JP4010521B2

JP4010521B2 - Stacked battery

Info

Publication number: JP4010521B2
Application number: JP34434097A
Authority: JP
Inventors: 修石田; 秀一和田
Original assignee: Hitachi Maxell Energy Ltd
Current assignee: Hitachi Maxell Energy Ltd
Priority date: 1997-11-28
Filing date: 1997-11-28
Publication date: 2007-11-21
Anticipated expiration: 2017-11-28
Also published as: JPH11162476A

Description

【０００１】
【発明の属する技術分野】
本発明は、積層形電池に関し、さらに詳しくは、製造時の歩留りが高く、生産性が優れ、かつ実質上の容量密度の低下が少なく、高容量密度の積層形電池に関する。
【０００２】
【従来の技術】
従来、シート状でフレキシブルな正極および負極を用い、隔離体としてシート状のゲル状電解質を用いた積層形電池としては、図７に示すように、正極１、負極２、ゲル状電解質３などの各構成要素を所望の寸法に切断した後、それらの各構成要素を要求容量に応じてそれぞれ同じ枚数で複数枚積層する、いわゆる「完全枚葉方式」を採用するか、または図８に示すように、正極１、負極２、ゲル状電解質３などの各構成要素を要求容量に応じた長さに切断し、それらを三枚重ねにしたものをまとめて折り曲げて積層する、いわゆる「折り曲げ方式」の２つが提案されている。
【０００３】
しかしながら、前者の完全枚葉方式は、構成要素の枚数が多くなるために電池の製造が極めて煩雑であり、特に隔離体として腰の弱いゲル状電解質を用いた場合には、そのハンドリング（取り扱い）が難しく、実用性に欠けるという問題があった。また、後者の折り曲げ方式は、前者の完全枚葉方式のように両面塗布電極（基材の両面に活物質含有ペーストを塗布し、加熱して基材の両面に活物質含有層を形成した電極を、簡略化して「両面塗布電極」という）を用いることができず、片面塗布電極（基材の片面に活物質含有ペーストを塗布し、加熱して基材の片面にのみ活物質含有層を形成した電極を、簡略化して「片面塗布電極」という）しか用いることができないため、積層体の正味の厚さが大きくなる上に、図８に示すように、折り曲げ部１０の膨らみが避けられないために、実質上の容量密度（ｍＡｈ／ｃｍ³）が低下し、また、電極基材からの活物質の剥離による利用率の低下や、二次電池においてはサイクル寿命が低下するという問題があった。もっとも、一部未塗布部のある両面塗布電極を用いることによって積層体の正味の厚さを完全枚葉方式と同じにすることができるが、電池の製造が複雑になり、また、片面塗布電極から一部未塗布部のある両面塗布電極に変更した時の厚さ減少は基材６枚分（後記の実施例および比較例のものでは１５０μｍの減少になる）であるのに対して、折り曲げに伴う厚さ増加は３５５μｍ（実測値）と大きく、一部未塗布部のある両面塗布電極の採用も、その有利性を充分に発揮できないという問題があった。
【０００４】
【発明が解決しようとする課題】
本発明は、上記のような従来技術における問題点を解決し、製造時の歩留りが高く、生産性に優れ、かつ実質上の容量密度の低下を抑制して、高容量密度の積層形電池を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、シート状の正極、シート状の負極などのシート状の電極を要求容量に応じて枚葉方式で複数枚積層し、隔離体としてのゲル状電解質を連続シート状で折り曲げて上記正極と負極との間に介在するように積層して積層電極体を構成し、上記電極積層体の最外部以外の電極を、基材の両面に活物質含有層を形成した両面塗布電極とすることによって、上記課題を解決したものである。
【０００６】
すなわち、本発明においては、電極を枚葉方式で複数枚積層することによって、電極として両面塗布電極の使用を可能にするとともに折り曲げ部の大きな膨らみを解消し、実質上の容量密度の低下を防止して容量密度を高め、かつ隔離体としてのゲル状電解質を折り曲げ方式で正極と負極との間に介在するように積層することによって、特に腰の弱いゲル状電解質を用いた場合でもハンドリングを容易にするとともに製造時の歩留りを高めて、生産性が優れ、かつ高容量密度の積層形電池を提供したものである。
【０００７】
【発明の実施の形態】
本発明は、その適用にあたって特に特定の電池に限られることはないが、後記の実施例で示すようないわゆるポリマー電池と呼ばれるリチウム二次電池が特に適している。
【０００８】
そして、電池の組立にあたっては、それぞれの正極のリード間を並列に接続し、かつそれぞれの負極のリード間を並列に接続し、電池全体としては、それぞれ１本ずつの正極端子と負極端子を外装体外に引き出しつつ、積層体全体を外装体で被覆する。この外装体としては、外面層にポリエチレンテレフタレートフィルムなどの樹脂フィルム、中間層にアルミニウム箔などの金属箔、内面層に変性ポリオレフィンフィルムなどの熱接着性フィルムを用いた三層構造のラミネートフィルムが好ましい。
【０００９】
【実施例】
つぎに、実施例を挙げて本発明をより具体的に説明する。ただし、本発明はそれらの実施例のみに限定されるものではない。
【００１０】
実施例１
まず、次の▲１▼、▲２▼、▲３▼に示すように、シート状の正極、シート状の負極、シート状のゲル状電解質を作製した。
【００１１】
▲１▼正極：
ＬｉＣｏＯ₂粉末４０重量部、鱗片状黒鉛粉末８重量部およびポリフッ化ビニリデン（以下、「ＰＶｄＦ」と略す）粉末５重量部を乾式で混合した後、さらに１．２２Ｍ（ｍｏｌ／ｌ）のＬｉＰＦ₆を含むエチレンカーボネート／プロピレンカーボネート（以下、「ＥＣ／ＰＣ」と略す）（５０／５０）溶液２５重量部を加えて混合して調製した活物質含有ペーストを、基材となる厚さ２５μｍのアルミニウム箔の両面にそれぞれ７５μｍの厚さに塗布した後、１２０℃で２０分間加熱して基材の両面に活物質含有層を形成することにより（上記の加熱によりＰＶｄＦが溶融し、温度が下がると上記ＰＶｄＦがゲル化し、その際に溶媒も含め全体がＰＶｄＦに取り込まれた状態で非流動化して柔軟性のある活物質含有層が形成される）、シート状の正極を作製した。このように基材の両面に活物質含有層を形成した正極を、簡略化して「両面塗布正極」という。これとは別に、基材の片面に上記と同様の活物質含有ペーストを塗布し、上記と同様に加熱して、基材の片面にのみ活物質含有層を形成した正極を、簡略化して「片面塗布正極」という。
【００１２】
そして、後記の電池組立のところで詳細に説明するように、この実施例１の積層形電池の組立にあたっては、両面塗布正極を３枚用い、片面塗布正極を１枚用い、その片面塗布正極が電極積層体の最外部に配置するように積層するが、いずれの正極もリードを設置するための箇所には活物質含有ペーストを塗布しなかった。また、上記ＥＣ／ＰＣ（５０／５０）はエチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）との比が体積比で５０：５０の混合溶媒であることを示している。
【００１３】
▲２▼負極：
球状黒鉛粉末４０重量部、鱗片状黒鉛粉末４重量部およびＰＶｄＦ粉末５重量部を乾式で混合した後、さらに１．２２ＭのＬｉＰＦ₆を含むＥＣ／ＰＣ（５０／５０）溶液５重量部を加えて混合して調製した活物質含有ペーストを、厚さ２５μｍの銅箔の両面にそれぞれ７５μｍの厚さに塗布した後、１２０℃で２０分間加熱して基材の両面に活物質含有層を形成することにより、シート状の負極を作製した。このように基材の両面に活物質含有ペーストを塗布し、加熱して基材の両面に活物質含有層を形成した負極を、簡略化して「両面塗布負極」という。また、これとは別に、基材の片面に上記と同様の活物質含有ペーストを塗布し、上記と同様に加熱して基材の片面にのみ活物質含有層を形成した負極を、簡略化して「片面塗布負極」という。この負極も、積層形電池の組立にあたっては、正極の場合と同様に、両面塗布負極を３枚用い、片面塗布負極を１枚用い、その片面塗布負極が電極積層体の最外部（ただし、正極の場合とは反対側の位置）に配置するように積層するが、いずれの負極においてもリードを設置するための箇所には活物質含有ペーストを塗布しなかった。
【００１４】
▲３▼ゲル状電解質：
２−エトキシエチルアクリレート５０重量部、トリエチレングリコールジメタクリレート１３重量部およびエチレングリコールエチルカーボネートメタクリレート３３重量部を混合した後、さらに過酸化ベンゾイル５重量部および１．２２ＭのＬｉＰＦ₆を含むＥＣ／ＰＣ（５０／５０）溶液３５重量部を加えて混合し、過酸化ベンゾイルが完全に溶解した後、その中に厚さ６０μｍ、坪量３０ｇ／ｍ²のポリブチレンテレフタレート不織布を浸漬した。溶液が上記不織布に完全に浸潤した後、７５μｍの隙間を有する２枚のガラス板の間に上記浸漬後の不織布を挟み込み、７５℃で２０分間加熱して、シート状のゲル状電解質を作製した。
【００１５】
上記のようにして得られたシート状の正極、負極およびゲル状電解質をそれぞれ図１、図２および図３に示す寸法に切断した。正極１は、図１に示すように、活物質塗布部（活物質含有層を形成した部分のことであるが、簡略化して、このように「活物質塗布部」という）１ａの寸法が７２ｍｍ×４０ｍｍであり、この活物質塗布部１ａには他の部分との識別が容易なようにドットを入れている。また、この図１には活物質塗布部１ａの寸法を示すための数値を記入しているが、その単位はｍｍである。そして、１ｂは正極１におけるリードであり、この部分には活物質含有ペーストが塗布されておらず、基材のアルミニウム箔が露出した状態でリード１ｂとして使用されている。この正極１は、電池組立にあたり、前記のように、両面塗布正極を３枚、片面塗布正極を１枚用いる。
【００１６】
負極２は、図２に示すように、活物質塗布部２ａの寸法が７４ｍｍ×４２ｍｍであり、この活物質塗布部２ａには他の部分との識別が容易なようにドットを入れている。また、この図２においても、活物質塗布部２ａの寸法を示すための数値を記入しているが、その単位はｍｍである。そして、２ｂは負極２におけるリードであり、この部分には活物質含有ペーストが塗布されておらず、基材の銅箔が露出した状態でリード２ｂとして使用されている。この負極２も、正極１の場合と同様に、電池組立にあたっては、前記のように、両面塗布負極を３枚、片面塗布負極を１枚用いる。
【００１７】
ゲル状電解質３は、この積層形電池において隔離体を構成するものであるが、このゲル状電解質３は、図３に示す通りシート状であって、そのサイズは５５７ｍｍ×４４ｍｍであり、電池組立にあたっては、これを１枚用いる。また、この図３においても、ゲル状電解質３の寸法を示すための数値を記入しているが、その単位はｍｍである。
【００１８】
電池の組立は、図４に示すように、まず、負極２を配置し（ただし、この負極２は片面塗布負極であり、その活物質塗布部を上面に配置する）、ついでゲル状電解質３、正極１の順に積層する。そして、ゲル状電解質３を折り曲げて正極１と負極２との間に介在するようにしつつ、負極２、ゲル状電解質３、正極１を積層し、以後、同様の操作を繰り返して、図５に示すように、正極１が４枚、負極２が４枚およびゲル状電解質３が１枚で構成される電極積層体を作製した。ただし、最後に積層した正極１は、片面塗布正極で、その活物質塗布部を下側、つまり、ゲル状電解質３を介して負極２と対向するように配置した。
【００１９】
つぎに、各正極のリード間を並列に接続し、かつ各負極のリード間を並列に接続し、それらの一方の端部を電池の正極端子５および負極端子６として外部に引き出し得るようにしつつ、上記電極積層体を、ポリエチレンテレフタレートフィルムを外面層とし、アルミニウム箔を中間層とし、変性ポリオレフィンフィルムを内層面とする三層ラミネートフィルム（厚さ１００μｍ）からなる外装体４で被覆して、図６に示す積層形電池を製造した。
【００２０】
この実施例１の電池を１００個製造し、３００ｍＡで１５分間充電した時の電圧を測定して短絡（３．０Ｖ未満は短絡、３．０Ｖ以上は正常）の発生の有無を調べたところ、短絡発生はまったくなかった。また、この電池は上記ラミネートフィルムからなる外装体を含んで総厚が１．９７５ｍｍであるが、２０℃における８０ｍＡ放電での放電容量は３９４ｍＡｈであり、８００ｍＡ放電での放電容量は２３６ｍＡｈであった。
【００２１】
比較例１
実施例１で作製したものと同様のゲル状電解質を７６ｍｍ×４４ｍｍのサイズの長方形状に切断し、隔離体としてこのゲル状電解質を７枚用い、正極および負極は実施例１と同様のものを用い、負極、ゲル状電解質、正極、………、負極、ゲル状電解質、正極の順に積層し、正極４枚、負極４枚およびゲル状電解質７枚で構成される電極積層体を作製した。その後、実施例１と同様にリード間の接続や外装体による被覆をして、図７に示す完全枚葉方式の積層形電池を製造した。
【００２２】
この比較例１の電池を１００個製造して前記実施例１と同様に短絡発生を調べたところ、１２個の電池に短絡が発生していた。その短絡の発生した電池を分解して調べたところ、いずれも隔離体として用いたゲル状電解質が軟らかすぎて、所定の位置に納まらなかったために正極と負極とが接触したことによるものであることが判明した。
【００２３】
この比較例１の電池の厚みは外装体のラミネートフィルムを含んだ状態で前記実施例１と同様に１．９７５ｍｍであり、また、この電池の８０ｍＡでの放電容量は実施例１と同様に３９４ｍＡｈであり、８００ｍＡ放電での放電容量も実施例１と同様に２３６ｍＡｈであった。
【００２４】
比較例２
幅４０ｍｍの片面塗布正極、幅４２ｍｍの片面塗布負極および隔離体として用いる幅４４ｍｍのゲル状電解質をそれぞれ７００ｍｍの長さに切断し、幅４４ｍｍ、長さ７６ｍｍ、深さ１０ｍｍの窪みを持つアクリル樹脂製治具を用いて、６回折り畳み、電極の端子部を形成するための長さを残して余分な部分を切断し、幅４４ｍｍ、長さ７５．５ｍｍ、高さ１００ｍｍのアクリル樹脂製角棒でゆっくり押さえつけ、仮固定した。ついで、端子部を適当な形状に切断し、活物質含有層を取り除いた（たとえば、エタノールを浸み込ませたガーゼなどで払拭する）後、前記実施例１と同様に外装体で被覆して、図８に示す折り曲げ方式の積層形電池を製造した。
【００２５】
この比較例２の電池を１００個製造して前記実施例１と同様に短絡発生の有無を調べたところ、１７個の電池に短絡が発生していた。短絡の発生した電池について、その原因を調べたところ、短絡発生の原因は折り曲げ作業時に、正極または負極が隔離体としてのゲル状電解質を突きぬけることによって正極と負極とが接触したことによるものであることが判明した。
【００２６】
この比較例２の電池の厚みは外装体としてのラミネートフィルムを含んだ状態で２．３１０ｍｍであり、前記実施例１や比較例１に比べて厚さが約１７％厚かった。また、この比較例２の電池は、折り曲げ部分にも活物質層が存在するために、充填容量は前記実施例１の電池や比較例１の電池よりも１０％程度高いにもかかわらず、８０ｍＡでの放電容量が実施例１の電池や比較例１の電池と同等の３９３ｍＡｈにすぎず、８００ｍＡでの放電容量は１８１ｍＡｈと前二者よりもかなり低かった。この原因は、活物質が基材から剥離したためであると考えられる。
【００２７】
上記実施例１の電池および比較例１〜２の電池の製造時における短絡発生電池個数、電池の厚み、８０ｍＡ放電での放電容量および８００ｍＡ放電での放電容量を表１にまとめて示す。
【００２８】
【表１】

【００２９】
表１に示す結果から明らかなように、実施例１の電池は、比較例１〜２の電池に比べて、製造時の短絡発生が少なく、歩留りが高く、生産性に優れていた。また、実施例１の電池は、折り曲げ方式の比較例２の電池に比べて、８００ｍＡｈでの放電容量が高く、高容量密度であった。
【００３０】
【発明の効果】
以上説明したように、本発明では、製造時の歩留まりが高く、生産性が優れ、かつ高容量密度の積層形電池を提供することができた。
【図面の簡単な説明】
【図１】本発明の積層形電池に用いる正極の一例を模式的に示す平面図である。
【図２】本発明の積層形電池に用いる負極の一例を模式的に示す平面図である。
【図３】本発明の積層形電池に用いるゲル状電解質の一例を模式的に示す平面図である。
【図４】本発明の積層形電池の組立中の状態を模式的に示す断面図である。
【図５】本発明の積層形電池の電極積層体の一例を模式的に示す断面図である。
【図６】本発明の積層形電池の一例を模式的に示す断面図である。
【図７】完全枚葉方式の積層形電池を模式的に示す断面図である。
【図８】折り曲げ方式の積層形電池を模式的に示す断面図である。
【符号の説明】
１正極
２負極
３ゲル状電解質
４外装体
５正極端子
６負極端子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated battery, and more particularly, to a laminated battery having a high capacity density with a high yield during production, excellent productivity, and substantially no decrease in capacity density.
[0002]
[Prior art]
Conventionally, as a laminated battery using a sheet-like flexible positive electrode and negative electrode and using a sheet-like gel electrolyte as a separator, as shown in FIG. 7, a positive electrode 1, a negative electrode 2, a gel electrolyte 3, etc. After each component is cut to a desired size, a so-called “complete single-wafer method” is employed in which a plurality of these components are stacked in the same number according to the required capacity, or as shown in FIG. In addition, a so-called “folding method” in which each component such as the positive electrode 1, the negative electrode 2, and the gel electrolyte 3 is cut to a length corresponding to the required capacity, and the three layers are folded and stacked together. These two have been proposed.
[0003]
However, the former complete single-wafer method is extremely cumbersome because of the increased number of components, and handling is particularly difficult when a weakly gelled electrolyte is used as a separator. However, it was difficult and lacked practicality. In addition, the latter bending method is a double-sided coated electrode as in the former complete single-wafer method (an electrode in which an active material-containing paste is applied on both sides of a substrate and heated to form an active material-containing layer on both sides of the substrate) Cannot be used as a “double-sided coated electrode”, but a single-sided coated electrode (active material-containing paste is coated on one side of the substrate and heated to form an active material-containing layer only on one side of the substrate) The formed electrode can only be used in a simplified manner (referred to as a “single-side coated electrode”), so that the net thickness of the laminate is increased and the bulging of the bent portion 10 is avoided as shown in FIG. Therefore, there is a problem that the substantial capacity density (mAh / cm ³ ) is reduced, the utilization factor is reduced due to the peeling of the active material from the electrode substrate, and the cycle life is reduced in the secondary battery. there were. However, the net thickness of the laminate can be made the same as that of the complete single-wafer method by using a double-sided coated electrode with a part of the uncoated part, but the manufacturing of the battery becomes complicated, and the single-sided coated electrode The thickness reduction when changing from a partly uncoated part to a double-sided coated electrode is 6 sheets of base material (in the examples and comparative examples described later, it is reduced by 150 μm), while bending The increase in the thickness accompanying this is as large as 355 μm (actual measurement value), and there is a problem that the advantage of using a double-sided coated electrode with a part of the uncoated part cannot be fully exhibited.
[0004]
[Problems to be solved by the invention]
The present invention solves the problems in the prior art as described above, has a high yield during production, is excellent in productivity, and suppresses a substantial decrease in capacity density, thereby providing a high capacity density laminated battery. The purpose is to provide.
[0005]
[Means for Solving the Problems]
In the present invention, a plurality of sheet-like electrodes such as a sheet-like positive electrode and a sheet-like negative electrode are laminated in a single-wafer method according to a required capacity, and a gel electrolyte as a separator is bent in a continuous sheet shape to form the positive electrode. A laminated electrode body is laminated so as to be interposed between the electrode and the negative electrode, and the electrodes other than the outermost part of the electrode laminated body are formed as a double-sided coated electrode in which an active material-containing layer is formed on both surfaces of the substrate. This solves the above problem.
[0006]
In other words, in the present invention, by laminating a plurality of electrodes in a single-wafer method, it is possible to use a double-sided coated electrode as an electrode, eliminate a large bulge of the bent portion, and prevent a substantial decrease in capacity density. In addition, the capacity density is increased and the gel electrolyte as a separator is laminated so that it is interposed between the positive electrode and the negative electrode in a folding manner, so that handling is easy even when using a gel electrolyte that is particularly weak. In addition, the present invention provides a laminated battery having high productivity and high capacity density by increasing the yield during manufacture.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is not particularly limited to a specific battery in its application, but a lithium secondary battery called a so-called polymer battery as shown in Examples described later is particularly suitable.
[0008]
When assembling the battery, the leads of the positive electrodes are connected in parallel and the leads of the negative electrodes are connected in parallel. As a whole battery, one positive electrode terminal and one negative electrode terminal are packaged. The entire laminate is covered with an exterior body while being pulled out of the body. As the outer package, a laminate film having a three-layer structure using a resin film such as a polyethylene terephthalate film as an outer surface layer, a metal foil such as an aluminum foil as an intermediate layer, and a heat adhesive film such as a modified polyolefin film as an inner layer is preferable. .
[0009]
【Example】
Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples.
[0010]
Example 1
First, as shown in the following (1), (2), and (3), a sheet-like positive electrode, a sheet-like negative electrode, and a sheet-like gel electrolyte were prepared.
[0011]
(1) Positive electrode:
After 40 parts by weight of LiCoO ₂ powder, 8 parts by weight of scaly graphite powder and 5 parts by weight of polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) powder were mixed in a dry process, 1.22 M (mol / l) LiPF _{6 was} further mixed. An active material-containing paste prepared by adding and mixing 25 parts by weight of an ethylene carbonate / propylene carbonate (hereinafter abbreviated as “EC / PC”) (50/50) solution containing 25 μm thick aluminum as a base material After applying to each thickness of 75 μm on both sides of the foil, by heating at 120 ° C. for 20 minutes to form an active material containing layer on both sides of the substrate (when PVdF is melted by the above heating and the temperature drops) The above PVdF is gelled, and in that case, the whole including the solvent is taken into the PVdF and is made non-fluidized to form a flexible active material containing layer), sheet The positive electrode was manufactured. The positive electrode in which the active material-containing layer is formed on both surfaces of the substrate in this way is simply referred to as “double-sided coated positive electrode”. Separately from this, an active material-containing paste similar to the above was applied to one side of the substrate, heated in the same manner as described above, and the positive electrode having an active material-containing layer formed only on one side of the substrate was simplified. It is called “single-side coated positive electrode”.
[0012]
Then, as will be described in detail in the battery assembly described later, in assembling the laminated battery of Example 1, three double-coated positive electrodes were used, one single-coated positive electrode was used, and the single-coated positive electrode was an electrode. Lamination was carried out so as to be arranged on the outermost part of the laminated body, but no active material-containing paste was applied to any positive electrode at a location for installing a lead. The EC / PC (50/50) indicates that the ratio of ethylene carbonate (EC) to propylene carbonate (PC) is a mixed solvent having a volume ratio of 50:50.
[0013]
(2) Negative electrode:
After 40 parts by weight of spherical graphite powder, 4 parts by weight of scaly graphite powder and 5 parts by weight of PVdF powder were mixed by dry process, 5 parts by weight of EC / PC (50/50) solution containing 1.22M LiPF ₆ was further added. The active material containing paste prepared by mixing was applied to both sides of a 25 μm thick copper foil to a thickness of 75 μm and then heated at 120 ° C. for 20 minutes to form an active material containing layer on both sides of the substrate. By doing this, a sheet-like negative electrode was produced. Thus, the negative electrode which apply | coated the active material containing paste on both surfaces of the base material, and heated and formed the active material content layer on both surfaces of the base material is simplified, and is called "double-sided coating negative electrode." Separately, a negative electrode in which an active material-containing paste similar to the above is applied to one side of a base material and heated in the same manner as described above to form an active material-containing layer only on one side of the base material is simplified. This is called “single-side coated negative electrode”. When assembling a laminated battery, this negative electrode also uses three double-sided negative electrodes and one single-sided negative electrode, as in the case of the positive electrode, and the single-sided negative electrode is the outermost part of the electrode stack (however, the positive electrode However, the active material-containing paste was not applied to the portion for installing the lead in any of the negative electrodes.
[0014]
(3) Gel electrolyte:
EC / PC containing 50 parts by weight of 2-ethoxyethyl acrylate, 13 parts by weight of triethylene glycol dimethacrylate and 33 parts by weight of ethylene glycol ethyl carbonate methacrylate, and further containing 5 parts by weight of benzoyl peroxide and 1.22M LiPF ₆ 35 parts by weight of a (50/50) solution was added and mixed, and after the benzoyl peroxide was completely dissolved, a polybutylene terephthalate nonwoven fabric having a thickness of 60 μm and a basis weight of 30 g / m ² was immersed therein. After the solution completely infiltrated into the non-woven fabric, the non-woven fabric after immersion was sandwiched between two glass plates having a gap of 75 μm and heated at 75 ° C. for 20 minutes to prepare a sheet-like gel electrolyte.
[0015]
The sheet-like positive electrode, negative electrode and gel electrolyte obtained as described above were cut into the dimensions shown in FIG. 1, FIG. 2, and FIG. 3, respectively. As shown in FIG. 1, the positive electrode 1 is an active material application portion (which is a portion where an active material-containing layer is formed, but is simply referred to as an “active material application portion”) 1a. The active material application part 1a is filled with dots so that it can be easily distinguished from other parts. Moreover, although the numerical value for showing the dimension of the active material application part 1a is entered in this FIG. 1, the unit is mm. Reference numeral 1b denotes a lead in the positive electrode 1, which is not coated with an active material-containing paste, and is used as the lead 1b with the aluminum foil of the base material exposed. As described above, the positive electrode 1 uses three double-coated positive electrodes and one single-coated positive electrode as described above.
[0016]
As shown in FIG. 2, the negative electrode 2 has an active material application part 2a with dimensions of 74 mm × 42 mm, and the active material application part 2a is provided with dots so that it can be easily distinguished from other parts. Also in FIG. 2, numerical values for indicating the dimensions of the active material application portion 2a are entered, and the unit is mm. Reference numeral 2b denotes a lead in the negative electrode 2. The active material-containing paste is not applied to this portion, and the lead 2b is used in a state where the copper foil of the base material is exposed. As in the case of the positive electrode 1, the negative electrode 2 also uses three double-coated negative electrodes and one single-coated negative electrode as described above for battery assembly.
[0017]
The gel electrolyte 3 constitutes a separator in this stacked battery. The gel electrolyte 3 is in the form of a sheet as shown in FIG. 3, and its size is 557 mm × 44 mm. In this case, one sheet is used. Also in FIG. 3, numerical values for indicating the dimensions of the gel electrolyte 3 are entered, and the unit is mm.
[0018]
As shown in FIG. 4, the battery is assembled by first disposing the negative electrode 2 (however, this negative electrode 2 is a single-side coated negative electrode, and its active material coating part is disposed on the top surface), and then the gel electrolyte 3, The positive electrodes 1 are stacked in this order. Then, the negative electrode 2, the gel electrolyte 3 and the positive electrode 1 are laminated while bending the gel electrolyte 3 so as to be interposed between the positive electrode 1 and the negative electrode 2. As shown, an electrode laminate composed of four positive electrodes 1, four negative electrodes 2, and one gel electrolyte 3 was produced. However, the positive electrode 1 laminated last was a single-sided positive electrode, and the active material application part was arranged on the lower side, that is, with the gel electrolyte 3 facing the negative electrode 2.
[0019]
Next, the leads of the positive electrodes are connected in parallel, and the leads of the negative electrodes are connected in parallel, and one end thereof can be drawn to the outside as the positive electrode terminal 5 and the negative electrode terminal 6 of the battery. The electrode laminate is covered with an outer package 4 made of a three-layer laminate film (thickness: 100 μm) having a polyethylene terephthalate film as an outer layer, an aluminum foil as an intermediate layer, and a modified polyolefin film as an inner layer. 6 was manufactured.
[0020]
100 batteries of Example 1 were manufactured, and the voltage when charged at 300 mA for 15 minutes was measured to determine whether or not a short circuit occurred (short circuit is less than 3.0V, normal is more than 3.0V). No short circuit occurred. In addition, this battery includes the outer package made of the laminate film and has a total thickness of 1.975 mm. The discharge capacity at 80 mA discharge at 20 ° C. is 394 mAh, and the discharge capacity at 800 mA discharge is 236 mAh. .
[0021]
Comparative Example 1
A gel electrolyte similar to that prepared in Example 1 was cut into a rectangular shape having a size of 76 mm × 44 mm, seven gel electrolytes were used as separators, and the positive electrode and the negative electrode were the same as in Example 1. The negative electrode, the gel electrolyte, the positive electrode,..., The negative electrode, the gel electrolyte, and the positive electrode were stacked in this order to prepare an electrode laminate composed of four positive electrodes, four negative electrodes, and seven gel electrolytes. Thereafter, in the same manner as in Example 1, the connection between the leads and the covering with the outer package were performed to manufacture a complete single-wafer type laminated battery shown in FIG.
[0022]
When 100 batteries of Comparative Example 1 were manufactured and the occurrence of a short circuit was examined in the same manner as in Example 1, a short circuit occurred in 12 batteries. When the battery in which the short-circuit occurred was disassembled and examined, the gel electrolyte used as a separator was too soft and did not fit in place, so the positive electrode and the negative electrode were in contact with each other. There was found.
[0023]
The thickness of the battery of Comparative Example 1 is 1.975 mm as in Example 1 in the state including the laminate film of the outer package, and the discharge capacity at 80 mA of this battery is 394 mAh as in Example 1. The discharge capacity at 800 mA discharge was 236 mAh as in Example 1.
[0024]
Comparative Example 2
A single-side coated positive electrode having a width of 40 mm, a single-side coated negative electrode having a width of 42 mm, and a gel electrolyte having a width of 44 mm used as a separator are each cut to a length of 700 mm, and an acrylic resin having a recess having a width of 44 mm, a length of 76 mm, and a depth of 10 mm Using a jig, folded 6 times, leaving the length to form the terminal part of the electrode, cutting the excess part, 44mm width, 75.5mm length, 100mm height acrylic resin square bar Pressed slowly and temporarily fixed. Next, the terminal part was cut into an appropriate shape, the active material-containing layer was removed (for example, wiped with gauze soaked with ethanol, etc.), and then covered with an exterior body in the same manner as in Example 1 above. Then, the folding type laminated battery shown in FIG. 8 was manufactured.
[0025]
When 100 batteries of Comparative Example 2 were manufactured and the presence or absence of occurrence of a short circuit was examined in the same manner as in Example 1, a short circuit occurred in 17 batteries. The cause of the short circuit occurred when the battery was short-circuited. The cause of the short-circuit occurred when the positive electrode or the negative electrode contacted the positive electrode and the negative electrode by penetrating the gel electrolyte as a separator during the bending operation. It turned out to be.
[0026]
The battery of Comparative Example 2 had a thickness of 2.310 mm including a laminate film as an outer package, and was about 17% thicker than Examples 1 and Comparative Example 1. Further, since the battery of Comparative Example 2 has an active material layer at the bent portion, the charging capacity is about 80% higher than that of the battery of Example 1 or the battery of Comparative Example 1, although it is 80 mA. The discharge capacity was only 393 mAh equivalent to the battery of Example 1 and the battery of Comparative Example 1, and the discharge capacity at 800 mA was 181 mAh, which was considerably lower than the former two. This cause is considered to be because the active material peeled from the base material.
[0027]
Table 1 summarizes the number of short-circuited batteries, the thickness of the battery, the discharge capacity at 80 mA discharge, and the discharge capacity at 800 mA discharge when the battery of Example 1 and Comparative Examples 1 and 2 were manufactured.
[0028]
[Table 1]

[0029]
As is clear from the results shown in Table 1, the battery of Example 1 was less likely to cause a short circuit during production, had a higher yield, and was more productive than the batteries of Comparative Examples 1 and 2. In addition, the battery of Example 1 had a higher discharge capacity at 800 mAh and a higher capacity density than the battery of Comparative Example 2 of the folding method.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a stacked battery having a high production yield, excellent productivity, and high capacity density.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing an example of a positive electrode used in a stacked battery of the present invention.
FIG. 2 is a plan view schematically showing an example of a negative electrode used in the stacked battery of the present invention.
FIG. 3 is a plan view schematically showing an example of a gel electrolyte used in the laminated battery of the present invention.
FIG. 4 is a cross-sectional view schematically showing a state in which the laminated battery of the present invention is being assembled.
FIG. 5 is a cross-sectional view schematically showing an example of an electrode laminate of the laminated battery of the present invention.
FIG. 6 is a cross-sectional view schematically showing an example of the laminated battery of the present invention.
FIG. 7 is a cross-sectional view schematically showing a complete single-wafer stacked battery.
FIG. 8 is a cross-sectional view schematically showing a folding type stacked battery.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Gel electrolyte 4 Exterior body 5 Positive electrode terminal 6 Negative electrode terminal

Claims

In a stacked battery comprising a sheet-like positive electrode, a sheet-like negative electrode, and a sheet-like gel electrolyte interposed between the sheet-like positive electrode and the sheet-like negative electrode,
The sheet-like positive electrode and the sheet-like negative electrode are stacked in a single-wafer method according to capacity, and the gel electrolyte is bent in a continuous sheet shape so as to be interposed between the sheet-like positive electrode and the sheet-like negative electrode. To form an electrode laminate,
A laminated battery characterized in that the electrode other than the outermost electrode of the electrode laminate is a double-sided coated electrode in which active material-containing layers are formed on both sides of a substrate .