JP4819154B2 - Non-aqueous electrolyte and lithium secondary battery - Google Patents
Non-aqueous electrolyte and lithium secondary battery Download PDFInfo
- Publication number
- JP4819154B2 JP4819154B2 JP2009202366A JP2009202366A JP4819154B2 JP 4819154 B2 JP4819154 B2 JP 4819154B2 JP 2009202366 A JP2009202366 A JP 2009202366A JP 2009202366 A JP2009202366 A JP 2009202366A JP 4819154 B2 JP4819154 B2 JP 4819154B2
- Authority
- JP
- Japan
- Prior art keywords
- carbonate
- aqueous electrolyte
- electrolyte solution
- battery
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims description 51
- 229910052744 lithium Inorganic materials 0.000 title claims description 34
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- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 63
- 239000008151 electrolyte solution Substances 0.000 claims description 63
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 37
- 229910013870 LiPF 6 Inorganic materials 0.000 claims description 33
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 32
- 229910003002 lithium salt Inorganic materials 0.000 claims description 25
- 150000005678 chain carbonates Chemical class 0.000 claims description 24
- 159000000002 lithium salts Chemical class 0.000 claims description 24
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 24
- -1 alkyl biphenyl Chemical compound 0.000 claims description 19
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical group COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 18
- 239000003125 aqueous solvent Substances 0.000 claims description 14
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- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 1
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- MBABOKRGFJTBAE-UHFFFAOYSA-N methyl methanesulfonate Chemical compound COS(C)(=O)=O MBABOKRGFJTBAE-UHFFFAOYSA-N 0.000 description 1
- 229940017219 methyl propionate Drugs 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 description 1
- 239000011356 non-aqueous organic solvent Substances 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- MHYFEEDKONKGEB-UHFFFAOYSA-N oxathiane 2,2-dioxide Chemical compound O=S1(=O)CCCCO1 MHYFEEDKONKGEB-UHFFFAOYSA-N 0.000 description 1
- 239000001254 oxidized starch Substances 0.000 description 1
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- 239000008188 pellet Substances 0.000 description 1
- YYSONLHJONEUMT-UHFFFAOYSA-N pentan-3-yl hydrogen carbonate Chemical compound CCC(CC)OC(O)=O YYSONLHJONEUMT-UHFFFAOYSA-N 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 229940014800 succinic anhydride Drugs 0.000 description 1
- HXJUTPCZVOIRIF-UHFFFAOYSA-N sulfolane Chemical compound O=S1(=O)CCCC1 HXJUTPCZVOIRIF-UHFFFAOYSA-N 0.000 description 1
- MBDNRNMVTZADMQ-UHFFFAOYSA-N sulfolene Chemical compound O=S1(=O)CC=CC1 MBDNRNMVTZADMQ-UHFFFAOYSA-N 0.000 description 1
- 150000005687 symmetric chain carbonates Chemical class 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- JLYXXMFPNIAWKQ-UHFFFAOYSA-N γ Benzene hexachloride Chemical compound ClC1C(Cl)C(Cl)C(Cl)C(Cl)C1Cl JLYXXMFPNIAWKQ-UHFFFAOYSA-N 0.000 description 1
Images
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
Description
本発明は、非水系電解液、およびそれを用いたリチウム二次電池に関するものである。詳しくは、高容量で、保存特性、サイクル特性に優れ、更にガス発生量が少なく、また、過充電による破裂・発火が抑制され安全性も向上したリチウム二次電池に関するものである。 The present invention relates to a non-aqueous electrolyte and a lithium secondary battery using the same. More specifically, the present invention relates to a lithium secondary battery having a high capacity, excellent storage characteristics and cycle characteristics, a small amount of gas generation, and a rupture / ignition caused by overcharging is suppressed to improve safety.
近年の電気製品の軽量化、小型化にともない、高いエネルギー密度を持つリチウム電池の開発が進められている。また、リチウム電池の適用分野が拡大するにつれて、その電池特性の改善が要望されている。リチウム電池の負極としては、金属リチウム、リチウムを吸蔵及び放出可能な金属化合物（金属単体、酸化物、リチウムとの合金など）、炭素質材料が用いられている。 With the recent reduction in weight and size of electrical products, development of lithium batteries with high energy density is underway. In addition, as the application field of lithium batteries expands, improvements in battery characteristics are desired. As a negative electrode of a lithium battery, metallic lithium, a metallic compound capable of occluding and releasing lithium (metal simple substance, oxide, alloy with lithium, etc.) and a carbonaceous material are used.
特に、炭素質材料について、例えばコークス、人造黒鉛、天然黒鉛等のリチウムを吸蔵・放出することが可能な炭素質材料を用いた非水系電解液二次電池が提案されている。このような非水系電解液二次電池では、リチウムが金属状態で存在しないためデンドライトの形成が抑制され、電池寿命と安全性を向上することができる。特に人造黒鉛、天然黒鉛等の黒鉛系炭素質材料を用いた非水系電解液二次電池は、高容量化の要求に応えるものとして注目されている。 In particular, as a carbonaceous material, for example, a nonaqueous electrolyte secondary battery using a carbonaceous material capable of inserting and extracting lithium such as coke, artificial graphite, and natural graphite has been proposed. In such a non-aqueous electrolyte secondary battery, since lithium does not exist in a metal state, formation of dendrites is suppressed, and battery life and safety can be improved. In particular, non-aqueous electrolyte secondary batteries using graphite-based carbonaceous materials such as artificial graphite and natural graphite are attracting attention as meeting the demand for higher capacity.
リチウム二次電池に用いる電解液は、通常、主としてリチウム塩と非水溶媒とから構成される。非水溶媒の主成分としては、エチレンカーボネートやプロピレンカーボネート等の環状カーボネート、ジメチルカーボネートやエチルメチルカーボネート等の鎖状カーボネート、γ−ブチロラクトン、γ−バレロラクトン等の環状カルボン酸エステルなどが用いられている。 The electrolytic solution used for the lithium secondary battery is usually mainly composed of a lithium salt and a non-aqueous solvent. As the main component of the non-aqueous solvent, cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate and ethyl methyl carbonate, cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone are used. Yes.
また、この二次電池の負荷特性、サイクル特性、保存特性、低温特性等の特性を改良するために、非水溶媒やリチウム塩について種々の検討がなされている。
例えば、非水溶媒として、非対称鎖状カーボネートと二重結合を有する環状カーボネートの混合物を用いると、二重結合を有する環状カーボネートが負極と優先的に反応して負極表面に良質の被膜を生成し、これにより非対称鎖状カーボネートに起因する負極表面上での不導体被膜の形成が抑制されるので、保存特性とサイクル特性が向上することが特許文献１に開示されている。
In addition, in order to improve characteristics such as load characteristics, cycle characteristics, storage characteristics, and low temperature characteristics of the secondary battery, various studies have been made on non-aqueous solvents and lithium salts.
For example, when a mixture of an asymmetric chain carbonate and a cyclic carbonate having a double bond is used as a non-aqueous solvent, the cyclic carbonate having a double bond preferentially reacts with the negative electrode to form a good-quality film on the negative electrode surface. Thus, since formation of a non-conductive film on the negative electrode surface due to the asymmetric chain carbonate is suppressed, Patent Document 1 discloses that storage characteristics and cycle characteristics are improved.
また、リチウム塩として、ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （ｎは１〜４）で表される第１の塩と、ＬｉＢＦ4 及び／又はＬｉＰＦ6 からなる第２の塩を４５：５５〜１：９９の比率で含有する電解液を用いると、第１の塩により正極表面に適当な厚さの保護被膜が形成され、その結果、正極と電解液の反応を抑えることができるので、ガス発生量を低減させ、高温下での充放電サイクル寿命と高温下での放電容量とを向上できることが特許文献２に開示されている。この特許文献２には、電解液の非水溶媒として、環状カーボネート、鎖状カーボネート、環状エーテル、鎖状エーテル、γ−ブチロラクトン等が挙げられており、実施例では、エチレンカーボネート、γ−ブチロラクトン、プロピレンカーボネート及びビニレンカーボネートの組合せ、エチレンカーボネートとジエチルカーボネートの組合せ、エチレンカーボネートとメチルエチルカーボネートの組合せ、及びエチレンカーボネートとγ−ブチロラクトンの組合せが用いられている。 Further, 45 as a lithium salt, a first salt represented by LiN (C n F 2n + 1 SO 2) 2 (n is 1-4), the second salt comprising LiBF 4 and / or LiPF 6 : When the electrolytic solution contained at a ratio of 55 to 1:99 is used, a protective film having an appropriate thickness is formed on the surface of the positive electrode by the first salt, and as a result, the reaction between the positive electrode and the electrolytic solution can be suppressed. Therefore, Patent Document 2 discloses that the amount of gas generation can be reduced, and the charge / discharge cycle life at high temperature and the discharge capacity at high temperature can be improved. In Patent Document 2, cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, γ-butyrolactone, and the like are listed as non-aqueous solvents for the electrolyte. In Examples, ethylene carbonate, γ-butyrolactone, Combinations of propylene carbonate and vinylene carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate, and ethylene carbonate and γ-butyrolactone are used.
しかしながら、近年のリチウム電池に対する高性能化への要求はますます高くなっており、高容量、高温保存特性、サイクル特性を高い次元で達成することが求められている。 電池を高容量化する方法としては、電極層を加圧して空隙を減少させ、電極層を高密度化したり、限られた電池体積の中にできるだけ多くの活物質を詰め込む設計が一般的となっている。しかし、電池を高容量化していくと新たな問題点も生じてくる。例えば、電池内の空隙を減少させると、電解液の分解で発生するガスがわずかであっても電池内圧は顕著に上昇してしまう。 However, the demand for higher performance of lithium batteries in recent years is increasing, and it is required to achieve high capacity, high temperature storage characteristics, and cycle characteristics at a high level. As a method for increasing the capacity of a battery, a design in which the electrode layer is pressurized to reduce voids to increase the density of the electrode layer or to pack as much active material as possible in a limited battery volume has become common. ing. However, as the capacity of the battery increases, new problems arise. For example, if the voids in the battery are reduced, the battery internal pressure will rise significantly even if only a small amount of gas is generated by the decomposition of the electrolyte.
また、電池を停電時のバックアップ電源や、ポータブル機器の電源として用いる場合に、電池の自己放電を補うために常に微弱電流を流し、充電状態に保持する連続充電方法が用いられる。こうした連続充電状態では電極の活性が常に高い状態であるので、電池の容量劣化が促進されたり、電解液の分解によるガスが発生しやすくなる。ガスの発生量が多くなると、過充電等により内圧が異常に上昇したときにこれを感知して安全弁を作動させる円筒電池では、安全弁が作動してしまうことがある。また、安全弁のない角形電池等では、電池が膨張したり、更には破裂することもある。 In addition, when the battery is used as a backup power source in the event of a power failure or a power source for a portable device, a continuous charging method is used in which a weak current is always applied to maintain the charged state in order to compensate for the battery self-discharge. In such a continuously charged state, the activity of the electrode is always high, so that capacity deterioration of the battery is promoted and gas due to decomposition of the electrolytic solution is likely to be generated. When the amount of gas generated increases, a safety valve may be activated in a cylindrical battery that activates the safety valve by detecting this when the internal pressure abnormally increases due to overcharge or the like. In addition, in a rectangular battery or the like without a safety valve, the battery may expand or further rupture.
したがって、リチウム二次電池においては、高容量、高温保存特性、サイクル特性だけでなく、連続充電特性についても改良が求められる。連続充電特性としては、容量劣化が少ないことだけでなく、ガス発生量を抑制することが強く求められている。
しかしながら、特許文献１の実施例に開示されている、（１）エチレンカーボネート、（２）メチルエチルカーボネート、及び（３）ビニレンカーボネートを含有する電解液を用いた二次電池では、サイクル特性は改善されるものの、連続充電後の放電特性の向上、及び、連続充電時のガス発生量の低減には、殆どの場合において効果がなかった。
Therefore, in the lithium secondary battery, not only high capacity, high temperature storage characteristics and cycle characteristics but also continuous charge characteristics are required to be improved. As continuous charging characteristics, not only is there little capacity deterioration, but there is a strong demand for suppressing gas generation.
However, in the secondary battery using the electrolyte solution containing (1) ethylene carbonate, (2) methyl ethyl carbonate, and (3) vinylene carbonate, which is disclosed in the example of Patent Document 1, cycle characteristics are improved. However, in most cases, there was no effect in improving the discharge characteristics after continuous charging and reducing the amount of gas generated during continuous charging.
また、特許文献２で開示されている、電解液を用いた二次電池では、連続充電後の放電特性の改善には効果が見られなかった。 Moreover, the secondary battery using the electrolytic solution disclosed in Patent Document 2 has no effect in improving the discharge characteristics after continuous charging.
本発明者らは、上記課題を解決すべく検討を重ねた結果、ＬｉＰＦ6 とＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （ｎ＝１、２）を特定の濃度で含有し、かつ、非水溶媒として３種類のカーボネートを主成分とする電解液を用いることによって、高い容量を維持しつつ、連続充電後の放電特性が改善され、さらに連続充電時のガス発生量も低減できると共に、過充電防止剤として特定の芳香族化合物の添加により、放電特性の低下を生じずに過充電による電池の破裂・発火を抑制できることを見出し、本発明を完成させるに至った。 As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention contain LiPF 6 and LiN (C n F 2n + 1 SO 2 ) 2 (n = 1, 2) at a specific concentration, and By using an electrolyte mainly composed of three types of carbonate as a non-aqueous solvent, while maintaining a high capacity, the discharge characteristics after continuous charging can be improved, and further the amount of gas generated during continuous charging can be reduced. It has been found that by adding a specific aromatic compound as an overcharge inhibitor, the battery can be prevented from being ruptured or ignited by overcharge without causing deterioration in discharge characteristics, and the present invention has been completed.
すなわち、本発明の要旨は、リチウム塩とこれを溶解する非水溶媒とから主としてなる非水系電解液であって、リチウム塩として、ＬｉＰＦ６ を０．２〜２モル／リットル、及びＬｉＮ（Ｃｎ Ｆ２ｎ＋１ＳＯ２ ）２ （但し、ｎ＝１又は２）を０．００１〜０．２モル／リットルの濃度で含有し、かつ、非水溶媒が、（１）エチレンカーボネート及び／又はプロピレンカーボネート、（２）鎖状カーボネート、及び（３）ビニレンカーボネートを主成分とし、リチウム塩を除く非水系電解液に占めるエチレンカーボネート、プロピレンカーボネート及び鎖状カーボネートの合計が８０重量％以上であると共に、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン、ジフェニルエーテル、ジベンゾフランから選ばれる芳香族化合物を含有することを特徴とする非水系電解液に存する。
That is, the gist of the present invention is a non-aqueous electrolyte mainly composed of a lithium salt and a non-aqueous solvent that dissolves the lithium salt. As the lithium salt, 0.2 to 2 mol / liter of LiPF 6 and LiN (C n F 2n + 1 SO 2 ) 2 (where n = 1 or 2) is contained at a concentration of 0.001 to 0.2 mol / liter, and the non-aqueous solvent is (1) ethylene carbonate and / or propylene carbonate , (2) a chain carbonate, and (3) as a main component vinylene carbonate, a non-aqueous electrolyte solution accounted ethylene carbonate, der total 80% or more by weight of propylene carbonate and linear carbonate Rutotomoni excluding lithium salt , Biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenze Consists in the non-aqueous electrolytic solution characterized by containing a t- amyl benzene, diphenyl ether, aromatic compound selected from dibenzofuran.
本発明によれば、高容量で、保存特性、サイクル特性に優れ、更に連続充電後の残存容量が大きく、ガス発生量が少なく、また、過充電による破裂・発火が抑制され安全性も向上したリチウム二次電池を提供することができ、非水系電解液電池の小型化、高性能化を達成することができる。 According to the present invention, it has a high capacity, excellent storage characteristics, cycle characteristics, a large remaining capacity after continuous charging, a small amount of gas generation, and an explosion and ignition due to overcharging are suppressed, thereby improving safety. A lithium secondary battery can be provided, and miniaturization and high performance of a non-aqueous electrolyte battery can be achieved.
以下、本発明の実施の形態について詳細に説明するが、以下に記載する構成要件の説明は、本発明の実施態様の一例（代表例）であり、これらの内容に特定はされない。
本発明に係る非水系電解液は、常用の非水系電解液と同じく、主としてリチウム塩及びこれを溶解する非水溶媒からなるが、その第一の特徴は、リチウム塩として、ＬｉＰＦ6 とＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （但しｎ＝１又は２）とを特定の濃度で含有する点にある。
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents.
The non-aqueous electrolyte solution according to the present invention is mainly composed of a lithium salt and a non-aqueous solvent that dissolves the lithium salt, as in the case of a conventional non-aqueous electrolyte solution. The first feature is that LiPF 6 and LiN ( C n F 2n + 1 SO 2 ) 2 (where n = 1 or 2) is contained at a specific concentration.
ＬｉＰＦ6 の非水系電解液中の濃度は、０．２〜２モル／リットルである。ＬｉＰＦ6 の濃度が高すぎても、低すぎても、電解液の電気伝導率が低くなり、電池性能が低下することがある。ＬｉＰＦ6 の濃度は、０．３モル／リットル以上、特に０．６モル／リットル以上であるのが好ましく、また、１．８モル／リットル以下、特に１．５モル／リットル以下であるのが好ましい。 The concentration of LiPF 6 in the non-aqueous electrolyte is 0.2 to 2 mol / liter. If the concentration of LiPF 6 is too high or too low, the electric conductivity of the electrolytic solution may be lowered, and the battery performance may be lowered. The concentration of LiPF 6 is preferably 0.3 mol / liter or more, particularly 0.6 mol / liter or more, and is 1.8 mol / liter or less, particularly 1.5 mol / liter or less. preferable.
ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （但し、ｎ＝１又は２）は、１種類でも２種類でもよいが、その非水系電解液中の濃度は、０．００１〜０．２モル／リットルである。濃度が低すぎると連続充電時のガス発生を十分抑えるのが困難になり、高すぎると高温保存後の電池特性が低下する傾向にある。このものの濃度は、０．０１モル／リットル以上、特に０．０２モル／リットル以上が好ましく、０．０３５モル／リットル以上とするのが最も好ましい。また、０．１８モル／リットル以下、特に０．１５モル／リットル以下、更には０．１モル／リットル以下が好ましい。 LiN (C n F 2n + 1 SO 2 ) 2 (where n = 1 or 2) may be one type or two types, but the concentration in the non-aqueous electrolyte is 0.001 to 0.2 mol. / Liter. If the concentration is too low, it will be difficult to sufficiently suppress gas generation during continuous charging, and if it is too high, battery characteristics after high-temperature storage will tend to deteriorate. The concentration of this is 0.01 mol / liter or more, particularly preferably 0.02 mol / liter or more, and most preferably 0.035 mol / liter or more. Further, it is preferably 0.18 mol / liter or less, particularly 0.15 mol / liter or less, more preferably 0.1 mol / liter or less.
また、非水系電解液に占める、ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 の割合を重量％で示す場合には、使用する電解液によって重量比は異なってくるが、一般に、ＬｉＮ（ＣＦ3 ＳＯ2 ）2 の場合、０．０２〜５重量％の範囲であり、４重量％以下、更には２．５重量％以下であるのが好ましい。但し１重量％未満でも効果は見られ、電池設計と電解液コストと電池特性の観点から、最適な量を使用することができる。 Further, occupying in the nonaqueous electrolytic solution, to indicate the percentage of LiN (C n F 2n + 1 SO 2) 2 weight%, the weight ratio by an electrolytic solution to be used varies, but generally, LiN (CF 3 SO 2 ) 2 is in the range of 0.02 to 5% by weight, preferably 4% by weight or less, more preferably 2.5% by weight or less. However, even if it is less than 1% by weight, an effect is seen, and an optimal amount can be used from the viewpoint of battery design, electrolyte cost, and battery characteristics.
ＬｉＰＦ6 に対する、ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 のモル比率は、通常０．００５以上、好ましくは０．０１以上であり、通常０．３以下、好ましくは０．２以下である。このモル比が大きすぎると、高温保存後の電池特性が低下する傾向にあり、逆に小さすぎると、連続充電時のガス発生を十分抑えるのが困難である。
非水系電解液中のリチウム塩の最も好ましい濃度は、ＬｉＰＦ6 が０．７５〜１．３モル／リットル、ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 が０．０３〜０．１２モル／リットルであり、両者の合計が１．４モル／リットル以下であるのものである。
For LiPF 6, LiN (C n F 2n + 1 SO 2) 2 molar ratio is usually 0.005 or higher, preferably 0.01 or more and usually 0.3 or less, preferably is 0.2 or less . If this molar ratio is too large, battery characteristics after high-temperature storage tend to be reduced. Conversely, if it is too small, it is difficult to sufficiently suppress gas generation during continuous charging.
The most preferable concentration of the lithium salt in the non-aqueous electrolyte is 0.75 to 1.3 mol / liter for LiPF 6 and 0.03 to 0.12 mol / liter for LiN (C n F 2n + 1 SO 2 ) 2. The total of both is 1.4 mol / liter or less.
本発明に係る非水系電解液は、本発明の効果を妨げない範囲で、ＬｉＰＦ6 及びＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （但し、ｎ＝１又は２）以外のこの用途に用い得ることが知られているリチウム塩を含んでいてもよい。これらのリチウム塩としては、ＬｉＣｌＯ4 等の無機リチウム塩、ＬｉＣＦ3 ＳＯ3 、ＬｉＣ（ＣＦ3 ＳＯ2 ）3 、ＬｉＰＦ4 （ＣＦ3 ）2 、ＬｉＰＦ4 （Ｃ2 Ｆ5 ）2 、ＬｉＰＦ4 （ＣＦ3 ＳＯ2 ）2 、ＬｉＰＦ4 （Ｃ2 Ｆ5 ＳＯ2 ）2 、ＬｉＢＦ2 （ＣＦ3 ）2 、ＬｉＢＦ2 （Ｃ2 Ｆ5 ）2 、ＬｉＢＦ2 （ＣＦ3 ＳＯ2 ）2 およびＬｉＢＦ2 （Ｃ2 Ｆ5 ＳＯ2 ）2 等の含フッ素有機酸リチウム塩などが挙げられる。 The non-aqueous electrolyte solution according to the present invention is used for this use other than LiPF 6 and LiN (C n F 2n + 1 SO 2 ) 2 (where n = 1 or 2) as long as the effects of the present invention are not hindered. It may contain a lithium salt known to obtain. These lithium salts include inorganic lithium salts such as LiClO 4 , LiCF 3 SO 3 , LiC (CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 ( CF 3 SO 2 ) 2 , LiPF 4 (C 2 F 5 SO 2 ) 2 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2 , LiBF 2 (CF 3 SO 2 ) 2 and LiBF 2 ( Examples thereof include fluorine-containing organic acid lithium salts such as C 2 F 5 SO 2 ) 2 .
これらのリチウム塩の非水系電解液中の濃度は、通常０．５モル／リットル以下であり、０．１モル／リットル以下が好ましい。
本発明に係る非水系電解液の非水溶媒は、（１）エチレンカーボネート及び／又はまたはプロピレンカーボネート、（２）鎖状カーボネート、及び（３）ビニレンカーボネートを主成分とする。
The concentration of these lithium salts in the non-aqueous electrolyte is usually 0.5 mol / liter or less, preferably 0.1 mol / liter or less.
The non-aqueous solvent of the non-aqueous electrolyte solution according to the present invention is mainly composed of (1) ethylene carbonate and / or propylene carbonate, (2) chain carbonate, and (3) vinylene carbonate.
（１）エチレンカーボネート及び／又はプロピレンカーボネート
エチレンカーボネート及びプロピレンカーボネートは、それぞれを単独で用いても、両者を併用してもよいが、エチレンカーボネート又はこれとプロピレンカーボネートを併用するのが好ましい。
エチレンカーボネートとプロピレンカーボネートを併用する場合には、エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の容量比（ＥＣ：ＰＣ）は、通常９９：１以下、好ましくは９５：５以下であり、通常４０：６０以上、好ましくは５０：５０以上である。プロピレンカーボネートが多すぎると、特に、負極に黒鉛を用いた場合に、プロピレンカーボネートが黒鉛表面で分解しやすくなるので好ましくない。なお、本明細書において、非水溶媒の容量は２５℃での値であるが、エチレンカーボネートの容量は融点での値である。
(1) Ethylene carbonate and / or propylene carbonate Although ethylene carbonate and propylene carbonate may be used alone or in combination, ethylene carbonate or propylene carbonate is preferably used in combination.
When ethylene carbonate and propylene carbonate are used in combination, the volume ratio (EC: PC) of ethylene carbonate (EC) to propylene carbonate (PC) is usually 99: 1 or less, preferably 95: 5 or less, usually 40 : 60 or more, preferably 50:50 or more. Too much propylene carbonate is not preferable, especially when graphite is used for the negative electrode, since propylene carbonate tends to decompose on the graphite surface. In this specification, the capacity of the non-aqueous solvent is a value at 25 ° C., whereas the capacity of ethylene carbonate is a value at the melting point.
（２）鎖状カーボネート
鎖状カーボネートとしては、ジメチルカーボネート、ジエチルカーボネート、ジ−ｎ−プロピルカーボネート、エチルメチルカーボネート、メチル−ｎ−プロピルカーボネート、エチル−ｎ−プロピルカーボネート等が挙げられる。なかでも炭素数５以下の鎖状カーボネートが好ましく、特に好ましいのは、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネートである。これらの鎖状カーボネートは、単独で用いても、２種以上を併用してもよい。
(2) Chain carbonate Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Of these, chain carbonates having 5 or less carbon atoms are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. These chain carbonates may be used alone or in combination of two or more.
本発明に係る非水系電解液おいては、（１）エチレンカーボネート及び／又はプロピレンカーボネートと（２）鎖状カーボネートとが合わさって、非水溶媒の主体となっているものが好ましい。通常、リチウム塩を除く非水系電解液に占めるエチレンカーボネート、プロピレンカーボネート及び鎖状カーボネートの合計が８０重量％以上となるようにする。この合計が８５重量％以上、特に９０重量％以上である非水系電解液は、サイクル特性と大電流放電特性のバランスがよいので好ましい。 In the non-aqueous electrolyte solution according to the present invention, it is preferable that (1) ethylene carbonate and / or propylene carbonate and (2) chain carbonate are combined to be a main component of the non-aqueous solvent. Usually, the total of ethylene carbonate, propylene carbonate and chain carbonate in the non-aqueous electrolyte solution excluding lithium salt is 80% by weight or more. A non-aqueous electrolyte having a total of 85% by weight or more, particularly 90% by weight or more is preferable because the balance between cycle characteristics and large current discharge characteristics is good.
非水系電解液中のエチレンカーボネートとプロピレンカーボネートの合計と、鎖状カーボネートの容量比は、通常１０：９０〜７０：３０である。好ましくは１０：９０〜５０：５０、特に好ましくは１５：８５〜４０：６０である。鎖状カーボネートが少なすぎると電解液の粘度が上昇し、多すぎるとリチウム塩の解離度が低下して、電解液の電気伝導率が低下する恐れがある。 The volume ratio of the total of ethylene carbonate and propylene carbonate in the non-aqueous electrolyte and the chain carbonate is usually 10:90 to 70:30. Preferably it is 10: 90-50: 50, Most preferably, it is 15: 85-40: 60. If the amount of chain carbonate is too small, the viscosity of the electrolytic solution increases. If the amount is too large, the degree of dissociation of the lithium salt decreases, and the electrical conductivity of the electrolytic solution may decrease.
本発明における、エチレンカーボネートと鎖状カーボネートの好ましい組み合わせの具体例としては、エチレンカーボネートとジメチルカーボネート、エチレンカーボネートとジエチルカーボネート、エチレンカーボネートとエチルメチルカーボネート、エチレンカーボネートとジメチルカーボネートとジエチルカーボネート、エチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、エチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネート等が挙げられる。これらのエチレンカーボネートと鎖状カーボネートとの組み合わせに、更にプロピレンカーボネートを加えた組み合わせも、好ましい組み合わせとして挙げられる。これらの中で、非対称鎖状カーボネートであるエチルメチルカーボネートを含有するものが更に好ましく、特に、エチレンカーボネートとジメチルカーボネートとエチルメチルカーボネート、エチレンカーボネートとジエチルカーボネートとエチルメチルカーボネート、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートとエチルメチルカーボネートのエチレンカーボネートと対称鎖状カーボネートと非対称鎖状カーボネートを含有するものが、サイクル特性と大電流放電特性のバランスが良いので好ましい。 Specific examples of preferred combinations of ethylene carbonate and chain carbonate in the present invention include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, and ethylene carbonate. Examples thereof include dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. A combination in which propylene carbonate is further added to the combination of ethylene carbonate and chain carbonate is also a preferable combination. Among these, those containing ethyl methyl carbonate, which is an asymmetric chain carbonate, are more preferable, in particular, ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate, Diethyl carbonate and ethyl methyl carbonate containing ethylene carbonate, symmetric chain carbonate, and asymmetric chain carbonate are preferred because of a good balance between cycle characteristics and large current discharge characteristics.
（３）ビニレンカーボネート
リチウム塩を除く非水系電解液に占めるビニレンカーボネートの割合は、通常０．０１重量％以上、好ましくは０．１重量％以上、特に好ましくは０．３重量％以上、最も好ましくは０．５重量％以上であり、８重量％以下、好ましくは５重量％以下、特に好ましくは３重量％以下である。ビニレンカーボネートは負極表面に被膜を形成して、サイクル特性を向上させる役目を果たしており、ビニレンカーボネートの割合が小さすぎると、十分にサイクル特性を向上させることができない。一方、割合が大きすぎると、高温保存時に、ガス発生により電池の内圧が上昇することがあるため、実用上好ましくない。
(3) Vinylene carbonate The proportion of vinylene carbonate in the non-aqueous electrolyte solution excluding lithium salt is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably 0.3% by weight or more, and most preferably Is 0.5% by weight or more, 8% by weight or less, preferably 5% by weight or less, particularly preferably 3% by weight or less. Vinylene carbonate plays a role in improving the cycle characteristics by forming a film on the negative electrode surface. If the proportion of vinylene carbonate is too small, the cycle characteristics cannot be sufficiently improved. On the other hand, if the ratio is too large, the internal pressure of the battery may increase due to gas generation during high temperature storage, which is not preferable in practice.
リチウム塩を除く非水系電解液に占めるエチレンカーボネート、プロピレンカーボネート、鎖状カーボネート及びビニレンカーボネートの合計は、８０重量％以上となるようにする。この合計は、９０重量％、特に９３重量％以上であるのが好ましい。
なお本発明に係る非水系電解液には、本発明の効果を妨げない範囲で、他の非水溶媒を含んでいてもよい。このような非水溶媒としては、例えば、ブチレンカーボネート等の炭素数５以上の環状カーボネート；テトラヒドロフラン、２−メチルテトラヒドロフラン等の環状エーテル；ジメトキシエタン、ジメトキシメタン等の鎖状エーテル；γ−ブチロラクトン、γ−バレロラクトン等の環状カルボン酸エステル；酢酸メチル、プロピオン酸メチル、プロピオン酸エチル、酪酸メチル等の鎖状カルボン酸エステルなどが挙げられる。これらは２種類以上を併用してもよい。
The total of ethylene carbonate, propylene carbonate, chain carbonate, and vinylene carbonate in the non-aqueous electrolyte solution excluding the lithium salt is 80% by weight or more. This total is preferably 90% by weight, in particular 93% by weight or more.
The nonaqueous electrolytic solution according to the present invention may contain other nonaqueous solvents as long as the effects of the present invention are not hindered. Examples of such non-aqueous solvents include cyclic carbonates having 5 or more carbon atoms such as butylene carbonate; cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; chain ethers such as dimethoxyethane and dimethoxymethane; γ-butyrolactone, γ -Cyclic carboxylic acid esters such as valerolactone; and chain carboxylic acid esters such as methyl acetate, methyl propionate, ethyl propionate, and methyl butyrate. Two or more of these may be used in combination.
非水電解液が他の溶媒を含有する場合、その濃度は、通常３０重量％以下である。
本発明に係る非水系電解液が、サイクル特性を低下させずに連続充電時のガス発生を抑制する理由は明らかではないが、次のように推察される。まず、ビニレンカーボネートは負極表面に安定な被膜を形成してサイクル特性を向上させる。しかし、ビニレンカーボネートは充電状態の正極材と反応しやすく、一定電圧で充電を継続する連続充電では、ガスの発生量を増加させる。更に、負極表面に形成された被膜成分も一部電解液中に溶解し、正極表面で反応してガスを発生する。これに対し、ＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 塩由来の分解物は、正極での上記の反応を抑制する。しかもこのものは、負極表面でのビニレンカーボネート由来の被膜形成を阻害せず、逆にこの塩の一部が負極表面で還元されて被膜を更に安定化させて、電解液への被膜成分の溶解を抑制する。このようにビニレンカーボネートとＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 との相互作用により、サイクル特性の向上とガス発生の抑制とが達成されるものと考えられる。
When the nonaqueous electrolytic solution contains another solvent, the concentration is usually 30% by weight or less.
The reason why the nonaqueous electrolytic solution according to the present invention suppresses gas generation during continuous charging without deteriorating cycle characteristics is not clear, but is presumed as follows. First, vinylene carbonate forms a stable film on the negative electrode surface to improve cycle characteristics. However, vinylene carbonate easily reacts with the positive electrode material in a charged state, and increases the amount of gas generated in continuous charging in which charging is continued at a constant voltage. Further, a part of the coating component formed on the negative electrode surface is also dissolved in the electrolytic solution and reacts on the positive electrode surface to generate gas. On the other hand, the decomposition product derived from LiN (C n F 2n + 1 SO 2 ) 2 salt suppresses the above reaction at the positive electrode. In addition, this does not inhibit the formation of vinylene carbonate-derived film on the negative electrode surface, and conversely, a part of this salt is reduced on the negative electrode surface to further stabilize the film and dissolve the film components in the electrolyte. Suppress. Thus, it is thought that the improvement of cycle characteristics and the suppression of gas generation are achieved by the interaction between vinylene carbonate and LiN (C n F 2n + 1 SO 2 ) 2 .
また、本発明の非水系電解液を用いることよって連続充電後の放電特性が改善される理由も明かではないが、負極上に形成されたビニレンカーボネートとＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 由来の複合被膜成分が、熱的に安定で、リチウムイオンの透過性に優れると共に、負極の被膜成分の溶解が抑制され、結果として電池内部の副反応が抑制されることにより、電極活物質の劣化が抑制され、良好な放電特性を達成されるものと推察される。 The reason why the discharge characteristics after continuous charging are improved by using the non-aqueous electrolyte of the present invention is not clear, but vinylene carbonate and LiN (C n F 2n + 1 SO 2 ) formed on the negative electrode. The composite coating component derived from 2 is thermally stable and excellent in lithium ion permeability, and dissolution of the coating component of the negative electrode is suppressed, and as a result, side reactions inside the battery are suppressed, so that the electrode active material It is presumed that the deterioration of this is suppressed and good discharge characteristics are achieved.
なお、本発明に係る非水系電解液には、特定の芳香族化合物からなる過充電防止剤が含有される。
過充電防止剤としては、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン、ジフェニルエーテル、ジベンゾフラン等の芳香族化合物などが挙げられる。これらは２種類以上併用して用いてもよい。２種以上併用する場合は、特に、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン等の芳香族化合物から選ばれるものと、ジフェニルエーテル、ジベンゾフラン等の含酸素芳香族化合物から選ばれるものとを併用するのが好ましい。非水系電解液が含有する過充電防止剤の含有量は、通常０．１〜５重量％である。非水系電解液に過充電防止剤を含有させることは、過充電による電池の破裂・発火を抑制することができ、電池の安全性が向上する。
In addition, the overcharge inhibitor which consists of a specific aromatic compound contains in the non-aqueous electrolyte solution which concerns on this invention.
Examples of the overcharge inhibitor include biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, aromatic compounds such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran. Two or more of these may be used in combination. When used in combination of two or more, those selected from aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, and diphenyl ether It is preferable to use in combination with those selected from oxygen-containing aromatic compounds such as dibenzofuran. The content of the overcharge inhibitor contained in the non-aqueous electrolyte is usually 0.1 to 5% by weight. Inclusion of an overcharge inhibitor in the non-aqueous electrolyte solution can suppress battery rupture / ignition due to overcharge and improve battery safety.
一般にこれらの過充電防止剤は、電解液の溶媒成分よりも正極および負極上で反応しやすいために、連続充電時や高温保存時においても電極の活性の高い部位で反応してしまい、これらの化合物が反応すると電池の内部抵抗が大きく上昇したり、ガス発生によって、連続充電後の放電特性や、高温保存後の放電特性を著しく低下させる原因となっていたが、本発明の電解液に添加した場合は、放電特性の低下を抑制することができる。 In general, these overcharge inhibitors react more easily on the positive electrode and the negative electrode than the solvent component of the electrolytic solution, and thus react at a highly active site of the electrode even during continuous charging or storage at high temperatures. When the compound reacts, the internal resistance of the battery is greatly increased, or the generation of gas causes the discharge characteristics after continuous charging and the discharge characteristics after high temperature storage to be significantly reduced. In this case, it is possible to suppress a decrease in discharge characteristics.
なお、本発明に係る非水系電解液には、必要に応じて他の成分、例えば従来公知の脱水剤、脱酸剤などの助剤を含有させてもよい。
高温保存後の容量維持特性やサイクル特性を改善するための助剤としては、ビニルエチレンカーボネート、フルオロエチレンカーボネート、トリフルオロプロピレンカーボネート、フェニルエチレンカーボネートおよびエリスリタンカーボネート等のカーボネート化合物；無水コハク酸、無水グルタル酸、無水マレイン酸、無水シトラコン酸、無水グルタコン酸、無水イタコン酸、無水ジグリコール酸、シクロヘキサンジカルボン酸無水物、シクロペンタンテトラカルボン酸二無水物およびフェニルコハク酸無水物等のカルボン酸無水物；１，３−プロパンスルトン、１，４−ブタンスルトン、メタンスルホン酸メチル、ブスルファン、スルホラン、スルホレン、ジメチルスルホンおよびテトラメチルチウラムモノスルフィド等の含硫黄化合物；１−メチル−２−ピロリジノン、１−メチル−２−ピペリドン、３−メチル−２−オキサゾリジノン、１，３−ジメチル−２−イミダゾリジノンおよびＮ−メチルスクシイミド等の含窒素化合物；ヘプタン、オクタン、シクロヘプタン等の炭化水素化合物などが挙げられる。これらは２種類以上併用して用いてもよい。非水系電解液がこれらの助剤を含有する場合、その濃度は、通常０．１〜５重量％である。
The non-aqueous electrolyte solution according to the present invention may contain other components, for example, auxiliary agents such as conventionally known dehydrating agents and deoxidizing agents, if necessary.
As auxiliary agents for improving capacity maintenance characteristics and cycle characteristics after high temperature storage, carbonate compounds such as vinyl ethylene carbonate, fluoroethylene carbonate, trifluoropropylene carbonate, phenylethylene carbonate and erythritan carbonate; succinic anhydride, anhydrous Carboxylic anhydrides such as glutaric acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride Sulfur-containing compounds such as 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone and tetramethylthiuram monosulfide Nitrogenous compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; heptane , Hydrocarbon compounds such as octane and cycloheptane. Two or more of these may be used in combination. When the non-aqueous electrolyte contains these auxiliaries, the concentration is usually 0.1 to 5% by weight.
本発明に係る非水系電解液は、（１）エチレンカーボネート及び／又はまたはプロピレンカーボネート、（２）鎖状カーボネート、及び（３）ビニレンカーボネートを主成分とする非水系有機溶媒に、ＬｉＰＦ6 及びＬｉＮ（Ｃn Ｆ2n+1ＳＯ2 ）2 （ｎ＝１又は２）、及び、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン、ジフェニルエーテル、ジベンゾフランから選ばれる芳香族化合物、並びに必要に応じて他の化合物を溶解することにより調製することができる。非水系電解液を調製するに際して、各原料は、予め、脱水しておくのが好ましい。通常５０ｐｐｍ以下、好ましくは３０ｐｐｍ以下まで脱水するのがよい。 The nonaqueous electrolytic solution according to the present invention includes (1) ethylene carbonate and / or propylene carbonate, (2) chain carbonate, and (3) a nonaqueous organic solvent mainly composed of vinylene carbonate, LiPF 6 and LiN. (C n F 2n + 1 SO 2 ) 2 (n = 1 or 2) and biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, It can be prepared by dissolving an aromatic compound selected from diphenyl ether and dibenzofuran and, if necessary, other compounds. When preparing the non-aqueous electrolyte solution, it is preferable to dehydrate each raw material in advance. Usually, it is good to dehydrate to 50 ppm or less, preferably 30 ppm or less.
本発明に係る非水系電解液は、二次電池、特にリチウム二次電池の電解液として用いるのに好適である。以下、この電解液を用いた本発明に係るリチウム二次電池について説明する。
本発明に係るリチウム二次電池は、電解液以外は従来公知のリチウム二次電池と同様であり、通常、正極と負極とが、本発明に係る電解液が含浸されている多孔膜を介して、ケースに収納された構造を有している。したがって、本発明に係る二次電池の形状は任意であり、例えば、円筒型、角型、ラミネート型、コイン型、大型等のいずれであってもよい。
The non-aqueous electrolyte solution according to the present invention is suitable for use as an electrolyte solution for a secondary battery, particularly a lithium secondary battery. Hereinafter, a lithium secondary battery according to the present invention using this electrolytic solution will be described.
The lithium secondary battery according to the present invention is the same as the conventionally known lithium secondary battery except for the electrolytic solution. Usually, the positive electrode and the negative electrode are interposed through the porous film impregnated with the electrolytic solution according to the present invention. It has a structure housed in a case. Therefore, the shape of the secondary battery according to the present invention is arbitrary, and may be any of, for example, a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large size.
本発明に係るリチウム二次電池は、前述のように連続充電状態におけるガス発生が少ないので、過充電等の異常時に電池内圧の上昇により作動する電流遮断装置を備えた電池の連続充電状態での電流遮断装置の異常作動を防止することができる。また、外装体の厚みが通常０．５ｍｍ以下、中でも０．４ｍｍ以下で、材質が金属アルミニウムまたはアルミニウム合金を主体とした電池や、体積容量密度が１１０ｍＡｈ／ｃｃ以上、更には１３０ｍＡｈ／ｃｃ以上、特に１４０ｍＡｈ／ｃｃ以上の電池は、電池内圧の上昇による電池の膨張という問題が生じやすいが、本発明に係る二次電池ではガス発生量が少ないので、このような問題が生ずるのを防止することができる。 Since the lithium secondary battery according to the present invention generates less gas in the continuous charge state as described above, the battery in the continuous charge state provided with a current interruption device that operates due to an increase in the internal pressure of the battery when an abnormality such as overcharge occurs. Abnormal operation of the current interrupt device can be prevented. Further, the thickness of the outer package is usually 0.5 mm or less, particularly 0.4 mm or less, and the material is mainly made of metal aluminum or aluminum alloy, the volume capacity density is 110 mAh / cc or more, further 130 mAh / cc or more, In particular, a battery of 140 mAh / cc or more is likely to have a problem of battery expansion due to an increase in battery internal pressure. However, since the secondary battery according to the present invention generates a small amount of gas, it is possible to prevent such a problem from occurring. Can do.
負極活物質としては、リチウムを吸蔵・放出可能な炭素質材料や金属化合物、リチウム金属およびリチウム合金を用いることができる。これらは単独で用いても、複数を併用しても良い。 As the negative electrode active material, a carbonaceous material or metal compound capable of inserting and extracting lithium, lithium metal and lithium alloy can be used. These may be used alone or in combination.
なかでも好ましいのは炭素質材料、特に、黒鉛や黒鉛の表面を黒鉛に比べて非晶質の炭素で被覆したものである。
黒鉛は、学振法によるＸ線回折で求めた格子面（００２面）のｄ値（層間距離）が０．３３５〜０．３３８ｎｍ、特に０．３３５〜０．３３７ｎｍであるものが好ましい。また、学振法によるＸ線回折で求めた結晶子サイズ（Ｌｃ）は、３０ｎｍ以上であるのが好ましく、５０ｎｍ以上、特に１００ｎｍ以上であるのが更に好ましい。灰分は、通常１重量％以下であるのが好ましく、０．５重量％以下、特に０．１重量％以下であるのが更に好ましい。
Particularly preferred is a carbonaceous material, in particular, graphite or a surface of graphite coated with amorphous carbon as compared with graphite.
Graphite preferably has a lattice plane (002 plane) d value (interlayer distance) of 0.335 to 0.338 nm, particularly 0.335 to 0.337 nm, as determined by X-ray diffraction using the Gakushin method. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is preferably 30 nm or more, more preferably 50 nm or more, and particularly preferably 100 nm or more. The ash content is usually preferably 1% by weight or less, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less.
黒鉛の表面を非晶質の炭素で被覆したものとして好ましいのは、Ｘ線回折における格子面（００２面）のｄ値が０．３３５〜０．３３８ｎｍである黒鉛を核材とし、その表面に該核材よりもＸ線回折における格子面（００２面）のｄ値が大きい炭素質材料が付着しており、かつ核材と核材よりもＸ線回折における格子面（００２面）のｄ値が大きい炭素質材料との割合が重量比で９９／１〜８０／２０であるものである。これを用いると、高い容量で、かつ電解液と反応しにくい負極を製造することができる。 The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material The ratio with respect to the carbonaceous material having a large is 99/1 to 80/20 by weight. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.
炭素質材料の粒径は、レーザー回折・散乱法によるメジアン径で、１μｍ以上であるのが好ましく、３μｍ以上、特に５μｍ以上であれば更に好ましく、最も好ましいのは７μｍ以上である。また、上限は、１００μｍ以下が好ましく、５０μｍ以下、特に４０μｍ以下であれば更に好ましく、最も好ましいのは３０μｍ以下である。
炭素質材料のＢＥＴ法による比表面積は、０．３ｍ2 ／ｇ以上であるのが好ましく、０．５ｍ2 ／ｇ以上、特に０．７ｍ2 ／ｇ以上であれば更に好ましい。最も好ましいのは０．８ｍ2 ／ｇ以上である。上限は２５．０ｍ2 ／ｇ以下が好ましく、２０．０ｍ2 ／ｇ以下、特に１５．０ｍ2 ／ｇ以下であるのが更に好ましく、最も好ましいのは１０．０ｍ2 ／ｇ以下である。
The particle size of the carbonaceous material is preferably 1 μm or more, more preferably 3 μm or more, particularly preferably 5 μm or more, and most preferably 7 μm or more, as a median diameter by a laser diffraction / scattering method. Further, the upper limit is preferably 100 μm or less, more preferably 50 μm or less, particularly preferably 40 μm or less, and most preferably 30 μm or less.
The specific surface area of the carbonaceous material according to the BET method is preferably 0.3 m 2 / g or more, more preferably 0.5 m 2 / g or more, and particularly preferably 0.7 m 2 / g or more. Most preferred is 0.8 m 2 / g or more. The upper limit is preferably 25.0 m 2 / g or less, 20.0 m 2 / g or less, particularly more preferably at 15.0 m 2 / g or less, and most preferred is less 10.0 m 2 / g.
また、炭素質材料は、アルゴンイオンレーザー光を用いたラマンスペクトルで分析したときに、１５７０〜１６２０ｃｍ-1の範囲にあるピークＰA のピーク強度ＩA と、１３００〜１４００ｃｍ-1の範囲にあるピークＰB のピーク強度ＩB との比で表されるＲ値（＝ＩB ／ＩA が、０．０１〜０．７の範囲であるものが好ましい。また、１５７０〜１６２０ｃｍ-1の範囲にあるピークの半値幅が、２６ｃｍ-1以下、特に２５ｃｍ-1以下であるものが好ましい。 Further, the carbonaceous material, when analyzed by Raman spectrum using argon ion laser light and the peak intensity I A of the peak P A in the range of 1570～1620Cm -1, in the range of 1300～1400Cm -1 R value (= I B / I A is preferably in the range of 0.01 to 0.7. The range of 1570 to 1620 cm −1 is represented by the ratio of the peak P B to the peak intensity I B. The half-width of the peak at is preferably 26 cm −1 or less, particularly 25 cm −1 or less.
リチウムを吸蔵・放出可能な金属化合物としては、Ａｇ、Ｚｎ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｐ、Ｓｂ、Ｂｉ、Ｃｕ、Ｎｉ、Ｓｒ、Ｂａ等の金属を含有する化合物が挙げられ、これらの金属は単体、酸化物、リチウムとの合金などとして用いられる。本発明においては、Ｓｉ、Ｓｎ、Ｇｅ及びＡｌから選ばれる元素を含有するものが好ましく、Ｓｉ、Ｓｎ及びＡｌから選ばれる金属の酸化物又はリチウム合金がより好ましい。 Examples of metal compounds capable of inserting and extracting lithium include compounds containing metals such as Ag, Zn, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, Cu, Ni, Sr, and Ba. These metals are used as simple substances, oxides, alloys with lithium, and the like. In the present invention, those containing an element selected from Si, Sn, Ge and Al are preferred, and oxides or lithium alloys of metals selected from Si, Sn and Al are more preferred.
リチウムを吸蔵・放出可能な金属化合物あるいはこの酸化物やリチウムとの合金は、一般に黒鉛に代表される炭素材料に比較し、単位重量あたりの容量が大きいので、より高エネルギー密度が求められるリチウムイオン二次電池において好適である。
正極活物質としては、リチウムコバルト酸化物、リチウムニッケル酸化物、リチウムマンガン酸化物等のリチウム遷移金属複合酸化物材料などのリチウムを吸蔵・放出可能な材料が挙げられる。これらの化合物は、Ｌｉx ＣｏＯ2 、Ｌｉx ＮｉＯ2 、Ｌｉx ＭｎＯ2 、Ｌｉx Ｃｏ1-y Ｍy Ｏ2 、Ｌｉx Ｎｉ1-y Ｍy Ｏ2 、Ｌｉx Ｍｎ1-y Ｍy Ｏ2 等であり、ここでＭはＦｅ、Ｃｏ、Ｎｉ、Ｍｎ、Ｍｇ、Ｃｕ、Ｚｎ、Ａｌ、Ｓｎ、Ｂ、Ｇａ、Ｃｒ、Ｖ、Ｓｒ、Ｔｉから選ばれる少なくとも１種であり、０．４≦ｘ≦１．２、０≦ｙ≦０．６である。
Lithium ions that require higher energy density because metal compounds that can occlude and release lithium, or their oxides and alloys with lithium, generally have a larger capacity per unit weight than carbon materials typified by graphite. It is suitable for a secondary battery.
Examples of the positive electrode active material include materials capable of inserting and extracting lithium, such as lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide. These compounds are Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , Li x Co 1 -y My O 2 , Li x Ni 1 -y My O 2 , Li x Mn 1 -y My O 2 or the like, where M is at least one selected from Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, V, Sr, Ti; 4 ≦ x ≦ 1.2 and 0 ≦ y ≦ 0.6.
特にＬｉx Ｃｏ1-y Ｍy Ｏ2 、Ｌｉx Ｎｉ1-y Ｍy Ｏ2 、Ｌｉx Ｍｎ1-y Ｍy Ｏ2 等で表される、コバルト、ニッケル、マンガンの一部を他の金属で置き換えたものは、その構造を安定化させることができるので好ましい。正極活物質は単独で用いても、複数を併用しても良い。
活物質を結着する結着剤としては、電極製造時に使用する溶媒や電解液に対して安定な材料であれば、任意のものを使用することができる。例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレン等のフッ素系樹脂、ポリエチレン、ポリプロピレン等のポリオレフィン、スチレン・ブタジエンゴム、イソプレンゴム、ブタジエンゴム等の不飽和結合を有するポリマー及びその共重合体、エチレン−アクリル酸共重合体、エチレン−メタクリル酸共重合体等のアクリル酸系ポリマー及びその共重合体などが挙げられる。
Especially represented by Li x Co 1-y M y O 2, Li x Ni 1-y M y O 2, Li x Mn 1-y M y O 2 , etc., cobalt, nickel, and other part of manganese A metal replacement is preferable because the structure can be stabilized. The positive electrode active materials may be used alone or in combination.
As the binder for binding the active material, any material can be used as long as it is a material that is stable with respect to the solvent and the electrolyte used in manufacturing the electrode. For example, fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefins such as polyethylene and polypropylene, polymers having unsaturated bonds such as styrene / butadiene rubber, isoprene rubber and butadiene rubber, and copolymers thereof, ethylene-acrylic Examples thereof include acrylic acid polymers such as acid copolymers and ethylene-methacrylic acid copolymers, and copolymers thereof.
電極中には、機械的強度や電気伝導度を高めるために増粘剤、導電材、充填剤などを含有させてもよい。
増粘剤としては、カルボキシルメチルセルロース、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、ガゼイン等が挙げられる。
The electrode may contain a thickener, a conductive material, a filler and the like in order to increase mechanical strength and electrical conductivity.
Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.
導電材としては、銅またはニッケル等の金属材料、グラファイトまたはカーボンブラック等の炭素材料などが挙げられる。
電極の製造は、常法によればよい。例えば、負極または正極活物質に、結着剤、増粘剤、導電材、溶媒等を加えてスラリー化し、これを集電体に塗布、乾燥した後に、プレスすることによって形成することができる。
Examples of the conductive material include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black.
The electrode may be manufactured by a conventional method. For example, it can be formed by adding a binder, a thickener, a conductive material, a solvent or the like to a negative electrode or a positive electrode active material to form a slurry, applying the slurry to a current collector, drying it, and then pressing it.
負極活物質層の乾燥、プレス後の密度は、通常１．４５ｇ／ｃｍ3 以上であり、好ましくは１．５５ｇ／ｃｍ3 以上、特に好ましくは１．６０ｇ／ｃｍ3 以上である。負極活物質層の密度が高いほど電池の容量が増加するので好ましい。また、正極物質層の乾燥、プレス後の密度は、通常３．０ｇ／ｃｍ3 以上である。正極活物質層の密度が低すぎると電池の容量が不十分となる。 Drying of the negative electrode active material layer, the density after pressing is usually 1.45 g / cm 3 or more, preferably 1.55 g / cm 3 or more, particularly preferably 1.60 g / cm 3 or more. A higher density of the negative electrode active material layer is preferable because the battery capacity increases. The density of the positive electrode material layer after drying and pressing is usually 3.0 g / cm 3 or more. If the density of the positive electrode active material layer is too low, the battery capacity becomes insufficient.
また、活物質に結着剤や導電材などを加えたものをそのままロール成形してシート電極としたり、圧縮成形によりペレット電極としたり、蒸着・スパッタ・メッキ等の手法で集電体上に電極材料の薄膜形成をすることもできる。
集電体としては各種のものが用いることができるが、通常は金属や合金が用いられる。負極の集電体としては、銅、ニッケル、ステンレス等が挙げられ、好ましいのは銅である。また、正極の集電体としては、アルミニウム、チタン、タンタル等の金属またはその合金が挙げられ、好ましいのはアルミニウムまたはその合金である。
In addition, a material obtained by adding a binder or a conductive material to an active material is roll-formed as it is to form a sheet electrode, a pellet electrode is formed by compression molding, and an electrode is formed on the current collector by a technique such as vapor deposition, sputtering, or plating. A thin film of material can also be formed.
Various types of current collectors can be used, but metals and alloys are usually used. Examples of the current collector for the negative electrode include copper, nickel, and stainless steel, and copper is preferred. Examples of the current collector for the positive electrode include metals such as aluminum, titanium, and tantalum, and alloys thereof, and aluminum or an alloy thereof is preferable.
正極と負極の間には、短絡を防止するために通常は多孔膜を介在させる。この場合、電解液は多孔膜に含浸させて用いる。多孔膜の材質や形状は、電解液に安定であり、かつ保液性に優れていれば、特に制限はなく、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または不織布等が好ましい。
本発明に係る電池に使用する電池の外装体の材質も任意であり、ニッケルメッキを施した鉄、ステンレス、アルミニウムまたはその合金、ニッケル、チタン等が用いられる。
A porous film is usually interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the electrolytic solution is used by impregnating the porous membrane. The material and shape of the porous film are not particularly limited as long as it is stable to the electrolytic solution and excellent in liquid retention, and a porous sheet or nonwoven fabric made of a polyolefin such as polyethylene or polypropylene is preferable.
The material of the battery casing used in the battery according to the present invention is also arbitrary, and nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
以下に、実施例および比較例を挙げて本発明をさらに具体的に説明するが、本発明は、その要旨を超えない限りこれらの実施例に限定されるものではない。
［負極（１）の製造］
Ｘ線回折における格子面（００２面）のｄ値が０．３３６ｎｍ、結晶子サイズ（Ｌｃ）が、６５２ｎｍ、灰分が０．０７重量％、レーザー回折・散乱法によるメジアン径が１２μｍ、ＢＥＴ法比表面積が７．５ｍ2 ／ｇ、アルゴンイオンレーザー光を用いたラマンスペクトル分析において１５７０〜１６２０ｃｍ-1の範囲のピークＰA （ピーク強度ＩA ）および１３００〜１４００ｃｍ-1の範囲のピークＰB （ピーク強度ＩB ）の強度比Ｒ＝ＩB ／ＩA が０．１２、１５７０〜１６２０ｃｍ-1の範囲のピークの半値幅が１９．９ｃｍ-1である天然黒鉛粉末９４重量部とポリフッ化ビニリデン（呉羽化学社製、商品名「ＫＦ−１０００」）６重量部を混合し、Ｎ−メチル−２−ピロリドンを加えスラリー状にした。このスラリーを厚さ１８μｍの銅箔の片面に均一に塗布、乾燥後、負極活物質層の密度が１．５ｇ／ｃｍ3 になるようにプレスして負極（１）を作製した。
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.
[Production of negative electrode (1)]
The d value of the lattice plane (002 plane) in X-ray diffraction is 0.336 nm, the crystallite size (Lc) is 652 nm, the ash content is 0.07 wt%, the median diameter by laser diffraction / scattering method is 12 μm, and the BET method ratio surface area of 7.5 m 2 / g, a peak P a (peak intensity I a) in the range of 1570～1620Cm -1 in the Raman spectrum analysis using an argon ion laser beam and scope of 1300～1400Cm -1 peak P B ( peak intensity I B) intensity ratio R = I B / I a natural graphite powder 94 parts by weight of polyvinylidene fluoride half width of a peak in the range of 0.12,1570～1620Cm -1 is 19.9Cm -1 of 6 parts by weight (manufactured by Kureha Chemical Co., Ltd., trade name “KF-1000”) was mixed, and N-methyl-2-pyrrolidone was added to form a slurry. This slurry was uniformly applied to one side of a 18 μm thick copper foil, dried, and then pressed so that the density of the negative electrode active material layer was 1.5 g / cm 3 to prepare a negative electrode (1).
［負極（２）の製造］
厚さ１２μｍの銅箔を用い、銅箔の両面にスラリーを均一に塗布した他は、負極（１）と同様に行って、負極（２）を作製した。
［正極（１）の製造］
ＬｉＣｏＯ2 ８５重量部、カーボンブラック６重量部とポリフッ化ビニリデン９重量部を混合し、Ｎ−メチル−２−ピロリドンを加えスラリー状し、これを厚さ２０μｍのアルミニウム箔の両面に均一に塗布、乾燥した後、正極活物質層の密度が３．０ｇ／ｃｍ3 になるようにプレスして正極（１）を作製した。
[Production of negative electrode (2)]
A negative electrode (2) was produced in the same manner as the negative electrode (1), except that a copper foil having a thickness of 12 μm was used and the slurry was uniformly applied to both sides of the copper foil.
[Production of positive electrode (1)]
Mix 85 parts by weight of LiCoO 2 , 6 parts by weight of carbon black and 9 parts by weight of polyvinylidene fluoride, add N-methyl-2-pyrrolidone to form a slurry, and apply it uniformly on both sides of an aluminum foil with a thickness of 20 μm. After drying, the positive electrode active material layer was pressed so as to have a density of 3.0 g / cm 3 to produce a positive electrode (1).
［正極（２）の製造］
厚さ１４μｍのアルミニウム箔を用いた他は正極（１）と同様に行って、正極（２）を作製した。
［シート状リチウム二次電池の製造］
正極（１）、負極（１）、およびポリエチレン製のセパレーターを、負極、セパレーター、正極、セパレーター、負極の順に積層して電池要素を作製し、この電池要素を正極及び負極の端子が外部にでるようにして、アルミニウム（厚さ４０μｍ）の両面を樹脂層で被覆したラミネートフィルムからなる袋内に収容した。次いで、これに、後述する電解液を注入したのち、真空封止を行い、シート状電池を作製した。
[Production of positive electrode (2)]
A positive electrode (2) was produced in the same manner as the positive electrode (1) except that an aluminum foil having a thickness of 14 μm was used.
[Manufacture of sheet-like lithium secondary batteries]
A positive electrode (1), a negative electrode (1), and a separator made of polyethylene are laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode to produce a battery element, and the positive and negative terminals of the battery element are exposed to the outside. Thus, it accommodated in the bag which consists of a laminate film which coat | covered both surfaces of aluminum (thickness 40 micrometers) with the resin layer. Subsequently, after injecting the electrolyte solution mentioned later into this, vacuum sealing was performed and the sheet-like battery was produced.
［円筒状リチウム二次電池の製造］
正極（２）と負極（２）を、正極と負極が直接接触しないように、ポリエチレン製のセパレーターとともに重ねて巻き取り、最外周をテープで止めて、渦巻き状電極体とした。次いで、図１に示すように、渦巻き状電極体４の上下に絶縁リング７を設置し、これを円筒状に成形した負極端子を兼ねるステンレス製の電池ケース内に挿入した。その後、渦巻き状電極体４の負極と接続されている負極端子６を電池ケース１の内部に溶接するとともに、電極体の正極と接続されている正極端子５を、電池内部のガス圧が所定以上に上昇すると作動する電流遮断装置８の底部と溶接した。この電流遮断装置と防爆弁とを封口板２の底部に取り付けた。電池ケース１内に後述する電解液を注入した後、電池ケース１の開口部を、封口板とポリプロピレン製の絶縁ガスケット３により封止し、体積容量密度が１３３ｍＡｈ／ｃｃの円筒型電池を作製した。
[Manufacture of cylindrical lithium secondary batteries]
The positive electrode (2) and the negative electrode (2) were rolled up with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact with each other, and the outermost periphery was stopped with a tape to obtain a spiral electrode body. Next, as shown in FIG. 1, insulating rings 7 were installed on the upper and lower sides of the spiral electrode body 4 and inserted into a stainless steel battery case that also served as a negative electrode terminal formed into a cylindrical shape. Thereafter, the negative electrode terminal 6 connected to the negative electrode of the spiral electrode body 4 is welded to the inside of the battery case 1, and the positive electrode terminal 5 connected to the positive electrode of the electrode body has a gas pressure inside the battery of a predetermined value or more. Welded to the bottom of the current interrupting device 8 which is activated when it is raised. The current interrupting device and the explosion-proof valve were attached to the bottom of the sealing plate 2. After injecting an electrolyte solution, which will be described later, into the battery case 1, the opening of the battery case 1 was sealed with a sealing plate and a polypropylene insulating gasket 3 to produce a cylindrical battery having a volume capacity density of 133 mAh / cc. .
（参考例１）
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を加え、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットル、ＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０５モル／リットルの割合となるように溶解して電解液とした。
得られた電解液を用いてシート状電池を作製し、連続充電特性の評価（ガス発生量、連続充電後の残存容量）を行った。結果を表−１に示す。
(Reference Example 1)
Under a dry argon atmosphere, 2 parts by weight of vinylene carbonate was added to 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), and then sufficiently dried LiPF 6 was added at 1.0 mol / liter, LiN (CF 3 SO 2 ) 2 was dissolved at a rate of 0.05 mol / liter to obtain an electrolytic solution.
A sheet-like battery was prepared using the obtained electrolytic solution, and evaluation of continuous charge characteristics (gas generation amount, remaining capacity after continuous charge) was performed. The results are shown in Table-1.
［シート状電池の容量評価］
シート状電池を、電極間の密着性を高めるためにガラス板で挟んだ状態で、２５℃において、０．２Ｃに相当する定電流で４．２Ｖまで充電した後、０．２Ｃに相当する定電流で３Ｖまで放電した。これを３サイクル行って電池を安定させ、４サイクル目は、０．５Ｃの定電流で４．２Ｖまで充電し、さらに４．２Ｖの定電圧で電流値が０．０５Ｃになるまで充電を行った後、０．２Ｃの定電流で３Ｖまで放電し、初期放電容量を求めた。
[Capacity evaluation of sheet batteries]
The sheet-like battery is charged to 4.2 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to enhance the adhesion between the electrodes, and then a constant value corresponding to 0.2 C is obtained. The current was discharged to 3V. This is done for 3 cycles to stabilize the battery. In the 4th cycle, the battery is charged to 4.2 V with a constant current of 0.5 C, and further charged to a current value of 0.05 C with a constant voltage of 4.2 V. Thereafter, the battery was discharged to 3 V at a constant current of 0.2 C, and the initial discharge capacity was determined.
［連続充電特性の評価］
容量評価の終了した電池を、エタノール浴中に浸して体積を測定した後、ガラス板に挟んだ状態で、６０℃において、０．５Ｃの定電流で４．２５Ｖに到達した後、定電圧充電に切り替え、１週間連続充電を行った。
電池を冷却させた後、エタノール浴中に浸して体積を測定し、連続充電前後の体積変化から発生したガス発生量を求めた。
発生ガス量の測定後、２５℃において、０．２Ｃの定電流で３Ｖまで放電させて、連続充電試験後の残存容量を測定し、連続充電試験前の放電容量を１００とした場合の連続充電後の残存容量を求めた。
[Evaluation of continuous charge characteristics]
After the capacity evaluation was completed, the volume was measured by immersing the battery in an ethanol bath, and after reaching 4.25 V at a constant current of 0.5 C at 60 ° C. in a state of being sandwiched between glass plates, constant voltage charging was performed. The battery was continuously charged for 1 week.
After the battery was cooled, it was immersed in an ethanol bath to measure the volume, and the amount of gas generated from the volume change before and after continuous charging was determined.
After measuring the amount of gas generated, discharge to 3V at a constant current of 0.2C at 25 ° C, measure the remaining capacity after the continuous charge test, and continuously charge when the discharge capacity before the continuous charge test is 100 The remaining residual capacity was determined.
（比較例１）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）に十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解して電解液とした。この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Comparative Example 1)
LiPF 6 sufficiently dried in a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7) was dissolved at a ratio of 1.0 mol / liter to obtain an electrolytic solution. A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（比較例２）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部にビニレンカーボネート２重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解して電解液とした。この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Comparative Example 2)
2 parts by weight of vinylene carbonate is added to 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), and sufficiently dried LiPF 6 is dissolved at a ratio of 1.0 mol / liter. The electrolyte was used. A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（比較例３）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＣＦ3 ＳＯ3 を０．０５モル／リットルの割合となるように溶解して電解液とした。この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Comparative Example 3)
To 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), 2 parts by weight of vinylene carbonate was added, and then 1.0 mol / liter of LiPF 6 and LiCF 3 SO 3 were sufficiently dried. An electrolyte was prepared by dissolving at a rate of 0.05 mol / liter. A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（参考例２）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（Ｃ2 Ｆ5 ＳＯ2 ）2 を０．０５モル／リットルの割合となるように溶解して電解液とした。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Reference Example 2)
To 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), 2 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added at 1.0 mol / liter and LiN (C 2 F 5 SO 2 ) 2 was dissolved at a rate of 0.05 mol / liter to obtain an electrolytic solution.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（参考例３）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．１モル／リットルの割合となるように溶解して電解液とした。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Reference Example 3)
To 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), 2 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added at 1.0 mol / liter and LiN (CF 3 SO 2 ) 2 was dissolved at a rate of 0.1 mol / liter to obtain an electrolytic solution.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（実施例１）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９６重量部に、ビニレンカーボネート２重量部とｔ−ブチルベンゼン２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．１モル／リットルの割合となるように溶解して電解液とした。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
Example 1
To 96 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), 2 parts by weight of vinylene carbonate and 2 parts by weight of t-butylbenzene were added, and then 1.0 mol of fully dried LiPF 6 was added. / Liter and LiN (CF 3 SO 2 ) 2 were dissolved in a ratio of 0.1 mol / liter to obtain an electrolytic solution.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（比較例４）
エチレンカーボネートとγ−ブチロラクトンとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解して電解液とした。この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Comparative Example 4)
2 parts by weight of vinylene carbonate is added to 98 parts by weight of a mixture of ethylene carbonate and γ-butyrolactone (volume ratio 3: 7), and then sufficiently dried LiPF 6 is adjusted to a ratio of 1.0 mol / liter. It melt | dissolved and it was set as the electrolyte solution. A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（比較例５）
エチレンカーボネートとγ−ブチロラクトンとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．１モル／リットルの割合となるように溶解して電解液とした。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−１に示す。
(Comparative Example 5)
To 98 parts by weight of a mixture of ethylene carbonate and γ-butyrolactone (volume ratio 3: 7), 2 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added to 1.0 mol / liter and LiN (CF 3 SO 2 ) 2 was dissolved at a rate of 0.1 mol / liter to obtain an electrolytic solution.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-1.
（参考例４）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比３：４：３）９８．５重量部に、ビニレンカーボネート１．５重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．２モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０１モル／リットルの割合となるように溶解して電解液とした。この電解液に占めるＬｉＮ（ＣＦ3 ＳＯ2 ）2 の割合は０．２重量％である。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−２に示す。
(Reference Example 4)
To 98.5 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 3: 4: 3), 1.5 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added to 1.2%. Mol / liter and LiN (CF 3 SO 2 ) 2 were dissolved so as to have a ratio of 0.01 mol / liter to obtain an electrolytic solution. The proportion of LiN (CF 3 SO 2 ) 2 in the electrolyte is 0.2% by weight.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-2.
（比較例６）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比３：４：３）９８．５重量部に、ビニレンカーボネート１．５重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．２モル／リットルの割合となるように溶解して電解液とした。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−２に示す。
(Comparative Example 6)
To 98.5 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 3: 4: 3), 1.5 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added to 1.2%. It melt | dissolved so that it might become a ratio of mol / liter, and it was set as the electrolyte solution.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-2.
（参考例５）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比３：４：３）９８．５重量部に、ビニレンカーボネート１．５重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．２モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０２モル／リットルの割合となるように溶解して電解液とした。この電解液に占めるＬｉＮ（ＣＦ3 ＳＯ2 ）2 の割合は０．４重量％である。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−２に示す。
(Reference Example 5)
To 98.5 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 3: 4: 3), 1.5 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added to 1.2%. Mol / liter and LiN (CF 3 SO 2 ) 2 were dissolved at a ratio of 0.02 mol / liter to obtain an electrolytic solution. The ratio of LiN (CF 3 SO 2 ) 2 in the electrolytic solution is 0.4% by weight.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-2.
（参考例６）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比３：４：３）９８．５重量部に、ビニレンカーボネート１．５重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．２モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０４モル／リットルの割合となるように溶解して電解液とした。この電解液に占めるＬｉＮ（ＣＦ3 ＳＯ2 ）2 の割合は０．９重量％である。
この電解液を用いた以外は、参考例１と同様にしてシート状電池を作製し、得られたシート状電池のガス発生量、連続充電後の残存容量を求めた。結果を表−２に示す。
(Reference Example 6)
To 98.5 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 3: 4: 3), 1.5 parts by weight of vinylene carbonate was added, and then sufficiently dried LiPF 6 was added to 1.2%. Mol / liter and LiN (CF 3 SO 2 ) 2 were dissolved at a ratio of 0.04 mol / liter to obtain an electrolytic solution. The ratio of LiN (CF 3 SO 2 ) 2 in the electrolytic solution is 0.9% by weight.
A sheet-like battery was produced in the same manner as in Reference Example 1 except that this electrolytic solution was used, and the amount of gas generated in the obtained sheet-like battery and the remaining capacity after continuous charging were determined. The results are shown in Table-2.
（参考例７）
乾燥アルゴン雰囲気下、エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部に、ビニレンカーボネート２重量部を添加し、次いで十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０５モル／リットルの割合となるように溶解して電解液とした。
得られた電解液を用いて、円筒状リチウム二次電池を作製し、得られた円筒状電池の連続充電後の残存容量、２００サイクル後の放電容量を求めた。結果を表−３に示す。
(Reference Example 7)
Under a dry argon atmosphere, 2 parts by weight of vinylene carbonate was added to 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), and then sufficiently dried LiPF 6 was adjusted to 1.0 mol / liter. LiN (CF 3 SO 2 ) 2 was dissolved at a rate of 0.05 mol / liter to obtain an electrolytic solution.
Using the obtained electrolytic solution, a cylindrical lithium secondary battery was produced, and the remaining capacity after continuous charging of the obtained cylindrical battery and the discharge capacity after 200 cycles were determined. The results are shown in Table-3.
［円筒状電池の容量評価］
円筒状電池を２５℃において、０．２Ｃに相当する定電流で４．２Ｖまで充電した後、０．２Ｃに相当する定電流で３Ｖまで放電した。これを３サイクル行って電池を安定させ、４サイクル目は、０．５Ｃの定電流で４．２Ｖまで充電し、さらに４．２Ｖの定電圧で電流値が０．０５Ｃになるまで充電を行った後、０．２Ｃの定電流で３Ｖまで放電し、初期放電容量を求めた。
[Capacity evaluation of cylindrical batteries]
The cylindrical battery was charged to 4.2 V with a constant current corresponding to 0.2 C at 25 ° C., and then discharged to 3 V with a constant current corresponding to 0.2 C. This is done for 3 cycles to stabilize the battery. In the 4th cycle, the battery is charged to 4.2 V with a constant current of 0.5 C, and further charged to a current value of 0.05 C with a constant voltage of 4.2 V. Thereafter, the battery was discharged to 3 V at a constant current of 0.2 C, and the initial discharge capacity was determined.
［連続充電特性の評価］
容量評価の終了した円筒状電池を、６０℃において、０．５Ｃの定電流で４．２Ｖに到達した後、定電圧充電に切り替え、２週間連続充電を行った。
電池を冷却させた後、２５℃において、０．２Ｃの定電流で３Ｖまで放電させて連続充電試験後の残存容量を測定し、連続充電試験前の放電容量を１００とした場合の連続充電後の残存容量を求めた。
[Evaluation of continuous charge characteristics]
The cylindrical battery for which the capacity evaluation was completed reached 4.2 V at a constant current of 0.5 C at 60 ° C., then switched to constant voltage charging, and continuously charged for 2 weeks.
After the battery is cooled, it is discharged to 3 V at a constant current of 0.2 C at 25 ° C., the remaining capacity after the continuous charge test is measured, and after the continuous charge when the discharge capacity before the continuous charge test is 100 The remaining capacity of was determined.
［サイクル特性の評価］
容量評価の終了した円筒状電池を、２５℃において、１Ｃの定電流で４．２Ｖまで充電後、４．２Ｖの定電圧で電流値が０．０５Ｃになるまで充電し、１Ｃの定電流で３Ｖまで放電をするサイクル試験を実施した。サイクル試験前の放電容量を１００とした場合の２００サイクル後の放電容量を求めた。
[Evaluation of cycle characteristics]
After the capacity evaluation is completed, the cylindrical battery is charged at a constant current of 1 C to 4.2 V at 25 ° C., and then charged at a constant voltage of 4.2 V until the current value becomes 0.05 C. At a constant current of 1 C A cycle test was conducted to discharge to 3V. The discharge capacity after 200 cycles when the discharge capacity before the cycle test was taken as 100 was determined.
（比較例７）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）に十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量、２００サイクル後の放電容量を求めた。結果を表−３に示す。
(Comparative Example 7)
Reference Example 7 except that an electrolytic solution in which LiPF 6 sufficiently dried in a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7) was dissolved at a ratio of 1.0 mol / liter was used. Similarly, a cylindrical battery was prepared, and the remaining capacity of the obtained cylindrical battery after continuous charging and the discharge capacity after 200 cycles were determined. The results are shown in Table-3.
（比較例８）
エチレンカーボネートとエチルメチルカーボネートとの混合物（容量比３：７）９８重量部にビニレンカーボネート２重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量、２００サイクル後の放電容量を求めた。結果を表−３に示す。
なお、この円筒状電池は、連続充電試験中に電池の内圧が上昇して電流遮断装置が作動したため、放電することはできなかった。
(Comparative Example 8)
2 parts by weight of vinylene carbonate was added to 98 parts by weight of a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7), and sufficiently dried LiPF 6 was dissolved at a rate of 1.0 mol / liter. A cylindrical battery was produced in the same manner as in Reference Example 7 except that the electrolytic solution was used, and the remaining capacity after continuous charging and the discharge capacity after 200 cycles of the obtained cylindrical battery were determined. The results are shown in Table-3.
The cylindrical battery could not be discharged because the internal pressure of the battery increased during the continuous charge test and the current interrupting device was activated.
（参考例８）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比２：４：４）９８重量部にビニレンカーボネート２重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０５モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量を求めた。結果を表−４に示す。
(Reference Example 8)
2 parts by weight of vinylene carbonate was added to 98 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 4: 4), and LiPF 6 was sufficiently dried to 1.0 mol / liter and LiN ( A cylindrical battery was prepared in the same manner as in Reference Example 7 except that an electrolytic solution in which CF 3 SO 2 ) 2 was dissolved at a rate of 0.05 mol / liter was used. The remaining capacity after continuous charging was determined. The results are shown in Table-4.
（比較例９）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比２：４：４）９８重量部にビニレンカーボネート２重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量を求めた。結果を表−４に示す。なお、この円筒状電池は、連続充電試験中に電池の内圧が上昇して電流遮断装置が作動したため、放電することはできなかった。
(Comparative Example 9)
2 parts by weight of vinylene carbonate is added to 98 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 4: 4), and LiPF 6 sufficiently dried is added at a ratio of 1.0 mol / liter. A cylindrical battery was produced in the same manner as in Reference Example 7 except that the dissolved electrolyte solution was used, and the remaining capacity after continuous charging of the obtained cylindrical battery was determined. The results are shown in Table-4. The cylindrical battery could not be discharged because the internal pressure of the battery increased during the continuous charge test and the current interrupting device was activated.
（実施例２）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比２：４：４）９７重量部にビニレンカーボネート２重量部とシクロヘキシルベンゼン１重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルとＬｉＮ（ＣＦ3 ＳＯ2 ）2 を０．０５モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量を求めた。結果を表−４に示す。
(Example 2)
2 parts by weight of vinylene carbonate and 1 part by weight of cyclohexylbenzene are added to 97 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 4: 4), and 1.0% of LiPF 6 which has been sufficiently dried is 1.0%. A cylindrical battery was produced and obtained in the same manner as in Reference Example 7 except that an electrolytic solution in which mol / liter and LiN (CF 3 SO 2 ) 2 were dissolved at a ratio of 0.05 mol / liter was used. The remaining capacity of the obtained cylindrical battery after continuous charging was determined. The results are shown in Table-4.
（比較例１０）
エチレンカーボネートとエチルメチルカーボネートとジメチルカーボネートとの混合物（容量比２：４：４）９７重量部にビニレンカーボネート２重量部とシクロヘキシルベンゼン１重量部を添加し、十分に乾燥したＬｉＰＦ6 を１．０モル／リットルの割合となるように溶解した電解液を用いた以外は、参考例７と同様にして円筒状電池を作製し、得られた円筒状電池の連続充電後の残存容量を求めた。結果を表−４に示す。なお、この円筒状電池は、連続充電試験中に電池の内圧が上昇して電流遮断装置が作動したため、放電することはできなかった。
(Comparative Example 10)
2 parts by weight of vinylene carbonate and 1 part by weight of cyclohexylbenzene are added to 97 parts by weight of a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio 2: 4: 4), and 1.0% of LiPF 6 which has been sufficiently dried is 1.0%. A cylindrical battery was produced in the same manner as in Reference Example 7 except that the electrolytic solution dissolved so as to have a mol / liter ratio was used, and the remaining capacity of the obtained cylindrical battery after continuous charging was determined. The results are shown in Table-4. The cylindrical battery could not be discharged because the internal pressure of the battery increased during the continuous charge test and the current interrupting device was activated.
表−１、２、４から明らかなように、本発明に係る電池は、連続充電した場合のガスの発生量が少なく、連続充電後の放電特性にも優れていることがわかる。
比較例４、５の鎖状カーボネートを含まないでエチレンカーボネートとγ−ブチロラクトンの混合溶媒にビニレンカーボネートが添加したものを用いた場合には、発生ガス量は極めて少ないが、連続充電後の放電特性は低下してしまい、更にＬｉＮ（ＣＦ3 ＳＯ2 ）2 を併用した効果もみられず、ガス発生の抑制と電池特性を両立させることはできない。
As is apparent from Tables 1, 2, and 4, the battery according to the present invention has a small amount of gas generated when continuously charged, and is excellent in discharge characteristics after continuous charging.
In the case of using a mixed solvent of ethylene carbonate and γ-butyrolactone added with vinylene carbonate without containing the chain carbonate of Comparative Examples 4 and 5, the amount of gas generated is very small, but the discharge characteristics after continuous charging In addition, the effect of using LiN (CF 3 SO 2 ) 2 in combination is not observed, and it is impossible to achieve both suppression of gas generation and battery characteristics.
また、表−３から明かなように、本発明に係る電池は、連続充電した場合のガスの発生量が少なく、サイクル特性にも優れていることがわかる。 Further, as is clear from Table 3, it can be seen that the battery according to the present invention has a small amount of gas generated when continuously charged and is excellent in cycle characteristics.
１ 電池ケース
２ 封口板
３ 絶縁ガスケット
４ 渦巻き状電極体
５ 正極端子
６ 負極端子
７ 絶縁リング
８ 電流遮断装置
DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation gasket 4 Spiral electrode body 5 Positive electrode terminal 6 Negative electrode terminal 7 Insulation ring 8 Current interruption device
Claims (13)
）２ （但し、ｎ＝１又は２）を０．００１〜０．２モル／リットルの濃度で含有し、かつ、非水溶媒が、（１）エチレンカーボネート及び／又はプロピレンカーボネート、（２）鎖状カーボネート、及び（３）ビニレンカーボネートを主成分とし、リチウム塩を除く非水系電解液に占めるエチレンカーボネート、プロピレンカーボネート及び鎖状カーボネートの合計が８０重量％以上であると共に、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン、ジフェニルエーテル、ジベンゾフランから選ばれる芳香族化合物を含有することを特徴とする非水系電解液。 A non-aqueous electrolyte mainly composed of a lithium salt and a non-aqueous solvent that dissolves the lithium salt. As the lithium salt, 0.2 to 2 mol / liter of LiPF 6 and LiN (C n F 2n + 1 SO 2
) 2 (where n = 1 or 2) at a concentration of 0.001 to 0.2 mol / liter, and the nonaqueous solvent is (1) ethylene carbonate and / or propylene carbonate, (2) chain Jo carbonate, and (3) as a main component vinylene carbonate, a non-aqueous electrolyte solution accounted ethylene carbonate, the total of 80 wt% or more der Rutotomoni propylene carbonate and a linear carbonate, biphenyl, alkyl biphenyl excluding lithium salt A non-aqueous electrolyte containing an aromatic compound selected from terphenyl, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran.
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| JP6066464B2 (en) * | 2012-03-14 | 2017-01-25 | セイコーインスツル株式会社 | Electrolytic solution for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same |
| KR101865444B1 (en) * | 2012-03-19 | 2018-06-07 | 미쯔비시 케미컬 주식회사 | Nonaqueous electrolyte and nonaqueous electrolyte cell |
| JP6018820B2 (en) * | 2012-07-04 | 2016-11-02 | 株式会社日本触媒 | Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery provided with the same |
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