JP7145092B2 - Method for manufacturing secondary battery - Google Patents

Method for manufacturing secondary battery Download PDF

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JP7145092B2
JP7145092B2 JP2019017637A JP2019017637A JP7145092B2 JP 7145092 B2 JP7145092 B2 JP 7145092B2 JP 2019017637 A JP2019017637 A JP 2019017637A JP 2019017637 A JP2019017637 A JP 2019017637A JP 7145092 B2 JP7145092 B2 JP 7145092B2
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直哉 亀田
健一 永光
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Sanyo Electric 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Description

本開示は、二次電池の製造方法に関する。 The present disclosure relates to a method for manufacturing a secondary battery.

二次電池の信頼性の向上を目的として、電池内に参照電極を設けて充放電時の正負極の電位を管理することが検討されている。参照電極の一例として、リン酸鉄リチウムが挙げられるが、参照電極の電位を安定させるためには、リン酸鉄リチウムからリチウムイオンを脱離させる必要がある。特許文献１には、リン酸鉄リチウムを含有する参照電極と、第４電極とを電池内に設置して、電池を密閉封止した後に参照電極と第４電極との間に電圧をかけてリン酸鉄リチウムからリチウムイオンを脱離させる方法と、別途リチウムイオンを脱離させた参照電極を用意して二次電池に組み込む方法が開示されている。 For the purpose of improving the reliability of a secondary battery, it has been studied to provide a reference electrode in the battery to control the potentials of the positive and negative electrodes during charging and discharging. An example of the reference electrode is lithium iron phosphate. In order to stabilize the potential of the reference electrode, it is necessary to desorb lithium ions from the lithium iron phosphate. In Patent Document 1, a reference electrode containing lithium iron phosphate and a fourth electrode are installed in a battery, and after the battery is hermetically sealed, a voltage is applied between the reference electrode and the fourth electrode. A method of desorbing lithium ions from lithium iron phosphate and a method of separately preparing a reference electrode from which lithium ions are desorbed and incorporating it into a secondary battery are disclosed.

特表２０１０－５３９６５７号公報Japanese Patent Publication No. 2010-539657

しかし、特許文献１に開示された方法では、電池ケース内に第４電極のためのスペースを確保しなくてはならないという問題がある。本開示の目的は、簡便な方法で参照電極を使用可能な状態にできる二次電池を提供することである。 However, the method disclosed in Patent Document 1 has a problem that a space for the fourth electrode must be secured in the battery case. An object of the present disclosure is to provide a secondary battery in which a reference electrode can be put into a usable state by a simple method.

本開示の一態様である二次電池は、正極と負極とを有する電極体と、電極体を収容する導電性の電池ケースと、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０.１≦ｘ≦０．９、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層と、参照電極層が浸されるように電池ケース内に配置された、リチウムイオンを含む電解質と、を備え、参照電極層は、電池ケースの内壁上に形成されており、負極と対向することを特徴とする。 A secondary battery that is one aspect of the present disclosure includes an electrode body having a positive electrode and a negative electrode, a conductive battery case that houses the electrode body, and a composition formula Li 1-x FeM y PO 4 (wherein M is one or more elements selected from Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, Y, La, Zn, Al, and Ga, 0.1≦x≦0.9 and 0≦y≦1), and an electrolyte containing lithium ions placed in a battery case so that the reference electrode layer is immersed and, wherein the reference electrode layer is formed on the inner wall of the battery case and faces the negative electrode.

本開示の一態様である二次電池の製造方法は、導電性の電池ケースの内壁上に、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０≦ｘ＜０．１、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層を形成する工程と、正極と負極とを有する電極体を、負極が参照電極層に対向するように、電極体の外側に隣接する多孔質の電極体ホルダを介して電池ケースに収容する工程と、電池ケースにリチウムイオンを含む電解質を少なくとも参照電極層が浸されるように注入する工程と、電池ケースを電源のプラス極に、負極を電源のマイナス極にそれぞれに接続して、参照電極層からリチウムイオンを脱離させる工程と、を有することを特徴とする。 A method for manufacturing a secondary battery, which is one aspect of the present disclosure, comprises forming Li 1-x FeM y PO 4 (wherein M is Mg, Nb, Cu, Mn, Ni) on the inner wall of a conductive battery case. , Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, Y, La, Zn, Al, and Ga, and 0≦x<0.1, 0 forming a reference electrode layer containing a compound that satisfies ≤ y ≤ 1; a step of housing the lithium ion-containing electrolyte in the battery case through a high-quality electrode body holder; a step of injecting an electrolyte containing lithium ions into the battery case so that at least the reference electrode layer is immersed; to the negative pole of a power supply to desorb lithium ions from the reference electrode layer.

本開示の一態様によれば、簡便な方法で参照電極を使用可能な状態にできる二次電池を提供できる。 According to one aspect of the present disclosure, it is possible to provide a secondary battery that enables a reference electrode to be used by a simple method.

実施形態の一例である二次電池の斜視図であって、角形外装体の手前側を外した状態での電池ケースの内部の構造と第１の参照電極形成領域を示す図である。1 is a perspective view of a secondary battery that is an example of an embodiment, showing the internal structure of a battery case and a first reference electrode formation region with the front side of a rectangular outer package removed. FIG. 実施形態の一例である電極体の斜視図である。1 is a perspective view of an electrode body that is an example of an embodiment; FIG. 図１中のＡ－Ａ線断面図である。FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1; 実施形態の他の一例である二次電池の斜視図であって、角形外装体の手前側を外した状態での第１の参照電極形成領域及び第２の参照電極形成領域を示す図である。FIG. 10 is a perspective view of a secondary battery that is another example of the embodiment, showing a first reference electrode formation region and a second reference electrode formation region with the front side of the rectangular outer package removed. . 実施形態の他の一例である二次電池の断面図である。FIG. 3 is a cross-sectional view of a secondary battery that is another example of an embodiment; 図１中のＡ－Ａ線断面図であって、参照電極層からリチウムイオンを脱離させる際の状態を示す図である。FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, showing a state when lithium ions are desorbed from the reference electrode layer;

二次電池に対して過充電を行った場合、正極側では電解質の酸化分解によりガスが発生したり、正極活物質の溶解が生じたりする可能性があり、また負極側では金属リチウムが析出する可能性がある。従来、正極と負極の電位差をモニターすることで過充電を抑制しているが、電極は使用により劣化するため、正極及び負極の電位を直接測定できる参照電極層を二次電池に設置できれば二次電池の信頼性をより向上させることができる。特許文献１は、リン酸鉄リチウムを含有する参照電極と、参照電極にリチウムイオンをドープ、または参照電極からリチウムイオンを脱離するための第４電極とを設置する方法を開示している。しかし、電池ケース内の容積は非常に限られた大きさしかないので、電池の実際の使用前にリチウムイオンをドープ、または脱離させるだけに使用される第４電極を設置するのは、電池の出力特性の観点から問題がある。 When a secondary battery is overcharged, gas may be generated on the positive electrode side due to oxidative decomposition of the electrolyte, or the positive electrode active material may dissolve, and metallic lithium may precipitate on the negative electrode side. there is a possibility. Conventionally, overcharging is suppressed by monitoring the potential difference between the positive and negative electrodes, but the electrodes deteriorate with use. Battery reliability can be further improved. Patent Document 1 discloses a method of installing a reference electrode containing lithium iron phosphate and a fourth electrode for doping the reference electrode with lithium ions or desorbing the lithium ions from the reference electrode. However, since the volume inside the battery case is very limited, installing a fourth electrode, which is only used for doping or desorbing lithium ions before the actual use of the battery, is not recommended for the battery. There is a problem from the viewpoint of the output characteristics of

本開示の一態様である二次電池は、正極と負極とを有する電極体と、電極体を収容する導電性の電池ケースと、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０.１≦ｘ≦０．９、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層と、参照電極層が浸されるように電池ケース内に配置された、リチウムイオンを含む電解質と、を備え、参照電極層は、電池ケースの内壁上に形成されており、負極と対向することを特徴とする。 A secondary battery that is one aspect of the present disclosure includes an electrode body having a positive electrode and a negative electrode, a conductive battery case that houses the electrode body, and a composition formula Li 1-x FeM y PO 4 (wherein M is one or more elements selected from Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, Y, La, Zn, Al, and Ga, 0.1≦x≦0.9 and 0≦y≦1), and an electrolyte containing lithium ions placed in a battery case so that the reference electrode layer is immersed and, wherein the reference electrode layer is formed on the inner wall of the battery case and faces the negative electrode.

本開示の一態様である二次電池が備える参照電極は、多くのリチウムイオンを含んでいるので、安定した電位となるためにはリチウムイオンを脱離させる必要がある。参照電極層と負極が電解質を介して互いに対向しているので、参照電極層と負極との間で電圧をかけたときに、参照電極に含まれるリチウムイオンが負極に移動しやすい。よって、参照電極層から十分な量のリチウムイオンを脱離させることができるので、参照電極層の電位が安定し、正極及び負極の電位を高精度で測定することができる。 Since the reference electrode included in the secondary battery which is one embodiment of the present disclosure contains many lithium ions, the lithium ions need to be desorbed in order to achieve a stable potential. Since the reference electrode layer and the negative electrode face each other with the electrolyte interposed therebetween, lithium ions contained in the reference electrode easily move to the negative electrode when a voltage is applied between the reference electrode layer and the negative electrode. Therefore, since a sufficient amount of lithium ions can be desorbed from the reference electrode layer, the potential of the reference electrode layer is stabilized, and the potentials of the positive and negative electrodes can be measured with high accuracy.

以下、本開示の実施形態の一例について詳細に説明する。本実施形態では、角形の金属製ケースである電池ケース２００を備えた角形電池を例示するが、電池ケースは角形に限定されず、例えば金属層及び樹脂層を含むラミネートシートで構成された電池ケースであってもよい。なお、ラミネートシートで構成された電池ケースを用いる場合、参照電極層が形成される部分及び電源のプラス極が当接される部分には樹脂層を設けないようにする。また、巻回型の電極体３を例示するが、積層型の電極体であってもよい。また、正極及び負極の両方において、各活物質層が各芯体の両面に形成される場合を例示するが、各活物質層は、各芯体の両面に形成される場合に限定されず、少なくとも一方の表面に形成されればよい。 An example of an embodiment of the present disclosure will be described in detail below. In this embodiment, a prismatic battery including a battery case 200 that is a prismatic metal case is exemplified, but the battery case is not limited to a prismatic shape. may be When using a battery case made of a laminate sheet, the resin layer should not be provided on the portion where the reference electrode layer is formed and the portion where the positive electrode of the power source is brought into contact. Moreover, although the winding-type electrode body 3 is exemplified, a laminated-type electrode body may be used. In both the positive electrode and the negative electrode, the case where each active material layer is formed on both sides of each core is exemplified, but each active material layer is not limited to the case where it is formed on both sides of each core. It may be formed on at least one surface.

図１に例示するように、二次電池１００は、正極と負極がセパレータを介して巻回され、平坦部及び一対の湾曲部を有する扁平状に成形された巻回型の電極体３と、電解質と、電極体３及び電解質を収容する電池ケース２００とを備える。電池ケース２００は、開口を有する有底筒状の角形外装体１、及び角形外装体１の開口を封口する封口板２を含む。角形外装体１及び封口板２はいずれも金属製であり、アルミニウム製又はアルミニウム合金製であることが好ましい。 As exemplified in FIG. 1, the secondary battery 100 includes a wound electrode body 3 formed in a flat shape having a flat portion and a pair of curved portions, in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; It includes an electrolyte, and a battery case 200 that houses the electrode body 3 and the electrolyte. The battery case 200 includes a bottomed tubular prismatic exterior body 1 having an opening and a sealing plate 2 that seals the opening of the prismatic exterior body 1 . Both the rectangular exterior body 1 and the sealing plate 2 are made of metal, preferably aluminum or aluminum alloy.

角形外装体１は、底面視略長方形状の底部、及び底部の周縁に立設した側壁部を有する。側壁部は、底部に対して垂直に形成される。角形外装体１の寸法は特に限定されないが、一例としては、横方向長さが６０～１６０ｍｍ、高さが６０～１００ｍｍ、厚みが１０～４０ｍｍである。本明細書では、説明の便宜上、角形外装体１の底部の長手方向に沿った方向を角形外装体１の「横方向」、底部に対して垂直な方向を「高さ方向」、横方向及び高さ方向に垂直な方向を「厚み方向」とする。 The square exterior body 1 has a substantially rectangular bottom when viewed from the bottom, and side walls erected along the periphery of the bottom. The sidewalls are formed perpendicular to the bottom. Although the dimensions of the rectangular exterior body 1 are not particularly limited, for example, the lateral length is 60 to 160 mm, the height is 60 to 100 mm, and the thickness is 10 to 40 mm. In this specification, for convenience of explanation, the direction along the longitudinal direction of the bottom of the prismatic exterior body 1 is the "horizontal direction" of the prismatic exterior body 1, the direction perpendicular to the bottom is the "height direction", the lateral direction and the Let the direction perpendicular to the height direction be the “thickness direction”.

電解質は、非水溶媒と、非水溶媒に溶解した電解質塩とを含む非水電解質である。非水溶媒には、例えばカーボネート類、エステル類、エーテル類、ニトリル類、アミド類、およびこれらの２種以上の混合溶媒等を用いてもよい。カーボネート類としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート、ビニレンカーボネート等の環状カーボネート類；ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルプロピルカーボネート、エチルプロピルカーボネート、メチルイソプロピルカーボネート等の鎖状カーボネート類が挙げられる。非水溶媒は、上記の溶媒の水素の少なくとも一部をフッ素等のハロゲン原子で置換したハロゲン置換体を含有していてもよい。なお、電解質は液体電解質に限定されず、ゲル状ポリマー等を用いた固体電解質であってもよい。電解質塩は、リチウム塩を含む。リチウム塩には、従来の二次電池１００において支持塩として一般に使用されているＬｉＰＦ６等を用いることができる。また、適宜ビニレンカーボネート（ＶＣ）等の添加剤を添加することもできる。 The electrolyte is a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents that can be used include carbonates, esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Carbonates include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinylene carbonate; dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate; , ethyl propyl carbonate, and methyl isopropyl carbonate. The non-aqueous solvent may contain a halogen-substituted product obtained by substituting at least part of the hydrogen atoms of the above solvent with halogen atoms such as fluorine. Note that the electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like. Electrolyte salts include lithium salts. LiPF 6 or the like, which is generally used as a supporting salt in the conventional secondary battery 100, can be used as the lithium salt. Additives such as vinylene carbonate (VC) can also be added as appropriate.

正極４は、金属製の正極芯体と、正極芯体の両面に形成された正極活物質層４１とを有する長尺体であって、短手方向における一方の端部に長手方向に沿って正極芯体が露出する帯状の正極芯体露出部４２が形成されたものである（後述の図２参照）。本実施形態では、正極４の巻外端から巻内端まで、即ち正極４の長手方向両端にわたって正極活物質層４１が正極芯体の両面に設けられている。同様に、負極５は、金属製の負極芯体と、負極芯体の両面に形成された負極活物質層５１とを有する長尺体であって、短手方向における一方の端部に長手方向に沿って負極芯体が露出する帯状の負極芯体露出部５２が形成されたものである。本実施形態では、負極５の巻外端から巻内端まで、即ち負極５の長手方向両端にわたって負極活物質層５１が負極芯体の両面に設けられている。電極体３は、巻軸方向一端側に正極芯体露出部４２が、巻軸方向他端側に負極芯体露出部５２がそれぞれ配置された状態で、セパレータ３０を介して正極４及び負極５が巻回された構造を有する。 The positive electrode 4 is an elongated body having a positive electrode core made of metal and positive electrode active material layers 41 formed on both sides of the positive electrode core. A strip-shaped positive electrode core exposed portion 42 is formed through which the positive electrode core is exposed (see FIG. 2 described later). In this embodiment, the positive electrode active material layer 41 is provided on both surfaces of the positive electrode core body from the outer end to the inner end of the positive electrode 4 , that is, over both longitudinal ends of the positive electrode 4 . Similarly, the negative electrode 5 is a long body having a negative electrode core made of metal and negative electrode active material layers 51 formed on both sides of the negative electrode core. A strip-shaped negative electrode core exposing portion 52 is formed along which the negative electrode core is exposed. In this embodiment, the negative electrode active material layer 51 is provided on both surfaces of the negative electrode substrate from the outer end of the negative electrode 5 to the inner end of the negative electrode 5 , ie, across both longitudinal ends of the negative electrode 5 . The electrode body 3 has the positive electrode core exposed portion 42 and the negative electrode core exposed portion 52 disposed on the one end side in the winding axis direction and the negative electrode core exposed portion 52, respectively, on the other end side in the winding axis direction. has a wound structure.

正極芯体露出部４２の積層部には正極集電体６が、負極芯体露出部５２の積層部には負極集電体８がそれぞれ接続される。好適な正極集電体６は、アルミニウム製又はアルミニウム合金製である。好適な負極集電体８は、銅又は銅合金製である。正極端子７は、封口板２の電池外部側に配置される正極外部導電部１３と、正極外部導電部１３に接続された正極ボルト部１４と、封口板２に設けられた貫通穴に挿入される正極挿入部１５とを有し、正極集電体６と電気的に接続されている。また、負極端子９は、封口板２の電池外部側に配置される負極外部導電部１６と、負極外部導電部１６に接続された負極ボルト部１７と、封口板２に設けられた貫通穴に挿入される負極挿入部１８とを有し、負極集電体８と電気的に接続されている。 The positive electrode current collector 6 is connected to the stacked portion of the positive electrode core exposed portion 42 , and the negative electrode current collector 8 is connected to the stacked portion of the negative electrode core exposed portion 52 . A suitable positive electrode current collector 6 is made of aluminum or an aluminum alloy. A suitable negative electrode current collector 8 is made of copper or a copper alloy. The positive electrode terminal 7 is inserted into a positive electrode external conductive portion 13 arranged on the battery exterior side of the sealing plate 2 , a positive electrode bolt portion 14 connected to the positive electrode external conductive portion 13 , and a through hole provided in the sealing plate 2 . The positive electrode insertion portion 15 is electrically connected to the positive electrode current collector 6 . The negative electrode terminal 9 is connected to a negative electrode external conductive portion 16 arranged on the battery exterior side of the sealing plate 2 , a negative electrode bolt portion 17 connected to the negative electrode external conductive portion 16 , and a through hole provided in the sealing plate 2 . It has a negative electrode insertion part 18 to be inserted, and is electrically connected to the negative electrode current collector 8 .

正極端子７及び正極集電体６は、それぞれ内部側絶縁部材及び外部側絶縁部材を介して封口板２に固定される。内部側絶縁部材は、封口板２と正極集電体６との間に配置され、外部側絶縁部材は封口板２と正極端子７との間に配置される。同様に、負極端子９及び負極集電体８は、それぞれ内部側絶縁部材及び外部側絶縁部材を介して封口板２に固定される。内部側絶縁部材は封口板２と負極集電体８との間に配置され、外部側絶縁部材は封口板２と負極端子９との間に配置される。 The positive electrode terminal 7 and the positive electrode current collector 6 are fixed to the sealing plate 2 via the inner side insulating member and the outer side insulating member, respectively. The inner insulating member is arranged between the sealing plate 2 and the positive electrode current collector 6 , and the outer insulating member is arranged between the sealing plate 2 and the positive electrode terminal 7 . Similarly, the negative electrode terminal 9 and the negative electrode current collector 8 are fixed to the sealing plate 2 via the inner side insulating member and the outer side insulating member, respectively. The inner insulating member is arranged between the sealing plate 2 and the negative electrode current collector 8 , and the outer insulating member is arranged between the sealing plate 2 and the negative electrode terminal 9 .

電極体３は、角形外装体１内に収容される。封口板２は、角形外装体１の開口縁部にレーザー溶接等により接続される。封口板２は電解質注液孔１０を有し、この電解質注液孔１０は電池ケース２００内に電解質を注液した後、封止栓により電解質注液孔１０が封止される。封口板２には、電池内部の圧力が所定値以上となった場合にガスを排出するためのガス排出弁１１が形成されている。 The electrode body 3 is accommodated in the rectangular exterior body 1 . The sealing plate 2 is connected to the edge of the opening of the rectangular exterior body 1 by laser welding or the like. The sealing plate 2 has an electrolyte pouring hole 10. After the electrolyte is injected into the battery case 200, the electrolyte pouring hole 10 is sealed with a sealing plug. The sealing plate 2 is formed with a gas discharge valve 11 for discharging gas when the pressure inside the battery reaches a predetermined value or more.

本開示の一態様である二次電池１００は、電極体３と電池ケース２００との間に配置され、リチウムイオンが通過可能な多孔質の電極体ホルダ１２をさらに備えることが好ましい（後述の図３参照）。電極体３と電池ケース２００との間に電極体ホルダ１２を挟むことにより、電極体３と電池ケース２００とが確実に接触しないようにすることができる。電極体ホルダ１２は、リチウムイオンを透過する多孔質のものであれば特に限定されないが、例えば絶縁性を有する多孔性シートが用いられる。電極体ホルダ１２は、例えばポリオレフィン、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、ポリイミド、ポリアミド、ポリアミドイミド、ポリエーテルサルフォン、ポリエーテルイミド、及びアラミドから選択される少なくとも１種を主成分とする多孔質基材を含み、ポリオレフィンが好ましく、特にポリエチレン、及びポリプロピレンが好ましい。電極体３と電池ケース２００との間は狭いので、電極体３が電極体ホルダ１２で覆われた状態で角形外装体１内に収容されるのが好ましい。 The secondary battery 100, which is one aspect of the present disclosure, preferably further includes a porous electrode body holder 12 that is disposed between the electrode body 3 and the battery case 200 and through which lithium ions can pass (Fig. 3). By sandwiching the electrode body holder 12 between the electrode body 3 and the battery case 200, the contact between the electrode body 3 and the battery case 200 can be reliably prevented. The electrode body holder 12 is not particularly limited as long as it is porous and permeable to lithium ions. For example, an insulating porous sheet is used. The electrode body holder 12 is a porous material mainly composed of at least one selected from, for example, polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamide, polyamideimide, polyethersulfone, polyetherimide, and aramid. Polyolefins are preferred, especially polyethylene and polypropylene, including the substrate. Since the space between the electrode body 3 and the battery case 200 is narrow, it is preferable that the electrode body 3 be covered with the electrode body holder 12 and housed in the rectangular exterior body 1 .

角形外装体１の内壁面は、第１の参照電極形成領域２０を有する。第１の参照電極形成領域２０は、負極芯体露出部５２に対向する領域である。第１の参照電極形成領域２０及び後述する第２の参照電極形成領域２１の少なくとも一方には参考電極層が形成される。 The inner wall surface of the rectangular exterior body 1 has a first reference electrode formation region 20 . The first reference electrode forming region 20 is a region facing the negative electrode substrate exposed portion 52 . A reference electrode layer is formed in at least one of the first reference electrode formation region 20 and a second reference electrode formation region 21 to be described later.

以下、電極体３及び参照電極層６０について詳説する。 The electrode body 3 and the reference electrode layer 60 will be described in detail below.

［電極体］
図２は電極体３の斜視図であり、電極体３の巻き終わり近傍を展開した図としている。図１に例示するように、電極体３は、正極芯体露出部４２と負極芯体露出部５２とが軸方向の反対側に位置するように、セパレータ３０を介して正極４及び負極５が巻回された構造を有する。電極体３において、負極５は、正極４よりも一回り大きな寸法を有し、正極活物質層４１と対向する領域には必ず負極活物質層５１が存在するように配置される。電極体３は、例えば軸方向長さが５０～１５０ｍｍ、幅が５０～９０ｍｍ、厚みが８～３８ｍｍの寸法を有する。 [Electrode body]
FIG. 2 is a perspective view of the electrode body 3, showing the electrode body 3 in the vicinity of the end of the winding. As exemplified in FIG. 1, the electrode body 3 includes the positive electrode 4 and the negative electrode 5 with the separator 30 interposed therebetween such that the positive electrode core exposed portion 42 and the negative electrode core exposed portion 52 are positioned on opposite sides in the axial direction. It has a wound structure. In the electrode body 3 , the negative electrode 5 is one size larger than the positive electrode 4 and is arranged so that the negative electrode active material layer 51 always exists in the region facing the positive electrode active material layer 41 . The electrode body 3 has, for example, an axial length of 50 to 150 mm, a width of 50 to 90 mm, and a thickness of 8 to 38 mm.

正極４は、正極芯体と、正極芯体上に設けられた正極活物質層４１とを有する。正極芯体には、アルミニウム、アルミニウム合金など正極４の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極芯体の厚みは、例えば１０～２０μｍである。正極活物質層４１は、正極活物質、アセチレンブラック等の導電助剤、及びポリフッ化ビニリデン（ＰＶｄＦ）等の結着剤を含み、正極芯体の両面に設けられることが好ましい。正極活物質層４１の厚みは、例えば正極芯体の両側の合計で５０～４００μｍである。正極４は、正極芯体上に正極活物質、導電助剤、及び結着剤等を含む正極活物質スラリーを塗布し、塗膜を乾燥させた後、圧縮して正極活物質層４１を正極芯体の両面に形成することにより作製できる。 The positive electrode 4 has a positive electrode core and a positive electrode active material layer 41 provided on the positive electrode core. For the positive electrode core, a foil of a metal such as aluminum or an aluminum alloy that is stable in the potential range of the positive electrode 4, a film in which the metal is arranged on the surface layer, or the like can be used. The thickness of the positive electrode core is, for example, 10 to 20 μm. The positive electrode active material layer 41 contains a positive electrode active material, a conductive aid such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably provided on both sides of the positive electrode core. The thickness of the positive electrode active material layer 41 is, for example, 50 to 400 μm in total on both sides of the positive electrode core. The positive electrode 4 is formed by coating a positive electrode core with a positive electrode active material slurry containing a positive electrode active material, a conductive aid, a binder, and the like, drying the coating film, and then compressing the positive electrode active material layer 41 to form a positive electrode. It can be produced by forming on both sides of the core.

正極活物質には、例えばリチウム金属複合酸化物が用いられる。リチウム金属複合酸化物に含有される金属元素としては、Ｎｉ、Ｃｏ、Ｍｎ、Ａｌ、Ｂ、Ｍｇ、Ｔｉ、Ｖ、Ｃｒ、Ｆｅ、Ｃｕ、Ｚｎ、Ｇａ、Ｓｒ、Ｚｒ、Ｎｂ、Ｉｎ、Ｓｎ、Ｔａ、Ｗ等が挙げられる。好適なリチウム金属複合酸化物の一例は、Ｎｉ、Ｃｏ、Ｍｎの少なくとも１種を含有するリチウム金属複合酸化物である。具体例としては、Ｎｉ、Ｃｏ、Ｍｎを含有するリチウム金属複合酸化物、Ｎｉ、Ｃｏ、Ａｌを含有するリチウム金属複合酸化物が挙げられる。なお、リチウム金属複合酸化物の粒子表面には、酸化タングステン、酸化アルミニウム、ランタノイド含有化合物等の無機化合物粒子などが固着していてもよい。 For example, a lithium metal composite oxide is used as the positive electrode active material. Metal elements contained in the lithium metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. are mentioned. An example of a suitable lithium metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co and Mn. Specific examples include lithium metal composite oxides containing Ni, Co and Mn, and lithium metal composite oxides containing Ni, Co and Al. Inorganic compound particles such as tungsten oxide, aluminum oxide, and lanthanide-containing compounds may adhere to the surfaces of the lithium metal composite oxide particles.

負極５は、負極芯体と、負極芯体上に設けられた負極活物質層５１とを有する。負極芯体には、銅、銅合金など負極５の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。負極芯体の厚みは、例えば５～１５μｍである。負極活物質層５１は、負極活物質、及びスチレンブタジエンゴム（ＳＢＲ）等の結着剤を含み、負極芯体の両面に設けられることが好ましい。負極活物質層５１の厚みは、例えば負極芯体の両側の合計で５０～４００μｍである。負極５は、負極芯体上に負極活物質、及び結着剤等を含む負極活物質スラリーを塗布し、塗膜を乾燥させた後、圧縮して負極活物質層５１を負極芯体の両面に形成することにより作製できる。 The negative electrode 5 has a negative electrode core and a negative electrode active material layer 51 provided on the negative electrode core. For the negative electrode core, a foil of a metal such as copper or a copper alloy that is stable in the potential range of the negative electrode 5, a film having the metal on the surface layer, or the like can be used. The thickness of the negative electrode core is, for example, 5 to 15 μm. The negative electrode active material layer 51 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is preferably provided on both sides of the negative electrode core. The thickness of the negative electrode active material layer 51 is, for example, 50 to 400 μm in total on both sides of the negative electrode core. The negative electrode 5 is formed by applying a negative electrode active material slurry containing a negative electrode active material, a binder, etc. on the negative electrode core, drying the coating film, and then compressing the negative electrode active material layer 51 onto both sides of the negative electrode core. can be produced by forming

負極活物質には、例えば鱗片状黒鉛、塊状黒鉛、土状黒鉛等の天然黒鉛、塊状人造黒鉛、黒鉛化メソフェーズカーボンマイクロビーズ等の人造黒鉛などの黒鉛が用いられる。負極活物質には、Ｓｉ、Ｓｎ等のリチウムと合金化する金属、当該金属を含有する合金、当該金属を含有する化合物等が用いられてもよく、これらが黒鉛と併用されてもよい。当該化合物の具体例としては、ＳｉＯｘ（０．５≦ｘ≦１．６）で表されるケイ素化合物が挙げられる。 As the negative electrode active material, for example, graphite such as natural graphite such as flake graphite, massive graphite, and earthy graphite, massive artificial graphite, and artificial graphite such as graphitized mesophase carbon microbeads is used. As the negative electrode active material, a metal such as Si or Sn that is alloyed with lithium, an alloy containing the metal, a compound containing the metal, or the like may be used, and these may be used in combination with graphite. Specific examples of the compound include silicon compounds represented by SiO x (0.5≦x≦1.6).

セパレータ３０には、イオン透過性及び絶縁性を有する多孔性シートが用いられる。セパレータ３０は、例えばポリオレフィン、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、ポリイミド、ポリアミド、ポリアミドイミド、ポリエーテルサルフォン、ポリエーテルイミド、及びアラミドから選択される少なくとも１種を主成分とする多孔質基材を含み、ポリオレフィンが好ましく、特にポリエチレン、及びポリプロピレンが好ましい。 A porous sheet having ion permeability and insulation is used for the separator 30 . The separator 30 is a porous substrate containing at least one selected from, for example, polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamide, polyamideimide, polyethersulfone, polyetherimide, and aramid as a main component. with polyolefins being preferred, particularly polyethylene and polypropylene being preferred.

セパレータ３０は、樹脂製の多孔質基材のみで構成されていてもよく、多孔質基材の少なくとも一方の面に無機物粒子等を含む耐熱層などが形成された複層構造であってもよい。また、樹脂製の多孔質基材が、ポリプロピレン／ポリエチレン／ポリプロピレン等の複層構造を有していてもよい。セパレータ３０の厚みは、例えば１０～３０μｍである。セパレータ３０は、例えば、平均孔径が０．０２～５μｍ、空孔率が３０～７０％である。一般的に、巻回型の電極体３は２枚のセパレータ３０を含むが、各セパレータ３０には同じものを用いることができる。 The separator 30 may be composed only of a resin-made porous substrate, or may have a multilayer structure in which a heat-resistant layer containing inorganic particles or the like is formed on at least one surface of the porous substrate. . Moreover, the resin-made porous substrate may have a multi-layer structure such as polypropylene/polyethylene/polypropylene. The thickness of the separator 30 is, for example, 10-30 μm. The separator 30 has, for example, an average pore diameter of 0.02 to 5 μm and a porosity of 30 to 70%. Generally, the wound electrode body 3 includes two separators 30, but each separator 30 can be the same.

電極体３は、セパレータ３０を介して巻回された正極４及び負極５の巻回体を扁平状にプレスして作製される。この場合、例えば略円筒形状の巻芯を用いて円筒状の巻回体を作製し、巻芯を取り除いた後、当該巻回体を径方向にプレスする。或いは、扁平状の巻芯を用いて正極４及び負極５を扁平状に巻回してもよい。この場合、巻芯を取り除いた後、さらにプレスして扁平状に成形してもよい。 The electrode body 3 is produced by pressing flat a wound body of the positive electrode 4 and the negative electrode 5 wound with the separator 30 interposed therebetween. In this case, for example, a cylindrical wound body is produced using a substantially cylindrical winding core, and after the winding core is removed, the wound body is radially pressed. Alternatively, the positive electrode 4 and the negative electrode 5 may be flatly wound using a flat winding core. In this case, after removing the winding core, it may be further pressed into a flat shape.

図２において、電極体３の最外周は正極４である。本願において最外周は、最も巻外側に配置された正極４又は負極５を意味し、セパレータ３０は除外する。例えば、電極体３の最外周が負極５の場合には、両極の芯体露出部を除く電極体３の外側表面の略全体を負極５が覆うことを意味する。電極体３の最外周が正極活物質層４１であると最外周の正極活物質層４１に対向する領域に負極活物質層５１が存在しないので、電極体３の最外周は正極芯体であることが好ましい。 In FIG. 2, the outermost periphery of the electrode assembly 3 is the positive electrode 4 . In the present application, the outermost circumference means the positive electrode 4 or the negative electrode 5 arranged on the outermost side of the winding, and excludes the separator 30 . For example, when the outermost periphery of the electrode body 3 is the negative electrode 5 , it means that the negative electrode 5 covers substantially the entire outer surface of the electrode body 3 excluding core exposed portions of both electrodes. If the outermost periphery of the electrode body 3 is the positive electrode active material layer 41, the negative electrode active material layer 51 does not exist in the region facing the outermost positive electrode active material layer 41, so the outermost periphery of the electrode body 3 is the positive electrode core. is preferred.

［参照電極層］
参照電極層６０は、正極４及び負極５の電位の絶対値を測定する際の基準となる電極である。具体的には、参照電極層６０と電気的に接続している電池ケース２００と正極端子７との間の電圧を測定して、参照電極層６０に対する正極４の電位が測定できる。参照電極層６０に対する負極５の電位は、別途計測したセル電圧から先に測定した参照電極層６０に対する正極４の電位を引いて算出できる。参照電極の電位を基準にして正極４及び負極５の電位を決定するので、参照電極層６０の電位は安定していることが好ましい。参照電極層６０は、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０.１≦ｘ≦０．９、０≦ｙ≦１を満たし、以下、「リン酸鉄リチウム」という場合がある）からなる化合物を含む。参照電極層６０は、電池ケース２００内壁上の所定の位置に、少なくともリン酸鉄リチウムを含む参照電極スラリーを塗布し、塗膜を乾燥させることにより作製できる。作製した参照電極層６０に含まれるリン酸鉄リチウムからリチウムイオンを脱離させることで、参照電極層６０の電位は安定化する。上記の組成式のリン酸鉄リチウムは、リチウムイオンを脱離させた後のリン酸鉄リチウムである。 [Reference electrode layer]
The reference electrode layer 60 is an electrode that serves as a reference when measuring the absolute values of the potentials of the positive electrode 4 and the negative electrode 5 . Specifically, the potential of the positive electrode 4 with respect to the reference electrode layer 60 can be measured by measuring the voltage between the battery case 200 electrically connected to the reference electrode layer 60 and the positive electrode terminal 7 . The potential of the negative electrode 5 with respect to the reference electrode layer 60 can be calculated by subtracting the previously measured potential of the positive electrode 4 with respect to the reference electrode layer 60 from the separately measured cell voltage. Since the potentials of the positive electrode 4 and the negative electrode 5 are determined based on the potential of the reference electrode, it is preferable that the potential of the reference electrode layer 60 is stable. The reference electrode layer 60 has a composition formula Li 1-x FeM y PO 4 (wherein M is Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, One or more elements selected from Y, La, Zn, Al, and Ga, satisfying 0.1 ≤ x ≤ 0.9 and 0 ≤ y ≤ 1, hereinafter referred to as "lithium iron phosphate" includes compounds consisting of The reference electrode layer 60 can be produced by applying a reference electrode slurry containing at least lithium iron phosphate to a predetermined position on the inner wall of the battery case 200 and drying the applied film. The potential of the reference electrode layer 60 is stabilized by desorbing lithium ions from the lithium iron phosphate contained in the reference electrode layer 60 thus produced. The lithium iron phosphate of the above composition formula is lithium iron phosphate after desorption of lithium ions.

参照電極層６０は、参照電極層６０の電位をより安定させるために、導電助剤をさらに含むことが好ましい。導電助剤としては、カーボンブラック、アセチレンブラック、ケッチェンブラック、黒鉛等の炭素材料が例示できる。 The reference electrode layer 60 preferably further contains a conductive aid in order to stabilize the potential of the reference electrode layer 60 . Examples of conductive aids include carbon materials such as carbon black, acetylene black, ketjen black, and graphite.

参照電極層６０は、リン酸鉄リチウム、導電助剤以外に、スチレンブタジエンゴム、ポリフッ化ビニリデン（ＰＶｄＦ）等の結着剤、及びカルボキシメチルセルロース（ＣＭＣ）等の増粘剤を含むことができる。 The reference electrode layer 60 can contain a binder such as styrene-butadiene rubber and polyvinylidene fluoride (PVdF), and a thickener such as carboxymethyl cellulose (CMC), in addition to lithium iron phosphate and a conductive aid.

参照電極層６０の厚さ及び大きさは、参照電極層６０の電位が安定している限りは特に限定されない。例えば、参照電極層６０の厚さは、１～２００μｍであることが好ましいく、１～５０μｍであることがより好ましく、１～１０μｍであることが更に好ましい。また、参照電極層６０の厚さは、大きさは1ｃｍ２～４００ｃｍ２であることが好ましく、３ｃｍ２～１５０ｃｍ２であることがより好ましく、５ｃｍ２～２５ｃｍであることが更に好ましい。また、参照電極層６０に含まれるチタン酸リチウムの割合は９０質量％以上であることが好ましい。 The thickness and size of the reference electrode layer 60 are not particularly limited as long as the potential of the reference electrode layer 60 is stable. For example, the thickness of the reference electrode layer 60 is preferably 1-200 μm, more preferably 1-50 μm, even more preferably 1-10 μm. The thickness of the reference electrode layer 60 is preferably 1 cm 2 to 400 cm 2 , more preferably 3 cm 2 to 150 cm 2 , and even more preferably 5 cm 2 to 25 cm. Moreover, the proportion of lithium titanate contained in the reference electrode layer 60 is preferably 90% by mass or more.

図３を参照しつつ参照電極層６０の形成される位置について説明する。図３は、図１中のＡ－Ａ線断面図である。電極体３は、角形外装体１の厚さ方向の略中央に角形外装体１に接触しないように設置されており、負極集電体８（図示しない）を介して封口板２に固定されている。参照電極層６０は、電池ケース２００の内壁上、より具体的には、角形外装体１の内側の側壁部又は底部に形成される。参照電極層６０を角形外装体１の上に層状に形成することで、角形外装体１と電気的に接続することができ、また、電池ケース２００内の容積を少なくすることもない。 The position where the reference electrode layer 60 is formed will be described with reference to FIG. FIG. 3 is a cross-sectional view taken along line AA in FIG. The electrode body 3 is installed substantially in the center of the rectangular outer body 1 in the thickness direction so as not to contact the rectangular outer body 1, and is fixed to the sealing plate 2 via the negative electrode current collector 8 (not shown). there is The reference electrode layer 60 is formed on the inner wall of the battery case 200 , more specifically, on the inner sidewall or bottom of the rectangular exterior body 1 . By forming the reference electrode layer 60 in a layered manner on the prismatic exterior body 1, it can be electrically connected to the prismatic exterior body 1, and the volume inside the battery case 200 is not reduced.

電極体３は、正極４と負極５とがセパレータ３０を介して巻かれた巻回型である。そして、電極体３は、巻軸方向の一方の端部に正極芯体露出部４２を有し、巻軸方向の他方の端部に負極芯体露出部５２を有している。また、電極体３の最外周は負極５であり、参照電極層６０は正極芯体露出部４２に対向する。 The electrode body 3 is a wound type in which the positive electrode 4 and the negative electrode 5 are wound with the separator 30 interposed therebetween. The electrode body 3 has a positive electrode core exposure portion 42 at one end in the winding direction, and has a negative electrode core exposure portion 52 at the other end in the winding direction. Further, the outermost periphery of the electrode body 3 is the negative electrode 5 , and the reference electrode layer 60 faces the positive electrode core exposed portion 42 .

図２に示すように電極体３の最外周は正極４であり、電極体３で負極５が巻外側に存在する部分は負極芯体露出部５２である。この場合、参照電極層６０は、負極芯体露出部５２に対向する位置、換言すれば図１の第１の参照電極形成領域２０に形成される。参照電極層６０と負極５との間には電解質があるので、参照電極層６０と負極５との間で電圧をかけたときに、参照電極層６０からリチウムイオンが負極５に移動しやすい。よって、参照電極層６０から十分な量のリチウムイオンを脱離させることができる。 As shown in FIG. 2 , the outermost periphery of the electrode body 3 is the positive electrode 4 , and the portion of the electrode body 3 where the negative electrode 5 exists on the outside of the winding is the negative electrode core exposed portion 52 . In this case, the reference electrode layer 60 is formed at a position facing the negative electrode substrate exposed portion 52, in other words, at the first reference electrode forming region 20 in FIG. Since there is an electrolyte between the reference electrode layer 60 and the negative electrode 5 , lithium ions easily move from the reference electrode layer 60 to the negative electrode 5 when a voltage is applied between the reference electrode layer 60 and the negative electrode 5 . Therefore, a sufficient amount of lithium ions can be released from the reference electrode layer 60 .

図２ではセパレータ３０が最外周の正極４の上に積層されているが、セパレータ３０は正極４の上に積層されていなくてもよい。この場合、図２で正極４の上に積層されている方のセパレータ３０を負極５の下に積層させることや、正極４の上に積層させている方のセパレータ３０の長さを短くすることができる。 Although the separator 30 is laminated on the outermost positive electrode 4 in FIG. 2 , the separator 30 may not be laminated on the positive electrode 4 . In this case, the separator 30 laminated on the positive electrode 4 in FIG. 2 is laminated under the negative electrode 5, or the length of the separator 30 laminated on the positive electrode 4 is shortened. can be done.

＜実施形態の他の一例＞
図４は、実施形態の他の一例である二次電池の斜視図であって、第１の参照電極形成領域２０及び第２の参照電極形成領域２１を示す図である。第２の参照電極形成領域２１は、角形外装体１の内壁面の一部であって、電極体３の正極芯体露出部４２と負極芯体露出部５２を除く部分に対向する領域である。また、図３の断面図に示す例と同様に、参照電極層６０は、電池ケース２００の内壁上、より具体的には、角形外装体１の内側の側壁部又は底部に形成される。 <Another example of the embodiment>
FIG. 4 is a perspective view of a secondary battery that is another example of the embodiment, showing a first reference electrode forming region 20 and a second reference electrode forming region 21. As shown in FIG. The second reference electrode formation region 21 is a part of the inner wall surface of the rectangular outer casing 1 and is a region that faces the part of the electrode body 3 excluding the positive electrode core exposed portion 42 and the negative electrode core exposed portion 52 . . 3, the reference electrode layer 60 is formed on the inner wall of the battery case 200, more specifically, on the inner side wall or bottom of the rectangular exterior body 1. As shown in FIG.

電極体３は、正極４と負極５とがセパレータ３０を介して巻かれた巻回型であり、巻軸方向の両端にはそれぞれ正極芯体露出部４２及び負極芯体露出部５２を有し、電極体３の最外周は負極５であり、参照電極層６０は電極体３の正極芯体露出部４２を除く部分に対向することを特徴とする。 The electrode body 3 is a wound type in which the positive electrode 4 and the negative electrode 5 are wound with the separator 30 interposed therebetween, and has a positive electrode core exposed portion 42 and a negative electrode core exposed portion 52 at both ends in the direction of the winding axis. , the outermost periphery of the electrode body 3 is the negative electrode 5, and the reference electrode layer 60 faces the portion of the electrode body 3 excluding the positive electrode core exposed portion .

実施形態の他の一例として、電極体３の最外周が負極５である場合には、電極体３の正極芯体露出部４２を除く部分で負極５が電極体３の巻外側に存在する。この場合、参照電極層６０は、電極体３の正極芯体露出部４２を除く部分に対向する位置、換言すれば図４の第１の参照電極形成領域２０又は第２の参照電極形成領域２１に形成される。よって、最外周が正極４の場合と比べて、参照電極層６０を形成する位置を広い範囲で選択することができる。 As another example of the embodiment, when the outermost circumference of the electrode body 3 is the negative electrode 5 , the negative electrode 5 exists on the winding outer side of the electrode body 3 except for the positive electrode core exposed portion 42 of the electrode body 3 . In this case, the reference electrode layer 60 is located at a position facing the portion of the electrode body 3 excluding the positive electrode core exposed portion 42, in other words, the first reference electrode formation region 20 or the second reference electrode formation region 21 in FIG. formed in Therefore, the position for forming the reference electrode layer 60 can be selected in a wider range than in the case where the outermost periphery is the positive electrode 4 .

セパレータ３０が、最外周の上に積層されているのが好ましい。この場合、最外周が角形外装体１に接触することを避けることができる。なお、電極体３と角形外装体１との間に電極体ホルダ１２がある場合にもセパレータ３０を最外周の上に積層してもよい。 A separator 30 is preferably laminated on the outermost periphery. In this case, the contact of the outermost periphery with the rectangular exterior body 1 can be avoided. Note that even when the electrode body holder 12 is between the electrode body 3 and the rectangular exterior body 1, the separator 30 may be laminated on the outermost periphery.

図５に例示するように、参照電極層６０は、二次電池１００の高さ方向中央で半分に分けた場合の底部側の側面上に少なくとも一部が形成されていることが好ましく、二次電池１００の高さ方向で４等分に分けた場合の最も底部側の側面上に少なくとも一部が形成されていることがより好ましい。電池ケース２００内に電解質で満たされていない部分がある場合にも、角形外装体１の底部側に参照電極層６０を形成しておくことで、参照電極層６０と負極５との間に電解質が確実に存在するようにすることができる。 As illustrated in FIG. 5, the reference electrode layer 60 is preferably at least partially formed on the side surface of the bottom side when the secondary battery 100 is divided in half at the center in the height direction. It is more preferable that at least a portion is formed on the side surface closest to the bottom when the battery 100 is divided into four equal parts in the height direction. By forming the reference electrode layer 60 on the bottom side of the rectangular outer body 1 even when there is a portion not filled with the electrolyte in the battery case 200, the electrolyte can be formed between the reference electrode layer 60 and the negative electrode 5. can be ensured to exist.

［二次電池の製造方法］
上述の構成を備えた二次電池１００は、例えば、下記の工程を経て製造される。
（１）導電性の電池ケース２００の内壁上に、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０≦ｘ＜０．１、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層６０を形成する工程。
（２）正極４と負極５とを有する電極体３を、負極５が参照電極層６０に対向するように、電極体３の外側に隣接する多孔質の電極体ホルダ１２を介して電池ケース２００に収容する工程。
（３）電池ケース２００にリチウムイオンを含む電解質を少なくとも参照電極層６０が浸されるように注入する工程。
（４）電池ケース２００を電源のプラス極に、正極４を電源のマイナス極にそれぞれに接続して、参照電極層からリチウムイオンを脱離させる工程（図６参照）。 [Method for manufacturing secondary battery]
The secondary battery 100 having the configuration described above is manufactured, for example, through the following steps.
(1) On the inner wall of the conductive battery case 200, a composition formula Li 1-x FeM y PO 4 (wherein M is Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, one or more elements selected from Co, Cr, V, Sc, Y, La, Zn, Al, and Ga, satisfying 0 ≤ x < 0.1 and 0 ≤ y ≤ 1). forming a reference electrode layer 60 comprising;
(2) The electrode body 3 having the positive electrode 4 and the negative electrode 5 is placed in the battery case 200 via the porous electrode body holder 12 adjacent to the outside of the electrode body 3 so that the negative electrode 5 faces the reference electrode layer 60 . The process of housing in
(3) A step of injecting an electrolyte containing lithium ions into the battery case 200 so that at least the reference electrode layer 60 is immersed.
(4) A step of desorbing lithium ions from the reference electrode layer by connecting the battery case 200 to the positive electrode of the power source and the positive electrode 4 to the negative electrode of the power source, respectively (see FIG. 6).

図６を参照して二次電池１００の製造方法の内、特に参照電極層６０からリチウムイオンを脱離させる工程について説明する。上述の（１）～（３）の工程により、角形外装体１と封口板２を有する電池ケース２００の中には、角形外装体１の側壁上又は底面上に形成された参照電極層６０と、電池ケース２００とは接触しないように正極集電体６及び負極集電体８を介して封口板２に固定された電極体３が配置される。電極体３の巻外側の負極５と参照電極層６０とは、お互いに対向し、参照電極層６０と負極５との間にはリチウムイオンを含有する電解質が存在する。 In particular, the step of desorbing lithium ions from the reference electrode layer 60 in the method of manufacturing the secondary battery 100 will be described with reference to FIG. Through the steps (1) to (3) described above, the battery case 200 having the rectangular outer body 1 and the sealing plate 2 contains the reference electrode layer 60 formed on the side wall or the bottom surface of the rectangular outer body 1. , the electrode body 3 is fixed to the sealing plate 2 via the positive electrode current collector 6 and the negative electrode current collector 8 so as not to come into contact with the battery case 200 . The negative electrode 5 on the outer side of the electrode body 3 and the reference electrode layer 60 face each other, and an electrolyte containing lithium ions is present between the reference electrode layer 60 and the negative electrode 5 .

次に上述の（４）の工程により、電池ケース２００を電源のプラス極に、正極４を電源のマイナス極にそれぞれに接続する。具体的には、電源のプラス極は、電池ケース２００に含まれる角形外装体１及び封口板２のいずれかに接続させ、一方電源のマイナス極は、負極端子９に接続させる。電池ケース２００上の参照電極層６０と、負極端子９に接続している負極５との間には電位差が生じるので、参照電極層６０中のリチウムイオンはマイナス極側の負極５に引き寄せられ、参照電極層６０に含まれるリン酸鉄リチウムからリチウムイオンが脱離される。リチウムイオンが脱離されたリン酸鉄リチウムは電位が安定化するので、参照電極層６０は、正極４又は負極５の電位を測定するための基準電極として使用することができるようになる。 Next, in step (4) described above, the battery case 200 is connected to the positive pole of the power supply, and the positive electrode 4 is connected to the negative pole of the power supply. Specifically, the positive pole of the power supply is connected to either the rectangular exterior body 1 or the sealing plate 2 included in the battery case 200 , while the negative pole of the power supply is connected to the negative terminal 9 . Since a potential difference is generated between the reference electrode layer 60 on the battery case 200 and the negative electrode 5 connected to the negative electrode terminal 9, the lithium ions in the reference electrode layer 60 are attracted to the negative electrode 5 on the negative electrode side. Lithium ions are desorbed from the lithium iron phosphate contained in the reference electrode layer 60 . Since the potential of lithium iron phosphate from which lithium ions are desorbed stabilizes, the reference electrode layer 60 can be used as a reference electrode for measuring the potential of the positive electrode 4 or the negative electrode 5 .

（４）の工程の前に電池ケース２００を封止する工程を行うことができる。なお、（４）の工程の後に電池ケース２００を封止する工程を行うこともできる。例えば、電池ケース２００の電解質注液孔１０が封止されない状態で参照電極層６０からリチウムを脱離した後、電池ケース２００の電解質注液孔１０を封止してもよい。この場合、参照電極層６０からのリチウムを脱離は、ドライ環境下で行うことが好ましい。但し、（４）の工程の前に電池ケース２００を封止する工程を行うことにより、リチウムが脱離された参照電極層６０が大気中の水分に触れることがなく、参照電極層６０の電位がより安定したものとなる。よって、（４）の工程の前に電池ケース２００を封止する工程を行うことがより好ましい。 A step of sealing the battery case 200 can be performed before the step (4). A step of sealing the battery case 200 may be performed after the step (4). For example, the electrolyte injection hole 10 of the battery case 200 may be sealed after lithium is desorbed from the reference electrode layer 60 in a state where the electrolyte injection hole 10 of the battery case 200 is not sealed. In this case, desorption of lithium from the reference electrode layer 60 is preferably performed in a dry environment. However, by performing the step of sealing the battery case 200 before the step (4), the reference electrode layer 60 from which lithium has been desorbed does not come into contact with moisture in the atmosphere, and the potential of the reference electrode layer 60 is reduced. becomes more stable. Therefore, it is more preferable to perform the step of sealing the battery case 200 before the step (4).

以下、実施例により本開示をさらに説明するが、本開示はこれらの実施例に限定されるものではない。また、各実施例及び各比較例に係る二次電池は、ドライルームを使用しない非ドライ環境下で作製し、参考例に係る二次電池はドライルーム内の管理されたドライ環境下で作製した。 EXAMPLES The present disclosure will be further described below with reference to Examples, but the present disclosure is not limited to these Examples. Further, the secondary batteries according to each example and each comparative example were produced in a non-dry environment without using a dry room, and the secondary batteries according to reference examples were produced under a controlled dry environment in a dry room. .

＜実施例１＞
［正極の作製］
正極活物質として、ＬｉＮｉ０．３５Ｃｏ０．３５Ｍｎ０．３０Ｏ２で表されるリチウム金属複合酸化物粒子を用いた。正極活物質と、Ｎ－メチル－２－ピロリドン（ＮＭＰ）中に分散されたポリフッ化ビニリデンと、アセチレンブラックとを、９１：２：７の固形分質量比で混合して、正極活物質スラリーを調製した。次に、正極活物質スラリーを厚み１５μｍのアルミニウム合金からなる正極芯体の両面に塗布し、塗膜を真空乾燥させてＮＭＰを揮発除去した。ただし、正極芯体の長手方向に沿う一方の端部には両面とも正極活物質スラリーを塗布せずに正極芯体を露出させて正極芯体露出部を設けた。圧延ロールを用いて乾燥した塗膜を圧縮した後、所定の極板サイズに切断し、正極集電体の両面に正極活物質層が形成された正極板を作製した。 <Example 1>
[Preparation of positive electrode]
As a positive electrode active material, lithium metal composite oxide particles represented by LiNi 0.35 Co 0.35 Mn 0.30 O 2 were used. The positive electrode active material, polyvinylidene fluoride dispersed in N-methyl-2-pyrrolidone (NMP), and acetylene black were mixed at a solid content mass ratio of 91:2:7 to form a positive electrode active material slurry. prepared. Next, the positive electrode active material slurry was applied to both sides of a positive electrode core made of an aluminum alloy and having a thickness of 15 μm, and the coating film was vacuum-dried to remove NMP by volatilization. However, the cathode active material slurry was not coated on both sides of the positive electrode core at one end along the longitudinal direction, and the positive electrode core was exposed to provide a positive electrode core exposed portion. After compressing the dried coating film using rolling rolls, it was cut into a predetermined electrode plate size to prepare a positive electrode plate having positive electrode active material layers formed on both sides of a positive electrode current collector.

［負極の作製］
天然黒鉛と、スチレンブタジエンゴム（ＳＢＲ）と、カルボキシメチルセルロース（ＣＭＣ）とを、９８：１：１の固形分質量比で混合し、水を適量加えて、負極活物質スラリーを調製した。次に、当該負極活物質スラリーを厚み８μｍの銅箔からなる負極芯体の両面に塗布し、塗膜を真空乾燥させて水を揮発除去した。ただし、負極芯体の長手方向に沿う一方の端部には両面とも負極活物質スラリーを塗布せずに負極芯体を露出させて負極芯体露出部を設けた。圧延ロールを用いて乾燥した塗膜を圧縮した後、所定の電極サイズに切断し、方形状の負極芯体の両面に負極活物質層が形成された負極を作製した。 [Preparation of negative electrode]
Natural graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed at a solid content mass ratio of 98:1:1, and an appropriate amount of water was added to prepare a negative electrode active material slurry. Next, the negative electrode active material slurry was applied to both sides of a negative electrode core made of a copper foil having a thickness of 8 μm, and the coating film was vacuum-dried to remove water by volatilization. However, a negative electrode core exposed portion was provided by exposing the negative electrode core without coating the negative electrode active material slurry on both sides of the negative electrode core along one end along the longitudinal direction. After compressing the dried coating film using rolling rolls, it was cut into a predetermined electrode size to produce a negative electrode in which a negative electrode active material layer was formed on both sides of a rectangular negative electrode core.

［電極体の作製］
上記正極及び上記負極を、それぞれの芯体露出部が互いに巻回体の軸方向反対側に位置するようにして、帯状のポリエチレン／ポリプロピレン製の微細多孔膜からなるセパレータを介して巻回した。その後、巻回体を径方向にプレスして扁平状に成形し、巻回型の電極体を作製した。巻回体は、巻内側からセパレータ／正極／セパレータ／負極の順に重ね合わせたものを、円筒状の巻芯に巻き付けて形成した（２枚のセパレータには同じものを用いた）。なお、電極体の最外周は正極とした。 [Fabrication of electrode body]
The positive electrode and the negative electrode were wound with a strip separator made of a polyethylene/polypropylene microporous film interposed therebetween such that the core exposed portions were located on opposite sides of the wound body in the axial direction. After that, the wound body was radially pressed to form a flat shape, thereby producing a wound electrode body. The wound body was formed by winding a stack of separator/positive electrode/separator/negative electrode in this order from the inside of the roll around a cylindrical winding core (the same separator was used for the two separators). The outermost periphery of the electrode body was used as the positive electrode.

［参照電極の作製］
組成式Ｌｉ１．０ＦｅＰＯ４のリン酸鉄リチウムと、カルボキシメチルセルロース（ＣＭＣ）と、スチレンブタジエンゴム（ＳＢＲ）とを、９８．９：０．７：０．４の固形分質量比で混合し、水を適量加えて、参照電極スラリーを調製した。次に参照電極スラリーを負極芯体露出部に対向するように電池ケースの側面の内壁に塗布量が１ｍｇ／ｃｍ２となるように塗布した。その後、電池ケースを乾燥させて参照電極スラリー調整時に分散媒として用いた水を除去して参照電極層を作製した。なお、参照電極層の形成面積は８ｃｍ２とした。 [Preparation of reference electrode]
Lithium iron phosphate of the composition formula Li1.0FePO4 , carboxymethyl cellulose ( CMC), and styrene-butadiene rubber (SBR) were mixed at a solid content mass ratio of 98.9:0.7:0.4. , an appropriate amount of water was added to prepare a reference electrode slurry. Next, the reference electrode slurry was applied to the inner wall of the side surface of the battery case so as to face the exposed portion of the negative electrode core so that the amount of application was 1 mg/cm 2 . After that, the battery case was dried to remove the water used as the dispersion medium when preparing the reference electrode slurry, thereby producing a reference electrode layer. The formation area of the reference electrode layer was 8 cm 2 .

［電解質の調製］
エチレンカーボネート（ＥＣ）と、エチルメチルカーボネート（ＥＭＣ）と、ジエチルカーボネート（ＤＥＣ）とを、３：３：４の体積比（２５℃、１気圧）で混合した。当該混合溶媒にＬｉＰＦ６を１ｍｏｌ／Ｌの濃度で溶解させ、さらに電解質の総質量に対して０．３質量％のビニレンカーボネート（ＶＣ）を添加して電解質を調製した。 [Preparation of electrolyte]
Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 3:3:4 (25° C., 1 atm). LiPF 6 was dissolved in the mixed solvent at a concentration of 1 mol/L, and vinylene carbonate (VC) was added in an amount of 0.3% by mass relative to the total mass of the electrolyte to prepare an electrolyte.

［二次電池の作製］
上記電極体、上記電解質、及びアルミニウム製の角形の電池ケースを用いて、二次電池（角形電池）を作製した。電極体を多孔質の電極体ホルダで覆い、電池ケースを構成する角形有底筒状の外装缶（横方向長さ１４８．０ｍｍ（内寸１４６．８ｍｍ）、厚み１７．５ｍｍ（内寸１６．５ｍｍ）、高さ６５．０ｍｍ（内寸６４．０ｍｍ））内に収容した。電池ケースを構成する封口板に正極端子を取り付けると共に、正極端子に正極集電体を接続した。また、封口板に負極端子を取り付けると共に、負極端子に負極集電体を接続した。そして、正極芯体露出部に正極集電体を、負極芯体露出部に負極集電体をそれぞれ溶接した。電解質を外装缶に注入し、電池ケースの開口部を封口板で塞いだ。 [Production of secondary battery]
A secondary battery (a prismatic battery) was produced using the electrode body, the electrolyte, and a prismatic battery case made of aluminum. The electrode body was covered with a porous electrode body holder, and a rectangular bottomed cylindrical outer can (lateral length 148.0 mm (inner dimension 146.8 mm), thickness 17.5 mm (inner dimension 16.8 mm) constituting a battery case was used. 5 mm) and 65.0 mm in height (inner dimension 64.0 mm)). A positive electrode terminal was attached to a sealing plate constituting a battery case, and a positive current collector was connected to the positive electrode terminal. A negative electrode terminal was attached to the sealing plate, and a negative electrode current collector was connected to the negative electrode terminal. Then, the positive electrode current collector was welded to the positive electrode core exposed portion, and the negative electrode current collector was welded to the negative electrode core exposed portion. The electrolyte was injected into the outer can, and the opening of the battery case was closed with a sealing plate.

［参照電極層からのリチウムイオンの脱離］
作製した二次電池の電池ケースを電源のプラス極に、負極端子を電源のマイナス極にそれぞれに接続して、０．００１５Ｉｔ（７．５ｍＡ）で６０秒間充電することで、参照電極層からリチウムイオンを脱離させた。リチウムイオンを脱離させた後の参照電極層の電位は、３．４５Ｖと考えられる。 [Desorption of Lithium Ions from Reference Electrode Layer]
By connecting the battery case of the prepared secondary battery to the positive electrode of the power source and connecting the negative electrode terminal to the negative electrode of the power source, respectively, and charging at 0.0015 It (7.5 mA) for 60 seconds, the lithium was removed from the reference electrode layer. ions were desorbed. The potential of the reference electrode layer after desorption of lithium ions is considered to be 3.45V.

＜実施例２＞
参照電極スラリーの固形分質量比を、組成式Ｌｉ１．０ＦｅＰＯ４のリン酸鉄リチウムと、アセチレンブラックと、カルボキシメチルセルロース（ＣＭＣ）と、スチレンブタジエンゴム（ＳＢＲ）とで、９６．９：２．０：０．７：０．４に変更した以外は、実施例１と同様の方法で二次電池を作製した。 <Example 2>
The solid content mass ratio of the reference electrode slurry was 96.9:2 with lithium iron phosphate of the composition formula Li 1.0 FePO 4 , acetylene black, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). A secondary battery was produced in the same manner as in Example 1, except that the ratio was changed to 0:0.7:0.4.

＜比較例１～３＞
比較例１～３は、以下を変更した以外は、実施例１と同様の方法で二次電池を作製した。
（１）比較例１：参照電極層を作製しなかった。
（２）比較例２：参照電極層を負極芯体露出部に対向しないような位置に作製した。
（３）比較例３：参照電極層を負極芯体露出部に対向しないような位置に作製し、参照電極層からのリチウムイオンの脱離も行わなかった。 <Comparative Examples 1 to 3>
In Comparative Examples 1 to 3, secondary batteries were produced in the same manner as in Example 1, except for the following changes.
(1) Comparative Example 1: No reference electrode layer was produced.
(2) Comparative Example 2: A reference electrode layer was formed at a position not facing the exposed portion of the negative electrode core.
(3) Comparative Example 3: A reference electrode layer was formed at a position not facing the exposed portion of the negative electrode core, and no lithium ions were desorbed from the reference electrode layer.

＜参考例＞
参照電極層の作製後で二次電池の作製前に、電解質を外装缶に注入し、多孔質の電極体ホルダを介して参照電極層に対向するように別途準備したリチウム電極を挿入した。外装缶を電源のマイナス極に、リチウム電極を電源のプラス極にそれぞれに接続して、０．００１５Ｉｔ（７．５ｍＡ）で６０秒間充電することで、参照電極層からリチウムイオンを脱離させた。その後、リチウム電極を抜き取った上で二次電池を作製した。 <Reference example>
After manufacturing the reference electrode layer and before manufacturing the secondary battery, the electrolyte was injected into the outer can, and a separately prepared lithium electrode was inserted so as to face the reference electrode layer via a porous electrode body holder. Lithium ions were desorbed from the reference electrode layer by connecting the outer can to the negative electrode of the power source and connecting the lithium electrode to the positive electrode of the power source, respectively, and charging at 0.0015 It (7.5 mA) for 60 seconds. . After that, the lithium electrode was removed, and a secondary battery was produced.

実施例１～２、比較例１～３、及び参考例の各二次電池をそれぞれ１０セルずつ作製し下記の方法により、参照電極層の安定性の評価を行い、評価結果を表１に示した。 10 cells each of the secondary batteries of Examples 1 and 2, Comparative Examples 1 and 3, and Reference Example were prepared, and the stability of the reference electrode layer was evaluated by the following method. The evaluation results are shown in Table 1. rice field.

［参照電極層の安定性の評価］
各二次電池を、２５℃の温度環境において、１Ｉｔ（５Ａ）で定電流充電した後、３．５２Ｖで２．５時定電圧充電し、充電深度（ＳＯＣ）を２０％とした。室温条件で２．５時間静置した後、電池ケースに対する正極の電圧（正極／電池ケース）を測定した。電池ケースに対する負極の電圧（負極／電池ケース）は、別途計測したセル電圧から電池ケースに対する正極の電圧を引いて算出した。１０セルについての測定結果から、正極／電池ケース及び負極／電池ケースの平均値と正極／電池ケースの標準偏差を算出した。また、定電圧充電時の電圧を３．６９Ｖにする以外はＳＯＣが２０％の場合と同様にして、二次電池のＳＯＣを５０％として、同様に測定した。また、定電圧充電時の電圧を３．９１Ｖにする以外はＳＯＣが２０％の場合と同様にして、二次電池のＳＯＣを８０％として、同様に測定した。 [Evaluation of stability of reference electrode layer]
Each secondary battery was charged at a constant current of 1 It (5 A) in a temperature environment of 25° C. and then charged at a constant voltage of 3.52 V for 2.5 hours to set the depth of charge (SOC) to 20%. After standing at room temperature for 2.5 hours, the voltage of the positive electrode with respect to the battery case (positive electrode/battery case) was measured. The voltage of the negative electrode with respect to the battery case (negative electrode/battery case) was calculated by subtracting the voltage of the positive electrode with respect to the battery case from the separately measured cell voltage. From the measurement results of 10 cells, the average value of the positive electrode/battery case and the negative electrode/battery case and the standard deviation of the positive electrode/battery case were calculated. In addition, the SOC of the secondary battery was set to 50% in the same manner as in the case of the SOC of 20% except that the voltage during constant-voltage charging was set to 3.69V, and the measurement was performed in the same manner. In addition, the SOC of the secondary battery was set to 80% in the same manner as in the case of the SOC of 20% except that the voltage during constant voltage charging was set to 3.91 V, and the measurement was performed in the same manner.

Figure 0007145092000001
Figure 0007145092000001

比較例１～３の二次電池はいずれもドライ環境下で作製した参考例の二次電池とは異なる正極／電池ケース及び負極／電池ケースの電位を示し、標準偏差も大きく不安定だった。 The secondary batteries of Comparative Examples 1 to 3 all showed different potentials of the positive electrode/battery case and negative electrode/battery case from the secondary batteries of the reference example produced in a dry environment, and the standard deviation was large and unstable.

一方、実施例１の二次電池は、ドライ環境下で作製した参考例の二次電池と略同じ正極／電池ケース及び負極／電池ケースの電位と標準偏差が得られた。実施例１の二次電池では、正極と負極とを有する電極体と、電極体を収容する導電性の電池ケースと、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０.１≦ｘ≦０．９、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層と、参照電極層が浸されるように電池ケース内に配置された、リチウムイオンを含む電解質と、を備え、参照電極層は、電池ケースの内壁上に形成されており、負極と対向することで、簡便な方法で参照電極層からリチウムイオンを脱離できる二次電池を提供できる。さらに、実施例２の二次電池では、標準偏差が実施例１よりも小さく、安定するようになった。電位をより安定にするために、参照電極層は導電助剤をさらに含むことが好ましい。 On the other hand, in the secondary battery of Example 1, substantially the same potentials and standard deviations of the positive electrode/battery case and negative electrode/battery case were obtained as in the secondary battery of the reference example fabricated in a dry environment. In the secondary battery of Example 1, an electrode body having a positive electrode and a negative electrode, a conductive battery case containing the electrode body, and a composition formula Li 1-x FeM y PO 4 (wherein M is Mg, Nb , Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, Y, La, Zn, Al, and Ga, and 0.1 ≤ x ≤ 0.9 and 0 ≤ y ≤ 1); In addition, the reference electrode layer is formed on the inner wall of the battery case, and by facing the negative electrode, it is possible to provide a secondary battery in which lithium ions can be desorbed from the reference electrode layer by a simple method. Furthermore, in the secondary battery of Example 2, the standard deviation was smaller than that of Example 1 and became stable. In order to make the potential more stable, the reference electrode layer preferably further contains a conductive aid.

１ 角形外装体、２ 封口板、３ 電極体、４ 正極、５ 負極、６ 正極集電体、７ 正極端子、８ 負極集電体、９ 負極端子、１０ 電解質注液孔、１１ ガス排出弁、１２ 電極体ホルダ、１３ 正極外部導電部、１４ 正極ボルト部、１５ 正極挿入部、１６ 負極外部導電部、１７ 負極ボルト部、１８ 負極挿入部、２０ 第１の参照電極形成領域、２１ 第２の参照電極形成領域、３０ セパレータ、４１ 正極活物質層、４２ 正極芯体露出部、５１ 負極活物質層、５２ 負極芯体露出部、６０ 参照電極層、１００ 二次電池、２００ 電池ケース 1 square exterior body, 2 sealing plate, 3 electrode body, 4 positive electrode, 5 negative electrode, 6 positive electrode current collector, 7 positive electrode terminal, 8 negative electrode current collector, 9 negative electrode terminal, 10 electrolyte injection hole, 11 gas discharge valve, 12 electrode body holder 13 positive electrode external conductive portion 14 positive electrode bolt portion 15 positive electrode insertion portion 16 negative electrode external conductive portion 17 negative electrode bolt portion 18 negative electrode insertion portion 20 first reference electrode forming region 21 second Reference electrode formation region 30 Separator 41 Positive electrode active material layer 42 Positive electrode core exposed portion 51 Negative electrode active material layer 52 Negative electrode core exposed portion 60 Reference electrode layer 100 Secondary battery 200 Battery case

Claims (7)

二次電池の製造方法であって、前記二次電池は、
正極と負極とを有する電極体と、
前記電極体を収容する導電性の電池ケースと、
組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０.１≦ｘ≦０．９、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層と、
前記参照電極層が浸されるように前記電池ケース内に配置された、リチウムイオンを含む電解質と、を備え、
前記電極体は、前記正極と前記負極とがセパレータを介して巻かれた巻回型であり、巻軸方向における一方の端部に正極芯体露出部を有し、巻軸方向における他方の端部に負極芯体露出部を有し、
前記電極体の最外周は前記正極であり、
前記参照電極層は、前記電池ケースの内壁上に形成されており、前記負極芯体露出部と対向し、
前記参照電極層と前記負極との間に電圧をかけたときに、前記参照電極層から前記負極に前記リチウムイオンが移動する、二次電池の製造方法。 A method for manufacturing a secondary battery, the secondary battery comprising:
an electrode body having a positive electrode and a negative electrode;
a conductive battery case housing the electrode body;
Composition formula Li 1-x FeM y PO 4 (wherein M is Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, V, Sc, Y, La, Zn, a reference electrode layer containing a compound consisting of one or more elements selected from Al and Ga and satisfying 0.1≦x≦0.9 and 0≦y≦1;
an electrolyte comprising lithium ions disposed within the battery case such that the reference electrode layer is submerged;
The electrode body is a wound type in which the positive electrode and the negative electrode are wound with a separator interposed therebetween, and has a positive electrode core exposed portion at one end in the direction of the winding axis and the other end in the direction of the winding axis. has a negative electrode core exposed part in the part,
The outermost periphery of the electrode body is the positive electrode,
The reference electrode layer is formed on the inner wall of the battery case and faces the negative electrode substrate exposed portion ,
A method for manufacturing a secondary battery, wherein the lithium ions move from the reference electrode layer to the negative electrode when a voltage is applied between the reference electrode layer and the negative electrode . 前記電極体と前記電池ケースとの間に配置され、リチウムイオンが通過可能な多孔質の電極体ホルダをさらに備える、請求項１に記載の二次電池の製造方法。 2. The method of manufacturing a secondary battery according to claim 1, further comprising a porous electrode body holder arranged between said electrode body and said battery case and through which lithium ions can pass. 前記セパレータが、前記最外周の上に積層されている、請求項１又は２に記載の二次電池の製造方法。 3. The method of manufacturing a secondary battery according to claim 1, wherein said separator is laminated on said outermost periphery. 前記参照電極層は、導電助剤をさらに含む、請求項１～３のいずれか１項に記載の二次電池の製造方法。 The method for manufacturing a secondary battery according to any one of claims 1 to 3 , wherein the reference electrode layer further contains a conductive aid. 前記参照電極層は、二次電池の高さ方向中央で半分に分けた場合の底部側の側面上に少なくとも一部が形成されている、請求項１～４のいずれか１項に記載の二次電池の製造方法。 5. The secondary battery according to any one of claims 1 to 4 , wherein the reference electrode layer is at least partially formed on the side surface of the bottom side when the secondary battery is divided in half at the center in the height direction. A method for manufacturing a secondary battery. 導電性の電池ケースの内壁上に、組成式Ｌｉ１－ｘＦｅＭｙＰＯ４（式中、ＭはＭｇ、Ｎｂ、Ｃｕ、Ｍｎ、Ｎｉ、Ｆｅ、Ｒｕ、Ｚｒ、Ｂ、Ｃａ、Ｃｏ、Ｃｒ、Ｖ、Ｓｃ、Ｙ、Ｌａ、Ｚｎ、Ａｌ、及びＧａから選択された１種以上の元素であり、０≦ｘ＜０．１、０≦ｙ≦１を満たす）からなる化合物を含む参照電極層を形成する工程と、
正極と負極とを有する電極体を、前記負極が前記参照電極層に対向するように、前記電極体の外側に隣接する多孔質の電極体ホルダを介して前記電池ケースに収容する工程と、
前記電池ケースにリチウムイオンを含む電解質を少なくとも前記参照電極層が浸されるように注入する工程と、
前記電池ケースを電源のプラス極に、前記負極を前記電源のマイナス極にそれぞれに接続して、前記参照電極層からリチウムイオンを脱離させる工程と、を有する二次電池の製造方法。 On the inner wall of the conductive battery case, a composition formula Li 1-x FeM y PO 4 (wherein M is Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, Ca, Co, Cr, one or more elements selected from V, Sc, Y, La, Zn, Al, and Ga, and satisfying 0≦x<0.1 and 0≦y≦1. forming a
housing an electrode body having a positive electrode and a negative electrode in the battery case via a porous electrode body holder adjacent to the outside of the electrode body so that the negative electrode faces the reference electrode layer;
injecting an electrolyte containing lithium ions into the battery case so that at least the reference electrode layer is immersed;
and connecting the battery case to the positive electrode of a power source and the negative electrode to the negative electrode of the power source, respectively, to desorb lithium ions from the reference electrode layer. 前記参照電極層からリチウムイオンを脱離させる工程の前に、前記電池ケースを封止する工程を有する請求項６に記載の二次電池の製造方法。 7. The method of manufacturing a secondary battery according to claim 6 , further comprising the step of sealing the battery case before the step of desorbing lithium ions from the reference electrode layer.
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