JP2015022896A - Method for manufacturing secondary battery - Google Patents

Method for manufacturing secondary battery Download PDF

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JP2015022896A
JP2015022896A JP2013150031A JP2013150031A JP2015022896A JP 2015022896 A JP2015022896 A JP 2015022896A JP 2013150031 A JP2013150031 A JP 2013150031A JP 2013150031 A JP2013150031 A JP 2013150031A JP 2015022896 A JP2015022896 A JP 2015022896A
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positive electrode
internal pressure
mixture composition
secondary battery
lithium
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史嵩 下舘
Fumitaka Shimodate
史嵩 下舘
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Toyota Motor Corp
Primearth EV Energy Co Ltd
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Primearth EV Energy Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a secondary battery by which a secondary battery arranged so that gas generation at normal time is preferably suppressed by providing a positive electrode including an internal pressure-suppressing agent can be manufactured in a simple and convenient way.SOLUTION: A method for manufacturing a secondary battery comprises at least the steps of: preparing a positive electrode mixture composition which includes a positive electrode active material, a binding agent, an internal pressure-suppressing agent, and solvent; applying the positive electrode mixture composition to a surface of a positive electrode current collector; and drying the positive electrode mixture composition to prepare a positive electrode. The internal pressure-suppressing agent contains at least one of lithium hydroxide (LiOH) and lithium oxide (LiO). In the positive electrode mixture composition, the percentage of solid components except the solvent is 80 mass% or larger.

Description

本発明は、二次電池の製造方法に関し、より詳しくは、正極活物質層に内圧抑制剤を含む二次電池の製造方法に関する。   The present invention relates to a method for manufacturing a secondary battery, and more particularly to a method for manufacturing a secondary battery including an internal pressure inhibitor in a positive electrode active material layer.

リチウムイオン電池等の二次電池は、既存の電池に比べて軽量かつエネルギー密度が高い電池を実現し得ることから、車両搭載用高出力電源等に好ましく利用されている。
かかる二次電池において、特に２０Ａｈ程度以上の大容量のものは多くのエネルギーを蓄え得るため、安全性を確実に高める対策が重要視されている。例えば、二次電池は、一般に所定の電圧領域（例えば、３．０Ｖ以上４．２Ｖ以下等）に収まるよう制御された状態で使用されるが、例えば、誤操作等により所定の電圧を超えて過充電状態に陥ることがあり得る。一般に、電池が過充電状態になると、電解液が分解されてガスが発生する。 Secondary batteries such as lithium-ion batteries are preferably used for vehicle-mounted high-output power supplies and the like because they can realize batteries that are lighter and have a higher energy density than existing batteries.
Among such secondary batteries, particularly those having a large capacity of about 20 Ah or more can store a large amount of energy, and therefore, measures for reliably increasing safety are regarded as important. For example, a secondary battery is generally used in a state where it is controlled so as to be within a predetermined voltage range (for example, 3.0 V or more and 4.2 V or less, etc.). It can fall into a charged state. Generally, when a battery is overcharged, the electrolyte is decomposed and gas is generated.

そこで、かかる過充電の進行を停止するために、電池ケースの内圧が所定値以上になると充電電流を遮断する電流遮断機構（ＣＩＤ）を備えた電池が提案されている。かかる電流遮断機構は、ガスの発生を圧力により検知して電池の充電経路を切断する。また、例えば、電池ケース内に電解質の分解に起因するＣＯ２等のガスの発生を抑制する目的で、電解液や正極活物質に酸化リチウムや水酸化リチウム等を配合することがなされてもいる（例えば、特許文献１および２参照）。かかる酸化リチウムや水酸化リチウムは、ＣＯ２等のガスを吸収することで、電池ケースの内圧が上昇するのを抑制する内圧抑制剤として機能すると考えられる。 Therefore, in order to stop the progress of such overcharging, a battery having a current interruption mechanism (CID) that interrupts the charging current when the internal pressure of the battery case becomes a predetermined value or more has been proposed. Such a current interrupting mechanism detects the generation of gas by pressure and cuts the charging path of the battery. Further, for example, lithium oxide, lithium hydroxide, or the like has been added to the electrolytic solution or the positive electrode active material for the purpose of suppressing generation of gas such as CO 2 due to decomposition of the electrolyte in the battery case. (For example, refer to Patent Documents 1 and 2). Such lithium oxide and lithium hydroxide are considered to function as an internal pressure suppressing agent that suppresses an increase in the internal pressure of the battery case by absorbing a gas such as CO 2 .

特開２００１−３４５１１８号公報JP 2001-345118 A 特開２００６−１７３０４９号公報JP 2006-173049 A 特開２０１２−１７４５６９号公報JP 2012-174469 A 特開２０１３−０７３７４９号公報JP 2013-073749 A

しかしながら、上記のような高容量の二次電池については、通常の充放電に際しても比較的多量のＣＯ２等のガスが発生し、電池の内圧が上昇し得る。そのため、ＣＩＤが備えられた構成の二次電池においては、通常の充放電時にＣＩＤが作動することの無いよう、ＣＩＤの作動圧を高目に設定することがなされている。しかしながら、ＣＩＤの作動圧を高く設定することは、異常時にＣＩＤが作動するまでの時間を遅延させることとなり、かかるＣＩＤの作動の遅延により電池温度が急激に上昇する可能性が生じるなど、安全性の低下に繋がり得るものとなっていた。 However, in the case of a secondary battery having a high capacity as described above, a relatively large amount of gas such as CO 2 is generated even during normal charging / discharging, and the internal pressure of the battery can be increased. Therefore, in a secondary battery having a configuration provided with a CID, the operating pressure of the CID is set high so that the CID does not operate during normal charge / discharge. However, setting the operating pressure of the CID high will delay the time until the CID operates in the event of an abnormality, and the delay in the operation of the CID may cause the battery temperature to rise rapidly. It was possible to lead to a decline.

一方で、内圧抑制剤である酸化リチウムおよび水酸化リチウムは溶媒に触れることで容易に電離し得る。そのため、かかる内圧抑制剤が電解液に配合されるとＣＯ２等のガス発生を抑制する効果が低くなりがちとなる。そのため、内圧抑制剤は、ガスが発生する正極に配合されることがより望ましい。しかしながら、酸化リチウムおよび水酸化リチウムは、正極の製造に際し、正極合材組成物中で電離して水酸化物イオンを生成し、正極合材組成物をゲル化させ、塗工を困難にするという問題があった（例えば、特許文献４参照）。そのため、例えば特許文献１の開示のように、酸化リチウムおよび水酸化リチウムが正極活物質に留まるように、煩雑な工程により酸化リチウムおよび水酸化リチウムを正極活物質に一体化させるなどの対策が必要があった。 On the other hand, lithium oxide and lithium hydroxide, which are internal pressure inhibitors, can be easily ionized by touching a solvent. Therefore, when such an internal pressure inhibitor is blended in the electrolyte, the effect of suppressing the generation of gas such as CO 2 tends to be low. Therefore, it is more desirable that the internal pressure suppressing agent is blended in the positive electrode that generates gas. However, lithium oxide and lithium hydroxide are ionized in the positive electrode mixture composition to produce hydroxide ions during the production of the positive electrode, causing the positive electrode mixture composition to gel, making coating difficult. There was a problem (see, for example, Patent Document 4). Therefore, for example, as disclosed in Patent Document 1, it is necessary to take measures such as integrating lithium oxide and lithium hydroxide into the positive electrode active material through complicated steps so that lithium oxide and lithium hydroxide remain in the positive electrode active material. was there.

本発明はかかる状況を鑑みて創出されたものであり、その目的は、内圧抑制剤を配設した正極を備えることで通常時のガス発生が好適に抑制されている二次電池を、簡便に製造することができる二次電池の製造方法を提供することである。   The present invention has been created in view of such a situation, and its purpose is to provide a secondary battery in which normal gas generation is suitably suppressed by including a positive electrode provided with an internal pressure inhibitor. It is providing the manufacturing method of the secondary battery which can be manufactured.

本発明は、上記課題を解決するべく、正極および負極を備える二次電池の製造方法を提供する。かかる製造方法は、少なくとも正極活物質と結着剤と内圧抑制剤と溶剤とを含む正極合材組成物を調製すること、および、上記正極合材組成物を正極集電体の表面に塗工し乾燥させて正極を用意すること、を包含する。そして、上記内圧抑制剤は、水酸化リチウム（ＬｉＯＨ）および酸化リチウム（Ｌｉ２Ｏ）の少なくとも１つを含み、上記正極合材組成物における上記溶剤以外の固形分の割合は８０質量％以上であることを特徴としている。
かかる構成によると、正極合材組成物における上記溶剤の割合が２０質量％以下と少量に抑えられているため、かかる組成物に内圧抑制剤を単独で配合しても電離が効果的に抑制され得る。したがって、正極合材組成物はゲル化し難く、塗工により簡便に正極を製造することができる。 In order to solve the above-described problems, the present invention provides a method for manufacturing a secondary battery including a positive electrode and a negative electrode. Such a manufacturing method includes preparing a positive electrode mixture composition containing at least a positive electrode active material, a binder, an internal pressure inhibitor, and a solvent, and coating the positive electrode mixture composition on the surface of the positive electrode current collector. And preparing a positive electrode by drying. Then, the pressure suppression agent comprises at least one of lithium hydroxide (LiOH) and lithium oxide (Li 2 O), the proportion of solid other than the above solvent component in the positive electrode material composition is 80 wt% or more It is characterized by being.
According to this configuration, since the proportion of the solvent in the positive electrode mixture composition is suppressed to a small amount of 20% by mass or less, ionization is effectively suppressed even if an internal pressure suppressor is added alone to such a composition. obtain. Therefore, the positive electrode mixture composition is hardly gelled, and the positive electrode can be easily produced by coating.

なお、ここに開示される製造方法においては、上記正極活物質としてリチウム複合金属酸化物を用い、上記リチウム複合金属酸化物に含まれるリチウム以外の金属元素の総モル数に対する、Ｌｉ２Ｏに換算した場合の上記内圧抑制剤のモル比が、０を超えて０．８以下となるように上記正極合材組成物を調製するのが好ましい。
かかる構成によると、内圧抑制剤の低下による抵抗の増大を抑えつつ、ガス発生の抑制効果がバランスよく得られる、適切な量の内圧抑制剤を正極に配合することができる。 In the production method disclosed herein, lithium composite metal oxide is used as the positive electrode active material, and converted to Li 2 O with respect to the total number of moles of metal elements other than lithium contained in the lithium composite metal oxide. In this case, it is preferable to prepare the positive electrode mixture composition so that the molar ratio of the internal pressure inhibitor exceeds 0 and becomes 0.8 or less.
According to such a configuration, an appropriate amount of an internal pressure inhibitor that can provide a well-balanced effect of suppressing gas generation while suppressing an increase in resistance due to a decrease in the internal pressure inhibitor can be blended in the positive electrode.

高充電状態で保存した二次電池のガス発生量を例示した図である。It is the figure which illustrated the gas generation amount of the secondary battery preserve | saved in the high charge state. 保存３６日目におけるガス発生量と２５℃内部抵抗とを、内圧抑制剤の配合量との関係で例示した図である。It is the figure which illustrated the gas generation amount and 25 degreeC internal resistance in the 36th preservation | save day by the relationship with the compounding quantity of an internal pressure inhibitor.

以下、本発明の好適な実施形態を説明する。なお、本明細書において特に言及している事項以外の事柄であって実施に必要な事柄は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。   Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

ここで開示される製造方法は、内圧抑制剤としての水酸化リチウム（ＬｉＯＨ）および酸化リチウム（Ｌｉ２Ｏ）の正極合材組成物への配合の仕方により特徴付けられており、本質的には、以下の工程を含む。
（１）少なくとも正極活物質と結着剤と内圧抑制剤と溶剤とを含む正極合材組成物を調製する。
（２）正極合材組成物を正極集電体の表面に塗工し乾燥させて正極を用意する。 The manufacturing method disclosed here is characterized by the way of compounding lithium hydroxide (LiOH) and lithium oxide (Li 2 O) as an internal pressure inhibitor into the positive electrode mixture composition, and essentially The following steps are included.
(1) A positive electrode mixture composition containing at least a positive electrode active material, a binder, an internal pressure inhibitor, and a solvent is prepared.
(2) The positive electrode mixture composition is applied to the surface of the positive electrode current collector and dried to prepare a positive electrode.

［１．正極合材組成物の調製］
少なくとも正極活物質と結着剤と内圧抑制剤と溶剤とを、含む正極合材組成物を調製する。正極活物質としては、層状系、スピネル系等のリチウム複合金属酸化物（例えば、ＬｉＮｉＯ２、ＬｉＣｏＯ２、ＬｉＦｅＯ２、ＬｉＭｎ２Ｏ４、ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．５Ｍｎ１．５Ｏ４，ＬｉＣｒＭｎＯ４、ＬｉＦｅＰＯ４等）を好適に採用し得る。これらのリチウム複合金属酸化物は、例えば、任意の金属元素がドープあるいは置換されていても良い。結着剤としては、ポリフッ化ビニリデン（ＰＶＤＦ）やポリエチレンオキサイド（ＰＥＯ）等の各種のポリマー材料を採用し得る。内圧抑制剤としては、水酸化リチウムおよび酸化リチウムの少なくとも１つ含むことができる。また、正極合材組成物は、必要に応じて、導電材やその他の各種の添加剤（例えば、界面活性剤等）を含むことができる。導電材としては、カーボンブラック（例えば、アセチレンブラックやケッチェンブラック）等の炭素材料を採用し得る。以上の固形分材料を、例えばＮ‐メチル‐２‐ピロリドン（ＮＭＰ）等の溶剤に分散させることで、正極合材組成物を調製することができる。 [1. Preparation of positive electrode composite composition]
A positive electrode mixture composition containing at least a positive electrode active material, a binder, an internal pressure inhibitor, and a solvent is prepared. Examples of the positive electrode active material include lithium composite metal oxides such as layered and spinel (for example, LiNiO 2 , LiCoO 2 , LiFeO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Mn 1.5 O 4 , LiCrMnO 4 , LiFePO 4, etc.) can be suitably employed. These lithium composite metal oxides may be doped or substituted with any metal element, for example. As the binder, various polymer materials such as polyvinylidene fluoride (PVDF) and polyethylene oxide (PEO) can be adopted. The internal pressure suppressor can include at least one of lithium hydroxide and lithium oxide. Moreover, the positive electrode composite composition can contain a conductive material and other various additives (for example, a surfactant and the like) as necessary. As the conductive material, a carbon material such as carbon black (for example, acetylene black or ketjen black) can be adopted. A positive electrode mixture composition can be prepared by dispersing the above solid material in a solvent such as N-methyl-2-pyrrolidone (NMP).

ここで、正極合材組成物の固形分の割合を８０質量％以上（例えば８２質量％以上）とし、溶剤を少なくすることで、正極合材組成物の性状を湿った粉状に調整する。固形分の割合の上限は特に制限はないが、例えば、９０質量％以下程度（例えば８５質量％以下）を目安とすることができる。これにより、内圧抑制剤である水酸化リチウムおよび酸化リチウムの電離が効果的に抑さえられ、水酸化物イオンの発生量が低減されて、正極合材組成物のゲル化が抑制される。
ここで、内圧抑制剤は、上記リチウム複合金属酸化物に含まれるリチウム以外の金属元素の総モル数に対し、Ｌｉ２Ｏに換算した場合のモル比が、０を超えて０．８以下の割合（モル比）となるよう含ませるのが好ましい。すなわち、水酸化リチウムと酸化リチウムとの間には、（Ｌｉ２Ｏ＋Ｈ２Ｏ＝２ＬｉＯＨ）の関係が見られることから、内圧抑制剤として水酸化リチウムを用いる場合は、上記金属元素の総モル数に対し、０を超えて１．６以下の割合となるよう含ませるようにする。水酸化リチウムと酸化リチウムとの両方を用いるようにしても良い。酸化リチウムを用いるのが、ガス発生抑制効果（ＣＯ２ガス吸収能であり得る。）がより一層高くなるために好ましい。 Here, the ratio of the solid content of the positive electrode mixture composition is 80% by mass or more (for example, 82% by mass or more), and the property of the positive electrode mixture composition is adjusted to a wet powder by reducing the solvent. The upper limit of the ratio of the solid content is not particularly limited, but can be, for example, about 90% by mass or less (for example, 85% by mass or less). Thereby, the ionization of lithium hydroxide and lithium oxide, which are internal pressure inhibitors, is effectively suppressed, the amount of hydroxide ions generated is reduced, and gelation of the positive electrode mixture composition is suppressed.
Here, the internal pressure suppressor has a molar ratio when converted to Li 2 O with respect to the total number of moles of metal elements other than lithium contained in the lithium composite metal oxide is more than 0 and 0.8 or less. It is preferable to make it contain so that it may become a ratio (molar ratio). That is, since a relationship of (Li 2 O + H 2 O = 2LiOH) is observed between lithium hydroxide and lithium oxide, when lithium hydroxide is used as an internal pressure suppressor, the total number of moles of the above metal elements On the other hand, it is included so as to have a ratio of more than 0 and 1.6 or less. Both lithium hydroxide and lithium oxide may be used. Lithium oxide is preferably used because the gas generation suppression effect (which may be CO 2 gas absorption ability) is further enhanced.

内圧抑制剤は、正極合材組成物中に少量でも配合することでＣＯ２等のガスの発生を抑制する効果が得られるために好ましい。内圧抑制剤の割合が多くなれば多くなるほど、ガス発生抑制効果が増大され得る。しかしながら、内圧抑制剤の割合が多すぎると、正極における電気化学反応が阻害され、内部抵抗が高まり得るために好ましくない。そのため、内圧抑制剤は、上記のＬｉ２Ｏに換算した場合のモル比の上限を０．８以下とするようにしている。 An internal pressure suppressor is preferable because an effect of suppressing the generation of gas such as CO 2 can be obtained by mixing even a small amount in the positive electrode mixture composition. As the ratio of the internal pressure inhibitor increases, the gas generation suppression effect can be increased. However, if the ratio of the internal pressure suppressor is too large, the electrochemical reaction at the positive electrode is hindered and the internal resistance can be increased, which is not preferable. For this reason, the internal pressure suppressor has an upper limit of 0.8 or less when converted to the above Li 2 O.

［２．正極の用意］
上記のとおりの正極合材組成物の集電体への塗工は、公知の各種の塗工装置を用いて行うことができる。正極集電体としては、導電性の良好な金属（例えばアルミニウム）からなる導電性部材を好適に採用し得る。
正極合材組成物は、例えば、コーターを用いて、集電体の片面または両面に正極合材組成物を塗布することができる（例えば、特許文献４参照）。コーターとしては、上記の正極合材組成物を集電体に塗布可能なものであればよく、例えば、スリットコーター、ダイコーター、グラビアコーター、ロールコーターや、ドクターブレードによるコーター、コンマコーターなどを用いることができる。
次いで、塗工された正極合材組成物を乾燥させて溶剤を除去することで、正極活物質層を備える正極を用意することができる。上記の通り、正極合材組成物は固形分の割合が多いため、かかる乾燥に比較的時間を要することなく実施することができる。例えば、１２０℃程度で数分〜数時間乾燥させることが挙げられる。 [2. Preparation of positive electrode]
Application of the positive electrode mixture composition as described above to the current collector can be performed using various known coating apparatuses. As the positive electrode current collector, a conductive member made of a metal having good conductivity (for example, aluminum) can be suitably employed.
The positive electrode mixture composition can be applied to one or both sides of a current collector using, for example, a coater (see, for example, Patent Document 4). As the coater, any coating material can be used as long as it can apply the positive electrode mixture composition to the current collector. For example, a slit coater, a die coater, a gravure coater, a roll coater, a doctor blade coater, a comma coater, or the like is used. be able to.
Next, a positive electrode including a positive electrode active material layer can be prepared by drying the coated positive electrode mixture composition and removing the solvent. As described above, since the positive electrode mixture composition has a high solid content ratio, the drying can be performed without requiring a relatively long time. For example, drying at about 120 ° C. for several minutes to several hours can be mentioned.

［二次電池の構築］
負極は、典型的には、負極活物質と結着剤と増粘材等と溶剤とを含む負極合材組成物を負極集電体上に塗工し、乾燥させて負極活物質層を形成することで、用意することができる。負極集電体としては、導電性の良好な金属（例えば銅）からなる導電性材料を好適に採用し得る。負極活物質としては、黒鉛（グラファイト）、難黒鉛化炭素（ハードカーボン）、易黒鉛化炭素（ソフトカーボン）等の炭素材料を用いることができ、なかでも黒鉛を好適に採用し得る。結着剤としては、スチレンブタジエンゴム（ＳＢＲ）等の各種ポリマー材料を採用し得る。増粘剤としては、カルボキシメチルセルロース（ＣＭＣ）等の各種のポリマー材料を採用し得る。溶剤としては、イオン交換水等の水を採用し得る。 [Construction of secondary battery]
The negative electrode is typically formed by applying a negative electrode mixture composition containing a negative electrode active material, a binder, a thickener, and a solvent onto a negative electrode current collector and drying to form a negative electrode active material layer. It can be prepared by doing. As the negative electrode current collector, a conductive material made of a metal having good conductivity (for example, copper) can be suitably used. As the negative electrode active material, a carbon material such as graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), or the like can be used, and among them, graphite can be preferably used. As the binder, various polymer materials such as styrene butadiene rubber (SBR) can be adopted. As the thickener, various polymer materials such as carboxymethyl cellulose (CMC) can be employed. As the solvent, water such as ion-exchanged water can be adopted.

上記の正極および負極を、セパレータを介して積層することで、電極体を構築することができる。セパレータとしては、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）等の樹脂から成る多孔質樹脂シートを好適に採用し得る。なかでも、多孔性樹脂シートの片面または両面に多孔質の耐熱層を備えるものが好ましい。なお、固体状の電解質を用いた電池（例えば、リチウムポリマー電池）では、上記電解質がセパレータを兼ねた構成となり得る。なお、長尺のシート状の正極および負極を用い、これらを積層して捲回することで捲回型の電極体を構築しても良い。   An electrode body can be constructed by laminating the above positive electrode and negative electrode via a separator. As the separator, a porous resin sheet made of a resin such as polyethylene (PE) or polypropylene (PP) can be suitably used. Especially, what equips one side or both surfaces of a porous resin sheet with a porous heat-resistant layer is preferable. Note that in a battery using a solid electrolyte (for example, a lithium polymer battery), the electrolyte can also serve as a separator. Note that a wound electrode body may be constructed by using a long sheet-like positive electrode and negative electrode, and laminating and winding them.

このように構築された電極体を電池ケース内に収容し、所定の非水電解液を電池ケース内に注入し、蓋をすることで、電池組立体を作製することができる。
非水電解液としては、典型的には有機溶媒（非水系溶媒）中に支持塩を含有させたものを用いる。支持塩としては、リチウム塩、ナトリウム塩等を用いることができ、なかでもＬｉＰＦ６、ＬｉＢＦ４等のリチウム塩を好適に採用し得る。有機溶媒としては、カーボネート類、エステル類、エーテル類等の非プロトン性溶媒を用いることができる。なかでも、カーボネート類、例えば、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）等を好適に採用し得る。
電池ケースには、例えば、電池ケースの内圧が所定の圧力となった場合に導電経路を遮断するＣＩＤが備えられていても良い。かかる電流遮断機構は、典型的には、電極体の正極と、電池ケースに設けられた正極外部接続端子との間の導電経路に配設される。 The battery assembly can be manufactured by housing the electrode body constructed in this manner in the battery case, injecting a predetermined non-aqueous electrolyte into the battery case, and closing the lid.
As the nonaqueous electrolytic solution, typically, an organic solvent (nonaqueous solvent) containing a supporting salt is used. As the supporting salt, a lithium salt, a sodium salt or the like can be used, and among them, a lithium salt such as LiPF 6 or LiBF 4 can be preferably used. As the organic solvent, aprotic solvents such as carbonates, esters and ethers can be used. Of these, carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) can be preferably used.
The battery case may be provided with, for example, a CID that cuts off the conductive path when the internal pressure of the battery case becomes a predetermined pressure. Such a current interruption mechanism is typically disposed in a conductive path between the positive electrode of the electrode body and the positive external connection terminal provided in the battery case.

次いで、上記組立体に対しておよそ０．１Ｃ〜２Ｃの充電レートで電池使用時の上限電圧（例えば３．７Ｖ〜４．２Ｖ）まで充電を行う。その後に、およそ０．１Ｃ〜２Ｃの放電レートで所定の電圧（例えば３Ｖ〜３．２Ｖ）まで放電を行う。また、上記充放電を複数回（例えば３回）繰り返すことが好ましい。このように組立体に対して充放電処理を行うことによって該組立体は使用可能な電池、即ち二次電池となる。   Next, the assembly is charged to an upper limit voltage (e.g., 3.7 V to 4.2 V) when the battery is used at a charging rate of approximately 0.1 C to 2 C. Thereafter, discharging is performed to a predetermined voltage (for example, 3 V to 3.2 V) at a discharge rate of approximately 0.1 C to 2 C. Moreover, it is preferable to repeat the said charging / discharging several times (for example, 3 times). By performing the charging / discharging process on the assembly in this manner, the assembly becomes a usable battery, that is, a secondary battery.

本実施形態に係る二次電池の正極には、正極活物質層中に内圧抑制剤が含まれている。かかる内圧抑制剤は、電池の充放電に伴い、正極においてＣＯ２等のガスが発生するのを好適に抑制することができる。換言すると、通常の電池使用時に電池ケースの内圧が上昇するのを好適に抑制することができる。その結果、例えば、ＣＩＤが備えられた二次電池においては、かかるＣＩＤの作動圧力における通常の電池使用時の内圧上昇分を従来よりも少なく考慮することができる（あるいは、考慮しなくても良い）。したがって、過充電等の異常時には、電池の内圧がより迅速に所定のＣＩＤ作動圧力にまで到達し、速やかに導電経路を遮断して更なる過充電を防止することができる。例えば、過充電に伴う発熱により二次電池の温度が急激に上昇する時間を余分に与えることなく、ＣＩＤを作動させることができる。これにより、より安全性が確保され、信頼性に優れた二次電池を提供することができる。以上より、本発明の製造方法は、電池容量が２０Ａｈ以上（例えば２０Ａｈ〜１００Ａｈ）の高容量型の二次電池、例えばプラグインハイブリッド自動車（ＰＨＶ）等の車両に搭載されるモーター用の動力源（駆動用電源）として用いられる二次電池の製造に適用することで、その優位性がより一層発揮されるために好ましい。 The positive electrode of the secondary battery according to the present embodiment includes an internal pressure inhibitor in the positive electrode active material layer. Such an internal pressure suppressor can suitably suppress the generation of gas such as CO 2 at the positive electrode as the battery is charged and discharged. In other words, it is possible to suitably suppress an increase in the internal pressure of the battery case during normal battery use. As a result, for example, in a secondary battery equipped with a CID, an increase in internal pressure during normal battery use at the operating pressure of the CID can be considered less than before (or need not be considered). ). Therefore, when an abnormality such as overcharge occurs, the internal pressure of the battery can reach the predetermined CID operating pressure more quickly, and the conduction path can be quickly blocked to prevent further overcharge. For example, the CID can be operated without giving extra time for the temperature of the secondary battery to rapidly increase due to the heat generated by overcharging. Thereby, the safety | security is ensured more and the secondary battery excellent in reliability can be provided. As described above, the manufacturing method of the present invention is a power source for a motor mounted on a vehicle such as a high capacity secondary battery having a battery capacity of 20 Ah or more (for example, 20 Ah to 100 Ah), for example, a plug-in hybrid vehicle (PHV). By applying to the manufacture of a secondary battery used as (power supply for driving), it is preferable because the superiority is further exhibited.

以下、一実施形態としてのリチウムイオン電池を製造する場合を例に、ここで開示される電池の製造方法について説明を行う。   Hereinafter, the manufacturing method of the battery disclosed here will be described by taking as an example the case of manufacturing a lithium ion battery as one embodiment.

＜例１〜例６＞
以下の手順で、正極活物質層を形成するための正極合材組成物を調製した。先ず、正極活物質粉末としてのＬｉ1.00Ｎｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ２粉末と、導電材としてのアセチレンブラック（ＡＢ）と、バインダとしてのポリフッ化ビニリデン（ＰＶｄＦ）とを、質量比が９４：３：３となるように混合した。次いで、かかる混合物に、内圧抑制剤としてのＬｉ２Ｏを、正極活物質に含まれるリチウム（Ｌｉ）以外の全金属元素の総モル数に対して０．８となるように混合した。すなわち、１モルのＬｉ1.00Ｎｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ２に対して０．８モルの割合となるようＬｉ２Ｏを混合した。以上の固形分材料に対し、溶媒としてのＮ−メチルピロリドン（ＮＭＰ）を、下記の表１に示した通り正極合材組成物の固形分の割合が７０質量％〜８５質量％となるように変化させて加えることで、例１〜６の組成物を調製した。そして、これらの組成物を２４時間保存した後の粘度を測定することで、保存後の組成物の性状を評価した。この実施形態では、例１〜６の組成物についてゲル化の有無を確認することで、かかる正極合材組成物の塗工が可能かどうかを評価した。その結果を、表１に併せて示した。
表１に示されるように、正極合材組成物にゲル化が見られたのは、固形分の割合を８０％よりも高い値としたものであることが確認できた。そして、正極合材組成物にＬｉ２Ｏを添加する場合であっても、固形分率を８０％以上とすることで、正極合材組成物のゲルを抑制でき、好適に塗工できることが確認できた。 <Example 1 to Example 6>
The positive electrode mixture composition for forming the positive electrode active material layer was prepared by the following procedure. First, Li 1.00 Ni 1/3 Co 1/3 Mn 1/3 O 2 powder as a positive electrode active material powder, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder, It mixed so that mass ratio might be set to 94: 3: 3. Next, Li 2 O as an internal pressure inhibitor was mixed with the mixture so that the total molar number of all metal elements other than lithium (Li) contained in the positive electrode active material was 0.8. That is, by mixing Li 2 O 1 mol of Li 1.00 Ni 1/3 Co 1/3 Mn 1/3 to relative O 2 of 0.8 mole ratio. As shown in Table 1 below, N-methylpyrrolidone (NMP) as a solvent is used for the above solid content material so that the solid content ratio of the positive electrode mixture composition is 70 mass% to 85 mass%. The compositions of Examples 1-6 were prepared by changing and adding. And the property of the composition after storage was evaluated by measuring the viscosity after storing these compositions for 24 hours. In this embodiment, whether or not coating of the positive electrode mixture composition was possible was evaluated by confirming the presence or absence of gelation in the compositions of Examples 1 to 6. The results are also shown in Table 1.
As shown in Table 1, it was confirmed that gelation was observed in the positive electrode mixture composition when the solid content was set to a value higher than 80%. Then, even if the addition of Li 2 O in the positive electrode mixture material composition, by setting the solid content ratio of 80% or more, can suppress gel positive electrode composite material composition, suitably confirmed that be coated did it.

Figure 2015022896
Figure 2015022896

＜例７〜例１１＞
上記例１〜６の場合と同様にして、正極合材組成物を調製した。ただし、正極合材組成物の固形分率は８５％で一定とし、内圧抑制剤としてのＬｉ２Ｏの割合を、正極活物質に含まれるリチウム（Ｌｉ）以外の全金属元素の総モル数に対し、下記の表２に示す値となるように変化させて添加した。
このようにして用意した正極合材組成物７〜１１を、厚みがおよそ１５μｍの長尺状アルミニウム箔（正極集電体）に塗布して正極活物質層を形成した。得られた正極を乾燥およびプレスし、シート状の正極（正極シート）を作製した。 <Example 7 to Example 11>
A positive electrode mixture composition was prepared in the same manner as in Examples 1 to 6 above. However, the solid content of the positive electrode mixture composition is constant at 85%, and the ratio of Li 2 O as an internal pressure inhibitor is set to the total number of moles of all metal elements other than lithium (Li) contained in the positive electrode active material. On the other hand, it was added while changing so as to have the values shown in Table 2 below.
The positive electrode mixture compositions 7 to 11 thus prepared were applied to a long aluminum foil (positive electrode current collector) having a thickness of about 15 μm to form a positive electrode active material layer. The obtained positive electrode was dried and pressed to produce a sheet-like positive electrode (positive electrode sheet).

次に、負極活物質としてのアモルファスコートグラファイト粉末と、結着剤としてのスチレンブタジエンゴム（ＳＢＲ）と、増粘剤としてのカルボキシメチルセルロース（ＣＭＣ）とを、質量比率が９８．３：１．０：０．７となるようにイオン交換水と混合して、ペースト状の組成物を調製した。この組成物を、厚みおよそ１０μｍの長尺状銅箔（負極集電体）に塗布して負極活物質層を形成した。得られた負極を乾燥およびプレスし、シート状の負極（負極シート）を作製した。   Next, an amorphous coated graphite powder as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener have a mass ratio of 98.3: 1.0. : It mixed with ion-exchange water so that it might be set to 0.7, and the paste-form composition was prepared. This composition was applied to a long copper foil (negative electrode current collector) having a thickness of about 10 μm to form a negative electrode active material layer. The obtained negative electrode was dried and pressed to prepare a sheet-like negative electrode (negative electrode sheet).

次に、上記で作製した正極シートと負極シートとを、セパレータ（ここでは、ポリエチレン（ＰＥ）層の両面にポリプロピレン（ＰＰ）層が積層された三層構造のものを用いた。）を介して重ね合わせて捲回し、得られた捲回電極体を側面方向から押しつぶして拉げさせることによって扁平形状に成形した。そして、かかる捲回電極体の正極集電体の端部に正極端子を、負極集電体の端部に負極端子を溶接によりそれぞれ接合した。
この電極体をＡｌ合金製の電池ケースに収容し、非水電解液を注入した。なお、非水電解液としては、エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）とジメチルカーボネート（ＤＭＣ）とを３：４：３の体積比率で含む混合溶媒に、電解質としてのＬｉＰＦ６をおよそ１ｍｏｌ／Ｌの濃度で溶解させたものを用いた。そして、かかる電池ケースの開口部に蓋体を装着し、溶接して接合することによって、定格容量が２０Ａｈのリチウム二次電池７〜１１を構築した。 Next, the positive electrode sheet and the negative electrode sheet produced as described above were passed through a separator (here, a three-layer structure in which a polypropylene (PP) layer was laminated on both sides of a polyethylene (PE) layer was used). The resulting wound electrode body was formed into a flat shape by crushing it from the side and dragging it. And the positive electrode terminal was joined to the edge part of the positive electrode collector of this winding electrode body, and the negative electrode terminal was joined to the edge part of the negative electrode collector, respectively.
This electrode body was accommodated in a battery case made of Al alloy, and a non-aqueous electrolyte was injected. As the non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3: 4: 3, and LiPF 6 as an electrolyte are approximately What was dissolved at a concentration of 1 mol / L was used. Lithium secondary batteries 7 to 11 having a rated capacity of 20 Ah were constructed by attaching a lid to the opening of the battery case and welding and joining.

上記のように用意したリチウム二次電池７〜１１について、コンディショニング処理を施した後、ＳＯＣ８０％まで充電し、かかる充電状態で６０℃の環境下に４０日間保存した。このとき、電池ケース内の内圧を測定する内圧センサーを取付けることで、保存時の内圧の変化をモニタリングし、その結果を経過日数と発生ガス量との関係として図１に示した。なお、図１の横軸は経過日数の平方根（√（日数））を示している。また、３６日目の発生ガス量と２５℃での内部抵抗とを測定し、内圧抑制剤の添加割合との関係として、図２および下記の表２に示した。   About the lithium secondary batteries 7-11 prepared as mentioned above, after performing a conditioning process, it charged to SOC80% and preserve | saved in the environment of 60 degreeC in this charge state for 40 days. At this time, by attaching an internal pressure sensor for measuring the internal pressure in the battery case, the change in internal pressure during storage was monitored, and the result is shown in FIG. 1 as the relationship between the number of days elapsed and the amount of gas generated. The horizontal axis of FIG. 1 indicates the square root of elapsed days (√ (days)). In addition, the amount of gas generated on the 36th day and the internal resistance at 25 ° C. were measured, and the relationship with the ratio of addition of the internal pressure inhibitor was shown in FIG. 2 and Table 2 below.

Figure 2015022896
Figure 2015022896

図１および図２、表２に示されるように、正極活物質層に配合するＬｉ２Ｏ量を増加させるほど、電池ケース内に発生するガスの量は減少することが確認できた。すなわち、正極活物質層に配合したＬｉ２Ｏが電池内部でのガス（ＣＯ２）の発生を効果的に抑制しているものと考えられる。しかしながら、Ｌｉ２Ｏの配合割合が０．８を超過すると、高温保存後の２５℃における抵抗が顕著に増大することから、Ｌｉ２Ｏの配合割合は０．８以下とするのが好ましいことがわかる。 1 and 2 and Table 2, it was confirmed that the amount of gas generated in the battery case decreased as the amount of Li 2 O blended in the positive electrode active material layer was increased. That is, it is considered that Li 2 O blended in the positive electrode active material layer effectively suppresses the generation of gas (CO 2 ) inside the battery. However, if the proportion of Li 2 O exceeds 0.8, the resistance at 25 ° C. after high-temperature storage increases remarkably. Therefore, the proportion of Li 2 O is preferably 0.8 or less. Recognize.

本発明に係る非水電解質二次電池（例えばリチウムイオン電池）は、大電流出力が可能であり、信頼性に優れることから、特に自動車等の車両に搭載されるモーター（電動機）用電源として好適に使用することができる。   The non-aqueous electrolyte secondary battery (for example, a lithium ion battery) according to the present invention can output a large current and has excellent reliability. Therefore, the non-aqueous electrolyte secondary battery is particularly suitable as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Can be used for

以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、請求の範囲を限定するものではない。請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。   As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (2)

正極および負極を備える二次電池を製造する方法であって、
少なくとも正極活物質と結着剤と内圧抑制剤と溶剤とを含む正極合材組成物を調製すること、および
前記正極合材組成物を正極集電体の表面に塗工し乾燥させて正極を用意すること、
を包含し、
前記内圧抑制剤は、水酸化リチウム（ＬｉＯＨ）および酸化リチウム（Ｌｉ２Ｏ）の少なくとも１つを含み、
前記正極合材組成物における前記溶剤以外の固形分の割合は８０質量％以上である、二次電池の製造方法。 A method for producing a secondary battery comprising a positive electrode and a negative electrode,
Preparing a positive electrode mixture composition containing at least a positive electrode active material, a binder, an internal pressure inhibitor, and a solvent; and applying the positive electrode mixture composition to a surface of a positive electrode current collector and drying the positive electrode To prepare,
Including
The internal pressure inhibitor includes at least one of lithium hydroxide (LiOH) and lithium oxide (Li 2 O),
The manufacturing method of the secondary battery whose ratio of solid content other than the said solvent in the said positive electrode compound-material composition is 80 mass% or more. 前記正極活物質としてリチウム複合金属酸化物を用い、
前記リチウム複合金属酸化物に含まれるリチウム以外の金属元素の総モル数に対する、Ｌｉ２Ｏに換算した場合の前記内圧抑制剤のモル比が、０を超えて０．８以下となるように前記正極合材組成物を調製する、請求項１に記載の製造方法。 Lithium composite metal oxide is used as the positive electrode active material,
The molar ratio of the internal pressure inhibitor when converted to Li 2 O with respect to the total number of moles of metal elements other than lithium contained in the lithium composite metal oxide is more than 0 and not more than 0.8. The manufacturing method of Claim 1 which prepares a positive electrode compound-material composition.
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Publication number Priority date Publication date Assignee Title
US11108041B2 (en) 2016-12-08 2021-08-31 Gs Yuasa International Ltd. Nonaqueous electrolyte energy storage device and method for producing the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11108041B2 (en) 2016-12-08 2021-08-31 Gs Yuasa International Ltd. Nonaqueous electrolyte energy storage device and method for producing the same

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