JP4363558B2

JP4363558B2 - Flat non-aqueous electrolyte secondary battery

Info

Publication number: JP4363558B2
Application number: JP2001338818A
Authority: JP
Inventors: 宗人早見; 祐一菊間
Original assignee: Hitachi Maxell Energy Ltd
Current assignee: Maxell Ltd
Priority date: 2001-11-05
Filing date: 2001-11-05
Publication date: 2009-11-11
Anticipated expiration: 2021-11-05
Also published as: JP2003142161A

Description

【０００１】
【発明の属する技術分野】
本発明は扁平形非水電解質二次電池に係り、さらに詳しくは内部ショートを防ぎかつ内部抵抗の上昇を抑えて電池性能を向上させた扁平形非水電解質二次電池に係る。
【０００２】
【従来の技術】
携帯電話やＰＤＡなどの小型情報端末を中心に使用機器の小形化が加速しており、主電源である二次電池についても小形化を図ることが要求されている。
【０００３】
これに対応して、扁平形非水電解質二次電池であって、正負極対向面（正極と負極がセパレータを介して対向している面）が扁平面に垂直な断面において少なくとも３面以上あり、この正負極対向面の総面積が絶縁ガスケットの開口面積より大きいような二次電池が開発されている（特開2001−068160号、特開2001−068143号）。例えば、正極と負極をセパレータを介して積層して正負極対向面を３面以上としたものや、正極と負極をセパレータを介して捲回して正負極対向面を３面以上としたものなどがある。
【０００４】
これらの電池は、電池群の最外側において、導電性の正極構成材および負極構成材がそれぞれ水平方向に露出しており、これらが直接、正極ケースおよび負極ケースに接触し、それによって集電が行われるようになっている。したがって、集電構造としては、円筒形電池のように電極群の中心部からタブ端子を取り出し、これを複雑に曲げ加工して安全素子や封口ピン、電池缶などに溶接する、というような複雑さがなく、作業性がよいという利点がある。
【０００５】
しかしながら、これらの電池は、電極群が捲回方式であっても積層方式であっても、電極群と正負極ケースが非常に近い位置にあるため、電極群のエッジ部が他極の電極ケースの側面に接触するなどして、内部ショートを起こすという問題がある。また、電極群作成時に捲回電極の巻き止めをする必要や、電極群の緩みを防ぐ必要がある。
【０００６】
これらの対策としては電極群の側面に絶縁性のテープを貼り付けることが有効であるが、電極群と電池ケースとの間にテープが入り込むと通電しにくくなり、電池の内部抵抗の増加につながり、電池特性の低下を招く。
【０００７】
【発明が解決しようとする課題】
本発明は上記のような状況に対処してなされたもので、前記した扁平形非水電解質二次電池の改良に係り、電池の内部抵抗の上昇を抑えながら内部ショートの発生を防止することを目的とするものである。
【０００８】
【課題を解決するための手段】
本発明は、負極端子を兼ねる金属製の負極ケースと、正極端子を兼ねる金属製の正極ケースが、絶縁ガスケットを介し嵌合されて封口され、その内部にセパレータを介して負極および正極を複数個積層して形成した電極群と非水電解質を内包し、該電極群の最外側には導電性を有する正極構成材と負極構成材が露出してそれぞれ正極ケースおよび負極ケースに接続し、各電極の端部に通電部が形成されて、正極通電部同士および負極通電部同士で束ねられている扁平形非水電解質二次電池において、前記電極群の最外側の導電性を有する正極構成材と負極構成材のそれぞれ面積率で１０〜５０％の範囲、及び前記通電部の全面が絶縁テープで被覆されていることを特徴とする扁平形非水電解質二次電池に関する。
【０００９】
絶縁テープの材質としては、ガラス質材料やポリテトラフルオロエチレン（ＰＴＦＥ）、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）、テトラフルオロエチレン−エチレン共重合体（ＥＴＦＥ）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、ポリフッ化ビニリデン（ＰＶＤＦ）などのフッ素樹脂、ポリイミド、液晶ポリマー（ＬＣＰ）、ポリフェニレンサルファイド（ＰＰＳ）、ポリブチレンテレフタレート（ＰＢＴ）、ポリエチレンテレフタレート（ＰＥＴ）、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリ塩化ビニル（ＰＶＣ）、アセテート樹脂から選ばれる樹脂が電解液やリチウムイオンに対して安定で好ましく、これらの材料に接着剤や粘着剤を、片面もしくは両面塗布したものを用いるのがよい。
【００１０】
絶縁テープに用いられる接着剤の材質としては、電解液やリチウムイオンに安定な物であれば何れのものでもよく、ゴム系、アクリル系、セルロース系、オレフィン系、フッ素系、シリコン系、サルファイド系、ビニル系などが挙げられ、電池正極作用物質の結着材として用いられているスチレンブタジエンゴム、カルボキシメチルセルロース、ポリフッ化ビニリデンなどを用いてもよい。
【００１１】
本発明では上記したように、電極群の最外側の導電性を有する正極構成材と負極構成材が、それぞれ部分的に絶縁テープにより覆われているので、電極群のエッジ部が他極の電極ケースの側面に接触することによる内部ショートの発生を防ぐことができ、また、捲回または積層した電極群の緩みを防ぐという効果もある。なお、絶縁テープによる被覆処理を各最外側電極構成材の面積の１０〜５０％の範囲としたのは、これより多いと内部抵抗が上昇し，これより少ないと絶縁テープの貼り付け強度が低く内部ショート防止効果が充分でないからである。
【００１２】
【発明の実施の形態】
以下、本発明の実施例を図面を参照して説明する。
（実施例１）
図１および図２は本実施例の扁平形非水電解質二次電池を説明するもので、図１は縦断面図、図２は図１におけるＡ−Ａ線より上方を見たときの部分図である。
【００１３】
本実施例１の電池の製造方法を以下に説明する。
まず、ＬｉＣｏＯ₂１００質量部に対し導電材としてアセチレンブラック５質量部と黒鉛粉末５質量部を加え、結着剤としてポリフッ化ビニリデンを５質量部加え、Ｎ−メチルピロリドンで希釈，混合し、スラリー状の正極合剤を得た。次にこの正極合剤を、正極集電体である厚さ０．０２ｍｍのアルミ箔の片面にドクターブレード法により塗工した後乾燥し、アルミ箔表面に正極作用物質含有層を形成した。以後、正極作用物質含有層の塗膜厚さが両面で０．１５ｍｍとなるまで塗工，乾燥を繰り返し、両面塗工した正極板２を作製した。
【００１４】
次に黒鉛化メソフェーズピッチ炭素繊維粉末１００質量部に結着剤としてスチレンブタジエンゴムとカルボキシメチルセルロースをそれぞれ２．５質量部を添加し、イオン交換水で希釈，混合し、スラリー状の負極合剤を得た。得られた負極合剤を負極集電体である厚さ０．０２ｍｍの銅箔に作用物質含有層の厚さが０．１５ｍｍとなるように正極の場合と同様に塗工，乾燥を繰り返し実施し、両面塗工した負極板４を作製した。
【００１５】
上記正・負極板は直径１２．５ｍｍの円型であるが、図２に示されるようにその周辺部に幅２ｍｍの延伸部があって、これが正極通電部２ａおよび負極通電部４ａを形成している。これらの正負極板を、セパレータ３を介して交互に複数枚積層し、正負極板の各周辺部に形成された通電部を抵抗溶接により溶接して束ね、電極群を形成した。
【００１６】
つぎに、絶縁テープ７を、図１，２に示すように上記電極群の通電部を含む部分に貼り付けた。貼り付け方は、絶縁テープで電極群の正極の最外面に、最外面面積に対して５％貼り、さらに電極群の側面を貼り付けながら負極の最外面に最外面面積に対して５％貼り付けた。同様にもう一方の絶縁テープを電極の対称側面に貼りつけた。すなわち、正・負極の最外面にはそれぞれ１０％に相当する面積に絶縁テープが貼られたことになる。
【００１７】
このようにして製作した積層電極群を用いて、図１に示すような扁平形非水電解質二次電池を以下のように作製した。なお、上記積層電極群の最外側電極は、電極集電体の片面にのみ作用物質を塗布した電極をそれぞれ用いており、作用物質の塗布していない側が各電極ケースに接触している。したがって、作用物質の塗布していない集電体表面のうち、テープが貼られていない部分、この実施例の場合には全表面の９０％の部分が電極ケースに接触していることになる。
【００１８】
作製した電極群を８５℃で１２時間乾燥した後、絶縁ガスケット６を一体化した負極金属ケース５の内底面に電極群の片面塗工負極板の未塗工側が金属ネットに接するように配置し、エチレンカーボネートとγ−ブチロラクトンを体積比１：１の割合で混合した溶媒に支持塩としてＬｉＢＦ₄を１ｍｏｌ／ｌの割合で溶解せしめた非水電解質を注液し、さらに電極群の片面塗工正極板の未塗工側に接するようにステンレス製の正極ケース１を嵌合し、上下反転後、正極ケースに加締め加工を実施し、封口し、厚さ３ｍｍ、直径２４．５ｍｍの実施例１の扁平形非水電解質二次電池を製作した。
【００１９】
（実施例２）
実施例１と同様にして、但し絶縁テープの貼り付け面積を正極の外表面面積に対して左右１５％づつ、負極の外表面面積に対して左右１５％づつとし、正極、負極のそれぞれについて全表面積の３０％を絶縁テープで貼り付けた。それ以外は実施例１と同様にして非水電解質二次電池を作製した。
【００２０】
（実施例３）
実施例１と同様にして、但し絶縁テープの貼り付け面積を正極の外表面面積に対して左右２５％づつ、負極の外表面面積に対して左右２５％づつとし、正極、負極のそれぞれについて全表面積の５０％を絶縁テープで貼り付けた。それ以外は実施例１と同様にして非水電解質二次電池を作製した。
【００２１】
（比較例１）
実施例１と同様にして、但し絶縁テープの貼り付け面積を正極の外表面面積に対して左右２．５％づつ、負極の外表面面積に対して左右２．５％づつとし、正極、負極のそれぞれについて全表面積の５％を絶縁テープで貼り付けた。それ以外は実施例１と同様にして非水電解質二次電池を作製した。
【００２２】
（比較例２）
実施例１と同様にして、但し絶縁テープの貼り付け面積を正極の外表面面積に対して左右３０％づつ、負極の外表面面積に対して左右３０％づつとし、正極、負極のそれぞれについて全表面積の６０％を絶縁テープで貼り付けた。それ以外は実施例１と同様にして非水電解質二次電池を作製した。
【００２３】
以上のとおり作製した実施例及び比較例の電池各５０個について、４．２Ｖ，３ｍＡの定電流定電圧で４８時間初充電を実施し、２０℃の雰囲気下で３０ｍＡの定電流にて放電を行い、閉路電圧が３．０Ｖになるまでの放電容量を測定した。この後、４．２Ｖ，３０ｍＡの定電流定電圧で３時間充電を行い、これを１サイクルとして１００回サイクルを繰り返した。初期放電容量に対する１００サイクル目の放電容量の維持率を表１に示す。
【００２４】
また、２０℃の雰囲気下で１８０ｍＡの定電流にて重負荷放電を行い、閉路電圧が３．０Ｖになるまでの放電容量を測定した。前述の３０ｍＡでの放電容量に対する１８０ｍＡでの放電容量の利用率を表１に示す。
【００２５】
【表１】

【００２６】
比較例１のように、電極最外面に貼られたテープの割合（％）が小さいものは、内部抵抗は小さくなるが、テープの貼り付け強度が低いので、充放電時の電極の膨張に伴ってテープが剥がれやすくなり、サイクル特性が劣化する。また、比較例２のように電極最外面に貼られたテープの割合（％）が大きいものは、サイクル試験時の不具合は起こらなくなるが、電池ケースと電極との接触が悪くなって内部抵抗が上昇し、作動電圧が低下して重負荷特性が低下する。実施例１〜３の電池においては、サイクル試験、重負荷特性のいずれについても不具合が起こらない。
【００２７】
なお、本発明の実施例は、非水電解質に非水溶媒を用いた扁平形非水溶媒二次電池を用いて説明したが、非水電解質にポリマー電解質を用いたポリマー二次電池や固体電解質を用いた固体電解質二次電池についても当然、適用可能であり、樹脂製セパレータの代りにポリマー薄膜や固体電解質膜を用いることも可能である。また、電池形状については正極ケースの加締め加工により封口するコイン形非水電解質をもとに説明したが、正負極電極を入れ替え、負極ケースの加締め加工により封口することも可能である。さらに、電池形状についても真円である必要はなく、小判形などの特殊形状を有する扁平形非水電解質二次電池においても適用可能である。
【００２８】
【発明の効果】
以上説明したとおり、本発明によれば、扁平形非水電解質二次電池において、内部抵抗の上昇を抑えながら内部ショートの発生を防止し、電池性能を向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施例である扁平形非水電解質二次電池の縦断面図。
【図２】図１におけるＡ−Ａ線より上方を見たときの図。
【符号の説明】
１…正極ケース、２…正極板、２ａ…正極通電部、３…セパレータ、４…負極板、４ａ…負極通電部、５…負極ケース、６…絶縁ガスケット、７…絶縁テープ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat non-aqueous electrolyte secondary battery, and more particularly to a flat non-aqueous electrolyte secondary battery that has improved battery performance by preventing internal short circuit and suppressing an increase in internal resistance.
[0002]
[Prior art]
The downsizing of devices used is accelerating mainly on small information terminals such as mobile phones and PDAs, and the secondary battery as the main power source is also required to be downsized.
[0003]
Correspondingly, the flat non-aqueous electrolyte secondary battery has positive and negative electrode facing surfaces (surfaces in which the positive electrode and the negative electrode face each other via a separator) in at least three planes in a cross section perpendicular to the flat surface. Secondary batteries have been developed in which the total area of the positive and negative electrode facing surfaces is larger than the opening area of the insulating gasket (Japanese Patent Laid-Open Nos. 2001-068160 and 2001-068143). For example, a positive electrode and a negative electrode are laminated via a separator so that the positive and negative electrode facing surfaces are three or more, or a positive electrode and a negative electrode are wound via a separator so that the positive and negative electrode facing surfaces are three or more. is there.
[0004]
In these batteries, the conductive positive electrode constituent material and negative electrode constituent material are respectively exposed in the horizontal direction on the outermost side of the battery group, and these are in direct contact with the positive electrode case and the negative electrode case, thereby collecting current. To be done. Therefore, the current collecting structure is complicated, such as taking out the tab terminal from the center of the electrode group like a cylindrical battery, bending it in a complicated manner, and welding it to a safety element, sealing pin, battery can, etc. There is an advantage that workability is good.
[0005]
However, in these batteries, regardless of whether the electrode group is a wound type or a stacked type, the electrode group and the positive and negative electrode cases are located very close to each other, so that the edge of the electrode group is an electrode case with another electrode. There is a problem that an internal short circuit occurs due to contact with the side surface. In addition, it is necessary to prevent winding of the wound electrode when creating the electrode group, and to prevent loosening of the electrode group.
[0006]
As countermeasures, it is effective to apply an insulating tape to the side of the electrode group. However, if the tape enters between the electrode group and the battery case, it becomes difficult to energize, leading to an increase in the internal resistance of the battery. The battery characteristics are degraded.
[0007]
[Problems to be solved by the invention]
The present invention has been made in response to the above-described situation, and relates to the improvement of the above-described flat nonaqueous electrolyte secondary battery, and prevents the occurrence of an internal short circuit while suppressing an increase in the internal resistance of the battery. It is the purpose.
[0008]
[Means for Solving the Problems]
In the present invention, a metal negative electrode case that also serves as a negative electrode terminal and a metal positive electrode case that also serves as a positive electrode terminal are fitted and sealed via an insulating gasket, and a plurality of negative electrodes and positive electrodes are interposed therein via a separator. The electrode group formed by stacking and the non-aqueous electrolyte are included, and the positive electrode constituent material and the negative electrode constituent material having conductivity are exposed on the outermost side of the electrode group and are connected to the positive electrode case and the negative electrode case , respectively. energizing portion on the end portion is formed of, in the positive electrode current portions and the negative electrode conducting portion flat-shaped non-aqueous electrolyte secondary batteries are bundled in each other, a positive electrode structure material having outermost conductivity of the electrode group The present invention relates to a flat non-aqueous electrolyte secondary battery in which the area ratio of each negative electrode constituent material is in the range of 10 to 50% and the entire surface of the current-carrying portion is covered with an insulating tape .
[0009]
As the material of the insulating tape, glassy material, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-par Fluoroalkyl vinyl ether copolymer (PFA), fluororesin such as polyvinylidene fluoride (PVDF), polyimide, liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene ( A resin selected from PE), polypropylene (PP), polyvinyl chloride (PVC), and acetate resin is preferable because it is stable against electrolytes and lithium ions. Properly good to use a material obtained by two-sided coating.
[0010]
The material of the adhesive used for the insulating tape may be any material as long as it is stable to an electrolytic solution or lithium ion, and is rubber-based, acrylic-based, cellulose-based, olefin-based, fluorine-based, silicon-based, sulfide-based. Styrene butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride, and the like that are used as binders for battery positive electrode active materials may be used.
[0011]
In the present invention, as described above, the outermost conductive positive electrode constituent material and negative electrode constituent material of the electrode group are partially covered with insulating tape, so that the edge portion of the electrode group is an electrode of the other electrode. The occurrence of an internal short circuit due to contact with the side surface of the case can be prevented, and there is also an effect of preventing loosening of the wound or stacked electrode group. It should be noted that the reason why the covering treatment with the insulating tape is in the range of 10 to 50% of the area of each outermost electrode constituent material is that if it exceeds this, the internal resistance increases, and if less than this, the adhesive strength of the insulating tape is low. This is because the internal short circuit prevention effect is not sufficient.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
FIGS. 1 and 2 illustrate a flat type nonaqueous electrolyte secondary battery according to this embodiment. FIG. 1 is a longitudinal sectional view, and FIG. 2 is a partial view when viewed from the line AA in FIG. It is.
[0013]
A method for manufacturing the battery of Example 1 will be described below.
First, 5 parts by mass of acetylene black and 5 parts by mass of graphite powder are added as conductive materials to 100 parts by mass of LiCoO ₂ , 5 parts by mass of polyvinylidene fluoride as a binder, diluted with N-methylpyrrolidone, mixed, and slurry A positive electrode mixture was obtained. Next, this positive electrode mixture was applied to one surface of a 0.02 mm thick aluminum foil as a positive electrode current collector by a doctor blade method and then dried to form a positive electrode active substance-containing layer on the aluminum foil surface. Thereafter, coating and drying were repeated until the coating film thickness of the positive electrode active material-containing layer became 0.15 mm on both sides, to produce a positive electrode plate 2 coated on both sides.
[0014]
Next, 2.5 parts by mass of styrene butadiene rubber and carboxymethyl cellulose as binders are added to 100 parts by mass of graphitized mesophase pitch carbon fiber powder, diluted and mixed with ion-exchanged water, and a slurry-like negative electrode mixture is prepared. Obtained. The obtained negative electrode mixture was repeatedly coated and dried in the same manner as in the case of the positive electrode so that the thickness of the active substance-containing layer was 0.15 mm on a 0.02 mm thick copper foil as a negative electrode current collector. Then, the negative electrode plate 4 coated on both sides was produced.
[0015]
The positive and negative electrode plates have a circular shape with a diameter of 12.5 mm. As shown in FIG. 2, there are extending portions with a width of 2 mm at the periphery thereof, which form the positive electrode energizing portion 2a and the negative electrode energizing portion 4a. ing. A plurality of these positive and negative electrode plates were alternately laminated via the separator 3, and the current-carrying portions formed on the peripheral portions of the positive and negative electrode plates were welded and bundled together by resistance welding to form an electrode group.
[0016]
Next, the insulating tape 7 was affixed on the part containing the electricity supply part of the said electrode group, as shown in FIG. Affixing is 5% of the outermost surface area of the positive electrode of the electrode group with insulating tape, and 5% of the outermost surface area of the negative electrode is bonded to the outermost surface of the negative electrode while adhering the side surfaces of the electrode group. It was. Similarly, the other insulating tape was attached to the symmetrical side surface of the electrode. That is, the insulating tape is applied to the outermost surfaces of the positive and negative electrodes in an area corresponding to 10%.
[0017]
A flat nonaqueous electrolyte secondary battery as shown in FIG. 1 was produced as follows using the multilayer electrode group thus produced. The outermost electrode of the laminated electrode group uses an electrode coated with an active substance only on one side of the electrode current collector, and the side not coated with the active substance is in contact with each electrode case. Therefore, of the surface of the current collector not coated with the active substance, the portion where the tape is not applied, in this embodiment, 90% of the entire surface is in contact with the electrode case.
[0018]
After the produced electrode group was dried at 85 ° C. for 12 hours, the inner surface of the negative electrode metal case 5 integrated with the insulating gasket 6 was placed so that the uncoated side of the single-side coated negative electrode plate of the electrode group was in contact with the metal net. Then, a non-aqueous electrolyte in which LiBF ₄ was dissolved as a supporting salt in a ratio of 1 mol / l was poured into a solvent in which ethylene carbonate and γ-butyrolactone were mixed at a volume ratio of 1: 1, and one-side coating of the electrode group was performed. A stainless steel positive electrode case 1 is fitted so as to be in contact with the uncoated side of the positive electrode plate, and after inverting upside down, the positive electrode case is crimped, sealed, and 3 mm thick and 24.5 mm in diameter. 1 flat nonaqueous electrolyte secondary battery was manufactured.
[0019]
(Example 2)
In the same manner as in Example 1, except that the area where the insulating tape was applied was 15% left and right with respect to the outer surface area of the positive electrode and 15% left and right with respect to the outer surface area of the negative electrode. 30% of the surface area was affixed with insulating tape. Other than that was carried out similarly to Example 1, and produced the nonaqueous electrolyte secondary battery.
[0020]
(Example 3)
In the same manner as in Example 1, except that the area where the insulating tape was applied was 25% left and right with respect to the outer surface area of the positive electrode and 25% left and right with respect to the outer surface area of the negative electrode. 50% of the surface area was affixed with insulating tape. Other than that was carried out similarly to Example 1, and produced the nonaqueous electrolyte secondary battery.
[0021]
(Comparative Example 1)
In the same manner as in Example 1, except that the insulating tape application area is 2.5% left and right with respect to the outer surface area of the positive electrode and 2.5% left and right with respect to the outer surface area of the negative electrode. For each of these, 5% of the total surface area was affixed with insulating tape. Other than that was carried out similarly to Example 1, and produced the nonaqueous electrolyte secondary battery.
[0022]
(Comparative Example 2)
In the same manner as in Example 1, except that the area where the insulating tape was applied was 30% left and right with respect to the outer surface area of the positive electrode and 30% left and right with respect to the outer surface area of the negative electrode. 60% of the surface area was affixed with insulating tape. Other than that was carried out similarly to Example 1, and produced the nonaqueous electrolyte secondary battery.
[0023]
For each of the 50 batteries of Examples and Comparative Examples manufactured as described above, initial charging was performed for 48 hours at a constant current and a constant voltage of 4.2 V, 3 mA, and discharging was performed at a constant current of 30 mA in an atmosphere of 20 ° C. The discharge capacity was measured until the closed circuit voltage reached 3.0V. Thereafter, charging was performed at a constant current and a constant voltage of 4.2 V, 30 mA for 3 hours, and this was regarded as one cycle and the cycle was repeated 100 times. Table 1 shows the maintenance rate of the discharge capacity at the 100th cycle relative to the initial discharge capacity.
[0024]
Moreover, heavy load discharge was performed at a constant current of 180 mA in an atmosphere of 20 ° C., and the discharge capacity until the closed circuit voltage reached 3.0 V was measured. Table 1 shows the utilization rate of the discharge capacity at 180 mA with respect to the discharge capacity at 30 mA.
[0025]
[Table 1]

[0026]
As in Comparative Example 1, when the ratio (%) of the tape affixed to the outermost surface of the electrode is small, the internal resistance is small, but the affixing strength of the tape is low. As a result, the tape easily peels off and the cycle characteristics deteriorate. Moreover, although the ratio (%) of the tape affixed to the outermost surface of the electrode as in Comparative Example 2 does not cause a failure during the cycle test, the contact between the battery case and the electrode deteriorates and the internal resistance decreases. As a result, the operating voltage decreases and the heavy load characteristic decreases. In the batteries of Examples 1 to 3, no trouble occurs in both the cycle test and the heavy load characteristics.
[0027]
In addition, although the Example of this invention demonstrated using the flat type nonaqueous solvent secondary battery which used the nonaqueous solvent for the nonaqueous electrolyte, the polymer secondary battery and solid electrolyte which used the polymer electrolyte for the nonaqueous electrolyte were demonstrated. Naturally, the present invention can also be applied to a solid electrolyte secondary battery using a polymer thin film, and a polymer thin film or a solid electrolyte membrane can be used instead of the resin separator. Further, the battery shape has been described based on the coin-type non-aqueous electrolyte that is sealed by crimping the positive electrode case, but it is also possible to replace the positive and negative electrodes and seal the negative electrode case by the crimping process. Further, the battery shape does not need to be a perfect circle, and can be applied to a flat nonaqueous electrolyte secondary battery having a special shape such as an oval shape.
[0028]
【The invention's effect】
As described above, according to the present invention, in a flat nonaqueous electrolyte secondary battery, it is possible to prevent the occurrence of an internal short circuit while suppressing an increase in internal resistance, and to improve battery performance.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a flat nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
FIG. 2 is a view when looking above the line AA in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 2 ... Positive electrode plate, 2a ... Positive electrode energization part, 3 ... Separator, 4 ... Negative electrode plate, 4a ... Negative electrode energization part, 5 ... Negative electrode case, 6 ... Insulation gasket, 7 ... Insulation tape.

Claims

A metal negative electrode case that also serves as a negative electrode terminal and a metal positive electrode case that also serves as a positive electrode terminal are fitted and sealed via an insulating gasket, and a plurality of negative and positive electrodes are laminated inside via a separator. The electrode group and the non-aqueous electrolyte are encapsulated, and the positive electrode constituent material and the negative electrode constituent material having conductivity are exposed on the outermost side of the electrode group, and are connected to the positive electrode case and the negative electrode case , respectively. In the flat nonaqueous electrolyte secondary battery in which the current-carrying part is formed and bundled between the positive-electrode current-carrying parts and the negative-electrode current-carrying parts ,
Flat, characterized in that 10-50% of the range in each area of the positive electrode structure material and the negative electrode constituting material having outermost conductivity of the electrode group, and the entire surface of the conducting part is covered with an insulating tape Type non-aqueous electrolyte secondary battery.