JP7093733B2 - Plates for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries - Google Patents

Plates for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries Download PDF

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JP7093733B2
JP7093733B2 JP2019027215A JP2019027215A JP7093733B2 JP 7093733 B2 JP7093733 B2 JP 7093733B2 JP 2019027215 A JP2019027215 A JP 2019027215A JP 2019027215 A JP2019027215 A JP 2019027215A JP 7093733 B2 JP7093733 B2 JP 7093733B2
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一輝 上田
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Primearth EV Energy Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は、充放電が可能である非水電解質二次電池の非水電解質二次電池用極板群、及び非水電解質二次電池に関する。 The present invention relates to a group of electrode plates for a non-aqueous electrolyte secondary battery of a non-aqueous electrolyte secondary battery capable of charging and discharging, and a non-aqueous electrolyte secondary battery.

非水電解質二次電池の一つであるリチウムイオン二次電池は、高いエネルギー密度を有し、高容量であることから、電気自動車（ＥＶ）やハイブリッド自動車（ＨＶ）等の駆動用電源として用いられている。リチウムイオン二次電池は、電極基材の両面に電極の活物質を含む電極合剤層を設けた正極板及び負極板をセパレータを介して積層した極板群を有し、正極板と負極板との間にセパレータを介して電解液を保持する。 Lithium-ion secondary batteries, which are one of the non-aqueous electrolyte secondary batteries, have high energy density and high capacity, and are therefore used as power sources for driving electric vehicles (EVs) and hybrid vehicles (HVs). Has been done. The lithium ion secondary battery has a positive electrode plate and a negative electrode plate in which an electrode mixture layer containing an active material of the electrode is provided on both sides of an electrode base material, and a negative electrode plate laminated via a separator, and has a positive electrode plate and a negative electrode plate. The electrolyte is held between the and the separator.

リチウムイオン二次電池は、電極合材層及びセパレータに電解液が浸透しているが、電極合剤層において電解液が偏在すると電流集中を生じさせてリチウムの析出要因となる。そこで、電解液を均一に分布させる技術の一例が特許文献１に記載されている。 In the lithium ion secondary battery, the electrolytic solution permeates the electrode mixture layer and the separator, but if the electrolytic solution is unevenly distributed in the electrode mixture layer, current concentration occurs and it becomes a cause of lithium precipitation. Therefore, Patent Document 1 describes an example of a technique for uniformly distributing an electrolytic solution.

特許文献１に記載の非水電解質二次電池は、極板群と非水電解質とを備える。極板群は、正極集電体上に所定の幅の正極活物質層が形成されている長尺状の正極板と、負極集電体上に正極活物質層を超える幅の負極活物質層が形成されている長尺状の負極板とが積層され捲回されている。正極活物質層及び負極活物質層の少なくとも一方の空隙率（体積％）は、捲回軸方向の中心を含む中央領域と捲回軸方向の両端部を含む一対の端部領域とで異なっていて、端部領域の空隙率が中央領域の空隙率よりも大きい。 The non-aqueous electrolyte secondary battery described in Patent Document 1 includes a plate group and a non-aqueous electrolyte. The electrode plate group consists of a long positive electrode plate in which a positive electrode active material layer having a predetermined width is formed on a positive electrode current collector, and a negative electrode active material layer having a width exceeding the positive electrode active material layer on the negative electrode current collector. Is formed by laminating and winding a long negative electrode plate. The porosity (% by volume) of at least one of the positive electrode active material layer and the negative electrode active material layer is different between the central region including the center in the winding axis direction and the pair of end regions including both ends in the winding axis direction. Therefore, the porosity in the end region is larger than the porosity in the central region.

特開２０１４－２０７２０１号公報Japanese Unexamined Patent Publication No. 2014-207201

非水電解質二次電池は、負極板に電解液が浸透しているが、充放電に伴って極板群に生じる膨張及び収縮により、例えば高電流負荷時には負極板から電解液が排出される。負極板から排出される電解液の速さや流量は不均一である。このため、負極板内における電解液の不均一化によって塩濃度の不均一が生じて、負極板と正極板との間を流れる電流密度が偏る。この結果、負極板において電流の集中する部分でリチウムが析出して容量劣化が生じたり、電流の流れ難い部分で抵抗が増加したりするおそれがある。 In the non-aqueous electrolyte secondary battery, the electrolytic solution permeates the negative electrode plate, but the electrolytic solution is discharged from the negative electrode plate, for example, when a high current load is applied due to the expansion and contraction of the electrode plates caused by charging and discharging. The speed and flow rate of the electrolytic solution discharged from the negative electrode plate are non-uniform. Therefore, the non-uniformity of the electrolytic solution in the negative electrode plate causes non-uniformity of the salt concentration, and the current density flowing between the negative electrode plate and the positive electrode plate is biased. As a result, lithium may precipitate in the portion of the negative electrode plate where the current is concentrated to cause capacity deterioration, or the resistance may increase in the portion where the current is difficult to flow.

例えば、特許文献１に記載の技術は、負極板の端部領域で空隙率が大きいため、極板群の膨張や収縮で電解液が排出されやすく、塩濃度の不均一化による容量劣化や抵抗増加のおそれがある。 For example, in the technique described in Patent Document 1, since the porosity is large in the end region of the negative electrode plate, the electrolytic solution is easily discharged due to the expansion and contraction of the electrode plate group, and the capacity deterioration and resistance due to the non-uniform salt concentration. There is a risk of increase.

本発明は、このような実情に鑑みてなされたものであり、その目的は、負極板における電解液分布の不均一化を抑制することのできる非水電解質二次電池用極板群、及び非水電解質二次電池を提供することにある。 The present invention has been made in view of such circumstances, and an object thereof is a non-aqueous electrolyte secondary battery electrode plate group capable of suppressing non-uniformity of the electrolyte distribution in the negative electrode plate, and a non-aqueous electrolyte secondary battery. The purpose is to provide a water electrolyte secondary battery.

上記課題を解決する非水電解質二次電池用極板群は、正極板と負極板とがセパレータを挟んで対向配置される非水電解質二次電池用極板群であって、前記負極板は、金属基板の表面に活物質を含む負極合剤層を有し、前記負極合剤層は、前記セパレータを挟んで前記正極板の正極合剤層に対向する対向部と前記正極合剤層に対向しない縁部に非対向部とを有し、前記負極合剤層の前記非対向部の少なくとも一部の空隙率は、前記対向部の空隙率に比べて小さい。 The electrode plate group for a non-aqueous electrolyte secondary battery that solves the above problems is a group of electrode plates for a non-aqueous electrolyte secondary battery in which a positive electrode plate and a negative electrode plate are arranged so as to face each other with a separator interposed therebetween. The surface of the metal substrate has a negative electrode mixture layer containing an active material, and the negative electrode mixture layer is formed on the facing portion facing the positive electrode mixture layer of the positive electrode plate and the positive electrode mixture layer with the separator interposed therebetween. The non-opposing portion has a non-opposing portion, and the void ratio of at least a part of the non-opposing portion of the negative electrode mixture layer is smaller than the void ratio of the facing portion.

上記課題を解決する非水電解質二次電池は、正極板と負極板とがセパレータを挟んで対向配置される極板群を有する非水電解質二次電池であって、前記極板群が上記記載の非水電解質二次電池用極板群である。 The non-aqueous electrolyte secondary battery that solves the above-mentioned problems is a non-aqueous electrolyte secondary battery having a group of plates in which a positive electrode plate and a negative electrode plate are arranged so as to face each other with a separator interposed therebetween, and the electrode plate group is described above. This is a group of electrode plates for non-aqueous electrolyte secondary batteries.

極板群には電解液が保持されているが、極板の膨張によって極板群から電解液が排出されると電解液の分布及び塩濃度の不均一化が生じる。この点、このような構成によれば、高電流負荷時に負極板から電解液が排出されようとしても、空隙率の小さい非対向部が電解液を排出させる流れを堰き止めて、電解液を負極板の対向部に保持させる。これにより、負極板において塩濃度の不均一化、いわゆる電解液分布の不均一化が抑制されるようになる。 The electrolytic solution is held in the electrode plate group, but when the electrolytic solution is discharged from the electrode plate group due to the expansion of the electrode plate, the distribution of the electrolytic solution and the salt concentration become non-uniform. In this respect, according to such a configuration, even if the electrolytic solution is to be discharged from the negative electrode plate at the time of high current load, the non-opposing portion having a small porosity blocks the flow of discharging the electrolytic solution, and the electrolytic solution is used as the negative electrode. Hold it on the opposite part of the plate. As a result, non-uniformity of salt concentration, so-called non-uniformity of electrolyte distribution, is suppressed in the negative electrode plate.

好ましい構成として、前記非対向部は、縁部のうちで二次電池の上下方向に延びている部分の空隙率が前記対向部の空隙率に比べて小さい。
電解液は、重力の影響を受ける極板群の上側や、電解液に浸かっている極板群の下側からよりも極板群の側面から流出しやすい。この点、このような構成によれば、二次電池の上下方向に延びている非対向部の空隙率を小さくすることで電解液の流出を抑制することができる。 As a preferred configuration, in the non-opposing portion, the porosity of the portion of the edge portion extending in the vertical direction of the secondary battery is smaller than the porosity of the facing portion.
The electrolytic solution is more likely to flow out from the side surface of the electrode plate group than from the upper side of the electrode plate group affected by gravity or from the lower side of the electrode plate group immersed in the electrolytic solution. In this respect, according to such a configuration, the outflow of the electrolytic solution can be suppressed by reducing the porosity of the non-opposing portion extending in the vertical direction of the secondary battery.

好ましい構成として、複数の前記正極板と複数の前記負極板とがそれぞれ前記セパレータを介して積層されている。
積層型は、上側や底部に近接している下側からは電解液が排出され難い。そこで、この構成によるように、二次電池の上下方向に延びている非対向部の空隙率を小さくすることで電解液の流出が抑制される。 As a preferred configuration, the plurality of positive electrode plates and the plurality of negative electrode plates are laminated via the separator, respectively.
In the laminated type, it is difficult for the electrolytic solution to be discharged from the upper side or the lower side close to the bottom. Therefore, as in this configuration, the outflow of the electrolytic solution is suppressed by reducing the porosity of the non-opposing portion extending in the vertical direction of the secondary battery.

好ましい構成として、長尺の前記正極板と長尺の前記負極板とが長尺の前記セパレータを介して積層されて長尺方向に捲回されている。
捲回型は、未開放部からは電解液が排出されない。そこで、この構成によるように、二次電池の捲回軸方向に開放部が延びているとき、開放部における非対向部の空隙率を小さくすることで電解液の流出を抑制することができる。 As a preferred configuration, the long positive electrode plate and the long negative electrode plate are laminated via the long separator and wound in the long direction.
In the winding type, the electrolytic solution is not discharged from the unopened portion. Therefore, according to this configuration, when the open portion extends in the winding axis direction of the secondary battery, the outflow of the electrolytic solution can be suppressed by reducing the porosity of the non-opposing portion in the open portion.

好ましい構成として、前記対向部の空隙率と前記非対向部の空隙率との差が５％以上である。
このような構成によれば、非対向部により対向部からの電解液の排出が堰き止められる。よって、対向部に電解液が保持されることで電解液の分布が均一化される。 As a preferred configuration, the difference between the porosity of the facing portion and the porosity of the non-opposing portion is 5% or more.
According to such a configuration, the non-opposing portion blocks the discharge of the electrolytic solution from the facing portion. Therefore, the distribution of the electrolytic solution is made uniform by holding the electrolytic solution in the facing portion.

好ましい構成として、前記空隙率の小さい前記非対向部は、前記非対向部の長手方向に対する幅が０．５ｍｍ以上である。
このような構成によれば、非対向部は、対向部からの電解液の排出を堰き止められる。 As a preferred configuration, the non-opposing portion having a small porosity has a width of 0.5 mm or more with respect to the longitudinal direction of the non-opposing portion.
According to such a configuration, the non-opposing portion can block the discharge of the electrolytic solution from the facing portion.

好ましい構成として、前記非水電解質二次電池は、リチウムイオン二次電池である。
このような構成によれば、リチウムイオン二次電池の負極板からの電解液の排出が抑制される。 As a preferred configuration, the non-aqueous electrolyte secondary battery is a lithium ion secondary battery.
According to such a configuration, the discharge of the electrolytic solution from the negative electrode plate of the lithium ion secondary battery is suppressed.

本発明によれば、負極板における電解液分布の不均一化を抑制することができる。 According to the present invention, it is possible to suppress non-uniformity of the electrolytic solution distribution in the negative electrode plate.

非水電解質二次電池の極板群及び非水電解質二次電池の一実施形態を示す概略図。The schematic diagram which shows the electrode plate group of the non-aqueous electrolyte secondary battery and one embodiment of a non-aqueous electrolyte secondary battery. 同実施形態において極板群の断面図。Sectional drawing of the electrode plate group in the same embodiment. 同実施形態において負極板の正面図。The front view of the negative electrode plate in the same embodiment. 同実施形態において負極板の上面図。Top view of the negative electrode plate in the same embodiment. 同実施形態において空隙率の差と、容量維持率との関係を示すグラフ。The graph which shows the relationship between the difference of porosity and the capacity retention rate in the same embodiment. 同実施形態において空隙率の差と、抵抗増加率を示すグラフ。The graph which shows the difference of the porosity and the resistance increase rate in the same embodiment.

図１～図６に従って、非水電解質二次電池用極板群、及び、非水電解質二次電池の一実施形態を説明する。なお、本実施形態では、非水電解質二次電池はリチウムイオン二次電池である。以下、説明の便宜上、非水電解質二次電池を二次電池と記す。 An embodiment of a non-aqueous electrolyte secondary battery electrode plate group and a non-aqueous electrolyte secondary battery will be described with reference to FIGS. 1 to 6. In the present embodiment, the non-aqueous electrolyte secondary battery is a lithium ion secondary battery. Hereinafter, for convenience of explanation, the non-aqueous electrolyte secondary battery will be referred to as a secondary battery.

本実施形態の二次電池は、バスバーで複数が接続されることにより組電池を構成する。組電池は、電気自動車もしくはハイブリッド自動車に搭載され、電動モータ等に電力を供給する。二次電池は、外形が直方体形状の密閉式電池である。 A plurality of secondary batteries of the present embodiment are connected by a bus bar to form an assembled battery. The assembled battery is mounted on an electric vehicle or a hybrid vehicle to supply electric power to an electric motor or the like. The secondary battery is a closed-type battery having a rectangular parallelepiped outer shape.

図１に示すように、二次電池１０は、上側に開口部を有する直方体形状の電池ケース１１と、電池ケース１１の開口部を封止する蓋体１２と、電池ケース１１の内部に収容される非水電解質二次電池用極板群としての極板群２０と、電池ケース１１内に注入された液体状の非水電解質としての電解液２７とを備える。電池ケース１１及び蓋体１２はアルミニウム合金等の金属で構成されている。二次電池１０は、電池ケース１１に蓋体１２を取り付けることで密閉された電槽が構成される。また二次電池１０は、蓋体１２に、電力の充放電に用いられる２つの外部端子１３を備えている。 As shown in FIG. 1, the secondary battery 10 is housed inside a rectangular battery case 11 having an opening on the upper side, a lid 12 for sealing the opening of the battery case 11, and the battery case 11. The electrode plate group 20 as the electrode plate group for the non-aqueous electrolyte secondary battery and the electrolytic solution 27 as the liquid non-aqueous electrolyte injected into the battery case 11 are provided. The battery case 11 and the lid 12 are made of a metal such as an aluminum alloy. The secondary battery 10 is configured by attaching a lid 12 to the battery case 11 to form a sealed battery case. Further, the secondary battery 10 is provided with two external terminals 13 used for charging / discharging electric power in the lid 12.

極板群２０は、正極板２１と負極板２２とが交互にそれらの間にセパレータ２３を挟んで積層方向（図１の紙面に垂直な方向）に積層されることで形成されている。本実施形態では、極板群２０は、正極板２１、負極板２２及びセパレータ２３がそれぞれ平面状に維持されたまま積層されることで積層型極板群を構成する。極板群２０は、長手方向の一端側（図１において右側）に正極板２１がはみ出た先端部分としての正極のリード部２１Ａと、同長手方向の他端側（図１において左側）に負極板２２がはみ出た先端部分としての負極のリード部２２Ａとを有する。 The electrode plate group 20 is formed by alternately laminating a positive electrode plate 21 and a negative electrode plate 22 in a laminating direction (direction perpendicular to the paper surface of FIG. 1) with a separator 23 sandwiched between them. In the present embodiment, the electrode plate group 20 constitutes a laminated electrode plate group by laminating the positive electrode plate 21, the negative electrode plate 22, and the separator 23 while keeping them flat. The electrode plate group 20 has a lead portion 21A of the positive electrode as a tip portion where the positive electrode plate 21 protrudes from one end side in the longitudinal direction (right side in FIG. 1) and a negative electrode on the other end side (left side in FIG. 1) in the same longitudinal direction. The plate 22 has a lead portion 22A of a negative electrode as a tip portion protruding from the plate 22.

正極のリード部２１Ａは、極板群２０の長手方向において正極板２１の端部のみが配置されている部分であって、正極板２１の端部が積層方向に機械的及び電気的に集合されている。また、正極のリード部２１Ａは、極板群２０の短手方向に沿って、外部端子１３に接続される集電板１４が溶接されている。 The lead portion 21A of the positive electrode is a portion in which only the end portion of the positive electrode plate 21 is arranged in the longitudinal direction of the electrode plate group 20, and the end portions of the positive electrode plate 21 are mechanically and electrically assembled in the stacking direction. ing. Further, the lead portion 21A of the positive electrode is welded with a current collector plate 14 connected to the external terminal 13 along the lateral direction of the electrode plate group 20.

負極のリード部２２Ａは、極板群２０の長手方向において負極板２２の端部のみが配置されている部分であって、負極板２２の端部が積層方向に機械的及び電気的に集合されている。また、負極のリード部２２Ａは、極板群２０の短手方向に沿って、外部端子１３に接続される集電板１４が溶接されている。 The lead portion 22A of the negative electrode is a portion in which only the end portion of the negative electrode plate 22 is arranged in the longitudinal direction of the electrode plate group 20, and the end portions of the negative electrode plate 22 are mechanically and electrically assembled in the stacking direction. ing. Further, the lead portion 22A of the negative electrode is welded with a current collector plate 14 connected to the external terminal 13 along the lateral direction of the electrode plate group 20.

セパレータ２３は、正極板２１及び負極板２２の間に電解液２７を保持するための多孔性ポリオレフィン膜、及び多孔性ポリ塩化ビニル膜等の多孔性ポリマー膜、又は、リチウムイオンもしくはイオン導電性ポリマー電解質膜を、単独、又は組み合わせて使用することもできる。 The separator 23 is a porous polyolefin film for holding the electrolytic solution 27 between the positive electrode plate 21 and the negative electrode plate 22, a porous polymer film such as a porous polyvinyl chloride film, or a lithium ion or ionic conductive polymer. The electrolyte membrane can also be used alone or in combination.

（電解液）
電解液２７は、非水溶媒に支持塩が含有された組成物である。ここで、非水溶媒としては、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）等からなる群から選択された一種または二種以上の材料を用いることができる。また、支持塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣ４Ｆ９ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＩ等から選択される一種または二種以上のリチウム化合物（リチウム塩）を用いることができる。 (Electrolytic solution)
The electrolytic solution 27 is a composition in which a supporting salt is contained in a non-aqueous solvent. Here, as the non-aqueous solvent, one or two selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. More than seed materials can be used. As supporting salts, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiI One or more kinds of lithium compounds (lithium salts) selected from the above can be used.

（正極板）
図２を参照して、正極板２１は、電極芯体である金属基板としての正極基材２１１の各表面２１１Ａにそれぞれ正極合剤が塗布された正極合剤層２１２を有している。正極基材２１１は、正極板２１の長手方向に長さＬ２１１を有し、導電性の良好な金属からなる導電性材料としてのアルミニウム合金からなる薄膜（箔）である。よって正極板２１は、正極合剤層２１２と、正極合剤が未塗布であるリード部２１Ａとを有している。リード部２１Ａは、正極板２１の長手方向に範囲Ｌ２１２を有している。 (Positive plate)
With reference to FIG. 2, the positive electrode plate 21 has a positive electrode mixture layer 212 in which a positive electrode mixture is applied to each surface 211A of the positive electrode base material 211 as a metal substrate which is an electrode core. The positive electrode base material 211 is a thin film (foil) made of an aluminum alloy as a conductive material having a length L211 in the longitudinal direction of the positive electrode plate 21 and made of a metal having good conductivity. Therefore, the positive electrode plate 21 has a positive electrode mixture layer 212 and a lead portion 21A to which the positive electrode mixture has not been applied. The lead portion 21A has a range L212 in the longitudinal direction of the positive electrode plate 21.

正極合剤は、正極活物質を含む。正極活物質は、遷移金属元素（すなわち、Ｎｉ、Ｃｏ、及びＭｎの少なくとも１種）の他に、付加的に、１種または複数種の元素を含有し得る。 The positive electrode mixture contains a positive electrode active material. The positive electrode active material may additionally contain one or more elements in addition to the transition metal element (ie, at least one of Ni, Co, and Mn).

また、正極合剤は、導電材を含んでいてもよい。導電材としては、例えばアセチレンブラック（ＡＢ）、ケッチェンブラック等のカーボンブラック、黒鉛（グラファイト）を用いることができる。 Further, the positive electrode mixture may contain a conductive material. As the conductive material, for example, carbon black such as acetylene black (AB) and Ketjen black, and graphite (graphite) can be used.

正極板２１は、正極活物質、導電材、溶媒、及び結着剤（バインダー）等を混練し、混練後に正極合剤層２１２を含んで生成される電極用スラリーを正極基材２１１に塗布して乾燥された正極合剤層２１２を有して作製される。ここで、溶媒としては、例えばＮＭＰ（Ｎ－メチル－２－ピロリドン）溶液を用いることができる。また、バインダーとしては、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）、スチレンブタジエンラバー（ＳＢＲ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、カルボキシメチルセルロース（ＣＭＣ）等を用いることができる。 The positive electrode plate 21 is kneaded with a positive electrode active material, a conductive material, a solvent, a binder, and the like, and after kneading, an electrode slurry generated including the positive electrode mixture layer 212 is applied to the positive electrode base material 211. It is produced by having a positive electrode mixture layer 212 which has been dried. Here, as the solvent, for example, an NMP (N-methyl-2-pyrrolidone) solution can be used. Further, as the binder, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC) and the like can be used.

（負極板）
次に、負極板２２は、電極芯体である金属基板としての負極基材２２１の各表面２２１Ａにそれぞれ負極合剤が塗布された負極合剤層２２２を有している。負極基材２２１は、負極板２２の長手方向に長さＬ２２１を有し、従来の二次電池の構成要素と同様の構成要素を用いることができ、導電性の良好な金属からなる導電性材料が好ましく用いられる。例えば、負極基材２２１は、銅やニッケルあるいはそれらの合金からなる薄膜（箔）である。よって負極板２２は、負極合剤層２２２と、負極合剤が未塗布であるリード部２２Ａとを有している。 (Negative electrode plate)
Next, the negative electrode plate 22 has a negative electrode mixture layer 222 in which a negative electrode mixture is coated on each surface 221A of the negative electrode base material 221 as a metal substrate which is an electrode core. The negative electrode base material 221 has a length L221 in the longitudinal direction of the negative electrode plate 22, and can use the same components as those of a conventional secondary battery, and is a conductive material made of a metal having good conductivity. Is preferably used. For example, the negative electrode base material 221 is a thin film (foil) made of copper, nickel, or an alloy thereof. Therefore, the negative electrode plate 22 has a negative electrode mixture layer 222 and a lead portion 22A to which the negative electrode mixture has not been applied.

負極合剤は、負極活物質３０（図４参照）を含む。負極活物質３０（図４参照）は、リチウムを吸蔵・放出可能な材料であり、例えば、黒鉛（グラファイト）等からなる粉末状の炭素材料を用いることができる。そして、負極板２２は、負極活物質３０（図４参照）、溶媒、及びバインダー等を正極板２１と同様に混練し、混練後に負極合剤層２２２を含んで生成される電極用スラリーを負極基材２２１に塗布して乾燥された負極合剤層２２２を有して作製される。バインダーは正極板２１と同様の材料を用いることができる。 The negative electrode mixture contains the negative electrode active material 30 (see FIG. 4). The negative electrode active material 30 (see FIG. 4) is a material capable of occluding and releasing lithium, and for example, a powdered carbon material made of graphite or the like can be used. Then, in the negative electrode plate 22, the negative electrode active material 30 (see FIG. 4), the solvent, the binder and the like are kneaded in the same manner as in the positive electrode plate 21, and after kneading, the electrode slurry generated containing the negative electrode mixture layer 222 is used as the negative electrode. It is produced by having a negative electrode mixture layer 222 that has been applied to the base material 221 and dried. As the binder, the same material as that of the positive electrode plate 21 can be used.

（極板の対向関係）
図２に示すように、極板群２０において、正極板２１は負極板２２よりも右側に突出されるようにリード部２１Ａが積層されており、負極板２２は正極板２１よりも左側に突出されるようにリード部２２Ａが積層される。セパレータ２３は、正極板２１と負極板２２との短絡を防止するように、正極板２１と負極板２２とが直接対向する範囲と同じか、又は広い範囲となるように、正極板２１と負極板２２との間に配置されている。 (Pole plate facing relationship)
As shown in FIG. 2, in the electrode plate group 20, the lead portion 21A is laminated so that the positive electrode plate 21 projects to the right side of the negative electrode plate 22, and the negative electrode plate 22 projects to the left side of the positive electrode plate 21. The lead portions 22A are laminated so as to be. The separator 23 has the positive electrode plate 21 and the negative electrode so as to prevent a short circuit between the positive electrode plate 21 and the negative electrode plate 22 so as to be the same as or wider than the range in which the positive electrode plate 21 and the negative electrode plate 22 directly face each other. It is arranged between the plate 22 and the plate 22.

正極板２１と負極板２２とは、対向配置されているが、負極板２２の負極合剤層２２２の範囲Ｌ２２３が、正極板２１の正極合剤層２１２の範囲Ｌ２１３を含み、かつ、それよりも広範囲となるように積層される。 The positive electrode plate 21 and the negative electrode plate 22 are arranged so as to face each other, but the range L223 of the negative electrode mixture layer 222 of the negative electrode plate 22 includes the range L213 of the positive electrode mixture layer 212 of the positive electrode plate 21 and more than that. Are also laminated so as to be widespread.

よって、負極合剤層２２２の範囲Ｌ２２３は、正極合剤層２１２に対向する範囲Ｌ２２５と、正極合剤層２１２に対向しないリード部２２Ａ側の縁部としての範囲Ｌ２２４と、正極合剤層２１２に対向しないリード部２２Ａの反対側の縁部としての範囲Ｌ２２６とを有している。正極合剤層２１２の範囲Ｌ２１３よりも長く確保される負極合剤層２２２の範囲Ｌ２２３は、負極板２２の範囲Ｌ２２４及び範囲Ｌ２２６の部分にそれぞれ非対向長さ、例えば０．５ｍｍ以上の長さを有する。 Therefore, the range L223 of the negative electrode mixture layer 222 includes the range L225 facing the positive electrode mixture layer 212, the range L224 as the edge portion on the lead portion 22A side not facing the positive electrode mixture layer 212, and the positive electrode mixture layer 212. It has a range L226 as an edge portion on the opposite side of the lead portion 22A that does not face the lead portion 22A. The range L223 of the negative electrode mixture layer 222 secured longer than the range L213 of the positive electrode mixture layer 212 has a non-opposing length, for example, 0.5 mm or more with respect to the portions L224 and L226 of the negative electrode plate 22, respectively. Have.

（負極合剤層の空隙率）
図３及び図４を参照して、負極板２２の負極合剤層２２２の空隙率について説明する。
図３に示すように、負極板２２は、図において左右方向である長手方向に、リード部２２Ａから順に、第１非対向部２２４、対向部２２５、及び第２非対向部２２６を有している。 (Porosity of negative electrode mixture layer)
The porosity of the negative electrode mixture layer 222 of the negative electrode plate 22 will be described with reference to FIGS. 3 and 4.
As shown in FIG. 3, the negative electrode plate 22 has a first non-opposing portion 224, a facing portion 225, and a second non-opposing portion 226 in the longitudinal direction, which is the left-right direction in the drawing, in this order from the lead portion 22A. There is.

リード部２２Ａは、負極基材２２１の各表面２２１Ａが露出した部分であり、範囲Ｌ２２２である。第１非対向部２２４は、正極合剤層２１２に対向しない部分であって、負極合剤層２２２の範囲Ｌ２２３のうちの範囲Ｌ２２４である。対向部２２５は、正極合剤層２１２に対向する部分であって、負極合剤層２２２の範囲Ｌ２２３のうちの範囲Ｌ２２５である。第２非対向部２２６は、正極合剤層２１２に対向しない部分であって、負極合剤層２２２の範囲Ｌ２２３のうちの範囲Ｌ２２６である。 The lead portion 22A is a portion where each surface 221A of the negative electrode base material 221 is exposed, and is in the range L222. The first non-opposing portion 224 is a portion that does not face the positive electrode mixture layer 212 and is the range L224 of the range L223 of the negative electrode mixture layer 222. The facing portion 225 is a portion facing the positive electrode mixture layer 212, and is a range L225 of the range L223 of the negative electrode mixture layer 222. The second non-opposing portion 226 is a portion that does not face the positive electrode mixture layer 212 and is the range L226 of the range L223 of the negative electrode mixture layer 222.

対向部２２５は、対向する正極板２１の正極合剤層２１２との間でリチウムイオンの授受が行われるため二次電池１０の充放電性能に大きな影響を及ぼす部分である。一方、第１非対向部２２４及び第２非対向部２２６は、対向していない正極板２１の正極合剤層２１２との間でリチウムイオンの授受が行われ難いため二次電池１０の充放電の性能に対する影響が相対的に小さい部分である。 The facing portion 225 is a portion that greatly affects the charge / discharge performance of the secondary battery 10 because lithium ions are exchanged between the facing positive electrode plate 21 and the positive electrode mixture layer 212. On the other hand, since it is difficult for lithium ions to be exchanged between the first non-opposing portion 224 and the second non-opposing portion 226 with the positive electrode mixture layer 212 of the non-opposing positive electrode plate 21, the secondary battery 10 is charged and discharged. This is the part where the effect on the performance of is relatively small.

図４に示すように、負極合剤層２２２は、対向部２２５の空隙率と、第１非対向部２２４及び第２非対向部２２６の空隙率とが相違する。なお、図示の便宜上、負極合剤層２２２は、負極合剤に含まれる負極活物質３０のみ図示し、バインダー等の他の物質の図示を割愛する。空隙率は、負極合剤層中の単位面積（断面積）当たりの負極合剤の間にある空間（空隙）の割合を示しており、負極合剤の密度が小さいと空隙率が大きくなり、逆に、負極合剤の密度が大きいと空隙率が小さくなる。本実施形態では、対向部２２５の空隙率に対して、第１非対向部２２４及び第２非対向部２２６の空隙率が小さくなっている。例えば、対向部２２５の空隙率と、第１非対向部２２４及び第２非対向部２２６の空隙率との間には、５％以上の差、好ましくは１０％以上の差がある。または、対向部２２５の空隙率は、第１非対向部２２４及び第２非対向部２２６の空隙率に対して０．９倍以下である。 As shown in FIG. 4, in the negative electrode mixture layer 222, the porosity of the facing portion 225 and the porosity of the first non-opposing portion 224 and the second non-opposing portion 226 are different. For convenience of illustration, the negative electrode mixture layer 222 shows only the negative electrode active material 30 contained in the negative electrode mixture, and the illustration of other substances such as a binder is omitted. The porosity indicates the ratio of the space (void) between the negative electrode mixture per unit area (cross-sectional area) in the negative electrode mixture layer, and the porosity increases when the density of the negative electrode mixture is small. On the contrary, when the density of the negative electrode mixture is high, the porosity becomes small. In the present embodiment, the porosity of the first non-opposing portion 224 and the second non-opposing portion 226 is smaller than the porosity of the facing portion 225. For example, there is a difference of 5% or more, preferably 10% or more, between the porosity of the facing portion 225 and the porosity of the first non-opposing portion 224 and the second non-opposing portion 226. Alternatively, the porosity of the facing portion 225 is 0.9 times or less the porosity of the first non-opposing portion 224 and the second non-opposing portion 226.

例えば、第１非対向部２２４及び第２非対向部２２６は、負極合剤の塗布回数が対向部２２５への塗布回数よりも多くなること、例えば二度塗りすることによって空隙率が小さくなる。 For example, in the first non-opposed portion 224 and the second non-opposed portion 226, the porosity becomes smaller when the number of times the negative electrode mixture is applied is larger than the number of times the negative electrode mixture is applied to the facing portion 225, for example, when the negative electrode mixture is applied twice.

本実施形態では、空隙率は、サンプルの断面において５０平方μｍにおける空隙面積の割合と定義した。また、サンプル数は１０とした。つまり、各サンプルにおいて測定した断面ＳＥＭ（走査型電子顕微鏡）の明るさを所定の閾値で二値化することで活物質等の占める面積（物質面積）を取得してから、各空隙率を「（５０平方μｍ－物質面積）／５０平方μｍ×１００％」で算出し、これらの平均を空隙率とした。 In this embodiment, porosity is defined as the proportion of void area at 50 square μm in the cross section of the sample. The number of samples was 10. That is, the area occupied by the active material or the like (material area) is obtained by binarizing the brightness of the cross-sectional SEM (scanning electron microscope) measured in each sample with a predetermined threshold value, and then each void ratio is set to ". (50 square μm-material area) / 50 square μm × 100% ”, and the average of these was taken as the void ratio.

このように、対向部２２５の空隙率に対して、第１非対向部２２４及び第２非対向部２２６の空隙率を小さくすることによって対向部２２５に浸透している電解液２７の負極板２２からの排出が抑制される。 In this way, the negative electrode plate 22 of the electrolytic solution 27 that permeates the facing portion 225 by reducing the porosity of the first non-facing portion 224 and the second non-facing portion 226 with respect to the porosity of the facing portion 225. Emissions from are suppressed.

（作用）
詳述すると、負極合剤層２２２は、負極合剤の間の空隙に電解液２７が流動可能に浸透している。空隙率が大きくて負極合剤の配置が疎であると、負極合剤層２２２中の流路が広くなるため電解液２７の流動抵抗が低くなる。逆に、空隙率が小さくて負極合剤の配置が密であると、負極合剤層２２２中の流路が狭くなるため電解液２７の流動抵抗が高くなる。 (Action)
More specifically, in the negative electrode mixture layer 222, the electrolytic solution 27 is fluidly permeated into the voids between the negative electrode mixture. When the porosity is large and the arrangement of the negative electrode mixture is sparse, the flow path in the negative electrode mixture layer 222 becomes wide and the flow resistance of the electrolytic solution 27 becomes low. On the contrary, when the porosity is small and the arrangement of the negative electrode mixture is dense, the flow path in the negative electrode mixture layer 222 becomes narrow and the flow resistance of the electrolytic solution 27 increases.

一般に、負極合剤層２２２は、電解液２７の浸透が充分であることが好ましい。しかし、放電による縮小と、充電による膨張とを繰り返す負極合剤層２２２は、膨張による加圧で空隙率が小さくなり浸透している電解液２７が排出される一方、収縮による減圧で空隙率が大きくなり外部の電解液２７が浸透する。このとき、負極合剤層２２２から電解液２７が排出される速度の方が、電解液２７が浸透する速度よりも早いため、電解液２７が排出されるとその後の充電時に電解液２７の分布の不均一や電解液２７の不足を生じる。電解液２７の不足は、電解液２７の浸透に時間を要する負極板２２の中心で大きくなるおそれがある。また、電解液２７の分布の不均一は、電池性能の低下を生じさせたり、電解液２７のあるところに集中する大電流がリチウム析出による短絡を生じさせたりするおそれがある。 In general, it is preferable that the negative electrode mixture layer 222 has sufficient penetration of the electrolytic solution 27. However, in the negative electrode mixture layer 222 that repeatedly shrinks due to discharge and expands due to charging, the porosity decreases due to pressurization due to expansion and the permeated electrolytic solution 27 is discharged, while the porosity increases due to decompression due to shrinkage. It becomes large and the external electrolytic solution 27 permeates. At this time, the rate at which the electrolytic solution 27 is discharged from the negative electrode mixture layer 222 is faster than the rate at which the electrolytic solution 27 permeates. Therefore, when the electrolytic solution 27 is discharged, the distribution of the electrolytic solution 27 during subsequent charging is performed. Non-uniformity and shortage of the electrolytic solution 27 occur. The shortage of the electrolytic solution 27 may increase at the center of the negative electrode plate 22, which requires time for the electrolytic solution 27 to permeate. Further, the non-uniform distribution of the electrolytic solution 27 may cause a deterioration in battery performance, or a large current concentrated in a certain place of the electrolytic solution 27 may cause a short circuit due to lithium precipitation.

本実施形態では、対向部２２５の空隙率に対して、第１非対向部２２４及び第２非対向部２２６に配置されている負極合剤の空隙率を小さくした。これにより、電解液２７が対向部２２５から第１非対向部２２４及び第２非対向部２２６への流れを抑制して、負極板２２から電解液２７が排出されることを抑制した。これにより、電解液２７の分布の不均一や電解液２７の不足の発生が抑制されるようになる。 In the present embodiment, the porosity of the negative electrode mixture arranged in the first non-opposing portion 224 and the second non-opposing portion 226 is made smaller than the porosity of the facing portion 225. As a result, the electrolytic solution 27 suppressed the flow from the opposed portion 225 to the first non-opposed portion 224 and the second non-opposed portion 226, and the electrolytic solution 27 was suppressed from being discharged from the negative electrode plate 22. As a result, the uneven distribution of the electrolytic solution 27 and the occurrence of a shortage of the electrolytic solution 27 can be suppressed.

図５及び図６を参照して、本実施形態の効果について説明する。
図５を参照して、負極合剤層２２２における対向部２２５の空隙率と第１非対向部２２４及び第２非対向部２２６の空隙率との差である空隙率の差と、二次電池１０の容量維持率との関係について説明する。二次電池１０の容量維持率は、二次電池１０の当初の放電容量に対する、所定の条件で使用後の二次電池１０の放電容量の割合である。ここで所定の条件は、環境温度２０℃において、ＳＯＣ（Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ：充電状態）０％から１００％まで電流２Ｃで充電し、ＳＯＣ１００％から０％まで電流２Ｃで放電することを１サイクルとし、このサイクルを所定回数、例えば１５００回行うことである。 The effect of this embodiment will be described with reference to FIGS. 5 and 6.
With reference to FIG. 5, the difference in porosity, which is the difference between the porosity of the facing portion 225 in the negative electrode mixture layer 222 and the porosity of the first non-opposing portion 224 and the second non-opposing portion 226, and the secondary battery. The relationship with the capacity retention rate of 10 will be described. The capacity retention rate of the secondary battery 10 is the ratio of the discharge capacity of the secondary battery 10 after use under predetermined conditions to the initial discharge capacity of the secondary battery 10. Here, the predetermined condition is that at an ambient temperature of 20 ° C., the SOC (State of Charge) is charged from 0% to 100% with a current of 2C and discharged from SOC 100% to 0% with a current of 2C as one cycle. , This cycle is performed a predetermined number of times, for example, 1500 times.

図５のプロットＬ５に示すように、容量維持率の測定結果は、空隙率の差が０．０％のとき８３％であり、空隙率の差が２．６％のとき８７％である。また、容量維持率の測定結果は、空隙率の差が５．０％のとき９５％であり、空隙率の差が５．８％のとき９４％であり、空隙率の差が８．０％のとき９５％である。 As shown in the plot L5 of FIG. 5, the measurement result of the capacity retention rate is 83% when the difference in porosity is 0.0%, and 87% when the difference in porosity is 2.6%. The measurement result of the capacity retention rate is 95% when the difference in porosity is 5.0%, 94% when the difference in porosity is 5.8%, and the difference in porosity is 8.0. When it is%, it is 95%.

つまり、容量維持率は、空隙率の差が５．０％以上であるとき、空隙率の差が０．０％である場合に比べて１２％大きく、空隙率の差が２．６％である場合に比べて８％大きい。よって、空隙率が５．０％以上であるとき、容量劣化が抑えられて、容量維持率が大きく維持されるようになる。 That is, the capacity retention rate is 12% larger when the difference in porosity is 5.0% or more than when the difference in porosity is 0.0%, and the difference in porosity is 2.6%. 8% larger than in some cases. Therefore, when the porosity is 5.0% or more, the capacity deterioration is suppressed and the capacity retention rate is largely maintained.

図６を参照して、空隙率の差と、二次電池１０の抵抗増加率との関係について説明する。なお、二次電池１０の抵抗増加率は、二次電池１０の当初の直流に対する内部抵抗（ＤＣ－ＩＲ）に対する、所定の条件で使用後の二次電池１０の内部抵抗の割合である。ここで所定の条件は、環境温度２０℃において、ＳＯＣ５０％から１０秒間、電流７Ｃの定電流充電（ＣＣ充電）し、充放電しない状態を１０分間維持した後、電流１Ｃで定電流定電圧放電（ＣＣＣＶ放電）し、充放電しない状態を１０分間の維持することを１サイクルとし、このサイクルを所定回数、例えば３００回行うことである。内部抵抗は、二次電池１０の直流電流と直流電圧との測定に基づいて測定される。 With reference to FIG. 6, the relationship between the difference in porosity and the resistance increase rate of the secondary battery 10 will be described. The resistance increase rate of the secondary battery 10 is the ratio of the internal resistance of the secondary battery 10 after use under predetermined conditions to the internal resistance (DC-IR) of the secondary battery 10 with respect to the initial direct current. Here, the predetermined condition is that the constant current charge (CC charge) with a current of 7C is performed for 10 seconds from 50% SOC at an ambient temperature of 20 ° C., the state of no charging / discharging is maintained for 10 minutes, and then the constant current constant voltage discharge is performed with a current of 1C. (CCCV discharge) is performed and the state of no charge / discharge is maintained for 10 minutes as one cycle, and this cycle is performed a predetermined number of times, for example, 300 times. The internal resistance is measured based on the measurement of the DC current and the DC voltage of the secondary battery 10.

図６のプロットＬ６に示すように、抵抗増加率の測定結果は、空隙率の差が０．０％のとき１３５％であり、空隙率の差が２．６％のとき１２７％である。また、抵抗増加率の測定結果は、空隙率の差が５．０％のとき１１１％であり、空隙率の差が５．８％のとき１１０％であり、空隙率の差が８．０％のとき１１２％である。 As shown in the plot L6 of FIG. 6, the measurement result of the resistance increase rate is 135% when the difference in porosity is 0.0%, and 127% when the difference in porosity is 2.6%. The measurement result of the resistance increase rate is 111% when the difference in porosity is 5.0%, 110% when the difference in porosity is 5.8%, and the difference in porosity is 8.0. When it is%, it is 112%.

つまり、抵抗増加率は、空隙率の差が５．０％以上であるとき、空隙率の差が０．０％である場合に比べて３３％～３５％小さく、空隙率の差が２．６％である場合に比べて２５％～２７％小さい。よって、空隙率が５．０％以上であるとき、抵抗増加率が小さく維持されるようになる。 That is, the resistance increase rate is 33% to 35% smaller when the difference in porosity is 5.0% or more than when the difference in porosity is 0.0%, and the difference in porosity is 2. It is 25% to 27% smaller than the case of 6%. Therefore, when the porosity is 5.0% or more, the resistance increase rate is kept small.

本実施形態によれば、以下に記載する効果が得られる。
（１）極板群２０には電解液２７が保持されているが、負極板２２の膨張によって極板群２０から電解液２７が排出されると電解液２７の分布及び塩濃度の不均一化が生じる。よって、高電流負荷時に負極板２２から電解液２７が排出されようとしても、空隙率の小さい第１非対向部２２４及び第２非対向部２２６で電解液２７の排出が抑えられ、電解液２７を負極板２２の対向部２２５に保持させる。これにより、負極板２２において塩濃度の不均一化、いわゆる電解液分布の不均一化が抑制されるようになる。 According to this embodiment, the effects described below can be obtained.
(1) The electrolytic solution 27 is held in the electrode plate group 20, but when the electrolytic solution 27 is discharged from the electrode plate group 20 due to the expansion of the negative electrode plate 22, the distribution of the electrolytic solution 27 and the salt concentration become non-uniform. Occurs. Therefore, even if the electrolytic solution 27 is to be discharged from the negative electrode plate 22 at the time of high current load, the discharge of the electrolytic solution 27 is suppressed by the first non-opposing portion 224 and the second non-opposing portion 226 having a small porosity, and the electrolytic solution 27 is discharged. Is held by the facing portion 225 of the negative electrode plate 22. As a result, non-uniformity of salt concentration, so-called non-uniformity of electrolyte distribution, is suppressed in the negative electrode plate 22.

（２）電解液２７は、重力の影響を受ける極板群２０の上側や、電解液に浸かっている極板群２０の下側からよりも極板群２０の側面から流出しやすい。よって、二次電池１０の上下方向に延びている第１非対向部２２４及び第２非対向部２２６の空隙率を小さくすることで電解液２７の流出を抑制することができる。 (2) The electrolytic solution 27 is more likely to flow out from the side surface of the electrode plate group 20 than from the upper side of the electrode plate group 20 affected by gravity or from the lower side of the electrode plate group 20 immersed in the electrolytic solution. Therefore, the outflow of the electrolytic solution 27 can be suppressed by reducing the porosity of the first non-opposing portion 224 and the second non-opposing portion 226 extending in the vertical direction of the secondary battery 10.

（３）積層型は、上側や底部に近接している下側からは電解液２７が排出され難い。そこで、二次電池１０の上下方向に延びている第１非対向部２２４及び第２非対向部２２６の空隙率を小さくすることで電解液２７の流出が抑制される。 (3) In the laminated type, the electrolytic solution 27 is unlikely to be discharged from the upper side or the lower side close to the bottom. Therefore, the outflow of the electrolytic solution 27 is suppressed by reducing the porosity of the first non-opposing portion 224 and the second non-opposing portion 226 extending in the vertical direction of the secondary battery 10.

（４）対向部２２５の空隙率と第１非対向部２２４及び第２非対向部２２６の空隙率との差を５％以上とすることで、第１非対向部２２４及び第２非対向部２２６により対向部２２５からの電解液２７の排出が堰き止められる。よって、対向部２２５には電解液２７が保持されることで電解液２７の分布が均一化される。 (4) By setting the difference between the porosity of the facing portion 225 and the porosity of the first non-facing portion 224 and the second non-facing portion 226 to 5% or more, the first non-opposing portion 224 and the second non-facing portion 224 and the second non-facing portion are set. The 226 blocks the discharge of the electrolytic solution 27 from the facing portion 225. Therefore, the electrolytic solution 27 is held in the facing portion 225, so that the distribution of the electrolytic solution 27 is made uniform.

（５）第１非対向部２２４及び第２非対向部２２６は、第１非対向部２２４及び第２非対向部２２６の長手方向に対する幅が０．５ｍｍ以上であるので、対向部２２５からの電解液２７の排出を堰き止められる。 (5) Since the width of the first non-opposed portion 224 and the second non-opposed portion 226 with respect to the longitudinal direction of the first non-opposed portion 224 and the second non-opposed portion 226 is 0.5 mm or more, the width from the facing portion 225 is increased. The discharge of the electrolytic solution 27 can be blocked.

（６）リチウムイオン二次電池の負極板２２からの電解液２７の排出が抑制される。
上記実施形態は、以下のように変更して実施することができる。上記実施形態及び以下の変更例は、技術的に矛盾しない範囲で互いに組み合わせて実施することができる。 (6) The discharge of the electrolytic solution 27 from the negative electrode plate 22 of the lithium ion secondary battery is suppressed.
The above embodiment can be modified and implemented as follows. The above embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

・上記実施形態では、極板群２０は、正極板２１及び負極板２２をセパレータ２３を介して積層した積層型の構造である場合について例示した。しかしこれに限らず、二次電池の形状や使用目的に応じて適宜変更してもよい。例えば、長尺の正極板及び長尺の負極板を長尺のセパレータを介して扁平に捲回した捲回型の構造であってもよい。扁平に捲回された極板群は、四方のうち、捲回される正極板等の長尺方向は電極基材で覆われている未開放部なので電解液は排出されず、積層断面が開放されている捲回軸方向両端の開放部から電解液が排出される。よって、負極板の捲回軸方向両端になる非対向部の空隙率を小さくすることで負極板からの電解液の流出を抑制し、電解液分布の不均一化を抑制することができる。 -In the above embodiment, the case where the electrode plate group 20 has a laminated structure in which the positive electrode plate 21 and the negative electrode plate 22 are laminated via the separator 23 is exemplified. However, the present invention is not limited to this, and may be appropriately changed depending on the shape of the secondary battery and the purpose of use. For example, it may have a winding structure in which a long positive electrode plate and a long negative electrode plate are flatly wound via a long separator. Of the four sides of the flatly wound electrode plate group, the long direction of the wound positive electrode plate is an unopened part covered with an electrode base material, so the electrolytic solution is not discharged and the laminated cross section is open. The electrolytic solution is discharged from the open portions at both ends in the winding axis direction. Therefore, by reducing the porosity of the non-opposing portions at both ends in the winding axis direction of the negative electrode plate, the outflow of the electrolytic solution from the negative electrode plate can be suppressed, and the non-uniformity of the electrolytic solution distribution can be suppressed.

・上記実施形態では、第１非対向部２２４の空隙率と、第２非対向部２２６の空隙率とが同じである場合について例示したが、これに限らず、空隙率は、対向部の空隙率よりも小さければ、相違していてもよい。 In the above embodiment, the case where the porosity of the first non-opposing portion 224 and the porosity of the second non-opposing portion 226 are the same has been illustrated, but the porosity is not limited to this, and the porosity is the void of the facing portion. If it is smaller than the rate, it may be different.

・上記実施形態では、第１非対向部２２４の空隙率や、第２非対向部２２６の空隙率が一定である場合について例示したが、これに限らず、対向部２２５の空隙率に比べて小さければ、第１非対向部において複数の空隙率があったり、第２非対向部において複数の空隙率があったりしてもよい。 In the above embodiment, the case where the porosity of the first non-opposing portion 224 and the porosity of the second non-opposing portion 226 are constant has been illustrated, but the present invention is not limited to this, and the porosity is higher than that of the facing portion 225. If it is small, there may be a plurality of porosities in the first non-opposing portion or a plurality of porosities in the second non-opposing portion.

・上記実施形態では、第１非対向部２２４の空隙率や、第２非対向部２２６の空隙率が対向部２２５の空隙率よりも小さい場合について例示したが、これに限らず、第１非対向部の一部の空隙率や第２非対向部の一部の空隙率が対向部２２５の空隙率に比べて小さくてもよい。 In the above embodiment, the porosity of the first non-opposing portion 224 and the porosity of the second non-opposing portion 226 are smaller than the porosity of the facing portion 225, but the present invention is not limited to this. The porosity of a part of the facing portion and the porosity of a part of the second non-opposing portion may be smaller than the porosity of the facing portion 225.

・上記実施形態では、第１非対向部２２４の空隙率、及び第２非対向部２２６の空隙率が対向部２２５の空隙率よりも小さい場合について例示したが、これに限らず、第１非対向部の空隙率及び第２非対向部の空隙率のいずれか一方の空隙率のみが対向部の空隙率より小さくてもよい。 In the above embodiment, the case where the porosity of the first non-opposing portion 224 and the porosity of the second non-opposing portion 226 are smaller than the porosity of the facing portion 225 has been illustrated, but the present invention is not limited to this. Only one of the porosity of the facing portion and the porosity of the second non-opposing portion may be smaller than the porosity of the facing portion.

・二次電池１０は、電気自動車もしくはハイブリッド自動車に搭載されなくてもよい。例えば、二次電池１０は、ガソリン自動車やディーゼル自動車等の車両に搭載されてもよい。また二次電池１０は、鉄道、船舶、及び航空機等の移動体や、ロボットや、情報処理装置等の電気製品の電源として用いられてもよい。 -The secondary battery 10 does not have to be mounted on an electric vehicle or a hybrid vehicle. For example, the secondary battery 10 may be mounted on a vehicle such as a gasoline vehicle or a diesel vehicle. Further, the secondary battery 10 may be used as a power source for moving objects such as railways, ships, and aircraft, and electric products such as robots and information processing devices.

１０…二次電池、１１…電池ケース、１２…蓋体、１３…外部端子、１４…集電板、２０…極板群、２１…正極板、２１Ａ…リード部、２２…負極板、２２Ａ…リード部、２３…セパレータ、２７…電解液、３０…負極活物質、２１１…正極基材、２１１Ａ…表面、２１２…正極合剤層、２２１…負極基材、２２１Ａ…表面、２２２…負極合剤層、２２４…第１非対向部、２２５…対向部、２２６…第２非対向部。
10 ... secondary battery, 11 ... battery case, 12 ... lid, 13 ... external terminal, 14 ... current collector plate, 20 ... electrode plate group, 21 ... positive electrode plate, 21A ... lead part, 22 ... negative electrode plate, 22A ... Lead portion, 23 ... separator, 27 ... electrolytic solution, 30 ... negative electrode active material, 211 ... positive electrode base material, 211A ... surface, 212 ... positive electrode mixture layer, 221 ... negative electrode base material, 221A ... surface, 222 ... negative electrode mixture Layer 224 ... 1st non-opposing portion, 225 ... Facing portion, 226 ... Second non-opposing portion.

Claims (7)

正極板と負極板とがセパレータを挟んで対向配置される非水電解質二次電池用極板群であって、
前記負極板は、金属基板の表面に活物質を含む負極合剤層を有し、
前記負極合剤層は、前記セパレータを挟んで前記正極板の正極合剤層に対向する対向部と前記正極合剤層に対向しない縁部に非対向部とを有し、
前記負極合剤層の前記非対向部の少なくとも一部であって、前記非対向部の長手方向に対する幅が０．５ｍｍ以上で、かつ前記対向部を含まない部分の空隙率は、前記対向部の空隙率に比べて小さい
非水電解質二次電池用極板群。 A group of electrode plates for a non-aqueous electrolyte secondary battery in which a positive electrode plate and a negative electrode plate are arranged so as to face each other with a separator in between.
The negative electrode plate has a negative electrode mixture layer containing an active material on the surface of a metal substrate.
The negative electrode mixture layer has a facing portion facing the positive electrode mixing layer of the positive electrode plate across the separator and a non-opposing portion at an edge portion not facing the positive electrode mixing layer.
The porosity of a portion of the negative electrode mixture layer that is at least a part of the non-opposing portion and has a width of 0.5 mm or more with respect to the longitudinal direction of the non-opposing portion and does not include the facing portion is the porosity of the facing portion. A group of electrode plates for non-aqueous electrolyte secondary batteries that are smaller than the porosity of. 前記非対向部は、縁部のうちで二次電池の上下方向に延びている部分の空隙率が前記対向部の空隙率に比べて小さい
請求項１に記載の非水電解質二次電池用極板群。 The non-aqueous electrolyte secondary battery electrode according to claim 1, wherein the non-opposing portion has a porosity of a portion of the edge portion extending in the vertical direction of the secondary battery smaller than the porosity of the facing portion. Board group. 複数の前記正極板と複数の前記負極板とがそれぞれ前記セパレータを介して積層されている
請求項２に記載の非水電解質二次電池用極板群。 The electrode plate group for a non-aqueous electrolyte secondary battery according to claim 2, wherein the plurality of positive electrode plates and the plurality of negative electrode plates are laminated via the separator, respectively. 長尺の前記正極板と長尺の前記負極板とが長尺の前記セパレータを介して積層されて長尺方向に捲回されている
請求項２に記載の非水電解質二次電池用極板群。 The electrode plate for a non-aqueous electrolyte secondary battery according to claim 2, wherein the long positive electrode plate and the long negative electrode plate are laminated via the long separator and wound in the long direction. group. 前記対向部の空隙率と前記非対向部の空隙率との差が５％以上である
請求項１～４のいずれか一項に記載の非水電解質二次電池用極板群。 The electrode plate group for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the difference between the porosity of the facing portion and the porosity of the non-opposing portion is 5% or more. 前記非水電解質二次電池は、リチウムイオン二次電池である
請求項１～５のいずれか一項に記載の非水電解質二次電池用極板群。 The non-aqueous electrolyte secondary battery is a lithium ion secondary battery.
The electrode plate group for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5 . 正極板と負極板とがセパレータを挟んで対向配置される極板群を有する非水電解質二次電池であって、
前記極板群が請求項１～６のいずれか一項に記載の非水電解質二次電池用極板群である
非水電解質二次電池。 A non-aqueous electrolyte secondary battery having a group of electrode plates in which a positive electrode plate and a negative electrode plate are arranged so as to face each other with a separator in between.
A non-aqueous electrolyte secondary battery in which the electrode plate group is the electrode plate group for the non-aqueous electrolyte secondary battery according to any one of claims 1 to 6 .
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