JP2004319101A

JP2004319101A - Storage element

Info

Publication number: JP2004319101A
Application number: JP2003107324A
Authority: JP
Inventors: Yoshiaki Ebine; 美明恵比根; Tomohiro Matsuura; 智浩松浦; Yoshiaki Matsumoto; 恵明松本
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2004-11-11
Anticipated expiration: 2023-04-11
Also published as: JP4397175B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage element capable of preventing occlusion of a bursting valve by a wound type electrode body by a simple structure. <P>SOLUTION: The storage element 1 comprises a wound type electrode body 7 in which a positive electrode sheet 3 and a negative electrode sheet 5 are wound through a separator, a container 9 housing the electrode body 7 and an electrolyte, a bursting valve 23 which adjusts the inner pressure of the container 9 by communicating between the inside and outside of the container 9 and which is provided in the nearly perpendicularly crossing direction to the winding axis of the electrode body 7, and an bursting auxiliary member 15 for preventing occlusion of the bursting valve 23 by the electrode body 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】本発明は、捲回型の電極体を備えた蓄電素子に関する。より詳細には、該電極体を収納した容器の内圧を調整する放圧弁を備える蓄電素子に関する。
【０００２】
【従来の技術】正極シートと負極シートとがセパレータを介して捲回された電極体（捲回型電極体）を、電解質とともに容器に収容した蓄電素子が知られている。このような蓄電素子の一つのタイプとして、ラミネートフィルム等からなる袋状容器に捲回型電極体を収容するとともに袋状容器の開口部を封止してなる密閉型蓄電素子がある。
一般に、密閉型の蓄電素子（典型的には非水系電解液を用いた蓄電素子）には、電極体の種類（捲回型、積層型等）を問わず、容器の内圧が高まった際に容器を開放して内圧調整を図る放圧弁（安全弁）が装備されている。例えば特許文献１には、ラミネートフィルムの封止部分の一部に他の部分よりも薄い封止部分を設けた密閉型の非水系電池が記載されている。この薄い封止部分が安全弁として作用し、電池内圧力が増加した場合には当該封止部分が剥離することにより電池内圧が調整される。
【０００３】
【特許文献１】特開平１１−８６８２３号公報
【０００４】
【発明が解決しようとする課題】ところで、容器に収容する電極体が捲回型であってその捲回軸に対して略直交する方向（横方向）に放圧弁を設けたタイプの蓄電素子を作製する場合、特許文献１に記載されるような構成では、その当該電極体の外周面によって安全弁（放圧弁）が塞がれる虞があり好ましくない。弁が塞がれてしまうと容器内外のガス流通が阻まれ、容器内圧を速やかに調整することが難しくなるからである。
【０００５】
そこで本発明は、捲回型電極体の捲回軸に対して略直交する方向に放圧弁が形成されたタイプの蓄電素子であって、容器内圧を安定的に調整し得る蓄電素子を提供することを目的とする。
【０００６】
【課題を解決するための手段、作用および効果】本発明により提供される蓄電素子は、正極シートと負極シートとがセパレータを介して捲回されている捲回型電極体と、その電極体および電解質を収容する容器と、その容器の内外を連通させて該容器の内圧を調整する放圧弁であって前記電極体の捲回軸に対して略直交する方向に設けられている放圧弁とを備える。そして、前記電極体による前記放圧弁の閉塞を防止する放圧補助手段をさらに備える。
なお、本明細書中において「蓄電素子」とは、電池（リチウムイオン電池、ニッケル水素電池等）およびキャパシタ（電気二重層キャパシタ等）の双方を包含する概念である。
【０００７】
本発明の蓄電素子は、別途、放圧弁の閉塞を防止する放圧補助手段を備えることによって、放圧弁の作動（開閉）に対する捲回型電極体（典型的には電極体の外周面）の干渉（典型的には接触）を防止し、放圧弁の閉塞を防止することができる。このため、本発明の蓄電素子によると、捲回型電極体による放圧弁の放圧（開閉）機能妨害を防止し、当該放圧弁によって容器内圧を安定的に調整することができる。
【０００８】
このような蓄電素子の好ましい一つは、前記放圧補助手段が、放圧弁に対向する前記電極体の外周部分が放圧弁側に張り出すのを抑制するように構成された放圧補助部材を備えることを特徴とする。この態様の蓄電素子によると、例えば捲回型電極体の内部でガスが発生して電極体が膨張若しくは変形し得る状態にある場合でも、放圧補助部材によって当該電極体の放圧弁方向への張り出し（進出）を抑止することができる。このため、電極体が放圧弁に接触することによる放圧弁の閉塞を防止することができる。典型的には、前記放圧補助部材は電極体と放圧弁との間に実質的に配置される。
【０００９】
ここで開示される蓄電素子の好ましい他の一つは、前記放圧補助部材が放圧弁の近傍に配置されており、前記電極体方向に向かって突出する凸部を有することを特徴とする。この態様の蓄電素子では、例えば捲回型電極体の内部でガスが発生して電極体が膨張若しくは変形し得る状態である場合でも、前記放圧補助部材の凸部が電極体を押圧することにより、その電極体の放圧弁方向への張り出し（進出）を抑止することができる。このため、放圧弁に捲回型電極体が接触することによる放圧弁の閉塞を防止することができる。
【００１０】
前記放圧補助部材は、捲回型電極体の放圧弁に対向する外面の少なくとも一部を被覆した状態で配置されていることが好ましい。この態様の蓄電素子では、当該被覆部分においてより確実に捲回型電極体と放圧弁との接触を防止することができる。この場合、放圧補助部材が板状またはシート状に形成されたものであることが好ましい。
【００１１】
ここで開示される蓄電素子において、前記放圧補助部材は通気可能な材質を用いて構成されていることが好ましい。この態様の蓄電素子によれば、該放圧補助部材を容器内に収容した場合でも、その放圧補助部材によって容器内におけるガスの流通（発生箇所から安全弁までのガスの移動）が妨げられることが少ない。したがってガスの放出を適切に行うことができる。
【００１２】
ここで開示される蓄電素子の好ましい他の一つは、前記放圧補助手段が、容器の電極体収容部分よりも放圧弁形成部分が窄まるように該容器の一部を外部から拘束し得る形状に設けられた放圧補助部材を備えることを特徴とする。この態様の蓄電素子では、容器外部に設けられた放圧補助部材によって、捲回型電極体の放圧弁方向への張り出し（進出）を確実に抑止することができる。また、放圧補助部材が容器の外部に設けられているので、その放圧補助部材が容器内におけるガスの流通（発生箇所から安全弁までのガスの移動）を妨げることがない。
【００１３】
ここで開示される蓄電素子として特に好ましい一つは、前記放圧補助手段が容器の少なくとも一部により構成されている（典型的には容器と一体に形成されている）ことを特徴とする。容器の一部が放圧補助手段を構成する放圧補助部材として機能し得るものであれば、蓄電素子を構築する部品数の増加（すなわち放圧補助部材として付加される部品による増加）が回避され、コスト増および組み立て工程の煩雑化を防止することができる。
【００１４】
【発明の実施の形態】本発明の好適な実施の形態を、図面を参照しつつ具体的ないくつかの実施例に基づいて詳細に説明する。なお、本明細書において特に言及している内容以外の技術的事項であって本発明の実施に必要な事項は、従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書および図面によって開示されている技術内容と当該分野における技術常識とに基づいて実施することができる。
【００１５】
（第１実施例）
本実施例は、捲回型電極体と放圧弁との間に、放圧補助手段を構成する放圧補助部材が配置されたリチウムイオン二次電池の一例である。図１は、本実施例に係る二次電池１を示す正面図である。また、図２は、図１の内部を示すためにその前面の絶縁フィルム１７の図示を省略した状態を示す説明図である。
【００１６】
図１および図２に示すように、この二次電池１は、正極シート（正極）３と負極シート（負極）５とを備える捲回型の電極体７と、この電極体７を収容する容器９と、電極体７の軸方向両端７ａ，７ｂにそれぞれ一端１１ａ，１３ａが接続された正極端子１１および負極端子１３と、本実施例に係る放圧補助部材１５とを備える。容器９は、二枚の絶縁フィルム１７，１９を合わせ、それらの外周にわたって熱溶着部２１を形成して構成されている。また、図示されるように、正極端子１１および負極端子１３の他端（開放末端）１１ｂ，１３ｂは、絶縁フィルム１７，１９の合わせ目（熱溶着部２１）から容器９を貫通して外方に突出している。これら正極端子１１および負極端子１３を介して、電極体７の側方（捲回軸に対して略直交する方向：図１および図２の上側）から電流を取り出すことができる。さらに、正極端子１１と負極端子１３との間にある熱溶着部２１には、後述する放圧弁２３が形成されている。そして、図２に示すように、放圧弁２３が形成された側の熱溶着部２１と電極体７との間には、当該電極体７の外周の一部を被覆した状態で、放圧補助部材１５が配置されている。
【００１７】
まず、捲回型電極体７について説明する。この電極体７は、長尺状の正極集電体の両面に正極活物質層が形成された正極シート３と、長尺状の負極集電体の両面に負極活物質層が形成された負極シート５と、二枚の長尺状のセパレータシート（図示せず）とを備える。これらのシートを、正極シート３、セパレータ、負極シート５、セパレータの順に積層し、捲回機等を用いて長尺方向に捲回する。この捲回体を径方向にプレスすることにより、偏平状に捲回された電極体７を作製することができる。このような捲回型電極体７において、正極シート３と負極シート５とは捲回軸方向に対して互いに位置をずらして積層されている。その結果、図２に模式的に示すように、電極体７の軸方向の一端７ａは主として正極シート３から構成され、軸方向の他端７ｂは主として負極シート５から構成されている。この電極体７の一端７ａにおいて、アルミニウム材料により板状に形成された正極端子１１の一端１１ａが正極シート３に接続（固定）されている。また、電極体７の他端７ｂにおいて、銅材料により板状（正極端子１１と同様の形状）に形成された負極端子１３の一端１３ａが負極シート５に接続（固定）されている。これらの端子１１，１３と電極体７との接続は超音波溶接等により実施することができる。
【００１８】
なお、正極シート３を構成する正極集電体としてはアルミニウム箔等を、負極シート５を構成する負極集電体としては銅箔等を用いることができる。上記正極活物質層を構成する正極活物質としては、ＬｉＭｎ_２Ｏ_４、ＬｉＣｏＯ_２、ＬｉＮｉＯ_２等の、従来のリチウムイオン二次電池に用いられる正極活物質の一種または二種以上を特に限定なく使用することができる。上記負極活物質層を構成する負極活物質としては、アモルファスカーボン、グラファイトカーボン等の、従来のリチウムイオン二次電池に用いられる負極活物質の一種または二種以上を特に限定なく使用することができる。これらの活物質層には、従来公知の結着剤、導電化剤等を適宜含有させることができる。また、セパレータシートとしては、例えば多孔質ポリオレフィン（ポリエチレン、ポリプロピレン等）シートを用いることができる。
【００１９】
このような電極体７を収容している容器９は、二枚の絶縁フィルム１７，１９により構成され、それらの絶縁フィルム１７，１９を外周にわたって相互に熱溶着した熱溶着部２１により封止されている。熱溶着部２１には、捲回型電極体７の捲回軸に対して略直交する方向であって放圧補助部材１５に対向する中央部分に、熱溶着部２１の他の部分に比べて相対的に接着強度（ここでは熱溶着の強度）の低い部分である放圧弁２３が形成されている。放圧弁２３は、このように他の部分に比べて接着強度が低い結果、容器９の内圧が増大した際に絶縁フィルム１７，１９間の接着（熱溶着）が破れ易い構造となっており、ここから容器９内（例えば電極体７）で発生したガスを容器外に放出して内圧増大を防止することができる。なお、放圧弁２３の設置部位を上とすると、捲回型電極体７はその捲回軸が横倒しとなるようにして容器９に収容されている。また、容器９内には図示しない液状電解質（電解液）が収容されており、電極体７に含浸されている。使用する電解液は特に限定されず、例えばジエチルカーボネートとエチレンカーボネートとの７：３（質量比）混合溶媒に１ｍｏｌ／リットルのＬｉＰＦ_６を溶解させたものを用いることができる。
【００２０】
次に、本実施例に係る放圧補助手段を構成する放圧補助部材１５について説明する。このような放圧補助部材１５の構成材料としては、蓄電素子の種類に応じて、その蓄電素子（本実施例ではリチウムイオン二次電池）を構成する電解質や蓄電素子の使用により生じる反応生成物に対して耐性を有する材料を適宜選択して用いることができる。通常は絶縁性材料を選択することが好ましい。例えば、ポリエチレン、ポリプロピレン等のポリオレフィン系樹脂、エチレン−プロピレン−ジエン共重合体（ＥＰＤＭ）等が好ましく選択される。また、ＰＰＳ（ポリフェニレンスルフィド樹脂）、ポリイミド樹脂、ポリアミドイミド樹脂、フッ素樹脂、ＰＥＥＫ（ポリエーテルエーテルケトン樹脂）、ＰＥＳ（ポリエーテルスルホン樹脂）等を用いてもよい。このような材料を通気可能に成形したものを放圧補助部材１５として用いることができる。例えば、厚み方向に貫通する孔、溝および／または外周の切欠きを有する形状としたものを用いることができる。あるいは、上記材料からなる多孔質体を用いてもよい。これにより、蓄電素子の過充電時等において容器内に発生し得るガスを放圧弁２３へと逃すためのガス抜き経路を、適切に確保することができる。
【００２１】
放圧補助部材１５の厚さは特に限定されない。一般に、放圧弁２３と電極体７との間に配置した放圧補助部材１５の厚さを大きくすると、電極体７の放圧弁２３方向への張り出し（進出）を強い押圧力で阻止し、優れた放圧弁２３の閉塞防止効果を発揮し得る。一方、放圧補助部材１５の厚さを過剰に大きくすると蓄電素子が大型化する傾向にある。これらのバランスから、電池および電極体のサイズによって異なり得るが、通常は放圧補助部材１５の厚さを凡そ０．２〜２ｍｍ程度とすることが適当である。また、放圧補助部材１５の幅は、捲回電極体７の張り出しを抑制し得る限り特に限定はないが、捲回電極体７（典型的には偏平状に捲回された電極体）の厚さに対して例えば０．５〜１．２倍程度とすることができる。また、放圧補助部材１５の長さは、本実施例のような一体形状の放圧補助部材１５では、電極体７の軸長とほぼ同等かやや短い程度の長さが好ましい。このことにより、容器９の内部空間において、捲回型電極体７の軸方向の両端付近に、容器９内で発生したガスが放圧補助部材の設置に阻害されることなく上方に抜ける隙間を確保することができる。なお、剛性の高い材料から形成された容器（例えば、後述する第２実施例のような金属製の角型容器）を用いる場合等には、蓄電素子の組み立てが容易であること等から、容器開口部の最大開口幅よりも放圧補助部材の幅を小さくすることが好ましい。
【００２２】
本実施例では、放圧補助部材１５として厚さ約０．５ｍｍのポリエチレンシートを用いた。放圧補助部材１５の幅は偏平状に捲回された電極体７の厚さとほぼ同等である。また、放圧補助部材１５の長さは、電極体７の両端に接続された正極端子１１と負極端子１３との間にほぼ収まる程度の長さである。この放圧補助部材１５には、気体の流通が可能な貫通孔またはスリット（図示せず）が多数設けられている。
【００２３】
次いで、正極端子１１および負極端子１３の接続された電極体７および放圧補助部材１５を容器９に収容して二次電池１を作製する方法について説明する。
図１および図２に示すように、容器９は二枚の長方形状の絶縁フィルム１７，１９からなる。図３にその断面を示すように、絶縁フィルム１７，１９の各々は、熱可塑性樹脂等からなる熱溶着層１７ａ，１９ａ、アルミニウム蒸着層１７ｂ，１９ｂ、および保護樹脂層１７ｃ，１９ｃをこの順に積層した構造を有する。これらの絶縁フィルム１７，１９を、互いの熱溶着層１７ａ，１９ａが向き合うように重ね合わせ、図１および図２に示すように、端子１１，１３の接続された電極体７をその間に挟む。このとき、両端子の一端２７，３１が絶縁フィルム１７，１９の間（合わせ目）から突出するように電極体７を配置する。そして、放圧補助部材１５を電極体７の軸方向に対して略垂直な方向であって正極端子１１と負極端子１３との間に配置し、二つの絶縁フィルム１７，１９を、その外周部に相当する熱溶着部２１において互いに熱溶着させる。これにより容器９が形成される。このとき、放圧弁２３に相当する部分は、絶縁フィルム１７，１９の熱溶着面積（その部分における熱溶着部２１の形成幅）を小さくすることで、その接着強度（熱溶着の強度）が熱溶着部２１の他の部分に比べて低くなるようにする。また、絶縁フィルム１７，１９の間に両端子１１，１３の他端１１ｂ，１３ｂが挟まれている部分では、絶縁フィルム１７、１９をその熱溶着部２１において両端子１１，１３の表面に熱溶着させるようにする。以上の手順によって図１および図２に示す構成の二次電池１が作製される。
【００２４】
このような二次電池１における本実施例の放圧補助部材１５の作用を説明する。例えば、二次電池１の過充電時等において容器９内でガスが発生する場合、電極体７の内部で発生したガスによって電極体７が膨張または変形することがある。本実施例のように電極体７が捲回型であってその捲回軸に対して略直交する方向に放圧弁２３が設けられた構成では、例えば捲回型電極体の捲回軸方向（図２の左右端）に放圧弁が設けられた構成に比べて、このような事象がより発生しやすい傾向にある。本実施例によると、かかる膨張または変形によって捲回型電極体７の外周面が放圧弁２３方向に張り出す（進行する）ようになったとしても、放圧弁２３と電極体７との間に配置された放圧補助部材１５が張り出してきた電極体７の外周面と当接し、その結果、電極体７を押圧してその放圧弁２３側への移動を阻止することができる。このことによって、電極体７が放圧弁２３を塞いでしまうことを未然に防止することができる。また、放圧補助部材１５に設けた貫通孔またはスリット（図示せず）によって、容器９内で生じたガスの放圧弁２３への移動が順調に行われ得る。
【００２５】
なお、本実施例の正極端子１１および負極端子１３においては、電極体７の捲回軸にほぼ直交する方向（ここでは図１および図２の上側）に正極端子１１および負極端子１３が延びているが、正極端子１１および負極端子１３はいずれの方向に延びていてもよい。例えば、本実施例の変更例である図４に示す蓄電素子１Ａのように、電極体７の軸方向の一端および他端（図４の左右方向）に正極端子１１および負極端子１３を、それぞれ電極体７の捲回軸方向に水平に接続し、それらの端子１１，１３が電極体７の軸方向において互いに反対方向に延びるように構成してもよい。
【００２６】
容器９の封止手段は熱溶着に限定されず、例えば接着剤等により封止してもよい。接着剤のタイプや組成は特に限定されず、例えばホットメルト型接着剤、エポキシ樹脂系接着剤等を用いることができる。また、上記実施例では容器９を絶縁フィルム製としたが、容器の材質はこれに限られない。例えば本実施例の変更例である図５に示す蓄電素子１Ｂのように、金属箔等の金属材料を袋状に形成して合わせ目（外周）を接着剤で接着し、その接着部分の一部の接着強度を他の部分よりも弱くして放圧弁２３を形成した金属製の容器９Ｂを使用して、第１実施例と同様の位置（放圧弁２３と電極体７の間）に放圧補助部材１５を配置してもよい。この場合、例えば電極体７の外周を図示しない絶縁シート（セパレータシートと同様のものでよい。）で覆うことにより、電極体７と金属製容器９Ｂとが導通することを回避することができる。
また、第１実施例の変更例である図６に示す蓄電素子１Ｃのように、円筒状に捲回された電極体７Ｃが金属製の円筒型容器９Ｃに収容された構成としてもよい。この場合にも、電極体７Ｃの捲回軸に直交する方向（円筒型容器９Ｃの外周壁）に、内圧上昇により容器９Ｃを開放し得る放圧弁２３Ｃ（例えば、円筒型容器９Ｃに設けられた図示しない貫通孔を弱く封止するシート状の封止部材等）を設け、電極体７Ｃの放圧弁２３Ｃに対向する外周を覆うように放圧補助部材１５Ｃを配置することにより、上記実施例と同様の効果を得ることができる。なお、図６では正極端子および負極端子の図示を省略している。
【００２７】
（第２実施例）
本実施例は、放圧補助手段として、正極端子および負極端子が電極体の外周に沿って延びる部分（フランジ部）と電極体外周との間に板状の放圧補助部材を配置したリチウムイオン二次電池の一例である。以下の説明では、第１実施例に係る部材と同様の機能を果たす部材については同じ符号を付し、その説明は省略する。図７は、本実施例に係る二次電池を示す分解斜視図である。また、図８は、図７におけるＶＩＩＩ−ＶＩＩＩ線断面図である。
これらの図に示されるように、本実施例に係る二次電池４１は、捲回型電極体７と、電極体７を収容する偏平な直方体状（角型または平型ともいう。）の容器４３と、電極体７の軸方向両端部に接続された正極端子５０および負極端子６０とを備える。正極端子５０および負極端子６０は、電極体７の軸方向両端からそれぞれ電極体７の外周に沿って延びる正フランジ部５４および負フランジ部６４を有する。正フランジ部５４および負フランジ部６４と電極体７の外周との間には、板状の放圧補助部材７０が配置されている。
【００２８】
この容器４３はアルミニウム製であって、有底四角筒状のケース体４５と、ケース体４５の上端開口部を封止する蓋体４７とを備える。蓋体４７には、その中央部分に、薄肉に形成された放圧弁４９が設けられている。放圧弁４９の中央部には、特に薄肉に形成された線状の薄肉部４９ａが形成されており、容器４３内圧の増大により破れ易い構造となっている。これにより容器４３内で発生したガスを放出して内圧増大を防止することができる。また、放圧弁の設置部位を上とすると、捲回型電極体７はその捲回軸が横倒しとなるようにして（すなわち、放圧弁４９の設置部位が電極体７の捲回軸に対して略直交する方向となる姿勢で）容器４３に収容されている。なお、電極体７の外周は、図示しない絶縁シート（ここでは上述のセパレータシートと同じもの）により覆われている。これにより、電極体７と容器４３とが導通することを回避している。容器４３内には図示しない液状電解質（電解液）が収容されており、電極体７に含浸されている。
【００２９】
正極端子５０はアルミニウム材料から成形され、電極体７の軸方向の一端において偏平方向（すなわち図７の上下方向）に延びる正接触部５２と、電極体７の捲回軸に対して略直交する方向（ここでは図７および図８の上方向）に延びる正端子部５６と、正接触部５２と正端子部５６の間にあって電極体７の外周に沿って延びる正フランジ部５４とを有する。図８に示すように、正接触部５２のうち正フランジ部５４と反対側の端部は、電極体７の軸方向の端部で正極シート３に溶接等により接続されている。
一方、負極端子６０は、銅材料を正極端子５０とほぼ同形状に成形したものであって、負接触部６２、負フランジ部６４および負端子部６６を有する。この負極端子６０は、正極端子５０とほぼ対称形となるように電極体７に取り付けられている。図８に示すように、負接触部６２のうち負フランジ部６４と反対側の端部は、電極体７の軸方向の端部で負極シート５に溶接等により接続されている。
また、図８に示すように、正端子部５６および負端子部６６は、蓋体４７を貫通して容器４３の外方に延びている。これら正負の端子部５６，６６を介して、電極体７の側方（捲回軸にほぼ直交する方向）から電流を取り出すことができる。そして、正負のフランジ部５４，６４と電極体７の外周との間に放圧補助部材７０が配置されている。以下、この放圧補助部材７０につき説明する。
【００３０】
放圧補助部材７０の構成材料としては、第１実施例と同様なものを使用可能である。軟化温度が１２０℃以上である樹脂が好適に用いられる。このような材料を板状、シート状あるいはフィルム状等に成形したものを放圧補助部材として用いることができる。その放圧補助部材７０は、電極体７の蓋体４７に面する側（図８において上側）を被覆するように配置されている。放圧補助部材７０の幅は、偏平状に捲回された電極体７の厚さに対して例えば１〜１．２倍程度とすることができる。また、放圧補助部材７０の長さは、正フランジ部５４と負フランジ部６４との距離よりも長くすることが好ましい。例えば、捲回型電極体７の軸長とほぼ同等の長さとすることができる。
放圧補助部材７０の厚さは特に限定されないが、電極体７の外周と容器４３との隙間の８０％以下に相当する厚さとすることが好ましく、より好ましくは６０％以下、さらに好ましくは４０％以下である。この範囲の厚さであると、図８に矢印で示すように電極体７から発生したガスを図７に示す放圧弁４９へと容易に流通（移動）させるスペースを確保することができ、内圧の増加を適切に防止することができる。特に、放圧補助部材７０の厚さが上記隙間の４０％以下であると、ガスの放出がスムーズであり、内圧の増加防止効果に特に優れる。
【００３１】
本実施例では、放圧補助部材７０として厚さ約０．５ｍｍのポリプロピレンプレート（板状部材）を用い、電極体７と蓋体４７に約２ｍｍの隙間を設けた。また、放圧補助部材７０の幅は電極体７の厚さとほぼ同等とし、長さは電極体７の軸長とほぼ同等とした。
なお、この放圧補助部材７０は、電極体７の破片等の異物の通過を阻止し得る一方でガスを通過可能な形状、例えば厚み方向に貫通する適度な大きさの孔および／または外周の切欠きを有する形状とすることができる。これにより、電池の過充電時等において発生し得るガスを容器外部へと逃すためのガス抜き経路をより適切に確保することができる。
【００３２】
かかる構成の二次電池４１を製造する際には、例えば図７に示すように、まず電極体７と正極端子５０と負極端子６０と放圧補助部材７０とを組み立てる。また、両端子５０，６０のフランジ部５４，６４の上にそれぞれ絶縁部材８０を配置し、その上から蓋体４７を被せる。蓋体４７を貫通した端子部５６，６６の周囲に絶縁パッキン８２を配置し、ナット５８，６８をネジ止めして端子部５６，６６と蓋体４７との間をシールする。そして、蓋体４７と連結された電極体７等を、ケース体４５の上端開口部からその内部に収容する。その後、ケース体４５の上端開口部に蓋体４７をレーザ溶接等により取り付けて容器４３を構成する。このようにして二次電池４１を得ることができる。なお、液状電解質（電解液）は、蓋体４７に設けられた電解液注入孔（図示せず）を通じて容器４３内に注入され、電極体７に含浸される。また、図８では絶縁パッキン８２およびナット５８，６８の図示を省略している。
【００３３】
次に本実施例の放圧補助部材７０の作用を説明する。例えば二次電池４１の過充電時等において、電極体７がガス発生（特に電極体７の内部からのガス発生）によって膨張または変形してその外周面が放圧弁４９方向に張り出す（進行する）ようになったとき、放圧弁４９と電極体７との間に配置された放圧補助部材７０が張り出してきた電極体７の外周面と当接する結果、電極体７を押圧してその放圧弁４９側への移動を阻止することができる。このため、電極体７が放圧弁２３を塞いでしまうことを未然に防止することができる。また、図８中に矢印で示すように、電極体７と容器４３との隙間から、発生したガスを放圧弁４９へと流通（移動）させて外部へと逃すことができる。
また、本実施例の二次電池４１では、図示されるように放圧補助部材７０が電極体７の上面部分を被覆しているので、電極体７が物理的影響若しくは電気化学的影響を受けて破損した場合、その遊離生成物（例えば電極体の断片）の放圧弁４９方向への移動を阻止することができる。このため、当該遊離生成物が放圧弁２３を塞いでしまうことを未然に防止することができる。
なお、正極端子および負極端子が電極体の軸方向に対していずれの方向に設けられていてもよいことは、第１実施例と同様である。
【００３４】
（第３実施例）
本実施例は、放圧補助手段として、容器の電極体収容部分よりも放圧弁形成部分が窄まるように容器の一部を外部から拘束する形状の放圧補助部材を容器外に備えたリチウムイオン二次電池の一例である。
図９は本実施例に係る二次電池１００を示す正面図であり、図１０はそのＸ−Ｘ線断面図である。この二次電池１００は、第１実施例の放圧補助部材１５の代わりに本実施例の放圧補助部材９０を設けたこと以外は、実質的に前記第１実施例と同様の構成である。したがって、第１実施例に係る部材と同様の機能を果たす部材については同じ符号を付し、その説明を省略する。
【００３５】
二次電池１００は、捲回型の電極体７と、この電極体７を収容する絶縁フィルム製の容器９と、電極体７の軸方向両端にそれぞれ一端が接続された正極端子１１および負極端子１３と、放圧補助部材９０とを備える。この放圧補助部材９０は、容器９の外側に配置されて、容器９の一部すなわち電極体７の側方部分（捲回軸に対して略直交する方向：図９〜図１０において上側）を拘束している。以下、放圧補助部材９０につきさらに詳細に説明する。
【００３６】
放圧補助部材９０は、二枚の長尺状の拘束部材９２と、これらを結合するボルト９４により構成される。これら二枚の拘束部材９２は、容器９の側方部９ａ（すなわち正極端子１１および負極端子１３が突出している側であって第１実施例と同様の放圧弁２３が設けられている側方部９ａ）を両サイドから挟むような状態で（図１０参照）、電極体７の捲回軸とほぼ平行に配置されている。その状態で、これら二枚の拘束部材９２は長手方向の両端付近においてボルト９４により締結されている。
なお、上記ボルト９４で締結されたときの２枚の拘束部材９２の間隔は、図１０によく示されるように、膨張もしくは変形した電極体７が放圧弁２３方向に張り出す（進行する）のを阻止し得る程度に容器９の側方部９ａを他の部分（電極体を収容している部分：例えば他の側方部分）よりも窄める（厚みが薄くなる）程度であればよい。一般に上記間隔が狭いほど電極体７の放圧弁２３方向への張り出し（進出）をより確実に阻止し得るが、同時に容器９内で発生したガスを速やかに放圧弁方向へ導き得るという観点からは、上記間隔は捲回型電極体７の厚さに対して例えば０．５〜１．０倍程度とすることが好ましい。また、拘束部材９２の長手方向の長さは、捲回型電極体７の軸長と同等かそれ以上とすることが好ましい。典型的には、本実施例のように、ボルトで締結された二枚の拘束部材９２間の間隔（幅）は、偏平状に捲回された電極体７の厚さの０．７〜０．９倍とすることができる。拘束部材９２の長手方向の長さは、例えば電極体７の軸長の０．８〜２倍（より好ましくは１．１〜１．５倍）とすることができる。
【００３７】
なお、正極端子１１および負極端子１３を電極体７に接続すること、および、容器９に電極体７を収容して二次電池１００を構築することは、第１実施例の放圧補助部材１５（図２参照）を容器９内に収容しない点を除いて、いずれも第１実施例と同様にすればよく、重複した説明は省略する。
そして、電極体７が収容された容器９に対し、上述した構成の放圧補助部材９０を配置する。まず、容器９の熱溶着部２１（放圧弁２３）が設けられた側（側方部９ａ）に、該容器９を挟んで二枚の拘束部材９２を、それらの長手方向が電極体７の捲回軸とほぼ平行になるように配置する。このとき、図９に示すように、拘束部材９２のうち電極体の捲回軸中心側（図９および図１０の下辺）の側端部９２ｂが熱溶着部２１（放圧弁２３）よりも上記捲回軸中心側に配置されるようにする。そして、放圧弁２３よりも捲回軸中心側において各拘束部材９２の側端部９２ｂを容器９（側方部９ａ）に外面から当接させ、これら二枚の締結部材９２を容器９よりも捲回軸方向の外方でボルト９４によって締結する。このことによって、図１０によく示されるように、容器９の側方部９ａを他の部分（電極体収容部分）よりも窄めて、所定の厚みに調整する（拘束する）ことができる。
【００３８】
本実施例の放圧補助部材９０の作用を説明する。例えば二次電池１００の過充電時等において、電極体７がガス発生によって膨張または変形してその外周面が放圧弁２３方向に張り出す（進行する）ようになったとき、二枚の放圧補助部材９０（拘束部材９２）が放圧弁２３よりも捲回軸中心側の容器９の幅を外側から拘束して容器９の一部（側方部分９ａ）を窄めていることから、図１０によく示されるように、その部分への電極体７への張り出し（進行）を阻止することができる。このため、電極体７が図９に示す放圧弁２３を塞いでしまうことを未然に防止することができる。一方、第２実施例と同様に、電極体７と容器９との隙間から、容器内で発生したガスを放圧弁２３へと逃すことができる。なお、正極端子および負極端子が電極体の軸方向のいずれの方向に設けられていてもよいことは、第１実施例と同様である。
【００３９】
（第４実施例）
本実施例は、容器（蓋体）に一体に形成された凸部が放圧補助手段としての放圧補助部材を構成し、その凸部に対応して形成される溝部によって通気路も確保されていることを特徴とするリチウムイオン二次電池の一例である。図１１は、本実施例に係る二次電池の容器の一部に相当する蓋体１１０であって、電極体７に面する側（すなわち電池の内側：図８参照）からみた平面図である。図１２は図１１のＸＩＩ−ＸＩＩ線断面図である。
本実施例の二次電池は、第２実施例の放圧補助部材７０が配置される代わりに、放圧補助部材として、凸部１１６が形成された蓋体１１０が配置されている以外は、前記第２実施例と同様の構成である。以下、第２実施例に係る部材と同様の構造・機能を有する部材については同じ符号を付し、その説明を省略する。
【００４０】
以下、蓋体１１０の構成について詳細に説明する。図１１および図１２に示すように、蓋体１１０の中央部分には薄肉に構成された放圧弁取付部１１１が設けられている。その放圧弁取付部１１１では蓋体１１０の電極体７に面する側（図１２の下側）が窪んでいる。また、放圧弁取付部１１１は開口部１１１ａを有し、この開口部１１１ａを閉塞するように放圧弁１１２が設置されている。放圧弁１１２の中心部は電極体７に面する側（図１２の下側）が窪んでおり、ここに特に薄肉に形成された線状薄肉部１１２ａが形成されて、容器内圧が増大した際に破れ易い構造となっている。これにより、容器内（例えば電極体）で発生したガスを放出して内圧増大を防止することができる。また、放圧弁取付部１１１の窪みに連なって、その窪みよりもやや小さい深さ（図１２参照）の溝部１１４が、蓋体１１０の長尺方向に放圧弁取付部１１１から線対称に三本づつ延びて、蓋体１１０の長尺方向の両端部よりも少し手前まで形成されている。溝部１１４の周囲は、溝部１１４よりも電極体７方向に隆起した（突出した）凸部１１６を構成している。
なお、溝部１１４の幅は、容器内で発生したガスを放圧弁１１２方向に誘導し得る程度であればよく特に限定されないが、電極体７の破片等の異物によって詰り難い程度の幅であることが好ましい。同様に、溝部１１４の深さは、ガスを放圧弁１１２方向に誘導し得る程度であればよく、異物によって詰り難い程度の深さであることが好ましい。また、図１１に示すように、溝部１１４は複数形成されていることが好ましい。
本実施例に係る二次電池は、第２実施例に係る放圧補助部材７０（図７，図８参照）を配置しない点、および、容器４３の蓋体４７を上述した本実施例に係る蓋体１１０に変更した点以外は、第２実施例と同様のプロセスにより製造することができる。
【００４１】
本実施例の放圧補助部材としての蓋体１１０の作用を説明する。例えば二次電池の過充電時等において、電極体７がガス発生によって膨張または変形してその外周面が放圧弁１１２方向に張り出す（進行する）ようになったとき、図１１に示すように蓋体１１０の下面に上述した凸部１１６が設けられている結果、当該凸部１１６が張り出してきた電極体７の外周面と当接し、その結果、電極体７を押圧してその移動を阻止することができる。このため、電極体７が容器（蓋体１１０）に設けられた放圧弁１１２を塞いでしまうことを未然に防止することができる。また、上述の溝部１１４によって、容器内で生じたガスの放圧弁１１２への移動は順調に行われ得る。本実施例の二次電池によれば、溝部１１４を設けることによって、ガス通路を確保しつつ電極体７と蓋体１１０との距離を比較的近づけることができる。このため、電池自体の体積効率を高め、その全体形状を小型化することができる。なお、正極端子および負極端子が電極体の軸方向のいずれの方向に設けられていてもよいことは、第１実施例と同様である。
【００４２】
以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。
例えば、上記実施例ではリチウムイオン二次電池につき説明したが、本発明は蓄電素子全般、例えばニッケル水素電池、ニッケルカドミウム電池等の他の種類の二次電池や、電気二重層キャパシタ等の各種蓄電素子にも適用することができる。電極を構成する活物質、集電体および端子ならびにセパレータ等の材質や電解液の組成等は、蓄電素子の種類に応じて適当に選択され得る。
また、本明細書または図面に説明した技術要素は、単独であるいは各種の組み合わせによって技術的有用性を発揮するものであり、出願時請求項記載の組み合わせに限定されるものではない。また、本明細書または図面に例示した技術は複数目的を同時に達成するものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。
【図面の簡単な説明】
【図１】第１実施例に係る二次電池を示す正面図である。
【図２】図１の前面の絶縁フィルムを省略した状態を示す説明図である。
【図３】第１実施例において使用した絶縁フィルムの積層構造を示す断面図である。
【図４】第１実施例の変形例を示す模式図である。
【図５】第１実施例の変形例を示す模式図である。
【図６】第１実施例の変形例を示す模式図である。
【図７】第２実施例に係る二次電池を示す分解斜視図である。
【図８】図７におけるＶＩＩＩ−ＶＩＩＩ線断面図である。
【図９】第３実施例に係る二次電池を示す正面図である。
【図１０】図９におけるＸ−Ｘ線断面図である。
【図１１】第４実施例に係る二次電池の蓋体１１０を示す平面図である。
【図１２】図１１におけるＸＩＩ−ＸＩＩ線断面図である。
【符号の説明】
１，４１，１００：リチウムイオン二次電池（蓄電素子）
７：捲回型電極体
９，４３：容器
１１，５０：正極端子
１３，６０：負極端子
１５，７０，９０：放圧補助部材
２１：熱溶着部
２３，４９，１１２：放圧弁
９２：拘束部材
９４：ボルト
１１０：蓋体（放圧補助部材）
１１４：溝部
１１６：凸部[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power storage device having a wound electrode body. More specifically, the present invention relates to a power storage device provided with a pressure relief valve for adjusting the internal pressure of a container containing the electrode body.
[0002]
2. Description of the Related Art There is known an electric storage element in which an electrode body (a wound electrode body) in which a positive electrode sheet and a negative electrode sheet are wound via a separator is housed in a container together with an electrolyte. As one type of such an electric storage element, there is a sealed electric storage element in which a wound-type electrode body is housed in a bag-shaped container made of a laminated film or the like and an opening of the bag-shaped container is sealed.
Generally, when the internal pressure of a container increases, regardless of the type of the electrode body (wound type, laminated type, etc.), a sealed type energy storage element (typically, an energy storage element using a non-aqueous electrolyte) is used. Equipped with a pressure relief valve (safety valve) for opening the container and adjusting the internal pressure. For example, Patent Literature 1 describes a sealed nonaqueous battery in which a part of a sealing portion of a laminate film is provided with a sealing portion thinner than other portions. The thin sealed portion acts as a safety valve, and when the internal pressure of the battery increases, the sealed portion peels off to adjust the internal pressure of the battery.
[0003]
[Patent Document 1] JP-A-11-86823
[0004]
By the way, an electric storage element of a type in which an electrode body accommodated in a container is a wound type and a pressure relief valve is provided in a direction (lateral direction) substantially perpendicular to the winding axis. In the case of manufacturing, the configuration described in Patent Document 1 is not preferable because the safety valve (pressure relief valve) may be blocked by the outer peripheral surface of the electrode body. If the valve is closed, gas flow inside and outside the container will be blocked, and it will be difficult to quickly adjust the pressure inside the container.
[0005]
Therefore, the present invention provides a storage element of a type in which a pressure relief valve is formed in a direction substantially perpendicular to a winding axis of a wound electrode body, wherein the storage element is capable of stably adjusting a container internal pressure. The purpose is to:
[0006]
Means for Solving the Problems, Function and Effect The power storage device provided by the present invention comprises a wound electrode body in which a positive electrode sheet and a negative electrode sheet are wound via a separator, A container for storing the electrolyte, and a pressure relief valve for communicating the inside and outside of the container to adjust the internal pressure of the container, the pressure relief valve being provided in a direction substantially orthogonal to the winding axis of the electrode body. Prepare. Further, the apparatus further includes pressure-releasing auxiliary means for preventing the pressure-releasing valve from being closed by the electrode body.
In this specification, the term “electric storage element” is a concept that includes both batteries (such as lithium-ion batteries and nickel-metal hydride batteries) and capacitors (such as electric double layer capacitors).
[0007]
The power storage element of the present invention is provided with a pressure-releasing auxiliary means for separately preventing the pressure-releasing valve from closing, so that the wound-type electrode body (typically, the outer peripheral surface of the electrode body) with respect to the operation (opening / closing) of the pressure-releasing valve. Interference (typically contact) can be prevented, and blockage of the pressure relief valve can be prevented. For this reason, according to the electric storage element of the present invention, it is possible to prevent the pressure-releasing valve from interfering with the pressure-releasing (opening / closing) function due to the wound electrode body, and to stably adjust the container internal pressure by the pressure-releasing valve.
[0008]
One preferable example of such a storage element is a pressure-releasing auxiliary member configured to suppress the outer peripheral portion of the electrode body facing the pressure-releasing valve from protruding toward the pressure-releasing valve. It is characterized by having. According to the power storage element of this aspect, for example, even when gas is generated inside the wound electrode body and the electrode body is in a state where it can expand or deform, the pressure-releasing auxiliary member moves the electrode body in the direction of the pressure-releasing valve. Overhang (advance) can be suppressed. Therefore, it is possible to prevent the pressure relief valve from being closed due to the electrode body coming into contact with the pressure relief valve. Typically, the pressure-releasing auxiliary member is substantially disposed between the electrode body and the pressure-releasing valve.
[0009]
Another preferable one of the electric storage elements disclosed herein is characterized in that the pressure-releasing auxiliary member is arranged near the pressure-releasing valve and has a convex portion protruding toward the electrode body. In the power storage element of this aspect, for example, even when gas is generated inside the wound electrode body and the electrode body is in a state where it can expand or deform, the convex portion of the pressure-releasing auxiliary member presses the electrode body. Thereby, the protrusion (progress) of the electrode body in the direction of the pressure relief valve can be suppressed. Therefore, it is possible to prevent the pressure-releasing valve from being closed due to the wound electrode body coming into contact with the pressure-releasing valve.
[0010]
It is preferable that the pressure-releasing auxiliary member is disposed so as to cover at least a part of the outer surface of the wound electrode body facing the pressure-releasing valve. In the power storage element of this aspect, contact between the wound electrode body and the pressure relief valve can be more reliably prevented at the covering portion. In this case, it is preferable that the pressure release auxiliary member is formed in a plate shape or a sheet shape.
[0011]
In the electric storage element disclosed herein, it is preferable that the pressure-releasing auxiliary member is configured using a material that can be ventilated. According to the power storage element of this aspect, even when the pressure-releasing auxiliary member is accommodated in the container, the gas-releasing assist member prevents gas flow in the container (movement of gas from the generation point to the safety valve). Less is. Therefore, the gas can be appropriately released.
[0012]
Another preferable one of the electric storage elements disclosed herein is that the pressure-releasing auxiliary means can restrain a part of the container from the outside such that the pressure-releasing valve forming part is narrower than the electrode body receiving part of the container. It is characterized by comprising a pressure-releasing auxiliary member provided in a shape. In the power storage element of this aspect, the protrusion (progress) of the wound electrode body in the direction of the pressure relief valve can be reliably suppressed by the pressure relief auxiliary member provided outside the container. Further, since the pressure-releasing auxiliary member is provided outside the container, the pressure-releasing auxiliary member does not hinder the flow of gas in the container (movement of gas from the generation point to the safety valve).
[0013]
One particularly preferable power storage element disclosed herein is characterized in that the pressure-releasing auxiliary means is constituted by at least a part of a container (typically formed integrally with the container). If a part of the container can function as a pressure-releasing auxiliary member constituting the pressure-releasing auxiliary means, it is possible to avoid an increase in the number of components constituting the power storage element (that is, an increase due to components added as the pressure-releasing auxiliary member). Therefore, it is possible to prevent an increase in cost and a complicated assembly process.
[0014]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail with reference to the drawings based on some specific examples. It should be noted that technical matters other than those specifically mentioned in the present specification and necessary for implementing the present invention can be grasped as design matters of those skilled in the art based on the conventional technology. The present invention can be implemented based on the technical contents disclosed in the present specification and the drawings and common technical knowledge in the relevant field.
[0015]
(First embodiment)
This embodiment is an example of a lithium ion secondary battery in which a pressure-releasing auxiliary member constituting a pressure-releasing auxiliary means is disposed between a wound electrode body and a pressure-releasing valve. FIG. 1 is a front view showing a secondary battery 1 according to the present embodiment. FIG. 2 is an explanatory view showing a state where the illustration of the insulating film 17 on the front surface is omitted to show the inside of FIG.
[0016]
As shown in FIGS. 1 and 2, the secondary battery 1 includes a wound electrode body 7 including a positive electrode sheet (positive electrode) 3 and a negative electrode sheet (negative electrode) 5, and a container that houses the electrode body 7. 9, a positive electrode terminal 11 and a negative electrode terminal 13 each having one end 11a, 13a connected to both ends 7a, 7b in the axial direction of the electrode body 7, and a pressure-releasing auxiliary member 15 according to the present embodiment. The container 9 is configured by combining two insulating films 17 and 19 and forming a heat-welded portion 21 over the outer periphery thereof. Further, as shown in the figure, the other ends (open ends) 11b and 13b of the positive electrode terminal 11 and the negative electrode terminal 13 pass through the container 9 from the joint (heat-welded portion 21) of the insulating films 17 and 19 and extend outward. It protrudes. Through the positive electrode terminal 11 and the negative electrode terminal 13, a current can be extracted from the side of the electrode body 7 (direction substantially orthogonal to the winding axis: the upper side in FIGS. 1 and 2). Further, a pressure release valve 23 described later is formed in the heat-welded portion 21 between the positive electrode terminal 11 and the negative electrode terminal 13. As shown in FIG. 2, between the heat-welded portion 21 on the side where the pressure relief valve 23 is formed and the electrode body 7, the pressure relief assist is provided in a state where a part of the outer periphery of the electrode body 7 is covered. A member 15 is arranged.
[0017]
First, the wound electrode body 7 will be described. The electrode body 7 includes a positive electrode sheet 3 in which a positive electrode active material layer is formed on both surfaces of a long positive electrode current collector, and a negative electrode in which a negative electrode active material layer is formed on both surfaces of a long negative electrode current collector. A sheet 5 and two long separator sheets (not shown) are provided. These sheets are laminated in the order of the positive electrode sheet 3, the separator, the negative electrode sheet 5, and the separator, and are wound in the longitudinal direction using a winding machine or the like. By pressing this wound body in the radial direction, the electrode body 7 wound in a flat shape can be manufactured. In such a wound electrode body 7, the positive electrode sheet 3 and the negative electrode sheet 5 are stacked with their positions shifted from each other in the winding axis direction. As a result, as schematically shown in FIG. 2, one end 7 a in the axial direction of the electrode body 7 is mainly composed of the positive electrode sheet 3, and the other end 7 b in the axial direction is mainly composed of the negative electrode sheet 5. At one end 7a of the electrode body 7, one end 11a of a positive electrode terminal 11 formed in a plate shape from an aluminum material is connected (fixed) to the positive electrode sheet 3. At the other end 7 b of the electrode body 7, one end 13 a of a negative electrode terminal 13 formed in a plate shape (same shape as the positive electrode terminal 11) from a copper material is connected (fixed) to the negative electrode sheet 5. The connection between these terminals 11 and 13 and the electrode body 7 can be performed by ultrasonic welding or the like.
[0018]
Note that an aluminum foil or the like can be used as a positive electrode current collector constituting the positive electrode sheet 3, and a copper foil or the like can be used as a negative electrode current collector constituting the negative electrode sheet 5. As the positive electrode active material constituting the positive electrode active material layer, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ One or more of the positive electrode active materials used in conventional lithium ion secondary batteries can be used without any particular limitation. As the negative electrode active material constituting the negative electrode active material layer, one or more of negative electrode active materials used in conventional lithium ion secondary batteries, such as amorphous carbon and graphite carbon, can be used without particular limitation. . These active material layers may appropriately contain conventionally known binders, conductive agents, and the like. As the separator sheet, for example, a porous polyolefin (polyethylene, polypropylene, etc.) sheet can be used.
[0019]
The container 9 accommodating such an electrode body 7 is constituted by two insulating films 17 and 19, and is sealed by a heat welding portion 21 in which the insulating films 17 and 19 are heat-welded to each other over the outer periphery. ing. The heat-welded portion 21 has a central portion facing the pressure-releasing auxiliary member 15 in a direction substantially orthogonal to the winding axis of the wound electrode body 7 and has a smaller diameter than the other portions of the heat-welded portion 21. The pressure relief valve 23 which is a portion having relatively low adhesive strength (here, the strength of heat welding) is formed. As described above, the pressure release valve 23 has a structure in which the adhesive strength between the insulating films 17 and 19 (heat welding) is easily broken when the internal pressure of the container 9 increases, as a result of the lower adhesive strength as compared with the other parts. From this, the gas generated in the container 9 (for example, the electrode body 7) can be discharged to the outside of the container to prevent the internal pressure from increasing. In addition, assuming that the installation site of the pressure relief valve 23 is upward, the wound electrode body 7 is accommodated in the container 9 such that the wound shaft is turned sideways. A liquid electrolyte (electrolyte solution) not shown is contained in the container 9 and is impregnated in the electrode body 7. The electrolytic solution to be used is not particularly limited. For example, 1 mol / liter of LiPF is added to a 7: 3 (mass ratio) mixed solvent of diethyl carbonate and ethylene carbonate. ₆ Can be used.
[0020]
Next, the pressure-releasing auxiliary member 15 constituting the pressure-releasing auxiliary means according to the present embodiment will be described. As a constituent material of the pressure release auxiliary member 15, depending on the type of the power storage element, an electrolyte constituting the power storage element (a lithium ion secondary battery in this embodiment) or a reaction product generated by using the power storage element is used. A material having resistance to the above can be appropriately selected and used. Usually, it is preferable to select an insulating material. For example, polyolefin resins such as polyethylene and polypropylene, ethylene-propylene-diene copolymer (EPDM) and the like are preferably selected. Further, PPS (polyphenylene sulfide resin), polyimide resin, polyamide imide resin, fluororesin, PEEK (polyether ether ketone resin), PES (polyether sulfone resin), or the like may be used. A material formed such that such a material can be ventilated can be used as the pressure release auxiliary member 15. For example, a shape having a hole, a groove, and / or a notch on the outer periphery penetrating in the thickness direction can be used. Alternatively, a porous body made of the above material may be used. This makes it possible to appropriately secure a gas vent path for releasing gas that may be generated in the container to the pressure release valve 23 when the power storage element is overcharged or the like.
[0021]
The thickness of the pressure release auxiliary member 15 is not particularly limited. In general, when the thickness of the pressure-releasing auxiliary member 15 disposed between the pressure-releasing valve 23 and the electrode body 7 is increased, the electrode body 7 is prevented from protruding (advancing) in the direction of the pressure-releasing valve 23 with a strong pressing force. The effect of preventing the pressure relief valve 23 from being blocked can be exhibited. On the other hand, if the thickness of the pressure-releasing auxiliary member 15 is excessively increased, the power storage element tends to be large. From these balances, it may vary depending on the size of the battery and the electrode body, but it is usually appropriate to set the thickness of the pressure-releasing auxiliary member 15 to about 0.2 to 2 mm. The width of the pressure-releasing auxiliary member 15 is not particularly limited as long as the protrusion of the wound electrode body 7 can be suppressed, but the width of the wound electrode body 7 (typically an electrode body wound flat) is not limited. For example, it can be about 0.5 to 1.2 times the thickness. The length of the pressure-releasing auxiliary member 15 is preferably substantially equal to or slightly shorter than the axial length of the electrode body 7 in the integral pressure-releasing auxiliary member 15 as in this embodiment. Accordingly, in the internal space of the container 9, a gap is formed near both ends in the axial direction of the wound electrode body 7 so that the gas generated in the container 9 can escape upward without being disturbed by the installation of the pressure-releasing auxiliary member. Can be secured. In the case where a container formed of a material having high rigidity (for example, a rectangular container made of metal as in a second embodiment described later) is used, the container is easily assembled because the storage element is easily assembled. It is preferable to make the width of the pressure release auxiliary member smaller than the maximum opening width of the opening.
[0022]
In the present embodiment, a polyethylene sheet having a thickness of about 0.5 mm was used as the pressure release auxiliary member 15. The width of the pressure-releasing auxiliary member 15 is substantially equal to the thickness of the electrode body 7 wound flat. Further, the length of the pressure-releasing auxiliary member 15 is such that it can be substantially fitted between the positive electrode terminal 11 and the negative electrode terminal 13 connected to both ends of the electrode body 7. The pressure relief auxiliary member 15 is provided with a large number of through holes or slits (not shown) through which gas can flow.
[0023]
Next, a method of manufacturing the secondary battery 1 by housing the electrode body 7 and the pressure-releasing auxiliary member 15 to which the positive electrode terminal 11 and the negative electrode terminal 13 are connected in the container 9 will be described.
As shown in FIGS. 1 and 2, the container 9 includes two rectangular insulating films 17 and 19. As shown in the cross section in FIG. 3, each of the insulating films 17 and 19 is formed by laminating a heat welding layers 17a and 19a made of a thermoplastic resin or the like, aluminum deposition layers 17b and 19b, and protective resin layers 17c and 19c in this order. It has the following structure. These insulating films 17 and 19 are overlapped so that the heat-bonded layers 17a and 19a face each other, and the electrode body 7 to which the terminals 11 and 13 are connected is sandwiched between them as shown in FIGS. At this time, the electrode body 7 is arranged such that the one ends 27 and 31 of both terminals protrude from between the insulating films 17 and 19 (joint). Then, the pressure-releasing auxiliary member 15 is disposed between the positive terminal 11 and the negative terminal 13 in a direction substantially perpendicular to the axial direction of the electrode body 7, and the two insulating films 17 and 19 are attached to the outer peripheral portions thereof. Are heat-welded to each other at a heat-welded portion 21 corresponding to. Thereby, the container 9 is formed. At this time, in the portion corresponding to the pressure relief valve 23, the bonding strength (strength of the heat welding) of the insulating films 17 and 19 is reduced by reducing the heat welding area of the insulating films 17 and 19 (the formation width of the heat welding portion 21 in that portion). The welding portion 21 is set lower than other portions. In the portion where the other ends 11b and 13b of the terminals 11 and 13 are sandwiched between the insulating films 17 and 19, the insulating films 17 and 19 are applied to the surfaces of the terminals 11 and 13 at the heat-welded portions 21 thereof. Weld it. By the above procedure, the secondary battery 1 having the configuration shown in FIGS. 1 and 2 is manufactured.
[0024]
The operation of the pressure-releasing auxiliary member 15 of this embodiment in such a secondary battery 1 will be described. For example, when gas is generated in the container 9 when the secondary battery 1 is overcharged, the electrode body 7 may expand or deform due to the gas generated inside the electrode body 7. In the configuration in which the electrode body 7 is a wound type and the pressure release valve 23 is provided in a direction substantially perpendicular to the winding axis as in the present embodiment, for example, the winding axis direction of the wound electrode body ( Such a phenomenon tends to occur more easily than a configuration in which a pressure relief valve is provided at the left and right ends in FIG. 2). According to the present embodiment, even if the outer peripheral surface of the wound electrode body 7 projects (progresses) toward the pressure relief valve 23 due to such expansion or deformation, the gap between the pressure relief valve 23 and the electrode body 7 is increased. The disposed pressure-releasing auxiliary member 15 abuts on the protruding outer peripheral surface of the electrode body 7, and as a result, can press the electrode body 7 and prevent its movement to the pressure-releasing valve 23 side. As a result, it is possible to prevent the electrode body 7 from blocking the pressure relief valve 23. Further, the gas generated in the container 9 can be smoothly moved to the pressure relief valve 23 by a through hole or a slit (not shown) provided in the pressure relief auxiliary member 15.
[0025]
In the positive electrode terminal 11 and the negative electrode terminal 13 of this embodiment, the positive electrode terminal 11 and the negative electrode terminal 13 extend in a direction substantially perpendicular to the winding axis of the electrode body 7 (here, the upper side in FIGS. 1 and 2). However, the positive terminal 11 and the negative terminal 13 may extend in any direction. For example, like a storage element 1A shown in FIG. 4 which is a modification of the present embodiment, a positive electrode terminal 11 and a negative electrode terminal 13 are provided at one end and the other end in the axial direction of the electrode body 7 (left and right directions in FIG. 4), respectively. The electrodes 11 may be connected horizontally in the direction of the winding axis of the electrode body 7 so that the terminals 11 and 13 extend in directions opposite to each other in the axial direction of the electrode body 7.
[0026]
The sealing means of the container 9 is not limited to the heat welding, but may be sealed with, for example, an adhesive. The type and composition of the adhesive are not particularly limited, and for example, a hot melt adhesive, an epoxy resin adhesive, or the like can be used. In the above embodiment, the container 9 is made of an insulating film, but the material of the container is not limited to this. For example, like a storage element 1B shown in FIG. 5 which is a modification of the present embodiment, a metal material such as a metal foil is formed in a bag shape, and the joint (outer periphery) is adhered with an adhesive. Using a metal container 9B in which the pressure-releasing valve 23 is formed by weakening the adhesive strength of the part compared with the other parts, the pressure is released to the same position (between the pressure-releasing valve 23 and the electrode body 7) as in the first embodiment. The pressure assisting member 15 may be provided. In this case, for example, by covering the outer periphery of the electrode body 7 with an insulating sheet (not shown, which may be the same as the separator sheet), conduction between the electrode body 7 and the metal container 9B can be avoided.
Further, as in a storage element 1C shown in FIG. 6 which is a modification of the first embodiment, a configuration in which a cylindrically wound electrode body 7C is accommodated in a metal cylindrical container 9C may be employed. Also in this case, in a direction perpendicular to the winding axis of the electrode body 7C (the outer peripheral wall of the cylindrical container 9C), a pressure relief valve 23C (for example, provided on the cylindrical container 9C) capable of opening the container 9C by increasing the internal pressure. By providing a sheet-shaped sealing member that weakly seals a through hole (not shown)) and arranging the pressure-releasing auxiliary member 15C so as to cover the outer periphery of the electrode body 7C facing the pressure-releasing valve 23C, the above-described embodiment is different from the above-described embodiment. Similar effects can be obtained. In FIG. 6, the illustration of the positive terminal and the negative terminal is omitted.
[0027]
(Second embodiment)
In the present embodiment, as a pressure-releasing auxiliary means, a lithium ion in which a plate-shaped pressure-releasing auxiliary member is arranged between a portion (flange portion) where the positive electrode terminal and the negative electrode terminal extend along the outer periphery of the electrode body and the outer periphery of the electrode body. It is an example of a secondary battery. In the following description, members performing the same functions as the members according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. FIG. 7 is an exploded perspective view showing the secondary battery according to the present embodiment. FIG. 8 is a sectional view taken along line VIII-VIII in FIG.
As shown in these drawings, the secondary battery 41 according to the present embodiment has a wound electrode body 7 and a flat rectangular parallelepiped (also called a square or flat) container that houses the electrode body 7. 43, and a positive electrode terminal 50 and a negative electrode terminal 60 connected to both axial ends of the electrode body 7. Each of the positive electrode terminal 50 and the negative electrode terminal 60 has a positive flange portion 54 and a negative flange portion 64 extending from both axial ends of the electrode body 7 along the outer periphery of the electrode body 7, respectively. A plate-shaped pressure relief auxiliary member 70 is arranged between the positive flange portion 54 and the negative flange portion 64 and the outer periphery of the electrode body 7.
[0028]
The container 43 is made of aluminum, and includes a case body 45 having a bottomed square cylindrical shape, and a lid body 47 for sealing an upper end opening of the case body 45. The lid 47 is provided with a pressure-releasing valve 49 formed in a thin portion at a central portion thereof. In the central part of the pressure relief valve 49, a linear thin part 49a formed particularly thin is formed, and has a structure easily broken by an increase in the internal pressure of the container 43. Thereby, the gas generated in the container 43 can be released to prevent the internal pressure from increasing. When the installation site of the pressure relief valve is set to the upper side, the wound electrode body 7 is configured such that its winding axis is turned sideways (that is, the installation site of the pressure relief valve 49 is set with respect to the winding axis of the electrode body 7). (In a direction substantially orthogonal to the direction). Note that the outer periphery of the electrode body 7 is covered with an insulating sheet (not shown) (here, the same as the above-described separator sheet). Thereby, conduction between the electrode body 7 and the container 43 is avoided. A liquid electrolyte (electrolyte solution) not shown is accommodated in the container 43, and is impregnated in the electrode body 7.
[0029]
The positive electrode terminal 50 is formed of an aluminum material, and is substantially orthogonal to a positive contact portion 52 extending in a flat direction (that is, a vertical direction in FIG. 7) at one axial end of the electrode body 7 and a winding axis of the electrode body 7. It has a positive terminal portion 56 extending in the direction (here, the upward direction in FIGS. 7 and 8), and a positive flange portion 54 extending between the positive contact portion 52 and the positive terminal portion 56 and extending along the outer periphery of the electrode body 7. As shown in FIG. 8, the end of the positive contact portion 52 opposite to the front flange portion 54 is connected to the positive electrode sheet 3 by welding or the like at the axial end of the electrode body 7.
On the other hand, the negative electrode terminal 60 is formed by molding a copper material into substantially the same shape as the positive electrode terminal 50, and has a negative contact portion 62, a negative flange portion 64, and a negative terminal portion 66. The negative electrode terminal 60 is attached to the electrode body 7 so as to be substantially symmetrical with the positive electrode terminal 50. As shown in FIG. 8, the end of the negative contact portion 62 opposite to the negative flange portion 64 is connected to the negative electrode sheet 5 at the axial end of the electrode body 7 by welding or the like.
As shown in FIG. 8, the positive terminal portion 56 and the negative terminal portion 66 extend outside the container 43 through the lid 47. Through these positive and negative terminal portions 56 and 66, a current can be extracted from the side of the electrode body 7 (direction substantially perpendicular to the winding axis). The pressure-releasing auxiliary member 70 is disposed between the positive and negative flange portions 54 and 64 and the outer periphery of the electrode body 7. Hereinafter, the pressure release auxiliary member 70 will be described.
[0030]
As the constituent material of the pressure release auxiliary member 70, the same material as that of the first embodiment can be used. A resin having a softening temperature of 120 ° C. or higher is preferably used. A material obtained by forming such a material into a plate shape, a sheet shape, a film shape, or the like can be used as a pressure release auxiliary member. The pressure-releasing auxiliary member 70 is arranged so as to cover the side of the electrode body 7 facing the lid 47 (the upper side in FIG. 8). The width of the pressure-releasing auxiliary member 70 can be, for example, about 1 to 1.2 times the thickness of the flat electrode body 7. Further, it is preferable that the length of the pressure-releasing auxiliary member 70 be longer than the distance between the positive flange portion 54 and the negative flange portion 64. For example, the length can be substantially equal to the axial length of the wound electrode body 7.
Although the thickness of the pressure-releasing auxiliary member 70 is not particularly limited, it is preferably set to a thickness corresponding to 80% or less of the gap between the outer periphery of the electrode body 7 and the container 43, more preferably 60% or less, and further preferably 40% or less. % Or less. When the thickness is in this range, a space for easily flowing (moving) the gas generated from the electrode body 7 to the pressure relief valve 49 shown in FIG. 7 can be secured as shown by an arrow in FIG. Can be appropriately prevented from increasing. In particular, when the thickness of the pressure release auxiliary member 70 is 40% or less of the gap, the gas is smoothly released, and the effect of preventing the internal pressure from increasing is particularly excellent.
[0031]
In this embodiment, a polypropylene plate (plate-like member) having a thickness of about 0.5 mm was used as the pressure release auxiliary member 70, and a gap of about 2 mm was provided between the electrode body 7 and the lid 47. The width of the pressure-releasing auxiliary member 70 was substantially equal to the thickness of the electrode body 7, and the length was substantially equal to the axial length of the electrode body 7.
The pressure-releasing auxiliary member 70 can prevent the passage of foreign substances such as fragments of the electrode body 7 while allowing gas to pass therethrough, for example, a moderately sized hole penetrating in the thickness direction and / or an outer peripheral portion. It can be shaped to have a notch. This makes it possible to more appropriately secure a gas vent path for releasing gas that may be generated when the battery is overcharged to the outside of the container.
[0032]
When manufacturing the secondary battery 41 having such a configuration, first, as shown in FIG. 7, for example, the electrode body 7, the positive electrode terminal 50, the negative electrode terminal 60, and the pressure release auxiliary member 70 are assembled. Further, the insulating members 80 are arranged on the flange portions 54 and 64 of the terminals 50 and 60, respectively, and the lid 47 is put on the insulating members 80 from above. An insulating packing 82 is arranged around the terminal portions 56 and 66 penetrating the lid 47, and nuts 58 and 68 are screwed to seal between the terminal portions 56 and 66 and the lid 47. Then, the electrode body 7 and the like connected to the lid body 47 are accommodated in the case body 45 from the upper end opening. Thereafter, the lid 43 is attached to the upper end opening of the case body 45 by laser welding or the like to form the container 43. Thus, the secondary battery 41 can be obtained. The liquid electrolyte (electrolyte) is injected into the container 43 through an electrolyte injection hole (not shown) provided in the lid 47 and is impregnated in the electrode body 7. In FIG. 8, the illustration of the insulating packing 82 and the nuts 58 and 68 is omitted.
[0033]
Next, the operation of the pressure-releasing auxiliary member 70 of this embodiment will be described. For example, when the secondary battery 41 is overcharged or the like, the electrode body 7 expands or deforms due to gas generation (particularly, gas generation from inside the electrode body 7), and its outer peripheral surface projects (progresses) toward the pressure relief valve 49. ), The pressure-releasing auxiliary member 70 disposed between the pressure-releasing valve 49 and the electrode body 7 comes into contact with the outer peripheral surface of the protruding electrode body 7, thereby pressing the electrode body 7 and releasing it. Movement to the pressure valve 49 side can be prevented. Therefore, it is possible to prevent the electrode body 7 from blocking the pressure relief valve 23. Further, as shown by arrows in FIG. 8, the generated gas can be circulated (moved) to the pressure relief valve 49 from the gap between the electrode body 7 and the container 43 to escape to the outside.
Further, in the secondary battery 41 of this embodiment, since the pressure-releasing auxiliary member 70 covers the upper surface portion of the electrode body 7 as shown in the figure, the electrode body 7 is physically or electrochemically affected. In the case of breakage, the release product (for example, a piece of the electrode body) can be prevented from moving in the direction of the pressure relief valve 49. Therefore, it is possible to prevent the released product from blocking the pressure relief valve 23.
Note that the positive terminal and the negative terminal may be provided in any direction with respect to the axial direction of the electrode body, as in the first embodiment.
[0034]
(Third embodiment)
In this embodiment, as a pressure-releasing auxiliary means, a lithium pressure-releasing member having a shape in which a part of the container is restrained from outside so that the pressure-releasing valve forming portion is narrower than the electrode body accommodating portion of the container is provided outside the container. It is an example of an ion secondary battery.
FIG. 9 is a front view showing the secondary battery 100 according to the present embodiment, and FIG. 10 is a sectional view taken along line XX. The secondary battery 100 has substantially the same configuration as that of the first embodiment except that the pressure-releasing auxiliary member 90 of the present embodiment is provided instead of the pressure-releasing auxiliary member 15 of the first embodiment. . Therefore, the same reference numerals are given to members that perform the same functions as the members according to the first embodiment, and description thereof is omitted.
[0035]
The secondary battery 100 includes a wound electrode body 7, a container 9 made of an insulating film for accommodating the electrode body 7, and a positive electrode terminal 11 and a negative electrode terminal each having one end connected to both axial ends of the electrode body 7. 13 and a pressure-releasing auxiliary member 90. This pressure-releasing auxiliary member 90 is arranged outside the container 9 and is a part of the container 9, that is, a side portion of the electrode body 7 (a direction substantially orthogonal to the winding axis: the upper side in FIGS. 9 to 10). Is restrained. Hereinafter, the pressure release auxiliary member 90 will be described in more detail.
[0036]
The pressure-releasing auxiliary member 90 is composed of two elongated restraining members 92 and a bolt 94 connecting these members. These two restraining members 92 are provided on the side 9a of the container 9 (ie, on the side where the positive electrode terminal 11 and the negative electrode terminal 13 protrude and on the side where the pressure relief valve 23 similar to that of the first embodiment is provided). The portion 9a) is arranged substantially parallel to the winding axis of the electrode body 7 so as to sandwich the portion 9a) from both sides (see FIG. 10). In this state, these two restraining members 92 are fastened by bolts 94 near both ends in the longitudinal direction.
The distance between the two restraining members 92 when fastened by the bolts 94 is such that the expanded or deformed electrode body 7 projects (progresses) in the direction of the pressure relief valve 23, as is well shown in FIG. The side portion 9a of the container 9 may be narrowed (thinner) than other portions (a portion containing the electrode body: for example, the other side portions) to such an extent that it can be prevented. . Generally, the narrower the gap, the more reliably the electrode body 7 can be prevented from protruding (advancing) in the direction of the pressure relief valve 23, but at the same time, the gas generated in the container 9 can be promptly guided toward the pressure relief valve. The distance is preferably, for example, about 0.5 to 1.0 times the thickness of the wound electrode body 7. Further, it is preferable that the length in the longitudinal direction of the restraining member 92 is equal to or longer than the axial length of the wound electrode body 7. Typically, as in the present embodiment, the interval (width) between the two restraining members 92 fastened by bolts is 0.7 to 0 of the thickness of the flatly wound electrode body 7. 0.9 times. The length of the restraining member 92 in the longitudinal direction can be, for example, 0.8 to 2 times (more preferably 1.1 to 1.5 times) the axial length of the electrode body 7.
[0037]
The connection of the positive electrode terminal 11 and the negative electrode terminal 13 to the electrode body 7 and the construction of the secondary battery 100 by housing the electrode body 7 in the container 9 require the pressure-releasing auxiliary member 15 of the first embodiment. Except for not accommodating (see FIG. 2) in the container 9, all may be the same as in the first embodiment, and redundant description will be omitted.
Then, the pressure-releasing auxiliary member 90 having the above-described configuration is disposed in the container 9 in which the electrode body 7 is stored. First, two restraining members 92 sandwiching the container 9 are provided on the side (side portion 9 a) of the container 9 where the heat-welded portion 21 (the pressure release valve 23) is provided. It is arranged to be substantially parallel to the winding axis. At this time, as shown in FIG. 9, the side end 92 b of the restraining member 92 on the center side of the winding axis of the electrode body (the lower side in FIGS. 9 and 10) is more than the heat-welded portion 21 (the pressure release valve 23). It should be arranged on the center side of the winding shaft. Then, the side end portion 92b of each restraining member 92 is brought into contact with the container 9 (side portion 9a) from the outer surface on the winding shaft center side with respect to the pressure relief valve 23, and these two fastening members 92 It is fastened by bolts 94 outside in the direction of the winding axis. As a result, as shown in FIG. 10, the side portion 9a of the container 9 can be made narrower than other portions (electrode body accommodating portions) and adjusted (restricted) to a predetermined thickness.
[0038]
The operation of the pressure-releasing auxiliary member 90 of this embodiment will be described. For example, when the secondary battery 100 is overcharged or the like, when the electrode body 7 expands or deforms due to gas generation and its outer peripheral surface protrudes (progresses) toward the pressure relief valve 23, the two sheets of pressure release Since the auxiliary member 90 (restraining member 92) restrains the width of the container 9 closer to the center of the winding shaft than the pressure relief valve 23 from the outside and narrows a part of the container 9 (side portion 9a), FIG. As well shown in FIG. 10, the protrusion (progress) of the electrode body 7 to that portion can be prevented. Therefore, it is possible to prevent the electrode body 7 from blocking the pressure relief valve 23 shown in FIG. On the other hand, similarly to the second embodiment, the gas generated in the container can be released to the pressure relief valve 23 from the gap between the electrode body 7 and the container 9. Note that the positive terminal and the negative terminal may be provided in any direction of the axial direction of the electrode body, as in the first embodiment.
[0039]
(Fourth embodiment)
In the present embodiment, the projection integrally formed on the container (lid) constitutes a pressure-releasing auxiliary member as pressure-releasing auxiliary means, and a ventilation path is also secured by a groove formed corresponding to the convex. This is an example of a lithium ion secondary battery characterized in that: FIG. 11 is a plan view of the lid 110 corresponding to a part of the container of the secondary battery according to the present embodiment, viewed from the side facing the electrode body 7 (that is, the inside of the battery: see FIG. 8). . FIG. 12 is a sectional view taken along line XII-XII in FIG.
The secondary battery of this embodiment is different from that of the second embodiment in that, instead of disposing the pressure-releasing auxiliary member 70, the lid 110 having the convex portion 116 is disposed as the pressure-releasing auxiliary member. The configuration is the same as that of the second embodiment. Hereinafter, members having the same structures and functions as the members according to the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0040]
Hereinafter, the configuration of the lid 110 will be described in detail. As shown in FIGS. 11 and 12, a pressure-releasing valve mounting portion 111 having a small thickness is provided at a central portion of the lid 110. In the pressure relief valve mounting portion 111, the side of the lid 110 facing the electrode body 7 (the lower side in FIG. 12) is depressed. Further, the pressure relief valve mounting part 111 has an opening 111a, and the pressure relief valve 112 is installed so as to close the opening 111a. The central part of the pressure relief valve 112 is concave on the side facing the electrode body 7 (the lower side in FIG. 12), and when the linear thin part 112a formed particularly thin is formed, the internal pressure of the container increases. It is easily broken. Thereby, the gas generated in the container (for example, the electrode body) can be released to prevent the internal pressure from increasing. In addition, three grooves 114 having a depth slightly smaller than the depression (see FIG. 12) connected to the depression of the pressure relief valve mounting portion 111 are symmetrically formed from the pressure relief valve mounting portion 111 in the longitudinal direction of the lid 110. The cover 110 is formed so as to extend slightly before the both ends in the longitudinal direction of the lid 110. The periphery of the groove 114 constitutes a protrusion 116 that protrudes (projects) in the direction of the electrode body 7 from the groove 114.
The width of the groove 114 is not particularly limited as long as the gas generated in the container can be guided in the direction of the pressure relief valve 112, and the width of the groove 114 is small enough to be hardly clogged by foreign matter such as a piece of the electrode body 7. Is preferred. Similarly, the depth of the groove 114 may be such that the gas can be guided in the direction of the pressure relief valve 112, and is preferably a depth that is hardly clogged by foreign matter. Further, as shown in FIG. 11, it is preferable that a plurality of grooves 114 are formed.
The secondary battery according to the present embodiment is different from the second embodiment in that the pressure-releasing auxiliary member 70 (see FIGS. 7 and 8) according to the second embodiment is not disposed and the lid 47 of the container 43 is the same as the above-described embodiment. It can be manufactured by the same process as that of the second embodiment except that the lid 110 is changed.
[0041]
The operation of the lid 110 as the pressure release auxiliary member of the present embodiment will be described. For example, when the secondary battery is overcharged or the like, when the electrode body 7 expands or deforms due to gas generation and its outer peripheral surface projects (progresses) toward the pressure relief valve 112, as shown in FIG. As a result of the above-described convex portion 116 being provided on the lower surface of the lid 110, the convex portion 116 comes into contact with the projecting outer peripheral surface of the electrode body 7, thereby pressing the electrode body 7 and preventing its movement. can do. For this reason, it is possible to prevent the electrode body 7 from blocking the pressure release valve 112 provided in the container (lid 110). Further, the gas generated in the container can be smoothly moved to the pressure relief valve 112 by the above-described groove 114. According to the secondary battery of the present embodiment, by providing the groove 114, the distance between the electrode body 7 and the lid body 110 can be made relatively short while securing a gas passage. Therefore, the volume efficiency of the battery itself can be increased, and the overall shape can be reduced. Note that the positive terminal and the negative terminal may be provided in any direction of the axial direction of the electrode body, as in the first embodiment.
[0042]
As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above.
For example, in the above embodiment, a lithium ion secondary battery has been described. However, the present invention is applicable to various types of power storage devices such as nickel hydrogen batteries, nickel cadmium batteries, and other types of secondary batteries, and electric double layer capacitors. It can also be applied to devices. The material of the active material, the current collector, the terminal, the separator, and the like constituting the electrode, the composition of the electrolytic solution, and the like can be appropriately selected depending on the type of the power storage element.
Further, the technical elements described in the present specification or the drawings exhibit technical utility singly or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.
[Brief description of the drawings]
FIG. 1 is a front view showing a secondary battery according to a first embodiment.
FIG. 2 is an explanatory view showing a state in which an insulating film on a front surface in FIG. 1 is omitted.
FIG. 3 is a sectional view showing a laminated structure of an insulating film used in the first embodiment.
FIG. 4 is a schematic diagram showing a modification of the first embodiment.
FIG. 5 is a schematic diagram showing a modification of the first embodiment.
FIG. 6 is a schematic diagram showing a modification of the first embodiment.
FIG. 7 is an exploded perspective view showing a secondary battery according to a second embodiment.
FIG. 8 is a sectional view taken along line VIII-VIII in FIG. 7;
FIG. 9 is a front view showing a secondary battery according to a third embodiment.
FIG. 10 is a sectional view taken along line XX in FIG. 9;
FIG. 11 is a plan view showing a lid 110 of a secondary battery according to a fourth embodiment.
12 is a sectional view taken along line XII-XII in FIG.
[Explanation of symbols]
1,41,100: Lithium ion secondary battery (storage element)
7: Wound electrode body
9, 43: Container
11, 50: Positive terminal
13, 60: negative electrode terminal
15, 70, 90: Pressure relief auxiliary member
21: Heat welding part
23, 49, 112: Pressure relief valve
92: restraining member
94: bolt
110: Lid (pressure release auxiliary member)
114: groove
116: convex

Claims

A wound electrode body in which a positive electrode sheet and a negative electrode sheet are wound via a separator,
A container for accommodating the electrode body and the electrolyte,
A pressure relief valve that communicates the inside and outside of the container to adjust the internal pressure of the container, the pressure relief valve being provided in a direction substantially orthogonal to a winding axis of the electrode body,
Pressure relief assisting means for preventing the pressure relief valve from being closed by the electrode body,
An energy storage device comprising:

The power storage element according to claim 1, wherein the pressure-releasing auxiliary means includes a pressure-releasing auxiliary member configured to suppress an outer peripheral portion of the electrode body facing the pressure-releasing valve from protruding toward the pressure-releasing valve.

The power storage device according to claim 2, wherein the pressure-releasing auxiliary member is disposed between the electrode body and the pressure-releasing valve.

The power storage element according to claim 2, wherein the pressure-releasing auxiliary member is disposed near the pressure-releasing valve, and has a convex portion that protrudes toward the electrode body.

The power storage element according to any one of claims 2 to 4, wherein the pressure-releasing auxiliary member is disposed so as to cover at least a part of an outer surface of the electrode body facing the pressure-releasing valve.

The power storage device according to any one of claims 2 to 5, wherein the pressure release auxiliary member is formed using a material that can be ventilated.

The pressure-releasing auxiliary means includes a pressure-releasing auxiliary member provided in a shape capable of restraining a part of the container from the outside such that a pressure-releasing valve forming portion is narrower than an electrode body accommodating portion of the container. 2. The power storage element according to 1.

The power storage device according to any one of claims 1 to 7, wherein the pressure release assisting means is constituted by at least a part of the container.