JP7458932B2 - Non-aqueous electrolyte for power storage devices and power storage devices - Google Patents
Non-aqueous electrolyte for power storage devices and power storage devices Download PDFInfo
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- JP7458932B2 JP7458932B2 JP2020135916A JP2020135916A JP7458932B2 JP 7458932 B2 JP7458932 B2 JP 7458932B2 JP 2020135916 A JP2020135916 A JP 2020135916A JP 2020135916 A JP2020135916 A JP 2020135916A JP 7458932 B2 JP7458932 B2 JP 7458932B2
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- Prior art keywords
- aqueous electrolyte
- electrolyte
- power storage
- general formula
- storage device
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims description 83
- 238000003860 storage Methods 0.000 title claims description 63
- -1 cyclic sulfate ester Chemical class 0.000 claims description 64
- 239000003792 electrolyte Substances 0.000 claims description 26
- 125000000217 alkyl group Chemical group 0.000 claims description 18
- 125000004432 carbon atom Chemical group C* 0.000 claims description 18
- 239000003125 aqueous solvent Substances 0.000 claims description 17
- 230000005611 electricity Effects 0.000 claims description 17
- 150000003839 salts Chemical class 0.000 claims description 16
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 13
- 229910000077 silane Inorganic materials 0.000 claims description 13
- 239000002904 solvent Substances 0.000 claims description 7
- 125000005843 halogen group Chemical group 0.000 claims description 6
- 125000003118 aryl group Chemical group 0.000 claims description 4
- 125000001424 substituent group Chemical group 0.000 claims description 4
- 125000002947 alkylene group Chemical group 0.000 claims description 3
- 125000000732 arylene group Chemical group 0.000 claims description 3
- 229910001290 LiPF6 Inorganic materials 0.000 claims description 2
- 229910052744 lithium Inorganic materials 0.000 description 47
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 43
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 27
- 150000001875 compounds Chemical class 0.000 description 25
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 23
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical class [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 19
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 15
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- 238000000354 decomposition reaction Methods 0.000 description 13
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- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 10
- 125000004122 cyclic group Chemical group 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 229910003002 lithium salt Inorganic materials 0.000 description 9
- 159000000002 lithium salts Chemical class 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 229910002804 graphite Inorganic materials 0.000 description 8
- 239000010439 graphite Substances 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 239000003990 capacitor Substances 0.000 description 7
- 239000010410 layer Substances 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 6
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- 238000006243 chemical reaction Methods 0.000 description 6
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 6
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- 238000009830 intercalation Methods 0.000 description 5
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- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 4
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- AVPYLKIIPLFMHQ-UHFFFAOYSA-N 1,2,6-oxadithiane 2,2,6,6-tetraoxide Chemical compound O=S1(=O)CCCS(=O)(=O)O1 AVPYLKIIPLFMHQ-UHFFFAOYSA-N 0.000 description 3
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- 229910017052 cobalt Inorganic materials 0.000 description 3
- 239000010941 cobalt Substances 0.000 description 3
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- RCIJMMSZBQEWKW-UHFFFAOYSA-N methyl propan-2-yl carbonate Chemical compound COC(=O)OC(C)C RCIJMMSZBQEWKW-UHFFFAOYSA-N 0.000 description 3
- KKQAVHGECIBFRQ-UHFFFAOYSA-N methyl propyl carbonate Chemical compound CCCOC(=O)OC KKQAVHGECIBFRQ-UHFFFAOYSA-N 0.000 description 3
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
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- OGYYMQPBYZBCNM-UHFFFAOYSA-N 1,2,7-oxadithiepane 2,2,7,7-tetraoxide Chemical compound O=S1(=O)CCCCS(=O)(=O)O1 OGYYMQPBYZBCNM-UHFFFAOYSA-N 0.000 description 2
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- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 2
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- 229910010941 LiFSI Inorganic materials 0.000 description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 2
- 229910013131 LiN Inorganic materials 0.000 description 2
- 229910013528 LiN(SO2 CF3)2 Inorganic materials 0.000 description 2
- 229910013385 LiN(SO2C2F5)2 Inorganic materials 0.000 description 2
- 229910012748 LiNi0.5Mn0.3Co0.2O2 Inorganic materials 0.000 description 2
- 229910015965 LiNi0.8Mn0.1Co0.1O2 Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 2
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- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 2
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- 238000009835 boiling Methods 0.000 description 2
- FWBMVXOCTXTBAD-UHFFFAOYSA-N butyl methyl carbonate Chemical compound CCCCOC(=O)OC FWBMVXOCTXTBAD-UHFFFAOYSA-N 0.000 description 2
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- AHUXYBVKTIBBJW-UHFFFAOYSA-N dimethoxy(diphenyl)silane Chemical compound C=1C=CC=CC=1[Si](OC)(OC)C1=CC=CC=C1 AHUXYBVKTIBBJW-UHFFFAOYSA-N 0.000 description 2
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Classifications
-
- 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
Landscapes
- Electric Double-Layer Capacitors Or The Like (AREA)
- Primary Cells (AREA)
- Secondary Cells (AREA)
Description
本発明は、化学的安定性を高い水準で維持できる蓄電デバイス用非水電解液および蓄電デバイスに関する。 TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte for a power storage device and a power storage device that can maintain a high level of chemical stability.
近年、蓄電デバイス、特にリチウム二次電池は、携帯電話やノート型パソコン等の小型電子機器、電気自動車や電力貯蔵用として広く使用されている。これらの電子機器や自動車は、真夏の高温下や極寒の低温下等広い温度範囲で使用される可能性があるため、広い温度範囲でバランス良く電気化学特性を向上させることが求められている。
特に地球温暖化防止のため、ＣＯ２排出量を削減することが急務となっており、リチウム二次電池やキャパシタ等の蓄電デバイスからなる蓄電装置を搭載した環境対応車の中でも、ハイブリッド電気自動車（ＨＥＶ）、プラグインハイブリッド電気自動車（ＰＨＥＶ）、バッテリー電気自動車（ＢＥＶ）の早期普及が求められている。自動車は移動距離が長いため、熱帯の非常に暑い地域から極寒の地域まで幅広い温度範囲の地域で使用される可能性がある。特にこれらの車載用の蓄電デバイスは、高温から低温まで幅広い温度範囲で使用しても電気化学特性が低下しないことが要求されている。従って、蓄電デバイス用材料にも同様に幅広い温度範囲での化学的安定性が要求される。
尚、本明細書において、リチウム二次電池という用語は、いわゆるリチウムイオン二次電池も含む概念として用いる。
In recent years, power storage devices, particularly lithium secondary batteries, have been widely used in small electronic devices such as mobile phones and notebook computers, electric vehicles, and for power storage. Since these electronic devices and automobiles may be used in a wide temperature range, such as high temperatures in midsummer or extremely low temperatures, there is a need to improve electrochemical properties in a well-balanced manner over a wide temperature range.
In particular, to prevent global warming, there is an urgent need to reduce CO2 emissions, and among environmentally friendly vehicles equipped with power storage devices such as lithium secondary batteries and capacitors, hybrid electric vehicles ( There is a need for the early spread of HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV). Because cars travel long distances, they may be used in regions with a wide range of temperatures, from extremely hot tropical regions to extremely cold regions. In particular, these in-vehicle power storage devices are required to have electrochemical properties that do not deteriorate even when used in a wide temperature range from high to low temperatures. Therefore, materials for power storage devices are similarly required to have chemical stability over a wide temperature range.
Note that in this specification, the term lithium secondary battery is used as a concept that also includes so-called lithium ion secondary batteries.
リチウム二次電池は、主にリチウムを吸蔵および放出可能な材料を含む正極および負極、リチウム塩と非水溶媒からなる非水電解液から構成され、非水溶媒としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）等のカーボネートが使用されている。
また、負極としては、金属リチウム、リチウムを吸蔵および放出可能な金属化合物（金属単体、酸化物、リチウムとの合金等）や炭素材料が知られており、特にリチウムを吸蔵および放出することが可能なコークス、人造黒鉛、天然黒鉛等の炭素材料を用いたリチウム二次電池が広く実用化されている。
A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of intercalating and releasing lithium, and a non-aqueous electrolyte consisting of a lithium salt and a non-aqueous solvent.The non-aqueous solvent includes ethylene carbonate (EC), Carbonates such as propylene carbonate (PC) are used.
In addition, as negative electrodes, metal lithium, metal compounds (metals, oxides, alloys with lithium, etc.) that can occlude and release lithium, and carbon materials are known, and in particular are capable of intercalating and releasing lithium. Lithium secondary batteries using carbon materials such as coke, artificial graphite, and natural graphite have been widely put into practical use.
例えば、天然黒鉛や人造黒鉛等の高結晶化した炭素材料を負極材料として用いたリチウム二次電池は、非水電解液中の溶媒が充電時に負極表面で還元分解することにより発生した分解物やガスが、電池の望ましい電気化学的反応を阻害するため、サイクル特性の低下を生じることが分かっている。また、非水溶媒の分解物が蓄積すると、負極へのリチウムの吸蔵および放出がスムーズにできなくなり、広い温度範囲で使用した場合における電気化学特性が低下しやすくなる。
更に、リチウム金属やその合金、スズまたはケイ素等の金属単体やその酸化物を負極材料として用いたリチウム二次電池は、初期の容量は高いもののサイクル中に微粉化が進むため、炭素材料の負極に比べて非水溶媒の還元分解が加速的に起こり、電池容量やサイクル特性のような電池性能が大きく低下することが知られている。また、これらの負極材料の微粉化や非水溶媒の分解物が蓄積すると、負極へのリチウムの吸蔵および放出がスムーズにできなくなり、広い温度範囲で使用した場合における電気化学特性が低下しやすくなる。
For example, in lithium secondary batteries that use highly crystallized carbon materials such as natural graphite or artificial graphite as negative electrode materials, decomposed products and Gases have been found to interfere with the desired electrochemical reactions of the cell, resulting in reduced cycling performance. Furthermore, when decomposed products of the non-aqueous solvent accumulate, lithium cannot be smoothly inserted into and released from the negative electrode, and the electrochemical properties tend to deteriorate when used over a wide temperature range.
Furthermore, although lithium secondary batteries that use lithium metal, its alloys, elemental metals such as tin or silicon, or their oxides as negative electrode materials have a high initial capacity, they become pulverized during the cycle, so carbon material negative electrodes cannot be used. It is known that the reductive decomposition of the non-aqueous solvent occurs more rapidly than in the conventional method, resulting in a significant drop in battery performance such as battery capacity and cycle characteristics. Additionally, if these negative electrode materials become pulverized or decomposed products of non-aqueous solvents accumulate, lithium cannot be absorbed and released smoothly into the negative electrode, and electrochemical properties tend to deteriorate when used over a wide temperature range. .
一方、正極として、例えばＬｉＣｏＯ２、ＬｉＭｎ２Ｏ４、ＬｉＮｉＯ２、ＬｉＦｅＰＯ４等を用いたリチウム二次電池は、非水電解液中の非水溶媒が充電状態で正極材料と非水電解液との界面において、局部的に一部酸化分解することにより発生した分解物やガスが電池の望ましい電気化学的反応を阻害するため、やはり広い温度範囲で使用した場合における電気化学特性の低下を生じることが分かっている。 On the other hand, in a lithium secondary battery using, for example, LiCoO 2 , LiMn 2 O 4 , LiNiO 2 , LiFePO 4 , etc. as the positive electrode, the non-aqueous solvent in the non-aqueous electrolyte interacts with the positive electrode material and the non-aqueous electrolyte in a charged state. At the interface, decomposition products and gas generated by localized partial oxidative decomposition inhibit the desired electrochemical reactions of the battery, resulting in a decrease in electrochemical properties when used over a wide temperature range. I know.
以上のように、正極上や負極上で非水電解液が分解するときの分解物やガスにより、リチウムイオンの移動が阻害されたり、電池が膨れたりすることで電池性能が低下していた。さらに、電解液の化学的安定性に関しても、幅広い温度範囲での安定性が求められている。これらの課題を改善するために、非水電解液に添加剤を添加することで、正極上や負極上で非水電解液の分解を抑制する技術が適用されている。
特許文献１には、環状硫酸エステルを非水電解液に添加することによりサイクル特性を向上させた電池が記載されている。
また、特許文献２には、特定の部位を有する環状スルホン化合物を非水電解液に添加することにより高温サイクル特性や電圧維持特性を向上させた電池が記載されている。
さらに、特許文献３には、有機シラン化合物を添加することにより非水電解液の安定性を向上させた電池が記載されている。
As described above, the decomposition products and gas generated when the non-aqueous electrolyte decomposes on the positive electrode and the negative electrode inhibit the movement of lithium ions and cause the battery to swell, resulting in a decrease in battery performance. Furthermore, regarding the chemical stability of the electrolyte, stability is required over a wide temperature range. In order to improve these problems, technology has been applied to suppress decomposition of the non-aqueous electrolyte on the positive electrode or the negative electrode by adding additives to the non-aqueous electrolyte.
Patent Document 1 describes a battery whose cycle characteristics are improved by adding a cyclic sulfate ester to a non-aqueous electrolyte.
Further, Patent Document 2 describes a battery in which high temperature cycle characteristics and voltage maintenance characteristics are improved by adding a cyclic sulfone compound having a specific site to a non-aqueous electrolyte.
Further, Patent Document 3 describes a battery in which the stability of the non-aqueous electrolyte is improved by adding an organic silane compound.
本発明は、高温保存後の非水電解液の着色を抑制し、かつ高温保存による環状硫酸エステルや環状スルホン化合物の分解を抑制できる蓄電デバイス用非水電解液および蓄電デバイスを提供することを目的とする。 An object of the present invention is to provide a non-aqueous electrolyte for a power storage device and a power storage device that can suppress coloring of the non-aqueous electrolyte after high-temperature storage and suppress decomposition of cyclic sulfuric esters and cyclic sulfone compounds due to high-temperature storage. shall be.
前述のとおり、車載用の蓄電デバイスは、高温から低温まで幅広い温度範囲で使用しても電気化学特性が低下しないことが要求されており、蓄電デバイス用材料にも同様に幅広い温度範囲での化学的安定性が要求されている。本発明者らは、上記従来技術の非水電解液の化学的安定性について詳細に検討した結果、前記特許文献１の環状硫酸エステルや前記特許文献２の特定の部位を有する環状スルホン化合物を含有する非水電解液は、一定期間の保存後に着色し、電池性能の効果を発揮できなくなることが判明した。
そこで、本発明者らは、上記課題を解決するために鋭意研究を重ね、非水溶媒に電解質塩と環状硫酸エステルおよびや環状スルホン化合物が溶解されている非水電解液において、有機シラン化合物を加えることで、非水電解液の化学的安定性が改善できることを見出し、本発明を完成した。なお、前記特許文献３には、有機シラン化合物を環状硫酸エステルまたは環状スルホン化合物と組合せた非水電解液の化学的安定性に関して記載はない。
As mentioned above, in-vehicle power storage devices are required to have electrochemical properties that do not deteriorate even when used in a wide temperature range from high to low temperatures, and materials for power storage devices are also required to have chemical properties that do not deteriorate over a wide temperature range. stability is required. As a result of detailed study on the chemical stability of the non-aqueous electrolyte of the above-mentioned prior art, the present inventors found that the non-aqueous electrolyte containing the cyclic sulfate ester of Patent Document 1 and the cyclic sulfone compound having a specific moiety of Patent Document 2 It has been found that the non-aqueous electrolyte becomes colored after being stored for a certain period of time, making it no longer effective in improving battery performance.
Therefore, the present inventors have conducted extensive research to solve the above problems, and have developed an organic silane compound in a non-aqueous electrolyte in which an electrolyte salt, a cyclic sulfate ester, and a semi-cyclic sulfone compound are dissolved in a non-aqueous solvent. It was discovered that the chemical stability of the non-aqueous electrolyte can be improved by adding it, and the present invention was completed. Note that Patent Document 3 does not describe the chemical stability of a non-aqueous electrolyte in which an organic silane compound is combined with a cyclic sulfate ester or a cyclic sulfone compound.
すなわち、本発明は、下記の（１）および（２）を提供するものである。 That is, the present invention provides the following (1) and (2).
（１）非水溶媒に電解質塩が溶解されている非水電解液において、一般式（Ｉ）で表される環状硫酸エステルおよび一般式（ＩＩ）で表される環状スルホン化合物から選ばれる１種以上と、一般式（ＩＩＩ）で表される有機シラン化合物とを含有することを特徴とする蓄電デバイス用非水電解液。
(1) In a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, one type selected from a cyclic sulfate ester represented by general formula (I) and a cyclic sulfone compound represented by general formula (II) A non-aqueous electrolyte for a power storage device, comprising the above and an organic silane compound represented by general formula (III).
（２）正極、負極および非水溶媒に電解質塩が溶解されている非水電解液を備えた蓄電デバイスであって、該非水電解液が前記（１）に記載の非水電解液であることを特徴とする蓄電デバイス。 (2) An electricity storage device comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, where the non-aqueous electrolyte is the non-aqueous electrolyte described in (1) above. A power storage device featuring:
本発明によれば、高温保存後の非水電解液の着色を抑制し、かつ高温保存による環状硫酸エステルや環状スルホン化合物の分解を抑制できる蓄電デバイス用非水電解液および蓄電デバイスを提供することができる。 According to the present invention, there is provided a non-aqueous electrolyte for a power storage device and a power storage device that can suppress coloring of the non-aqueous electrolyte after high-temperature storage and suppress decomposition of cyclic sulfuric esters and cyclic sulfone compounds due to high-temperature storage. I can do it.
本発明は、蓄電デバイス用非水電解液および蓄電デバイスに関する。 The present invention relates to a non-aqueous electrolyte for an electricity storage device and an electricity storage device.
〔非水電解液〕
本発明の非水電解液は、非水溶媒に電解質塩が溶解されている非水電解液において、一般式（Ｉ）で表される環状硫酸エステルおよび一般式（ＩＩ）で表される環状スルホン化合物から選ばれる１種以上と、一般式（ＩＩＩ）で表される有機シラン化合物とを含有することを特徴とする蓄電デバイス用非水電解液である。
[Non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention includes a cyclic sulfuric ester represented by general formula (I) and a cyclic sulfone represented by general formula (II), in which an electrolyte salt is dissolved in a non-aqueous solvent. This is a non-aqueous electrolyte for a power storage device, characterized by containing one or more selected from compounds and an organic silane compound represented by general formula (III).
本発明の非水電解液が、化学的な安定性を改善できる理由は必ずしも明らかではないが、以下のように考える。
非水電解液中において、一般式（Ｉ）で表される環状硫酸エステルや一般式（ＩＩ）で表される特定の部位を有する環状スルホン化合物が、一定時間経過した際に、電解質塩、特にＬｉＰＦ６と徐々に反応することで、環状構造が分解され、発生した一部の分解物が非水電解液の着色を促していると推測される。そこで、非水電解液に一般式（ＩＩＩ）で表される有機シラン化合物を更に添加することで、電解質塩と一般式（Ｉ）に記載される環状硫酸エステルや一般式（ＩＩ）で表される特定の部位を有する環状スルホン化合物との反応が抑制されると考えられる。このため、非水電解液の着色が抑えられ、更に環状硫酸エステルや環状スルホン化合物の分解を抑制できると考えられる。
The reason why the non-aqueous electrolyte of the present invention can improve chemical stability is not necessarily clear, but it is considered as follows.
In a non-aqueous electrolyte, when a cyclic sulfuric ester represented by general formula (I) or a cyclic sulfone compound having a specific moiety represented by general formula (II) passes for a certain period of time, electrolyte salts, especially It is presumed that the cyclic structure is decomposed by the gradual reaction with LiPF 6 , and some of the decomposed products generated promote coloring of the non-aqueous electrolyte. Therefore, by further adding an organic silane compound represented by the general formula (III) to the nonaqueous electrolyte, it is possible to combine the electrolyte salt with the cyclic sulfate ester described in the general formula (I) and the organic silane compound represented by the general formula (II). It is thought that the reaction with a cyclic sulfone compound having a specific site is suppressed. Therefore, it is thought that coloring of the non-aqueous electrolyte can be suppressed, and furthermore, decomposition of the cyclic sulfuric ester and the cyclic sulfone compound can be suppressed.
本発明の非水電解液は、下記一般式（Ｉ）で表される環状硫酸エステルおよび一般式（ＩＩ）で表される環状スルホン化合物から選ばれる１種以上と、一般式（ＩＩＩ）で表される有機シラン化合物とを含む。 The nonaqueous electrolyte of the present invention contains at least one compound selected from the group consisting of cyclic sulfate esters represented by the following general formula (I) and cyclic sulfone compounds represented by the following general formula (II), and an organosilane compound represented by the following general formula (III).
〔一般式（Ｉ）で表される化合物〕
前記一般式（Ｉ）において、Ｒ１およびＲ２はそれぞれ独立に、水素原子または炭素数１～６のアルキル基を示し、Ｒ１とＲ２が互いに結合し環を形成してもよく、炭素数１～４のアルキル基が好ましく、炭素数１または２のアルキル基がより好ましい。
[Compound represented by general formula (I)]
In the general formula (I), R 1 and R 2 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1 and R 2 may combine with each other to form a ring, and An alkyl group having 1 to 4 carbon atoms is preferred, and an alkyl group having 1 or 2 carbon atoms is more preferred.
前記Ｒ１およびＲ２の具体例としては、水素原子、メチル基、エチル基、ｎ－プロピル基、ｎ－ブチル基、ｎ－ペンチル基、もしくはｎ－ヘキシル基などの直鎖のアルキル基またはｉｓｏ－プロピル基、ｉｓｏ－ブチル基、ｓｅｃ－ブチル基もしくはｔｅｒｔ－ブチル基などの分枝のアルキル基が好適に挙げられ、水素原子、メチル基、エチル基、ｎ－プロピル基またはｎ－ブチル基が好ましく、水素原子、メチル基またはエチル基がより好ましい。 Specific examples of R1 and R2 include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, or another linear alkyl group; or an isopropyl group, an isobutyl group, a sec-butyl group, an tert-butyl group, or another branched alkyl group; a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an n-butyl group is preferable, and a hydrogen atom, a methyl group, or an ethyl group is more preferable.
また、Ｒ１およびＲ２が互いに結合し環を形成する場合の具体例としては、シクロブチル構造、シクロペンチル構造、シクロヘキシル構造、シクロヘプチル構造またはシクロオクチル構造を有するものが好適に挙げられ、シクロペンチル構造またはシクロヘキシル構造を有するものがより好ましい。 Further, specific examples of R 1 and R 2 bonding to each other to form a ring include those preferably having a cyclobutyl structure, a cyclopentyl structure, a cyclohexyl structure, a cycloheptyl structure, or a cyclooctyl structure; Those having a cyclohexyl structure are more preferred.
前記一般式（Ｉ）で表される環状硫酸エステルとしては、具体的に以下の化合物が好適に挙げられる。 Specific examples of the cyclic sulfate ester represented by the general formula (I) include the following compounds:
上記好適例の中でも化合物Ａ１～Ａ３、Ａ１２、Ａ１３、Ａ１４、Ａ１６またはＡ１７が好ましく、１，３，２－ジオキサチオラン－２，２－ジオキシド（化合物Ａ１）、４，５－ジメチル－１，３，２－ジオキサチオラン－２，２－ジオキシド（化合物Ａ１２）またはテトラヒドロ－４Ｈ－シクロペンタ［ｄ］［１，３，２］ジオキサチオール２，２－ジオキシド（化合物Ａ１６）がより好ましい。 Among the above preferred examples, compounds A1 to A3, A12, A13, A14, A16, and A17 are preferred, and 1,3,2-dioxathiolane-2,2-dioxide (compound A1), 4,5-dimethyl-1,3,2-dioxathiolane-2,2-dioxide (compound A12), and tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol 2,2-dioxide (compound A16) are more preferred.
前記一般式（ＩＩ）で表される環状スルホン化合物としては、具体的に以下の化合物が好適に挙げられる。 As the cyclic sulfone compound represented by the general formula (II), the following compounds are specifically preferred.
上記好適例の中でも化合物Ｃ１～Ｃ３、Ｃ１１、またはＣ１６が好ましく、１，２，５－オキサジチラン ２，２，５，５－テトラオキシド（Ｃ１）、１，２，６－オキサジチアン ２，２，６，６－テトラオキシド（Ｃ２）、または１，２，７－オキサジチエパン ２，２，７，７－テトラオキシド（Ｃ３）がより好ましく、１，２，６－オキサジチアン ２，２，６，６－テトラオキシド（Ｃ２）がさらに好ましい。 Among the above preferred examples, compounds C1 to C3, C11, or C16 are preferred, with 1,2,5-oxadithilane 2,2,5,5-tetraoxide (C1), 1,2,6-oxadithiane 2,2,6,6-tetraoxide (C2), or 1,2,7-oxadithiepane 2,2,7,7-tetraoxide (C3) being more preferred, and 1,2,6-oxadithiane 2,2,6,6-tetraoxide (C2) being even more preferred.
本発明の非水電解液において、非水電解液に含有される前記一般式（Ｉ）で表される環状硫酸エステルおよび前記一般式（ＩＩ）で表される環状スルホン化合物の含有量はそれぞれ、非水電解液中に、非水電解液全量に対して、０．００１～５質量％であることが好ましい。該含有量が５質量％以下であれば、電極上に過度に被膜が形成されるおそれが少なく、また０．００１質量％以上であれば被膜の強度が高まるので上記範囲であることが好ましい。該含有量は、非水電解液中に０．０５質量％以上がより好ましく、０．１質量％以上が更に好ましい。また、３質量％以下がより好ましく、２質量％以下が更に好ましい。 In the nonaqueous electrolyte of the present invention, the contents of the cyclic sulfate ester represented by the general formula (I) and the cyclic sulfone compound represented by the general formula (II) contained in the nonaqueous electrolyte are as follows: In the nonaqueous electrolyte, it is preferably 0.001 to 5% by mass based on the total amount of the nonaqueous electrolyte. If the content is 5% by mass or less, there is little possibility that a film will be excessively formed on the electrode, and if the content is 0.001% by mass or more, the strength of the film will increase, so the above range is preferable. The content is more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more in the nonaqueous electrolyte. Further, the content is more preferably 3% by mass or less, and even more preferably 2% by mass or less.
〔一般式（ＩＩＩ）で表される化合物〕
前記一般式（ＩＩＩ）において、Ｒ３およびＲ４はそれぞれ独立に、炭素数１～３のアルキル基を示し、炭素数１または２のアルキル基がより好ましい。
[Compound represented by general formula (III)]
In the general formula (III), R 3 and R 4 each independently represent an alkyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 or 2 carbon atoms.
前記Ｒ３およびＲ４の具体例としては、メチル基、エチル基、ｎ－プロピル基またはｉｓｏ－プロピル基が好適に挙げられ、メチル基またはエチル基がより好ましい。 Specific examples of R 3 and R 4 include preferably a methyl group, an ethyl group, an n-propyl group, or an iso-propyl group, with a methyl group or an ethyl group being more preferred.
前記一般式（ＩＩＩ）において、Ｒ５およびＲ６はそれぞれ独立に、炭素数１～３のアルキル基または置換基を有していてもよいアリール基を示す。 In the general formula (III), R 5 and R 6 each independently represent an alkyl group having 1 to 3 carbon atoms or an aryl group which may have a substituent.
前記Ｒ５およびＲ６の具体例としては、メチル基、エチル基、ｎ－プロピル基、ｉｓｏ－プロピル基、フェニル基、トリル基またはキシリル基が好適に挙げられ、メチル基またはフェニル基がより好ましい。 Specific examples of R 5 and R 6 include preferably a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, a phenyl group, a tolyl group, and a xylyl group, with a methyl group or a phenyl group being more preferable. .
前記一般式（ＩＩＩ）で表される有機シラン化合物としては、具体的に以下の化合物が好適に挙げられる。 As the organic silane compound represented by the general formula (III), the following compounds can be specifically mentioned.
上記好適例の中でも化合物Ｂ１、Ｂ２またはＢ１０が好ましく、ジメトキシジメチルシラン（化合物B１）またはジフェニルジメトキシシラン（化合物Ｂ１０）がより好ましい。 Among the above preferred examples, compounds B1, B2, or B10 are preferred, and dimethoxydimethylsilane (compound B1) or diphenyldimethoxysilane (compound B10) is more preferred.
本発明の非水電解液において、非水電解液に含有される前記一般式（ＩＩ）で表される有機シラン化合物の含有量は、非水電解液中に、非水電解液全量に対して、０．０１～０．５質量％であることが好ましい。該含有量は、高温保存後の一般式（Ｉ）の化合物残存量の点から、０．３質量％以下がより好ましい。また、非水電解液の着色抑制の点から、０．０１質量％以上であることが好ましく、０．０５質量％以上であることがより好ましい。 In the non-aqueous electrolyte of the present invention, the content of the organic silane compound represented by the general formula (II) contained in the non-aqueous electrolyte is determined based on the total amount of the non-aqueous electrolyte. , preferably 0.01 to 0.5% by mass. The content is more preferably 0.3% by mass or less in terms of the amount of the compound of general formula (I) remaining after high-temperature storage. Further, from the viewpoint of suppressing coloration of the non-aqueous electrolyte, the content is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more.
本発明の非水電解液において、前記一般式（Ｉ）で表される化合物および一般式（ＩＩ）で表される環状スルホン化合物から選ばれる１種以上と一般式（ＩＩＩ）で表される化合物とを、以下に述べる非水溶媒と電解質塩とを組合せることにより、高温保存後の非水電解液の着色と環状硫酸エステルや環状スルホン化合物の分解をより抑制できる。 In the non-aqueous electrolyte of the present invention, one or more compounds selected from the compound represented by the general formula (I) and the cyclic sulfone compound represented by the general formula (II) and the compound represented by the general formula (III) By combining these with a non-aqueous solvent and an electrolyte salt described below, coloring of the non-aqueous electrolyte after storage at high temperatures and decomposition of the cyclic sulfuric ester or cyclic sulfone compound can be further suppressed.
〔非水溶媒〕
本発明の非水電解液に使用される非水溶媒としては、環状カーボネート、鎖状エステル、ラクトン、エーテルおよびアミドから選ばれる１種または２種以上が好適に挙げられる。
[Non-aqueous solvent]
The non-aqueous solvent used in the non-aqueous electrolyte of the present invention is preferably one or more selected from cyclic carbonates, chain esters, lactones, ethers, and amides.
なお、「鎖状エステル」なる用語は、鎖状カーボネートおよび鎖状カルボン酸エステルを含む概念として用いる。 Note that the term "chain ester" is used as a concept including chain carbonates and chain carboxylic acid esters.
環状カーボネートとしては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、１，２－ブチレンカーボネート、２，３－ブチレンカーボネート、４－フルオロ－１，３－ジオキソラン－２－オン（ＦＥＣ）、トランスもしくはシス－４，５－ジフルオロ－１，３－ジオキソラン－２－オン（以下、両者を総称して「ＤＦＥＣ」という）、ビニレンカーボネート（ＶＣ）、ビニルエチレンカーボネート（ＶＥＣ）および４－エチニル－１，３－ジオキソラン－２－オン（ＥＥＣ）から選ばれる一種または二種以上が挙げられ、エチレンカーボネート、プロピレンカーボネート、４－フルオロ－１，３－ジオキソラン－２－オン、ビニレンカーボネートおよび４－エチニル－１，３－ジオキソラン－２－オンから選ばれる一種または二種以上がより好適である。 Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter collectively referred to as "DFEC"), vinylene carbonate (VC), vinylethylene carbonate (VEC) and 4-ethynyl-1, One or more selected from 3-dioxolan-2-one (EEC), including ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate and 4-ethynyl-1 , 3-dioxolan-2-one, or two or more thereof are more preferable.
これらの溶媒は一種類で使用してもよく、また二種類以上を組合せて使用した場合は、広い温度範囲での電気化学特性の改善効果が更に向上するので好ましく、３種類以上を組合せて使用することが特に好ましい。これらの環状カーボネートの好適な組合せとしては、ＥＣとＰＣ、ＥＣとＶＣ、ＰＣとＶＣ、ＶＣとＦＥＣ、ＥＣとＦＥＣ、ＰＣとＦＥＣ、ＦＥＣとＤＦＥＣ、ＥＣとＤＦＥＣ、ＰＣとＤＦＥＣ、ＶＣとＤＦＥＣ、ＶＥＣとＤＦＥＣ、ＶＣとＥＥＣ、ＥＣとＥＥＣ、ＥＣとＰＣとＶＣ、ＥＣとＰＣとＦＥＣ、ＥＣとＶＣとＦＥＣ、ＥＣとＶＣとＶＥＣ、ＥＣとＶＣとＥＥＣ、ＥＣとＥＥＣとＦＥＣ、ＰＣとＶＣとＦＥＣ、ＥＣとＶＣとＤＦＥＣ、ＰＣとＶＣとＤＦＥＣ、ＥＣとＰＣとＶＣとＦＥＣまたはＥＣとＰＣとＶＣとＤＦＥＣ等が好ましい。前記の組合せのうち、ＥＣとＶＣ、ＥＣとＦＥＣ、ＰＣとＦＥＣ、ＥＣとＰＣとＶＣ、ＥＣとＰＣとＦＥＣ、ＥＣとＶＣとＦＥＣ、ＥＣとＶＣとＥＥＣ、ＥＣとＥＥＣとＦＥＣ、ＰＣとＶＣとＦＥＣまたはＥＣとＰＣとＶＣとＦＥＣ等の組合せがより好ましい。 These solvents may be used alone, or if two or more are used in combination, the effect of improving electrochemical properties over a wide temperature range is further improved, so it is preferable to use a combination of three or more. It is particularly preferable to do so. Preferred combinations of these cyclic carbonates include EC and PC, EC and VC, PC and VC, VC and FEC, EC and FEC, PC and FEC, FEC and DFEC, EC and DFEC, PC and DFEC, and VC and DFEC. , VEC and DFEC, VC and EEC, EC and EEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and VEC, EC and VC and EEC, EC and EEC and FEC, PC and VC and FEC, EC and VC and DFEC, PC and VC and DFEC, EC and PC and VC and FEC, or EC and PC and VC and DFEC, etc. are preferable. Among the above combinations, EC and VC, EC and FEC, PC and FEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and EEC, EC and EEC and FEC, and PC and A combination of VC and FEC, EC, PC, VC and FEC, etc. is more preferable.
鎖状エステルとしては、メチルエチルカーボネート（ＭＥＣ）、メチルプロピルカーボネート（ＭＰＣ）、メチルイソプロピルカーボネート（ＭＩＰＣ）、メチルブチルカーボネートおよびエチルプロピルカーボネートから選ばれる１種または２種以上の非対称鎖状カーボネート、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、ジプロピルカーボネートおよびジブチルカーボネートから選ばれる１種または２種以上の対称鎖状カーボネート、ピバリン酸メチル、ピバリン酸エチル、ピバリン酸プロピル等のピバリン酸エステル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピル、酢酸メチルおよび酢酸エチルから選ばれる１種または２種以上の鎖状カルボン酸エステルが好適に挙げられる。 As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate and ethyl propyl carbonate, dimethyl One or more symmetrical chain carbonates selected from carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate and dibutyl carbonate, pivalate esters such as methyl pivalate, ethyl pivalate, propyl pivalate, propion Preferred examples include one or more chain carboxylic acid esters selected from methyl acid, ethyl propionate, propyl propionate, methyl acetate, and ethyl acetate.
前記鎖状エステルの中でも、ジメチルカーボネート、メチルエチルカーボネート、メチルプロピルカーボネート、メチルイソプロピルカーボネート、メチルブチルカーボネート、プロピオン酸メチル、酢酸メチルおよび酢酸エチルから選ばれるメチル基を有する鎖状エステルが好ましく、特にメチル基を有する鎖状カーボネートが好ましい。 Among the chain esters, chain esters having a methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate, and ethyl acetate are preferable, and particularly methyl A linear carbonate having a group is preferred.
また、鎖状カーボネートを用いる場合には、２種以上を用いることが好ましい。さらに対称鎖状カーボネートと非対称鎖状カーボネートの両方が含まれるとより好ましく、対称鎖状カーボネートの含有量が非対称鎖状カーボネートより多く含まれると更に好ましい。 Moreover, when using chain carbonates, it is preferable to use two or more types. Furthermore, it is more preferable that both a symmetrical linear carbonate and an asymmetrical linear carbonate are included, and it is even more preferable that the content of a symmetrical linear carbonate is greater than that of an asymmetrical linear carbonate.
本発明の非水電解液に用いる非水溶媒における鎖状エステルの含有量は、特に制限されないが、非水電解液全量に対して、５～９０質量％の範囲で用いるのが好ましい。該含有量が５質量％以上であれば非水電解液の粘度が高くなりすぎず、より好ましくは１０質量％以上であり、さらに好ましくは３０質量％以上であり、特に好ましくは５０質量％以上である。また、９０質量％以下であれば非水電解液の電気伝導度が低下するおそれが少ないので、上記範囲であることが好ましい。 The content of the chain ester in the nonaqueous solvent used in the nonaqueous electrolyte of the present invention is not particularly limited, but is preferably in the range of 5 to 90% by mass relative to the total amount of the nonaqueous electrolyte. If the content is 5% by mass or more, the viscosity of the nonaqueous electrolyte does not become too high, and it is more preferably 10% by mass or more, even more preferably 30% by mass or more, and particularly preferably 50% by mass or more. Also, if it is 90% by mass or less, there is little risk of the electrical conductivity of the nonaqueous electrolyte decreasing, so the above range is preferable.
〔電解質塩〕
本発明に使用される電解質塩としては、下記のリチウム塩が好適に挙げられる。
リチウム塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４等の無機リチウム塩、ＬｉＮ（ＳＯ２Ｆ）２〔ＬｉＦＳＩ〕、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２、ＬｉＣＦ３ＳＯ３、ＬｉＣ（ＳＯ２ＣＦ３）３、ＬｉＰＦ４（ＣＦ３）２、ＬｉＰＦ３（Ｃ２Ｆ５）３、ＬｉＰＦ３（ＣＦ３）３、ＬｉＰＦ３（ｉｓｏ－Ｃ３Ｆ７）３、ＬｉＰＦ５（ｉｓｏ－Ｃ３Ｆ７）等の鎖状のフッ化アルキル基を含有するリチウム塩や、（ＣＦ２）２（ＳＯ２）２ＮＬｉ、（ＣＦ２）３（ＳＯ２）２ＮＬｉ等の環状のフッ化アルキレン鎖を有するリチウム塩等が好適に挙げられ、これらの中から選ばれる少なくとも１種のリチウム塩を含むことが好ましく、これらの１種または２種以上を混合して使用することができる。
これらの中でも、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２およびＬｉＮ（ＳＯ２Ｆ）２〔ＬｉＦＳＩ〕から選ばれる１種または２種以上を含むことがより好ましく、ＬｉＰＦ６を含むことがもっとも好ましい。
電解質塩のそれぞれの濃度は、前記の非水電解液全量に対して、４質量％以上であることが好ましく、９質量％以上がより好ましく、１３質量％以上が更に好ましく、また、２８質量％以下であることが好ましく、２３質量％以下がより好ましく、２０質量％以下が更に好ましい。
[Electrolyte salt]
As the electrolyte salt used in the present invention, the following lithium salts are preferably mentioned.
Examples of lithium salts include inorganic lithium salts such as LiPF 6 , LiBF 4 , and LiClO 4 , LiN(SO 2 F) 2 [LiFSI], LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiCF 3 SO 3 , LiC(SO 2 CF 3 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (CF 3 ) 3 , LiPF 3 (iso-C 3 F 7 ) 3 , LiPF 5 (iso-C 3 F 7 ) and other lithium salts containing a chain fluorinated alkyl group, (CF 2 ) 2 (SO 2 ) 2 NLi, (CF 2 ) 3 (SO 2 ) 2 Preferred examples include lithium salts having a cyclic fluorinated alkylene chain such as NLi, and it is preferable to include at least one lithium salt selected from these, and one or more of these may be mixed. can be used.
Among these, one or more selected from LiPF 6 , LiBF 4 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 and LiN(SO 2 F) 2 [LiFSI] More preferably, LiPF 6 is included, and most preferably LiPF 6 is included.
The concentration of each electrolyte salt is preferably 4% by mass or more, more preferably 9% by mass or more, even more preferably 13% by mass or more, and 28% by mass, based on the total amount of the non-aqueous electrolyte. It is preferably at most 23% by mass, more preferably at most 20% by mass.
〔非水電解液の製造〕
本発明の非水電解液は、例えば、前記の非水溶媒を混合し、これに前記の電解質塩および該非水電解液に対して前記一般式（Ｉ）および前記一般式（ＩＩ）で表される化合物から選ばれる１種以上と一般式（ＩＩＩ）で表される化合物とを添加することにより得ることができる。
この際、用いる非水溶媒および非水電解液に加える化合物は、生産性を著しく低下させない範囲内で、予め精製して、不純物が極力少ないものを用いることが好ましい。
[Manufacture of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention can be prepared, for example, by mixing the above-mentioned non-aqueous solvent, with which the above-mentioned electrolyte salt and the non-aqueous electrolyte are expressed by the above-mentioned general formula (I) and the above-mentioned general formula (II). It can be obtained by adding one or more selected from compounds represented by formula (III) and a compound represented by general formula (III).
At this time, it is preferable that the non-aqueous solvent used and the compound added to the non-aqueous electrolyte be purified in advance and contain as few impurities as possible within a range that does not significantly reduce productivity.
本発明の非水電解液は、下記の第１～第４の蓄電デバイスに使用することができ、非水電解質として、液体状のものだけでなくゲル化されているものも使用し得る。更に本発明の非水電解液は固体高分子電解質用としても使用できる。中でも電解質塩にリチウム塩を使用する第１の蓄電デバイス用（即ち、リチウム電池用）または第４の蓄電デバイス用（即ち、リチウムイオンキャパシタ用）として用いることが好ましく、リチウム電池用として用いることが更に好ましく、リチウム二次電池用として用いることが最も適している。 The non-aqueous electrolyte of the present invention can be used in the following first to fourth electricity storage devices, and as the non-aqueous electrolyte, not only liquid ones but also gelled ones can be used. Furthermore, the non-aqueous electrolyte of the present invention can also be used as a solid polymer electrolyte. Among them, it is preferable to use it for the first electricity storage device (i.e., for lithium batteries) or the fourth electricity storage device (i.e., for lithium ion capacitors) that uses lithium salt as the electrolyte salt, and it is preferable to use it for lithium batteries. More preferably, it is most suitable for use in lithium secondary batteries.
〔第１の蓄電デバイス（リチウム電池）〕
本発明の第１の蓄電デバイスであるリチウム二次電池は、正極、負極および非水溶媒に電解質塩が溶解されている前記非水電解液からなる。非水電解液以外の正極、負極等の構成部材は特に制限なく使用できる。
例えば、リチウム二次電池用正極活物質としては、コバルト、マンガンおよびニッケルからなる群より選ばれる１種または２種以上を含有するリチウムとの複合金属酸化物が使用される。これらの正極活物質は、１種単独で用いるかまたは２種以上を組合せて用いることができる。
このようなリチウム複合金属酸化物としては、例えば、ＬｉＣｏＯ２、ＬｉＣｏ１－ｘＭｘＯ２（但し、ＭはＳｎ、Ｍｇ、Ｆｅ、Ｔｉ、Ａｌ、Ｚｒ、Ｃｒ、Ｖ、Ｇａ、ＺｎおよびＣｕから選ばれる１種または２種以上の元素、０．００１≦ｘ≦０．０５）、ＬｉＭｎ２Ｏ４、ＬｉＮｉＯ２、ＬｉＣｏ１－ｘＮｉｘＯ２（０．０１＜ｘ＜１）、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．５Ｍｎ０．３Ｃｏ０．２Ｏ２、ＬｉＮｉ０．８Ｍｎ０．１Ｃｏ０．１Ｏ２、ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２、Ｌｉ２ＭｎＯ３とＬｉＭＯ２（Ｍは、Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅ等の遷移金属）との固溶体およびＬｉＮｉ１／２Ｍｎ３／２Ｏ４から選ばれる１種以上が好適に挙げられ、２種以上がより好適である。また、ＬｉＣｏＯ２とＬｉＭｎ２Ｏ４、ＬｉＣｏＯ２とＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４とＬｉＮｉＯ２のように併用してもよい。
[First electricity storage device (lithium battery)]
The lithium secondary battery, which is the first electricity storage device of the present invention, is composed of a positive electrode, a negative electrode, and the non-aqueous electrolyte in which an electrolyte salt is dissolved in the non-aqueous solvent. Components other than the non-aqueous electrolyte, such as a positive electrode and a negative electrode, can be used without particular restriction.
For example, as a positive electrode active material for a lithium secondary battery, a composite metal oxide containing lithium and one or more selected from the group consisting of cobalt, manganese, and nickel is used. These positive electrode active materials can be used alone or in combination of two or more.
Such lithium composite metal oxides include, for example, LiCoO 2 , LiCo 1-x M x O 2 (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and Cu). One or more elements selected from 0.001≦x≦0.05), LiMn 2 O 4 , LiNiO 2 , LiCo 1-x Ni x O 2 (0.01<x<1), LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 , LiNi 0.8 Co 0 .15 A solid solution of Al 0.05 O 2 , Li 2 MnO 3 and LiMO 2 (M is a transition metal such as Co, Ni, Mn, Fe, etc.) and 1 selected from LiNi 1/2 Mn 3/2 O 4 Preferably, more than one type is used, and two or more types are more preferably used. Furthermore, they may be used in combination, such as LiCoO 2 and LiMn 2 O 4 , LiCoO 2 and LiNiO 2 , and LiMn 2 O 4 and LiNiO 2 .
高充電電圧で動作するリチウム複合金属酸化物を使用すると、充電時における電解液との反応によりサイクル特性が低下しやすいが、本発明に係るリチウム二次電池ではこれらの電気化学特性の低下を抑制することができる。
特にＮｉを含む正極活物質の場合にＮｉの触媒作用により正極表面での非水溶媒の分解が起き、電池の抵抗が増加しやすい傾向にある。特に高温環境下での電気化学特性が低下しやすい傾向にあるが、本発明に係るリチウム二次電池ではこれらの電気化学特性の低下を抑制することができるので好ましい。特に、正極活物質中の全遷移金属元素の原子濃度に対するＮｉの原子濃度の割合が、３０ａｔｏｍｉｃ％を超える正極活物質を用いた場合に上記効果が顕著になるので好ましく、５０ａｔｏｍｉｃ％以上が更に好ましく、７５％以上が特に好ましい。具体的には、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．５Ｍｎ０．３Ｃｏ０．２Ｏ２、ＬｉＮｉ０．８Ｍｎ０．１Ｃｏ０．１Ｏ２、ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２等が好適に挙げられる。
When a lithium composite metal oxide that operates at a high charging voltage is used, the cycle characteristics tend to deteriorate due to reaction with the electrolyte during charging, but the lithium secondary battery according to the present invention suppresses the deterioration of these electrochemical characteristics. can do.
In particular, in the case of a positive electrode active material containing Ni, the catalytic action of Ni causes decomposition of the nonaqueous solvent on the surface of the positive electrode, which tends to increase the resistance of the battery. Although electrochemical properties tend to deteriorate particularly in high-temperature environments, the lithium secondary battery according to the present invention is preferable because it can suppress the decline in these electrochemical properties. In particular, it is preferable to use a positive electrode active material in which the ratio of the atomic concentration of Ni to the atomic concentration of all transition metal elements in the positive electrode active material exceeds 30 atomic% because the above effect becomes remarkable, and the ratio of Ni to the atomic concentration of all transition metal elements in the positive electrode active material is more preferably 50 atomic% or more. , 75% or more is particularly preferred. Specifically, LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 , Preferred examples include LiNi 0.8 Co 0.15 Al 0.05 O 2 and the like.
更に、正極活物質として、リチウム含有オリビン型リン酸塩を用いることもできる。特に鉄、コバルト、ニッケルおよびマンガンから選ばれる少なくとも１種以上含むリチウム含有オリビン型リン酸塩が好ましい。その具体例としては、ＬｉＦｅＰＯ４、ＬｉＣｏＰＯ４、ＬｉＮｉＰＯ４、ＬｉＭｎＰＯ４等が挙げられる。
これらのリチウム含有オリビン型リン酸塩の一部は他元素で置換してもよく、鉄、コバルト、ニッケル、マンガンの一部をＣｏ、Ｍｎ、Ｎｉ、Ｍｇ、Ａｌ、Ｂ、Ｔｉ、Ｖ、Ｎｂ、Ｃｕ、Ｚｎ、Ｍｏ、Ｃａ、Ｓｒ、ＷおよびＺｒ等から選ばれる１種以上の元素で置換する、またはこれらの他元素を含有する化合物や炭素材料で被覆することもできる。これらの中では、ＬｉＦｅＰＯ４またはＬｉＭｎＰＯ４が好ましい。
また、リチウム含有オリビン型リン酸塩は、例えば前記の正極活物質と混合して用いることもできる。
Furthermore, a lithium-containing olivine-type phosphate can also be used as the positive electrode active material. Particularly preferred is a lithium-containing olivine-type phosphate containing at least one selected from iron, cobalt, nickel, and manganese. Specific examples include LiFePO 4 , LiCoPO 4 , LiNiPO 4 , LiMnPO 4 and the like.
A part of these lithium-containing olivine-type phosphates may be substituted with other elements, and a part of iron, cobalt, nickel, and manganese may be replaced with Co, Mn, Ni, Mg, Al, B, Ti, V, and Nb. , Cu, Zn, Mo, Ca, Sr, W, Zr, etc., or may be coated with a compound or carbon material containing these other elements. Among these, LiFePO4 or LiMnPO4 are preferred.
Moreover, the lithium-containing olivine-type phosphate can also be used, for example, in mixture with the above-mentioned positive electrode active material.
また、リチウム一次電池用正極としては、ＣｕＯ、Ｃｕ２Ｏ、Ａｇ２Ｏ、Ａｇ２ＣｒＯ４、ＣｕＳ、ＣｕＳＯ４、ＴｉＯ２、ＴｉＳ２、ＳｉＯ２、ＳｎＯ、Ｖ２Ｏ５、Ｖ６Ｏ１２、ＶＯｘ、Ｎｂ２Ｏ５、Ｂｉ２Ｏ３、Ｂｉ２Ｐｂ２Ｏ５，Ｓｂ２Ｏ３、ＣｒＯ３、Ｃｒ２Ｏ３、ＭｏＯ３、ＷＯ３、ＳｅＯ２、ＭｎＯ２、Ｍｎ２Ｏ３、Ｆｅ２Ｏ３、ＦｅＯ、Ｆｅ３Ｏ４、Ｎｉ２Ｏ３、ＮｉＯ、ＣｏＯ３、ＣｏＯなどの、１種もしくは２種以上の金属元素の酸化物あるいはカルコゲン化合物、ＳＯ２、ＳＯＣｌ２などの硫黄化合物、一般式（ＣＦｘ）ｎで表されるフッ化炭素（フッ化黒鉛）などが挙げられる。中でも、ＭｎＯ２、Ｖ２Ｏ５、フッ化黒鉛などが好ましい。 In addition, as positive electrodes for lithium primary batteries, CuO, Cu 2 O, Ag 2 O, Ag 2 CrO 4 , CuS, CuSO 4 , TiO 2 , TiS 2 , SiO 2 , SnO, V 2 O 5 , V 6 O 12 , VOx , Nb2O5 , Bi2O3 , Bi2Pb2O5 , Sb2O3 , CrO3 , Cr2O3 , MoO3 , WO3 , SeO2 , MnO2 , Mn2O3 , Fe 2 O 3 , FeO, Fe 3 O 4 , Ni 2 O 3 , NiO, CoO 3 , CoO, etc., oxides or chalcogen compounds of one or more metal elements, SO 2 , SOCl 2 , etc. Examples include sulfur compounds, fluorinated carbon (fluorinated graphite) represented by the general formula (CF x ) n , and the like. Among these, MnO 2 , V 2 O 5 , fluorinated graphite, and the like are preferred.
正極の導電剤は、化学変化を起こさない電子伝導材料であれば特に制限はない。例えば、天然黒鉛（鱗片状黒鉛等）、人造黒鉛等のグラファイト、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラック等のカーボンブラック等が挙げられる。また、グラファイトとカーボンブラックを適宜混合して用いてもよい。導電剤の正極合剤への添加量は、１～１０質量％が好ましく、特に２～５質量％が好ましい。 The conductive agent for the positive electrode is not particularly limited as long as it is an electron conductive material that does not undergo chemical changes. Examples include graphite such as natural graphite (scaly graphite, etc.), artificial graphite, and carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black. Further, graphite and carbon black may be mixed and used as appropriate. The amount of the conductive agent added to the positive electrode mixture is preferably 1 to 10% by mass, particularly preferably 2 to 5% by mass.
正極は、前記の正極活物質をアセチレンブラック、カーボンブラック等の導電剤、およびポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、スチレンとブタジエンの共重合体（ＳＢＲ）、アクリロニトリルとブタジエンの共重合体（ＮＢＲ）、カルボキシメチルセルロース（ＣＭＣ）、エチレンプロピレンジエンターポリマー等の結着剤と混合し、これに１－メチル－２－ピロリドン等の高沸点溶剤を加えて混練して正極合剤とした後、この正極合剤を集電体のアルミニウム箔やステンレス製のラス板等に塗布して、乾燥、加圧成型した後、５０℃～２５０℃程度の温度で、２時間程度真空下で加熱処理することにより作製することができる。
正極の集電体を除く部分の密度は、通常は１．５ｇ／ｃｍ３以上であり、電池の容量をさらに高めるため、好ましくは２ｇ／ｃｍ３以上であり、より好ましくは、３ｇ／ｃｍ３以上であり、更に好ましくは、３．６ｇ／ｃｍ３以上である。また、４ｇ／ｃｍ３以下が好ましい。
The positive electrode is prepared by mixing the positive electrode active material with a conductive agent such as acetylene black or carbon black, and a binder such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), a copolymer of acrylonitrile and butadiene (NBR), carboxymethyl cellulose (CMC), or an ethylene propylene diene terpolymer, adding a high boiling point solvent such as 1-methyl-2-pyrrolidone to the mixture and kneading it to form a positive electrode mixture, applying the positive electrode mixture to a collector of aluminum foil or a stainless steel lath plate, drying, pressurizing, and then heat-treating the mixture at a temperature of about 50° C. to 250° C. for about 2 hours under vacuum.
The density of the positive electrode excluding the current collector is usually 1.5 g/cm3 or more, and in order to further increase the capacity of the battery, it is preferably 2 g/ cm3 or more, more preferably 3 g/ cm3 or more, and even more preferably 3.6 g/ cm3 or more. Also, it is preferably 4 g/ cm3 or less.
リチウム二次電池用負極活物質としては、リチウム金属やリチウム合金、およびリチウムを吸蔵および放出することが可能な炭素材料〔易黒鉛化炭素や、（００２）面の面間隔が０．３７ｎｍ（ナノメータ）以上の難黒鉛化炭素や、（００２）面の面間隔が０．３４ｎｍ以下の黒鉛など〕、スズ（単体）、スズ化合物、ケイ素（単体）、ケイ素化合物、Ｌｉ４Ｔｉ５Ｏ１２などのチタン酸リチウム化合物等を１種単独または２種以上を組合せて用いることができる。
これらの中では、リチウムイオンの吸蔵および放出能力において、人造黒鉛や天然黒鉛等の高結晶性の炭素材料を使用することが更に好ましく、格子面（００２）の面間隔（ｄ００２）が０．３４０ｎｍ以下、特に０．３３５～０．３３７ｎｍである黒鉛型結晶構造を有する炭素材料を使用することが特に好ましい。
複数の扁平状の黒鉛質微粒子が互いに非平行に集合或いは結合した塊状構造を有する人造黒鉛粒子や、例えば鱗片状天然黒鉛粒子に圧縮力、摩擦力、剪断力等の機械的作用を繰り返し与え、球形化処理を施した黒鉛粒子を用いることにより、負極の集電体を除く部分の密度を１．５ｇ／ｃｍ３以上の密度に加圧成形したときの負極シートのＸ線回折測定から得られる黒鉛結晶の（１１０）面のピーク強度Ｉ（１１０）と（００４）面のピーク強度Ｉ（００４）の比Ｉ（１１０）／Ｉ（００４）が０．０１以上となると一段と正極活物質からの金属溶出量の改善と、充電保存特性が向上するので好ましく、０．０５以上となることがより好ましく、０．１以上となることが更に好ましい。また、過度に処理し過ぎて結晶性が低下し電池の放電容量が低下する場合があるので、０．５以下が好ましく、０．３以下がより好ましい。
また、高結晶性の炭素材料（コア材）はコア材よりも低結晶性の炭素材料によって被膜されていると、サイクル特性が一段と良好となるので好ましい。被覆の炭素材料の結晶性は、ＴＥＭにより確認することができる。
高結晶性の炭素材料を使用すると、充電時において非水電解液と反応し、界面抵抗の増加によってサイクル特性を低下させる傾向があるが、本発明に係るリチウム二次電池ではサイクル特性が良好となる。
Negative electrode active materials for lithium secondary batteries include lithium metal, lithium alloys, and carbon materials capable of intercalating and deintercalating lithium [e.g., easily graphitizable carbon, and (002) plane spacing of 0.37 nm (nanometer). ) or more non-graphitizable carbon, graphite with a (002) plane spacing of 0.34 nm or less], tin (single substance), tin compounds, silicon (single substance), silicon compounds, Li 4 Ti 5 O 12 , etc. Lithium titanate compounds and the like can be used alone or in combination of two or more.
Among these, it is more preferable to use highly crystalline carbon materials such as artificial graphite and natural graphite in terms of lithium ion absorption and desorption ability, and the interplanar spacing (d 002 ) of the lattice plane (002) is 0. It is particularly preferred to use a carbon material with a graphite-type crystal structure of 340 nm or less, in particular 0.335 to 0.337 nm.
Repeatedly applying mechanical effects such as compressive force, frictional force, and shearing force to artificial graphite particles having a block structure in which a plurality of flat graphite fine particles are aggregated or combined nonparallelly to each other, or for example, to scaly natural graphite particles, Obtained from X-ray diffraction measurements of the negative electrode sheet when the negative electrode sheet is pressure-molded to a density of 1.5 g/cm3 or higher by using graphite particles subjected to spheroidization treatment, excluding the current collector. When the ratio I(110)/I(004) of the peak intensity I(110) of the (110) plane of the graphite crystal to the peak intensity I(004) of the (004) plane becomes 0.01 or more, the amount of light from the positive electrode active material increases. It is preferable because it improves the amount of metal eluted and the charge storage characteristics, more preferably 0.05 or more, and even more preferably 0.1 or more. Moreover, since excessive treatment may reduce crystallinity and reduce the discharge capacity of the battery, the ratio is preferably 0.5 or less, and more preferably 0.3 or less.
Further, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material that is lower in crystallinity than the core material because the cycle characteristics will be even better. The crystallinity of the coating carbon material can be confirmed by TEM.
When a highly crystalline carbon material is used, it tends to react with the non-aqueous electrolyte during charging and reduce cycle characteristics due to an increase in interfacial resistance. However, the lithium secondary battery according to the present invention has good cycle characteristics. Become.
また、負極活物質としてのリチウムを吸蔵および放出可能な金属化合物としては、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｐ、Ｓｂ、Ｂｉ、Ａｌ、Ｇａ、Ｉｎ、Ｔｉ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｇ、Ｍｇ、Ｓｒ、Ｂａ等の金属元素を少なくとも１種含有する化合物が挙げられる。これらの金属化合物は単体、合金、酸化物、窒化物、硫化物、硼化物、リチウムとの合金等、何れの形態で用いてもよいが、単体、合金、酸化物、リチウムとの合金の何れかが高容量化できるので好ましい。中でも、Ｓｉ、ＧｅおよびＳｎから選ばれる少なくとも１種の元素を含有するものが好ましく、ＳｉおよびＳｎから選ばれる少なくとも１種の元素を含むものが電池を高容量化できるので特に好ましい。 Metal compounds capable of intercalating and deintercalating lithium as negative electrode active materials include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, and Cu. Examples include compounds containing at least one metal element such as , Zn, Ag, Mg, Sr, and Ba. These metal compounds may be used in any form such as a simple substance, an alloy, an oxide, a nitride, a sulfide, a boride, an alloy with lithium, etc.; This is preferable because it can increase the capacity. Among these, those containing at least one element selected from Si, Ge, and Sn are preferable, and those containing at least one element selected from Si and Sn are particularly preferable because they can increase the capacity of the battery.
負極は、上記の正極の作製と同様な導電剤、結着剤、高沸点溶剤を用いて混練して負極合剤とした後、この負極合剤を集電体の銅箔等に塗布して、乾燥、加圧成型した後、５０℃～２５０℃程度の温度で２時間程度真空下加熱処理することにより作製することができる。
負極の集電体を除く部分の密度は、通常は１．１ｇ／ｃｍ３以上であり、電池の容量をさらに高めるため、好ましくは１．５ｇ／ｃｍ３以上であり、特に好ましくは１．７ｇ／ｃｍ３以上である。また、２ｇ／ｃｍ３以下が好ましい。
The negative electrode can be produced by kneading a conductive agent, a binder, and a high boiling point solvent in the same manner as in the production of the positive electrode described above to form a negative electrode mixture, applying this negative electrode mixture to a copper foil or the like current collector, drying, pressurizing and molding, and then heat treating the mixture in a vacuum at a temperature of about 50° C. to 250° C. for about 2 hours.
The density of the negative electrode excluding the current collector is usually 1.1 g/cm3 or more, and in order to further increase the capacity of the battery, it is preferably 1.5 g/ cm3 or more, particularly preferably 1.7 g/cm3 or more. Also, it is preferably 2 g/ cm3 or less.
また、リチウム一次電池用の負極活物質としては、リチウム金属またはリチウム合金が挙げられる。 Furthermore, examples of the negative electrode active material for lithium primary batteries include lithium metal or lithium alloy.
リチウム電池の構造には特に限定はなく、単層または複層のセパレータを有するコイン型電池、円筒型電池、角型電池、ラミネート電池等を適用できる。
電池用セパレータとしては、特に制限はされないが、ポリプロピレン、ポリエチレン等のポリオレフィンの単層または積層の微多孔性フィルム、織布、不織布等を使用できる。
There is no particular limitation on the structure of the lithium battery, and a coin-type battery having a single-layer or multi-layer separator, a cylindrical battery, a square battery, a laminate battery, etc. can be used.
The battery separator is not particularly limited, but may be a single-layer or multi-layer microporous film, woven fabric, nonwoven fabric, or the like, made of polyolefin such as polypropylene or polyethylene.
本発明におけるリチウム二次電池は、充電終止電圧が４．２Ｖ以上、特に４．３Ｖ以上の場合にもサイクル特性に優れ、更に、４．４Ｖ以上においても特性は良好である。放電終止電圧は、通常２．８Ｖ以上、更には２．５Ｖ以上とすることができるが、本願発明におけるリチウム二次電池は、２．０Ｖ以上とすることができる。電流値については特に限定されないが、通常０．１～３０Ｃの範囲で使用される。また、本発明におけるリチウム電池は、－４０～１００℃、好ましくは－１０～８０℃で充放電することができる。 The lithium secondary battery according to the present invention has excellent cycle characteristics even when the end-of-charge voltage is 4.2 V or higher, particularly 4.3 V or higher, and also has good characteristics even when the charge end voltage is 4.4 V or higher. The end-of-discharge voltage can normally be 2.8V or more, and even 2.5V or more, but the lithium secondary battery according to the present invention can have a discharge end voltage of 2.0V or more. The current value is not particularly limited, but is usually used in the range of 0.1 to 30C. Furthermore, the lithium battery of the present invention can be charged and discharged at -40 to 100°C, preferably -10 to 80°C.
本発明においては、リチウム電池の内圧上昇の対策として、電池蓋に安全弁を設けたり、電池缶やガスケット等の部材に切り込みを入れる方法も採用することができる。また、過充電防止の安全対策として、電池の内圧を感知して電流を遮断する電流遮断機構を電池蓋に設けることができる。 In the present invention, as a measure against an increase in the internal pressure of a lithium battery, it is also possible to provide a safety valve on the battery lid or to make a cut in a member such as a battery can or gasket. Further, as a safety measure to prevent overcharging, a current cutoff mechanism that senses the internal pressure of the battery and cuts off the current can be provided on the battery cover.
〔第２の蓄電デバイス（電気二重層キャパシタ）〕
第２の蓄電デバイスは、電解液と電極界面の電気二重層容量を利用してエネルギーを貯蔵する蓄電デバイスである。本発明の一例は、電気二重層キャパシタである。この蓄電デバイスに用いられる最も典型的な電極活物質は、活性炭である。二重層容量は概ね表面積に比例して増加する。
[Second Electricity Storage Device (Electric Double Layer Capacitor)]
The second electricity storage device is an electricity storage device that stores energy by utilizing the electric double layer capacity of the electrolyte and the electrode interface. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used in this electricity storage device is activated carbon. The double layer capacity increases roughly in proportion to the surface area.
〔第３の蓄電デバイス〕
第３の蓄電デバイスは、電極のドープ／脱ドープ反応を利用してエネルギーを貯蔵する蓄電デバイスである。この蓄電デバイスに用いられる電極活物質として、酸化ルテニウム、酸化イリジウム、酸化タングステン、酸化モリブデン、酸化銅等の金属酸化物や、ポリアセン、ポリチオフェン誘導体等のπ共役高分子が挙げられる。これらの電極活物質を用いたキャパシタは、電極のドープ／脱ドープ反応にともなうエネルギー貯蔵が可能である。
[Third electricity storage device]
The third electricity storage device is an electricity storage device that stores energy by utilizing doping/dedoping reactions of electrodes. Examples of electrode active materials used in this electricity storage device include metal oxides such as ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide, and copper oxide, and π-conjugated polymers such as polyacene and polythiophene derivatives. Capacitors using these electrode active materials are capable of storing energy associated with doping/undoping reactions of the electrodes.
〔第４の蓄電デバイス（リチウムイオンキャパシタ）〕
第４の蓄電デバイスは、負極であるグラファイト等の炭素材料へのリチウムイオンのインターカレーションを利用してエネルギーを貯蔵する蓄電デバイスである。リチウムイオンキャパシタ（ＬＩＣ）と呼ばれる。正極は、例えば活性炭電極と電解液との間の電気ニ重層を利用したものや、π共役高分子電極のドープ／脱ドープ反応を利用したもの等が挙げられる。電解液には少なくともＬｉＰＦ６などのリチウム塩が含まれる。
[Fourth Power Storage Device (Lithium Ion Capacitor)]
The fourth type of power storage device is a power storage device that stores energy by utilizing the intercalation of lithium ions into a carbon material such as graphite, which is the negative electrode. It is called a lithium ion capacitor (LIC). The positive electrode may be, for example, one that utilizes an electric double layer between an activated carbon electrode and an electrolyte, or one that utilizes a doping/dedoping reaction of a π-conjugated polymer electrode. The electrolyte contains at least a lithium salt such as LiPF6 .
以下、本発明の化合物を用いた電解液の実施例を示すが、本発明は、これらの実施例に限定されるものではない。 Examples of electrolytes using the compounds of the present invention will be shown below, but the present invention is not limited to these Examples.
実施例１～４、参考例１、比較例１～２
〔非水電解液の調製〕
表１に記載の溶媒および電解質塩を一定量で混合し、調製した基準電解液に対して、表１に記載の一般式（Ｉ）の環状硫酸エステル、一般式（ＩＩ）の環状スルホン化合物および一般式（ＩＩＩ）の有機シラン化合物をそれぞれ加えて、非水電解液を調製した。
Examples 1 to 4, Reference Example 1, Comparative Examples 1 to 2
[Preparation of non-aqueous electrolyte]
The cyclic sulfate ester of general formula (I), the cyclic sulfone compound of general formula (II) and An organic silane compound of general formula (III) was added to prepare a non-aqueous electrolyte.
〔非水電解液の化学的安定性評価〕
＜高温保存試験＞
上記の方法で作製した非水電解液を用いて４０℃の恒温槽中、２８日間保存を行った。保存後、これらの電解液を２５℃に冷却した後、電解液の化学的安定性を測定するため、以下の評価を行った。
[Chemical stability evaluation of non-aqueous electrolyte]
<High temperature storage test>
The non-aqueous electrolyte prepared by the above method was stored in a constant temperature bath at 40° C. for 28 days. After storage, these electrolytic solutions were cooled to 25° C., and then the following evaluation was performed to measure the chemical stability of the electrolytic solutions.
＜高温保存後における着色度合の測定＞
電解液の着色度合であるＡＰＨＡ（ハーゼン色数）を測定した（日本電色工業製測色色差計ＺＥ６０００）。
<Measurement of degree of coloring after high temperature storage>
APHA (Hazen color number), which is the degree of coloring of the electrolytic solution, was measured (Nippon Denshoku Kogyo's colorimeter ZE6000).
＜高温保存後における電解液中の環状硫酸エステル残存量の測定＞
電解液中の環状硫酸エステルや環状スルホン化合物の残存量は、１Ｈ－ＮＭＲの内標定量法により算出した（４００ＭＨｚ；重溶媒なし、内標：（トリフルオロメトキシ）ベンゼン、日本電子製ＪＮＭ－ＥＣＺ４００Ｒ）。
電解液の化学的安定性評価結果を表１に示す。
<Measurement of residual amount of cyclic sulfate ester in electrolyte after high temperature storage>
The residual amounts of cyclic sulfuric esters and cyclic sulfone compounds in the electrolyte were calculated by 1 H-NMR internal standard determination method (400 MHz; no heavy solvent, internal standard: (trifluoromethoxy)benzene, JEOL JNM- ECZ400R).
Table 1 shows the chemical stability evaluation results of the electrolyte.
なお、表１に示す実施例および比較例においては、非水電解液全体に対する表中記載の化合物の含有量が、表１に示す量となるように、非水電解液を調製した。 In the Examples and Comparative Examples shown in Table 1, the non-aqueous electrolyte was prepared such that the content of the compounds listed in the table relative to the entire non-aqueous electrolyte was as shown in Table 1.
上記表１において、環状硫酸エステルのみを添加した比較例１や環状スルホン化合物のみを添加した比較例２では、高温保存後に電解液の着色に伴うＡＰＨＡ値の上昇および環状硫酸エステルや環状スルホン化合物の分解が確認された。一方で、本発明の一般式（ＩＩＩ）で表される有機シラン化合物を含む実施例１～実施例４では、ＡＰＨＡ値の上昇および環状硫酸エステルや環状スルホン化合物の分解の両方が抑制されている。また、有機シラン化合物の含有量としては、０.３質量％以下の場合、特に好ましい効果を発揮する。これらの結果から、本発明の非水電解液は、高温保存後の非水電解液の着色を抑制し、かつ高温保存による環状硫酸エステルや環状スルホン化合物の分解を抑制できる蓄電デバイス用非水電解液を提供することが出来る。 In Table 1 above, in Comparative Example 1 in which only cyclic sulfate ester was added and Comparative Example 2 in which only cyclic sulfone compound was added, the APHA value increased due to coloring of the electrolyte after high temperature storage, and the cyclic sulfate ester and cyclic sulfone compound increased. Decomposition was confirmed. On the other hand, in Examples 1 to 4 containing the organosilane compound represented by the general formula (III) of the present invention, both the increase in the APHA value and the decomposition of the cyclic sulfate ester and the cyclic sulfone compound are suppressed. . Moreover, particularly favorable effects are exhibited when the content of the organic silane compound is 0.3% by mass or less. From these results, the non-aqueous electrolyte of the present invention is a non-aqueous electrolyte for power storage devices that can suppress coloring of the non-aqueous electrolyte after high-temperature storage and suppress decomposition of cyclic sulfate esters and cyclic sulfone compounds due to high-temperature storage. liquid can be provided.
本発明の非水電解液を使用すれば、高温保存後の非水電解液の着色を抑制し、かつ高温保存による環状硫酸エステルや環状スルホン化合物の分解を抑制できる蓄電デバイス用非水電解液を提供することができ、広い温度範囲における電気化学特性に優れた蓄電デバイスを得ることができる。特にハイブリッド電気自動車、プラグインハイブリッド電気自動車、バッテリー電気自動車等に搭載されるリチウム二次電池等の蓄電デバイス用の非水電解液として使用すると、広い温度範囲で電気化学特性が低下しにくい蓄電デバイスを得ることができる。 By using the non-aqueous electrolyte of the present invention, a non-aqueous electrolyte for power storage devices that can suppress coloring of the non-aqueous electrolyte after high-temperature storage and suppress decomposition of cyclic sulfuric esters and cyclic sulfone compounds due to high-temperature storage can be obtained. Accordingly, it is possible to obtain a power storage device with excellent electrochemical properties over a wide temperature range. In particular, when used as a non-aqueous electrolyte for power storage devices such as lithium secondary batteries installed in hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., power storage devices whose electrochemical properties do not easily deteriorate over a wide temperature range. can be obtained.
Claims (3)
前記一般式（ＩＩＩ）で表される有機シラン化合物の含有量が０．３質量％以下である蓄電デバイス用非水電解液。
（式中、Ｒ１およびＲ２はそれぞれ独立に、水素原子または炭素数１～６のアルキル基を示し、Ｒ１とＲ２が互いに結合し環を形成してもよい。）
（式中、Ｘ1は少なくとも一つの水素原子がハロゲン原子で置換されていてもよい炭素数２～４のアルキレン基、少なくとも一つの水素原子がハロゲン原子で置換されていてもよい炭素数２～４のアルケニレン基、少なくとも一つの水素原子がハロゲン原子で置換されていてもよいアリーレン基またはビシクロ環である。）
（式中、Ｒ３およびＲ４はそれぞれ独立に、炭素数１～３のアルキル基を示し、Ｒ５およびＲ６はそれぞれ独立に、炭素数１～３のアルキル基または置換基を有していてもよいアリール基を示す。） In a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, one or more selected from a cyclic sulfate ester represented by general formula (I) and a cyclic sulfone compound represented by general formula (II), A non-aqueous electrolyte for a power storage device, characterized in that it contains an organic silane compound represented by general formula (III) ,
A non-aqueous electrolyte for a power storage device in which the content of an organic silane compound represented by the general formula (III) is 0.3% by mass or less .
(In the formula, R 1 and R 2 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1 and R 2 may be bonded to each other to form a ring.)
(In the formula, X 1 is an alkylene group having 2 to 4 carbon atoms, in which at least one hydrogen atom may be substituted with a halogen atom; 4, an arylene group or a bicyclo ring in which at least one hydrogen atom may be substituted with a halogen atom.)
(In the formula, R 3 and R 4 each independently represent an alkyl group having 1 to 3 carbon atoms, and R 5 and R 6 each independently have an alkyl group having 1 to 3 carbon atoms or a substituent. (Indicates an optional aryl group.)
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| WO2019073831A1 (en) | 2017-10-11 | 2019-04-18 | 株式会社Adeka | Method for preventing decomposition of silyl ester compound |
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| JP2003242991A (en) | 2002-02-04 | 2003-08-29 | Lithdyne Internatl Inc | Stabilized lithium electrochemical cell containing alkoxysilane |
| JP2010232117A (en) | 2009-03-30 | 2010-10-14 | Hitachi Vehicle Energy Ltd | Lithium secondary battery |
| JP2011124047A (en) | 2009-12-09 | 2011-06-23 | Sony Corp | Lithium ion secondary battery, anode for lithium ion secondary battery, power tool, electric vehicle, and power storage system |
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