JP2016201174A - Negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents
Negative electrode for lithium ion secondary battery and lithium ion secondary battery Download PDFInfo
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Abstract
Description
本発明は、リチウムイオン二次電池負極及びリチウムイオン二次電池に関し、特に結着剤を含まなくても集電体との高い密着力と高出力を供する負極に関する。 The present invention relates to a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery, and more particularly to a negative electrode that provides high adhesion to a current collector and high output even without a binder.
ノート型コンピュータ、スマートフォンに代表される携帯電話、タブレット等電子機器の高機能化の進展に伴い、電子機器の消費電力が増大していること、電子機器に小型化が求められていることから、二次電池に対して高エネルギー密度、高出力化が求められている。また、近年、マイクロハイブリッド車、ハイブリッド車などの車載用途としての需要も増えており、高エネルギー密度、高出力化が更に求められている。そして、これらの要求を満たす二次電池として最も有力であるものが、リチウムイオン二次電池である。 With the progress of higher functionality of electronic devices such as notebook computers, mobile phones represented by smartphones, tablets, etc., the power consumption of electronic devices is increasing, and downsizing of electronic devices is required. High energy density and high output are required for secondary batteries. In recent years, demand for in-vehicle applications such as micro hybrid vehicles and hybrid vehicles has increased, and higher energy density and higher output are further demanded. And what is most prominent as a secondary battery which satisfy | fills these requirements is a lithium ion secondary battery.
一般に用いられているリチウムイオン二次電池は、正負電極、電解液、セパレータ
、集電体、外装材から構成され、前記正負電極はそれぞれ正極活物質と負極活物質、導電助材、結着剤等を含む、いわゆる電極材料として集電体上に形成される。
A commonly used lithium ion secondary battery is composed of positive and negative electrodes, an electrolyte, a separator, a current collector, and an exterior material. The positive and negative electrodes are a positive electrode active material, a negative electrode active material, a conductive additive, and a binder, respectively. Are formed on the current collector as a so-called electrode material.
リチウムイオン二次電池の高出力化の対策としては、リチウムイオンの電極材料間（電極層内）の移動を高速化するために、電極の薄膜化や絶縁性を呈する結着剤の低減といった対策が以前から知られている。 As measures to increase the output of lithium ion secondary batteries, measures such as reducing the thickness of the electrodes and reducing the binder that exhibits insulating properties to speed up the movement of lithium ion between electrode materials (within the electrode layer) Has been known for some time.
例えば、対策として特許文献１では、活物質の原料塗液を集電体に塗布し、それを高温で焼結することで結着剤の無い電極層作製方法が開示されている。しかしながら、特許文献１では、原料塗工後のオーブン内での活物質作製時に、高温焼結という時間、コストのかかる工程が必要であり、生産性、コスト、商品化の実現性の低さ等が問題としてある。 For example, Patent Document 1 discloses a method for producing an electrode layer without a binder by applying a raw material coating solution of an active material to a current collector and sintering it at a high temperature as a countermeasure. However, in Patent Document 1, a time-consuming and costly process of high-temperature sintering is required when preparing an active material in an oven after raw material coating, and productivity, cost, low feasibility of commercialization, etc. There is a problem.
また、特許文献２では、蒸着法により薄膜化をし、高出力電池を作製する手法が開示されているが、蒸着法で電極層を作製するため、従来のウエットプロセスと比較して生産コストが上がるという問題がある。 Further, Patent Document 2 discloses a method for producing a high-power battery by thinning by vapor deposition, but since the electrode layer is produced by vapor deposition, the production cost is lower than that of a conventional wet process. There is a problem of going up.
一方、マイクロハイブリッド車などの従来以上の高出力化が要求される電池電極においては、さらに薄膜化することや結着剤を低減することにより、より一層の電極層内のリチウムイオン移動の高速化や抵抗低減を実現する必要がある。そのためには、極限の薄膜化（電極層中の全ての粒子が、粒子表面の一部分で負極集電体と接しているような薄い膜厚の電極層の作製）と絶縁性である結着剤フリーの電極層の作製が必要であった。しかしながら、従来技術では、極限の薄膜化を実現したとしても、材料同士をつなぎ、かつ、集電体と材料の密着性を持たせる結着剤の存在は必要不可欠であり、極めて難解な問題である。 On the other hand, in battery electrodes that require higher output than before, such as micro-hybrid vehicles, the speed of lithium ion movement in the electrode layer is further increased by making the film thinner and reducing the binder. It is necessary to reduce resistance. For this purpose, an extremely thin film (production of a thin electrode layer in which all particles in the electrode layer are in contact with the negative electrode current collector at a part of the particle surface) and an insulating binder It was necessary to prepare a free electrode layer. However, in the prior art, even if an extremely thin film is realized, it is indispensable to have a binder that connects the materials and provides adhesion between the current collector and the material. is there.
本発明は、負極の製造工程を煩雑化することなく、低コストで密着力に優れ、高出力を
呈するリチウムイオン二次電池負極とそれを具備したリチウムイオン二次電池の提供を目的とする。
An object of the present invention is to provide a lithium ion secondary battery negative electrode that is excellent in adhesion, low cost, and exhibits high output without complicating the negative electrode manufacturing process, and a lithium ion secondary battery including the lithium ion secondary battery.
本発明の請求項１に係る発明は、表面に突起物を有する負極集電体上に粒子状の負極活物質が形成されてなるリチウムイオン二次電池負極であって、
粒子状の全ての負極活物質は、少なくともその粒子表面の一部分が負極集電体と接していることを特徴とするリチウムイオン二次電池負極である。
The invention according to claim 1 of the present invention is a lithium ion secondary battery negative electrode in which a particulate negative electrode active material is formed on a negative electrode current collector having protrusions on its surface,
All the particulate negative electrode active materials are negative electrodes for lithium ion secondary batteries, wherein at least a part of the particle surface is in contact with the negative electrode current collector.
また、請求項２に係る発明は、前記突起物の形状は円錐または円柱からなり、その底辺の直径が１μｍ以上で、且つ負極活物質の粒径以下であることを特徴とする請求項１に記載のリチウムイオン二次電池負極である。 The invention according to claim 2 is characterized in that the shape of the protrusion is a cone or a cylinder, the diameter of the base is 1 μm or more and the particle diameter of the negative electrode active material or less. It is a lithium ion secondary battery negative electrode of description.
また、請求項３に係る発明は、前記突起物の高さが負極活物質の粒径の半分以上であることを特徴とする請求項１または２に記載のリチウムイオン二次電池負極である。 The invention according to claim 3 is the lithium ion secondary battery negative electrode according to claim 1 or 2, wherein the height of the protrusion is at least half of the particle size of the negative electrode active material.
また、請求項４に係る発明は、前記突起物はそれぞれの隣接する間隔が１μｍ以上の等間隔で、且つ、負極活物質の粒径の２倍以下で配置されたことを特徴とする請求項１〜３のいずれかに記載のリチウムイオン二次電池負極である。 The invention according to claim 4 is characterized in that the protrusions are arranged at equal intervals of 1 μm or more and less than twice the particle size of the negative electrode active material. It is a lithium ion secondary battery negative electrode in any one of 1-3.
また、請求項５に係る発明は、請求項１〜４のいずれかに記載のリチウムイオン二次電池負極を具備したリチウムイオン二次電池である。 Moreover, the invention which concerns on Claim 5 is a lithium ion secondary battery which comprised the lithium ion secondary battery negative electrode in any one of Claims 1-4.
請求項１に記載の発明によれば、負極集電体の表面に突起物を有し、また負極活物質が粒子状であることにより、双方の表面積が大きくなり、粒子状の全ての負極活物質は少なくともその一部分が負極集電体と接することができる。また、負極集電体の表面に突起物を有することで、粒状の負極活物質が突起物に絡みつき（アンカー効果）、密着性が向上する。これらの結果、従来、密着性向上の目的で含有されていた結着剤がなくても密着性の向上が可能となり、且つ、その分抵抗値の低減が可能となり高出力が可能な電極を提供することができる。 According to the first aspect of the present invention, since the negative electrode current collector has protrusions on the surface and the negative electrode active material is in the form of particles, both surface areas are increased, and all the negative electrode active materials in the form of particles are formed. At least a part of the substance can be in contact with the negative electrode current collector. Moreover, by having a protrusion on the surface of the negative electrode current collector, the granular negative electrode active material is entangled with the protrusion (anchor effect), and adhesion is improved. As a result, it is possible to improve the adhesion without the binder that has been included for the purpose of improving the adhesion, and to provide an electrode capable of reducing the resistance value and high output. can do.
また、請求項２に記載の発明によれば、前記突起物の形状が円錐または円柱からなり、その底辺の直径が１μｍ以上で、且つ負極活物質の粒径以下であることにより、負極活物質を固化（プレス）して電極層を形成する際に、突起物が負極活物質で覆われるため電極としての機能を損なうことがなく、高い出力を呈することができる。 According to the invention described in claim 2, the shape of the protrusion is a cone or a cylinder, and the diameter of the base is 1 μm or more and not more than the particle size of the negative electrode active material. When the electrode layer is formed by solidifying (pressing) the protrusion, the protrusion is covered with the negative electrode active material, so that the function as an electrode is not impaired and high output can be exhibited.
また、請求項３に記載の発明によれば、前記突起物の高さが負極活物質の粒径の半分以上であれば、負極活物質を突起物中に絡みつくアンカー効果が有効に働き、結着剤がなくても固化後の密着性を向上することができる。 According to the invention described in claim 3, if the height of the protrusion is more than half of the particle size of the negative electrode active material, the anchor effect that entangles the negative electrode active material in the protrusion works effectively. Even if there is no adhesive, the adhesiveness after solidification can be improved.
また、請求項４に記載の発明によれば、前記突起物のそれぞれの隣接する間隔を１μｍ以上の等間隔で、且つ、負極活物質の粒径の２倍以下に配置することでアンカー効果が有効に働き、結着剤がなくても固化後の密着性を向上することができる。 According to the invention described in claim 4, the anchor effect is obtained by arranging the adjacent intervals of the protrusions at equal intervals of 1 μm or more and not more than twice the particle size of the negative electrode active material. It works effectively and can improve the adhesion after solidification even without a binder.
また、請求項５に記載の発明によれば、請求項１〜４のいずれかに記載のリチウムイオン二次電池負極を具備することで、高出力を呈するリチウムイオン二次電池を提供することができる。 According to the invention described in claim 5, by providing the lithium ion secondary battery negative electrode according to any one of claims 1 to 4, it is possible to provide a lithium ion secondary battery exhibiting high output. it can.
本発明によれば、負極の製造工程を煩雑化することなく、低コストで密着力に優れ、高
出力を呈するリチウムイオン二次電池負極とそれを具備したリチウムイオン二次電池の提供が可能となる。
According to the present invention, it is possible to provide a lithium ion secondary battery negative electrode that exhibits low power, excellent adhesion, and high output without complicating the negative electrode manufacturing process, and a lithium ion secondary battery including the lithium ion secondary battery. Become.
以下、本発明のリチウムイオン二次電池負極及びそれを具備したリチウムイオン二次電池について図に基づき具体的に説明する。 Hereinafter, the lithium ion secondary battery negative electrode of the present invention and the lithium ion secondary battery including the same will be specifically described with reference to the drawings.
図１に示すように、本発明に係るリチウムイオン二次電池負極は、表面に突起物２を有する負極集電体１に、粒子状の負極活物質３が形成されて、且つ粒子状の全ての負極活物質３の粒子表面の一部分が負極集電体１に接していることを特徴とするリチウムイオン二次電池負極である。 As shown in FIG. 1, a lithium ion secondary battery negative electrode according to the present invention includes a negative electrode current collector 1 having protrusions 2 on the surface, a particulate negative electrode active material 3 formed thereon, and all the particulate particles. A portion of the particle surface of the negative electrode active material 3 is in contact with the negative electrode current collector 1. This is a lithium ion secondary battery negative electrode.
（負極）
負極に含まれる負極活物質３は、粒子状で電気抵抗が小さいものであれば特に限定されるものではなくが、例えば、リチウム等の金属材料、ケイ素、スズ等を含有する合金系材料、グラファイト、コークス等の炭素材料のような、リチウムイオンを吸蔵・放出できる化合物を単独または組み合わせて用いることができる。
(Negative electrode)
The negative electrode active material 3 contained in the negative electrode is not particularly limited as long as it is particulate and has a small electric resistance. For example, a metal material such as lithium, an alloy-based material containing silicon, tin, etc., graphite A compound capable of inserting and extracting lithium ions, such as a carbon material such as coke, can be used alone or in combination.
また、粒子状の負極活物質３の粒径は、後述する突起物２の形成加工のし易さや密着力向上に係るアンカー効果を考慮して、メジアン径（Ｄ５０）で１μｍ〜１００μｍが好ましい。なお、メジアン径（Ｄ５０）とは、粉体のある粒子径から二つに分けたとき、大きい側と小さい側とが等量となる粒子径を意味している。 In addition, the particle size of the particulate negative electrode active material 3 is preferably 1 μm to 100 μm in terms of median diameter (D50) in consideration of the ease of forming the protrusions 2 described later and the anchor effect related to improvement in adhesion. The median diameter (D50) means a particle diameter in which the larger side and the smaller side are equivalent when divided from a certain particle diameter of the powder into two.
負極活物質３としてリチウム金属箔を用いる場合、銅等の金属集電体上にリチウム箔を圧着して形成することができる。また負極活物質として合金材料、炭素材料を用いる場合は、負極活物質と結着材、導電助剤等を水、ＮＭＰ等の溶媒中で混合した後、銅等の金属集電体上に塗布、乾燥することで形成することができる。なお、結着材を用いた場合においては、最終的に結着材を電極層から取り除くことが必要であり、例えば乾燥工程により結着材を昇華させて除去することができる。 When a lithium metal foil is used as the negative electrode active material 3, it can be formed by pressure bonding a lithium foil on a metal current collector such as copper. When using an alloy material or carbon material as the negative electrode active material, the negative electrode active material, a binder, a conductive additive, etc. are mixed in a solvent such as water or NMP, and then applied onto a metal current collector such as copper. It can be formed by drying. In the case where the binder is used, it is necessary to finally remove the binder from the electrode layer. For example, the binder can be removed by sublimation by a drying process.
負極集電体１は、集電性に優れ、かつ、集電体加工時の応力に耐え得るだけの機械強度を持つものが良く。銅箔、ステンレス製の箔などから成る集電体を使用することができる。 The negative electrode current collector 1 preferably has excellent current collecting properties and has sufficient mechanical strength to withstand the stress during current collector processing. A current collector made of copper foil, stainless steel foil, or the like can be used.
負極集電体１の厚みは、集電体加工時の応力に耐え得るだけの機械強度を持ち、かつ、電池容量の大幅な低下を招かない厚みが好ましく、２０μｍ以下が好ましい。さらに好ましくは１５μｍ以下である。厚みが２０μｍを超える集電体は、電池の体積エネルギー密度を下げるといった観点から好ましくない。 The thickness of the negative electrode current collector 1 is preferably a thickness that has sufficient mechanical strength to withstand the stress during current collector processing and does not cause a significant decrease in battery capacity, and is preferably 20 μm or less. More preferably, it is 15 μm or less. A current collector having a thickness exceeding 20 μm is not preferable from the viewpoint of reducing the volumetric energy density of the battery.
負極集電体１の表面に形成される突起物２の形状は、粒子状の負極活物質３を塗布、乾燥した後のプレス加工においてに、前記負極活物質３が突起物２に引っかかりアンカー効果を有するものであれば特に限定するものではないが、中でも負極集電体１に接する底部
が円形である円錐や円柱は形成のし易さから好ましい。
The shape of the protrusions 2 formed on the surface of the negative electrode current collector 1 is that the negative electrode active material 3 is caught by the protrusions 2 in the pressing process after the particulate negative electrode active material 3 is applied and dried, and the anchor effect In particular, a cone or cylinder having a circular bottom portion in contact with the negative electrode current collector 1 is preferable because it is easy to form.
以下、図２に示す負極の製造プロセスを説明する。 Hereinafter, the manufacturing process of the negative electrode shown in FIG. 2 will be described.
図２（ａ）に示すように、負極集電体１の表面に突起物２を形成する。次に、図２（ｂ）に示すように、表面に突起物２が形成された負極集電体１の全面に、粒子状の負極活物質３を塗布、乾燥して仮に負極の電極層を形成する。その後さらにプレスにより前記電極層を押しつぶして、図２（ｃ）に示すように、粒子状の負極活物質３の全てがその一部を負極集電体１に接触した状態で電極層が形成される。 As shown in FIG. 2A, the protrusion 2 is formed on the surface of the negative electrode current collector 1. Next, as shown in FIG. 2 (b), a particulate negative electrode active material 3 is applied to the entire surface of the negative electrode current collector 1 having protrusions 2 formed on the surface, and dried to temporarily form a negative electrode layer. Form. Thereafter, the electrode layer is further crushed by pressing, and as shown in FIG. 2C, the electrode layer is formed in a state where all of the particulate negative electrode active material 3 is in contact with the negative electrode current collector 1. The
突起物２を形成する方法としては、突起物２が等間隔に形成される方法であれば特に限定されず、エッチング法、めっき法、研磨法などが挙げられる。また、突起物２に用いる材料としては、集電性に優れ、加工時の応力に耐え得る強度を有する材料であれば特に限定するものではないが、加工性や品質を考慮すると負極集電体１と同一の材料を用いることが好ましい。 The method for forming the protrusions 2 is not particularly limited as long as the protrusions 2 are formed at equal intervals, and examples thereof include an etching method, a plating method, and a polishing method. Further, the material used for the protrusions 2 is not particularly limited as long as it has excellent current collecting property and has strength that can withstand stress during processing. However, in consideration of workability and quality, the negative electrode current collector 1 is preferably used.
例えば、めっき法により突起物２を形成する場合には、金属物質であり、かつＬｉ参照極に対する電位が０Ｖ付近でも溶解しない材料が好ましく、銅、ニッケル、金、銀等が好ましい。コスト面から、銅、ニッケルが特に好ましい。 For example, when the protrusion 2 is formed by plating, a material that is a metal substance and does not dissolve even when the potential with respect to the Li reference electrode is around 0 V is preferable, and copper, nickel, gold, silver, or the like is preferable. In view of cost, copper and nickel are particularly preferable.
以下、突起物２の形状が円錐または円柱である場合を例に、本発明をより詳細に説明する。 Hereinafter, the present invention will be described in more detail using a case where the shape of the protrusion 2 is a cone or a cylinder as an example.
前記突起物２の底辺の直径は、１μｍ以上かつ負極活物質３の直径以下の大きさが好ましい。突起物２の底辺の直径が１μｍ未満では、突起物２の機械強度が弱く、アンカー効果が十分に発揮されない。また、突起物２の底辺の直径が負極活物質の直径よりも大きいと、負極活物質３が突起物２に乗った際に十分なアンカー効果が発揮されず、負極活物質３が負極集電体１から滑落する可能性があり品質が低下する恐れがある。 The diameter of the bottom of the protrusion 2 is preferably 1 μm or more and not more than the diameter of the negative electrode active material 3. If the diameter of the base of the protrusion 2 is less than 1 μm, the mechanical strength of the protrusion 2 is weak and the anchor effect is not sufficiently exhibited. Further, if the diameter of the bottom of the protrusion 2 is larger than the diameter of the negative electrode active material, a sufficient anchor effect is not exhibited when the negative electrode active material 3 rides on the protrusion 2, and the negative electrode active material 3 becomes negative electrode current collector. There is a possibility of sliding off from the body 1, and there is a risk that the quality will deteriorate.
突起物２の高さは、めっき法で形成する場合には、負極活物質３の直径の半分以上であれば特に限定は無い。負極活物質３の直径の半分未満では、アンカー効果が十分に発揮されない。また、エッチング法や研磨法で形成する場合には、負極集電体１の機械強度を著しく落とすものではないことが好ましく、５μｍ以下が好ましい。 The height of the protrusion 2 is not particularly limited as long as it is formed by a plating method as long as it is at least half the diameter of the negative electrode active material 3. If it is less than half the diameter of the negative electrode active material 3, the anchor effect is not sufficiently exhibited. Moreover, when forming by an etching method or a grinding | polishing method, it is preferable that the mechanical strength of the negative electrode electrical power collector 1 is not reduced significantly, and 5 micrometers or less are preferable.
突起物２間の間隔は１μｍ以上かつ負極活物質３の直径の２倍以下であることが好ましい。間隔が１μｍ未満だと、負極活物質３が突起物２に引っかからず十分なアンカー効果が発揮されない。直径の２倍より長い間隔だと、負極活物質３が突起物の無い部分に乗った際に十分なアンカー効果が発揮されず、負極活物質３が負極集電体１から滑落する可能性があり品質が低下する恐れがある。 The interval between the protrusions 2 is preferably 1 μm or more and not more than twice the diameter of the negative electrode active material 3. When the distance is less than 1 μm, the negative electrode active material 3 is not caught by the protrusions 2 and a sufficient anchor effect is not exhibited. If the interval is longer than twice the diameter, a sufficient anchor effect is not exhibited when the negative electrode active material 3 rides on a portion where there is no protrusion, and the negative electrode active material 3 may slide down from the negative electrode current collector 1. There is a risk of quality degradation.
次に、図３、４に示すリチウムイオン二次電池の作製について以下に説明する。 Next, the production of the lithium ion secondary battery shown in FIGS. 3 and 4 will be described below.
前記正極、負極、非水電解液、セパレータ７を、電解液の漏洩防止、外気進入の防止等を目的としたアルミニウムやステンレス製の角型または円筒型の容器、あるいはアルミラミネートフィルムのような容器に収納して、リチウムイオン二次電池を作製することができる。 The positive electrode, the negative electrode, the non-aqueous electrolyte, and the separator 7 are made of aluminum or stainless steel square or cylindrical containers or containers such as an aluminum laminate film for the purpose of preventing leakage of the electrolyte, preventing the ingress of outside air, and the like. The lithium ion secondary battery can be manufactured.
電極と容器の端子をつなぐタブは特に限定されるものではなく、正極タブ９にはアルミニウム、ステンレス、ニッケル等を、負極タブ１０には銅、ニッケル等を使用することが出来る。正極タブ９及び負極タブ１０にはシーラント８と呼ばれる変性ポリプロピレンで
出来た樹脂が付随しており、電池素子が収納される金属性の容器やアルミラミネートフィルム１１との間の絶縁性を保っている。
The tab that connects the electrode and the terminal of the container is not particularly limited. Aluminum, stainless steel, nickel, or the like can be used for the positive electrode tab 9, and copper, nickel, or the like can be used for the negative electrode tab 10. Resin made of modified polypropylene called sealant 8 is attached to the positive electrode tab 9 and the negative electrode tab 10, and insulation between the metallic container in which the battery element is stored and the aluminum laminate film 11 is maintained. .
本発明に係るリチウムイオン二次電池に用いる負極以外の他の主要な部材について以下に説明する。 Other main members other than the negative electrode used in the lithium ion secondary battery according to the present invention will be described below.
電解液としては、特に限定されるものではなく、有機溶媒などの溶媒に支持塩を溶解させたもの、電解質兼溶媒であるイオン液体、そのイオン液体に更に支持塩を溶解させたもの等を挙げることができる。 The electrolytic solution is not particularly limited, and examples thereof include a solution in which a supporting salt is dissolved in a solvent such as an organic solvent, an ionic liquid that is an electrolyte and solvent, and a solution in which a supporting salt is further dissolved in the ionic liquid. be able to.
有機溶媒としては、カーボネート類、ハロゲン化炭化水素、エーテル類、ケトン類、ニトリル類、ラクトン類、オキソラン化合物等を用いることができる。また、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート等の混合溶媒を用いることもできる。 As the organic solvent, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane compounds and the like can be used. A mixed solvent such as propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate can also be used.
支持塩は特に限定されるものではなく、例えばＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＮ（ＦＳＯ２）２、ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ４Ｆ９ＳＯ２）、ＬｉＮ（ＣＦ３ＳＯ２）２等を挙げることができる。 The supporting salt is not particularly limited. For example, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiN (FSO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), mention may be made of LiN (CF 3 SO 2) 2 and the like.
また、イオン液体も常温で液体である塩であれば特に限定されるものではなく、例えばアルキルアンモニウム塩、ピロリジニウム塩、ピラゾリウム塩、ピペリジニウム塩、イミダゾリウム塩、ピリジニウム塩、スルホニウム塩、ホスホニウム塩などを挙げることがはできる。また、広い電位領域において電気化学的に安定であると更に好ましい。 In addition, the ionic liquid is not particularly limited as long as it is a salt that is liquid at room temperature. I can list them. Further, it is more preferable that it is electrochemically stable in a wide potential region.
次に正極について説明する。正極集電体５にはアルミニウムから成る集電体を使用することができ、正極材料としては正極活物質、結着剤、導電剤等をＮ−メチルピロリドンなどの溶媒中で混合した後、集電体上に積層塗布、乾燥することで形成することができる。 Next, the positive electrode will be described. As the positive electrode current collector 5, a current collector made of aluminum can be used. As a positive electrode material, a positive electrode active material, a binder, a conductive agent, and the like are mixed in a solvent such as N-methylpyrrolidone, and then collected. It can be formed by laminating and drying on an electric body.
また、正極活物質としては、特に限定されるものではなく、従来公知の活物質を使用することが出来る。例えばリチウムイオンを放出出来るリチウム遷移金属複合酸化物を挙げることができて、その一例として、ＬｉＮｉＯ２、ＬｉＭｎＯ２、ＬｉＣｏＯ２、ＬｉＦｅＰＯ４等を挙げることができる。また、上記リチウム遷移金属酸化物を複数混合して使用することもできる。 Moreover, it does not specifically limit as a positive electrode active material, A conventionally well-known active material can be used. For example, a lithium transition metal composite oxide capable of releasing lithium ions can be mentioned, and examples thereof include LiNiO 2 , LiMnO 2 , LiCoO 2 , LiFePO 4, and the like. Further, a plurality of lithium transition metal oxides may be mixed and used.
正極結着材は、ポリフッ化ビニリデン、ポリテトラフルオロエチレン等の化学的、物理的に安定な材料が好ましい。また、導電助剤は、ケッチェンブラック、アセチレンブラック、カーボンブラック、グラファイト、カーボンナノチューブ、非晶質炭素等を挙げることができる。 The positive electrode binder is preferably a chemically and physically stable material such as polyvinylidene fluoride or polytetrafluoroethylene. Examples of the conductive assistant include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon.
低温昇華樹脂は、一時的に負極電極層の結着性を有し、かつ、４００℃以下で昇華する樹脂が好ましく、ブチラール、エチルセルロース、カルボキシメチルセルロース、変性ポリカーボネート等が挙げられる。低温昇華といった観点から、変性ポリカーボネートが特に好ましい。 The low-temperature sublimation resin is preferably a resin that temporarily has a binding property to the negative electrode layer and sublimates at 400 ° C. or lower, and examples thereof include butyral, ethyl cellulose, carboxymethyl cellulose, and modified polycarbonate. From the viewpoint of low temperature sublimation, modified polycarbonate is particularly preferred.
また、導電剤としては、例えばアセチレンブラック、ケッチェンブラック、カーボンブラック、グラファイト、カーボンナノチューブ等の公知の材料を使用することができる。 Moreover, as a electrically conductive agent, well-known materials, such as acetylene black, ketjen black, carbon black, a graphite, a carbon nanotube, can be used, for example.
また、正極と負極との接触を防止するためのセパレータとしては、ポリエチレン、ポリ
プロピレンなどのポリオレフィン製や芳香族ポリアミド樹脂製の微孔膜または不織布、無機セラミック粉末を含む多孔質の樹脂コートなどを挙げることができる。
Examples of the separator for preventing contact between the positive electrode and the negative electrode include microporous membranes or non-woven fabrics made of polyolefins such as polyethylene and polypropylene and aromatic polyamide resins, and porous resin coats containing inorganic ceramic powders. be able to.
以下、実施例を用いて本発明を説明する。 Hereinafter, the present invention will be described using examples.
（実施例１）
(正極の作製)
ＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２（日本化学産業製）８９質量部、アセチレンブラック（ＨＳ−１００，電気化学工業製）３質量部、ポリフッ化ビニリデン（♯７２００，クレハ・バッテリー・マテリアルズ・ジャパン製）３質量部をＮＭＰに添加し、分散処理を行い、均質なペーストを調製した。このペーストをアルミニウム集電体上にダイコーターで塗布し、乾燥処理を行った。乾燥処理後の正極電極層の片面の目付け量は２９．５ｇ／ｍ２であった。次に、正極電極層の密度が約２．９ｇ/ｃｍ３になるように、ロールプレス機で加圧処理して正極を作製した。
Example 1
(Preparation of positive electrode)
89 parts by mass of LiNi 0.5 Co 0.2 Mn 0.3 O 2 (manufactured by Nippon Chemical Industry), 3 parts by mass of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo), polyvinylidene fluoride (# 7200, Kureha Battery) (Made by Materials Japan) 3 parts by mass was added to NMP and dispersed to prepare a homogeneous paste. This paste was applied onto an aluminum current collector with a die coater and dried. The basis weight of one surface of the positive electrode layer after the drying treatment was 29.5 g / m 2 . Next, a positive electrode was produced by pressure treatment with a roll press so that the density of the positive electrode layer was about 2.9 g / cm 3 .
(負極の作製)
負極集電体として厚さ１２μｍの未処理の電解銅箔を使用した。次に、この未処理の電解銅箔上に、硬化後の膜厚が２０μｍとなるようにレジストを塗布し、フォトリソグラフィー法によりマスク露光、現像して、凹部の底部径８μｍの円柱を間隔２０μｍとなるようにパターニングした。その後、上記で形成したレジスト凹部に銅ペーストを充填し、焼結してレジスト除去し、円柱状の突起物を有する負極集電体を作製した。
(Preparation of negative electrode)
An untreated electrolytic copper foil having a thickness of 12 μm was used as the negative electrode current collector. Next, a resist is coated on the untreated electrolytic copper foil so that the film thickness after curing is 20 μm, and mask exposure and development are performed by a photolithography method, and a column having a bottom diameter of 8 μm is formed at intervals of 20 μm. It patterned so that it might become. Thereafter, the resist recesses formed above were filled with a copper paste and sintered to remove the resist, thereby producing a negative electrode current collector having cylindrical protrusions.
別途、負極活物質として球状天然黒鉛（ＳＭＧ，日立化成製）９０質量部、導電助剤として塊状人造黒鉛（ＳＦＧ−６，ＴＩＭＣＡＬ製）７質量部、一時的な結着剤として、変性ポリカーボネートを２部水に投入し、分散処理を行い、負極電極層形成用の均一なペーストを調製した。 Separately, 90 parts by mass of spherical natural graphite (SMG, manufactured by Hitachi Chemical Co., Ltd.) as the negative electrode active material, 7 parts by mass of massive artificial graphite (SFG-6, manufactured by TIMCAL) as the conductive additive, and modified polycarbonate as a temporary binder. 2 parts of water was added and dispersion treatment was performed to prepare a uniform paste for forming the negative electrode layer.
次に、作製した負極集電体の突起物側の全面に、ダイコーターを用いて上記ペーストを塗布、乾燥して負極電極層を得た。なお、乾燥後の塗布量は１０．８ｇ／ｍ２であった。
その後、負極電極層の密度が約１．３ｇ/ｃｍ３になるようにロールプレス機で加圧処理した。その後、熱風乾燥オーブン（１２０℃）を用いて、一時的な結着剤として用いた変性ポリカーボネートを負極電極層から除去（昇華）した。
Next, the paste was applied to the entire surface of the produced negative electrode current collector on the protrusion side using a die coater and dried to obtain a negative electrode layer. The coating amount after drying was 10.8 g / m 2 .
Then, it pressed with the roll press machine so that the density of a negative electrode layer might be about 1.3 g / cm < 3 >. Thereafter, the modified polycarbonate used as a temporary binder was removed (sublimated) from the negative electrode layer using a hot air drying oven (120 ° C.).
(ラミネートタイプのリチウムイオン二次電池の作製)
得られた正極は図５、負極は図６に示すように打ち抜いた。尚、正極寸法は６０ｍｍ×８０ｍｍとし、端部１０ｍｍ×８０ｍｍは集電体部とした。負極寸法は６２ｍｍ×８２ｍｍとし、端部１２ｍｍ×８２ｍｍは集電体部とした。
作製した各電極は、ポリエチレン製セパレータ（ハイポア，旭化成イーマテリアルズ製）で包み、各電極を図４に示すような形で積層し、タブ付けして１体の電極体とした。正極にはアルミニウムタブ（４ｍｍ×９２ｍｍ、厚み１５０μｍ）を、負極にはニッケルタブ（４ｍｍ×９２ｍｍ、厚み１５０μｍ）を使用した。尚、各電池は積層枚数を変え、全て電池容量が約１Ａｈになるように設計し、電池素子を作製した。
(Production of laminate-type lithium ion secondary battery)
The obtained positive electrode was punched as shown in FIG. 5, and the negative electrode was punched as shown in FIG. The positive electrode dimension was 60 mm × 80 mm, and the end portion 10 mm × 80 mm was the current collector portion. The negative electrode dimension was 62 mm × 82 mm, and the end 12 mm × 82 mm was the current collector part.
Each produced electrode was wrapped in a polyethylene separator (Hypore, manufactured by Asahi Kasei E-Materials), and each electrode was laminated in the form shown in FIG. 4 and tabbed to form a single electrode body. An aluminum tab (4 mm × 92 mm, thickness 150 μm) was used for the positive electrode, and a nickel tab (4 mm × 92 mm, thickness 150 μm) was used for the negative electrode. Each battery was designed to have a battery capacity of about 1 Ah by changing the number of stacked layers to produce a battery element.
得られた電池素子を予め作製したアルミラミネートフィルムに内包し、電解液を注入した後、アルミラミネートフィルムを熱溶着により封止して、ラミネートタイプのリチウムイオン二次電池を作製した。なお、用いた電解液は、エチレンカーボネートとジエチルカーボネートとを体積比で３：７に混合した混合有機溶媒中に、ＬｉＰＦ６が１モル/Ｌ濃度になるように添加し、更にビニレンカーボネートを重量比で２％添加して調製した。 The obtained battery element was encapsulated in an aluminum laminate film prepared in advance, and an electrolyte solution was injected. Then, the aluminum laminate film was sealed by heat welding to produce a laminate type lithium ion secondary battery. The electrolytic solution used was added to a mixed organic solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 so that the concentration of LiPF6 was 1 mol / L, and further vinylene carbonate was added in a weight ratio. To prepare 2%.
（実施例２）
正極電極層の乾燥後の塗布量を１００．０ｇ／ｍ２、負極電極層の乾燥後の塗布量を３８．８ｇ／ｍ２にした以外は実施例１と同様にしてリチウムイオン二次電池を作製した。
(Example 2)
A lithium ion secondary battery was prepared in the same manner as in Example 1 except that the coating amount after drying of the positive electrode layer was 100.0 g / m 2 and the coating amount after drying of the negative electrode layer was 38.8 g / m 2. Produced.
(比較例１)
負極電極層の変性ポリカーボネートをＳＢＲ１質量部、カルボキシメチルセルロース１質量部とし、ロールプレス後の昇華工程を除いたこと以外は実施例１と同様にしてリチウムイオン二次電池を作製した。
(Comparative Example 1)
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the modified polycarbonate of the negative electrode layer was 1 part by mass of SBR and 1 part by mass of carboxymethylcellulose, and the sublimation step after roll pressing was omitted.
(比較例２)
負極集電体に、１２μｍの未処理電解銅箔を使用した以外は比較例１と同様にしてリチウムイオン二次電池を作製した。
(Comparative Example 2)
A lithium ion secondary battery was produced in the same manner as in Comparative Example 1 except that 12 μm untreated electrolytic copper foil was used as the negative electrode current collector.
(比較例３)
正極電極層の乾燥後の塗布量を１００．０ｇ／ｍ２、負極電極層の乾燥後の塗布量を３８．８ｇ／ｍ２にした以外は比較例１と同様にしてリチウムイオン二次電池を作製した。
(Comparative Example 3)
A lithium ion secondary battery was prepared in the same manner as in Comparative Example 1, except that the coating amount after drying of the positive electrode layer was 100.0 g / m 2 and the coating amount after drying of the negative electrode layer was 38.8 g / m 2. Produced.
(比較例４)
負極集電体に、１２μｍの未処理電解銅箔を使用した以外は、実施例１に従い電池の作製を試みた。しかしながら、一時的な結着剤として用いた変性ポリカーボネートを除去するための乾燥（昇華）工程後、密着力の低下により負極活物質が集電体から剥離（滑落）し、電池を作製することができなかった。
(Comparative Example 4)
A battery was tried in accordance with Example 1 except that 12 μm untreated electrolytic copper foil was used for the negative electrode current collector. However, after the drying (sublimation) step for removing the modified polycarbonate used as a temporary binder, the negative electrode active material peels off (slides) from the current collector due to a decrease in adhesion, and a battery can be produced. could not.
（評価及び方法）
実施例１、２及び比較例１〜３で作製したラミネートタイプのリチウムイオン二次電池について、以下の方法で放電負荷試験を行い電池の出力として評価した。結果を以下の表１に記す。
(Evaluation and method)
The laminate type lithium ion secondary batteries produced in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a discharge load test by the following method and evaluated as the battery output. The results are shown in Table 1 below.
・放電負荷試験〜各ラミネート電池を１０個作製し、電池電圧が４．２Ｖまで充電し、その後所定のＣレート（０．２Ｃ、０．５Ｃ、１Ｃ、２Ｃ、３Ｃ、５Ｃ、１０Ｃ、２０Ｃ）で放電した。 -Discharge load test-10 each laminated battery is manufactured, the battery voltage is charged to 4.2 V, and then a predetermined C rate (0.2 C, 0.5 C, 1 C, 2 C, 3 C, 5 C, 10 C, 20 C) Was discharged.
（比較結果）
負極活物質粒子の粒径を測定するために粒度分布測定を行った。粒度分布測定には、日本電子製のＳＡＬＤ−３１００を使用した。結果、Ｄ２５＝１０．２μｍ、Ｄ５０＝１２．３μｍ、Ｄ７５＝１５．５μｍであり、当該負極集電体の突起物は、本特許の請求項の条件を満たすものであることが確認された。
(Comparison result)
In order to measure the particle size of the negative electrode active material particles, the particle size distribution was measured. For measurement of particle size distribution, SALD-3100 manufactured by JEOL Ltd. was used. As a result, D25 = 10.2 μm, D50 = 12.3 μm, D75 = 15.5 μm, and it was confirmed that the protrusions of the negative electrode current collector satisfy the conditions of the claims of this patent.
負極の表面、断面のＳＥＭ観察を行った。ＳＥＭには、日本電子株式会社製のＪＳＭ−７１００Ｆを使用した。 SEM observation of the surface and cross section of the negative electrode was performed. JSM-7100F manufactured by JEOL Ltd. was used for SEM.
ＳＥＭ観察の結果から、実施例１、比較例１、２の負極電極層においては、電極層中の全ての粒子が負極集電体と接していた。一方で、実施例２、比較例３の負極電極層においては、粒子が重なり合う様子が観察され、全ての粒子が負極集電体と接しているとはいえなかった。 From the results of SEM observation, in the negative electrode layers of Example 1 and Comparative Examples 1 and 2, all particles in the electrode layer were in contact with the negative electrode current collector. On the other hand, in the negative electrode layer of Example 2 and Comparative Example 3, it was observed that the particles overlapped, and it could not be said that all the particles were in contact with the negative electrode current collector.
実施例１と比較例１、実施例２と比較例３を比較すると、５Ｃ以降で実施例１、２の出
力が優れており、結着剤を入れなかったことによる出力の向上が確認された。
When Example 1 and Comparative Example 1 were compared, and Example 2 and Comparative Example 3 were compared, the outputs of Examples 1 and 2 were excellent after 5C, and an improvement in output due to the absence of a binder was confirmed. .
以上より、負極電極を薄膜化し、かつ、突起物を有する負極集電体を使用したリチウムイオン二次電池は高出力電池として有用であることが確認された。 From the above, it was confirmed that a lithium ion secondary battery using a negative electrode current collector having a negative electrode electrode made thin and having protrusions is useful as a high-power battery.
１： 負極集電体
２： 突起物
３： 負極活物質
４： 負極層（負極の電極層）
５： 正極集電体
６： 正極層（正極の電極層）
７： セパレータ
８： シーラント
９： 正極タブ
１０： 負極タブ
１１： アルミラミネートフィルム
1: Negative electrode current collector 2: Projection 3: Negative electrode active material 4: Negative electrode layer (electrode layer of negative electrode)
5: Positive electrode current collector 6: Positive electrode layer (positive electrode layer)
7: Separator 8: Sealant 9: Positive electrode tab 10: Negative electrode tab 11: Aluminum laminate film
Claims (5)
粒子状の全ての負極活物質は、少なくともその粒子表面の一部分が負極集電体と接していることを特徴とするリチウムイオン二次電池負極。 A lithium ion secondary battery negative electrode in which a particulate negative electrode active material is formed on a negative electrode current collector having protrusions on the surface,
A negative electrode for a lithium ion secondary battery, wherein all of the particulate negative electrode active materials are in contact with a negative electrode current collector at least a part of the particle surface.
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| JP2015078313A JP2016201174A (en) | 2015-04-07 | 2015-04-07 | Negative electrode for lithium ion secondary battery and lithium ion secondary battery |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015078313A JP2016201174A (en) | 2015-04-07 | 2015-04-07 | Negative electrode for lithium ion secondary battery and lithium ion secondary battery |
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| JP2016201174A true JP2016201174A (en) | 2016-12-01 |
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| JP2015078313A Pending JP2016201174A (en) | 2015-04-07 | 2015-04-07 | Negative electrode for lithium ion secondary battery and lithium ion secondary battery |
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2015
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