JP2012174577A - Negative electrode plate of lithium secondary battery, negative electrode, and lithium secondary battery - Google Patents
Negative electrode plate of lithium secondary battery, negative electrode, and lithium secondary battery Download PDFInfo
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Description
本発明はリチウム二次電池用負極電極板、この電極板を用いたリチウム二次電池用負極およびリチウム二次電池に関する。 The present invention relates to a negative electrode plate for a lithium secondary battery, a negative electrode for a lithium secondary battery using the electrode plate, and a lithium secondary battery.
リチウムイオンの吸蔵、放出が可能な材料を用いて負極を形成したリチウム二次電池は、金属リチウムを用いて負極を形成したリチウム電池に比べて、デンドライトの析出を抑制することができ、安全性を高めた電池として市場投入されてきた。近年、このリチウム二次電池を車載用途にと開発されつつあり、電池重量とコストが課題となっている。 Lithium secondary batteries that have a negative electrode formed using a material capable of occluding and releasing lithium ions can suppress the deposition of dendrites compared to lithium batteries that have a negative electrode formed using metallic lithium. Has been put on the market as an improved battery. In recent years, this lithium secondary battery is being developed for in-vehicle use, and battery weight and cost have become issues.
この課題に対して、電極材料自身の性能向上を図り、電池の容量を向上させることで小型軽量化を図る工夫が色々と成されてきた。またコスト低減に関しては特に正極材のコストが電池コスト全体の約４０％弱を占めるために、正極材のコスト低減化が望まれている。しかしこれらの工夫によって大きく重量やコスト低減が可能であろうが、高容量化や各種正極材の登場により、結果として活物質量の増加による重量増と正極材種の多様化による量産効果の低下により、コスト低減が進んでいないのが現状である。
従来、負極電極材の集電体としては、鉄、クロム、ニッケル、マンガン、チタン、モリブデン、バナジウム、ニオブ、アルミニウム、銅、銀、金、白金、ステンレスまたはカーボンが例示されている（特許文献１、２）。
In response to this problem, various attempts have been made to reduce the size and weight by improving the performance of the electrode material itself and improving the capacity of the battery. Regarding cost reduction, since the cost of the positive electrode material occupies about 40% of the total battery cost, it is desired to reduce the cost of the positive electrode material. However, these devices can greatly reduce the weight and cost, but with the increase in capacity and the advent of various positive electrode materials, as a result, the weight increase due to the increase in the amount of active material and the diversification of the positive electrode material types will reduce the mass production effect. As a result, cost reduction is not progressing.
Conventionally, examples of current collectors for negative electrode materials include iron, chromium, nickel, manganese, titanium, molybdenum, vanadium, niobium, aluminum, copper, silver, gold, platinum, stainless steel, and carbon (Patent Document 1). 2).
しかしながら、負極電極材の集電体として導電性金属箔が提案されているが、特許文献１および２の実施例で使用されている負極集電体は全て銅箔である。またアルミニウムを負極電極材の集電体として使用している例は知られていない。 However, although a conductive metal foil has been proposed as a current collector for the negative electrode material, all of the negative electrode current collectors used in Examples of Patent Documents 1 and 2 are copper foils. Moreover, the example which uses aluminum as a collector of a negative electrode material is not known.
本発明は以上のような問題に対処するためになされたもので、電池の軽量化とコスト低減が可能であるとともに、車載用途として使用可能な負極電極板、負極およびリチウム二次電池の提供を目的とする。 The present invention has been made to address the above-described problems, and provides a negative electrode plate, a negative electrode, and a lithium secondary battery that can reduce the weight and cost of the battery and can be used as an in-vehicle application. Objective.
本発明のリチウム二次電池用負極電極板は、集電体の少なくとも一主面に負極活性物質が配される負極電極板において、上記集電体は、表面に導電性カーボン被覆層を有する金属箔であり、集電を担う該金属箔の一部にアルミニウムを用いることを特徴とする。特に金属箔がアルミニウム箔であることを特徴とする。 The negative electrode plate for a lithium secondary battery according to the present invention is a negative electrode plate in which a negative electrode active material is disposed on at least one main surface of a current collector, wherein the current collector is a metal having a conductive carbon coating layer on the surface. It is a foil, and aluminum is used for a part of the metal foil for collecting current. In particular, the metal foil is an aluminum foil.
本発明のリチウム二次電池負極は、上記リチウム二次電池用負極電極板の少なくとも一主面に、炭素材、合金、合金酸化物、およびチタン酸リチウムから選ばれた少なくとも１つの負極活性物質を有することを特徴とする。
本発明のリチウム二次電池は、正極および上記本発明の負極間にセパレータを介して、捲回または積層してなる電極群に有機電解液を浸透または浸漬させてリチウムイオンの吸蔵・放出を繰返し行なうリチウム二次電池であることを特徴とする。
In the lithium secondary battery negative electrode of the present invention, at least one main surface of the negative electrode plate for a lithium secondary battery includes at least one negative electrode active material selected from a carbon material, an alloy, an alloy oxide, and lithium titanate. It is characterized by having.
The lithium secondary battery of the present invention repeatedly occludes / releases lithium ions by infiltrating or immersing the organic electrolyte in a wound or laminated electrode group via a separator between the positive electrode and the negative electrode of the present invention. It is a lithium secondary battery to be performed.
本発明のリチウム二次電池用負極電極板は、集電を担う金属箔の一部として、表面に導電性カーボン被覆層を有するアルミニウム、特にアルミニウム箔を用いるので、従来集電箔として使用されていた銅箔に比較して、材料価格および重量の低減を図ることができる。 The negative electrode plate for a lithium secondary battery of the present invention uses aluminum having a conductive carbon coating layer on the surface as a part of the metal foil responsible for current collection, in particular, aluminum foil, and thus has been conventionally used as a current collection foil. Compared with copper foil, the material price and weight can be reduced.
本発明のリチウム二次電池用負極電極板は、集電を担う金属箔の一部にアルミニウムを用い、その表面に導電性カーボン被覆層を有する。
金属箔としては、アルミニウム箔、または、ニッケル、鉄、ステンレス、チタン、もしくは銅などの金属とアルミニウムとのクラッド材を用いた箔、これら金属表面にアルミニウムが被覆された箔などが挙げられる。
さらにアルミニウム箔は純アルミニウム金属箔でなくてもアルミニウムと他の金属との合金箔でもよい。またアルミニウム元素をアルマイト処理法、溶射法等で表面積を増加させる事も可能であり、アルミニウム箔をパンチングや突起状の穴あけ加工等を施してもよい。
これらの中で、材料価格、入手のし易さ、優れた導電率などから純アルミニウム金属箔が好ましい。
The negative electrode plate for a lithium secondary battery of the present invention uses aluminum as a part of a metal foil for collecting current and has a conductive carbon coating layer on the surface thereof.
Examples of the metal foil include an aluminum foil, a foil using a clad material of a metal such as nickel, iron, stainless steel, titanium, or copper and aluminum, and a foil in which the metal surface is coated with aluminum.
Furthermore, the aluminum foil may not be a pure aluminum metal foil but may be an alloy foil of aluminum and another metal. Further, the surface area of the aluminum element can be increased by an alumite treatment method, a thermal spraying method, or the like, and the aluminum foil may be subjected to punching or protrusion-like drilling.
Among these, pure aluminum metal foil is preferable from the viewpoint of material price, availability, and excellent conductivity.
金属箔の表面に、導電性カーボン被覆層を形成する。本発明においては、特にアルミニウム箔表面に導電性を有するカーボン被覆層が形成されていればよい。導電性を有するカーボン層の形成方法としては、アセチレンブラック、ケッチェンブラック、黒鉛結晶などの導電性カーボンを溶媒に分散させてスラリー状などの塗工液を形成し、この塗工液をアルミニウム箔の表面に塗布乾燥する方法、アルミニウム箔の表面に有機物あるいは高分子化合物溶液を塗布して還元性雰囲気で熱分解する方法、イオンデポジット法、カーボン圧着法、アルミニウム箔の表面に化学的蒸着法（ＣＶＤ）および／または物理的蒸着法（ＰＶＤ）により薄膜を形成する方法等が挙げられる。 A conductive carbon coating layer is formed on the surface of the metal foil. In the present invention, it is only necessary that a carbon coating layer having conductivity is formed on the surface of the aluminum foil. As a method for forming a conductive carbon layer, a conductive liquid such as acetylene black, ketjen black, and graphite crystals is dispersed in a solvent to form a slurry-like coating liquid. A method of coating and drying on the surface of aluminum, a method of applying organic matter or polymer compound solution to the surface of aluminum foil and thermally decomposing in a reducing atmosphere, an ion deposit method, a carbon pressure bonding method, a chemical vapor deposition method on the surface of aluminum foil ( CVD) and / or a method of forming a thin film by physical vapor deposition (PVD).
上記電極板を用いたリチウム二次電池に使用される負極の一例について説明する。
リチウム二次電池用負極は、リチウム二次電池用負極電極板の少なくとも一主面に、炭素材、合金、合金酸化物、およびチタン酸リチウムから選ばれた少なくとも１つの負極活性物質を有する。すなわち、リチウムイオンの吸蔵・放出が可能な負極活性物質と導電性カーボンとアルミニウム箔とが複合化、または層状に形成されたものを用いる。
リチウムイオンの吸蔵・放出が可能な負極活性物質としては、炭素材、シリコン系またはスズ系合金やそれらの酸化物混合体、また該酸化物混合体と炭素材との複合体、さらにはチタン酸リチウムなどを挙げることができる。これらの中で、近年、安全性の観点からチタン酸リチウム、高容量化の観点からスズやシリコン酸化物およびそれらの金属混合体が用いられつつある。
本発明では、炭素材は、チタン酸リチウムやスズ、シリコン金属および酸化物混合体負極に対して、軽量とコスト低減に効果をもたらすものと考えられる。また、本発明に類似のＬｉ−Ａｌ合金を負極に用いた電池の大電流充放電が困難なことと金属リチウムの析出による安全性の低下も防止できる。
An example of the negative electrode used for the lithium secondary battery using the electrode plate will be described.
The negative electrode for a lithium secondary battery has at least one negative electrode active material selected from a carbon material, an alloy, an alloy oxide, and lithium titanate on at least one main surface of the negative electrode plate for a lithium secondary battery. That is, a negative electrode active material capable of occluding and releasing lithium ions, a conductive carbon, and an aluminum foil are used in a composite or layered form.
Examples of the negative electrode active substance capable of occluding and releasing lithium ions include carbon materials, silicon-based or tin-based alloys, oxide mixtures thereof, composites of the oxide mixture and carbon materials, and titanic acid. Lithium etc. can be mentioned. Among these, in recent years, lithium titanate is being used from the viewpoint of safety, and tin, silicon oxide, and metal mixtures thereof are being used from the viewpoint of increasing capacity.
In this invention, it is thought that a carbon material brings an effect in light weight and a cost reduction with respect to lithium titanate, tin, a silicon metal, and an oxide mixed negative electrode. In addition, it is possible to prevent a battery using a Li—Al alloy similar to the present invention as a negative electrode from being difficult to charge and discharge at a large current and to reduce safety due to deposition of metallic lithium.
また、本発明ではスズまたはシリコン系負極の短寿命を解決するため、金属スズまたはシリコンを内包したスズまたはシリコン酸化物の粉体表面に炭素材を配した金属スズまたはシリコン金属粒子内包スズまたはシリコン酸化物粉体と、導電性カーボン粉体および導電性カーボン繊維から選ばれた少なくとも１つの導電材とを混合することで活物質表面の炭素材と導電材とを化学的に結合させた材料が、負極材として最も効果を発揮すると考えられる。 Further, in the present invention, in order to solve the short life of tin or silicon-based negative electrode, metal tin or silicon metal particle-encapsulated tin or silicon in which a carbon material is arranged on the surface of tin or silicon oxide powder encapsulating metal tin or silicon A material obtained by chemically combining the carbon material and the conductive material on the surface of the active material by mixing the oxide powder with at least one conductive material selected from conductive carbon powder and conductive carbon fiber. It is considered that the most effective as a negative electrode material.
リチウム二次電池用正極は、活物質として、層状またはスピネル状のリチウム含有金属酸化物やその固溶体、リチウム含有金属リン酸化合物やリチウム含有金属珪酸化物およびそれらのフッ化物、さらにはリチウム含有化合物を主材料とし、該材料と、バインダーと、導電材から構成されている。 The positive electrode for a lithium secondary battery includes, as an active material, a layered or spinel lithium-containing metal oxide or a solid solution thereof, a lithium-containing metal phosphate compound, a lithium-containing metal silicate and a fluoride thereof, and further a lithium-containing compound. The main material is composed of the material, a binder, and a conductive material.
層状、スピネル状リチウム含有金属酸化物としては、ＬｉＣｏＯ2、Ｌｉ（Ｎｉ／Ｃｏ／Ｍｎ）Ｏ2、ＬｉＭｎ2Ｏ4また固溶体としてＬｉ2ＭｎＯ3-ＬｉＭＯ2（Ｍ＝Ｎｉ,Ｃｏ,Ｍｎ）などが挙げられ、リチウム含有金属リン酸化合物としては、ＬｉＦｅＰＯ4、ＬｉＣｏＰＯ4、ＬｉＭｎＰＯ4などが挙げられ、珪酸化物としてはＬｉＦｅＳｉＯ4等が挙げられる。またフッ化物としてはＬｉ2ＦｅＰＯ4・Ｆ等がある。リチウム含有化合物としては、ＬｉＴｉ2（ＰＯ4）3、ＬｉＦｅＯ2などが挙げられる。
これらの中で、電気化学特性、安全性やコスト面で、リチウム含有金属リン酸化合物としてのオリビン形リチウム金属燐酸化物であるＬｉＦｅＰＯ4を用いることが好ましい。
Layered and spinel-like lithium-containing metal oxides include LiCoO 2 , Li (Ni / Co / Mn) O 2 , LiMn 2 O 4 , and Li 2 MnO 3 —LiMO 2 (M = Ni, Co, Mn) as a solid solution. Examples of the lithium-containing metal phosphate compound include LiFePO 4 , LiCoPO 4 , and LiMnPO 4, and examples of the siliceous oxide include LiFeSiO 4 . Examples of the fluoride include Li 2 FePO 4 · F. Examples of the lithium-containing compound include LiTi 2 (PO 4 ) 3 and LiFeO 2 .
Among these, it is preferable to use LiFePO 4 which is an olivine type lithium metal phosphate as a lithium-containing metal phosphate compound in terms of electrochemical characteristics, safety and cost.
リチウム二次電池に使用できるセパレータは、正極および負極を電気的に絶縁して電解液を保持するものである。上記セパレータは合成樹脂製フィルムや繊維または無機繊維製などを挙げることができ、その具体例としては、ポリエチレンやポリプロピレンフィルムやこれらの樹脂製の織布や不織布、またガラス繊維やセルロース繊維製のものなどを挙げることができる。 A separator that can be used in a lithium secondary battery is one that electrically insulates a positive electrode and a negative electrode to hold an electrolytic solution. Examples of the separator include synthetic resin films, fibers or inorganic fibers. Specific examples thereof include polyethylene and polypropylene films, woven and nonwoven fabrics made of these resins, glass fibers and cellulose fibers. And so on.
リチウム二次電池において、上述する電極群が浸漬される電解液としては、リチウム塩を含む非水電解液またはイオン伝導ポリマーなどを用いることが好ましい。
リチウム塩を含む非水電解液における非水溶媒としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＭＥＣ）等が挙げられる。
また、上記非水溶媒に溶解できるリチウム塩としては、六フッ化リン酸リチウム（ＬｉＰＦ6）、ホウ四フッ化リチウム（ＬｉＢＦ4）、トリフルオロメタンスルホン酸リチウム（ＬｉＳＯ3ＣＦ4）等が挙げられる。
In the lithium secondary battery, it is preferable to use a non-aqueous electrolyte containing a lithium salt, an ion conductive polymer, or the like as the electrolyte in which the electrode group described above is immersed.
Examples of the non-aqueous solvent in the non-aqueous electrolyte containing a lithium salt include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC).
Examples of lithium salts that can be dissolved in the non-aqueous solvent include lithium hexafluorophosphate (LiPF 6 ), lithium borotetrafluoride (LiBF 4 ), and lithium trifluoromethanesulfonate (LiSO 3 CF 4 ). .
本発明のリチウム二次電池電極材において、結着剤は、電池内の雰囲気下、物理的、化学的に安定な材料であって、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂、スチレンブタジエンゴムやアクリル酸ポリマー等の分散形樹脂を用いることができる。 In the lithium secondary battery electrode material of the present invention, the binder is a material that is physically and chemically stable under the atmosphere in the battery, and contains fluorine such as polytetrafluoroethylene, polyvinylidene fluoride, and fluororubber. Resin, thermoplastic resins such as polypropylene and polyethylene, and dispersion resins such as styrene butadiene rubber and acrylic acid polymer can be used.
本発明の負極活性物質および正極活性物質に使用できる炭素材は、結晶系または非晶質系どちらでも選択可能である。具体的には、人造黒鉛、天然黒鉛、易黒鉛化炭素材、および非晶質炭素材から選ばれた少なくとも１つの炭素材である。これらの中で非晶質炭素材が好ましい。
非晶質炭素材は、結晶構造が乱層または非晶質であるものが好ましく、具体的にはアセチレンブラック、ケッチェンブラック、および黒鉛結晶を含む粉体が挙げられる。
The carbon material that can be used for the negative electrode active material and the positive electrode active material of the present invention can be selected from either a crystalline system or an amorphous system. Specifically, it is at least one carbon material selected from artificial graphite, natural graphite, graphitizable carbon material, and amorphous carbon material. Among these, an amorphous carbon material is preferable.
The amorphous carbon material preferably has a disordered layer or an amorphous crystal structure, and specific examples thereof include acetylene black, ketjen black, and powder containing graphite crystals.
本発明に使用できる導電材は、導電性カーボン粉体および導電性カーボン繊維から選ばれた少なくとも１つの導電材であることが好ましい。
導電性カーボン粉体としては、具体的にはアセチレンブラック、ケッチェンブラック、および黒鉛結晶を含む粉体から選ばれた少なくとも１つであることが好ましい。
カーボン繊維としては、導電性を有するカーボン繊維である。例えば、カーボン繊維、グラファイト繊維、気相成長炭素繊維、カーボンナノファイバーおよびカーボンナノチューブのうちの少なくとも１種類を含有することが好ましい。カーボン繊維の繊維径としては５ｎｍ〜２００ｎｍであることが好ましく、１０ｎｍ〜１００ｎｍであることがより好ましい。また、繊維長が１００ｎｍ〜５０μｍであることが好ましく、１μｍ〜３０μｍであることがより好ましい。
The conductive material that can be used in the present invention is preferably at least one conductive material selected from conductive carbon powder and conductive carbon fiber.
Specifically, the conductive carbon powder is preferably at least one selected from powders containing acetylene black, ketjen black, and graphite crystals.
As carbon fiber, it is carbon fiber which has electroconductivity. For example, it is preferable to contain at least one of carbon fiber, graphite fiber, vapor grown carbon fiber, carbon nanofiber, and carbon nanotube. The fiber diameter of the carbon fiber is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm. Moreover, it is preferable that fiber length is 100 nm-50 micrometers, and it is more preferable that they are 1 micrometer-30 micrometers.
本発明のリチウム二次電池電極材としては、導電性カーボン粉体および導電性カーボン繊維を併用することが好ましく、配合割合としては、質量比で［導電性カーボン粉体／導電性カーボン繊維＝（２〜８）／（１〜３）］であることが好ましい。
また、リチウム二次電池電極材全体に対して、導電材は１〜１２質量％、好ましくは４〜８質量％配合することができる。
As the lithium secondary battery electrode material of the present invention, it is preferable to use conductive carbon powder and conductive carbon fiber in combination, and the mixing ratio is [conductive carbon powder / conductive carbon fiber = ( 2-8) / (1-3)].
Moreover, 1-12 mass% of electrically conductive materials can be mix | blended with respect to the whole lithium secondary battery electrode material, Preferably 4-8 mass% can be mix | blended.
本発明のリチウム二次電池において、電池の出力特性、長寿命化だけでなく、車載用として将来求められる小型軽量電池としての高容量材料として効果の大きい電極の組み合わせとして次のように考える。
すなわち、正極材としては長寿命で低コスト、かつ安全性の高い、粉体表面に非晶質炭素材コートを施したオリビン形ＬｉＦｅＰＯ4を用い、この正極主材に導電性アセチレンブラックとカーボンナノチューブとを結合させて用いることが好ましい。
In the lithium secondary battery of the present invention, not only the output characteristics and long life of the battery, but also a combination of electrodes that are highly effective as a high-capacity material as a small and lightweight battery that will be required in the future for in-vehicle use is considered as follows.
That is, as the positive electrode material, olivine-type LiFePO 4 having a long life, low cost, and high safety, which is coated with an amorphous carbon material coating on the powder surface, is used, and conductive acetylene black and carbon nanotubes are used as the positive electrode main material. And are preferably used in combination.
一方、対向の負極は高容量、高回生および長寿命を考慮して金属シリコン、またはスズ内包のシリコン、またはスズ酸化物粉体の表面に非晶質炭素材をコートし、この粉体と導電性カーボン（アセチレンブラックやカーボンナノチューブ等）を結合させて、さらに表面にカーボンコートした黒鉛粉体（人造黒鉛または易黒鉛粉体）とも結合させたものを用いることが最良と考える。 On the other hand, the opposite negative electrode is coated with an amorphous carbon material on the surface of metallic silicon, tin-encapsulated silicon or tin oxide powder in consideration of high capacity, high regeneration and long life, and this powder and conductive It is considered best to use a product obtained by bonding a functional carbon (acetylene black, carbon nanotubes, etc.) and a graphite powder (artificial graphite or easy graphite powder) coated with carbon on the surface.
参考例１
リチウム二次電池の正極を以下の方法で製造した。
二次粒子径が２〜３μｍの導電性カーボンが表面にコートされたオリビン型リン酸鉄リチウムを正極活物質とし、該活物質８４重量部に、導電剤として８重量部の導電性カーボンおよび２重量部の導電性カーボン繊維体の混合体と、結着剤として６重量部のポリフッ化ビニリデンを添加した。これに分散溶媒として、Ｎ−メチルピロリドンを添加し、混練して、正極合剤（正極スラリー）を作製した。
２０μｍ厚さで、１５０ｍｍ幅のアルミニウム箔を準備する。上記正極スラリーを該アルミニウム箔の両面に塗布、乾燥した。その後、プレス、裁断してリチウム二次電池用の正極を得た。アルミニウム箔の両面に正極スラリーを塗布・乾燥後、プレスした時の正極総厚さは１６０μｍであった。
Reference example 1
A positive electrode of a lithium secondary battery was produced by the following method.
The olivine type lithium iron phosphate coated on the surface with conductive carbon having a secondary particle size of 2 to 3 μm is used as a positive electrode active material, and 84 parts by weight of the active material is mixed with 8 parts by weight of conductive carbon and 2 A mixture of parts by weight of conductive carbon fiber body and 6 parts by weight of polyvinylidene fluoride as a binder were added. To this, N-methylpyrrolidone was added as a dispersion solvent and kneaded to prepare a positive electrode mixture (positive electrode slurry).
An aluminum foil having a thickness of 20 μm and a width of 150 mm is prepared. The positive electrode slurry was applied to both sides of the aluminum foil and dried. Then, the positive electrode for lithium secondary batteries was obtained by pressing and cutting. The total thickness of the positive electrode when pressed after applying and drying the positive electrode slurry on both sides of the aluminum foil was 160 μm.
実施例１
リチウム二次電池の負極を以下の方法で製造した。
１５μｍ厚さで、１５０ｍｍ幅の導電性カーボンコートしたアルミニウム箔を準備する。導電性カーボンコートは、アセチレンブラック２重量部を含むスラリーを作製し、このスラリーを塗布、１００℃×１分間乾燥して製造した。導電性カーボンのコート層の厚さは１μｍであった。
次に、炭素材９０重量部にアセチレンブラック５重量部添加し、結着剤としてポリフッ化ビニリデン溶液を用いてスラリーを作製した。当該スラリーを導電性カーボンコートしたアルミニウム箔に塗工して乾燥を行ない、その後、プレス、裁断してリチウム二次電池用の負極を得た。該アルミニウム箔の両面に負極スラリーを塗布・乾燥後、プレスした時の負極総厚さは１２０μｍであった。
Example 1
A negative electrode of a lithium secondary battery was produced by the following method.
An aluminum foil coated with conductive carbon and having a thickness of 15 μm and a width of 150 mm is prepared. The conductive carbon coat was produced by preparing a slurry containing 2 parts by weight of acetylene black, applying the slurry, and drying at 100 ° C. for 1 minute. The thickness of the conductive carbon coating layer was 1 μm.
Next, 5 parts by weight of acetylene black was added to 90 parts by weight of the carbon material, and a slurry was prepared using a polyvinylidene fluoride solution as a binder. The slurry was applied to an aluminum foil coated with conductive carbon and dried, and then pressed and cut to obtain a negative electrode for a lithium secondary battery. The total thickness of the negative electrode when pressed after applying and drying the negative electrode slurry on both sides of the aluminum foil was 120 μm.
比較例１
炭素材とバインダーおよび導電材は実施例１の負極板と同じものを用いた。ただ、ここでは集電箔として、導電性カーボンコートをしていない１０μｍ厚さの銅箔を用いた。その他の作製方法は実施例１と同一の方法で作製した。
Comparative Example 1
The same carbon material, binder, and conductive material as the negative electrode plate of Example 1 were used. However, here, a copper foil having a thickness of 10 μm without conducting carbon coating was used as the current collector foil. Other manufacturing methods were manufactured in the same manner as in Example 1.
実施例２
実施例１で作製した負極と、参考例１で作製した正極を用いて３．４Ｖ−２０ｍＡｈのアルミラミネートフィルムパック式リチウムイオン電池を作製した。電解液にはエチレンカーボネート（ＥＣ）、メチルエチルカーボネート（ＭＥＣ）を、体積比で（ＥＣ：ＭＥＣ＝３０：７０）に混合した溶液中に６フッ化リン酸リチウム（ＬｉＰＦ6）を１ｍｏｌ／ｌ溶解したものを用いた。正・負極のセパレータには、ポリエチレン（ＰＥ）樹脂製の厚さ２０μｍのフィルムを用いた。
Example 2
Using the negative electrode produced in Example 1 and the positive electrode produced in Reference Example 1, a 3.4 V-20 mAh aluminum laminated film pack type lithium ion battery was produced. 1 mol / l of lithium hexafluorophosphate (LiPF 6 ) in a solution obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (MEC) in a volume ratio (EC: MEC = 30: 70) as the electrolyte solution. The dissolved one was used. As the positive / negative separator, a film made of polyethylene (PE) resin having a thickness of 20 μm was used.
比較例２
比較例１で作製した負極を用いる以外は、実施例２と同一の方法でリチウム二次電池を作製した。
Comparative Example 2
A lithium secondary battery was produced in the same manner as in Example 2 except that the negative electrode produced in Comparative Example 1 was used.
実施例２および比較例２で得られたリチウム二次電池について、先ずは４ｍＡと８ｍＡの定電流にて２．０Ｖまでの放電容量を測定し、４ｍＡ時の容量に対する８ｍＡ時の容量比率を算出した。
次いで、それぞれの電池を５０％充電した状態に調整し、それぞれ４ｍＡ、８ｍＡ、１２ｍＡで回路解放時から１０秒間だけ放電し、１０秒後の電圧を測定して、それぞれの放電電流時の開路電圧からの電圧降下に対する電流値との関係をプロットしたＩ−Ｖ特性直線から、直線の傾きを最小二乗法にて算出した値を求め、これを電池の５０％充電時の直流抵抗値とした。それぞれの試験結果を表１、表２にまとめた。
For the lithium secondary batteries obtained in Example 2 and Comparative Example 2, first, the discharge capacity up to 2.0 V was measured at a constant current of 4 mA and 8 mA, and the capacity ratio at 8 mA to the capacity at 4 mA was calculated. did.
Next, each battery was adjusted to 50% charged state, discharged at 4 mA, 8 mA, and 12 mA for 10 seconds after the circuit was released. The voltage after 10 seconds was measured, and the open circuit voltage at each discharge current. A value obtained by calculating the slope of the straight line by the least square method was obtained from an IV characteristic line in which the relationship between the voltage drop from the current and the current value was plotted, and this was used as the direct current resistance value when the battery was charged at 50%. The test results are summarized in Tables 1 and 2.
表１および表２より、実施例２に示すように、負極箔にカーボンコートしたアルミニウム箔を用いた場合でも比較例２の銅箔を用いたものと同様に、電池特性が得られることがわかり、この結果アルミニウム箔による軽量化とコスト低減化の電池を提供可能となった。これはチタン酸リチウムを負極主材として用いた電池で集電体にアルミニウム箔を用いた場合のように、チタン酸リチウムのアノード酸化反応が１．５Ｖ（Ｖ vs. Ｌｉ＋／Ｌｉ）近傍でアルミニウムが溶出する電位から極めて卑であることより、アルミニウム箔を集電体として用いることの理論とは異なり、正極から充電反応時、リチウムイオンが負極炭素材表面に拡散してきた際、リチウムイオンは炭素材内にインターカレートしてアルミニウム箔は、還元反応であるために溶出しない。
また一部のリチウムイオンはアルミニウム箔表面のカーボンコート層を拡散してアルミニウム材に到達して金属リチウムとして析出しても、金属アルミニウム原子内に拡散してＬｉＡｌ合金となる。ＬｉＡｌ合金は状態図上、自由な配合比で合金化するので内部拡散したＬｉイオン量に規制はない。しかし、カーボンコートすることによりこの部分でリチウムイオンがインターカレートすることとなり、さらに基材であるアルミニウム元素部分に到達する量は極めて規制され、安全性に関わる金属リチウムの析出は防止できる。一方、放電時はこれらの炭素材内のリチウムや合金化したリチウムがイオン化して正極へ拡散する。この際の負極酸化反応電位は０．４Ｖ（Ｖ.ｖｓ. Ｌｉ＋／Ｌｉ）であり、リチウム金属析出の電位よりも卑であるので、金属リチウムとして安定に析出せず、アルミニウム箔が銅箔の代替え箔として使用でき得るものと考える。
From Table 1 and Table 2, as shown in Example 2, it can be seen that even when a carbon-coated aluminum foil is used for the negative electrode foil, battery characteristics can be obtained as in the case of using the copper foil of Comparative Example 2. As a result, it has become possible to provide a battery that is reduced in weight and cost by aluminum foil. This is because a battery using lithium titanate as a negative electrode main material and an aluminum foil is used as a current collector, the anodic oxidation reaction of lithium titanate is aluminum in the vicinity of 1.5 V (V vs. Li + / Li). Unlike the theory of using an aluminum foil as a current collector, the lithium ion diffuses to the surface of the negative electrode carbon material during the charging reaction from the positive electrode. The aluminum foil intercalated in the material does not elute because it is a reduction reaction.
Even if some lithium ions diffuse through the carbon coat layer on the surface of the aluminum foil to reach the aluminum material and precipitate as metallic lithium, they diffuse into metallic aluminum atoms to form a LiAl alloy. Since the LiAl alloy is alloyed at a free blending ratio on the phase diagram, there is no restriction on the amount of Li ions diffused internally. However, the carbon coating causes lithium ions to intercalate at this portion, and the amount reaching the aluminum element portion as the base material is extremely restricted, so that precipitation of metallic lithium related to safety can be prevented. On the other hand, during discharge, lithium in these carbon materials and alloyed lithium are ionized and diffused to the positive electrode. The negative electrode oxidation reaction potential at this time is 0.4 V (V.vs. Li + / Li), which is lower than the potential for lithium metal deposition, so that it does not deposit stably as metallic lithium, and the aluminum foil is a copper foil. It can be used as a substitute foil.
このような本発明のアルミニウム箔は、主材とした炭素材を塗布しないカーボンコートアルミニウム箔のみでも同様な結果が得られた。また、アルミニウム箔をパンチングや突起状の穴あけ加工等を施しても同等以上の効果が得られた。 Similar results were obtained with such an aluminum foil of the present invention using only a carbon-coated aluminum foil without applying a carbon material as a main material. Moreover, even if the aluminum foil was subjected to punching or projecting drilling, the same or better effect was obtained.
本発明のリチウム二次電池の負極電極材は、アルミニウムを負極集電材として使用するために軽量かつ低コストの車載等の産業用電池への展開が可能となった。 Since the negative electrode material of the lithium secondary battery of the present invention uses aluminum as a negative electrode current collector, it has become possible to develop it into a lightweight and low-cost industrial battery such as a vehicle.
Claims (4)
前記集電体は、表面に導電性カーボン被覆層を有する金属箔であり、集電を担う該金属箔の一部にアルミニウムを用いることを特徴とするリチウム二次電池用負極電極板。 In the negative electrode plate for a lithium secondary battery in which the negative electrode active material is disposed on at least one main surface of the current collector,
The negative electrode plate for a lithium secondary battery, wherein the current collector is a metal foil having a conductive carbon coating layer on a surface thereof, and aluminum is used as a part of the metal foil responsible for current collection.
前記負極が請求項３記載のリチウム二次電池用負極であることを特徴とするリチウム二次電池。 In a lithium secondary battery in which an organic electrolyte is infiltrated or immersed in a group of electrodes wound or laminated through a separator between a positive electrode and a negative electrode, and lithium ions are repeatedly occluded and released,
The lithium secondary battery according to claim 3, wherein the negative electrode is a negative electrode for a lithium secondary battery.
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