JP2024015751A - Electrode for power storage device, and power storage device - Google Patents
Electrode for power storage device, and power storage device Download PDFInfo
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Abstract
Description
本明細書では、蓄電デバイス用電極及び蓄電デバイスを開示する。 This specification discloses an electrode for a power storage device and a power storage device.
従来、蓄電デバイスとしては、正極活物質と、正極活物質に隣接する複数の集電線とこの集電線が並列接続する接続部とを備える櫛歯構造の正極集電部と、を有する正極と、負極活物質と、負極活物質に隣接する複数の集電線とこの集電線が並列接続する接続部を備え正極集電部の櫛歯構造と逆向きに配設された櫛歯構造の負極集電部と、を有する負極と、を備えるものが提案されている（例えば、特許文献１参照）。この蓄電デバイスでは、シート状の電極において内部短絡時の徐放電機構を発現することができる。 Conventionally, as an electricity storage device, a positive electrode has a positive electrode active material, a positive electrode current collecting part having a comb-teeth structure, which includes a plurality of current collecting wires adjacent to the positive electrode active material, and a connection part where the current collecting wires are connected in parallel; A negative electrode current collector with a comb-tooth structure, which includes a negative electrode active material, a plurality of current collector wires adjacent to the negative electrode active material, and a connecting portion where these current collector wires are connected in parallel, and is arranged in the opposite direction to the comb-tooth structure of the positive electrode current collector. A negative electrode having a negative electrode and a negative electrode has been proposed (see, for example, Patent Document 1). In this electricity storage device, the sheet-like electrode can exhibit a slow discharge mechanism when an internal short circuit occurs.
しかしながら、特許文献１では、シート状の電極において内部短絡時の徐放電機構を発現し、安全性をより高めることができるが、まだ十分でなく、更なる改良が望まれていた。 However, in Patent Document 1, a slow discharge mechanism is developed in the case of an internal short circuit in a sheet-like electrode, and safety can be further improved, but this is still insufficient and further improvements have been desired.
本開示は、このような課題に鑑みなされたものであり、安全性をより高めることができる蓄電デバイス用電極及び蓄電デバイスを提供することを主目的とする。 The present disclosure has been made in view of such problems, and a main purpose of the present disclosure is to provide an electrode for a power storage device and a power storage device that can further improve safety.
上述した目的を達成するために鋭意研究したところ、本発明者らは、櫛歯状の集電線を活物質内部に埋設し、この集電線を接続部に並列接続させ、この集電線の１本当たりの抵抗を所定の範囲とすることによって、櫛歯構造の自由度を高めつつ、例えば、内部短絡時などの安全性をより高めることができることを見いだし、本明細書で開示する発明を完成するに至った。 As a result of intensive research to achieve the above-mentioned object, the present inventors buried comb-shaped current collecting wires inside the active material, connected these current collecting wires in parallel to the connection parts, and discovered that one of the current collecting wires The inventors have discovered that by setting the contact resistance within a predetermined range, it is possible to increase the degree of freedom of the comb tooth structure and to further enhance safety in the event of an internal short circuit, for example, and have completed the invention disclosed herein. reached.
即ち、本明細書で開示する蓄電デバイス用電極は、
電極活物質と、
前記電極活物質に隣接する複数の集電線と該集電線が並列接続する接続部とを備える櫛歯構造を有する集電体と、を備え、
１本の前記集電線の抵抗Ｒが０．４Ω以上であるものである。
That is, the electrode for a power storage device disclosed in this specification is
electrode active material;
A current collector having a comb-teeth structure including a plurality of current collecting wires adjacent to the electrode active material and a connection portion where the current collecting wires are connected in parallel,
The resistance R of one current collector wire is 0.4Ω or more.
本明細書で開示する蓄電デバイスは、
上述の蓄電デバイス用電極と、
前記蓄電デバイス用電極に隣接されキャリアイオンを伝導するイオン伝導媒体と、を備え、
前記蓄電デバイス用電極は、正極及び負極のうち少なくとも一方であるものである。
The electricity storage device disclosed herein is
The above-mentioned electrode for a power storage device,
an ion conductive medium that is adjacent to the electricity storage device electrode and that conducts carrier ions;
The electricity storage device electrode is at least one of a positive electrode and a negative electrode.
本開示は、安全性をより高めることができる。このような効果が得られる理由は、以下のように推察される。例えば、シート電極の集電部を櫛歯構造にすることによって、全体がシート状の集電部に比して、内部短絡時の電流集中を抑制し、高安全を担保することができる。一方、この櫛歯構造を有する電極を備えた蓄電デバイスでは、電極の大きさによって、電流集中を抑制できる集電線の幅、厚さなど、その構造は異なるものと推察される。ここで、本開示では、蓄電デバイスには上限電圧が規定されていることから、例えば内部短絡による温度上昇が加速的に起きる熱暴走の開始温度範囲と、集電線１本の抵抗との関係を検討し、この集電線１本の抵抗を規定することにより、安全性を担保するものとした。すなわち、集電線が長くなるような電極面積が大きい電池では、集電線の幅、厚さを大きくしても規定の抵抗を満足することが出来るので、集電部の自由度を高めることができ、更に、櫛歯構造の作製を容易にすることができる。また、集電部は主に、正極はアルミニウム、負極は銅を用いているが、これらのように体積抵抗率の異なる集電部を用いた場合にも、集電線１本の抵抗が規定値を満足すれば集電線の長さ、幅、厚さを任意に設計することができ、更に内部短絡時の熱暴走の発生などをより抑制することができる。 The present disclosure can further improve safety. The reason why such an effect is obtained is inferred as follows. For example, by forming the current collecting portion of the sheet electrode into a comb-teeth structure, it is possible to suppress current concentration in the event of an internal short circuit and ensure high safety, compared to a current collecting portion that is entirely sheet-like. On the other hand, in a power storage device equipped with an electrode having a comb-teeth structure, it is assumed that the structure, such as the width and thickness of the current collection line that can suppress current concentration, differs depending on the size of the electrode. Here, in the present disclosure, since an upper limit voltage is specified for a power storage device, for example, the relationship between the temperature range at which thermal runaway starts, where the temperature rises at an accelerated rate due to an internal short circuit, and the resistance of one current collection wire is determined. After careful consideration, it was decided that safety would be ensured by specifying the resistance of this single current collector wire. In other words, in a battery with a large electrode area that requires a long current collector wire, the specified resistance can be satisfied even if the width and thickness of the current collector wire are increased, so the flexibility of the current collector section can be increased. Furthermore, the comb structure can be easily produced. In addition, the current collectors mainly use aluminum for the positive electrode and copper for the negative electrode, but even when current collectors with different volume resistivities are used, the resistance of one current collector wire will not exceed the specified value. If the following is satisfied, the length, width, and thickness of the current collector wire can be arbitrarily designed, and furthermore, the occurrence of thermal runaway due to internal short circuit can be further suppressed.
（蓄電デバイス用電極）
実施形態で説明する本開示の蓄電デバイス用電極は、蓄電デバイスに用いられる電極である。この電極は、正極としてもよいし、負極としてもよいが、正極であることが好ましい。正極は、負極に比して導電性が低いため、本開示の集電構造を採用する意義が高い。この電極は、電極活物質と、電極活物質が隣接する集電部とを備える。この蓄電デバイス用電極は、シート状であることが好ましい。電極活物質は、層状に形成された電極活物質層に含まれるものとしてもよい。電極活物質層には、電極活物質のほか、例えば、必要に応じて、導電材や結着材などを含むものとしてもよい。この電極活物質層は、蓄電デバイスにおいて詳述する。
(Electrode for electricity storage device)
The electrode for a power storage device of the present disclosure described in the embodiments is an electrode used for a power storage device. This electrode may be a positive electrode or a negative electrode, but is preferably a positive electrode. Since the positive electrode has lower conductivity than the negative electrode, it is highly significant to employ the current collecting structure of the present disclosure. This electrode includes an electrode active material and a current collecting portion adjacent to the electrode active material. This electrode for an electricity storage device is preferably in the form of a sheet. The electrode active material may be included in an electrode active material layer formed in a layered manner. In addition to the electrode active material, the electrode active material layer may also contain, for example, a conductive material, a binding material, etc., as necessary. This electrode active material layer will be described in detail in the electricity storage device.
集電部は、電極活物質に隣接する複数の集電線と集電線が並列接続する接続部とを備える。集電線は、電極活物質に隣接し、この電極活物質と接触している部分では他の集電線と互いに電気的に接続していないことが、内部短絡時の通電性を考慮すると好ましい。この集電部は、櫛歯構造を有している。集電部は、１本の集電線の抵抗Ｒが０．４Ω以上であるものとする。１本の集電線の抵抗Ｒが０．４Ω以上との条件を満たすものとすれば、集電線の幅Ｗ、長さＬ、厚さｔ、体積抵抗率ρ及びその間隔ｓがどのような値であっても、蓄電デバイスの内部短絡が生じた場合において、熱暴走の発生を防止することができる。集電線の幅Ｗ、厚さｔとし、それぞれの体積抵抗率をρとすると、集電線１本の抵抗Ｒは、Ｒ＝ρ・Ｌ／（Ｗ・ｔ）で表され、例えば、櫛歯の長さＬが長くなった場合には、櫛歯幅Ｗ、櫛歯厚さｔを大きくすることで抵抗Ｒに対して上記条件を満たすものとすることができる。また、この集電線は、接続部に並列接続されるため、通常の集電時にはその全体としての抵抗を低減することができる。また、集電線の間隔ｓは、内部短絡には関係せず、通常の集電性能を考慮してその大きさを設定すればよい。１本の集電線の抵抗Ｒは、０．４Ω以上であり、０．５Ω以上が好ましく、１Ω以上としてもよい。また、この１本の集電線の抵抗Ｒは、１０Ω以下が好ましく、５Ω以下がより好ましく、２Ω以下としてもよい。 The current collecting section includes a plurality of current collecting wires adjacent to the electrode active material and a connection section where the current collecting wires are connected in parallel. In consideration of current conductivity in the event of an internal short circuit, it is preferable that the current collecting wire is adjacent to the electrode active material and is not electrically connected to other current collecting wires at the portion in contact with the electrode active material. This current collector has a comb-teeth structure. In the current collecting unit, the resistance R of one current collecting wire is 0.4Ω or more. Assuming that the resistance R of one current collector wire satisfies the condition of 0.4Ω or more, what values are the width W, length L, thickness t, volume resistivity ρ, and interval s of the current collector wire? Even if an internal short circuit occurs in the power storage device, thermal runaway can be prevented from occurring. Assuming that the width W and thickness t of the current collector wire are the same, and the volume resistivity of each wire is ρ, the resistance R of one current collector wire is expressed as R=ρ・L/(W・t). When the length L becomes longer, the above conditions for the resistance R can be satisfied by increasing the comb tooth width W and the comb tooth thickness t. Moreover, since this current collection line is connected in parallel to the connection portion, the overall resistance can be reduced during normal current collection. Further, the interval s between the current collecting wires is not related to internal short circuits, and may be set in consideration of normal current collecting performance. The resistance R of one current collection wire is 0.4Ω or more, preferably 0.5Ω or more, and may be 1Ω or more. Moreover, the resistance R of this one current collection wire is preferably 10Ω or less, more preferably 5Ω or less, and may be 2Ω or less.
接続部は、集電線が接続される一体物であり、例えば、帯状の部位としてもよい。接続部は、集電線と一体で形成されているものとしてもよいし、別部材としてもよい。この接続部は、集電線と同じ材質としてもよいし、異なる材質としてもよいが、同じ材質であることが好ましい。接続部は、本数Ｎが１０本以上である集電線が並列接続されているものとしてもよいし、５０本以上や１００本以上、２００本以上、５００本以上の集電線が並列接続されているものとしてもよい。並列接続の本数Ｎに応じて、接続部を介して単セルにかかる抵抗が決定されるため、所望の充放電特性に応じて、集電線の並列接続の本数Ｎや接続部の体積抵抗率の高さなどを適宜設定すればよい。また、集電線の本数Ｎが多くなると単位体積あたりの活物質量が減少することから、エネルギー密度の観点もふまえて、この集電線の本数Ｎを適宜設定すればよい。 The connection part is an integral part to which the current collecting wire is connected, and may be, for example, a band-shaped part. The connection portion may be formed integrally with the current collector wire, or may be formed as a separate member. This connection part may be made of the same material as the current collector wire, or may be made of a different material, but preferably the same material. The connection part may be one in which current collector wires in which the number N is 10 or more are connected in parallel, or 50 or more, 100 or more, 200 or more, or 500 or more current collector wires are connected in parallel. It can also be used as a thing. Since the resistance applied to a single cell through the connection part is determined depending on the number N of parallel connections, the number N of parallel connection of current collector wires and the volume resistivity of the connection part are determined depending on the desired charge/discharge characteristics. The height etc. may be set appropriately. Furthermore, as the number N of current collecting wires increases, the amount of active material per unit volume decreases, so the number N of current collecting wires may be appropriately set in consideration of the energy density.
集電線は、上述したように、１本の集電線の抵抗Ｒが０．４Ω以上を満たせば、長さＬ、幅Ｗ、厚さｔ、体積抵抗率ρ及び間隔ｓは、蓄電デバイスに要求される性能に応じて任意の値とすることができる。１本の集電線の長さＬは、例えば、５０ｍｍ以上５０００ｍｍ以下の範囲とすることができる。１本の集電線の厚さｔは、例えば、５μｍ以上５０μｍ以下の範囲とすることができる。幅Ｗと間隔ｓとは、同じ値としてもよいし、異なる値としてもよいが、積層時の支持性を考慮すると、同じ値である方が望ましい。集電線の幅Ｗは、１００μｍ以上が好ましく、２００μｍ以上がより好ましく、５００μｍ以上としてもよい。また、集電線の幅Ｗは、２ｍｍ以上とすることができ、更に２ｍｍを超えるものとしてもよいし、３ｍｍ以上とすることもできる。集電線の幅Ｗが２ｍｍ以上では、例えば、入出力の大きな大型の蓄電デバイスにも適用することができる。集電線の幅Ｗは、５ｍｍ以下が好ましく、３ｍｍ以下がより好ましく、１ｍｍ以下としてもよい。集電線の間隔ｓは、１００μｍ以上が好ましく、２００μｍ以上がより好ましく、５００μｍ以上としてもよい。また、集電線の間隔ｓは、１０００μｍ以下がより好ましく、７５０μｍ以下としてもよい。集電線と接続部の体積抵抗率ρは、同じであってもよいし、異なってもよい。集電線や接続部は、体積抵抗率が５．０×１０-6Ωｍ以下であるものとしてもよいし、５×１０-7Ωｍ以下であるものとしてもよいし、５×１０-8Ωｍ以下であるものとしてもよい。 As mentioned above, if the resistance R of one current collection wire satisfies 0.4Ω or more, the length L, width W, thickness t, volume resistivity ρ, and spacing s meet the requirements of the power storage device. It can be set to any value depending on the desired performance. The length L of one current collection wire can be, for example, in a range of 50 mm or more and 5000 mm or less. The thickness t of one current collector wire can be, for example, in a range of 5 μm or more and 50 μm or less. The width W and the spacing s may be the same value or may be different values, but in consideration of supportability during lamination, it is preferable that the width W and the spacing s be the same value. The width W of the current collector wire is preferably 100 μm or more, more preferably 200 μm or more, and may be 500 μm or more. Further, the width W of the current collector wire can be 2 mm or more, and can also be more than 2 mm, or can be 3 mm or more. When the width W of the current collection line is 2 mm or more, it can be applied to, for example, a large-sized electricity storage device with large input and output. The width W of the current collector wire is preferably 5 mm or less, more preferably 3 mm or less, and may be 1 mm or less. The interval s between the current collector wires is preferably 100 μm or more, more preferably 200 μm or more, and may be 500 μm or more. Moreover, the interval s between the current collector wires is more preferably 1000 μm or less, and may be 750 μm or less. The volume resistivity ρ of the current collecting wire and the connection portion may be the same or different. The current collector wire and the connection part may have a volume resistivity of 5.0×10 -6 Ωm or less, 5×10 -7 Ωm or less, or 5×10 -8 Ωm or less .
集電部は、銅、ニッケル、ステンレス鋼、チタン、アルミニウム、焼成炭素、導電性高分子、導電性ガラス、Ａｌ－Ｃｄ合金などのほか、接着性、導電性及び耐還元性向上の目的で、例えば銅などの表面をカーボン、ニッケル、チタンや銀などで処理した集電線や接続部を有するものとしてもよい。正極に用いられる集電部は、アルミニウムによって形成されることが好ましい。また、負極に用いられる集電部は、Ｃｕによって形成されることが好ましい。 The current collector is made of copper, nickel, stainless steel, titanium, aluminum, fired carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as other materials for the purpose of improving adhesiveness, conductivity, and reduction resistance. For example, it may have a current collecting wire or a connecting portion whose surface is made of copper or the like and is treated with carbon, nickel, titanium, silver, or the like. The current collector used in the positive electrode is preferably formed of aluminum. Moreover, it is preferable that the current collector used for the negative electrode be formed of Cu.
（蓄電デバイス）
実施形態で説明する本開示の蓄電デバイスは、上述した蓄電デバイス用電極と、蓄電デバイス用電極に隣接されキャリアイオンを伝導するイオン伝導媒体と、を備える。この蓄電デバイスは、正極活物質を有する正極と、負極活物質を有する負極と、正極と負極との間に介在しイオンを伝導するイオン伝導媒体と、を備え、正極及び負極のうち少なくとも一方が上述した蓄電デバイス用電極であるものとしてもよい。蓄電デバイスは、例えば、蓄電デバイス用電極が正極及び負極であり、正極の櫛歯構造と負極の櫛歯構造との櫛歯方向が逆向きであり、集電線１本の抵抗Ｒが０．４Ω以上であるものとしてもよい。なお集電線において、集電線の長さＬ、幅Ｗ、厚さｔ及び体積抵抗率ρとしたときに、抵抗Ｒは、抵抗Ｒ＝ρ・Ｌ／（Ｗ・ｔ）で表される。この蓄電デバイスは、例えば、電気二重層キャパシタやハイブリッドキャパシタ、疑似電気二重層キャパシタ、アルカリ金属二次電池、アルカリ金属イオン電池などとしてもよい。蓄電デバイスのキャリアイオンは、リチウムイオンやナトリウムイオン、カリウムイオンなどのアルカリ金属イオンやマグネシウムイオンやストロンチウムイオン、カルシウムイオンなどの第２族イオンなどが挙げられる。ここでは、説明の便宜のため、リチウムイオンをキャリアとするリチウムイオン二次電池をその主たる一例として以下説明する。
(Electricity storage device)
The power storage device of the present disclosure described in the embodiments includes the above-described power storage device electrode and an ion conductive medium that is adjacent to the power storage device electrode and conducts carrier ions. This electricity storage device includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and an ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts ions, and at least one of the positive electrode and the negative electrode is It may be the electrode for an electricity storage device described above. In the power storage device, for example, the electrodes for the power storage device are a positive electrode and a negative electrode, the comb tooth structure of the positive electrode and the comb tooth structure of the negative electrode are in opposite directions, and the resistance R of one current collection wire is 0.4Ω. It may be more than that. In addition, in the current collector wire, when the length L, width W, thickness t, and volume resistivity ρ of the current collector wire, the resistance R is expressed as resistance R=ρ·L/(W·t). This power storage device may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, an alkali metal secondary battery, an alkali metal ion battery, or the like. Examples of carrier ions for power storage devices include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and Group 2 ions such as magnesium ions, strontium ions, and calcium ions. Here, for convenience of explanation, a lithium ion secondary battery using lithium ions as a carrier will be described as a main example.
ここで、本実施形態で開示する蓄電デバイスについて図面を用いて説明する。図１は、蓄電デバイス１０の一例を示す模式図であり、図１Ａが図１ＢのＡ－Ａ断面図、図１Ｂが蓄電デバイス１０の側面図、図１Ｃが図１ＢのＢ－Ｂ断面図であり、図１Ｄが正極集電部３０の説明図である。図２は、蓄電デバイス１０の断面の一例を示す模式図である。蓄電デバイス１０は、負極１２と、セパレータ１５と、正極１６とを備えている。単セル１１は、負極１２と、セパレータ１５と、正極１６とにより構成されている。この蓄電デバイス１０は、シート状の負極１２と、シート状のセパレータ１５と、シート状の正極１６とが積層された構造を有する。また、この蓄電デバイス１０は、負極１２とセパレータ１５と正極１６とを有する単セル１１を更に積層した構造を有するものとしてもよい。 Here, the electricity storage device disclosed in this embodiment will be explained using the drawings. FIG. 1 is a schematic diagram showing an example of a power storage device 10, in which FIG. 1A is a cross-sectional view taken along line AA in FIG. 1B, FIG. 1B is a side view of power storage device 10, and FIG. 1C is a cross-sectional view taken along line BB in FIG. 1B. 1D is an explanatory diagram of the positive electrode current collector 30. FIG. 2 is a schematic diagram showing an example of a cross section of the electricity storage device 10. Electricity storage device 10 includes a negative electrode 12, a separator 15, and a positive electrode 16. The single cell 11 includes a negative electrode 12, a separator 15, and a positive electrode 16. This electricity storage device 10 has a structure in which a sheet-like negative electrode 12, a sheet-like separator 15, and a sheet-like positive electrode 16 are stacked. Moreover, this electricity storage device 10 may have a structure in which unit cells 11 each having a negative electrode 12, a separator 15, and a positive electrode 16 are further stacked.
負極１２は、負極活物質層１３と、負極集電部２０とを含む。この負極１２は、負極活物質層１３と負極集電部２０とを密着させて形成したものとしてもよいし、例えば負極活物質に必要に応じて導電材や結着材を混合し、適当な溶剤を加えてペースト状の負極合材としたものを、負極集電部２０が埋設されるように塗布乾燥し、必要に応じて電極密度を高めるべく圧縮して形成してもよい。負極活物質層１３には、負極活物質と、導電材と、結着材とを含むものとしてもよい。負極活物質としては、リチウム、リチウム合金、スズ化合物などの無機化合物、リチウムイオンを吸蔵・放出可能な炭素質材料、複数の元素を含む複合酸化物、導電性ポリマーなどが挙げられる。炭素質材料は、例えば、コークス類、ガラス状炭素類、グラファイト類、難黒鉛化性炭素類、熱分解炭素類、炭素繊維などが挙げられる。このうち、人造黒鉛、天然黒鉛などのグラファイト類が、金属リチウムに近い作動電位を有し、高い作動電圧での充放電が可能であり支持塩としてリチウム塩を使用した場合に自己放電を抑え、且つ充電時における不可逆容量を少なくできるため、好ましい。複合酸化物としては、例えば、リチウムチタン複合酸化物やリチウムバナジウム複合酸化物などが挙げられる。負極活物質としては、このうち、炭素質材料が安全性の面から見て好ましい。 Negative electrode 12 includes a negative electrode active material layer 13 and a negative electrode current collector 20 . The negative electrode 12 may be formed by closely adhering the negative electrode active material layer 13 and the negative electrode current collector 20, or, for example, may be formed by mixing a conductive material or a binder with the negative electrode active material as necessary. A paste-like negative electrode composite material may be formed by adding a solvent, which is coated and dried so that the negative electrode current collector 20 is buried therein, and, if necessary, compressed to increase the electrode density. The negative electrode active material layer 13 may include a negative electrode active material, a conductive material, and a binding material. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys, and tin compounds, carbonaceous materials capable of intercalating and deintercalating lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite have operating potentials close to those of metallic lithium, and can be charged and discharged at high operating voltages.When using lithium salts as supporting salts, they suppress self-discharge. In addition, it is preferable because irreversible capacity during charging can be reduced. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. Among these, carbonaceous materials are preferable as the negative electrode active material from the viewpoint of safety.
導電材は、正極の電池性能に悪影響を及ぼさない電子伝導性材料であれば特に限定されず、例えば、天然黒鉛（鱗状黒鉛、鱗片状黒鉛）や人造黒鉛などの黒鉛、アセチレンブラック、カーボンブラック、ケッチェンブラック、カーボンウィスカ、ニードルコークス、炭素繊維、金属（銅、ニッケル、アルミニウム、銀、金など）などの１種又は２種以上を混合したものを用いることができる。これらの中で、導電材としては、電子伝導性及び塗工性の観点より、カーボンブラック及びアセチレンブラックが好ましい。結着材は、活物質粒子及び導電材粒子を繋ぎ止める役割を果たすものであり、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶｄＦ）、フッ素ゴム等の含フッ素樹脂、或いはポリプロピレン、ポリエチレン等の熱可塑性樹脂、エチレンプロピレンジエンゴム（ＥＰＤＭ）、スルホン化ＥＰＤＭゴム、天然ブチルゴム（ＮＢＲ）等を単独で、あるいは２種以上の混合物として用いることができる。また、水系バインダーであるセルロース系やスチレンブタジエンゴム（ＳＢＲ）の水分散体等を用いることもできる。正極活物質、導電材、結着材を分散させる溶剤としては、例えばＮ－メチルピロリドン、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、ジエチレントリアミン、Ｎ，Ｎ－ジメチルアミノプロピルアミン、エチレンオキシド、テトラヒドロフランなどの有機溶剤を用いることができる。また、水に分散剤、増粘剤等を加え、ＳＢＲなどのラテックスで活物質をスラリー化してもよい。増粘剤としては、例えば、カルボキシメチルセルロース、メチルセルロースなどの多糖類を単独で、あるいは２種以上の混合物として用いることができる。塗布方法としては、例えば、アプリケータロールなどのローラコーティング、スクリーンコーティング、ドクターブレイド方式、スピンコーティング、バーコータなどが挙げられ、これらのいずれかを用いて任意の厚さ・形状とすることができる。 The conductive material is not particularly limited as long as it is an electronically conductive material that does not adversely affect the battery performance of the positive electrode, and examples thereof include graphite such as natural graphite (scaly graphite, flaky graphite) and artificial graphite, acetylene black, carbon black, One or a mixture of two or more of Ketjen black, carbon whiskers, needle coke, carbon fiber, metals (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, carbon black and acetylene black are preferred as the conductive material from the viewpoint of electronic conductivity and coatability. The binder plays a role of binding the active material particles and the conductive material particles, and includes, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resin such as fluororubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM rubber, natural butyl rubber (NBR), etc. can be used alone or as a mixture of two or more. Furthermore, an aqueous binder such as a cellulose binder or an aqueous dispersion of styrene-butadiene rubber (SBR) can also be used. Examples of solvents for dispersing the positive electrode active material, conductive material, and binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, and N,N-dimethylaminopropylamine. Organic solvents such as , ethylene oxide, and tetrahydrofuran can be used. Alternatively, the active material may be slurried with latex such as SBR by adding a dispersant, a thickener, etc. to water. As the thickener, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used alone or as a mixture of two or more. Application methods include, for example, roller coating using an applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. Any of these methods can be used to obtain an arbitrary thickness and shape.
負極集電部２０は、集電線２３と、接続部２１とを有する櫛歯構造の部材である。集電線２３は、負極活物質に隣接した複数の線状の部材であり、負極活物質と接触している部分では互いに電気的に接続していないことが好ましい。集電線２３は、その断面形状が正方形や長方形の矩形としてもよいし、円柱や楕円柱、六角柱や八角形柱など多角形柱としてもよい。接続部２１は、集電線２３と負極活物質とが接触していない外部で複数の集電線２３を並列接続する連続体である部材である。接続部２１は、集電線２３の配列方向を長手方向とする箔状又は板状の部材である。 The negative electrode current collector 20 is a member with a comb-like structure that includes a current collector wire 23 and a connecting portion 21 . The current collector wires 23 are a plurality of linear members adjacent to the negative electrode active material, and preferably are not electrically connected to each other in the portions that are in contact with the negative electrode active material. The current collector wire 23 may have a square or rectangular cross-sectional shape, or may have a polygonal column such as a cylinder, an elliptical column, a hexagonal column, or an octagonal column. The connecting portion 21 is a continuous member that connects a plurality of current collecting wires 23 in parallel at an outside where the current collecting wires 23 and the negative electrode active material are not in contact with each other. The connecting portion 21 is a foil-like or plate-like member whose longitudinal direction is the direction in which the current collector wires 23 are arranged.
集電線２３には、銅、ニッケル、ステンレス鋼、チタン、アルミニウム、焼成炭素、導電性高分子、導電性ガラス、Ａｌ－Ｃｄ合金などのほか、接着性、導電性及び耐還元性向上の目的で、例えば銅などの表面をカーボン、ニッケル、チタンや銀などで処理したものも用いることができる。これらについては、表面を酸化処理することも可能である。負極集電部２０は、図２に示すように、端部以外では集電線２３が負極活物質層１３に埋設された構造を有するものとしてもよい。 The current collector wire 23 is made of copper, nickel, stainless steel, titanium, aluminum, fired carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as other materials for the purpose of improving adhesiveness, conductivity, and reduction resistance. For example, it is also possible to use copper whose surface is treated with carbon, nickel, titanium, silver, or the like. It is also possible to oxidize the surface of these materials. As shown in FIG. 2, the negative electrode current collector 20 may have a structure in which the current collector wire 23 is buried in the negative electrode active material layer 13 except for the ends.
正極１６は、正極活物質層１７と、正極集電部３０とを有するものとしてもよい。正極活物質層１７は、正極活物質と、必要に応じて導電材と、結着材とを含むものとしてもよい。正極１６は、例えば正極活物質と導電材と結着材とを混合し、適当な溶剤を加えてペースト状の正極合材としたものを、正極集電部３０が埋設されるように塗布乾燥し、必要に応じて電極密度を高めるべく圧縮して形成してもよい。正極活物質は、例えば、キャリアであるリチウムを吸蔵放出可能な材料が挙げられる。正極活物質としては、例えば、リチウムと遷移金属とを有する化合物、例えば、リチウムと遷移金属元素とを含む酸化物や、リチウムと遷移金属元素とを含むリン酸化合物などが挙げられる。具体的には、基本組成式をＬｉ(1-x)ＭｎＯ2（０≦ｘ≦１など、以下同じ）やＬｉ(1-x)Ｍｎ2Ｏ4などとするリチウムマンガン複合酸化物、基本組成式をＬｉ(1-x)ＣｏＯ2などとするリチウムコバルト複合酸化物、基本組成式をＬｉ(1-x)ＮｉＯ2などとするリチウムニッケル複合酸化物、基本組成式をＬｉ(1-x)ＣｏaＮｉbＭｎcＯ2（ａ＞０、ｂ＞０、ｃ＞０、ａ＋ｂ＋ｃ＝１）、Ｌｉ(1-x)ＣｏaＮｉbＭｎcＯ4（０＜ａ＜１、０＜ｂ＜１、１≦ｃ＜２、ａ＋ｂ＋ｃ＝２）などとするリチウムコバルトニッケルマンガン複合酸化物、基本組成式をＬｉＶ2Ｏ3などとするリチウムバナジウム複合酸化物、基本組成式をＶ2Ｏ5などとする遷移金属酸化物などを用いることができる。また、基本組成式をＬｉＦｅＰＯ4とするリン酸鉄リチウム化合物などを正極活物質として用いることができる。これらのうち、リチウムコバルトニッケルマンガン複合酸化物、例えば、ＬｉＣｏ1/3Ｎｉ1/3Ｍｎ1/3Ｏ2やＬｉＮｉ0.4Ｃｏ0.3Ｍｎ0.3Ｏ2などが好ましい。なお、「基本組成式」とは、他の元素、例えば、ＡｌやＭｇなどの成分を含んでもよい趣旨である。また、正極に用いられる導電材、結着材、溶剤などは、それぞれ負極１２で例示したものを用いることができる。 The positive electrode 16 may include a positive electrode active material layer 17 and a positive electrode current collector 30. The positive electrode active material layer 17 may include a positive electrode active material, and if necessary, a conductive material and a binding material. The positive electrode 16 is made by, for example, mixing a positive electrode active material, a conductive material, and a binder, and adding an appropriate solvent to form a paste-like positive electrode mixture, which is coated and dried so that the positive electrode current collector 30 is buried therein. However, if necessary, it may be formed by compressing it to increase the electrode density. Examples of the positive electrode active material include materials that can intercalate and deintercalate lithium, which is a carrier. Examples of the positive electrode active material include compounds containing lithium and a transition metal, such as oxides containing lithium and a transition metal element, and phosphoric acid compounds containing lithium and a transition metal element. Specifically, lithium-manganese composite oxides with basic composition formulas such as Li (1-x) MnO 2 (0≦x≦1, etc., the same applies hereinafter) and Li (1-x) Mn 2 O 4 , etc. Lithium cobalt composite oxide with the formula Li (1-x) CoO 2 etc., lithium nickel composite oxide with the basic composition formula Li (1-x) NiO 2 etc., the basic composition formula Li (1-x) Co a Ni b Mn c O 2 (a>0, b>0, c>0, a+b+c=1), Li (1-x) Co a Ni b Mn c O 4 (0<a<1, 0<b Lithium cobalt nickel manganese composite oxide with <1, 1≦c<2, a+b+c=2), etc., lithium vanadium composite oxide with basic composition formula such as LiV 2 O 3 , etc., and lithium vanadium composite oxide with basic composition formula such as V 2 O 5 Transition metal oxides and the like can be used. Further, a lithium iron phosphate compound having the basic composition formula LiFePO 4 or the like can be used as the positive electrode active material. Among these, lithium cobalt nickel manganese composite oxides such as LiCo 1/3 Ni 1/3 Mn 1/3 O 2 and LiNi 0.4 Co 0.3 Mn 0.3 O 2 are preferred. Note that the "basic compositional formula" may include other elements such as Al and Mg. Further, as the conductive material, binding material, solvent, etc. used in the positive electrode, those exemplified for the negative electrode 12 can be used.
正極１６において、正極活物質の含有量は、より多いことが好ましく、正極１６の質量全体に対して７０質量％以上であることが好ましく、８０質量％以上であることがより好ましい。導電材の含有量は、正極１６の全体の質量に対して０質量％以上２０質量％以下の範囲であることが好ましく、０質量％以上１０質量％以下の範囲であることがより好ましい。このような範囲では、電池容量の低下を抑制し、導電性を十分に付与することができる。また、結着材の含有量は、正極１６の質量全体に対して０．１質量％以上５質量％以下の範囲であることが好ましく、０．２質量％以上３質量％以下の範囲であることがより好ましい。 In the positive electrode 16, the content of the positive electrode active material is preferably larger, preferably 70% by mass or more, and more preferably 80% by mass or more based on the entire mass of the positive electrode 16. The content of the conductive material is preferably in the range of 0% by mass or more and 20% by mass or less, and more preferably in the range of 0% by mass or more and 10% by mass or less, based on the entire mass of the positive electrode 16. Within this range, a decrease in battery capacity can be suppressed and sufficient conductivity can be provided. Further, the content of the binder is preferably in the range of 0.1% by mass or more and 5% by mass or less, and preferably in the range of 0.2% by mass or more and 3% by mass or less, based on the entire mass of the positive electrode 16. It is more preferable.
正極集電部３０は、接続部３１と、集電線３３と、を有する櫛歯構造の部材である。集電線３３は、正極活物質に隣接した複数の線状の部材であり、正極活物質と接触している部分では互いに電気的に接続していないことが好ましい。集電線３３は、その断面形状が正方形や長方形の矩形としてもよいし、円柱や楕円柱、六角柱や八角形柱など多角形柱としてもよい。接続部３１は、集電線３３と正極活物質とが接触していない外部で複数の集電線３３を並列接続する連続体である部材である。接続部３１は、集電線３３の配列方向を長手方向とする箔状又は板状の部材である。 The positive electrode current collector 30 is a member with a comb-teeth structure including a connecting portion 31 and a current collecting wire 33. The current collector wires 33 are a plurality of linear members adjacent to the positive electrode active material, and preferably do not electrically connect to each other in the portions that are in contact with the positive electrode active material. The current collector wire 33 may have a square or rectangular cross-sectional shape, or may have a polygonal column such as a cylinder, an elliptical column, a hexagonal column, or an octagonal column. The connecting portion 31 is a continuous member that connects a plurality of current collecting wires 33 in parallel outside the current collecting wires 33 and the positive electrode active material where they are not in contact with each other. The connecting portion 31 is a foil-like or plate-like member whose longitudinal direction is the direction in which the current collector wires 33 are arranged.
集電線３３には、銅、ニッケル、ステンレス鋼、チタン、アルミニウム、焼成炭素、導電性高分子、導電性ガラス、Ａｌ－Ｃｄ合金などのほか、接着性、導電性及び耐還元性向上の目的で、例えば銅などの表面をカーボン、ニッケル、チタンや銀などで処理したものも用いることができる。これらについては、表面を酸化処理することも可能である。正極集電部３０は、図２に示すように、端部以外では集電線３３が正極活物質層１７に埋設された構造を有するものとしてもよい。 The current collector wire 33 is made of copper, nickel, stainless steel, titanium, aluminum, fired carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as other materials for the purpose of improving adhesiveness, conductivity, and reduction resistance. For example, it is also possible to use copper whose surface is treated with carbon, nickel, titanium, silver, or the like. It is also possible to oxidize the surface of these materials. As shown in FIG. 2, the positive electrode current collecting section 30 may have a structure in which the current collecting wire 33 is buried in the positive electrode active material layer 17 except for the ends.
セパレータ１５は、キャリアイオン（例えばリチウムイオン）のイオン伝導を阻害せず負極１２と正極１６とを絶縁するものである。また、セパレータ１５は、イオン伝導媒体を含むものとしてもよい。セパレータ１５としては、電極構造体１０の使用範囲に耐えうる組成であれば特に限定されないが、例えば、ポリプロピレン製不織布やポリフェニレンスルフィド製不織布などの高分子不織布、ポリエチレンやポリプロピレンなどのオレフィン系樹脂の薄い微多孔膜が挙げられる。これらは単独で用いてもよいし、複数を混合して用いてもよい。このセパレータ１５の厚さは、例えば、５μｍ以上であることが好ましく、８μｍ以上であることがより好ましく、１０μｍ以上であるものとしてもよい。この厚さが５μｍ以上では、絶縁性を確保する上で好ましい。また、セパレータ１５の厚さは、１５μｍ以下であることが好ましく、１０μｍ以下であることがより好ましい。この厚さが１５μｍ以下では、イオン伝導性の低下を抑制できる点や、セルに占める体積をより低減する上で好ましい。なお、セパレータ１５をイオン伝導媒体としての固体電解質としてもよい。固体電解質としては、例えば、無機固体電解質や、高分子固体電解質などが挙げられる。 The separator 15 insulates the negative electrode 12 and the positive electrode 16 without inhibiting ion conduction of carrier ions (for example, lithium ions). Further, the separator 15 may include an ion conductive medium. The separator 15 is not particularly limited as long as it has a composition that can withstand the usage range of the electrode structure 10. Examples include microporous membranes. These may be used alone or in combination. The thickness of the separator 15 is, for example, preferably 5 μm or more, more preferably 8 μm or more, and may be 10 μm or more. It is preferable that the thickness is 5 μm or more in order to ensure insulation. Further, the thickness of the separator 15 is preferably 15 μm or less, more preferably 10 μm or less. When the thickness is 15 μm or less, it is preferable in terms of suppressing a decrease in ion conductivity and further reducing the volume occupied in the cell. Note that the separator 15 may be a solid electrolyte as an ion conductive medium. Examples of the solid electrolyte include inorganic solid electrolytes and polymer solid electrolytes.
イオン伝導媒体としては、支持塩を含む非水系電解液や非水系ゲル電解液などを用いることができる。非水系電解液の溶媒としては、例えば、カーボネート類、エステル類、エーテル類、ニトリル類、フラン類、スルホラン類及びジオキソラン類などが挙げられ、これらを単独又は混合して用いることができる。具体的には、カーボネート類としてエチレンカーボネート（ＥＣ）やプロピレンカーボネート、ビニレンカーボネート、ブチレンカーボネート、クロロエチレンカーボネートなどの環状カーボネート類や、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、エチル－ｎ－ブチルカーボネート、メチル－ｔ－ブチルカーボネート、ジ－ｉ－プロピルカーボネート、ｔ－ブチル－ｉ－プロピルカーボネートなどの鎖状カーボネート類、γ－ブチルラクトン、γ－バレロラクトンなどの環状エステル類、ギ酸メチル、酢酸メチル、酢酸エチル、酪酸メチルなどの鎖状エステル類、ジメトキシエタン、エトキシメトキシエタン、ジエトキシエタンなどのエーテル類、アセトニトリル、ベンゾニトリルなどのニトリル類、テトラヒドロフラン、メチルテトラヒドロフラン、などのフラン類、スルホラン、テトラメチルスルホランなどのスルホラン類、１，３－ジオキソラン、メチルジオキソランなどのジオキソラン類などが挙げられる。この電解液には、電極構造体１０のキャリアであるイオンを含む支持塩を溶解したものとしてもよい。支持塩としては、例えば、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＳｂＦ6、ＬｉＳｉＦ6、ＬｉＡｌＦ4、ＬｉＳＣＮ、ＬｉＣｌＯ4、ＬｉＣｌ、ＬｉＦ、ＬｉＢｒ、ＬｉＩ、ＬｉＡｌＣｌ4などが挙げられる。このうち、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4などの無機塩、及びＬｉＣＦ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3などの有機塩からなる群より選ばれる１種又は２種以上の塩を組み合わせて用いることが電気特性の点から見て好ましい。この支持塩は、電解液中の濃度が０．１ｍｏｌ／Ｌ以上５ｍｏｌ／Ｌ以下であることが好ましく、０．５ｍｏｌ／Ｌ以上２ｍｏｌ／Ｌ以下であることがより好ましい。 As the ion conductive medium, a nonaqueous electrolyte containing a supporting salt, a nonaqueous gel electrolyte, or the like can be used. Examples of the solvent for the nonaqueous electrolyte include carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, and these can be used alone or in combination. Specifically, carbonates include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, as well as dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate, and ethyl carbonate. - Chain carbonates such as n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, Chain esters such as methyl formate, methyl acetate, ethyl acetate, and methyl butyrate; ethers such as dimethoxyethane, ethoxymethoxyethane, and diethoxyethane; nitrites such as acetonitrile and benzonitrile; and furans such as tetrahydrofuran and methyltetrahydrofuran. Examples include sulfolanes such as sulfolane, tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. This electrolytic solution may have a supporting salt containing ions, which is a carrier of the electrode structure 10, dissolved therein. Examples of the supporting salt include LiPF 6 , LiBF 4 , LiAsF 6 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiSbF 6 , LiSiF 6 , LiAlF 4 , LiSCN, Examples include LiClO 4 , LiCl, LiF, LiBr, LiI, LiAlCl 4 and the like. Among these, 1 selected from the group consisting of inorganic salts such as LiPF 6 , LiBF 4 and LiClO 4 and organic salts such as LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 and LiC(CF 3 SO 2 ) 3 From the viewpoint of electrical properties, it is preferable to use a species or a combination of two or more kinds of salts. The concentration of this supporting salt in the electrolytic solution is preferably 0.1 mol/L or more and 5 mol/L or less, more preferably 0.5 mol/L or more and 2 mol/L or less.
蓄電デバイス１０は、電極に内部短絡が生じたときの内部温度が１６０℃以下になるように構成されていることが好ましい。なお、蓄電デバイス１０は、集電部が櫛歯構造を有し、その集電線１本の抵抗Ｒが０．４Ω以上であり、この内部短絡が生じたときの内部温度の最高温度を１６０℃以下とすることができる。図３は、蓄電デバイス１０の内部短絡が起きた一例を示す模式図である。図３に示すように、例えば、正極集電部、負極集電部の両方が櫛歯状で櫛歯方向を逆向きに対向させた場合、電極内のどこで短絡しても、櫛歯状の正／負集電部を合計Ｌ（集電線１本分の長さ）に亘って電流が通るため、集電線１本分の抵抗Ｒによって短絡電流が制限される。このため、内部短絡による発熱がより抑制される。 It is preferable that the electricity storage device 10 is configured such that the internal temperature is 160° C. or lower when an internal short circuit occurs in the electrodes. In addition, in the electricity storage device 10, the current collecting part has a comb-teeth structure, the resistance R of one current collecting wire is 0.4Ω or more, and the maximum internal temperature when this internal short circuit occurs is 160°C. It can be as follows. FIG. 3 is a schematic diagram showing an example in which an internal short circuit occurs in the power storage device 10. As shown in FIG. 3, for example, if both the positive electrode current collector and the negative electrode current collector are comb-shaped and the comb-teeth directions are opposite to each other, no matter where in the electrode there is a short circuit, the comb-teeth-shaped Since current passes through the positive/negative current collectors over a total length L (the length of one current collector wire), the short circuit current is limited by the resistance R of one current collector wire. Therefore, heat generation due to internal short circuits is further suppressed.
この蓄電デバイスの形状は、特に限定されないが、例えばコイン型、ボタン型、シート型、積層型、円筒型、偏平型、角型などが挙げられる。また、こうした電池を複数直列に接続して電気自動車等に用いる大型のものなどに適用してもよい。 The shape of this power storage device is not particularly limited, and examples thereof include a coin shape, a button shape, a sheet shape, a stacked type, a cylindrical shape, a flat shape, a square shape, and the like. Furthermore, a plurality of such batteries may be connected in series and applied to large batteries used in electric vehicles and the like.
以上詳述した蓄電デバイス１０では、安全性をより高めることができる。このような効果が得られる理由は、以下のように推察される。例えば、シート電極の集電部を櫛歯構造にすることによって、全体がシート状の集電部に比して、内部短絡時の電流集中を抑制し、高安全を担保することができる。一方、この櫛歯構造を有する電極を備えた蓄電デバイスでは、電極の大きさによって、電流集中を抑制できる集電線の幅、厚さなど、その構造は異なるものと推察される。ここで、蓄電デバイス１０には上限電圧が規定されていることから、例えば内部短絡による温度上昇が加速的に起きる熱暴走の開始温度範囲と、集電線１本の抵抗との関係を検討し、この集電線１本の抵抗を規定することにより、安全性を担保するものとした。すなわち、集電線が長くなるような電極面積が大きい電池では、集電線の幅、厚さを大きくしても規定の抵抗を満足することが出来るので、集電部の自由度を高めることができ、更に、櫛歯構造の作製を容易にすることができる。また、集電部は主に、正極はアルミニウム、負極は銅を用いているが、これらのように体積抵抗率の異なる集電部を用いた場合にも、集電線１本の抵抗が規定値を満足すれば集電線の長さ、幅、厚さを任意に設計することができ、更に内部短絡時の熱暴走の発生などをより抑制することができる。 In the power storage device 10 described in detail above, safety can be further improved. The reason why such an effect is obtained is inferred as follows. For example, by forming the current collecting portion of the sheet electrode into a comb-teeth structure, it is possible to suppress current concentration in the event of an internal short circuit and ensure high safety, compared to a current collecting portion that is entirely sheet-like. On the other hand, in a power storage device equipped with an electrode having a comb-teeth structure, it is assumed that the structure, such as the width and thickness of the current collection line that can suppress current concentration, differs depending on the size of the electrode. Here, since an upper limit voltage is specified for the electricity storage device 10, for example, the relationship between the temperature range at which thermal runaway starts, where the temperature rises at an accelerated rate due to an internal short circuit, and the resistance of one current collection wire is considered, By specifying the resistance of this single current collector wire, safety was ensured. In other words, in a battery with a large electrode area that requires a long current collector wire, the specified resistance can be satisfied even if the width and thickness of the current collector wire are increased, so the flexibility of the current collector section can be increased. Furthermore, the comb structure can be easily produced. In addition, the current collectors mainly use aluminum for the positive electrode and copper for the negative electrode, but even when current collectors with different volume resistivities are used, the resistance of one current collector wire will not exceed the specified value. If the following is satisfied, the length, width, and thickness of the current collector wire can be arbitrarily designed, and furthermore, the occurrence of thermal runaway due to internal short circuit can be further suppressed.
なお、本開示は上述した実施形態に何ら限定されることはなく、本開示の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。 It goes without saying that the present disclosure is not limited to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.
例えば、上述した実施形態では、蓄電デバイスのキャリアをリチウムイオンとしたが、特にこれに限定されず、ナトリウムイオンやカリウムイオンなどのアルカリ金属イオン、カルシウムイオンやマグネシウムイオンなどの２族元素イオンとしてもよい。また、正極活物質は、キャリアのイオンを含むものとすればよい。また、電解液を非水系電解液としたが、水溶液系電解液としてもよい。 For example, in the above-described embodiment, the carrier of the electricity storage device is a lithium ion, but the carrier is not limited to this, and may also be an alkali metal ion such as a sodium ion or a potassium ion, or a group 2 element ion such as a calcium ion or a magnesium ion. good. Further, the positive electrode active material may contain carrier ions. Further, although the electrolytic solution is a non-aqueous electrolytic solution, it may be an aqueous electrolytic solution.
上述した実施形態では、正極活物質を遷移金属複合酸化物としたが、特に限定されず、例えば、キャパシタに用いられる炭素材料としてもよい。炭素材料としては、特に限定されるものではないが、例えば、活性炭類、コークス類、ガラス状炭素類、黒鉛類、難黒鉛化性炭素類、熱分解炭素類、炭素繊維類、カーボンナノチューブ類、ポリアセン類などが挙げられる。このうち、高比表面積を示す活性炭類が好ましい。炭素材料としての活性炭は、比表面積が１０００ｍ2／ｇ以上であることが好ましく、１５００ｍ2／ｇ以上であることがより好ましい。比表面積が１０００ｍ2／ｇ以上では、放電容量をより高めることができる。この活性炭の比表面積は、作製の容易性から３０００ｍ2／ｇ以下であることが好ましく、２０００ｍ2／ｇ以下であることがより好ましい。なお、正極では、イオン伝導媒体に含まれるアニオン及びカチオンの少なくとも一方を吸着、脱離して蓄電するものと考えられるが、さらに、イオン伝導媒体に含まれるアニオン及びカチオンの少なくとも一方を挿入、脱離して蓄電するものとしてもよい。 In the embodiments described above, the positive electrode active material is a transition metal composite oxide, but is not particularly limited, and may be, for example, a carbon material used in a capacitor. Carbon materials include, but are not particularly limited to, activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, Examples include polyacenes. Among these, activated carbons exhibiting a high specific surface area are preferred. The activated carbon as a carbon material preferably has a specific surface area of 1000 m 2 /g or more, more preferably 1500 m 2 /g or more. When the specific surface area is 1000 m 2 /g or more, the discharge capacity can be further increased. The specific surface area of this activated carbon is preferably 3000 m 2 /g or less, more preferably 2000 m 2 /g or less from the viewpoint of ease of production. Note that the positive electrode is thought to store electricity by adsorbing and desorbing at least one of anions and cations contained in the ion conductive medium, but it also absorbs and desorbs at least one of anions and cations contained in the ion conductive medium. It may also be used to store electricity.
上述した実施形態では、櫛歯構造を有する蓄電デバイス用電極を正極及び負極に用いるものとしたが、特にこれに限定されない。例えば、蓄電デバイスは、蓄電デバイス用電極が正極及び負極のうち一方であり、蓄電デバイス用電極に対向する対極はシート状の集電部を有し、蓄電デバイス用電極は、集電線と接続部との接続部分に集電線の先端側に比してより抵抗が高い高抵抗部を有し、１本の集電線の抵抗Ｒが０．４Ω以上であるものとしてもよい。図４は、別の蓄電デバイス１０Ｂの一例を示す模式図であり、図４Ａが図４ＢのＡ－Ａ断面図、図４Ｂが蓄電デバイス１０Ｂの側面図、図４Ｃが図４ＢのＢ－Ｂ断面図である。蓄電デバイス１０Ｂは、正極１６Ｂは、櫛歯状の正極集電部３０Ｂを備えるが、シート状の負極集電部２０Ｂを備えた負極１２Ｂを有する単セル１１Ｂを備えている。また、正極集電部３０Ｂは、接続部３１と集電線３３との接続部分に高抵抗部３４を有している。高抵抗部３４は、集電線３３の先端側に比してより抵抗が高ければよく、体積抵抗率ρが大きい材質で形成されていてもよいし、幅Ｗや厚さｔが先端部に比して狭く形成されているものとしてもよい。この高抵抗部３４を有すれば、集電線３３の先端側、根元側のいずれで内部短絡が生じた場合でも、長さＬに係わらず、抵抗Ｒによる電流の抑制を図ることができ、発熱をより抑制することができる。なお、図４では、負極１２Ｂがシート状の負極集電部２０Ｂを備えるものとしたが、正極１６がシート状の正極集電部を備えるものとしてもよい。 In the embodiments described above, electrodes for power storage devices having a comb-teeth structure are used as the positive electrode and the negative electrode, but the present invention is not particularly limited thereto. For example, in an electricity storage device, the electrode for the electricity storage device is one of a positive electrode and a negative electrode, the counter electrode facing the electrode for the electricity storage device has a sheet-like current collecting part, and the electrode for the electricity storage device has a current collecting line and a connecting part. A high resistance part having a higher resistance than the tip end side of the current collecting wire may be provided at the connection portion with the current collecting wire, and the resistance R of one current collecting wire may be 0.4Ω or more. FIG. 4 is a schematic diagram showing an example of another power storage device 10B, in which FIG. 4A is a cross-sectional view taken along line AA in FIG. 4B, FIG. 4B is a side view of power storage device 10B, and FIG. 4C is a cross-sectional view taken along line BB in FIG. 4B. It is a diagram. The power storage device 10B includes a single cell 11B having a positive electrode 16B having a comb-shaped positive electrode current collecting portion 30B, and a negative electrode 12B having a sheet-like negative electrode current collecting portion 20B. Further, the positive electrode current collector 30B has a high resistance portion 34 at the connection portion between the connection portion 31 and the current collection wire 33. The high resistance part 34 only needs to have a higher resistance than the tip side of the current collecting wire 33, and may be formed of a material with a large volume resistivity ρ, and the width W and thickness t may be higher than that of the tip side. It may be formed narrowly. If this high resistance part 34 is provided, even if an internal short circuit occurs at either the tip side or the base side of the current collecting wire 33, the current can be suppressed by the resistance R regardless of the length L, and heat generation can be further suppressed. Note that in FIG. 4, the negative electrode 12B includes the sheet-shaped negative electrode current collector 20B, but the positive electrode 16 may include a sheet-shaped positive electrode current collector.
本開示は、以下の［１］～［６］のいずれかに示すものとしてもよい。
［１］ 電極活物質と、
前記電極活物質に隣接する複数の集電線と該集電線が並列接続する接続部とを備える櫛歯構造を有する集電部と、を備え、
１本の前記集電線の抵抗Ｒが０．４Ω以上である、
蓄電デバイス用電極。
［２］ 前記集電線の幅Ｗが２ｍｍ以上である、［１］に記載の蓄電デバイス用電極。
［３］ １本の前記集電線の抵抗Ｒが５Ω以下である、［１］又は［２］に記載の蓄電デバイス用電極。
［４］ ［１］～［３］のいずれか１つに記載の蓄電デバイス用電極と、
前記記蓄電デバイス用電極に隣接されキャリアイオンを伝導するイオン伝導媒体と、を備え、
前記記蓄電デバイス用電極は、正極及び負極のうち少なくとも一方である、蓄電デバイス。
［５］ 前記蓄電デバイス用電極は、正極及び負極であり、
前記正極の前記櫛歯構造と前記負極の前記櫛歯構造との櫛歯方向が逆向きであり、
１本の前記集電線の抵抗Ｒが０．４Ω以上である、［４］に記載の蓄電デバイス。
［６］ 前記蓄電デバイス用電極は、正極及び負極のうち一方であり、
前記蓄電デバイス用電極に対向する対極は、シート状の集電部を有し、
前記蓄電デバイス用電極は、前記集電線と前記接続部との接続部分に前記集電線の先端側に比してより抵抗が高い高抵抗部を有し、１本の前記集電線の抵抗が０．４Ω以上である、［４］に記載の蓄電デバイス。
The present disclosure may be disclosed in any of [1] to [6] below.
[1] Electrode active material,
A current collecting section having a comb-teeth structure including a plurality of current collecting wires adjacent to the electrode active material and a connection section where the current collecting wires are connected in parallel,
The resistance R of one current collection wire is 0.4Ω or more,
Electrodes for power storage devices.
[2] The electrode for an electricity storage device according to [1], wherein the current collection line has a width W of 2 mm or more.
[3] The electrode for an electricity storage device according to [1] or [2], wherein the resistance R of one current collection wire is 5Ω or less.
[4] The electrode for an electricity storage device according to any one of [1] to [3],
an ion-conducting medium that is adjacent to the storage device electrode and that conducts carrier ions;
The electricity storage device, wherein the electricity storage device electrode is at least one of a positive electrode and a negative electrode.
[5] The electrodes for the electricity storage device are a positive electrode and a negative electrode,
The comb tooth structure of the positive electrode and the comb tooth structure of the negative electrode have opposite comb tooth directions,
The electricity storage device according to [4], wherein the resistance R of one current collection wire is 0.4Ω or more.
[6] The electrode for an electricity storage device is one of a positive electrode and a negative electrode,
The counter electrode facing the electricity storage device electrode has a sheet-like current collector,
The electrode for a power storage device has a high resistance part having a higher resistance than the tip end side of the current collecting wire at a connecting portion between the current collecting wire and the connecting portion, and the resistance of one current collecting wire is 0. .4Ω or more, the electricity storage device according to [4].
以下には、上述した蓄電デバイス用電極及び蓄電デバイスを具体的に作製した例を実験例として説明する。なお、実験例３、４は、本開示の実施例の一例であり、実験例１、２は、参考例の一例である。 Below, an example in which the above-described electrode for a power storage device and a power storage device were specifically produced will be described as an experimental example. Note that Experimental Examples 3 and 4 are examples of embodiments of the present disclosure, and Experimental Examples 1 and 2 are examples of reference examples.
（櫛歯集電構造を有する電極構造体を備えたリチウム電池）
実験で用いたリチウムイオン二次電池（ＬｉＢ）の概要を以下に説明する。図５は、試験用セルの説明図であり、図５Ａが従来の金属箔集電体を有する標準リチウムイオン二次電池（ＬＩＢ）の写真、図５Ｂが櫛歯集電部を有する実施例のＬＩＢの写真、図５Ｃが櫛歯集電部の拡大写真である。図５Ｂ，Ｃに示すように、ポリイミド（ＰＩ）フィルム上にストライプ状のアルミニウムもしくは銅をイオンプレート法で形成し、櫛歯集電体を作製した。この櫛歯集電体を従来の集電体のアルミニウム箔や銅箔の代わりとして電極と積層した。電極材料には正極活物質としてＬｉＮｉ0.5Ｃｏ0.2Ｍｎ0.3Ｏ2：ＮＭＣ）と、負極活物質としてグラファイトとを用い、電池容量を６２０Ｗｈ／Ｌ、１Ａｈに設計した。
(Lithium battery equipped with an electrode structure having a comb-teeth current collection structure)
An outline of the lithium ion secondary battery (LiB) used in the experiment will be explained below. FIG. 5 is an explanatory diagram of a test cell, where FIG. 5A is a photograph of a standard lithium ion secondary battery (LIB) having a conventional metal foil current collector, and FIG. 5B is a photograph of an example having a comb-teeth current collector. The photo of LIB, FIG. 5C, is an enlarged photo of the comb-tooth current collector. As shown in FIGS. 5B and 5C, striped aluminum or copper was formed on a polyimide (PI) film by an ion plate method to produce a comb-shaped current collector. This comb-shaped current collector was laminated with an electrode in place of the conventional aluminum foil or copper foil. The electrode materials used were LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NMC) as a positive electrode active material and graphite as a negative electrode active material, and the battery capacity was designed to be 620 Wh/L and 1 Ah.
正極活物質（ＬｉＮｉ0.5Ｃｏ0.2Ｍｎ0.3Ｏ2）と、導電材としてのアセチレンブラック（デンカ社製ＨＳ－１００）と、導電材としての気相成長炭素繊維（昭和電工製ＶＧＣＦ）と、結着材としてのポリフッ化ビニリデン（クレハ製ＰＶｄＦ７３０５）とを質量比で９０：４：２：４となるよう配合したものにＮ－メチルピロリドンを加えて正極合材ペーストとした。この正極合材ペーストを支持体としてのＡｌ箔（厚さ１０μｍ）上に塗布し、正極合材の厚さが１５０μｍ、縦１０ｍｍ×横８０ｍｍのサイズとなるように正極合材層を形成した。この上に、Ａｌ製の集電線（幅５００μｍ、厚さ８μｍ、間隔５００μｍ、長さ７０ｍｍ、体積抵抗率０．０２５Ωμｍ）の１０本をＡｌ箔製の接続部に接続した櫛歯構造の正極集電部を、集電線の先端から７０ｍｍの部分を正極活物質層とし、集電部が外部に１０ｍｍ露出した状態で配置した。このシートを加熱乾燥させて塗布シートを作製し、その後塗布シートをロールプレスに通して高密度化させ、Ａｌ箔を剥離することにより、１５０μｍの正極合材層に櫛歯状の正極集電部の集電線が隣接した正極シートを得た。負極活物質として黒鉛を９５質量％、結着剤としてポリフッ化ビニリデンを５質量％混合し、正極と同様にスラリー状合材とした。この負極合材ペーストを支持体としてのＣｕ箔（厚さ２０μｍ）上に塗布し、負極合材の厚さが１５０μｍ、縦１０ｍｍ×横８０ｍｍのサイズとなるように負極合材層を形成した。この上に、Ｃｕ製の集電線（幅５００μｍ、厚さ５μｍ、間隔５００μｍ、長さ７０ｍｍ、体積抵抗率０．０１５５Ωμｍ）の１０本をＣｕ箔製の接続部に接続した櫛歯構造の負極集電部を、集電線の先端から７０ｍｍの部分を負極活物質層とし、集電部が外部に１０ｍｍ露出した状態で配置した。このシートを加熱乾燥させて塗布シートを作製し、その後塗布シートをロールプレスに通して高密度化させ、Ｃｕ箔を剥離することにより、１５０μｍの負極合材層に櫛歯状の負極集電部の集電線が隣接した負極シートを得た。集電線の厚さを変更することにより、Ａｌ抵抗が４３８ｍΩ、Ｃｕ抵抗が４３８ｍΩの電極構造体とした。上記の正極シートと負極シートを活物質層側で対向させ、その間にポリエチレン製セパレータを挟み電極構造体とし、Ａｌ製のケースに収容し、非水電解液を含侵させた後に密閉してリチウムイオン二次電池である試験用電池とした（実施例）。非水電解液には、エチレンカーボネート、ジメチルカーボネート、エチルメチルカーボネートを体積％で３０／４０／３０の割合で混合した混合溶媒に、ＬｉＰＦ6を１Ｍの濃度で溶解させたものを用いた。また、櫛歯構造の集電部をＡｌ箔及びＣｕ箔に変更したものを従来構造の試験用電池（比較例）とした。 A positive electrode active material (LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), acetylene black (HS-100 manufactured by Denka) as a conductive material, vapor grown carbon fiber (VGCF manufactured by Showa Denko) as a conductive material, and a binder. N-methylpyrrolidone was added to a mixture of polyvinylidene fluoride (PVdF7305 manufactured by Kureha) in a mass ratio of 90:4:2:4 to obtain a positive electrode composite paste. This positive electrode composite material paste was applied onto an Al foil (thickness: 10 μm) as a support to form a positive electrode composite material layer such that the thickness of the positive electrode composite material was 150 μm and the size of the positive electrode composite material was 10 mm long×80 mm wide. On top of this, 10 Al current collector wires (width 500 μm, thickness 8 μm, spacing 500 μm, length 70 mm, volume resistivity 0.025 Ω μm) were connected to Al foil connection parts to form a positive electrode assembly with a comb-teeth structure. The current collector was placed in such a manner that a portion 70 mm from the tip of the current collector wire was used as a positive electrode active material layer, and 10 mm of the current collector was exposed to the outside. This sheet is heated and dried to produce a coated sheet, and then the coated sheet is passed through a roll press to increase the density. By peeling off the Al foil, a comb-shaped positive electrode current collector is formed on a 150 μm positive electrode composite layer. A positive electrode sheet with adjacent current collecting wires was obtained. 95% by mass of graphite as a negative electrode active material and 5% by mass of polyvinylidene fluoride as a binder were mixed to form a slurry-like composite material similarly to the positive electrode. This negative electrode composite material paste was applied onto a Cu foil (thickness: 20 μm) as a support to form a negative electrode composite material layer such that the negative electrode composite material had a thickness of 150 μm and a size of 10 mm in length×80 mm in width. On top of this, ten Cu current collector wires (width 500 μm, thickness 5 μm, spacing 500 μm, length 70 mm, volume resistivity 0.0155 Ωμm) were connected to Cu foil connections to form a negative electrode assembly with a comb-teeth structure. The current collector was placed in such a manner that a portion 70 mm from the tip of the current collector wire was used as a negative electrode active material layer, and 10 mm of the current collector was exposed to the outside. This sheet is heated and dried to produce a coated sheet, and then the coated sheet is passed through a roll press to increase the density, and the Cu foil is peeled off to form a comb-shaped negative electrode current collector on a 150 μm negative electrode composite layer. A negative electrode sheet with adjacent current collecting wires was obtained. By changing the thickness of the current collector wire, an electrode structure with an Al resistance of 438 mΩ and a Cu resistance of 438 mΩ was obtained. The above positive electrode sheet and negative electrode sheet are placed facing each other on the active material layer side, and a polyethylene separator is sandwiched between them to form an electrode structure.The electrode structure is housed in an Al case, impregnated with a non-aqueous electrolyte, and then sealed to lithium. The test battery was an ion secondary battery (Example). The nonaqueous electrolyte used was one in which LiPF 6 was dissolved at a concentration of 1M in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a ratio of 30/40/30 by volume. In addition, a test battery having a conventional structure (comparative example) was prepared by changing the comb-shaped current collecting part to an Al foil and a Cu foil.
（内部短絡試験：釘刺し試験）
図６は、実験装置（図６Ａ）、試験用セル（図６Ｂ）及び刺し釘（図６Ｃ）の説明写真である。電池の内部短絡を模擬し、電池の温度上昇を測定する試験を図６Ａに示した実験装置を用いて行った。実験装置は、刺し釘を固定したボール盤と、ＸＹＺステージと、抵抗測定器と、ダイヤルゲージと、熱電対と、ＰＣとを備える。この装置では、ボール盤の先端に刺し釘を固定し、その下方にＸＹＺステージ上に試験用電池を固定し、ダイヤルゲージにて試験セルの高さを測定しながら試験セルを一定速度で上昇させ、温度と、直流抵抗と、変位とを測定し、ＰＣに入力する構成とした。評価用電池の表面に、熱電対を設置して固定し、評価用電池を断熱板で挟み、釘を４ｍｍ突き刺してその変位と温度変化とを測定した。なお、内部短絡の条件は、例えば、異物混入、リチウム析出、損傷など様々であるが、釘刺し４ｍｍは厳しい条件に相当する。
(Internal short circuit test: nail penetration test)
FIG. 6 is an explanatory photograph of the experimental apparatus (FIG. 6A), the test cell (FIG. 6B), and the stabbing nail (FIG. 6C). A test was conducted using the experimental apparatus shown in FIG. 6A to simulate an internal short circuit in the battery and measure the temperature rise in the battery. The experimental equipment includes a drilling machine with a fixed nail, an XYZ stage, a resistance measuring device, a dial gauge, a thermocouple, and a PC. In this device, a nail is fixed to the tip of a drill press, a test battery is fixed below it on an XYZ stage, and the test cell is raised at a constant speed while measuring the height of the test cell with a dial gauge. The structure was such that temperature, DC resistance, and displacement were measured and input into a PC. A thermocouple was installed and fixed on the surface of the evaluation battery, the evaluation battery was sandwiched between heat insulating plates, and a nail was penetrated 4 mm to measure its displacement and temperature change. Note that there are various conditions for internal short circuits, such as foreign matter contamination, lithium precipitation, damage, etc., but a nail penetration of 4 mm corresponds to severe conditions.
図７は、金属箔集電部を備えた試験セルの釘刺し試験結果である。図８は、櫛歯構造集電部を備えた試験セルの釘刺し試験結果である。従来の金属箔を集電体に用いた電池の場合、釘刺し深さ４ｍｍで温度は５００℃を超え、熱暴走に至った。電圧は４．１Ｖから０Ｖへ急激に低下しており、電池内部、短絡部、集電部を合わせた抵抗が小さいことが示されている。それに対し、櫛歯集電体を用いた電池の場合、釘刺し深さ４ｍｍで温度は１００℃程度に抑えられた。１００℃は電極が熱分解反応を起こす１６０℃より低く、電池の安全性が確保されていると判断できた。電圧低下は０．５Ｖ程度であり、櫛歯集電部の抵抗が大きく、電流が制限されていることが示された。 FIG. 7 shows the nail penetration test results of a test cell equipped with a metal foil current collector. FIG. 8 shows the results of a nail penetration test of a test cell equipped with a comb-shaped current collector. In the case of a battery using a conventional metal foil as a current collector, the temperature exceeded 500° C. at a nail penetration depth of 4 mm, leading to thermal runaway. The voltage dropped rapidly from 4.1V to 0V, indicating that the combined resistance inside the battery, the short circuit, and the current collector was small. On the other hand, in the case of a battery using a comb-teeth current collector, the temperature was suppressed to about 100° C. at a nail penetration depth of 4 mm. The temperature of 100°C was lower than the temperature of 160°C at which the electrode caused a thermal decomposition reaction, and it was determined that the safety of the battery was ensured. The voltage drop was about 0.5V, indicating that the resistance of the comb-shaped current collector was large and the current was limited.
次に、リチウムイオン二次電池の内部短絡時の温度上昇を計算するためのモデル概要について検討した結果を説明する。内部短絡に伴う放電を計算するための電気化学モデルと短絡部に集中するジュール熱の電池セルへの広がりを計算するための伝熱モデルを組み合わせた。マルチフィジックスの計算プラットフォームであるＣｏｍｓｏｌを採用し、電気化学モデルの構築にはバッテリデザインモジュール、伝熱モデルの構築には伝熱モジュールを用いた。電気化学の計算では、電解液ポテンシャルφｌ、電解塩濃度ｃｌ、固体電極ポテンシャルφｓの３変数を求めた。支配方程式はＯｈｍ則であり、電位差による電流を求めた。Ｊは電解塩の拡散流束、Ｒは反応生成項、ｉは電流、Ｑは電流生成項、Ｄは拡散係数、ｔは輸率、Ｆはファラデー定数、σは電子伝導度、Ｒは気体定数、Ｔは温度、ｆは熱力学因子、添え字ｌは液体中、ｓは固体中を示す。電気化学の計算は以下に示した式を用いた。 Next, we will explain the results of a study on the outline of a model for calculating the temperature rise in the event of an internal short circuit in a lithium ion secondary battery. We combined an electrochemical model to calculate the discharge associated with an internal short circuit and a heat transfer model to calculate the spread of Joule heat concentrated at the short circuit to the battery cell. We adopted Comsol, a multiphysics calculation platform, and used the battery design module to build the electrochemical model and the heat transfer module to build the heat transfer model. In the electrochemical calculation, three variables were determined: electrolyte potential φl, electrolyte salt concentration cl, and solid electrode potential φs. The governing equation was Ohm's law, and the current due to the potential difference was determined. J is the diffusion flux of the electrolytic salt, R is the reaction production term, i is the current, Q is the current production term, D is the diffusion coefficient, t is the transference number, F is the Faraday constant, σ is the electronic conductivity, and R is the gas constant , T is temperature, f is thermodynamic factor, subscript l indicates in liquid, and s indicates in solid. The equation shown below was used for electrochemical calculations.
正極と負極ともに多孔体電極を仮定した。多孔体電極を構成する粒子は球形とし、平均粒径を設定する。粒子内部のリチウムイオンの移動はＦｉｃｋ則に従う拡散とした。Ｃはリチウムイオン濃度、Ｄは拡散係数、νは平衡係数、ｉは平衡電流、ｎは電荷数、εは多孔体の空隙率である。 Porous electrodes were assumed for both the positive and negative electrodes. The particles constituting the porous electrode are spherical, and the average particle size is set. The movement of lithium ions inside the particles was assumed to be diffusion according to Fick's law. C is the lithium ion concentration, D is the diffusion coefficient, ν is the equilibrium coefficient, i is the equilibrium current, n is the number of charges, and ε is the porosity of the porous body.
電極界面でのリチウムイオンの挿入脱離はＢｕｔlｅｒ－Ｖｏｌｍｅｒ則で記述される。電極上でアノード反応とカソード反応の両方が起こるとして、その差によって電流が決まる。αは反応係数、ηは活性化過電圧、ａはアノード反応、ｃはカソード反応である。 The insertion and desorption of lithium ions at the electrode interface is described by the Butler-Volmer law. Assuming that both anodic and cathodic reactions occur on the electrode, the difference between them determines the current. α is the reaction coefficient, η is the activation overvoltage, a is the anodic reaction, and c is the cathodic reaction.
短絡部に集中するジュール熱のセル全体への広がりはＦｉｃｋ則で記述される。 The spread of Joule heat concentrated at the short circuit portion throughout the cell is described by Fick's law.
上記の計算モデルで用いる物性値には、Ｃｏｍｓｏｌライブラリ、論文からの引用値、実験で取得した値を用いた。電池電圧４．１Ｖ（１００％充電状態）、容量が１Ａｈおよび１０ＡｈのＬｉ電池において、１本の櫛歯抵抗Ｒが２０～１０００ｍΩの場合について、内部短絡抵抗（Ｒ－ｓｈｏｒｔ）が１～１５００ｍΩで短絡したときのジュール発熱による短絡局所の最高温度を計算によって求めた。図９は、電池容量が１Ａｈの場合の短絡抵抗と電池温度と集電線１本の抵抗との関係の計算結果である。図９の右には、釘刺し短絡部に電流が集中し、ジュール熱が広がるシミュレーションの一例を示した。また、電池容量が１Ａｈと１０Ａｈの場合の内部短絡箇所の最高温度の計算結果を表１にまとめた。 For the physical property values used in the above calculation model, the Comsol library, values quoted from papers, and values obtained through experiments were used. For Li batteries with a battery voltage of 4.1V (100% charged state) and a capacity of 1Ah and 10Ah, when one comb tooth resistance R is 20 to 1000mΩ, the internal short circuit resistance (R-short) is 1 to 1500mΩ. The maximum temperature in the short circuit area due to Joule heat generation when the short circuit occurs was determined by calculation. FIG. 9 is a calculation result of the relationship between short circuit resistance, battery temperature, and resistance of one current collection wire when the battery capacity is 1 Ah. The right side of FIG. 9 shows an example of a simulation in which current concentrates at the nail penetration short circuit and Joule heat spreads. Further, Table 1 summarizes the calculation results of the maximum temperature at the internal short circuit when the battery capacity is 1 Ah and 10 Ah.
図９、表１に示すように、従来の金属集電箔を用いた場合を想定したＲ＝２０ｍΩの場合、１Ａｈ電池でも最高温度が３８６℃に到達し、熱暴走開始温度である１６０℃を超えることがわかった。また、１０Ａｈ電池では短絡箇所へのジュール熱の供給が放熱を上回り続けるため３９００℃にも達することがわかった。櫛歯集電部の集電線の幅Ｗと間隔ｓとが１０００μｍを想定した、櫛歯１本の抵抗Ｒ＝２００ｍΩの場合、いずれの電池容量でも最高温度は２５０℃以上であり、熱暴走開始温度以上になった。櫛歯集電部の集電線の幅Ｗと間隔ｓが５００μｍを想定したＲ＝４００ｍΩ以上の場合、短絡抵抗によらず最高温度が１６０℃以下となり、熱暴走開始温度に到達しなかった。さらに、１０Ａｈ電池でも１Ａｈ電池と最高温度はほぼ同じであった。これは、発熱が小さいために放熱とバランスし、温度が上昇しないことを意味すると推察された。以上より、集電線１本の抵抗Ｒ≧４００ｍΩ（０．４Ω）を満たす場合、電池容量が１０Ａｈ以上であっても、熱暴走開始温度には到達しないことが計算結果から示された。１Ａｈ電池の計算結果は、上述した実験結果と対応しており、櫛歯集電機構によって、内部短絡時の温度上昇を抑えられることが計算でも確認できた。さらに、短絡抵抗が変化しても櫛歯集電機構による温度上昇抑制が働くことが示された。 As shown in Figure 9 and Table 1, when R = 20 mΩ, which assumes the case of using a conventional metal current collector foil, the maximum temperature reaches 386°C even in a 1Ah battery, and the temperature at which thermal runaway starts is 160°C. I found out that it can be exceeded. In addition, it was found that in a 10Ah battery, the supply of Joule heat to the short circuit continues to exceed the heat dissipation, so the temperature reaches 3900°C. When the resistance R of one comb tooth is 200 mΩ, assuming that the width W and the interval s of the current collecting wires of the comb tooth current collector are 1000 μm, the maximum temperature is 250°C or higher for any battery capacity, and thermal runaway starts. The temperature has exceeded the temperature. When R = 400 mΩ or more assuming that the width W and the spacing s of the current collecting wires of the comb-teeth current collecting part were 500 μm, the maximum temperature was 160° C. or less regardless of the short circuit resistance, and the thermal runaway starting temperature was not reached. Furthermore, the maximum temperature of the 10Ah battery was almost the same as that of the 1Ah battery. This was inferred to mean that the heat generation is small, so it is balanced with heat radiation, and the temperature does not rise. From the above, the calculation results showed that when the resistance R of one current collection wire satisfies R≧400 mΩ (0.4Ω), even if the battery capacity is 10 Ah or more, the temperature at which thermal runaway starts is not reached. The calculation results for the 1Ah battery corresponded to the experimental results described above, and the calculations also confirmed that the comb-tooth current collection mechanism suppressed the temperature rise in the event of an internal short circuit. Furthermore, it was shown that the comb-teeth current collection mechanism works to suppress temperature rise even if the short-circuit resistance changes.
以上の事から、櫛歯集電電池は集電線１本の抵抗Ｒが４００ｍΩ（０．４Ω）以上の場合に、内部短絡が発生しても熱暴走しない安全な電池となることが明らかとなった。なお、櫛歯構造の集電線１本の抵抗Ｒは、ρ・Ｌ／（Ｗ・ｔ）で表される。 From the above, it is clear that when the resistance R of one current collector wire is 400 mΩ (0.4 Ω) or more, the comb-teeth current collector battery becomes a safe battery that will not run away due to thermal runaway even if an internal short circuit occurs. Ta. Note that the resistance R of one current collector wire having a comb-teeth structure is expressed as ρ·L/(W·t).
参考として、集電体がＡｌとＣｕの場合について、櫛歯構造の集電線１本の抵抗Ｒが４００ｍΩ以上となる集電線の長さＬ、幅Ｗ、厚さｔを表２にまとめた。正極集電部、負極集電部の両方が櫛歯状で櫛歯方向を逆向きに対向させることで、電極内のどこで短絡しても櫛歯状の正／負集電部を合計長さＬ（櫛歯１本分の長さ）だけ通るため、櫛歯１本分の抵抗によって短絡電流が制限される。Ａｌ櫛歯とＣｕ櫛歯の幅をＷ、厚さをｔとし、それぞれの体積抵抗率をρとすると、１本の櫛歯の抵抗Ｒは、Ｒ=ρ・Ｌ／（Ｗ・ｔ）で表され、櫛歯の長さＬが長くなった場合には、櫛歯幅Ｗ、櫛歯厚さｔを大きくすることで抵抗Ｒを等しくすることができる。櫛歯の長さＬが長いほど、櫛歯幅Ｗ、櫛歯厚さｔを大きく設計することができることが分かった。 For reference, Table 2 summarizes the length L, width W, and thickness t of the current collector wire such that the resistance R of one current collector wire having a comb-teeth structure is 400 mΩ or more for the case where the current collector is Al and Cu. Both the positive and negative current collectors are comb-shaped and the comb-teeth directions are opposite to each other, so that even if there is a short circuit anywhere in the electrode, the comb-shaped positive/negative current collectors can be connected to the total length. Since only L (the length of one comb tooth) passes, the short circuit current is limited by the resistance of one comb tooth. When the width of the Al comb teeth and the Cu comb teeth is W, the thickness is t, and the volume resistivity of each is ρ, the resistance R of one comb tooth is R=ρ・L/(W・t). When the length L of the comb teeth becomes longer, the resistance R can be made equal by increasing the comb tooth width W and the comb tooth thickness t. It has been found that the longer the length L of the comb teeth, the larger the comb tooth width W and the comb tooth thickness t can be designed.
電池の内部短絡時に電流集中とジュール加熱を抑え、電池の安全を確保するための回路抵抗が示されたことから、正極集電部のみを櫛歯構造として、負極集電体は従来の箔状集電部を用いるか、又は、負極集電部のみを櫛歯構造として、正極集電体は従来の箔状集電部を用いる設計が可能となる（図４参照）。この構造では、１方の電極のみが櫛歯構造のため、櫛歯の根元に、例えば、幅Ｗが狭い、厚さｔが薄い、体積抵抗率ρが大きいなどの高抵抗なネック部を設けることで片極のみの櫛歯集電構造でも両極櫛歯集電構造とほぼ同等の高安全が達成できるものと推察された。 Since the circuit resistance was shown to suppress current concentration and Joule heating and ensure battery safety in the event of an internal short circuit in the battery, only the positive electrode current collector has a comb-tooth structure, and the negative electrode current collector has a conventional foil-like structure. By using a current collector or by making only the negative electrode current collector have a comb-tooth structure, the positive electrode current collector can be designed using a conventional foil-like current collector (see FIG. 4). In this structure, since only one electrode has a comb tooth structure, a neck portion with high resistance such as a narrow width W, a thin thickness t, and a large volume resistivity ρ is provided at the root of the comb teeth. Therefore, it was inferred that a comb-tooth current collector structure with only one pole can achieve a high level of safety almost equivalent to that of a bipolar comb-teeth current collector structure.
なお、本開示は上述した実施例に何ら限定されることはなく、本開示の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。 It goes without saying that the present disclosure is not limited to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.
１０，１０Ｂ 蓄電デバイス、１１ 単セル、１２，１２Ｂ 負極、１３ 負極活物質層、１５ セパレータ、１６，１６Ｂ 正極、１７ 正極活物質層、２０，２０Ｂ 負極集電部、２１ 接続部、２３ 集電線、３０，３０Ｂ 正極集電部、３１ 接続部、３３ 集電線、３４ 高抵抗部、Ｌ 長さ、ｓ 間隔、ｔ 厚さ、Ｗ 幅。 10, 10B electricity storage device, 11 single cell, 12, 12B negative electrode, 13 negative electrode active material layer, 15 separator, 16, 16B positive electrode, 17 positive electrode active material layer, 20, 20B negative electrode current collector, 21 connection part, 23 current collector wire , 30, 30B positive electrode current collector section, 31 connection section, 33 current collection line, 34 high resistance section, L length, s spacing, t thickness, W width.
Claims (6)
前記電極活物質に隣接する複数の集電線と該集電線が並列接続する接続部とを備える櫛歯構造を有する集電部と、を備え、
１本の前記集電線の抵抗Ｒが０．４Ω以上である、
蓄電デバイス用電極。 electrode active material;
A current collecting section having a comb-teeth structure including a plurality of current collecting wires adjacent to the electrode active material and a connection section where the current collecting wires are connected in parallel,
The resistance R of one current collection wire is 0.4Ω or more,
Electrodes for power storage devices.
前記蓄電デバイス用電極に隣接されキャリアイオンを伝導するイオン伝導媒体と、を備え、
前記蓄電デバイス用電極は、正極及び負極のうち少なくとも一方である、蓄電デバイス。 The electrode for an electricity storage device according to claim 1 or 2,
an ion conductive medium that is adjacent to the electricity storage device electrode and that conducts carrier ions;
The electricity storage device, wherein the electricity storage device electrode is at least one of a positive electrode and a negative electrode.
前記正極の前記櫛歯構造と前記負極の前記櫛歯構造との櫛歯方向が逆向きであり、
１本の前記集電線の抵抗Ｒが０．４Ω以上である、請求項４に記載の蓄電デバイス。 The electrodes for the electricity storage device are a positive electrode and a negative electrode,
The comb tooth structure of the positive electrode and the comb tooth structure of the negative electrode have opposite comb tooth directions,
The electricity storage device according to claim 4, wherein the resistance R of one current collection line is 0.4Ω or more.
前記蓄電デバイス用電極に対向する対極は、シート状の集電部を有し、
前記蓄電デバイス用電極は、前記集電線と前記接続部との接続部分に前記集電線の先端側に比してより抵抗が高い高抵抗部を有し、１本の前記集電線の抵抗Ｒが０．４Ω以上である、請求項４に記載の蓄電デバイス。 The electricity storage device electrode is one of a positive electrode and a negative electrode,
The counter electrode facing the electricity storage device electrode has a sheet-like current collector,
The electrode for an electricity storage device has a high resistance part having a higher resistance than the tip end side of the current collecting wire at a connecting portion between the current collecting wire and the connecting portion, and the resistance R of one current collecting wire is such that the resistance R of one current collecting wire is The electricity storage device according to claim 4, which has a resistance of 0.4Ω or more.
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