JP3615432B2

JP3615432B2 - Electrode and lithium secondary battery

Info

Publication number: JP3615432B2
Application number: JP27705799A
Authority: JP
Inventors: 義人近野; 一成大北; 俊之能間; 育郎米津
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1999-09-29
Filing date: 1999-09-29
Publication date: 2005-02-02
Anticipated expiration: 2019-09-29
Also published as: JP2001102051A

Description

【０００１】
【発明の属する技術分野】
本発明は、リチウム二次電池に用いて好適な電極、及びその電極を用いたリチウム二次電池に関する。
【０００２】
【従来の技術】
近年、電気自動車に必要な高エネルギー密度、且つ高出力密度を達成することのできる二次電池として、リチウム二次電池が期待されている。
【０００３】
電気自動車などに必要な大容量、高出力密度の電池は、発進時や急加速時に大電流を通電する必要があり、エネルギー効率向上やジュール発熱低減の観点から集電性の向上による電池内部抵抗の低減が必須となっている。特に円筒型の大容量の二次電池では帯状の電極が長尺となるため、電位分布を小さくし集電性を向上させるため、複数の集電タブを配設する必要があり、芯体と集電タブをスポット、レーザー、超音波等で溶着していたが、電気的接触性は必ずしも良好でなく、大電流通電時に溶着部での発熱が問題となっている。
【０００４】
上記問題を解決するものとして、例えば、特開平８−１１５７４４号公報には、集電タブの代わりに、芯体の端部に活物質の未塗布部を設け、それを金属製の円形状集電板に溶接により接続し、その集電板を集電端子に接続した集電方法を用いたリチウム二次電池が提案されている。
【０００５】
しかしながら、リチウム二次電池では有機系電解液を用いているため巻電極が圧迫した状態であるため、上記公報に示された集電方法を用いたリチウム二次電池では、有機系電解液が電極に含浸し難いという問題がある。
【０００６】
また、特開平９−９２３３５号公報には、正負極未塗布部の芯体を短冊状に加工し、複数の短冊状リードを束ねて正極集電端子、及び負極集電端子に接続した二次電池が提案されている。
【０００７】
しかしながら、この公報に示されているリチウム二次電池においても、短冊状リード間の隙間から電解液の含浸が可能であるが、多数の短冊状リードを束ねて正、負極集電端子に接続する必要があるなど製造工程が複雑なものになるという問題がある。
【０００８】
【発明が解決しようとする課題】
本発明は上記従来例の欠点に鑑み為されたものであり、製造工程を複雑とすることなく電解液が含浸し易くなるように構成した電極、及びその電極を用いたリチウム二次電池を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明の電解液を用いるリチウム二次電池用電極は、帯状の正極と帯状の負極とがセパレータを介して巻回してあり、前記正極及び負極の少なくとも一方の芯体の端部には活物質が付着していない未塗布部分が設けられ、該未塗布部は前記セパレータより露出し、且つ開孔部が設けられていることを特徴とする。
【００１０】
このような構成の電極では、リチウム二次電池等に用いた場合、前記開孔部から電解液が浸透し、電極への電解液の含浸が促進される。
【００１１】
特に、本発明の電極では、前記未塗布部分における開孔部の開孔率が１０％以上、８０％以下である場合、リチウム二次電池等に用いた場合、良好な充放電が可能となる。
【００１２】
また、前記正極の芯体としては、アルミニウム箔が適している。
【００１３】
また、前記負極の芯体としては、銅箔或いはニッケル箔が適している。
【００１４】
また、本発明のリチウム二次電池は、上述の本発明の電極を備え、該電極の前記未塗布部分より端子への電気的接続が行われていることを特徴とする。
【００１５】
このような構成のリチウム二次電池では、電極への電解液の含浸が促進され、良好な充放電が行われる。
【００１６】
リチウムイオンの吸蔵、放出可能な正極の活物質材料としては、金属酸化物が適するが、具体的には、ＬｉＣｏＯ₂、ＬｉＮｉＯ₂、ＬｉＣｏ_1-XＮｉ_XＯ₂、ＬｉＭｎ₂Ｏ₄及びこれらの複合化合物からなる群から選択された少なくとも1種の材料を挙げることができる。
【００１７】
また、本発明で使用される負極の活物質材料としては、黒鉛、コークス等の炭素材料、リチウム金属、リチウム合金、ＬｉXＦｅ₂Ｏ₃、Ｌｉ_XＷＯ₂等の金属酸化物材料、ポリアセチレン等の導電性高分子材料等が挙げられる。特に黒鉛からなる炭素材料を用いた場合、優れた効果が発揮される。前記炭素材料に用いられる黒鉛、コークス材料としては、粉砕したものをそのまま用いてもよく、５００℃〜３７００℃の範囲で加熱処理したものを用いてもよい。また、黒鉛のＸ線広角回折法による（００２）面の面間隔ｄ002の値は３．３５Å以上、３．３７Å以下、Ｃ軸方向の結晶子長さＬｃは４００Å以上が好ましい。
【００１８】
尚、電解液、電解質、セパレータなどの電池構成部材についても、従来のリチウム二次電池用として実用され或いは提案されている種々の材料を使用することが可能である。
【００１９】
例えば、電解質としてはリチウムイオンを含むＬｉＰＦ₆、ＬｉＣｌＯ₄、ＬｉＣＦ₃ＳＯ₃等の電解質が挙げられる。また、電解液の有機溶媒としてはエチレンカーボネート、ジエチルカーボネート、ジメトキシメタン、スルホラン等を単独、あるいは混合して用いることができる。電解液としてはこれら溶媒に前記電解質を０．７〜１．５Ｍ（ｍｏｌ／ｌ）程度の割合で溶解させた溶液が挙げられる。
【００２０】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。
【００２１】
[正極の作製]
正極芯体となるアルミニウム箔（厚み２０μｍ）の活物質の未塗布部に相当する部分に、未塗布部における開孔率５％になるように、円形の開孔部を形成した。尚、活物質の塗布部に相当する部分には全く開孔部を形成していない。
【００２２】
正極活物質、即ち正極材料としてのＬｉＣｏＯ₂は、リチウムの水酸化物とコバルトの水酸化物を混合し、空気中で８００℃で２４時間焼成することにより得たものである。この正極材料と導電材としての人造黒鉛とを重量比９０：５で混合し、正極合剤を作製した。そして、結着剤であるＰＶｄＦ（ポリフッ化ビニリデン）をＮＭＰ（Ｎ−メチル２−ピロリドン）に溶解させ、ＮＭＰ溶液を調整した。正極合剤とポリフッ化ビニリデンの重量比が９５：５になるよう正極合剤とＮＭＰ溶液を混練してスラリーを調整し、このスラリーを上述の開孔部が形成されたアルミニウム箔の長手方向の片側に２０ｍｍの未塗布部を残して、ドクターブレード法により塗布して塗布部を形成し、接着し、１５０℃で２時間真空乾燥させ、更に未塗布部が２０ｍｍに対して、塗工部が２２０ｍｍとなるよう幅２４０ｍｍに切断、圧延して、正極を作製した。尚、正極の厚みは１５０μｍである。
【００２３】
図１は本実施例のリチウム二次電池用正極の模式的断面図である。図１において、１１は塗布部、１２は未塗布部、１３は開孔部である。
【００２４】
[負極の作製]
負極芯体となる銅箔（厚み２０μｍ）の活物質の未塗布部に相当する部分に、未塗布部における開孔率５％になるように、円形の開孔部を形成した。尚、活物質の塗布部に相当する部分には全く開孔部を形成していない。
【００２５】
負極活物質、即ち負極材料として、炭素塊（ｄ００２＝３．３５６Å；Ｌｃ＞１０００Å）に空気流を噴射、粉砕（ジェット粉砕）してふるいにかけ、粒子径１０μｍの黒鉛粉末を得た。また結着剤であるポリフッ化ビニリデンをＮＭＰに溶解させ、ＮＭＰ溶液を調整した。この黒鉛粉末とポリフッ化ビニリデンの重量比が９０：１０になるよう混練してスラリーを調製した。このスラリーを未塗布部の開孔率が５％になるよう加工した負極芯体としての銅箔の両面にドクターブレード法により塗布し、１５０℃で２時間真空乾燥して負極を作製した。また、この負極の厚みは、芯体も含めて、１５０μｍである。尚、負極の模式的断面図については図示を省略するが、図１に示した正極と同様の形状である。
【００２６】
[電解液の作製]
電解液としては、エチレンカーボネートとジメトキシメタンを体積比1：1で混合した溶媒に、ＬｉＰＦ₆を１Ｍの割合で溶解して電解液を調製した。
【００２７】
[電池の組立]
図２に示すように、上述の工程により作製された正極１及び負極２を、ポリプロピレン製の微多孔性薄膜からなるセパレータ３を介して巻回し、円筒状の巻電極を作製した。この時、正極１の未塗布部１２はセパレータ３の一方の端部側から露出し、負極２の未塗布部２２はセパレータ３の他方の端部側から露出している。次に、巻電極の両端に直径５８ｍｍのニッケル製円形集電板を抵抗溶接により固定し、続いて該ニッケル製円形集電板と正負極集電端子を接続した。次に、電解液３００ｇを注液した後、電池缶内部を４ｋｇｆ／ｃｍ²に加圧し、２４時間静置し、大型の円筒型リチウム二次電池Ａ１を作製した。この電池の寸法は、直径６０ｍｍ、長さ３２０ｍｍである。尚、この電池の設計容量は７０Ａｈである。
【００２８】
次に、正極及び負極共に、活物質の未塗布部における開孔部の開孔率が夫々、１０％、３０％、６０％、８０％、９０％である芯体を用いた以外は、上述の電池Ａ１と同様にして大型の円筒型リチウム二次電池Ａ２、Ａ３、Ａ４、Ａ５、Ａ６を夫々、各２セルづつ作製した。
【００２９】
尚、上述のリチウム二次電池Ａ１〜Ａ６では、活物質の未塗布部における開孔部の開孔率が所望の値になるように、開孔部を下記のパターン配列で形成した。
【００３０】
即ち、電池Ａ１では、図３に示すように、開孔率が５％となるように、直径４ｍｍの円形の開孔部を８．５８ｍｍ間隔で１列形成した。
【００３１】
電池Ａ２では、図４に示すように、開孔率が１０％となるように、直径４ｍｍの円形の開孔部を２．２９ｍｍ間隔で１列形成した。
【００３２】
電池Ａ３では、図５に示すように、開孔率が３０％となるように、直径４ｍｍ
の円形の開孔部を２．２９ｍｍ間隔で３列形成した。
【００３３】
電池Ａ４では、図６に示すように、開孔率が６０％となるように、直径６ｍｍの円形の開孔部を１ｍｍ間隔で３列形成した。
【００３４】
電池Ａ５では、図７に示すように、開孔率が８０％となるように、一辺１７．９ｍｍの正方形の開孔部を２．１ｍｍ間隔で１列形成した。
【００３５】
電池Ａ６では、図８に示すように、開孔率が９０％となるように、一辺１９ｍｍの正方形の開孔部を１ｍｍ間隔で１列形成した。
＜比較例＞
正極芯体のアルミニウム箔、負極芯体の銅箔は、未塗布部に相当する部位が開孔加工されていないものを用いる以外は、上述の電池Ａ１と同様にして、比較電池Ｘを作製した。
（実験１）
これらの本発明の電池Ａ１〜電池Ａ６及び比較例の電池Ｘを用いて、注液工程時の電解液含浸量を求めた。尚、電解液含浸量は、加圧含浸で２４時間経過後に電池を開缶、電極群を取り出し、速やかに電極群の重量を計量することにより求めた。
【００３６】
次に電池Ａ１〜電池Ａ６及び電池Ｘについて、充放電容量試験を行った。充放電条件は以下の通りである。
【００３７】
充電：８．７５Ａ（１／８Ｃ）の定電流で、８時間若しくは充電電圧が４．２Ｖになるまで充電
休止：３０分
放電：８．７５Ａ（１／８Ｃ）の定電流で、２．７Ｖになるまで放電
ここで求められた充電容量に対する放電容量の比を、充放電効率と定義する。
【００３８】
さらに電池Ａ１〜電池Ａ６及び電池Ｘについて１Ｃ放電率で負荷特性試験を行った。測定条件は以下の通りである。
【００３９】
充電：８．７５Ａ（１／８Ｃ）の定電流で、８時間若しくは充電電圧が４．２Ｖになるまで充電
休止：30分
放電：７０Ａ（１Ｃ）の定電流で、２．７Ｖになるまで放電
この試験の後、１／８Ｃでの放電容量に対する１Ｃでの放電容量の比、放電容量（１Ｃ）／放電容量（１／８Ｃ）を求めた。
【００４０】
以上の結果を、表1に示す。
【００４１】
【表１】

【００４２】
表１から判るように、正極の芯体及び負極の芯体の活物質の未塗布部分に開孔部を設けた電池Ａ１〜Ａ６では、開孔部を設けなかった電池Ｘと比較して、電解液の含浸量が多くなり、充電容量、充放電効率、及び放電容量（１Ｃ）／放電容量（１／８Ｃ）が向上した。
【００４３】
特に、１０〜８０％の範囲である電池Ａ２、Ａ３、Ａ４、Ａ５では、１／８Ｃ（８．７５Ａ）の充電電流で８時間充電を行うことが出来、充放電効率が９９．５％以上、放電容量（１Ｃ）／放電容量（１／８Ｃ）が９５％以上の良好な結果が得られた。
【００４４】
一方、開孔率が５％、０％である電池Ａ１、Ｘは、電解液の含浸量が２３０ｇ、１８０ｇと少なく、１／８Ｃ（８．７５Ａ）の充電電流では、充電時間が８時間に達する前に、充電終止電圧４．２Ｖで充電モードが終了したため、定格の７０Ａｈの充電が行えなかった。
【００４５】
また、開孔率が９０％である電池Ａ６の場合、電解液の含浸量は２９０ｇと十分であるが、充電容量は６５Ａｈと低い。これは、芯体の未塗布部の開孔率が大きいため、集電性が低下し、電池内部抵抗が上昇した結果、過電圧が増加し、充電時間が８時間に達する以前に充電終止電圧４．２Ｖで充電モードが終了したためである。更に、放電容量（１Ｃ）／放電容量（１／８Ｃ）が９０％以下と低く、集電性低下の影響が顕著である。
【００４６】
（実験２）
この実験２では、負極芯体として銅箔の代わりに厚み２０μmのニッケル箔を用いた以外は、上述の電池Ａ３と同様にして電池Ａ７を作製し、上述の実験１と同様の実験を行った。その結果を電池Ａ３の実験結果と併せて表２に示す。
【００４７】
【表２】

【００４８】
表２から判るように、電解液の含浸量は、２７８ｇと十分であり、放電容量（１Ｃ）／放電容量（１／８Ｃ）は９６％以上と大きく、負荷特性は良好であり、負極芯体としてニッケル箔でも使用可能である。
【００４９】
上述の実施例では、渦巻き電極体を有した円筒形電池に適用する場合について説明したが、本発明の電池はその形状に特に制限はなく、角形など、種々の形状の非水系電解質電池に適用することが可能である。
【００５０】
【発明の効果】
本発明によれば、リチウム二次電池等に用いた場合、電解液の含浸が促進され、良好な充放電を行うことが可能となる電極を提供し得る。
【００５１】
また、本発明によれば、電極への電解液の含浸が促進され、良好な充放電を行うことが出来るリチウム二次電池を提供し得る。
【図面の簡単な説明】
【図１】本発明の電極の正極の構造を示す図である。
【図２】本発明の電極の概略構造を示す斜視図である。
【図３】本発明の電池Ａ１における開孔部のパターンを示す図である。
【図４】本発明の電池Ａ２における開孔部のパターンを示す図である。
【図５】本発明の電池Ａ３における開孔部のパターンを示す図である。
【図６】本発明の電池Ａ４における開孔部のパターンを示す図である。
【図７】本発明の電池Ａ５における開孔部のパターンを示す図である。
【図８】本発明の電池Ａ６における開孔部のパターンを示す図である。
【符号の説明】
１正極
１１塗布部
１２未塗布部
１３開孔部
２負極
２２未塗布部
３セパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode suitable for use in a lithium secondary battery, and a lithium secondary battery using the electrode.
[0002]
[Prior art]
In recent years, lithium secondary batteries have been expected as secondary batteries that can achieve the high energy density and high output density required for electric vehicles.
[0003]
Large capacity, high power density batteries required for electric vehicles, etc. must be energized with a large current during start-up or rapid acceleration, and the internal resistance of the battery is improved by improving current collection from the viewpoint of improving energy efficiency and reducing Joule heat generation. Reduction is essential. In particular, since a strip-shaped electrode is long in a cylindrical large capacity secondary battery, it is necessary to dispose a plurality of current collecting tabs in order to reduce potential distribution and improve current collecting performance. Although the current collecting tab was welded with a spot, laser, ultrasonic wave, etc., the electrical contact property was not necessarily good, and heat generation at the welded portion became a problem when a large current was applied.
[0004]
In order to solve the above problem, for example, in JP-A-8-115744, an active material uncoated portion is provided at an end of a core body instead of a current collecting tab, and this is formed into a metal circular collector. A lithium secondary battery using a current collecting method in which a current collector plate is connected by welding and the current collector plate is connected to a current collector terminal has been proposed.
[0005]
However, since the lithium secondary battery uses an organic electrolyte, the wound electrode is in a pressed state. Therefore, in the lithium secondary battery using the current collection method disclosed in the above publication, the organic electrolyte is an electrode. There is a problem that it is difficult to impregnate.
[0006]
Japanese Patent Laid-Open No. 9-92335 discloses a secondary body in which the core of the uncoated portion of the positive and negative electrodes is processed into a strip shape, and a plurality of strip leads are bundled and connected to the positive electrode current collector terminal and the negative electrode current collector terminal. Batteries have been proposed.
[0007]
However, in the lithium secondary battery disclosed in this publication, it is possible to impregnate the electrolytic solution from the gap between the strip-shaped leads. However, a large number of strip-shaped leads are bundled and connected to the positive and negative current collecting terminals. There is a problem that the manufacturing process becomes complicated such as necessity.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the drawbacks of the above conventional examples, and provides an electrode configured to be easily impregnated with an electrolyte without complicating the manufacturing process, and a lithium secondary battery using the electrode. It is intended to do.
[0009]
[Means for Solving the Problems]
An electrode for a lithium secondary battery using the electrolytic solution of the present invention has a strip-shaped positive electrode and a strip-shaped negative electrode wound around a separator, and an active material is provided at the end of at least one core of the positive electrode and the negative electrode. An unapplied part to which no adhesion is applied is provided, the unapplied part is exposed from the separator, and an opening is provided.
[0010]
In the electrode having such a configuration, when used in a lithium secondary battery or the like, the electrolytic solution permeates from the opening , and the impregnation of the electrolytic solution into the electrode is promoted.
[0011]
In particular, in the electrode of the present invention, when the aperture ratio of the aperture portion in the uncoated portion is 10% or more and 80% or less, when used for a lithium secondary battery or the like, good charge / discharge is possible. .
[0012]
Further, an aluminum foil is suitable as the positive electrode core.
[0013]
Further, a copper foil or a nickel foil is suitable as the core of the negative electrode.
[0014]
The lithium secondary battery of the present invention includes the above-described electrode of the present invention, and is characterized in that electrical connection is made from the uncoated portion of the electrode to a terminal.
[0015]
In the lithium secondary battery having such a configuration, the impregnation of the electrode with the electrolytic solution is promoted, and good charge / discharge is performed.
[0016]
As the active material of the positive electrode capable of occluding and releasing lithium ions, metal oxides are suitable. Specifically, LiCoO ₂ , LiNiO ₂ , LiCo _1-X Ni _X O ₂ , LiMn ₂ O ₄ and these Mention may be made of at least one material selected from the group consisting of complex compounds.
[0017]
As the active material of the negative electrode used in the present invention, graphite, carbon materials such as coke, a lithium metal, lithium _{_{_{alloys, LiXFe 2 O 3, Li X}}} WO 2 or the like of the metal oxide materials, conductive, such as polyacetylene A functional polymer material. In particular, when a carbon material made of graphite is used, an excellent effect is exhibited. As the graphite and coke material used for the carbon material, a pulverized material may be used as it is, or a heat-treated material in the range of 500 ° C. to 3700 ° C. may be used. Further, the value of the (002) plane spacing d002 of the graphite by the X-ray wide angle diffraction method is preferably 3.35 mm or more and 3.37 mm or less, and the crystallite length Lc in the C axis direction is 400 mm or more.
[0018]
It should be noted that various materials that have been put to practical use or have been proposed for conventional lithium secondary batteries can also be used for battery components such as electrolytes, electrolytes, and separators.
[0019]
For example, electrolytes include electrolytes such as LiPF ₆ , LiClO ₄ , and LiCF ₃ SO ₃ containing lithium ions. Further, as the organic solvent for the electrolytic solution, ethylene carbonate, diethyl carbonate, dimethoxymethane, sulfolane and the like can be used alone or in combination. Examples of the electrolytic solution include solutions obtained by dissolving the electrolyte in these solvents at a ratio of about 0.7 to 1.5 M (mol / l).
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention are described below.
[0021]
[Preparation of positive electrode]
A portion corresponding to the uncoated portion of the active material of positive electrode substrate to become aluminum foil (thickness 20 [mu] m), such that the open area ratio 5% in uncoated portion, to form a circular opening. In addition, the opening part is not formed at all in the part corresponding to the application part of the active material.
[0022]
The positive electrode active material, that is, LiCoO ₂ as the positive electrode material is obtained by mixing lithium hydroxide and cobalt hydroxide and firing in air at 800 ° C. for 24 hours. This positive electrode material and artificial graphite as a conductive material were mixed at a weight ratio of 90: 5 to prepare a positive electrode mixture. Then, PVdF (polyvinylidene fluoride) as a binder was dissolved in NMP (N-methyl 2-pyrrolidone) to prepare an NMP solution. The positive electrode mixture and the NMP solution were kneaded so that the weight ratio of the positive electrode mixture and polyvinylidene fluoride was 95: 5 to prepare a slurry, and this slurry was adjusted in the longitudinal direction of the aluminum foil in which the above-described apertures were formed. Applying by a doctor blade method, leaving an uncoated part of 20 mm on one side, forming a coated part, bonding, and vacuum drying at 150 ° C. for 2 hours. The positive electrode was produced by cutting and rolling to a width of 240 mm to be 220 mm. The positive electrode has a thickness of 150 μm.
[0023]
FIG. 1 is a schematic cross-sectional view of a positive electrode for a lithium secondary battery of this example. In FIG. 1, 11 is a coating part, 12 is an uncoated part, 13 is an opening part .
[0024]
[Preparation of negative electrode]
A portion corresponding to the uncoated portion of the active material of the negative electrode substrate to become copper foil (thickness 20 [mu] m), such that the open area ratio 5% in uncoated portion, to form a circular opening. In addition, the opening part is not formed at all in the part corresponding to the application part of the active material.
[0025]
As a negative electrode active material, that is, a negative electrode material, an air stream was jetted into a carbon lump (d002 = 3.356Å; Lc> 1000Å) and pulverized (jet pulverized), and sieved to obtain a graphite powder having a particle diameter of 10 μm. Further, polyvinylidene fluoride as a binder was dissolved in NMP to prepare an NMP solution. A slurry was prepared by kneading the graphite powder and polyvinylidene fluoride in a weight ratio of 90:10. This slurry was applied to both sides of a copper foil as a negative electrode core processed so that the open area ratio of the uncoated portion was 5% by a doctor blade method, and vacuum dried at 150 ° C. for 2 hours to prepare a negative electrode. Moreover, the thickness of this negative electrode is 150 micrometers including a core. In addition, although illustration is abbreviate | omitted about schematic sectional drawing of a negative electrode, it is the same shape as the positive electrode shown in FIG.
[0026]
[Preparation of electrolyte]
As an electrolytic solution, LiPF ₆ was dissolved at a ratio of 1M in a solvent in which ethylene carbonate and dimethoxymethane were mixed at a volume ratio of 1: 1 to prepare an electrolytic solution.
[0027]
[Battery assembly]
As shown in FIG. 2, the positive electrode 1 and the negative electrode 2 produced by the above-described steps were wound through a separator 3 made of a polypropylene microporous thin film to produce a cylindrical wound electrode. At this time, the uncoated portion 12 of the positive electrode 1 is exposed from one end side of the separator 3, and the uncoated portion 22 of the negative electrode 2 is exposed from the other end side of the separator 3. Next, a nickel circular current collector plate having a diameter of 58 mm was fixed to both ends of the wound electrode by resistance welding, and then the nickel circular current collector plate and the positive and negative electrode current collector terminals were connected. Next, after 300 g of the electrolyte solution was injected, the inside of the battery can was pressurized to 4 kgf / cm ² and allowed to stand for 24 hours to produce a large cylindrical lithium secondary battery A1. The battery has a diameter of 60 mm and a length of 320 mm. The design capacity of this battery is 70 Ah.
[0028]
Next, both the positive electrode and the negative electrode described above except that the cores having the open area ratios of 10%, 30%, 60%, 80%, and 90% in the uncoated areas of the active material were used. In the same manner as the battery A1, large cylindrical lithium secondary batteries A2, A3, A4, A5, and A6 were produced in two cells each.
[0029]
In the above-described lithium secondary batteries A1 to A6, the apertures were formed in the following pattern arrangement so that the aperture ratio of the apertures in the active material unapplied area was a desired value.
[0030]
That is, in the battery A1, as shown in FIG. 3, one row of circular apertures having a diameter of 4 mm was formed at intervals of 8.58 mm so that the aperture ratio was 5%.
[0031]
In battery A2, as shown in FIG. 4, circular apertures with a diameter of 4 mm were formed in a row at intervals of 2.29 mm so that the aperture ratio was 10%.
[0032]
In battery A3, as shown in FIG. 5, the diameter is 4 mm so that the hole area ratio is 30%.
Three circular apertures were formed at intervals of 2.29 mm.
[0033]
In battery A4, as shown in FIG. 6, three rows of circular apertures with a diameter of 6 mm were formed at intervals of 1 mm so that the aperture ratio was 60%.
[0034]
In battery A5, as shown in FIG. 7, square openings having a side of 17.9 mm were formed in one row at intervals of 2.1 mm so that the opening ratio was 80%.
[0035]
In the battery A6, as shown in FIG. 8, square holes having a side of 19 mm were formed in a row at intervals of 1 mm so that the hole area ratio was 90%.
<Comparative example>
A comparative battery X was produced in the same manner as the battery A1 described above except that the aluminum foil of the positive electrode core and the copper foil of the negative electrode core were not subjected to opening processing at the portion corresponding to the uncoated portion. .
(Experiment 1)
Using these batteries A1 to A6 of the present invention and the battery X of the comparative example, the amount of electrolyte impregnation during the liquid injection process was determined. The electrolytic solution impregnation amount was determined by opening the battery after 24 hours by pressure impregnation, taking out the electrode group, and quickly weighing the electrode group.
[0036]
Next, a charge / discharge capacity test was performed on the batteries A1 to A6 and the battery X. The charge / discharge conditions are as follows.
[0037]
Charging: 8.75 A (1/8 C) constant current , 8 hours or until charging voltage reaches 4.2 V Charging pause: 30 minutes Discharging: 8.75 A (1/8 C ) constant current, 2.7 V The ratio of the discharge capacity to the charge capacity determined here is defined as charge / discharge efficiency.
[0038]
Further, a load characteristic test was performed on the batteries A1 to A6 and the battery X at a 1C discharge rate. The measurement conditions are as follows.
[0039]
Charging: 8.75A (1 / 8C) constant current , 8 hours or until charging voltage reaches 4.2V Charging pause: 30 minutes Discharge: 70A ( 1C ) constant current, discharging until 2.7V After this test, the ratio of the discharge capacity at 1C to the discharge capacity at 1 / 8C, discharge capacity (1C) / discharge capacity (1 / 8C) was determined.
[0040]
The results are shown in Table 1.
[0041]
[Table 1]

[0042]
As can be seen from Table 1, the battery A1~A6 provided an opening in the uncoated portion of the active material of the core and the core of the negative electrode of the positive electrode, as compared to the battery X was not provided an opening, The amount of electrolyte impregnation increased, and the charge capacity, charge / discharge efficiency, and discharge capacity (1C) / discharge capacity (1 / 8C) were improved.
[0043]
In particular, the batteries A2, A3, A4, and A5 in the range of 10 to 80% can be charged with a charging current of 1 / 8C (8.75 A) for 8 hours, and the charge / discharge efficiency is 99.5% or more. The discharge capacity (1C) / discharge capacity (1 / 8C) was 95% or more.
[0044]
On the other hand, the batteries A1 and X having an opening ratio of 5% and 0% have a small amount of electrolyte impregnation of 230 g and 180 g, respectively, and the charging time is 8 hours at a charging current of 1/8 C (8.75 A). Since the charge mode was terminated at the end-of-charge voltage of 4.2 V before reaching, the rated 70 Ah could not be charged.
[0045]
Further, in the case of the battery A6 having a porosity of 90%, the amount of electrolyte impregnation is 290 g, but the charging capacity is as low as 65 Ah. This is because the open area ratio of the uncoated portion of the core is large, the current collecting performance is lowered, and the battery internal resistance is increased. As a result, the overvoltage increases, and the charge end voltage 4 before the charging time reaches 8 hours. This is because the charging mode is terminated at 2V. Furthermore, the discharge capacity (1C) / discharge capacity (1 / 8C) is as low as 90% or less, and the influence of the decrease in current collection is remarkable.
[0046]
(Experiment 2)
In Experiment 2, a battery A7 was produced in the same manner as the battery A3 described above except that a nickel foil having a thickness of 20 μm was used instead of the copper foil as the negative electrode core, and the same experiment as the experiment 1 was performed. . The results are shown in Table 2 together with the experimental results of the battery A3.
[0047]
[Table 2]

[0048]
As can be seen from Table 2, the amount of impregnation with the electrolyte is 278 g, the discharge capacity (1C) / discharge capacity (1 / 8C) is as large as 96% or more, the load characteristics are good, and the negative electrode core Nickel foil can also be used.
[0049]
In the above-described embodiments, the case where the present invention is applied to a cylindrical battery having a spiral electrode body has been described. However, the battery of the present invention is not particularly limited in its shape, and is applicable to non-aqueous electrolyte batteries having various shapes such as a square shape. Is possible.
[0050]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, when used for a lithium secondary battery etc., the impregnation of electrolyte solution is accelerated | stimulated and the electrode which can perform favorable charging / discharging can be provided.
[0051]
Moreover, according to this invention, the impregnation of the electrolyte solution to an electrode is accelerated | stimulated and the lithium secondary battery which can perform favorable charging / discharging can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing the structure of a positive electrode of an electrode of the present invention.
FIG. 2 is a perspective view showing a schematic structure of an electrode of the present invention.
FIG. 3 is a diagram showing a pattern of openings in the battery A1 of the present invention.
FIG. 4 is a diagram showing a pattern of openings in battery A2 of the present invention.
FIG. 5 is a diagram showing a pattern of openings in battery A3 of the present invention.
FIG. 6 is a diagram showing a pattern of openings in battery A4 of the present invention.
FIG. 7 is a diagram showing a pattern of openings in battery A5 of the present invention.
FIG. 8 is a diagram showing a pattern of openings in battery A6 of the present invention.
[Description of marks Nos.]
DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Application | coating part 12 Unapplied part 13

Opening part

2 Negative electrode 22 Unapplied part 3 Separator

Claims

In an electrode for a lithium secondary battery using an electrolytic solution in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound through a separator, an active material is attached to an end portion of at least one of the positive electrode and the negative electrode. An uncoated part is provided, the uncoated part is exposed from the separator, and an opening is provided . An electrode for a lithium secondary battery using an electrolytic solution.

The non opening ratio of the openings in the coating portion of 10% or more, a lithium secondary battery electrode using an electrolytic solution of claim 1, wherein the 80% or less.

The electrode for a lithium secondary battery using an electrolytic solution according to claim 1 or 2, wherein the core of the positive electrode is made of an aluminum foil.

4. The electrode for a lithium secondary battery using an electrolytic solution according to claim 1, wherein the negative electrode core is made of a copper foil or a nickel foil.

A lithium secondary battery electrode using the electrolytic solution according to claim 1, 2, 3, or 4 is provided, and an electrical connection is made from the uncoated portion of the electrode to a terminal. Next battery.