JP2008004441A - Lithium secondary battery, separator for lithium secondary battery, electrode for lithium secondary battery, nonaqueous electrolyte for lithium secondary battery, and armor for lithium secondary battery - Google Patents
Lithium secondary battery, separator for lithium secondary battery, electrode for lithium secondary battery, nonaqueous electrolyte for lithium secondary battery, and armor for lithium secondary battery Download PDFInfo
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- JP2008004441A JP2008004441A JP2006174189A JP2006174189A JP2008004441A JP 2008004441 A JP2008004441 A JP 2008004441A JP 2006174189 A JP2006174189 A JP 2006174189A JP 2006174189 A JP2006174189 A JP 2006174189A JP 2008004441 A JP2008004441 A JP 2008004441A
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- Prior art keywords
- fine particles
- separator
- secondary battery
- lithium secondary
- temperature
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Cell Separators (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Sealing Battery Cases Or Jackets (AREA)
Abstract
Description
本発明は、高温環境下においても安全なリチウム二次電池と、該リチウム二次電池を構成するための部材に関するものである。 The present invention relates to a lithium secondary battery that is safe even in a high temperature environment, and a member for constituting the lithium secondary battery.
非水電池の一種であるリチウムイオン電池は、エネルギー密度が高いという特徴から、携帯電話やノート型パーソナルコンピューターなどの携帯機器の電源として広く用いられている。携帯機器の高性能化に伴ってリチウムイオン電池の高容量化が更に進む傾向にあり、安全性の確保が重要となっている。 Lithium ion batteries, which are a type of non-aqueous battery, are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. As the performance of portable devices increases, the capacity of lithium ion batteries tends to increase further, and ensuring safety is important.
現行のリチウムイオン電池では、正極と負極の間に介在させるセパレータとして、例えば厚みが２０〜３０μｍ程度のポリオレフィン系の多孔性フィルムが使用されている。また、セパレータの素材としては、電池の熱暴走温度以下でセパレータの構成樹脂を溶融させて空孔を閉塞させ、これにより電池の内部抵抗を上昇させて短絡の際などに電池の安全性を向上させる所謂シャットダウン効果を確保するため、融点の低いポリエチレンが適用されることがある。 In the current lithium ion battery, as a separator interposed between a positive electrode and a negative electrode, for example, a polyolefin-based porous film having a thickness of about 20 to 30 μm is used. In addition, as separator material, the constituent resin of the separator is melted below the thermal runaway temperature of the battery to close the pores, thereby increasing the internal resistance of the battery and improving the safety of the battery in the event of a short circuit. In order to ensure the so-called shutdown effect, polyethylene having a low melting point may be applied.
ところで、こうしたセパレータとしては、例えば、多孔化と強度向上のために一軸延伸あるいは二軸延伸したフィルムが用いられている。このようなセパレータは、単独で存在する膜として供給されるため、作業性などの点で一定の強度が要求され、これを上記延伸によって確保している。しかし、このような延伸フィルムでは結晶化度が増大しており、シャットダウン温度も、電池の熱暴走温度に近い温度にまで高まっているため、電池の安全性確保のためのマージンが十分とは言い難い。 By the way, as such a separator, for example, a uniaxially stretched film or a biaxially stretched film is used for increasing the porosity and improving the strength. Since such a separator is supplied as a single film, a certain strength is required in terms of workability and the like, and this is ensured by the above stretching. However, with such a stretched film, the degree of crystallinity has increased, and the shutdown temperature has increased to a temperature close to the thermal runaway temperature of the battery. Therefore, it can be said that the margin for ensuring the safety of the battery is sufficient. hard.
また、上記延伸によってフィルムにはひずみが生じており、これが高温に曝されると、残留応力によって収縮が起こるという問題がある。収縮温度は、融点、すなわちシャットダウン温度と非常に近いところに存在する。このため、ポリオレフィン系の多孔性フィルムセパレータを使用するときには、充電異常時などに電池の温度がシャットダウン温度に達すると、電流を直ちに減少させて電池の温度上昇を防止しなければならない。空孔が十分に閉塞せず電流を直ちに減少できなかった場合には、電池の温度は容易にセパレータの収縮温度にまで上昇するため、内部短絡による発火の危険性があるからである。 Further, the film is distorted by the stretching, and there is a problem that when this is exposed to high temperature, shrinkage occurs due to residual stress. The shrinkage temperature is very close to the melting point, ie the shutdown temperature. For this reason, when a polyolefin-based porous film separator is used, when the battery temperature reaches the shutdown temperature in the case of abnormal charging, the current must be immediately decreased to prevent the battery temperature from rising. This is because if the pores are not sufficiently closed and the current cannot be reduced immediately, the battery temperature easily rises to the contraction temperature of the separator, and there is a risk of ignition due to an internal short circuit.
このような熱収縮による短絡を防ぐために、耐熱性の樹脂を用いた微多孔膜や不織布をセパレータとして用いる方法が提案されている。例えば特許文献１には、全芳香族ポリアミドの微多孔膜を用いたセパレータが、特許文献２にはポリイミド多孔膜を用いたセパレータが開示されている。また、特許文献３には、ポリアミド不織布を用いたセパレータ、特許文献４にはアラミド繊維を用いた不織布を基材としたセパレータ、特許文献５にはポロプロピレン（ＰＰ）不織布を用いたセパレータ、特許文献６にはポリエステル不織布を用いたセパレータに関する技術が開示されている。
In order to prevent such a short circuit due to heat shrinkage, a method using a microporous film or a nonwoven fabric using a heat-resistant resin as a separator has been proposed. For example, Patent Document 1 discloses a separator using a wholly aromatic polyamide microporous film, and
しかし、ポリアミドやポリイミドといった耐熱性の樹脂を用いた微多孔膜は高温での寸法安定性に優れ、薄型化が可能であるが高コストである。また、ポリアミドやアラミド繊維といった耐熱性の繊維を用いた不織布も、寸法安定性に優れるが、高コストである。更に、これらの耐熱性材料を用いたセパレータは、高温時に孔が閉塞するいわゆるシャットダウン特性を持たないために、外部短絡や内部短絡といった電池の温度が急激に上昇する異常時の安全性を十分に確保することができない。 However, a microporous film using a heat-resistant resin such as polyamide or polyimide is excellent in dimensional stability at high temperatures and can be thinned, but is expensive. Nonwoven fabrics using heat-resistant fibers such as polyamide and aramid fibers are also excellent in dimensional stability but are expensive. Furthermore, since the separators using these heat-resistant materials do not have a so-called shutdown characteristic that closes the holes at high temperatures, the safety at the time of abnormalities such as external short-circuits and internal short-circuits where the temperature of the battery suddenly rises is sufficient. It cannot be secured.
このような問題を解決する技術として、例えば、特許文献７には高温時に電解液の含有率が高くなるポリマーからなるセパレータが示されている。また、特許文献８には、マイクロカプセルなどの熱膨張性の粒子を含有するセパレータが提案されている。 As a technique for solving such a problem, for example, Patent Document 7 discloses a separator made of a polymer in which the content of the electrolytic solution becomes high at a high temperature. Patent Document 8 proposes a separator containing thermally expandable particles such as microcapsules.
しかしながら、特許文献７に記載の技術では、セパレータとして、電解液を含有するポリマーのフィルムを用いているために、強度の低下を招き易く、例えば、セパレータを薄くして電池を高容量化することが困難である。また、特許文献８に記載の技術では、セパレータ中の粒子の熱膨張が不可逆に起こるため、セパレータや電池の製造工程において、熱膨張が生じる温度以上での処理ができず、特に十分な乾燥を行う必要のあるリチウム二次電池においては、乾燥工程における温度管理を厳密に行わなければならないといった問題がある。 However, in the technique described in Patent Document 7, since a polymer film containing an electrolytic solution is used as the separator, the strength is likely to decrease. For example, the separator is thinned to increase the capacity of the battery. Is difficult. Further, in the technique described in Patent Document 8, since thermal expansion of particles in the separator occurs irreversibly, in the manufacturing process of the separator or battery, it is not possible to perform processing at a temperature higher than the temperature at which thermal expansion occurs, and particularly sufficient drying is performed. In the lithium secondary battery that needs to be performed, there is a problem that temperature control in the drying process must be strictly performed.
また、微多孔膜を用いずに、例えば特許文献９に記載されているようなゲル状の電解質を用いる方法についても検討されている。しかし、ゲル状電解質は、熱収縮性はないものの機械的強度が弱く、特に高温時の機械強度低下により短絡などが発生する可能性があり、さらに、シャットダウン機能が付与されていないために、特に円筒形や角形といった缶に封入された形態の電池などにおいては、安全性を十分に確保することができないといった問題がある。また、ゲル状電解質を用いる技術では、喩え、特許文献１０に記載されているように、その機械強度の確保のために粒子や繊維状物で補強した場合であっても、シャットダウン機能が付与されるわけではないので、やはり安全性に関する問題は生じることになる。 Further, a method using a gel electrolyte as described in, for example, Patent Document 9 without using a microporous membrane has been studied. However, the gel electrolyte is not heat-shrinkable, but its mechanical strength is weak, and a short circuit may occur due to a decrease in mechanical strength, particularly at high temperatures. In a battery in a form enclosed in a can such as a cylindrical shape or a rectangular shape, there is a problem that safety cannot be sufficiently ensured. Moreover, in the technique using a gel electrolyte, as described in Patent Document 10, a shutdown function is imparted even when reinforced with particles or fibrous materials to ensure its mechanical strength. As a result, safety issues still arise.
一方、特許文献１１には、基体となるポリフッ化ビニリデンなどの樹脂を含む溶液に、架橋されたＰＭＭＡなどの微粒子を分散させ、これを塗布・乾燥させることにより、多孔質樹脂膜の空隙内に架橋微粒子を保持させた、保液性に優れるセパレータを形成する技術が示されている。 On the other hand, in Patent Document 11, fine particles such as cross-linked PMMA are dispersed in a solution containing a resin such as polyvinylidene fluoride serving as a base, and this is applied and dried, so that the voids in the porous resin film are obtained. A technique for forming a separator that retains crosslinked fine particles and has excellent liquid retention is shown.
しかしながら、本発明者らの検討によれば、特許文献１１に開示の上記多孔質樹脂膜は、実質的には高分子ゲル電解質膜と同じであり、電解液を流通可能な細孔は形成されず、また、電解液により膨潤した架橋微粒子により、前記空隙も塞がれてしまうため、温度上昇に伴って電池の内部抵抗が上昇し電池の反応を阻害するいわゆるシャットダウン機能も有していないことが判明した。 However, according to the study by the present inventors, the porous resin membrane disclosed in Patent Document 11 is substantially the same as the polymer gel electrolyte membrane, and pores through which the electrolyte can flow are formed. In addition, since the voids are blocked by the crosslinked fine particles swollen by the electrolytic solution, the internal resistance of the battery rises with increasing temperature and does not have a so-called shutdown function that inhibits the battery reaction. There was found.
本発明は上記事情に鑑みてなされたものであり、その目的は、安全性や信頼性に優れたリチウム二次電池と、該リチウム二次電池を構成し得るセパレータ、電極、非水電解液および外装体を提供することにある。 The present invention has been made in view of the above circumstances, and the object thereof is a lithium secondary battery excellent in safety and reliability, and a separator, an electrode, a non-aqueous electrolyte, and a lithium secondary battery that can constitute the lithium secondary battery. It is to provide an exterior body.
上記目的を達成し得た本発明のリチウム二次電池は、少なくとも正極、負極、セパレータおよび非水電解液を、外装体内に配置してなり、非水電解液を吸収して膨潤することが可能であり、かつ温度の上昇により膨潤度が増大する微粒子（Ａ）を電池内に有し、上記微粒子（Ａ）が非水電解液と接触していることを特徴とするものである。 The lithium secondary battery of the present invention that has achieved the above-mentioned object has at least a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte arranged in the exterior body, and can absorb and swell the non-aqueous electrolyte. In addition, the battery has fine particles (A) whose degree of swelling increases as the temperature rises, and the fine particles (A) are in contact with a non-aqueous electrolyte.
また、少なくとも上記微粒子（Ａ）を含有するリチウム二次電池用セパレータ；少なくとも上記微粒子（Ａ）およびリチウムを吸蔵放出することのできる活物質を含有するリチウム二次電池用電極（正極または負極）；少なくとも上記微粒子（Ａ）を含有するリチウム二次電池用非水電解液；少なくとも上記微粒子（Ａ）が内面に付着しているリチウム二次電池用外装体；も、本発明に含まれる。 Further, a separator for a lithium secondary battery containing at least the fine particles (A); an electrode for a lithium secondary battery (positive electrode or negative electrode) containing at least the fine particles (A) and an active material capable of occluding and releasing lithium; A non-aqueous electrolyte for a lithium secondary battery containing at least the fine particles (A); an outer package for a lithium secondary battery having at least the fine particles (A) attached to the inner surface thereof are also included in the present invention.
本発明によれば、安全性や信頼性に優れたリチウム二次電池を提供することができる。 According to the present invention, a lithium secondary battery excellent in safety and reliability can be provided.
本発明のリチウム二次電池は、少なくとも、非水電解液（以下、単に「電解液」と略すことがある）を吸収して膨潤することが可能であり、かつ温度の上昇により膨潤度が増大する微粒子（Ａ）［以下、「膨潤性微粒子（Ａ）」という］を含有しており、該微粒子（Ａ）が、電池内で、非水電解液と接触している。 The lithium secondary battery of the present invention can swell by absorbing at least a non-aqueous electrolyte (hereinafter sometimes simply referred to as “electrolyte”), and the degree of swelling increases as the temperature rises. Fine particles (A) [hereinafter referred to as “swellable fine particles (A)”], and the fine particles (A) are in contact with the non-aqueous electrolyte in the battery.
本発明のリチウム二次電池が高温に曝されると、膨潤性微粒子（Ａ）における温度上昇に伴って膨潤度が増大する性質（以下、「熱膨潤性」という場合がある）により、膨潤性微粒子（Ａ）が電池内の電解液を吸収して膨潤する。そのため、電池内で放電に必要な電解液量が不足する所謂「液枯れ」の状態となるので、高温時には、電池内でのＬｉイオンの伝導性が著しく減少し、電池内でのＬｉイオンの伝導性が著しく減少する（すなわち、シャットダウン機能が発現する）ため、例えば短絡や過充電といった電池の異常発生時における安全性を向上させることができる。 When the lithium secondary battery of the present invention is exposed to a high temperature, the swelling degree increases as the temperature of the swellable fine particles (A) increases (hereinafter sometimes referred to as “thermal swellability”). The fine particles (A) swell by absorbing the electrolytic solution in the battery. As a result, the amount of electrolyte necessary for discharge in the battery is in a so-called “liquid withstand” state, and at high temperatures, the conductivity of Li ions in the battery is significantly reduced, and Li ions in the battery are reduced. Since the conductivity is remarkably reduced (that is, the shutdown function is manifested), for example, the safety when a battery abnormality such as a short circuit or overcharge occurs can be improved.
本発明の電池において、膨潤性微粒子（Ａ）は、電池内で非水電解液と直接接触していれば、その存在箇所は特に限定されない。例えば、セパレータ、電極（正極または負極）、または非水電解液が膨潤性微粒子（Ａ）を含有していてもよく、外装体の内面に膨潤性微粒子（Ａ）が付着していてもよい。また、例えば、本発明の電池が、外装体として所謂外装缶（電池缶）を有し、該外装缶の開口部が、樹脂製の封口体を用いて封口される態様の場合には、該封口体の内面側に、膨潤性微粒子（Ａ）が付着している態様であっても構わない。 In the battery of the present invention, the location of the swellable fine particles (A) is not particularly limited as long as they are in direct contact with the non-aqueous electrolyte in the battery. For example, a separator, an electrode (positive electrode or negative electrode), or a nonaqueous electrolytic solution may contain swellable fine particles (A), and the swellable fine particles (A) may adhere to the inner surface of the outer package. Further, for example, in the case where the battery of the present invention has a so-called exterior can (battery can) as an exterior body and the opening of the exterior can is sealed using a resin sealing body, It may be an embodiment in which the swellable fine particles (A) are attached to the inner surface side of the sealing body.
膨潤性微粒子（Ａ）としては、上記の熱膨潤性を示す温度が、７５〜１２５℃であることが好ましい。熱膨潤性を示す温度が高すぎると、電池内の活物質の熱暴走反応を十分に抑制できず、電池の安全性向上効果が十分に確保できないことがある。また、熱膨潤性を示す温度が低すぎると、通常の使用温度域における電池内でのリチウムイオンの伝導性が低くなりすぎて、機器の使用に支障をきたす場合が生じることがある。すなわち、本発明の電池では、電池内のＬｉイオンの伝導性が著しく減少する温度（所謂シャットダウン温度）をおよそ８０〜１３０℃の範囲とするため、膨潤性微粒子（Ａ）が温度上昇により熱膨潤性を示し始める温度は、７５〜１２５℃の範囲にあることが好ましい。 As the swellable fine particles (A), the temperature exhibiting the above-mentioned heat swellability is preferably 75 to 125 ° C. If the temperature exhibiting thermal swellability is too high, the thermal runaway reaction of the active material in the battery may not be sufficiently suppressed, and the battery safety improvement effect may not be sufficiently ensured. Moreover, when the temperature which shows heat swelling property is too low, the conductivity of the lithium ion in the battery in a normal use temperature range will become low too much, and it may cause trouble in use of an apparatus. That is, in the battery of the present invention, the temperature at which the conductivity of Li ions in the battery is remarkably reduced (so-called shutdown temperature) is in the range of about 80 to 130 ° C., so that the swellable fine particles (A) are thermally swollen due to the temperature rise. It is preferable that the temperature which starts showing the property is in the range of 75 to 125 ° C.
また、膨潤性微粒子（Ａ）としては、１２０℃において測定される、下記式で定義される膨潤度Ｂが、２以上であるものが好ましい。
Ｂ ＝ （Ｖ１／Ｖ０）−１ （１）
［上記式（１）中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃まで昇温させ、さらに前記温度（１２０℃）で１時間経過後における微粒子の体積（ｃｍ３）を意味する］
Further, as the swellable fine particles (A), those having a degree of swelling B defined by the following formula measured at 120 ° C. of 2 or more are preferable.
B = (V 1 / V 0 ) -1 (1)
[In the above formula (1), V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the non-aqueous electrolyte at 25 ° C., and V 1 is introduced into the non-aqueous electrolyte at 25 ° C. 24 hours later, the temperature of the non-aqueous electrolyte is raised to 120 ° C., and the volume of fine particles (cm 3 ) after 1 hour at the temperature (120 ° C.)]
上記のような膨潤度を有する膨潤性微粒子（Ａ）は、熱膨潤性を示し始める前記温度（７５〜１２５℃のいずれかの温度）を超えた環境下において、その膨潤度が大きく増大する。そのため、このような性質を有する膨潤性微粒子（Ａ）を含有する電池では、内部温度が特定の温度（例えば、上記の７５〜１２５℃）を超えた時点で、膨潤性微粒子（Ａ）が電池内の電解液を更に吸収して大きく膨張することにより、Ｌｉイオンの伝導性を著しく低下させるため、より確実に電池の安全性を確保することが可能となる。なお、上記式（１）で定義される膨潤性微粒子（Ａ）の膨潤度は、大きくなりすぎると電池の変形を発生させることもあり、１０以下であるのが望ましい。 The swelling degree of the swellable fine particles (A) having the above degree of swelling greatly increases in an environment exceeding the temperature (any one of 75 to 125 ° C.) at which the thermal swellability starts to be exhibited. Therefore, in the battery containing the swellable fine particles (A) having such properties, the swellable fine particles (A) are in the battery when the internal temperature exceeds a specific temperature (for example, 75 to 125 ° C.). By further absorbing the electrolyte inside and expanding greatly, the conductivity of Li ions is remarkably reduced, so that the safety of the battery can be ensured more reliably. The swelling degree of the swellable fine particles (A) defined by the above formula (1) may cause battery deformation if it becomes too large, and is preferably 10 or less.
上記式（１）で定義される膨潤性微粒子（Ａ）の具体的な測定は、以下の方法により行うことができる。予め電解液中に常温で２４時間浸漬したときの膨潤度、および１２０℃における上記式（１）で定義される膨潤度が分かっているバインダ樹脂の溶液またはエマルジョンに、膨潤性微粒子（Ａ）を混合してスラリーを調製し、これをＰＥＴシートやガラス板などの基材上にキャストしてフィルムを作製し、その質量を測定する。次にこのフィルムを常温（２５℃）の電解液中に２４時間浸漬して質量を測定し、更に電解液を１２０℃に加熱昇温させ、該温度で１時間後における質量を測定し、下記式（２）〜（８）によって膨潤度Ｂを算出する［なお、下記式（２）〜（８）は、常温から１２０℃までの昇温による電解液以外の成分の体積増加は無視できるものとしている］。 Specific measurement of the swellable fine particles (A) defined by the above formula (1) can be performed by the following method. The swellable fine particles (A) are added to a binder resin solution or emulsion in which the degree of swelling when immersed in an electrolytic solution at room temperature for 24 hours and the degree of swelling defined by the above formula (1) at 120 ° C. is known. A slurry is prepared by mixing, and this is cast on a substrate such as a PET sheet or a glass plate to produce a film, and its mass is measured. Next, the film was immersed in an electrolytic solution at room temperature (25 ° C.) for 24 hours, and the mass was measured. Further, the electrolytic solution was heated to 120 ° C., and the mass after 1 hour was measured at the temperature. The degree of swelling B is calculated by the formulas (2) to (8). [In the following formulas (2) to (8), the volume increase of components other than the electrolyte due to the temperature rise from room temperature to 120 ° C. can be ignored. It is said].
Ｖｉ ＝ Ｍｉ×Ｗ／ＰＡ （２）
ＶＢ ＝ （Ｍ０−Ｍｉ）／ＰＢ （３）
ＶＣ ＝ Ｍ１／Ｐｃ−Ｍ０／ＰＢ （４）
ＶＶ ＝ Ｍｉ×（１−Ｗ）／ＰＶ （５）
Ｖ０ ＝ Ｖｉ＋ＶＢ−ＶＶ×（ＢＢ＋１） （６）
ＶＤ ＝ ＶＶ×（ＢＢ＋１） （７）
Ｂ ＝ 〔｛Ｖ０＋ＶＣ−ＶＤ×（ＢＣ＋１）｝／Ｖ０〕−１ （８）
V i = M i × W / P A (2)
V B = (M 0 −M i ) / P B (3)
V C = M 1 / P c -M 0 / P B (4)
V V = M i × (1−W) / P V (5)
V 0 = V i + V B −V V × (B B +1) (6)
V D = V V × (B B +1) (7)
B = [{V 0 + V C −V D × (B C +1)} / V 0 ] −1 (8)
ここで、上記式（２）〜（８）中、
Ｖｉ：電解液に浸漬する前の膨潤性微粒子（Ａ）の体積（ｃｍ３）、
Ｖ０：電解液中に常温で２４時間浸漬後の膨潤性微粒子（Ａ）の体積（ｃｍ３）、
ＶＢ：電解液中に常温で２４時間浸漬後に、フィルムに吸収された電解液の体積（ｃｍ３）、
Ｖｃ：電解液中に常温に２４時間浸漬した時点から、電解液を１２０℃まで昇温させ、更に前記温度で１時間経過するまでの間に、フィルムに吸収された電解液の体積（ｃｍ３）、
ＶＶ：電解液に浸漬する前のバインダ樹脂の体積（ｃｍ３）、
ＶＤ：電解液中に常温で２４時間浸漬後のバインダ樹脂の体積（ｃｍ３）、
Ｍｉ：電解液に浸漬する前のフィルムの質量（ｇ）、
Ｍ０：電解液中に常温で２４時間浸漬後のフィルムの質量（ｇ）、
Ｍｌ：電解液中に常温で２４時間浸漬した後、電解液を１２０℃まで昇温させ、更に前記温度で１時間経過した後におけるフィルムの質量（ｇ）、
Ｗ：電解液に浸漬する前のフィルム中の膨潤性微粒子（Ａ）の質量比率、
ＰＡ：電解液に浸漬する前の膨潤性微粒子（Ａ）の比重（ｇ／ｃｍ３）、
ＰＢ：常温における電解液の比重（ｇ／ｃｍ３）、
ＰＣ：１２０℃での電解液の比重（ｇ／ｃｍ３）、
ＰＶ：電解液に浸漬する前のバインダ樹脂の比重（ｇ／ｃｍ３）、
ＢＢ：電解液中に常温で２４時間浸漬後のバインダ樹脂の膨潤度、
ＢＣ：上記（１）式で定義される昇温時のバインダ樹脂の膨潤度
である。
Here, in the above formulas (2) to (8),
V i : Volume (cm 3 ) of the swellable fine particles (A) before being immersed in the electrolytic solution,
V 0 : volume (cm 3 ) of swellable fine particles (A) after being immersed in an electrolytic solution at room temperature for 24 hours,
V B : volume of the electrolyte solution (cm 3 ) absorbed in the film after being immersed in the electrolyte solution at room temperature for 24 hours,
V c : The volume of the electrolytic solution absorbed by the film (cm) during the period from when the electrolytic solution was immersed in the electrolytic solution at room temperature for 24 hours until the electrolytic solution was heated to 120 ° C. and further passed for 1 hour at the above temperature. 3 ),
V V : volume (cm 3 ) of the binder resin before being immersed in the electrolytic solution,
V D : volume of the binder resin (cm 3 ) after being immersed in the electrolytic solution at room temperature for 24 hours,
M i : mass (g) of the film before being immersed in the electrolytic solution,
M 0 : mass (g) of the film after being immersed in the electrolytic solution at room temperature for 24 hours,
M l : After immersing in the electrolyte solution at room temperature for 24 hours, the electrolyte solution was heated to 120 ° C., and the mass (g) of the film after 1 hour at the above temperature,
W: Mass ratio of the swellable fine particles (A) in the film before being immersed in the electrolytic solution,
P A : Specific gravity (g / cm 3 ) of the swellable fine particles (A) before being immersed in the electrolytic solution,
P B : Specific gravity of electrolyte at room temperature (g / cm 3 ),
P C: electrolyte specific gravity at 120 ℃ (g / cm 3) ,
P V : Specific gravity (g / cm 3 ) of the binder resin before being immersed in the electrolytic solution,
B B : degree of swelling of the binder resin after being immersed in the electrolyte at room temperature for 24 hours,
B C : Swelling degree of the binder resin at the time of temperature rise defined by the above formula (1).
また、膨潤性微粒子（Ａ）は、下記式（９）で定義される常温（２５℃）における膨潤度ＢＲが、０以上１以下であることが好ましい。
ＢＲ ＝ （Ｖ０／Ｖｉ）−１ （９）
上記式（９）中、Ｖ０およびＶｉは、上記式（２）〜（８）について説明したものと同じである。
Also, swellable microparticles (A) is the swelling degree B R at room temperature (25 ° C.) which is defined by the following equation (9) is preferably 0 or more and 1 or less.
B R = (V 0 / V i ) -1 (9)
In the above formula (9), V 0 and V i are the same as those described for the above formulas (2) to (8).
すなわち、膨潤性微粒子（Ａ）は、常温においては、電解液を吸収しない（ＢＲ＝０）ものであっても、若干の電解液を吸収するものであってもよく、電池の通常使用温度範囲（例えば、７０℃以下）では、温度によらず電解液の吸収量があまり変化せず、従って膨潤度もあまり変化しないが、温度の上昇によって電解液の吸収量が大きくなり、膨潤度が増大するものであればよい。 That is, the swellable fine particles (A) may be those that do not absorb the electrolyte solution (B R = 0) or those that slightly absorb the electrolyte solution at normal temperature. In the range (for example, 70 ° C. or less), the absorption amount of the electrolytic solution does not change so much regardless of the temperature, and thus the degree of swelling does not change so much. It only needs to increase.
膨潤性微粒子（Ａ）としては、好ましくは上記膨潤度ＢやＢＲを満足しており、また、電気絶縁性を有しており、電気化学的に安定で、更に後述する電解液や、膨潤性微粒子（Ａ）を含有させる構成要素（セパレータ、電極など）の製造に液状組成物を用いる場合には、その溶媒に安定であり、高温状態で電解液に溶解しないものであれば、特に制限はない。なお、本明細書でいう「電気化学的に安定な」とは、電池の充放電の際に化学変化が生じないことを意味する。 The swellable particles (A), and preferably has satisfied the swelling degree B or B R, also has an electrically insulating, electrochemically stable, further described below electrolyte, swelling When a liquid composition is used for the production of components (separator, electrode, etc.) containing the conductive fine particles (A), it is particularly limited as long as it is stable to the solvent and does not dissolve in the electrolytic solution at a high temperature. There is no. As used herein, “electrochemically stable” means that no chemical change occurs during charging / discharging of the battery.
なお、従来公知のリチウム二次電池では、例えば、リチウム塩を有機溶媒に溶解した溶液が非水電解液として用いられている（リチウム塩や有機溶媒の種類、リチウム塩濃度などの詳細は、後記のリチウム二次電池の説明において記載する）。よって、膨潤性微粒子（Ａ）としては、リチウム塩の有機溶媒溶液中で、７５〜１２５℃のいずれかの温度に達した時に上記の熱膨潤性を示し始め、好ましくは該溶液中において膨潤度Ｂが上記の値を満足するように膨潤し得るものが推奨される。 In the known lithium secondary battery, for example, a solution in which a lithium salt is dissolved in an organic solvent is used as the non-aqueous electrolyte (details such as the type of lithium salt and the organic solvent, the lithium salt concentration are described later). Described in the description of the lithium secondary battery). Therefore, as the swellable fine particles (A), in the organic solvent solution of the lithium salt, when the temperature reaches any of 75 to 125 ° C., the above-mentioned thermal swellability starts to be exhibited. Those that can swell so that B satisfies the above values are recommended.
具体的な膨潤性微粒子（Ａ）の構成材料としては、例えば、樹脂架橋体が挙げられる。具体的には、ポリスチレン（ＰＳ）、アクリル樹脂、ポリアルキレンオキシド、フッ素樹脂、スチレンブタジエンゴム（ＳＢＲ）などやこれらの誘導体の架橋体；尿素樹脂；ポリウレタン；などが例示できる。膨潤性微粒子（Ａ）は、これらの構成材料のみで構成されていてもよく、電解液に対して安定な無機微粒子や有機微粒子［例えば、後記の微粒子（Ｃ）に該当する無機微粒子や有機微粒子など］をコアとし、上記の構成材料をシェルとして複合化したコアシェル構造の微粒子であってもよい。また、膨潤性微粒子（Ａ）は、上記の構成材料を１種単独で含有していてもよく、２種以上を含有していても構わない。更に、膨潤性微粒子（Ａ）は、構成成分として、上記の構成材料の他に、必要に応じて、樹脂に添加される公知の各種添加剤（例えば、酸化防止剤など）を含有していても構わない。 Specific examples of the constituent material of the swellable fine particles (A) include a crosslinked resin. Specific examples include polystyrene (PS), acrylic resin, polyalkylene oxide, fluorine resin, styrene butadiene rubber (SBR) and the like, and crosslinked products of these derivatives; urea resin; polyurethane; The swellable fine particles (A) may be composed of only these constituent materials, and are stable with respect to the electrolytic solution, such as inorganic fine particles and organic fine particles [for example, inorganic fine particles and organic fine particles corresponding to fine particles (C) described later] Etc.] may be used as a core, and fine particles having a core-shell structure in which the above-described constituent materials are combined as a shell may be used. Further, the swellable fine particles (A) may contain the above-mentioned constituent materials alone or in combination of two or more. Furthermore, the swellable fine particles (A) contain, as a constituent component, various known additives (for example, antioxidants) that are added to the resin, if necessary, in addition to the constituent materials described above. It doesn't matter.
上記の樹脂架橋体では、一旦温度上昇により膨張しても温度を下げることにより再び収縮するというように、温度変化に伴う体積変化に可逆性があり、また、これらの樹脂架橋体は、電解液を含まない所謂乾燥状態においては、熱膨張する温度よりも更に高い温度まで安定である。そのため、例えば、上記の樹脂架橋体で構成される膨潤性微粒子（Ａ）をセパレータや電極に含有させる場合には、セパレータの乾燥や電池作製の際の電極群の乾燥といった加熱プロセスを通しても、膨潤性微粒子（Ａ）の熱膨潤性が損なわれることはないため、こうした加熱プロセスでの取り扱いが容易となる。さらに、上記可逆性を有することにより、一旦、温度上昇によりシャットダウン機能が働いた場合であっても、電池内の温度低下により安全性が確保された場合は、再度電池として使用することも可能である。 In the above-mentioned resin cross-linked body, even if it expands due to a temperature rise once, the volume change accompanying the temperature change is reversible such that it shrinks again by lowering the temperature. In a so-called dry state that does not contain water, it is stable up to a temperature higher than the temperature of thermal expansion. Therefore, for example, when the swellable fine particles (A) composed of the above-mentioned crosslinked resin are contained in the separator or electrode, the swelling also occurs through a heating process such as drying of the separator or drying of the electrode group during battery production. Since the thermal swellability of the conductive fine particles (A) is not impaired, the handling in such a heating process becomes easy. Furthermore, by having the above reversibility, even if the shutdown function is activated once due to the temperature rise, it can be used again as the battery if the safety is ensured by the temperature drop in the battery. is there.
上記の構成材料の中でも、架橋ＰＳ、架橋アクリル樹脂［例えば、架橋ポリメチルメタクリレート（ＰＭＭＡ）］、架橋フッ素樹脂［例えば、架橋ポリフッ化ビニリデン（ＰＶＤＦ）］が好ましく、架橋ＰＭＭＡが特に好ましい。 Among the above-described constituent materials, crosslinked PS, crosslinked acrylic resin [for example, crosslinked polymethyl methacrylate (PMMA)] and crosslinked fluororesin [for example, crosslinked polyvinylidene fluoride (PVDF)] are preferable, and crosslinked PMMA is particularly preferable.
これら樹脂架橋体の微粒子が温度上昇により膨潤するメカニズムについては、詳細は明らかでないが、例えば架橋ＰＭＭＡでは、粒子の主体をなすＰＭＭＡのガラス転移点（Ｔｇ）が１００℃付近にあるため、ＰＭＭＡのＴｇ付近で架橋ＰＭＭＡ粒子が柔軟になって、より多くの電解液を吸収して膨潤するといったメカニズムが考えられる。従って、膨潤性微粒子（Ａ）のガラス転移点は、およそ７５〜１２５℃の範囲にあるものが望ましいと考えられる。 Although the details of the mechanism by which the fine particles of these resin crosslinked bodies swell due to temperature rise are not clear, for example, in crosslinked PMMA, the glass transition point (Tg) of PMMA, which is the main component of the particles, is around 100 ° C. It is conceivable that the cross-linked PMMA particles become flexible near Tg and absorb more electrolyte and swell. Therefore, it is considered that the glass transition point of the swellable fine particles (A) is preferably in the range of about 75 to 125 ° C.
本発明の電池に係る各構成要素に、膨潤性微粒子（Ａ）を含有させる場合には、それぞれ下記の含有量であることが好ましい。セパレータの場合には、例えば、２０体積％以上８０体積％以下であることが好ましい。電極（正極または負極）の場合には、例えば、正極合剤層中または負極剤層中、５体積％以上２０体積％以下であることが好ましい。非水電解液の場合には、例えば、１０体積％以上５０体積％以下であることが好ましい。外装体の場合には、例えば、内面に付着している膨潤性微粒子（Ａ）の総量と、電池内の非水電解液量の合計に対して、１０体積％以上５０体積％以上となるようにすることが好ましい。なお、リチウム二次電池として、本発明のセパレータ、電極、非水電解液、外装体のいずれか複数を組み合わせて用いる場合には、上記したそれぞれの含有量は更に少なくてもよく、例えば、電池内の非水電解液量と、電池内の膨潤性微粒子（Ａ）の総量の合計に対して、膨潤性微粒子（Ａ）の総量が、５体積％以上であればよく、また、２０体積％以下であることが好ましい。 When each constituent element according to the battery of the present invention contains the swellable fine particles (A), the following contents are preferable. In the case of a separator, for example, it is preferably 20% by volume or more and 80% by volume or less. In the case of an electrode (positive electrode or negative electrode), for example, it is preferably 5% by volume or more and 20% by volume or less in the positive electrode mixture layer or the negative electrode layer. In the case of a non-aqueous electrolyte, for example, it is preferably 10% by volume or more and 50% by volume or less. In the case of the exterior body, for example, the total amount of the swellable fine particles (A) adhering to the inner surface and the total amount of the non-aqueous electrolyte in the battery is 10% by volume or more and 50% by volume or more. It is preferable to make it. When the lithium secondary battery is used in combination with any one of the separator, electrode, non-aqueous electrolyte, and exterior body of the present invention, the respective contents described above may be further reduced. The total amount of the swellable fine particles (A) may be 5% by volume or more with respect to the total amount of the nonaqueous electrolyte solution in the battery and the total amount of the swellable fine particles (A) in the battery. The following is preferable.
膨潤性微粒子（Ａ）の大きさとしては、例えば、セパレータに含有させる場合であれば、その乾燥時における粒径がセパレータの厚みより小さければよいが、セパレータの厚みの１／３〜１／１００の平均粒径を有することが好ましい。また、膨潤性微粒子（Ａ）を電極に含有させる場合には、膨潤性微粒子（Ａ）の粒径は、電極の含有する活物質の粒径と同等以下であることが好ましい。更に、膨潤性微粒子（Ａ）を非水電解液に含有させる場合には、膨潤性微粒子（Ａ）は、非水電解液を電池内に注入するためのノズルなどが目詰まりを起こさない程度の粒径であることが好ましい。具体的には、膨潤性微粒子（Ａ）の平均粒径が、０．１〜２０μｍであることが好ましい。また、膨潤性微粒子（Ａ）が電池内のセパレータ、電極および非水電解液以外の箇所に存在する場合にも、その平均粒径は、０．１〜２０μｍであることが好ましい。なお、ここでいう膨潤性微粒子（Ａ）の平均粒径は、レーザー散乱粒度分布計（例えば、ＨＯＲＩＢＡ社製「ＬＡ−９２０」）を用い、微粒子を膨潤しない媒体（例えば水）に分散させて測定した数平均粒子径である。 As the size of the swellable fine particles (A), for example, in the case of inclusion in the separator, the particle size at the time of drying may be smaller than the thickness of the separator, but 1/3 to 1/100 of the thickness of the separator. It is preferable to have an average particle size of When the swellable fine particles (A) are contained in the electrode, the particle size of the swellable fine particles (A) is preferably equal to or less than the particle size of the active material contained in the electrode. Further, when the swellable fine particles (A) are contained in the non-aqueous electrolyte, the swellable fine particles (A) are such that the nozzle for injecting the non-aqueous electrolyte into the battery is not clogged. The particle size is preferred. Specifically, the average particle diameter of the swellable fine particles (A) is preferably 0.1 to 20 μm. Moreover, also when swellable microparticles | fine-particles (A) exist in locations other than the separator in a battery, an electrode, and a non-aqueous electrolyte, it is preferable that the average particle diameter is 0.1-20 micrometers. The average particle size of the swellable fine particles (A) here is determined by dispersing the fine particles in a non-swelling medium (for example, water) using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by HORIBA). The measured number average particle diameter.
本発明のセパレータは、膨潤性微粒子（Ａ）を有する多孔質膜であればよいが、具体的な態様としては、下記（１）〜（３）の態様が挙げられる。 Although the separator of this invention should just be a porous film which has swellable microparticles | fine-particles (A), the following aspects (1)-(3) are mentioned as a specific aspect.
（１）の態様に係るセパレータは、膨潤性微粒子（Ａ）が多数集合してセパレータを形成しているものである。この態様には、膨潤性微粒子（Ａ）と繊維状物（Ｂ）が均一に分散した状態でセパレータを形成している態様も含まれる。 The separator according to the aspect (1) is one in which a large number of swellable fine particles (A) are aggregated to form a separator. This embodiment includes an embodiment in which the separator is formed in a state where the swellable fine particles (A) and the fibrous material (B) are uniformly dispersed.
（２）の態様に係るセパレータは、繊維状物（Ｂ）が多数集合して、これらのみによりシート状物を形成しているもの、例えば織布、不織布（紙を含む）といった形態のものを用い、このシート状物中に膨潤性微粒子（Ａ）を含有させたものである。 The separator according to the aspect (2) is a separator in which a large number of fibrous materials (B) are assembled to form a sheet-like material only, for example, a woven fabric or a nonwoven fabric (including paper). Used, the sheet-like material contains swellable fine particles (A).
（３）の態様に係るセパレータは、従来公知の樹脂製多孔性フィルム中に、膨潤性微粒子（Ａ）を含有させたものである。なお、この態様でも、上記多孔性フィルムが、膨潤性微粒子（Ａ）と共に繊維状物（Ｂ）を含有していてもよい。多孔性フィルムを構成する樹脂としては、ポリオレフィン（ポリエチレン、ポリプロピレン、エチレン−プロピレン共重合体など）の他、ポリイミド、ポリアミドイミド、ポリサルフォン、ポリエーテルサルフォンなどの耐熱性の樹脂が挙げられる。 The separator according to the aspect (3) is one in which swellable fine particles (A) are contained in a conventionally known resinous porous film. In this embodiment, the porous film may contain the fibrous material (B) together with the swellable fine particles (A). Examples of the resin constituting the porous film include heat-resistant resins such as polyimide, polyamideimide, polysulfone, and polyethersulfone in addition to polyolefin (polyethylene, polypropylene, ethylene-propylene copolymer, etc.).
なお、（１）の態様のセパレータでは、製造後に残留するような応力を掛けない製法により製造できるため、残留応力が殆どまたは全くなく、熱収縮が生じないため、かかる点からも電池内で異常発熱した際の安全性をより向上させることができる。 In addition, since the separator of the aspect (1) can be manufactured by a manufacturing method that does not apply stress that remains after manufacturing, there is little or no residual stress, and heat shrinkage does not occur. The safety when heat is generated can be further improved.
また、（２）の態様のセパレータでも、特に繊維状物（Ｂ）が１５０℃で実質的に変形しない繊維状物（Ｂ）を含有させることで、１５０℃といった高温状態においても、セパレータの形状を安定に保つことが可能となる。そのため、例えば、従来のＰＥ製多孔性フィルムで構成されるセパレータで生じていた熱収縮に起因する短絡の発生が防止できることから、かかる点からも電池内で異常発熱した際の安全性を更に向上させることができる。なお、本発明でいう上記繊維状物における「１５０℃で実質的に変形しない」とは、上記繊維状物により構成され、セパレータを形成するためのシート状物の形態で、軟化などによる実質的な寸法変化が生じないことをいい、具体的には、１５０℃（またはそれ以下の温度）でのシート状物の長さの変化、すなわち室温での長さに対する収縮の割合（収縮率）が５％以下のものをいう。 In the separator of the aspect (2), the shape of the separator can be obtained even at a high temperature of 150 ° C., particularly when the fibrous material (B) contains a fibrous material (B) that does not substantially deform at 150 ° C. Can be kept stable. Therefore, for example, it is possible to prevent the occurrence of a short circuit due to thermal shrinkage that has occurred in separators composed of conventional PE porous films, which also improves safety when abnormal heat is generated in the battery. Can be made. The term “substantially not deformed at 150 ° C.” in the fibrous material referred to in the present invention means a sheet-like material that is composed of the fibrous material and forms a separator, and is substantially due to softening or the like. In particular, the change in the length of the sheet at 150 ° C. (or lower temperature), that is, the ratio of shrinkage to the length at room temperature (shrinkage rate) 5% or less.
また、（３）の態様のセパレータでも、上記例示の耐熱性の樹脂で構成されるものの場合には、電池が高温に曝されても、セパレータの熱収縮に起因する短絡の発生を防止できるため、高温時における電池の安全性を更に高めることができる。 In addition, in the case of the separator of the aspect (3), in the case where the separator is composed of the above exemplified heat resistant resin, even if the battery is exposed to a high temperature, it is possible to prevent the occurrence of a short circuit due to the thermal contraction of the separator. The safety of the battery at high temperatures can be further increased.
なお、（１）の態様と（２）の態様をあわせた形態、すなわち、繊維状物（Ｂ）で構成される独立したシート状物中に、繊維状物（Ｂ）と膨潤性微粒子（Ａ）が分散されている形態を有していてもよい。 In addition, in the form which combined the aspect of (1) and the aspect of (2), ie, the independent sheet-like thing comprised with a fibrous substance (B), fibrous substance (B) and swellable microparticles | fine-particles (A ) May be dispersed.
本発明の電池が有するセパレータでは、１５０℃での熱収縮率が１％以下であることが好ましく、このような熱収縮率を有する場合には、電池内が１５０℃程度になっても、セパレータの収縮が殆ど生じないため、正負極の接触による短絡が防止できることから、高温での電池の安全性が更に高めることができる。セパレータの上記態様のうち、（１）および（２）の態様、並びに耐熱性の樹脂で構成される（３）の態様のセパレータであれば、上記の熱収縮率を確保できる。 In the separator of the battery of the present invention, it is preferable that the heat shrinkage rate at 150 ° C. is 1% or less. When such a heat shrinkage rate is obtained, even if the inside of the battery reaches about 150 ° C., the separator Since the shrinkage of the battery hardly occurs, the short circuit due to the contact between the positive and negative electrodes can be prevented, so that the safety of the battery at a high temperature can be further improved. Among the above-described aspects of the separator, the above-described heat shrinkage rate can be secured if the separator is the aspect of (1) and (2) and the aspect of (3) composed of a heat-resistant resin.
また、本発明の電池が、本発明のセパレータでないセパレータ［膨潤性微粒子（Ａ）を含有しないセパレータ］を有している場合でも、このセパレータが、膨潤性微粒子（Ａ）の含有しない他は、上記（２）の態様と同じ態様のセパレータや、上記（３）の態様のうち、耐熱性の樹脂で構成されるものと同じ態様のセパレータである場合には、１５０℃での熱収縮率を１％以下にできるため、高温での電池の安全性を更に高めることができる。 In addition, even when the battery of the present invention has a separator that is not the separator of the present invention [a separator that does not contain the swellable fine particles (A)], this separator does not contain the swellable fine particles (A), In the case of the separator having the same aspect as the aspect of (2) above, or the separator having the same aspect as that of the heat resistant resin among the aspects of (3) above, the heat shrinkage rate at 150 ° C. is Since it can be made 1% or less, the safety of the battery at high temperatures can be further enhanced.
なお、セパレータにおける「１５０℃の熱収縮率」とは、セパレータを恒温槽に入れ、温度を１５０℃まで上昇させて３０分放置した後に取り出して、恒温槽に入れる前のセパレータの長さと比較することで求められる長さの減少割合を百分率で表したものである。 The “150 ° C. heat shrinkage rate” of the separator is compared with the length of the separator before putting the separator in a thermostatic bath, raising the temperature to 150 ° C., leaving it for 30 minutes, and putting it in the thermostatic bath. The percentage of decrease in length required by this is expressed as a percentage.
セパレータを構成する繊維状物（Ｂ）は、１５０℃で実質的に変形せず、電気絶縁性を有しており、電気化学的に安定で、更に下記に詳述する電解液や、セパレータ製造の際に使用する膨潤性微粒子（Ａ）を含有する液状組成物に用いる溶媒に安定であれば、特に制限はない。なお、本発明でいう「繊維状物」とは、アスペクト比［長尺方向の長さ／長尺方向に直交する方向の幅（直径）］が４以上のものを意味している。本発明に係る繊維状物（Ｂ）のアスペクト比は、１０以上であることが好ましい。 The fibrous material (B) constituting the separator is not substantially deformed at 150 ° C., has an electrical insulating property, is electrochemically stable, and further produces an electrolytic solution and a separator as described in detail below. If it is stable to the solvent used for the liquid composition containing the swellable fine particles (A) used in this case, there is no particular limitation. The “fibrous material” referred to in the present invention means that having an aspect ratio [length in the longitudinal direction / width (diameter) in a direction perpendicular to the longitudinal direction] of 4 or more. The aspect ratio of the fibrous material (B) according to the present invention is preferably 10 or more.
繊維状物（Ｂ）の具体的な構成材料としては、例えば、セルロース、セルロース変成体（カルボキシメチルセルロースなど）、ポリプロピレン（ＰＰ）、ポリエステル［ポリエチレンテレフタレート（ＰＥＴ）、ポリエチレンナフタレート（ＰＥＮ）、ポリブチレンテレフタレート（ＰＢＴ）など］、ポリアクリロニトリル（ＰＡＮ）、ポリアラミド、ポリアミドイミド、ポリイミドなどの樹脂；ガラス、アルミナ、シリカなどの無機材料（無機酸化物）；などが挙げられる。繊維状物（Ｂ）は、これらの構成材料の１種を含有していてもよく、２種以上を含有していても構わない。また、繊維状物（Ｂ）は、構成成分として、上記の構成材料の他に、必要に応じて、公知の各種添加剤（例えば、樹脂である場合には酸化防止剤など）を含有していても構わない。 Specific constituent materials of the fibrous material (B) include, for example, cellulose, modified cellulose (such as carboxymethyl cellulose), polypropylene (PP), polyester [polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene. Terephthalate (PBT), etc.], polyacrylonitrile (PAN), polyaramid, polyamideimide, polyimide and other resins; glass, alumina, silica and other inorganic materials (inorganic oxides); and the like. The fibrous material (B) may contain one kind of these constituent materials, or may contain two or more kinds. Further, the fibrous material (B) contains, as necessary, various known additives (for example, an antioxidant in the case of a resin) in addition to the above-described constituent materials. It doesn't matter.
繊維状物（Ｂ）の直径は、セパレータの厚み以下であれば良いが、例えば、０．０１〜５μｍであることが好ましい。径が大きすぎると、繊維状物同士の絡み合いが不足して、これらで構成されるシート状物の強度、延いてはセパレータの強度が小さくなって取り扱いが困難となることがある。また、径が小さすぎると、セパレータの空隙が小さくなりすぎて、イオン透過性が低下する傾向にあり、電池の負荷特性を低下させてしまうことがある。 Although the diameter of a fibrous material (B) should just be below the thickness of a separator, it is preferable that it is 0.01-5 micrometers, for example. If the diameter is too large, the entanglement between the fibrous materials may be insufficient, and the strength of the sheet-like material constituted by these, and consequently the strength of the separator may be reduced, making it difficult to handle. On the other hand, if the diameter is too small, the gap of the separator becomes too small, and the ion permeability tends to be lowered, and the load characteristics of the battery may be lowered.
セパレータの（２）の態様における繊維状物（Ｂ）の含有量は、全構成成分中、例えば、１０体積％以上、より好ましくは３０体積％以上であって、９０体積％以下、より好ましくは８０体積％以下であることが望ましい。セパレータ（シート状物）中での繊維状物（Ｂ）の存在状態は、例えば、長軸（長尺方向の軸）の、セパレータ面に対する角度が平均で３０°以下であることが好ましく、２０°以下であることがより好ましい。 The content of the fibrous material (B) in the aspect (2) of the separator is, for example, 10% by volume or more, more preferably 30% by volume or more and 90% by volume or less, more preferably, in all the constituent components. It is desirable that it is 80 volume% or less. For example, the state of the fibrous material (B) in the separator (sheet-like material) is preferably such that the angle of the long axis (axis in the longitudinal direction) with respect to the separator surface is 30 ° or less on average, 20 More preferably, it is not more than 0 °.
また、本発明のセパレータでは、（１）〜（３）のいずれの態様によらず、本発明のセパレータでは、膨潤性微粒子（Ａ）および繊維状物（Ｂ）以外にも、無機微粒子（Ｃ）や熱溶融性微粒子（Ｄ）を含有していてもよい。このような無機微粒子（Ｃ）および熱溶融性微粒子（Ｄ）としては、電気絶縁性を有しており、電気化学的に安定で、更に電解液や、セパレータ製造の際に使用する膨潤性微粒子（Ａ）を含有する液状組成物に用いる溶媒に安定であり、また、電池の作動電圧範囲において酸化還元といった副反応しない微粒子であればよい。 Further, in the separator of the present invention, regardless of any of the aspects (1) to (3), in the separator of the present invention, in addition to the swellable fine particles (A) and the fibrous material (B), inorganic fine particles (C ) Or heat-meltable fine particles (D). Such inorganic fine particles (C) and heat-meltable fine particles (D) have electrical insulating properties, are electrochemically stable, and are further swellable fine particles used in the production of electrolytes and separators. Any fine particles that are stable to the solvent used in the liquid composition containing (A) and do not undergo side reactions such as oxidation-reduction in the operating voltage range of the battery may be used.
無機微粒子（Ｃ）（無機粉末）の具体例としては、例えば、酸化鉄、ＳｉＯ２、Ａｌ２Ｏ３、ＴｉＯ２、ＢａＴｉＯ２、ＺｒＯなどの酸化物微粒子；窒化アルミニウム、窒化ケイ素などの窒化物微粒子；フッ化カルシウム、フッ化バリウム、硫酸バリウムなどの難溶性のイオン結晶微粒子；シリコン、ダイヤモンドなどの共有結合性結晶微粒子；モンモリロナイトなどの粘土微粒子；ベーマイト、ゼオライト、アパタイト、カオリン、ムライト、スピネル、オリビンなどの鉱物資源由来物質あるいはこれらの人造物；などが挙げられる。また、金属微粒子；ＳｎＯ２、スズ−インジウム酸化物（ＩＴＯ）などの酸化物微粒子；カーボンブラック、グラファイトなどの炭素質微粒子；などの導電性微粒子の表面を、電気絶縁性を有する材料［例えば、上記の無機微粒子（Ｃ）を構成する材料など］で表面処理することで、電気絶縁性を持たせた微粒子であってもよい。上記の無機微粒子の中でも、Ａｌ２Ｏ３、ＳｉＯ２、ベーマイトが好ましい。 Specific examples of the inorganic fine particles (C) (inorganic powder) include, for example, oxide fine particles such as iron oxide, SiO 2 , Al 2 O 3 , TiO 2 , BaTiO 2 , and ZrO; nitrides such as aluminum nitride and silicon nitride Fine particles; refractory ionic crystal fine particles such as calcium fluoride, barium fluoride, and barium sulfate; Covalent crystal fine particles such as silicon and diamond; clay fine particles such as montmorillonite; boehmite, zeolite, apatite, kaolin, mullite, spinel, And materials derived from mineral resources such as olivine or artificial products thereof. Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO 2 and tin-indium oxide (ITO); carbonaceous fine particles such as carbon black and graphite; Fine particles imparted with electrical insulation properties by surface treatment with the above-described materials constituting the inorganic fine particles (C)] may be used. Among the above inorganic fine particles, Al 2 O 3 , SiO 2 and boehmite are preferable.
無機微粒子（Ｃ）の形状としては、例えば、所謂球状に近い形状であってもよく、板状であってもよい。より好ましくは、板状の粒子である。代表的なものとしては、板状のＡｌ２Ｏ３や板状のベーマイトなどが挙げられる。 The shape of the inorganic fine particles (C) may be, for example, a so-called spherical shape or a plate shape. More preferably, it is a plate-like particle. Typical examples include plate-like Al 2 O 3 and plate-like boehmite.
板状の無機微粒子（Ｃ）の場合には、これをセパレータに含有させる際に特定の手法（後述する）を採用することにより、板状面をセパレータの面と平行に配向させることができる。セパレータ内において板状の無機微粒子（Ｃ）を上記のように配向させた場合には、リチウムデンドライトによる突き刺しや電極表面の活物質の突起による突き刺しを、より効果的に防ぐことができる。板状粒子の場合には、そのアスペクト比（板状粒子中の最大長さと板状粒子の厚みの比）は、例えば、５〜１００であることが好ましい。 In the case of the plate-like inorganic fine particles (C), the plate-like surface can be oriented parallel to the surface of the separator by adopting a specific method (described later) when this is contained in the separator. When the plate-like inorganic fine particles (C) are oriented in the separator as described above, the puncture by the lithium dendrite and the puncture by the active material projection on the electrode surface can be more effectively prevented. In the case of plate-like particles, the aspect ratio (ratio of the maximum length in the plate-like particles to the thickness of the plate-like particles) is preferably 5 to 100, for example.
なお、無機微粒子（Ｃ）は、上記の例示のものを１種単独で使用してもよく、２種以上を併用してもよい。 As the inorganic fine particles (C), those exemplified above may be used singly or in combination of two or more.
熱溶融性微粒子（Ｄ）としては、８０〜１３０℃で融解するもの、すなわち、ＪＩＳ Ｋ ７１２１の規定に準じて、示差走査熱量計（ＤＳＣ）を用いて測定される融解温度が８０〜１３０℃であるものが好的である。具体的な熱溶融性微粒子（Ｄ）の構成材料としては、ポリエチレン（ＰＥ）、エチレン由来の構造単位が８５モル％以上の共重合ポリオレフィン、またはポリオレフィン誘導体（塩素化ポリエチレンなど）、ポリオレフィンワックス、石油ワックス、カルナバワックスなどが挙げられる。上記共重合ポリオレフィンとしては、エチレン−ビニルモノマー共重合体、より具体的には、エチレン−酢酸ビニル共重合体（ＥＶＡ）、エチレン−メチルアクリレート共重合体、またはエチレン−エチルアクリレート共重合体が例示できる。また、ポリシクロオレフィンなどを用いることもできる。熱溶融性微粒子（Ｄ）は、これらの構成材料の１種のみを有していてもよく、２種以上を有していても構わない。これらの中でも、ＰＥ、ポリオレフィンワックス、またはエチレン由来の構造単位が８５モル％以上のＥＶＡが好適である。また、熱溶融性微粒子（Ｄ）は、構成成分として、上記の構成材料の他に、必要に応じて、樹脂に添加される公知の各種添加剤（例えば、酸化防止剤など）を含有していても構わない。 The heat-meltable fine particles (D) are those that melt at 80 to 130 ° C., that is, the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121 is 80 to 130 ° C. What is is preferred. Specific constituent materials of the heat-meltable fine particles (D) include polyethylene (PE), a copolymerized polyolefin having a structural unit derived from ethylene of 85 mol% or more, or a polyolefin derivative (such as chlorinated polyethylene), polyolefin wax, petroleum Examples thereof include wax and carnauba wax. Examples of the copolymer polyolefin include an ethylene-vinyl monomer copolymer, more specifically, an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl acrylate copolymer, or an ethylene-ethyl acrylate copolymer. it can. Moreover, polycycloolefin etc. can also be used. The heat-meltable fine particles (D) may have only one kind of these constituent materials, or may have two or more kinds. Among these, PE, polyolefin wax, or EVA having a structural unit derived from ethylene of 85 mol% or more is preferable. Further, the heat-meltable fine particles (D) contain, as a constituent component, various known additives (for example, antioxidants) that are added to the resin as necessary in addition to the constituent materials described above. It doesn't matter.
また、本発明のセパレータは、上記例示の無機微粒子（Ｃ）をコアとし、上記例示の熱溶融性微粒子（Ｄ）を構成し得る樹脂をシェルとして複合化したコアシェル構造の複合微粒子（Ｅ）を含有していてもよい。 In addition, the separator of the present invention includes core-shell composite fine particles (E) in which the above-exemplified inorganic fine particles (C) are used as a core and a resin capable of constituting the above-described exemplary hot-melt fine particles (D) is used as a shell. You may contain.
上記の無機微粒子（Ｃ）は、セパレータ中に含有されることで、該セパレータの形状安定性（特に高温時における形状安定性）向上に寄与し得る。また、無機微粒子（Ｃ）が特に板状粒子である場合には、上記の通り、リチウムデンドライトや活物質表面の突起による突き刺しに起因する短絡を防止する効果の向上も期待できる。更に、セパレータが熱溶融性微粒子（Ｄ）やコアシェル構造の複合微粒子（Ｅ）を含有することで、該セパレータを有する電池において、内部の温度が上昇した場合に、熱溶融性微粒子（Ｄ）自体や複合微粒子（Ｅ）のシェル部分が溶融してセパレータの空隙を塞いてイオンの移動を遮断するため、膨潤性微粒子（Ａ）の上記効果と相まって、高温時における電池の安全性をより向上させることができる。 When the inorganic fine particles (C) are contained in the separator, they can contribute to improving the shape stability (particularly, shape stability at high temperatures) of the separator. In addition, when the inorganic fine particles (C) are particularly plate-like particles, as described above, an improvement in the effect of preventing a short circuit due to piercing by protrusions on the surface of the lithium dendrite or the active material can be expected. Further, when the separator contains the heat-meltable fine particles (D) and the core-shell structured fine particles (E), when the internal temperature rises in the battery having the separator, the heat-meltable fine particles (D) itself In addition, the shell part of the composite fine particles (E) melts to block the gaps in the separator and block the movement of ions, and therefore, combined with the above effect of the swellable fine particles (A), further improves the safety of the battery at high temperatures. be able to.
本発明のセパレータにおいて、熱溶融性微粒子（Ｄ）および／または複合微粒子（Ｅ）の含有量は、セパレータの全構成成分中、５〜４０体積％であることが好ましい。これらの微粒子の含有量が少なすぎると、これらを含有させることによるシャットダウン効果が小さくなることがあり、多すぎると、高温時の形状安定性が低下し、電池の高温時における安全性確保に支障をきたす場合がある。また、セパレータにおける無機微粒子（Ｃ）の含有量は、全構成成分中、例えば２０〜６０体積％であることが好ましい。無機微粒子（Ｃ）の含有量が少なすぎると、リチウムデンドライトや活物質の突起による突き刺しに起因する短絡を防止する効果が小さくなることがあり、多すぎると、膨潤性微粒子（Ａ）や熱溶融性微粒子（Ｄ）の含有量が少なくなるため、電池の高温時におけるＬｉイオン伝導性を低下させる効果が弱くなり、安全性を確保しづらくなることがある。 In the separator of the present invention, the content of the heat-meltable fine particles (D) and / or the composite fine particles (E) is preferably 5 to 40% by volume in all the constituent components of the separator. If the content of these fine particles is too small, the shutdown effect due to the inclusion of these may be reduced, and if too large, the shape stability at high temperatures is reduced, which hinders the safety of the battery at high temperatures. May result. Moreover, it is preferable that content of the inorganic fine particle (C) in a separator is 20-60 volume% in all the structural components, for example. If the content of the inorganic fine particles (C) is too small, the effect of preventing a short circuit due to the piercing by the protrusion of the lithium dendrite or the active material may be reduced. If the content is too large, the swellable fine particles (A) or heat melting may occur. Since the content of the conductive fine particles (D) is reduced, the effect of lowering the Li ion conductivity at a high temperature of the battery is weakened, and it may be difficult to ensure safety.
無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）および複合微粒子（Ｅ）の粒径としては、膨潤性微粒子（Ａ）と同じ測定法で測定される数平均粒子径で、例えば、０．００１μｍ以上、より好ましくは０．１μｍ以上であって、１５μｍ以下、より好ましくは１μｍ以下であることが推奨される。 The particle diameters of the inorganic fine particles (C), the hot-melt fine particles (D), and the composite fine particles (E) are the number average particle diameters measured by the same measurement method as the swellable fine particles (A), for example, 0.001 μm. As described above, it is recommended that the thickness is 0.1 μm or more, 15 μm or less, and more preferably 1 μm or less.
また、繊維状物（Ｂ）同士をシート状物とするために結着したり、繊維状物（Ｂ）で構成されるシート状物と膨潤性微粒子（Ａ）やその他の粒子［無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）］などとを結着したりする目的で、セパレータはバインダ（Ｆ）を含有していてもよい。 In addition, the fibrous materials (B) are bound to form a sheet-like material, or the sheet-like material composed of the fibrous material (B) and the swellable fine particles (A) and other particles [inorganic fine particles ( The separator may contain a binder (F) for the purpose of binding C), heat-meltable fine particles (D), composite fine particles (E)] and the like.
バインダ（Ｆ）としては、電気化学的に安定且つ電解液に対して安定で、更に膨潤性微粒子（Ａ）や繊維状物（Ｂ）、無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）などを良好に接着できるものであれば良いが、例えば、ＥＶＡ（酢酸ビニル由来の構造単位が２０〜３５モル％のもの）、エチレン−エチルアクリレート共重合体などのエチレン−アクリレート共重合体、フッ素系ゴム、ＳＢＲ、カルボキシメチルセルロース（ＣＭＣ）、ヒドロキシエチルセルロース（ＨＥＣ）、ポリビニルアルコール（ＰＶＡ）、ポリビニルブチラール（ＰＶＢ）、ポリビニルピロリドン（ＰＶＰ）、ポリウレタン、エポキシ樹脂などが挙げられ、これらを単独で使用してもよく、２種以上を併用しても構わない。なお、これらバインダ（Ｆ）を使用する場合には、後記するセパレータ形成用の液状組成物の溶媒に溶解するか、または分散させたエマルジョンの形態で用いることができる。 As the binder (F), it is electrochemically stable and stable with respect to the electrolytic solution. Further, the swellable fine particles (A), the fibrous material (B), the inorganic fine particles (C), the heat-meltable fine particles (D), The composite fine particles (E) or the like may be used as long as they can be satisfactorily adhered. For example, EVA (with a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylate such as ethylene-ethyl acrylate copolymer Copolymer, fluorine rubber, SBR, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, epoxy resin, etc. May be used alone or in combination of two or more. When these binders (F) are used, they can be used in the form of an emulsion dissolved or dispersed in a solvent of a liquid composition for forming a separator described later.
なお、例えば、熱溶融性微粒子（Ｄ）や複合微粒子（Ｅ）が単独で接着性を有する場合には、これらがバインダ（Ｆ）を兼ねることもできる。 For example, when the heat-meltable fine particles (D) and the composite fine particles (E) have adhesiveness alone, they can also serve as the binder (F).
電池の短絡防止効果をより高め、セパレータの強度を確保して取り扱い性を良好にしつつ、電池のエネルギー密度をより高める観点から、セパレータの厚みは、例えば、３μｍ以上、より好ましくは５μｍ以上であって、５０μｍ以下、より好ましくは３０μｍ以下であることが望ましい。 The thickness of the separator is, for example, 3 μm or more, more preferably 5 μm or more, from the viewpoint of further improving the battery short-circuit prevention effect, ensuring the separator strength and improving the handleability while further improving the energy density of the battery. Therefore, it is desirable that it is 50 μm or less, more preferably 30 μm or less.
また、セパレータの空隙率としては、乾燥した状態で、例えば、２０％以上、より好ましくは３０％以上であって、７０％以下、より好ましくは６０％以下であることが望ましい。セパレータの空隙率が小さすぎると、イオン透過性が小さくなることがあり、また、空隙率が大きすぎると、セパレータの強度が不足することがある。なお、セパレータの空隙率：Ｐ（％）は、セパレータの厚み、面積あたりの質量、構成成分の密度から、次式を用いて各成分ｉについての総和を求めることにより計算できる。
Ｐ ＝ Σ ａｉρｉ ／（ｍ／ｔ）
ここで、上記式中、ａｉ：質量％で表した成分ｉの比率、ρｉ：成分ｉの密度（ｇ／ｃｍ３）、ｍ：セパレータの単位面積あたりの質量（ｇ／ｃｍ２）、ｔ：セパレータの厚み（ｃｍ）である。
In addition, the porosity of the separator is, for example, 20% or more, more preferably 30% or more, and preferably 70% or less, more preferably 60% or less in a dry state. If the porosity of the separator is too small, the ion permeability may be reduced, and if the porosity is too large, the strength of the separator may be insufficient. The porosity of the separator: P (%) can be calculated by calculating the sum of each component i from the thickness of the separator, the mass per area, and the density of the constituent components using the following formula.
P = Σ a i ρ i / (m / t)
Here, in the above formula, a i : ratio of component i expressed by mass%, ρ i : density of component i (g / cm 3 ), m: mass per unit area of separator (g / cm 2 ), t: The thickness (cm) of the separator.
なお、常温で電解液中に２４時間浸漬し、膨潤性微粒子（Ａ）が膨潤した後のセパレータの空隙率は、１０％以上であることが好ましい。 In addition, it is preferable that the porosity of the separator after being immersed in an electrolyte solution at room temperature for 24 hours and swelling the swellable fine particles (A) is 10% or more.
また、本発明のセパレータは、ＪＩＳ Ｐ ８１１７に準拠した方法で行われ、０．８７９ｇ／ｍｍ２の圧力下で１００ｍｌの空気が膜を透過する秒数で示されるガーレー値が、１０〜３００ｓｅｃであることが望ましい。透気度が大きすぎると、イオン透過性が小さくなり、他方、小さすぎると、セパレータの強度が小さくなることがある。更に、セパレータの強度としては、直径１ｍｍのニードルを用いた突き刺し強度で５０ｇ以上であることが望ましい。かかる突き刺し強度が小さすぎると、リチウムのデンドライト結晶が発生した場合に、セパレータの突き破れによる短絡が発生する場合がある。 The separator of the present invention is performed by a method in accordance with JIS P 8117, and the Gurley value indicated by the number of seconds that 100 ml of air passes through the membrane under a pressure of 0.879 g / mm 2 is 10 to 300 sec. It is desirable to be. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the separator may be reduced. Further, the strength of the separator is desirably 50 g or more in terms of piercing strength using a needle having a diameter of 1 mm. If the piercing strength is too small, a short circuit may occur due to the piercing of the separator when lithium dendrite crystals are generated.
本発明のセパレータの製造方法としては、例えば、下記の（I）〜（III）の方法が採用できる。（I）の方法は、１５０℃で実質的に変形しないイオン透過性のシート状物に、膨潤性微粒子（Ａ）を含む液状組成物（スラリーなど）を塗布または含浸させた後、所定の温度で乾燥する製造方法である。（I）の方法によって、（２）の態様のセパレータを製造することができる。 As a manufacturing method of the separator of the present invention, for example, the following methods (I) to (III) can be employed. In the method (I), a liquid composition (slurry or the like) containing swellable fine particles (A) is applied to or impregnated into an ion-permeable sheet-like material that does not substantially deform at 150 ° C. It is a manufacturing method to dry with. By the method (I), the separator according to the embodiment (2) can be produced.
すなわち、（I）の方法でいう「シート状物」には、繊維状物（Ｂ）で構成されたシート状物（各種織布、不織布など）が該当する。具体的には、上記例示の各材料を構成成分に含む繊維状物の少なくとも１種で構成される織布や、これら繊維状物同士が絡み合った構造を有する不織布などの多孔質シートなどが挙げられる。より具体的には、紙、ＰＰ不織布、ポリエステル不織布（ＰＥＴ不織布、ＰＥＮ不織布、ＰＢＴ不織布など）、ＰＡＮ不織布などの不織布などが例示できる。 That is, the “sheet-like material” referred to in the method (I) corresponds to a sheet-like material (various woven fabrics, non-woven fabrics, etc.) composed of the fibrous material (B). Specifically, a woven fabric composed of at least one type of fibrous material containing each of the exemplified materials as a constituent component, a porous sheet such as a nonwoven fabric having a structure in which these fibrous materials are entangled with each other, and the like. It is done. More specifically, non-woven fabrics such as paper, PP non-woven fabric, polyester non-woven fabric (PET non-woven fabric, PEN non-woven fabric, PBT non-woven fabric, etc.) and PAN non-woven fabric can be exemplified.
本発明のセパレータを形成するための上記液状組成物は、膨潤性微粒子（Ａ）や、必要に応じて、無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）、バインダ（Ｆ）などを含有し、これらを溶媒（分散媒を含む、以下同じ）に分散させたものである［バインダ（Ｆ）については溶解していてもよい］。液状組成物に用いられる溶媒は、膨潤性微粒子（Ａ）や無機微状粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）を均一に分散でき、また、バインダ（Ｆ）を均一に溶解または分散できるものであれば良いが、例えば、トルエンなどの芳香族炭化水素；テトラヒドロフランなどのフラン類；メチルエチルケトン、メチルイソブチルケトンなどのケトン類；などの有機溶媒が好適である。なお、これらの溶媒に、界面張力を制御する目的で、アルコール（エチレングリコール、プロピレングリコールなど）、または、モノメチルアセテートなどの各種プロピレンオキサイド系グリコールエーテルなどを適宜添加しても良い。また、バインダ（Ｆ）が水溶性である場合、エマルジョンとして使用する場合などでは、水を溶媒としてもよく、この際にもアルコール類（メチルアルコール、エチルアルコール、イソプロピルアルコール、エチレングリコールなど）を適宜加えて界面張力を制御することもできる。 The liquid composition for forming the separator of the present invention comprises swellable fine particles (A), and if necessary, inorganic fine particles (C), hot-melt fine particles (D), composite fine particles (E), binders ( F) and the like, and these are dispersed in a solvent (including a dispersion medium, the same applies hereinafter) [the binder (F) may be dissolved]. The solvent used in the liquid composition can uniformly disperse the swellable fine particles (A), the inorganic fine particles (C), the hot-melt fine particles (D), and the composite fine particles (E), and the binder (F). Organic solvents such as aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; are suitable as long as they can be dissolved or dispersed uniformly. In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the binder (F) is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) are appropriately used. In addition, the interfacial tension can be controlled.
上記液状組成物では、膨潤性微粒子（Ａ）、無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）、バインダ（Ｆ）を含む固形分含量を、例えば１０〜４０質量％とすることが好ましい。 In the liquid composition, the solid content including swellable fine particles (A), inorganic fine particles (C), hot-melt fine particles (D), composite fine particles (E), and binder (F) is, for example, 10 to 40% by mass. It is preferable that
上記シート状物が、紙、ＰＰ不織布、ポリエステル不織布などの不織布のように、繊維状物（Ｂ）で構成されるものであって、特にその空隙の開口径が比較的大きい場合（例えば、空隙の開口径が５μｍ以上の場合）には、これが電池の短絡の要因となりやすい。よって、この場合には、膨潤性微粒子（Ａ）の一部または全部がシート状物の空隙内に存在する構造とすることが好ましい。また、膨潤性微粒子（Ａ）以外の微粒子［無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）］の一部または全部が、シート状物の空隙内に存在する構造とすることがより好ましい。このような構造とすることで、膨潤性微粒子（Ａ）以外の微粒子を用いることによる効果［無機微粒子（Ｃ）であれば、セパレータの形状安定性の向上効果、熱溶融性微粒子（Ｄ）や複合微粒子（Ｅ）であればシャットダウン効果］がより有効に発揮されるようになる。シート状物の空隙内に膨潤性微粒子（Ａ）や無機微粒子（Ｃ）、熱溶融性微粒子（Ｄ）、複合微粒子（Ｅ）を存在させるには、例えば、上記した液状組成物をシート状物に含浸させた後、一定のギャップを通し、余分の液状組成物を除去した後、乾燥するなどの工程を用いればよい。 When the sheet-like material is composed of a fibrous material (B), such as a nonwoven fabric such as paper, PP nonwoven fabric, and polyester nonwoven fabric, and the opening diameter of the void is relatively large (for example, void This is likely to cause a short circuit of the battery. Therefore, in this case, it is preferable to have a structure in which part or all of the swellable fine particles (A) are present in the voids of the sheet-like material. In addition, a structure in which part or all of fine particles other than the swellable fine particles (A) [inorganic fine particles (C), hot-melt fine particles (D), composite fine particles (E)] are present in the voids of the sheet-like material More preferably. By adopting such a structure, the effect of using fine particles other than the swellable fine particles (A) [in the case of inorganic fine particles (C), the effect of improving the shape stability of the separator, the hot-melt fine particles (D) and If the composite fine particles (E) are used, the shutdown effect] is more effectively exhibited. In order to allow the swellable fine particles (A), inorganic fine particles (C), hot-melt fine particles (D), and composite fine particles (E) to exist in the voids of the sheet-like material, for example, the above-mentioned liquid composition is used as the sheet-like material. After the impregnation, a process such as drying after removing a surplus liquid composition through a certain gap may be used.
なお、セパレータ中において、無機微粒子（Ｃ）が板状の場合に、その配向性を高めて、板状の無機微粒子（Ｃ）を用いることによる上記効果をより有効に発揮させるためには、上記液状組成物を含浸させたシート状物において、該液状組成物にシェアをかければよい。例えば、（I）の製造方法においては、無機微粒子（Ｃ）などをシート状物の空隙内に存在させる方法として上述した液状組成物をシート状物に含浸させた後、一定のギャップを通す方法により、液状組成物にシェアをかけることが可能であり、無機微粒子（Ｃ）の配向性を高めることができる。また、液状組成物の溶媒を乾燥により除去することでも、板状の無機微粒子（Ｃ）の配向性を高めることが可能である。 In the separator, when the inorganic fine particles (C) are in the form of a plate, in order to enhance the orientation and more effectively exert the above-described effects by using the plate-like inorganic fine particles (C), In the sheet-like material impregnated with the liquid composition, it is sufficient to share the liquid composition. For example, in the production method (I), as a method for causing the inorganic fine particles (C) and the like to be present in the voids of the sheet-like material, the above-mentioned liquid composition is impregnated into the sheet-like material, and then a certain gap is passed through. Thus, it is possible to share the liquid composition, and the orientation of the inorganic fine particles (C) can be improved. Also, the orientation of the plate-like inorganic fine particles (C) can be improved by removing the solvent of the liquid composition by drying.
また、膨潤性微粒子（Ａ）、無機微粒子（Ｃ）、熱溶融性粒子（Ｄ）および複合微粒子（Ｅ）のそれぞれの持つ効果をより有効に発揮させるために、それぞれの粒子を偏在させて、セパレータの面に平行方向に集まった形態としてもよい。このような形態とするには、例えば、ダイコーターやリバースロールコーターのヘッドやロールを２つ用いて、シート状物の裏表両方向から別々の塗料、例えば、膨潤性微粒子（Ａ）を主体とした液状組成物と無機微粒子（Ｃ）を主体とした液状組成物を別々に塗布し、乾燥する方法が採用できる。 Further, in order to more effectively exert the respective effects of the swellable fine particles (A), inorganic fine particles (C), heat-meltable particles (D) and composite fine particles (E), the respective particles are unevenly distributed, It is good also as a form which gathered in the direction parallel to the surface of a separator. In order to achieve such a form, for example, using two heads and rolls of a die coater or a reverse roll coater, separate paints, for example, swellable fine particles (A) are mainly used from both the front and back sides of the sheet-like material. A method in which a liquid composition and a liquid composition mainly composed of inorganic fine particles (C) are separately applied and dried can be employed.
本発明のセパレータの（II）の製造方法は、上記液状組成物に、更に必要に応じて繊維状物（Ｂ）を含有させ、これをフィルムや金属箔などの基材上に塗布し、所定の温度で乾燥した後に、該基材から剥離する方法である。（II）の方法によって、（１）の態様のセパレータを製造することができる。なお、（II）の方法で使用する液状組成物は、繊維状物（Ｂ）を含有させることが必須である点を除き、（I）の方法で用いる液状組成物と同じであり、繊維状物（Ｂ）を含めた固形分量が、例えば１０〜４０質量％であることが好ましい。また、（II）の方法によって、電池を構成する正極または負極の少なくとも一方の表面にセパレータを形成し、セパレータと電極を一体化した構造としてもよい。 In the separator (II) production method of the present invention, the liquid composition further contains a fibrous material (B) as necessary, and this is applied onto a substrate such as a film or metal foil, In this method, the substrate is dried at a temperature of 1, and then peeled off from the substrate. By the method of (II), the separator of the aspect of (1) can be manufactured. The liquid composition used in the method (II) is the same as the liquid composition used in the method (I) except that it is essential to contain the fibrous material (B). The solid content including the product (B) is preferably 10 to 40% by mass, for example. Moreover, it is good also as a structure which formed the separator in the surface of at least one of the positive electrode or negative electrode which comprises a battery, and integrated the separator and the electrode by the method of (II).
（III）の製造方法は、上記（３）の態様のセパレータを製造する方法であるが、膨潤性微粒子（Ａ）や繊維状物（Ｂ）、その他の微粒子を配合しつつ、従来公知の製法で多孔性フィルムを製造する方法が採用できる。 The production method (III) is a method for producing the separator according to the above aspect (3), and a conventionally known production method while incorporating the swellable fine particles (A), fibrous materials (B), and other fine particles. A method for producing a porous film can be employed.
なお、本発明のセパレータは、上記に示した各構造に限定されるものではない。例えば、膨潤性微粒子（Ａ）は、個々に独立して存在していてもよく、互いに、または繊維状物（Ｂ）に、一部が融着されていても構わない。もしくは、膨潤性微粒子（Ａ）と無機微粒子（Ｃ）を複合化した状態で用いてもよい。膨潤性微粒子（Ａ）と無機微粒子（Ｃ）の複合粒子は、ホソカワミクロン社製の「メカノフュージョン」、奈良製作所製の「ハイブリダイザー」、スプレードライヤー、ボールミル、振動ミルといった従来公知の装置を用いて作製することができる。 In addition, the separator of this invention is not limited to each structure shown above. For example, the swellable fine particles (A) may be present individually and may be partially fused to each other or to the fibrous material (B). Alternatively, the swellable fine particles (A) and the inorganic fine particles (C) may be used in a composite state. The composite particles of the swellable fine particles (A) and the inorganic fine particles (C) are obtained by using conventionally known devices such as “Mechanofusion” manufactured by Hosokawa Micron, “Hybridizer” manufactured by Nara Seisakusho, spray dryer, ball mill, and vibration mill. Can be produced.
本発明のリチウム二次電池を構成するためのセパレータとしては、膨潤性微粒子（Ａ）を含有する上記本発明のセパレータを用いることができるが、リチウム二次電池のセパレータ以外の構成要素が膨潤性微粒子（Ａ）を含有している場合には、膨潤性微粒子（Ａ）を含有しないセパレータを用いてもよい。なお、膨潤性微粒子（Ａ）を含有しないセパレータは、膨潤性微粒子（Ａ）を含有しないことを除き、本発明のセパレータと同じ構成とすることができる。 As the separator for constituting the lithium secondary battery of the present invention, the separator of the present invention containing the swellable fine particles (A) can be used, but components other than the lithium secondary battery separator are swellable. When the fine particles (A) are contained, a separator that does not contain the swellable fine particles (A) may be used. In addition, the separator which does not contain swellable microparticles | fine-particles (A) can be set as the same structure as the separator of this invention except not containing swellable microparticles | fine-particles (A).
本発明の電極のうち、正極としては、膨潤性微粒子（Ａ）を含有すること以外は、従来公知のリチウム二次電池に用いられている正極、すなわち、Ｌｉを吸蔵放出可能な活物質を含有する正極であれば特に制限はない。例えば、活物質として、Ｌｉ１＋ｘＭＯ２（−０．１＜ｘ＜０．１、Ｍ：Ｃｏ、Ｎｉ、Ｍｎなど）で表されるリチウム含有遷移金属酸化物；ＬｉＭｎ２Ｏ４などのリチウムマンガン酸化物；ＬｉＭｎ２Ｏ４のＭｎの一部を他元素で置換したＬｉＭｎｘＭ（１−ｘ）Ｏ２；オリビン型ＬｉＭＰＯ４（Ｍ：Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅ）；ＬｉＭｎ０．５Ｎｉ０．５Ｏ２；Ｌｉ（１＋ａ）ＭｎｘＮｉｙＣｏ（１−ｘ−ｙ）Ｏ２(−０．１＜ａ＜０．１、０＜ｘ＜０．５、０＜ｙ＜０．５）；などを適用することが可能であり、これらの正極活物質に公知の導電助剤（カーボンブラックなどの炭素材料など）やポリフッ化ビニリデン（ＰＶＤＦ）などの結着剤、更には膨潤性微粒子（Ａ）などを適宜添加した正極合剤を、集電体を芯材として成形体（すなわち、正極合剤層）に仕上げたものなどを用いることができる。 Among the electrodes of the present invention, the positive electrode contains a positive electrode used in a conventionally known lithium secondary battery, that is, an active material capable of occluding and releasing Li, except that the positive electrode contains swellable fine particles (A). If it is a positive electrode which does, there will be no restriction | limiting in particular. For example, as an active material, lithium-containing transition metal oxide represented by Li 1 + x MO 2 (−0.1 <x <0.1, M: Co, Ni, Mn, etc.); lithium manganese such as LiMn 2 O 4 Oxide; LiMn x M (1-x) O 2 in which part of Mn of LiMn 2 O 4 is substituted with another element; olivine type LiMPO 4 (M: Co, Ni, Mn, Fe); LiMn 0.5 Ni 0.5 O 2 ; Li (1 + a) Mn x Ni y Co (1-xy) O 2 (−0.1 <a <0.1, 0 <x <0.5, 0 <y <0. 5); can be applied to these positive electrode active materials, binders such as known conductive assistants (carbon materials such as carbon black) and polyvinylidene fluoride (PVDF), and swelling properties. A positive electrode mixture to which fine particles (A) and the like are appropriately added is used as a current collector. Shaped body as a core material (i.e., positive electrode mixture layer) such as those finished can be used.
正極の集電体としては、アルミニウムなどの金属の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、厚みが１０〜３０μｍのアルミニウム箔が好適に用いられる。 As the current collector of the positive electrode, a metal foil such as aluminum, a punching metal, a net, an expanded metal, or the like can be used. Usually, an aluminum foil having a thickness of 10 to 30 μm is preferably used.
正極合剤層中の膨潤性微粒子（Ａ）の含有量としては、上記の通り、５体積％以上２０体積％以下であることが好ましい。また、正極合剤層では、正極活物質の含有量は、５０〜９５体積％、導電助剤の含有量は、１〜１０体積％、バインダの含有量は、１〜１０体積％であることが好ましい。 As described above, the content of the swellable fine particles (A) in the positive electrode mixture layer is preferably 5% by volume or more and 20% by volume or less. In the positive electrode mixture layer, the content of the positive electrode active material is 50 to 95% by volume, the content of the conductive additive is 1 to 10% by volume, and the content of the binder is 1 to 10% by volume. Is preferred.
正極側のリード部は、通常、正極作製時に、集電体の一部に正極合剤層を形成せずに集電体の露出部を残し、そこをリード部とすることによって設けられる。ただし、リード部は必ずしも当初から集電体と一体化されたものであることは要求されず、集電体にアルミニウム製の箔などを後から接続することによって設けてもよい。 The lead portion on the positive electrode side is normally provided by leaving the exposed portion of the current collector without forming the positive electrode mixture layer on a part of the current collector and forming the lead portion at the time of producing the positive electrode. However, the lead portion is not necessarily integrated with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.
本発明の電極のうち、負極としては、膨潤性微粒子（Ａ）を含有すること以外は、従来公知のリチウム二次電池に用いられている負極、すなわち、Ｌｉを吸蔵放出可能な活物質を含有する負極であれば特に制限はない。例えば、活物質として、黒鉛、熱分解炭素類、コークス類、ガラス状炭素類、有機高分子化合物の焼成体、メソカーボンマイクロビーズ（ＭＣＭＢ）、炭素繊維などの、リチウムを吸蔵、放出可能な炭素系材料の１種または２種以上の混合物が用いられる。また、Ｓｉ，Ｓｎ、Ｇｅ，Ｂｉ，Ｓｂ、Ｉｎなどの元素およびその合金、リチウム含有窒化物、または酸化物などのリチウム金属に近い低電圧で充放電できる化合物、もしくはリチウム金属やリチウム／アルミニウム合金も負極活物質として用いることができる。これらの負極活物質に導電助剤（カーボンブラックなどの炭素材料など）やＰＶＤＦなどの結着剤、更には膨潤性微粒子（Ａ）などを適宜添加した負極合剤を、集電体を芯材として成形体（負極合剤層）に仕上げたものや、上記の各種合金やリチウム金属の箔を単独、若しくは集電体上に形成したものなどの負極剤層を有するものが用いられる。 Among the electrodes of the present invention, the negative electrode contains a negative electrode used in a conventionally known lithium secondary battery, that is, an active material capable of occluding and releasing Li, except that it contains swellable fine particles (A). If it is a negative electrode to perform, there will be no restriction | limiting in particular. For example, carbon that can occlude and release lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers as active materials One type or a mixture of two or more types of system materials is used. In addition, elements such as Si, Sn, Ge, Bi, Sb, In and their alloys, lithium-containing nitrides, oxides and other compounds that can be charged and discharged at a low voltage close to lithium metal, or lithium metals and lithium / aluminum alloys Can also be used as a negative electrode active material. A negative electrode mixture obtained by appropriately adding a conductive additive (carbon material such as carbon black), a binder such as PVDF, and further swellable fine particles (A) to these negative electrode active materials, and a current collector as a core material As such, those having a negative electrode material layer such as those formed into a molded body (negative electrode mixture layer) or those formed from the above-mentioned various alloys and lithium metal foils alone or on a current collector are used.
なお、負極が上記の負極合剤層を有する場合には、膨潤性微粒子（Ａ）は、負極合剤層中に含有させればよいが、例えば、負極が、上記の各種合金やリチウム金属の箔を単独、若しくは集電体上に形成したものなどの場合には、これら負極活物質に係る負極剤層の表面に、膨潤性微粒子（Ａ）を付着させればよい。負極剤層表面に、膨潤性微粒子（Ａ）を付着させる方法としては、例えば、膨潤性微粒子（Ａ）を、バインダ［例えば、セパレータに係るバインダ（Ｆ）の具体例として例示した各種樹脂・ゴムなど］と共に、溶剤に分散させたスラリーなどを調製し、これを負極剤層表面にスプレー塗布などする方法が挙げられる。上記の膨潤性微粒子（Ａ）含有スラリーには、必要に応じて、分散を高めるための分散助剤や、粘度を調整するための増粘剤などを加えてもよい。 In addition, when a negative electrode has said negative electrode mixture layer, what is necessary is just to contain swellable microparticles | fine-particles (A) in a negative electrode mixture layer, For example, a negative electrode is said various alloys and lithium metal. When the foil is used alone or formed on a current collector, the swellable fine particles (A) may be attached to the surface of the negative electrode agent layer related to these negative electrode active materials. As a method for attaching the swellable fine particles (A) to the surface of the negative electrode agent layer, for example, the swellable fine particles (A) are used as binders [for example, various resins and rubbers exemplified as specific examples of the binder (F) related to separators]. Etc.] and a slurry dispersed in a solvent is prepared, and this is sprayed onto the surface of the negative electrode layer. If necessary, the above-mentioned swellable fine particle (A) -containing slurry may contain a dispersion aid for enhancing dispersion, a thickener for adjusting viscosity, and the like.
負極に集電体を用いる場合には、集電体としては、銅製やニッケル製の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、銅箔が用いられる。この負極集電体は、高エネルギー密度の電池を得るために負極全体の厚みを薄くする場合、厚みの上限は３０μｍであることが好ましく、また、下限は５μｍであることが望ましい。 When a current collector is used for the negative electrode, a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used as the current collector, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm.
負極剤層中の膨潤性微粒子（Ａ）の含有量としては、上記の通り、５体積％以上２０体積％以下であることが好ましい。また、負極合剤層では、負極活物質の含有量は、７０〜９９体積％、導電助剤の含有量は、１〜１０体積％、バインダの含有量は、１〜１０体積％であることが好ましい。 As described above, the content of the swellable fine particles (A) in the negative electrode agent layer is preferably 5% by volume or more and 20% by volume or less. In the negative electrode mixture layer, the content of the negative electrode active material is 70 to 99% by volume, the content of the conductive additive is 1 to 10% by volume, and the content of the binder is 1 to 10% by volume. Is preferred.
負極側のリード部も、正極側のリード部と同様に、通常、負極作製時に、集電体の一部に負極剤層（負極活物質を有する層、負極合剤層を含む）を形成せずに集電体の露出部を残し、そこをリード部とすることによって設けられる。ただし、この負極側のリード部は必ずしも当初から集電体と一体化されたものであることは要求されず、集電体に銅製の箔などを後から接続することによって設けてもよい。 As with the lead portion on the negative electrode side, the negative electrode layer (including a layer having a negative electrode active material and a negative electrode mixture layer) is usually formed on a part of the current collector during the preparation of the negative electrode. Without leaving the exposed portion of the current collector, it is provided as a lead portion. However, the lead portion on the negative electrode side is not necessarily integrated with the current collector from the beginning, and may be provided by connecting a copper foil or the like to the current collector later.
なお、本発明のリチウム二次電池では、電極以外の構成要素が膨潤性微粒子（Ａ）を有している場合には、電極は、膨潤性微粒子（Ａ）を含有していなくでもよい。また、電極の一方が膨潤性微粒子（Ａ）を含有している場合には、他方の電極は膨潤性微粒子（Ａ）を含有していなくてもよい。膨潤性微粒子（Ａ）を含有しない正極または負極は、膨潤性微粒子（Ａ）を含有しないことを除き、本発明の正極または負極と同じ構成が採用できる。 In the lithium secondary battery of the present invention, when the component other than the electrode has the swellable fine particles (A), the electrode may not contain the swellable fine particles (A). When one of the electrodes contains swellable fine particles (A), the other electrode may not contain the swellable fine particles (A). The positive electrode or negative electrode that does not contain the swellable fine particles (A) can employ the same configuration as the positive electrode or negative electrode of the present invention except that it does not contain the swellable fine particles (A).
本発明の電池に係る電極は、正極と負極とを、セパレータを介して積層した積層体や、更にこれを巻回した電極巻回体の形態で用いることができる。 The electrode according to the battery of the present invention can be used in the form of a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, or an electrode wound body in which this is wound.
非水電解液としては、上述したように、リチウム塩を有機溶媒に溶解した溶液が用いられる。リチウム塩としては、溶媒中で解離してＬｉ＋イオンを形成し、電池として使用される電圧範囲で分解などの副反応を起こさないものであれば特に制限は無い。例えば、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６ 、ＬｉＳｂＦ６ などの無機リチウム塩；ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ２）２〔ここでＲｆはフルオロアルキル基〕などの有機リチウム塩；などを用いることができる。 As described above, a solution obtained by dissolving a lithium salt in an organic solvent is used as the nonaqueous electrolytic solution. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li + ions and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, inorganic lithium salts such as LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 ; LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (n ≧ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group]; it can.
電解液に用いる有機溶媒としては、上記のリチウム塩を溶解し、電池として使用される電圧範囲で分解などの副反応を起こさないものであれば特に限定されない。例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ビニレンカーボネートなどの環状カーボネート；ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネートなどの鎖状カーボネート；プロピオン酸メチルなどの鎖状エステル；γ−ブチロラクトンといった環状エステル；ジメトキシエタン、ジエチルエーテル、１，３−ジオキソラン、ジグライム、トリグライム、テトラグライムなどの鎖状エーテル；ジオキサン、テトラヒドロフラン、２−メチルテトラヒドロフランなどの環状エーテル；アセトニトリル、プロピオニトリル、メトキシプロピオニトリルといったニトリル類；エチレングリコールサルファイトなどの亜硫酸エステル類；などが挙げられ、これらを１種単独で用いてもよいし、２種以上を併用しても構わない。なお、より良好な特性の電池とするためには、エチレンカーボネートと鎖状カーボネートの混合溶媒など、高い導電率を得ることができる組み合わせで用いることが望ましい。また、これらの電解液に安全性や充放電サイクル性、高温貯蔵性といった特性を向上させる目的で、ビニレンカーボネート類、１，３−プロパンサルトン、ジフェニルジスルフィド、シクロヘキサン、ビフェニル、フルオロベンゼン、ｔ−ブチルベンゼンなどの添加剤を適宜加えることもできる。 The organic solvent used in the electrolytic solution is not particularly limited as long as it dissolves the above lithium salt and does not cause side reactions such as decomposition in the voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; Chain ethers such as ethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; Sulfites such as ethylene glycol sulfite; and the like, and these may be used alone. , It may be used in combination of two or more thereof. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. In addition, for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of these electrolytes, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexane, biphenyl, fluorobenzene, t- Additives such as butylbenzene can also be added as appropriate.
このリチウム塩の電解液中の濃度としては、０．５〜１．５ｍｏｌ／ｌとすることが好ましく、０．９〜１．２５ｍｏｌ／ｌとすることがより好ましい。 The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.
また、上記の非水電解液を含有してゲル化するような高分子材料を添加して、非水電解液をゲル状にして電池に用いてもよい。ゲル状電解質を構成する具体的な材料としては、ＰＶＤＦ、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体（ＰＶＤＦ−ＨＦＰ）やそれらの誘導体；架橋構造を有するポリエチレンオキシドやポリエチレンオキシド構造を主鎖または側鎖に有する高分子材料；ＰＡＮ；特開２００２−１１０２４５号公報に開示されているような、オキセタン基や脂環式エポキシ基を側鎖に持ち、側鎖オキセタン基、エポキシ基が反応することによって電解液でゲル化する（メタ）アクリレート系樹脂；などが挙げられる。 Alternatively, a polymer material that contains the nonaqueous electrolyte and gels may be added to make the nonaqueous electrolyte into a gel and used for the battery. Specific materials constituting the gel electrolyte include PVDF, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and derivatives thereof; polyethylene oxide having a crosslinked structure or polyethylene oxide structure on the main chain or side. PAN; having an oxetane group or an alicyclic epoxy group in the side chain as disclosed in JP 2002-110245 A, and reacting the side chain oxetane group or the epoxy group (Meth) acrylate-based resin that gels with an electrolytic solution;
本発明のリチウム二次電池が本発明の非水電解液を有する場合には、該非水電解液には、上記のリチウム塩を上記の有機溶媒に溶解した溶液（更には、上記のゲル化用の高分子材料）に、更に膨潤性微粒子（Ａ）を含有させたもの［好ましくは、上記の好適含有量で膨潤性微粒子（Ａ）を含有させたもの］を用いる。ただし、本発明のリチウム二次電池の非水電解液以外の構成要素が膨潤性微粒子（Ａ）を含有している場合には、非水電解液には、本発明の非水電解液以外の非水電解液［膨潤性微粒子（Ａ）を含有していない上記非水電解液］を用いても構わない。 When the lithium secondary battery of the present invention has the non-aqueous electrolyte of the present invention, the non-aqueous electrolyte includes a solution in which the above lithium salt is dissolved in the above organic solvent (further, the above-mentioned gelation gel The polymer material) further containing swellable fine particles (A) [preferably, those containing the swellable fine particles (A) at the above-mentioned preferred content] is used. However, when the constituents other than the non-aqueous electrolyte of the lithium secondary battery of the present invention contain the swellable fine particles (A), the non-aqueous electrolyte includes other than the non-aqueous electrolyte of the present invention. A nonaqueous electrolytic solution [the above nonaqueous electrolytic solution containing no swellable fine particles (A)] may be used.
なお、本発明の非水電解液を調製するにあたっては、電池内に注入する非水電解液に予め膨潤性微粒子（Ａ）を混合しておいてもよいが、例えば、電池の外装体内に膨潤性微粒子（Ａ）を入れておき、その後に、膨潤性微粒子（Ａ）を含有しない非水電解液を注入して、電池内で本発明の非水電解液としてもよい。 In preparing the non-aqueous electrolyte of the present invention, the swellable fine particles (A) may be mixed in advance with the non-aqueous electrolyte to be injected into the battery. The non-aqueous electrolyte of the present invention may be used in the battery by injecting the non-aqueous electrolyte not containing the swellable fine particles (A).
本発明のリチウム二次電池の形態としては、スチール缶やアルミニウム缶などを外装体（外装缶）として使用した筒形（角筒形や円筒形など）などが挙げられる。また、金属を蒸着したラミネートフィルムを外装体としたソフトパッケージ電池とすることもできる。 Examples of the form of the lithium secondary battery of the present invention include a tubular shape (such as a rectangular tube shape or a cylindrical shape) using a steel can, an aluminum can, or the like as an exterior body (exterior can). Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.
なお、リチウム二次電池の外装体に、本発明の外装体［膨潤性微粒子（Ａ）が内面に付着している外装体］を用いる場合には、本発明の外装体は、以下のようにして製造できる。例えば、膨潤性微粒子（Ａ）を、バインダ［例えば、セパレータに係るバインダ（Ｆ）の具体例として例示した各種樹脂・ゴムなど］と共に、水または溶剤に分散させたスラリーなどを調製し、これを外装体内面にスプレー塗布などする方法が挙げられる。また、ラミネートフィルム製の外装体の場合には、上記の膨潤性微粒子（Ａ）含有スラリーを、スプレー、ダイコーター、リバースコーター、グラビアコーターといった各種塗布装置を用いて、ラミネートフィルムにおける外装体内面となる面に塗布しておく方法も採用できる。なお、上記の膨潤性微粒子（Ａ）含有スラリーには、必要に応じて、分散を高めるための分散助剤や、粘度を調整するための増粘剤などを加えてもよい。 When the outer package of the present invention [the outer package in which the swellable fine particles (A) are adhered to the inner surface] is used for the outer package of the lithium secondary battery, the outer package of the present invention is as follows. Can be manufactured. For example, a slurry in which swellable fine particles (A) are dispersed in water or a solvent together with a binder [for example, various resins and rubbers exemplified as specific examples of the binder (F) relating to the separator] is prepared. Examples of the method include spray coating on the inner surface of the exterior body. Further, in the case of a laminate film exterior body, the above-described swellable fine particle (A) -containing slurry can be applied to the exterior body inner surface of the laminate film using various coating devices such as sprays, die coaters, reverse coaters, and gravure coaters. A method of applying to the surface can also be adopted. The swellable fine particle (A) -containing slurry may contain a dispersion aid for enhancing dispersion, a thickener for adjusting viscosity, and the like, if necessary.
他方、本発明のリチウム二次電池では、外装体以外の構成要素が膨潤性微粒子（Ａ）を含有している場合には、外装体には、膨潤性微粒子（Ａ）が内面に付着していない従来公知の外装体を用いることもできる。 On the other hand, in the lithium secondary battery of the present invention, when the constituent elements other than the outer package contain the swellable fine particles (A), the swellable fine particles (A) are adhered to the inner surface of the outer package. A conventionally known exterior body that is not present can also be used.
なお、上記本発明の外装体の製造方法は、電池の外装体内に膨潤性微粒子（Ａ）を入れておき、その後に膨潤性微粒子（Ａ）を含有しない非水電解液を注入して、電池内で本発明の非水電解液とする場合において、膨潤性微粒子（Ａ）を外装体内に入れる方法として応用できる。すなわち、膨潤性微粒子（Ａ）を外装体内に入れるにあたり、バインダを含有させない他は、上記と同様に調製した膨潤性微粒子（Ａ）含有スラリーを用いて、上記本発明の外装体の製造方法を実施すればよい。 In the above-described method for producing an outer package of the present invention, the swellable fine particles (A) are placed in the outer package of the battery, and then a non-aqueous electrolyte containing no swellable fine particles (A) is injected. When the non-aqueous electrolyte of the present invention is used, it can be applied as a method of putting the swellable fine particles (A) into the exterior body. That is, when the swellable fine particles (A) are put into the exterior body, except that the binder is not included, the swellable fine particle (A) -containing slurry prepared in the same manner as described above is used to manufacture the exterior body of the present invention. Just do it.
本発明のリチウム二次電池は、従来公知のリチウム二次電池が用いられている各種用途と同じ用途に適用することができる。 The lithium secondary battery of the present invention can be applied to the same uses as various uses in which conventionally known lithium secondary batteries are used.
以下、実施例に基づいて本発明を詳細に述べる。ただし、下記実施例は本発明を制限するものではなく、前・後記を逸脱しない範囲で変更実施をすることは、全て本発明の技術的範囲に包含される。なお、本実施例における膨潤性微粒子（Ａ）の膨潤度Ｂは、全て実施例１のリチウム二次電池に用いた電解液中で、測定温度を１２０℃にして測定した上記式（１）で定義される膨潤度であり、同膨潤度ＢＲは、全て実施例１のリチウム二次電池に用いた電解液中で測定した上記式（９）で定義される膨潤度である。 Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention, and all modifications made without departing from the preceding and following descriptions are included in the technical scope of the present invention. In addition, the swelling degree B of the swellable fine particles (A) in this example is all expressed by the above formula (1) measured at a measurement temperature of 120 ° C. in the electrolytic solution used in the lithium secondary battery of Example 1. a degree of swelling is defined, the swelling degree B R is a degree of swelling is defined by all the above formula were measured in an electrolytic solution used in the lithium secondary battery of example 1 (9).
実施例１
＜セパレータの作製＞
膨潤性微粒子（Ａ）として架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径１μｍ、ＢＲ＝０．５、Ｂ＝４］：１０００ｇ、水８００ｇ、イソプロピルアルコール（ＩＰＡ）２００ｇ、およびバインダ（Ｆ）としてＰＶＢ：３７５ｇを容器に入れ、スリーワンモーターで１時間撹拌して分散させ、均一なスラリーとした。このスラリー中に、厚みが１５μｍのＰＰ製不織布を通し、引き上げ塗布によりスラリーを塗布した後、乾燥して、厚みが２０μｍのセパレータを得た。このセパレータの走査型電子顕微鏡写真を図１に示す。各々の架橋ＰＭＭＡ粒子１の間、あるいは架橋ＰＭＭＡ粒子１とＰＰ製不織布２との間に微小な空孔が形成され、多孔質膜となっていることが確認された。また、上記セパレータの断面観察では、不織布の空隙内に膨潤性微粒子（Ａ）が存在していることが確認できた。
Example 1
<Preparation of separator>
Cross-linked PMMA (“Gantz Pearl (trade name)” manufactured by Ganz Kasei Co., Ltd., average particle size 1 μm, BR = 0.5, B = 4): 1000 g, water 800 g, isopropyl alcohol (IPA) as swellable fine particles (A) 200 g and PVB: 375 g as a binder (F) were put in a container and dispersed by stirring for 1 hour with a three-one motor to obtain a uniform slurry. A non-woven fabric made of PP having a thickness of 15 μm was passed through this slurry, and the slurry was applied by pulling and then dried to obtain a separator having a thickness of 20 μm. A scanning electron micrograph of this separator is shown in FIG. It was confirmed that minute pores were formed between the respective crosslinked PMMA particles 1 or between the crosslinked PMMA particles 1 and the PP
＜正極の作製＞
正極活物質であるＬｉＣｏＯ２：８０質量部、導電助剤であるアセチレンブラック：１０質量部、およびバインダであるＰＶＤＦ：５質量部を、Ｎ−メチル−２−ピロリドン（ＮＭＰ）を溶剤として均一になるように混合して、正極合剤含有ペーストを調製した。このペーストを、集電体となる厚さ１５μｍのアルミニウム箔の両面に、活物質塗布長が表面２８０ｍｍ、裏面２１０ｍになるように間欠塗布し、乾燥した後、カレンダー処理を行って、全厚が１５０μｍになるように正極合剤層の厚みを調整し、幅４３ｍｍになるように切断して、長さ２８０ｍｍ、幅４３ｍｍの正極を作製した。さらにこの正極のアルミニウム箔の露出部にタブ付けを行った。
<Preparation of positive electrode>
LiCoO 2 as a positive electrode active material: 80 parts by mass, acetylene black as a conductive additive: 10 parts by mass, and PVDF as a binder: 5 parts by mass uniformly using N-methyl-2-pyrrolidone (NMP) as a solvent It mixed so that positive electrode mixture containing paste might be prepared. This paste was intermittently applied to both sides of an aluminum foil having a thickness of 15 μm as a current collector so that the active material application length was 280 mm on the front surface and 210 m on the back surface, dried, and then subjected to a calendering treatment to obtain a total thickness. The thickness of the positive electrode mixture layer was adjusted to 150 μm, and the positive electrode mixture layer was cut to a width of 43 mm to produce a positive electrode having a length of 280 mm and a width of 43 mm. Further, the exposed portion of the aluminum foil of the positive electrode was tabbed.
＜負極の作製＞
負極活物質である黒鉛：９０質量部と、バインダであるＰＶＤＦ：５質量部とを、ＮＭＰを溶剤として均一になるように混合して負極合剤含有ペーストを調製した。この負極合剤含有ペーストを、銅箔からなる厚さ１０μｍの集電体の両面に、活物質塗布長が表面２９０ｍｍ、裏面２３０ｍｍになるように間欠塗布し、乾燥した後、カレンダー処理を行って全厚が１４２μｍになるように負極合剤層の厚みを調整し、幅４５ｍｍになるように切断して、長さ２９０ｍｍ、幅４５ｍｍの負極を作製した。さらにこの負極の銅箔の露出部にタブ付けを行った。
<Production of negative electrode>
A negative electrode mixture-containing paste was prepared by mixing 90 parts by mass of graphite as a negative electrode active material and 5 parts by mass of PVDF as a binder so as to be uniform using NMP as a solvent. This negative electrode mixture-containing paste was intermittently applied on both sides of a 10 μm-thick current collector made of copper foil so that the active material application length was 290 mm on the front surface and 230 mm on the back surface, dried, and then subjected to calendar treatment. The thickness of the negative electrode mixture layer was adjusted so that the total thickness was 142 μm, and the negative electrode mixture layer was cut to have a width of 45 mm to produce a negative electrode having a length of 290 mm and a width of 45 mm. Further, a tab was attached to the exposed portion of the copper foil of the negative electrode.
＜電池の組み立て＞
上記のようにして得られた正極と負極とを、上記のセパレータを介して渦巻状に巻回して巻回電極体とした。この巻回電極体を押しつぶして扁平状にし、厚さ４ｍｍ、幅３４ｍｍ、高さ５０ｍｍのアルミニウム缶に装填し、電解液（エチレンカーボネートとエチルメチルカーボネートを１：２の体積比で混合した溶媒に、ＬｉＰＦ６を１．２ｍｏｌ／ｌの濃度で溶解させた溶液）を注入し、レーザー封止を行ってリチウム二次電池を作製した。
<Battery assembly>
The positive electrode and the negative electrode obtained as described above were spirally wound through the separator to obtain a wound electrode body. The wound electrode body is crushed into a flat shape, loaded into an aluminum can having a thickness of 4 mm, a width of 34 mm, and a height of 50 mm, and an electrolytic solution (a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 2). , A solution in which LiPF 6 was dissolved at a concentration of 1.2 mol / l) was injected, and laser sealing was performed to produce a lithium secondary battery.
実施例２
実施例１で調製したセパレータ作製用のスラリーと同じスラリーに、更に、無機微粒子（Ｃ）としてアルミナ（Ａｌ２Ｏ３）微粒子（平均粒径：１μｍ）：３００ｇを加え、スリーワンモーターで３時間撹拌して分散させ、均一なスラリーとした。このスラリー中に、厚みが２８μｍのＰＢＴ製メルトブロー不織布を通し、引き上げ塗布によりスラリーを塗布した後、乾燥して、厚みが３５μｍのセパレータを得た。なお、このセパレータの断面を走査型電子顕微鏡で観察したところ、不織布の空隙内に膨潤性微粒子（Ａ）が存在していることが確認できた。
Example 2
To the same slurry as the separator-prepared slurry prepared in Example 1, alumina (Al 2 O 3 ) fine particles (average particle size: 1 μm): 300 g was further added as inorganic fine particles (C), and the mixture was stirred with a three-one motor for 3 hours. And dispersed into a uniform slurry. A PBT meltblown nonwoven fabric having a thickness of 28 μm was passed through this slurry, and the slurry was applied by pulling up and then dried to obtain a separator having a thickness of 35 μm. In addition, when the cross section of this separator was observed with the scanning electron microscope, it has confirmed that the swellable fine particle (A) existed in the space | gap of a nonwoven fabric.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
実施例３
バインダ（Ｆ）として、ＳＢＲラテックス：１００ｇおよびＣＭＣ：３０ｇ、並びに水：４０００ｇを容器に入れ、均一に溶解するまで室温にて撹拌した。さらに膨潤性微粒子（Ａ）として、架橋ＰＭＭＡの水分散体［ガンツ化成社製「スタフィロイド（商品名）」、平均粒径０．３μｍ、ＢＲ＝０．５、Ｂ＝４］：２５００ｇを加え、ディスパーで、２８００ｒｐｍの条件で１時間撹拌して分散させた。これに、無機微粒子（Ｃ）として板状ベーマイト（平均粒径：１μｍ、アスペクト比：１０）：３０００ｇを加え、ディスパーで、２８００ｒｐｍの条件で３時間撹拌して、均一なスラリーとした。このスラリーを、アプリケーターを用いて、ギャップを５０μｍにして厚みが２３μｍのＰＰ製湿式不織布上に摺り切り塗布し、乾燥して、厚み：３０μｍのセパレータを得た。
Example 3
As a binder (F), SBR latex: 100 g and CMC: 30 g and water: 4000 g were put in a container and stirred at room temperature until evenly dissolved. Furthermore, as a swellable fine particle (A), an aqueous dispersion of crosslinked PMMA [“STAPHYLOID (trade name)” manufactured by Gantz Kasei Co., Ltd., average particle size 0.3 μm, B R = 0.5, B = 4]: 2500 g In addition, the mixture was stirred and dispersed with a disper at 2800 rpm for 1 hour. To this, plate-like boehmite (average particle diameter: 1 μm, aspect ratio: 10): 3000 g was added as inorganic fine particles (C), and the mixture was stirred with a disper at 2800 rpm for 3 hours to obtain a uniform slurry. Using an applicator, this slurry was applied to a wet nonwoven fabric made of PP having a thickness of 23 μm with a gap of 50 μm, and dried to obtain a separator having a thickness of 30 μm.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
実施例４
実施例３で調製したセパレータ作製用のスラリーと同じスラリーに、更に熱溶融性微粒子（Ｄ）としてＰＥエマルジョン（平均粒径：１μｍ、融点：１２５℃）：１０００ｇを加え、ディスパーで、２８００ｒｐｍの条件で１時間撹拌して分散させた。このスラリーを、アプリケーターを用いて、ギャップを５０μｍにして厚みが２３μｍのＰＰ製湿式不織布上に摺り切り塗布し、乾燥して、厚み：３０μｍのセパレータを得た。
Example 4
To the same slurry as the separator-prepared slurry prepared in Example 3, PE emulsion (average particle size: 1 μm, melting point: 125 ° C.): 1000 g was further added as heat-meltable fine particles (D), and the condition of 2800 rpm with a disper was added. And stirred for 1 hour to disperse. Using an applicator, this slurry was applied to a wet nonwoven fabric made of PP having a thickness of 23 μm with a gap of 50 μm, and dried to obtain a separator having a thickness of 30 μm.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
実施例５
実施例１で調製したセパレータ作製用のスラリーと同じスラリーに、更に無機微粒子（Ｃ）として板状アルミナ微粒子（平均粒径：２μｍ、アスペクト比：２５）：１５００ｇを加え、均一になるまで室温で撹拌し、スラリーを得た。このスラリーを、アプリケーターを用いて、ギャップを５０μｍにして厚みが１５μｍのＰＥＴ製湿式不織布上に摺り切り塗布し、乾燥して、厚み：２５μｍのセパレータを得た。
Example 5
To the same slurry as the separator preparation slurry prepared in Example 1, 1500 g of plate-like alumina fine particles (average particle size: 2 μm, aspect ratio: 25) are further added as inorganic fine particles (C) at room temperature until uniform. Stir to obtain a slurry. Using an applicator, this slurry was applied onto a wet nonwoven fabric made of PET having a gap of 50 μm and a thickness of 15 μm, and dried to obtain a separator having a thickness of 25 μm.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
実施例６
バインダ（Ｆ）としてＥＶＡエマルジョン（酢酸ビニル由来の構造単位が２０モル％）：１００ｇ、および膨潤性微粒子（Ａ）として実施例３で用いたものと同じ架橋ＰＭＭＡ：１０００ｇを容器に入れ、ディスパーで、２８００ｒｐｍの条件で１時間撹拌して分散させて均一なスラリーとした。このスラリーに、繊維状物（Ｂ）として、アルミナ繊維（平均繊維径：３μｍ、アスペクト比：３００００）：１０００ｇを加え、均一になるまで室温にて撹拌した。このようにして得られたスラリーを、ダイコーターを用いて、塗布厚：５０μｍでＰＥＴ基材上に塗布し、乾燥した後、ＰＥＴ基材から剥離して厚みが１５μｍのセパレータを得た。セパレータの断面を走査型電子顕微鏡で観察したところ、アルミナ繊維のアスペクト比は１０以上であり、また、セパレータ面に対する平均角度は１０°以下であった。
Example 6
EVA binder (20 mol% of structural unit derived from vinyl acetate) as binder (F): 100 g, and the same crosslinked PMMA used in Example 3 as swelling fine particles (A): 1000 g in a container, The mixture was stirred and dispersed for 1 hour at 2800 rpm to obtain a uniform slurry. To this slurry was added alumina fiber (average fiber diameter: 3 μm, aspect ratio: 30000): 1000 g as a fibrous material (B), and the mixture was stirred at room temperature until uniform. The slurry thus obtained was applied onto a PET substrate at a coating thickness of 50 μm using a die coater, dried, and then peeled from the PET substrate to obtain a separator having a thickness of 15 μm. When the cross section of the separator was observed with a scanning electron microscope, the aspect ratio of the alumina fibers was 10 or more, and the average angle with respect to the separator surface was 10 ° or less.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
実施例７
実施例１で作製したものと同じ負極の片面に、実施例５で調製したセパレータ作製用のスラリーと同じスラリーを、ダイコーターを用いて厚みが１５μｍになるように塗布し、乾燥して、セパレータを一体化した負極を作製した。
Example 7
The same slurry as the separator preparation slurry prepared in Example 5 was applied to one side of the same negative electrode as that prepared in Example 1 so as to have a thickness of 15 μm using a die coater, and dried. A negative electrode integrated with was produced.
上記の負極と、実施例１で作製したものと同じ正極とを、負極表面のセパレータを介して重ね合わせて渦巻状に巻回して巻回電極体とし、これを押しつぶして扁平状にした。この扁平状の巻回電極体を用いた他は、実施例１と同様にしてリチウム二次電池を作製した。 The above negative electrode and the same positive electrode as that produced in Example 1 were overlapped via a separator on the negative electrode surface and wound into a spiral shape to obtain a wound electrode body, which was crushed into a flat shape. A lithium secondary battery was produced in the same manner as in Example 1 except that this flat wound electrode body was used.
実施例８
＜セパレータの作製＞
膨潤性微粒子（Ａ）として架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径２μｍ、ＢＲ＝０．８、Ｂ＝１．８］：１０００ｇ、水８００ｇ、イソプロピルアルコール（ＩＰＡ）２００ｇ、およびバインダ（Ｆ）としてＰＶＢ：３７５ｇを容器に入れ、スリーワンモーターで１時間撹拌して分散させ、均一なスラリーとした。このスラリー中に、厚みが１５μｍのＰＰ製メルトブロー不織布を通し、引き上げ塗布によりスラリーを塗布した後、乾燥して、厚みが２０μｍのセパレータを得た。なお、このセパレータの断面を走査型電子顕微鏡で観察したところ、不織布の空隙内に膨潤性微粒子（Ａ）が存在していることが確認できた。
Example 8
<Preparation of separator>
Crosslinked PMMA [Ganz Chemical Co., Ltd. "Ganz Pearl (trade name)", an average particle diameter of 2μm, B R = 0.8, B = 1.8] as swellable particles (A): 1000 g, water 800 g, isopropyl alcohol ( (IPA) 200 g and PVB: 375 g as a binder (F) were put in a container, and stirred and dispersed with a three-one motor for 1 hour to obtain a uniform slurry. A PP meltblown nonwoven fabric having a thickness of 15 μm was passed through the slurry, and the slurry was applied by pulling up and then dried to obtain a separator having a thickness of 20 μm. In addition, when the cross section of this separator was observed with the scanning electron microscope, it has confirmed that the swellable fine particle (A) existed in the space | gap of a nonwoven fabric.
＜負極の作製＞
負極活物質である黒鉛：９０質量部と、バインダであるＳＢＲラテックス：５質量部およびＣＭＣとを、水中で均一になるように混合して負極合剤含有ペーストを調製した。この負極合剤含有ペーストを、銅箔からなる厚さ１０μｍの集電体の両面に、活物質塗布長が表面２９０ｍｍ、裏面２３０ｍｍになるように間欠塗布し、乾燥した後、カレンダー処理を行って全厚が１４２μｍになるように負極合剤層の厚みを調整し、幅４５ｍｍになるように切断して、長さ２９０ｍｍ、幅４５ｍｍの負極を作製した。さらにこの負極の銅箔の露出部にタブ付けを行った。
<Production of negative electrode>
A negative electrode active material-containing paste was prepared by mixing 90 parts by mass of graphite as a negative electrode active material, 5 parts by mass of SBR latex as a binder, and CMC so as to be uniform in water. This negative electrode mixture-containing paste was intermittently applied on both sides of a 10 μm-thick current collector made of copper foil so that the active material application length was 290 mm on the front surface and 230 mm on the back surface, dried, and then subjected to calendar treatment. The thickness of the negative electrode mixture layer was adjusted so that the total thickness was 142 μm, and the negative electrode mixture layer was cut to have a width of 45 mm to produce a negative electrode having a length of 290 mm and a width of 45 mm. Further, a tab was attached to the exposed portion of the copper foil of the negative electrode.
上記のセパレータおよび上記の負極を用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator and the above negative electrode were used.
実施例９
実施例８で調製したセパレータ作製用のスラリーと同じスラリーに、更に、無機微粒子（Ｃ）としてアルミナ微粒子（平均粒径：０．４μｍ）：３００ｇを加え、スリーワンモーターで３時間撹拌して分散させ、均一なスラリーとした。このスラリー中に、厚みが２８μｍのＰＢＴ製メルトブロー不織布を通し、引き上げ塗布によりスラリーを塗布した後、乾燥して、厚みが３５μｍのセパレータを得た。なお、このセパレータの断面を走査型電子顕微鏡で観察したところ、不織布の空隙内に膨潤性微粒子（Ａ）が存在していることが確認できた。
Example 9
To the same slurry as that for preparing the separator prepared in Example 8, alumina fine particles (average particle size: 0.4 μm): 300 g were added as inorganic fine particles (C), and the mixture was stirred and dispersed with a three-one motor for 3 hours. A uniform slurry was obtained. A PBT meltblown nonwoven fabric having a thickness of 28 μm was passed through this slurry, and the slurry was applied by pulling up and then dried to obtain a separator having a thickness of 35 μm. In addition, when the cross section of this separator was observed with the scanning electron microscope, it has confirmed that the swellable fine particle (A) existed in the space | gap of a nonwoven fabric.
上記のセパレータを用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 8 except that the above separator was used.
実施例１０
バインダ（Ｆ）としてＳＢＲラテックス：１００ｇおよびＣＭＣ:３０ｇ、並びに水：６０００ｇを容器に入れ、均一に溶解するまで室温にて撹拌した。更に、膨潤性微粒子（Ａ）として、架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径４μｍ、ＢＲ＝０．８、Ｂ＝１．５］：１０００ｇを加え、ディスパーで、２８００ｒｐｍの条件で３時間撹拌して、均一なスラリーとした。このスラリーを、アプリケーターを用いて、ギャップを３０μｍにして厚みが２０μｍのポリイミド製微多孔膜上に摺り切り塗布し、乾燥して、厚みが３０μｍのセパレータを得た。
Example 10
As a binder (F), SBR latex: 100 g and CMC: 30 g, and water: 6000 g were put in a container and stirred at room temperature until evenly dissolved. Further, as the swellable fine particles (A), cross-linked PMMA [“Gantz Pearl (trade name)” manufactured by Ganz Kasei Co., Ltd., average particle diameter of 4 μm, B R = 0.8, B = 1.5]: 1000 g was added, Then, the mixture was stirred for 3 hours at 2800 rpm to obtain a uniform slurry. Using an applicator, this slurry was applied to a polyimide microporous film having a gap of 30 μm and a thickness of 20 μm, and dried to obtain a separator having a thickness of 30 μm.
上記のセパレータを用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 8 except that the above separator was used.
実施例１１
実施例１で調製した正極合剤含有ペーストに、更に膨潤性微粒子（Ａ）として、架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径４μｍ、ＢＲ＝０．８、Ｂ＝１．５］を１０質量部加え、均一になるまで撹拌して得られた正極合剤含有ペーストを用いた以外は、実施例１と同様にして正極を作製した。
Example 11
The positive electrode mixture-containing paste prepared in Example 1, further as swellable particles (A), crosslinked PMMA [Ganz Chemical Co., Ltd. "Ganz Pearl (trade name)", an average particle diameter of 4 [mu] m, B R = 0.8, B = 1.5] was added in an amount of 10 parts by mass, and a positive electrode mixture-containing paste obtained by stirring until uniform was used to produce a positive electrode in the same manner as in Example 1.
上記正極を用い、更に、セパレータとして厚みが２０μｍのポリイミド製微多孔膜を用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 8 except that the positive electrode was used and a polyimide microporous film having a thickness of 20 μm was used as the separator.
実施例１２
実施例８で調製した負極合剤含有ペーストに、更に膨潤性微粒子（Ａ）として、架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径４μｍ、ＢＲ＝０．８、Ｂ＝１．５］を１０質量部加え、均一になるまで撹拌して得られた負極合剤含有ペーストを用いた以外は、実施例８と同様にして負極を作製した。
Example 12
The negative electrode mixture-containing paste prepared in Example 8, further as swellable particles (A), crosslinked PMMA [Ganz Chemical Co., Ltd. "Ganz Pearl (trade name)", an average particle diameter of 4 [mu] m, B R = 0.8, B = 1.5] was added in an amount of 10 parts by mass, and a negative electrode mixture was prepared in the same manner as in Example 8 except that the negative electrode mixture-containing paste obtained by stirring until uniform was used.
上記負極と、実施例１で作製したものと同じ正極を用いた以外は、実施例１１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 11 except that the same negative electrode as that used in Example 1 was used.
実施例１３
実施例１で調製した非水電解液に、更に膨潤性微粒子（Ａ）として、架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径２μｍ、ＢＲ＝０．８、Ｂ＝１．８］を１０質量％となるように加えて、非水電解液を調製した。
Example 13
The non-aqueous electrolyte solution prepared in Example 1, further as swellable particles (A), crosslinked PMMA [Ganz Chemical Co., Ltd. "Ganz Pearl (trade name)", an average particle diameter of 2μm, B R = 0.8, B = 1.8] was added so that it might become 10 mass%, and the nonaqueous electrolyte solution was prepared.
上記の非水電解液を用い、更に、セパレータとして厚みが２０μｍのポリイミド製微多孔膜を用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 8 except that the above non-aqueous electrolyte was used and a polyimide microporous film having a thickness of 20 μm was used as the separator.
実施例１４
実施例８で作製したものと同じ負極の片面に、実施例８で調製したセパレータ作製用のスラリーと同じスラリーを、ダイコーターを用いて、厚みが１５μｍとなるように塗布し、乾燥して、セパレータを一体化した負極を作製した。
Example 14
The same slurry as the separator preparation slurry prepared in Example 8 was applied to one side of the same negative electrode as that prepared in Example 8 using a die coater so as to have a thickness of 15 μm, and dried. A negative electrode integrated with a separator was produced.
上記の負極と、実施例１で作製したものと同じ正極とを、負極表面のセパレータを介して重ね合わせて渦巻状に巻回して巻回電極体とし、これを押しつぶして扁平状にした。この扁平状の巻回電極体を用いた他は、実施例１と同様にしてリチウム二次電池を作製した。 The above negative electrode and the same positive electrode as that produced in Example 1 were overlapped via a separator on the negative electrode surface and wound into a spiral shape to obtain a wound electrode body, which was crushed into a flat shape. A lithium secondary battery was produced in the same manner as in Example 1 except that this flat wound electrode body was used.
実施例１５
実施例１で用いたものと同じ外装缶に、予め膨潤性微粒子（Ａ）として、架橋ＰＭＭＡ［ガンツ化成社製「ガンツパール（商品名）」、平均粒径２μｍ、ＢＲ＝０．８、Ｂ＝１．８］を０．３ｇ注入した。
Example 15
The same outer can as used in Example 1, in advance as swellable particles (A), crosslinked PMMA [Ganz Chemical Co., Ltd. "Ganz Pearl (trade name)", an average particle diameter of 2 [mu] m, B R = 0.8, B = 1.8] was injected in an amount of 0.3 g.
上記の外装缶を用い、更に、セパレータとして厚みが２０μｍのポリイミド製微多孔膜を用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 8 except that the above-described outer can was used and a polyimide microporous film having a thickness of 20 μm was used as the separator.
比較例１
無機微粒子（Ｃ）としてアルミナ（Ａｌ２Ｏ３）微粒子（平均粒径：０．４μｍ）：３０００ｇ、水８００ｇ、イソプロピルアルコール（ＩＰＡ）２００ｇ、およびバインダ（Ｆ）としてＰＶＢ：３７５ｇを容器に入れ、スリーワンモーターで１時間撹拌して分散させ、均一なスラリーとした。このスラリー中に、厚みが１５μｍのＰＰ製メルトブロー不織布を通し、引き上げ塗布によりスラリーを塗布した後、乾燥して、厚みが２０μｍのセパレータを得た。
Comparative Example 1
As inorganic fine particles (C), alumina (Al 2 O 3 ) fine particles (average particle size: 0.4 μm): 3000 g, water 800 g, isopropyl alcohol (IPA) 200 g, and PVB: 375 g as a binder (F) are put in a container, The mixture was stirred and dispersed with a three-one motor for 1 hour to obtain a uniform slurry. A PP meltblown nonwoven fabric having a thickness of 15 μm was passed through the slurry, and the slurry was applied by pulling up and then dried to obtain a separator having a thickness of 20 μm.
上記のセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。 A lithium secondary battery was produced in the same manner as in Example 1 except that the above separator was used.
比較例２
無機微粒子（Ｃ）に替えて、ＰＥエマルジョン（平均粒径：１μｍ、融点：１２５℃）を用いた以外は、比較例１と同様にしてセパレータを作製した。このセパレータを用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。
Comparative Example 2
A separator was prepared in the same manner as in Comparative Example 1 except that PE emulsion (average particle diameter: 1 μm, melting point: 125 ° C.) was used instead of the inorganic fine particles (C). A lithium secondary battery was produced in the same manner as in Example 1 except that this separator was used.
比較例３
従来公知のセパレータとして、厚みが２０μｍのＰＥ製微多孔膜を用いた以外は、実施例１と同様にしてリチウム二次電池を作製した。
Comparative Example 3
A lithium secondary battery was produced in the same manner as in Example 1, except that a PE microporous film having a thickness of 20 μm was used as a conventionally known separator.
比較例４
架橋ＰＭＭＡ微粒子に代えて、架橋されていないＰＭＭＡ微粒子を用いた以外は、実施例８と同様にしてセパレータを作製し、このセパレータを用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。
Comparative Example 4
A lithium secondary battery was produced in the same manner as in Example 8 except that this separator was used except that uncrosslinked PMMA fine particles were used instead of the crosslinked PMMA fine particles. Was made.
比較例５
セパレータとして、厚みが２０μｍのポリイミド製微多孔膜を用いた以外は、実施例８と同様にしてリチウム二次電池を作製した。
Comparative Example 5
A lithium secondary battery was produced in the same manner as in Example 8 except that a polyimide microporous film having a thickness of 20 μm was used as the separator.
＜セパレータの加熱特性＞
実施例１〜６、８〜１０および比較例１〜５のセパレータ、並びに実施例７および１４で作製したセパレータ一体化負極を用いて、下記の方法によりセパレータの加熱特性を測定した。
<Heating characteristics of separator>
Using the separators of Examples 1 to 6, 8 to 10 and Comparative Examples 1 to 5, and the separator integrated negative electrode produced in Examples 7 and 14, the heating characteristics of the separator were measured by the following method.
実施例１〜６、８〜１０および比較例１〜５のセパレータに関しては、各セパレータを４ｃｍ×４ｃｍの大きさに切り出し、端子付きの２枚のステンレス板で挟み込み、アルミラミネート製の袋に端子が袋の外に出るように挿入し、実施例１で使用したものと同じ電解液を注入して封止し、試験用の試料を作製した。 Regarding the separators of Examples 1 to 6, 8 to 10 and Comparative Examples 1 to 5, each separator was cut into a size of 4 cm × 4 cm, sandwiched between two stainless steel plates with terminals, and terminals in an aluminum laminate bag. Was inserted so as to come out of the bag, and the same electrolyte as that used in Example 1 was injected and sealed to prepare a test sample.
また、実施例７および１４で作製したセパレータ一体化負極に関しては、片面のみに活物質およびセパレータが塗布されている部分を４ｃｍ×４ｃｍに切り出して端子を取り付け、セパレータ面に上記で使用したのと同じ端子付きのステンレス板を対向させて、アルミラミネート製の袋に端子が袋の外に出るように挿入し、実施例１で使用したものと同じ電解液を注入して封止し、試験用の試料を作製した。 In addition, regarding the separator integrated negative electrode produced in Examples 7 and 14, the part where the active material and the separator were applied only on one side was cut out to 4 cm × 4 cm, the terminal was attached, and the separator was used as described above. Insert the same electrolyte solution used in Example 1 into the aluminum laminate bag so that the terminal comes out of the bag, facing the stainless steel plate with the same terminal, and test it. A sample of was prepared.
上記の試験用の試料を恒温槽内に入れ、室温から毎分１℃の割合で温度を上昇させて抵抗を測定し、抵抗値が５倍以上に上昇する温度を測定し、この温度を各試料のシャットダウン温度とした。また、温度を１５０℃まで上昇させて３０分放置した後、試料を取り出し、解体してセパレータを取り出して、試験前の長さと比較し、長さの減少割合（すなわち、セパレータの収縮率）を求めた。結果を表１に示す。 The above test sample is placed in a thermostatic chamber, and the resistance is measured by increasing the temperature from room temperature at a rate of 1 ° C./min. The temperature at which the resistance value rises five times or more is measured. The shutdown temperature of the sample was used. Also, after raising the temperature to 150 ° C. and leaving it for 30 minutes, the sample is taken out, disassembled and the separator is taken out, and compared with the length before the test, the rate of decrease in length (ie, the shrinkage rate of the separator) Asked. The results are shown in Table 1.
表１から、以下のことが分かる。従来品に相当する比較例３のセパレータでは、熱収縮率が大きく、これを用いた電池では、内部温度が１５０℃に達するまでの間に、セパレータの収縮が生じて、正極と負極が接触することによる短絡の虞がある。これに対し、実施例１〜１０および１４のセパレータでは、熱収縮が殆ど見られず、目視レベルでは実質的に変形が生じていない。よって、これらを用いた電池では、内部温度が１５０℃に達しても、セパレータによって正極と負極との接触が十分に妨げられて、短絡の発生が防止され得る。また、実施例１〜１０および１４のセパレータでは、恒温槽での加熱前に対して、加熱後では抵抗値が５倍以上に増大する温度が、比較例３に対して低く、より安全性を向上することが可能となっている。 Table 1 shows the following. The separator of Comparative Example 3 corresponding to the conventional product has a large heat shrinkage rate. In the battery using this, the separator shrinks until the internal temperature reaches 150 ° C., and the positive electrode and the negative electrode are in contact with each other. There is a risk of short circuit. On the other hand, in the separators of Examples 1 to 10 and 14, almost no heat shrinkage was observed, and no substantial deformation occurred at the visual level. Therefore, in the battery using these, even if the internal temperature reaches 150 ° C., the separator can sufficiently prevent the contact between the positive electrode and the negative electrode, thereby preventing the occurrence of a short circuit. Further, in the separators of Examples 1 to 10 and 14, the temperature at which the resistance value increases by 5 times or more after heating is lower than that in Comparative Example 3 before heating in the thermostatic bath, and the safety is further improved. It is possible to improve.
また、実施例１〜６、８〜１０のセパレータについて、通気性を有することを確認するため、透気度の測定を行ったところ、いずれのセパレータも、ガーレー値で表される透気度が５０〜１００（ｓｅｃ／１００ｍｌ）であり、充分な通気性を有する多孔質膜となっていることが確認された。 Moreover, about the separator of Examples 1-6, 8-10, in order to confirm having air permeability, when the air permeability was measured, all the separators had air permeability represented by Gurley values. It was 50-100 (sec / 100 ml), and it was confirmed that it was a porous film having sufficient air permeability.
次に、実施例１〜１５および比較例１、３、５のリチウム二次電池について、電気化学的評価（放電容量割合）および安全性試験を行った。結果を表２に示す。なお、比較例２、４の電池については電池を作製した段階で内部短絡が発生していたため、以降の試験を中止した。 Next, the lithium secondary batteries of Examples 1 to 15 and Comparative Examples 1, 3, and 5 were subjected to electrochemical evaluation (discharge capacity ratio) and safety test. The results are shown in Table 2. In addition, about the battery of the comparative examples 2 and 4, since the internal short circuit had generate | occur | produced in the step which produced the battery, subsequent tests were stopped.
＜放電容量割合＞
実施例１〜１５および比較例１、３、５の電池について、０．２Ｃでの定電流充電（４．２Ｖまで）と４．２Ｖでの定電圧充電による充電（定電流充電と定電圧充電の合計時間１５時間）の後、３．０Ｖまで、０．２Ｃで放電を行い、充放電効率を求めた。なお充放電効率はそれぞれ電池１０個の平均値として求めた。
<Discharge capacity ratio>
For the batteries of Examples 1 to 15 and Comparative Examples 1, 3, and 5, constant current charging at 0.2 C (up to 4.2 V) and charging by constant voltage charging at 4.2 V (constant current charging and constant voltage charging) Thereafter, the battery was discharged at 0.2 C up to 3.0 V and the charge / discharge efficiency was determined. In addition, charging / discharging efficiency was calculated | required as an average value of 10 batteries, respectively.
＜安全性試験＞
実施例１〜１５および比較例１、３、５の電池を１５０℃の高温層中に３０分間放置して、セパレータの収縮による内部短絡の発生の有無について調べ、高温時における安全性を確認した。内部短絡の発生がなかったものを○、短絡が発生したものを×で示した。また、各電池について、以下の外部短絡試験を行い、セパレータのシャットダウンにより電池の異常発熱が抑制されるか否かを調べ、外部短絡時における安全性を確認した。外部短絡試験は、満充電状態の電池の正極と負極とを強制的に短絡させ、シャットダウンが生じた後に電池の温度が低下したものを○、シャットダウン機能が働かなかったものを×で示した。上記それぞれの結果を表２に示した。
<Safety test>
The batteries of Examples 1 to 15 and Comparative Examples 1, 3, and 5 were left in a high-temperature layer at 150 ° C. for 30 minutes to examine whether or not an internal short circuit occurred due to the shrinkage of the separator, and safety at high temperatures was confirmed. . The case where no internal short circuit occurred was indicated by ○, and the case where a short circuit occurred was indicated by ×. Each battery was subjected to the following external short-circuit test to examine whether or not abnormal battery heat generation was suppressed by the shutdown of the separator, and the safety at the time of external short-circuit was confirmed. In the external short-circuit test, the positive electrode and negative electrode of the fully charged battery were forcibly short-circuited, and the case where the temperature of the battery decreased after the shutdown occurred was indicated by ◯, and the case where the shutdown function did not work was indicated by x. The respective results are shown in Table 2.
表２から分かるように、実施例１〜１５のリチウム二次電池では、充放電効率が良好で実用レベルにあった。これに対し、比較例１の電池は充放電効率が低く、実用レベルに達しておらず、比較例２、４の電池は、上記の通り、電池を作製した段階で内部短絡が発生しており、これらの電池は信頼性が不十分であった。また、実施例１〜１５のリチウム二次電池では、１５０℃に放置した際の内部短絡の発生が防止され、安全性が向上していた。更に、外部短絡による安全性試験では、比較例１、５の電池ではシャットダウンが生じなかったのに対し、実施例１〜１５の電池は、シャットダウン機能が発現して電池の温度が低下し、安全性に優れることが分かった。 As can be seen from Table 2, in the lithium secondary batteries of Examples 1 to 15, the charge / discharge efficiency was good and at a practical level. On the other hand, the battery of Comparative Example 1 has low charge / discharge efficiency and has not reached the practical level, and the batteries of Comparative Examples 2 and 4 have an internal short circuit when the battery is manufactured as described above. These batteries were unreliable. Moreover, in the lithium secondary batteries of Examples 1 to 15, the occurrence of an internal short circuit when left at 150 ° C. was prevented, and the safety was improved. Furthermore, in the safety test using an external short circuit, the batteries of Comparative Examples 1 and 5 did not shut down, whereas the batteries of Examples 1 to 15 exhibited a shutdown function and the temperature of the battery was lowered. It turned out that it is excellent in property.
１ 架橋ＰＭＭＡ粒子
２ ＰＰ製不織布
1
Claims (16)
非水電解液を吸収して膨潤することが可能であり、かつ温度の上昇により膨潤度が増大する微粒子（Ａ）を電池内に有し、上記微粒子（Ａ）が非水電解液と接触していることを特徴とするリチウム二次電池。 A lithium secondary battery in which at least a positive electrode, a negative electrode, a separator, and a nonaqueous electrolytic solution are disposed in an exterior body,
The battery has fine particles (A) that can absorb and swell by absorbing a non-aqueous electrolyte, and the degree of swelling increases as the temperature rises, and the fine particles (A) come into contact with the non-aqueous electrolyte. A lithium secondary battery characterized by comprising:
Ｂ ＝ （Ｖ１／Ｖ０）−１
［上記式中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃に昇温し、前記温度で１時間経過後における微粒子の体積（ｃｍ３）を意味する。］ The lithium secondary battery according to claim 1, wherein the fine particles (A) have a degree of swelling B defined by the following formula of 2 or more.
B = (V 1 / V 0 ) -1
[In the above formula, V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the nonaqueous electrolyte at 25 ° C., and V 1 is 24 after being introduced into the nonaqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after a period of time, and the volume of fine particles (cm 3 ) after 1 hour at the above temperature is meant. ]
Ｂ ＝ （Ｖ１／Ｖ０）−１
［上記式中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃に昇温し、前記温度で１時間経過後における微粒子の体積（ｃｍ３）を意味する。］ The lithium secondary battery separator according to claim 9, wherein the fine particles (A) have a swelling degree B defined by the following formula of 2 or more.
B = (V 1 / V 0 ) -1
[In the above formula, V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the nonaqueous electrolyte at 25 ° C., and V 1 is 24 after being introduced into the nonaqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after a period of time, and the volume of fine particles (cm 3 ) after 1 hour at the above temperature is meant. ]
Ｂ ＝ （Ｖ１／Ｖ０）−１
［上記式中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃に昇温し、前記温度で１時間経過後における微粒子の体積（ｃｍ３）を意味する。］ The electrode for a lithium secondary battery according to claim 11, wherein the fine particles (A) have a swelling degree B defined by the following formula of 2 or more.
B = (V 1 / V 0 ) -1
[In the above formula, V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the nonaqueous electrolyte at 25 ° C., and V 1 is 24 after being introduced into the nonaqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after a period of time, and the volume of fine particles (cm 3 ) after 1 hour at the above temperature is meant. ]
Ｂ ＝ （Ｖ１／Ｖ０）−１
［上記式中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃に昇温し、前記温度で１時間経過後における微粒子の体積（ｃｍ３）を意味する。］ The non-aqueous electrolyte for a lithium secondary battery according to claim 13, wherein the fine particles (A) have a swelling degree B defined by the following formula of 2 or more.
B = (V 1 / V 0 ) -1
[In the above formula, V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the nonaqueous electrolyte at 25 ° C., and V 1 is 24 after being introduced into the nonaqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after a period of time, and the volume of fine particles (cm 3 ) after 1 hour at the above temperature is meant. ]
Ｂ ＝ （Ｖ１／Ｖ０）−１
［上記式中、Ｖ０は、２５℃の非水電解液に投入してから２４時間後における微粒子の体積（ｃｍ３）、Ｖ１は、２５℃の非水電解液に投入してから２４時間後に非水電解液を１２０℃に昇温し、前記温度で１時間経過後における微粒子の体積（ｃｍ３）を意味する。］
16. The package for a lithium secondary battery according to claim 15, wherein the fine particles (A) have a swelling degree B defined by the following formula of 2 or more.
B = (V 1 / V 0 ) -1
[In the above formula, V 0 is the volume of fine particles (cm 3 ) 24 hours after being introduced into the nonaqueous electrolyte at 25 ° C., and V 1 is 24 after being introduced into the nonaqueous electrolyte at 25 ° C. The temperature of the non-aqueous electrolyte is raised to 120 ° C. after a period of time, and the volume of fine particles (cm 3 ) after 1 hour at the above temperature is meant. ]
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009026674A (en) * | 2007-07-23 | 2009-02-05 | Hitachi Vehicle Energy Ltd | Lithium ion cell |
| JP2010056036A (en) * | 2008-08-29 | 2010-03-11 | Teijin Ltd | Non-aqueous electrolyte battery separator, method of manufacturing the same, and non-aqueous electrolyte secondary battery using the separator |
| WO2011040562A1 (en) | 2009-09-30 | 2011-04-07 | 日本ゼオン株式会社 | Porous membrane for secondary battery, and secondary battery |
| JP2014049292A (en) * | 2012-08-31 | 2014-03-17 | Tdk Corp | Nonaqueous electrolyte for lithium ion secondary battery and lithium ion secondary battery |
-
2006
- 2006-06-23 JP JP2006174189A patent/JP2008004441A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009026674A (en) * | 2007-07-23 | 2009-02-05 | Hitachi Vehicle Energy Ltd | Lithium ion cell |
| JP2010056036A (en) * | 2008-08-29 | 2010-03-11 | Teijin Ltd | Non-aqueous electrolyte battery separator, method of manufacturing the same, and non-aqueous electrolyte secondary battery using the separator |
| WO2011040562A1 (en) | 2009-09-30 | 2011-04-07 | 日本ゼオン株式会社 | Porous membrane for secondary battery, and secondary battery |
| JP2014049292A (en) * | 2012-08-31 | 2014-03-17 | Tdk Corp | Nonaqueous electrolyte for lithium ion secondary battery and lithium ion secondary battery |
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