JP6946803B2 - Manufacturing method of lithium ion secondary battery - Google Patents

Manufacturing method of lithium ion secondary battery Download PDF

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JP6946803B2
JP6946803B2 JP2017139238A JP2017139238A JP6946803B2 JP 6946803 B2 JP6946803 B2 JP 6946803B2 JP 2017139238 A JP2017139238 A JP 2017139238A JP 2017139238 A JP2017139238 A JP 2017139238A JP 6946803 B2 JP6946803 B2 JP 6946803B2
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JP2019021510A (en
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北吉　雅則
雅則 北吉
久尚 小島
小島　　久尚
平藤　哲司
哲司 平藤
卓 塩見
卓 塩見
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Toyota Motor Corp
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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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本発明は、正極板、セパレータ及び負極板を含む電極体と、電解液とを備えるリチウムイオン二次電池の製造方法に関する。 The present invention relates to a method for manufacturing a lithium ion secondary battery including an electrode body including a positive electrode plate, a separator and a negative electrode plate, and an electrolytic solution.

リチウムイオン二次電池（以下、単に「電池」ともいう）の製造に当たっては、電極体のうち正極板とセパレータの間に、鉄や銅などの金属異物が混入することが考えられる。このような金属異物は、組み立てた電池内に電解液を注液した後に電解液中に徐々に溶解するため、金属異物の近傍には金属異物由来の金属イオンが高い濃度で存在する。本充電の際、負極電位が低下すると、この濃度の高い金属イオンが負極板上で集中的にデンドライト状に析出することがある。また、本充電で正極電位が高くなると、本充電の際に残存していた金属異物が正極板上で溶解した後、その金属イオンが負極板上で集中的にデンドライト状に析出することもある。これらの析出した金属は、セパレータを突き破って負極板から正極板まで達し、短絡を生じるおそれがある。 In the manufacture of a lithium ion secondary battery (hereinafter, also simply referred to as “battery”), it is conceivable that a metallic foreign substance such as iron or copper is mixed between the positive electrode plate and the separator in the electrode body. Since such metal foreign matter is gradually dissolved in the electrolytic solution after the electrolytic solution is injected into the assembled battery, metal ions derived from the metallic foreign matter are present at a high concentration in the vicinity of the metal foreign matter. When the negative electrode potential drops during main charging, metal ions with a high concentration may be concentrated on the negative electrode plate in the form of dendrites. Further, when the positive electrode potential becomes high in the main charge, the metal foreign matter remaining in the main charge may be dissolved on the positive electrode plate, and then the metal ions may be concentratedly deposited in a dendrite shape on the negative electrode plate. .. These precipitated metals may break through the separator and reach from the negative electrode plate to the positive electrode plate, causing a short circuit.

このような短絡が生じるのを防止するべく、例えば特許文献１では、正極電位が金属異物の溶解電位を上回る電位となるまで電池を充電（予備充電）した上で、この正極電位で電池を所定時間にわたり放置し、その後、この電池に初期コンディショニング充電（本充電）を行うことが記載されている（特許文献１の請求項１等を参照）。放置により、金属異物を電解液中に溶解させると共に、金属異物由来の金属イオンを金属異物が存在していた場所から広範囲に拡散させて、その後の本充電で金属異物由来の金属が負極板上で集中的にデンドライト状に析出するのを防止し、短絡を防止できるためと考えられる。 In order to prevent such a short circuit from occurring, for example, in Patent Document 1, the battery is charged (pre-charged) until the positive electrode potential exceeds the dissolution potential of the metal foreign matter, and then the battery is determined at this positive electrode potential. It is described that the battery is left to stand for an extended period of time, and then the battery is subjected to initial conditioning charging (main charging) (see claim 1 and the like of Patent Document 1). By leaving it to stand, the metal foreign matter is dissolved in the electrolytic solution, and the metal ions derived from the metal foreign matter are diffused over a wide range from the place where the metal foreign matter was present. It is considered that this is because it is possible to prevent intensive deposition in the form of dendrites and prevent short circuits.

国際公開第２０１３／０３５１８７号International Publication No. 2013/03518

しかしながら、上述の特許文献１の手法では、金属異物が正極板に接触していない場合には、金属異物の電位が正極電位（金属異物の溶解電位を超える電位）とならないため、金属異物が溶解し難く、その結果、金属異物由来の金属が負極板上に集中的にデンドライト状に析出して短絡が生じることがあった。
また、上述の特許文献１の手法では、予備充電後の電池の放置のみによって金属異物由来の金属イオンの拡散を行っているので、上述の短絡を防止するには、金属イオンを広範囲に拡散させるべく、電池の放置時間を長くとる必要があった。 However, in the method of Patent Document 1 described above, when the metallic foreign matter is not in contact with the positive electrode plate, the potential of the metallic foreign matter does not become the positive electrode potential (potential exceeding the melting potential of the metallic foreign matter), so that the metallic foreign matter is dissolved. As a result, metal derived from a metallic foreign substance may be concentrated on the negative electrode plate in the form of dendrite, resulting in a short circuit.
Further, in the method of Patent Document 1 described above, metal ions derived from metal foreign substances are diffused only by leaving the battery after precharging. Therefore, in order to prevent the above-mentioned short circuit, the metal ions are diffused over a wide range. Therefore, it was necessary to take a long time to leave the battery.

本発明は、かかる現状に鑑みてなされたものであって、正極板とセパレータの間に混入した金属異物の電解液中への溶解を促進させると共に、溶解した金属異物由来の金属イオンの拡散を促進させて、金属異物に起因した短絡を防止できるリチウムイオン二次電池の製造方法を提供することを目的とする。 The present invention has been made in view of the current situation, and promotes the dissolution of the metal foreign matter mixed between the positive electrode plate and the separator in the electrolytic solution, and diffuses the metal ions derived from the dissolved metal foreign matter. It is an object of the present invention to provide a method for manufacturing a lithium ion secondary battery which can be promoted to prevent a short circuit caused by a metal foreign substance.

上記課題を解決するための本発明の一態様は、正極活物質にリチウム遷移金属複合酸化物を含む正極板、及び、負極活物質に炭素材料を含む負極板がセパレータを介して互いに重なった電極体と、電解液と、を備えるリチウムイオン二次電池の製造方法であって、上記電極体を有する未注液のリチウムイオン二次電池内に、上記電解液を注液する注液工程と、上記注液工程の後に、上記リチウムイオン二次電池の上記電極体を、上記正極板、上記セパレータ及び上記負極板の積層方向に第１圧力Ｐ１で押圧する第１押圧工程と、上記電極体を上記第１圧力Ｐ１で押圧した状態で、上記リチウムイオン二次電池を、正極電位が鉄の溶解電位よりも高く、かつ、負極電位が上記電解液中に溶解した鉄イオンの析出電位よりも高い第１電池電圧Ｖ１まで予備充電する予備充電工程と、上記予備充電工程の後に、上記リチウムイオン二次電池を加温し上記電解液の粘度を下げた状態で、上記リチウムイオン二次電池の上記電極体を、上記第１圧力Ｐ１よりも高い第２圧力Ｐ２で上記積層方向に押圧する第２押圧工程と、上記第２押圧工程の後に、上記第１電池電圧Ｖ１よりも高い第２電池電圧Ｖ２まで上記リチウムイオン二次電池をコンディショニング充電する本充電工程と、を備え、上記第１圧力Ｐ１は、０．６０〜０．８０ＭＰａであり、上記第２圧力Ｐ２は、０．８０〜１．８ＭＰａであるリチウムイオン二次電池の製造方法である。 One aspect of the present invention for solving the above problems is an electrode in which a positive electrode plate containing a lithium transition metal composite oxide as a positive electrode active material and a negative electrode plate containing a carbon material as a negative electrode active material are overlapped with each other via a separator. A method for manufacturing a lithium ion secondary battery comprising a body and an electrolytic solution, wherein the electrolytic solution is injected into an uninjected lithium ion secondary battery having the electrode body, and a liquid injection step. After the liquid injection step, the electrode body of the lithium ion secondary battery is pressed with the first pressure P1 in the stacking direction of the positive electrode plate, the separator and the negative electrode plate, and the electrode body is pressed. In the state of being pressed by the first pressure P1, the positive electrode potential of the lithium ion secondary battery is higher than the dissolution potential of iron, and the negative electrode potential is higher than the precipitation potential of iron ions dissolved in the electrolytic solution. After the pre-charging step of pre-charging to the first battery voltage V1 and the pre-charging step, the lithium ion secondary battery is heated to reduce the viscosity of the electrolytic solution, and the lithium ion secondary battery is described above. After the second pressing step of pressing the electrode body in the stacking direction with the second pressure P2 higher than the first pressure P1 and the second pressing step, the second battery voltage higher than the first battery voltage V1. The main charging step of conditioning and charging the lithium ion secondary battery up to V2 is provided , the first pressure P1 is 0.60 to 0.80 MPa, and the second pressure P2 is 0.80 to 1. This is a method for manufacturing a lithium ion secondary battery at 8 MPa.

上述のリチウムイオン二次電池の製造方法では、注液工程の後、第１押圧工程で電池の電極体を積層方向に第１圧力Ｐ１で押圧し、この状態で予備充電工程を行って、電池を上述の第１電池電圧Ｖ１まで充電する。電極体を積層方向に押圧することで、正極板とセパレータとの間隔が狭くなって、正極板とセパレータの間に混入した金属異物が、より確実に正極板に接触することとなる。このため、予備充電工程において、正極板の正極電位が高くなったときに、正極板に接触する金属異物の電位も高くなって、正極板上で金属異物（特に鉄の異物）が電解液中に溶解し易くなる。一方、負極電位は低くなり過ぎないため、負極板上で金属異物（特に鉄の異物）由来の金属が析出し難い。 In the method for manufacturing a lithium ion secondary battery described above, after the liquid injection step, the electrode body of the battery is pressed at the first pressure P1 in the stacking direction in the first pressing step, and a precharging step is performed in this state to perform the battery. Is charged to the above-mentioned first battery voltage V1. By pressing the electrode body in the stacking direction, the distance between the positive electrode plate and the separator is narrowed, and the metal foreign matter mixed between the positive electrode plate and the separator comes into contact with the positive electrode plate more reliably. Therefore, in the precharging step, when the positive electrode potential of the positive electrode plate becomes high, the potential of the metallic foreign matter in contact with the positive electrode plate also becomes high, and the metallic foreign matter (particularly the iron foreign matter) is contained in the electrolytic solution on the positive electrode plate. It becomes easy to dissolve in. On the other hand, since the negative electrode potential does not become too low, it is difficult for metal derived from metal foreign matter (particularly iron foreign matter) to precipitate on the negative electrode plate.

また、上述の製造方法では、予備充電工程の後、第２押圧工程において、電池を加温し電解液の粘度を下げた状態で、電極体を第１圧力Ｐ１よりも高い第２圧力Ｐ２で積層方向に押圧する。これにより、正極板と負極板との間隔が狭くなって、これらの間における電解液が押し出され、この電解液に含まれる金属異物由来の金属イオンの拡散が促進される。
かくして、上述の製造方法では、製造過程で正極板とセパレータの間に金属異物が混入したとしても、この金属異物の電解液への溶解を促進させると共に、溶解した金属異物由来の金属イオンの拡散を促進させることができ、金属異物に起因した短絡を防止できる。 Further, in the above-mentioned manufacturing method, in the second pressing step after the precharging step, the electrode body is subjected to a second pressure P2 higher than the first pressure P1 in a state where the battery is heated and the viscosity of the electrolytic solution is lowered. Press in the stacking direction. As a result, the distance between the positive electrode plate and the negative electrode plate is narrowed, the electrolytic solution is extruded between them, and the diffusion of metal ions derived from metal foreign substances contained in the electrolytic solution is promoted.
Thus, in the above-mentioned manufacturing method, even if a metal foreign substance is mixed between the positive electrode plate and the separator in the manufacturing process, the dissolution of the metal foreign substance in the electrolytic solution is promoted and the metal ion derived from the dissolved metal foreign substance is diffused. Can be promoted, and short circuits caused by metallic foreign substances can be prevented.

第１押圧工程における「第１圧力Ｐ１」は、０．６０〜０．８０ＭＰａである。第１圧力Ｐ１が低すぎると、正極板とセパレータの間に混入した金属異物が正極板に接触できないおそれがある。一方、第１圧力Ｐ１が高すぎると、正極板と負極板の間隔が狭くなりすぎて、これらの間の電解液の量が減って、金属異物が電解液中に溶解し難くなるからである。 The "first pressure P1" in the first pressing step is 0.60 to 0.80 MPa. If the first pressure P1 is too low, the metal foreign matter mixed between the positive electrode plate and the separator may not come into contact with the positive electrode plate. On the other hand, if the first pressure P1 is too high, the distance between the positive electrode plate and the negative electrode plate becomes too narrow, the amount of the electrolytic solution between them decreases, and it becomes difficult for the metal foreign matter to dissolve in the electrolytic solution. ..

第２押圧工程における「第２圧力Ｐ２」は、０．８０〜１．８ＭＰａである。第２圧力Ｐ２が低すぎると、この第２押圧工程における正極板と負極板の間隔の減少が少なく、電解液が押し出され難い。一方、第２圧力Ｐ２が高すぎると、正極板と負極板の間隔が狭くなりすぎて、これらの間の電解液の量が少なくなりすぎるからである。 The "second pressure P2" in the second pressing step is 0.80 to 1.8 MPa. If the second pressure P2 is too low, the decrease in the distance between the positive electrode plate and the negative electrode plate in this second pressing step is small, and it is difficult for the electrolytic solution to be extruded. On the other hand, if the second pressure P2 is too high, the distance between the positive electrode plate and the negative electrode plate becomes too narrow, and the amount of the electrolytic solution between them becomes too small.

「第２押圧工程」における電池温度Ｔｅは、電解液の粘度を十分に下げるべく、２５℃以上、更には、３０℃以上とするのが好ましい。一方、この電池温度Ｔｅは、６０℃以下、更には、５０℃以下とするのが好ましい。電池温度Ｔｅを高くし過ぎると、電池が劣化したり、電池の低温時の入出力特性が低下するなど、電池の特性が変化するおそれがあるからである。 The battery temperature Te in the "second pressing step" is preferably 25 ° C. or higher, more preferably 30 ° C. or higher in order to sufficiently reduce the viscosity of the electrolytic solution. On the other hand, the battery temperature Te is preferably 60 ° C. or lower, more preferably 50 ° C. or lower. This is because if the battery temperature Te is set too high, the characteristics of the battery may change, such as deterioration of the battery or deterioration of the input / output characteristics of the battery at a low temperature.

本充電工程における「コンディショニング充電」とは、電池性能を安定化させるために行う充電である。具体的には、電池をＳＯＣ７０％に相当する電池電圧以上、更には、ＳＯＣ９０％に相当する電池電圧以上に充電するのが好ましい。このように高い充電状態まで充電を行うことで、この本充電工程の際に金属異物が残っている場合でも、この金属異物を正極板上で溶解させることができる。また、良好なＳＥＩ（Solid Electrolyte Interphase）皮膜が負極板で形成され、電池のサイクル特性が良好になるなど、電池性能が向上し得るからである。 "Conditioning charging" in this charging process is charging performed to stabilize the battery performance. Specifically, it is preferable to charge the battery to a battery voltage corresponding to SOC 70% or higher, and further to a battery voltage corresponding to SOC 90% or higher. By charging to such a high charging state, even if metallic foreign matter remains during this main charging step, the metallic foreign matter can be dissolved on the positive electrode plate. Further, a good SEI (Solid Electrolyte Interphase) film is formed on the negative electrode plate, and the cycle characteristics of the battery are improved, so that the battery performance can be improved.

更に、上記のリチウムイオン二次電池の製造方法であって、前記予備充電工程の後、前記第２押圧工程の前に、前記第１電池電圧Ｖ１の状態で前記電池を０．５時間以上放置する充電後放置工程を備えるリチウムイオン二次電池の製造方法とするのが好ましい。 Further, in the above method for manufacturing a lithium ion secondary battery, the battery is left for 0.5 hours or more in the state of the first battery voltage V1 after the precharging step and before the second pressing step. It is preferable to use a method for manufacturing a lithium ion secondary battery including a step of leaving the battery after charging.

予備充電工程後、第２押圧工程前に上述の充電後放置工程を行って電池を第１電池電圧Ｖ１の状態で０．５時間以上放置することで、この放置中にも正極板上に残存する金属異物が電解液中に溶解する。このため、金属異物をより確実に電解液中に溶解させることができる。なお、この充電後放置工程で電池を放置する時間は、１時間以上とするのが更に好ましい。 After the pre-charging step and before the second pressing step, the above-mentioned post-charging leaving step is performed to leave the battery at the first battery voltage V1 for 0.5 hours or more, so that the battery remains on the positive electrode plate even during this leaving. Metallic foreign matter dissolves in the electrolytic solution. Therefore, the metal foreign matter can be more reliably dissolved in the electrolytic solution. The time for leaving the battery in the leaving step after charging is more preferably 1 hour or more.

更に、上記のリチウムイオン二次電池の製造方法であって、前記予備充電工程及び前記充電後放置工程を、上記リチウムイオン二次電池を加温し前記電解液の粘度を下げた状態で行うリチウムイオン二次電池の製造方法とするのが好ましい。 Further, in the method for manufacturing a lithium ion secondary battery, the preliminary charging step and the post-charging leaving step are performed in a state where the lithium ion secondary battery is heated and the viscosity of the electrolytic solution is lowered. It is preferable to use a method for manufacturing an ion secondary battery.

予備充電工程及び充電後放置工程を、電池を加温し電解液の粘度を下げた状態で行うことで、これらの工程中においても、電解液の粘度を下げたことにより、金属異物由来の金属イオンの拡散を促進させることができる。 By performing the pre-charging step and the step of leaving after charging in a state where the battery is heated and the viscosity of the electrolytic solution is lowered, the viscosity of the electrolytic solution is lowered even during these steps, so that the metal derived from the metal foreign matter is obtained. It can promote the diffusion of ions.

実施形態に係るリチウムイオン二次電池の斜視図である。It is a perspective view of the lithium ion secondary battery which concerns on embodiment. 実施形態に係るリチウムイオン二次電池の断面図である。It is sectional drawing of the lithium ion secondary battery which concerns on embodiment. 実施形態に係るリチウムイオン二次電池の製造工程を示すフローチャートである。It is a flowchart which shows the manufacturing process of the lithium ion secondary battery which concerns on embodiment. 実施例及び比較例に係るリチウムイオン二次電池の平面図である。It is a top view of the lithium ion secondary battery which concerns on Example and comparative example. 実施例及び比較例に係る電極体等の平面図である。It is a top view of the electrode body and the like which concerns on Example and the comparative example. 比較例に係るリチウムイオン二次電池の製造工程を示すフローチャートである。It is a flowchart which shows the manufacturing process of the lithium ion secondary battery which concerns on a comparative example. 本充電工程後のセパレータの正極側表面のうち、金属異物を配置した部位の写真を図面化したものであり、（ａ）は実施例に係るセパレータの写真を図面化したものであり、（ｂ）は比較例に係るセパレータの写真を図面化したものである。A photograph of a portion of the surface on the positive electrode side of the separator after the main charging step on which a metal foreign substance is arranged is drawn, and (a) is a drawing of a photograph of the separator according to the embodiment (b). ) Is a drawing of a photograph of the separator according to the comparative example.

以下、本発明の実施形態を、図面を参照しつつ説明する。図１及び図２に、本実施形態に係るリチウムイオン二次電池（以下、単に「電池」ともいう）１の斜視図及び断面図を示す。なお、以下では、電池１の電池縦方向ＢＨ、電池横方向ＣＨ及び電池厚み方向ＤＨを、図１及び図２に示す方向と定めて説明する。この電池１は、ハイブリッドカーやプラグインハイブリッドカー、電気自動車等の車両などに搭載される角型で密閉型のリチウムイオン二次電池である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a perspective view and a cross-sectional view of a lithium ion secondary battery (hereinafter, also simply referred to as “battery”) 1 according to the present embodiment. In the following description, the battery vertical direction BH, the battery horizontal direction CH, and the battery thickness direction DH of the battery 1 are defined as the directions shown in FIGS. 1 and 2. The battery 1 is a square and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid car, a plug-in hybrid car, or an electric vehicle.

電池１は、電池ケース１０と、この内部に収容された電極体２０と、電池ケース１０に支持された正極端子部材５０及び負極端子部材６０等から構成される。また、電池ケース１０内には、電解液１７が収容されており、その一部は電極体２０内に含浸されている。本実施形態の電解液１７は、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）及びメチルエチルカーボネート（ＭＥＣ）を体積比３０：４０：３０で混合した非水溶媒に、ＬｉＰＦ6 を１．１Ｍの濃度で溶解した非水電解液である。 The battery 1 is composed of a battery case 10, an electrode body 20 housed therein, a positive electrode terminal member 50 supported by the battery case 10, a negative electrode terminal member 60, and the like. Further, the electrolytic solution 17 is housed in the battery case 10, and a part of the electrolytic solution 17 is impregnated in the electrode body 20. The electrolytic solution 17 of the present embodiment contains LiPF 6 of 1.1 M in a non-aqueous solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 30:40:30. It is a non-aqueous electrolyte solution dissolved at a concentration.

電池ケース１０は、直方体箱状で金属（本実施形態ではアルミニウム）からなる。この電池ケース１０は、上側のみが開口した有底角筒状のケース本体部材１１と、このケース本体部材１１の開口を閉塞する形態で溶接された矩形板状のケース蓋部材１３とから構成される。ケース蓋部材１３には、アルミニウムからなる正極端子部材５０がケース蓋部材１３と絶縁された状態で固設されている。この正極端子部材５０は、電池ケース１０内で電極体２０のうち正極板２１に接続し導通する一方、ケース蓋部材１３を貫通して電池外部まで延びている。また、ケース蓋部材１３には、銅からなる負極端子部材６０がケース蓋部材１３と絶縁された状態で固設されている。この負極端子部材６０は、電池ケース１０内で電極体２０のうち負極板３１に接続し導通する一方、ケース蓋部材１３を貫通して電池外部まで延びている。 The battery case 10 has a rectangular parallelepiped shape and is made of metal (aluminum in this embodiment). The battery case 10 is composed of a bottomed square cylindrical case body member 11 having an opening only on the upper side, and a rectangular plate-shaped case lid member 13 welded in a form of closing the opening of the case body member 11. NS. A positive electrode terminal member 50 made of aluminum is fixed to the case lid member 13 in a state of being insulated from the case lid member 13. The positive electrode terminal member 50 is connected to and conducts with the positive electrode plate 21 of the electrode body 20 in the battery case 10, while penetrating the case lid member 13 and extending to the outside of the battery. Further, a negative electrode terminal member 60 made of copper is fixed to the case lid member 13 in a state of being insulated from the case lid member 13. The negative electrode terminal member 60 is connected to and conductive to the negative electrode plate 31 of the electrode body 20 in the battery case 10, while penetrating the case lid member 13 and extending to the outside of the battery.

電極体２０は、扁平状をなし、横倒しにした状態で電池ケース１０内に収容されている。電極体２０と電池ケース１０の間には、絶縁フィルムからなる袋状の絶縁フィルム包囲体１９が配置されている。電極体２０は、帯状の正極板２１と帯状の負極板３１とを、帯状で樹脂製の多孔質膜からなる一対のセパレータ４１，４１を介して互いに重ね、軸線周りに捲回して扁平状に圧縮したものである。 The electrode body 20 has a flat shape and is housed in the battery case 10 in a state of being laid on its side. A bag-shaped insulating film enclosure 19 made of an insulating film is arranged between the electrode body 20 and the battery case 10. In the electrode body 20, the strip-shaped positive electrode plate 21 and the strip-shaped negative electrode plate 31 are overlapped with each other via a pair of strip-shaped and resin porous membrane separators 41 and 41, and wound around the axis to form a flat shape. It is compressed.

正極板２１は、帯状のアルミニウム箔からなる正極集電箔の両主面の所定位置に、正極活物質層を帯状に設けてなる。この正極活物質層は、正極活物質、導電材及び結着剤からなる。本実施形態では、正極活物質として、リチウム遷移金属複合酸化物、具体的には、リチウムニッケルコバルトマンガン系複合酸化物を用いている。また、負極板３１は、帯状の銅箔からなる負極集電箔の両主面の所定位置に、負極活物質層を帯状に設けてなる。この負極活物質層は、負極活物質、結着剤及び増粘剤からなる。本実施形態では、負極活物質として、炭素材料、具体的には、黒鉛を用いている。 The positive electrode plate 21 is formed by providing a strip-shaped positive electrode active material layer at predetermined positions on both main surfaces of a positive electrode current collecting foil made of a strip-shaped aluminum foil. The positive electrode active material layer is composed of a positive electrode active material, a conductive material and a binder. In the present embodiment, a lithium transition metal composite oxide, specifically, a lithium nickel cobalt manganese-based composite oxide is used as the positive electrode active material. Further, the negative electrode plate 31 is provided with a negative electrode active material layer in a band shape at predetermined positions on both main surfaces of the negative electrode current collector foil made of a band-shaped copper foil. The negative electrode active material layer is composed of a negative electrode active material, a binder and a thickener. In this embodiment, a carbon material, specifically graphite, is used as the negative electrode active material.

次いで、上記電池１の製造方法について説明する（図３参照）。まず、「組立工程Ｓ１」において、未注液の電池１ｘを組み立てる。具体的には、正極板２１及び負極板３１を、一対のセパレータ４１，４１を介して互いに重ねて捲回し、扁平状に圧縮して電極体２０を形成する。次に、ケース蓋部材１３を用意し、これに正極端子部材５０及び負極端子部材６０を固設する（図１及び図２参照）。その後、正極端子部材５０及び負極端子部材６０を、電極体２０の正極板２１及び負極板３１にそれぞれ溶接する。次に、電極体２０に絶縁フィルム包囲体１９を被せて、これらをケース本体部材１１内に挿入すると共に、ケース本体部材１１の開口をケース蓋部材１３で塞ぐ。そして、ケース本体部材１１とケース蓋部材１３とを溶接して電池ケース１０を形成する。かくして、未注液の電池１ｘが形成される。なお、この組立工程Ｓ１において、電池１ｘの電極体２０内、具体的には正極板２１とセパレータ４１の間に、鉄や銅などの金属異物が混入することがある。 Next, a method for manufacturing the battery 1 will be described (see FIG. 3). First, in the "assembly step S1", the uninjected battery 1x is assembled. Specifically, the positive electrode plate 21 and the negative electrode plate 31 are wound on top of each other via a pair of separators 41 and 41 and compressed into a flat shape to form the electrode body 20. Next, the case lid member 13 is prepared, and the positive electrode terminal member 50 and the negative electrode terminal member 60 are fixedly attached to the case lid member 13 (see FIGS. 1 and 2). After that, the positive electrode terminal member 50 and the negative electrode terminal member 60 are welded to the positive electrode plate 21 and the negative electrode plate 31 of the electrode body 20, respectively. Next, the electrode body 20 is covered with the insulating film enclosing body 19, and these are inserted into the case main body member 11, and the opening of the case main body member 11 is closed with the case lid member 13. Then, the case body member 11 and the case lid member 13 are welded to form the battery case 10. Thus, an uninjected battery 1x is formed. In this assembly step S1, metallic foreign substances such as iron and copper may be mixed in the electrode body 20 of the battery 1x, specifically between the positive electrode plate 21 and the separator 41.

次に、「注液工程Ｓ２」において、この未注液の電池１ｘ内に電解液１７を注液する。具体的には、電解液１７を注液孔１３ｈから電池ケース１０内に注液して、その後、封止部材１５で注液孔１３ｈを封止する。その後、この電池１を６．５時間放置して、注液した電解液１７を更に電極体２０内に含浸させる。この注液工程Ｓ２は、２０℃の温度下で行う。なお、組立工程Ｓ１で混入した金属異物は、電解液１７の注液後に電解液１７中に徐々に溶解する。 Next, in the “liquid injection step S2”, the electrolytic solution 17 is injected into the uninjected battery 1x. Specifically, the electrolytic solution 17 is injected into the battery case 10 from the injection hole 13h, and then the injection hole 13h is sealed by the sealing member 15. Then, the battery 1 is left to stand for 6.5 hours, and the injected electrolytic solution 17 is further impregnated into the electrode body 20. This liquid injection step S2 is performed at a temperature of 20 ° C. The metal foreign matter mixed in the assembly step S1 is gradually dissolved in the electrolytic solution 17 after the electrolytic solution 17 is injected.

次に、「第１押圧工程Ｓ３」において、電池１の電極体２０を、正極板２１、セパレータ４１及び負極板３１の積層方向ＳＨ（図１参照、図２において紙面に直交する方向）に第１圧力Ｐ１で押圧する。具体的には、電池ケース１０の幅広な側面１０ｃを一対の板状の押圧治具（不図示）で電池厚み方向ＤＨに挟んで、電池１を電池厚み方向ＤＨに押圧した状態で拘束することにより、電極体２０を積層方向ＳＨに第１圧力Ｐ１（本実施形態では、Ｐ１＝０．７０ＭＰａ）で押圧する。このような第１押圧工程Ｓ３を行うことで、正極板２１とセパレータ４１との間隔が狭くなって、正極板２１とセパレータ４１の間に混入した金属異物が、より確実に正極板２１に接触することとなる。 Next, in the "first pressing step S3", the electrode body 20 of the battery 1 is placed in the stacking direction SH of the positive electrode plate 21, the separator 41, and the negative electrode plate 31 (see FIG. 1, the direction orthogonal to the paper surface in FIG. 2). Press with 1 pressure P1. Specifically, the wide side surface 10c of the battery case 10 is sandwiched between a pair of plate-shaped pressing jigs (not shown) in the battery thickness direction DH, and the battery 1 is restrained in a state of being pressed in the battery thickness direction DH. the (in this embodiment, P1 = 0.70 M Pa) first pressure P1 of the electrode body 20 in the stacking direction SH is pressed. By performing the first pressing step S3 in this way, the distance between the positive electrode plate 21 and the separator 41 is narrowed, and the metallic foreign matter mixed between the positive electrode plate 21 and the separator 41 comes into contact with the positive electrode plate 21 more reliably. Will be done.

次に、「充電前放置工程Ｓ４」において、電池１を放置する。本実施形態では、電池１を１時間放置する。この充電前放置工程Ｓ４は、放置開始から５分間で電池温度Ｔｅを２０℃から５０℃まで加温する。そして、残りの５５分間は、電池温度Ｔｅ＝５０℃を保持し、後述する予備充電工程Ｓ５を電池温度Ｔｅ＝５０℃で行う。本実施形態で用いた前述の電解液１７は、２０℃における粘度が３．６５ｃＰであるのに対し、５０℃における粘度が１．９５ｃＰである。従って、電池１を電池温度Ｔｅ＝２０℃から５０℃に加温することにより、電解液１７の粘度は約半分（１．９５／３．６５＝０．５３）まで下がる。 Next, in the "pre-charging leaving step S4", the battery 1 is left. In this embodiment, the battery 1 is left for 1 hour. In this pre-charging leaving step S4, the battery temperature Te is heated from 20 ° C. to 50 ° C. within 5 minutes from the start of leaving. Then, the battery temperature Te = 50 ° C. is maintained for the remaining 55 minutes, and the preliminary charging step S5 described later is performed at the battery temperature Te = 50 ° C. The above-mentioned electrolytic solution 17 used in the present embodiment has a viscosity at 20 ° C. of 3.65 cP, whereas a viscosity at 50 ° C. is 1.95 cP. Therefore, by heating the battery 1 from the battery temperature Te = 20 ° C. to 50 ° C., the viscosity of the electrolytic solution 17 is reduced to about half (1.95 / 3.65 = 0.53).

次に、「予備充電工程Ｓ５」において、電極体２０を第１圧力Ｐ１で押圧した状態で、電池１を第１電池電圧Ｖ１（本実施形態では、Ｖ１＝２．０Ｖ）まで予備充電する。この第１電池電圧Ｖ１は、正極電位が鉄が溶解する溶解電位（３．２Ｖ vs. Li/Li+）よりも高く、負極電位が電解液１７中に溶解した鉄イオンが析出する析出電位（２．３Ｖ vs. Li/Li+）よりも高くなる電池電圧である。具体的には、電池１に充放電装置を接続して、５０℃の温度下において、定電流定電圧（ＣＣＣＶ）充電により、０．５Ｃの定電流で電池電圧Ｖｅが約０Ｖから第１電池電圧Ｖ１＝２．０Ｖになるまで充電した後、この第１電池電圧Ｖ１＝２．０Ｖを２分間維持した。 Next, in the "preliminary charging step S5", the battery 1 is precharged to the first battery voltage V1 (V1 = 2.0V in this embodiment) while the electrode body 20 is pressed by the first pressure P1. In this first battery voltage V1, the positive electrode potential is higher than the dissolution potential (3.2 V vs. Li / Li +) in which iron dissolves, and the negative electrode potential is the precipitation potential (2) in which iron ions dissolved in the electrolytic solution 17 are precipitated. The battery voltage is higher than .3V vs. Li / Li +). Specifically, a charging / discharging device is connected to the battery 1, and the battery voltage Ve changes from about 0 V to the first battery at a constant current of 0.5 C by charging with a constant current constant voltage (CCCV) at a temperature of 50 ° C. After charging until the voltage V1 = 2.0V, the first battery voltage V1 = 2.0V was maintained for 2 minutes.

このような予備充電工程Ｓ５を行うと、正極電位が高くなり鉄の溶解電位を超えて、正極板２１上で金属異物が電解液１７中に溶解し易くなる。特に、電極体２０を第１圧力Ｐ１で押圧した状態とすることで、前述のように、正極板２１とセパレータ４１の間に混入した金属異物が、より確実に正極板２１に接触しているので、正極板２１上で金属異物が溶解し易い。一方、負極電位は低くなり過ぎないため（鉄イオンの析出電位よりも高い状態のままであるため）、負極板３１上で金属異物由来の金属が析出し難い。 When such a precharging step S5 is performed, the positive electrode potential becomes high and exceeds the dissolution potential of iron, so that the metal foreign matter is easily dissolved in the electrolytic solution 17 on the positive electrode plate 21. In particular, by pressing the electrode body 20 with the first pressure P1, as described above, the metal foreign matter mixed between the positive electrode plate 21 and the separator 41 is more reliably in contact with the positive electrode plate 21. Therefore, the metal foreign matter is easily dissolved on the positive electrode plate 21. On the other hand, since the negative electrode potential does not become too low (because it remains higher than the precipitation potential of iron ions), it is difficult for metal derived from metallic foreign matter to precipitate on the negative electrode plate 31.

次に、「充電後放置工程Ｓ６」において、電池１を放置する。本実施形態では、電池１を３．５時間放置する。この充電後放置工程Ｓ６は、引き続き５０℃の温度下で行う。このような充電後放置工程Ｓ６を行うことで、この放置中にも正極板２１上に存在する金属異物が電解液１７中に溶解する。このため、金属異物をより確実に電解液１７中に溶解させることができる。 Next, in the "leaving step S6 after charging", the battery 1 is left unattended. In this embodiment, the battery 1 is left for 3.5 hours. This post-charging leaving step S6 is continuously performed at a temperature of 50 ° C. By performing the leaving step S6 after charging as described above, the metal foreign matter existing on the positive electrode plate 21 is dissolved in the electrolytic solution 17 even during the leaving. Therefore, the metal foreign matter can be more reliably dissolved in the electrolytic solution 17.

次に、「第２押圧工程Ｓ７」において、電池１の電極体２０を第１圧力Ｐ１よりも高い第２圧力Ｐ２で積層方向ＳＨに押圧する。具体的には、この第２押圧工程Ｓ７は、引き続き５０℃の温度下で行う。電池ケース１０の幅広な側面１０ｃを前述の一対の押圧治具（不図示）で電池厚み方向ＤＨに挟んで、電極体２０を積層方向ＳＨに第２圧力Ｐ２（本実施形態では、Ｐ２＝１．３ＭＰａ）で押圧する。このような第２押圧工程Ｓ７を行うことで、正極板２１と負極板３１の間隔が狭くなって、これらの間における電解液１７が押し出され、この電解液１７に含まれる金属異物由来の金属イオンの拡散が促進される。特に、電池１の加温により（本実施形態では、電池温度Ｔｅ＝５０℃）、電解液１７の粘度が低くなっているので、電解液１７が押し出され易く、金属イオンが拡散し易い。 Next, in the "second pressing step S7", the electrode body 20 of the battery 1 is pressed in the stacking direction SH at a second pressure P2 higher than the first pressure P1. Specifically, this second pressing step S7 is continuously performed at a temperature of 50 ° C. The wide side surface 10c of the battery case 10 is sandwiched between the pair of pressing jigs (not shown) described above in the battery thickness direction DH, and the electrode body 20 is placed in the stacking direction SH at a second pressure P2 (P2 = 1 in this embodiment). .3 pressed by M Pa). By performing such a second pressing step S7, the distance between the positive electrode plate 21 and the negative electrode plate 31 is narrowed, the electrolytic solution 17 is extruded between them, and the metal derived from the metal foreign substance contained in the electrolytic solution 17 is extruded. Ion diffusion is promoted. In particular, since the viscosity of the electrolytic solution 17 is lowered by heating the battery 1 (in this embodiment, the battery temperature Te = 50 ° C.), the electrolytic solution 17 is easily extruded and metal ions are easily diffused.

次に、「本充電工程Ｓ８」において、電池１に本充電（コンディショニング充電）を行う。具体的には、電池１に充放電装置を接続して、引き続き５０℃の温度下において、定電流定電圧（ＣＣＣＶ）充電により、１Ｃの定電流で電池電圧Ｖｅが第２電池電圧Ｖ２＝４．１Ｖになるまで充電した後、この第２電池電圧Ｖ２＝４．１Ｖを２分間維持した。この本充電工程Ｓ８を行うと、負極電位が下がり、鉄イオンの析出電位よりも低くなるため、負極板３１上で鉄等の金属異物由来の金属が析出し易くなる。しかし、本実施形態では、本充電工程Ｓ８の開始時には、金属異物は既に溶解してしまって存在せず、また、金属異物由来の金属イオンが金属異物が存在した場所から広範囲に拡散しており、金属イオンの濃度が高くなった部位が存在しない。このため、金属異物由来の金属が負極板３１上で集中的にデンドライト状に析出することがなく、金属異物に起因した短絡が生じない。 Next, in the "main charging step S8", the battery 1 is fully charged (conditioning charging). Specifically, a charging / discharging device is connected to the battery 1, and the battery voltage Ve is set to the second battery voltage V2 = 4 at a constant current of 1C by continuously charging at a constant current constant voltage (CCCV) at a temperature of 50 ° C. After charging until it became .1 V, this second battery voltage V2 = 4.1 V was maintained for 2 minutes. When this main charging step S8 is performed, the negative electrode potential is lowered and becomes lower than the precipitation potential of iron ions, so that metal derived from a metallic foreign substance such as iron is likely to be deposited on the negative electrode plate 31. However, in the present embodiment, at the start of the main charging step S8, the metal foreign matter has already melted and does not exist, and the metal ions derived from the metal foreign matter are widely diffused from the place where the metal foreign matter exists. , There is no site where the concentration of metal ions is high. Therefore, the metal derived from the metal foreign matter does not concentrate in a dendrite shape on the negative electrode plate 31, and a short circuit due to the metal foreign matter does not occur.

次に、「エージング工程Ｓ９」において、電池１を放置してエージングする。具体的には、本充電後の電池１を、６０℃の温度下において、端子開放した状態で２０ｈｒにわたり放置してエージングする。 Next, in the "aging step S9", the battery 1 is left to age. Specifically, the fully charged battery 1 is left at a temperature of 60 ° C. for 20 hours with its terminals open for aging.

次に、「短絡検知工程Ｓ１０」において、電池１を端子開放した状態で放置して放電させて（自己放電させて）、放置中の電池電圧Ｖｅの電圧低下量ΔＶｅを測定し、当該電池１の内部短絡の有無を検知する。具体的には、電池１を２０℃の温度下で端子開放した状態で放置して、エージング工程Ｓ９の終了時（短絡検知工程Ｓ１０の開始時）から２日経過後に測定した電池電圧Ｖａと、エージング工程Ｓ９の終了時（短絡検知工程Ｓ１０の開始時）から７日経過後に測定した電池電圧Ｖｂとから、電圧低下量ΔＶｅ＝Ｖａ−Ｖｂを算出する。そして、取得した当該電池１の電圧低下量ΔＶｅを、予め定めた基準低下量ΔＶｒと比較し、電圧低下量ΔＶｅが基準低下量ΔＶｒよりも大きい場合（ΔＶｅ＞ΔＶｒ）に、当該電池１に内部短絡が生じている不良品と判定し、その電池１を除去する。一方、当該電池１の電圧低下量ΔＶｅが基準低下量ΔＶｒよりも小さい場合（ΔＶｅ≦ΔＶｒ）には、当該電池１を内部短絡の無い良品と判定する。
短絡検知工程Ｓ１０の後は、良品と判定された電池１について、他の各種検査を行う。かくして、電池１が完成する。 Next, in the "short circuit detection step S10", the battery 1 is left open and discharged (self-discharged), and the voltage decrease amount ΔVe of the battery voltage Ve during the leave is measured, and the battery 1 is measured. Detects the presence or absence of an internal short circuit. Specifically, the battery voltage Va measured two days after the end of the aging step S9 (the start of the short circuit detection step S10) after leaving the battery 1 in a state where the terminals are open at a temperature of 20 ° C. The voltage decrease amount ΔVe = Va−Vb is calculated from the battery voltage Vb measured 7 days after the end of the aging step S9 (the start of the short circuit detection step S10). Then, the acquired voltage reduction amount ΔVe of the battery 1 is compared with a predetermined reference reduction amount ΔVr, and when the voltage reduction amount ΔVe is larger than the reference reduction amount ΔVr (ΔVe> ΔVr), the inside of the battery 1 is inside. It is determined that the product is defective due to a short circuit, and the battery 1 is removed. On the other hand, when the voltage drop amount ΔVe of the battery 1 is smaller than the reference drop amount ΔVr (ΔVe ≦ ΔVr), the battery 1 is determined to be a non-defective product without an internal short circuit.
After the short-circuit detection step S10, various other inspections are performed on the battery 1 determined to be a non-defective product. Thus, the battery 1 is completed.

（実施例及び比較例）
次いで、本発明の効果を検証するために行った試験の結果について説明する。実施例及び比較例として、図４及び図５に示すラミネート型のリチウムイオン二次電池（以下、単に「電池」ともいう）１００をそれぞれ製造した。
これらの電池１００は、ラミネートフィルムを袋状にした外装体１１０の内部に、電極体１２０、電解液１１７等が収容されている。このうち電極体１２０は、１枚の矩形状の正極板１２１と、１枚の矩形状の負極板１３１とを、１枚の矩形状のセパレータ１４１を介して互いに重ねたものである。 (Examples and comparative examples)
Next, the results of tests conducted to verify the effects of the present invention will be described. As Examples and Comparative Examples, laminated lithium ion secondary batteries (hereinafter, also simply referred to as “batteries”) 100 shown in FIGS. 4 and 5, respectively, were manufactured.
In these batteries 100, the electrode body 120, the electrolytic solution 117, and the like are housed inside the outer body 110 in which the laminated film is shaped like a bag. Of these, the electrode body 120 is formed by stacking one rectangular positive electrode plate 121 and one rectangular negative electrode plate 131 on top of each other via one rectangular separator 141.

正極板１２１は、矩形状のアルミニウム箔からなる正極集電箔の一方の主面（負極板１３１と対向する側の主面）の所定位置に、正極活物質層を２３ｍｍ×２３ｍｍの大きさに矩形状に設けてなる。また、この正極板１２１には、帯状のアルミニウム板からなる正極タブ１５０が接合され、外装体１１０の内部から外部に延出している。一方、負極板１３１は、矩形状の銅箔からなる負極集電箔の一方の主面（正極板１２１と対向する側の主面）の所定位置に、負極活物質層を２５ｍｍ×２５ｍｍの大きさに矩形状に設けてなる。また、この負極板１３１には、帯状の銅板からなる負極タブ１６０が接合され、外装体１１０の内部から外部に延出している。 The positive electrode plate 121 has a positive electrode active material layer having a size of 23 mm × 23 mm at a predetermined position on one main surface (main surface on the side facing the negative electrode plate 131) of the positive electrode current collecting foil made of rectangular aluminum foil. It is provided in a rectangular shape. Further, a positive electrode tab 150 made of a strip-shaped aluminum plate is joined to the positive electrode plate 121, and extends from the inside of the exterior body 110 to the outside. On the other hand, the negative electrode plate 131 has a negative electrode active material layer having a size of 25 mm × 25 mm at a predetermined position on one main surface (main surface on the side facing the positive electrode plate 121) of the negative electrode current collecting foil made of rectangular copper foil. It is provided in a rectangular shape. Further, a negative electrode tab 160 made of a strip-shaped copper plate is joined to the negative electrode plate 131, and extends from the inside of the exterior body 110 to the outside.

なお、これらの電池１００においては、未注液の電池１００ｘを組み立てる際に、正極板１２１の正極活物質層の中央部とセパレータ１４１との間に、金属異物として、直径２００μｍ、厚み１０μｍの大きさの円板状をなす鉄の塊をそれぞれ配置した。 In these batteries 100, when assembling the uninjected battery 100x, a large metal foreign substance having a diameter of 200 μm and a thickness of 10 μm is provided between the central portion of the positive electrode active material layer of the positive electrode plate 121 and the separator 141. Each of the iron lumps forming a disk shape was placed.

実施例では、実施形態と同様に（図３参照）、注液工程Ｓ２の後、第１押圧工程Ｓ３、充電前放置工程Ｓ４、予備充電工程Ｓ５、充電後放置工程Ｓ６、第２押圧工程Ｓ７を行ってから、本充電工程Ｓ８を行った。その後は、エージング工程Ｓ９及び短絡検知工程Ｓ１０は行わずに、電池１００を解体して、セパレータ１４１の正極側表面うち、金属異物と接触していた部分を、走査型電子顕微鏡で観察し、金属異物の溶解状態（溶け残り具合）を調査した。また、負極板１３１上にデンドライト状に金属（鉄）が析出しているか否かを確認した。 In the embodiment, as in the embodiment (see FIG. 3), after the liquid injection step S2, the first pressing step S3, the pre-charging leaving step S4, the pre-charging step S5, the post-charging leaving step S6, and the second pressing step S7. After that, the main charging step S8 was performed. After that, without performing the aging step S9 and the short circuit detection step S10, the battery 100 was disassembled, and the portion of the positive electrode side surface of the separator 141 that was in contact with the metal foreign matter was observed with a scanning electron microscope, and the metal was observed. The dissolved state of the foreign matter (the degree of undissolved residue) was investigated. Further, it was confirmed whether or not metal (iron) was deposited in a dendrite shape on the negative electrode plate 131.

一方、比較例では、図６に示すように、注液工程Ｓ２の後、押圧工程Ｓ３Ａを行って、本充電工程Ｓ８を行った。この比較例の押圧工程Ｓ３Ａは、実施例（実施形態）の第２押圧工程Ｓ７と同様に、電池１００の電極体１２０を第２圧力Ｐ２で積層方向ＳＨに押圧する。但し、この比較例では、この押圧工程Ｓ３Ａ及びその後の本充電工程Ｓ８を、５０℃の温度下ではなく、２０℃の温度下で行った。本充電工程Ｓ８の後は、実施例と同様に、電池１００を解体して、金属異物の溶解状態を調査した。また、負極板１３１上にデンドライト状に金属（鉄）が析出しているか否かを確認した。 On the other hand, in the comparative example, as shown in FIG. 6, after the liquid injection step S2, the pressing step S3A was performed, and the main charging step S8 was performed. In the pressing step S3A of this comparative example, the electrode body 120 of the battery 100 is pressed in the stacking direction SH by the second pressure P2, similarly to the second pressing step S7 of the embodiment (embodiment). However, in this comparative example, the pressing step S3A and the subsequent main charging step S8 were performed not at a temperature of 50 ° C. but at a temperature of 20 ° C. After the main charging step S8, the battery 100 was disassembled and the dissolved state of the metal foreign matter was investigated in the same manner as in the examples. Further, it was confirmed whether or not metal (iron) was deposited in a dendrite shape on the negative electrode plate 131.

その結果、比較例の電池１００では、図７（ｂ）に示すように、予め配置した金属（鉄）異物が殆ど溶解しないで残っていた。また、負極板１３１上にデンドライト状に金属（鉄）が析出していた。一方、実施例の電池１００では、図７（ａ）に示すように、金属（鉄）異物が殆ど溶解していた。また、負極板１３１上にデンドライト状に金属（鉄）が析出していなかった。このような結果となった理由は、以下であると考えられる。 As a result, in the battery 100 of the comparative example, as shown in FIG. 7B, the metal (iron) foreign matter arranged in advance remained almost undissolved. Further, metal (iron) was deposited in a dendrite shape on the negative electrode plate 131. On the other hand, in the battery 100 of the example, as shown in FIG. 7A, most of the metal (iron) foreign matter was dissolved. Further, no metal (iron) was deposited in a dendrite shape on the negative electrode plate 131. The reason for this result is considered to be as follows.

即ち、比較例では、前述の第１押圧工程Ｓ３及び予備充電工程Ｓ５を行っていないため、本充電工程Ｓ８以前に、正極板１２１上で電解液１１７中に溶解する金属異物の量が少ない。また、正極板１２１とセパレータ１４１の間に配置した金属異物が、正極板１２１に接触していないため、本充電工程Ｓ８の際に、金属異物の電位が上がり難く、金属異物が溶解し難い。このため、金属異物の多くが溶解しないで残ったと考えられる。また、本充電の際に、金属異物の一部が溶解した金属イオンが負極板１３１上で集中的にデンドライト状に析出したと考えられる。 That is, in the comparative example, since the above-mentioned first pressing step S3 and precharging step S5 are not performed, the amount of metal foreign matter dissolved in the electrolytic solution 117 on the positive electrode plate 121 is small before the main charging step S8. Further, since the metal foreign matter arranged between the positive electrode plate 121 and the separator 141 does not come into contact with the positive electrode plate 121, the potential of the metal foreign matter does not easily rise during the main charging step S8, and the metal foreign matter does not easily dissolve. Therefore, it is considered that most of the metallic foreign substances remained undissolved. Further, it is considered that during the main charging, metal ions in which a part of the metal foreign matter was dissolved were concentrated and deposited in a dendrite shape on the negative electrode plate 131.

これに対し、実施例では、第１押圧工程Ｓ３及び予備充電工程Ｓ５を行っている。第１押圧工程Ｓ３で電極体１２０を積層方向ＳＨに押圧することで、正極板１２１とセパレータ１４１との間隔が狭くなって、正極板１２１とセパレータ１４１の間に配置した金属異物が、正極板１２１に接触した。このため、予備充電工程Ｓ５において、正極板１２１の正極電位が高くなったときに、金属異物の電位も高くなって、正極板１２１上で金属異物が電解液中に溶解した。一方、負極電位は低くなり過ぎないため、負極板１３１上で金属異物由来の金属が析出し難い。 On the other hand, in the embodiment, the first pressing step S3 and the precharging step S5 are performed. By pressing the electrode body 120 in the stacking direction SH in the first pressing step S3, the distance between the positive electrode plate 121 and the separator 141 is narrowed, and the metallic foreign matter arranged between the positive electrode plate 121 and the separator 141 is removed from the positive electrode plate. Contacted 121. Therefore, in the preliminary charging step S5, when the positive electrode potential of the positive electrode plate 121 is increased, the potential of the metallic foreign matter is also increased, and the metallic foreign matter is dissolved in the electrolytic solution on the positive electrode plate 121. On the other hand, since the negative electrode potential does not become too low, it is difficult for metal derived from a metallic foreign substance to precipitate on the negative electrode plate 131.

また、実施例では、第２押圧工程Ｓ７において、電池１００を加温し電解液１１７の粘度を下げた状態で、電極体１２０を第１圧力Ｐ１よりも高い第２圧力Ｐ２で積層方向ＳＨに押圧している。これにより、正極板１２１と負極板１３１の間隔が狭くなって、これらの間における電解液１１７が押し出され、この電解液１１７に含まれる金属異物由来の金属イオンの拡散が促進される。特に、電池１００の加温によって電解液１１７の粘度が低くなっているので、電解液１１７が押し出され易く、金属イオンの拡散が促進される。その結果、金属イオンが負極板１３１上で集中的にデンドライト状に析出するのが防止されたと考えられる。 Further, in the embodiment, in the second pressing step S7, in a state where the battery 100 is heated and the viscosity of the electrolytic solution 117 is lowered, the electrode body 120 is set to the stacking direction SH at a second pressure P2 higher than the first pressure P1. Pressing. As a result, the distance between the positive electrode plate 121 and the negative electrode plate 131 is narrowed, the electrolytic solution 117 is extruded between them, and the diffusion of metal ions derived from metal foreign substances contained in the electrolytic solution 117 is promoted. In particular, since the viscosity of the electrolytic solution 117 is lowered by heating the battery 100, the electrolytic solution 117 is easily extruded and the diffusion of metal ions is promoted. As a result, it is considered that the metal ions were prevented from being concentratedly deposited in a dendrite shape on the negative electrode plate 131.

以上で説明したように、電池１の製造方法では、注液工程Ｓ２の後、第１押圧工程Ｓ３で電池１の電極体２０を積層方向ＳＨに第１圧力Ｐ１で押圧し、この状態で予備充電工程Ｓ５を行って、電池１を第１電池電圧Ｖ１まで充電している。電極体２０を積層方向ＳＨに押圧することで、正極板２１とセパレータ４１との間隔が狭くなって、正極板２１とセパレータ４１の間に混入した金属異物が、より確実に正極板２１に接触することとなる。このため、予備充電工程Ｓ５において、正極板２１の正極電位が高くなったときに、正極板２１に接触する金属異物の電位も高くなって、正極板２１上で金属異物（特に鉄の異物）が電解液１７中に溶解し易くなる。一方、負極電位は低くなり過ぎないため、負極板３１上で金属異物（特に鉄の異物）由来の金属が析出し難い。 As described above, in the method for manufacturing the battery 1, after the liquid injection step S2, the electrode body 20 of the battery 1 is pressed in the stacking direction SH with the first pressure P1 in the first pressing step S3, and the battery 1 is prepared in this state. The charging step S5 is performed to charge the battery 1 to the first battery voltage V1. By pressing the electrode body 20 in the stacking direction SH, the distance between the positive electrode plate 21 and the separator 41 is narrowed, and the metallic foreign matter mixed between the positive electrode plate 21 and the separator 41 comes into contact with the positive electrode plate 21 more reliably. Will be done. Therefore, in the preliminary charging step S5, when the positive electrode potential of the positive electrode plate 21 becomes high, the potential of the metallic foreign matter in contact with the positive electrode plate 21 also becomes high, and the metallic foreign matter (particularly the iron foreign matter) is placed on the positive electrode plate 21. Is easily dissolved in the electrolytic solution 17. On the other hand, since the negative electrode potential does not become too low, it is difficult for metal derived from metal foreign matter (particularly iron foreign matter) to precipitate on the negative electrode plate 31.

また、電池１の製造方法では、予備充電工程Ｓ５の後、第２押圧工程Ｓ７において、電池１を加温し電解液１７の粘度を下げた状態で、電極体２０を第１圧力Ｐ１よりも高い第２圧力Ｐ２で積層方向ＳＨに押圧している。これにより、正極板２１と負極板３１の間隔が狭くなって、これらの間における電解液１７が押し出され、この電解液１７に含まれる金属異物由来の金属イオンの拡散が促進される。
かくして、電池１の製造方法では、製造過程で正極板２１とセパレータ４１の間に金属異物が混入したとしても、この金属異物の電解液１７への溶解を促進させると共に、溶解した金属異物由来の金属イオンの拡散を促進させることができ、金属異物に起因した短絡を防止できる。 Further, in the method for manufacturing the battery 1, after the pre-charging step S5, in the second pressing step S7, the electrode body 20 is made higher than the first pressure P1 in a state where the battery 1 is heated and the viscosity of the electrolytic solution 17 is lowered. It is pressed in the stacking direction SH with a high second pressure P2. As a result, the distance between the positive electrode plate 21 and the negative electrode plate 31 is narrowed, the electrolytic solution 17 is extruded between them, and the diffusion of metal ions derived from metal foreign substances contained in the electrolytic solution 17 is promoted.
Thus, in the method for manufacturing the battery 1, even if a metallic foreign substance is mixed between the positive electrode plate 21 and the separator 41 in the manufacturing process, the dissolution of the metallic foreign substance in the electrolytic solution 17 is promoted and the dissolved metallic foreign substance is derived. It is possible to promote the diffusion of metal ions and prevent short circuits caused by foreign metals.

また、電池１の製造方法では、第１押圧工程Ｓ３における第１圧力Ｐ１を、０．６０〜０．８０ＭＰａとしている。第１圧力Ｐ１が低すぎないので、正極板２１とセパレータ４１の間に混入した金属異物が正極板２１に接触し易い。一方、第１圧力Ｐ１が高すぎないので、正極板２１と負極板３１の間隔が狭くなりすぎて、これらの間の電解液１７の量が減って、金属異物が電解液１７中に溶解し難くなるのを防止できる。 In the manufacturing method of the battery 1, the first pressure P1 in the first pressing step S3, it is set to 0.60 to 0.80 M Pa. Since the first pressure P1 is not too low, the metallic foreign matter mixed between the positive electrode plate 21 and the separator 41 easily comes into contact with the positive electrode plate 21. On the other hand, since the first pressure P1 is not too high, the distance between the positive electrode plate 21 and the negative electrode plate 31 becomes too narrow, the amount of the electrolytic solution 17 between them decreases, and the metal foreign matter dissolves in the electrolytic solution 17. It can be prevented from becoming difficult.

また、第２押圧工程Ｓ７における第２圧力Ｐ２を、０．８０〜１．８ＭＰａとしている。第２圧力Ｐ２が低すぎないので、正極板２１と負極板３１の間隔が適切に狭くなって、電解液１７が押し出され易い。一方、第２圧力Ｐ２が高すぎないので、正極板２１と負極板３１の間隔が狭くなりすぎず、これらの間の電解液１７の量が少なくなりすぎない。
また、第２押圧工程Ｓ７における電池温度Ｔｅを、２５℃以上、更には、３０℃以上としているので、電解液１７の粘度が適切に下がる。一方で、この電池温度Ｔｅを、６０℃以下、更には、５０℃以下としているので、電池１が劣化したり、電池１の低温時の入出力特性が低下するなど、電池の特性が変化するのを防止できる。 Further, the second pressure P2 in the second pressing step S7, and a from .80 to 1.8 M Pa. Since the second pressure P2 is not too low, the distance between the positive electrode plate 21 and the negative electrode plate 31 is appropriately narrowed, and the electrolytic solution 17 is likely to be extruded. On the other hand, since the second pressure P2 is not too high, the distance between the positive electrode plate 21 and the negative electrode plate 31 is not too narrow, and the amount of the electrolytic solution 17 between them is not too small.
Further, since the battery temperature Te in the second pressing step S7 is 25 ° C. or higher, further 30 ° C. or higher, the viscosity of the electrolytic solution 17 is appropriately lowered. On the other hand, since the battery temperature Te is set to 60 ° C. or lower, further 50 ° C. or lower, the characteristics of the battery change, such as deterioration of the battery 1 or deterioration of the input / output characteristics of the battery 1 at a low temperature. Can be prevented.

また、電池１の製造方法では、予備充電工程Ｓ５の後、第２押圧工程Ｓ７の前に充電後放置工程Ｓ６を行って電池１を第１電池電圧Ｖ１で０．５時間以上放置している。この放置中にも正極板２１上に残存する金属異物が電解液１７中に溶解するので、金属異物をより確実に電解液１７中に溶解させることができる。
また、電池１の製造方法では、予備充電工程Ｓ５及び充電後放置工程Ｓ６を、電池１を加温し電解液１７の粘度を下げた状態で行っているので、これらの工程中においても、電解液１７の粘度を下げたことにより、金属異物由来の金属イオンの拡散を促進させることができる。 Further, in the method of manufacturing the battery 1, the battery 1 is left at the first battery voltage V1 for 0.5 hours or more by performing the post-charging leaving step S6 after the pre-charging step S5 and before the second pressing step S7. .. Since the metal foreign matter remaining on the positive electrode plate 21 is dissolved in the electrolytic solution 17 even during this leaving, the metal foreign matter can be more reliably dissolved in the electrolytic solution 17.
Further, in the method for manufacturing the battery 1, since the pre-charging step S5 and the post-charging leaving step S6 are performed in a state where the battery 1 is heated and the viscosity of the electrolytic solution 17 is lowered, electrolysis is performed even during these steps. By lowering the viscosity of the liquid 17, it is possible to promote the diffusion of metal ions derived from metal foreign substances.

以上において、本発明を実施形態に即して説明したが、本発明は上述の実施形態に限定されるものではなく、その要旨を逸脱しない範囲で、適宜変更して適用できることは言うまでもない。
例えば、実施形態では、第１押圧工程Ｓ３及び第２押圧工程Ｓ７において、拘束部材で電池１を拘束して電極体２０を積層方向ＳＨに押圧したが、これに限られない。例えば、油圧プレスなどのプレス機で電池１を押圧して電極体２０を積層方向ＳＨに押圧してもよい。また、電池１におもりを載せるなどして電極体２０を積層方向ＳＨに押圧してもよい。 Although the present invention has been described above in accordance with the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, in the first pressing step S3 and the second pressing step S7, the battery 1 is restrained by the restraining member and the electrode body 20 is pressed in the stacking direction SH, but the present invention is not limited to this. For example, the battery 1 may be pressed by a press machine such as a hydraulic press to press the electrode body 20 in the stacking direction SH. Further, the electrode body 20 may be pressed in the stacking direction SH by placing a weight on the battery 1.

１，１００ 電池
１ｘ，１００ｘ （未注液の）電池
１７，１１７ 電解液
２０，１２０ 電極体
２，１２１ 正極板
３１，１３１ 負極板
４１，１４１ セパレータ
Ｓ１ 組立工程
Ｓ２ 注液工程
Ｓ３ 第１押圧工程
Ｓ４ 充電前放置工程
Ｓ５ 予備充電工程
Ｓ６ 充電後放置工程
Ｓ７ 第２押圧工程
Ｓ８ 本充電工程
Ｓ９ エージング工程
Ｓ１０ 短絡検知工程
Ｓ３Ａ 押圧工程 1,100 Battery 1x, 100x (uninjected) Battery 17,117 Electrolyte 20,120 Electrode 2,121 Positive electrode plate 31,131 Negative electrode plate 41,141 Separator S1 Assembly step S2 Lubrication step S3 First pressing step S4 Pre-charging leaving step S5 Pre-charging step S6 Post-charging leaving step S7 Second pressing step S8 Main charging step S9 Aging step S10 Short circuit detection step S3A Pressing step

Claims (1)

正極活物質にリチウム遷移金属複合酸化物を含む正極板、及び、負極活物質に炭素材料を含む負極板がセパレータを介して互いに重なった電極体と、電解液と、を備えるリチウムイオン二次電池の製造方法であって、
上記電極体を有する未注液のリチウムイオン二次電池内に、上記電解液を注液する注液工程と、
上記注液工程の後に、上記リチウムイオン二次電池の上記電極体を、上記正極板、上記セパレータ及び上記負極板の積層方向に第１圧力Ｐ１で押圧する第１押圧工程と、
上記電極体を上記第１圧力Ｐ１で押圧した状態で、上記リチウムイオン二次電池を、正極電位が鉄の溶解電位よりも高く、かつ、負極電位が上記電解液中に溶解した鉄イオンの析出電位よりも高い第１電池電圧Ｖ１まで予備充電する予備充電工程と、
上記予備充電工程の後に、上記リチウムイオン二次電池を加温し上記電解液の粘度を下げた状態で、上記リチウムイオン二次電池の上記電極体を、上記第１圧力Ｐ１よりも高い第２圧力Ｐ２で上記積層方向に押圧する第２押圧工程と、
上記第２押圧工程の後に、上記第１電池電圧Ｖ１よりも高い第２電池電圧Ｖ２まで上記リチウムイオン二次電池をコンディショニング充電する本充電工程と、を備え、
上記第１圧力Ｐ１は、０．６０〜０．８０ＭＰａであり、
上記第２圧力Ｐ２は、０．８０〜１．８ＭＰａである
リチウムイオン二次電池の製造方法。 A lithium ion secondary battery including a positive electrode plate containing a lithium transition metal composite oxide as a positive electrode active material, an electrode body in which a negative electrode plate containing a carbon material as a negative electrode active material is overlapped with each other via a separator, and an electrolytic solution. It is a manufacturing method of
A liquid injection step of injecting the electrolytic solution into an uninjected lithium ion secondary battery having the electrode body, and a liquid injection step.
After the liquid injection step, a first pressing step of pressing the electrode body of the lithium ion secondary battery with a first pressure P1 in the stacking direction of the positive electrode plate, the separator, and the negative electrode plate.
In a state where the electrode body is pressed by the first pressure P1, in the lithium ion secondary battery, the positive electrode potential is higher than the iron dissolution potential and the negative electrode potential is the precipitation of iron ions dissolved in the electrolytic solution. A pre-charging process that pre-charges up to the first battery voltage V1, which is higher than the potential, and
After the precharging step, in a state where the lithium ion secondary battery is heated to reduce the viscosity of the electrolytic solution, the electrode body of the lithium ion secondary battery is placed in a second position higher than the first pressure P1. The second pressing step of pressing in the stacking direction with the pressure P2, and
After the second pressing step, a main charging step of conditioning and charging the lithium ion secondary battery to a second battery voltage V2 higher than the first battery voltage V1 is provided .
The first pressure P1 is 0.60 to 0.80 MPa.
The second pressure P2 is 0.80 to 1.8 MPa . A method for manufacturing a lithium ion secondary battery.
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