JP5088856B2 - Electrode for lithium secondary battery and lithium secondary battery - Google Patents
Electrode for lithium secondary battery and lithium secondary battery Download PDFInfo
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Description
本発明は、非水電解液の注液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リチウム二次電池用電極に関するものである。 The present invention relates to a lithium secondary battery excellent in the pouring property of a non-aqueous electrolyte and an electrode for a lithium secondary battery that can constitute the lithium secondary battery.
近年、パソコン、携帯電話などのコードレス機器の普及に伴い、その電源である二次電池はますます小型化、高エネルギー密度化が要望されている。そして、電池の高エネルギー密度化を電極の高密度化により達成する試みがなされているが、電極を高密度にすると、その空隙量が減少するため、電池作製時において、非水電解液の電池への注液時間が長くなることから、大量生産に不向きになるという問題がある。 In recent years, with the widespread use of cordless devices such as personal computers and mobile phones, secondary batteries as power sources are increasingly required to be smaller and have higher energy density. Attempts have been made to achieve higher energy density of the battery by increasing the density of the electrode. However, when the electrode is increased in density, the amount of voids is reduced. Since the time for injecting the solution into the liquid becomes long, there is a problem that it is not suitable for mass production.
このような事情を受けて、電極の表面積の向上や、電極の濡れ性の向上により、電池における非水電解液の注液性を改善して、上記の問題を解決することが試みられている。 Under such circumstances, attempts have been made to solve the above problems by improving the pouring property of the non-aqueous electrolyte in the battery by improving the surface area of the electrode and improving the wettability of the electrode. .
電極の表面積の向上により非水電解液の注液性を改善する技術としては、例えば、特許文献１に、電池電極表面に凹部を形成する手法が提案されている。また、電極の濡れ性の向上により非水電解液の注液性を改善する技術としては、例えば、負極材料自身を表面改質する手法が特許文献２に、電解液に添加剤を加えることで濡れ性の向上を図る手法が特許文献３に、高比表面積の無機物質を電極中へ混合する手法が特許文献４に、それぞれ記載されている。
As a technique for improving the pouring property of the nonaqueous electrolytic solution by increasing the surface area of the electrode, for example,
しかしながら、電極の表面に凹部を形成することにより表面積を向上させる手法では、注液性の改善を図ることは可能であるが、電極反応が不均一になりやすく、これによる電池の充放電サイクル特性の低下が懸念される。また、負極材料の表面改質や添加剤の使用による手法では、充放電を繰り返す充放電サイクルに伴って、改質部分や添加剤が変化することよる充放電サイクル特性の低下が懸念される。更に、電極中へ無機物質を混合する手法では、かかる無機物質の混合量の増加に伴って、電極のエネルギー密度の低下、ひいては電池の容量低下が生じてしまうといった問題がある。 However, the method of improving the surface area by forming a recess on the surface of the electrode can improve the liquid injection property, but the electrode reaction tends to be non-uniform, and the charge / discharge cycle characteristics of the battery due to this. There is concern about the decline. Further, in the method using surface modification of the negative electrode material or use of an additive, there is a concern that the charge / discharge cycle characteristics may be deteriorated due to a change in the modified portion or the additive along with a charge / discharge cycle in which charge / discharge is repeated. Furthermore, the technique of mixing an inorganic substance into the electrode has a problem that the energy density of the electrode is lowered and the capacity of the battery is lowered as the amount of the inorganic substance mixed is increased.
また、電池を大型化、高容量化する場合に、電極反応が不均一であると、部分的な発熱などにより安全性に問題を生じやすくなる。 Further, when the battery is increased in size and capacity, if the electrode reaction is not uniform, a problem in safety is likely to occur due to partial heat generation.
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、容量低下を可及的に抑制しつつ、非水電解液の注液性を向上させ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リチウム二次電池用電極を提供することにある。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lithium secondary battery in which the liquid injection property of a non-aqueous electrolyte is improved while suppressing a decrease in capacity as much as possible, and the lithium It is providing the electrode for lithium secondary batteries which can comprise a secondary battery.
上記目的を達成し得た本発明のリチウム二次電池用電極（以下、単に「電極」という場合がある）は、集電体の片面または両面に活物質を含有する合剤層を有してなるリチウム二次電池用電極であって、上記合剤層は、その表面側に凹凸を有し、上記合剤層の凹部に、絶縁性酸化物を含有しかつ活物質を含有しない酸化物含有部を有しており、上記合剤層の活物質の一部は、電極の表面に露出しており、上記合剤層の表面側における、上記合剤層と上記酸化物含有部とで構成され、上記酸化物と上記活物質とが混在する領域の厚みが、当該領域を含む合剤層の全厚みの１〜２０％であることを特徴とするものである。
更に、本発明のリチウム二次電池用電極の製造方法は、集電体の片面または両面に活物質を含有する合剤層を有してなるリチウム二次電池用電極の製造方法であって、絶縁性酸化物とバインダとを含む酸化物含有組成物を調製する工程と、表面側に凹凸を有する上記合剤層の表面に上記酸化物含有組成物を塗布し、上記絶縁性酸化物と上記バインダとを含有しかつ活物質を含有しない酸化物含有部を形成する工程とを有し、上記合剤層の活物質の一部を電極の表面に露出させ、かつ上記合剤層と上記酸化物含有部とで構成され、上記酸化物と上記活物質とが混在する領域の厚みを、当該領域を含む合剤層の全厚みの１〜２０％とすることを特徴とする。
The electrode for a lithium secondary battery of the present invention that can achieve the above object (hereinafter sometimes simply referred to as “electrode”) has a mixture layer containing an active material on one side or both sides of a current collector. An electrode for a lithium secondary battery, wherein the mixture layer has irregularities on the surface side, and an oxide containing an insulating oxide and no active material in the concave portion of the mixture layer Part of the active material of the mixture layer is exposed on the surface of the electrode, and is composed of the mixture layer and the oxide-containing portion on the surface side of the mixture layer is, the thickness of the region where the oxide and the above active material is mixed-is characterized in that 1 to 20% of the total thickness of the mixture layer containing the region.
Furthermore, the method for producing an electrode for a lithium secondary battery of the present invention is a method for producing an electrode for a lithium secondary battery comprising a mixture layer containing an active material on one side or both sides of a current collector, A step of preparing an oxide-containing composition containing an insulating oxide and a binder; and the oxide-containing composition is applied to the surface of the mixture layer having irregularities on the surface side, and the insulating oxide and the above Forming an oxide-containing part that contains a binder and does not contain an active material, and exposes a part of the active material of the mixture layer on the surface of the electrode, and the mixture layer and the oxidation is composed of a goods-containing portion, the oxide and the above active material and the thickness of the area to mixed-, characterized in that 1 to 20% of the total thickness of the mixture layer containing the region.
また、本発明のリチウム二次電池は、正極、負極および非水電解液を有するものであって、正極および負極の少なくとも一方の電極が、本発明のリチウム二次電池用電極であることを特徴とするものである。 The lithium secondary battery of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte, and at least one of the positive electrode and the negative electrode is the electrode for the lithium secondary battery of the present invention. It is what.
本発明では、電極と非水電解液との親和性を高めて、非水電解液の注液性を向上させるために、合剤層（正極では正極合剤層、負極では負極合剤層）の表面の凹部に、絶縁性の酸化物を存在させた電極を、正極および／または負極として使用する。しかし、上記酸化物の量が多くなると、電極内での活物質量が減少するため、電池の容量低下が生じてしまう。そこで、本発明では、上記合剤層において、上記酸化物が存在する箇所を、合剤層の表面から全厚みに対して１〜２０％の厚み部分までの領域とし、しかも、上記合剤層の活物質の一部を電極の表面に露出させて、上記酸化物と共に活物質も存在する領域（表面から厚み方向に一定の厚みまでの表面層全体を指し、この範囲内では、上記酸化物含有部すなわち絶縁性酸化物と上記合剤層すなわち活物質とが混在するため、以下、この領域を「混在層」と記載）とすることで、上記酸化物の使用量を低減しつつ、その作用（電極と非水電解液との親和性向上作用）を有効に引き出し、更には活物質の充填量の低下を抑えて、電池容量低下の可及的抑制と非水電解液の注液性向上を両立させている。
In the present invention, a mixture layer (a positive electrode mixture layer for the positive electrode and a negative electrode mixture layer for the negative electrode) is used to increase the affinity between the electrode and the non-aqueous electrolyte and improve the liquid injection property of the non-aqueous electrolyte. An electrode in which an insulating oxide is present in a concave portion on the surface of is used as a positive electrode and / or a negative electrode. However, when the amount of the oxide increases, the amount of the active material in the electrode decreases, resulting in a decrease in battery capacity. Therefore, in the present invention, the portion where the oxide is present in the mixture layer is a region from the surface of the mixture layer to a thickness portion of 1 to 20% of the total thickness, and the mixture layer A part of the active material is exposed on the surface of the electrode, and the active material is present together with the oxide (refers to the entire surface layer from the surface to a certain thickness in the thickness direction. Since the inclusion part, that is, the insulating oxide and the mixture layer, that is, the active material are mixed, the region is referred to as “ mixed layer ” below, thereby reducing the amount of the oxide used. The action (affinity improvement effect of electrode and non-aqueous electrolyte) is effectively drawn out, and further, the decrease in the filling amount of the active material is suppressed, the battery capacity decrease is suppressed as much as possible and the non-aqueous electrolyte is injected. Both improvements are achieved.
本発明によれば、容量低下を可及的に抑制しつつ、非水電解液の注液性を向上させたリチウム二次電池と、該リチウム二次電池を構成できるリチウム二次電池用電極を提供することができる。これにより、本発明に係るリチウム二次電池は、製造工程での非水電解液の注液にかかる時間を短縮できるため、生産性の優れたものとなる。 According to the present invention, there is provided a lithium secondary battery in which the liquid injection property of a non-aqueous electrolyte is improved while suppressing a decrease in capacity as much as possible, and an electrode for a lithium secondary battery that can constitute the lithium secondary battery. Can be provided. Thereby, since the lithium secondary battery which concerns on this invention can shorten the time concerning injection | pouring of the non-aqueous electrolyte in a manufacturing process, it becomes the thing excellent in productivity.
また、電極反応の均一性を高めることができるので、特に、大型・高容量リチウム二次電池における安全性を向上させることができる。 In addition, since the uniformity of the electrode reaction can be improved, the safety in a large-sized and high-capacity lithium secondary battery can be improved.
以下、本発明を詳細に説明する。本発明の電極は、リチウム二次電池の正極または負極として用いられるものである。リチウム二次電池用正極として使用される本発明の電極は、正極活物質、導電助剤およびバインダなどを含有する合剤層（正極合剤層）が、集電体の片面または両面に形成されてなるものである。 Hereinafter, the present invention will be described in detail. The electrode of the present invention is used as a positive electrode or a negative electrode of a lithium secondary battery. In the electrode of the present invention used as a positive electrode for a lithium secondary battery, a mixture layer (positive electrode mixture layer) containing a positive electrode active material, a conductive additive and a binder is formed on one side or both sides of a current collector. It will be.
正極活物質は、リチウムイオンを吸蔵・放出可能なものであれば特に制限はなく、例えば、従来公知のリチウム二次電池などに用いられているものを使用すればよい。具体的には、例えば、Ｌｉ１＋ｘＭ１＋ｙＯ２（Ｍは、Ｃｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｍｇなどより選択され、−０．１＜ｘ＜０．２、−０．１＜ｙ＜０．１）などの式で表される層状のリチウム含有酸化物、ＬｉＭｎ２Ｏ4またはそのＭｎの一部を他の元素Ｍ（Ｍ：Ｃｏ、Ｎｉ、Ｆｅなど）で置換したＬｉＭｎｘＭ（１−ｘ）Ｏ２（０＜ｘ＜０．５）などの式で表されるスピネル構造のリチウム含有酸化物、オリビン型ＬｉＭＰＯ４（Ｍ：Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅなど）などを用いることができる。上記層状のリチウム含有酸化物としては、コバルト酸リチウムのほか、リチウム含有マンガンニッケル酸化物〔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〕などを例示することができる。 The positive electrode active material is not particularly limited as long as it can occlude and release lithium ions. For example, a material used for a conventionally known lithium secondary battery may be used. Specifically, for example, Li 1 + x M 1 + y O 2 (M is selected from Co, Ni, Mn, Al, Mg, etc., −0.1 <x <0.2, −0.1 <y <0 LiMn x M (1 ) in which a layered lithium-containing oxide represented by a formula such as .1), LiMn 2 O 4 or a part of Mn thereof is substituted with another element M (M: Co, Ni, Fe, etc.) -X) A spinel-structured lithium-containing oxide represented by a formula such as O 2 (0 <x <0.5), olivine-type LiMPO 4 (M: Co, Ni, Mn, Fe, etc.), or the like is used. it can. Examples of the layered lithium-containing oxide include lithium cobalt oxide and lithium-containing manganese nickel oxide [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, etc.) and the like can be exemplified.
導電助剤としては、例えば、カーボンブラック、アセチレンブラック、繊維状炭素、黒鉛などが挙げられるが、これらに限定される訳ではない。また、バインダとしては、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレンなどが挙げられるが、これらに限定される訳ではない。 Examples of the conductive assistant include, but are not limited to, carbon black, acetylene black, fibrous carbon, graphite, and the like. Examples of the binder include, but are not limited to, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene.
正極に用いる集電体としては、耐酸化性や電解液に対する耐性を有し、かつ電気抵抗が十分に小さいものであれば、特に制限はないが、通常は、アルミニウム箔またはアルミニウム合金箔が用いられる。集電体の厚みは、例えば、１２〜２０μｍであることが好ましい。 The current collector used for the positive electrode is not particularly limited as long as it has oxidation resistance and resistance to an electrolytic solution, and the electrical resistance is sufficiently small. Usually, an aluminum foil or an aluminum alloy foil is used. It is done. The thickness of the current collector is preferably 12 to 20 μm, for example.
また、リチウム二次電池用負極として使用される本発明の電極は、負極活物質にＰＶＤＦなどのバインダ、更には必要に応じて導電助剤を含有してなる負極合剤層を、集電体の片面または両面に形成してなるものである。活物質としては、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、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などの合金またはリチウム含有窒化物、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／Ａｌ合金も負極活物質として用いることができる。 Further, the electrode of the present invention used as a negative electrode for a lithium secondary battery includes a negative electrode mixture layer containing a binder such as PVDF in a negative electrode active material, and further a conductive additive as necessary. Formed on one side or both sides. As active materials, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, mesocarbon microbeads, carbon fibers and other carbon-based materials that can occlude and release lithium Alternatively, a mixture of two or more kinds is used. Further, an alloy such as Si, Sn, Ge, Bi, Sb, In, or a compound that can be charged and discharged at a low voltage close to lithium metal such as lithium-containing nitride or oxide, or lithium metal or lithium / Al alloy is also used as the negative electrode active material. Can be used as
負極に集電体を使用する場合には、かかる集電体としては、電解液に対して耐性を有し電気抵抗が十分に低いものであれば特に制限はないが、通常は銅箔または銅合金箔が使用される。集電体の厚みは、例えば、６〜１２μｍであることが好ましい。 When a current collector is used for the negative electrode, the current collector is not particularly limited as long as it has resistance to an electrolyte and has a sufficiently low electric resistance. Alloy foil is used. The thickness of the current collector is preferably 6 to 12 μm, for example.
本発明の電極は、上記の正極における正極合剤層または上記の負極における負極合剤層において、絶縁性の酸化物（以下、単に「酸化物」という場合がある）を、合剤層表面を含む特定領域（正極または負極に係る活物質と上記酸化物とが混在する混在層）内に含有している。なお、本発明でいう上記酸化物に係る「絶縁性」とは、具体的には、酸化物を５０ＭＰａに圧縮して測定される電気伝導度が１．０×１０６Ω・ｃｍ以上であることを意味している。 In the electrode of the present invention, in the positive electrode mixture layer in the positive electrode or the negative electrode mixture layer in the negative electrode, an insulating oxide (hereinafter sometimes simply referred to as “oxide”) is applied to the surface of the mixture layer. It contains in the specific area | region (The mixed layer in which the active material which concerns on a positive electrode or a negative electrode, and the said oxide are mixed). Note that the “insulating property” related to the oxide in the present invention specifically means that the electric conductivity measured by compressing the oxide to 50 MPa is 1.0 × 10 6 Ω · cm or more. It means that.
上記酸化物の存在によって、正極や負極と非水電解液（以下、単に「電解液」という場合がある）との親和性を高めることができるため、正極表面や負極表面での電解液の拡散性が向上する。その結果、電解液の注液性が向上する。また、上記酸化物の使用によって、正極と負極とが接触することによる短絡を抑制し安全性を高める効果を得ることもできる。 The presence of the oxide can increase the affinity between the positive electrode and the negative electrode and a non-aqueous electrolyte (hereinafter sometimes simply referred to as “electrolyte”), so that the diffusion of the electrolyte on the positive electrode surface and the negative electrode surface Improves. As a result, the pouring property of the electrolytic solution is improved. In addition, the use of the oxide can also achieve an effect of suppressing short circuit due to contact between the positive electrode and the negative electrode and improving safety.
上記酸化物としては、絶縁性で、かつ電池内での電解液や電位に対して安定性を有する酸化物であれば特に制限はなく、いわゆる複合酸化物であってもよい。具体的には、アルミナ、ベーマイト、ムライト、ジルコニア、マイカなどが挙げられる。 The oxide is not particularly limited as long as it is insulative and has stability with respect to the electrolytic solution and potential in the battery, and may be a so-called composite oxide. Specific examples include alumina, boehmite, mullite, zirconia, and mica.
上記酸化物は粒子状であることが好ましく、また、上記酸化物の表面積を小さくして、よりその作用を有効に発揮させるためには、その平均粒径は、１μｍ以下であることが好ましく、０．５μｍ以下であることがより好ましい。なお、混在層内において、上記酸化物をより良好に分散させる観点からは、上記酸化物の平均粒径は、０．０１μｍ以上であることが好ましい。 The oxide is preferably in the form of particles, and the average particle size is preferably 1 μm or less in order to reduce the surface area of the oxide and more effectively exert its action. More preferably, it is 0.5 μm or less. In addition, from the viewpoint of better dispersing the oxide in the mixed layer, the average particle diameter of the oxide is preferably 0.01 μm or more.
本明細書でいう上記酸化物の平均粒径は、レーザー散乱粒度分布計（日機装社製「マイクロトラック ９３４０−ＵＰＡ」）を用い、上記酸化物を媒体（例えば水）に分散させて測定した数平均粒子径である。 The average particle diameter of the oxide referred to in the present specification is a number measured by dispersing the oxide in a medium (for example, water) using a laser scattering particle size distribution meter (“MICROTRACK 9340-UPA” manufactured by Nikkiso Co., Ltd.). Average particle size.
図１に、上記酸化物を含有する電極の断面模式図を示す。図１中、１は合剤層（正極合剤層または負極合剤層）、２は活物質（正極活物質または負極活物質）、３は絶縁性酸化物、４は集電体である。なお、図１では、合剤層１の構造の理解を容易にするために、合剤層１中に存在し得るバインダや導電助剤については図示していない。
In FIG. 1, the cross-sectional schematic diagram of the electrode containing the said oxide is shown. In FIG. 1, 1 is a mixture layer (positive electrode mixture layer or negative electrode mixture layer), 2 is an active material (positive electrode active material or negative electrode active material), 3 is an insulating oxide, and 4 is a current collector. In addition, in FIG. 1, in order to make an understanding of the structure of the
合剤層１において、上記酸化物３の存在する混在層の厚みは、上記混在層を含む合剤層１の全厚みの１％以上２０％以下であり、かかる混在層では上記酸化物３は活物質２（正極であれば正極活物質、負極であれば負極活物質）と混在している。そして、合剤層１の表面では、活物質２の一部が電極表面に露出している。
In the
このように、本発明では、上記酸化物の存在する混在層を合剤層の表面側の狭い領域とし、しかも混在層では上記酸化物と活物質とを混在させ、合剤層の混在層以外の部分（集電体側の部分）では、実質的に上記酸化物を含有しないようにすることで、上記酸化物の有する作用（合剤層と電解液との親和性向上作用）を有効に発揮させつつ酸化物の使用量を少なくし、電極中の活物質の充填量の低下を抑制して、容量低下の抑制と電解液の注液性の向上を達成している。また、合剤層表面では、上記酸化物で被覆されているだけではなく、その活物質の一部が電極表面に露出しているため、電極の充放電反応が上記酸化物により阻害されにくく、高い反応効率を維持することができる。なお、合剤層の混在層以外の部分において、「実質的に上記酸化物を含有しない」とは、電極の製造時に不可避的に上記酸化物が混入するような場合を除き、積極的には上記酸化物を含有させないことを意味している。
Thus, in the present invention, the mixed layer in which the oxide is present is a narrow region on the surface side of the mixture layer, and the mixed layer is mixed with the oxide and the active material, except for the mixed layer of the mixture layer. In this part (current collector side part), by effectively not containing the oxide, the action of the oxide (improvement of the compatibility between the mixture layer and the electrolyte) is effectively exhibited. Thus, the amount of oxide used is reduced, and the decrease in the filling amount of the active material in the electrode is suppressed, thereby suppressing the decrease in capacity and improving the liquid injection property of the electrolytic solution. Further, the surface of the mixture layer, the only been covered above Symbol oxide without a part of the active material is exposed on the electrode surface, the charge and discharge reactions of the electrode is less likely to be inhibited by the oxide High reaction efficiency can be maintained. In addition, in the part other than the mixed layer of the mixture layer, “substantially does not contain the oxide” means that the oxide is unavoidably excluded during the manufacture of the electrode. This means that the oxide is not contained.
混在層の厚みが、合剤層の全厚みに対して１％未満であると、上記酸化物の含有量が少なくなりすぎて、電解液の注液性向上効果が不十分となる。また、混在層の厚みが、合剤層の全厚みに対して２０％を超えると、上記酸化物の含有量が多くなりすぎて、電池の容量が低下してしまう。混在層の厚みは、混在層を含む合剤層の全厚みに対して、２％以上であることがより好ましく、また、１０％未満であることがより好ましい。 When the thickness of the mixed layer is less than 1% with respect to the total thickness of the mixture layer, the content of the oxide becomes too small, and the effect of improving the pouring property of the electrolytic solution becomes insufficient. Moreover, when the thickness of the mixed layer exceeds 20% with respect to the total thickness of the mixture layer, the content of the oxide is excessively increased, and the capacity of the battery is reduced. The thickness of the mixed layer is more preferably 2% or more, and more preferably less than 10%, based on the total thickness of the mixture layer including the mixed layer.
なお、正極合剤層の表面に上記酸化物が存在する場合、負極合剤層の表面に上記酸化物が存在する場合のいずれにおいても、活物質と上記酸化物とが混在している混在層では、上記酸化物の含有量が、１０質量％以上、より好ましくは２０質量％以上であって、９０質量％以下、より好ましくは５０質量％以下であることが望ましい。上記の領域における上記酸化物の含有量が少なすぎると、上記酸化物を使用することによる効果が小さくなることがあり、多すぎると、活物質の充填量が低下して、電池の容量が小さくなることがある。
In the case where the oxide is present on the surface of the positive electrode mixture layer, in either case where the oxide is present on the surface of the negative electrode mixture layer is also mixed layer and the active material and the oxide are mixed Then, it is desirable that the content of the oxide is 10% by mass or more, more preferably 20% by mass or more, and 90% by mass or less, more preferably 50% by mass or less. If the content of the oxide in the above region is too small, the effect of using the oxide may be small. If it is too large, the active material filling amount is reduced and the battery capacity is small. May be.
また、合剤層全体で同じ活物質を用いてもよいが、混在層に含まれる活物質と、これより集電体側にある合剤層に含まれる活物質とは、異なっていてもよい。例えば、混在層の導電性を向上させるため、導電性の高い活物質（例えば、コバルト酸リチウムなど）を混在層に含有させ、これより集電体側にある合剤層には他の活物質、例えば、スピネル構造のリチウム含有酸化物やリチウム含有マンガンニッケル酸化物など、安全性の高い活物質を含有させることもできる。 In addition, the same active material may be used for the entire mixture layer, but the active material contained in the mixed layer may be different from the active material contained in the mixture layer on the current collector side. For example, in order to improve the conductivity of the mixed layer, an active material with high conductivity (for example, lithium cobaltate) is included in the mixed layer, and the mixture layer on the current collector side contains another active material, For example, a highly safe active material such as a lithium-containing oxide having a spinel structure or a lithium-containing manganese nickel oxide can be contained.
混在層における上記酸化物の含有量は、電極を作製する際の各原材料の仕込み量から把握することができるが、電極の状態であっても、例えば以下の方法により測定できる。
（１）合剤層を表面から削って行き、上記酸化物がなくなる厚みを検出することで、電極合剤層の厚み方向での酸化物の存在（すなわち、混在層の領域）を確認する。
（２）合剤層における上記酸化物が存在する箇所でのサンプリングを行う。
（３）合剤層が正極合剤層である場合には、サンプリングした試料を正極活物質および酸化物を溶解し得る溶媒に溶解させ、残渣（導電助剤およびバインダ）と溶解物（正極活物質および酸化物）とを分離する。また、合剤層が負極合剤層である場合には、サンプリングした試料を酸化物を溶解し得る溶媒に溶解させ、残渣（負極活物質、バインダ、導電助剤）と溶解物（酸化物）とを分離する。上記溶媒としては、例えば、塩酸、硫酸などの酸を用いることができる。
（４）分離した上記溶解物の組成分析を行い、その中に含まれる上記酸化物量を求めて、サンプリングした試料中の上記酸化物の含有量を算出する。溶解物の分析には、ＩＣＰ発光分光分析装置または原子吸光分光光度計などが使用でき、これらによって溶解物中の成分を定量分析することができる。
The content of the oxide in the mixed layer can be ascertained from the amount of each raw material charged when the electrode is manufactured, but even in the state of the electrode, it can be measured by the following method, for example.
(1) The mixture layer is shaved from the surface, and the presence of the oxide in the thickness direction of the electrode mixture layer (that is, the mixed layer region) is confirmed by detecting the thickness at which the oxide disappears.
(2) Sampling is performed at the location where the oxide is present in the mixture layer.
(3) When the mixture layer is a positive electrode mixture layer, the sampled sample is dissolved in a solvent capable of dissolving the positive electrode active material and the oxide, and the residue (conductive auxiliary agent and binder) and dissolved matter (positive electrode active material) Substances and oxides). When the mixture layer is a negative electrode mixture layer, the sampled sample is dissolved in a solvent capable of dissolving the oxide, and the residue (negative electrode active material, binder, conductive additive) and dissolved matter (oxide) And are separated. As said solvent, acids, such as hydrochloric acid and a sulfuric acid, can be used, for example.
(4) The composition of the separated dissolved material is analyzed, the amount of the oxide contained therein is obtained, and the content of the oxide in the sampled sample is calculated. For the analysis of the lysate, an ICP emission spectrophotometer or an atomic absorption spectrophotometer can be used, whereby the components in the lysate can be quantitatively analyzed.
本発明の電極である正極（上記酸化物を含有する正極）は、例えば、以下の方法により製造することができる。まず、正極活物質、導電助剤、バインダなどを含む正極合剤を、Ｎ−メチル−２−ピロリドン（ＮＭＰ）などを溶剤（分散媒）として均一に混合して、ペースト状やスラリー状の正極合剤含有組成物を調製する（バインダは、ＮＭＰなどに予め溶解または分散していてもよい。以下の酸化物含有組成物についても同様。）。また、これとは別に、上記酸化物、正極活物質、導電助剤およびバインダなどを、ＮＭＰなどに均一に混合して、ペースト状やスラリー状などの酸化物含有組成物を調製する。次に、集電体の表面に、正極合剤含有組成物を塗布し、乾燥させた後、正極合剤含有組成物の塗膜表面に酸化物含有組成物を塗布し、乾燥させ、カレンダー処理などにより厚みを調節して、上記酸化物含有組成物の塗膜（酸化物含有部）を形成し、上記酸化物含有部と上記正極合剤とが混在、すなわち、上記酸化物と正極活物質とが混在する混在層を有する正極合剤層を備えた正極を得ることができる。
The positive electrode (the positive electrode containing the above oxide) that is the electrode of the present invention can be produced, for example, by the following method. First, a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like is uniformly mixed using N-methyl-2-pyrrolidone (NMP) or the like as a solvent (dispersion medium) to obtain a paste-like or slurry-like positive electrode A mixture-containing composition is prepared (the binder may be previously dissolved or dispersed in NMP or the like. The same applies to the following oxide-containing compositions). Separately, the oxide, the positive electrode active material, the conductive additive, the binder, and the like are uniformly mixed with NMP to prepare an oxide-containing composition such as a paste or slurry. Next, the positive electrode mixture-containing composition is applied to the surface of the current collector and dried, and then the oxide-containing composition is applied to the coating film surface of the positive electrode mixture-containing composition and dried. The thickness is adjusted by, for example, to form a coating film (oxide containing part) of the oxide-containing composition, and the oxide containing part and the positive electrode mixture are mixed, that is, the oxide and the positive electrode active material. A positive electrode provided with a positive electrode mixture layer having a mixed layer in which can be mixed can be obtained.
また、正極活物質や導電助剤を添加せずに酸化物含有組成物を調製し、集電体表面に正極合剤含有組成物を塗布し、乾燥して形成した塗膜の表面に、この酸化物含有組成物を摺り切り塗布して、上記塗膜の表面の空隙部に酸化物含有組成物を充填し、その後乾燥させ、カレンダー処理などにより厚みを調節する方法でも、上記酸化物と正極活物質とが混在する混在層を有する正極合剤層を備えた正極を得ることができる。つまり、正極合剤層含有組成物を塗布し、乾燥して得られる塗膜は、多孔質構造であり、その表面に空隙が存在するなど、表面が凹凸であるため、その空隙部（凹部）に、活物質を含有しない酸化物含有組成物を入れて乾燥することで、正極合剤層の表面に、活物質を含有しない塗膜（酸化物含有部）を形成し、上記酸化物と活物質とが混在する混在層を設けることができる。この場合、酸化物含有組成物の塗布量が多すぎると、正極合剤層の表面が全て酸化物含有組成物で被覆され、活物質が混在しない層が形成されるため、電極表面に正極合剤層の活物質の一部が露出する程度に塗布量を制限する必要がある。
In addition, an oxide-containing composition was prepared without adding a positive electrode active material or a conductive additive, and the positive electrode mixture-containing composition was applied to the surface of the current collector and dried to form a coating film surface. The oxide and positive electrode can also be applied by scraping and coating the oxide-containing composition, filling the voids on the surface of the coating film with the oxide-containing composition, and then drying and adjusting the thickness by calendaring or the like. A positive electrode provided with a positive electrode mixture layer having a mixed layer in which an active material is mixed can be obtained. That is, the coating film obtained by applying and drying the positive electrode mixture layer-containing composition has a porous structure, and there are voids on the surface thereof. Then, an oxide-containing composition that does not contain an active material is added and dried to form a coating film (oxide-containing portion) that does not contain an active material on the surface of the positive electrode mixture layer. A mixed layer in which substances are mixed can be provided. In this case, when the coating amount of the oxide-containing composition is too much, the coated surface of the positive electrode mixture layer at all oxide-containing composition, since a layer active material is not mixed is formed, the positive electrode to the electrode surface It is necessary to limit the coating amount to such an extent that a part of the active material of the agent layer is exposed.
正極を製造するための上記正極合剤含有組成物においては、その固形分（すなわち、正極合剤）全量中、正極活物質を９０〜９９質量％、導電助剤を０．５〜５質量％、バインダを０．５〜５質量％とすることが好ましい。 In the positive electrode mixture-containing composition for producing the positive electrode, the total amount of the solid content (that is, the positive electrode mixture) is 90 to 99% by mass of the positive electrode active material and 0.5 to 5% by mass of the conductive assistant. The binder is preferably 0.5 to 5% by mass.
また、正極を製造するための上記酸化物含有組成物のうち、正極活物質や導電助剤を含有する組成物では、かかる組成物のみによって混在層が形成されることから、酸化物含有組成物の固形分全量中の上記酸化物の含有量は、１０質量％以上、より好ましくは２０質量％以上であって、９０質量％以下、より好ましくは８０質量％以下とすることが望ましい。そして、この酸化物含有組成物における固形分全量中、正極活物質は５〜８１質量％、導電助剤は０．１〜４．５質量％、バインダは１〜４.５質量％とすることが好ましい。 In addition, among the oxide-containing compositions for producing the positive electrode, in the composition containing the positive electrode active material and the conductive auxiliary agent, a mixed layer is formed only by such a composition. Therefore, the oxide-containing composition The content of the oxide in the total solid content is 10% by mass or more, more preferably 20% by mass or more, and 90% by mass or less, more preferably 80% by mass or less. And in solid content whole quantity in this oxide containing composition, a positive electrode active material shall be 5-81 mass%, a conductive support agent shall be 0.1-4.5 mass%, and a binder shall be 1-4.5 mass%. Is preferred.
他方、正極を製造するための上記酸化物含有組成物のうち、正極活物質や導電助剤を含有させない組成物では、酸化物含有組成物の固形分全量中、上記酸化物を９０〜９９質量％、バインダを１〜１０質量％とすることが好ましい。 On the other hand, among the oxide-containing compositions for producing the positive electrode, in the composition not containing the positive electrode active material and the conductive auxiliary agent, the oxide is 90 to 99 mass in the total solid content of the oxide-containing composition. %, And the binder is preferably 1 to 10% by mass.
なお、上記酸化物を含有しない正極を使用して電池を構成する場合（負極のみに本発明の電極を用いて電池を構成する場合）には、上記の酸化物含有組成物の塗布、乾燥工程を省略して製造した正極を用いればよい。 In addition, when a battery is constituted using a positive electrode not containing the oxide (when a battery is constituted by using the electrode of the present invention only for the negative electrode), a coating and drying step of the oxide-containing composition described above A positive electrode manufactured by omitting the above may be used.
上記のようにして得られる正極では、正極合剤層の総厚み（集電体の両側に正極合剤層が形成されている場合では、両正極合剤層の合計厚み）を、４０〜１６０μｍとすることが好ましい。 In the positive electrode obtained as described above, the total thickness of the positive electrode mixture layer (when the positive electrode mixture layers are formed on both sides of the current collector, the total thickness of both positive electrode mixture layers) is 40 to 160 μm. It is preferable that
また、本発明の電極である負極（上記酸化物を含有する負極）についても、上記酸化物を含有する正極について説明した方法と、同様の方法を用いて製造することができる。 負極を製造するための上記負極合剤含有組成物においては、その固形分（すなわち、負極合剤）全量中、負極活物質を９０〜９８質量％、バインダを２〜１０質量％とすることが好ましく、また、導電助剤を使用する場合には、導電助剤を１〜５質量％とすることが好ましい。 Moreover, the negative electrode (negative electrode containing the said oxide) which is an electrode of this invention can also be manufactured using the method similar to the method demonstrated about the positive electrode containing the said oxide. In the negative electrode mixture-containing composition for producing the negative electrode, the total amount of the solid content (that is, the negative electrode mixture) may be 90 to 98% by mass of the negative electrode active material and 2 to 10% by mass of the binder. Moreover, when using a conductive support agent, it is preferable that a conductive support agent shall be 1-5 mass%.
また、負極を製造するための上記酸化物含有組成物のうち、負極活物質を含有する組成物では、かかる組成物のみによって混在層が形成されることから、酸化物含有組成物の固形分全量中の上記酸化物の含有量は、１０質量％以上、より好ましくは３０質量％以上であって、９０質量％以下、より好ましくは７０質量％以下とすることが望ましい。そして、この酸化物含有組成物における固形分全量中、負極活物質は５．５〜８０質量％、バインダは３〜１０質量％とすることが好ましく、更に、導電助剤を使用する場合には、導電助剤は０．１〜４．５質量％とすることが好ましい。 Further, among the oxide-containing compositions for producing the negative electrode, in the composition containing the negative electrode active material, since the mixed layer is formed only by such a composition, the total solid content of the oxide-containing composition The content of the oxide in the content is 10% by mass or more, more preferably 30% by mass or more, and is preferably 90% by mass or less, more preferably 70% by mass or less. And in the solid content whole quantity in this oxide containing composition, it is preferable that a negative electrode active material shall be 5.5-80 mass%, a binder shall be 3-10 mass%, and also when using a conductive support agent. The conductive auxiliary is preferably 0.1 to 4.5% by mass.
他方、負極を製造するための上記酸化物含有組成物のうち、負極活物質を含有させない組成物では、酸化物含有組成物の固形分全量中、上記酸化物を９０〜９９質量％、バインダを１〜１０質量％とすることが好ましい。 On the other hand, among the oxide-containing compositions for producing the negative electrode, in the composition not containing the negative electrode active material, 90 to 99% by mass of the oxide and binder in the total solid content of the oxide-containing composition. It is preferable to set it as 1-10 mass%.
なお、上記酸化物を含有しない負極合剤層を有する負極を使用して電池を構成する場合（正極のみに本発明の電極を用いて電池を構成する場合）には、上記の酸化物含有組成物の塗布、乾燥工程を省略して製造した負極を用いればよい。また、負極活物質に上記例示の合金やリチウム金属などを用いる場合には、これらの箔のみで構成された負極や、これらの箔が集電体に貼り合わされてなる構造の負極を用いることもできる。 In the case where a battery is formed using a negative electrode having a negative electrode mixture layer that does not contain the oxide (when the battery is formed using the electrode of the present invention only for the positive electrode), the above oxide-containing composition is used. A negative electrode manufactured by omitting the application and drying steps of the product may be used. In addition, when the above-exemplified alloy or lithium metal is used for the negative electrode active material, a negative electrode composed only of these foils or a negative electrode having a structure in which these foils are bonded to a current collector may be used. it can.
上記のようにして得られる負極では、負極合剤層の総厚み（集電体の両側に負極合剤層が形成されている場合では、両負極合剤層の合計厚み）を、４０〜１６０μｍとすることが好ましい。 In the negative electrode obtained as described above, the total thickness of the negative electrode mixture layer (when the negative electrode mixture layers are formed on both sides of the current collector, the total thickness of both negative electrode mixture layers) is 40 to 160 μm. It is preferable that
本発明のリチウム二次電池は、正極および負極の少なくとも一方に本発明の電極を用いていればよく、その他の構成や構造については特に制限はなく、従来公知のリチウム二次電池で採用されている各種構成や構造を適用することができる。 The lithium secondary battery of the present invention only needs to use the electrode of the present invention for at least one of the positive electrode and the negative electrode, and there is no particular limitation on the other configuration and structure, and it is adopted in a conventionally known lithium secondary battery. Various configurations and structures can be applied.
なお、上記の通り、本発明の電池に用いる電極のうち、正極は正極合剤層を有するものであるが、負極については、負極合剤層を有する場合と、負極合剤層を有しない場合（負極活物質として、リチウム金属や合金の箔を用いる場合）があり得る。本発明の電池では、正極が正極合剤層を有し、負極は負極合剤層を有しないものである場合には、正極のみが本発明の電極であればよい。他方、正極が正極合剤層を有し、負極が負極合剤層を有する場合には、正極合剤層のみ、または負極合剤層のみが本発明の電極であればよいが、正極、負極の両者が本発明の電極であることがより好ましい。 As described above, among the electrodes used in the battery of the present invention, the positive electrode has a positive electrode mixture layer, but the negative electrode has a negative electrode mixture layer and a negative electrode mixture layer. (When using a foil of lithium metal or alloy as the negative electrode active material). In the battery of the present invention, when the positive electrode has a positive electrode mixture layer and the negative electrode does not have a negative electrode mixture layer, only the positive electrode may be the electrode of the present invention. On the other hand, when the positive electrode has a positive electrode mixture layer and the negative electrode has a negative electrode mixture layer, only the positive electrode mixture layer or only the negative electrode mixture layer may be the electrode of the present invention. It is more preferable that both of these are the electrodes of the present invention.
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 battery include a cylindrical shape (such as a rectangular tube shape or a cylindrical shape) using a steel can or an aluminum can as an outer 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.
正極と負極とを仕切る多孔質の隔離材（セパレータ）としては、強度が十分で且つ電解液を多く保持できるものがよく、そのような観点から、厚さが１０〜５０μｍで開口率が３０〜７０％の、ポリエチレン、ポリプロピレン、またはエチレン−プロピレン共重合体を含む微多孔フィルムや不織布などが好ましい。 As a porous separator (separator) for partitioning the positive electrode and the negative electrode, those having sufficient strength and capable of holding a large amount of electrolyte are preferable. From such a viewpoint, the thickness is 10 to 50 μm and the aperture ratio is 30 to 30%. A microporous film or nonwoven fabric containing 70% polyethylene, polypropylene, or ethylene-propylene copolymer is preferred.
電解液としては、例えば、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、プロピオン酸メチル、エチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート、γ−ブチロラクトン、エチレングリコールサルファイト、１，２−ジメトキシエタン、１，３−ジオキソラン、テトラヒドロフラン、２−メチル−テトラヒドロフラン、ジエチルエーテルなどの１種のみからなる有機溶媒、あるいは２種以上の混合溶媒に、例えば、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＳｂＦ６、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〕などのリチウム塩から選ばれる少なくとも１種を溶解させることによって調製した電解液が使用される。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。これらの電解液には、充放電サイクル特性や電池貯蔵時の特性を向上させるために、従来公知の各種添加剤を適宜加えることができる。
Examples of the electrolytic solution include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propionate, ethylene carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, ethylene glycol sulfite, 1,2-dimethoxyethane, 1,3- dioxolane, tetrahydrofuran, 2-methyl - tetrahydrofuran, organic solvent consists of only one type, such as diethyl ether or a mixture of two or more solvents, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6,
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適用されている各種用途に用いることができる。 The lithium secondary battery of the present invention can be used for various applications to which a conventionally known lithium secondary battery is applied.
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・後記の趣旨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、後記の各実施例のうち、実施例１、実施例２、実施例５および実施例６が、本発明の実施例に該当する。 Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. Of the following examples, Example 1, Example 2, Example 5, and Example 6 correspond to examples of the present invention.
実施例１
＜正極の作製＞
平均粒径が０．４μｍのアルミナ微粒子［住友化学社製「スミコランダムＡＡ０４（商品名）」］：９７質量部と、バインダであるＰＶＤＦ：３質量部とを、ＮＭＰを溶剤として均一になるように混合して、酸化物含有ペーストを調製した。
Example 1
<Preparation of positive electrode>
Alumina fine particles having an average particle size of 0.4 μm [“SUMIKORANDAN AA04 (trade name)” manufactured by Sumitomo Chemical Co., Ltd.]: 97 parts by mass and PVDF as a binder: 3 parts by mass so that NMP is used as a solvent. To prepare an oxide-containing paste.
また、正極活物質であるＬｉＣｏＯ２：９５質量部、導電助剤であるアセチレンブラック：２．５質量部、およびバインダであるＰＶＤＦ：２．５質量部を、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。 Further, 95 parts by mass of LiCoO 2 as a positive electrode active material, 2.5 parts by mass of acetylene black as a conductive auxiliary agent, and 2.5 parts by mass of PVDF as a binder are made uniform with NMP as a solvent. By mixing, a positive electrode mixture-containing paste was prepared.
上記の正極合剤含有ペーストを、集電体となる厚みが１５μｍのアルミニウム箔の片面に塗布し、１００℃の熱風乾燥炉で乾燥させた。その後、集電体の他面にも、正極合剤含有ペーストを塗布し、同様にして乾燥させた。乾燥後、上記の酸化物含有ペーストを、集電体表面に形成した正極合剤含有ペースト塗膜の表面に摺り切り塗布して、上記塗膜の表面空隙部に酸化物含有ペーストを充填し、１００℃の熱風乾燥炉で乾燥後、カレンダー処理を行って、全厚が１３７μｍ（正極合剤層が片面あたり６１μｍ）と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正極を作製した。正極の集電体の露出部には、タブ付けを行った。 The above positive electrode mixture-containing paste was applied to one side of an aluminum foil having a thickness of 15 μm serving as a current collector, and dried in a hot air drying oven at 100 ° C. Then, the positive electrode mixture-containing paste was applied to the other surface of the current collector and dried in the same manner. After drying, the oxide-containing paste is applied to the surface of the positive electrode mixture-containing paste coating film formed on the current collector surface, and the oxide-containing paste is filled into the surface voids of the coating film, After drying in a hot air drying oven at 100 ° C., calendar treatment is performed, and the thickness of the positive electrode mixture layer is adjusted so that the total thickness is 137 μm (the positive electrode mixture layer is 61 μm per side), so that the width becomes 43 mm. The positive electrode was produced by cutting. The exposed portion of the positive electrode current collector was tabbed.
得られた正極における正極合剤層中のアルミナ量は２質量％であり、また、アルミナと正極活物質とが混在する混在層におけるアルミナの含有量は、２０質量％であった。混在層は、正極合剤層の表面から６μｍの厚さ（すなわち、混在層の厚みは正極合剤層の厚みの１０％）で形成され、正極合剤層の表面では、正極活物質の一部が露出していた。 The amount of alumina in the positive electrode mixture layer in the positive electrode obtained was 2% by mass, and the content of alumina in the mixed layer in which alumina and the positive electrode active material were mixed was 20% by mass. The mixed layer is formed with a thickness of 6 μm from the surface of the positive electrode mixture layer (that is, the thickness of the mixed layer is 10% of the thickness of the positive electrode mixture layer). The part was exposed.
＜負極の作製＞
負極活物質である黒鉛：９５質量部と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。そのペーストを集電体となる厚みが８μｍの銅箔の片側に塗布した後、１００℃熱風乾燥炉にて乾燥した。その後、集電体の他面にも、負極合剤含有ペーストを塗布し、同様にして乾燥させた。その後カレンダー処理を行って全厚が１３６μｍ（負極合剤層が片側あたり６４μｍ）になるように負極合剤層の厚みを調整し、幅４４ｍｍになるように切断して負極を作製した。負極の集電体の露出部には、タブ付けを行った。
<Production of negative electrode>
A negative electrode active material-containing paste was prepared by mixing 95 parts by mass of graphite serving as the negative electrode active material and 5 parts by mass of PVDF so as to be uniform using NMP as a solvent. The paste was applied to one side of a copper foil having a thickness of 8 μm serving as a current collector, and then dried in a 100 ° C. hot air drying furnace. Thereafter, the negative electrode mixture-containing paste was applied to the other surface of the current collector and dried in the same manner. Thereafter, calendar treatment was performed to adjust the thickness of the negative electrode mixture layer so that the total thickness was 136 μm (the negative electrode mixture layer was 64 μm per side), and the negative electrode was produced by cutting to a width of 44 mm. The exposed portion of the negative electrode current collector was tabbed.
＜電池の組み立て＞
上記の正極と上記の負極とを、セパレータである微多孔性ポリエチレン（厚み２０μｍ）を介して重ね、渦巻状に巻回して、巻回電極体とした。この巻回電極体を、幅３４ｍｍ、厚み４ｍｍ、高さ５０ｍｍのアルミニウム製有底筒状の外装缶内に装填した。そして、正極の集電タブを正極端子に、負極の集電タブを負極端子に、それぞれ溶接した。この外装缶内に、非水電解液（エチレンカーボネートとメチルエチルカーボネートとを、体積比で１：２で混合した溶媒中に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させたもの）を注入した。非水電解液を電極に十分に浸透させた後、外装缶の開口部を封口して、角形のリチウム二次電池を得た。
<Battery assembly>
The above positive electrode and the above negative electrode were overlapped via a microporous polyethylene (thickness 20 μm) as a separator and wound in a spiral shape to obtain a wound electrode body. The wound electrode body was loaded into an aluminum bottomed cylindrical outer can having a width of 34 mm, a thickness of 4 mm, and a height of 50 mm. The positive current collecting tab was welded to the positive electrode terminal, and the negative current collecting tab was welded to the negative electrode terminal. In this outer can, a non-aqueous electrolyte (LiPF 6 dissolved at a concentration of 1.0 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2) was used. Injected. After fully infiltrating the non-aqueous electrolyte into the electrode, the opening of the outer can was sealed to obtain a prismatic lithium secondary battery.
実施例２
酸化物含有ペーストの塗布を行わずにカレンダー処理を施し、正極の全厚を１３５μｍ（正極合剤層が片面あたり６０μｍ）となるように調整した以外は、実施例１と同様にして正極を作製した。
Example 2
A positive electrode was produced in the same manner as in Example 1, except that the calendar treatment was performed without applying the oxide-containing paste, and the total thickness of the positive electrode was adjusted to 135 μm (the positive electrode mixture layer was 60 μm per side). did.
実施例１と同様にして調製した負極合剤含有ペーストを、集電体となる厚みが８μｍの銅箔の片側に塗布した後、１００℃熱風乾燥炉にて乾燥した。次いで、集電体の他面にも、負極合剤含有ペーストを塗布し、同様にして乾燥させた。その後、実施例１と同様にして調製した酸化物含有ペーストを、集電体表面に形成した負極合剤含有ペースト塗膜の表面に摺り切り塗布して、上記塗膜の表面空隙部に酸化物含有ペーストを充填し、１００℃の熱風乾燥炉で乾燥後、カレンダー処理を行って、全厚が１３８μｍ（負極合剤層が片面あたり６５μｍ）となるように負極合剤層の厚みを調整し、以下、実施例１と同様にして、負極を作製した。 A negative electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to one side of a copper foil having a thickness of 8 μm serving as a current collector, and then dried in a 100 ° C. hot air drying oven. Next, the negative electrode mixture-containing paste was applied to the other surface of the current collector and dried in the same manner. Thereafter, the oxide-containing paste prepared in the same manner as in Example 1 was applied to the surface of the negative electrode mixture-containing paste coating film formed on the current collector surface, and the oxide was applied to the surface voids of the coating film. Filled with the containing paste, dried in a hot air drying oven at 100 ° C., and then calendered to adjust the thickness of the negative electrode mixture layer so that the total thickness was 138 μm (the negative electrode mixture layer was 65 μm per side), Thereafter, a negative electrode was produced in the same manner as in Example 1.
得られた負極における負極合剤層中のアルミナ量は３質量％であり、アルミナと負極活物質とが混在する混在層におけるアルミナの含有量は、２４質量％であった。混在層は、負極合剤層の表面から８μｍの厚さ（すなわち、混在層の厚みは負極合剤層の厚みの１２％）で形成され、負極合剤層の表面では、負極活物質の一部が露出していた。 The amount of alumina in the negative electrode mixture layer in the obtained negative electrode was 3% by mass, and the content of alumina in the mixed layer in which alumina and the negative electrode active material were mixed was 24% by mass. The mixed layer is formed with a thickness of 8 μm from the surface of the negative electrode mixture layer (that is, the thickness of the mixed layer is 12% of the thickness of the negative electrode mixture layer). The part was exposed.
上記の正極と負極を用いた以外は、実施例１と同様にして、角形のリチウム二次電池を作製した。 A square lithium secondary battery was produced in the same manner as in Example 1 except that the above positive electrode and negative electrode were used.
実施例３
平均粒径が０．４μｍのアルミナ微粒子［住友化学社製「スミコランダムＡＡ０４（商品名）」］：２０質量部、正極活物質であるＬｉＣｏＯ２：７５質量部、導電助剤であるアセチレンブラック：２．０質量部、およびバインダであるＰＶＤＦ：３．０質量部を、ＮＭＰを溶剤として均一になるように混合して、酸化物含有ペーストを調製した。
Example 3
Alumina fine particles having an average particle diameter of 0.4 μm [Sumiko Random AA04 (trade name) manufactured by Sumitomo Chemical Co., Ltd.]: 20 parts by mass, LiCoO 2 as a positive electrode active material: 75 parts by mass, acetylene black as a conductive auxiliary agent: An oxide-containing paste was prepared by mixing 2.0 parts by mass and 3.0 parts by mass of PVDF as a binder so as to be uniform using NMP as a solvent.
実施例１と同様にして調製した正極合剤含有ペーストを、集電体となる厚みが１５μｍのアルミニウム箔の片面に塗布し、更に上記の酸化物含有ペーストを塗布した後に、１００℃の熱風乾燥炉で乾燥させた。その後、集電体の他面にも、正極合剤含有ペーストと酸化物含有ペーストとを塗布し、同様にして乾燥させた。その後カレンダー処理を行って、全厚が１３７μｍ（正極合剤層が片面あたり６１μｍ）となるように正極合剤層の厚みを調整し、以下、実施例１と同様にして正極を作製した。 The positive electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to one surface of an aluminum foil having a thickness of 15 μm serving as a current collector, and the oxide-containing paste was further applied, followed by hot air drying at 100 ° C. Dry in oven. Thereafter, a positive electrode mixture-containing paste and an oxide-containing paste were applied to the other surface of the current collector and dried in the same manner. Thereafter, calendar treatment was performed to adjust the thickness of the positive electrode mixture layer so that the total thickness was 137 μm (the positive electrode mixture layer was 61 μm per side), and a positive electrode was produced in the same manner as in Example 1 below.
得られた正極では、アルミナと正極活物質とが混在する混在層が、正極合剤層の表面から４μｍの厚さ（すなわち、混在層の厚みは正極合剤層の厚みの７％）で形成され、正極合剤層の表面では、正極活物質の一部が露出していた。また、混在層におけるアルミナの含有量は、２０質量％であった。 In the obtained positive electrode, the mixed layer in which alumina and the positive electrode active material are mixed is formed with a thickness of 4 μm from the surface of the positive electrode mixture layer (that is, the thickness of the mixed layer is 7% of the thickness of the positive electrode mixture layer). In addition, a part of the positive electrode active material was exposed on the surface of the positive electrode mixture layer. Moreover, content of the alumina in the mixed layer was 20% by mass.
上記の正極を用いた以外は、実施例１と同様にして角形のリチウム二次電池を作製した。 A rectangular lithium secondary battery was produced in the same manner as in Example 1 except that the positive electrode was used.
実施例４
酸化物含有ペーストの塗布を行わずにカレンダー処理を施し、正極の全厚を１３３μｍ（正極合剤層が片面あたり５９μｍ）となるように調整した以外は、実施例１と同様にして正極を作製した。
Example 4
A positive electrode was produced in the same manner as in Example 1, except that the calendar treatment was performed without applying the oxide-containing paste, and the total thickness of the positive electrode was adjusted to 133 μm (the positive electrode mixture layer was 59 μm per side). did.
平均粒径が０．４μｍのアルミナ微粒子［住友化学社製「スミコランダムＡＡ０４（商品名）」］：２６質量部、負極活物質である黒鉛：７０質量部、およびバインダであるＰＶＤＦ：４質量部を、ＮＭＰを溶剤として均一になるように混合して、酸化物含有ペーストを調製した。 Alumina fine particles having an average particle diameter of 0.4 μm [Sumiko Random AA04 (trade name) manufactured by Sumitomo Chemical Co., Ltd.]: 26 parts by mass, graphite as a negative electrode active material: 70 parts by mass, and PVDF as a binder: 4 parts by mass Were mixed so as to be uniform using NMP as a solvent to prepare an oxide-containing paste.
実施例１と同様にして調製した負極合剤含有ペーストを、集電体となる厚みが８μｍの銅箔の片側に塗布し、更に上記の酸化物含有ペーストを塗布した後に、１００℃熱風乾燥炉にて乾燥した。その後、集電体の他面にも、負極合剤含有ペーストと酸化物含有ペーストとを塗布し、同様にして乾燥させた。その後カレンダー処理を行って、全厚が１４０μｍ（負極合剤層が片側あたり６６μｍ）になるように負極合剤層の厚みを調整し、以下、実施例１と同様にして、負極を作製した。 A negative electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to one side of a copper foil having a thickness of 8 μm serving as a current collector, and the oxide-containing paste was further applied, followed by a 100 ° C. hot air drying furnace. Dried. Thereafter, a negative electrode mixture-containing paste and an oxide-containing paste were applied to the other surface of the current collector and dried in the same manner. Thereafter, calendar treatment was performed, and the thickness of the negative electrode mixture layer was adjusted so that the total thickness was 140 μm (the negative electrode mixture layer was 66 μm per side). Thereafter, a negative electrode was produced in the same manner as in Example 1.
得られた負極では、アルミナと負極活物質とが混在する混合層が、負極合剤層の表面から４μｍの厚み（すなわち、混在層の厚みは負極合剤層の厚みの６％）で形成され、負極合剤層の表面では、負極活物質の一部が露出していた。また、混在層におけるアルミナの含有量は、２６質量％であった。 In the obtained negative electrode, a mixed layer in which alumina and the negative electrode active material are mixed is formed with a thickness of 4 μm from the surface of the negative electrode mixture layer (that is, the thickness of the mixed layer is 6% of the thickness of the negative electrode mixture layer). On the surface of the negative electrode mixture layer, a part of the negative electrode active material was exposed. The content of alumina in the mixed layer was 26% by mass.
上記の正極と負極を用いた以外は、実施例１と同様にして、角形のリチウム二次電池を作製した。 A square lithium secondary battery was produced in the same manner as in Example 1 except that the above positive electrode and negative electrode were used.
比較例１
酸化物含有ペーストの塗布を行わずにカレンダー処理を施し、正極の全厚を１３５μｍ（正極合剤層が片面あたり６０μｍ）となるように調整した以外は、実施例１と同様にして正極を作製した。また、カレンダー処理によって、全厚を１３８μｍ（負極合剤層が片側あたり６５μｍ）になるように負極合剤層の厚みを調整した以外は、実施例１と同様にして負極を作製した。
Comparative Example 1
A positive electrode was produced in the same manner as in Example 1, except that the calendar treatment was performed without applying the oxide-containing paste, and the total thickness of the positive electrode was adjusted to 135 μm (the positive electrode mixture layer was 60 μm per side). did. Further, a negative electrode was produced in the same manner as in Example 1 except that the thickness of the negative electrode mixture layer was adjusted by calendering so that the total thickness was 138 μm (the negative electrode mixture layer was 65 μm per side).
上記の正極と負極を用いた以外は、実施例１と同様にして、角形のリチウム二次電池を作製した。 A square lithium secondary battery was produced in the same manner as in Example 1 except that the above positive electrode and negative electrode were used.
比較例２
実施例１と同様にして調製した正極合剤含有ペーストを、集電体となる厚みが１５μｍのアルミニウム箔の片面に塗布し、更に実施例１と同様にして調製した酸化物含有ペーストを塗布した後に、１００℃の熱風乾燥炉で乾燥させた。次いで、集電体の他面にも、正極合剤含有ペーストと酸化物含有ペーストとを塗布し、同様にして乾燥させた。その後、カレンダー処理を行って、全厚が１３９μｍ（正極合剤層が片面あたり６２μｍ）となるように正極合剤層の厚みを調整し、その後は実施例１と同様にして正極を作製した。
Comparative Example 2
The positive electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to one surface of an aluminum foil having a thickness of 15 μm serving as a current collector, and the oxide-containing paste prepared in the same manner as in Example 1 was further applied. Later, it was dried in a hot air drying oven at 100 ° C. Next, the positive electrode mixture-containing paste and the oxide-containing paste were applied to the other surface of the current collector and dried in the same manner. Thereafter, calendering was performed to adjust the thickness of the positive electrode mixture layer so that the total thickness was 139 μm (the positive electrode mixture layer was 62 μm per side), and then the positive electrode was produced in the same manner as in Example 1.
得られた正極では、正極活物質が存在せずにアルミナのみが存在する層が、正極合剤層の表面から４μｍの厚みで形成され、正極合剤層の表面では、正極活物質の露出は見られなかった。 In the obtained positive electrode, a layer in which only the alumina is present without the presence of the positive electrode active material is formed with a thickness of 4 μm from the surface of the positive electrode mixture layer, and the positive electrode active material is exposed on the surface of the positive electrode mixture layer. I couldn't see it.
また、カレンダー処理によって、全厚を１３４μｍ（負極合剤層が片側あたり６３μｍ）になるように負極合剤層の厚みを調整した以外は、実施例１と同様にして負極を作製した。 Further, a negative electrode was produced in the same manner as in Example 1 except that the thickness of the negative electrode mixture layer was adjusted by calendering so that the total thickness was 134 μm (the negative electrode mixture layer was 63 μm per side).
上記の正極と負極を用いた以外は、実施例１と同様にして、角形のリチウム二次電池を作製した。 A square lithium secondary battery was produced in the same manner as in Example 1 except that the above positive electrode and negative electrode were used.
比較例３
実施例１と同様にして調製した負極合剤含有ペーストを、集電体となる厚みが８μｍの銅箔の片側に塗布し、更に実施例１と同様にして調製した酸化物含有ペーストを塗布した後に、１００℃熱風乾燥炉にて乾燥した。次いで、集電体の他面にも、負極合剤含有ペーストと酸化物含有ペーストとを塗布し、同様にして乾燥させた。その後カレンダー処理を行って、全厚が１４２μｍ（負極合剤層が片側あたり６７μｍ）になるように負極合剤層の厚みを調整し、その後は実施例１と同様にして、負極を作製した。
Comparative Example 3
The negative electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to one side of a copper foil having a thickness of 8 μm serving as a current collector, and the oxide-containing paste prepared in the same manner as in Example 1 was further applied. Later, it was dried in a 100 ° C. hot air drying oven. Next, the negative electrode mixture-containing paste and the oxide-containing paste were applied to the other surface of the current collector and dried in the same manner. Thereafter, calendar treatment was performed to adjust the thickness of the negative electrode mixture layer so that the total thickness was 142 μm (the negative electrode mixture layer was 67 μm per side). Thereafter, the negative electrode was produced in the same manner as in Example 1.
得られた負極では、負極活物質が存在せずにアルミナのみが存在する層が、負極合剤層の表面から４μｍの厚みで形成され、負極合剤層の表面では、負極活物質の露出は見られなかった。 In the obtained negative electrode, a layer in which only the alumina is present without the negative electrode active material is formed with a thickness of 4 μm from the surface of the negative electrode mixture layer, and the negative electrode active material is exposed on the surface of the negative electrode mixture layer. I couldn't see it.
また、カレンダー処理によって、全厚を１３１μｍ（正極合剤層が片側あたり５８μｍ）になるように正極合剤層の厚みを調整した以外は、実施例２と同様にして正極を作製した。 Further, a positive electrode was produced in the same manner as in Example 2, except that the thickness of the positive electrode mixture layer was adjusted by calendering so that the total thickness was 131 μm (the positive electrode mixture layer was 58 μm per side).
上記の正極と負極を用いた以外は、実施例１と同様にして、角形のリチウム二次電池を作製した。 A square lithium secondary battery was produced in the same manner as in Example 1 except that the above positive electrode and negative electrode were used.
実施例１〜４および比較例１〜３の各リチウム二次電池の組み立てに用いたものと同じ正極および負極について、電池組み立てに用いたものと同じ非水電解液を接触させてから０．１秒後の接触角を測定した。測定には、動的吸収計（Ｆｉｂｒｏ社製「ＤＡＴ １１００ ＭＫＩＩ」）を用いた。結果を表１に示す。 About the same positive electrode and negative electrode as those used for assembling the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3, the same non-aqueous electrolyte as that used for battery assembly was brought into contact with 0.1 to 0.1 The contact angle after 2 seconds was measured. A dynamic absorption meter (“DAT 1100 MKII” manufactured by Fibro) was used for the measurement. The results are shown in Table 1.
表１に示す結果から、実施例のリチウム二次電池に使用している電極のうち、絶縁性酸化物であるアルミナを含有させたもの（実施例１、３の正極、実施例２、４の負極）は、いずれも、アルミナを含有させていない比較例１の正極および負極に比べて、非水電解液の濡れ性が向上していることが確認できた。特に、実施例２、４の負極において、非水電解液に対する濡れ性向上の効果が顕著である。なお、比較例２の正極および比較例３の負極についても、表面に絶縁性酸化物よりなる層を形成したことにより、非水電解液に対する濡れ性が向上している。 From the results shown in Table 1, among the electrodes used in the lithium secondary batteries of the examples, those containing alumina, which is an insulating oxide (the positive electrodes of Examples 1 and 3, Examples 2 and 4) It was confirmed that the negative electrode) improved the wettability of the non-aqueous electrolyte as compared with the positive electrode and the negative electrode of Comparative Example 1 that did not contain alumina. In particular, in the negative electrodes of Examples 2 and 4, the effect of improving the wettability with respect to the non-aqueous electrolyte is remarkable. In addition, also about the positive electrode of the comparative example 2, and the negative electrode of the comparative example 3, the wettability with respect to a non-aqueous electrolyte is improving by forming the layer which consists of an insulating oxide on the surface.
次に、実施例１〜４および比較例１〜３の各リチウム二次電池について、下記の容量測定、および電解液に浸漬した際の重量増加量測定を行った。結果を表２に示す。 Next, for each of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3, the following capacity measurement and weight increase measurement when immersed in an electrolytic solution were performed. The results are shown in Table 2.
＜容量測定＞
実施例１〜４および比較例１〜３の各リチウム二次電池について、２５℃で０．５Ｃの電流値での定電流充電（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２．５時間）の後、０．５Ｃの電流値で３．０Ｖまで放電を行って、各電池の容量（放電容量）を測定した。各電池の容量は、比較例１の電池の容量を１００としたときの相対値で表す。
<Capacity measurement>
About each lithium secondary battery of Examples 1-4 and Comparative Examples 1-3, constant current charging (up to 4.2 V) at a current value of 0.5 C at 25 ° C. and charging by constant voltage charging at 4.2 V After (constant current charging and constant voltage charging total time 2.5 hours), the battery was discharged to 3.0 V at a current value of 0.5 C, and the capacity (discharge capacity) of each battery was measured. The capacity of each battery is expressed as a relative value when the capacity of the battery of Comparative Example 1 is 100.
＜重量増加量測定＞
実施例１〜４および比較例１〜３の各リチウム二次電池について、電解液を注入する前の状態のもの（外装缶に巻回電極体を挿入後、注液口以外を封止したもの）を用意し、これらの電池組み立て体を電池製造に用いたものと同じ電解液に浸漬し、２分間減圧した後の重量増加量を測定した。各電池の重量増加量は、比較例１の電池の結果を１００としたときの相対値で表す。重量増加量が多いほど、電解液の注液性が良好であることを意味している。
<Weight increase measurement>
About each lithium secondary battery of Examples 1-4 and Comparative Examples 1-3, the state before injecting the electrolytic solution (after sealing the portion other than the liquid injection port after inserting the wound electrode body into the outer can ) Was prepared, and these battery assemblies were immersed in the same electrolyte solution used for battery production, and the weight increase after decompression for 2 minutes was measured. The weight increase amount of each battery is expressed as a relative value when the result of the battery of Comparative Example 1 is 100. It means that the greater the amount of weight increase, the better the pouring property of the electrolyte.
表２から以下のことが分かる。電極の電解液に対する濡れ性が良好であった比較例２および３の電池では、電解液の注液性は向上しているものの、電池容量が比較例１の電池に比べて３％以上低下している。これは、電極合剤層中の活物質の充填量が減少した結果である。これに対し、実施例１〜４の電池では、ほぼ比較例１と同等の電池容量を維持しており、電池容量の低下を抑制しつつ電解液の注液性を向上し得ることが確認できた。 Table 2 shows the following. In the batteries of Comparative Examples 2 and 3 in which the wettability of the electrode to the electrolytic solution was good, the electrolyte capacity was improved, but the battery capacity decreased by 3% or more compared to the battery of Comparative Example 1. ing. This is a result of a decrease in the filling amount of the active material in the electrode mixture layer. On the other hand, in the batteries of Examples 1 to 4, it was confirmed that the battery capacity substantially the same as that of Comparative Example 1 was maintained, and the electrolyte injection property could be improved while suppressing the decrease in battery capacity. It was.
実施例５
正極活物質としてＬｉＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２を用いた以外は、実施例１と同様にして、アルミニウム箔の両面にそれぞれ５０μｍの厚みで正極合剤層を形成し、全厚が１１５μｍの電極とした。なお、この正極合剤層の表面から５μｍの厚さの部分（すなわち、正極合剤層の厚みの１０％）を混在層とした。この電極を幅６３ｍｍ×長さ１１３ｍの大きさになるように切断して正極を作製した。なお、正極端子を取り付けられるよう、正極合剤層の一部には、１５ｍｍ×１５．５ｍｍの大きさの集電体露出部を設けた。
Example 5
Except that LiNi 1/3 Mn 1/3 Co 1/3 O 2 was used as the positive electrode active material, a positive electrode mixture layer was formed on each side of the aluminum foil with a thickness of 50 μm in the same manner as in Example 1, The electrode had a total thickness of 115 μm. A portion having a thickness of 5 μm from the surface of the positive electrode mixture layer (that is, 10% of the thickness of the positive electrode mixture layer) was defined as a mixed layer. This electrode was cut to a size of 63 mm wide × 113 m long to produce a positive electrode. In addition, the collector exposed part of the magnitude | size of 15 mm x 15.5 mm was provided in a part of positive mix layer so that a positive electrode terminal could be attached.
負極は、集電体片面での負極合剤層の厚みを５１μｍ（負極全厚：１１０μｍ）とし、幅６３ｍｍ×長さ１１３ｍの大きさになるように切断した以外は、実施例１と同様にして作製した。なお、負極端子を取り付けられるよう、負極合剤層の一部には、１５ｍｍ×１３ｍｍの大きさの集電体露出部を設けた。 The negative electrode was the same as in Example 1 except that the thickness of the negative electrode mixture layer on one side of the current collector was 51 μm (negative electrode total thickness: 110 μm) and was cut to a size of 63 mm wide × 113 m long. Made. A current collector exposed portion having a size of 15 mm × 13 mm was provided on a part of the negative electrode mixture layer so that the negative electrode terminal could be attached.
上記負極１５枚と正極１４枚とを、厚み２５μｍ、空孔率５４％のセパレータを介して交互に積層し、正極には幅１５ｍｍ、厚み０．２ｍｍのアルミタブを、負極には幅１５ｍｍ、厚み０．２ｍｍのニッケルメッキした銅タブを、それぞれ超音波溶接により溶接して正極端子および負極端子とし、それぞれの溶接箇所を１５ｍｍ×２５ｍｍのポリイミドテープを貼り付けて保護し、電極積層体を作製した。 The negative electrode 15 and the positive electrode 14 are alternately laminated via a separator having a thickness of 25 μm and a porosity of 54%, an aluminum tab having a width of 15 mm and a thickness of 0.2 mm for the positive electrode, and a width of 15 mm and a thickness for the negative electrode. A 0.2 mm nickel-plated copper tab was welded by ultrasonic welding to form a positive electrode terminal and a negative electrode terminal, and each welded portion was protected by applying a 15 mm × 25 mm polyimide tape to produce an electrode laminate. .
この電極積層体を、前記非水電解液とともにアルミラミネートフィルムよりなる収容容器内に収容し、開口部を封口して４Ａｈの容量のリチウム二次電池を作製した。 This electrode laminate was accommodated in an accommodation container made of an aluminum laminate film together with the non-aqueous electrolyte, and the opening was sealed to produce a lithium secondary battery having a capacity of 4 Ah.
実施例６
正極活物質としてＬｉＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２を用い、酸化物含有ペーストの塗布を行わずにカレンダー処理を施した以外は、実施例１と同様にして、アルミニウム箔の両面にそれぞれ４５μｍの厚みで正極合剤層を形成し、全厚が１０５μｍの正極を作製した。
Example 6
In the same manner as in Example 1, except that LiNi 1/3 Mn 1/3 Co 1/3 O 2 was used as the positive electrode active material and the calendar treatment was performed without applying the oxide-containing paste, A positive electrode mixture layer having a thickness of 45 μm was formed on both surfaces to produce a positive electrode having a total thickness of 105 μm.
負極は、実施例２と同様にして、集電体片面での負極合剤層の厚み：５６μｍ（負極全厚：１２０μｍ）、混在層の厚み：５μｍ（すなわち、負極合剤層の厚みの９％）で形成し、実施例５と同じ大きさに切断して作製した。 In the same manner as in Example 2, the negative electrode had a negative electrode mixture layer thickness on one side of the current collector: 56 μm (negative electrode total thickness: 120 μm), and a mixed layer thickness: 5 μm (that is, the negative electrode mixture layer thickness 9). %) And cut into the same size as in Example 5 to produce.
上記正極および負極を用い、実施例５と同様にして４Ａｈの容量のリチウム二次電池を作製した。 Using the positive electrode and the negative electrode, a lithium secondary battery having a capacity of 4 Ah was produced in the same manner as in Example 5.
比較例４
実施例５で用いた正極に替えて、混在層を形成していない実施例６の正極を用いた以外は、実施例５と同様にしてリチウム二次電池を作製した。
Comparative Example 4
Instead of the positive electrode used in Example 5, a lithium secondary battery was produced in the same manner as in Example 5, except that the positive electrode of Example 6 in which no mixed layer was formed was used.
実施例５〜６および比較例４の各リチウム二次電池について、２５℃で０．５Ｃの電流値での定電流充電（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２．５時間）の後、充電状態の電池２個を重ねて釘刺し試験（釘刺し速度：１ｍｍ／ｓ）をそれぞれ５回ずつ行い、異常昇温など異常の発生の有無を調べた。表３に結果を示す。 For each of the lithium secondary batteries of Examples 5 to 6 and Comparative Example 4, constant current charging (up to 4.2 V) at a current value of 0.5 C at 25 ° C. and charging by constant voltage charging at 4.2 V (constant) After total charging time of 2.5 hours for current charging and constant voltage charging), two charged batteries are stacked, and a nail penetration test (nail penetration speed: 1 mm / s) is performed 5 times each. The presence or absence of occurrence of was investigated. Table 3 shows the results.
正極または負極の合剤層の表面側に、活物質と絶縁性酸化物とが混在する混在層を形成した実施例５および６のリチウム二次電池では、注液性を向上させることにより電極反応の均一性を向上させることができたため、４Ａｈと高容量であるにもかかわらず、安全性を高めることができた。 In the lithium secondary batteries of Examples 5 and 6 in which the mixed layer in which the active material and the insulating oxide are mixed is formed on the surface side of the positive electrode or negative electrode mixture layer, the electrode reaction is improved by improving the liquid injection property. As a result, it was possible to improve safety even though the capacity was as high as 4 Ah.
１ 合剤層
２ 活物質
３ 非電気伝導性の酸化物
４ 集電体
1 Mixture layer 2
Claims (15)
上記合剤層は、その表面側に凹凸を有し、上記合剤層の凹部に、絶縁性酸化物を含有しかつ活物質を含有しない酸化物含有部を有しており、
上記合剤層の活物質の一部は、電極の表面に露出しており、
上記合剤層の表面側における、上記合剤層と上記酸化物含有部とで構成され、上記酸化物と上記活物質とが混在する領域の厚みが、当該領域を含む合剤層の全厚みの１〜２０％であることを特徴とするリチウム二次電池用電極。 An electrode for a lithium secondary battery having a mixture layer containing an active material on one side or both sides of a current collector,
The mixture layer has irregularities on its surface side, and has an oxide-containing portion that contains an insulating oxide and does not contain an active material in the recess of the mixture layer.
Part of the active material of the mixture layer is exposed on the surface of the electrode,
The surface side of the mixture layer is composed of the above mixture layer and the oxide-containing portion, the thickness of the region where the oxide and the above active material is mixed-is, the total of the mixture layer including the region The electrode for lithium secondary batteries characterized by being 1 to 20% of thickness.
絶縁性酸化物とバインダとを含む酸化物含有組成物を調製する工程と、
表面側に凹凸を有する上記合剤層の表面に上記酸化物含有組成物を塗布し、上記絶縁性酸化物と上記バインダとを含有しかつ活物質を含有しない酸化物含有部を形成する工程とを有し、
上記合剤層の活物質の一部を電極の表面に露出させ、かつ上記合剤層と上記酸化物含有部とで構成され、上記酸化物と上記活物質とが混在する領域の厚みを、当該領域を含む合剤層の全厚みの１〜２０％とすることを特徴とするリチウム二次電池用電極の製造方法。 A method for producing an electrode for a lithium secondary battery comprising a mixture layer containing an active material on one side or both sides of a current collector,
Preparing an oxide-containing composition comprising an insulating oxide and a binder;
Applying the oxide-containing composition to the surface of the mixture layer having irregularities on the surface side, and forming an oxide-containing portion containing the insulating oxide and the binder and containing no active material ; Have
It exposes a portion of the active material of the mixture layer on the surface of the electrode, and is composed of the above mixture layer and the oxide-containing portion, the thickness of the region where the oxide and the above active material is mixed- , method for producing a lithium secondary battery electrode, which comprises 1 to 20% of the total thickness of the mixture layer containing the region.
The manufacturing method of the electrode for lithium secondary batteries in any one of Claims 9-14 which contains the carbonaceous material which can occlude and discharge | release lithium as said active material.
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| JP5961922B2 (en) * | 2010-05-31 | 2016-08-03 | 日産自動車株式会社 | Negative electrode for secondary battery and method for producing the same |
| JPWO2015004841A1 (en) * | 2013-07-08 | 2017-03-02 | パナソニック株式会社 | Nonaqueous electrolyte secondary battery |
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