JP3282546B2 - Anode material for lithium ion secondary battery and its electrode - Google Patents
Anode material for lithium ion secondary battery and its electrodeInfo
- Publication number
- JP3282546B2 JP3282546B2 JP18397597A JP18397597A JP3282546B2 JP 3282546 B2 JP3282546 B2 JP 3282546B2 JP 18397597 A JP18397597 A JP 18397597A JP 18397597 A JP18397597 A JP 18397597A JP 3282546 B2 JP3282546 B2 JP 3282546B2
- Authority
- JP
- Japan
- Prior art keywords
- powder
- electrode
- diameter
- intermetallic compound
- small
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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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
Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【発明の属する技術分野】本発明は、リチウムイオン２
次電池用負極金属間化合物粉末と、それを用いて作製し
たリチウムイオン２次電池用の負極に関する。本発明に
かかるリチウム２次電池用の負極粉末を用いて作製した
電極は、活物質であるリチウムの利用率が高く、長期寿
命に優れるリチウムイオン２次電池を構成することがで
きる。BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a negative electrode intermetallic compound powder for a secondary battery and a negative electrode for a lithium ion secondary battery manufactured using the same. The electrode manufactured using the negative electrode powder for a lithium secondary battery according to the present invention can constitute a lithium ion secondary battery having a high utilization rate of lithium as an active material and an excellent long-term life.
【０００２】[0002]
【従来の技術】携帯用の小型電気・電子機器の普及に伴
い、Ni−水素電池やリチウムイオン電池といった新型の
２次電池の開発が盛んになってきている。2. Description of the Related Art With the spread of portable small electric and electronic devices, new types of secondary batteries such as Ni-hydrogen batteries and lithium ion batteries have been actively developed.
【０００３】この中でリチウムイオン電池は、リチウム
を負極活物質とし、非水溶媒を電解液に用いる電池であ
る。リチウムが非常に卑な金属であるため、高電圧を取
り出すことができ、エネルギー密度の高い電池となるこ
とから、１次電池として大量に使用されている。しかし
金属リチウムを２次電池に適用すると、充放電の繰り返
しによって負極からリチウムがデンドライト状に成長
し、絶縁体であるセパレータを貫通して正極と短絡する
ようになるため、充放電の繰り返しのサイクル寿命が短
いという欠点があった。[0003] Among them, a lithium ion battery is a battery using lithium as a negative electrode active material and a non-aqueous solvent as an electrolyte. Since lithium is a very base metal, a high voltage can be obtained and a battery having a high energy density is used. Therefore, lithium is widely used as a primary battery. However, when metal lithium is applied to a secondary battery, the repetition of charge and discharge causes lithium to grow in a dendrite shape from the negative electrode, and penetrates the separator, which is an insulator, to short-circuit with the positive electrode. There was a drawback that the life was short.
【０００４】このような金属リチウムを負極に用いた２
次電池の問題点を解決する一つの手段として、リチウム
イオンを吸蔵・放出することのできる炭素質材料 (例、
天然黒鉛、人造黒鉛、石油コークス、樹脂焼成体、炭素
繊維、熱分解炭素、カーボンブラック、メソフェーズ小
球体、バルクメソフェーズなど) を負極材料として用い
ることが提案された。例えば、特開昭57−208079号公
報、特開平４−115458号、同５−234584号、同５−3079
58号公報など。[0004] The use of such metallic lithium for the negative electrode 2
One way to solve the problems of secondary batteries is to use a carbonaceous material that can store and release lithium ions (eg,
It has been proposed to use natural graphite, artificial graphite, petroleum coke, fired resin, carbon fiber, pyrolytic carbon, carbon black, mesophase spherules, bulk mesophase, etc.) as the negative electrode material. For example, JP-A-57-208079, JP-A-4-115458, JP-A-5-234584, and JP-A-5-3079
No. 58 publication.
【０００５】この炭素質材料から負極を構成したリチウ
ムイオン２次電池では、充放電時の負極での反応は、リ
チウムイオン (Li+ ) が炭素 (黒鉛) の層間に出入りす
るだけである。すなわち充電時には、負極の炭素質材料
に電子が送り込まれて炭素は負に帯電し、正極に吸蔵さ
れていたリチウムイオンが脱離して負に帯電した負極の
炭素質材料に吸蔵 (インターカレート) される。逆に、
放電時には負極の炭素質材料に吸蔵されていたリチウム
イオンが脱離 (デインターカレート) して、正極に吸蔵
される。このような機構を用いることで金属リチウムの
負極での析出を防ぐことができ、デンドライトの析出に
よる負極劣化の問題を回避することができる。[0005] In a lithium ion secondary battery comprising a negative electrode made of this carbonaceous material, the reaction at the negative electrode during charge / discharge is only that lithium ions (Li + ) enter and exit between carbon (graphite) layers. That is, during charging, electrons are sent to the carbonaceous material of the negative electrode, carbon is negatively charged, and lithium ions occluded in the positive electrode are desorbed and occluded in the negatively charged carbonaceous material of the negative electrode (intercalation). Is done. vice versa,
During discharge, lithium ions occluded in the carbonaceous material of the negative electrode are desorbed (deintercalated) and occluded in the positive electrode. By using such a mechanism, precipitation of metallic lithium on the negative electrode can be prevented, and the problem of deterioration of the negative electrode due to precipitation of dendrite can be avoided.
【０００６】しかし、上記のような炭素質材料を負極に
用いたリチウムイオン２次電池では、放電容量が小さか
ったり、あるいはリチウムイオンの吸蔵量の大きい高結
晶性の黒鉛質材料のものは、初期放電容量は高くても、
１サイクル目のクーロン効率(放電容量／充電容量) ×1
00 ＜％＞) が極端に低下するため余分な電気量を消費
してしまうという欠点があった。However, in a lithium ion secondary battery using the above carbonaceous material for the negative electrode, a highly crystalline graphitic material having a small discharge capacity or a large lithium ion occlusion amount has a low initial capacity. Even if the discharge capacity is high,
Coulomb efficiency in the first cycle (discharge capacity / charge capacity) x 1
00 <%>) is extremely reduced, so that an extra amount of electricity is consumed.
【０００７】さらに、高結晶性のものはリチウムイオン
の出入りによる格子体積の膨張・収縮が繰り返し行われ
るため負極材料に割れが生じ、電池としてのサイクル特
性が優れないという欠点があった。[0007] Furthermore, the high crystallinity has the disadvantage that the negative electrode material is cracked due to the expansion and contraction of the lattice volume due to the ingress and egress of lithium ions, and the cycle characteristics of the battery are not excellent.
【０００８】この炭素質材料に代わって金属間化合物を
リチウムイオンのホスト材料に用いる方法が提案され
た。これら金属間化合物にはFeSi2 、YSi2、MoSi2 など
が挙げられ、これを用いることで放電容量は黒鉛系炭素
質材料のもつ理論容量372mAh/gを超えるほど向上し、電
解液の反応によって生じる不可逆容量が低下することで
１サイクル目のクーロン効率が向上した。特開平７−24
0201号公報、特開平５−159780号公報および特開平９−
63651 号公報参照。このように、リチウムイオン２次電
池用の負極材料として金属間化合物粉末は、今まさに検
討が進められている。A method has been proposed in which an intermetallic compound is used as a lithium ion host material instead of the carbonaceous material. These intermetallic compounds include FeSi 2 , YSi 2 , MoSi 2, etc., and by using them, the discharge capacity is increased as the theoretical capacity of the graphite-based carbonaceous material exceeds 372 mAh / g. The reduction in the generated irreversible capacity improved the coulomb efficiency in the first cycle. JP 7-24
No. 0201, JP-A-5-159780 and JP-A-9-159
See 63651. As described above, an intermetallic compound powder as a negative electrode material for a lithium ion secondary battery is now being studied.
【０００９】このような材料を用いて作製するリチウム
イオン２次電池も、炭素質材料を使用して作製する電池
と同様の方法で作製が行われる。金属間化合物を用いた
リチウムイオン２次電池用の電極は、粉末状にした金属
間化合物をバインダとなる有機物と混合し、スラリまた
はペースト状とした後、これを電極基板上に塗布または
充填し、乾燥後に金属間化合物粉末の充填密度を高める
ためロール圧延等により加圧することにより作製するこ
とが一般的な方法である。A lithium ion secondary battery manufactured using such a material is manufactured in the same manner as a battery manufactured using a carbonaceous material. An electrode for a lithium ion secondary battery using an intermetallic compound is prepared by mixing a powdered intermetallic compound with an organic substance serving as a binder to form a slurry or paste, and then applying or filling the slurry on an electrode substrate. It is a common method to produce the powder by pressurizing by rolling or the like in order to increase the packing density of the intermetallic compound powder after drying.
【００１０】こうして作製されたシート状の電極を負極
とし、有機系電解液 (ジエチルカーボネート、プロピレ
ンカーボネート等) を含浸させたポリプロピレン製のセ
パレータを間に挟んで、コバルト酸リチウムなどを塗布
したアルミ製のシート状正極と一緒に渦巻き状に巻い
て、円筒形の密閉容器内に収容すると、円筒形のリチウ
ムイオン２次電池が製造される。The sheet-like electrode thus prepared is used as a negative electrode, and a separator made of aluminum impregnated with an organic electrolytic solution (diethyl carbonate, propylene carbonate, etc.) is interposed between the electrodes, and lithium cobaltate or the like is coated thereon. When spirally wound together with the sheet-shaped positive electrode of the above and accommodated in a cylindrical airtight container, a cylindrical lithium ion secondary battery is manufactured.
【００１１】金属間化合物を用いた電極作製方法には上
記のような方法と、もう１つ別の金属間化合物電極の作
製方法として、有機物バインダを使用せずに成形した
後、高温に加熱して金属間化合物粉末を焼結させる方法
も考えられる。この焼結電極は絶縁性の有機物を含んで
いないので、合金粉末の充填密度が上がり、高容量の電
池を作製することができるが、高温の加熱工程が必要で
あって高価である上、得られた電極に可撓性がなく、渦
巻き状に曲げ加工することが困難であるため、次に述べ
る角型電池として使用するか、あるいは加工性を維持す
るために焼結の程度を弱くし、電気的特性をある程度犠
牲にする必要があった。The method for producing an electrode using an intermetallic compound includes the above-described method, and another method for producing an intermetallic compound electrode is to form without using an organic binder, and then heat to a high temperature. A method of sintering the intermetallic compound powder by sintering is also conceivable. Since this sintered electrode does not contain an insulating organic substance, the packing density of the alloy powder is increased, and a high-capacity battery can be manufactured. Since the electrode is not flexible and difficult to bend into a spiral shape, it is used as a prismatic battery described below, or the degree of sintering is reduced to maintain workability, The electrical properties had to be sacrificed to some extent.
【００１２】角型のリチウムイオン２次電池は、矩形に
裁断した複数枚のシート状の負極、正極、およびセパレ
ータを矩形容器内に組み込んだものである。しかし、複
数枚の極板やセパレータを組み込むため電池の構造が複
雑になり、円筒形電池に比べてかなり高価な電池にな
る。A prismatic lithium ion secondary battery is one in which a plurality of sheet-shaped negative electrodes, positive electrodes, and separators cut into a rectangular shape are incorporated in a rectangular container. However, since a plurality of electrode plates and separators are incorporated, the structure of the battery becomes complicated, and the battery becomes considerably more expensive than a cylindrical battery.
【００１３】リチウムイオン２次電池用負極金属材料の
粉末化法は、溶解した金属間化合物を金属製等の鋳型に
鋳造した後、得られたインゴットを粉砕する方法と、ガ
スアトマイズ法や回転電極法等により直接粉末状の金属
間化合物を得る方法とに大別される。得られる粉末の形
状は、前者の方法では不定形であり、後者の方法ではほ
ぼ球形である。他に、回転ドラム法等により得た薄帯状
の金属間化合物粉末を粉砕して得た不定形の粉末もあ
る。The method of pulverizing a negative electrode metal material for a lithium ion secondary battery includes a method in which a molten intermetallic compound is cast into a mold made of metal or the like, and then the obtained ingot is pulverized, and a gas atomizing method or a rotating electrode method. The method is roughly classified into a method of directly obtaining a powdery intermetallic compound by the method described above. The shape of the obtained powder is irregular in the former method and almost spherical in the latter method. In addition, there is also amorphous powder obtained by pulverizing a ribbon-shaped intermetallic compound powder obtained by a rotating drum method or the like.
【００１４】このようにして得た金属間化合物を電極と
して使用する場合、金属間化合物の粉末が電気的接触を
保った状態で電極上に存在する必要があり、何らかの原
因で電気的接触が断たれた粉末粒子が存在すると、その
粒子は電極反応に寄与できなくなり、電気を貯える機能
を示さなくなる。電極作製時や電池の使用中にこのよう
な粉末粒子が多く存在すると、リチウムイオンを多く収
納し得る高容量の金属間化合物粉末を用いても、あるい
は粉末の充填密度が高くても、電極容量は低下してしま
う。この粉末間の電気的接触の欠如は、特に有機物バイ
ンダを用いた電極で問題となり、これは電気伝導性の低
い有機物が粉末粒子間に存在することに起因すると考え
られる。さらに金属間化合物の組成により、合金の導電
性は大きく異なり、特に硅化物を主体とする金属間化合
物の中でSiの組成割合が多いものは上記のような導電性
の低下が起こりやすい。When the thus obtained intermetallic compound is used as an electrode, the powder of the intermetallic compound must be present on the electrode while maintaining the electrical contact, and the electrical contact is interrupted for some reason. If the powder particles are present, the particles cannot contribute to the electrode reaction and no longer have the function of storing electricity. If such powder particles are present in a large amount during the production of the electrode or during the use of the battery, the electrode capacity can be increased even if a high-capacity intermetallic compound powder capable of accommodating a large amount of lithium ions is used, or the packing density of the powder is high. Will decrease. This lack of electrical contact between the powders is particularly problematic in electrodes using organic binders, which is believed to be due to the presence of organics with low electrical conductivity between the powder particles. Further, the conductivity of the alloy greatly differs depending on the composition of the intermetallic compound. Particularly, in the case of an intermetallic compound mainly composed of silicide, a compound having a large composition ratio of Si tends to cause the above-described decrease in conductivity.
【００１５】これを改善する手法として、球形の金属間
化合物粉末を用いて電極への粉末充填率を向上させる方
法が考えられるが、球形粉末は粉末粒子間の接触が点接
触となり、電気的接触面積が小さいため、金属間化合物
粉末の充填密度は高くなっても電極として利用可能な容
量が小さくなることが起こりうるのである。またさら
に、電極に塗布された金属間化合物粉末は、電池の充放
電 (すなわち、リチウムイオンの吸収・脱離) の繰り返
し毎に起こる体積の膨張・収締による歪み等が原因とな
って、細かなひび割れにより微粉化することが考えら
れ、接触点の少ない球形粉末の場合には、ヒビ割れによ
り１つの粒子が分割され、接触点が粒子本体から切り離
される確率が高く、充放電の繰り返しにより容量が低下
しやすいという問題もある。従って金属間化合物粉末の
充填密度を上げる手法だけでは電極としての容量を上げ
ることができず、粉末粒子間の電気的接触を多くする工
夫が必要であることは明らかである。As a method of improving this, it is conceivable to use a spherical intermetallic compound powder to improve the powder filling rate in the electrode. In the case of the spherical powder, the contact between the powder particles becomes point contact, and the electrical contact is made. Because of the small area, even if the packing density of the intermetallic compound powder is increased, the capacity available as an electrode may be reduced. In addition, the intermetallic compound powder applied to the electrode is finely divided due to volume expansion / strain due to repetition of battery charge / discharge (i.e., lithium ion absorption / desorption) and other factors. In the case of a spherical powder with few contact points, it is likely that one particle is divided by a crack and the contact point is likely to be separated from the particle body. There is also a problem that is easily reduced. Therefore, it is apparent that the capacity as an electrode cannot be increased only by increasing the packing density of the intermetallic compound powder, and that a device for increasing the electrical contact between the powder particles is necessary.
【００１６】また金属間化合物粉末の電気的接触を改善
する方法として、粉末表面を金属被覆する方法や金属粉
末を混合する方法が考えられる。しかし表面被覆処理は
高価であり、また金属粉を混合する方法では、容積が限
定されている電池の場合、金属粉を添加した量だけ金属
間化合物粉末の充填量を減らさなければならないため、
電極容量はむしろ低下するという問題がある。As a method for improving the electrical contact of the intermetallic compound powder, a method of coating the surface of the powder with a metal or a method of mixing a metal powder can be considered. However, the surface coating treatment is expensive, and in the method of mixing metal powder, in the case of a battery having a limited volume, the filling amount of the intermetallic compound powder must be reduced by the amount to which the metal powder is added,
There is a problem that the electrode capacity is rather reduced.
【００１７】[0017]
【発明が解決しようとする課題】以上に説明したよう
に、ＰＶＤＦなどの有機物バインダを含有する非焼結型
のリチウムイオン２次電池用の金属間化合物電極におい
て、金属間化合物粉末の充填密度と粉末間の電気的接触
の両者を同時に改善できる手段は未だ確立していないの
が現状である。As described above, in a non-sintering type intermetallic compound electrode for a lithium ion secondary battery containing an organic binder such as PVDF, the packing density of intermetallic compound powder and At present, means for simultaneously improving both electrical contact between powders has not been established yet.
【００１８】本発明の目的は、この充填密度と粉末間の
電気的接触の両者を改善することができ、金属間化合物
粉末の電極での利用率が高く、繰り返し充放電による利
用率低下が抑制された金属間化合物粉末と、それを用い
た２次電池用のバインダ含有電極を提供することであ
る。An object of the present invention is to improve both the packing density and the electrical contact between the powders, so that the utilization of the intermetallic compound powder at the electrode is high and the reduction in the utilization due to repeated charging and discharging is suppressed. And a binder-containing electrode for a secondary battery using the powder.
【００１９】[0019]
【課題を解決するための手段】本発明者らは、リチウム
イオン２次電池用のバインダ含有金属間化合物電極にお
ける金属間化合物粉末の利用率に関して研究を行った。
ここで金属間化合物粉末の利用率とは、負極活物質であ
る金属間化合物粉末がリチウムイオン２次電池の充放電
過程で有効利用された割合を示す指標であり、実際にリ
チウムイオン２次電池に使用する負極材料の理論放電容
量に対する比率である。Means for Solving the Problems The present inventors have studied on the utilization of intermetallic compound powder in a binder-containing intermetallic compound electrode for a lithium ion secondary battery.
Here, the utilization rate of the intermetallic compound powder is an index indicating the rate at which the intermetallic compound powder, which is the negative electrode active material, is effectively used in the charge / discharge process of the lithium ion secondary battery. Is the ratio of the negative electrode material to the theoretical discharge capacity.
【００２０】理論放電容量の値は、例えばFeSi2 を負極
材料に用いたとき、FeSi2:１モルに対してLi：１モルが
反応し、LiFeSi2 を生成するまで電気量を消費したとき
の容量を用いた。The value of the theoretical discharge capacity, for example, when using the FeSi 2 in the negative electrode material, FeSi 2: Li per 1 mol: 1 mol are reacted, when consumed electricity quantity until generating a LiFeSi 2 Volume was used.
【００２１】ここに、不定形粉末でほぼ正規分布に従う
粒度分布を有する金属間化合物粉末とこの金属間化合物
粉末に対して10％の銅粉末とPVDF２％をバインダとして
混合し、NMP を用いてこれをスラリとした後、ドクター
ブレード法にて電極を作製した。このリチウムイオン２
次電池用電極 (Ａ電極という) で得られた最大放電容量
を比較する。この電極ＡはPVDFが極微量であって、さら
に通常導電材として用いる黒鉛粉より導電性に優れるCu
粉を用いるため放電容量は通常の電極より大きい値を示
すが、サイクル特性が非常に悪く実用的なレベルではな
い電極である。Here, an intermetallic compound powder having a particle size distribution substantially conforming to a normal distribution as an amorphous powder, 10% of copper powder and 2% of PVDF are mixed as a binder with respect to the intermetallic compound powder, and the mixture is mixed with NMP. Was made into a slurry, and an electrode was produced by a doctor blade method. This lithium ion 2
Compare the maximum discharge capacities obtained with the secondary battery electrode (referred to as electrode A). This electrode A has a very small amount of PVDF and is more conductive than graphite powder which is usually used as a conductive material.
Since the powder is used, the discharge capacity is larger than that of a normal electrode, but the cycle characteristics are very poor and the electrode is not at a practical level.
【００２２】次に、同様の金属間化合物粉末と金属粉末
に対して黒鉛粉10％、PVDFバインダ10％が混合されたリ
チウムイオン２次電池用負極を作製し、これを電極Ｂと
する。これとＡ電極とを放電容量について比較した結
果、電極Ａの方が活物質単位重量当たりの放電容量が高
く、電極Ｂでは活物質の利用率が低下した。これは電極
Ｂでは、絶縁性の有機物が金属間化合物粉末間に多く存
在することにより、粉末間の電気的接触が妨げられたた
めである。Next, a negative electrode for a lithium ion secondary battery in which 10% of graphite powder and 10% of PVDF binder were mixed with the same intermetallic compound powder and metal powder was prepared, and this was designated as electrode B. As a result of comparing the discharge capacity with the A electrode, the discharge capacity per unit weight of the active material was higher in the electrode A, and the utilization rate of the active material was lower in the electrode B. This is because, in the electrode B, the electrical contact between the powders was hindered by the presence of many insulating organic substances between the intermetallic compound powders.
【００２３】次に球形粉末の影響を調査した。粉末の充
填密度が高い球形粉から作製した有機物バインダである
PVDFを10％含有する電極は、不定形の粉砕粉を用いた同
様の電極に比べて粉末の充填密度が高いため、電極の単
位面積当たりの活物質の付着量は多くなるが、充放電試
験で実際の放電容量を調べると、両者の間に放電容量の
大きな差はなかった。つまり、球形粉は充填率が向上す
るため、金属間化合物粉末の付着量は増大するが、電気
的接触が点接触となって活物質の利用率が粉砕粉より低
くなるため、電極の放電容量向上には必ずしも結びつか
ないことが判明した。Next, the influence of the spherical powder was investigated. Organic binder made from spherical powder with high packing density
An electrode containing 10% PVDF has a higher powder packing density than a similar electrode using amorphous pulverized powder, so the amount of active material deposited per unit area of the electrode is larger. When the actual discharge capacity was examined, there was no large difference in the discharge capacity between the two. In other words, the spherical powder has an improved filling rate, so that the amount of the intermetallic compound powder attached increases, but the electrical contact becomes a point contact and the utilization rate of the active material becomes lower than that of the pulverized powder, so that the discharge capacity of the electrode is reduced. It turns out that it does not necessarily lead to improvement.
【００２４】そこで、平均粒径の異なる大小２種類の不
定形粉末を混合した粉末を用いて同じPVDFバインダ10％
の電極を作製したところ、電極容量に大きな向上が認め
られた。さらにそれだけではなく、平均粒径の異なる大
小２種類の球形粉に粉末を変更すると、前述の電極容量
にさらなる向上が認められた。これは粒径の小さな粒子
が大きな粒子の間に入り、電気的接触点数が増加するこ
とにより、活物質の利用率が向上したため容量が向上し
たものと考えられる。Therefore, the same PVDF binder of 10% is used by using a powder obtained by mixing two types of irregular shaped powders having different average particle sizes.
When the electrode was manufactured, a great improvement in the electrode capacity was recognized. Furthermore, when the powder was changed to two kinds of large and small spherical powders having different average particle diameters, further improvement in the above-mentioned electrode capacity was recognized. This is considered to be due to the fact that the small particles enter between the large particles and the number of electrical contact points increases, so that the utilization rate of the active material is improved and the capacity is improved.
【００２５】この点についてさらに検討した結果、大径
粉末と小径粉末が粒径比および混合比が一定範囲内にあ
る時に、特に充填密度が高く電極容量が高くなること、
この中で、大径粉末は球形であるが、小径粉末は球形粉
ではなくても、粉砕粉のように不定形粉末でも特に大き
い利用率の向上が得られることを見出し、本発明に到達
した。As a result of further study on this point, when the particle diameter ratio and the mixing ratio of the large-diameter powder and the small-diameter powder are within a certain range, particularly, the packing density is high and the electrode capacity is high.
Among them, the large-diameter powder has a spherical shape, but the small-diameter powder is not a spherical powder, and it has been found that a particularly large improvement in the utilization factor can be obtained even with an irregular-shaped powder such as a pulverized powder. .
【００２６】ここに、本発明は、平均粒子径の比が大径
粉末：小径粉末＝２：１〜20：１である大小２種類の金
属間化合物粉末を、大径粉末：小径粉末の重量比＝５：
１〜1.5 ：１の割合で混合した大径粉末と小径粉末との
混合物からなり、前記大径粉末はガスアトマイズ法また
は回転電極法により作られたリチウムイオン２次電池用
負極材料である。本発明の好適態様にあっては、小径粉
末が不定形粉末であるものである。In the present invention, two types of large and small intermetallic compound powders having an average particle diameter ratio of large-diameter powder: small-diameter powder = 2: 1 to 20: 1 are used for the weight of large-diameter powder: small-diameter powder. Ratio = 5:
1.5: Ri Do a mixture of a large径粉end and a small-diameter powder mixed in a ratio of 1, the large径粉weekend gas atomizing method also
Is a negative electrode material for a lithium ion secondary battery manufactured by a rotating electrode method . In a preferred embodiment of the present invention, the small-diameter powder
The powder is amorphous powder.
【００２７】さらに別の面からは、本発明は、平均粒径
が大径粉末：小径粉末＝２：１〜20：１である、大小２
種類の金属間化合物粉末を、大径粉末：小径粉末の重量
比＝５：１〜1.5 ：１の割合で混合した大径粉末と小径
粉末との混合物と有機物バインダとから成るリチウムイ
オン２次電池電極用負極である。From a further aspect, the present invention provides a method for producing a powder having a large particle size of 2: 1 to 20: 1 having an average particle diameter of 2: 1 to 20: 1.
A lithium ion secondary battery comprising a mixture of a large-diameter powder and a small-diameter powder obtained by mixing various kinds of intermetallic compound powders at a weight ratio of large-diameter powder: small-diameter powder = 5: 1 to 1.5: 1, and an organic binder. It is a negative electrode for an electrode.
【００２８】本発明のさらに別の態様によればまた、上
記金属間化合物粉末の混合物とPVDFなどの有機物バイン
ダから作製されたリチウムイオン２次電池用電極も提供
される。According to still another aspect of the present invention, there is also provided an electrode for a lithium ion secondary battery produced from a mixture of the above-mentioned intermetallic compound powder and an organic binder such as PVDF.
【００２９】ここで、球形粉末とは、実質的に球形の形
状を有していればよく、具体的にはアスペクト比２以下
の球形粉末までが許容される。このような球形粉末は、
ガスアトマイズ法や回転電極法により得ることができ
る。一方、不定形粉末とは、球形粉末以外の全ての粉末
を意味するが、代表的には粉砕粉である。前述した薄帯
状の金属間化合物を粉砕した粉末も不定形粉末に含まれ
る。Here, the spherical powder only needs to have a substantially spherical shape, and specifically, a spherical powder having an aspect ratio of 2 or less is acceptable. Such spherical powders
It can be obtained by a gas atomizing method or a rotating electrode method. On the other hand, the amorphous powder means all powders except the spherical powder, but is typically a pulverized powder. The powder obtained by pulverizing the above-mentioned ribbon-shaped intermetallic compound is also included in the amorphous powder.
【００３０】金属間化合物粉末の粒径は、粒径が最大と
なる方向で測定した粒径を意味し、平均粒径は体積累積
が50％となる粒径である。平均粒径は、例えば、レーザ
ー回折式粒度分布測定装置 (例えば、日機装製マイクロ
トラックFRA)により求めることができる。The particle size of the intermetallic compound powder means a particle size measured in a direction in which the particle size is maximized, and the average particle size is a particle size at which the volume accumulation becomes 50%. The average particle size can be determined by, for example, a laser diffraction type particle size distribution analyzer (for example, Nikkiso Microtrac FRA).
【００３１】[0031]
【発明の実施の形態】本発明にかかる金属間化合物粉末
の混合物は、充填密度と粉末間の電気的接触面積とを改
善するのに有効な粒子形態および粒径を規定した点に特
徴があり、それらの効果は金属間化合物の組成いかんに
よらず得ることができる。従って、金属間化合物の組成
は特に制限されず、リチウムイオン２次電池等の２次電
池の電極として利用可能な任意の組成のものでよい。BEST MODE FOR CARRYING OUT THE INVENTION The mixture of the intermetallic compound powder according to the present invention is characterized in that the particle morphology and particle size effective for improving the packing density and the electric contact area between the powders are specified. These effects can be obtained regardless of the composition of the intermetallic compound. Therefore, the composition of the intermetallic compound is not particularly limited, and may be any composition that can be used as an electrode of a secondary battery such as a lithium ion secondary battery.
【００３２】この種の代表的な金属間化合物は、リチウ
ムイオンを吸収、収納しうる金属間化合物である。この
ようなものは前述の FeSi2、NiSi2 、MoSi2 、ＷSi2 、
Mg2Si などの硅化物である。もちろん、これにＡサイ
ト、Ｂサイトのいずれを問わず置換元素を添加したもの
であっても構わない。例えばＡサイトには、Mn、Co、M
o、Cr、Nb、Ｖ、Cu、Fe、Ni、Ｗ、Ti、Zr、Ta、Ｂサイト
には、Si、Ｃ、Ga、Sm、Pb、Al、Ｐが置換してもよい。A typical intermetallic compound of this type is an intermetallic compound capable of absorbing and storing lithium ions. These are the aforementioned FeSi 2 , NiSi 2 , MoSi 2 , WSi 2 ,
It is a silicide such as Mg 2 Si. Needless to say, a material obtained by adding a substitution element to any of the A site and the B site may be used. For example, site A contains Mn, Co, M
The sites of o, Cr, Nb, V, Cu, Fe, Ni, W, Ti, Zr, Ta, and B may be replaced with Si, C, Ga, Sm, Pb, Al, and P.
【００３３】溶製による金属間化合物の製造方法には、
急冷凝固法とインゴット法がある。急冷凝固法として
は、ガスアトマイズ法や回転電極法といった球形粉末を
得る方法と、回転ドラム上や水冷銅板に注湯して薄帯状
の金属間化合物を得る方法とに大別される。インゴット
や薄帯状の金属間化合物は、その後に粉砕して粉末化す
る必要がある。The method for producing an intermetallic compound by melting includes:
There are a rapid solidification method and an ingot method. The rapid solidification method is roughly classified into a method of obtaining a spherical powder such as a gas atomizing method and a rotating electrode method, and a method of pouring a molten metal on a rotating drum or a water-cooled copper plate to obtain a thin intermetallic compound. The ingot and the ribbon-shaped intermetallic compound must be subsequently pulverized and pulverized.
【００３４】粉砕法としては、機械的な粉砕 (例、イン
ゴットで粗粉砕と微粉砕の組合わせ) の他に、水素を吸
蔵させた時の体積膨張を利用した粉砕も可能である。ま
た、メカニカルアロイング法による粉末作製も有効な手
段の一つである。As a pulverization method, in addition to mechanical pulverization (eg, a combination of coarse pulverization and fine pulverization with an ingot), pulverization utilizing volume expansion when hydrogen is absorbed is also possible. Powder production by mechanical alloying is also an effective means.
【００３５】急冷凝固法で製造した金属間化合物粉末
は、急冷歪みを緩和するために熱処理を施すことが好ま
しい。また、金属間化合物粉末の表面活性を高めるため
に、酸などで表面処理することが考えられるが、本発明
で用いる金属間化合物粉末についても、このような各種
の表面処理を適用してもよい。The intermetallic compound powder produced by the rapid solidification method is preferably subjected to a heat treatment in order to reduce rapid strain. In addition, in order to enhance the surface activity of the intermetallic compound powder, surface treatment with an acid or the like may be considered. For the intermetallic compound powder used in the present invention, such various surface treatments may be applied. .
【００３６】本発明の好適態様では、平均粒径の異なる
大小２種類の金属間化合物粉末を使用し、大径粉末は球
形粉末であるとさらに負極活物質の利用率が大きくなる
ことは前述の通りである。従って大径粉末は、ガスアト
マイズ法または回転電極法で作製することができる。中
でも、真球に近いほぼ完全な球状の球形粉末が得られる
ガスアトマイズ法が好ましい。In the preferred embodiment of the present invention, two types of large and small intermetallic compound powders having different average particle sizes are used, and when the large-diameter powder is a spherical powder, the utilization rate of the negative electrode active material is further increased. It is on the street. Therefore, the large-diameter powder can be produced by a gas atomizing method or a rotating electrode method. Among them, a gas atomization method that can obtain a nearly perfect spherical spherical powder close to a true sphere is preferable.
【００３７】小径粉末の方は、球形粉末でも不定形粉末
でもよいので、上述したいずれの方法で金属間化合物粉
末を作製してもよい。例えば、インゴットを粉砕した粉
砕粉も使用することができる。しかし、一般に急冷凝固
法で作製した金属間化合物の方が、冷却速度の遅いイン
ゴット法で作製したものより、偏析が少なく耐食性に優
れることから、急冷凝固法で作製した球形粉末 (例、ガ
スアトマイズ粉) や不定形粉末 (薄帯状の金属間化合物
を粉砕したもの) が好ましい。また、低融点化合物のた
め真空中の溶解が不向きな合金組成の場合、メカニカル
アロイング法による粉末作製が好ましい。Since the small-diameter powder may be a spherical powder or an amorphous powder, the intermetallic compound powder may be prepared by any of the above-described methods. For example, pulverized powder obtained by pulverizing an ingot can be used. However, intermetallic compounds produced by rapid solidification generally have less segregation and better corrosion resistance than those produced by the ingot method, which has a lower cooling rate.Therefore, spherical powders produced by rapid solidification (e.g., gas atomized powder) ) And amorphous powders (pulverized ribbon-shaped intermetallic compounds) are preferred. Further, in the case of an alloy composition which is not suitable for melting in a vacuum because of a low melting point compound, powder production by a mechanical alloying method is preferable.
【００３８】２種類の金属間化合物粉末の平均粒径比
は、大径粉末：小径粉末＝２：１〜20：１とする。大小
の金属間化合物粉末がこの範囲内の粒径比にあれば、有
機物バインダの電極を作製した時に、活物質の利用率を
著しく向上させることができる。小径粉末の平均粒径
が、大径粉末の平均粒径の1/20より小さいか、あるいは
1/2 より大きくなると、大小２種類の金属間化合物粉末
を混合しても、活物質の利用率はあまり改善されない。The average particle size ratio of the two kinds of intermetallic compound powders is set to large powder: small powder = 2: 1 to 20: 1. If the large and small intermetallic compound powders have a particle size ratio within this range, the utilization rate of the active material can be significantly improved when an organic binder electrode is produced. The average particle size of the small-diameter powder is smaller than 1/20 of the average particle size of the large-diameter powder, or
When the ratio is larger than 1/2, even if two types of intermetallic compound powders, large and small, are mixed, the utilization rate of the active material is not so much improved.
【００３９】例えば、小径粉末の平均粒径が小さすぎる
と、大径粉末間の空隙を小径粉末が埋めても、隙間が大
きいため、充填密度は向上するものの、電気的接触は改
善されないので、活物質の利用率はさほど向上しない
上、比表面積が増大するため、１サイクル目のクーロン
効率が低下する。逆に、小径粉末の平均粒径が大きすぎ
ると、大径粉末の配置が乱れるため、充填密度が低下す
ると同時に、大径粒子間の接触も悪くなり、活物質の利
用率の向上は得られない。この平均粒径比は、好ましく
は大径粉末：小径粉末＝３：１〜５：１である。For example, if the average particle size of the small-diameter powder is too small, even if the small-diameter powder fills the gaps between the large-diameter powders, the gaps are large and the packing density is improved, but the electrical contact is not improved. The utilization rate of the active material does not improve so much, and the specific surface area increases, so that the Coulomb efficiency in the first cycle decreases. Conversely, if the average particle size of the small-diameter powder is too large, the arrangement of the large-diameter powder is disturbed, so that the packing density is reduced, and at the same time, the contact between the large-diameter particles is deteriorated, and the utilization rate of the active material is improved. Absent. This average particle size ratio is preferably large diameter powder: small diameter powder = 3: 1 to 5: 1.
【００４０】なお、本発明の趣旨からは大径粉末の平均
粒径は制限されないが、実際の電極の厚みが100 μｍ程
度であり、実用的観点からは20〜120 μｍの範囲内、特
に30〜50μｍの範囲内が好ましい。大径粉末の平均粒径
が小さすぎると、さらに小さい小径粉末の平均粒径が小
さくなりすぎ、比表面積が大きくなり過ぎて、１サイク
ル目のクーロン効率が低下してしまう。Although the average particle size of the large-diameter powder is not limited for the purpose of the present invention, the actual thickness of the electrode is about 100 μm, and from a practical point of view, it is in the range of 20 to 120 μm, especially 30 μm. It is preferably within the range of 50 μm. If the average particle size of the large-diameter powder is too small, the average particle size of the smaller-diameter powder becomes too small, the specific surface area becomes too large, and the coulomb efficiency in the first cycle decreases.
【００４１】上述した大小２種類の金属間化合物粉末の
混合粉末を用いて、有機物バインダの電極の活物質の利
用率を著しく向上させるには、この２種類の粉末の混合
比を、大径粉末：小径粉末の重量比＝５：１〜1.5 ：１
の範囲内とすることが適切である。小径粉末が大径粉末
の1/5 より少ないと、大径粉末の間隙に入る小径粉末が
少なすぎて、十分な利用率の改善効果が得られない。小
径粉末が大径粉末の1/1.5 より多くなると、大径粉末の
間隙に充填するのに必要な量より小径粉末が多くなりす
ぎ、大径粉末の配列が乱れて、充填密度が低下するだけ
でなく、比表面積が大きい小径粉末が増加するため、耐
食性が劣化し、充放電繰り返し寿命が低下する。この混
合比は、好ましくは大径粉末：小径粉末の重量比＝４：
１〜1.5：１の範囲内である。In order to significantly improve the utilization rate of the active material of the electrode of the organic binder by using the mixed powder of the above-mentioned two kinds of large and small intermetallic compound powders, the mixing ratio of the two kinds of powders is changed to the large-diameter powder. : Weight ratio of small diameter powder = 5: 1 to 1.5: 1
It is appropriate to be within the range. If the small-diameter powder is less than 1/5 of the large-diameter powder, the small-diameter powder entering the gap between the large-diameter powders is too small, and a sufficient effect of improving the utilization cannot be obtained. If the small-diameter powder is larger than 1 / 1.5 of the large-diameter powder, the small-diameter powder becomes too large to fill the gap between the large-diameter powders, the arrangement of the large-diameter powder is disturbed, and the packing density is reduced. In addition, the small-diameter powder having a large specific surface area increases, so that the corrosion resistance is deteriorated and the charge / discharge cycle life is shortened. The mixing ratio is preferably such that the weight ratio of large-diameter powder: small-diameter powder = 4:
It is in the range of 1-1.5: 1.
【００４２】このように、大小２種類の金属間化合物粉
末を使用する本発明において、電極特性が改善される適
正な平均粒径比および混合比は、充填密度が最大となる
平均粒径比および混合比よりかなり広い範囲である。こ
れは、最大充填密度に必要な条件より大径粉末がやや多
いか、少なくなっても、不完全な充填状態となるため、
かえって一部の接触点では局所的に高い接触面圧で接す
ることになり、この接触点で良好な電気的接触が実現す
るためと考えられる。As described above, in the present invention using two types of intermetallic compound powders, large and small, the proper average particle size ratio and mixing ratio for improving the electrode characteristics are determined by the average particle size ratio and the maximum packing density. The range is much wider than the mixing ratio. This is because even if the large-diameter powder is slightly more or less than the condition required for the maximum packing density, it will be in an incomplete filling state,
Rather, some of the contact points come into contact locally with a high contact surface pressure, and it is considered that good electrical contact is realized at these contact points.
【００４３】すなわち、最大充填密度が得られる混合条
件では、小径粉末が大径粉末の間隙にきれいに納まるた
めに、接触点数が多く、各接触点に加わる圧力がほぼ均
等となり、良好な電気的接触が得られる。一方、最大充
填密度が得られる条件より平均粒径比または混合比が少
しずれた条件では、粉末間の接触点数は減少するもの
の、一部の接触点では強い圧力が加わるため、そのよう
な接触点における電気的接触が良好となる。その結果、
電極全体の電気伝導性は最大充填密度の場合と同様に改
善され、最大充填密度となる混合条件よりも広い範囲
で、改善された電極特性を得ることができる。In other words, under the mixing conditions for obtaining the maximum packing density, the small-diameter powder fits neatly into the gaps between the large-diameter powders, so that the number of contact points is large, the pressure applied to each contact point is almost equal, and good electrical contact is obtained. Is obtained. On the other hand, under conditions where the average particle size ratio or the mixing ratio is slightly deviated from the conditions under which the maximum packing density is obtained, although the number of contact points between the powders decreases, strong pressure is applied at some of the contact points. Good electrical contact at the point. as a result,
The electrical conductivity of the entire electrode is improved as in the case of the maximum packing density, and improved electrode characteristics can be obtained in a wider range than the mixing condition that results in the maximum packing density.
【００４４】前述したように、大径粉末としては球形粉
末を使用した方が好ましい。大径粉末が不定形であると
充填密度が低下するため、放電容量を十分に高くするこ
とができない上、比表面積が増大するので、耐食性劣化
による充放電繰り返し寿命の低下が大きくなる。As described above, it is preferable to use a spherical powder as the large-diameter powder. If the large-diameter powder is amorphous, the packing density decreases, so that the discharge capacity cannot be sufficiently increased, and the specific surface area increases.
【００４５】しかし、大径粉末の間隙に充填される小径
粉末の方は、球形粉末と不定形粉末とのいずれでもよ
い。小径粉末が不定形粉末であると、球形粉末を使用し
た場合に比べて、充填密度はやや減少するものの、電極
特性はむしろ改善される。これは、粉砕した不定形の粉
末粒子には平面が多数あるため、曲面で構成される球形
粉末より粉末接触面積が大きくなり、利用率の改善効果
の点では球形粉末より優れているためである。すなわ
ち、不定形の小径粉末を使用する場合は、充填性は不明
ではあるが、利用率が向上するため、電極としての特性
は、より充填密度が高くなる小径粉末が球形粉末である
場合と同様に、改善することができる。However, the small-diameter powder to be filled in the gap between the large-diameter powder may be either a spherical powder or an irregular-shaped powder. When the small-diameter powder is an irregular-shaped powder, the packing density is slightly reduced as compared with the case where the spherical powder is used, but the electrode characteristics are rather improved. This is because pulverized amorphous powder particles have a large number of flat surfaces, so that the powder contact area is larger than a spherical powder composed of curved surfaces, and is superior to a spherical powder in terms of an effect of improving the utilization factor. . That is, when using amorphous small-diameter powder, the filling property is unknown, but the utilization factor is improved, so that the characteristics as an electrode are the same as when the small-diameter powder having a higher packing density is a spherical powder. Can be improved.
【００４６】本発明にかかる金属間化合物粉末の混合物
と有機物バインダとを使用して、従来と同様の方法によ
り２次電池用の電極を作製することができる。有機物バ
インダの例は、PVDF、PVA 、PTFE、PEO 、PMMA等であ
る。有機物バインダの使用量は、金属間化合物粉末の結
合に必要な範囲内で少量とすることが好ましく、通常は
合金粉末の0.1 〜10重量％程度で十分である。Using the mixture of the intermetallic compound powder and the organic binder according to the present invention, an electrode for a secondary battery can be manufactured in the same manner as in the prior art. Examples of organic binders are PVDF, PVA, PTFE, PEO, PMMA and the like. The amount of the organic binder used is preferably as small as possible within a range necessary for bonding the intermetallic compound powder, and usually about 0.1 to 10% by weight of the alloy powder is sufficient.
【００４７】電極の作製は、例えば、前述のバインダと
溶剤(NMP、DMF など) を混合し、良く攪拌した後、これ
に金属間化合物粉末の混合物を投入、ホモジナイザ、ガ
ラスビーズなどで十分に攪拌を行う。このようにして得
られた混練物をスラリまたはペースト状にし、これを電
極基板 (例えば、Cu金属箔、ステンレス箔など) にドク
ターブレード法、スクリーン印刷法などによって塗布
し、乾燥して溶媒を除去した後、ロール加圧もしくはプ
レスして成形することにより行うことができる。また、
これらの攪拌方法、塗布法、プレス方法はこれによるも
のではなく、攪拌方法は均一にできれば良く、さらに塗
布法は基板に対して平滑に塗着できるものであれば良
く、プレス方法も、基板全体に均一に圧力がかかる方法
であれば構わない。For the production of the electrode, for example, the above-mentioned binder and a solvent (NMP, DMF, etc.) are mixed and stirred well, and then a mixture of the intermetallic compound powder is added thereto, and the mixture is sufficiently stirred with a homogenizer, glass beads or the like. I do. The kneaded material thus obtained is formed into a slurry or paste, which is applied to an electrode substrate (for example, Cu metal foil, stainless steel foil, etc.) by a doctor blade method, a screen printing method, etc., and dried to remove the solvent. After that, the pressing can be performed by pressing or pressing with a roll. Also,
The stirring method, the coating method, and the pressing method are not based on this. The stirring method only needs to be uniform, and the coating method may be any method that can smoothly apply to the substrate. Any method can be used as long as pressure is applied uniformly.
【００４８】[0048]
【実施例】以下に述べる実施例では、NiSi2 という化学
組成を持つ硅化物の金属間化合物を用いた。この金属間
化合物の作製に用いた原料は、純度99.999％のSi、純度
99.9％のフレーク状Niであった。EXAMPLES In the examples described below, a silicide intermetallic compound having a chemical composition of NiSi 2 was used. The raw materials used to make this intermetallic compound were Si with a purity of 99.999%,
It was 99.9% flaky Ni.
【００４９】これらの原料を所定比率に混合し、急冷凝
固法であるArガスアトマイズ法 (30kg/ch)により金属間
化合物の球形粉末 (アトマイズ粉) を、ロール急冷法に
より鋳造した薄片 (５kg/ch)の機械粉砕 (軽くハンマー
で粉砕した後、Arガス雰囲気中アトリションミルで微粉
砕) により金属間化合物の不定形粉末 (粉砕粉またはロ
ール急冷薄片粉砕粉) をそれぞれ作製した。アトマイズ
粉と粉砕粉の各々に、純度99.99 ％のAr雰囲気中で900
℃×15hrの熱処理を施した。These raw materials were mixed at a predetermined ratio, and a flake (5 kg / ch) obtained by casting a spherical powder (atomized powder) of an intermetallic compound by an Ar gas atomizing method (30 kg / ch) as a rapid solidification method by a roll quenching method. ) Was mechanically pulverized (lightly pulverized with a hammer, and then finely pulverized with an attrition mill in an Ar gas atmosphere) to prepare amorphous powders of intermetallic compounds (pulverized powder or roll-quenched flaked powder). Each of the atomized powder and the pulverized powder is 900 ppm in a 99.99% pure Ar atmosphere.
A heat treatment of 15 ° C. × 15 hours was performed.
【００５０】アトマイズ粉と粉砕粉のいずれも篩い分け
により、平均粒径の異なる各種の粉末を調製した。この
分級における各平均粒径の粉末の粒度分布は次の通りで
ある。Both the atomized powder and the pulverized powder were sieved to prepare various powders having different average particle diameters. The particle size distribution of the powder of each average particle size in this classification is as follows.
【００５１】 平均粒径 (μm) 粉砕粉粒度分布 (μm) アトマイス゛ 粉粒度分布 (μm) 100 45〜250 52〜250 65 32〜125 37〜125 50 25〜75 28〜75 30 〜60 5〜60 25 〜45 5〜45 18 〜30 5〜30 8 〜20 〜15 5 〜15 〜10 3 〜10 〜10 Average particle size (μm) Particle size distribution of pulverized powder (μm) Atomize ゛ Particle size distribution of powder (μm) 100 45-250 52-250 65 32-125 37-125 50 25-75 28-75 30-60 5-60 25 to 45 5 to 45 18 to 30 5 to 30 8 to 20 to 15 5 to 15 to 10 3 to 10 to 10
【００５２】なお、大径粉末の平均粒径を100 μｍにし
たのは、小径粉末との平均粒径比を算出し易くするため
であり、この平均粒径が大径粉末に最適であるというこ
とではない。[0052] The Contact, had an average particle diameter of the powder large径粉to 100 [mu] m is for the purpose of easily calculating the average particle size ratio between the small-diameter powder, the average particle size is optimal in the late large径粉That is not to say.
【００５３】以下の実施例において、この金属間化合物
の混合粉末100 ｇの粉末に対して10wt％の有機物バイン
ダ(PVDF)、アセチレンブラック５wt％を添加し、さらに
NMP120ｇを投入し、混練した。得られた金属間化合物粉
末のペーストを表面を電解粗面処理した銅箔にドクター
ブレード法を用いて塗布し、乾燥した後、1.0 ton/cm2
の圧力でロール加圧により成形して、金属間化合物粉末
を基板上に担持させ、電極を作製した。この電極の金属
間化合物粉末の担持量は最大で５ｇを目標とした。In the following examples, 10 wt% of an organic binder (PVDF) and 5 wt% of acetylene black were added to 100 g of the mixed powder of the intermetallic compound.
120 g of NMP was charged and kneaded. The paste of the obtained intermetallic compound powder was applied to a copper foil whose surface was electrolytically roughened using a doctor blade method, and dried, and then 1.0 ton / cm 2
Then, the powder was formed by pressing with a roll under the pressure described above, and the intermetallic compound powder was supported on a substrate to produce an electrode. The target amount of the intermetallic compound powder carried on this electrode was 5 g at the maximum.
【００５４】この電極を負極とし、正極、参照極にも金
属Liを用い、正極と負極の間のポリプロピレン製のセパ
レータを配し、これらを挟んで両側からネジなどで固定
し、通常のリチウムイオン２次電池を構成した。これは
電池の充填・放電反応に伴う体積変化によって負極活物
質が基板からはずれても、構成粒子間の接触を保てるよ
うにするためである。この電池を0.2 mA/cm2の電流でLi
基準電位に対して0.0Vまで充電、同じように0.2 mA/cm2
の電流でLi基準電位に対して1.5Vまで放電を行った時の
放電容量の大きさを比較した。This electrode was used as a negative electrode, metal Li was also used for the positive electrode and the reference electrode, a polypropylene separator was disposed between the positive electrode and the negative electrode, and these were sandwiched and fixed from both sides with screws or the like. A secondary battery was constructed. This is because the contact between the constituent particles can be maintained even if the negative electrode active material is displaced from the substrate due to the volume change accompanying the charging / discharging reaction of the battery. Li this battery 0.2 mA / cm 2 current
Charges to 0.0 V with respect to reference potential, similarly 0.2 mA / cm 2
The magnitudes of the discharge capacities when the discharge was performed to 1.5 V with respect to the Li reference potential at the currents of the above were compared.
【００５５】これと比較するための容量として、金属間
化合物粉末の理論放電容量の値は、例えばNiSi2 を負極
材料に用いた時、NiSi2 １モルに対してLi 1モルが反応
し、LiNiSi2 を生成するまで電気量を消費したときの容
量、855mAh/cm3を用いた。これらの結果から、次式によ
り粉末利用率を算出し、電極特性を判定した。粉末利用
率が90％以上あれば、金属間化合物電極性能は合格であ
る。As a capacity for comparison, the theoretical discharge capacity of the intermetallic compound powder is as follows. For example, when NiSi 2 is used for the negative electrode material, 1 mole of Li reacts with 1 mole of NiSi 2 , and LiNiSi A capacity of 855 mAh / cm 3 when the amount of electricity was consumed until generating 2 was used. From these results, the powder utilization was calculated by the following equation, and the electrode characteristics were determined. If the powder utilization is 90% or more, the intermetallic compound electrode performance is acceptable.
【００５６】[0056]
【数１】粉末利用率(%) ＝｛実際の放電容量(mAh)/理論
放電容量(mAh) ｝×100 混合粉末によるサイクル寿命特性の評価は、試験用リチ
ウムイオン２次電池の充放電試験を100 サイクル行い、
第１サイクルと100 サイクル後の放電容量を求め、次式
によりサイクル寿命(%) を求め90％以上を合格とした。[Equation 1] Powder utilization rate (%) = {actual discharge capacity (mAh) / theoretical discharge capacity (mAh)} x 100 The evaluation of the cycle life characteristics of the mixed powder is based on the charge / discharge test of a test lithium ion secondary battery. 100 cycles
The discharge capacity after the first cycle and after 100 cycles was determined, the cycle life (%) was determined by the following equation, and 90% or more was determined to be acceptable.
【００５７】[0057]
【数２】サイクル寿命(%) ＝｛100 サイクル後の放電容
量(mAh)/第１サイクル放電容量(mAh) ｝×100 また３つ目の電極試験の指標として、第１サイクル目の
クーロン効率を次のように設定した。このクーロン効率
は90％以上であれば合格とした。Cycle life (%) = {discharge capacity after 100 cycles (mAh) / first cycle discharge capacity (mAh)} x 100 Also, as an index of the third electrode test, the coulomb efficiency in the first cycle Was set as follows. If the Coulomb efficiency was 90% or more, it was judged as acceptable.
【００５８】[0058]
【数３】クーロン効率(%) ＝｛放電容量(mAh)/充電容量
(mAh) ｝×100 混合粉末の充填密度は、タップ試験により評価した。こ
の試験ではホソカワミクロン社製パウダーテスタにより
タップ密度を求めた。このタップ密度が物質の理論比重
の65％以上であれば充填密度は十分であり、70％以上で
あれば充填密度は非常に高い。例えばNiSi2 を例にとる
と、材料本来の比重は4.83と見積もることができるの
で、タップ密度が3.13以上のときを合格とした。以上の
試験結果を、大小２種類の粉末の平均粒径および混合比
と共に表１に示す。[Equation 3] Coulomb efficiency (%) = ｛discharge capacity (mAh) / charge capacity
(mAh)｝ × 100 The packing density of the mixed powder was evaluated by a tap test. In this test, the tap density was determined using a powder tester manufactured by Hosokawa Micron Corporation. If the tap density is 65% or more of the theoretical specific gravity of the substance, the packing density is sufficient, and if it is 70% or more, the packing density is very high. For example, taking NiSi 2 as an example, the original specific gravity of the material can be estimated to be 4.83, so the case where the tap density is 3.13 or more is judged as acceptable. The above test results are shown in Table 1 together with the average particle size and the mixing ratio of the two types of powder, large and small.
【００５９】[0059]
【００６０】[0060]
【００６１】[0061]
【００６２】[0062]
【００６３】(実施例１) 次に大径粉末と小径粉末の両方ともがアトマイズ粉、す
なわち、球形粉末である金属間化合物の混合粉末につい
て例示する。(Example 1 ) Next, an example is given of a mixed powder of an intermetallic compound in which both the large-diameter powder and the small-diameter powder are atomized powders, that is, spherical powders.
【００６４】篩い分けで得られた平均粒径100 μｍのア
トマイズ法の球形粉末を大径粉末として使用し、これを
平均粒径がより小さいアトマイズ法の球形粉末と所定比
率で混合した。なお、前述と同様に、大径粉末の平均粒
径を100 μｍにしたのは、小径粉末との平均粒径比を算
出し易くするためであり、この平均粒径が大径粉末に最
適であるということではない。The atomized spherical powder having an average particle diameter of 100 μm obtained by sieving was used as a large-diameter powder, and this was mixed with the atomized spherical powder having a smaller average particle diameter at a predetermined ratio. As described above, the reason why the average particle size of the large-diameter powder is set to 100 μm is to make it easier to calculate the average particle size ratio with the small-diameter powder. That is not to say.
【００６５】この金属間化合物の混合粉末100 ｇの粉末
に対して10wt％の有機物バインダ(PVDF)、アセチレンブ
ラック５wt％を添加し、さらにNMP100ｇを投入し、混練
した。実施例１の場合とNMP の量が異なるのは、金属間
化合物粉末の形状が大径粒子、小径粒子とも球形の時は
流動性が優れており、ドクターブレード法で厚みを調整
するにはNMP の量を減らす必要があるからである。得ら
れた合金粉末のペーストを表面を電解粗面処理した銅箔
にドクターブレード法を用いて塗布し、乾燥した後、1.
0 ton/cm2 の圧力でロール加圧により成形して、金属間
化合物粉末を基板上に担持させ、電極を作製した。この
電極の金属間化合物粉末の担持量は最大で５ｇを目標と
した。10 wt% of an organic binder (PVDF) and 5 wt% of acetylene black were added to 100 g of the mixed powder of the intermetallic compound, and 100 g of NMP was further added and kneaded. The amount of NMP is different from that in Example 1 because the intermetallic compound powder has excellent fluidity when both the large-diameter particles and the small-diameter particles are spherical. This is because it is necessary to reduce the amount. The paste of the obtained alloy powder was applied to a copper foil whose surface was electrolytically roughened using a doctor blade method, dried, and then dried.
An electrode was formed by molding by roll pressing at a pressure of 0 ton / cm 2 , supporting the intermetallic compound powder on the substrate. The target amount of the intermetallic compound powder carried on this electrode was 5 g at the maximum.
【００６６】また、大径粉末の粒径の影響を調査するた
めに、平均粒径65、50、25μｍの粉末を大径粉末として
用い、上記と同様の処理を行って電極を作成した。Further, in order to investigate the influence of the particle size of the large-diameter powder, powder having an average particle size of 65, 50, and 25 μm was used as the large-diameter powder, and an electrode was prepared by performing the same treatment as described above.
【００６７】この電極を用い、前述の充電・放電方式と
同じような方法で電極試験を行った。また、タップ密
度、利用率などについても同上の方法で行った。この結
果を表２に示す。Using this electrode, an electrode test was performed in the same manner as in the above-described charge / discharge method. Further, tap density, utilization rate, and the like were also measured in the same manner. Table 2 shows the results.
【００６８】[0068]
【表１】 [Table 1]
【００６９】表１から、たとえ球形粉末でも大径粉末だ
けの単一粉末では、タップ密度、粉末利用率のいずれも
不定形粉末の時に比べると改善はなされるが、不十分で
あることがわかる。また、小径粉末に相当するより平均
粒径の小さい不定形粉末だけでも、やはりタップ密度、
粉末利用率のいずれも大きな改善が見られなかった。From Table 1 , it can be seen that a single powder consisting of only a large diameter powder, even a spherical powder, improves both tap density and powder utilization as compared with amorphous powder, but is insufficient. In addition, even with an amorphous powder having an average particle diameter smaller than that of a small-diameter powder alone, the tap density,
No significant improvement in powder utilization was seen.
【００７０】これに対し、本発明に従って大径粉末に小
径粉末を混合すると、タップ密度、粉末利用率のいずれ
も大きく改善され、放電容量が高く、サイクル寿命の長
い、高性能のリチウムイオン２次電池が得られることが
わかる。On the other hand, when the small-diameter powder is mixed with the large-diameter powder according to the present invention, both the tap density and the powder utilization are greatly improved, and the discharge capacity is high, the cycle life is long, and the high performance lithium ion secondary battery is used. It can be seen that a battery is obtained.
【００７１】一方、大径粉末に小径粉末を混合しても、
小径粉末の平均粒径が本発明の範囲外であるか、小径粉
末の混合比が本発明の範囲外であると、粉末の利用率や
容量低下率はなお不十分なままであり、タップ密度の向
上もそれほど大きくなかった。小径粉末の粒径があまり
に小さいと、比表面積が大きくなり過ぎ、電解液との接
触面積が増加するため、クーロン効率が低下する。ま
た、大径粉末の粒径を変えた場合、大径粉末の粒径が25
μｍ、小径粉末の粒径が５μｍになると、クーロン効率
が他より相対的に低下する。On the other hand, even if the small-diameter powder is mixed with the large-diameter powder,
If the average particle size of the small-diameter powder is out of the range of the present invention, or the mixing ratio of the small-diameter powder is out of the range of the present invention, the powder utilization and capacity reduction rate are still insufficient, and the tap density The improvement was not so large. If the particle size of the small-diameter powder is too small, the specific surface area becomes too large, and the contact area with the electrolytic solution increases, so that the Coulomb efficiency decreases. When the particle size of the large-diameter powder is changed, the particle size of the large-diameter powder is 25%.
When the particle diameter of the small-diameter powder is 5 μm, the Coulomb efficiency is relatively lower than the others.
【００７２】（実施例２） 小径粉末として、ガスアトマイズ法で得られた球形粉末
に代えて、ロール急冷薄片粉砕粉である不定形粉末を使
用した以外は、実施例２にあるような方法を繰り返し
た。試験結果を、大小２種類の粉末の平均粒径および混
合比と共に表２に示す。(Example 2 ) The method as in Example 2 was repeated except that, as the small-diameter powder, an irregular-shaped powder which was a crushed roll quenched powder was used instead of the spherical powder obtained by the gas atomizing method. Was. The test results are shown in Table 2 together with the average particle size and the mixing ratio of the two types of powder, large and small.
【００７３】[0073]
【表２】 [Table 2]
【００７４】表２から、本発明に従って不定形の小径粉
末を球形の大径粉末に混合した混合粉末は、小径粉末も
球形粉末である実施例１に比べて、タップ密度 (すなわ
ち、充填密度) が低下することがわかる。しかし、粉末
の利用率は、逆に不定形の小径粉末を用いた方が、球形
粉末を用いた実施例１より良好な結果が得られた。充填
密度が低いにもかかわらず、粉末利用率が高くなるの
は、前述したように、実施例１のように球形粉末同士を
混合した場合に比べて、不定形粉末を混合すると接触面
積が大きくなるためであると考えられる。From Table 2 , it can be seen that the mixed powder obtained by mixing the amorphous small-sized powder with the spherical large-sized powder according to the present invention has a higher tap density (ie, packing density) than Example 1 in which the small-sized powder is also a spherical powder. It can be seen that is decreased. However, as for the utilization rate of the powder, a better result was obtained when the irregular-sized small-diameter powder was used than in Example 1 using the spherical powder. Although the packing density is low, the powder utilization rate increases as described above, compared with the case where spherical powders are mixed together as in Example 1 , when the irregular shaped powder is mixed, the contact area is large. It is thought to be.
【００７５】本実施例で不定形粉末として用いたロール
急冷薄片粉砕粉は、冷却速度が非常に早いため成分偏析
が少なく、これとアトマイズ粉を混合して使用した場
合、格子間にLiイオンが挿入されるとすると放電容量に
最大なると考えられる。そのため、不定形粉末をインゴ
ット粉砕粉にすると放電容量がやや少なくなることが考
えられるが、熱処理温度、時間などを調節すれば放電容
量の低下はごく僅かに押さえることができると考えられ
る。The quenched roll quenched powder used as the irregular-shaped powder in this example has a very high cooling rate and therefore has little component segregation. When this is mixed with atomized powder, Li ions are generated between lattices. If inserted, it is considered that the discharge capacity is maximized. For this reason, it is considered that when the amorphous powder is converted into ingot pulverized powder, the discharge capacity is slightly reduced. However, it is considered that the decrease in the discharge capacity can be suppressed very slightly by adjusting the heat treatment temperature and time.
【００７６】平均粒径が100 μｍの大径の不定形粉末だ
けからなる単一粉末では、粉末のタップ密度 (充填密
度) は、同じ平均粒径の球形粉末だけの時に比べて低く
なったが、接触面積が大きいため、粉末利用率は高くな
った。In the case of a single powder consisting only of a large-sized amorphous powder having an average particle size of 100 μm, the tap density (packing density) of the powder was lower than that of a spherical powder having the same average particle size. And the contact area was large, so that the powder utilization rate was high.
【００７７】一方、小径粉末の平均粒径または混合比が
本発明の範囲外である比較例では、実施例２の時と同様
に、粉末の利用率と容量低下率のどちらも十分に改善す
ることができなかった。On the other hand, in the comparative example in which the average particle size or the mixing ratio of the small-diameter powder is out of the range of the present invention, similarly to the case of Example 2, both the powder utilization and the capacity reduction rate are sufficiently improved. I couldn't do that.
【００７８】[0078]
【００７９】[0079]
【００８０】[0080]
【発明の効果】本発明の金属間化合物粉末は、有機物バ
インダを使用して電極を作製した時に、粉末の充填密度
と電気的接触の良好な電極を得ることができる。その結
果、この電極を用いてリチウムイオン２次電池とした時
に、負極活物質の金属間化合物粉末の利用率が高く、放
電容量の高い２次電池になる。また、大径粉末が球形で
あり、比表面積が比較的小さい時は特に耐食性も良好で
あり、充放電繰り返し寿命も改善され、高性能のリチウ
ムイオン２次電池用電極が得られる。また、リチウムイ
オン２次電池に限らず他のアルカリ金属およびアルカリ
土類金属等の金属イオンを利用した２次電池の金属イオ
ンを吸蔵・放出する電極材料あるいは電極を得ることが
できる。According to the intermetallic compound powder of the present invention, when an electrode is produced using an organic binder, an electrode having good powder packing density and good electrical contact can be obtained. As a result, when a lithium ion secondary battery is formed using this electrode, a secondary battery having a high utilization rate of the intermetallic compound powder of the negative electrode active material and a high discharge capacity is obtained. In addition, when the large-diameter powder is spherical and the specific surface area is relatively small, the corrosion resistance is particularly good, the charge / discharge cycle life is improved, and a high-performance electrode for a lithium ion secondary battery is obtained. In addition, an electrode material or an electrode capable of inserting and extracting metal ions of a secondary battery using not only lithium ion secondary batteries but also other metal ions such as alkali metals and alkaline earth metals can be obtained.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平８−227708（ＪＰ，Ａ) 特開 平９−27314（ＪＰ，Ａ) 特公 平７−36332（ＪＰ，Ｂ２) (58)調査した分野(Int.Cl.7，ＤＢ名) H01M 4/58 H01M 4/02 H01M 10/40 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-227708 (JP, A) JP-A-9-27314 (JP, A) JP-B-7-36332 (JP, B2) (58) Field (Int.Cl. 7 , DB name) H01M 4/58 H01M 4/02 H01M 10/40
Claims (4)
２：１〜20：１である大小２種類の金属間化合物粉末
を、大径粉末：小径粉末の重量比＝５：１〜1.5 ：１の
割合で混合した大径粉末と小径粉末との混合物からな
り、前記大径粉末はガスアトマイズ法または回転電極法
により作られたリチウムイオン２次電池用負極材料。1. The ratio of the average particle diameter is large powder: small powder =
A mixture of a large-diameter powder and a small-diameter powder in which two large and small intermetallic compound powders of 2: 1 to 20: 1 are mixed at a weight ratio of large-diameter powder: small-diameter powder = 5: 1 to 1.5: 1. From
The large-diameter powder is obtained by a gas atomizing method or a rotating electrode method.
Negative electrode material for lithium-ion secondary batteries made by Nissan.
１記載のリチウムイオン２次電池用負極材料。2. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein the small-diameter powder is an irregular-shaped powder.
１または２記載のリチウムイオン２次電池用負極材料。3. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein the intermetallic compound is a silicide.
イオン２次電池用負極材料と有機物バインダとから作製
されたリチウムイオン２次電池用負極。4. A negative electrode for a lithium ion secondary battery produced from the negative electrode material for a lithium ion secondary battery according to claim 1 and an organic binder.
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|---|---|---|---|
| JP18397597A JP3282546B2 (en) | 1997-07-09 | 1997-07-09 | Anode material for lithium ion secondary battery and its electrode |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18397597A JP3282546B2 (en) | 1997-07-09 | 1997-07-09 | Anode material for lithium ion secondary battery and its electrode |
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| Publication Number | Publication Date |
|---|---|
| JPH1131509A JPH1131509A (en) | 1999-02-02 |
| JP3282546B2 true JP3282546B2 (en) | 2002-05-13 |
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| JP18397597A Expired - Fee Related JP3282546B2 (en) | 1997-07-09 | 1997-07-09 | Anode material for lithium ion secondary battery and its electrode |
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Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4465756B2 (en) * | 1999-11-19 | 2010-05-19 | パナソニック株式会社 | Non-aqueous electrolyte secondary battery, alloy for the battery, and manufacturing method thereof |
| KR20130090913A (en) | 2005-10-20 | 2013-08-14 | 미쓰비시 가가꾸 가부시키가이샤 | Lithium secondary cell and nonaqueous electrolytic solution for use therein |
| JP5158578B2 (en) * | 2007-06-26 | 2013-03-06 | Ｎｅｃエナジーデバイス株式会社 | Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same |
| JP5361233B2 (en) * | 2008-03-31 | 2013-12-04 | 三洋電機株式会社 | Lithium secondary battery and manufacturing method thereof |
| JP5267976B2 (en) * | 2008-05-27 | 2013-08-21 | Ｎｅｃエナジーデバイス株式会社 | Negative electrode for lithium ion secondary battery and lithium ion secondary battery using the same |
| JP2010033830A (en) * | 2008-07-28 | 2010-02-12 | Nec Tokin Corp | Negative electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery using the same |
| JP5181002B2 (en) * | 2009-08-21 | 2013-04-10 | 尾池工業株式会社 | Scale-like thin film fine powder dispersion or scale-like thin film fine powder, paste using the same, battery electrode, and lithium secondary battery |
| EP2811551A4 (en) * | 2012-04-18 | 2015-08-19 | Lg Chemical Ltd | Electrode having multi-layer structure and manufacturing method therefor |
| JP6331463B2 (en) * | 2014-02-25 | 2018-05-30 | 新日鐵住金株式会社 | Negative electrode active material |
| JP5907223B2 (en) * | 2014-09-08 | 2016-04-26 | 信越化学工業株式会社 | Negative electrode active material for non-aqueous electrolyte secondary battery, negative electrode and method for producing non-aqueous electrolyte secondary battery |
| CN105406079A (en) * | 2015-12-17 | 2016-03-16 | 佛山市南海区欣源电子有限公司 | Lithium ion battery negative pole piece and preparation method thereof |
| CN110212239A (en) * | 2019-05-21 | 2019-09-06 | 东莞东阳光科研发有限公司 | A kind of full solid state polymer solid electrolyte and preparation method thereof |
| KR20240043755A (en) * | 2021-07-06 | 2024-04-03 | 스트라투스 머티리얼즈 인코포레이티드 | Lithium-rich nickel manganese oxide battery cathode materials and methods |
| WO2023133106A1 (en) * | 2022-01-04 | 2023-07-13 | Straus Materials Inc. | Microwave-processed, ultra-rapid quenched lithium-rich lithium manganese nickel oxide and methods of making the same |
| CN115178733B (en) * | 2022-05-12 | 2024-03-22 | 南京晨光集团有限责任公司 | Large-particle-size powder evaluation and recycling method for high-power selective laser melting |
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