JP5392809B2 - Lithium secondary battery - Google Patents

Lithium secondary battery Download PDF

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JP5392809B2
JP5392809B2 JP2008186984A JP2008186984A JP5392809B2 JP 5392809 B2 JP5392809 B2 JP 5392809B2 JP 2008186984 A JP2008186984 A JP 2008186984A JP 2008186984 A JP2008186984 A JP 2008186984A JP 5392809 B2 JP5392809 B2 JP 5392809B2
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notch
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JP2010027368A (en
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英明 佐々木
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Envision AESC Energy Devices Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Description

本発明は、リチウム二次電池に関する。   The present invention relates to a lithium secondary battery.

リチウム二次電池などの非水電解液二次電池は、近年、携帯電話、ノート型パソコンなどの電源として広く用いられている。これらの非水電解液二次電池は、従来のアルカリ蓄電池などの二次電池に比べて、体積が小さく、あるいは重量容量密度が大きく、しかも高電圧を取り出すことが可能であるので、小型機器用の電源として広く採用され、今日のモバイル機器の発展に大きく寄与している。また、近年では小型の携帯用電子機器用途以外にも、環境問題に対する配慮と省エネルギー化に対する意識の高まりから、電気自動車（ＥＶ）や電力貯蔵分野といった大容量で高い寿命特性と信頼性が要求される用途への需要が高まっている。   In recent years, non-aqueous electrolyte secondary batteries such as lithium secondary batteries have been widely used as power sources for mobile phones, notebook computers, and the like. These non-aqueous electrolyte secondary batteries have a smaller volume or a larger weight capacity density and can take out a higher voltage than secondary batteries such as conventional alkaline storage batteries. Widely adopted as a power source for mobile phones, it contributes greatly to the development of today's mobile devices. In recent years, in addition to small-sized portable electronic devices, high capacity and high life characteristics and reliability are demanded in electric vehicles (EV) and power storage fields due to increased consideration for environmental issues and energy saving. There is a growing demand for applications.

電池の寿命特性としては、特に繰り返し充放電に対する放電容量の劣化が少ないことが求められる。このようなサイクル特性は、従来の小型電子機器用途においては、例えば５００サイクル後に初期容量の６０〜７０％程度の容量を保持していれば良いと考えられていた。しかしながら、上記のＥＶや電力貯蔵用途のリチウム二次電池では、数千サイクル以上の長寿命特性が必要と考えられている。   As the life characteristics of the battery, it is particularly required that the deterioration of the discharge capacity due to repeated charge / discharge is small. Such a cycle characteristic is considered to be sufficient if a capacity of about 60 to 70% of the initial capacity is maintained after 500 cycles, for example, in a conventional small electronic device application. However, it is considered that the above-mentioned lithium secondary battery for EV and power storage needs long life characteristics of several thousand cycles or more.

一方、リチウム二次電池では、充放電を繰り返すことによって電極内部で非水電解液が分解されることによって電解液不足が生じ、その結果として電池抵抗の増大や容量劣化などの特性劣化を生じることが指摘されている。この現象は液枯れと呼ばれており、充放電にともなう電極活物質層の体積膨張や、負極あるいは正極において電解液が還元分解や酸化分解を受ける結果、電解液が不足してセパレータ及び電極活物質層内部に電解液が十分に満たされない領域が生じる。そのような領域ではリチウムイオンの拡散が阻害されるため、抵抗が増大したり、活物質へのリチウムイオンの挿入・脱離がスムーズに行えず容量劣化を引き起こすものと考えられる。特に、高いサイクル寿命が要求されるリチウム二次電池に対しては、このような液枯れによる特性劣化を抑えることが重要である。   On the other hand, in a lithium secondary battery, the non-aqueous electrolyte is decomposed inside the electrode due to repeated charge and discharge, resulting in insufficient electrolyte, resulting in characteristic deterioration such as increase in battery resistance and capacity deterioration. Has been pointed out. This phenomenon is called liquid withering. As a result of volume expansion of the electrode active material layer due to charge and discharge, and electrolyte solution undergoing reductive decomposition or oxidative decomposition at the negative electrode or the positive electrode, the electrolyte solution becomes insufficient and the separator and electrode A region where the electrolyte solution is not sufficiently filled is formed inside the material layer. In such a region, since diffusion of lithium ions is inhibited, it is considered that resistance increases, and that lithium ions cannot be smoothly inserted into or extracted from the active material, resulting in capacity deterioration. In particular, for lithium secondary batteries that require a high cycle life, it is important to suppress such deterioration of the characteristics due to liquid drainage.

液枯れの影響を抑制する方法としては、例えば、電解液不足による特性劣化が生じないように予め十分な量の電解液をセル内に収容しておく方法が考えられる。   As a method for suppressing the influence of the liquid withering, for example, a method in which a sufficient amount of the electrolytic solution is accommodated in the cell in advance so as not to cause characteristic deterioration due to the shortage of the electrolytic solution is conceivable.

例えば、特許文献１，２においてはそれぞれ電解液の含浸性の向上のため又は、電解液の透過を可能にするため、正極と負極とセパレータからなる巻回体の電極に電解液が透過可能な貫通孔を設ける方法が記載されている。   For example, in Patent Documents 1 and 2, in order to improve the impregnation property of the electrolyte solution or to allow the electrolyte solution to pass therethrough, the electrolyte solution can pass through the electrode of the wound body composed of the positive electrode, the negative electrode, and the separator. A method of providing a through hole is described.

特許文献１、２に見られるような巻回型のセル構造を有するリチウム二次電池は、現在最も多用されている円筒形または角形の電池であって、外装体としては一般に円筒型または角型の金属缶が用いられる。巻回体は硬く変形しにくい金属缶に内接すように挿入されるが、この場合、電極活物質層が膨張したとしても金属缶がそれを押さえるために、電極とセパレータとの密着性は維持しやすい。また、セルに収容する電解液量によってセル形状が変化することはない。   The lithium secondary battery having a wound cell structure as found in Patent Documents 1 and 2 is a cylindrical or prismatic battery that is most frequently used at present, and generally has a cylindrical or prismatic outer casing. Metal cans are used. The wound body is inserted so as to be inscribed in a hard and hard-to-deform metal can. In this case, even if the electrode active material layer expands, the metal can holds it down, so the adhesion between the electrode and the separator is Easy to maintain. In addition, the cell shape does not change depending on the amount of electrolyte contained in the cell.

他方、正極、負極、セパレータを交互に複数回積層させた後、それぞれの負極集電体同士および正極集電体同士を接続した、積層型の構造が提案されている。このような積層型電池はデッドスペースが少ないために体積効率を高めやすく高容量化も可能な構造である。また、放熱性に優れるため大電流負荷時のセル温度の上昇を抑え、電池の劣化を抑制する効果も期待されている。この場合、外装体としては一般にアルミ箔と樹脂とが積層されたアルミラミネートフィルムが用いられている。アルミラミネートフィルは柔軟性を有し容易に変形するため、セルに電解液を過剰に入れると、セル体積が増大したりセル形状が変化したりする。また、セル内の電解液の分布が不均一になり電極内における電池反応の不均一化を引き起こし、電池性能を低下させる原因にもなる。   On the other hand, a stacked structure has been proposed in which a positive electrode, a negative electrode, and a separator are alternately stacked a plurality of times, and then each negative electrode current collector and each positive electrode current collector are connected. Since such a stacked battery has a small dead space, it is easy to increase volumetric efficiency and increase the capacity. Moreover, since it is excellent in heat dissipation, the effect which suppresses the raise of the cell temperature at the time of a heavy current load, and suppresses deterioration of a battery is also anticipated. In this case, an aluminum laminate film in which an aluminum foil and a resin are laminated is generally used as the exterior body. Since the aluminum laminate film has flexibility and easily deforms, when an electrolyte is excessively added to the cell, the cell volume increases or the cell shape changes. In addition, the distribution of the electrolyte solution in the cell becomes non-uniform, causing non-uniform battery reaction in the electrode, which also causes a decrease in battery performance.

以上から明らかなように、アルミラミネート外装体を用いる積層型ラミネートセルからなるリチウム二次電池では、金属缶に巻回体を収容する円筒型や角型セルでは見られない影響が現れるため、液枯れを防止するためにそのセル形状に応じて適切な手段を講じる必要がある。   As is clear from the above, in lithium secondary batteries composed of laminated laminate cells using an aluminum laminate exterior, an effect that cannot be seen in a cylindrical or rectangular cell containing a wound body in a metal can appears. In order to prevent withering, it is necessary to take appropriate measures according to the cell shape.

すなわち、特許文献１、２は巻回体を金属缶に収容した構成であって、アルミラミネート外装体を用いた積層型セルについては記載されておらず、また、正極と負極に具備される貫通孔の大きさおよびその位置関係、収容する電解液量についても特に規定されておらず、液枯れを効果的に抑制して電池性能を向上させる目的に対して、十分ではなかった。   That is, Patent Documents 1 and 2 are configurations in which a wound body is housed in a metal can, and there is no description of a stacked cell using an aluminum laminate exterior body, and the through holes provided in the positive electrode and the negative electrode The size of the pores, the positional relationship thereof, and the amount of the electrolytic solution to be accommodated are not particularly specified, and are not sufficient for the purpose of effectively suppressing the drainage and improving the battery performance.

また、特許文献３においては、多孔質集電体の空孔部分に電解液を保持することによってリチウムイオンの移動性を向上させて、放電負荷特性を向上させることが記載されている。液枯れについては一切記載がないものの、多孔質状の集電体に保持した電解液が不足した電解液を補うことによって、液枯れを抑制する効果を発現することが推定される。しかしながら、多孔質集電体は強度に乏しくハンドリングも悪いため量産性に難があり、また通常の集電体よりも厚みが大きくなるため体積当たりの容量が低いといった問題がある。   Patent Document 3 describes that the mobility of lithium ions is improved by holding an electrolyte in the pores of a porous current collector, thereby improving the discharge load characteristics. Although there is no description about the liquid withering, it is presumed that the effect of suppressing the liquid withering is expressed by supplementing the electrolyte that is insufficient in the electrolyte retained in the porous current collector. However, the porous current collector has a problem that it is difficult to mass-produce due to poor strength and handling, and the capacity per volume is low because the thickness is larger than that of a normal current collector.

特開２００１−０７６７６１号公報JP 2001-076761 A 特開平０９−１６７６１３号公報JP 09-167613 A 特開２００５−２９４１６８号公報JP 2005-294168 A

本発明の課題は、積層型ラミネートセルからなるリチウム二次電池において、液枯れを効果的に防止することによって、充放電サイクルを繰り返した際の容量劣化の少ないリチウム二次電池を提供することである。   An object of the present invention is to provide a lithium secondary battery with less capacity deterioration when the charge / discharge cycle is repeated by effectively preventing liquid withstand in a lithium secondary battery comprising a laminated laminate cell. is there.

上記課題を解決するために、本発明のリチウム二次電池は、正極と負極とがセパレータを介して交互に積層されてなる積層体と、該積層体を収容するラミネート外装体からなるリチウム二次電池において、正極と負極が切欠き部を有し、かつ前記セパレータを介して前記負極の切欠き部は前記正極の切欠き部よりも小さく、かつ負極の切欠き部は積層方向から見て正極の切欠き部の内側に収まる位置にあり、前記切欠き部には非水電解液が収容され、前記積層体の体積に対する前記積層体に形成されたすべての切欠き部の体積の比率が５％〜１５％であって、前記積層体内の総空孔体積に対して１．１〜１．４倍の前記非水電解液を収容することを特徴とする。 In order to solve the above problems, a lithium secondary battery of the present invention is a lithium secondary battery comprising a laminate in which positive electrodes and negative electrodes are alternately laminated via separators, and a laminate outer package containing the laminate. In the battery, the positive electrode and the negative electrode have a notch, the notch of the negative electrode is smaller than the notch of the positive electrode through the separator, and the notch of the negative electrode is a positive electrode when viewed from the stacking direction. position near that fits inside the notch of is, in the notch nonaqueous electrolyte is contained, the ratio of the volume of all the cutout portion formed in the laminate to the volume of the laminate The nonaqueous electrolyte solution is contained in an amount of 5% to 15% and 1.1 to 1.4 times the total pore volume in the laminated body .

前記正極の切欠き部と前記負極の切欠き部に挟まれるセパレータの部分に負極の切欠き部よりも小さい切欠き部を、積層方向から見て前記負極の切欠き部の内側に収まる位置に有するとよい。 Notch and the notches have smaller than notch of the negative electrode to the notch portion of the separator sandwiched between the negative electrode, a position that fits inside the notch of the negative electrode when viewed from the stacking direction of the positive electrode It is good to have.

前記積層体の負極、正極、セパレータの切欠き部が積層体の積層方向に連続して繋がっているとよい。 The negative electrode of the laminate, a positive electrode, may notched portion of the separator is continuously connected in the stacking direction of the stacked body.

本発明によれば、少なくとも正極と負極に貫通孔又は切欠き部を備え、正極の貫通孔又は切欠き部よりも負極の貫通孔又は切欠き部を小さくして、かつ負極の貫通孔又は切欠き部が積層方向から見て正極の貫通孔又は切欠き部の内側に収まる位置に配置することによって、上記貫通孔又は切欠き部に電解液を保持するとともに負極へのリチウム金属の析出を防止することができ、サイクル寿命の向上を図ることができる。   According to the present invention, at least the positive electrode and the negative electrode are provided with through holes or notches, the negative electrode through holes or notches are made smaller than the positive electrode through holes or notches, and the negative electrode through holes or notches are formed. By disposing the notch in a position that fits inside the through hole or notch of the positive electrode when viewed from the stacking direction, electrolyte is held in the through hole or notch and lithium metal is prevented from depositing on the negative electrode. And the cycle life can be improved.

次に本発明の実施の形態について説明する。   Next, an embodiment of the present invention will be described.

（本発明における電池構成）
本発明におけるリチウム二次電池は、正極集電体およびリチウムイオンを吸蔵、放出し得る正極活物質を含有する正極活物質層と、負極集電体およびリチウムイオンを吸蔵、放出し得る負極活物質を含有する負極活物質層とが、セパレータを介して対向して配置され、リチウム塩を溶解した非水電解液とともにアルミラミネート外装体に収容されて、構成されている。 (Battery configuration in the present invention)
The lithium secondary battery according to the present invention includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium ions, and a negative electrode current collector and negative electrode active material capable of occluding and releasing lithium ions And a negative electrode active material layer containing a non-aqueous electrolyte solution in which a lithium salt is dissolved and placed in an aluminum laminate exterior body.

（集電体）
正極集電体としてはアルミニウム、ステンレス鋼、ニッケル、チタンまたはこれらの合金などを用いることができ、負極集電体としては銅、ステンレス鋼、ニッケル、チタンまたはこれらの合金を用いることができる。 (Current collector)
Aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used as the positive electrode current collector, and copper, stainless steel, nickel, titanium, or an alloy thereof can be used as the negative electrode current collector.

（セパレータ）
セパレータとしては、ポリプロピレン、ポリエチレンなどのポリオレフィン、フッ素樹脂などの多孔性フィルムが用いられる。 (Separator)
As the separator, a polyolefin film such as polypropylene or polyethylene, or a porous film such as a fluororesin is used.

（正極）
正極活物質としては通常リチウム含有複合酸化物が用いられ、具体的にはＬｉＭＯ2（ＭはＭｎ、Ｆｅ、Ｃｏ、Ｎｉより選ばれる１種のみ、または２種以上の混合物であり、一部をＭｇ、Ａｌ、Ｔｉなどその他カチオンで置換してもよい）、ＬｉＭｎ2Ｏ4など汎用の材料を用いることができる。また、ＬｉＦｅＰＯ4で表されるオリビン型材料を用いることもできる。これらから選択された正極活物質と、カーボンブラックなどの導電助剤とを、ＰＶｄＦ（ポリフッ化ビニリデン）などの結着剤とともにＮ−メチル−２−ピロリドン（ＮＭＰ）などの溶剤中に分散混練し、このスラリーをホットプレート上にてドクターブレードなどを用いてアルミニウム箔などの正極集電体に塗布後、溶媒を乾燥させるなどの方法により正極活物質層を得ることができる。例えば、この塗布工程を正極集電体の両面に対して行うことによって、両面に正極活物質層が形成された正極を得ることができる。得られた正極は、電極プレスにより圧縮して適当な密度に調整する。 (Positive electrode)
As the positive electrode active material, a lithium-containing composite oxide is usually used. Specifically, LiMO 2 (M is one kind selected from Mn, Fe, Co, Ni, or a mixture of two or more kinds, and a part thereof is used. General-purpose materials such as LiMn 2 O 4 and other cations such as Mg, Al, and Ti may be used. An olivine type material represented by LiFePO 4 can also be used. A positive electrode active material selected from these and a conductive aid such as carbon black are dispersed and kneaded in a solvent such as N-methyl-2-pyrrolidone (NMP) together with a binder such as PVdF (polyvinylidene fluoride). A positive electrode active material layer can be obtained by applying the slurry to a positive electrode current collector such as an aluminum foil using a doctor blade on a hot plate and then drying the solvent. For example, by performing this coating process on both surfaces of the positive electrode current collector, a positive electrode having a positive electrode active material layer formed on both surfaces can be obtained. The obtained positive electrode is compressed to an appropriate density by an electrode press.

（負極）
負極活物質としては、黒鉛、非晶質炭素などの炭素材料、あるいはＬｉ金属、Ｓｉ、Ｓｎ、Ａｌ、などのＬｉと合金を形成する材料、Ｓｉ酸化物、ＳｉとＳｉ以外の他金属元素を含むＳｉ複合酸化物、Ｓｎ酸化物、ＳｎとＳｎ以外の他金属元素を含むＳｎ複合酸化物、Ｌｉ4Ｔｉ5Ｏ12などを単独または混合して用いることができる。これらから選択された負極活物質と、必要に応じて導電助剤とを、ＰＶｄＦなどの結着剤とともにＮＭＰなどの溶剤中に分散混練したスラリー、および銅箔などの負極集電体を用いて、正極と同様な方法にて負極集電体両面に負極活物質層を形成した負極を得ることができる。 (Negative electrode)
Examples of the negative electrode active material include carbon materials such as graphite and amorphous carbon, materials that form an alloy with Li such as Li metal, Si, Sn, and Al, Si oxide, and other metal elements other than Si and Si. Si composite oxide containing, Sn oxide, Sn composite oxide containing other metal elements other than Sn and Sn, Li 4 Ti 5 O 12 and the like can be used alone or in combination. Using a slurry obtained by dispersing and kneading a negative electrode active material selected from these materials and, if necessary, a conductive additive in a solvent such as NMP together with a binder such as PVdF, and a negative electrode current collector such as a copper foil A negative electrode in which a negative electrode active material layer is formed on both surfaces of the negative electrode current collector can be obtained by the same method as for the positive electrode.

必要により導電助剤としては、カーボンブラック、アセチレンブラックなどの炭素質粉末を用いることができる。   If necessary, carbonaceous powders such as carbon black and acetylene black can be used as the conductive assistant.

結着剤としては、ＰＶｄＦやポリテトラフルオロエチレンなどのフッ素系樹脂、ポリオレフィン系樹脂、スチレン系樹脂、アクリル系樹脂、ポリイミド系樹脂などを用いることができる。   As the binder, fluorine resins such as PVdF and polytetrafluoroethylene, polyolefin resins, styrene resins, acrylic resins, polyimide resins and the like can be used.

活物質と導電助剤と結着剤の重量比は、正極では、活物質：導電助剤：結着剤＝８０〜９５：２〜１０：２〜１０、負極では、活物質：導電助剤：結着剤＝８０〜９８：０〜５：２〜１０の範囲が好ましい。   The weight ratio of the active material, the conductive auxiliary agent and the binder is as follows: active material: conductive auxiliary agent: binding agent = 80 to 95: 2 to 10: 2 to 10 for the positive electrode, and active material: conductive auxiliary agent for the negative electrode. : Binder = 80 to 98: 0 to 5: 2 to 10 is preferable.

本発明では、上記のように製造された負極と正極に対して、貫通孔又は切欠き部を１つ以上設けて、正極と負極をセパレータを介して積層させた積層体を構成する。その際、負極の孔は正極の孔よりも小さく、かつセパレータを介して負極の貫通孔又は切欠き部は積層方向から見て正極の貫通孔又は切欠き部の内側に収まる位置に配置される。また、負極の貫通孔又は切欠き部と正極の貫通孔又は切欠き部に挟まれるセパレータの部分に負極の貫通孔又は切欠き部よりも小さい貫通孔又は切欠き部を、積層方向から見て負極の貫通孔又は切欠き部の内側に収まる位置に設けてもよい。また、負極、正極、セパレータのそれぞれの貫通孔が積層方向に連続して繋がっている構成とすることができる。   In the present invention, one or more through-holes or notches are provided for the negative electrode and the positive electrode manufactured as described above, and the positive electrode and the negative electrode are stacked via a separator. At that time, the hole of the negative electrode is smaller than the hole of the positive electrode, and the through hole or notch of the negative electrode is arranged in a position that fits inside the through hole or notch of the positive electrode when viewed from the stacking direction via the separator. . In addition, a through hole or notch that is smaller than the through hole or notch of the negative electrode is seen from the lamination direction in the through hole or notch of the negative electrode and the separator sandwiched between the through hole or notch of the positive electrode. You may provide in the position settled inside the through-hole or notch of a negative electrode. Moreover, it can be set as the structure by which each through-hole of the negative electrode, the positive electrode, and the separator was connected continuously in the lamination direction.

図１は、本発明の実施の形態の一例を示す積層型のリチウム二次電池の積層構成を示す断面図である。図１において、１が負極活物質層、２が正極活物質層、３が負極集電体、４が正極集電体、５がセパレータ、６が負極貫通孔、７が正極貫通孔、８がセパレータ貫通孔である。上下に連続する４つの黒丸は、中間の積層構造が繰り返すことを示している。両面塗布された正極および負極がセパレータを介して順次積層される。負極貫通孔６は正極貫通孔７よりも小さく、積層方向から見て正極貫通孔７の中に収まる位置に配置する。   FIG. 1 is a cross-sectional view showing a stacked configuration of a stacked lithium secondary battery showing an example of an embodiment of the present invention. In FIG. 1, 1 is a negative electrode active material layer, 2 is a positive electrode active material layer, 3 is a negative electrode current collector, 4 is a positive electrode current collector, 5 is a separator, 6 is a negative electrode through hole, 7 is a positive electrode through hole, and 8 is It is a separator through-hole. Four black circles continuous in the vertical direction indicate that the intermediate laminated structure repeats. A positive electrode and a negative electrode coated on both sides are sequentially laminated via a separator. The negative electrode through hole 6 is smaller than the positive electrode through hole 7 and is disposed at a position that fits in the positive electrode through hole 7 when viewed from the stacking direction.

同様にセパレータ貫通孔８は負極貫通孔６よりも小さく、積層方向から見て負極貫通孔６の中に収まる位置に配置する。このように貫通孔の中に電解液を保持することによって、充放電サイクルにともない積層体内の電解液が消費された場合でも、貫通孔内に保持された電解液が電極活物質層およびセパレータを通して電解液の不足部分に供給されるため、液枯れによる容量劣化を抑制することができる。また、負極貫通孔が正極貫通孔に内包される位置に配置することで、負極上におけるリチウム金属の析出が起こりにくくなり、それによる特性劣化を防止することができる。すなわち、このような配置としない場合、正極活物質層の対向面に負極活物質層が存在しない場所ができてしまい、そのような場所では充電時に正極側から負極側へ移動するリチウムイオンを受け入れることができず、リチウム金属として負極上に析出してしまう。リチウム金属の析出による容量損失や正負極間のショート不良、電極反応の不均一化による特性劣化などを引き起こし、結果としてサイクル寿命の低下を招いてしまう。なお、本図では最外層を負極とした構成を示したが、最外層は正極であっても構わない。また、図には示していないが正極集電体同士および負極集電体同士は電気的に接続されている。   Similarly, the separator through-hole 8 is smaller than the negative electrode through-hole 6 and is disposed at a position that fits in the negative electrode through-hole 6 when viewed from the stacking direction. By holding the electrolytic solution in the through hole in this way, the electrolytic solution held in the through hole passes through the electrode active material layer and the separator even when the electrolytic solution in the laminated body is consumed with the charge / discharge cycle. Since it is supplied to the insufficient portion of the electrolytic solution, it is possible to suppress the capacity deterioration due to the liquid withering. In addition, by disposing the negative electrode through hole at a position included in the positive electrode through hole, it is difficult for lithium metal to precipitate on the negative electrode, thereby preventing deterioration of characteristics. That is, if such an arrangement is not used, a place where the negative electrode active material layer does not exist is formed on the opposite surface of the positive electrode active material layer, and in such a place, lithium ions that move from the positive electrode side to the negative electrode side during charging are received. And cannot be deposited on the negative electrode as lithium metal. Capacitance loss due to lithium metal deposition, short circuit failure between positive and negative electrodes, characteristic deterioration due to non-uniform electrode reaction, and the like are caused, resulting in a decrease in cycle life. In addition, although the structure which used the outermost layer as the negative electrode was shown in this figure, the outermost layer may be a positive electrode. Although not shown in the figure, the positive electrode current collectors and the negative electrode current collectors are electrically connected.

セパレータにも貫通孔を設けることにより層積層体内部に保持する電解液量をさらに増やすことができ、液枯れを防止する効果をよりいっそう得ることができる。この場合、負極と正極がショートしないように積層方向から見て正極の貫通孔より負極の貫通孔が内側に、さらに負極の貫通孔よりセパレータの貫通孔が内側に配置する必要がある。   Providing through-holes in the separator can further increase the amount of electrolytic solution retained inside the layered laminate, thereby further obtaining the effect of preventing liquid withering. In this case, it is necessary to arrange the through hole of the negative electrode inside the through hole of the positive electrode and the through hole of the separator inside the through hole of the negative electrode so as not to short-circuit the negative electrode and the positive electrode.

積層体の各層の正極、負極、セパレータの貫通孔が連続して繋がるような連通孔として配置することが好ましい。こうすることによって、積層体に電解液を注液する際に連通孔を通して積層体内部への電解液の浸み込みを容易にすることができる。また、積層体を作製する際に、位置決めピンを通す孔としてこの連通孔を利用することができる。   It is preferable to arrange as a communication hole in which the positive electrode, the negative electrode, and the through hole of the separator of each layer of the laminate are continuously connected. By so doing, it is possible to facilitate the penetration of the electrolytic solution into the laminated body through the communication hole when the electrolytic solution is injected into the laminated body. Moreover, when producing a laminated body, this communicating hole can be utilized as a hole which lets a positioning pin pass.

上記のようして構成された貫通孔を有する積層体の正極および負極にそれぞれ電力を外部に取り出すためのタブが溶接され、一端が開口部となっている袋状のアルミラミネート外装体に両極のタブが開口部から出るように収めた後、所定の量の電解液が注液される。減圧下にて含浸した後、開口部を熱溶着により封止することで本発明の積層型のリチウム二次電池が構成される。   Tabs for extracting electric power to the outside are welded to the positive electrode and the negative electrode of the laminate having the through holes configured as described above, respectively, and both ends are attached to the bag-shaped aluminum laminate outer package having one end as an opening. After the tab is stored so as to exit from the opening, a predetermined amount of electrolyte is injected. After impregnation under reduced pressure, the opening is sealed by heat welding to constitute the stacked lithium secondary battery of the present invention.

ここで、積層体の体積（Ｖｓ）(即ち、正極、負極、セパレータの積層方向から見た貫通孔も含む面積と厚さから求めたそれぞれの体積の合算値)に対する積層体に形成した正極、負極、セパレータ全ての貫通孔の体積の合算値（Ｖｈ）の比率（Ｖｈ／Ｖｓ）を５％〜１５％とすることが望ましい。Ｖｈ／Ｖｓが大きいほど積層体が保持する電解液量は増大して液枯れによるサイクル容量劣化は抑えられるものの、その分、初期の電池容量が減少してしまう。液枯れによる容量劣化を防止するためには、Ｖｈ／Ｖｓの値を５％以上確保することが好ましいが、一方、Ｖｈ／Ｖｓが１５％を超えると、初期の電池容量の低下が２０％以上に達する場合があり、実用的ではなくなってしまう。したがって、Ｖｈ／Ｖｓは５％〜１５％とすることが望ましい。   Here, the positive electrode formed in the laminated body with respect to the volume (Vs) of the laminated body (that is, the sum of the respective volumes obtained from the area and thickness including the through holes as viewed from the lamination direction of the positive electrode, the negative electrode, and the separator), It is desirable that the ratio (Vh / Vs) of the total volume (Vh) of the through holes of all the negative electrodes and separators is 5% to 15%. As Vh / Vs increases, the amount of electrolyte retained by the laminate increases and cycle capacity deterioration due to liquid erosion can be suppressed, but the initial battery capacity decreases accordingly. In order to prevent capacity deterioration due to liquid withstand, it is preferable to secure a value of Vh / Vs of 5% or more. On the other hand, when Vh / Vs exceeds 15%, the initial decrease in battery capacity is 20% or more. May become impractical. Therefore, Vh / Vs is desirably 5% to 15%.

積層型ラミネートセルに収容可能な電解液量は、積層体が有するすべての空孔体積に比例すると考えられる。ここで、積層体が有する総空孔体積（Ｖｔ）は、負極活物質層、正極活物質層およびセパレータが有する空孔体積に、積層体が有する貫通孔の体積（Ｖｈ）を加えることで求められる。積層体の総空孔体積（Ｖｔ）に対する電解液の体積（Ｖｌ）の比率（Ｖｌ／Ｖｔ）が１．１より小さいと、液枯れによる電解液不足を十分に抑制できないため不十分である。一方、Ｖｌ／Ｖｔが１．４を越えて過剰に電解液を入れようとすると、真空封止する際に電解液が溢れ出てしまう不具合が発生したり、余剰な電解液がセル内に不均一に分布する結果、電極反応が不均一化して電池特性の低下を招いたり、積層体と外装体の間に入り込んだ余剰電解液が表面に滞留して凹凸やしわができ外観不良の原因になる場合がある。したがって、積層体の総空孔体積に対する電解液の体積比率は１．１〜１．４倍とすることが望ましい。   The amount of the electrolyte solution that can be accommodated in the laminate-type laminate cell is considered to be proportional to the total volume of pores of the laminate. Here, the total void volume (Vt) of the laminate is obtained by adding the volume (Vh) of the through hole of the laminate to the pore volume of the negative electrode active material layer, the positive electrode active material layer, and the separator. It is done. If the ratio (Vl / Vt) of the volume (Vl) of the electrolytic solution to the total pore volume (Vt) of the laminate is smaller than 1.1, it is not sufficient because the shortage of the electrolytic solution due to liquid dying cannot be sufficiently suppressed. On the other hand, if Vl / Vt exceeds 1.4 and an attempt is made to add an excessive amount of electrolyte, there may be a problem that the electrolyte overflows during vacuum sealing, or excess electrolyte does not enter the cell. As a result of the uniform distribution, the electrode reaction becomes non-uniform, leading to deterioration of battery characteristics, or excess electrolyte that has entered between the laminate and the exterior body stays on the surface, causing irregularities and wrinkles, resulting in poor appearance. There is a case. Therefore, the volume ratio of the electrolytic solution to the total pore volume of the laminate is desirably 1.1 to 1.4 times.

図２は、図１に示す積層体を上から見た平面図であり、積層体の中央に円形の貫通孔が連続して配置されて連通孔１０を構成している。孔は少なくとも１つ以上あればよく、複数配置してもかまわない。製造上の容易さや電極の強度の観点から決めることができる。孔の形状は特に限定されないが、一般的に円形状や楕円形状の方が電極面に沿った外力に対して応力を分散する効果があり電極強度の低下をより抑えることができる。四角形状の場合は四隅にＲをつけるなどしてもよい。孔の大きさは特に限定されるものではなく、収容する電解液量と孔の数によって決めることができる。孔の場所も特に限定されるものではないが、タブ（図示せず）の近傍は電流が集中するため電流の流れを妨げる原因になる場合があるので、避けた方が好ましい。図３は、貫通孔の代わりに電極側面に凹状の切欠き部１１を形成した別の構成例である。この場合、電解液はこの切欠き部とラミネート外装体とで囲まれる空間に収容される。これは電極側面に設けられた貫通孔の一種と見なせる。負極、正極、セパレータに形成される切欠き部の大きさと配置の仕方は、貫通孔のそれと同様に構成することができる。   FIG. 2 is a plan view of the laminated body shown in FIG. 1 as viewed from above. A circular through hole is continuously arranged at the center of the laminated body to form a communication hole 10. There may be at least one hole, and a plurality of holes may be arranged. It can be determined from the viewpoint of ease of manufacture and the strength of the electrode. The shape of the hole is not particularly limited, but generally a circular shape or an elliptical shape has an effect of dispersing stress against an external force along the electrode surface, and a decrease in electrode strength can be further suppressed. In the case of a square shape, R may be added to the four corners. The size of the hole is not particularly limited, and can be determined by the amount of electrolytic solution to be accommodated and the number of holes. The location of the hole is not particularly limited, but it is preferable to avoid the vicinity of the tab (not shown) because the current concentrates and may interfere with the current flow. FIG. 3 shows another configuration example in which a concave notch 11 is formed on the side surface of the electrode instead of the through hole. In this case, the electrolytic solution is accommodated in a space surrounded by the notch and the laminate outer package. This can be regarded as a kind of through hole provided on the side surface of the electrode. The size and arrangement of the notches formed in the negative electrode, the positive electrode, and the separator can be configured in the same manner as that of the through hole.

実際には、積層体が有する空孔部分以外に、正極、負極の外周とセパレータの外周にかなりの余剰スペースがあり、これらのスペースにも電解液を収容することができるため、積層体の総空孔体積に対する電解液量を最大で１．４倍までとすることできる。一方、このようなスペースは積層体の形状や積層体とラミネート外装体との配置、真空封止の状態などに大きく依存するため、収容する電解液量をコントロールすることが困難であり、またこのようなスペースだけで十分な電解量を確保することは困難な場合が多い。すなわち、貫通孔や切欠き部を備えることにより電解液量をより広範囲にかつ容易にコントロールすることができる。   Actually, in addition to the pores of the laminate, there are considerable excess spaces on the outer periphery of the positive and negative electrodes and on the outer periphery of the separator. The amount of the electrolyte with respect to the pore volume can be up to 1.4 times. On the other hand, such a space greatly depends on the shape of the laminated body, the arrangement of the laminated body and the laminate outer package, the state of vacuum sealing, and the like, so it is difficult to control the amount of electrolyte contained. It is often difficult to ensure a sufficient amount of electrolysis only in such a space. That is, by providing the through hole and the notch, the amount of the electrolyte can be controlled in a wider range and easily.

以上説明したように、本発明によれば、積層体の負極、正極、セパレータに適切な配置で貫通孔を備えることにより、また積層体の空孔体積に対して適切な量の電解液を収容することによって、充放電サイクルにおける液枯れによる放電容量の劣化が少ない積層型リチウム二次電池を提供することができる。   As described above, according to the present invention, the negative electrode, the positive electrode, and the separator of the laminate are provided with through holes in an appropriate arrangement, and an appropriate amount of electrolyte is accommodated with respect to the pore volume of the laminate. By doing so, it is possible to provide a multilayer lithium secondary battery in which the deterioration of the discharge capacity due to the liquid withering in the charge / discharge cycle is small.

（電解液）
電解液は、電解質が溶解された非水溶媒を用いることができる。電解質は、リチウム二次電池の場合にはリチウム塩を用い、これを非水溶媒中に溶解させる。リチウム塩としては、リチウムイミド塩、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＳｂＦ6などが挙げられる。この中でも特にＬｉＰＦ6、ＬｉＢＦ4が好ましい。リチウムイミド塩としてはＬｉＮ（ＣkＦ2k+1ＳＯ2）（ＣmＦ2m+1ＳＯ2）（ｋ、ｍはそれぞれ独立して１または２である）が挙げられる。これらは単独で、または複数種を組み合わせて用いることができる。 (Electrolyte)
As the electrolytic solution, a nonaqueous solvent in which an electrolyte is dissolved can be used. In the case of a lithium secondary battery, the electrolyte uses a lithium salt, which is dissolved in a non-aqueous solvent. The lithium salt, lithium imide salt, LiPF 6, LiAsF 6, LiAlCl 4, LiClO 4, LiBF 4, etc. LiSbF 6 and the like. Of these, LiPF 6 and LiBF 4 are particularly preferable. Examples of the lithium imide salt include LiN (C k F 2k + 1 SO 2 ) (C m F 2m + 1 SO 2 ) (k and m are each independently 1 or 2). These can be used alone or in combination of two or more.

また非水溶媒としては、環状カーボネート類、鎖状カーボネート類、脂肪族カルボン酸エステル類、γ−ラクトン類、環状エーテル類、鎖状エーテル類およびそれらのフッ化誘導体の有機溶媒から選ばれた少なくとも１種類の有機溶媒を用いる。より具体的には、環状カーボネート類：プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ブチレンカーボネート（ＢＣ）、およびこれらの誘導体鎖状カーボネート類：ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、ジプロピルカーボネート（ＤＰＣ）、およびこれらの誘導体、脂肪族カルボン酸エステル類：ギ酸メチル、酢酸メチル、プロピオン酸エチル、およびこれらの誘導体、γ−ラクトン類：γ−ブチロラクトン、およびこれらの誘導体、環状エーテル類：テトラヒドロフラン、２−メチルテトラヒドロフラン鎖状エーテル類：１、２−エトキシエタン（ＤＥＥ）、エトキシメトキシエタン（ＥＭＥ）、ジエチルエーテル、およびこれらの誘導体、その他：ジメチルスルホキシド、１、３−ジオキソラン、ホルムアミド、アセトアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、リン酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、メチルスルホラン、１、３−ジメチル−２−イミダゾリジノン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、エチルエーテル、１、３−プロパンスルトン、アニソール、Ｎ−メチルピロリドン、フッ素化カルボン酸エステル、これらを１種または２種以上を混合して使用することができる。   The non-aqueous solvent is at least selected from organic solvents such as cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, γ-lactones, cyclic ethers, chain ethers and their fluorinated derivatives. One kind of organic solvent is used. More specifically, cyclic carbonates: propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and their derivative chain carbonates: dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl Methyl carbonate (EMC), dipropyl carbonate (DPC), and derivatives thereof, aliphatic carboxylic acid esters: methyl formate, methyl acetate, ethyl propionate, and derivatives thereof, γ-lactones: γ-butyrolactone, and These derivatives, cyclic ethers: tetrahydrofuran, 2-methyltetrahydrofuran chain ethers: 1, 2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, and derivatives thereof, Other: dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1, 3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, fluorinated carboxylic acid ester, 1 type (s) or 2 or more types can be mixed and used.

さらに電解液添加剤として、一般的な、例えば、ビニレンカーボネート（ＶＣ）などを用いることも可能である。   Furthermore, it is also possible to use common, for example, vinylene carbonate (VC) as the electrolyte solution additive.

以下に本発明の実施例について詳細に説明するが、本発明は以下の実施例のみに限定されるものではない。   Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.

（負極の作製）
負極活物質として平均粒径３０μｍの人造黒鉛粉末と、結着剤としてＰＶｄＦとを重量比９５：５でＮＭＰ中に均一に分散させてスラリーを作製した。このスラリーを負極集電体となる厚み１５μｍの銅箔上に塗布後、１２５℃にて１０分間ＮＭＰを蒸発させることにより負極活物質層を形成した。同様にもう一方の面に負極活物質層を形成して、プレスすることにより両面に活物質層を備えた負極を作製した。負極集電体を除いた厚みは１００μｍ、活物質層の空孔率は２５％となるように電極密度を調整した。 (Preparation of negative electrode)
An artificial graphite powder having an average particle diameter of 30 μm as a negative electrode active material and PVdF as a binder were uniformly dispersed in NMP at a weight ratio of 95: 5 to prepare a slurry. After applying this slurry on a 15 μm thick copper foil serving as a negative electrode current collector, NMP was evaporated at 125 ° C. for 10 minutes to form a negative electrode active material layer. Similarly, a negative electrode active material layer was formed on the other surface and pressed to prepare a negative electrode having an active material layer on both surfaces. The electrode density was adjusted so that the thickness excluding the negative electrode current collector was 100 μm, and the porosity of the active material layer was 25%.

（正極の作製）
正極活物質として平均粒径１０μｍのＬｉＭｎ2Ｏ4粉末と、結着剤としてＰＶｄＦと、導電助剤としてカーボンブラックとを重量比を９２：４：４でＮＭＰ中に均一に分散させてスラリーを作製した。そのスラリーを正極集電体となる厚み２０μｍのアルミ箔上に塗布後、１２５℃にて１０分間ＮＭＰを蒸発させることにより正極活物質層を形成した。同様にもう一方の面にも正極活物質層を形成し、プレスすることにより両面に活物質層を備えた正極を作製した。正極集電体を除いた厚みは１６０μｍ、活物質層の空孔率は２５％となるように電極密度を調整した。 (Preparation of positive electrode)
A slurry is obtained by uniformly dispersing LiMn 2 O 4 powder having an average particle diameter of 10 μm as a positive electrode active material, PVdF as a binder, and carbon black as a conductive auxiliary agent in NMP at a weight ratio of 92: 4: 4. Produced. The slurry was applied on a 20 μm thick aluminum foil serving as a positive electrode current collector, and then NMP was evaporated at 125 ° C. for 10 minutes to form a positive electrode active material layer. Similarly, a positive electrode active material layer was formed on the other surface and pressed to produce a positive electrode having an active material layer on both surfaces. The electrode density was adjusted so that the thickness excluding the positive electrode current collector was 160 μm, and the porosity of the active material layer was 25%.

電解液は、溶媒としてＥＣ：ＤＥＣ＝３０：７０（体積％）に、電解質として１ｍｏｌ／ＬのＬｉＰＦ6を溶解したものを用いた。セパレータはポリエチレンおよびポリプロピレンの積層品からなる厚み２５μｍ、空孔率４０％のものを用いた。 As the electrolytic solution, EC: DEC = 30: 70 (volume%) as a solvent and 1 mol / L LiPF 6 as an electrolyte were dissolved. The separator used was a laminated product of polyethylene and polypropylene having a thickness of 25 μm and a porosity of 40%.

（貫通孔の形成）
上記のように作製した負極を５０ｍｍ×５０ｍｍの負極活物質層とその角に５ｍｍ×５ｍｍの未塗布部が延出した形状に切り出し、負極活物質層の中央に直径１１ｍｍの貫通孔を設けた。同様に、上記のように作製した正極を４６ｍｍ×４６ｍｍの正極活物質層と５ｍｍ×５ｍｍの未塗布部が延出した形状に切り出し、正極活物質層の中央に負極よりも４ｍｍ大きい直径１５ｍｍの貫通孔を設けた。セパレータを６０ｍｍ×６０ｍｍに切り出して、その中央に負極よりも４ｍｍ小さい７ｍｍの貫通孔を設けた。 (Formation of through holes)
The negative electrode produced as described above was cut out into a shape in which a negative electrode active material layer of 50 mm × 50 mm and an uncoated portion of 5 mm × 5 mm extended at its corner, and a through hole having a diameter of 11 mm was provided in the center of the negative electrode active material layer. . Similarly, the positive electrode produced as described above was cut into a shape in which a positive electrode active material layer of 46 mm × 46 mm and an uncoated portion of 5 mm × 5 mm were extended, and the positive electrode active material layer had a diameter of 15 mm that was 4 mm larger than the negative electrode. A through hole was provided. The separator was cut into 60 mm × 60 mm, and a 7 mm through hole 4 mm smaller than the negative electrode was provided at the center.

（ラミネート型電池の作製）
貫通孔を備えた負極、正極、セパレータをそれぞれ６枚、５枚、１０枚用意し、積層体の最外層が負極となるように、負極と正極をセパレータを介して順次積層した。その際、正極の未塗布部同士と負極の未塗布部同士が重なるようにして、両極の未塗布部は積層体の左右に位置するように配置した。これらの作業は、セパレータの貫通孔より１ｍｍ小さい直径６ｍｍの位置決めピンとＬ字型のガイドとを有する冶具を用いて、各積層物の貫通孔を位置決めピンに通しＬ字型のガイドに積層物の角を合わせるようにして積層を行った。積層体の体積は負極、正極およびセパレータの面積と厚み、使用した枚数から計算して求めた。また、同様に積層体の有する貫通孔の体積は負極、正極およびセパレータの厚みと貫通孔の面積、および使用した枚数から計算して求めた。これらの値を用いて計算した積層体の体積に対する貫通孔の体積比率は５．２％であった。幅５ｍｍ、長さ２０ｍｍ、厚み０．１ｍｍのアルミ製のタブを正極未塗布部に、同サイズのニッケル製のタブを負極未塗布部に、タブと集電体および集電体同士が電気的に接続されるように超音波溶接を行って一体化した。次に、２枚の７０ｍｍ×７０ｍｍのポリプロピレンとアルミ箔からなるアルミラミネートフィルムの三辺を熱融着により接着して作製した電池外装体の一辺の開口部から、タブが開口部から突出する向きで上記積層体を挿入した。各積層物の体積にその空孔率を乗じた値に貫通孔の体積（Ｖｈ）を加えることにより求めた積層体の総空孔体積（Ｖｔ）と同量の電解液を注液して減圧下にて含浸させた後、開口部を真空封止することで、積層型ラミネートセルからなるリチウム二次電池を作製した。 (Production of laminated battery)
Six, five, and ten negative electrodes, positive electrodes, and separators each having a through hole were prepared, and the negative electrode and the positive electrode were sequentially stacked via the separator so that the outermost layer of the laminate was the negative electrode. At that time, the uncoated portions of the positive electrode and the uncoated portions of the negative electrode were overlapped, and the uncoated portions of both electrodes were arranged so as to be located on the left and right of the laminate. These operations are carried out using a jig having a 6 mm diameter positioning pin and an L-shaped guide that is 1 mm smaller than the through-hole of the separator, and passing the through-hole of each laminate through the positioning pin to the L-shaped guide. Lamination was performed so that the corners were aligned. The volume of the laminate was calculated from the area and thickness of the negative electrode, positive electrode and separator, and the number of sheets used. Similarly, the volume of the through hole of the laminate was calculated from the thickness of the negative electrode, the positive electrode and the separator, the area of the through hole, and the number of the used holes. The volume ratio of the through holes to the volume of the laminate calculated using these values was 5.2%. An aluminum tab having a width of 5 mm, a length of 20 mm, and a thickness of 0.1 mm is applied to the positive electrode uncoated part, a nickel tab of the same size is applied to the negative electrode uncoated part, and the tab, the current collector and the current collector are electrically connected to each other. Were integrated by ultrasonic welding so that they were connected to each other. Next, the direction in which the tab protrudes from the opening from the opening on one side of the battery exterior body produced by bonding the three sides of the two 70 mm × 70 mm polypropylene and aluminum foils by heat-sealing The above laminate was inserted. The electrolyte was injected in the same amount as the total pore volume (Vt) of the laminate obtained by adding the volume of the through-hole (Vh) to the value obtained by multiplying the volume of each laminate by its porosity. After impregnating underneath, the opening was vacuum-sealed to produce a lithium secondary battery comprising a laminated laminate cell.

以上は、負極と正極とセパレータの貫通孔の直径がそれぞれ１１ｍｍ、１５ｍｍ、７ｍｍで、積層体と貫通孔の体積比率（Ｖｈ／Ｖｓ）が５．２％であって、積層体の総空孔体積(Ｖｔ)と電解液の体積(Ｖｌ)の比率（Ｖｌ／Ｖｔ）が１．０倍の場合の実施例である。同様に、負極と正極とセパレータの貫通孔の直径が、それぞれ８ｍｍ、１２ｍｍ、４ｍｍであって積層体と貫通孔の体積比率（Ｖｈ／Ｖｓ）が３．１％の場合、それぞれ１６ｍｍ、２０ｍｍ、１２ｍｍであってＶｈ／Ｖｓが９．９％の場合、それぞれ１６ｍｍ、２０ｍｍ、１２ｍｍであってＶｈ／Ｖｓが１４．９％の場合、それぞれ２４ｍｍ、２８ｍｍ、２０ｍｍであってＶｈ／Ｖｓが２０．９％の場合、また貫通孔がない各場合について、積層体の総空孔体積と電解液の体積比率（Ｖｌ／Ｖｔ）を１．０、１．１、１．２、１．４、１．６倍とした積層型ラミネート電池を作製した。   In the above, the diameters of the through holes of the negative electrode, the positive electrode, and the separator are 11 mm, 15 mm, and 7 mm, respectively, and the volume ratio (Vh / Vs) of the laminated body to the through holes is 5.2%. In this example, the ratio (Vl / Vt) of the volume (Vt) to the volume (Vl) of the electrolyte is 1.0 times. Similarly, when the diameters of the through holes of the negative electrode, the positive electrode, and the separator are 8 mm, 12 mm, and 4 mm, respectively, and the volume ratio (Vh / Vs) of the laminate to the through holes is 3.1%, 16 mm, 20 mm, When 12 mm and Vh / Vs is 9.9%, respectively 16 mm, 20 mm, and 12 mm and Vh / Vs is 14.9%, they are 24 mm, 28 mm, and 20 mm, respectively, and Vh / Vs is 20. In the case of 9% and no through-hole, the total void volume of the laminate and the volume ratio (Vl / Vt) of the electrolyte solution are 1.0, 1.1, 1.2, 1.4, 1 A laminated laminate battery having a magnification of 6 times was produced.

（測定方法）
１２０ｍＡの定電流で４．２Ｖまで充電した後、合計で５時間定電圧充電を行った。次に３．０Ｖまで定電流放電して初期放電容量を測定した。図４に、積層体と貫通孔の体積比率（Ｖｈ／Ｖｓ）に対するセル容量の相対比率、即ち貫通孔がない場合を１００％とした時の初期放電容量の相対値を示す。このときの積層体の総空孔体積に対する電解液の体積比率（Ｖｌ／Ｖｔ）は１．２倍である。貫通孔の体積比率（Ｖｈ／Ｖｓ）が大きいほど正極活物質量の減少により初期放電容量は減少する。初期放電容量の低下が２０％以上となると実用的ではなくなるため、積層体に対する貫通孔の体積比率は１５％以下とすることが望ましい。 (Measuring method)
After charging to 4.2 V with a constant current of 120 mA, constant voltage charging was performed for a total of 5 hours. Next, a constant current was discharged to 3.0 V, and an initial discharge capacity was measured. FIG. 4 shows the relative ratio of the cell capacity to the volume ratio (Vh / Vs) of the laminate and the through hole, that is, the relative value of the initial discharge capacity when the case where there is no through hole is 100%. At this time, the volume ratio (Vl / Vt) of the electrolytic solution to the total pore volume of the laminate is 1.2 times. The larger the volume ratio (Vh / Vs) of the through holes, the lower the initial discharge capacity due to the decrease in the amount of the positive electrode active material. When the decrease in the initial discharge capacity is 20% or more, it becomes impractical, so the volume ratio of the through holes to the laminate is preferably 15% or less.

次に、６００ｍＡの定電流で４．２Ｖまで充電した後、合計で２．５時間定電圧充電を行ってから、６００ｍＡで３．０Ｖまで定電流放電するという充放電の繰り返しを５００回行った。（背景技術で数千サイクル必要と記載されているので５００サイクルでも目安になることを断り書きしておいた方がよい）初期放電容量に対する５００サイクル後の放電容量の比率（％）を５００サイクル後容量維持率（％）として算出した。試験温度は加速試験条件として常温よりも高い４５℃とした。なお、電池の劣化は温度が高いほど加速され、４５℃の劣化は常温の劣化の数倍になると予想される。したがって、４５℃サイクルの５００サイクルは常温サイクルの１０００サイクル以上に相当すると考えられる。図５に、積層体と貫通孔の体積比率（Ｖｈ／Ｖｓ）が３．１％、５．２％、９．９％、１４．９％の各場合において、積層体の総空孔体積に対する電解液の体積比率（Ｖｌ／Ｖｔ）を１．０、１．１、１．２、１．４と変化させたときの５００サイクル後容量維持率（％）を示す。ここで、Ｖｌ／Ｖｔが１．６倍については、真空封止時に開口部から電解液が溢れ出てしまう不具合が発生し、また封止後のセルについても表面が凸凹状になる外観不良が発生したため不適等と判断して、サイクル特性の測定は行わなかった。Ｖｈ／Ｖｓが３％では十分な容量維持率は得られなかったが、Ｖｈ／Ｖｓを５％以上とし、積層体の総空孔体積と電解液の体積比率（Ｖｌ／Ｖｔ）を１．１倍以上とすることで良好なサイクル容量維持率が得られた。   Next, after charging to 4.2 V at a constant current of 600 mA, charging and discharging was repeated 500 times, in which constant voltage charging was performed for 2.5 hours in total, and then constant current discharging was performed to 600 V at 3.0 V. . (It is better to note that 500 cycles is a guideline because it is described that several thousand cycles are required in the background art) The ratio (%) of the discharge capacity after 500 cycles to the initial discharge capacity is 500 cycles It was calculated as a post capacity retention rate (%). The test temperature was 45 ° C., which is higher than normal temperature, as an accelerated test condition. Note that the deterioration of the battery is accelerated as the temperature increases, and the deterioration at 45 ° C. is expected to be several times the deterioration at normal temperature. Therefore, 500 cycles of 45 ° C. cycle is considered to correspond to 1000 cycles or more of normal temperature cycles. FIG. 5 shows that the volume ratio (Vh / Vs) of the laminate to the through holes is 3.1%, 5.2%, 9.9%, and 14.9% with respect to the total pore volume of the laminate. The capacity retention rate (%) after 500 cycles when the volume ratio (Vl / Vt) of the electrolytic solution is changed to 1.0, 1.1, 1.2, and 1.4 is shown. Here, when Vl / Vt is 1.6 times, there is a problem that the electrolyte overflows from the opening at the time of vacuum sealing, and also the appearance defect that the surface of the sealed cell becomes uneven. Since it occurred, it was judged to be inappropriate and the cycle characteristics were not measured. When Vh / Vs was 3%, a sufficient capacity retention rate was not obtained, but Vh / Vs was 5% or more, and the total void volume of the laminate and the volume ratio (Vl / Vt) of the electrolyte were 1.1. A good cycle capacity retention rate was obtained by setting it to be twice or more.

以上の結果から、初期の放電容量の減少を２０％以内に抑えつつ、液枯れによるサイクル劣化を防止するのに必要な電解液量を備え、かつセル作製時の不具合およびセルの外観不良等が発生しないようにするためには、積層体に対する貫通孔の体積比率が５％〜１５％で、積層体の総空孔体積に対する電解液の体積比率を１．１〜１．４倍とすると良いことがわかる。   From the above results, it is possible to provide the amount of electrolyte necessary to prevent cycle deterioration due to liquid depletion while suppressing the decrease in the initial discharge capacity to within 20%, and there are problems during cell fabrication and cell appearance defects. In order to avoid the occurrence, the volume ratio of the through holes to the laminate is 5% to 15%, and the volume ratio of the electrolytic solution to the total pore volume of the laminate is preferably 1.1 to 1.4 times. I understand that.

（比較例１）
負極と正極とセパレータの貫通孔の直径をそれぞれ２０ｍｍ、１６ｍｍ、１２ｍｍとして、積層体の総空孔体積と電解液の体積比率（Ｖｌ／Ｖｔ）を１．２倍とした以外は実施例と同様な方法にて積層型ラミネートセルを作製して、４５℃のサイクル特性を測定した。５００サイクル後容量維持率は、２０〜３０％と低い値であった。 (Comparative Example 1)
The diameter of the through hole of the negative electrode, the positive electrode, and the separator was 20 mm, 16 mm, and 12 mm, respectively, and the same as in the examples except that the total pore volume of the laminate and the volume ratio (Vl / Vt) of the electrolyte were 1.2 times A laminated laminate cell was prepared by a simple method, and the cycle characteristics at 45 ° C. were measured. The capacity retention rate after 500 cycles was as low as 20-30%.

（比較例２）
負極と正極とセパレータの貫通孔の直径をそれぞれ１６ｍｍ、１６ｍｍ、１２ｍｍとして、積層体の総空孔体積と電解液の体積比率（Ｖｌ／Ｖｔ）を１．２倍とした以外は実施例と同様な方法にて積層型ラミネートセルを作製して、４５℃のサイクル特性を測定した。５００サイクル後容量維持率は、４０〜６０％と低い値であった。セルによる容量維持率のバラツキも大きかった。 (Comparative Example 2)
The diameter of the through holes of the negative electrode, the positive electrode, and the separator was 16 mm, 16 mm, and 12 mm, respectively, and the same as in the examples except that the total pore volume of the laminate and the volume ratio (Vl / Vt) of the electrolyte were 1.2 times A laminated laminate cell was prepared by a simple method, and the cycle characteristics at 45 ° C. were measured. The capacity retention rate after 500 cycles was a low value of 40 to 60%. The variation in capacity maintenance rate by cell was also large.

比較例１、２で用いたセルを分解したところ、負極貫通孔の周囲にリチウム金属の析出が認められた。これは、負極貫通孔が正極貫通孔より大きいと、負極活物質層と対向しない正極活物質層が存在することになり、充電時にその正極活物質層から放出されるリチウムイオンの受け入れができずリチウム金属として析出したものと考えられる。同じ貫通孔のサイズであっても積層ずれの程度により、上記のようなリチウム金属の析出が引き起こされたものと考えられる。リチウム金属の析出による容量の損失、および電極間のショートや電極反応の不均一化により、サイクル劣化が大きくなったと考えられる。   When the cells used in Comparative Examples 1 and 2 were disassembled, lithium metal deposition was observed around the negative electrode through hole. This is because if the negative electrode through hole is larger than the positive electrode through hole, there will be a positive electrode active material layer that does not face the negative electrode active material layer, and lithium ions released from the positive electrode active material layer during charging cannot be accepted. It is thought that it precipitated as lithium metal. It is considered that the lithium metal deposition as described above was caused by the degree of stacking deviation even with the same through-hole size. It is considered that the cycle deterioration was increased due to the loss of capacity due to the deposition of lithium metal, the short between electrodes, and the non-uniformity of the electrode reaction.

（実施例２）
貫通孔を備える代わりに、正極側面に幅１２ｍｍ、長さ１６ｍｍの正極の切欠き部を設け、この正極の切欠き部に内包される位置に幅８ｍｍ、長さ１４ｍｍの負極の切欠き部を設け、この負極の切欠き部に内包される位置に幅４ｍｍ、長さ１２ｍｍのセパレータの切欠き部を設けた以外は、実施例１と同様にして積層型ラミネートセルを作製して、４５℃のサイクル特性を測定した。このときの積層体の体積に対する凹状の切欠き部の体積比率は６．０％であった。電解液量は、実施例と同様に計算した積層体の総空孔体積に対して１．２倍とした。５００サイクル後の容量維持率は８０％となり貫通孔と同等の結果が得られた。このことから、電極内部の貫通孔の中ではなく電極側面部の切欠き部と外装体とで囲まれる領域に電解液を収容しても同じ効果が得られることを確認した。 (Example 2)
Instead of providing a through hole, a positive electrode notch with a width of 12 mm and a length of 16 mm is provided on the side surface of the positive electrode, and a negative electrode notch with a width of 8 mm and a length of 14 mm is provided at a position enclosed by the notch of the positive electrode. A laminated laminate cell was prepared in the same manner as in Example 1 except that a separator cutout having a width of 4 mm and a length of 12 mm was provided at a position enclosed in the cutout portion of the negative electrode, The cycle characteristics of were measured. The volume ratio of the concave notch to the volume of the laminated body at this time was 6.0%. The amount of the electrolytic solution was 1.2 times the total pore volume of the laminate calculated in the same manner as in the example. The capacity retention after 500 cycles was 80%, and the same result as the through hole was obtained. From this, it was confirmed that the same effect can be obtained even if the electrolytic solution is accommodated in a region surrounded by the cutout portion of the side surface portion of the electrode and the exterior body, not in the through hole inside the electrode.

本発明の積層型のリチウム二次電池の積層構成を示す断面図。Sectional drawing which shows the laminated structure of the laminated type lithium secondary battery of this invention. 本発明の積層型リチウム二次電池の積層体に具備された連通孔の一例を示す平面図。The top view which shows an example of the communicating hole comprised in the laminated body of the laminated | stacked lithium secondary battery of this invention. 本発明の積層型リチウム二次電池の積層体に具備された凹状の切欠き部の一例を示す平面図。The top view which shows an example of the concave notch part comprised by the laminated body of the laminated | stacked lithium secondary battery of this invention. 積層体と貫通孔の体積比率（Ｖｈ／Ｖｓ）とセル容量の相対比率の関係を示す図。The figure which shows the relationship between the volume ratio (Vh / Vs) of a laminated body and a through-hole, and the relative ratio of cell capacity. 積層体の体積に対する貫通孔の体積比率（Ｖｈ／Ｖｓ）を３．１，５．２，９．９，１４．９％とした場合の、積層体の総空孔体積に対する電解液の体積比率と４５℃における５００サイクル後容量維持率（％）の関係を示す図。The volume ratio of the electrolyte to the total pore volume of the laminate when the volume ratio (Vh / Vs) of the through holes to the volume of the laminate is 3.1, 5.2, 9.9, 14.9% The figure which shows the relationship between the capacity maintenance rate (%) after 500 cycles at 45 ° C.

符号の説明Explanation of symbols

１ 負極活物質層
２ 正極活物質層
３ 負極集電体
４ 正極集電体
５ セパレータ
６ 負極貫通孔
７ 正極貫通孔
８ セパレータ貫通孔
１０ 連通孔
１１ 切欠き部 DESCRIPTION OF SYMBOLS 1 Negative electrode active material layer 2 Positive electrode active material layer 3 Negative electrode collector 4 Positive electrode collector 5 Separator 6 Negative electrode through-hole 7 Positive electrode through-hole 8 Separator through-hole 10 Communication hole 11 Notch

Claims (3)

正極と負極とがセパレータを介して交互に積層されてなる積層体と、該積層体を収容するラミネート外装体からなるリチウム二次電池において、正極と負極が切欠き部を有し、かつ前記セパレータを介して前記負極の切欠き部は前記正極の切欠き部よりも小さく、かつ負極の切欠き部は積層方向から見て正極の切欠き部の内側に収まる位置にあり、前記切欠き部には非水電解液が収容され、前記積層体の体積に対する前記積層体に形成されたすべての切欠き部の体積の比率が５％〜１５％であって、前記積層体内の総空孔体積に対して１．１〜１．４倍の前記非水電解液を収容することを特徴とするリチウム二次電池。 In a lithium secondary battery including a laminate in which a positive electrode and a negative electrode are alternately laminated via a separator, and a laminate outer body that accommodates the laminate, the positive electrode and the negative electrode have a notch, and the separator notch of the negative electrode through the above smaller than the cutout portion of the positive electrode, and the cutout portion of the negative electrode Ri position near that fits inside the notch of the positive electrode when viewed from the laminating direction, the notch Contains a non-aqueous electrolyte, the ratio of the volume of all the notches formed in the laminate to the volume of the laminate is 5% to 15%, and the total pore volume in the laminate Lithium secondary battery characterized by containing 1.1 to 1.4 times the non-aqueous electrolyte . 前記積層体中の前記正極の切欠き部と前記負極の切欠き部に挟まれるセパレータの部分に前記負極の切欠き部よりも小さい切欠き部を、積層方向から見て前記負極の切欠き部の内側に収まる位置に有することを特徴とする請求項１に記載のリチウム二次電池。   A notch portion of the negative electrode as viewed from the stacking direction is formed at a portion of the separator sandwiched between the notch portion of the positive electrode and the notch portion of the negative electrode in the laminate, as viewed from the stacking direction. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is located in a position that fits inside the battery. 前記積層体の負極、正極、セパレータの切欠き部が積層体の積層方向に連続して繋がっていることを特徴とする請求項２に記載のリチウム二次電池。   The lithium secondary battery according to claim 2, wherein the negative electrode, the positive electrode, and the notch of the separator of the laminate are continuously connected in the stacking direction of the laminate.
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