JP2020194739A - Lithium ion secondary battery and manufacturing method thereof - Google Patents
Lithium ion secondary battery and manufacturing method thereof Download PDFInfo
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- JP2020194739A JP2020194739A JP2019100658A JP2019100658A JP2020194739A JP 2020194739 A JP2020194739 A JP 2020194739A JP 2019100658 A JP2019100658 A JP 2019100658A JP 2019100658 A JP2019100658 A JP 2019100658A JP 2020194739 A JP2020194739 A JP 2020194739A
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- Prior art keywords
- positive electrode
- negative electrode
- lithium
- ion secondary
- secondary battery
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 65
- 238000004519 manufacturing process Methods 0.000 title claims description 40
- 239000003792 electrolyte Substances 0.000 claims abstract description 76
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 40
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 40
- 239000007774 positive electrode material Substances 0.000 claims abstract description 38
- ANFWGAAJBJPAHX-UHFFFAOYSA-N bis(fluorosulfonyl)azanide;1-ethyl-3-methylimidazol-3-ium Chemical compound CC[N+]=1C=CN(C)C=1.FS(=O)(=O)[N-]S(F)(=O)=O ANFWGAAJBJPAHX-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000007773 negative electrode material Substances 0.000 claims abstract description 28
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 claims abstract description 8
- NDZWKTKXYOWZML-UHFFFAOYSA-N trilithium;difluoro oxalate;borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-].FOC(=O)C(=O)OF NDZWKTKXYOWZML-UHFFFAOYSA-N 0.000 claims abstract description 8
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- 238000000034 method Methods 0.000 claims description 40
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Classifications
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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
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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
- 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
Description
本発明は、リチウムイオン二次電池及びリチウムイオン二次電池の製造方法に関する。 The present invention relates to a lithium ion secondary battery and a method for manufacturing a lithium ion secondary battery.
リチウムイオン二次電池は、軽量で高エネルギー密度の二次電池であり、その特性を活かして、ノートパソコン、携帯電話等のポータブル機器の電源に使用されている。
近年では、リチウムイオン二次電池は、ポータブル機器等の民生用途にとどまらず、車載用途、太陽光発電、風力発電等といった自然エネルギー向け大規模蓄電システム用途などとしても展開されている。
Lithium-ion secondary batteries are lightweight, high-energy density secondary batteries, and are used as power sources for portable devices such as notebook computers and mobile phones by taking advantage of their characteristics.
In recent years, lithium-ion secondary batteries have been developed not only for consumer applications such as portable devices, but also for in-vehicle applications, large-scale power storage system applications for natural energy such as solar power generation and wind power generation.
リチウムイオン二次電池の電解質としては、有機溶媒にリチウム塩を溶解した電解液が一般的に用いられている。また、有機溶媒は揮発しやすいため、有機溶媒の代わりに不揮発性のイオン液体を用い、イオン液体にリチウム塩を溶解した電解質をリチウムイオン二次電池に用いる場合がある。
ここでイオン液体とは、カチオンとアニオンから構成され、比較的低温、例えば２５℃程度にて液体状態となる塩をいう。
As the electrolyte of the lithium ion secondary battery, an electrolytic solution in which a lithium salt is dissolved in an organic solvent is generally used. Further, since the organic solvent is easily volatilized, a non-volatile ionic liquid may be used instead of the organic solvent, and an electrolyte obtained by dissolving a lithium salt in the ionic liquid may be used for the lithium ion secondary battery.
Here, the ionic liquid is a salt composed of cations and anions and which becomes a liquid state at a relatively low temperature, for example, about 25 ° C.
しかしながら、イオン液体を電解質に用いたリチウムイオン二次電池では、十分な充放電サイクル特性が得られないという問題がある。そこで、正極活物質を含む正極と、負極活物質を含む負極と、常温溶融塩を含有する非水電解質とを備える非水電解質二次電池において、前記非水電解質を注入した後、初回充電前に、電位走査により、前記負極の電位を前記常温溶融塩のカチオンが還元分解する電位以下まで掃引した非水電解質二次電池が提案されている（例えば、特許文献１を参照）。常温溶融塩（イオン液体）のカチオンを還元分解させることにより、負極表面に安定な被膜を形成することができ、これにより、その後の充電による常温溶融塩のカチオンの分解が抑制され、充放電サイクル特性に優れた非水電解質二次電池となる。 However, a lithium ion secondary battery using an ionic liquid as an electrolyte has a problem that sufficient charge / discharge cycle characteristics cannot be obtained. Therefore, in a non-aqueous electrolyte secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte containing a room temperature molten salt, after the non-aqueous electrolyte is injected, before the first charge. In addition, a non-aqueous electrolyte secondary battery in which the potential of the negative electrode is swept to a potential equal to or lower than the potential at which the cation of the room temperature molten salt is reduced and decomposed by potential scanning has been proposed (see, for example, Patent Document 1). By reducing and decomposing the cations of the room temperature molten salt (ionic liquid), a stable film can be formed on the surface of the negative electrode, which suppresses the decomposition of the cations of the room temperature molten salt by subsequent charging and the charge / discharge cycle. It is a non-aqueous electrolyte secondary battery with excellent characteristics.
ここで、特許文献１に記載されている方法以外にもリチウムイオン二次電池の充放電サイクル特性を高めることができるリチウムイオン二次電池、及びその製造方法が求められている。 Here, in addition to the method described in Patent Document 1, a lithium ion secondary battery capable of enhancing the charge / discharge cycle characteristics of the lithium ion secondary battery and a method for manufacturing the lithium ion secondary battery are required.
本開示の一形態は上記従来の事情に鑑みてなされたものであり、充放電サイクル特性に優れるリチウムイオン二次電池及びその製造方法を提供することを目的とする。 One form of the present disclosure has been made in view of the above-mentioned conventional circumstances, and an object of the present disclosure is to provide a lithium ion secondary battery having excellent charge / discharge cycle characteristics and a method for manufacturing the same.
前記課題を達成するための具体的手段は以下の通りである。
＜１＞ 正極活物質を含む正極と、負極活物質を含む負極と、１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド、リチウムビスオキサレートボラート及びリチウムジフルオロ（オキサラト）ボレートの少なくとも一方、並びにリチウム塩を含む電解質と、を備えるリチウムイオン二次電池。
＜２＞ 前記負極活物質が黒鉛を含む前記＜１＞に記載のリチウムイオン二次電池。
＜３＞ 前記正極活物質が層状型リチウム・ニッケル・マンガン・コバルト複合酸化物を含む前記＜１＞又は＜２＞に記載のリチウムイオン二次電池。
Specific means for achieving the above-mentioned problems are as follows.
<1> A positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and at least 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide, lithium bisoxalate borate, and lithium difluoro (oxalate) borate. On the other hand, a lithium ion secondary battery comprising an electrolyte containing a lithium salt.
<2> The lithium ion secondary battery according to <1>, wherein the negative electrode active material contains graphite.
<3> The lithium ion secondary battery according to <1> or <2>, wherein the positive electrode active material contains a layered lithium / nickel / manganese / cobalt composite oxide.
＜４＞ 正極活物質を含む正極と、負極活物質を含む負極と、１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド、リチウムビスオキサレートボラート及びリチウムジフルオロ（オキサラト）ボレートの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程を有するリチウムイオン二次電池の製造方法。
＜５＞ 前記正極及び前記負極の少なくとも一方の電極を１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド、リチウムビスオキサレートボラート及びリチウムジフルオロ（オキサラト）ボレートの少なくとも一方、並びにリチウム塩を含む電解質に浸漬させる工程と、浸漬させた後の前記電極を熱処理する工程と、を有し、前記電極の熱処理後に、熱処理した前記電極を用いて前記電池容器に収容する工程を行う前記＜４＞に記載のリチウムイオン二次電池の製造方法。
＜６＞ 前記正極、前記負極及び前記電解質が収容された前記電池容器を熱処理する工程をさらに有する前記＜４＞に記載のリチウムイオン二次電池の製造方法。
＜７＞ 前記浸漬させる工程にて用いる前記電解質のリチウム塩濃度が０．５ｍｏｌ／ｋｇ〜２．５ｍｏｌ／ｋｇである前記＜５＞に記載のリチウムイオン二次電池の製造方法。
＜８＞ 前記電池容器に収容される前記電解質のリチウム塩濃度が０．５ｍｏｌ／ｋｇ〜２．５ｍｏｌ／ｋｇである前記＜４＞〜＜７＞のいずれか１つに記載のリチウムイオン二次電池の製造方法。
＜９＞ 前記負極活物質が黒鉛を含む前記＜４＞〜＜８＞のいずれか１つに記載のリチウムイオン二次電池の製造方法。
＜１０＞ 前記正極活物質が層状型リチウム・ニッケル・マンガン・コバルト複合酸化物を含む前記＜４＞〜＜９＞のいずれか１つに記載のリチウムイオン二次電池の製造方法。
<4> A positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and at least 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide, lithium bisoxalate borate, and lithium difluoro (oxalate) borate. On the other hand, a method for manufacturing a lithium ion secondary battery, which comprises a step of accommodating an electrolyte containing a lithium salt in a battery container.
<5> At least one of the positive electrode and the negative electrode is 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide, lithium bisoxalate borate, and lithium difluoro (oxalate) borate, and a lithium salt. The step of immersing the electrode in the electrolyte containing the above, and the step of heat-treating the electrode after the immersion is performed, and after the heat treatment of the electrode, the step of accommodating the heat-treated electrode in the battery container is performed. 4> The method for manufacturing a lithium ion secondary battery.
<6> The method for producing a lithium ion secondary battery according to <4>, further comprising a step of heat-treating the positive electrode, the negative electrode, and the battery container containing the electrolyte.
<7> The method for producing a lithium ion secondary battery according to <5>, wherein the lithium salt concentration of the electrolyte used in the dipping step is 0.5 mol / kg to 2.5 mol / kg.
<8> The lithium ion secondary according to any one of <4> to <7>, wherein the lithium salt concentration of the electrolyte contained in the battery container is 0.5 mol / kg to 2.5 mol / kg. How to make a battery.
<9> The method for producing a lithium ion secondary battery according to any one of <4> to <8>, wherein the negative electrode active material contains graphite.
<10> The method for producing a lithium ion secondary battery according to any one of <4> to <9>, wherein the positive electrode active material contains a layered lithium-nickel-manganese-cobalt composite oxide.
本開示の一形態によれば、充放電サイクル特性に優れるリチウムイオン二次電池及びその製造方法を提供することができる。 According to one embodiment of the present disclosure, it is possible to provide a lithium ion secondary battery having excellent charge / discharge cycle characteristics and a method for manufacturing the same.
以下、本発明を実施するための形態について詳細に説明する。但し、本発明は以下の実施形態に限定されるものではない。以下の実施形態において、その構成要素（要素ステップ等も含む）は、特に明示した場合を除き、必須ではない。数値及びその範囲についても同様であり、本発明を制限するものではない。また、本開示中の技術的思想の範囲内において、当業者による様々な変更及び修正が可能である。
本開示において「工程」との語には、他の工程から独立した工程に加え、他の工程と明確に区別できない場合であってもその工程の目的が達成されれば、当該工程も含まれる。
本開示において「〜」を用いて示された数値範囲には、「〜」の前後に記載される数値がそれぞれ最小値及び最大値として含まれる。
本開示中に段階的に記載されている数値範囲において、一つの数値範囲で記載された上限値又は下限値は、他の段階的な記載の数値範囲の上限値又は下限値に置き換えてもよい。また、本開示中に記載されている数値範囲において、その数値範囲の上限値又は下限値は、実施例に示されている値に置き換えてもよい。
本開示において各成分は該当する物質を複数種含んでいてもよい。各成分に該当する物質が複数種存在する場合、各成分の含有率は、特に断らない限り、当該複数種の物質の合計の含有率を意味する。
本開示において各成分に該当する粒子は複数種含んでいてもよい。各成分に該当する粒子が複数種存在する場合、各成分の粒子径は、特に断らない限り、当該複数種の粒子の混合物についての値を意味する。
本開示において「層」又は「膜」との語には、当該層又は膜が存在する領域を観察したときに、当該領域の全体に形成されている場合に加え、当該領域の一部にのみ形成されている場合も含まれる。
本開示において、正極合剤又は負極合剤の「固形分」とは、正極合剤のスラリー又は負極合剤のスラリーから有機溶剤等の揮発性成分を除いた残りの成分を意味する。
本開示において、リチウム塩は、リチウムビスオキサレートボラート及びリチウムジフルオロ（オキサラト）ボレート以外のリチウム塩を意味する。
Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention. In addition, various changes and modifications by those skilled in the art can be made within the scope of the technical idea disclosed in the present disclosure.
In the present disclosure, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other process. ..
The numerical range indicated by using "~" in the present disclosure includes the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present disclosure, each component may contain a plurality of applicable substances. When a plurality of substances corresponding to each component are present, the content rate of each component means the total content rate of the plurality of substances unless otherwise specified.
In the present disclosure, a plurality of types of particles corresponding to each component may be contained. When a plurality of types of particles corresponding to each component are present, the particle size of each component means a value for a mixture of the plurality of types of particles unless otherwise specified.
In the present disclosure, the term "layer" or "membrane" is used only in a part of the region in addition to the case where the layer or the membrane is formed in the entire region when the region in which the layer or the membrane exists is observed. The case where it is formed is also included.
In the present disclosure, the "solid content" of the positive electrode mixture or the negative electrode mixture means the remaining components obtained by removing volatile components such as organic solvents from the slurry of the positive electrode mixture or the slurry of the negative electrode mixture.
In the present disclosure, lithium salt means a lithium salt other than lithium bisoxalate oxalate and lithium difluoro (oxalate) oxalate.
＜リチウムイオン二次電池＞
本開示のリチウムイオン二次電池は、正極活物質を含む正極と、負極活物質を含む負極と、１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド（以下、「ＥＭＩ−ＦＳＩ」とも称する。）、リチウムビスオキサレートボラート（以下、「ＬｉＢＯＢ」とも称する。）及びリチウムジフルオロ（オキサラト）ボレート（以下、「ＬｉＤＦＯＢ」とも称する。）の少なくとも一方、並びにリチウム塩を含む電解質と、を備える。
本開示のリチウムイオン二次電池では、前述の電解質を用いることにより、充放電サイクル特性に優れる。
<Lithium-ion secondary battery>
The lithium ion secondary battery of the present disclosure includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (hereinafter, also referred to as "EMI-FSI"). ), Lithium bisoxalate borate (hereinafter, also referred to as “LiBOB”) and lithium difluoro (oxalate) bolate (hereinafter, also referred to as “LiDFOB”), and an electrolyte containing a lithium salt. Be prepared.
The lithium ion secondary battery of the present disclosure is excellent in charge / discharge cycle characteristics by using the above-mentioned electrolyte.
本開示のリチウムイオン二次電池にて用いる正極、負極及び電解質の好ましい構成について以下に説明する。 Preferred configurations of the positive electrode, the negative electrode and the electrolyte used in the lithium ion secondary battery of the present disclosure will be described below.
（正極）
本開示のリチウムイオン二次電池は、正極活物質を含む正極を備える。正極活物質を含む正極としては、リチウムイオン二次電池に適用可能な正極であれば特に限定されない。例えば、正極は、正極集電体及びその表面に配置され、かつ正極活物質を含む正極合剤層を有する構成であってもよい。
(Positive electrode)
The lithium ion secondary battery of the present disclosure includes a positive electrode containing a positive electrode active material. The positive electrode containing the positive electrode active material is not particularly limited as long as it is a positive electrode applicable to a lithium ion secondary battery. For example, the positive electrode may be arranged on the positive electrode current collector and its surface, and may have a positive electrode mixture layer containing a positive electrode active material.
正極活物質としては、層状型リチウム・ニッケル・マンガン・コバルト複合酸化物（以下、「ＮＭＣ」とも称する。）を含むことが好ましい。ＮＭＣは、高容量であり、且つ安全性にも優れる傾向にある。
ＮＭＣの含有率は、電池の高容量化の観点から、正極合剤層全量に対して６５質量％以上であることが好ましく、７０質量％以上であることがより好ましく、８０質量％以上であることがさらに好ましい。
The positive electrode active material preferably contains a layered lithium-nickel-manganese-cobalt composite oxide (hereinafter, also referred to as "NMC"). NMC tends to have a high capacity and excellent safety.
From the viewpoint of increasing the capacity of the battery, the content of NMC is preferably 65% by mass or more, more preferably 70% by mass or more, and 80% by mass or more with respect to the total amount of the positive electrode mixture layer. Is even more preferable.
ＮＭＣとしては、以下の組成式（化１）で表されるものを用いることが好ましい。
Ｌｉ（１＋δ）ＭｎｘＮｉｙＣｏ（１−ｘ−ｙ−ｚ）ＭｚＯ２・・・（化１）
組成式（化１）において、（１＋δ）はＬｉ（リチウム）の組成比を、ｘはＭｎ（マンガン）の組成比を、ｙはＮｉ（ニッケル）の組成比を、（１−ｘ−ｙ−ｚ）はＣｏ（コバルト）の組成比を、各々示す。ｚは、元素Ｍの組成比を示す。Ｏ（酸素）の組成比は２である。
元素Ｍは、Ｔｉ（チタン）、Ｚｒ（ジルコニウム）、Ｎｂ（ニオブ）、Ｍｏ（モリブデン）、Ｗ（タングステン）、Ａｌ（アルミニウム）、Ｓｉ（シリコン）、Ｇａ（ガリウム）、Ｇｅ（ゲルマニウム）及びＳｎ（錫）からなる群より選択される少なくとも１種の元素であることが好ましい。
また、−０．１５＜δ＜０．１５、０．１＜ｘ≦０．５、０．６＜ｘ＋ｙ＋ｚ＜１．０、０≦ｚ≦０．１である。
As the NMC, it is preferable to use one represented by the following composition formula (Chemical formula 1).
Li (1 + δ) Mn x Ni y Co (1-x-y-z) M z O 2 ··· ( of 1)
In the composition formula (Chemical formula 1), (1 + δ) is the composition ratio of Li (lithium), x is the composition ratio of Mn (manganese), and y is the composition ratio of Ni (nickel), (1-xy-. z) indicates the composition ratio of Co (cobalt), respectively. z indicates the composition ratio of the element M. The composition ratio of O (oxygen) is 2.
The elements M are Ti (titanium), Zr (zirconium), Nb (niobium), Mo (molybdenum), W (tungsten), Al (aluminum), Si (silicon), Ga (gallium), Ge (germanium) and Sn. It is preferably at least one element selected from the group consisting of (tin).
Further, −0.15 <δ <0.15, 0.1 <x ≦ 0.5, 0.6 <x + y + z <1.0, 0 ≦ z ≦ 0.1.
また、正極活物質としては、ＮＭＣ以外のものを用いてもよい。
ＮＭＣ以外の正極活物質としては、この分野で常用されるものを使用でき、スピネル型リチウムマンガン複合酸化物（ｓｐ−Ｍｎ）、ＮＭＣ及びｓｐ−Ｍｎ以外のリチウム含有複合金属酸化物、オリビン型リチウム塩、カルコゲン化合物、二酸化マンガン等が挙げられる。
正極活物質は１種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。
Further, as the positive electrode active material, a material other than NMC may be used.
As the positive electrode active material other than NMC, those commonly used in this field can be used, and spinel-type lithium manganese composite oxide (sp-Mn), lithium-containing composite metal oxide other than NMC and sp-Mn, and olivine-type lithium. Examples include salts, chalcogen compounds, manganese dioxide and the like.
One type of positive electrode active material may be used alone, or two or more types may be used in combination.
次に、正極合剤層及び正極集電体について詳細に説明する。正極合剤層は、正極活物質、結着剤等を含有し、正極集電体上に配置される。正極合剤層の形成方法に制限はなく、例えば、次のように形成される。正極活物質、結着剤及び必要に応じて用いられる導電剤、増粘剤等の他の材料を乾式で混合してシート状にし、これを正極集電体に圧着する（乾式法）ことで正極合剤層を形成することができる。また、正極活物質、結着剤及び必要に応じて用いられる導電剤、増粘剤等の他の材料を分散溶媒に溶解又は分散させて正極合剤のスラリーとし、これを正極集電体に塗布し、乾燥する（湿式法）ことで正極合剤層を形成することができる。
正極活物質としては、前述したように、層状型リチウム・ニッケル・マンガン・コバルト複合酸化物（ＮＭＣ）が用いられることが好ましい。正極活物質は、粉状（粒状）で用いられ、混合される。
ＮＭＣ等の正極活物質の粒子としては、塊状、多面体状、球状、楕円球状、板状、針状、柱状等の形状を有するものを用いることができる。
ＮＭＣ等の正極活物質の粒子の平均粒子径（ｄ５０）（一次粒子が凝集して二次粒子を形成している場合には二次粒子の平均粒子径（ｄ５０））は、タップ密度（充填性）、電極の形成の際における他の材料との混合性の観点から、１μｍ〜３０μｍであることが好ましく、３μｍ〜２５μｍであることがより好ましく、５μｍ〜１５μｍであることがさらに好ましい。正極活物質の粒子の平均粒子径（ｄ５０）は、例えば、レーザー光散乱法を利用した粒子径分布測定装置（ＳＡＬＤ−３０００、株式会社島津製作所）を用いて体積基準の粒度分布を測定し、ｄ５０（メジアン径）として求められる体積平均粒子径である。
Next, the positive electrode mixture layer and the positive electrode current collector will be described in detail. The positive electrode mixture layer contains a positive electrode active material, a binder, and the like, and is arranged on the positive electrode current collector. There is no limitation on the method of forming the positive electrode mixture layer, and the positive electrode mixture layer is formed as follows, for example. By mixing the positive electrode active material, the binder and other materials such as the conductive agent and the thickener used as necessary in a dry manner to form a sheet, and crimping this to the positive electrode current collector (dry method). A positive electrode mixture layer can be formed. In addition, a positive electrode active material, a binder, and other materials such as a conductive agent and a thickener used as needed are dissolved or dispersed in a dispersion solvent to form a slurry of a positive electrode mixture, which is used as a positive electrode current collector. A positive electrode mixture layer can be formed by applying and drying (wet method).
As the positive electrode active material, as described above, a layered lithium-nickel-manganese-cobalt composite oxide (NMC) is preferably used. The positive electrode active material is used in powder form (granular) and mixed.
As the particles of the positive electrode active material such as NMC, those having a shape such as a mass, a polyhedron, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, or a columnar shape can be used.
The average particle size (d50) of the particles of the positive electrode active material such as NMC (the average particle size (d50) of the secondary particles when the primary particles are aggregated to form the secondary particles) is the tap density (filling). Properties), from the viewpoint of mixing with other materials when forming the electrode, it is preferably 1 μm to 30 μm, more preferably 3 μm to 25 μm, and even more preferably 5 μm to 15 μm. For the average particle size (d50) of the particles of the positive electrode active material, for example, a volume-based particle size distribution is measured using a particle size distribution measuring device (SALD-3000, Shimadzu Corporation) using a laser light scattering method. It is a volume average particle diameter obtained as d50 (median diameter).
ＮＭＣ等の正極活物質の粒子の７７Ｋでの窒素吸着測定より求められる比表面積（以下、単に「比表面積」とも称する。）の範囲は、０．２ｍ２／ｇ〜４．０ｍ２／ｇであることが好ましく、０．３ｍ２／ｇ〜２．５ｍ２／ｇであることがより好ましく、０．４ｍ２／ｇ〜１．５ｍ２／ｇであることがさらに好ましい。
正極活物質の粒子の比表面積が０．２ｍ２／ｇ以上であれば、優れた電池性能が得られる傾向にある。また、正極活物質の粒子の比表面積が４．０ｍ２／ｇ以下であると、タップ密度が上がりやすく、結着剤、導電剤等の他の材料との混合性が良好になる傾向にある。比表面積は、ＪＩＳ Ｚ ８８３０：２０１３に準じて窒素吸着能から測定することができる。比表面積の測定を行う際には、試料表面及び構造中に吸着している水分がガス吸着能に影響を及ぼすと考えられることから、まず、加熱による水分除去の前処理を行うことが好ましい。
前処理では、０．０５ｇの測定試料を投入した測定用セルを、真空ポンプで１０Ｐａ以下に減圧した後、１１０℃で加熱し、３時間以上保持した後、減圧した状態を保ったまま常温（２５℃）まで自然冷却する。この前処理を行った後、評価温度を７７Ｋとし、評価圧力範囲を相対圧（飽和蒸気圧に対する平衡圧力）にて１未満として測定する。窒素吸着を多点法で測定し、ＢＥＴ法により比表面積を算出する。
The positive electrode active specific surface area determined from nitrogen adsorption measurements at 77K particulate substances NMC like (hereinafter, simply referred to as "specific surface area".) Range is a 0.2m 2 /g~4.0m 2 / g preferably there, more preferably 0.3m 2 /g~2.5m 2 / g, still more preferably 0.4m 2 /g~1.5m 2 / g.
When the specific surface area of the particles of the positive electrode active material is 0.2 m 2 / g or more, excellent battery performance tends to be obtained. Further, when the specific surface area of the particles of the positive electrode active material is 4.0 m 2 / g or less, the tap density tends to increase, and the mixing property with other materials such as a binder and a conductive agent tends to be good. .. The specific surface area can be measured from the nitrogen adsorption capacity according to JIS Z 8830: 2013. When measuring the specific surface area, it is considered that the water adsorbed on the sample surface and the structure affects the gas adsorption capacity. Therefore, it is preferable to first perform a pretreatment for removing water by heating.
In the pretreatment, the measurement cell in which 0.05 g of the measurement sample is charged is decompressed to 10 Pa or less with a vacuum pump, heated at 110 ° C., held for 3 hours or more, and then kept at room temperature (reduced pressure). Naturally cool to 25 ° C.). After this pretreatment, the evaluation temperature is set to 77K, and the evaluation pressure range is measured as a relative pressure (equilibrium pressure with respect to saturated vapor pressure) of less than 1. Nitrogen adsorption is measured by the multipoint method, and the specific surface area is calculated by the BET method.
正極用の導電剤としては、銅、ニッケル等の金属材料；天然黒鉛、人造黒鉛等の黒鉛（グラファイト）；アセチレンブラック等のカーボンブラック；ニードルコークス等の無定形炭素等の炭素材料などが挙げられる。なお、正極用の導電剤は、１種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。
正極合剤層の質量に対する導電剤の含有率は、０．０１質量％〜５０質量％であることが好ましく、０．１質量％〜３０質量％であることがより好ましく、１質量％〜１５質量％であることがさらに好ましい。導電剤の含有率が０．０１質量％以上であると充分な導電性を得やすい傾向にある。導電剤の含有率が５０質量％以下であれば、電池容量の低下を抑制することができる傾向にある。
Examples of the conductive agent for the positive electrode include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. .. As the conductive agent for the positive electrode, one type may be used alone, or two or more types may be used in combination.
The content of the conductive agent with respect to the mass of the positive electrode mixture layer is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 30% by mass, and 1% by mass to 15% by mass. It is more preferably by mass%. When the content of the conductive agent is 0.01% by mass or more, sufficient conductivity tends to be easily obtained. When the content of the conductive agent is 50% by mass or less, the decrease in battery capacity tends to be suppressed.
正極用の結着剤としては、特に限定されず、湿式法により正極合剤層を形成する場合には、分散溶媒に対する溶解性又は分散性が良好な材料が選択される。具体的には、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリイミド、セルロース等の樹脂系高分子；ＳＢＲ（スチレン−ブタジエンゴム）、ＮＢＲ（アクリロニトリル−ブタジエンゴム）等のゴム状高分子、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン、ポリテトラフルオロエチレン−フッ化ビニリデン共重合体、フッ素化ポリフッ化ビニリデン等のフッ素系高分子；アルカリ金属イオン（特にリチウムイオン）のイオン伝導性を有する高分子組成物などが挙げられる。なお、正極用の結着剤は、１種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。
正極の安定性の観点から、結着剤としては、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン−フッ化ビニリデン共重合体等のフッ素系高分子を用いることが好ましい。
正極合剤層の質量に対する結着剤の含有率は、０．１質量％〜６０質量％であることが好ましく、１質量％〜４０質量％であることがより好ましく、３質量％〜１０質量％であることがさらに好ましい。
結着剤の含有率が０．１質量％以上であると、正極活物質を充分に結着でき、充分な正極合剤層の機械的強度が得られ、サイクル特性等の電池性能が向上する傾向にある。結着剤の含有率が６０質量％以下であると、充分な電池容量及び導電性が得られる傾向にある。
The binder for the positive electrode is not particularly limited, and when the positive electrode mixture layer is formed by the wet method, a material having good solubility or dispersibility in the dispersion solvent is selected. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polyimide, and cellulose; rubber-like polymers such as SBR (styrene-butadiene rubber) and NBR (acrylonitrile-butadiene rubber), polyvinylidene fluoride (PVdF). , Polytetrafluoroethylene, polytetrafluoroethylene-vinylidene fluoride copolymer, polyvinylidene fluoride, and other fluoropolymers; polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), etc. Can be mentioned. As the binder for the positive electrode, one type may be used alone, or two or more types may be used in combination.
From the viewpoint of the stability of the positive electrode, it is preferable to use a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or polyvinylidene fluoride-vinylidene fluoride copolymer as the binder.
The content of the binder with respect to the mass of the positive electrode mixture layer is preferably 0.1% by mass to 60% by mass, more preferably 1% by mass to 40% by mass, and 3% by mass to 10% by mass. It is more preferably%.
When the content of the binder is 0.1% by mass or more, the positive electrode active material can be sufficiently bound, sufficient mechanical strength of the positive electrode mixture layer can be obtained, and battery performance such as cycle characteristics is improved. There is a tendency. When the content of the binder is 60% by mass or less, sufficient battery capacity and conductivity tend to be obtained.
湿式法又は乾式法を用いて正極集電体上に形成された正極合剤層は、正極活物質の充填密度を向上させるため、ハンドプレス又はローラープレス等により圧密化することが好ましい。
圧密化した正極合剤層の密度は、入出力特性及び安全性のさらなる向上の観点から、２．０ｇ／ｃｍ３〜３．５ｇ／ｃｍ３の範囲であることが好ましく、２．３ｇ／ｃｍ３〜３．２ｇ／ｃｍ３の範囲であることがより好ましく、２．５ｇ／ｃｍ３〜３．０ｇ／ｃｍ３の範囲であることがさらに好ましい。
また、正極合剤層を形成する際の正極合剤のスラリーの正極集電体への片面塗布量は、エネルギー密度及び入出力特性の観点から、正極合剤の固形分として、３０ｇ／ｍ２〜１７０ｇ／ｍ２であることが好ましく、４０ｇ／ｍ２〜１６０ｇ／ｍ２であることがより好ましく、４０ｇ／ｍ２〜１５０ｇ／ｍ２であることがさらに好ましい。
The positive electrode mixture layer formed on the positive electrode current collector by the wet method or the dry method is preferably consolidated by a hand press, a roller press, or the like in order to improve the packing density of the positive electrode active material.
The density of compacted positive electrode mixture layer is preferably from the viewpoint of further improvement of the input-output characteristics and safety, in the range of 2.0g / cm 3 ~3.5g / cm 3 , 2.3g / cm more preferably 3 in a range of ~3.2g / cm 3, more preferably in the range of 2.5g / cm 3 ~3.0g / cm 3 .
In addition, the amount of the positive mixture slurry applied to the positive current collector on one side when forming the positive mixture layer is 30 g / m 2 as the solid content of the positive mixture from the viewpoint of energy density and input / output characteristics. it is preferably ~170g / m 2, more preferably from 40g / m 2 ~160g / m 2 , further preferably 40g / m 2 ~150g / m 2 .
正極集電体の材質としては特に制限はなく、中でも金属材料が好ましく、アルミニウムがより好ましい。正極集電体の形状としては特に制限はなく、種々の形状に加工された材料を用いることができる。金属材料については、金属箔、金属板、金属薄膜、エキスパンドメタル等が挙げられ、中でも、金属薄膜を用いることが好ましい。なお、薄膜は適宜メッシュ状に形成してもよい。
正極集電体の平均厚みは特に限定されるものではなく、正極集電体として必要な強度及び良好な可とう性が得られる観点から、１μｍ〜１ｍｍであることが好ましく、３μｍ〜１００μｍであることがより好ましく、５μｍ〜１００μｍであることがさらに好ましい。
The material of the positive electrode current collector is not particularly limited, and among them, a metal material is preferable, and aluminum is more preferable. The shape of the positive electrode current collector is not particularly limited, and materials processed into various shapes can be used. Examples of the metal material include a metal foil, a metal plate, a metal thin film, an expanded metal, and the like, and among them, it is preferable to use a metal thin film. The thin film may be formed in a mesh shape as appropriate.
The average thickness of the positive electrode current collector is not particularly limited, and is preferably 1 μm to 1 mm, preferably 3 μm to 100 μm, from the viewpoint of obtaining the strength required for the positive electrode current collector and good flexibility. More preferably, it is more preferably 5 μm to 100 μm.
（負極）
本開示のリチウムイオン二次電池は、負極活物質を含む負極を備える。負極活物質を含む負極としては、リチウムイオン二次電池に適用可能な負極であれば特に限定されない。例えば、負極は、負極集電体及びその表面に配置され、かつ負極活物質を含む負極合剤層を有する構成であってもよい。
(Negative electrode)
The lithium ion secondary battery of the present disclosure includes a negative electrode containing a negative electrode active material. The negative electrode containing the negative electrode active material is not particularly limited as long as it is a negative electrode applicable to a lithium ion secondary battery. For example, the negative electrode may be arranged on the negative electrode current collector and its surface, and may have a negative electrode mixture layer containing a negative electrode active material.
負極活物質としては、黒鉛、低結晶性炭素、メゾフェーズカーボン等の炭素材料が挙げられ、充放電容量を大きくしやすいことから、黒鉛が好ましい。黒鉛としては、人造黒鉛、天然黒鉛、黒鉛化メゾフェーズカーボン、黒鉛化炭素繊維等が挙げられ、黒鉛の形状としては、鱗片状、球状、塊状等が挙げられる。
負極活物質は、１種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 negative electrode active material include carbon materials such as graphite, low crystallinity carbon, and mesophase carbon, and graphite is preferable because it is easy to increase the charge / discharge capacity. Examples of graphite include artificial graphite, natural graphite, graphitized mesophase carbon, graphitized carbon fiber, and the like, and examples of the shape of graphite include scaly, spherical, and massive shapes.
As the negative electrode active material, one type may be used alone, or two or more types may be used in combination.
炭素材料、好ましくは黒鉛の平均粒子径は、２μｍ〜３０μｍであることが好ましく、２．５μｍ〜２５μｍであることがより好ましく、３μｍ〜２０μｍであることがさらに好ましく、５μｍ〜２０μｍであることが特に好ましい。平均粒子径が３０μｍ以下であると、放電容量及び放電特性が向上する傾向にある。平均粒子径が２μｍ以上であると、初回充放電効率が向上する傾向にある。
なお、平均粒子径（ｄ５０）は、前述の正極活物質の場合と同様にして測定することができる。
The average particle size of the carbon material, preferably graphite, is preferably 2 μm to 30 μm, more preferably 2.5 μm to 25 μm, further preferably 3 μm to 20 μm, and 5 μm to 20 μm. Especially preferable. When the average particle size is 30 μm or less, the discharge capacity and the discharge characteristics tend to improve. When the average particle size is 2 μm or more, the initial charge / discharge efficiency tends to improve.
The average particle size (d50) can be measured in the same manner as in the case of the positive electrode active material described above.
炭素材料、好ましくは黒鉛の比表面積の範囲は、０．５ｍ２／ｇ〜１０ｍ２／ｇであることが好ましく、０．８ｍ２／ｇ〜８ｍ２／ｇであることがより好ましく、１ｍ２／ｇ〜７ｍ２／ｇであることがさらに好ましく、１．５ｍ２／ｇ〜６ｍ２／ｇであることが特に好ましい。
比表面積が０．５ｍ２／ｇ以上であると、優れた電池性能が得られる傾向にある。また、比表面積が１０ｍ２／ｇ以下であると、タップ密度が上がりやすく、結着剤、導電剤等のほかの材料との混合性が良好になる傾向にある。
比表面積は、前述の正極活物質の場合と同様にして測定することができる。
Carbon material, preferably in the range of the specific surface area of the graphite is preferably 0.5m 2 / g~10m 2 / g, more preferably 0.8m 2 / g~8m 2 / g, 1m 2 / G～7m further preferably from 2 / g, particularly preferably 1.5m 2 / g~6m 2 / g.
When the specific surface area is 0.5 m 2 / g or more, excellent battery performance tends to be obtained. Further, when the specific surface area is 10 m 2 / g or less, the tap density tends to increase, and the miscibility with other materials such as a binder and a conductive agent tends to be good.
The specific surface area can be measured in the same manner as in the case of the positive electrode active material described above.
炭素材料、好ましくは黒鉛の含有率は、電池の高容量化の観点から、負極合剤層全量に対して８０質量％以上であることが好ましく、８５質量％以上であることがより好ましく、９０質量％以上であることがさらに好ましい。 The content of the carbon material, preferably graphite, is preferably 80% by mass or more, more preferably 85% by mass or more, and more preferably 90% by mass, based on the total amount of the negative electrode mixture layer, from the viewpoint of increasing the capacity of the battery. It is more preferably mass% or more.
次に、負極合剤層及び負極集電体について詳細に説明する。負極合剤層は、負極活物質、結着剤等を含有し、負極集電体上に配置される。負極合剤層の形成方法に制限はなく、例えば、次のように形成される。負極活物質、結着剤及び必要に応じて用いられる導電剤、増粘剤等の他の材料を分散溶媒に溶解又は分散させて負極合剤のスラリーとし、これを負極集電体に塗布し、乾燥する（湿式法）ことで負極合剤層を形成することができる。 Next, the negative electrode mixture layer and the negative electrode current collector will be described in detail. The negative electrode mixture layer contains a negative electrode active material, a binder, and the like, and is arranged on the negative electrode current collector. There is no limitation on the method of forming the negative electrode mixture layer, and the negative electrode mixture layer is formed as follows, for example. Negative electrode active material, binder and other materials such as conductive agent and thickener used as needed are dissolved or dispersed in a dispersion solvent to form a slurry of negative electrode mixture, which is applied to the negative electrode current collector. The negative electrode mixture layer can be formed by drying (wet method).
負極用の導電剤としては、アセチレンブラック等のカーボンブラック、ニードルコークス等の無定形炭素などを用いることができる。負極用の導電剤は、１種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。このように、負極合剤に導電剤を添加することにより、電極の抵抗を低減する等の効果が得られる傾向にある。 As the conductive agent for the negative electrode, carbon black such as acetylene black, amorphous carbon such as needle coke, or the like can be used. As the conductive agent for the negative electrode, one type may be used alone, or two or more types may be used in combination. As described above, by adding the conductive agent to the negative electrode mixture, the effect of reducing the resistance of the electrode tends to be obtained.
負極合剤層の質量に対する導電剤の含有率は、導電性の向上及び初期不可逆容量の低減の観点から、１質量％〜４５質量％であることが好ましく、２質量％〜４２質量％であることがより好ましく、３質量％〜４０質量％であることがさらに好ましい。導電剤の含有率が１質量％以上であると充分な導電性を得やすい傾向にある。導電剤の含有率が４５質量％以下であると電池容量の低下を抑制することができる傾向にある。 The content of the conductive agent with respect to the mass of the negative electrode mixture layer is preferably 1% by mass to 45% by mass, preferably 2% by mass to 42% by mass, from the viewpoint of improving the conductivity and reducing the initial irreversible capacity. More preferably, it is more preferably 3% by mass to 40% by mass. When the content of the conductive agent is 1% by mass or more, sufficient conductivity tends to be easily obtained. When the content of the conductive agent is 45% by mass or less, the decrease in battery capacity tends to be suppressed.
負極用の結着剤としては、非水電解液又は電極の形成の際に用いる分散溶媒に対して安定な材料であれば、特に制限はない。具体的には、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、セルロース、ニトロセルロース等の樹脂系高分子；ＳＢＲ（スチレン−ブタジエンゴム）、ＮＢＲ（アクリロニトリル−ブタジエンゴム）等のゴム状高分子；ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン等のフッ素系高分子；アルカリ金属イオン（特にリチウムイオン）のイオン伝導性を有する高分子組成物などが挙げられる。なお、負極用の結着剤は、１種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。これらの中でも、ＳＢＲ、ポリフッ化ビニリデンに代表されるフッ素系高分子等を用いることが好ましい。 The binder for the negative electrode is not particularly limited as long as it is a non-aqueous electrolytic solution or a material stable to the dispersion solvent used for forming the electrode. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber) and NBR (acrylonitrile-butadiene rubber); polyvinylidene fluoride (PVdF). ), Polytetrafluoroethylene, polyvinylidene fluoride and the like; and examples thereof include polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions). As the binder for the negative electrode, one type may be used alone, or two or more types may be used in combination. Among these, it is preferable to use a fluoropolymer represented by SBR and polyvinylidene fluoride.
負極合剤層の質量に対する結着剤の含有率は、０．１質量％〜２０質量％であることが好ましく、０．５質量％〜１５質量％であることがより好ましく、０．６質量％〜１０質量％であることがさらに好ましい。
結着剤の含有率が０．１質量％以上であると、負極活物質を充分に結着でき、充分な負極合剤層の機械的強度が得られる傾向にある。結着剤の含有率が２０質量％以下であると、充分な電池容量及び導電性が得られる傾向にある。
The content of the binder with respect to the mass of the negative electrode mixture layer is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and 0.6% by mass. It is more preferably% to 10% by mass.
When the content of the binder is 0.1% by mass or more, the negative electrode active material can be sufficiently bound, and a sufficient mechanical strength of the negative electrode mixture layer tends to be obtained. When the content of the binder is 20% by mass or less, sufficient battery capacity and conductivity tend to be obtained.
なお、結着剤として、ポリフッ化ビニリデンに代表されるフッ素系高分子を主要成分として用いる場合の負極合剤層の質量に対する結着剤の含有率は、１質量％〜１５質量％であることが好ましく、２質量％〜１０質量％であることがより好ましく、３質量％〜８質量％であることがさらに好ましい。 When a fluorine-based polymer typified by polyvinylidene fluoride is used as the main component as the binder, the content of the binder with respect to the mass of the negative electrode mixture layer is 1% by mass to 15% by mass. Is preferable, 2% by mass to 10% by mass is more preferable, and 3% by mass to 8% by mass is further preferable.
増粘剤は、スラリーの粘度を調整するために使用される。増粘剤としては、特に制限はなく、具体的には、例えば、カルボキシメチルセルロース、メチルセルロース、ヒドロキシメチルセルロース、エチルセルロース、ポリビニルアルコール、酸化スターチ、リン酸化スターチ、カゼイン及びこれらの塩が挙げられる。増粘剤は、１種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。 Thickeners are used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One type of thickener may be used alone, or two or more types may be used in combination.
負極合剤層の質量に対する増粘剤の含有率は、入出力特性及び電池容量の観点から、０．１質量％〜５質量％であることが好ましく、０．５質量％〜３質量％であることがより好ましく、０．６質量％〜２質量％であることがさらに好ましい。 The content of the thickener with respect to the mass of the negative electrode mixture layer is preferably 0.1% by mass to 5% by mass, preferably 0.5% by mass to 3% by mass, from the viewpoint of input / output characteristics and battery capacity. More preferably, it is more preferably 0.6% by mass to 2% by mass.
スラリーを形成するための分散溶媒としては、負極活物質、結着剤、及び必要に応じて用いられる導電剤、増粘剤等を溶解又は分散することが可能な溶媒であれば、その種類に制限はなく、水系溶媒又は有機系溶媒のどちらを用いてもよい。水系溶媒の例としては、水、アルコール、水とアルコールとの混合溶媒等が挙げられる。有機系溶媒の例としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、テトラヒドロフラン（ＴＨＦ）、トルエン、アセトン、ジエチルエーテル、ジメチルスルホキシド、ベンゼン、キシレン、ヘキサン等が挙げられる。特に水系溶媒を用いる場合、増粘剤を用いることが好ましい。 As the dispersion solvent for forming the slurry, any solvent can be used as long as it can dissolve or disperse the negative electrode active material, the binder, and the conductive agent, thickener, etc. used as needed. There is no limitation, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol, a mixed solvent of water and alcohol, and the like. Examples of organic solvents include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethyl sulfoxide. , Benzene, xylene, hexane and the like. In particular, when an aqueous solvent is used, it is preferable to use a thickener.
負極合剤層の密度は、０．７ｇ／ｃｍ３〜２ｇ／ｃｍ３であることが好ましく、０．８ｇ／ｃｍ３〜１．９ｇ／ｃｍ３であることがより好ましく、０．９ｇ／ｃｍ３〜１．８ｇ／ｃｍ３であることがさらに好ましい。
負極合剤層の密度が０．７ｇ／ｃｍ３以上であると、負極活物質間の導電性が向上し電池抵抗の増加を抑制することができ、単位容積あたりの容量を向上できる傾向にある。負極合剤層の密度が２ｇ／ｃｍ３以下であると、初期不可逆容量の増加及び負極集電体と負極活物質との界面付近への非水電解液の浸透性の低下による放電特性の劣化を招くおそれが少なくなる傾向にある。
また、負極合剤層を形成する際の負極合剤のスラリーの負極集電体への片面塗布量は、エネルギー密度及び入出力特性の観点から、負極合剤の固形分として、３０ｇ／ｍ２〜１５０ｇ／ｍ２であることが好ましく、４０ｇ／ｍ２〜１４０ｇ／ｍ２であることがより好ましく、４５ｇ／ｍ２〜１３０ｇ／ｍ２であることがさらに好ましい。
Density of the negative electrode mixture layer is preferably 0.7g / cm 3 ~2g / cm 3 , more preferably from 0.8g / cm 3 ~1.9g / cm 3 , 0.9g / cm It is more preferably 3 to 1.8 g / cm 3 .
When the density of the negative electrode mixture layer is 0.7 g / cm 3 or more, the conductivity between the negative electrode active materials is improved, the increase in battery resistance can be suppressed, and the capacity per unit volume tends to be improved. .. When the density of the negative electrode mixture layer is 2 g / cm 3 or less, the initial irreversible capacity increases and the discharge characteristics deteriorate due to the decrease in the permeability of the non-aqueous electrolyte solution near the interface between the negative electrode current collector and the negative electrode active material. There is a tendency that the risk of inviting is reduced.
Further, the amount of the negative electrode mixture slurry applied to the negative electrode current collector on one side when forming the negative electrode mixture layer is 30 g / m 2 as the solid content of the negative electrode mixture from the viewpoint of energy density and input / output characteristics. is preferably to 150 g / m 2, more preferably from 40g / m 2 ~140g / m 2 , further preferably 45g / m 2 ~130g / m 2 .
負極集電体の材質としては特に制限はなく、具体例としては、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼等の金属材料が挙げられる。中でも、加工のし易さとコストの観点から銅が好ましい。 The material of the negative electrode current collector is not particularly limited, and specific examples thereof include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is preferable from the viewpoint of ease of processing and cost.
負極集電体の形状としては特に制限はなく、種々の形状に加工された材料を用いることができる。具体例としては、金属箔、金属板、金属薄膜、エキスパンドメタル等が挙げられる。中でも、金属箔が好ましく、銅箔がより好ましい。銅箔には、圧延法により形成された圧延銅箔と、電解法により形成された電解銅箔とがあり、どちらも負極集電体として好適である。
負極集電体の平均厚みは特に限定されるものではない。例えば、５μｍ〜５０μｍであることが好ましく、８μｍ〜４０μｍであることがより好ましく、９μｍ〜３０μｍであることがさらに好ましい。
なお、負極集電体の平均厚みが２５μｍ未満の場合、純銅よりも強銅合金（リン青銅、チタン銅、コルソン合金、Ｃｕ−Ｃｒ−Ｚｒ合金等）を用いることでその強度を向上させることができる。
The shape of the negative electrode current collector is not particularly limited, and materials processed into various shapes can be used. Specific examples include metal foils, metal plates, metal thin films, expanded metals, and the like. Among them, metal foil is preferable, and copper foil is more preferable. The copper foil includes a rolled copper foil formed by a rolling method and an electrolytic copper foil formed by an electrolytic method, both of which are suitable as a negative electrode current collector.
The average thickness of the negative electrode current collector is not particularly limited. For example, it is preferably 5 μm to 50 μm, more preferably 8 μm to 40 μm, and even more preferably 9 μm to 30 μm.
When the average thickness of the negative electrode current collector is less than 25 μm, the strength can be improved by using a strong copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) rather than pure copper. it can.
本開示のリチウムイオン二次電池が備える正極及び負極の少なくとも一方の電極は、電極表面に被膜を備えていてもよく、ホウ素を含む被膜を備えていてもよい。これにより、その後の充放電による電解質中の成分の分解、活物質の劣化等がより抑制され、充放電サイクル特性により優れるリチウムイオン二次電池が得られる。電極表面に被膜を形成する方法としては、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢ並びにリチウム塩を含む電解質に電極を浸漬させて熱処理する方法が挙げられる。 At least one electrode of the positive electrode and the negative electrode included in the lithium ion secondary battery of the present disclosure may have a coating film on the electrode surface, or may have a coating film containing boron. As a result, decomposition of components in the electrolyte and deterioration of the active material due to subsequent charge / discharge are further suppressed, and a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained. Examples of the method of forming a film on the electrode surface include a method of immersing the electrode in an electrolyte containing EMI-FSI, LiBOB and LiDFOB, and a lithium salt to heat-treat the electrode.
（電解質）
本開示のリチウムイオン二次電池は、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質を備える。ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質（以下、単に「電解質」とも称する。）は、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方並びにリチウム塩をＥＭＩ−ＦＳＩに溶解させることにより調製すればよい。
(Electrolytes)
The lithium ion secondary battery of the present disclosure comprises at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt. At least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt (hereinafter, also simply referred to as “electrolyte”) are prepared by dissolving at least one of LiBOB and LiDFOB and a lithium salt in EMI-FSI. Just do it.
電解質は、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方を含んでいればよく、ＬｉＢＯＢ及びＬｉＤＦＯＢのどちらか一方を含んでいてもよく、ＬｉＢＯＢ及びＬｉＤＦＯＢの両方を含んでいてもよい。 The electrolyte may contain at least one of LiBOB and LiDFOB, may contain either LiBOB or LiDFOB, or may contain both LiBOB and LiDFOB.
電池容器に収容される電解質のＬｉＢＯＢ及びＬｉＤＦＯＢの合計濃度は、電解質の全量に対して０．１質量％〜５質量％であることが好ましく、０．２質量％〜３質量％であることがより好ましく、０．３質量％〜１．５質量％であることがさらに好ましい。 The total concentration of LiBOB and LiDFOB of the electrolyte contained in the battery container is preferably 0.1% by mass to 5% by mass, and preferably 0.2% by mass to 3% by mass, based on the total amount of the electrolyte. More preferably, it is 0.3% by mass to 1.5% by mass.
リチウム塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＦＳＩ（リチウムビス（フルオロスルホニル）イミド）、ＬｉＴＦＳＩ（リチウムビス（トリフルオロメタンスルホニル）イミド）、ＬｉＣｌＯ４、ＬｉＢ（Ｃ６Ｈ５）４、ＬｉＣＨ３ＳＯ３、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＳＯ２ＣＦ２ＣＦ３）２等が挙げられる。リチウム塩は、１種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。 Lithium salts include LiPF 6 , LiBF 4 , LiFSI (lithium bis (fluorosulfonyl) imide), LiTFSI (lithium bis (trifluoromethanesulfonyl) imide), LiClO 4 , LiB (C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN (SO 2 CF 2 CF 3 ) 2, and the like. One type of lithium salt may be used alone, or two or more types may be used in combination.
電池容器に収容される電解質のリチウム塩濃度は、例えば、電気伝導度の観点から、０．５ｍｏｌ／ｋｇ〜２．５ｍｏｌ／ｋｇであることが好ましく、０．８ｍｏｌ／ｋｇ〜２．０ｍｏｌ／ｋｇであることがより好ましく、１．０ｍｏｌ／ｋｇ〜１．８ｍｏｌ／ｋｇであることがさらに好ましい。 The lithium salt concentration of the electrolyte contained in the battery container is, for example, preferably 0.5 mol / kg to 2.5 mol / kg, preferably 0.8 mol / kg to 2.0 mol / kg, from the viewpoint of electrical conductivity. Is more preferable, and 1.0 mol / kg to 1.8 mol / kg is even more preferable.
（セパレータ）
本開示のリチウムイオン二次電池は、正極と負極との間に正極及び負極間を絶縁するセパレータを備えていてもよい。セパレータとしては、正極及び負極間を絶縁しつつ、イオン透過性を有し、かつ、正極側における酸化性及び負極側における還元性に対する耐性を備えるものであれば特に制限はない。このような特性を満たすセパレータの材料（材質）としては、樹脂、無機物等が用いられる。
樹脂としては、オレフィン系高分子、フッ素系高分子、セルロース系高分子、ポリイミド、ナイロン等が用いられる。中でも、ポリエチレン、ポリプロピレン等のポリオレフィンを原料とする多孔性シート又は不織布などを用いることが好ましい。
無機物としては、アルミナ、二酸化ケイ素等の酸化物類、窒化アルミニウム、窒化ケイ素等の窒化物類、ガラスなどが用いられる。例えば、繊維形状又は粒子形状の上記無機物を、不織布としたもの、織布としたもの又は微多孔性フィルム等の薄膜形状の基材に付着させたものをセパレータとして用いることができる。薄膜形状の基材としては、孔径が０．０１μｍ〜１μｍであり、平均厚みが５μｍ〜５０μｍのものが好適に用いられる。また、繊維形状又は粒子形状の上記無機物を、樹脂等の結着剤を用いて複合多孔層としたものをセパレータとして用いることもできる。また、この複合多孔層を他のセパレータの表面に形成し、多層セパレータとしてもよい。さらに、この複合多孔層を、正極又は負極の表面に形成し、セパレータとしてもよい。
(Separator)
The lithium ion secondary battery of the present disclosure may include a separator that insulates between the positive electrode and the negative electrode between the positive electrode and the negative electrode. The separator is not particularly limited as long as it insulates between the positive electrode and the negative electrode, has ion permeability, and has resistance to oxidizing property on the positive electrode side and reducing property on the negative electrode side. As the material (material) of the separator satisfying such characteristics, a resin, an inorganic substance, or the like is used.
As the resin, an olefin polymer, a fluorine polymer, a cellulosic polymer, a polyimide, nylon and the like are used. Above all, it is preferable to use a porous sheet or non-woven fabric made of polyolefin such as polyethylene or polypropylene.
As the inorganic substance, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and glass are used. For example, a fiber-shaped or particle-shaped inorganic substance attached to a thin-film-shaped base material such as a non-woven fabric, a woven cloth, or a microporous film can be used as a separator. As the thin film-shaped substrate, those having a pore diameter of 0.01 μm to 1 μm and an average thickness of 5 μm to 50 μm are preferably used. Further, a fiber-shaped or particle-shaped inorganic substance formed into a composite porous layer by using a binder such as a resin can also be used as a separator. Further, this composite porous layer may be formed on the surface of another separator to form a multilayer separator. Further, this composite porous layer may be formed on the surface of the positive electrode or the negative electrode to serve as a separator.
＜リチウムイオン二次電池の製造方法＞
本開示のリチウムイオン二次電池の製造方法は、正極活物質を含む正極と、負極活物質を含む負極と、１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド、リチウムビスオキサレートボラート及びリチウムジフルオロ（オキサラト）ボレートの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程を有する。
本開示のリチウムイオン二次電池の製造方法では、前述の電解質を電池容器に収容することにより、充放電サイクル特性に優れるリチウムイオン二次電池を製造可能である。
<Manufacturing method of lithium ion secondary battery>
The method for producing a lithium ion secondary battery of the present disclosure includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide, and a lithium bisoxalate bo. It comprises a step of accommodating at least one of a rat and a lithium difluoro (oxalate) electrode, and an electrolyte containing a lithium salt, in a battery container.
In the method for manufacturing a lithium ion secondary battery of the present disclosure, a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be manufactured by accommodating the above-mentioned electrolyte in a battery container.
（収容工程）
本開示の製造方法は、正極と、負極と、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程（収容工程）を有する。この工程では、リチウムイオン二次電池の各構成部材が電池容器に収容される。また、正極と負極との間に正極及び負極間を絶縁するセパレータが配置されるように、セパレータを電池容器に収容してもよい。
(Accommodation process)
The manufacturing method of the present disclosure includes a step (containment step) of accommodating a positive electrode, a negative electrode, at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt in a battery container. In this step, each component of the lithium ion secondary battery is housed in the battery container. Further, the separator may be housed in the battery container so that the separator that insulates between the positive electrode and the negative electrode is arranged between the positive electrode and the negative electrode.
例えば、正極及び負極、並びに必要に応じて正極と負極との間にセパレータを電池容器内に配置した状態にて、電池容器内にＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質を供給してもよい。 For example, the positive electrode and the negative electrode, and if necessary, at least one of EMI-FSI, LiBOB, and LiDFOB, and a lithium salt are contained in the battery container with the separator placed in the battery container between the positive electrode and the negative electrode. An electrolyte may be supplied.
以下、本開示のリチウムイオン二次電池の製造方法の好ましい態様である第一実施形態及び第二実施形態について説明する。 Hereinafter, the first embodiment and the second embodiment, which are preferred embodiments of the method for manufacturing the lithium ion secondary battery of the present disclosure, will be described.
［第一実施形態］
本開示の第一実施形態に係るリチウムイオン二次電池の製造方法は、正極活物質を含む正極及び負極活物質を含む負極の少なくとも一方の電極をＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質に浸漬させる工程と、浸漬させた後の電極を熱処理する工程と、を有し、電極の熱処理後に、熱処理した電極を用いて電池容器に収容する工程、を行う。
本実施形態の製造方法では、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質に電極を浸漬させて熱処理することにより、電極表面に被膜を形成することができる。これにより、その後の充放電による電解質中の成分の分解、活物質の劣化等が抑制され、充放電サイクル特性により優れるリチウムイオン二次電池が得られる。
また、本実施形態の製造方法では、電池反応を行わずに、簡易な方法にて充放電サイクル特性により優れるリチウムイオン二次電池が得られる。
[First Embodiment]
In the method for producing a lithium ion secondary battery according to the first embodiment of the present disclosure, at least one electrode of a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material is used as at least one of EMI-FSI, LiBOB and LiDFOB, and It has a step of immersing it in an electrolyte containing a lithium salt and a step of heat-treating the electrode after the immersion, and after the heat treatment of the electrode, a step of accommodating the heat-treated electrode in a battery container is performed.
In the production method of the present embodiment, a film can be formed on the electrode surface by immersing the electrode in at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt and heat-treating the electrode. As a result, decomposition of components in the electrolyte and deterioration of the active material due to subsequent charge / discharge are suppressed, and a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained.
Further, in the manufacturing method of the present embodiment, a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained by a simple method without performing a battery reaction.
（浸漬工程）
本実施形態の製造方法は、正極活物質を含む正極及び負極活物質を含む負極の少なくとも一方の電極を、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質に浸漬させる工程（浸漬工程）を有する。本工程では、例えば、容器内にリチウム塩であるリチウムビス（フルオロスルホニル）イミドを１．２ｍｏｌ／ｋｇの濃度でＥＭＩ−ＦＳＩに溶解し、かつ、電解質の全量に対して０．５質量％となるようにＬｉＢＯＢ又はＬｉＤＦＯＢをＥＭＩ−ＦＳＩに添加して調製した電解質を充填し、正極及び負極の少なくとも一方の電極を容器内の電解質に浸漬させてもよい。
なお、浸漬工程にて用いる電解質のリチウム塩の濃度は、０．５ｍｏｌ／ｋｇ〜２．５ｍｏｌ／ｋｇであることが好ましく、０．８ｍｏｌ／ｋｇ〜２．０ｍｏｌ／ｋｇであることがより好ましく、１．０ｍｏｌ／ｋｇ〜１．８ｍｏｌ／ｋｇであることがさらに好ましい。
また、浸漬工程にて用いる電解質のＬｉＢＯＢ及びＬｉＤＦＯＢの合計濃度は、電解質の全量に対して０．１質量％〜５質量％であることが好ましく、０．２質量％〜３質量％であることがより好ましく、０．３質量％〜１．５質量％であることがさらに好ましい。
また、リチウム塩の具体例としては、電池容器に収容される電解質に含まれるリチウム塩の具体例と同様である。
(Immersion process)
The production method of the present embodiment is a step of immersing at least one electrode of the positive electrode containing the positive electrode active material and the negative electrode containing the negative electrode active material in at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt ( Immersion step). In this step, for example, lithium bis (fluorosulfonyl) imide, which is a lithium salt, is dissolved in EMI-FSI at a concentration of 1.2 mol / kg in a container, and 0.5% by mass based on the total amount of the electrolyte. The electrolyte prepared by adding LiBOB or LiDFOB to EMI-FSI may be filled so that at least one of the positive electrode and the negative electrode may be immersed in the electrolyte in the container.
The concentration of the lithium salt of the electrolyte used in the dipping step is preferably 0.5 mol / kg to 2.5 mol / kg, more preferably 0.8 mol / kg to 2.0 mol / kg. It is more preferably 1.0 mol / kg to 1.8 mol / kg.
The total concentration of LiBOB and LiDFOB of the electrolyte used in the dipping step is preferably 0.1% by mass to 5% by mass, and 0.2% by mass to 3% by mass, based on the total amount of the electrolyte. Is more preferable, and 0.3% by mass to 1.5% by mass is further preferable.
Further, specific examples of the lithium salt are the same as specific examples of the lithium salt contained in the electrolyte contained in the battery container.
ここで、電極及び電解質が大気、水分等と接触しない条件下で電極を電解質に浸漬させることが好ましく、例えば、不活性ガス雰囲気下で電極を電解質に浸漬させることが好ましい。
また、電極を電解質に浸漬させる際、後述の電極熱処理工程にて電極表面に被膜を好適に形成する観点から、液体状態の電解質に電極を浸漬させることが好ましく、例えば、２５℃にて電解質に電極を浸漬させてもよい。
Here, it is preferable to immerse the electrode in the electrolyte under conditions where the electrode and the electrolyte do not come into contact with the atmosphere, moisture, or the like. For example, it is preferable to immerse the electrode in the electrolyte in an inert gas atmosphere.
Further, when the electrode is immersed in the electrolyte, it is preferable to immerse the electrode in the electrolyte in a liquid state from the viewpoint of preferably forming a film on the electrode surface in the electrode heat treatment step described later, for example, in the electrolyte at 25 ° C. The electrodes may be immersed.
なお、本実施形態の製造方法では、正極及び負極の少なくとも一方の電極を、電解質に浸漬させればよく、電解質に浸漬させた電極について、後述の電極熱処理工程にて熱処理を行えばよい。すなわち、本実施形態の製造方法では、正極及び負極の両方の電極を電解質に浸漬し、電解質に浸漬させた両方の電極に熱処理を行う構成であってもよく、正極及び負極の一方の電極を電解質に浸漬し、電解質に浸漬させた一方の電極に熱処理を行う構成であってもよい。 In the manufacturing method of the present embodiment, at least one electrode of the positive electrode and the negative electrode may be immersed in the electrolyte, and the electrode immersed in the electrolyte may be heat-treated in the electrode heat treatment step described later. That is, in the manufacturing method of the present embodiment, both the positive electrode and the negative electrode may be immersed in the electrolyte, and both the electrodes immersed in the electrolyte may be heat-treated, and one of the positive electrode and the negative electrode may be used. The electrode may be immersed in an electrolyte and one of the electrodes immersed in the electrolyte may be heat-treated.
（電極熱処理工程）
本実施形態の製造方法は、浸漬させた後の電極を熱処理する工程（電極熱処理工程）を有する。電極を熱処理する条件としては、電解質中の成分が熱分解して電極表面に被膜が形成される条件であればよい。
(Electrode heat treatment process)
The manufacturing method of the present embodiment includes a step of heat-treating the electrode after immersion (electrode heat treatment step). The conditions for heat-treating the electrode may be any condition as long as the components in the electrolyte are thermally decomposed to form a film on the electrode surface.
例えば、熱処理の温度としては、３５℃〜１００℃であってもよく、４０℃〜８０℃であってもよく、４５℃〜６０℃であってもよい。熱処理の温度が３５℃以上であることにより、電解質中の成分の熱分解による被膜が形成しやすい傾向にあり、熱処理の温度が１００℃以下であることにより、過剰な熱分解反応を抑制できる傾向にある。
なお、熱処理の温度とは、電極を熱処理するときの雰囲気の温度を指す。
For example, the temperature of the heat treatment may be 35 ° C. to 100 ° C., 40 ° C. to 80 ° C., or 45 ° C. to 60 ° C. When the heat treatment temperature is 35 ° C. or higher, a film tends to be easily formed by thermal decomposition of the components in the electrolyte, and when the heat treatment temperature is 100 ° C. or lower, an excessive thermal decomposition reaction tends to be suppressed. It is in.
The heat treatment temperature refers to the temperature of the atmosphere when the electrodes are heat-treated.
また、熱処理の時間としては、２時間〜２４時間であってもよく、３時間〜１８時間であってもよく、５時間〜１２時間であってもよく、６時間〜８時間であってもよい。熱処理の時間が２時間以上であることにより、電解質中の成分の熱分解による被膜が形成しやすい傾向にあり、熱処理の時間が２４時間以下であることにより、リチウムイオン二次電池の製造効率及び放電負荷特性に優れる傾向にある。 The heat treatment time may be 2 hours to 24 hours, 3 hours to 18 hours, 5 hours to 12 hours, or 6 hours to 8 hours. Good. When the heat treatment time is 2 hours or more, a film tends to be easily formed by thermal decomposition of the components in the electrolyte, and when the heat treatment time is 24 hours or less, the manufacturing efficiency of the lithium ion secondary battery and It tends to have excellent discharge load characteristics.
また、熱処理の雰囲気としては、熱処理の際に大気、水分等が侵入しないことが好ましく、例えば、減圧雰囲気又は不活性ガス雰囲気が好ましい。 Further, as the atmosphere of the heat treatment, it is preferable that the air, moisture and the like do not enter during the heat treatment, and for example, a reduced pressure atmosphere or an inert gas atmosphere is preferable.
（熱処理後収容工程）
本実施形態の製造方法は、電極の熱処理後に、正極と、負極と、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程（熱処理後収容工程）を有する。この工程では、リチウムイオン二次電池の各構成部材が電池容器に収容される。また、正極と負極との間に正極及び負極間を絶縁するセパレータが配置されるように、セパレータを電池容器に収容してもよい。
(Accommodation process after heat treatment)
The manufacturing method of the present embodiment is a step of accommodating a positive electrode, a negative electrode, at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt in a battery container after heat treatment of the electrode (post-heat treatment accommodating step). ). In this step, each component of the lithium ion secondary battery is housed in the battery container. Further, the separator may be housed in the battery container so that the separator that insulates between the positive electrode and the negative electrode is arranged between the positive electrode and the negative electrode.
例えば、電極の熱処理後に、正極及び負極、並びに必要に応じて正極と負極との間にセパレータを電池容器内に配置した状態にて、電池容器内にＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質を供給してもよい。 For example, after heat treatment of the electrodes, at least one of EMI-FSI, LiBOB, and LiDFOB is placed in the battery container with a separator placed in the battery container between the positive electrode and the negative electrode and, if necessary, between the positive electrode and the negative electrode. Also, an electrolyte containing a lithium salt may be supplied.
［第二実施形態］
本開示の第二実施形態に係るリチウムイオン二次電池の製造方法は、正極活物質を含む正極と、負極活物質を含む負極と、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程と、前記正極、前記負極及び前記電解質が収容された前記電池容器を熱処理する工程と、を有する。第二実施形態の製造方法では、正極、負極及び電解質を電池容器に収容した後に、電池容器を熱処理する点で、前述の第一実施形態の製造方法と異なる。
本実施形態の製造方法では、正極と、負極と、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容した後に電池容器を熱処理することにより、正極及び負極の表面に被膜を形成することができ、これにより、その後の充放電による電解質中の成分の分解、活物質の劣化等が抑制され、充放電サイクル特性により優れるリチウムイオン二次電池が得られる。
また、本実施形態の製造方法では、電池反応を行わずに、簡易な方法にて充放電サイクル特性により優れるリチウムイオン二次電池が得られる。
なお、正極、負極及び電解質の好ましい構成、並びに製造されるリチウムイオン二次電池の好ましい構成については、前述の第一実施形態と同様であるため、その説明を省略する。
[Second Embodiment]
In the method for producing a lithium ion secondary battery according to the second embodiment of the present disclosure, a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, at least one of EMI-FSI, LiBOB and LiDFOB, and a lithium salt are used. It has a step of accommodating the containing electrolyte in a battery container, and a step of heat-treating the positive electrode, the negative electrode, and the battery container containing the electrolyte. The manufacturing method of the second embodiment is different from the manufacturing method of the first embodiment described above in that the positive electrode, the negative electrode and the electrolyte are housed in the battery container and then the battery container is heat-treated.
In the production method of the present embodiment, the positive electrode, the negative electrode, at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt are housed in the battery container, and then the battery container is heat-treated to obtain the positive electrode and the negative electrode. A film can be formed on the surface of the negative electrode, which suppresses the decomposition of components in the electrolyte and the deterioration of the active material due to the subsequent charge / discharge, and a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained. ..
Further, in the manufacturing method of the present embodiment, a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained by a simple method without performing a battery reaction.
Since the preferred configurations of the positive electrode, the negative electrode and the electrolyte, and the preferred configurations of the lithium ion secondary battery to be manufactured are the same as those in the above-described first embodiment, the description thereof will be omitted.
（熱処理前収容工程）
本実施形態の製造方法は、正極活物質を含む正極と、負極活物質を含む負極と、ＥＭＩ−ＦＳＩ、ＬｉＢＯＢ及びＬｉＤＦＯＢの少なくとも一方、並びにリチウム塩を含む電解質と、を電池容器に収容する工程（熱処理前収容工程）を有する。この工程では、リチウムイオン二次電池の各構成部材が電池容器に収容される。また、正極と負極との間に正極及び負極間を絶縁するセパレータが配置されるように、セパレータを電池容器に収容してもよい。
(Accommodation process before heat treatment)
The manufacturing method of the present embodiment is a step of accommodating a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, at least one of EMI-FSI, LiBOB and LiDFOB, and an electrolyte containing a lithium salt in a battery container. (Pre-heat treatment accommodating step). In this step, each component of the lithium ion secondary battery is housed in the battery container. Further, the separator may be housed in the battery container so that the separator that insulates between the positive electrode and the negative electrode is arranged between the positive electrode and the negative electrode.
（電池熱処理工程）
本実施形態の製造方法は、正極、負極及び電解質が収容された前記電池容器を熱処理する工程を有する。電池容器を熱処理する条件としては、電解質中の成分が熱分解して正極及び負極の表面に被膜が形成される条件であればよい。
(Battery heat treatment process)
The manufacturing method of the present embodiment includes a step of heat-treating the battery container containing the positive electrode, the negative electrode, and the electrolyte. The conditions for heat-treating the battery container may be any conditions as long as the components in the electrolyte are thermally decomposed to form a film on the surfaces of the positive electrode and the negative electrode.
例えば、熱処理の温度としては、３５℃〜１００℃であってもよく、４０℃〜８０℃であってもよく、４５℃〜６０℃であってもよい。熱処理の温度が３５℃以上であることにより、電解質中の成分の熱分解による被膜が形成しやすい傾向にあり、熱処理の温度が１００℃以下であることにより、過剰な熱分解反応を抑制できる傾向にある。
なお、熱処理の温度とは、電池容器を熱処理するときの雰囲気の温度を指す。
For example, the temperature of the heat treatment may be 35 ° C. to 100 ° C., 40 ° C. to 80 ° C., or 45 ° C. to 60 ° C. When the heat treatment temperature is 35 ° C. or higher, a film tends to be easily formed by thermal decomposition of the components in the electrolyte, and when the heat treatment temperature is 100 ° C. or lower, an excessive thermal decomposition reaction tends to be suppressed. It is in.
The heat treatment temperature refers to the temperature of the atmosphere when the battery container is heat-treated.
また、熱処理の時間としては、２時間〜２４時間であってもよく、３時間〜１８時間であってもよく、５時間〜１２時間であってもよく、６時間〜８時間であってもよい。熱処理の時間が２時間以上であることにより、電解質中の成分の熱分解による被膜が形成しやすい傾向にあり、熱処理の時間が２４時間以下であることにより、放電負荷特性に優れる傾向にある。 The heat treatment time may be 2 hours to 24 hours, 3 hours to 18 hours, 5 hours to 12 hours, or 6 hours to 8 hours. Good. When the heat treatment time is 2 hours or more, a film tends to be easily formed by thermal decomposition of the components in the electrolyte, and when the heat treatment time is 24 hours or less, the discharge load characteristics tend to be excellent.
また、熱処理の雰囲気としては、熱処理の際に大気、水分等が侵入しないことが好ましく、例えば、減圧雰囲気又は不活性ガス雰囲気が好ましい。また電池容器を封止した後に熱処理を行うことが好ましい。
Further, as the atmosphere of the heat treatment, it is preferable that the air, moisture and the like do not enter during the heat treatment, and for example, a reduced pressure atmosphere or an inert gas atmosphere is preferable. Further, it is preferable to perform heat treatment after sealing the battery container.
以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
＜正極の作製＞
層状型リチウム・ニッケル・マンガン・コバルト複合酸化物（正極活物質）９０質量部、アセチレンブラック（導電剤）５質量部、ポリフッ化ビニリデン（結着剤）５質量部、を加えて混合し正極合剤を調製した。正極合剤を分散媒としてのＮ−メチル−２−ピロリドンに分散し、スラリー状としたものを厚さ２０μｍのアルミニウム箔上に、分散媒の乾燥後の塗工量が１００ｇ／ｍ２になるように塗工して１００℃で１時間乾燥し、正極合剤層を形成した。乾燥後、プレスすることにより、正極合剤層の密度を２．６ｇ／ｃｍ３に調整した。なお、正極合剤層の密度は、式：正極合剤層の密度＝（正極の質量−正極集電体［アルミニウム箔］の質量）／（正極合剤層の厚み×正極合剤層の面積）から算出した。これを直径１２ｍｍに打ち抜き、正極とした。
<Preparation of positive electrode>
90 parts by mass of layered lithium / nickel / manganese / cobalt composite oxide (positive electrode active material), 5 parts by mass of acetylene black (conductive agent), and 5 parts by mass of polyvinylidene fluoride (binding agent) are added and mixed to form a positive electrode. The agent was prepared. The positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a dispersion medium, and the slurry is placed on an aluminum foil having a thickness of 20 μm, and the amount of the dispersion medium applied after drying is 100 g / m 2 . The mixture was coated and dried at 100 ° C. for 1 hour to form a positive electrode mixture layer. After drying, the density of the positive electrode mixture layer was adjusted to 2.6 g / cm 3 by pressing. The density of the positive electrode mixture layer is as follows: Formula: Density of positive electrode mixture layer = (mass of positive electrode-mass of positive electrode current collector [aluminum foil]) / (thickness of positive electrode mixture layer x area of positive electrode mixture layer) ). This was punched to a diameter of 12 mm to obtain a positive electrode.
＜負極の作製＞
黒鉛（負極活物質、日立化成株式会社）９５質量部、アセチレンブラック（導電剤）３質量部、スチレンブタジエンゴム（結着剤）１質量部、及びカルボキシメチルセルロース（増粘剤）１質量部を加えて混合し負極合剤を調製した。負極合剤を分散媒としての水に分散し、スラリー状としたものを厚さ２０μｍの銅箔上に、分散媒の乾燥後の塗工量が５４ｇ／ｍ２になるように塗工して８０℃で１時間乾燥し、負極合剤層を形成した。乾燥後、プレスすることにより、負極合剤層の密度を１．６ｇ／ｃｍ３に調整した。なお、負極合剤層の密度は、式：負極合剤層の密度＝（負極の質量−集電体［銅箔］の質量）／（負極合剤層の厚み×負極合剤層の主面の面積）から算出した。これを直径１２ｍｍに打ち抜き、負極とした。
<Manufacturing of negative electrode>
Add 95 parts by mass of graphite (negative electrode active material, Hitachi Kasei Co., Ltd.), 3 parts by mass of acetylene black (conductive agent), 1 part by mass of styrene-butadiene rubber (binder), and 1 part by mass of carboxymethyl cellulose (thickener). To prepare a negative electrode mixture. The negative electrode mixture is dispersed in water as a dispersion medium, and the slurry is coated on a copper foil having a thickness of 20 μm so that the amount of the dispersion medium applied after drying is 54 g / m 2. It was dried at 80 ° C. for 1 hour to form a negative electrode mixture layer. After drying, the density of the negative electrode mixture layer was adjusted to 1.6 g / cm 3 by pressing. The density of the negative electrode mixture layer is as follows: Formula: Density of negative electrode mixture layer = (mass of negative electrode-mass of current collector [copper foil]) / (thickness of negative electrode mixture layer x main surface of negative electrode mixture layer) Area). This was punched to a diameter of 12 mm and used as a negative electrode.
［実施例１］
＜評価用セルの作製＞
正極、直径１４ｍｍに打ち抜いたポリエチレン系微多孔膜セパレータ、負極及び３極式ＨＳセル（宝泉株式会社）を用いて評価用セルを作製した。負極及びセパレータを重ねた後、１．２ｍｏｌ／ｋｇとなるようにリチウムビス（フルオロスルホニル）イミド（ＬｉＦＳＩ）を１−エチル−３−メチルイミダゾリウムビス（フルオロスルホニル）イミド（ＥＭＩ−ＦＳＩ）に溶解させ、さらに、電解質の全量に対して０．５質量％となるようにリチウムビスオキサレートボラート（ＬｉＢＯＢ）をＥＭＩ−ＦＳＩに添加して調製した電解質を３極式ＨＳセルに注液し、その後負極と対向するように正極を重ねてセル内に配置した。
評価用セルは、露点−８０℃以下で、アルゴン雰囲気下のグローブボックス内で作製した。
[Example 1]
<Preparation of evaluation cell>
An evaluation cell was prepared using a positive electrode, a polyethylene-based microporous membrane separator punched to a diameter of 14 mm, a negative electrode, and a 3-pole HS cell (Hosen Co., Ltd.). After stacking the negative electrode and the separator, lithium bis (fluorosulfonyl) imide (LiFSI) is dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (EMI-FSI) so as to be 1.2 mol / kg. Further, the electrolyte prepared by adding lithium bisoxalate boronate (LiBOB) to EMI-FSI so as to be 0.5% by mass with respect to the total amount of the electrolyte was injected into the triode HS cell. After that, the positive electrode was overlapped and arranged in the cell so as to face the negative electrode.
The evaluation cell was prepared in a glove box under an argon atmosphere at a dew point of −80 ° C. or lower.
＜評価用セルの熱処理＞
熱処理として、評価用セルを５０℃に設定した恒温槽内に６時間静置した。その後、評価用セルを取り出し、室温で１２時間静置した。
<Heat treatment of evaluation cell>
As a heat treatment, the evaluation cell was allowed to stand in a constant temperature bath set at 50 ° C. for 6 hours. Then, the evaluation cell was taken out and allowed to stand at room temperature for 12 hours.
＜サイクル試験＞
熱処理後の評価用セルについて、充放電装置を用いて、以下の充放電条件の下で測定した。
（１）初回サイクルは電流値０．１Ｃで、終止電圧４．２Ｖまで充電し、その後、定電圧で電流値が設定電流値の１／１０になるまで充電する定電流定電圧（ＣＣＣＶ）充電を行った。その後、電流値０．１Ｃで、終止電圧３．０Ｖまで定電流（ＣＣ）放電を行った。なお、Ｃとは「電流値（Ａ）／電池容量（Ａｈ）」を意味する。
（２）次いで、電流値１Ｃで、終止電圧４．２Ｖまで充電し、その後、定電圧で電流値が設定電流値の１／１０になるまでＣＣＣＶ充電を行った。その後、電流値１Ｃで、終止電圧３．０ＶまでＣＣ放電を行った。このサイクルを２００サイクル行った。
サイクル試験の結果から、下記式を用いてクーロン効率（％）及び容量維持率（％）を算出した。クーロン効率及び容量維持率は、その値が大きいほど電池として優れているといえる。
クーロン効率（％）＝［（２）で得られた１０サイクル目の放電容量／（２）の１０サイクル目の充電容量］×１００
容量維持率（％）＝［（２）で得られた２００サイクル目の放電容量／（２）の１サイクル目の放電容量］×１００
<Cycle test>
The evaluation cell after the heat treatment was measured using a charging / discharging device under the following charging / discharging conditions.
(1) In the first cycle, the current value is 0.1C, the final voltage is charged to 4.2V, and then the constant voltage is charged until the current value becomes 1/10 of the set current value. Was done. Then, a constant current (CC) discharge was performed with a current value of 0.1 C to a final voltage of 3.0 V. In addition, C means "current value (A) / battery capacity (Ah)".
(2) Next, the current value was 1C and the final voltage was 4.2V, and then the CCCV was charged at a constant voltage until the current value became 1/10 of the set current value. After that, CC discharge was performed with a current value of 1C to a final voltage of 3.0V. This cycle was performed 200 cycles.
From the results of the cycle test, the Coulomb efficiency (%) and the capacity retention rate (%) were calculated using the following formulas. It can be said that the larger the Coulomb efficiency and the capacity retention rate, the better the battery.
Coulomb efficiency (%) = [Discharge capacity in the 10th cycle obtained in (2) / Charge capacity in the 10th cycle in (2)] x 100
Capacity retention rate (%) = [Discharge capacity in the 200th cycle obtained in (2) / Discharge capacity in the first cycle of (2)] x 100
［実施例２］
リチウム塩濃度を表１に示す条件に変更した以外は実施例１と同様にして評価用セルの作製を行い、熱処理を行わずに評価用セルを用いてサイクル試験を行った。
[Example 2]
An evaluation cell was prepared in the same manner as in Example 1 except that the lithium salt concentration was changed to the conditions shown in Table 1, and a cycle test was conducted using the evaluation cell without heat treatment.
［実施例３］
リチウム塩濃度を表１に示す条件に変更し、評価用セルの熱処理の条件を５０℃、１２時間に変更した以外は実施例１と同様にして評価用セルの作製及び評価用セルの熱処理を行い、熱処理をした評価用セルを用いてサイクル試験を行った。
[Example 3]
The evaluation cell was prepared and the evaluation cell was heat-treated in the same manner as in Example 1 except that the lithium salt concentration was changed to the conditions shown in Table 1 and the heat treatment condition of the evaluation cell was changed to 50 ° C. for 12 hours. The cycle test was performed using the heat-treated evaluation cell.
［実施例４］
添加剤をＬｉＢＯＢからリチウムジフルオロ（オキサラト）ボレート（ＬｉＤＦＯＢ）に変更した以外は実施例３と同様にして評価用セルの作製及び評価用セルの熱処理を行い、熱処理をした評価用セルを用いてサイクル試験を行った。
[Example 4]
The evaluation cell was prepared and the evaluation cell was heat-treated in the same manner as in Example 3 except that the additive was changed from LiBOB to lithium difluoro (oxalate) borate (LiDFOB), and the cycle was performed using the heat-treated evaluation cell. The test was conducted.
［実施例５］
添加剤として、ＬｉＢＯＢ及びＬｉＤＦＯＢを電解質の全量に対してそれぞれ０．５質量％用いた以外は実施例３と同様にして評価用セルの作製を行い、熱処理を行わずに評価用セルを用いてサイクル試験を行った。
[Example 5]
An evaluation cell was prepared in the same manner as in Example 3 except that LiBOB and LiDFOB were used as additives in an amount of 0.5% by mass based on the total amount of the electrolyte, and the evaluation cell was used without heat treatment. A cycle test was performed.
［実施例６］
添加剤として、ＬｉＢＯＢ及びＬｉＤＦＯＢを電解質の全量に対してそれぞれ０．５質量％用いた以外は実施例３と同様にして評価用セルの作製を行い、熱処理をした評価用セルを用いてサイクル試験を行った。
[Example 6]
An evaluation cell was prepared in the same manner as in Example 3 except that 0.5% by mass of LiBOB and LiDFOB were used as additives with respect to the total amount of the electrolyte, and a cycle test was performed using the heat-treated evaluation cell. Was done.
［比較例１］
添加剤であるＬｉＢＯＢを用いなかった以外は実施例１と同様にして評価用セルの作製を行い、熱処理を行わずに評価用セルを用いてサイクル試験を行った。
[Comparative Example 1]
An evaluation cell was prepared in the same manner as in Example 1 except that LiBOB, which is an additive, was not used, and a cycle test was conducted using the evaluation cell without heat treatment.
［比較例２］
添加剤であるＬｉＢＯＢを用いなかった以外は実施例２と同様にして評価用セルの作製を行い、熱処理を行わずに評価用セルを用いてサイクル試験を行った。
[Comparative Example 2]
An evaluation cell was prepared in the same manner as in Example 2 except that LiBOB, which is an additive, was not used, and a cycle test was conducted using the evaluation cell without heat treatment.
各実施例及び各比較例におけるクーロン効率（％）及び容量維持率（％）の結果を表１に示す。 Table 1 shows the results of the Coulomb efficiency (%) and the capacity retention rate (%) in each Example and each Comparative Example.
実施例１〜実施例６では、比較例１及び２と比較してクーロン効率（％）及び容量維持率に優れており、充放電サイクル特性に優れることが確認された。 It was confirmed that in Examples 1 to 6, the coulomb efficiency (%) and the capacity retention rate were excellent as compared with Comparative Examples 1 and 2, and the charge / discharge cycle characteristics were excellent.
また、実施例２と実施例３とを比較すると、評価用セルの熱処理を行った実施例３は、評価用セルの熱処理を行っていない実施例２よりも、容量維持率に優れていた。
さらに、実施例５と実施例６とを比較すると、評価用セルの熱処理を行った実施例６は、評価用セルの熱処理を行っていない実施例５よりも、容量維持率に優れていた。
Further, comparing Example 2 and Example 3, Example 3 in which the evaluation cell was heat-treated was superior in capacity retention rate to Example 2 in which the evaluation cell was not heat-treated.
Further, comparing Example 5 and Example 6, Example 6 in which the evaluation cell was heat-treated was superior in capacity retention rate to Example 5 in which the evaluation cell was not heat-treated.
Claims (10)
浸漬させた後の前記電極を熱処理する工程と、
を有し、前記電極の熱処理後に、熱処理した前記電極を用いて前記電池容器に収容する工程を行う請求項４に記載のリチウムイオン二次電池の製造方法。 An electrolyte containing at least one of the positive electrode and the negative electrode of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide, lithium bisoxalate borate and lithium difluoro (oxalate) borate, and a lithium salt. And the process of immersing in
The step of heat-treating the electrode after immersion and
The method for manufacturing a lithium ion secondary battery according to claim 4, wherein the step of accommodating the heat-treated electrode in the battery container after the heat treatment of the electrode is performed.
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