JP2013206544A - Cylindrical lithium ion secondary battery - Google Patents
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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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- 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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Abstract
Description
本発明は、電池径および容量が小さい円筒形リチウムイオン二次電池に関し、より詳しくは、円筒形リチウムイオン二次電池の耐過放電特性の向上に関する。 The present invention relates to a cylindrical lithium ion secondary battery having a small battery diameter and capacity, and more particularly to improvement of overdischarge resistance of a cylindrical lithium ion secondary battery.
電池を用いた機器の応用範囲は拡大しており、特に、リチウムイオン電池は軽量、高容量、高出力であるため、パソコンや携帯電話、携帯型電子機器の駆動用電源として広く用いられている。これらの機器の電源としては、従来、直径が２０ｍｍ程度、高さが５０ｍｍ程度のものが広く用いられている。 The range of application of battery-based devices is expanding. In particular, lithium-ion batteries are widely used as power sources for driving personal computers, mobile phones, and portable electronic devices because of their light weight, high capacity, and high output. . Conventionally, power supplies for these devices have been widely used having a diameter of about 20 mm and a height of about 50 mm.
近年は、さらに携帯型電子機器の小型化や、眼鏡や補聴器などの高機能化に伴い、小型で高容量、高出力な電源が求められている。特に、眼鏡や補聴器などの使用においては、人の生活において、長時間、身に着ける場合があり、特に軽量で小型の電源が要望されている。具体的には、直径が３〜６ｍｍ程度、高さが２０〜４５ｍｍ程度である。 In recent years, along with further downsizing of portable electronic devices and higher functions of glasses, hearing aids, and the like, there has been a demand for power supplies with small size, high capacity, and high output. In particular, when using glasses, hearing aids, and the like, they may be worn for a long time in human life, and a particularly lightweight and compact power supply is desired. Specifically, the diameter is about 3 to 6 mm and the height is about 20 to 45 mm.
従来から広く用いられている、直径が２０ｍｍ程度、高さが５０ｍｍ程度のリチウムイオン電池では、一般的に電池が０Ｖに至ることによる劣化を防止するために、過放電防止機能（セイフティユニット）を電池と共に備えているが、セイフティユニットの大きさが電池に対し十分小さいので、大きさの影響はあまり問題とはならない。また、セイフティユニットは、機器に搭載された電池が所定の電圧に至ると、電池から機器への放電を遮断する。しかし、遮断後もセイフティユニットは電池の電圧をモニターするための微小電流を消費する。従来の電源は、２０００ｍＡｈ程度と非常に高容量であるため、機器の漏れ電流の影響が小さく、セイフティユニットの消費電流のために電池が放電しても、０Ｖに至るまでの期間が長い。 In a lithium ion battery having a diameter of about 20 mm and a height of about 50 mm, which has been widely used in the past, an overdischarge prevention function (safety unit) is generally provided to prevent deterioration due to the battery reaching 0V. Although equipped with the battery, the size of the safety unit is sufficiently small compared to the battery, so the influence of the size is not a problem. In addition, the safety unit blocks discharge from the battery to the device when the battery mounted on the device reaches a predetermined voltage. However, even after shutting down, the safety unit consumes a minute current for monitoring the battery voltage. Since the conventional power source has a very high capacity of about 2000 mAh, the influence of the leakage current of the device is small, and even if the battery is discharged due to the current consumption of the safety unit, the period until reaching 0 V is long.
一方、直径が３〜６ｍｍ程度、高さが２０〜４５ｍｍ程度の電池では、一般的なセイフティユニットは数ｍｍ角であり、電池に対し大きいので、電源と共にセイフティユニットを備えると、小型であるメリットが小さくなってしまう。また、機器側に過放電防止機能を備えることにより、小型のメリットを活かすことも可能であるが、容量が５ｍＡｈから２００ｍＡｈ程度の電池の場合、待機中の機器の消費電流の影響は非常に大きく、過放電防止機能を備えても、その消費電流のために電池が放電し、０Ｖに至るまでの期間が著しく短い。 On the other hand, for batteries with a diameter of about 3 to 6 mm and a height of about 20 to 45 mm, the general safety unit is a few mm square and is larger than the battery. Will become smaller. In addition, by providing an overdischarge prevention function on the device side, it is possible to take advantage of the small size, but in the case of a battery with a capacity of about 5 mAh to 200 mAh, the influence of the current consumption of the standby device is very large. Even if the overdischarge prevention function is provided, the battery discharges due to the consumption current, and the period until it reaches 0 V is remarkably short.
従来リチウムイオン電池は０Ｖ（過放電）に至ると、正極と負極の単極電位は３．４Ｖ付近となる。一般的に負極は集電体として銅を用いている。銅は３．４Ｖ以上で溶解と析出が発生する。そのため電池が０Ｖ（過放電）に至ると、電池が劣化する。 When a conventional lithium ion battery reaches 0V (overdischarge), the unipolar potential of the positive electrode and the negative electrode is around 3.4V. In general, the negative electrode uses copper as a current collector. Copper dissolves and precipitates at 3.4 V or higher. Therefore, when the battery reaches 0V (over discharge), the battery deteriorates.
例えば特許文献１では、過放電によるリチウムイオン電池の劣化を防止するため、負極に金属リチウム箔を貼付し、電位差あるいは濃度差によりリチウムを炭素材中に拡散させたことを特徴とする非水電解液二次電池が開示されている。これにより、過放電時の負極の電位はリチウムに対して１．５Ｖ前後までしか上昇しないため、耐過放電特性を向上させることができると記載されている。 For example, in Patent Document 1, in order to prevent the deterioration of a lithium ion battery due to overdischarge, a metal lithium foil is attached to the negative electrode, and lithium is diffused into the carbon material due to a potential difference or a concentration difference. A liquid secondary battery is disclosed. Accordingly, it is described that the potential of the negative electrode during overdischarge only rises to about 1.5 V with respect to lithium, and thus the overdischarge resistance can be improved.
また特許文献２では、電極間の電圧（電池電圧）がゼロ（過放電）のときの正極と負極のリチウムに対する単極電位が、負極電極の基体（集電体）の基体溶解電位よりも低いレベルであることが提案されている。集電体として、銅よりも溶解電位の高い材料を用いることが記載されている。 In Patent Document 2, the unipolar potential with respect to lithium of the positive electrode and the negative electrode when the voltage between the electrodes (battery voltage) is zero (overdischarge) is lower than the substrate dissolution potential of the substrate (current collector) of the negative electrode. Proposed to be level. It is described that a material having a higher dissolution potential than copper is used as a current collector.
従来、過放電における電池の劣化は、原因を負極として考えられ、負極に対し、種々の取り組みがなされてきた。しかしながら、負極の改善による効果が、正極の劣化を引き起こす場合があった。 Conventionally, battery deterioration due to overdischarge is considered to be caused by a negative electrode, and various efforts have been made for the negative electrode. However, the effect of improving the negative electrode sometimes causes deterioration of the positive electrode.
特許文献１では、正極に遷移金属のリチウム含有複合酸化物を用いとあるが、実質的には、活物質としてコバルト酸リチウム（ＬｉＣｏＯ２）について記載されている。コバルト酸リチウムは、１．５Ｖ程度の低い電位においても、比較的安定であるため、過放電時の負極の電位（即ち正極の電位）がリチウムに対して１．５Ｖ前後であることにより、耐過放電特性を向上することができる。 In Patent Document 1, a lithium-containing composite oxide of a transition metal is used for a positive electrode, but substantially describes lithium cobaltate (LiCoO 2 ) as an active material. Since lithium cobaltate is relatively stable even at a low potential of about 1.5 V, the negative electrode potential during overdischarge (that is, the positive electrode potential) is around 1.5 V with respect to lithium. Overdischarge characteristics can be improved.
しかしながら、正極活物質として、一般式ＬｉＭＯ２あるいはＬｉＭ２Ｏ４で表されるリチウム含有複合酸化物（但しＭはニッケル単独か、ニッケルの一部を他の遷移金属で置換した金属）を用いると、１．９Ｖ以下の電位で低い電位ほど、また長期間になるほど、正極活物質の構造が変化し劣化が進行する。そのため、負極にリチウムを貼付け、過放電（電池電圧０V）時の負極の電位（即ち正極の電位）を１．５Ｖ程度の低い電位にすると、負極の劣化は抑制されるが、正極が劣化するため、効果を得るのは困難である。 However, when a lithium-containing composite oxide represented by the general formula LiMO 2 or LiM 2 O 4 (where M is nickel alone or a metal obtained by substituting a part of nickel with another transition metal) is used as the positive electrode active material. The structure of the positive electrode active material changes and the deterioration progresses as the electric potential is 1.9 V or less and the electric potential is lower and the electric potential is longer. Therefore, when lithium is pasted on the negative electrode and the potential of the negative electrode during overdischarge (battery voltage 0 V) (that is, the potential of the positive electrode) is set to a low potential of about 1.5 V, the deterioration of the negative electrode is suppressed, but the positive electrode is deteriorated. Therefore, it is difficult to obtain an effect.
特許文献２では、負極の集電体を銅よりも溶解電位の高い材料を用いることにより、耐過放電特性を向上できることが提案されている。しかしながら、特許文献２にあるようなチタニウムやチタニウム合金を用いると、抵抗が高いため出力の低下を招く。特に、直径が３〜６ｍｍ程度、高さが２０〜４５ｍｍ程度の小さな電池では、電極が小さいために集電体の抵抗の影響は大きく、出力が大きく低下してしまう。 Patent Document 2 proposes that the overdischarge resistance can be improved by using a negative electrode current collector made of a material having a higher dissolution potential than copper. However, when titanium or a titanium alloy as disclosed in Patent Document 2 is used, the output is lowered due to high resistance. In particular, in a small battery having a diameter of about 3 to 6 mm and a height of about 20 to 45 mm, since the electrodes are small, the influence of the resistance of the current collector is large, and the output is greatly reduced.
そこで、本発明は、出力が低下することなく、電池が過放電状態において、正極および負極が安定な電位範囲にあることにより、良好な耐過放電特性を有する円筒形リチウムイオン二次電池を提供する。 Accordingly, the present invention provides a cylindrical lithium ion secondary battery having good overdischarge resistance characteristics when the positive electrode and the negative electrode are in a stable potential range when the battery is in an overdischarge state without lowering the output. To do.
上記課題を解決するために、本発明は、正極活物質として一般式ＬｉＭＯ２あるいはＬｉＭ２Ｏ４で表されるリチウム含有複合酸化物（但しＭはニッケル単独か、ニッケルの一部を他の遷移金属で置換した金属）を含む正極と、負極活物質として炭素材を、負極集電体として銅をそれぞれ用いた負極と、をセパレータを介して対向配置させ巻回してなる電極群が、非水電解液とともに外装缶に収納され、封止された円筒形リチウムイオン二次電池であり、負極は、金属リチウム箔を貼付し、電位差あるいは濃度差により前記リチウムを炭素材中に拡散させ、０．２Ｉｔで放電し、電池電圧が０Ｖに至り、電池が０Ｖで保持された１０日後に、前記負極の電位がリチウムに対し２．０Ｖ以上、３．２Ｖ以下であることを特徴とする円筒形リチウムイオン二次電池である。 In order to solve the above-described problems, the present invention provides a lithium-containing composite oxide represented by the general formula LiMO 2 or LiM 2 O 4 as a positive electrode active material (where M is nickel alone or a part of nickel is replaced with another transition). An electrode group comprising a positive electrode including a metal substituted with a metal, a negative electrode using a carbon material as a negative electrode active material, and copper as a negative electrode current collector, facing each other through a separator, is non-aqueous. A cylindrical lithium ion secondary battery housed in an outer can together with an electrolytic solution and sealed. A negative electrode has a metallic lithium foil attached thereto, and the lithium is diffused into the carbon material by a potential difference or a concentration difference. 10 days after the discharge of 2 It, the battery voltage reaches 0 V, and the battery is held at 0 V, the potential of the negative electrode is 2.0 V or more and 3.2 V or less with respect to lithium. It is a um ion secondary battery.
本発明の円筒形リチウムイオン二次電池は、過放電状態において、正極および負極が、両者の安定な電位範囲にあるため劣化を抑制できる。また、負極の集電体は銅であるため抵抗が小さく、良好な出力特性を得ることができる。 The cylindrical lithium ion secondary battery of the present invention can suppress deterioration in the overdischarged state because the positive electrode and the negative electrode are in the stable potential range of both. Further, since the current collector of the negative electrode is copper, the resistance is small and good output characteristics can be obtained.
本発明によれば、過放電状態において、正極および負極の劣化が抑制されるため、良好な耐過放電特性有する円筒形リチウムイオン二次電池を提供することができる。 According to the present invention, since the deterioration of the positive electrode and the negative electrode is suppressed in the overdischarge state, it is possible to provide a cylindrical lithium ion secondary battery having good overdischarge resistance.
本発明は、正極活物質として一般式ＬｉＭＯ２あるいはＬｉＭ２Ｏ４で表されるリチウム含有複合酸化物（但しＭはニッケル単独か、ニッケルの一部を他の遷移金属で置換した金属）を含む正極と、負極活物質として炭素材を、負極集電体として銅をそれぞれ用いた負極と、を用い、負極は、負極または外装缶に金属リチウム箔を貼付し、電位差あるいは濃度差により前記リチウムを炭素材中に拡散させ、０．２Ｉｔで放電し、電池電圧が０Ｖに至り、電池が０Ｖで保持された１０日後に、前記負極の電位がリチウムに対し２．０Ｖ以上、３．２Ｖ以下であることにより、過放電状態において正極および負極が、両者の安定な電位範囲にあるため劣化を抑制でき、良好な耐過放電特性の円筒形リチウムイオン二次電池を提供することができる。 The present invention includes a lithium-containing composite oxide represented by the general formula LiMO 2 or LiM 2 O 4 as a positive electrode active material (where M is nickel alone or a metal obtained by substituting part of nickel with another transition metal). Using a positive electrode and a negative electrode using a carbon material as a negative electrode active material and copper as a negative electrode current collector, a metal lithium foil is attached to the negative electrode or an outer can, and the lithium is applied by a potential difference or a concentration difference. After 10 days after diffusion into the carbon material, discharge at 0.2 It, the battery voltage reaches 0 V, and the battery is held at 0 V, the potential of the negative electrode is 2.0 V or more and 3.2 V or less with respect to lithium. Therefore, in the overdischarge state, the positive electrode and the negative electrode are in the stable potential range of both, so that deterioration can be suppressed, and a cylindrical lithium ion secondary battery with good overdischarge resistance can be provided. The
負極集電体は、最外周側に露出部が設けられ、金属リチウム箔は、負極集電体の露出部に貼付し、電位差あるいは濃度差によりリチウムを炭素材中に拡散させることが好ましい。 The negative electrode current collector is preferably provided with an exposed portion on the outermost peripheral side, and the metal lithium foil is preferably attached to the exposed portion of the negative electrode current collector, and lithium is diffused into the carbon material by a potential difference or a concentration difference.
金属リチウム箔は、負極集電体の最外周側に設けられた露出部に貼り付けることが好ましい。負極集電体の最外周側に設けられた露出部に、金属リチウム箔を貼り付ける工程が簡便であり、構成された電極群を用いた電池は、従来の金属リチウム箔を貼り付けていない電極群と同様の製造法で電池を製造できるため、生産工程を変更することがなく好ましい。 The metal lithium foil is preferably attached to the exposed portion provided on the outermost peripheral side of the negative electrode current collector. The process of attaching the metal lithium foil to the exposed portion provided on the outermost peripheral side of the negative electrode current collector is simple, and the battery using the configured electrode group does not have the conventional metal lithium foil attached. Since a battery can be manufactured by the same manufacturing method as the group, it is preferable without changing the production process.
電極群の最外周の曲率半径が３．０ｍｍ以下であり、負極集電体は、負極リードが電気的に接続されており、金属リチウム箔の厚みは、負極リードの厚み以下であり、幅は外装缶の内径円周の１／３以下であることにより、直径が３〜６ｍｍ程度の小さな電池であっても、貼り付けられた金属リチウム箔が構成された電極群径に影響することがないので好ましい。さらに好ましくは、金属リチウム箔の幅が、負極リードの幅以下である。金属リチウム箔の厚みが、負極リードの厚み以上では、貼り付けられた金属リチウム箔が構成された電極群径を大きくする可能性があるため好ましくない。また、幅が外装缶の内径円周の１／２以上では貼り付けられた金属リチウム箔が構成された電極群径を大きくする可能性があるため好ましくない。 The curvature radius of the outermost circumference of the electrode group is 3.0 mm or less, the negative electrode current collector is electrically connected to the negative electrode lead, the thickness of the metal lithium foil is equal to or less than the thickness of the negative electrode lead, and the width is By being 1/3 or less of the inner diameter circumference of the outer can, even a small battery having a diameter of about 3 to 6 mm does not affect the diameter of the electrode group in which the attached metal lithium foil is configured. Therefore, it is preferable. More preferably, the width of the metal lithium foil is equal to or less than the width of the negative electrode lead. If the thickness of the metal lithium foil is equal to or greater than the thickness of the negative electrode lead, the diameter of the electrode group in which the attached metal lithium foil is configured may be increased. Further, if the width is ½ or more of the inner diameter circumference of the outer can, the diameter of the electrode group in which the adhered metal lithium foil is formed is not preferable.
外装缶と負極集電体とが電気的に接続されており、金属リチウム箔は外装缶内部に貼付し、電位差あるいは濃度差により前記リチウムを炭素材中に拡散させることにより、従来と同様の電極群を用いることができるため、電極群の構成に係わる工程の変更がないため好ましい。 The outer can and the negative electrode current collector are electrically connected, the metal lithium foil is stuck inside the outer can, and the lithium is diffused into the carbon material by a potential difference or a concentration difference. Since a group can be used, there is no change in the process related to the configuration of the electrode group, which is preferable.
金属リチウム箔は、外装缶内部の底部や側部に貼り付けることができる。 A metal lithium foil can be affixed on the bottom part or side part inside an exterior can.
金属リチウム箔は、電極群の最外周側に設けられた露出部、または外装缶内部、のどち
らかまたは両者に貼付けられたことにより、負極炭素材中に拡散させることができる。
The metal lithium foil can be diffused into the negative electrode carbon material by being attached to either or both of the exposed portion provided on the outermost peripheral side of the electrode group and the inside of the outer can.
公称容量が５ｍＡｈ以上、２００ｍＡｈ以下の電池であることが好ましい。容量が小さいため過放電に至る期間短いので、本発明の構成とすることで過放電に至っても劣化が抑制されるため好ましい。 A battery having a nominal capacity of 5 mAh or more and 200 mAh or less is preferable. Since the capacity is small and the period until overdischarge is short, the configuration of the present invention is preferable because deterioration is suppressed even if overdischarge occurs.
負極に貼り付ける金属リチウム箔の容量は、負極活物質の炭素材の飽和可逆容量に対してその１．２％以上１１．０％以下が好ましい。１．２％以上１１．０％以下であることで、電池の過放電状態での負極の電位がリチウムに対し２．０Ｖ以上、３．２Ｖ以下となるため好ましい。１．２％未満では非常に長期にわたり過放電状態が継続された場合に、負極電位が徐々に上昇して３．４Ｖ以上に至る可能性があり、それにより負極の溶解析出が発生するため好ましくない。また、１１．０％を超えると、正極の電位が１．９Ｖ以下に至る可能性があり、それにより正極の劣化を引き起こすため好ましくない。 The capacity of the metal lithium foil attached to the negative electrode is preferably 1.2% or more and 11.0% or less with respect to the saturation reversible capacity of the carbon material of the negative electrode active material. It is preferable that it is 1.2% or more and 11.0% or less because the potential of the negative electrode in an overdischarged state of the battery is 2.0 V or more and 3.2 V or less with respect to lithium. If it is less than 1.2%, when the overdischarge state is continued for a very long time, the potential of the negative electrode may gradually rise to 3.4 V or more, which causes dissolution and precipitation of the negative electrode. Absent. On the other hand, if it exceeds 11.0%, the potential of the positive electrode may reach 1.9 V or less, thereby causing deterioration of the positive electrode.
以下、本発明に係る円筒形リチウムイオン二次電池の一実施の形態を、図面を参照しながら説明する。 Hereinafter, an embodiment of a cylindrical lithium ion secondary battery according to the present invention will be described with reference to the drawings.
図１に示すように、本発明の円筒形リチウムイオン二次電池１０は、有底円筒形の外装缶１１、外装缶１１内に収容された電極群１２、および外装缶１１を封止する封口板１４、絶縁ガスケット１３、上部リング３１を備えている。 As shown in FIG. 1, a cylindrical lithium ion secondary battery 10 of the present invention includes a bottomed cylindrical outer can 11, an electrode group 12 accommodated in the outer can 11, and a sealing for sealing the outer can 11. A plate 14, an insulating gasket 13, and an upper ring 31 are provided.
電極群１２は、負極１５と、正極１６と、負極１５と正極１６との間を隔離するセパレータ１７とを備えている。この電極群１２には非水電解質が接触している。 The electrode group 12 includes a negative electrode 15, a positive electrode 16, and a separator 17 that separates the negative electrode 15 from the positive electrode 16. The electrode group 12 is in contact with a nonaqueous electrolyte.
負極１５は、負極リード１８が接続されており、負極リード１８は外装缶１１と接続されている。これにより、負極１５は外装缶１１と電気的に接続されている。 A negative electrode lead 18 is connected to the negative electrode 15, and the negative electrode lead 18 is connected to the outer can 11. Thereby, the negative electrode 15 is electrically connected to the outer can 11.
外装缶１１の底面および側面の外側は外部に露出し、外部負極端子として用いられる。 The outer surface of the bottom surface and side surface of the outer can 11 is exposed to the outside and used as an external negative electrode terminal.
正極１６は、正極リード１９が接続されており、正極リード１９は封口板１４と接続されている。これにより、正極１６は封口板１４と電気的に接続されている。 A positive electrode lead 19 is connected to the positive electrode 16, and the positive electrode lead 19 is connected to the sealing plate 14. Thereby, the positive electrode 16 is electrically connected to the sealing plate 14.
図２、図３に示すように、正極１６は、正極集電体６２、および正極集電体６２の両面に形成された正極活物質層６１を有し、正極リード１９が接続されている。正極集電体６２の片面に形成された正極活物質層６１の厚みは３０μｍ以上、９０μｍ以下が好ましく、３０μｍ以上、７０μｍ以下がさらに好ましい。また、正極１６の総厚みは、８０μｍ以上、１８０μｍ以下が好ましい。 As shown in FIGS. 2 and 3, the positive electrode 16 includes a positive electrode current collector 62 and a positive electrode active material layer 61 formed on both surfaces of the positive electrode current collector 62, and the positive electrode lead 19 is connected thereto. The thickness of the positive electrode active material layer 61 formed on one surface of the positive electrode current collector 62 is preferably 30 μm or more and 90 μm or less, and more preferably 30 μm or more and 70 μm or less. The total thickness of the positive electrode 16 is preferably 80 μm or more and 180 μm or less.
正極集電体６２には、金属箔が用いられ、好ましくは、アルミニウム箔またはアルミニウム合金箔である。電池の小型化および正極集電体６２の強度の観点から、正極集電体６２は、厚み１０μｍ以上、５０μｍ以下が好ましい。 A metal foil is used for the positive electrode current collector 62, and preferably an aluminum foil or an aluminum alloy foil. From the viewpoint of downsizing of the battery and the strength of the positive electrode current collector 62, the positive electrode current collector 62 preferably has a thickness of 10 μm or more and 50 μm or less.
正極１６に含まれる正極活物質は、一般式ＬｉＭＯ２あるいはＬｉＭ２Ｏ４で表されるリチウム含有複合酸化物（但しＭはニッケル単独か、ニッケルの一部を他の遷移金属で置換した金属）を含む。 The positive electrode active material contained in the positive electrode 16 is a lithium-containing composite oxide represented by the general formula LiMO 2 or LiM 2 O 4 (where M is nickel alone or a part of nickel is substituted with another transition metal). including.
特に、電池の小型化および高エネルギー密度化の観点から、正極活物質には、一般式：ＬｉｘＮｉｙＭ１−ｙＯ２（式中、Ｍは、Ｎａ、Ｍｇ、Ｓｃ、Ｙ、Ｍｎ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｃｒ、Ｐｂ、ＳｂおよびＢからなる群より選ばれる少なくとも一種であり、０＜ｘ≦１．２、０．５＜ｙ≦１．０）で表されるリチウム含有複合酸化物を用いる
のが好ましい。
In particular, from the viewpoint of battery miniaturization and high energy density, the positive electrode active material includes a general formula: Li x Ni y M 1-y O 2 (where M is Na, Mg, Sc, Y, Mn , Fe, Co, Cu, Zn, Al, Cr, Pb, Sb and B, represented by 0 <x ≦ 1.2 and 0.5 <y ≦ 1.0) It is preferable to use a lithium-containing composite oxide.
また、同様に電池の小型化および高エネルギー密度化の観点から、正極活物質には、一般式：ＬｉｘＮｉｙＣｏｚＭ１−ｙ−ｚＯ２（式中、Ｍは、Ｍｇ、Ｂａ、Ａｌ、Ｔｉ、Ｓｒ、Ｃａ、Ｖ、Ｆｅ、Ｃｕ、Ｂｉ、Ｙ、Ｚｒ、Ｍｏ、Ｔｃ、Ｒｕ、Ｔａ、およびＷからなる群より選ばれる少なくとも一種であり、０．９≦ｘ≦１．２、０．３≦ｙ≦０．９、０．０５≦ｚ≦０．５、０．０１≦１−ｙ−ｚ≦０．３）で表されるリチウム含有複合酸化物を用いるのが好ましい。 Similarly, from the viewpoint of downsizing and high energy density of the battery, the positive electrode active material, the general formula: Li x Ni y Co z M 1-y-z O 2 ( where, M is, Mg, Ba , Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, and W, and at least 0.9 ≦ x ≦ 1. 2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3) is preferably used. .
正極結着剤としては、例えば、フッ素系樹脂、スチレン−ブタジエン系ゴム、フッ素系ゴム、ポリアクリル酸、またはポリフッ化ビニリデンが用いられる。 As the positive electrode binder, for example, fluorine resin, styrene-butadiene rubber, fluorine rubber, polyacrylic acid, or polyvinylidene fluoride is used.
正極結着剤を用いる場合、正極活物質中の正極結着剤の含有量は、正極活物質１００質量部あたり１〜５質量部であるのが好ましい。 When using a positive electrode binder, it is preferable that content of the positive electrode binder in a positive electrode active material is 1-5 mass parts per 100 mass parts of positive electrode active materials.
正極導電剤としては、例えば、グラファイト類、カーボンブラック類、炭素繊維、金属繊維、または導電性を有する有機材料が用いられる。 As the positive electrode conductive agent, for example, graphites, carbon blacks, carbon fibers, metal fibers, or conductive organic materials are used.
正極導電剤を用いる場合、正極活物質中の正極導電剤の含有量は、正極活物質１００質量部あたり０．５質量部以上、５質量部以下であるのが好ましい。 When the positive electrode conductive agent is used, the content of the positive electrode conductive agent in the positive electrode active material is preferably 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the positive electrode active material.
正極リード１９の材質としては、例えば、アルミニウムを用いるのが好ましく、チタンやニッケル等の金属を用いることもできる。 As the material of the positive electrode lead 19, for example, aluminum is preferably used, and a metal such as titanium or nickel can also be used.
図４に示すように、負極１５は、負極集電体５１および負極集電体５１の両面に形成された負極活物質層５２を有し、負極リード１８が接続されている。さらに、金属リチウム箔５３が、負極集電体の露出部に貼り付けられている。負極活物質層５２は位相差があってもよい。負極１５の総厚みは、８０μｍ以上、２５０μｍ以下が好ましい。 As shown in FIG. 4, the negative electrode 15 has a negative electrode current collector 51 and a negative electrode active material layer 52 formed on both surfaces of the negative electrode current collector 51, and the negative electrode lead 18 is connected thereto. Furthermore, the metal lithium foil 53 is affixed on the exposed part of the negative electrode current collector. The negative electrode active material layer 52 may have a phase difference. The total thickness of the negative electrode 15 is preferably 80 μm or more and 250 μm or less.
金属リチウム箔５３は、負極集電体５１の最外周側の露出部に貼り付けることが好ましく、最外周側の中心を向いた露出部に貼り付けることが好ましい。また、金属リチウム箔５３は、構成した電極群において、負極リード１８と共に電極群径に影響を与えない位置に貼り付けることが好ましい。例えば、図４に示すように、金属リチウム箔５３と負極リード１８が負極集電体５１を介して、表裏の位置で重ならないように貼り付けることが好ましい。 The metal lithium foil 53 is preferably attached to the exposed portion on the outermost peripheral side of the negative electrode current collector 51, and is preferably attached to the exposed portion facing the center on the outermost peripheral side. Moreover, it is preferable to affix the metal lithium foil 53 at a position that does not affect the electrode group diameter together with the negative electrode lead 18 in the configured electrode group. For example, as shown in FIG. 4, it is preferable that the metal lithium foil 53 and the negative electrode lead 18 are attached via the negative electrode current collector 51 so as not to overlap at the front and back positions.
負極集電体５１には、銅の金属箔が用いられる。負極集電体５１として銅を用いることにより、抵抗が低いため高出力が得られる。 A copper metal foil is used for the negative electrode current collector 51. By using copper as the negative electrode current collector 51, a high output can be obtained because the resistance is low.
負極１５に含まれる負極活物質は、リチウムイオン二次電池で使用可能な炭素材であればよく、特に限定されない。例えば、従来からリチウムイオン二次電池に用いられている天然黒鉛や人造黒鉛などの黒鉛材料、非晶質炭素材料などが挙げられる。 The negative electrode active material contained in the negative electrode 15 may be any carbon material that can be used in a lithium ion secondary battery, and is not particularly limited. Examples thereof include graphite materials such as natural graphite and artificial graphite conventionally used for lithium ion secondary batteries, and amorphous carbon materials.
負極結着剤は必要に応じて、例えば、スチレンブタジエンゴム、ポリフッ化ビニリデンなどを用いることができるが、これに限定されない。 As the negative electrode binder, for example, styrene butadiene rubber, polyvinylidene fluoride, and the like can be used, but are not limited thereto.
また、必要に応じて、増粘剤として、カルボキシメチルセルロースなどを用いることができるが、これに限定されない。 Moreover, carboxymethylcellulose etc. can be used as a thickener as needed, However, It is not limited to this.
負極リード１８の材質としては、銅やニッケル等の金属を用いることができる。 As a material of the negative electrode lead 18, a metal such as copper or nickel can be used.
負極リードの幅は、１ｍｍ以上、２ｍｍ以下が好ましく、１．５ｍｍ以下がさらに好ましい。１ｍｍ未満では、集電体への溶接において強度が不十分になるため好ましくなく、２．０ｍｍを超えると、群構成が困難になるため好ましくない。 The width of the negative electrode lead is preferably 1 mm or more and 2 mm or less, and more preferably 1.5 mm or less. If it is less than 1 mm, it is not preferable because the strength becomes insufficient in welding to the current collector, and if it exceeds 2.0 mm, it is not preferable because the group configuration becomes difficult.
また、負極リードの厚みは０．０５ｍｍ以上、０．１５ｍｍ以下が好ましく、０．１ｍｍ以下が特に好ましい。０．０５ｍｍ未満では、負極リリードの強度が不十分となるため好ましくなく、０．１５ｍｍを超えると、電極群の径の増大に寄与するため好ましくない。 Further, the thickness of the negative electrode lead is preferably 0.05 mm or more and 0.15 mm or less, and particularly preferably 0.1 mm or less. If it is less than 0.05 mm, the strength of the negative electrode relead becomes insufficient, which is not preferable, and if it exceeds 0.15 mm, it contributes to an increase in the diameter of the electrode group, which is not preferable.
非水電解液は、溶質および非水溶媒を含む。 The nonaqueous electrolytic solution includes a solute and a nonaqueous solvent.
溶質は、非水溶媒に溶解する支持塩である。支持塩としては、例えば、ヘキサフルオロリン酸リチウム（ＬｉＰＦ６）、過塩素酸リチウム（ＬｉＣｌＯ４）、テトラフルオロ硼酸リチウム（ＬｉＢＦ４）、トリフルオロメタンスルホン酸リチウム（ＬｉＣＦ３ＳＯ３）、リチウムビス（トリフルオロメチルスルホニル）イミド（ＬｉＮ（ＣＦ３ＳＯ２）２）、リチウムビス（ペンタフルオロエチルスルホニル）イミド（ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２）、リチウムビス（トリフルオロメチルスルホニル）（ペンタフルオロエチルスルホニル）イミド（ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ２Ｆ５ＳＯ２））、またはリチウムトリス（トリフルオロメチルスルホニル）メチド（ＬｉＣ（ＣＦ３ＳＯ２）３）が用いられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。 A solute is a supporting salt that dissolves in a non-aqueous solvent. Examples of the supporting salt include lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis ( Trifluoromethylsulfonyl) imide (LiN (CF 3 SO 2 ) 2 ), lithium bis (pentafluoroethylsulfonyl) imide (LiN (C 2 F 5 SO 2 ) 2 ), lithium bis (trifluoromethylsulfonyl) (pentafluoro Ethylsulfonyl) imide (LiN (CF 3 SO 2 ) (C 2 F 5 SO 2 )) or lithium tris (trifluoromethylsulfonyl) methide (LiC (CF 3 SO 2 ) 3 ) is used. These may be used alone or in combination of two or more.
非水溶媒としては、例えば、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ブチレンカーボネート（ＢＣ）、ビニレンカーボネート（ＶＣ）、ビニルエチレンカーボネート（ＶＥＣ）、１，２−ジメトキシエタン（ＤＭＥ）、１，２−ジエトキシエタン（ＤＥＥ）、γ‐ブチロラクトン（γ‐ＢＬ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、Ｎ，Ｎ−ジメチルホルムアミド、テトラヒドロフラン（ＴＨＦ）、２−メチルテトラヒドロフラン、ジメチルスルホキシド、ホルムアミド、アセトアミド、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、トリメトキシメタン、ジオキソラン、ジオキソラン誘導体、スルホラン、メチルスルホラン、プロピレンカーボネート誘導体、またはテトラヒドロフラン誘導体が用いられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。 Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,2-dimethoxyethane (DME), 1 , 2-diethoxyethane (DEE), γ-butyrolactone (γ-BL), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), N, N-dimethylformamide, tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide, formamide, acetamide, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, trimethoxymethane, dioxolane, dioxolane derivatives, sulfolane, methyl Rusulfolane, a propylene carbonate derivative, or a tetrahydrofuran derivative is used. These may be used alone or in combination of two or more.
また、例えば、液状電解質、ゲル状電解質、固体状電解質（高分子固体電解質）を非水電解液として用いてもよい。 Further, for example, a liquid electrolyte, a gel electrolyte, or a solid electrolyte (polymer solid electrolyte) may be used as the non-aqueous electrolyte.
セパレータ１７としては、例えば微多孔性の薄膜、織布、または不織布が用いられる。これらは、イオン透過度が大きく、適度な機械的強度および絶縁性を有することが好ましい。セパレータ１７の材質としては、例えば、ポリプロピレンおよびポリエチレンのようなポリオレフィンが挙げられる。 As the separator 17, for example, a microporous thin film, a woven fabric, or a non-woven fabric is used. These have a high ion permeability and preferably have an appropriate mechanical strength and insulating property. Examples of the material of the separator 17 include polyolefin such as polypropylene and polyethylene.
特に、ポリオレフィンからなる微多孔性の薄膜は、耐久性に優れ、一定の温度に上昇すると孔が閉塞する、いわゆるシャットダウン機能を有するため、リチウムイオン電池などのリチウムイオン二次電池用のセパレータとして好適に用いられる。 In particular, a microporous thin film made of polyolefin is excellent in durability and has a so-called shutdown function that closes the pores when the temperature rises to a certain temperature. Therefore, it is suitable as a separator for lithium ion secondary batteries such as lithium ion batteries. Used for.
セパレータの厚みは、一般的に１０μｍ以上、３００μｍ以下であるが、好ましくは４０μｍ以下、より好ましくは５μｍ以上、３０μｍ以下である。セパレータは、１種の材料からなる単層膜でもよく、２種以上の材料からなる複合膜または多層膜でもよい。 The thickness of the separator is generally 10 μm or more and 300 μm or less, preferably 40 μm or less, more preferably 5 μm or more and 30 μm or less. The separator may be a single layer film made of one material, or a composite film or multilayer film made of two or more materials.
絶縁ガスケット１３の材質には、例えば、ポリプロピレン、ポリエチレン、ポリフェニレンサルファイド、ポリエーテルエーテルケトン、ポリアミド、ポリイミド、ポリテトラフルオロエチレン、液晶ポリマー、パーフルオロアルコキシエチレンの共重合体が用いられる。これらを単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらを、無機繊維などのフィラーと組み合わせて用いてもよい。絶縁ガスケットは、電池の気密性を高めるために、シール材でコーティングしてもよい。 As the material of the insulating gasket 13, for example, a copolymer of polypropylene, polyethylene, polyphenylene sulfide, polyether ether ketone, polyamide, polyimide, polytetrafluoroethylene, liquid crystal polymer, and perfluoroalkoxyethylene is used. These may be used alone or in combination of two or more. You may use these in combination with fillers, such as an inorganic fiber. The insulating gasket may be coated with a sealing material to increase the airtightness of the battery.
上記実施形態の電極材料および電解液の組成は特に限定されず、公知の材料および組成を適宜選択すればよい。 The composition of the electrode material and the electrolytic solution in the above embodiment is not particularly limited, and known materials and compositions may be appropriately selected.
以下、本発明の実施例を詳細に説明するが、本発明は、これらの実施例に限定されない。 Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.
（実施例１）
以下の手順に従って、図１に示す円筒形リチウムイオン二次電池１０を作製した。
Example 1
The cylindrical lithium ion secondary battery 10 shown in FIG. 1 was produced according to the following procedure.
（１）正極の作製
正極活物質としてニッケル酸リチウム１００質量部、導電剤としてアセチレンブラック４質量部、および結着剤としてポリフッ化ビニリデン４質量部に、分散媒としてＮ−メチル−２−ピロリドン（ＮＭＰ）を加え、正極スラリーを調製した。この正極スラリーを正極集電体（厚み１５μｍ）の両面に塗布し、乾燥後、圧延して、正極１６（厚み０．１４ｍｍ）を得た。
(1) Production of positive electrode 100 parts by mass of lithium nickelate as a positive electrode active material, 4 parts by mass of acetylene black as a conductive agent, 4 parts by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone (as a dispersion medium) NMP) was added to prepare a positive electrode slurry. This positive electrode slurry was applied to both surfaces of a positive electrode current collector (thickness: 15 μm), dried and rolled to obtain positive electrode 16 (thickness: 0.14 mm).
正極１６は、作製時に、正極活物質層を有しない領域（正極集電体が露出する部分）を設け、正極リード１９を接続し、図２および図３に示すような構成とした。 The positive electrode 16 was provided with a region having no positive electrode active material layer (portion where the positive electrode current collector was exposed) at the time of production, and connected to the positive electrode lead 19 to have a configuration as shown in FIGS.
（２）負極の作製
図４に示す負極１５を作製した。図４は負極１５の巻き内側面の平面図である。負極活物質として人造黒鉛粉末１００質量部、結着剤として日本ゼオン製スチレン−メタクリル酸−ブタジエン共重合体を１質量部、増粘剤としてカルボキシメチルセルロース（ＣＭＣ）１質量部を混合し、これらを脱イオン水に分散させてスラリーを作製した。負極集電体５１（厚み１０μｍ）上の両面に塗布し、乾燥後、圧延して、負極１５（厚み０．１５ｍｍ）を得た。
(2) Production of negative electrode A negative electrode 15 shown in FIG. 4 was produced. FIG. 4 is a plan view of the wound inner side surface of the negative electrode 15. 100 parts by mass of artificial graphite powder as a negative electrode active material, 1 part by mass of styrene-methacrylic acid-butadiene copolymer manufactured by Nippon Zeon as a binder, and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener are mixed. A slurry was prepared by dispersing in deionized water. It apply | coated to both surfaces on the negative electrode collector 51 (thickness 10 micrometers), and after drying, it rolled and obtained the negative electrode 15 (thickness 0.15 mm).
なお、負極作製時に、負極１５の一方の端部の片面（電極群の最内周における巻回の内側）には、負極活物質層５２を有しない領域（負極集電体５１が露出する部分）を設けた。また、他方の端部は、負極集電体５１の両面に、負極活物質層５２を有しない領域（負極集電体５１が露出する部分）を設け、負極リード１８を接続した。負極リード１８は幅１．５ｍｍ、厚み０．１ｍｍを用いた。 In addition, at the time of producing the negative electrode, a region having no negative electrode active material layer 52 (a portion where the negative electrode current collector 51 is exposed) is formed on one surface of one end of the negative electrode 15 (inside the winding on the innermost circumference of the electrode group). ). In addition, the other end portion was provided with a region not having the negative electrode active material layer 52 (portion where the negative electrode current collector 51 was exposed) on both surfaces of the negative electrode current collector 51, and the negative electrode lead 18 was connected thereto. The negative electrode lead 18 had a width of 1.5 mm and a thickness of 0.1 mm.
また、負極活物質層５２を有しない領域で、正極１６と対向せず、構成した電極群において、負極リード１８と共に電極群径に影響を与えない位置に金属リチウム箔５３を貼り付けた。貼り付けた金属リチウム箔５３の容量は炭素材の飽和可逆容量に対し４．９％とした。金属リチウム箔５３の寸法は、幅（巻回方向と垂直方向）１２ｍｍ、長さ（巻回方向）１ｍｍ、厚み０．１ｍｍとした。 Further, in a region where the negative electrode active material layer 52 is not provided, the metal lithium foil 53 is pasted at a position which does not face the positive electrode 16 and does not affect the diameter of the electrode group together with the negative electrode lead 18 in the configured electrode group. The capacity of the attached metal lithium foil 53 was 4.9% with respect to the saturation reversible capacity of the carbon material. The dimensions of the metal lithium foil 53 were 12 mm in width (direction perpendicular to the winding direction), 1 mm in length (winding direction), and 0.1 mm in thickness.
なお、負極の飽和可逆容量は以下の要領によって算出した。正極活物質として炭素材料を、負極活物質としてリチウム金属をそれぞれ用い、２０℃において、電流密度０．５ｍＡ／ｃｍ２の定電流充放電を上限１．０Ｖから下限０Ｖの間で、５サイクル繰り返した。
このときの可逆容量を飽和可逆容量とした。
The saturation reversible capacity of the negative electrode was calculated according to the following procedure. A carbon material is used as the positive electrode active material and lithium metal is used as the negative electrode active material, and constant current charge / discharge at a current density of 0.5 mA / cm 2 is repeated 5 cycles between an upper limit of 1.0 V and a lower limit of 0 V at 20 ° C. It was.
The reversible capacity at this time was defined as a saturated reversible capacity.
（３）電極群の作製
巻芯を用い、巻芯のスリット部にセパレータを挟み込み、折り返して、２枚の構成とし、正極、セパレータ、負極、セパレータが順次重なり、正極合剤形成部と負極合剤形成部が対向するようにして、巻芯を中心にして巻回し、電極群を構成した。巻き終わりは、テープを貼り付け、群を固定した。
(3) Production of electrode group Using a winding core, the separator is sandwiched between the slits of the winding core and folded to form two sheets. The electrode group was configured by winding around the core such that the agent forming portions face each other. At the end of winding, tape was applied to fix the group.
（４）電解液の調製
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）の混合溶媒に、ＬｉＰＦ６を溶解させて、非水電解液を得た。ＥＣおよびＥＭＣの質量比は、１：１とした。非水電解液中のＬｉＰＦ６の濃度は１．０ｍｏｌ／Ｌとした。
(4) Preparation of Electrolytic Solution LiPF 6 was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) to obtain a nonaqueous electrolytic solution. The mass ratio of EC and EMC was 1: 1. The concentration of LiPF 6 in the non-aqueous electrolyte was 1.0 mol / L.
（５）円筒形リチウムイオン電池の作製
構成した電極群１２を外装缶１１に挿入し、負極リード１８と外装缶１１を接続した。続いて、正極リード１９と封口板１４を接続した。外装缶１１内に、電解液を注液し、封口して電池とした。このようにして、公称容量３５ｍＡｈの円筒形リチウムイオン二次電池１０（直径３．５ｍｍ、高さ３５ｍｍ）を得た。
(5) Production of Cylindrical Lithium Ion Battery The configured electrode group 12 was inserted into the outer can 11 and the negative electrode lead 18 and the outer can 11 were connected. Subsequently, the positive electrode lead 19 and the sealing plate 14 were connected. An electrolyte solution was poured into the outer can 11 and sealed to obtain a battery. In this way, a cylindrical lithium ion secondary battery 10 (diameter 3.5 mm, height 35 mm) having a nominal capacity of 35 mAh was obtained.
（実施例２）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し１．２％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）３ｍｍ、長さ（巻回方向）１ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Example 2)
The capacity of the metal lithium foil attached to the negative electrode current collector was 1.2% with respect to the saturation reversible capacity of the carbon material. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a width (winding direction and perpendicular direction) of 3 mm, a length (winding direction) of 1 mm, and a thickness of 0.1 mm.
（実施例３）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し２．４％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）６ｍｍ、長さ（巻回方向）１ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Example 3)
The capacity of the metal lithium foil attached to the negative electrode current collector was 2.4% with respect to the saturation reversible capacity of the carbon material. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a width (direction perpendicular to the winding direction) of 6 mm, a length (winding direction) of 1 mm, and a thickness of 0.1 mm.
（実施例４）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し７．３％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）６ｍｍ、長さ（巻回方向）３ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
Example 4
The capacity of the metal lithium foil attached to the negative electrode current collector was 7.3% with respect to the saturation reversible capacity of the carbon material. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a width (winding direction and perpendicular direction) of 6 mm, a length (winding direction) of 3 mm, and a thickness of 0.1 mm.
（実施例５）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し１１．０％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）９ｍｍ、長さ（巻回方向）３ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Example 5)
The capacity of the metal lithium foil attached to the negative electrode current collector was 11.0% with respect to the saturation reversible capacity of the carbon material. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a width (direction perpendicular to the winding direction) of 9 mm, a length (winding direction) of 3 mm, and a thickness of 0.1 mm.
（実施例６）
負極集電体に金属リチウム箔を貼り付けずに電極群を構成した。また、外装缶に電極群を挿入する前に、外装缶内の壁面であって、外装缶の底部から中部にかけて、炭素材の飽和可逆容量に対し４．９％の容量の金属リチウム箔を貼り付けた。金属リチウム箔の寸法は、長さ（電池の高さ方向）１６ｍｍ、幅（電池の高さと垂直方向）１ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Example 6)
An electrode group was formed without attaching a metal lithium foil to the negative electrode current collector. In addition, before inserting the electrode group into the outer can, a metal lithium foil having a capacity of 4.9% with respect to the saturation reversible capacity of the carbon material is applied to the wall surface in the outer can from the bottom to the middle. I attached. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a length (battery height direction) of 16 mm, a width (battery height and vertical direction) of 1 mm, and a thickness of 0.1 mm. .
（比較例１）
負極集電体に金属リチウム箔を貼り付けずに電極群を構成した以外、実施例１と同様の方法により、電池を作製した。
(Comparative Example 1)
A battery was produced in the same manner as in Example 1 except that the electrode group was formed without attaching a metal lithium foil to the negative electrode current collector.
（比較例２）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し０．８％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）２ｍｍ、長さ（巻回方向）１ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Comparative Example 2)
The capacity of the metal lithium foil attached to the negative electrode current collector was 0.8% with respect to the saturation reversible capacity of the carbon material. A battery was produced in the same manner as in Example 1, except that the metal lithium foil had a width (direction perpendicular to the winding direction) of 2 mm, a length (winding direction) of 1 mm, and a thickness of 0.1 mm.
（比較例３）
負極集電体に貼り付けた金属リチウム箔の容量は炭素材の飽和可逆容量に対し１４．７％とした。金属リチウム箔の寸法は、幅（巻回方向と垂直方向）１２ｍｍ、長さ（巻回方向）３ｍｍ、厚み０．１ｍｍとした以外、実施例１と同様の方法により、電池を作製した。
(Comparative Example 3)
The capacity of the metal lithium foil attached to the negative electrode current collector was 14.7% with respect to the saturation reversible capacity of the carbon material. A battery was fabricated in the same manner as in Example 1, except that the metal lithium foil had a width (direction perpendicular to the winding direction) of 12 mm, a length (winding direction) of 3 mm, and a thickness of 0.1 mm.
（Ａ）正極および負極の単極電位の確認
以上の実施例１から実施例６および比較例１、比較例２の電極群を３個ずつ構成し、リチウム金属を参照電極として、３極式セルを構成した。
(A) Confirmation of the monopolar potential of the positive electrode and the negative electrode The three electrode groups of the above-described Example 1 to Example 6, Comparative Example 1, and Comparative Example 2 are configured, and lithium metal is used as a reference electrode. Configured.
（Ｂ）初期容量の確認
以上のようにして作製した実施例および比較例の電池を３個ずつと、（Ａ）で作製した３極式セルの３個ずつを、下記（１）〜（４）の順に充放電した。
（１）０．０５Ｉｔの定電流で４時間充電した後、電池の閉路電圧が２．５Ｖに達するまで０．０５Ｃの定電流で放電した。
（２）電池の閉路電圧が４．１Ｖに達するまで０．１Ｉｔの定電流で充電した後、電池の閉路電圧が２．５Ｖに達するまで０．１Ｉｔの定電流で放電した。
（３）電池の閉路電圧が４．１Ｖに達するまで０．１Ｉｔの定電流で充電した後、電池の閉路電圧が２．５Ｖに達するまで０．１Ｉｔの定電流で放電した。
（４）電池の閉路電圧が４．２Ｖに達するまで０．１Ｉｔの定電流で充電した後、電池の閉路電圧が２．５Ｖに達するまで０．１Ｉｔの定電流で放電した。
(B) Confirmation of initial capacity Three batteries of the examples and comparative examples prepared as described above and three of the three-electrode cells prepared in (A) were respectively prepared in the following (1) to (4 ) In this order.
(1) After charging for 4 hours at a constant current of 0.05 It, the battery was discharged at a constant current of 0.05 C until the closed circuit voltage of the battery reached 2.5V.
(2) After charging with a constant current of 0.1 It until the closed circuit voltage of the battery reached 4.1 V, the battery was discharged with a constant current of 0.1 It until the closed circuit voltage of the battery reached 2.5 V.
(3) After charging with a constant current of 0.1 It until the closed circuit voltage of the battery reached 4.1 V, the battery was discharged with a constant current of 0.1 It until the closed circuit voltage of the battery reached 2.5 V.
(4) After charging with a constant current of 0.1 It until the closed circuit voltage of the battery reached 4.2 V, the battery was discharged with a constant current of 0.1 It until the closed circuit voltage of the battery reached 2.5 V.
なお、Ｉｔは時間率を表す。設計容量Ｃ（ｍＡｈ）に相当する電気量を時間ｔ（時間）で流す場合、電流値Ｉ（ｍＡ）はＣ／ｔと表される。 In addition, It represents a time rate. When an amount of electricity corresponding to the design capacity C (mAh) is supplied at time t (time), the current value I (mA) is expressed as C / t.
上記（４）の放電において、放電電圧をモニタリングし、放電容量を確認した。全ては良品であり、この時の放電容量を初期容量とした。 In the discharge of (4) above, the discharge voltage was monitored to confirm the discharge capacity. All were good products, and the discharge capacity at this time was defined as the initial capacity.
（Ｃ）耐過放電特性評価
２０℃の環境下において、０．２Ｉｔで放電し、電池電圧が０Ｖに至ったのち、６２０Ωの抵抗を接続し、電池を０Ｖで保持した。
(C) Overdischarge resistance evaluation Under an environment of 20 ° C., the battery was discharged at 0.2 It, and after the battery voltage reached 0 V, a 620Ω resistor was connected, and the battery was held at 0 V.
１０日後に３極セルにて、正極と負極の単極電位をモニターした。（表１）に、モニターした３個の３極式セルの単極電位の平均を示す。 Ten days later, the monopolar potential of the positive electrode and the negative electrode was monitored in a tripolar cell. Table 1 shows the average unipolar potential of the three monitored tripolar cells.
また、６０日後に、上記（４）の条件にて充放電し、放電電圧をモニタリングすることにより、放電容量を確認し、回復容量とした。（表１）に、確認した３個の電池の初期の容量に対する回復容量の比率を平均で示す。 In addition, after 60 days, charging / discharging was performed under the above condition (4), and the discharge voltage was monitored to confirm the discharge capacity, which was taken as the recovery capacity. In Table 1, the ratio of the recovery capacity to the initial capacity of the three confirmed batteries is shown as an average.
なお、比較例１では６０日後に３個のうち１個が内部短絡のため、回復容量は得られなかった。内部短絡した電池を分解したところ、正極側に銅の析出が確認された。 In Comparative Example 1, a recovery capacity could not be obtained because one of the three was internally shorted after 60 days. When the internally short-circuited battery was disassembled, copper deposition was confirmed on the positive electrode side.
表１に示すように、本発明の実施例１から実施例６では、２０℃の環境下において、０．２Ｉｔで放電し、電池電圧が０Ｖに至り、電池が０Ｖで保持された１０日後に、負極の電位がリチウムに対し２．０Ｖ以上、３．２Ｖ以下であった。一方、比較例１では３．４Ｖ以上であり、比較例２では１．８９Ｖであった。 As shown in Table 1, in Examples 1 to 6 of the present invention, discharge was performed at 0.2 It in a 20 ° C. environment, the battery voltage reached 0 V, and 10 days after the battery was held at 0 V. The potential of the negative electrode was 2.0 V or more and 3.2 V or less with respect to lithium. On the other hand, in Comparative Example 1, it was 3.4 V or higher, and in Comparative Example 2, it was 1.89 V.
また、６０日後の初期に対する回復容量は、本発明の実施例１から実施例５では、６０％以上であったのに対し、比較例２および３では５４．８％以下と大きく低下しており、比較例１では３個のうち１個が内部短絡していた。実施例１から実施例６では、過放電時の正極及び負極の電位が両者の安定な電位範囲にあったために良好な耐過放電特性を示したと考えられる。 Further, the recovery capacity with respect to the initial value after 60 days was 60% or more in Examples 1 to 5 of the present invention, whereas it was greatly reduced to 54.8% or less in Comparative Examples 2 and 3. In Comparative Example 1, one of the three was internally short-circuited. In Examples 1 to 6, it is considered that the positive and negative electrode potentials at the time of overdischarge were in a stable potential range of both, and thus excellent overdischarge characteristics were exhibited.
一方、比較例１では負極の電位が上昇し、３．４Ｖ以上に到ったことにより、負極集電体の銅が溶解析出し、内部短絡が発生したと考えられる。
また、比較例２では、過放電状態が継続された期間に、負極電位が徐々に上昇して３．４Ｖ以上に至った可能性があり、負極集電体の銅が溶出し、内部短絡には至らなかったが、負極の抵抗が増大し、容量が大きく低下したと考えられる。
On the other hand, in Comparative Example 1, the potential of the negative electrode increased and reached 3.4 V or higher, so that it was considered that copper of the negative electrode current collector was dissolved and precipitated and an internal short circuit occurred.
Further, in Comparative Example 2, there is a possibility that the negative electrode potential gradually increased to 3.4 V or more during the period in which the overdischarge state was continued, and the copper of the negative electrode current collector was eluted, causing an internal short circuit. However, it is considered that the resistance of the negative electrode increased and the capacity greatly decreased.
比較例３では、正極の電位が１．８９Ｖまで低下したことにより、正極の結晶構造の変化が進行し、容量が大きく低下したと考えられる。 In Comparative Example 3, it is considered that since the potential of the positive electrode decreased to 1.89 V, the change in the crystal structure of the positive electrode progressed and the capacity significantly decreased.
本発明の電池は、各種の電子機器、特に、各種の携帯型電子機器における電源として好適に用いることができる。 The battery of the present invention can be suitably used as a power source in various electronic devices, in particular, various portable electronic devices.
１０ 円筒形リチウムイオン二次電池
１１ 外装缶
１２ 電極群
１３ 絶縁ガスケット
１４ 封口板
１５ 負極
１６ 正極
１７ セパレータ
１８ 負極リード
１９ 正極リード
３１ 上部リング
５１ 負極集電体
５２ 負極活物質層
５３ 金属リチウム箔
６１ 正極活物質層
６２ 正極集電体
DESCRIPTION OF SYMBOLS 10 Cylindrical lithium ion secondary battery 11 Exterior can 12 Electrode group 13 Insulation gasket 14 Sealing plate 15 Negative electrode 16 Positive electrode 17 Separator 18 Negative electrode lead 19 Positive electrode lead 31 Upper ring 51 Negative electrode current collector 52 Negative electrode active material layer 53 Metal lithium foil 61 Positive electrode active material layer 62 Positive electrode current collector
Claims (5)
前記負極、または前記外装缶には、金属リチウム箔を貼付し、電位差あるいは濃度差により前記リチウムを前記炭素材中に拡散させ、
０．２Ｉｔで放電し、電池電圧が０Ｖに至り、電池が０Ｖで保持された１０日後に、前記負極の電位がリチウムに対し２．０Ｖ以上、３．２Ｖ以下である円筒形リチウムイオン二次電池。 A positive electrode containing a lithium-containing composite oxide represented by the general formula LiMO 2 or LiM 2 O 4 as a positive electrode active material (where M is nickel alone or a metal in which a part of nickel is substituted with another transition metal), and a negative electrode An electrode group formed by placing a carbon material as an active material and a negative electrode using copper as a negative electrode current collector, and facing each other through a separator, is housed in an outer can together with a non-aqueous electrolyte, An outer can and the negative electrode current collector are electrically connected and sealed cylindrical lithium ion secondary battery,
A metal lithium foil is attached to the negative electrode or the outer can, and the lithium is diffused into the carbon material by a potential difference or a concentration difference.
Cylindrical lithium ion secondary in which the potential of the negative electrode is 2.0 V or more and 3.2 V or less with respect to lithium 10 days after discharging at 0.2 It, the battery voltage reaches 0 V, and the battery is held at 0 V battery.
前記金属リチウム箔は、前記負極集電体の露出部に貼付し、電位差あるいは濃度差により前記リチウムを炭素材中に拡散させたことを特徴とする請求項１記載の円筒形リチウムイオン二次電池。 The negative electrode current collector is provided with an exposed portion on the outermost periphery side,
2. The cylindrical lithium ion secondary battery according to claim 1, wherein the metal lithium foil is attached to an exposed portion of the negative electrode current collector, and the lithium is diffused into the carbon material by a potential difference or a concentration difference. .
前記負極集電体は、負極リードが電気的に接続されており、
前記金属リチウム箔の厚みは前記負極リードの厚み以下であり、幅は外装缶の内径円周の１／３以下であることを特徴とする請求項１または２に記載の円筒形リチウムイオン二次電池。 The radius of curvature of the outermost periphery of the electrode group is 3.0 mm or less,
The negative electrode current collector has a negative electrode lead electrically connected thereto,
3. The cylindrical lithium ion secondary according to claim 1, wherein the thickness of the metal lithium foil is equal to or less than the thickness of the negative electrode lead, and the width is equal to or less than ３ of the inner circumference of the outer can. battery.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113078423A (en) * | 2021-03-30 | 2021-07-06 | 国联汽车动力电池研究院有限责任公司 | Voltage-temperature coupling measurement method and device |
| US11121374B2 (en) | 2017-11-30 | 2021-09-14 | Lg Chem, Ltd. | Positive electrode for lithium secondary battery and lithium secondary battery including same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US11121374B2 (en) | 2017-11-30 | 2021-09-14 | Lg Chem, Ltd. | Positive electrode for lithium secondary battery and lithium secondary battery including same |
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| CN113078423A (en) * | 2021-03-30 | 2021-07-06 | 国联汽车动力电池研究院有限责任公司 | Voltage-temperature coupling measurement method and device |
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