JP5871302B2 - Negative electrode for secondary battery and secondary battery - Google Patents
Negative electrode for secondary battery and secondary battery Download PDFInfo
- Publication number
- JP5871302B2 JP5871302B2 JP2011169932A JP2011169932A JP5871302B2 JP 5871302 B2 JP5871302 B2 JP 5871302B2 JP 2011169932 A JP2011169932 A JP 2011169932A JP 2011169932 A JP2011169932 A JP 2011169932A JP 5871302 B2 JP5871302 B2 JP 5871302B2
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- negative electrode
- secondary battery
- electrode active
- active material
- conductive material
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Classifications
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- 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
- Sealing Battery Cases Or Jackets (AREA)
- Cell Electrode Carriers And Collectors (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、二次電池用負極およびそれを用いた二次電池に関する。より詳細には、本発明はチタン含有酸化物を負極活物質に用いたリチウムイオン二次電池用負極に関する。 The present invention relates to a negative electrode for a secondary battery and a secondary battery using the same. More specifically, the present invention relates to a negative electrode for a lithium ion secondary battery using a titanium-containing oxide as a negative electrode active material.
近年、地球温暖化を抑制するために、発生する二酸化炭素の低減が求められている。例えば自動車業界では、ガソリン車から二酸化炭素の排出量が少ない二次電池を搭載した電気自動車やハイブリッド車へのシフトが拡大している。中でも走行距離、安全性、信頼性に影響するリチウムイオン二次電池の開発が注目されている。リチウムイオン二次電池は一般に、正極集電体および負極集電体、正極活物質層および負極活物質層、非水電解液、セパレーター、外装材とから成る。 In recent years, in order to suppress global warming, reduction of generated carbon dioxide is required. For example, in the automobile industry, the shift from gasoline vehicles to electric vehicles and hybrid vehicles equipped with secondary batteries that emit less carbon dioxide is expanding. In particular, the development of lithium ion secondary batteries that affect mileage, safety, and reliability has attracted attention. A lithium ion secondary battery generally comprises a positive electrode current collector and a negative electrode current collector, a positive electrode active material layer and a negative electrode active material layer, a non-aqueous electrolyte, a separator, and an exterior material.
一般的に普及しているリチウムイオン二次電池は、正極活物質としてリチウムを含む遷移金属の酸化物が用いられ、正極活物質は正極集電体としてのアルミニウム箔上に形成され、また負極活物質としては黒鉛などの炭素材料を用い、負極活物質は負極集電体としての銅箔上に形成され、それらがリチウム塩電解質を溶解した非水性の有機溶媒を含む電解液の中に、セパレーターを介して配置されている。 In general lithium ion secondary batteries, a transition metal oxide containing lithium is used as a positive electrode active material. The positive electrode active material is formed on an aluminum foil as a positive electrode current collector. A carbon material such as graphite is used as a material, and a negative electrode active material is formed on a copper foil as a negative electrode current collector, and a separator is placed in an electrolyte solution containing a non-aqueous organic solvent in which a lithium salt electrolyte is dissolved. Is arranged through.
リチウムイオン二次電池の充放電は、充電時には正極活物質に保持されたリチウムイオンが脱インターカレートして電解液中に放出され、負極活物質では炭素材料の結晶層間に電解液中のリチウムイオンが吸蔵されることで進行する。また放電は充電とは逆の反応が進み、リチウムイオンは負極活物質から放出され、正極活物質に吸蔵されることで進行する。 When charging and discharging a lithium ion secondary battery, lithium ions held in the positive electrode active material are deintercalated and released into the electrolytic solution during charging, and in the negative electrode active material, lithium in the electrolytic solution is interposed between the crystal layers of the carbon material. It progresses as ions are occluded. Discharge proceeds in a reverse reaction to charging, and lithium ions are released from the negative electrode active material and occluded by the positive electrode active material.
しかしながら、上記の系では１００％放電に近くなると負極電位が０V付近になることでデンドライトが析出し、本来電子輸送に使用されるリチウムイオンを消費し、さらには負極集電体を腐食劣化させ、最悪の場合は析出物がセパレーターを突き破りショートの原因となってしまう。そのため、上記の系の電池材料構成では充放電電圧の精密な制御が必要であり、正極活物質と負極活物質間の電位差が理論上大きくても、その一部しか使用できない。 However, in the above system, when the discharge is close to 100%, dendrite is precipitated because the negative electrode potential is close to 0 V, consumes lithium ions originally used for electron transport, and further corrodes and degrades the negative electrode current collector. In the worst case, the precipitate breaks through the separator and causes a short circuit. Therefore, the above-described battery material configuration requires precise control of the charge / discharge voltage, and even if the potential difference between the positive electrode active material and the negative electrode active material is theoretically large, only a part thereof can be used.
そこで最近、電位の高い負極活物質の研究開発が盛んに行われている。例えばチタン含有酸化物のひとつであるチタン酸リチウムは電位が１．５Ｖ程度と、炭素材料の電位より高いため、デンドライトの析出が起こらない。また充放電を繰り返しても、炭素材料を用いた場合に比べて、体積膨張率が小さいため、サイクル特性も良好である。例えば特許文献１には、平均粒径が０．０１μｍ以上、１μｍ未満のチタン酸リチウムからなる一次粒子を、平均粒径５〜１００μｍの粒状に凝集させた二次粒子を負極活物質に用い、導電助材として平均粒径３０ｎｍ〜１μｍのグラファイトを用いた二次電池が提案されている。 Recently, research and development of a negative electrode active material having a high potential has been actively conducted. For example, lithium titanate, which is one of titanium-containing oxides, has a potential of about 1.5 V, which is higher than the potential of the carbon material, so that dendrite does not precipitate. Moreover, even if charging / discharging is repeated, since the volume expansion coefficient is small compared with the case where a carbon material is used, cycle characteristics are also good. For example, Patent Document 1 uses, as a negative electrode active material, secondary particles obtained by aggregating primary particles made of lithium titanate having an average particle size of 0.01 μm or more and less than 1 μm into particles having an average particle size of 5 to 100 μm. A secondary battery using graphite having an average particle size of 30 nm to 1 μm as a conductive aid has been proposed.
また近年、二酸化チタンも負極活物資として有望であることが報告されている。特許文献２には、含水酸化チタンを含むスラリーを噴霧乾燥し、有機バインダーを加熱除去して得られた二次粒子の空隙量が０．００５〜１．０ｃｍ３／ｇのチタン酸化物を負極活物質として用い、導電助材としてアセチレンブラックを用いた二次電池が記載されている。 In recent years, it has been reported that titanium dioxide is also promising as a negative electrode active material. In Patent Document 2, a slurry containing hydrous titanium oxide is spray-dried, and a titanium oxide having a secondary particle void amount of 0.005 to 1.0 cm 3 / g obtained by heating and removing an organic binder is used as a negative electrode. A secondary battery that uses acetylene black as an active material and acetylene black as a conductive aid is described.
一般にチタン含有酸化物は、黒鉛などの炭素材料を用いた負極活物質に比較して、電気伝導性が低い。例えば特許文献１に記載されているような、チタン含有酸化物と、少量の導電助材とを含む負極活物質層を有する二次電池は、負極活物質間同士の接触抵抗や、負極活物質と集電体の界面の接触抵抗が高く、結果として二次電池の内部抵抗やインピーダンスが上昇し、大電流に対する急速な充放電が出来なくなってしまう問題点があった。 In general, a titanium-containing oxide has lower electrical conductivity than a negative electrode active material using a carbon material such as graphite. For example, a secondary battery having a negative electrode active material layer containing a titanium-containing oxide and a small amount of a conductive additive as described in Patent Document 1 is a contact resistance between negative electrode active materials or a negative electrode active material. As a result, there is a problem that the internal resistance and impedance of the secondary battery increase and rapid charge / discharge for a large current cannot be performed.
そこでチタン含有酸化物を負極活物質として用いる場合には、負極活物質層の導電性を向上させる対策として、特許文献２に記載されているように大量の導電助材を負極活物質層に添加したり、負極活物質の表面に導電材料をコーティングしたりすることが行われている。しかしこれらの対策では、電気容量に寄与しない材料が負極活物質層に加わる分、負極活物質層の体積基準または質量基準の容量が低下してしまい好ましくない。 Therefore, when a titanium-containing oxide is used as the negative electrode active material, a large amount of a conductive additive is added to the negative electrode active material layer as described in Patent Document 2 as a measure for improving the conductivity of the negative electrode active material layer. In other words, the surface of the negative electrode active material is coated with a conductive material. However, these measures are not preferable because the volume-based or mass-based capacity of the negative electrode active material layer is reduced by the amount of the material that does not contribute to the electric capacity added to the negative electrode active material layer.
本発明は、チタン含有酸化物を負極活物質に用いた場合でも、導電助材を大量に負極活物質層に加えることなく、二次電池の内部抵抗やインピーダンスが小さく、大電流で急速な充放電が可能な二次電池を提供することを目的とする。 Even when a titanium-containing oxide is used for the negative electrode active material, the present invention reduces the internal resistance and impedance of the secondary battery without adding a large amount of conductive additive to the negative electrode active material layer, and allows rapid charging with a large current. An object is to provide a secondary battery capable of discharging.
本発明は以下の［１］〜［１６］に示される二次電池に関する。
［１］
金属箔と、
該金属箔の片面または両面に形成された、負極活物質としてチタン含有酸化物を含む負極活物質層とを有し、
前記金属箔と前記負極活物質層との間に、導電材を含む皮膜が形成されている二次電池用負極。
［２］ 前記負極活物質層が、導電助材をさらに含む［１］に記載の二次電池用負極。
［３］ 前記導電助材が、前記負極活物質層中に０．５〜２質量％含まれることを特徴とした［２］に記載の二次電池用負極。
［４］ 前記導電助材が、カーボンブラック、黒鉛、気相成長炭素繊維、カーボンナノファイバー、カーボンナノチューブよりなる群から選ばれる１種以上の炭素質材料である［３］に記載の二次電池用負極。
［５］ 前記導電材を含む皮膜が、導電材として炭素質材料を含み、該導電材に用いられる炭素質材料とは異なる炭素質材料を、前記負極活物質層中の導電助材として含む［４］に記載の二次電池用負極。
［６］ 前記導電材を含む皮膜が、カーボンブラック、黒鉛、気相成長炭素繊維、カーボンナノファイバー、カーボンナノチューブよりなる群から選ばれる１種以上の炭素質材料を導電材として含む［１］〜［５］のいずれか１項に記載の二次電池用負極。
［７］ 前記導電材を含む皮膜が、結着材を含む［１］〜［６］のいずれか１項に記載の二次電池用負極。
［８］ 前記結着材が多糖類を含む［７］に記載の二次電池用負極。
［９］ 前記多糖類に、有機酸がエステル結合している［８］に記載の二次電池用負極。
［１０］ 前記負極活物質が二酸化チタンである［１］〜［９］のいずれか１項に記載の二次電池用負極。
［１１］ 前記負極活物質がチタン酸リチウムである［１］〜［９］のいずれか１項に記載の二次電池用負極。
［１２］ 前記金属箔がアルミニウム箔である［１］〜［１１］のいずれか１項に記載の二次電池用負極。
［１３］ 前記導電材を含む皮膜の厚みが、０．１μｍ以上５μｍ以下である［１］〜［１２］のいずれか１項に記載の二次電池用負極。
［１４］ ［１］〜［１３］のいずれか１項に記載の負極を有する二次電池。
［１５］ 前記負極が、正極、セパレータおよび非水電解液とともに、外装材に封入されている［１４］に記載の二次電池。
［１６］ 前記外装材が、アルミニウム箔の両側にポリマー層を有するものである［１５］に記載の二次電池。
The present invention relates to secondary batteries shown in the following [1] to [16].
[1]
Metal foil,
A negative electrode active material layer containing a titanium-containing oxide as a negative electrode active material, formed on one or both sides of the metal foil,
Wherein between the metal foil and the active material layer, a negative electrode for a secondary battery coating is formed comprising a conductive material.
[2] The negative electrode for a secondary battery according to [1], wherein the negative electrode active material layer further includes a conductive additive.
[3] The negative electrode for a secondary battery according to [2], wherein the conductive auxiliary material is contained in the negative electrode active material layer in an amount of 0.5 to 2% by mass.
[4] The secondary battery according to [3], wherein the conductive additive is at least one carbonaceous material selected from the group consisting of carbon black, graphite, vapor grown carbon fiber, carbon nanofiber, and carbon nanotube. Negative electrode.
[5] The film containing the conductive material includes a carbonaceous material as a conductive material, and includes a carbonaceous material different from the carbonaceous material used for the conductive material as a conductive additive in the negative electrode active material layer. 4] The negative electrode for secondary batteries as described in 4).
[6] The film containing the conductive material includes, as a conductive material, one or more carbonaceous materials selected from the group consisting of carbon black, graphite, vapor grown carbon fiber, carbon nanofiber, and carbon nanotube. The negative electrode for a secondary battery according to any one of [5].
[7] The negative electrode for a secondary battery according to any one of [1] to [6], wherein the film including the conductive material includes a binder.
[8] The negative electrode for a secondary battery according to [7], wherein the binder contains a polysaccharide.
[9] The negative electrode for a secondary battery according to [8], wherein an organic acid is ester-bonded to the polysaccharide.
[10] The negative electrode for a secondary battery according to any one of [1] to [9], wherein the negative electrode active material is titanium dioxide.
[11] The negative electrode for a secondary battery according to any one of [1] to [9], wherein the negative electrode active material is lithium titanate.
[12] The negative electrode for a secondary battery according to any one of [1] to [11], wherein the metal foil is an aluminum foil.
[13] The negative electrode for a secondary battery according to any one of [1] to [12], wherein the film including the conductive material has a thickness of 0.1 μm or more and 5 μm or less.
[14] A secondary battery having the negative electrode according to any one of [1] to [13].
[15] The secondary battery according to [14], wherein the negative electrode is enclosed in an exterior material together with a positive electrode, a separator, and a non-aqueous electrolyte.
[16] The secondary battery according to [15], wherein the exterior material has polymer layers on both sides of an aluminum foil.
本発明に係る負極は、チタン含有酸化物の負極活物質を用いていながら、負極活物質層に添加する導電助材が少なくても、二次電池としたときの内部抵抗を大幅に低減することができる。従って、サイクル特性ならびに急速充放電特性が向上した二次電池を得ることができる。本発明に係る負極を用いた二次電池の内部抵抗が小さいのは、内部抵抗の要因の一つである負極活物質と負極集電体との間の接触抵抗が低減されるためであると考えられる。 While the negative electrode according to the present invention uses a negative electrode active material of a titanium-containing oxide, the internal resistance of a secondary battery can be greatly reduced even if the conductive auxiliary material added to the negative electrode active material layer is small. Can do. Therefore, a secondary battery with improved cycle characteristics and rapid charge / discharge characteristics can be obtained. The reason why the internal resistance of the secondary battery using the negative electrode according to the present invention is small is that the contact resistance between the negative electrode active material and the negative electrode current collector, which is one of the factors of the internal resistance, is reduced. Conceivable.
［二次電池用負極］
本発明に係る二次電池用負極は、金属箔と、該金属箔の片面または両面に形成された負極活物質層とを有し、前記金属箔と負極活物質層との間に、導電材を含む皮膜が形成されている。本発明に係る二次電池用負極は、金属箔、導電材を含む皮膜、負極活物質層のみで構成されても良いし、保護層など二次電池用負極に用いられる公知の部材をさらに有するものであっても良い。
[Anode for secondary battery]
The negative electrode for a secondary battery according to the present invention has a metal foil and a negative electrode active material layer formed on one or both sides of the metal foil, and a conductive material between the metal foil and the negative electrode active material layer. Is formed. The negative electrode for a secondary battery according to the present invention may be composed only of a metal foil, a film containing a conductive material, a negative electrode active material layer, and further includes a known member used for a negative electrode for a secondary battery such as a protective layer. It may be a thing.
（金属箔）
金属箔の材質には特に制限はなく、通常、リチウムイオン二次電池の集電体に用いられるものを用いることができる。好ましくは、安価なこと、表面の酸化膜が安定しており、品質のバラつきが出にくいことから、アルミニウムまたはその合金の箔である（以下これらをまとめてアルミニウム箔と言う）。アルミニウム箔の材質には特に制限はなく、二次電池の集電体として公知のものを用いることができ、好ましくは純アルミニウム箔またはアルミニウムを９５質量％以上含むアルミニウム合金箔である。純アルミニウム箔の例としてはＡ１０８５材が挙げられ、アルミニウム合金箔の例としては、Ａ３００３材（Ｍｎ添加系）が挙げられる。
(Metal foil)
There is no restriction | limiting in particular in the material of metal foil, Usually, what is used for the collector of a lithium ion secondary battery can be used. Preferably, the foil is made of aluminum or an alloy thereof (hereinafter collectively referred to as an aluminum foil) because it is inexpensive, has a stable oxide film on the surface, and is unlikely to vary in quality. There is no restriction | limiting in particular in the material of aluminum foil, A well-known thing can be used as a collector of a secondary battery, Preferably it is aluminum alloy foil which contains 95 mass% or more of pure aluminum foil or aluminum. A1085 material is mentioned as an example of pure aluminum foil, A3003 material (Mn addition type | system | group) is mentioned as an example of aluminum alloy foil.
アルミニウム箔は厚さによって特に制限されないが、二次電池の小型化や、アルミニウム箔およびそれを用いて得られる集電体、電極等のハンドリング性などの観点から、通常５μｍ〜２００μｍ厚、ロールトゥトール製法を行う場合、好ましくは５μｍ厚〜１００μｍ厚のものを用いる。 The aluminum foil is not particularly limited by the thickness, but from the viewpoint of miniaturization of the secondary battery, and handling properties of the aluminum foil and the current collector, electrode, etc. obtained from the aluminum foil, it is usually 5 μm to 200 μm thick, roll toe When performing the toll manufacturing method, a 5 μm to 100 μm thickness is preferably used.
アルミニウム箔の形状は、孔の開いていない箔でもよいし、二次元状のメッシュ箔、三次元状の網状の箔やパンチングメタル箔など、孔の開いている箔でもよい。 The shape of the aluminum foil may be a foil without a hole, or a foil with a hole such as a two-dimensional mesh foil, a three-dimensional net-like foil, or a punching metal foil.
アルミニウム箔の表面は公知の表面処理を施されていても良く、例えば、機械的表面加工、エッチング、化成処理、陽極酸化、ウォッシュプライマー、コロナ放電、グロー放電などが挙げられる。表面処理の中でもアルミニウム箔表面の自然酸化膜以外に絶縁性の膜を形成させる場合は、集電体としての機能を低減させないように厚みを制御する必要性がある。 The surface of the aluminum foil may be subjected to a known surface treatment, such as mechanical surface processing, etching, chemical conversion treatment, anodization, wash primer, corona discharge, glow discharge and the like. In the surface treatment, when an insulating film is formed other than the natural oxide film on the surface of the aluminum foil, it is necessary to control the thickness so as not to reduce the function as a current collector.
（導電材を含む皮膜）
導電材を含む皮膜は、金属箔と、後述の負極活物質層との間に形成されており、その厚さは、０．１μｍ以上５μｍ以下が好ましく、より好ましくは０．５μｍ以上３μｍ以下、さらに好ましくは１μｍ以上２μｍ以下である。厚さがこの範囲であると、クラックやピンホールがない均一な皮膜を形成することができ、また膜厚に起因する電池重量の増加や、負極の内部抵抗を小さくすることができる。導電材を含む皮膜の厚みは、負極を切断して厚み方向の断面を切り出し、切り出した断面をＴＥＭ（透過型電子顕微鏡）で観察して測定する。好ましくは３視野以上、また１視野につき好ましくは３箇所以上で厚さを測定する。この際、導電材を含む皮膜に著しく凹凸がある場合は、最小厚部分と最大厚部分を必ず測定点に含める。全ての測定箇所での厚みを算術平均したものを導電材を含む皮膜の厚さとする。
(Film containing conductive material)
The film containing the conductive material is formed between the metal foil and a negative electrode active material layer described later, and the thickness is preferably 0.1 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less, More preferably, they are 1 micrometer or more and 2 micrometers or less. When the thickness is within this range, a uniform film free from cracks and pinholes can be formed, the battery weight can be increased due to the film thickness, and the internal resistance of the negative electrode can be reduced. The thickness of the film containing a conductive material is measured by cutting the negative electrode to cut out a cross section in the thickness direction, and observing the cut cross section with a TEM (transmission electron microscope). The thickness is preferably measured at 3 or more fields, and preferably at 3 or more sites per field of view. At this time, if the film containing the conductive material is significantly uneven, the minimum thickness portion and the maximum thickness portion are always included in the measurement points. The arithmetic average of the thicknesses at all measurement points is taken as the thickness of the film containing the conductive material.
導電材を含む皮膜は、金属箔の一部に形成されていてもよいし、全面に形成されていてもよい。金属箔の主面のみならず、端面にも形成されていてよい。金属箔の一部に導電材を含む皮膜を形成する場合、金属箔表面のある範囲前面に形成されていてもよいし、ドットパターン、ラインアンドスペースパターンなどのパターン上に形成されていてもよい。 The film containing a conductive material may be formed on a part of the metal foil or may be formed on the entire surface. It may be formed not only on the main surface of the metal foil but also on the end surface. When a film containing a conductive material is formed on a part of the metal foil, it may be formed on a certain area front surface of the metal foil surface, or may be formed on a pattern such as a dot pattern or a line and space pattern. .
＜導電材＞
上記導電材を含む皮膜は導電材を含む。導電材としては金属粉や炭素質材料が挙げられ、好ましくは炭素質材料である。
<Conductive material>
The film containing the conductive material includes a conductive material. Examples of the conductive material include metal powder and carbonaceous material, and carbonaceous material is preferable.
金属粉としては、金、銀、銅、ニッケル、鉄、亜鉛などの粉末が挙げられる。 Examples of the metal powder include gold, silver, copper, nickel, iron, and zinc powder.
炭素質材料としては、アセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラックや、人造や天然の黒鉛、炭素繊維、気相成長炭素繊維、カーボンナノチューブ、カーボンナノファイバーなどが好適である。これらの炭素質材料は１種単独でまたは２種以上を組み合わせて用いることができる。上記炭素質材料は金、銀、銅、ニッケル、鉄、亜鉛などの金属の粉末でコーティングされていてもよい。 As the carbonaceous material, carbon black such as acetylene black, ketjen black and furnace black, artificial and natural graphite, carbon fiber, vapor grown carbon fiber, carbon nanotube, carbon nanofiber, and the like are suitable. These carbonaceous materials can be used alone or in combination of two or more. The carbonaceous material may be coated with a metal powder such as gold, silver, copper, nickel, iron, and zinc.
導電材は、球状、不定形状などの粒子であってもよいし、針状や棒状などの異方形状のものであってもよい。 The conductive material may be particles having a spherical shape or an indefinite shape, or may have an anisotropic shape such as a needle shape or a rod shape.
粒子状の導電材は、その粒子サイズによって特に制限されないが、数平均一次粒径が１０ｎｍ〜５μｍのものが好ましく、１０ｎｍ〜１００ｎｍのものがより好ましい。導電材の数平均一次粒径は、電子顕微鏡を用いて１００〜１０００個の導電材粒子の一次粒径を計測し、これを平均することによって得られる。球状の場合は球換算径、不定形状の場合は、最大長径を粒子径とする。 The particulate conductive material is not particularly limited by the particle size, but the number average primary particle size is preferably 10 nm to 5 μm, more preferably 10 nm to 100 nm. The number average primary particle size of the conductive material can be obtained by measuring the primary particle size of 100 to 1000 conductive material particles using an electron microscope and averaging them. In the case of a sphere, the particle diameter is the sphere equivalent diameter, and in the case of an indefinite shape, the maximum long diameter is the particle diameter.
異方形状の導電材は質量あたりの表面積が大きく、集電体や電極活物質等との接触面積が大きくなるので、少量の添加でも集電体と電極活物質との間もしくは電極活物質同士間の導電性を高くすることができる。特に効果的な異方形状の導電性付与材としては、カーボンナノチューブやカーボンナノファイバーが挙げられる。カーボンナノチューブやカーボンナノファイバーは平均繊維径が通常０．００１〜０．５μｍ、好ましくは０．００３〜０．２μｍであり、平均繊維長が通常１〜１００μｍ、好ましくは１〜３０μｍであるものが導電性向上において好適である。導電材の平均繊維径および平均繊維長は、電子顕微鏡を用いて１００〜１０００本の導電材繊維の繊維径および繊維長を観察し、個数基準の平均値を求めることによって得られる。 An anisotropically shaped conductive material has a large surface area per mass and a large contact area with the current collector and electrode active material, etc., so even if a small amount is added, it is between the current collector and the electrode active material or between the electrode active materials. The conductivity between them can be increased. Particularly effective anisotropic conductivity imparting materials include carbon nanotubes and carbon nanofibers. Carbon nanotubes and carbon nanofibers have an average fiber diameter of usually 0.001 to 0.5 μm, preferably 0.003 to 0.2 μm, and an average fiber length of usually 1 to 100 μm, preferably 1 to 30 μm. It is suitable for improving conductivity. The average fiber diameter and the average fiber length of the conductive material can be obtained by observing the fiber diameter and fiber length of 100 to 1000 conductive material fibers using an electron microscope and obtaining the average value based on the number.
導電材は、皮膜中に完全に埋没していても、皮膜から一部露出した状態で固定化されていてもよく、皮膜の導電性が得られる状態であれば、皮膜中での分散状態は制限されない。その際、導電材が脱落しないことが好ましく、皮膜中の他の材料や、上述の金属箔あるいは負極活物質層との結着性が良好になるように、導電材を含む皮膜の厚みと、導電材の粒径を選定することができる。 The conductive material may be completely buried in the film or may be fixed in a state of being partially exposed from the film, and if the conductivity of the film is obtained, the dispersion state in the film is Not limited. At that time, it is preferable that the conductive material does not fall off, the thickness of the film containing the conductive material, so that the other materials in the film and the above-described metal foil or the negative electrode active material layer has good binding properties, The particle size of the conductive material can be selected.
導電材は、導電材を含む皮膜中に好ましくは３０〜８０質量％、より好ましくは３０〜７０質量％含まれる。この割合で導電材を含むことによって、導電材を含む皮膜の導電性が向上し、アルミニウム箔と負極活物質層の間の電気伝導性が向上する。 The conductive material is preferably contained in the film containing the conductive material in an amount of 30 to 80% by mass, more preferably 30 to 70% by mass. By including the conductive material at this ratio, the conductivity of the film including the conductive material is improved, and the electrical conductivity between the aluminum foil and the negative electrode active material layer is improved.
＜結着材＞
導電材を含む皮膜は結着材を含んでも良い。導電材を含む皮膜が結着材を含む場合、その含有量は、導電材を含む皮膜中に好ましくは２０〜１００質量％、より好ましくは２０〜７０質量％含まれる。
<Binder>
The film containing a conductive material may contain a binder. When the film containing the conductive material contains the binder, the content thereof is preferably 20 to 100% by mass, more preferably 20 to 70% by mass, in the film containing the conductive material.
結着材は、導電材同士、あるいは導電材と金属箔、導電材と負極活物質層を結着できるものであれば特に制限はないが、重量平均分子量で１．０×１０４〜２．０×１０５、より好ましくは５．０×１０４〜２．０×１０５のポリマーであると、導電材を含む皮膜を形成する際の作業性や、皮膜の強度に優れる。重量分子量は、ゲルパーミエーションクロマトグラフィーを用いて、ポリスチレンやプルランなどの標準サンプルに換算した値として求めることができる。ポリマーの例としては、アクリル系重合体、ビニル系重合体、ポリフッ化ビニリデン、スチレンブタジエンゴム、多糖類などが挙げられる。 The binder is not particularly limited as long as it can bind the conductive materials, or the conductive material and the metal foil, or the conductive material and the negative electrode active material layer, but the weight average molecular weight is 1.0 × 10 4 to 2. When the polymer is 0 × 10 5 , more preferably 5.0 × 10 4 to 2.0 × 10 5 , the workability when forming a film containing a conductive material and the strength of the film are excellent. A weight molecular weight can be calculated | required as a value converted into standard samples, such as a polystyrene and a pullulan, using a gel permeation chromatography. Examples of the polymer include acrylic polymers, vinyl polymers, polyvinylidene fluoride, styrene butadiene rubber, polysaccharides, and the like.
アクリル系重合体の例としては、アクリル酸、メタクリル酸、イタコン酸、（メタ）アクリロイルモルホリン、Ｎ，Ｎ−ジメチル（メタ）アクリルアミド、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、グリセリン（メタ）アクリレートなどのアクリル系単量体を重合して得られるものが挙げられる。 Examples of acrylic polymers include acrylic acid, methacrylic acid, itaconic acid, (meth) acryloylmorpholine, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycerin (meth) Examples thereof include those obtained by polymerizing acrylic monomers such as acrylates.
ビニル系重合体の例としては、ポリビニルアセタール、エチレン−ビニルアルコール共重合体、ポリビニルアルコール、ポリ（Ｎ−ビニルホルムアミド）、ポリ（Ｎ−ビニル−２−ピロリドン）などのビニル系単量体を重合して得られるものが挙げられる。 Examples of vinyl polymers include polymerizing vinyl monomers such as polyvinyl acetal, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, poly (N-vinylformamide), and poly (N-vinyl-2-pyrrolidone). Can be obtained.
多糖類は単糖類が重縮合した重合体であり、ホモ多糖、ヘテロ多糖のいずれでもよい。具体例としては、キチン、キトサン、セルロース及びそれらの誘導体が挙げられ、好ましくはキトサンである。 A polysaccharide is a polymer in which monosaccharides are polycondensed, and may be either a homopolysaccharide or a heteropolysaccharide. Specific examples include chitin, chitosan, cellulose and derivatives thereof, preferably chitosan.
上述の結着材は１種単独で皮膜としてもよいし、２種以上を含む皮膜としてもよい。２種以上の樹脂を用いて皮膜とする場合は、２種以上の樹脂が互いに混合されていてもよいし、樹脂同士が架橋構造を形成していたり、相互貫入ポリマー構造または半相互貫入ポリマー構造を形成していてもよいが、好ましくは架橋構造、相互貫入ポリマー構造または半相互貫入ポリマー構造を形成する。 The above-mentioned binders may be used alone or as a film containing two or more kinds. When forming a film using two or more kinds of resins, two or more kinds of resins may be mixed with each other, the resins may form a cross-linked structure, an interpenetrating polymer structure or a semi-interpenetrating polymer structure Preferably, it forms a cross-linked structure, an interpenetrating polymer structure or a semi-interpenetrating polymer structure.
＜多糖類＞
上述の結着材のうち、多糖類を用いると、耐非水電解性が非常に良好な皮膜が得られる。これは多糖類を含む皮膜の膜密度が高いためであると考えられる。
<Polysaccharides>
Among the above-mentioned binders, when a polysaccharide is used, a film with very good non-aqueous electrolysis resistance can be obtained. This is considered to be because the film density of the film containing the polysaccharide is high.
多糖類は誘導体化されていてもよく、誘導体の例としてはヒドロキシアルキル化されたもの、カルボキシアルキル化されたもの、硫酸エステル化されたものなどが挙げられる。特にヒドロキシアルキル化されていると、溶媒への溶解度を高くでき、導電材を含む皮膜の形成が容易になることから好ましい。ヒドロキシアルキル基の例としては、ヒドロキシエチル基、ヒドロキシプロピル基、グリセリル基などが挙げられ、好ましくはグリセリル基である。ヒドロキシアルキル化多糖類は、公知の方法で製造することができる。 The polysaccharide may be derivatized, and examples of the derivative include hydroxyalkylated, carboxyalkylated, sulfate esterified and the like. In particular, hydroxyalkylation is preferable because solubility in a solvent can be increased and formation of a film containing a conductive material is facilitated. Examples of the hydroxyalkyl group include a hydroxyethyl group, a hydroxypropyl group, a glyceryl group, and the like, preferably a glyceryl group. The hydroxyalkylated polysaccharide can be produced by a known method.
＜導電材を含む皮膜に含まれる添加剤＞
導電材を含む皮膜には上記の樹脂および導電材の他、分散安定剤、増粘剤、沈降防止剤、皮張り防止剤、消泡剤、静電塗装性改良剤、タレ防止剤、レベリング剤、架橋触媒、ハジキ防止剤などの添加剤を含んでもよい。
<Additives contained in films containing conductive materials>
In addition to the above resins and conductive materials, coatings containing conductive materials include dispersion stabilizers, thickeners, anti-settling agents, anti-skinning agents, antifoaming agents, electrostatic coating property improving agents, anti-sagging agents, and leveling agents. In addition, additives such as a crosslinking catalyst and a repellency inhibitor may be included.
＜有機酸＞
導電材を含む皮膜が結着材として多糖類を含む場合は、添加剤として有機酸を含むことが好ましい。有機酸は後述する塗工液中で、多糖類の溶媒への分散性を向上させる働きをもつ。有機酸は２価以上の有機酸であると、塗工液の加熱乾燥時に多糖類にエステル結合することにより、多糖類を架橋し、導電材を含む皮膜の耐電解液性を向上させられることから好ましく、さらには架橋密度の観点から３価以上の有機酸であることがより好ましい。有機酸は、導電材を含む皮膜中に遊離成分として存在していてもよいが、上述の通り多糖類に結合した形で存在することが好ましい。有機酸が遊離成分として存在する場合、遊離酸として存在してもよいし、酸無水物などの誘導体として存在してもよい。
<Organic acid>
When the film containing a conductive material contains a polysaccharide as a binder, it is preferable to contain an organic acid as an additive. The organic acid has a function of improving the dispersibility of the polysaccharide in the solvent in the coating solution described later. When the organic acid is an organic acid having a valence of 2 or more, the polysaccharide can be cross-linked by ester bonding to the polysaccharide during heating and drying of the coating solution, thereby improving the electrolytic solution resistance of the film containing the conductive material. From the viewpoint of crosslink density, trivalent or higher organic acids are more preferable. The organic acid may be present as a free component in the film containing the conductive material, but is preferably present in a form bound to the polysaccharide as described above. When the organic acid is present as a free component, it may be present as a free acid or a derivative such as an acid anhydride.
例えば、有機酸として後述のカルボン酸を用いる場合、皮膜中で多糖類に有機酸が結合していることは、皮膜に対して赤外分光分析を行うことで確認できる。カルボン酸は、遊離の状態では１７０９ｃｍ−１付近にカルボキシル基の吸収に起因する単独ピークを有する。このカルボキシル基が多糖類と結合することで、酸からエステルに構造が変化し、高波数側にピークがシフトする。ピークシフトは１７３５ｃｍ−１付近まで起こり、１７０９ｃｍ−１からのシフト量で簡易的に結合度合いが算出できる。 For example, when a carboxylic acid described later is used as the organic acid, it can be confirmed that the organic acid is bound to the polysaccharide in the film by performing infrared spectroscopic analysis on the film. Carboxylic acid has a single peak due to absorption of a carboxyl group in the vicinity of 1709 cm −1 in a free state. When this carboxyl group is bonded to the polysaccharide, the structure changes from an acid to an ester, and the peak shifts to the high wavenumber side. Peak shift occurs to the vicinity of 1735 cm -1, it can be calculated simply coupled degree shift amount from 1709 cm -1.
導電材を含む皮膜中に添加する有機酸としてはカルボン酸、スルホン酸、ホスホン酸などが挙げられるが、好ましくはカルボン酸である。カルボン酸の例としては、フタル酸、トリメリット酸、ピロメリット酸、コハク酸、マレイン酸、クエン酸、１，２，３，４−ブタンテトラカルボン酸などが挙げられ、好ましくはピロメリット酸または１，２，３，４−ブタンテトラカルボン酸である。これら有機酸は、１種単独でまたは２種以上を組み合わせて用いることができる。 Examples of the organic acid added to the film containing the conductive material include carboxylic acid, sulfonic acid, and phosphonic acid, and carboxylic acid is preferable. Examples of carboxylic acids include phthalic acid, trimellitic acid, pyromellitic acid, succinic acid, maleic acid, citric acid, 1,2,3,4-butanetetracarboxylic acid, preferably pyromellitic acid or 1,2,3,4-butanetetracarboxylic acid. These organic acids can be used singly or in combination of two or more.
有機酸は多糖類１００質量部に対し、好ましくは４０〜１２０質量部、より好ましくは４０〜９０質量部含まれる。 The organic acid is preferably contained in an amount of 40 to 120 parts by mass, more preferably 40 to 90 parts by mass with respect to 100 parts by mass of the polysaccharide.
（負極活物質層）
＜負極活物質＞
負極活物質に用いるチタン含有酸化物としては、二酸化チタンまたはチタン酸リチウムが挙げられる。負極活物質は、負極活物質層中に好ましくは７８〜９４．５質量％、より好ましくは８０〜９０質量％含まれる。
(Negative electrode active material layer)
<Negative electrode active material>
Examples of the titanium-containing oxide used for the negative electrode active material include titanium dioxide and lithium titanate. The negative electrode active material is preferably contained in the negative electrode active material layer at 78 to 94.5% by mass, more preferably 80 to 90% by mass.
＜二酸化チタン＞
二酸化チタンの製造方法は特に限定されず、チタン塩化物から精製する塩素法やチタン硫酸塩から精製する硫酸法など出発原料の異なる製法、また気相法、液相法、固相法など反応条件の異なる製法、いずれからも選ぶことが可能である。また純度、結晶型、結晶性、粒径、凝集状態など、求める負極活物質の特性に合わせて選択できる。
<Titanium dioxide>
The production method of titanium dioxide is not particularly limited, and production conditions with different starting materials such as chlorine method purified from titanium chloride and sulfuric acid method purified from titanium sulfate, and reaction conditions such as gas phase method, liquid phase method, solid phase method, etc. You can choose from any of the different manufacturing methods. Moreover, it can select according to the characteristic of the negative electrode active material to seek, such as purity, a crystal form, crystallinity, a particle size, and an aggregation state.
一般的に知られている結晶型として、アナターゼ型、ルチル型、ブルッカイト型、ブロンズ型があるが、中でもブルッカイト型やブロンズ型は結晶密度が比較的小さく、リチウムイオンを吸蔵しやすいため容量が高く好ましい。また負極活物質として用いる二酸化チタンは、アモルファス相を含んでも良い。結晶型の解析はＸ線回折装置を用いて行うことができる。 Commonly known crystal types include anatase type, rutile type, brookite type, and bronze type. Among them, brookite type and bronze type have a relatively low crystal density and high capacity because they easily absorb lithium ions. preferable. Further, titanium dioxide used as the negative electrode active material may contain an amorphous phase. Crystalline analysis can be performed using an X-ray diffractometer.
二酸化チタンの一次粒径は特に制限されないが、数平均の一次粒径として０．００５〜５μｍが好ましく、０．０１〜１μｍがより好ましい。数平均一次粒径がこのはんいであると、負極活物質粉末のハンドリング性と、負極活物質層への充填密度を両立することができる。数平均一次粒径は、電子顕微鏡を用いて１００〜１０００個の二酸化チタン粒子の一次粒径を計測し、これを平均することによって得られる。球状の場合は球換算径、不定形状の場合は、最大長径を粒子径とする。 The primary particle diameter of titanium dioxide is not particularly limited, but the number average primary particle diameter is preferably 0.005 to 5 μm, more preferably 0.01 to 1 μm. When the number average primary particle size is this, both the handleability of the negative electrode active material powder and the packing density in the negative electrode active material layer can be achieved. The number average primary particle size is obtained by measuring the primary particle size of 100 to 1000 titanium dioxide particles using an electron microscope and averaging the measured particle sizes. In the case of a sphere, the particle diameter is the sphere equivalent diameter, and in the case of an indefinite shape, the maximum long diameter is the particle diameter.
＜チタン酸リチウム＞
次に本発明のチタン酸リチウムについて説明する。チタン酸リチウムとしては、二次電池の負極活物質として、公知のものを用いることができる。一般的には、スピネル型のチタン酸リチウム（Ｌｉ４Ｔｉ５Ｏ１２）と、ラムスデライト型のチタン酸リチウム（Ｌｉ２Ｔｉ３Ｏ７）とが知られているが、ラムスデライト型チタン酸リチウムの方がより高容量であり、好ましく用いられる。
<Lithium titanate>
Next, the lithium titanate of the present invention will be described. As lithium titanate, a well-known thing can be used as a negative electrode active material of a secondary battery. Generally, spinel type lithium titanate (Li 4 Ti 5 O 12 ) and ramsdellite type lithium titanate (Li 2 Ti 3 O 7 ) are known. Is higher capacity and is preferably used.
一次粒径は特に制限されないが、上述の二酸化チタンと同じ理由で、数平均の一次粒径として０．００５〜５μｍが好ましく、０．０１〜１μｍがより好ましい。 The primary particle size is not particularly limited, but for the same reason as titanium dioxide described above, the number average primary particle size is preferably 0.005 to 5 μm, more preferably 0.01 to 1 μm.
＜導電助材＞
本発明に使用される負極活物質であるチタン含有酸化物は、そのままでは導電性が低いため、負極活物質層に導電助材を添加することが好ましい。導電助材は、負極活物質表面または負極活物質間に存在することにより、電子のやりとりを円滑にする役目があり、導電性を有することが好ましい。導電助材としては炭素質材料が好ましく選ばれる。
<Conductive aid>
Since the titanium-containing oxide which is the negative electrode active material used in the present invention has low conductivity as it is, it is preferable to add a conductive additive to the negative electrode active material layer. The conductive additive has a role of facilitating exchange of electrons by being present on the surface of the negative electrode active material or between the negative electrode active materials, and preferably has conductivity. A carbonaceous material is preferably selected as the conductive additive.
炭素質材料としては、アセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラックや、人造や天然の黒鉛、炭素繊維、気相成長炭素繊維、カーボンナノチューブ、カーボンナノファイバーなどが好適である。これらの炭素質材料は１種単独でまたは２種以上を組み合わせて用いることができる。 As the carbonaceous material, carbon black such as acetylene black, ketjen black and furnace black, artificial and natural graphite, carbon fiber, vapor grown carbon fiber, carbon nanotube, carbon nanofiber, and the like are suitable. These carbonaceous materials can be used alone or in combination of two or more.
また、導電材を含む皮膜に含まれる導電材として炭素質材料が用いられる場合、導電助材の炭素質材料と同じであっても、異なっていてもよいが、異なっている方がネットワークの形成がより立体的となり、導電性が良好となるので好ましい。特に導電材を含む皮膜の炭素質材料がアセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラックおよび／または黒鉛であり、導電助材が炭素繊維、気相成長炭素繊維、カーボンナノチューブ、カーボンナノファイバーなどの繊維状の炭素質材料の組み合わせがより好ましい。これは、導電材を含む皮膜にカーボンブラックおよび／または黒鉛を用いる場合、集電体上に薄く、均一に被覆できることから負極集電体と負極活物質の接触抵抗が低くなる。一方、導電助材に繊維状の炭素質材料を用いることにより、負極活物質粒子間の導電パスが得られ、添加量が少なくても十分な導電性が得られる。 In addition, when a carbonaceous material is used as the conductive material included in the film containing the conductive material, it may be the same as or different from the carbonaceous material of the conductive additive, but the different one is the formation of the network. Is more three-dimensional and preferable in terms of conductivity. In particular, the carbonaceous material of the film containing a conductive material is carbon black and / or graphite such as acetylene black, ketjen black, and furnace black, and the conductive auxiliary is carbon fiber, vapor-grown carbon fiber, carbon nanotube, carbon nanofiber. A combination of fibrous carbonaceous materials such as is more preferable. This is because, when carbon black and / or graphite is used for the film containing a conductive material, the current collector can be thinly and uniformly coated, so that the contact resistance between the negative electrode current collector and the negative electrode active material is lowered. On the other hand, by using a fibrous carbonaceous material as the conductive additive, a conductive path between the negative electrode active material particles can be obtained, and sufficient conductivity can be obtained even if the addition amount is small.
導電助材の添加量は好ましくは負極活物質層中に０．５〜２質量％、より好ましくは０．５〜１質量％である。導電助材の添加量がこの範囲であると、負極活物質の添加量を減らすことなく、負極活物質間の導電性を向上することができる。 The addition amount of the conductive additive is preferably 0.5 to 2% by mass, more preferably 0.5 to 1% by mass in the negative electrode active material layer. When the addition amount of the conductive additive is within this range, the conductivity between the negative electrode active materials can be improved without reducing the addition amount of the negative electrode active material.
導電助材は、球状、不定形状などの粒子であってもよいし、針状や棒状などの異方形状のものであってもよい。 The conductive additive may be spherical or irregularly shaped particles, or may be of an anisotropic shape such as a needle shape or a rod shape.
粒子状の導電助材は、その粒子サイズによって特に制限されないが、数平均一次粒径が１０ｎｍ〜５μｍのものが好ましく、１０ｎｍ〜１００ｎｍのものがより好ましい。導電助材の数平均一次粒径は、電子顕微鏡を用いて１００〜１０００個の導電助材粒子の一次粒径を計測し、これを平均することによって得られる。球状の場合は球換算径、不定形状の場合は、最大長径を粒子径とする。カーボンナノチューブやカーボンナノファイバーは平均繊維径が通常０．００１〜０．５μｍ、好ましくは０．００３〜０．２μｍであり、平均繊維長が通常１〜１００μｍ、好ましくは１〜３０μｍであるものが導電性向上において好適である。導電材の平均繊維径および平均繊維長は、電子顕微鏡を用いて１００〜１０００本の導電材繊維の繊維径および繊維長を観察し、個数基準の平均値を求めることによって得られる。 The particulate conductive additive is not particularly limited by the particle size, but the number average primary particle diameter is preferably 10 nm to 5 μm, more preferably 10 nm to 100 nm. The number average primary particle size of the conductive additive is obtained by measuring the primary particle size of 100 to 1000 conductive additive particles using an electron microscope and averaging the measured particle sizes. In the case of a sphere, the particle diameter is the sphere equivalent diameter, and in the case of an indefinite shape, the maximum long diameter is the particle diameter. Carbon nanotubes and carbon nanofibers have an average fiber diameter of usually 0.001 to 0.5 μm, preferably 0.003 to 0.2 μm, and an average fiber length of usually 1 to 100 μm, preferably 1 to 30 μm. It is suitable for improving conductivity. The average fiber diameter and the average fiber length of the conductive material can be obtained by observing the fiber diameter and fiber length of 100 to 1000 conductive material fibers using an electron microscope and obtaining the average value based on the number.
＜結着材＞
負極活物質層は、結着材を含んでも良い。結着材としては特に制限はなく、リチウムイオン二次電池の電極に用いられる公知の結着材を用いることができる。例として、ポリフッ化ビニリデンを挙げられる。結着材を用いる場合、負極活物質層中に好ましくは５〜２０質量％、より好ましくは１０〜１５質量％の結着材を含むようにすると、剥離や亀裂が起こらず、導電性が確保された負極が得られる。
<Binder>
The negative electrode active material layer may include a binder. There is no restriction | limiting in particular as a binder, The well-known binder used for the electrode of a lithium ion secondary battery can be used. An example is polyvinylidene fluoride. When the binder is used, the negative electrode active material layer preferably contains 5 to 20% by mass, more preferably 10 to 15% by mass of the binder, so that peeling or cracking does not occur and conductivity is ensured. A negative electrode is obtained.
＜添加剤＞
負極活物質層は上述の負極活物質、導電助材、結着材の他、増粘剤など、リチウムイオン二次電池の負極活物質層に用いられる公知の添加剤を含んでも良い。
<Additives>
The negative electrode active material layer may contain known additives used for the negative electrode active material layer of the lithium ion secondary battery, such as a thickener, in addition to the above-described negative electrode active material, conductive additive, and binder.
［二次電池用負極の製造方法］
本発明に係る二次電池用負極は、金属箔の片面または両面に導電材を含む皮膜を形成した後、導電材を含む皮膜上に負極活物質層を設けることによって製造される。
[Method for producing secondary battery negative electrode]
The negative electrode for a secondary battery according to the present invention is produced by forming a film containing a conductive material on one or both surfaces of a metal foil and then providing a negative electrode active material layer on the film containing the conductive material.
（皮膜の形成）
金属箔上に導電材を含む皮膜を形成する方法としては、スパッタ法、蒸着法、化学気相成長法などの気相法と、ディップ法、印刷法などの塗布法とが挙げられる。好ましくはロールトゥロール方式による連続的加工でき、低コスト化が可能な塗布法を用いることが好ましい。
(Formation of film)
Examples of the method for forming a film containing a conductive material on a metal foil include vapor phase methods such as sputtering, vapor deposition, and chemical vapor deposition, and coating methods such as dipping and printing. It is preferable to use a coating method that can be continuously processed by a roll-to-roll method and can reduce costs.
塗布法により導電材を含む皮膜を形成するには、導電材を含む塗工液を金属箔に塗布、乾燥する。導電材を含む皮膜に結着材や添加剤を含む場合、塗工液として、該結着材や添加剤そのものを含むものを用いても良いし、結着材や添加剤の前駆体を含む塗工液を用いて、塗工液の乾燥、その他の後処理によって、皮膜中で結着材や添加剤に変換されるようにしてもよい。 In order to form a film containing a conductive material by a coating method, a coating solution containing a conductive material is applied to a metal foil and dried. When the film containing the conductive material contains a binder or an additive, a coating liquid containing the binder or the additive itself may be used, or a binder or an additive precursor is included. You may make it convert into a binder and an additive in a film | membrane by drying of a coating liquid and other post-processes using a coating liquid.
例えば導電材を含む皮膜に、上述の有機酸を含む場合、塗工液としては遊離の有機酸を含むものを用いても良いし、酸無水物やエステルなどの酸誘導体を含むものを用いて、加熱により遊離の有機酸または多糖類に結合した有機酸となるようにしても良い。塗工液の加熱、乾燥により副生物が出ないことから、好ましくは遊離の有機酸または酸無水物を含む塗工液を用いる。 For example, when the above-mentioned organic acid is included in the film containing the conductive material, the coating liquid may contain a free organic acid, or may contain an acid derivative such as an acid anhydride or ester. It may be made to become a free organic acid or an organic acid bonded to a polysaccharide by heating. Since no by-product is produced by heating and drying of the coating solution, a coating solution containing a free organic acid or acid anhydride is preferably used.
また導電材を含む皮膜に、結着材としてアクリル系重合体やビニル系重合体を含む場合、塗工液としては上記の重合体そのものを含むものを用いても良いし、重合体を構成する単量体を含む塗工液を用いて、加熱、光照射などの方法により、皮膜中で重合体になるようにしても良い。 In the case where the film containing the conductive material contains an acrylic polymer or vinyl polymer as the binder, a coating liquid containing the above polymer itself may be used as the coating liquid. You may make it become a polymer in a film | membrane by methods, such as a heating and light irradiation, using the coating liquid containing a monomer.
導電材を含む皮膜の形成用の塗工液に用いる溶媒の例としては、Ｎ−メチルピロリドン、γ−ブチロラクトンなどの非プロトン性極性溶媒や、エタノール、イソプロピルアルコール、ｎ−プロピルアルコールなどのプロトン性極性溶媒、水などが挙げられる。塗工液中の溶媒の量は、２０〜９９質量％であることが好ましく、５０〜９８質量％であることがより好ましい。溶媒の量をこのようにすることにより、塗布などの作業性に優れ、塗工液を塗布、乾燥して得られる導電材を含む皮膜の塗布量を好適なものとすることができる。 Examples of the solvent used in the coating liquid for forming a film containing a conductive material include aprotic polar solvents such as N-methylpyrrolidone and γ-butyrolactone, and protic properties such as ethanol, isopropyl alcohol, and n-propyl alcohol. Examples include polar solvents and water. The amount of the solvent in the coating liquid is preferably 20 to 99% by mass, and more preferably 50 to 98% by mass. By setting the amount of the solvent in this way, it is excellent in workability such as coating, and the coating amount of the film containing the conductive material obtained by coating and drying the coating liquid can be made suitable.
導電材を含む皮膜の形成用の塗工液をアルミニウム箔に塗布する方法は特に制限されず、二次電池の製造に用いられる公知の塗布方法がそのまま採用できる。 The method for applying the coating liquid for forming a film containing a conductive material to the aluminum foil is not particularly limited, and a known application method used for manufacturing a secondary battery can be employed as it is.
具体的には、キャスト法、バーコーター法、ディップ法、印刷法などが挙げられる。これらのうち、塗布膜の厚さを制御しやすい点から、バーコート、グラビアコート、グラビアリバースコート、ロールコート、マイヤーバーコート、ブレードコート、ナイフコート、エアーナイフコート、コンマコート、スロットダイヤコート、スライドダイコート、ディップコートが好ましい。両面に塗布する場合は、片面ずつ塗布操作を行ってもよいし、両面に同時に塗布操作を行ってもよい。 Specific examples include a casting method, a bar coater method, a dip method, and a printing method. Among these, from the point that it is easy to control the thickness of the coating film, bar coat, gravure coat, gravure reverse coat, roll coat, Meyer bar coat, blade coat, knife coat, air knife coat, comma coat, slot diamond coat, A slide die coat and a dip coat are preferred. In the case of applying to both sides, the application operation may be performed on each side, or the application operation may be performed on both sides simultaneously.
金属箔への塗工液の塗布量は、乾燥後質量で、好ましくは０．１〜５ｇ／ｍ２、より好ましくは０．５〜３ｇ／ｍ２である。このような塗布量とすることにより、膜厚抵抗を増大させることなく、集電体表面を均一に被覆することが可能である。 The application amount of the coating liquid to the metal foil is preferably 0.1 to 5 g / m 2 , more preferably 0.5 to 3 g / m 2 in terms of mass after drying. By setting it as such application quantity, it is possible to coat | cover the collector surface uniformly, without increasing film thickness resistance.
塗布量の測定は、金属箔の、導電材を皮膜が形成された箇所を切り出して、導電材を含む皮膜の正確な面積と、導電材を含む皮膜がついた金属箔の質量を測定し、その後、剥離剤を用いて皮膜を剥離する。剥離後の金属箔の質量を測定し、導電材を含む皮膜がついたアルミニウム箔の質量と、皮膜を剥離した後の金属箔の質量との差分として導電材を含む皮膜の質量を求め、切り出した金属箔の面積で除すことで塗布量の算出を行う。剥離剤は、アルミニウム箔を侵すものでなければ、一般的な塗料や樹脂の剥離剤を使用することが可能である。 The amount of coating is measured by cutting out the portion of the metal foil where the conductive material film is formed, measuring the exact area of the film containing the conductive material, and the mass of the metal foil with the film containing the conductive material, Thereafter, the film is peeled off using a peeling agent. Measure the mass of the metal foil after peeling, determine the mass of the film containing the conductive material as the difference between the mass of the aluminum foil with the film containing the conductive material and the mass of the metal foil after peeling the film, and cut it out The coating amount is calculated by dividing by the area of the metal foil. As long as the release agent does not attack the aluminum foil, a general paint or resin release agent can be used.
塗工液の乾燥方法は特に制限されないが、好ましくは１００〜３００℃、より好ましくは１２０〜２５０℃の温度範囲内で、１０秒間〜１０分間加熱する。このような条件で加熱することにより、導電材を含む皮膜中の結着材や添加剤が分解することなく、皮膜中の溶媒を完全に除去することでき、表面形状が良好な皮膜を、ハイスループットで形成することができる。また加熱により結着材や添加剤となる前駆体を含む塗工液を用いる場合には、前駆体から結着材や添加剤へ転化する反応を充分に進行させることができる。 Although the drying method of a coating liquid is not restrict | limited in particular, Preferably it heats for 10 second to 10 minutes within the temperature range of 100-300 degreeC, More preferably, 120-250 degreeC. By heating under such conditions, it is possible to completely remove the solvent in the film without decomposing the binder and additives in the film containing the conductive material. It can be formed with a throughput. Moreover, when using the coating liquid containing the precursor used as a binder and an additive by heating, the reaction which converts into a binder and an additive from a precursor can fully advance.
（負極活物質層の形成）
二次電池の負極は、上記の導電材を含む皮膜上に、導電助材を含む負極活物質層を形成して得られる。この際、導電材を含む皮膜と負極活物質層の間に他の層が形成されてもよいが、好ましくは導電材を含む皮膜に接して負極活物質層が設けられる。負極の形成方法は特に制限はなく、二次電池の製造に用いられている公知の方法を採用することができる。例えば、塗布法により負極活物質層を形成する場合、負極活物質と、必要に応じて導電助材や結着材とを、溶媒に分散させた塗工液を用いる。ここで用いる溶媒は、上述の導電材を含む皮膜を変質させるものでなければ特に制限は無く、Ｎ−メチル−２−ピロリドンなどを用いることができる。塗布の方法としては、ダイコーターなどを用いることができ、塗工液を塗布後、乾燥することで得ることが出来る。最終的にプレス処理を行い、電極密度を上げることも可能である。
(Formation of negative electrode active material layer)
The negative electrode of the secondary battery is obtained by forming a negative electrode active material layer containing a conductive additive on a film containing the conductive material. At this time, another layer may be formed between the film containing the conductive material and the negative electrode active material layer, but the negative electrode active material layer is preferably provided in contact with the film containing the conductive material. There is no restriction | limiting in particular in the formation method of a negative electrode, The well-known method used for manufacture of a secondary battery is employable. For example, when the negative electrode active material layer is formed by a coating method, a coating liquid in which a negative electrode active material and, if necessary, a conductive additive or a binder are dispersed in a solvent is used. The solvent used here is not particularly limited as long as it does not alter the film containing the above conductive material, and N-methyl-2-pyrrolidone or the like can be used. As a coating method, a die coater or the like can be used, and it can be obtained by applying and then drying a coating solution. It is also possible to increase the electrode density by finally pressing.
［二次電池］
本発明に係る二次電池は、上述の負極を有する。二次電池は通常、この他に正極、セパレータおよび電解質を有し、これらが外装材に封入されている。
[Secondary battery]
The secondary battery according to the present invention has the above-described negative electrode. A secondary battery usually has a positive electrode, a separator, and an electrolyte in addition to these, and these are enclosed in an exterior material.
（正極）
正極は、二次電池に使用されるものであれば特に制限はない。多くの場合、正極は正極活物質と、導電助材と、結着材とを含む。正極活物質としては、例えば、コバルト酸リチウム（ＬｉＣｏＯ２）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、ニッケル酸リチウム（ＬｉＮｉＯ２）、Ｃｏ、Ｍｎ、Ｎｉの３元系リチウム化合物（Ｌｉ（ＣｏｘＭｎｙＮｉｚ）Ｏ２）、イオウ系（ＴｉＳ２）、オリビン系（ＬｉＦｅＰＯ４、ＬｉＭｎＰＯ４）などを用いることができる。導電助材としては、例え倍、アセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラックや、人造や天然の黒鉛、炭素繊維、気相成長炭素繊維、カーボンナノチューブ、カーボンナノファイバーなどが挙げられる。結着材としては例えば、ポリフッ化ビニリデンが挙げられる。
(Positive electrode)
If a positive electrode is used for a secondary battery, there will be no restriction | limiting in particular. In many cases, the positive electrode includes a positive electrode active material, a conductive additive, and a binder. Examples of the positive electrode active material include lithium cobaltate (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), lithium nickelate (LiNiO 2 ), Co, Mn, and Ni ternary lithium compounds (Li (CoxMnyNiz)). O 2 ), sulfur (TiS 2 ), olivine (LiFePO 4 , LiMnPO 4 ) and the like can be used. Examples of the conductive aid include carbon black such as fold, acetylene black, ketjen black, and furnace black, artificial and natural graphite, carbon fiber, vapor grown carbon fiber, carbon nanotube, and carbon nanofiber. An example of the binder is polyvinylidene fluoride.
（セパレーター）
セパレーターとしては、二次電池に用いられる公知のものが使用できる。例として、ポリエチレンやポリプロピレン性の多孔性のマイクロポーラスフィルムが挙げられる。電解質として後述のポリマー電解質を用いる場合、セパレーターが省かれることもある。
(separator)
As a separator, a well-known thing used for a secondary battery can be used. Examples include polyethylene and polypropylene porous microporous films. When using the polymer electrolyte described later as the electrolyte, the separator may be omitted.
（電解質）
電解質は、二次電池中に非水電解液として存在する場合と、ポリマー電解質として存在する場合がある。いずれもリチウムイオン二次電池に使用されている公知の材料を用いることが可能である。
(Electrolytes)
The electrolyte may exist as a non-aqueous electrolyte or a polymer electrolyte in the secondary battery. Any of the known materials used for lithium ion secondary batteries can be used.
非水電解液は、非水溶媒中に電解質を含んでなる。非水溶媒の例としては、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）などの環状炭酸エステル類、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）などの鎖状炭酸エステル類や、その他の脂肪酸エステル類が挙げられ、これらを単独で、または２種以上を任意の割合で混合して用いる。また電解質としては、例えば、六フッ化リン酸リチウム（ＬｉＰＦ６）、四フッ化ホウ酸リチウム（ＬｉＢＦ４）などの含フッ素リチウム塩が挙げられる。 The nonaqueous electrolytic solution contains an electrolyte in a nonaqueous solvent. Examples of non-aqueous solvents include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC), and chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). And other fatty acid esters, and these are used alone or in admixture of two or more at any ratio. Examples of the electrolyte include fluorine-containing lithium salts such as lithium hexafluorophosphate (LiPF 6 ) and lithium tetrafluoroborate (LiBF 4 ).
ポリマー電解質としては、ポリエチレンオキサイド誘導体及び該誘導体を含む重合体、ポリプロピレンオキサイド誘導体及び該誘導体を含む重合体、リン酸エステル重合体、ポリカーボネート誘導体及び該誘導体を含む重合体等に上記の電解質塩を含有させたものが挙げられる。 The polymer electrolyte contains the above electrolyte salt in a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative. Can be mentioned.
（外装材）
外装材は二次電池に使用されている公知の外装材を選ぶことが出来る。例えばラミネート包材や金属缶が挙げられるが、二次電池の大型化や軽量化に関しては単位重量が軽いラミネート包材が好適である。ラミネート包材の構成は特に限定されないが、金属箔の両側にポリマー層を有するものが挙げられる。
(Exterior material)
As the exterior material, a known exterior material used for a secondary battery can be selected. For example, a laminate wrapping material and a metal can can be mentioned, but a laminate wrapping material having a light unit weight is suitable for increasing the size and weight of the secondary battery. Although the structure of a laminate packaging material is not specifically limited, What has a polymer layer on both sides of metal foil is mentioned.
ポリマー層のうち、二次電池の外側になる外側層は通常、耐熱性、突き刺し強度、滑性、印刷性などの観点から考慮して選定される。具体的には例えば、ポリアミドや、ポリアミドにポリエステルを積層したものなどが用いられる。ここで用いられるポリエステルとしてはポリエチレンテレフタレート、ポリエチレンナフタレート、ポリブチレンテレフタレートなどが挙げられる。また電池製造工程中で、外側層のポリアミドに電解液が付着するおそれを考慮し、ポリアミド層の表面に、耐電解液性を向上するためのコーティング層が施される場合もある。このようなコーティング層には、含フッ素ポリマー、アクリルポリマー、ポリウレタン、ポリエステル、ポリシリコーンから選ばれた少なくとも１種のポリマーが用いられる。 Of the polymer layers, the outer layer that is the outside of the secondary battery is usually selected in view of heat resistance, puncture strength, lubricity, printability, and the like. Specifically, for example, polyamide or a laminate of polyamide on polyamide is used. Examples of the polyester used here include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. In consideration of the possibility that the electrolyte solution adheres to the polyamide of the outer layer during the battery manufacturing process, a coating layer for improving the electrolyte solution resistance may be applied to the surface of the polyamide layer. For such a coating layer, at least one polymer selected from fluorine-containing polymers, acrylic polymers, polyurethanes, polyesters, and polysilicones is used.
ポリマー層のうち、二次電池の内側になる内側層は、加熱により溶融して、二次電池を袋状に封止することができれば特に限定されない。好ましくはポリオレフィンを主成分とする層であり、より好ましくはポリプロピレンを主成分とする層である。内側層は複数の層を積層したものでもよい。例えば、金属箔側に酸変性ポリプロピレン層を有し、その上にポリプロピレンシートを有するものが挙げられる。またランダムポリプロピレンとブロックポリプロピレンが積層されたものも使用することも出来る。内層側は２０〜１５０μｍの厚みであると、加熱による封止性が良好であり、好ましい。 Of the polymer layers, the inner layer that becomes the inner side of the secondary battery is not particularly limited as long as it can be melted by heating to seal the secondary battery in a bag shape. A layer mainly composed of polyolefin is preferable, and a layer mainly composed of polypropylene is more preferable. The inner layer may be a laminate of a plurality of layers. For example, what has an acid-modified polypropylene layer on the metal foil side and has a polypropylene sheet on it is mentioned. Moreover, what laminated | stacked random polypropylene and block polypropylene can also be used. When the inner layer side has a thickness of 20 to 150 μm, the sealing property by heating is good, which is preferable.
外装材に用いる金属箔としてはアルミニウム箔、ステンレス箔、ニッケル箔、などが挙げられる。特にアルミニウム箔は軽量で安価であるので好ましい。アルミニウム箔の材質は特に限定されないが、加工性を考慮すると軟質箔が好ましく、強度を考慮して、Ａ８０２１、Ａ８０７９などのアルミニウム―鉄系合金箔が一般的に選ばれる。また水分バリア性、強度および加工性を考慮すると、厚みとしては２０〜１００μｍの範囲が好ましい。 Examples of the metal foil used for the exterior material include aluminum foil, stainless steel foil, and nickel foil. Aluminum foil is particularly preferable because it is light and inexpensive. The material of the aluminum foil is not particularly limited, but a soft foil is preferable in consideration of workability, and an aluminum-iron alloy foil such as A8021, A8079 is generally selected in consideration of strength. In consideration of moisture barrier properties, strength, and workability, the thickness is preferably in the range of 20 to 100 μm.
ラミネート包材はこの他、外側層と金属箔、内側層と金属箔との間に接着剤層など、他の層を有していても良い。 In addition, the laminate packaging material may have other layers such as an outer layer and a metal foil, and an adhesive layer between the inner layer and the metal foil.
（二次電池の用途）
二次電池は、電源システムに適用することができる。そして、この電源システムは、自動車；鉄道、船舶、航空機などの輸送機器；携帯電話、携帯情報端末、携帯電子計算機などの携帯機器；事務機器；太陽光発電システム、風力発電システム、燃料電池システムなどの発電システム；などに適用することができる。
(Use of secondary battery)
The secondary battery can be applied to a power supply system. And this power supply system includes automobiles; transport equipment such as railways, ships and airplanes; portable equipment such as mobile phones, personal digital assistants and portable electronic computers; office equipment; solar power generation systems, wind power generation systems, fuel cell systems, etc. It can be applied to the power generation system.
次に実施例および比較例を示し、本発明をさらに具体的に説明する。なお本発明は、本実施例によってその範囲が制限されるものではない。本発明に係る二次電池および電源システムは、本発明の要旨を変更しない範囲において適宜変更して実施することができる。 Next, the present invention will be described more specifically with reference to examples and comparative examples. The scope of the present invention is not limited by this embodiment. The secondary battery and the power supply system according to the present invention can be implemented with appropriate modifications without departing from the scope of the present invention.
［実施例１］
（導電材を含む皮膜の形成用塗工液の調製）
以下の材料を、表１に示す配合量で用いた。
導電材：アセチレンブラック（電気化学工業（株）製デンカブラック（登録商標）（粉状）、数平均一次粒径３５ｎｍ）
結着材：グリセリル化キトサン（大日精化工業（株）製、脱アセチル化度８６ｍｏｌ％、重量平均分子量８．６×１０４）
溶媒：Ｎ−メチルピロリドン（試薬特級）、２−プロパノール（試薬特級）
[Example 1]
(Preparation of coating solution for forming film containing conductive material)
The following materials were used in the amounts shown in Table 1.
Conductive material: Acetylene black (Denka Black (registered trademark) (powder), manufactured by Denki Kagaku Kogyo Co., Ltd., number average primary particle size 35 nm)
Binder: Glycerylated chitosan (manufactured by Dainichi Seika Kogyo Co., Ltd., degree of deacetylation 86 mol%, weight average molecular weight 8.6 × 10 4 )
Solvent: N-methylpyrrolidone (reagent special grade), 2-propanol (reagent special grade)
上記の材料ディゾルバータイプの撹拌機を用いて回転数３００ｒｐｍで１０分間分散し、さらにホモジナイザー（家田貿易（株）製、製品名ＰＲＯ２００）を用いて２００００ｒｐｍで３０秒間処理し、十分に分散した塗工液を作製した。 Disperse coating at a rotational speed of 300 rpm for 10 minutes using the above material dissolver type stirrer, and further processed at 20000 rpm for 30 seconds using a homogenizer (product name: PRO200, manufactured by Ieda Trading Co., Ltd.) and sufficiently dispersed A liquid was prepared.
（負極の作製）
＜導電材を含む皮膜の形成＞
次にアルカリ洗浄したＡ１０８５材からなる厚さ３０μｍのアルミニウム箔を用意した。マイヤーバーを用いて、バーコーター法でアルミニウム箔の片面の全面に、上記の塗工液を塗布した。その後、大気中１８０℃にて３分間加熱乾燥した。同様に、金属箔のもう一方の面にも上記の塗工液を塗布、加熱乾燥し、金属箔の両面に導電材を含む皮膜を形成した。
(Preparation of negative electrode)
<Formation of film containing conductive material>
Next, an aluminum foil having a thickness of 30 μm made of A1085 material washed with alkali was prepared. Using the Mayer bar, the above coating solution was applied to the entire surface of one side of the aluminum foil by the bar coater method. Thereafter, it was dried by heating at 180 ° C. in the atmosphere for 3 minutes. Similarly, the above-mentioned coating solution was applied to the other surface of the metal foil and heated and dried to form a film containing a conductive material on both surfaces of the metal foil.
＜導電材を含む皮膜の特性＞
得られた導電材を含む皮膜付きアルミニウム箔を、ＦＩＢ（集束イオンビーム）で切断して断面を切り出し、白金を蒸着した。続いて、ＴＥＭ（日立製作所製、型式：Ｈ−９５００）を用いて、まず、ＥＤＸ（エネルギー分散Ｘ線分光法）で元素分析し、アルミニウム箔表面の酸化膜と、導電材を含む皮膜との境界を決定した。次に、無作為に選んだ５視野で写真を撮影し、それぞれについて無作為に選んだ５箇所で導電材を含む皮膜の厚さを測定した。全ての厚み測定結果を算術平均して求めた導電材を含む皮膜の厚さを表１に示す。
<Characteristics of film containing conductive material>
The obtained aluminum foil with a film containing a conductive material was cut with FIB (focused ion beam) to cut out a cross section, and platinum was deposited. Subsequently, using TEM (manufactured by Hitachi, model: H-9500), first, elemental analysis is performed by EDX (energy dispersive X-ray spectroscopy), and an oxide film on the surface of the aluminum foil and a film containing a conductive material The boundary was determined. Next, photographs were taken with 5 fields of view selected at random, and the thickness of the film containing the conductive material was measured at 5 points selected at random. Table 1 shows the thickness of the film containing the conductive material obtained by arithmetically averaging all the thickness measurement results.
次にアルミニウム箔の、導電材を含む皮膜が形成された部分１０ｃｍ×１０ｃｍを切り出し、剥離剤として三彩加工（株）製、製品名ネオリバー♯３４６を用いて、上述の方法で塗膜の塗布量を測定した。結果を表１に示す。 Next, a 10 cm × 10 cm portion of the aluminum foil on which the film containing the conductive material was formed was cut out, and the coating film was applied by the above-mentioned method using the product name Neo River # 346 manufactured by Sansai Processing Co., Ltd. as the release agent. The amount was measured. The results are shown in Table 1.
＜負極活物質層の形成＞
上述の導電材を含む皮膜付きアルミニウム箔を９ｃｍ×９ｃｍの大きさに切り出した。負極活物質としてブルッカイト型二酸化チタン粉（昭和電工（株）製、商品名ＮＴＢ−１）８６質量部、導電助材としてカーボンナノチューブ（昭和電工（株）製、商品名ＶＧＣＦ−Ｈ）２質量部、バインダーとしてポリフッ化ビニリデン（（株）クレハ製、商品名ＫＦポリマー＃９２１０）１２質量部、分散溶剤としてＮ−メチル−２−ピロリドン（工業用グレード）９４質量部を混合したスラリーを導電材を含む皮膜付きアルミニウム箔の両面に塗布し、乾燥、プレスして片面あたり８１μｍ厚の負極活物質層を形成して負極とした。
<Formation of negative electrode active material layer>
A coated aluminum foil containing the above conductive material was cut into a size of 9 cm × 9 cm. 86 parts by mass of brookite-type titanium dioxide powder (trade name NTB-1 manufactured by Showa Denko KK) as the negative electrode active material, and 2 parts by mass of carbon nanotube (product name VGCF-H manufactured by Showa Denko KK) as the conductive additive , A slurry obtained by mixing 12 parts by mass of polyvinylidene fluoride (trade name KF polymer # 9210) manufactured by Kureha Co., Ltd. as a binder and 94 parts by mass of N-methyl-2-pyrrolidone (industrial grade) as a dispersion solvent is used as a conductive material. The film was coated on both sides of the coated aluminum foil, dried and pressed to form a negative electrode active material layer having a thickness of 81 μm per side to obtain a negative electrode.
（正極の作製）
一方、アルカリ洗浄したＡ１０８５材からなる厚さ３０μｍのアルミニウム箔の両面に正極活物質としてコバルト酸リチウム（日本化学工業（株）製、商品名セルシードＣ）８４質量部、導電助材としてアセチレンブラック（電気化学工業（株）製、商品名デンカブラック（粉状））６質量部、バインダーとしてポリフッ化ビニリデン（（株）クレハ製、商品名ＫＦポリマー＃１１２０）１０質量部、分散溶剤としてＮ−メチル−２−ピロリドン（工業用グレード）９５質量部を混合したスラリーを塗布後乾燥し、プレスして片面あたり７０μｍ厚の正極活物質層を形成したものを正極とした。
(Preparation of positive electrode)
On the other hand, 84 parts by mass of lithium cobaltate (trade name Cellseed C, manufactured by Nippon Chemical Industry Co., Ltd.) as a positive electrode active material on both surfaces of a 30 μm-thick aluminum foil made of alkali-cleaned A1085 material, and acetylene black ( 6 parts by mass of Denka Black (powder) manufactured by Denki Kagaku Kogyo Co., Ltd., 10 parts by mass of polyvinylidene fluoride (manufactured by Kureha Co., Ltd., trade name KF Polymer # 1120) as a binder, N-methyl as a dispersion solvent A slurry in which 95 parts by mass of -2-pyrrolidone (industrial grade) was mixed was applied, dried, and pressed to form a positive electrode active material layer having a thickness of 70 μm per side.
（二次電池の作製）
上記の正極と負極の間にセパレーター（ＰＯＬＹＰＯＲＥ Ｉｎｔｅｒｎａｔｉｏｎａｌ，Ｉｎｃ．製、商品名Ｃｅｌｇａｒｄ（登録商標）２５００）を組み込み、負極および正極にアルミタブ電極をおのおの超音波溶接機で取り付けた。これらを予め袋状にしたアルミラミネート包材（昭和電工パッケージング（株）製、ドライラミタイプ）に入れ、６０℃の真空乾燥機で水分を除去した後、非水電解液として、濃度１ＭのＬｉＰＦ６溶液（溶媒としてエチレンカーボネート（ＥＣ）：ジメチルカーボネート（ＤＭＣ）：ジエチルカーボネート（ＤＥＣ）＝１：１：１ｖ／ｖ、１質量％ビニルクロライド添加）（キシダ化学（株）製）を注入し、真空雰囲気で２４時間含浸させ、アルミラミネート包材の開口部を真空シーラーで封止することで、二次電池を作製した。
(Production of secondary battery)
A separator (manufactured by POLYPORE International, Inc., trade name Celgard (registered trademark) 2500) was incorporated between the positive electrode and the negative electrode, and aluminum tab electrodes were attached to the negative electrode and the positive electrode, respectively, by an ultrasonic welder. These are put into a bag-shaped aluminum laminate packaging (made by Showa Denko Packaging Co., Ltd., dry lamination type), and after removing moisture with a vacuum dryer at 60 ° C., as a non-aqueous electrolyte, the concentration is 1M. LiPF 6 solution (ethylene carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (DEC) = 1: 1: 1 v / v, 1% by weight vinyl chloride added) (made by Kishida Chemical Co., Ltd.) as a solvent was injected. The secondary battery was fabricated by impregnating in a vacuum atmosphere for 24 hours and sealing the opening of the aluminum laminate packaging material with a vacuum sealer.
（二次電池の評価）
二次電池を以下のようにして評価した。
内部抵抗はインピーダンスメーター（日置電機（株）製、型式３５３２−８０）を用い、ＡＣインピーダンス法で、測定周波数１ｋＨｚにて測定した。
(Evaluation of secondary battery)
The secondary battery was evaluated as follows.
The internal resistance was measured using an impedance meter (manufactured by Hioki Electric Co., Ltd., Model 3532-80) by the AC impedance method at a measurement frequency of 1 kHz.
さらにサイクル特性を測定した。測定は充放電装置（東洋システム（株）製）を用い、電流レートを０．２Ｃ、２Ｃ 、２０Ｃ と変えて２００サイクル後の初期容量維持率を、０．２Ｃに対する容量維持率を１００％として表示した。なお、カット電圧は１．０〜３．０ＶでＳＯＣは１００％として測定した。 Furthermore, cycle characteristics were measured. The measurement was performed using a charge / discharge device (manufactured by Toyo System Co., Ltd.), changing the current rate to 0.2C, 2C, and 20C, and setting the initial capacity maintenance rate after 200 cycles to 100% as the capacity maintenance rate for 0.2C. displayed. The cut voltage was 1.0 to 3.0 V and the SOC was 100%.
（実施例２）
導電材を含む皮膜の形成用の塗工液の配合を表１に示す通りとし、負極活物質を特開２００８−１１７６２５号公報に記載のブロンズ型二酸化チタンに変えた他は、実施例１と同様に二次電池を作製し、評価を行った。
(Example 2)
The composition of the coating liquid for forming a film containing a conductive material was as shown in Table 1, and the negative electrode active material was changed to bronze-type titanium dioxide described in JP-A-2008-117625. Similarly, secondary batteries were produced and evaluated.
（実施例３）
導電材を含む皮膜を形成するための塗工液の配合を表１に示す通りとし、負極活物質をスピネル型チタン酸リチウム（石原産業製、商品名ＸＡ−１０５）に変えた他は、実施例１と同様に二次電池を作製し、評価を行った。
(Example 3)
The composition of the coating liquid for forming a film containing a conductive material was as shown in Table 1, and the negative electrode active material was changed to spinel type lithium titanate (product name XA-105, manufactured by Ishihara Sangyo). A secondary battery was prepared and evaluated in the same manner as in Example 1.
（比較例１）
導電材を含む皮膜を設けない負極集電体を用いた他は、実施例１と同様にして二次電池の作製、評価を行った。
(Comparative Example 1)
A secondary battery was fabricated and evaluated in the same manner as in Example 1 except that a negative electrode current collector without a coating containing a conductive material was used.
（比較例２）
導電材を含む皮膜を設けない負極集電体を用いた他は、実施例２と同様にして二次電池の作製、評価を行った。
(Comparative Example 2)
A secondary battery was fabricated and evaluated in the same manner as in Example 2 except that a negative electrode current collector without a coating containing a conductive material was used.
（比較例３）
導電材を含む皮膜を設けない負極集電体を用いた他は、実施例３と同様にして二次電池の作製、評価を行った。
(Comparative Example 3)
A secondary battery was fabricated and evaluated in the same manner as in Example 3 except that a negative electrode current collector without a coating containing a conductive material was used.
実施例および比較例で作製した二次電池の評価結果を表１に示す。 Table 1 shows the evaluation results of the secondary batteries produced in the examples and comparative examples.
Claims (10)
該金属箔の片面または両面に形成された、負極活物質としてチタン含有酸化物を含み、導電助材をさらに含む負極活物質層とを有し、
前記金属箔と前記負極活物質層との間に、導電材を含む皮膜が該金属箔と該負極活物質層に接して形成されており、
前記導電材を含む皮膜の厚みが、０．１μｍ以上５μｍ以下であり、
前記導電助材が、前記負極活物質層中に０．５〜２質量％含まれており、
前記導電材がカーボンブラックおよび／または黒鉛であり、
前記導電助材が繊維状の炭素質材料である二次電池用負極。 Metal foil,
A negative electrode active material layer formed on one or both sides of the metal foil, including a titanium-containing oxide as a negative electrode active material, and further including a conductive additive;
Between the negative electrode active material layer and the metal foil, film containing a conductive material is formed in contact with the metal foil and the negative electrode active material layer,
The thickness of the film containing the conductive material state, and are more 5μm or less 0.1 [mu] m,
The conductive additive is included in the negative electrode active material layer in an amount of 0.5 to 2% by mass,
The conductive material is carbon black and / or graphite;
The negative electrode for secondary batteries whose said conductive support material is a fibrous carbonaceous material .
The secondary battery according to claim 9 , wherein the exterior material has a polymer layer on both sides of an aluminum foil.
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| KR20140009504A (en) * | 2011-04-26 | 2014-01-22 | 쇼와 덴코 가부시키가이샤 | Secondary battery |
| CN104247098A (en) * | 2012-04-27 | 2014-12-24 | 昭和电工株式会社 | Anode for secondary battery, method for producing same, and secondary battery |
| JP6219113B2 (en) * | 2013-09-30 | 2017-10-25 | 株式会社東芝 | Secondary battery |
| EP3121881A4 (en) * | 2014-03-19 | 2017-11-08 | Kabushiki Kaisha Toshiba | Nonaqueous electrolyte secondary battery, assembled battery and battery pack |
| KR20180101461A (en) * | 2016-01-07 | 2018-09-12 | 닛산 가가쿠 가부시키가이샤 | Electrodes for energy storage devices |
| WO2017119287A1 (en) * | 2016-01-07 | 2017-07-13 | 日産化学工業株式会社 | Electrode for energy storage devices |
| CN109585904B (en) * | 2017-09-29 | 2021-11-23 | 辉能科技股份有限公司 | Flexible lithium battery |
| EP3780164A4 (en) * | 2018-03-30 | 2021-10-20 | Kabushiki Kaisha Toshiba | Electrode, battery, and battery pack |
| WO2020144905A1 (en) * | 2019-01-08 | 2020-07-16 | 株式会社カネカ | Negative electrode for nonaqueous electrolyte secondary batteries and nonaqueous electrolyte secondary battery |
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| JP2002270175A (en) * | 2001-03-09 | 2002-09-20 | Asahi Glass Co Ltd | Secondary power source |
| JP5092196B2 (en) * | 2004-12-28 | 2012-12-05 | 日産自動車株式会社 | Bipolar battery |
| JP4593488B2 (en) * | 2005-02-10 | 2010-12-08 | 昭和電工株式会社 | Secondary battery current collector, secondary battery positive electrode, secondary battery negative electrode, secondary battery, and production method thereof |
| JP5038751B2 (en) * | 2006-08-04 | 2012-10-03 | 協立化学産業株式会社 | Coating liquid for electrode plate production, undercoat agent and use thereof |
| JP5093643B2 (en) * | 2006-11-02 | 2012-12-12 | 独立行政法人産業技術総合研究所 | Lithium secondary battery active material, method for producing the same, and lithium secondary battery using the same |
| CN101515640B (en) * | 2008-02-22 | 2011-04-20 | 比亚迪股份有限公司 | Cathode and lithium ion secondary battery containing same |
| EP2262047B1 (en) * | 2008-03-05 | 2015-04-29 | GS Yuasa International Ltd. | Non-aqueous electrolyte battery |
| JP5438299B2 (en) * | 2008-10-14 | 2014-03-12 | 株式会社東芝 | Nonaqueous electrolyte battery and battery pack |
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| EP2419752A1 (en) * | 2009-04-17 | 2012-02-22 | Time Medical Holdings Company Limited | Cryogenically cooled superconductor gradient coil module for magnetic resonance imaging |
| JP5594663B2 (en) * | 2009-06-25 | 2014-09-24 | 独立行政法人産業技術総合研究所 | Alkali metal titanate compound, method for producing the same, electrode active material containing the alkali metal titanate compound, and electricity storage device using the electrode active material |
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