実現するリチウムイオン二次電池用の負極材料を得ることができる。 According to the present invention, a negative electrode material for a lithium ion secondary battery that achieves a high capacity and good cycle characteristics can be obtained.
以下図面に基づいて、本発明の実施形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
（１．ナノサイズ粒子）
（１−１．ナノサイズ粒子の構成）
第１の実施形態に係るナノサイズ粒子１について説明する。
図１は、ナノサイズ粒子１を示す概略断面図である。ナノサイズ粒子１は、第１の相３と第２の相５を有しており、第１の相３は、球形状を形成しており、複数の第２の相５が第１の相３の中に分散している。
(1. Nano-sized particles)
(1-1. Configuration of nano-sized particles)
The nanosize particle 1 according to the first embodiment will be described.
FIG. 1 is a schematic cross-sectional view showing a nano-sized particle 1. The nano-sized particle 1 has a first phase 3 and a second phase 5, the first phase 3 forms a spherical shape, and a plurality of second phases 5 are first phases. 3 are dispersed.
第１の相３は、元素Ａの単体であり、元素ＡはＳｉ、Ｓｎ、Ａｌ、Ｐｂ、Ｓｂ、Ｂｉ、Ｇｅ、ＩｎおよびＺｎからなる群より選ばれた少なくとも１種の元素である。元素Ａは、リチウムを吸蔵しやすい元素である。なお、第１の相３は、元素Ａを主成分とする固溶体であってもよい。元素Ａと固溶体を形成する元素は、元素Ａを選ぶことができる前記群より選ばれた元素でもよいし、前記群に挙げられていない元素であってもよい。第１の相３はリチウムを吸蔵可能である。 The first phase 3 is a simple element A, and the element A is at least one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. The element A is an element that easily stores lithium. Note that the first phase 3 may be a solid solution containing the element A as a main component. The element that forms a solid solution with the element A may be an element selected from the group in which the element A can be selected, or an element not listed in the group. The first phase 3 can occlude lithium.
球形状とは、球形や楕円体形に限られるものではなく、表面がおおむね滑らかな曲面で構成されていることを意味し、破砕法により形成されるような表面に角を有する形状とは異なる形状である。 The spherical shape is not limited to a spherical shape or an ellipsoidal shape, but means that the surface is composed of a generally smooth curved surface, which is different from a shape having a corner on the surface as formed by the crushing method. It is.
第２の相５は、元素Ａと元素Ｄとの化合物であり、結晶質である。元素ＤがＦｅ、Ｃｏ、Ｎｉ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｓｒ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｔｃ、Ｒｕ、Ｒｈ、Ｂａ、ランタノイド元素（ＣｅおよびＰｍを除く）、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、ＯｓおよびＩｒからなる群より選ばれた少なくとも１種の元素である。元素Ｄは、リチウムを吸蔵しにくい元素であり、元素ＡとＤＡｘ（１＜ｘ≦３)である化合物を形成可能である。大部分の元素Ａに対して、例えば、ＦｅＳｉ２やＣｏＳｉ２のようにｘ＝２であるが、Ｒｈ３Ｓｉ４（ＲｈＳｉ１．３３）のようにｘ＝１．３３となる場合や、Ｒｕ２Ｓｉ３（ＲｕＳｉ１．５）のようにｘ＝１．５となる場合、Ｓｒ３Ｓｉ５（ＳｒＳｉ１．６７）のようにｘ＝１．６７となる場合、Ｍｎ４Ｓｉ７（ＭｎＳｉ１．７５）やＴｃ４Ｓｉ７（ＴｃＳｉ１．７５）のようにｘ＝１．７５となる場合、さらにＩｒＳｉ３のようにｘ＝３となる場合がある。第２の相５は、リチウムをほとんど吸蔵しない。 The second phase 5 is a compound of element A and element D and is crystalline. Element D is Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf And at least one element selected from the group consisting of Ta, W, Re, Os and Ir. The element D is an element that does not easily store lithium, and can form a compound that is the element A and DA x (1 <x ≦ 3). For most of the elements A, for example, x = 2 such as FeSi 2 or CoSi 2 , but x = 1.33 such as Rh 3 Si 4 (RhSi 1.33 ), or Ru When x = 1.5, such as 2 Si 3 (RuSi 1.5 ), when x = 1.67 , such as Sr 3 Si 5 (SrSi 1.67 ), Mn 4 Si 7 (MnSi 1 .75 ) and Tc 4 Si 7 (TcSi 1.75 ), x = 1.75, and further IrSi 3 may be x = 3. The second phase 5 hardly absorbs lithium.
また、ナノサイズ粒子は、元素Ｄに加えて、元素Ｄ´を含んでも良い。元素Ｄ´は、元素Ｄを選ぶことができる群より選ばれた元素であり、元素Ｄと元素Ｄ´は種類の異なる元素である。図２（ｂ）に示すナノサイズ粒子８は、元素Ｄと元素Ｄ´を含み、元素Ａと元素Ｄの化合物である第２の相５に加えて、他の第２の相６を有する。他の第２の相６は、元素Ａと元素Ｄ´の化合物である。ナノサイズ粒子８は、元素Ｄと元素Ｄ´からなる固溶体（図示せず）を形成してもよい。例えば、第２の相５がＳｉとＦｅの化合物であり、他の第２の相６がＳｉとＣｏの化合物であり、元素Ｄと元素Ｄ´からなる固溶体がＦｅとＣｏの固溶体である場合が挙げられる。 In addition to the element D, the nano-sized particles may include the element D ′. The element D ′ is an element selected from a group in which the element D can be selected, and the element D and the element D ′ are different types of elements. 2B includes the element D and the element D ′, and has the other second phase 6 in addition to the second phase 5 that is a compound of the element A and the element D. The other second phase 6 is a compound of element A and element D ′. The nano-sized particles 8 may form a solid solution (not shown) composed of the element D and the element D ′. For example, when the second phase 5 is a compound of Si and Fe, the other second phase 6 is a compound of Si and Co, and the solid solution composed of the elements D and D ′ is a solid solution of Fe and Co Is mentioned.
ナノサイズ粒子１の平均粒径は、好ましくは２〜３００ｎｍであり、より好ましくは５０〜２００ｎｍである。ホールペッチの法則により、粒径サイズが小さいと、降伏応力が高まるため、ナノサイズ粒子１の平均粒径が２〜３００ｎｍであれば、粒径サイズが十分小さく、降伏応力が十分大きく、充放電により微粉化しにくい。なお、平均粒径が２ｎｍより小さいと、ナノサイズ粒子の合成後の取扱いが困難となり、平均粒径が３００ｎｍより大きいと、粒径サイズが大きくなってしまい、降伏応力が十分でない。 The average particle size of the nano-sized particles 1 is preferably 2 to 300 nm, more preferably 50 to 200 nm. According to Hall Petch's law, if the particle size is small, the yield stress increases. Therefore, if the average particle size of the nano-sized particles 1 is 2 to 300 nm, the particle size is sufficiently small and the yield stress is sufficiently large. Difficult to pulverize. When the average particle size is smaller than 2 nm, it becomes difficult to handle the nano-sized particles after synthesis. When the average particle size is larger than 300 nm, the particle size becomes large and the yield stress is not sufficient.
元素Ａと元素Ｄの合計に対する元素Ｄの原子比率が０．０１〜３０％であることが好ましい。この原子比率が０．０１〜３０％であると、ナノサイズ粒子１をリチウムイオン二次電池の負極材料に用いた際に、サイクル特性と高容量を両立できる。一方、０．０１％を下回ると、ナノサイズ粒子１のリチウム吸蔵時の体積膨張を抑制できず、３０％を超えると、高容量であるメリットが特になくなってしまう。なお、ナノサイズ粒子が元素Ｄ´を含む場合は、元素Ａと元素Ｄと元素Ｄ´の合計に対する、元素Ｄと元素Ｄ´の合計の原子比率が０．０１〜３０％であることが好ましい。 It is preferable that the atomic ratio of the element D with respect to the sum of the element A and the element D is 0.01 to 30%. When the atomic ratio is 0.01 to 30%, both the cycle characteristics and the high capacity can be achieved when the nano-sized particles 1 are used as the negative electrode material of the lithium ion secondary battery. On the other hand, if it is less than 0.01%, the volume expansion at the time of occlusion of lithium of the nano-sized particles 1 cannot be suppressed, and if it exceeds 30%, the merit of high capacity is particularly lost. When the nano-sized particles include the element D ′, the atomic ratio of the total of the element D and the element D ′ with respect to the total of the element A, the element D, and the element D ′ is preferably 0.01 to 30%. .
特に、第１の相が主としてアモルファスシリコンであり、第２の相が結晶質シリサイドであることが好ましい。また、第１の相がリンまたはホウ素を添加したシリコンであることが好ましい。リンまたはホウ素を添加することでシリコンの導電性を高めることができる。リンの代わりに、インジウムやガリウムを用いることができ、ホウ素の代わりにヒ素を用いることも可能である。第１の相のシリコンの導電性を高めることで、このようなナノサイズ粒子を用いた負極は、内部抵抗が小さくなり、大電流を流すことが可能となり、良好なハイレート特性を有する。 In particular, it is preferable that the first phase is mainly amorphous silicon and the second phase is crystalline silicide. The first phase is preferably silicon to which phosphorus or boron is added. The conductivity of silicon can be increased by adding phosphorus or boron. Indium or gallium can be used instead of phosphorus, and arsenic can be used instead of boron. By increasing the conductivity of the first phase silicon, the negative electrode using such nano-sized particles has a low internal resistance, allows a large current to flow, and has a good high-rate characteristic.
なお、微粒子は通常は凝集して存在しているので、ナノサイズ粒子の平均粒径は、ここでは一次粒子の平均粒径を指す。粒子の計測は、電子顕微鏡（ＳＥＭ）の画像情報と動的光散乱光度計（ＤＬＳ）の体積基準メディアン径を併用する。平均粒径は、ＳＥＭ画像によりあらかじめ粒子形状を確認し、画像解析ソフトウェア（例えば、旭化成エンジニアリング製「Ａ像くん」（登録商標））で粒径を求めたり、粒子を溶媒に分散してＤＬＳ（例えば、大塚電子製ＤＬＳ−８０００）により測定したりすることが可能である。微粒子が十分に分散しており、凝集していなければ、ＳＥＭとＤＬＳでほぼ同じ測定結果が得られる。また、ナノサイズ粒子の形状が、アセチレンブラックのような高度に発達したストラクチャー形状である場合にも、ここでは一次粒径で平均粒径を定義し、ＳＥＭ写真の画像解析で平均粒径を求めることができる。 Since the fine particles are usually present in an aggregated state, the average particle size of the nano-sized particles here refers to the average particle size of the primary particles. For particle measurement, image information of an electron microscope (SEM) and a volume-based median diameter of a dynamic light scattering photometer (DLS) are used in combination. For the average particle size, the particle shape is confirmed in advance using an SEM image, the particle size is obtained using image analysis software (for example, “A Image-kun” (registered trademark) manufactured by Asahi Kasei Engineering), or DLS ( For example, it can be measured by Otsuka Electronics DLS-8000). If the fine particles are sufficiently dispersed and not agglomerated, almost the same measurement results can be obtained with SEM and DLS. Even when the shape of the nano-sized particles is a highly developed structure such as acetylene black, the average particle size is defined by the primary particle size here, and the average particle size is obtained by image analysis of the SEM photograph. be able to.
なお、図１（ａ）においては、第１の相３中に、複数の第２の相５が分散しているが、単一の第２の相５が分散していてもよい。 In FIG. 1A, a plurality of second phases 5 are dispersed in the first phase 3, but a single second phase 5 may be dispersed.
また、図１（ｂ）に示すナノサイズ粒子２のように、一部の第２の相５が表面に露出していてもよい。つまり、必ずしも第２の相５の周囲の全てを第１の相３で覆っている必要はなく、第２の相５の周囲の一部のみを第１の相で覆っていてもよい。 Moreover, a part of the second phase 5 may be exposed on the surface like the nano-sized particles 2 shown in FIG. That is, it is not always necessary to cover the entire periphery of the second phase 5 with the first phase 3, and only a part of the periphery of the second phase 5 may be covered with the first phase.
また、図２（ａ）に示すナノサイズ粒子７のように、第１の相３中に元素Ａの微結晶４が形成されていても良い。元素Ａの微結晶４はナノサイズ粒子１に示す第２の相５の重量比率が十分小さいときに生じやすい。つまり、元素Ｄの原子比率が少ないほど、元素Ａの結晶相が増える。さらに、図２（ｂ）に示すナノサイズ粒子８のように、元素Ｄと元素Ｄ´を含み、他の第２の相６が形成されていても良い。例えば、元素Ａがシリコンであり、元素Ｄが鉄であり、元素Ｄ´がコバルトであり、第１の相３がシリコンであり、第２の相５が鉄シリサイドであり、他の第２の相６がコバルトシリサイドである場合が挙げられる。この際、第１の相３中に鉄とコバルトの固溶体が形成されていても良い。 Moreover, the microcrystal 4 of the element A may be formed in the 1st phase 3 like the nanosized particle 7 shown to Fig.2 (a). The microcrystal 4 of the element A is likely to be generated when the weight ratio of the second phase 5 shown in the nanosize particle 1 is sufficiently small. That is, the smaller the atomic ratio of element D, the more the crystal phase of element A increases. Furthermore, like the nanosized particle 8 shown in FIG.2 (b), the other 2nd phase 6 containing the element D and element D 'may be formed. For example, the element A is silicon, the element D is iron, the element D ′ is cobalt, the first phase 3 is silicon, the second phase 5 is iron silicide, and the other second An example is when phase 6 is cobalt silicide. At this time, a solid solution of iron and cobalt may be formed in the first phase 3.
なお、ナノサイズ粒子１の最表面に酸素が結合しても良い。空気中にナノサイズ粒子１を取り出すと、空気中の酸素がナノサイズ粒子１の表面の元素と反応するからである。 Note that oxygen may be bonded to the outermost surface of the nano-sized particle 1. This is because when the nano-sized particles 1 are taken out into the air, oxygen in the air reacts with elements on the surface of the nano-sized particles 1.
（１−２．ナノサイズ粒子の製造方法）
ナノサイズ粒子１の製造方法を説明する。ナノサイズ粒子１は、気相合成法により合成される。特に、原料粉末を、プラズマ化し、１万Ｋ相当にまで加熱し、その後冷却することで、ナノサイズ粒子１を製造可能である。
(1-2. Method for producing nano-sized particles)
A method for producing the nano-sized particles 1 will be described. The nanosize particles 1 are synthesized by a gas phase synthesis method. In particular, the nano-sized particles 1 can be produced by converting the raw material powder into plasma and heating it to about 10,000 K, followed by cooling.
ナノサイズ粒子１の製造に用いられる製造装置の一具体例を、図３に基づいて説明する。図３に示すナノサイズ粒子製造装置９において、反応チャンバー１１の上部外壁には、プラズマ発生用の高周波コイル１７が巻き付けてある。高周波コイル１７には、高周波電源１８より、数ＭＨｚの交流電圧が印加される。好ましい周波数は４ＭＨｚである。なお、高周波コイル１７を巻きつける上部外壁は石英ガラスなどで構成された円筒形の２重管となっており、その隙間に冷却水を流してプラズマによる石英ガラスの溶融を防止している。 A specific example of a manufacturing apparatus used for manufacturing the nano-sized particles 1 will be described with reference to FIG. In the nanosize particle manufacturing apparatus 9 shown in FIG. 3, a high frequency coil 17 for generating plasma is wound around the upper outer wall of the reaction chamber 11. An AC voltage of several MHz is applied to the high frequency coil 17 from the high frequency power source 18. A preferred frequency is 4 MHz. The upper outer wall around which the high-frequency coil 17 is wound is a cylindrical double tube made of quartz glass or the like, and cooling water is passed through the gap to prevent the quartz glass from melting by plasma.
また、反応チャンバー１１の上部には、原料粉末供給口１３と共に、シースガス供給口１５が設けてある。原料粉末フィーダーから供給される原料粉末１４は、キャリアガス（ヘリウム、アルゴンなどの希ガス）とともに原料粉末供給口１３を通してプラズマ１９中に供給される。また、シースガス１６はシースガス供給口１５を通して反応チャンバー１１に供給される。シースガス１６は、アルゴンガスと酸素ガスの混合ガスなどである。なお、原料粉末供給口１３は、必ずしも図３のようにプラズマ１９の上部に設置する必要はなく、プラズマ１９の横方向にノズルを設置することもできる。また、原料粉末供給口１３を冷却水により水冷してもよい。なお、プラズマに供給するナノサイズ粒子の原料の性状は、粉末だけに限られず、原料粉末のスラリーやガス状の原料を供給しても良い。 A sheath gas supply port 15 is provided in the upper part of the reaction chamber 11 together with the raw material powder supply port 13. The raw material powder 14 supplied from the raw material powder feeder is supplied into the plasma 19 through the raw material powder supply port 13 together with a carrier gas (rare gas such as helium and argon). The sheath gas 16 is supplied to the reaction chamber 11 through the sheath gas supply port 15. The sheath gas 16 is a mixed gas of argon gas and oxygen gas or the like. In addition, the raw material powder supply port 13 does not necessarily need to be installed above the plasma 19 as shown in FIG. 3, and a nozzle can be installed in the lateral direction of the plasma 19. The raw material powder supply port 13 may be water-cooled with cooling water. In addition, the property of the raw material of the nanosize particles supplied to the plasma is not limited to the powder, and a slurry of the raw material powder or a gaseous raw material may be supplied.
反応チャンバー１１は、プラズマ反応部の圧力の保持や、製造された微粉末の分散を抑制する役割を果たす。反応チャンバー１１も、プラズマによる損傷を防ぐため、水冷されている。また、反応チャンバー１１の側部には、吸引管が接続してあり、その吸引管の途中には合成された微粉末を捕集するためのフィルター２１が設置してある。反応チャンバー１１からフィルター２１を連結する吸引管も、冷却水により水冷されている。反応チャンバー１１内の圧力は、フィルター２１の下流側に設置されている真空ポンプの吸引能力によって調整する。 The reaction chamber 11 plays a role of holding the pressure in the plasma reaction part and suppressing the dispersion of the produced fine powder. The reaction chamber 11 is also water-cooled to prevent damage due to plasma. A suction tube is connected to the side of the reaction chamber 11, and a filter 21 for collecting the synthesized fine powder is installed in the middle of the suction tube. The suction pipe connecting the filter 21 from the reaction chamber 11 is also water-cooled with cooling water. The pressure in the reaction chamber 11 is adjusted by the suction capacity of a vacuum pump installed on the downstream side of the filter 21.
ナノサイズ粒子１の製造方法は、プラズマから気体、液体を経由して固体となりナノサイズ粒子１を析出させるボトムアップの手法なので、液滴の段階で球形状となり、ナノサイズ粒子１は球形状となる。一方、破砕法やメカノケミカル法などの大きな粒子を小さくするトップダウンの手法では、粒子の形状はいびつでごつごつしたものとなり、ナノサイズ粒子１の球形状の形状とは大きく異なる。 The manufacturing method of the nano-sized particle 1 is a bottom-up method in which the nano-sized particle 1 is deposited from the plasma through a gas or liquid to be solid, so that the nano-sized particle 1 has a spherical shape at the droplet stage. Become. On the other hand, in the top-down method of reducing large particles such as the crushing method and the mechanochemical method, the shape of the particles is rugged and is very different from the spherical shape of the nano-sized particles 1.
（１−３．ナノサイズ粒子１の効果）
第１の相３がリチウムを吸蔵すると、体積膨張するが、第２の相５は、リチウムを吸蔵しないため、第２の相５に接する第１の相３の膨張は、抑えられる。つまり、第１の相３がリチウムを吸蔵して体積膨張をしようとしても、第２の相５が膨張しにくいため、第１の相３と第２の相５との界面は滑りにくく、第２の相５がくさびやピンのような効果を発揮し、ナノサイズ粒子全体の膨張を抑制する。そのため、第２の相５を有しない粒子に比べて、第２の相５を有するナノサイズ粒子１は、リチウムを吸蔵する際に膨張しにくく、リチウムの吸蔵量が抑制される。そのため、第１の実施形態によれば、ナノサイズ粒子１は、リチウムを吸蔵させても、体積膨張が抑えられ、サイクル特性時の放電容量の低下が抑制される。
(1-3. Effects of nano-sized particles 1)
When the first phase 3 occludes lithium, the volume expands. However, the second phase 5 does not occlude lithium, and therefore the expansion of the first phase 3 in contact with the second phase 5 is suppressed. That is, even if the first phase 3 occludes lithium and tries to expand its volume, the second phase 5 hardly expands, so the interface between the first phase 3 and the second phase 5 is difficult to slip, Phase 5 of 2 exhibits an effect like a wedge or a pin, and suppresses expansion of the entire nano-sized particle. Therefore, compared with the particle | grains which do not have the 2nd phase 5, the nanosize particle | grains 1 which have the 2nd phase 5 are hard to expand | swell when occluding lithium, and the occlusion amount of lithium is suppressed. Therefore, according to 1st Embodiment, even if the nanosized particle 1 occludes lithium, volume expansion is suppressed and the fall of the discharge capacity at the time of cycling characteristics is suppressed.
また、前述のとおり、ナノサイズ粒子１は、膨張しにくいため、ナノサイズ粒子１を、大気中に出したとしても、大気中の酸素と反応しにくい。第２の相５を有しないナノ粒子は、表面保護せずに大気中に放置すると、表面から酸素と反応し、表面から粒子内部へと酸化が進行するため、ナノ粒子全体が酸化する。しかしながら、本発明のナノサイズ粒子１を大気中に放置した場合、粒子の最表面は酸素と反応するが、全体としてナノサイズ粒子が膨張しにくいため、酸素が内部に侵入しにくく、ナノサイズ粒子１の中心部まで酸化が及ぶことはない。従って、通常の金属ナノ粒子は比表面積が大きく、酸化して発熱や体積膨張が生じやすいが、本発明のナノサイズ粒子１は有機物や金属酸化物で特別な表面コートを行う必要が無く、大気中で粉体のまま扱うことが出来る。工業的利用価値が大きい。 Further, as described above, since the nano-sized particles 1 are difficult to expand, even if the nano-sized particles 1 are put out into the atmosphere, they hardly react with oxygen in the atmosphere. When the nanoparticles not having the second phase 5 are left in the air without protecting the surface, they react with oxygen from the surface, and oxidation proceeds from the surface to the inside of the particles, so that the whole nanoparticles are oxidized. However, when the nano-sized particles 1 of the present invention are left in the atmosphere, the outermost surface of the particles reacts with oxygen, but since the nano-sized particles are difficult to expand as a whole, oxygen is less likely to enter the interior, Oxidation does not reach the center of 1. Accordingly, normal metal nanoparticles have a large specific surface area and are likely to oxidize and generate heat and volume expansion. However, the nano-sized particles 1 of the present invention do not need to be specially coated with organic substances or metal oxides, It can be handled as powder. Industrial use value is great.
（２．リチウムイオン二次電池の作製）
（２−１．リチウムイオン二次電池用負極の作製）
まず、リチウムイオン二次電池用負極の製造方法を説明する。図４に示すように、ミキサー２３に、スラリー原料２７を投入し、混練してスラリー２５を形成する。スラリー原料２７は、ナノサイズ粒子１、導電助剤、結着剤、増粘剤、溶媒などである。
(2. Preparation of lithium ion secondary battery)
(2-1. Production of negative electrode for lithium ion secondary battery)
First, the manufacturing method of the negative electrode for lithium ion secondary batteries is demonstrated. As shown in FIG. 4, slurry raw material 27 is put into mixer 23 and kneaded to form slurry 25. The slurry raw material 27 is the nano-sized particles 1, the conductive auxiliary agent, the binder, the thickener, the solvent, and the like.
スラリー２５中の固形分において、ナノサイズ粒子２５〜９０重量％、導電助剤５〜７０重量％、結着剤１〜１０重量％を含む。 The solid content in the slurry 25 includes 25 to 90% by weight of nano-sized particles, 5 to 70% by weight of a conductive additive, and 1 to 10% by weight of a binder.
ミキサー２３は、スラリーの調製に用いられる一般的な混練機を用いることができ、ニーダー、撹拌機、分散機、混合機などと呼ばれるスラリーを調製可能な装置を用いてもよい。また、増粘剤としてはカルボキシメチルセルロース、メチルセルロース等の多糖類等を１種または２種以上の混合物として用いることが適している。また、溶媒としては水を用いることができる。また、有機系スラリーを調製するときは、溶媒としてＮ−メチル−２−ピロリドンを用いることができる。 As the mixer 23, a general kneader used for preparing a slurry can be used, and an apparatus capable of preparing a slurry called a kneader, a stirrer, a disperser, a mixer, or the like may be used. Moreover, as a thickener, it is suitable to use polysaccharides, such as carboxymethylcellulose and methylcellulose, as a 1 type, or 2 or more types of mixture. Moreover, water can be used as a solvent. Further, when preparing an organic slurry, N-methyl-2-pyrrolidone can be used as a solvent.
導電助剤は、炭素、銅、スズ、亜鉛、ニッケル、銀からなる群より選ばれた少なくとも１種の導電性物質からなる粉末である。炭素、銅、スズ、亜鉛、ニッケル、銀の単体の粉末でもよいし、それぞれの合金の粉末でもよい。例えば、ファーネスブラックやアセチレンブラックなどの一般的なカーボンブラックを使用できる。特に、ナノサイズ粒子１の元素Ａが導電性の低いシリコンである場合、ナノサイズ粒子１の表面には、シリコンが露出することとなり、導電性が低くなるため、カーボンナノホーンを導電助剤として加えることが好ましい。ここで、カーボンナノホーン（ＣＮＨ）とは、グラフェンシートを円錐形に丸めた構造をしており、実際の形態は多数のＣＮＨが頂点を外側に向けて、放射状のウニの様な形態の集合体として存在する。ＣＮＨのウニ様集合体の外径は５０ｎｍ〜２５０ｎｍ程度である。特に、平均粒径８０ｎｍ程度のＣＮＨが好ましい。 The conductive assistant is a powder made of at least one conductive material selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver. A single powder of carbon, copper, tin, zinc, nickel, or silver may be used, or a powder of each alloy may be used. For example, general carbon black such as furnace black and acetylene black can be used. In particular, when the element A of the nano-sized particle 1 is silicon having low conductivity, silicon is exposed on the surface of the nano-sized particle 1 and the conductivity becomes low. Therefore, carbon nanohorn is added as a conductive aid. It is preferable. Here, the carbon nanohorn (CNH) has a structure in which a graphene sheet is rounded into a conical shape, and the actual form is an aggregate of a shape like a radial sea urchin with many CNHs facing the apex to the outside. Exists as. The outer diameter of the CNH sea urchin-like aggregate is about 50 nm to 250 nm. In particular, CNH having an average particle size of about 80 nm is preferable.
導電助剤の平均粒径も一次粒子の平均粒径を指す。アセチレンブラックのような高度にストラクチャー形状が発達している場合にも、ここでは一次粒径で平均粒径を定義し、ＳＥＭ写真の画像解析で平均粒径を求めることができる。 The average particle size of the conductive assistant also refers to the average particle size of the primary particles. Even when the structure shape is highly developed such as acetylene black, the average particle diameter can be defined by the primary particle diameter here, and the average particle diameter can be obtained by image analysis of the SEM photograph.
また、粒子状の導電助剤とワイヤー形状の導電助剤の両方を用いても良い。ワイヤー形状の導電助剤は導電性物質のワイヤーであり、粒子状の導電助剤に挙げられた導電性物質を用いることができる。ワイヤー形状の導電助剤は、カーボンファイバー、カーボンナノチューブ、銅ナノワイヤー、ニッケルナノワイヤーなどの外径が３００ｎｍ以下の線状体を用いることができる。ワイヤー形状の導電助剤を用いることで、負極活物質や集電体などと電気的接続が保持しやすくなり集電性能が向上するとともに、ポーラス膜状の負極に繊維状物質が増え、負極にクラックが生じにくくなる。例えば粒子状の導電助剤として銅粉末を用い、ワイヤー形状の導電助剤として気相成長炭素繊維（ＶＧＣＦ：Ｖａｐｏｒ Ｇｒｏｗｎ Ｃａｒｂｏｎ Ｆｉｂｅｒ）を用いることが考えられる。なお、粒子状の導電助剤を加えずに、ワイヤー形状の導電助剤のみを用いても良い。 Moreover, you may use both a particulate-form conductive support agent and a wire-shaped conductive support agent. The wire-shaped conductive aid is a wire made of a conductive material, and the conductive materials listed in the particulate conductive aid can be used. As the wire-shaped conductive assistant, a linear body having an outer diameter of 300 nm or less, such as carbon fiber, carbon nanotube, copper nanowire, or nickel nanowire, can be used. By using a wire-shaped conductive aid, electrical connection with the negative electrode active material or current collector is easily maintained, and the current collection performance is improved. Cracks are less likely to occur. For example, it is conceivable to use copper powder as the particulate conductive auxiliary agent and to use vapor grown carbon fiber (VGCF) as the wire-shaped conductive auxiliary agent. In addition, you may use only a wire-shaped conductive support agent, without adding a particulate-form conductive support agent.
ワイヤー形状の導電助剤の長さは、好ましくは０．１μｍ〜２ｍｍである。導電助剤の外径は、好ましくは４ｎｍ〜１０００ｎｍであり、より好ましくは２５ｎｍ〜２００ｎｍである。導電助剤の長さが０．１μｍ以上であれば、導電助剤の生産性を上げるのには十分な長さであり、長さが２ｍｍ以下であれば、スラリーの塗布が容易である。また、導電助剤の外径が４ｎｍより太い場合、合成が容易であり、外径が１０００ｎｍより細い場合、スラリーの混練が容易である。導電物質の外径と長さの測定方法は、ＳＥＭによる画像解析により行った。 The length of the wire-shaped conductive assistant is preferably 0.1 μm to 2 mm. The outer diameter of the conductive aid is preferably 4 nm to 1000 nm, more preferably 25 nm to 200 nm. If the length of the conductive auxiliary agent is 0.1 μm or more, the length is sufficient to increase the productivity of the conductive auxiliary agent, and if the length is 2 mm or less, application of the slurry is easy. Further, when the outer diameter of the conductive auxiliary agent is larger than 4 nm, the synthesis is easy, and when the outer diameter is thinner than 1000 nm, the slurry is easily kneaded. The measuring method of the outer diameter and length of the conductive material was performed by image analysis using SEM.
結着剤は、樹脂の結着剤であり、ポリフッ化ビニリデン（ＰＶｄＦ）、スチレンブタジエンゴム（ＳＢＲ）などのフッ素樹脂やゴム系の有機材料を用いることができる。 The binder is a resin binder, and a fluororesin such as polyvinylidene fluoride (PVdF) and styrene butadiene rubber (SBR) or a rubber-based organic material can be used.
次に、図５に示すように、例えば、コーター２９を用いて、集電体３１の片面に、スラリー２５を塗布する。コーターは、スラリーを集電体に塗布可能な一般的な塗工装置を用いることができ、例えばロールコーターやドクターブレードによるコーター、コンマコーター、ダイコーターである。 Next, as illustrated in FIG. 5, the slurry 25 is applied to one surface of the current collector 31 using, for example, a coater 29. As the coater, a general coating apparatus capable of applying the slurry to the current collector can be used. For example, a coater using a roll coater or a doctor blade, a comma coater, or a die coater.
集電体３１は、銅、ニッケル、ステンレスからなる群より選ばれた少なくとも１種の金属からなる箔である。それぞれを単独で用いてもよいし、それぞれの合金でもよい。厚さは４μｍ〜３５μｍが好ましく、さらに８μｍ〜１８μｍがより好ましい。 The current collector 31 is a foil made of at least one metal selected from the group consisting of copper, nickel, and stainless steel. Each may be used alone or may be an alloy of each. The thickness is preferably 4 μm to 35 μm, and more preferably 8 μm to 18 μm.
その後、５０〜１５０℃程度で乾燥し、厚みを調整するため、ロールプレスを通して、リチウムイオン二次電池用負極を得る。 Then, in order to dry at about 50-150 degreeC and adjust thickness, the negative electrode for lithium ion secondary batteries is obtained through a roll press.
（２−２．リチウムイオン二次電池用正極の作製）
まず、正極活物質、導電助剤、結着剤および溶媒を混合して正極活物質の組成物を準備する。前記正極活物質の組成物をアルミ箔などの金属集電体上に直接塗布・乾燥し、正極を準備する。
(2-2. Production of positive electrode for lithium ion secondary battery)
First, a positive electrode active material, a conductive additive, a binder, and a solvent are mixed to prepare a positive electrode active material composition. The composition of the positive electrode active material is directly applied on a metal current collector such as an aluminum foil and dried to prepare a positive electrode.
前記正極活物質としては、一般的に使われるものであればいずれも使用可能であり、例えばＬｉＣｏＯ２、ＬｉＭｎ２Ｏ４、ＬｉＭｎＯ２、ＬｉＮｉＯ２、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３、ＬｉＦｅＰＯ４などの化合物である。 Any positive electrode active material can be used as long as it is generally used. For example, LiCoO 2 , LiMn 2 O 4 , LiMnO 2 , LiNiO 2 , LiCo 1/3 Ni 1/3 Mn 1/3. And compounds such as LiFePO 4 .
導電助剤としては、例えばカーボンブラックを使用し、結着剤としては、例えばポリフッ化ビニリデン（ＰＶｄＦ）、水溶性アクリル系バインダーを使用し、溶媒としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、水などを使用する。このとき、正極活物質、導電助剤、結着剤および溶媒の含量は、リチウムイオン二次電池で通常的に使用するレベルである。 For example, carbon black is used as the conductive assistant, polyvinylidene fluoride (PVdF), a water-soluble acrylic binder is used as the binder, and N-methyl-2-pyrrolidone (NMP) is used as the solvent. Use water, etc. At this time, the contents of the positive electrode active material, the conductive additive, the binder, and the solvent are at levels that are normally used in lithium ion secondary batteries.
（２−３．セパレータ）
セパレータとしては、正極と負極の電子伝導を絶縁する機能を有し、リチウムイオン二次電池で通常的に使われるものであればいずれも使用可能である。例えば、微多孔性のポリオレフィンフィルムを使用できる。
(2-3. Separator)
Any separator can be used as long as it has a function of insulating electronic conduction between the positive electrode and the negative electrode and is usually used in a lithium ion secondary battery. For example, a microporous polyolefin film can be used.
（２−４．電解液・電解質）
リチウムイオン二次電池、Ｌｉポリマー電池などにおける電解液および電解質には、有機電解液（非水系電解液）、無機固体電解質、高分子固体電解質等が使用できる。
有機電解液の溶媒の具体例として、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート等のカーボネート；ジエチルエーテル、ジブチルエーテル、エチレングリコールジメチルエーテル、エチレングリコールジエチルエーテル、エチレングリコールジブチルエーテル、ジエチレングリコールジメチルエーテル等のエーテル；ベンゾニトリル、アセトニトリル、テトラヒドロフラン、２−メチルテトラヒドロフラン、γ―ブチロラクトン、ジオキソラン、４−メチルジオキソラン、Ｎ，Ｎ−ジメチルホルムアミド、ジメチルアセトアミド、ジメチルクロロベンゼン、ニトロベンゼン等の非プロトン性溶媒、あるいはこれらの溶媒のうちの２種以上を混合した混合溶媒が挙げられる。
(2-4. Electrolytic solution / electrolyte)
An organic electrolyte (non-aqueous electrolyte), an inorganic solid electrolyte, a polymer solid electrolyte, or the like can be used as an electrolyte and an electrolyte in a lithium ion secondary battery, a Li polymer battery, or the like.
Specific examples of the organic electrolyte solvent include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate; diethyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di Ethers such as butyl ether and diethylene glycol dimethyl ether; aprotic such as benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylchlorobenzene, nitrobenzene Solvent, or two or more of these solvents Mixed solvent of thereof.
有機電解液の電解質には、ＬｉＰＦ６、ＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＡｌＯ４、ＬｉＡｌＣｌ４、ＬｉＳｂＦ６、ＬｉＳＣＮ、ＬｉＣｌ、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ３、ＬｉＣ４Ｆ９ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２等のリチウム塩からなる電解質の１種または２種以上を混合させたものを用いることができる。 The electrolyte of the organic electrolyte includes LiPF 6 , LiClO 4 , LiBF 4 , LiAlO 4 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 3 , LiC 4 F 9 SO 3 , LiN (CF 3 SO 2 ) A mixture of one or more electrolytes made of a lithium salt such as 2 can be used.
有機電解液の添加材として、負極活物質の表面に有効な固体電解質界面被膜を形成できる化合物を添加することが望ましい。例えば、分子内に不飽和結合を有し、充電時に還元重合できる物質、例えばビニレンカーボネート（ＶＣ）などを添加する。 As an additive for the organic electrolyte, it is desirable to add a compound capable of forming an effective solid electrolyte interface coating on the surface of the negative electrode active material. For example, a substance having an unsaturated bond in the molecule and capable of reductive polymerization during charging, such as vinylene carbonate (VC), is added.
また、上記の有機電解液に代えて高分子固体電解質を用いる場合には、リチウムイオンに対するイオン導電性の高い高分子である、ポリエチレンオキサイド、ポリプロピレンオキサイド、ポリエチレンイミン等からなるポリマーに電解液を含ませてゲル化したポリマーを用いることができる。 In addition, when a polymer solid electrolyte is used instead of the organic electrolyte, the electrolyte is contained in a polymer made of polyethylene oxide, polypropylene oxide, polyethyleneimine, or the like, which is a polymer having high ion conductivity with respect to lithium ions. A gelled polymer can be used.
さらに、リチウム窒化物、リチウムハロゲン化物、リチウム酸素酸塩、Ｌｉ４ＳｉＯ４、Ｌｉ４ＳｉＯ４−ＬｉＩ−ＬｉＯＨ、Ｌｉ３ＰＯ４−Ｌｉ４ＳｉＯ４、Ｌｉ２ＳｉＳ３、Ｌｉ３ＰＯ４−Ｌｉ２Ｓ−ＳｉＳ２、硫化リン化合物などの無機材料を無機固体電解質として用いてもよい。 Further, lithium nitride, lithium halide, lithium oxyacid salt, Li 4 SiO 4, Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li Inorganic materials such as 2 S—SiS 2 and phosphorus sulfide compounds may be used as the inorganic solid electrolyte.
（２−５．リチウムイオン二次電池の組立て）
前述したような正極と負極との間にセパレータを配置して、電池素子を形成する。このような電池素子を巻回、または積層して円筒形の電池ケースや角形の電池ケースに入れた後、電解液を注入して、リチウムイオン二次電池とする。
(2-5. Assembly of lithium ion secondary battery)
A battery element is formed by disposing a separator between the positive electrode and the negative electrode as described above. After winding or stacking such battery elements into a cylindrical battery case or a rectangular battery case, an electrolytic solution is injected to obtain a lithium ion secondary battery.
（２−６．第１の実施形態に係るリチウムイオン二次電池の効果）
第１の実施形態によれば、ナノサイズ粒子１を負極材料として用いるリチウムイオン二次電池は、ナノサイズ粒子１が炭素よりも単位体積あたりの容量の高い元素Ａを有するため、従来のリチウムイオン二次電池よりも容量が大きく、かつナノサイズ粒子１が微粉化しにくいためサイクル特性が良い。
(2-6. Effects of the lithium ion secondary battery according to the first embodiment)
According to the first embodiment, the lithium ion secondary battery using the nano-sized particles 1 as the negative electrode material has the element A having a higher capacity per unit volume than carbon, and thus the conventional lithium ions Since the capacity is larger than that of the secondary battery and the nano-sized particles 1 are not easily pulverized, the cycle characteristics are good.
以下、本発明について実施例および比較例を用いて具体的に説明する。
［実施例１］
（ナノサイズ粒子の作製）
図３の装置を用い、シリコン粉末と鉄粉末とをモル比でＳｉ：Ｆｅ＝３：１になるように混合し、乾燥させた混合粉末を原料粉末として、反応チャンバー内に発生させたＡｒガスのプラズマ中にキャリアガスで連続的に供給することにより、シリコンと鉄のナノサイズ粒子を作製した。
Hereinafter, the present invention will be specifically described using examples and comparative examples.
[Example 1]
(Production of nano-sized particles)
Ar gas generated in the reaction chamber using the mixed powder obtained by mixing silicon powder and iron powder in a molar ratio of Si: Fe = 3: 1 and using the mixed powder as a raw material powder using the apparatus of FIG. The silicon and iron nano-sized particles were prepared by continuously supplying the plasma with a carrier gas.
さらに詳細には、下記の通りの方法で製造した。反応チャンバー内を真空ポンプで排気した後、Ａｒガスを導入して大気圧とした。この排気とＡｒガス導入を３回繰り返して、反応容器内の残留空気を排気した。その後、反応容器内にプラズマガスとしてＡｒガスを１３Ｌ／ｍｉｎの流量で導入し、高周波コイルに交流電圧をかけて、高周波電磁場（周波数４ＭＨｚ）により高周波プラズマを発生させた。この時のプレート電力は、２０ｋＷとした。原料粉末を供給するキャリアガスは、１．０Ｌ／ｍｉｎの流速のＡｒガスを用いた。反応終了後１２時間以上徐酸化処理を施した後、得られた微粉末をフィルターで回収した。 More specifically, it was produced by the following method. After evacuating the reaction chamber with a vacuum pump, Ar gas was introduced to atmospheric pressure. This exhaustion and Ar gas introduction were repeated three times to exhaust the residual air in the reaction vessel. Thereafter, Ar gas was introduced into the reaction vessel as a plasma gas at a flow rate of 13 L / min, an AC voltage was applied to the high frequency coil, and high frequency plasma was generated by a high frequency electromagnetic field (frequency 4 MHz). The plate power at this time was 20 kW. Ar gas having a flow rate of 1.0 L / min was used as a carrier gas for supplying the raw material powder. After the completion of the reaction, a gradual oxidation treatment was performed for 12 hours or more, and the obtained fine powder was collected with a filter.
（ナノサイズ粒子の構成の評価）
ナノサイズ粒子の粒子形状の観察は、透過型電子顕微鏡（日立ハイテク製、Ｈ−９０００ ＵＨＲ）を用いて行った。ナノサイズ粒子のＴＥＭ写真を図６（ａ）〜（ｃ）に示す。図６（ａ）〜（ｃ）より、粒径約５０〜１５０ｎｍ程度のナノサイズ粒子が観察され、それぞれのナノサイズ粒子はそれぞれ球形状である。
(Evaluation of the composition of nano-sized particles)
Observation of the particle shape of the nano-sized particles was performed using a transmission electron microscope (H-9000 UHR, manufactured by Hitachi High-Tech). TEM photographs of the nano-sized particles are shown in FIGS. 6A to 6C, nano-sized particles having a particle size of about 50 to 150 nm are observed, and each nano-sized particle has a spherical shape.
ナノサイズ粒子の粒子形状と組成分析を、走査透過型電子顕微鏡（日本電子製、ＪＥＭ ３１００ＦＥＦ）を用いてＳＴＥＭ−ＥＤＳ（Ｓｃａｎｎｉｎｇ Ｔｒａｎｓｍｉｓｓｉｏｎ Ｅｌｅｃｔｒｏｎ Ｍｉｃｒｏｓｃｏｐｅ−Ｅｎｅｒｇｙ Ｄｉｓｐｅｒｓｉｖｅ Ｓｐｅｃｔｒｏｓｃｏｐｙ： 走査透過型電子顕微鏡−エネルギー分散型Ｘ線分析）分析を行った。図７（ａ）は、第１の観察箇所における明視野ＳＴＥＭ像であり、図７（ｂ）は、第１の観察箇所における暗視野ＳＴＥＭ像であり、図７（ｃ）は、ナノサイズ粒子のＥＤＳ測定箇所を示す明視野ＳＴＥＭ像である。図７（ａ）と図７（ｂ）を用い、粒子が重なっていない箇所を選び、図７（ｃ）に示す１２箇所の測定箇所を選択し、複数の粒子でなく、単独の粒子の組成を分析した。図８はＳＴＥＭ−ＥＤＳ分析結果を示し、表１は分析結果を数値化した表である。図８と表１の各分析点を示す数字は、図７（ｃ）で示す分析箇所に対応する。また、表１と表２では、ＳｉとＦｅのＫ殻由来のピークのカウントから原子比率を求めた。表１より、シリコンと鉄の原子比率は、各測定箇所で仕込み比である原子比率の３：１に近い値をとっており、各分析箇所でＳｉとＦｅの組成が同程度であることがわかる。また、図９（ａ）は、第２の観察箇所における明視野ＳＴＥＭ像であり、図９（ｂ）は、第２の観察箇所における暗視野ＳＴＥＭ像であり、図９（ｃ）は、ナノサイズ粒子のＥＤＳ測定箇所を示す明視野ＳＴＥＭ像である。第１の観察箇所と同様に、図９（ｃ）に示す１２箇所の測定箇所を選択し、粒子の組成を分析した。図１０はＳＴＥＭ−ＥＤＳ分析結果を示し、表２は分析結果を数値化した表である。図１０と表２の各分析点を示す数字は、図９（ｃ）で示す分析箇所に対応する。表２より、シリコンと鉄の原子比率は、各測定箇所で仕込み比である原子比率の３：１に近い値をとっており、各分析箇所でＳｉとＦｅの組成が同程度であることがわかる。実施例に係るサンプルが、シリコン粉末と鉄粉末の混合物でなく、ナノサイズ粒子に鉄とシリコンの両方が存在しており、それぞれのナノサイズ粒子は同様の組成を有することがわかる。 The particle shape and composition analysis of the nano-sized particles were performed using a scanning transmission electron microscope (JEM 3100FEF, manufactured by JEOL Ltd.) using a STEM-EDS (Scanning Transmission Electron Microscope-Energy Dispersive Spectroscopy: Scanning Transmission Electron Microscope). Line analysis). FIG. 7 (a) is a bright field STEM image at the first observation location, FIG. 7 (b) is a dark field STEM image at the first observation location, and FIG. 7 (c) is a nano-sized particle. It is a bright field STEM image which shows the EDS measurement location of. 7 (a) and 7 (b) are used to select locations where the particles do not overlap, select 12 measurement locations shown in FIG. 7 (c), and not a plurality of particles, but a composition of single particles. Was analyzed. FIG. 8 shows the STEM-EDS analysis results, and Table 1 is a table in which the analysis results are digitized. The numbers indicating the analysis points in FIG. 8 and Table 1 correspond to the analysis points shown in FIG. In Tables 1 and 2, the atomic ratio was determined from the count of peaks derived from the K shell of Si and Fe. From Table 1, the atomic ratio of silicon and iron takes a value close to 3: 1 of the atomic ratio, which is the charging ratio at each measurement location, and the composition of Si and Fe is about the same at each analysis location. Recognize. 9A is a bright-field STEM image at the second observation location, FIG. 9B is a dark-field STEM image at the second observation location, and FIG. It is a bright-field STEM image which shows the EDS measurement location of size particle | grains. Similarly to the first observation location, 12 measurement locations shown in FIG. 9C were selected, and the composition of the particles was analyzed. FIG. 10 shows the STEM-EDS analysis results, and Table 2 is a table in which the analysis results are digitized. The numbers indicating the analysis points in FIG. 10 and Table 2 correspond to the analysis points shown in FIG. From Table 2, the atomic ratio of silicon and iron takes a value close to the atomic ratio of 3: 1, which is the charging ratio at each measurement location, and the composition of Si and Fe is about the same at each analysis location. Recognize. It can be seen that the sample according to the example is not a mixture of silicon powder and iron powder, and both iron and silicon are present in the nano-sized particles, and each nano-sized particle has a similar composition.
ナノサイズ粒子を、ＣｕＫα線を用いた粉末Ｘ線回折装置（リガク製、ＲＩＮＴ−ＵｌｔｉｍａＩＩＩ）により同定した。図１１は、実施例１に係るナノサイズ粒子のＸ線回折（ＸＲＤ）パターンである。２θが１８度付近、３８度付近、４８度付近、４９度付近などにＦｅＳｉ２由来のピークが観察され、２８度付近にＳｉ由来のピークが観察される。ＦｅＳｉ２由来のピーク強度が高く鋭く、Ｓｉ由来のピークがわずかしか観察されないことから、結晶性のＦｅＳｉ２と、アモルファスのＳｉが含まれ、結晶性のＳｉはわずかしか存在しないことがわかる。なお、鉄由来のピークは観察されなかった。 Nano-sized particles were identified by a powder X-ray diffractometer (Rigaku Ultimate, RINT-UltimaIII) using CuKα rays. FIG. 11 is an X-ray diffraction (XRD) pattern of nano-sized particles according to Example 1. A peak derived from FeSi 2 is observed when 2θ is around 18 degrees, around 38 degrees, around 48 degrees, around 49 degrees, etc., and a peak derived from Si is observed around 28 degrees. Since the peak intensity derived from FeSi 2 is high and sharp, and only a few Si-derived peaks are observed, it can be seen that crystalline FeSi 2 and amorphous Si are contained, and there is little crystalline Si. In addition, the peak derived from iron was not observed.
以上の分析結果より、実施例１に係るナノサイズ粒子では、結晶質のＦｅＳｉ２が、主にアモルファスのＳｉで覆われており、全体として球形状であることがわかる。 From the above analysis results, it can be seen that in the nano-sized particles according to Example 1, crystalline FeSi 2 is mainly covered with amorphous Si and has a spherical shape as a whole.
実施例１に係るナノサイズ粒子の形成過程を考察する。図１２は、鉄とシリコンの２元系状態図である。シリコン粉末と鉄粉末とをモル比でＳｉ：Ｆｅ＝３：１になるように混合したので、原料粉末でのｍｏｌｅ Ｓｉ／（Ｆｅ＋Ｓｉ）＝０．７５となる。図１２中の太線は、ｍｏｌｅ Ｓｉ／（Ｆｅ＋Ｓｉ）＝０．７５を示す線である。高周波コイルにより生成したプラズマは、１万Ｋ相当となるので、状態図の温度範囲をはるかに超え、鉄原子とシリコン原子が均一に混合したプラズマが得られる。プラズマが冷却すると、プラズマから気体へ、気体から液体へと変化する過程で球状の液滴が成長し、１４７０Ｋ程度にまで冷却すると、Ｆｅ３Ｓｉ７とＳｉの両方が析出する。その後、１２２０Ｋ程度にまで冷却すると、Ｆｅ３Ｓｉ７が、ＦｅＳｉ２に相変化する。よって、シリコンと鉄のプラズマが冷却すると、粒子内にＦｅＳｉ２とＳｉを有するナノサイズ粒子が形成される。その際、ＦｅとＳｉは親和性が高いため、ＦｅＳｉ２は、Ｓｉ中に取り込まれると考えられる。 The formation process of nano-sized particles according to Example 1 will be considered. FIG. 12 is a binary system phase diagram of iron and silicon. Since silicon powder and iron powder were mixed so that the molar ratio was Si: Fe = 3: 1, mole Si / (Fe + Si) = 0.75 in the raw material powder. The thick line in FIG. 12 is a line indicating mole Si / (Fe + Si) = 0.75. Since the plasma generated by the high frequency coil is equivalent to 10,000 K, the temperature is far beyond the temperature range of the phase diagram, and a plasma in which iron atoms and silicon atoms are uniformly mixed is obtained. When the plasma is cooled, spherical droplets grow in the process of changing from plasma to gas and from gas to liquid, and when cooled to about 1470K, both Fe 3 Si 7 and Si are deposited. Then, when cooled to about 1220K, Fe 3 Si 7 is a phase change to a FeSi 2. Therefore, when the silicon and iron plasma is cooled, nano-sized particles having FeSi 2 and Si are formed in the particles. At that time, since Fe and Si have high affinity, FeSi 2 is considered to be taken into Si.
（ナノサイズ粒子のサイクル特性の評価）
（ｉ）負極スラリーの調製
実施例１に係る平均粒径１００ｎｍのナノサイズ粒子４５．５ｗｔ％とアセチレンブラック（平均粒径３５ｎｍ、電気化学工業株式会社製、粉状品）４７．５ｗｔ％の比率でミキサーに投入した。さらに結着剤としてスチレンブタジエンラバー（ＳＢＲ）４０ｗｔ％のエマルジョン（日本ゼオン（株）製、ＢＭ４００Ｂ）を固形分換算で２ｗｔ％、スラリーの粘度を調整する増粘剤としてカルボキシメチルセルロースナトリウム（ダイセル化学工業（株）製、＃２２００）１ｗｔ％溶液を固形分換算で５ｗｔ％の割合で混合してスラリーを作製した。
（ｉｉ）負極の作製
調製したスラリーを自動塗工装置のドクターブレードを用いて、厚さ１０μｍの集電体用電解銅箔（古河電気工業（株）製、ＮＣ−ＷＳ）上に１５μｍの厚みで塗布し、７０℃で乾燥させてリチウムイオン二次電池用負極を製造した。
（ｉｉｉ）特性評価
リチウムイオン二次電池用負極と、１ｍｏｌ／ＬのＬｉＰＦ６を含むエチレンカーボネートとジエチルカーボネートの混合溶液からなる電解液と、金属Ｌｉ箔対極を用いて３つの異なるリチウム二次電池を構成し、充放電特性を調べた。特性の評価は、初回の放電容量および５０サイクルの充電・放電後の放電容量を測定し、放電容量の低下率を算出することによって行った。放電容量は、シリサイドを形成するなどリチウムの吸蔵・放出をしないようなシリコンを除き、リチウムの吸蔵・放出に有効な活物質Ｓｉの重量を基準として算出した。まず、２５℃環境下において、電流値を０．１Ｃ、電圧値を０．０２Ｖまで定電流定電圧条件で充電を行い、電流値が０．０５Ｃに低下した時点で充電を停止した。次いで、電流値０．１Ｃの条件で、金属Ｌｉに対する電圧が１．５Ｖとなるまで放電を行い、０．１Ｃ初期放電容量を測定した。なお、１Ｃとは、１時間で満充電できる電流値である。また、充電と放電はともに２５℃環境下において行った。次いで、０．２Ｃでの充放電速度で上記充放電を５０サイクル繰り返した。０．２Ｃ初期放電容量に対する、充放電を５０サイクル繰り返したときの放電容量の割合を百分率で求め、容量維持率とした。
(Evaluation of cycle characteristics of nano-sized particles)
(I) Preparation of negative electrode slurry Ratio of 45.5 wt% of nano-sized particles having an average particle diameter of 100 nm and acetylene black (average particle diameter of 35 nm, manufactured by Denki Kagaku Kogyo Co., Ltd.) according to Example 1 to 47.5 wt% And put it into the mixer. Furthermore, styrene butadiene rubber (SBR) 40 wt% emulsion (manufactured by ZEON Corporation, BM400B) as a binder is 2 wt% in terms of solid content, and carboxymethylcellulose sodium (Daicel Chemical Industries) as a thickener to adjust the viscosity of the slurry. Co., Ltd., # 2200) A 1 wt% solution was mixed at a rate of 5 wt% in terms of solid content to prepare a slurry.
(Ii) Production of negative electrode Using the doctor blade of the automatic coating apparatus, the prepared slurry was 15 μm thick on a 10 μm thick electrolytic copper foil for current collector (Furukawa Electric Co., Ltd., NC-WS). And dried at 70 ° C. to produce a negative electrode for a lithium ion secondary battery.
(Iii) Characteristic evaluation Three different lithium secondary batteries using a negative electrode for a lithium ion secondary battery, an electrolytic solution composed of a mixed solution of ethylene carbonate and diethyl carbonate containing 1 mol / L LiPF 6 , and a metal Li foil counter electrode The charge and discharge characteristics were examined. The evaluation of the characteristics was performed by measuring the initial discharge capacity and the discharge capacity after 50 cycles of charge / discharge, and calculating the reduction rate of the discharge capacity. The discharge capacity was calculated on the basis of the weight of the active material Si effective for lithium insertion / extraction except for silicon that does not occlude / release lithium such as formation of silicide. First, in a 25 ° C. environment, charging was performed under constant current and constant voltage conditions until the current value was 0.1 C and the voltage value was 0.02 V, and the charging was stopped when the current value decreased to 0.05 C. Next, discharging was performed under the condition of a current value of 0.1 C until the voltage with respect to the metal Li became 1.5 V, and a 0.1 C initial discharge capacity was measured. 1C is a current value that can be fully charged in one hour. Both charging and discharging were performed in a 25 ° C. environment. Next, the above charge / discharge cycle was repeated 50 cycles at a charge / discharge rate of 0.2C. The ratio of the discharge capacity when charging / discharging was repeated 50 cycles with respect to the 0.2 C initial discharge capacity was obtained as a percentage, and was defined as the capacity maintenance ratio.
［実施例２］
実施例１で作製した平均粒径１００ｎｍのナノサイズ粒子を用いる。ナノサイズ粒子と、カーボンナノホーン（ＮＥＣ（株）製、平均粒径８０ｎｍ）をナノサイズ粒子：ＣＮＨ＝７：３（重量比）の割合で磨砕機（（株）奈良機械製作所製、ミラーロ）で精密混合させた後、精密混合品６５ｗｔ％とアセチレンブラック２８ｗｔ％の比率でミキサーに投入する以外は実施例１と同様の方法で、リチウムイオン二次電池を構成し、サイクル特性を測定した。
[Example 2]
Nano-sized particles having an average particle diameter of 100 nm prepared in Example 1 are used. Nanosize particles and carbon nanohorn (manufactured by NEC Corporation, average particle size 80 nm) at a ratio of nanosize particles: CNH = 7: 3 (weight ratio) with a grinder (Mararo, Nara Machinery Co., Ltd.) After precisely mixing, a lithium ion secondary battery was constructed and cycle characteristics were measured in the same manner as in Example 1, except that 65% by weight of the precisely mixed product and 28% by weight of acetylene black were charged into the mixer.
［比較例１］
ナノサイズ粒子に代えて、平均粒径６０ｎｍのシリコンナノ粒子（Ｈｅｆｅｉ Ｋａｉ’ｅｒ ＮａｎｏＴｅｃｈ製）を用い、実施例１と同様の方法で、リチウムイオン二次電池を構成し、サイクル特性を測定した。
[Comparative Example 1]
A lithium ion secondary battery was constructed in the same manner as in Example 1 using silicon nanoparticles having an average particle diameter of 60 nm (manufactured by Hefei Kai'er NanoTech) instead of the nano-sized particles, and cycle characteristics were measured.
［比較例２］
ナノサイズ粒子に代えて、比較例１の平均粒径６０ｎｍのシリコンナノ粒子を用い、実施例２と同様の方法で、リチウムイオン二次電池を構成し、サイクル特性を測定した。
[Comparative Example 2]
A lithium ion secondary battery was constructed in the same manner as in Example 2 using silicon nanoparticles having an average particle diameter of 60 nm of Comparative Example 1 instead of the nano-sized particles, and cycle characteristics were measured.
実施例２と比較例２のそれぞれ３つの電池のサイクル特性を図１３に示す。実施例１、実施例２、比較例１、比較例２の放電容量と容量維持率を表１に示す。表１における数値は、それぞれ３つの電池の平均値である。 FIG. 13 shows the cycle characteristics of three batteries of Example 2 and Comparative Example 2, respectively. Table 1 shows the discharge capacities and capacity retention rates of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. The numerical values in Table 1 are average values of three batteries.
図１３に示すように、サイクルを重ねるごとに、比較例２では急激に放電容量が低下する。そのため、表１に示すように、５０サイクル後容量維持率は、実施例２では６２％であるのに対し、比較例２では３０％まで低下する。また、５０サイクル後容量維持率は、実施例１では５５％であるのに対し、比較例１では、２３％である。よって、実施例に係るナノサイズ粒子は、比較例に係るシリコンナノ粒子に比べて、容量低下が抑えられ、サイクル特性が良好であることがわかる。 As shown in FIG. 13, each time the cycle is repeated, in Comparative Example 2, the discharge capacity rapidly decreases. Therefore, as shown in Table 1, the capacity retention rate after 50 cycles is 62% in Example 2, while it is reduced to 30% in Comparative Example 2. Further, the capacity maintenance rate after 50 cycles is 55% in the first example, whereas it is 23% in the first comparative example. Therefore, it turns out that the nanosize particle which concerns on an Example has the capacity | capacitance fall suppressed compared with the silicon nanoparticle which concerns on a comparative example, and its cycling characteristics are favorable.
また、実施例１と実施例２、比較例１と比較例２をそれぞれ比較すると、カーボンナノホーンを添加することで、初期放電容量が高くなり、５０サイクル後容量維持率も向上することがわかる。 Further, when Example 1 and Example 2 and Comparative Example 1 and Comparative Example 2 are respectively compared, it can be seen that the addition of carbon nanohorn increases the initial discharge capacity and improves the capacity retention after 50 cycles.
なお、実施例１においては、シリコンと鉄の２元系でナノサイズ粒子を作製したが、本発明のナノサイズ粒子は、シリコンと鉄の２元系に限るものではない。例えば、図１４に示すＣｏ（コバルト）とＳｉ（シリコン）の２元系状態図においても、ｍｏｌｅ Ｓｉ／（Ｃｏ＋Ｓｉ）＝０．７５のプラズマを冷却すると、ＣｏＳｉ２とＳｉが析出することから、ＣｏＳｉ２をＳｉが覆うナノサイズ粒子が得られることが推測される。図１４中の太線は、ｍｏｌｅ Ｓｉ／（Ｃｏ＋Ｓｉ）＝０．７５を示す線である。 In Example 1, nano-sized particles were prepared using a binary system of silicon and iron. However, the nano-sized particles of the present invention are not limited to a binary system of silicon and iron. For example, even in the binary phase diagram of Co (cobalt) and Si (silicon) shown in FIG. 14, when the plasma of mole Si / (Co + Si) = 0.75 is cooled, CoSi 2 and Si are precipitated. It is presumed that nano-sized particles in which CoSi 2 is covered with Si are obtained. The thick line in FIG. 14 is a line indicating mole Si / (Co + Si) = 0.75.
同様に、図１５に示すＦｅ（鉄）とＳｎ（スズ）の２元系状態図においても、ｍｏｌｅ Ｓｎ／（Ｆｅ＋Ｓｎ）＝０．７５のプラズマを冷却すると、ＦｅＳｎ２とＳｎが析出することから、ＦｅＳｎ２をＳｎが覆うナノサイズ粒子が得られることが推測される。図１５中の太線は、ｍｏｌｅ Ｓｎ／（Ｆｅ＋Ｓｎ）＝０．７５を示す線である。 Similarly, in the binary phase diagram of Fe (iron) and Sn (tin) shown in FIG. 15, when the plasma of mole Sn / (Fe + Sn) = 0.75 is cooled, FeSn 2 and Sn are precipitated. It is presumed that nano-sized particles in which Sn covers FeSn 2 are obtained. The thick line in FIG. 15 is a line indicating mole Sn / (Fe + Sn) = 0.75.
Ｓｉを元素Ａとして用い、Ｆｅを元素Ｄとして用いる場合以外に、元素ＡをＳｉ、Ｓｎ、Ａｌ、Ｐｂ、Ｓｂ、Ｂｉ、Ｇｅ、ＩｎおよびＺｎから選択し、元素ＤをＦｅ、Ｃｏ、Ｎｉ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｓｒ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｔｃ、Ｒｕ、Ｒｈ、Ｂａ、ランタノイド元素（ＣｅおよびＰｍを除く）、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、ＯｓおよびＩｒから選択したどの組合せにおいても、同様の２元系状態図が得られ、ＤＡｘ（１＜ｘ≦３)なる化合物が得られる。よって、以上の元素Ａと元素Ｄの組合せにおいて、第２の相の一部または全部を第１の相が覆う構成を有するナノサイズ粒子が得られるものと考えられる。 In addition to using Si as the element A and Fe as the element D, the element A is selected from Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn, and the element D is Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, Ta, W, Re, Os and In any combination selected from Ir, a similar binary phase diagram is obtained, and a compound of DA x (1 <x ≦ 3) is obtained. Therefore, in the combination of the element A and the element D described above, it is considered that nano-sized particles having a configuration in which the first phase covers part or all of the second phase are obtained.
他の第２の相を有するナノサイズ粒子の形成過程を考察する。図１６は、コバルトと鉄の２元系状態図である。コバルト粉末と鉄粉末との混合粉末を、プラズマから冷却すると、コバルト単体と鉄コバルト固溶体、鉄単体と鉄コバルト固溶体、または鉄コバルト固溶体のみが析出する。よって、シリコンと鉄とコバルトを含有するプラズマが冷却すると、粒子内にＦｅＳｉ２とＣｏＳｉ２とＳｉを有するナノサイズ粒子が形成される。この際、シリコンと鉄とコバルトの含有量によっては、ナノサイズ粒子内に鉄コバルト固溶体が析出することがある。その際、ＦｅとＳｉ、ＣｏとＳｉは親和性が高いため、ＦｅＳｉ２やＣｏＳｉ２、鉄コバルト固溶体は、Ｓｉ中に取り込まれると考えられる。 Consider the formation process of nano-sized particles having other second phases. FIG. 16 is a binary system phase diagram of cobalt and iron. When the mixed powder of cobalt powder and iron powder is cooled from plasma, only cobalt and iron cobalt solid solution, iron alone and iron cobalt solid solution, or only iron cobalt solid solution is deposited. Thus, the plasma containing silicon and iron and cobalt cools, nano-sized particles having FeSi 2 and CoSi 2 and Si in the particles are formed. At this time, depending on the contents of silicon, iron, and cobalt, iron-cobalt solid solution may precipitate in the nano-sized particles. At that time, since Fe and Si, Co and Si have high affinity, FeSi 2 , CoSi 2 , and iron cobalt solid solution are considered to be taken into Si.
以上、添付図面を参照しながら、本発明の好適な実施形態について説明したが、本発明は係る例に限定されない。当業者であれば、本願で開示した技術的思想の範疇内において、各種の変更例または修正例に想到しえることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。 The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.
１、２………ナノサイズ粒子
３………第１の相
４………元素Ａの微結晶
５………第２の相
６………他の第２の相
７、８………ナノサイズ粒子
９………ナノサイズ粒子製造装置
１１………反応チャンバー
１３………原料粉末供給口
１４………原料粉末
１５………シースガス供給口
１６………シースガス
１７………高周波コイル
１９………プラズマ
２１………フィルター
２３………ミキサー
２５………スラリー
２７………スラリー原料
２９………コーター
３１………集電体
３３………負極
1, 2 ……… Nano-sized particles 3 ……… First phase 4 ……… Element A crystallites 5 ……… Second phase 6 ……… Other second phases 7, 8 ……… Nano-sized particle 9 ...... Nano-sized particle production device 11 ......... Reaction chamber 13 ......... Raw powder supply port 14 ...... Raw powder 15 ...... Sheath gas supply port 16 ...... Sheath gas 17 ...... High frequency coil 19 ......... Plasma 21 ......... Filter 23 ......... Mixer 25 ......... Slurry 27 ......... Slurry raw material 29 ......... Coater 31 ......... Current collector 33 ......... Negative electrode
Claims (10)
前記元素ＡがＳｉであり、
前記元素ＤがＦｅ、Ｃｏ、Ｎｉ、Ｃａ、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｓｒ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｔｃ、Ｒｕ、Ｒｈ、Ｂａ、ランタノイド元素（Ｃｅ、およびＰｍを除く）、Ｈｆ、Ｔａ、Ｗ、Ｒｅ、ＯｓおよびＩｒからなる群より選ばれた少なくとも１種の元素であり、
前記元素Ａの単体または固溶体である、球形状の第１の相と、
前記元素Ａと前記元素Ｄとの化合物である第２の相を少なくとも有し、
前記第２の相が前記第１の相の中にあり、
前記第２の相の一部または全部が、前記第１の相に覆われており、
平均粒径が２〜３００ｎｍであることを特徴とするナノサイズ粒子を負極活物質として含むリチウムイオン二次電池用負極材料。 Including different types of elements A and D,
The element A is Si ;
The element D is Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, a lanthanoid element (except for Ce and Pm). At least one element selected from the group consisting of Hf, Ta, W, Re, Os and Ir,
A spherical first phase which is a simple substance or a solid solution of the element A;
Having at least a second phase which is a compound of the element A and the element D;
The second phase is in the first phase;
A part or all of the second phase is covered by the first phase ;
A negative electrode material for a lithium ion secondary battery comprising nano-sized particles having an average particle diameter of 2 to 300 nm as a negative electrode active material .
前記元素Ｄ´が、前記第２の相を構成する前記元素Ｄとは種類の異なる元素であり、
前記ナノサイズ粒子が、前記元素Ａと前記元素Ｄ´との化合物である他の第２の相をさらに有し、
前記他の第２の相が前記第１の相の中にあり、
前記他の第２の相の一部または全部が、前記第１の相に覆われている
ことを特徴とする請求項１に記載のリチウムイオン二次電池用負極材料。 The nano-sized particles are Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm) ), And further includes an element D ′ that is at least one element selected from the group consisting of Hf, Ta, W, Re, Os, and Ir,
The element D ′ is an element of a different type from the element D constituting the second phase,
The nano-sized particles further have another second phase which is a compound of the element A and the element D ′;
The other second phase is in the first phase;
2. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein a part or all of the other second phase is covered with the first phase.
請求項９に記載の負極と、
前記正極と前記負極との間に配置されたセパレータとを有し、
リチウムイオン伝導性を有する電解質中に、前記正極と前記負極と前記セパレータとを設けたことを特徴とするリチウムイオン二次電池。 A positive electrode capable of inserting and extracting lithium ions;
A negative electrode according to claim 9 ;
Having a separator disposed between the positive electrode and the negative electrode;
A lithium ion secondary battery, wherein the positive electrode, the negative electrode, and the separator are provided in an electrolyte having lithium ion conductivity.
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