JP2011192561A - Manufacturing method for nonaqueous electrolyte secondary battery - Google Patents

Manufacturing method for nonaqueous electrolyte secondary battery Download PDF

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JP2011192561A
JP2011192561A JP2010058628A JP2010058628A JP2011192561A JP 2011192561 A JP2011192561 A JP 2011192561A JP 2010058628 A JP2010058628 A JP 2010058628A JP 2010058628 A JP2010058628 A JP 2010058628A JP 2011192561 A JP2011192561 A JP 2011192561A
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lithium salt
secondary battery
positive electrode
electrolyte
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Hiroyoshi Shirakata
宏宜 白方
Shinya Miyazaki
晋也 宮崎
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Sanyo Electric Co Ltd
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Sanyo Electric Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems on a manufacturing process such as increase of a takt time accompanying viscosity rise of electrolyte and quality unevenness caused by poor liquid permeability, in preparing a nonaqueous electrolyte secondary battery having electrolyte concentration which excels in high-rate discharge cycles. <P>SOLUTION: A manufacturing method for a nonaqueous electrolyte secondary battery, having a cathode with a cathode active material, an anode with an anode active material, a nonaqueous solvent, and the nonaqueous electrolyte with electrolyte salt of 1.5-1.8 mol/L, includes a cathode production process of applying a mixture containing an active material, a conductive agent, a binder, and a lithium salt soluble to the nonaqueous solvent on a metal foil used as a cathode collector. The amount of addition of the lithium salt in the mixture is 0.1-3 mass% to the total mass of the active material, the conductive agent, and the binder, and the cathode production process and a battery assembling process are performed, under an environment where the dew point is -20°C or below. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、ハイレート放電サイクル特性に優れた非水電解液二次電池の製造方法に関する。   The present invention relates to a method for producing a non-aqueous electrolyte secondary battery excellent in high rate discharge cycle characteristics.

近年、携帯電話、ノートパソコン、ＰＤＡといった携帯端末用の電源として、高エネルギー密度を有する非水電解液二次電池が広く普及している。これは、非水電解液二次電池のエネルギー密度が高く、高電圧が得られることから携帯端末機器の小型、軽量化の要望に適合したことが大きい。   In recent years, non-aqueous electrolyte secondary batteries having a high energy density are widely used as power sources for portable terminals such as mobile phones, notebook computers, and PDAs. This is because the energy density of the non-aqueous electrolyte secondary battery is high and a high voltage can be obtained, so that it is suitable to meet the demands for reducing the size and weight of portable terminal devices.

また、電動工具、電動アシスト自転車、電気自動車（ＥＶ）、ハイブリッド電気自動車（ＨＥＶ）といった高出力特性が要求される用途には、従来ニッケルカドミウム電池、ニッケル水素電池等の水溶液系二次電池が用いられていた。しかし、非水電解液二次電池は、その軽量、高エネルギー密度、高電圧といった長所から、高出力が要求される用途への広がりを見せており、非水電解液二次電池の更なる高出力化、サイクル特性の改善が要望されている。   Conventionally, aqueous secondary batteries such as nickel cadmium batteries and nickel metal hydride batteries have been used for applications requiring high output characteristics such as electric tools, electric assist bicycles, electric vehicles (EV), and hybrid electric vehicles (HEV). It was done. However, non-aqueous electrolyte secondary batteries are spreading to applications that require high output due to their advantages such as light weight, high energy density, and high voltage. There is a demand for improved output and cycle characteristics.

非水電解液二次電池の代表例であるリチウムイオン二次電池は、負極活物質に炭素質材料を用い、正極活物質にはリチウム金属複合酸化物が用いられる。これらは、いずれもリチウムイオンを電気化学的に吸蔵、放出することができる。セパレータには、ポリオレフィン製の微多孔膜が用いられ、電解液には、エチレンカーボネートやプロピレンカーボネートといった環状カーボネートと、ジメチルカーボネート、メチルエチルカーボネートいった鎖状カーボネートの非水系の混合溶媒に、ＬｉＰＦ６やＬｉＢＦ４といったリチウム塩を電解質として溶解させたものが用いられている。 A lithium ion secondary battery, which is a typical example of a nonaqueous electrolyte secondary battery, uses a carbonaceous material as a negative electrode active material and a lithium metal composite oxide as a positive electrode active material. These can both occlude and release lithium ions electrochemically. A microporous membrane made of polyolefin is used for the separator, and a non-aqueous mixed solvent of a cyclic carbonate such as ethylene carbonate or propylene carbonate and a chain carbonate such as dimethyl carbonate or methyl ethyl carbonate is used as the electrolyte, and LiPF 6 And lithium salt such as LiBF 4 dissolved as an electrolyte is used.

非水系溶媒は、水系溶媒に比べてイオン伝導度が低いため、高出力用途には不向きと考えられていた。しかし、非水電解液二次電池においても極板を薄長化することにより、電流密度を下げ、高出力特性の向上が図られている。   Non-aqueous solvents have been considered unsuitable for high-power applications because of their lower ionic conductivity than aqueous solvents. However, even in a non-aqueous electrolyte secondary battery, the electrode plate is thinned to reduce the current density and improve the high output characteristics.

ところが、高出力放電でのサイクルを繰り返した場合、電極内部の反応の不均一に起因するサイクル特性の低下という課題があった。   However, when a cycle with high output discharge is repeated, there is a problem that cycle characteristics are deteriorated due to non-uniform reaction inside the electrode.

上記高容量化と、サイクル特性の低下の改善に関しては、特許文献１、２において、電解液中のリチウム塩の濃度を上げることで高出力特性、サイクル特性が改善されたことが記載されている。   Regarding the above-mentioned increase in capacity and improvement in cycle characteristics, Patent Documents 1 and 2 describe that high output characteristics and cycle characteristics are improved by increasing the concentration of lithium salt in the electrolyte. .

特許文献１には、正極の空孔が２５％以下であり、かつ非水電解質のリチウム塩濃度がイオン伝導度のピークとなる濃度を超えている非水電解質二次電池が開示されている。   Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which the vacancies of the positive electrode are 25% or less and the lithium salt concentration of the non-aqueous electrolyte exceeds the concentration at which the peak of ionic conductivity is reached.

特許文献２には、有機溶媒に対するＬｉＰＦ６の濃度を１．２ｍｏｌ／Ｌ以上、１．６ｍｏｌ／Ｌ以下に規定した非水電解液二次電池が開示されている。  Patent Document 2 discloses a nonaqueous electrolyte secondary battery in which the concentration of LiPF6 with respect to an organic solvent is specified to be 1.2 mol / L or more and 1.6 mol / L or less.

これら先行技術はいずれも電解液濃度を上げることで、電極反応に十分なリチウムイオンが供給され、高出力特性やサイクル特性が改善されたものである。   In any of these prior arts, by increasing the concentration of the electrolyte, lithium ions sufficient for electrode reaction are supplied, and high output characteristics and cycle characteristics are improved.

発明者らが確認したところ、電解液濃度を上げることで、特にハイレート放電時のサイクル特性の向上は見られた。しかし、上記先行技術はいずれも、注液に供するリチウム塩濃度を上げるものであり、注液工程で高濃度の電解液を使用することとなる。しかし、リチウム塩濃度を上げると、粘度が増大し、極板への液浸透性が低下することになる。そのため、注液工程のタクト時間の増加や、液浸透性不足による品質バラツキなど、製造工程における不具合が顕在化した。   As a result of confirmation by the inventors, improvement in cycle characteristics, particularly during high-rate discharge, was observed by increasing the electrolyte concentration. However, any of the above prior arts increases the concentration of lithium salt used for injection, and a high concentration electrolytic solution is used in the injection step. However, when the lithium salt concentration is increased, the viscosity increases and the liquid permeability to the electrode plate decreases. Therefore, problems in the manufacturing process, such as an increase in tact time of the liquid injection process and quality variations due to insufficient liquid permeability, have become apparent.

特開２００３−１７３８２１号公報JP 2003-173821 A 特開２００３−２４３０２９号公報JP 2003-243029 A

本発明は、ハイレート放電サイクル特性に必要な電解液濃度を有する非水電解液二次電池を提供するにあたり、注液工程に見られた上記不具合を解決すべき課題とする。   This invention makes it the subject which should solve the said malfunction seen in the liquid injection process in providing the non-aqueous-electrolyte secondary battery which has electrolyte concentration required for a high-rate discharge cycle characteristic.

本発明は、正極活物質を有する正極と、負極活物質を有する負極と、１．５〜１．８ｍｏｌ／Ｌの電解質塩濃度を有する非水電解液を備える非水電解液二次電池の製造方法において、正極集電体上に活物質、導電剤、結着剤及び非水溶媒に可溶なリチウム塩を含む活物質スラリーを塗布する正極作製工程を備え、前記合剤中のリチウム塩の添加量は、活物質、導電剤、結着剤の総質量に対して０．１〜３質量％であり、前記正極作製工程及び電池組立工程が露点−２０℃以下に制御されていることを特徴とする非水電解液二次電池の製造方法である。   The present invention provides a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte solution having an electrolyte salt concentration of 1.5 to 1.8 mol / L. In the method, the method includes a positive electrode preparation step of applying an active material slurry containing a lithium salt soluble in an active material, a conductive agent, a binder, and a non-aqueous solvent on a positive electrode current collector, and the lithium salt in the mixture The addition amount is 0.1 to 3% by mass with respect to the total mass of the active material, the conductive agent, and the binder, and the positive electrode preparation step and the battery assembly step are controlled to a dew point of −20 ° C. or lower. It is the manufacturing method of the nonaqueous electrolyte secondary battery characterized.

本発明の構成によれば、最終的に必要となる電解液中のリチウム塩の一部をあらかじめ正極に担持させることとなるため、注液工程の段階では、正極に含むリチウム塩を相殺した濃度の電解液を注液することになる。そのため、注液工程の段階では、組立後の電池中のリチウム塩濃度に比べて、低濃度の電解液を使用することができる。したがって、従来のように注液工程に供される電解液濃度を上げる場合に比べて、液浸透性の低下による不具合を回避することができる。本発明では、電池中のリチウム塩の濃度は１．５〜１．８ｍｏｌ／Ｌとすることが好ましい。当該範囲であれば、優れたハイレート放電サイクル特性を示す非水電解液二次電池が得られるからである。なお、ここでいう電池中のリチウムイオン濃度とは、注液工程で使用される電解液のリチウム塩濃度ではなく、正極中に添加されたリチウム塩と注液工程で使用される電解液中に含まれるリチウム塩のモル数を合算して、溶媒体積で除した値を意味している。   According to the configuration of the present invention, since a part of the lithium salt in the electrolytic solution that is finally required is supported on the positive electrode in advance, the concentration that offsets the lithium salt contained in the positive electrode at the stage of the liquid injection process The electrolyte solution is injected. Therefore, at the stage of the liquid injection process, it is possible to use an electrolyte solution having a lower concentration than the lithium salt concentration in the assembled battery. Therefore, it is possible to avoid problems due to a decrease in liquid permeability as compared with the case where the concentration of the electrolytic solution used in the liquid injection process is increased as in the prior art. In the present invention, the concentration of the lithium salt in the battery is preferably 1.5 to 1.8 mol / L. This is because a non-aqueous electrolyte secondary battery exhibiting excellent high-rate discharge cycle characteristics can be obtained within this range. The lithium ion concentration in the battery here is not the lithium salt concentration of the electrolyte used in the injection step, but the lithium salt added in the positive electrode and the electrolyte used in the injection step. It means a value obtained by adding together the number of moles of lithium salt contained and dividing by the solvent volume.

正極極板に添加するリチウム塩としては、非水電解液に可溶で、電池内部で安定に存在できるもの、例えば、電解質として用いられるリチウム塩であれば特に限定されない。しかし、式量の小さいリチウム塩は単位質量あたりのＬｉ含有量が多いので、式量の小さいＬｉＰＦ６又はＬｉＢＦ４を使用することが好ましい。これらは、２種混合して使用することもできるが、特に、電解質として用いられているリチウム塩と同一のものを使用することが特に好ましい。また、これらのリチウム塩は吸湿性を有するため、活物質スラリーの調製から塗布、乾燥、圧延に至るまでの正極作製工程及び電池組立工程は、露点−２０℃以下、より好ましくは露点−４０℃以下の環境下で行うことが好ましい。 The lithium salt added to the positive electrode plate is not particularly limited as long as it is soluble in a non-aqueous electrolyte and can be stably present inside the battery, for example, a lithium salt used as an electrolyte. However, since a lithium salt with a small formula weight has a large Li content per unit mass, it is preferable to use LiPF 6 or LiBF 4 with a small formula weight. These can be used as a mixture of two types, but it is particularly preferable to use the same lithium salt used as the electrolyte. Moreover, since these lithium salts have hygroscopicity, the positive electrode preparation process and battery assembly process from preparation of active material slurry to coating, drying and rolling are performed at a dew point of −20 ° C. or less, more preferably at a dew point of −40 ° C. It is preferable to carry out under the following environment.

正極へのリチウム塩の添加量としては、活物質、導電剤及び結着剤の総質量に対して、０．１質量％以上、３質量％以下であることが好ましい。０．１質量％未満では、電池中の電解質塩濃度の増加に寄与する量が少ないため、本発明の効果は見られず、３質量％を超えると、活物質スラリーを集電体上へ均一に塗布するのが困難となるためである。   The addition amount of the lithium salt to the positive electrode is preferably 0.1% by mass or more and 3% by mass or less with respect to the total mass of the active material, the conductive agent, and the binder. If the amount is less than 0.1% by mass, the amount of the electrolyte salt concentration in the battery is small, so the effect of the present invention is not seen. If the amount exceeds 3% by mass, the active material slurry is uniformly distributed on the current collector. It is because it becomes difficult to apply to.

本発明における正極活物質としては、リチウムイオンを電気化学的に吸蔵、放出することができる材料であれば特に限定されない。例えば、層状構造を有するリチウムコバルト複合酸化物、リチウムニッケル複合酸化物、リチウムニッケルマンガンコバルト複合酸化物、スピネル型構造を有するリチウムマンガン複合酸化物、オリビン型構造を有するリン酸鉄リチウム等が挙げられる。これらは、１種又は２種以上を混合して使用することができる。中でも、層状構造を有するリチウムニッケルマンガンコバルト複合酸化物とスピネル型マンガン複合酸化物の混合物は、容量と熱的安定性のバランスが優れることから好ましい。   The positive electrode active material in the present invention is not particularly limited as long as it is a material capable of electrochemically occluding and releasing lithium ions. For example, lithium cobalt composite oxide having a layered structure, lithium nickel composite oxide, lithium nickel manganese cobalt composite oxide, lithium manganese composite oxide having a spinel structure, lithium iron phosphate having an olivine structure, etc. . These can be used 1 type or in mixture of 2 or more types. Among these, a mixture of a lithium nickel manganese cobalt composite oxide and a spinel manganese composite oxide having a layered structure is preferable because of a good balance between capacity and thermal stability.

本発明における負極活物質としては、リチウムイオンを電気化学的に吸蔵、放出することができる材料であれば特に限定されない。例えば、黒鉛及びコークス等の炭素材料、酸化錫等の金属酸化物、ケイ素及び錫等のリチウムと合金化してリチウムを吸蔵することができる金属、金属リチウム等が挙げられる。中でも黒鉛系の炭素材料は、リチウムの吸蔵・放出に伴う体積変化が少なく、可逆性に優れることから好ましい。   The negative electrode active material in the present invention is not particularly limited as long as it is a material that can electrochemically occlude and release lithium ions. Examples thereof include carbon materials such as graphite and coke, metal oxides such as tin oxide, metals that can be alloyed with lithium such as silicon and tin, and lithium, and metal lithium. Among these, a graphite-based carbon material is preferable because it has a small volume change due to insertion and extraction of lithium and is excellent in reversibility.

本発明に用いる非水溶媒としては、環状カーボネート、鎖状カーボネートの混合物を使用することができる。環状カーボネートとしては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、フルオロエチレンカーボネートなどが挙げられ、鎖状カーボネートとしては、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネート、メチルプロピルカーボネート、メチルブチルカーボネートなどが挙げられる。溶媒の粘度、イオン伝導度の観点から、環状カーボネートと鎖状カーボネートを体積比１０：９０〜４０：６０の範囲で使用することが好ましい。   As the non-aqueous solvent used in the present invention, a mixture of a cyclic carbonate and a chain carbonate can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, and methyl butyl carbonate. From the viewpoint of the viscosity and ionic conductivity of the solvent, it is preferable to use a cyclic carbonate and a chain carbonate in a volume ratio of 10:90 to 40:60.

本発明に用いる電解質塩としては、非水電解液二次電池に一般的に使用されているものを使用することができる。具体的には、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２、ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ４Ｆ９ＳＯ２）、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣ（Ｃ２Ｆ５ＳＯ２）３、ＬｉＡｓＦ６、ＬｉＣｌＯ４、Ｌｉ２Ｂ１０Ｃｌ１０、Ｌｉ２Ｂ１２Ｃｌ１２など及びそれらの混合物が例示される。これらの中でも、ＬｉＰＦ６（ヘキサフルオロリン酸リチウム）又はＬｉＢＦ４（テトラフルオロホウ酸リチウム）が好ましく用いられる。注液工程で使用する電解液の電解質濃度としては、１．２〜１．７ｍｏｌ／Ｌの範囲が好ましい。１．２ｍｏｌ／Ｌ未満では、電池内の電解液濃度を１．５ｍｏｌ／Ｌ以上とするのに正極に添加するリチウム塩として３質量％を超える量を添加しなければならないため極板工程に問題が生じ、１．７ｍｏｌ／Ｌを超えると液浸透性が大幅に低下するため注液工程に問題が生じるからである。 As electrolyte salt used for this invention, what is generally used for the nonaqueous electrolyte secondary battery can be used. Specifically, LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , LiAsF 6 , LiClO 4 , Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 and the like, and mixtures thereof are exemplified. . Among these, LiPF 6 (lithium hexafluorophosphate) or LiBF 4 (lithium tetrafluoroborate) is preferably used. The electrolyte concentration of the electrolytic solution used in the pouring step is preferably in the range of 1.2 to 1.7 mol / L. If the concentration is less than 1.2 mol / L, there is a problem in the electrode plate process because an amount exceeding 3 mass% must be added as a lithium salt to be added to the positive electrode in order to make the electrolyte concentration in the battery 1.5 mol / L or more This is because when the amount exceeds 1.7 mol / L, the liquid permeability is significantly reduced, and thus a problem occurs in the liquid injection process.

以下、本願発明を実施するための最良の形態を実施例及び比較例を用いて詳細に説明する。ただし、以下に示す実施例は、本発明の技術思想を具体化するための非水電解質二次電池の製造方法の一例を例示するものであって、本発明をこの実施例に特定することを意図するものではなく、本発明は特許請求の範囲に示した技術思想を逸脱することなく種々の変更を行ったものにも均しく適用し得るものである。   Hereinafter, the best mode for carrying out the present invention will be described in detail using examples and comparative examples. However, the following examples illustrate an example of a manufacturing method of a nonaqueous electrolyte secondary battery for embodying the technical idea of the present invention, and the present invention is specified as this example. The present invention is not intended, and the present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

（実施例１）
（正極の作製）
炭酸リチウムと、Ｎｉ０．３３Ｍｎ０．３３Ｃｏ０．３４（ＯＨ）２で表される共沈水酸化物を混合し、空気雰囲気中で１０００℃で２０時間焼成して、ニッケルマンガンコバルト酸リチウム（ＬｉＮｉ０．３３Ｍｎ０．３３Ｃｏ０．３４Ｏ２）を得た。また、公知の方法でスピネル型マンガン酸リチウム（ＬｉＭｎ２Ｏ４）を得た。 Example 1
(Preparation of positive electrode)
Lithium carbonate and a coprecipitated hydroxide represented by Ni 0.33 Mn 0.33 Co 0.34 (OH) 2 were mixed and baked at 1000 ° C. for 20 hours in an air atmosphere to obtain lithium nickel manganese cobaltate (LiNi 0.33 Mn 0.33 Co 0.34 O 2 ) was obtained. Moreover, spinel type lithium manganate (LiMn 2 O 4 ) was obtained by a known method.

露点−４０℃以下の環境下で、上記ニッケルマンガンコバルト酸リチウムとスピネル型マンガン酸リチウムを質量比６：４で混合して得られた正極活物質９４質量部と、導電剤としてのアセチレンブラック３質量部と、結着剤としてのポリフッ化ビニリデン（ＰＶＤＦ）３質量部を混合し、Ｎ−メチル−２−ピロリドン（ＮＭＰ）溶液へ分散させ、最後に活物質、導電剤、結着剤の総質量に対して０．５質量％のＬｉＰＦ６を添加して正極スラリーを調製した。この正極スラリーを集電体となる厚さ２０μｍアルミニウム箔の両面に塗布、乾燥して、正極活物質層を形成した。その後、圧延ローラーを用いて所定の厚みにまで圧延し、短辺の長さが５５ｍｍ、長辺の長さが７５０ｍｍの正極極板を作製した。 In an environment having a dew point of −40 ° C. or lower, 94 parts by mass of a positive electrode active material obtained by mixing the above nickel manganese cobaltate and spinel type lithium manganate at a mass ratio of 6: 4, and acetylene black 3 as a conductive agent Part by mass and 3 parts by mass of polyvinylidene fluoride (PVDF) as a binder are mixed and dispersed in an N-methyl-2-pyrrolidone (NMP) solution, and finally the total of the active material, conductive agent, and binder A positive electrode slurry was prepared by adding 0.5% by mass of LiPF 6 to the mass. This positive electrode slurry was applied to both surfaces of a 20 μm thick aluminum foil serving as a current collector and dried to form a positive electrode active material layer. Then, it rolled to the predetermined thickness using the rolling roller, and produced the positive electrode plate whose short side length is 55 mm and long side length is 750 mm.

（負極の作製）
負極活物質として黒鉛粉末９８質量部と、結着剤としてスチレンブタジエンゴム（ＳＢＲ）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、水に分散させて負極スラリーを調製した。このスラリーを負極集電体となる厚さ１０μｍの銅箔の両面にドクターブレード法により塗布、乾燥して負極集電体の両面に負極活物質層を形成した。この後、圧延ローラーを用いて圧延し、短辺の長さが５７ｍｍ、長辺の長さが８００ｍｍの負極を作製した。 (Preparation of negative electrode)
98 parts by mass of graphite powder as a negative electrode active material, 1 part by mass of styrene butadiene rubber (SBR) as a binder and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener are mixed and dispersed in water to prepare a negative electrode slurry. did. This slurry was applied to both surfaces of a 10 μm thick copper foil serving as a negative electrode current collector by a doctor blade method and dried to form a negative electrode active material layer on both surfaces of the negative electrode current collector. Thereafter, rolling was performed using a rolling roller to prepare a negative electrode having a short side length of 57 mm and a long side length of 800 mm.

（巻回電極群の作製）
露点−４０℃以下の環境下で、上述した方法で作製した正極および負極を、ポリエチレン製微多孔膜を介在させて巻回し、巻回電極群を作製した。 (Production of wound electrode group)
Under a dew point of −40 ° C. or lower, the positive electrode and the negative electrode prepared by the above-described method were wound with a polyethylene microporous film interposed therebetween to prepare a wound electrode group.

（非水電解液の作製）
エチレンカーボネートとジメチルカーボネートを体積比３：７で混合した非水溶媒に、電解質としてＬｉＰＦ６を１．５ｍｏｌ／Ｌとなるように溶解させ、電解液を作製した。さらに、前記電解液に対して２質量％のビニレンカーボネートを添加し、注液工程に供される非水電解液とした。 (Preparation of non-aqueous electrolyte)
LiPF 6 was dissolved as an electrolyte in a non-aqueous solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 so as to be 1.5 mol / L, thereby preparing an electrolytic solution. Furthermore, 2 mass% vinylene carbonate was added with respect to the said electrolyte solution, and it was set as the nonaqueous electrolyte solution used for a liquid injection process.

（電池の作製）
巻回電極群を電池外装缶へ挿入し、上記非水電解液を注液し、開口部を封口することにより、定格容量１５００ｍＡｈである直径１８ｍｍ、高さ６５ｍｍの円筒形の実施例１にかかるリチウムイオン二次電池を作製した。 (Production of battery)
A wound electrode group is inserted into a battery outer can, and the nonaqueous electrolyte solution is injected therein, and the opening portion is sealed, whereby a cylindrical example 1 having a rated capacity of 1500 mAh and a diameter of 18 mm and a height of 65 mm is applied. A lithium ion secondary battery was produced.

（実施例２）
ＬｉＰＦ６の正極への添加量を１．０質量％とした以外は、上記実施例１と同様にして実施例２にかかるリチウムイオン二次電池を作製した。 (Example 2)
A lithium ion secondary battery according to Example 2 was produced in the same manner as in Example 1 except that the amount of LiPF 6 added to the positive electrode was 1.0% by mass.

（実施例３）
ＬｉＰＦ６の正極への添加量を２．０質量％とした以外は、上記実施例１と同様にして実施例３にかかるリチウムイオン二次電池を作製した。 (Example 3)
A lithium ion secondary battery according to Example 3 was produced in the same manner as in Example 1 except that the amount of LiPF 6 added to the positive electrode was 2.0% by mass.

（実施例４）
正極へ添加したリチウム塩をＬｉＢＦ４とした以外は、上記実施例２と同様にして実施例４にかかるリチウムイオン二次電池を作製した。 Example 4
A lithium ion secondary battery according to Example 4 was fabricated in the same manner as in Example 2 except that the lithium salt added to the positive electrode was LiBF 4 .

（比較例１）
正極へＬｉＰＦ６を添加しなかったこと以外は、上記実施例１と同様にして比較例１にかかるリチウムイオン二次電池を作製した。 (Comparative Example 1)
A lithium ion secondary battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that LiPF 6 was not added to the positive electrode.

（比較例２）
正極へ添加したＬｉＰＦ６を５質量％とした以外は、上記実施例１と同様に比較例２にかかるリチウムイオン二次電池を作製しようとしたが、活物質の塗布面の凹凸が大きく、電池の作製をすることができなかった。 (Comparative Example 2)
An attempt was made to produce a lithium ion secondary battery according to Comparative Example 2 as in Example 1 except that LiPF 6 added to the positive electrode was changed to 5% by mass. Could not be made.

（比較例３）
正極へのＬｉＰＦ６の添加量を１．０質量％とし、注液工程に供した非水電解液のリチウム塩濃度を１．２ｍｏｌ／Ｌとしたこと以外は上記実施例１と同様にして比較例３にかかるリチウムイオン二次電池を作製した。 (Comparative Example 3)
Comparison was made in the same manner as in Example 1 except that the amount of LiPF 6 added to the positive electrode was 1.0% by mass, and the lithium salt concentration of the nonaqueous electrolytic solution used in the pouring step was 1.2 mol / L. A lithium ion secondary battery according to Example 3 was produced.

（比較例４）
注液工程に供した非水電解液のリチウム塩濃度を１．７ｍｏｌ／Ｌとしたこと以外は上記比較例１と同様にして比較例４にかかるリチウムイオン二次電池を作製した。 (Comparative Example 4)
A lithium ion secondary battery according to Comparative Example 4 was produced in the same manner as Comparative Example 1 except that the lithium salt concentration of the nonaqueous electrolytic solution subjected to the pouring step was 1.7 mol / L.

（比較例５）
注液工程に供した非水電解液のリチウム塩濃度を１．８ｍｏｌ／Ｌとしたこと以外は上記比較例１と同様にして比較例５にかかるリチウムイオン二次電池を作製した。 (Comparative Example 5)
A lithium ion secondary battery according to Comparative Example 5 was produced in the same manner as Comparative Example 1 except that the lithium salt concentration of the nonaqueous electrolytic solution subjected to the pouring step was 1.8 mol / L.

（比較例６）
注液工程に供した非水電解液のリチウム塩濃度を１．９ｍｏｌ／Ｌとしたこと以外は上記比較例１と同様にして比較例６にかかるリチウムイオン二次電池を作製した。 (Comparative Example 6)
A lithium ion secondary battery according to Comparative Example 6 was produced in the same manner as Comparative Example 1 except that the lithium salt concentration of the nonaqueous electrolytic solution subjected to the pouring step was 1.9 mol / L.

（サイクル特性試験）
実施例１〜４、比較例１、３、４にかかる電池について、定電流１Ｉｔ（＝１５００ｍＡ）で４．２Ｖまで充電し、その後定電圧で１／５０Ｉｔ（３０ｍＡ）になるまで充電する。その後、２５０００ｍＡで２．７５Ｖになるまで放電し、その放電容量を測定した。この充放電サイクルを１００サイクル繰り返し、以下の式よりサイクル維持率として、サイクル特性の比較評価の指標とした。
サイクル維持率（％）＝（１００サイクル目放電容量）／（１サイクル目放電容量）
×１００
結果をまとめて表１に示した。 (Cycle characteristic test)
The batteries according to Examples 1 to 4 and Comparative Examples 1, 3, and 4 are charged to 4.2 V at a constant current of 1 It (= 1500 mA), and then charged to 1/50 It (30 mA) at a constant voltage. Then, it discharged until it became 2.75V at 25000mA, and the discharge capacity was measured. This charge / discharge cycle was repeated 100 times, and was used as an index for comparative evaluation of cycle characteristics as a cycle maintenance rate from the following formula.
Cycle retention rate (%) = (100th cycle discharge capacity) / (First cycle discharge capacity)
× 100
The results are summarized in Table 1.

Figure 2011192561
Figure 2011192561

表１には、サイクル維持率とともに、注液工程で使用した電解液のリチウム塩濃度と電池中のリチウム塩濃度を記載した。正極中に含まれるリチウム塩は、電池組立後に電解液中に溶解するため、電池中のリチウム塩濃度が実質的な電池の電解液濃度を示すことになる。    In Table 1, the lithium salt concentration of the electrolytic solution used in the pouring step and the lithium salt concentration in the battery are shown together with the cycle maintenance rate. Since the lithium salt contained in the positive electrode is dissolved in the electrolytic solution after the battery is assembled, the lithium salt concentration in the battery indicates the substantial electrolytic solution concentration of the battery.

表１から、電池中のリチウム塩濃度を１．５〜１．８ｍｏｌ／Ｌとすることにより優れたハイレート放電サイクル特性が得られることがわかる。したがって、電池中のリチウム塩濃度としては１．５〜１．８ｍｏｌ／Ｌに規定することが好ましい。   From Table 1, it can be seen that excellent high-rate discharge cycle characteristics can be obtained by setting the lithium salt concentration in the battery to 1.5 to 1.8 mol / L. Therefore, the lithium salt concentration in the battery is preferably regulated to 1.5 to 1.8 mol / L.

実施例２と比較例４を比較すると、実施例２のサイクル特性が若干優れていることがわかる。これは、正極に添加されたリチウム塩が電解液中に溶解することにより、極板内部に細孔が形成され、サイクル特性に有利になったものと推察される。   When Example 2 and Comparative Example 4 are compared, it can be seen that the cycle characteristics of Example 2 are slightly superior. This is presumed that the lithium salt added to the positive electrode is dissolved in the electrolytic solution, so that pores are formed inside the electrode plate, which is advantageous in cycle characteristics.

実施例２、４の結果から、正極に添加するリチウム塩をＬｉＰＦ６からＬｉＢＦ４に変えても同等のサイクル特性の向上効果が認められる。この効果は正極に添加したリチウム塩による電解液中のリチウムイオン濃度の増加によるものである。したがって、正極に添加するリチウム塩は、有機溶媒に可溶で電池中で安定に存在できるもの、すなわち非水電解液二次電池の電解質塩として使用されるリチウム塩であれば、均しく本発明の効果を奏するものと考えられる。 From the results of Examples 2 and 4 , even if the lithium salt added to the positive electrode is changed from LiPF 6 to LiBF 4 , the same effect of improving cycle characteristics is recognized. This effect is due to an increase in the lithium ion concentration in the electrolyte solution due to the lithium salt added to the positive electrode. Therefore, the lithium salt added to the positive electrode can be used as long as it is soluble in an organic solvent and can be stably present in a battery, that is, a lithium salt used as an electrolyte salt of a nonaqueous electrolyte secondary battery. It is thought that there is an effect of.

表１中の比較例２にデータが記載されていないのは、ＬｉＰＦ６の添加量を５質量％としたとき、活物質スラリーを均一に集電体上に塗布することができず、電池評価に耐える極板を作製することができなかったことによる。したがって、正極に添加するリチウム塩の添加量は３質量％以下であることが好ましい。 The data is not described in Comparative Example 2 in Table 1 because when the addition amount of LiPF 6 is 5% by mass, the active material slurry cannot be uniformly applied on the current collector, and the battery evaluation This is because it was not possible to produce an electrode plate that can withstand. Accordingly, the amount of lithium salt added to the positive electrode is preferably 3% by mass or less.

（吸液性評価）
実施例２及び比較例１、４、５、６の注液前の仕掛品に、それぞれに注液すべき電解液２ｍｌを開口部上方からスポイトで滴下した。そして、電解液の液面が電極群に完全に浸透するまでの時間を測定して、吸液性を評価した。結果をまとめて表２に示した。吸液時間は、実施例２の吸液時間を１００とした指数で記載した。 (Liquid absorption evaluation)
2 ml of the electrolyte to be injected into each of the in-process products before injection of Example 2 and Comparative Examples 1, 4, 5, and 6 was dropped from above the opening with a dropper. And the time until the liquid level of the electrolytic solution completely penetrates into the electrode group was measured to evaluate the liquid absorbency. The results are summarized in Table 2. The liquid absorption time is described as an index with the liquid absorption time of Example 2 as 100.

Figure 2011192561
Figure 2011192561

表２から、注液工程の電解液濃度を上げるに従い、電解液の吸液時間が増加することがわかる。そして、実施例２と比較例４を比較すると、電池中のリチウム塩濃度はともに１．７ｍｏｌ／Ｌであるが、実施例２の吸液時間は１０％以上短縮されていることがわかる。これは、リチウム塩の一部を正極に担持させることで、注液工程に供される電解液濃度を下げることができるため、電解液の浸透性を改善することができたことによる。本発明は、高出力用途に適した非水電解液二次電池の望ましい製造方法であることがわかる。    From Table 2, it can be seen that as the electrolyte concentration in the liquid injection process is increased, the liquid absorption time of the electrolyte increases. When Example 2 and Comparative Example 4 are compared, the lithium salt concentration in the battery is 1.7 mol / L, but the liquid absorption time of Example 2 is reduced by 10% or more. This is because by allowing a part of the lithium salt to be supported on the positive electrode, it is possible to reduce the concentration of the electrolytic solution used in the liquid injection process, and thus it is possible to improve the permeability of the electrolytic solution. It turns out that this invention is a desirable manufacturing method of the non-aqueous-electrolyte secondary battery suitable for a high output use.

以上説明したように、本発明によると、ハイレート放電サイクルに優れた非水電解液二次電池を製造工程における不具合を解消することができるため、産業上の利用可能性は大きい。   As described above, according to the present invention, problems in the manufacturing process of a non-aqueous electrolyte secondary battery excellent in high-rate discharge cycle can be solved, and thus industrial applicability is great.

Claims (2)

正極活物質を有する正極と、負極活物質を有する負極と、１．５〜１．８ｍｏｌ／Ｌのリチウム塩濃度を有する非水電解液とを備える非水電解液二次電池の製造方法において、
正極集電体となる金属箔上に、活物質、導電剤、結着剤及び非水溶媒に可溶なリチウム塩を含む合剤を塗布する正極作製工程を備え、
前記合剤中のリチウム塩の添加量は、活物質、導電剤、結着剤の総質量に対して０．１〜３質量％であり、
前記正極作製工程及び電池組立工程が露点−２０℃以下の環境下で行われる特徴とする非水電解液二次電池の製造方法。 In a method for producing a nonaqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a nonaqueous electrolyte solution having a lithium salt concentration of 1.5 to 1.8 mol / L,
A positive electrode preparation step of applying a mixture containing a lithium salt soluble in an active material, a conductive agent, a binder and a non-aqueous solvent on a metal foil to be a positive electrode current collector,
The addition amount of the lithium salt in the mixture is 0.1 to 3% by mass with respect to the total mass of the active material, the conductive agent and the binder,
The method for producing a nonaqueous electrolyte secondary battery, wherein the positive electrode preparation step and the battery assembly step are performed in an environment having a dew point of -20 ° C or lower. 前記リチウム塩がＬｉＰＦ６又はＬｉＢＦ４の少なくとも一方から選ばれることを特徴とする請求項１記載の非水電解液二次電池の製造方法。 The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium salt is selected from at least one of LiPF 6 and LiBF 4 .
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US9673446B2 (en) 2012-02-28 2017-06-06 Hitachi Maxell, Ltd. Lithium ion secondary battery containing a negative electrode material layer containing Si and O as constituent elements
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