JP2021036512A - Electrolytic solution for fluoride ion batteries, and fluoride ion battery - Google Patents
Electrolytic solution for fluoride ion batteries, and fluoride ion battery Download PDFInfo
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- 239000008151 electrolyte solution Substances 0.000 title claims abstract description 133
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 title claims abstract description 126
- -1 alkali metal cation Chemical class 0.000 claims abstract description 38
- 229910001515 alkali metal fluoride Inorganic materials 0.000 claims abstract description 32
- 239000003960 organic solvent Substances 0.000 claims abstract description 31
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 28
- 239000001257 hydrogen Substances 0.000 claims abstract description 28
- 150000002596 lactones Chemical class 0.000 claims abstract description 20
- 150000002148 esters Chemical class 0.000 claims abstract description 19
- 150000004673 fluoride salts Chemical class 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 11
- 239000000243 solution Substances 0.000 claims abstract description 9
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 5
- XJHCXCQVJFPJIK-UHFFFAOYSA-M caesium fluoride Chemical compound [F-].[Cs+] XJHCXCQVJFPJIK-UHFFFAOYSA-M 0.000 claims description 172
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 48
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 claims description 39
- 239000003792 electrolyte Substances 0.000 claims description 30
- 238000004519 manufacturing process Methods 0.000 claims description 25
- 229910003002 lithium salt Inorganic materials 0.000 claims description 24
- 159000000002 lithium salts Chemical class 0.000 claims description 24
- 159000000009 barium salts Chemical class 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 20
- 239000011259 mixed solution Substances 0.000 claims description 18
- 239000005486 organic electrolyte Substances 0.000 claims description 17
- 239000000203 mixture Substances 0.000 claims description 16
- 238000005187 foaming Methods 0.000 claims description 14
- 238000001704 evaporation Methods 0.000 claims description 12
- 230000008020 evaporation Effects 0.000 claims description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 10
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 claims description 10
- 239000011698 potassium fluoride Substances 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 9
- PAPBSGBWRJIAAV-UHFFFAOYSA-N ε-Caprolactone Chemical compound O=C1CCCCCO1 PAPBSGBWRJIAAV-UHFFFAOYSA-N 0.000 claims description 8
- AHLATJUETSFVIM-UHFFFAOYSA-M rubidium fluoride Chemical compound [F-].[Rb+] AHLATJUETSFVIM-UHFFFAOYSA-M 0.000 claims description 7
- 229910013063 LiBF 4 Inorganic materials 0.000 claims description 5
- 229910013684 LiClO 4 Inorganic materials 0.000 claims description 5
- 229910013870 LiPF 6 Inorganic materials 0.000 claims description 5
- 230000005587 bubbling Effects 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 235000003270 potassium fluoride Nutrition 0.000 claims description 4
- 238000007865 diluting Methods 0.000 claims description 2
- 238000005868 electrolysis reaction Methods 0.000 claims 1
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- 238000010494 dissociation reaction Methods 0.000 abstract description 12
- 230000005593 dissociations Effects 0.000 abstract description 12
- 238000009835 boiling Methods 0.000 abstract description 11
- 238000007614 solvation Methods 0.000 abstract description 11
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- 239000002904 solvent Substances 0.000 description 31
- 238000000034 method Methods 0.000 description 20
- 238000006243 chemical reaction Methods 0.000 description 19
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- 150000003839 salts Chemical class 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 13
- 238000006722 reduction reaction Methods 0.000 description 13
- 238000000655 nuclear magnetic resonance spectrum Methods 0.000 description 12
- 230000002441 reversible effect Effects 0.000 description 11
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 10
- 238000002484 cyclic voltammetry Methods 0.000 description 9
- 229910052709 silver Inorganic materials 0.000 description 9
- 239000004332 silver Substances 0.000 description 9
- 238000001228 spectrum Methods 0.000 description 9
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 239000006227 byproduct Substances 0.000 description 8
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- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 7
- 239000000654 additive Substances 0.000 description 7
- 150000001450 anions Chemical class 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 6
- 230000000996 additive effect Effects 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 6
- 239000011701 zinc Substances 0.000 description 6
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- 239000013078 crystal Substances 0.000 description 5
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- 229910052725 zinc Inorganic materials 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 4
- 150000001447 alkali salts Chemical class 0.000 description 4
- 238000006115 defluorination reaction Methods 0.000 description 4
- 238000003411 electrode reaction Methods 0.000 description 4
- 229910001512 metal fluoride Inorganic materials 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- RTBFRGCFXZNCOE-UHFFFAOYSA-N 1-methylsulfonylpiperidin-4-one Chemical compound CS(=O)(=O)N1CCC(=O)CC1 RTBFRGCFXZNCOE-UHFFFAOYSA-N 0.000 description 3
- 208000005156 Dehydration Diseases 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- JFCQEDHGNNZCLN-UHFFFAOYSA-N anhydrous glutaric acid Natural products OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
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- 238000006297 dehydration reaction Methods 0.000 description 3
- 238000003682 fluorination reaction Methods 0.000 description 3
- 150000002222 fluorine compounds Chemical class 0.000 description 3
- 150000002431 hydrogen Chemical class 0.000 description 3
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- SJZRECIVHVDYJC-UHFFFAOYSA-N 4-hydroxybutyric acid Chemical compound OCCCC(O)=O SJZRECIVHVDYJC-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 239000003125 aqueous solvent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- 229910001417 caesium ion Inorganic materials 0.000 description 2
- NCMHKCKGHRPLCM-UHFFFAOYSA-N caesium(1+) Chemical compound [Cs+] NCMHKCKGHRPLCM-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 2
- 229940006165 cesium cation Drugs 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002608 ionic liquid Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- GEWWCWZGHNIUBW-UHFFFAOYSA-N 1-(4-nitrophenyl)propan-2-one Chemical compound CC(=O)CC1=CC=C([N+]([O-])=O)C=C1 GEWWCWZGHNIUBW-UHFFFAOYSA-N 0.000 description 1
- 229910020366 ClO 4 Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- 239000002879 Lewis base Substances 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- 241001465382 Physalis alkekengi Species 0.000 description 1
- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 238000001237 Raman spectrum Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- NVIANCROYQGROD-UHFFFAOYSA-N bis(fluorosulfonyl)azanide Chemical compound FS(=O)(=O)[N-]S(F)(=O)=O NVIANCROYQGROD-UHFFFAOYSA-N 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 229930188620 butyrolactone Natural products 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 238000001460 carbon-13 nuclear magnetic resonance spectrum Methods 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000001364 causal effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 229920000547 conjugated polymer Polymers 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 238000002845 discoloration Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000000806 fluorine-19 nuclear magnetic resonance spectrum Methods 0.000 description 1
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 150000007527 lewis bases Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 230000000269 nucleophilic effect Effects 0.000 description 1
- 150000002892 organic cations Chemical class 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
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- 238000012360 testing method Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Secondary Cells (AREA)
Abstract
Description
本発明は、フッ化物イオン伝導性を付与したフッ化物イオン電池用有機電解液に関する。 The present invention relates to an organic electrolytic solution for a fluoride ion battery to which fluoride ion conductivity is imparted.
高電圧かつ高エネルギー密度の蓄電池としてＬｉイオン電池（ＬＩＢ）が知られている。ＬＩＢは正極および負極ホスト結晶中へのＬｉ＋イオンの可逆的挿入・脱挿入反応を利用したカチオンベースの電池であり、非水溶媒（有機電解液）中に溶解したリチウム塩の解離で生じたＬｉ＋イオンが両極の間を移動することで系内の電荷量と物質量のバランスが保たれる。 A Li-ion battery (LIB) is known as a storage battery having a high voltage and a high energy density. LIB is a cation-based battery that utilizes the reversible insertion / removal reaction of Li + ions into the positive and negative host crystals, and is caused by the dissociation of lithium salts dissolved in a non-aqueous solvent (organic electrolyte). The balance between the amount of charge and the amount of substance in the system is maintained by the movement of Li + ions between the two electrodes.
また、上記ＬＩＢのエネルギー密度を大幅に向上させる革新型の電池としてフッ化物イオン（Ｆ−）と金属との反応による多価の金属フッ化物の生成とその逆反応（金属フッ化物の脱フッ化反応）を利用したアニオンベースのフッ化物イオン電池（図１）がある。この電池で両極の間を移動するのはハロゲン化物イオンの中で最も軽いＦ−イオン（Ｍ＝１９）であり、さらに１金属原子あたり場合により２〜３個もしくはそれ以上の数のＦ−イオン（およびそれと同数の電子）が電極反応に関与することが、上記の高いエネルギー密度をもたらす最大の要因である。 In addition, as an innovative battery that greatly improves the energy density of the LIB, the formation of polyvalent metal fluoride by the reaction of fluoride ion (F − ) with a metal and its reverse reaction (fluoride of the metal fluoride). There is an anion-based fluoride ion cell (FIG. 1) that utilizes a reaction). It is the lightest F- ion (M = 19) among the halide ions that moves between the two electrodes in this battery, and in some cases 2-3 or more F - ions per metal atom. The involvement of (and the same number of ions) in the electrode reaction is the largest factor that results in the high energy density described above.
上記フッ化物イオン電池はＬＩＢの必須部材であるところのホスト格子を必要としない。Ｆ−イオンが電極反応と電解質中の電荷移動の両者で主役を演じるこの種の電池はＦＩＢ（Ｆｌｕｏｒｉｄｅ Ｉｏｎ Ｂａｔｔｅｒｙ）あるいはＦ−イオンの双方向移動の役割を強調したＦＳＢ（Ｆｌｕｏｒｉｄｅ Ｓｈｕｔｔｌｅ Ｂａｔｔｅｒｙ）の略称で知られている。 The fluoride ion battery does not require a host grid, which is an essential member of the LIB. F - abbreviation emphasized the role of bi-directional movement of the ion FSB (Fluoride Shuttle Battery) - ions of this kind of the battery plays a leading role in both the charge transfer in the electrolyte and the electrode reaction FIB (Fluoride Ion Battery) or F Is known for.
フッ化物イオン電池の基本要素の一つとなる金属フッ化物の還元（放電）反応については固体電解質が注目された１９７０年代の研究ですでに少なくない数の報告がなされている。しかし、二次電池として本質的に欠かせない充放電の有意な可逆性が全固体電池の枠内で不完全ながらも確かめられたのは、比較的最近になってからのことである。 Regarding the reduction (discharge) reaction of metal fluoride, which is one of the basic elements of fluoride ion batteries, a considerable number of reports have already been made in the 1970s research, which attracted attention to solid electrolytes. However, it was only relatively recently that the significant reversibility of charge and discharge, which is essentially essential for secondary batteries, was confirmed, albeit incompletely, within the framework of all-solid-state batteries.
また、一般的には固体電解質のイオン導電性と固体／固体界面での電気化学的反応性などに関する制約により、固体ＦＩＢ電池の室温動作の報告はごく最近発表された一例に止まっている。 Also, in general, due to restrictions on the ionic conductivity of solid electrolytes and the electrochemical reactivity at the solid / solid interface, reports of room temperature operation of solid FIB batteries are only one of the most recently published examples.
フッ化物イオンの輸送に非水系電解液を用いる湿式電池では原理的に上記の制約は除かれる。その目的に利用できる電解液に関する先行特許や学術論文も例に事欠かない。代表的な例としては、様々なフッ化物塩を比較的容易に溶解させるイオン液体を用いる手法（特許文献１）があり、その他、高沸点汎用有機溶媒に所謂アニオンレセプター（アニオンアクセプター）なるものを添加することで、フッ化物の溶解を促進する手法も報告されている。 In a wet battery that uses a non-aqueous electrolyte solution for transporting fluoride ions, the above restrictions are basically removed. There is no shortage of prior patents and academic papers on electrolytes that can be used for that purpose. As a typical example, there is a method using an ionic liquid that dissolves various fluoride salts relatively easily (Patent Document 1), and in addition, a so-called anion receptor (anion acceptor) in a high boiling point general-purpose organic solvent. A method of promoting the dissolution of fluoride by adding the above has also been reported.
フッ化物イオン電池を駆動するための電解液としては、フッ化物イオン伝導性と正負両極におけるフッ化物イオンの反応性の両方を担保できる形で、少なくとも１ｍＭ以上の濃度のフッ化物イオンが存在することが望ましい。 As the electrolytic solution for driving the fluoride ion battery, there must be a fluoride ion having a concentration of at least 1 mM or more in a form capable of ensuring both the fluoride ion conductivity and the reactivity of the fluoride ion at both the positive and negative poles. Is desirable.
しかしフッ化物イオンは極めて強いルイス塩基で求核反応性が高く、例えばプロトンとの反応で容易にフッ化水素（ＨＦ）を生成し、電解液の中で単独で安定なイオンとして存在させることは困難であった。 However, fluoride ion is an extremely strong Lewis base and has high nucleophilic reactivity. For example, it is not possible to easily generate hydrogen fluoride (HF) by reaction with a proton and allow it to exist alone in an electrolytic solution as a stable ion. It was difficult.
さらに、フッ化物イオンを電解液に溶解させるための前駆物質としてはアルカリ金属フッ化物を用いることが望ましいが、金属フッ化物の結晶格子エネルギーが非常に大きいため、これを高沸点汎用有機溶媒にそのまま単純解離溶解させることも困難であった。 Furthermore, it is desirable to use alkali metal fluoride as a precursor for dissolving fluoride ions in the electrolytic solution, but since the crystal lattice energy of metal fluoride is very large, this can be used as it is in a high boiling point general-purpose organic solvent. It was also difficult to simply dissociate and dissolve.
これらの問題を避けるための手法としてこれまで提案され開発が進められてきたのが、上記のイオン液体系やアニオンアクセプターを用いた技術であるが、電解液の安定性や限られた電位窓など実用課題が少なくなかった。 As a method for avoiding these problems, the technology using the above-mentioned ionic liquid system and anion acceptor has been proposed and developed so far, but the stability of the electrolytic solution and the limited potential window There were many practical issues such as.
本発明は、上記実情に鑑みてなされたものであり、通常の方法では解離溶解しないアルカリ金属フッ化物を、特定の高沸点有機溶媒にアルカリ金属カチオンおよびフッ化物イオンの形で単純溶媒和イオン化解離させたフッ化物イオン電池用の、フッ化物塩の溶解性と化学的および電気化学的安定性に優れた電解液を提供することを主目的とする。 The present invention has been made in view of the above circumstances, and a simple solvation ionization dissociation of an alkali metal fluoride, which is not dissociated and dissolved by a usual method, in the form of an alkali metal cation and a fluoride ion in a specific high boiling point organic solvent. An object of the present invention is to provide an electrolytic solution having excellent solubility of a fluoride salt and excellent chemical and electrochemical stability for a fluoride ion battery.
上記課題を達成するために、本発明者等が鋭意研究を重ねた。その結果、特定の高沸点有機溶媒にα位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒とアルカリ金属フッ化物からなる電解液とすることで、フッ化物塩が解離しやすくなり、フッ化物塩の溶解性が向上し、化学的および電気化学的安定性が改善されることを見出した。詳しくは、特定の高沸点有機溶媒を用い、複数の中間段階を経る新たな溶解プロセスを経ることで、アルカリ金属フッ化物が少なくとも１ｍＭ以上の濃度で当該溶媒に単純溶解分散したフッ化物イオン伝導性電解液を調製できることを見出した。本発明は、このような知見に基づくものである。 In order to achieve the above problems, the present inventors have conducted extensive research. As a result, the fluoride salt is easily dissociated by preparing an electrolytic solution composed of an ester-based or lactone-based single or mixed organic solvent having α-hydrogen in a specific high-boiling organic solvent and an alkali metal fluoride, and the fluoride salt is easily dissociated. It has been found that the solubility of fluorides is improved and the chemical and electrochemical stability is improved. Specifically, by using a specific high-boiling organic solvent and undergoing a new dissolution process through a plurality of intermediate steps, fluoride ion conductivity in which alkali metal fluoride is simply dissolved and dispersed in the solvent at a concentration of at least 1 mM or more. We have found that electrolytes can be prepared. The present invention is based on such findings.
すなわち本発明においては、特定の高沸点有機溶媒であるα位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒（単に「α位水素を有するエステル系／ラクトン系溶媒」又は「α位水素をもつ溶媒」ともいう）と、アルカリ金属カチオンおよびフッ化物イオンを有するアルカリ金属フッ化物と、を含有することを特徴とするフッ化物イオン伝導性有機電解液を提供する。 That is, in the present invention, an ester-based or lactone-based single or mixed organic solvent having α-position hydrogen, which is a specific high-boiling organic solvent (simply “ester-based / lactone-based solvent having α-position hydrogen” or “α-position hydrogen”. Provided is a fluoride ion conductive organic electrolytic solution containing an alkali metal cation and an alkali metal fluoride having a fluoride ion.
本発明によれば、添加剤を別途添加しない場合であっても、フッ化物イオン電池を動作させるに十分な反応活性を同時に有したフッ化物イオン伝導性有機電解液が作製できるため、電池の大容量化が格段に容易になる。ここでいう余分な添加剤とは、有機溶媒、アルカリ金属フッ化物、電解液に共溶解可能な任意のリチウム塩および電解液に共溶解可能な任意のバリウム塩以外の他の添加剤をいうものとする。 According to the present invention, a fluoride ion conductive organic electrolytic solution having sufficient reaction activity at the same time to operate a fluoride ion battery can be produced even when no additive is added separately, so that the size of the battery is large. Capacity increase becomes much easier. The term "extra additive" as used herein refers to an additive other than an organic solvent, an alkali metal fluoride, an arbitrary lithium salt co-dissolvable in an electrolytic solution, and an arbitrary barium salt co-dissolvable in an electrolytic solution. And.
上記発明においては、上記高沸点有機溶媒が、２００℃以上の沸点を有するα位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒であることが好ましい。 In the above invention, the high boiling point organic solvent is preferably an ester-based or lactone-based single or mixed organic solvent having α-hydrogen having a boiling point of 200 ° C. or higher.
上記発明においては、上記アルカリ金属フッ化物が、フッ化セシウム、フッ化ルビジウム、フッ化カリウムのいずれか１つ、もしくはそれらの２つ以上の混合物であることが好ましい。 In the above invention, the alkali metal fluoride is preferably any one of cesium fluoride, rubidium fluoride, and potassium fluoride, or a mixture of two or more thereof.
上記発明においては、該フッ化物イオン伝導性有機電解液の負高電位での安定性と反応性を確保するために、当該電解液に共溶解可能な任意のリチウム塩、好ましくはＬｉＦＳＡ、ＬｉＴＦＳＡ、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣｌＯ４のいずれか１つもしくはそれらの２つ以上の混合物、および／または当該電解液に共溶解可能な任意のバリウム塩、好ましくはＢａ（ＦＳＡ）２、Ｂａ（ＴＦＳＡ）２、Ｂａ（ＢＦ４）２のいずれかもしくはそれらの混合物、好ましくはＬｉＦＳＡ、ＬｉＴＦＳＡ、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣｌＯ４のいずれか１つまたはそれらの２つ以上の混合物をそれぞれに、解離溶解したアルカリ金属フッ化物の濃度の少なくとも３倍以上、好ましくは５倍以上の濃度で混合することが好ましい。これは過剰のリチウムカチオンあるいはバリウムカチオンとフッ化物イオンの相互作用により、フッ化物イオンの負高電位領域での反応性が制御できるためである。 In the above invention, in order to ensure the stability and reactivity of the fluoride ion conductive organic electrolytic solution at a negative high potential, any lithium salt co-dissolvable in the electrolytic solution, preferably LiFSA, LiTFSA, is used. One or a mixture of any one or more of LiBF 4 , LiPF 6 , LiClO 4 and / or any barium salt co-dissolvable in the electrolyte, preferably Ba (FSA) 2 , Ba (TFSA). 2. Any one of Ba (BF 4 ) 2 or a mixture thereof, preferably any one of LiFSA, LiTFSA, LiBF 4 , LiPF 6 , LiClO 4 or a mixture thereof, was dissociated and dissolved in each. It is preferable to mix at a concentration of at least 3 times or more, preferably 5 times or more the concentration of the alkali metal fluoride. This is because the reactivity of fluoride ions in the negative high potential region can be controlled by the interaction between excess lithium cations or barium cations and fluoride ions.
本発明によれば、多様な金属種とそのフッ化物の間の可逆反応を制御することが可能になるため、本発明による電解液を用いることで、２〜３Ｖ級の室温で動作する大容量フッ化物イオン二次電池を構築する道が開かれる。 According to the present invention, it is possible to control the reversible reaction between various metal species and their fluorides. Therefore, by using the electrolytic solution according to the present invention, a large capacity operating at room temperature of 2 to 3 V class is used. It opens the way for building fluoride ion secondary batteries.
本発明のフッ化物イオン伝導性有機電解液は、α位水素を有するエステル系／ラクトン系溶媒とアルカリ金属フッ化物からなり、添加剤を別途添加しない場合であっても、電気化学的安定性に優れ、多様な金属種とそのフッ化物の間の可逆反応を引起す反応活性を同時に有する。このため、出力電圧も大きくとれ、もって大容量フッ化物イオン二次電池に適したフッ化物イオン伝導性有機電解液を提供することができる。 The fluoride ion conductive organic electrolyte solution of the present invention is composed of an ester / lactone solvent having α-hydrogen and an alkali metal fluoride, and has excellent electrochemical stability even when no additive is added separately. It is excellent and has a reaction activity that causes a reversible reaction between various metal species and their fluorides at the same time. Therefore, a large output voltage can be obtained, and a fluoride ion conductive organic electrolytic solution suitable for a large-capacity fluoride ion secondary battery can be provided.
以下、本発明のフッ化物イオン伝導性有機電解液（フッ化物イオン電池用電解液）およびこれを用いたフッ化物イオン電池の実施形態について詳細に説明する。 Hereinafter, a fluoride ion conductive organic electrolytic solution (electrolyte solution for a fluoride ion battery) of the present invention and an embodiment of a fluoride ion battery using the same will be described in detail.
［塩の溶解度を決定する因子］
任意の溶媒に塩を溶解させる場合、その溶解量を決定する因子としては、熱力学的上限と速度論的な制限の両方を考慮する必要がある。
[Factors that determine salt solubility]
When a salt is dissolved in any solvent, both the thermodynamic upper limit and the kinetic limitation must be considered as factors that determine the amount of the salt dissolved.
本発明に係るα位水素を有する溶媒であるＧＢＬ（γ−ブチロラクトン）のような非水溶媒にも、ＣｓＦ（フッ化セシウム）やＫＦ（フッ化カリウム）等のアルカリ金属フッ化物（単に「アルカリ塩」、「フッ化物塩」ともいう）はみかけ上、ほとんど溶解しないが、これは該溶媒中の該アルカリ塩の熱力学的な溶解量の上限がゼロに近いことを意味しない。 Alkali metal fluorides such as CsF (cesium fluoride) and KF (potassium fluoride) can also be used in non-aqueous solvents such as GBL (γ-butyrolactone), which is a solvent having α-hydrogen according to the present invention (simply "alkali"). (Also referred to as "salt" and "fluoride salt") apparently hardly dissolve, but this does not mean that the upper limit of the thermodynamic dissolution amount of the alkali salt in the solvent is close to zero.
すなわち後述するように、α位水素を有する溶媒中では、α位水素とフッ化物イオンとの特異的な相互作用による安定化により、該アルカリ塩であるＣｓＦが単純解離溶解した５０ｍＭ程度のモル濃度の電解液が本来は作製できるはずである。これが熱力学的上限である。 That is, as will be described later, in a solvent having α-position hydrogen, a molar concentration of about 50 mM in which CsF, which is the alkali salt, is simply dissociated and dissolved by stabilization by a specific interaction between α-position hydrogen and fluoride ions. It should be possible to prepare the electrolytic solution of. This is the thermodynamic upper limit.
具体的に、溶解した該アルカリ塩（例えば、ＣｓＦ）の解離度を１００％とすれば、上記濃度のＣｓ＋イオンとＦ−イオンに相当する溶解度積は比較的小さく、これに対応する溶解の標準自由エネルギー変化は正、つまり熱力学的には溶解反応は確かに不利ではあるが、５０ｍＭ程度を上限とする溶解は熱力学的に可能である。 Specifically, assuming that the degree of dissociation of the dissolved alkali salt (for example, CsF) is 100%, the solubility product corresponding to the above-mentioned concentrations of Cs + ion and F - ion is relatively small, and the corresponding dissolution The standard free energy change is positive, that is, the dissolution reaction is thermodynamically disadvantageous, but dissolution up to about 50 mM is thermodynamically possible.
それにも拘わらず、通常の方法（単純攪拌）でこのレベルの濃度が現実的に達成できないのは、ＣｓＦ結晶の格子エネルギー（Ｍａｄｅｌｕｎｎｇエネルギー）が非常に大きく、これをバリヤーとする速度論的な制約によるものである。 Nevertheless, the reason why this level of concentration cannot be realistically achieved by the usual method (simple stirring) is that the lattice energy (Maderunng energy) of the CsF crystal is very large, and this is a kinetic constraint that makes this a barrier. It is due to.
事実、液温を１３０℃以上に保って、数時間以上攪拌すれば、通常の方法でも当該塩の解離溶解による有意なイオン伝導度を発現させることができる。但し、この方法では溶媒自身がＣｓＦ固体の触媒的な作用もあって容易に熱的副反応を起こし、何らかの共役重合物の生成により液が濃い褐色を呈するに至る。多量の副生物が混在するこのような状態はフッ化物イオン電池用電解液として使用することはできない。 In fact, if the liquid temperature is maintained at 130 ° C. or higher and the mixture is stirred for several hours or longer, significant ionic conductivity due to dissociation and dissolution of the salt can be exhibited by a usual method. However, in this method, the solvent itself easily causes a thermal side reaction due to the catalytic action of the CsF solid, and the liquid becomes dark brown due to the formation of some conjugated polymer. Such a state in which a large amount of by-products are mixed cannot be used as an electrolytic solution for a fluoride ion battery.
α位水素を有する溶媒自身のこの熱的な反応に関連して、特にＧＢＬはそれ単独の高温加熱でもしばしば黄色〜褐色に着色する。ところが、本発明に係る開発のある段階で、意図的に数％の純水を加えて加熱したところ、この変色が抑制できることに気づいた。直接的な因果関係はないが、本調製法はこの観察に端を発している。 In connection with this thermal reaction of the solvent itself with alpha hydrogen, especially GBL, even with its own high temperature heating, often turns yellow to brown. However, at a certain stage of development according to the present invention, it was noticed that this discoloration could be suppressed when a few percent of pure water was intentionally added and heated. Although not directly causal, this preparation method stems from this observation.
［電解液の調製方法］
以下、α位水素を有する溶媒のうち、ＧＢＬを代表的な例として本特許の電解液を作製するための具体的な手順とその原理を説明する。
[Preparation method of electrolyte]
Hereinafter, a specific procedure and its principle for producing the electrolytic solution of the present patent will be described using GBL as a typical example among the solvents having hydrogen at the α-position.
上記アルカリ塩であるＣｓＦもＫＦも純水には数Ｍ以上の高濃度で容易に溶解する。本法ではまず、この濃厚水溶液（１．５Ｍ程度）を過剰のＧＢＬと、水の割合が１０ｖ％（体積％）程度になるように混合し、攪拌加熱する。作業雰囲気は大気中でも支障ない。 Both CsF and KF, which are the alkali salts, are easily dissolved in pure water at a high concentration of several M or more. In this method, first, this concentrated aqueous solution (about 1.5 M) is mixed with excess GBL so that the ratio of water is about 10 v% (volume%), and the mixture is stirred and heated. The working atmosphere does not interfere with the atmosphere.
高濃度ＣｓＦ水溶液中のイオンは複数の水分子による溶媒和で強く安定化されている。この溶媒和エネルギーはＣｓＦ結晶の格子エネルギーを上回る大きさであり、このことが該塩を純水中で高濃度で溶解できる理由である。 The ions in the high-concentration CsF aqueous solution are strongly stabilized by solvation with a plurality of water molecules. This solvation energy is larger than the lattice energy of CsF crystals, which is the reason why the salt can be dissolved in pure water at a high concentration.
逆に、このように複数の水分子で強く溶媒和されて安定化しているＣｓ＋イオンとＦ−イオンの周りの水分子を一度（一挙）にＧＢＬ分子に置換すること自体も、固体粉末を溶解させる以上に速度論的には困難である。 Conversely, thus more solvated strongly water molecules are stabilized Cs + ions and F - also themselves be substituted water molecules around the ions once (once) to GBL molecule, a solid powder It is more difficult in terms of speed than to dissolve it.
しかし本法では、こうした一挙的な溶媒和置換は起こらない。上記混合液を攪拌加熱すると、液温が１１０℃付近で水の蒸発による発泡が始まる。１２０℃付近でこの定常的な蒸発が続くような加熱条件を設定すると、１０分程度で見かけ上、水がほぼ全て蒸発し発泡が収まる。 However, in this method, such solvation substitution does not occur at once. When the mixed solution is stirred and heated, foaming due to evaporation of water starts when the solution temperature is around 110 ° C. When heating conditions are set so that this steady evaporation continues at around 120 ° C., almost all of the water apparently evaporates in about 10 minutes and the foaming stops.
上記の時間の間に、各イオンの周りでは、溶媒和水分子が段階的に徐々にＧＢＬ分子で置換される状況が生まれる。このようにして、極度に大きな速度論的バリヤーを伴うことなく、溶媒和構造が水からＧＢＬに段階的に変換され、最終的に５０ｍＭ程度の熱力学的な上限濃度がスムーズに達成できる。これが本発明の基本コンセプトであり、実施例１の「多段階の溶解過程を経る」（または上記した「複数の中間段階を経る新たな溶解プロセスを経る」）の意味するところである。 During the above time, a situation arises around each ion in which the solvated water molecules are gradually and gradually replaced by GBL molecules. In this way, the solvated structure is gradually converted from water to GBL without an extremely large kinetic barrier, and finally a thermodynamic upper limit concentration of about 50 mM can be smoothly achieved. This is the basic concept of the present invention, which is the meaning of "going through a multi-step dissolution process" (or "going through a new dissolution process through a plurality of intermediate steps") in Example 1.
但し、上記の発泡が収まった液には、まだ水分が０．１ｖ％以上のレベルで残存している。これを使用目的に合わせた必要なレベルまで低下させるためには、さらに攪拌加熱を延長する必要があり、場合により加熱温度を１５０℃程度まで高めたり、不活性ガスの同時バブリングにより脱水を促進する工夫が必要である。これが実施例２の「さらに追加処理を加えて」の意味するところである（実施例２では前者の追加加熱を実施）。 However, in the liquid in which the above foaming is contained, water still remains at a level of 0.1 v% or more. In order to reduce this to the required level according to the purpose of use, it is necessary to further extend the stirring heating, and in some cases, the heating temperature is raised to about 150 ° C., or the simultaneous bubbling of the inert gas promotes dehydration. Ingenuity is required. This is the meaning of "additional additional treatment" in Example 2 (in Example 2, the former additional heating is carried out).
上記の追加の加熱等の処理は、上記電解液の作製時に完全には抑制できない副次的な生成物を蒸発により取り除くためにも有効である。後の実施例では、水分の低減も含めて必要最小限の加熱処理を経たものを＜ステージＩ電解液＞と称し、さらに追加加熱等の条件を厳しくして水分や副次的な生成物を極限まで取り除いたものを＜ステージＩＩ電解液＞と称して区別している。 The above-mentioned additional treatments such as heating are also effective for removing by evaporation of secondary products that cannot be completely suppressed during the preparation of the above-mentioned electrolytic solution. In the later examples, the one that has undergone the minimum necessary heat treatment including the reduction of water content is referred to as <Stage I electrolyte>, and the conditions such as additional heating are further tightened to remove water and secondary products. Those removed to the utmost limit are referred to as <stage II electrolyte> to distinguish them.
なお後の実施例では、その副次的な生成物の正体についても詳しく説明しているが、この副次的な生成物は該塩の解離溶解には全く関与しておらず、添加剤（意図的なもの）を使用しなくとも優れた性能を発揮しうるフッ化物イオン電池用電解液の定義にも抵触しない。 In the later examples, the identity of the by-product is also described in detail, but this by-product is not involved in the dissociation and dissolution of the salt at all, and the additive ( It does not violate the definition of an electrolyte for fluoride ion batteries that can exhibit excellent performance without using intentional ones).
［α位水素を有する溶媒］
α位に水素をもつ溶媒分子としては、特に制限されるものではないが、ＧＢＬ（γ−ブチロラクトン）とε−カプロラクトンのいずれか一つもしくはそれらの混合物が好ましい。これらが好ましいのは、この部位（α位水素部位）が微妙な強さの一種のアニオンアクセプターとして働き、解離溶解したフッ化物イオンの適度な溶媒和を可能にするためである。本実施形態のフッ化物イオン伝導性有機電解液中のフッ化物イオンはイオン伝導を担うのみならず、正・負極におけるフッ化反応を効率的に引起すものでなければならない。フッ化物イオンを強く束縛するような溶媒や添加物はこの目的に適さない。
[Solvent with α-hydrogen]
The solvent molecule having hydrogen at the α-position is not particularly limited, but any one of GBL (γ-butyrolactone) and ε-caprolactone or a mixture thereof is preferable. These are preferable because this site (α-position hydrogen site) acts as a kind of anion acceptor having a delicate strength and enables appropriate solvation of dissociated and dissolved fluoride ions. Fluoride ion conductivity of the present embodiment Fluoride ions in the organic electrolytic solution must not only be responsible for ion conduction but also efficiently induce a fluoride reaction in the positive and negative electrodes. Solvents and additives that strongly bind fluoride ions are not suitable for this purpose.
ただし、本実施形態で利用できる有機溶媒は必ずしも上記の条件に制約されるものではなく、フッ化物イオンの伝導性と電極反応性を阻害するものでなければ、任意の高沸点有機溶媒を選択する余地がある。 However, the organic solvent that can be used in the present embodiment is not necessarily limited to the above conditions, and any high boiling point organic solvent is selected as long as it does not inhibit the conductivity and electrode reactivity of fluoride ions. There is room.
［アルカリ金属フッ化物塩］
電極反応に直接与るイオン伝導性フッ化物イオンは、有機フッ化物塩の溶解によっても電解液中に導入することができるが、共存する有機カチオンの電気化学的安定性の問題などの理由で高容量フッ化物イオン電池には適さない。その他の条件として二次電池の重量エネルギー密度への影響も考慮すると、フッ化物イオンの最も望ましいソースは、フッ化リチウム（ＬｉＦ）、フッ化ナトリウム（ＮａＦ）、フッ化カリウム（ＫＦ）、フッ化ルビジウム（ＲｂＦ）、フッ化セシウム（ＣｓＦ）等のアルカリ金属フッ化物である。
[Alkali metal fluoride salt]
Ion-conducting fluoride ions that directly affect the electrode reaction can be introduced into the electrolytic solution by dissolving the organic fluoride salt, but they are high due to problems such as the electrochemical stability of coexisting organic cations. Not suitable for capacitive fluoride ion batteries. Considering the effect on the weight energy density of the secondary battery as another condition, the most desirable sources of fluoride ions are lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), and fluoride. It is an alkali metal fluoride such as rubidium (RbF) and cesium fluoride (CsF).
上記のアルカリ金属フッ化物の内、どの化合物が実際に使用できるかはフッ化物結晶の格子エネルギーに依存する。例えばＬｉＦは純水にさえほとんど溶解しないため、本実施形態によっても高沸点有機溶媒であるα位水素を有するエステル系／ラクトン系溶媒中で単純溶媒和イオン化解離させることは至難である。これらの点を考慮すれば、アルカリ金属フッ化物の内、フッ化セシウム（ＣｓＦ）、フッ化ルビジウム（ＲｂＦ）、フッ化カリウム（ＫＦ）のいずれか１つもしくはそれらの２つ以上の混合物であるのが好ましい。また、電極反応に直接与るイオン伝導性フッ化物イオン（解離溶解で生成したフッ化物イオン）の１９Ｆ−ＮＭＲ化学シフトは、−１５０±１０ｐｐｍの範囲にあるのが好ましい。本実施形態の電解液に特徴的な化学シフト値であるためである。さらに、電解液中のフッ化物イオンの濃度は、少なくとも１ｍＭ以上であるのが好ましい。フッ化物イオン濃度が１ｍＭ以上であれば、フッ化物イオン電池を駆動するための電解液として、フッ化物イオンの伝導性と正負両極におけるフッ化物イオンの反応性の両方を担保できる。 Which of the above alkali metal fluorides can actually be used depends on the lattice energy of the fluoride crystals. For example, since LiF is hardly dissolved even in pure water, it is extremely difficult to dissociate by simple solvation ionization in an ester / lactone solvent having α-hydrogen, which is a high boiling point organic solvent, even in this embodiment. Considering these points, among the alkali metal fluorides, any one of cesium fluoride (CsF), rubidium fluoride (RbF), and potassium fluoride (KF) or a mixture of two or more thereof. Is preferable. Further, the 19 F-NMR chemical shift of the ionic conductive fluoride ion (fluoride ion generated by dissociation dissolution) directly exerted on the electrode reaction is preferably in the range of −150 ± 10 ppm. This is because the chemical shift value is characteristic of the electrolytic solution of the present embodiment. Further, the concentration of fluoride ions in the electrolytic solution is preferably at least 1 mM or more. When the fluoride ion concentration is 1 mM or more, both the conductivity of fluoride ions and the reactivity of fluoride ions at both positive and negative poles can be ensured as the electrolytic solution for driving the fluoride ion battery.
［混合リチウム塩］
アルカリ金属フッ化物のみが１ｍＭ以上の濃度で解離溶解した該フッ化物イオン伝導性電解液は、負高電位領域でフッ化物イオン由来の溶媒が関与した副還元反応を生じやすく、亜鉛よりも更に卑な金属のフッ化反応と競合して本来の電池動作を妨げる。この問題は、ＬｉＦＳＡ（ＦＳＡ：ビス（フルオロスルホニル）アミド）に代表される、本実施形態の電解液に共溶解可能な任意のリチウム塩を該電解液に過剰に混合することで容易に解決でき、アルミニウムやランタンなどの最も卑な金属種のフッ化反応を利用した電池を動作させることが可能になる。
[Mixed lithium salt]
The fluoride ion conductive electrolyte solution in which only alkali metal fluoride is dissociated and dissolved at a concentration of 1 mM or more is likely to cause a side reduction reaction involving a fluoride ion-derived solvent in a negative high potential region, and is even more base than zinc. It competes with the fluoride reaction of various metals and interferes with the original battery operation. This problem can be easily solved by excessively mixing an arbitrary lithium salt co-dissolvable in the electrolytic solution of the present embodiment, represented by LiFSA (FSA: bis (fluorosulfonyl) amide), in the electrolytic solution. , It will be possible to operate batteries that utilize the fluorination reaction of the most base metal species such as aluminum and lanterns.
上記の混合電解液の作製において、過剰に添加するリチウム塩の濃度は、解離したアルカリ金属フッ化物の濃度の少なくとも３倍以上、好ましくは５倍以上、より好ましくは１０倍程度に調製することが望ましい。このリチウム塩の濃度（添加量）が３倍以上であれば、フッ化物イオンとリチウムイオンが不溶性の固形物を形成しないためフッ化物イオン濃度を低下させることもなく望ましい。 In the preparation of the above mixed electrolytic solution, the concentration of the lithium salt added in excess may be adjusted to be at least 3 times or more, preferably 5 times or more, more preferably about 10 times the concentration of the dissociated alkali metal fluoride. desirable. When the concentration (addition amount) of this lithium salt is 3 times or more, it is desirable that the fluoride ion concentration is not lowered because the fluoride ion and the lithium ion do not form an insoluble solid substance.
該リチウム塩のアニオン種としては、ＦＳＡ−以外にＴＦＳＡ−、ＢＦ４ −、ＰＦ６ −、ＣｌＯ４ −でも差し支えない。即ち、過剰に添加するリチウム塩は、ＬｉＦＳＡ、ＬｉＴＦＳＡ、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣｌＯ４のいずれか１つまたはそれらの２つ以上の混合物であるのが好ましい。 As the anion species of the lithium salt, TFSA − , BF 4 − , PF 6 − , and ClO 4 − may be used in addition to FSA − . That is, the lithium salt to be added in excess is preferably any one of LiFSA, LiTFSA, LiBF 4 , LiPF 6 , and LiClO 4 or a mixture of two or more thereof.
［混合バリウム塩］
リチウム塩ほどの効果は期待できないものの、Ｂａ（ＦＳＡ）２に代表されるバリウム塩を該電解液に過剰に混合することでも負高電位領域での不可逆還元電流を抑制することができる。上記の混合電解液の作製において、過剰に添加するバリウム塩の濃度は、解離したアルカリ金属フッ化物の濃度の少なくとも３倍以上、好ましくは５倍以上、より好ましくは１０倍程度に調製することが望ましい。このバリウム塩の濃度（添加量）が３倍以上であれば、フッ化物イオンとリチウムイオンが不溶性の固形物を形成しないためフッ化物イオン濃度を低下させることもなく望ましい。該バリウム塩のアニオン種としては、ＦＳＡ−以外にＴＦＳＡ−、ＢＦ４ −でも差し支えない。即ち、過剰に添加するバリウム塩は、Ｂａ（ＦＳＡ）２、Ｂａ（ＴＦＳＡ）２、Ｂａ（ＢＦ４）２のいずれか１つまたはそれらの２つ以上の混合物であるのが好ましい。
[Mixed barium salt]
Although not as effective as a lithium salt, an irreversible reduction current in a negative high potential region can be suppressed by excessively mixing a barium salt typified by Ba (FSA) 2 with the electrolytic solution. In the preparation of the above mixed electrolytic solution, the concentration of the barium salt added in excess may be adjusted to be at least 3 times or more, preferably 5 times or more, more preferably about 10 times the concentration of the dissociated alkali metal fluoride. desirable. When the concentration (addition amount) of this barium salt is 3 times or more, it is desirable that the fluoride ion concentration is not lowered because the fluoride ion and the lithium ion do not form an insoluble solid substance. Examples of the anionic species of the barium salt, FSA - except the TFSA -, BF 4 - but no problem. That is, the barium salt to be added in excess is preferably any one of Ba (FSA) 2 , Ba (TFSA) 2 , and Ba (BF 4 ) 2 or a mixture of two or more thereof.
［フッ化物イオン電池］
本発明のフッ化物イオン電池の実施形態は、上述したフッ化物イオン伝導性電解液を使用するかぎり特に限定されるものではない。上述したフッ化物イオン伝導性電解液を使用することで、出力電圧も大きくとれ、もって大容量のフッ化物イオン電池を提供できる。また、本発明のフッ化物イオン電池は、一次電池であっても良く、二次電池であっても良いが、繰り返し充放電ができる二次電池であることが好ましい。
[Fluoride ion battery]
The embodiment of the fluoride ion battery of the present invention is not particularly limited as long as the above-mentioned fluoride ion conductive electrolytic solution is used. By using the above-mentioned fluoride ion conductive electrolytic solution, a large output voltage can be obtained, and a large capacity fluoride ion battery can be provided. Further, the fluoride ion battery of the present invention may be a primary battery or a secondary battery, but is preferably a secondary battery that can be repeatedly charged and discharged.
［フッ化物イオン伝導性有機電解液の製造方法］
本発明のフッ化物イオン伝導性有機電解液の製造方法の実施形態は、上記した［電解液の調製方法］で説明した通りである。具体的に、本発明の他の形態に係るフッ化物イオン伝導性有機電解液の製造方法は、アルカリ金属フッ化物を水に溶解させて水溶液を得ることと、α位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒と前記水溶液とを混合して第１の混合溶液を得ることと、前記混合溶液に加熱処理を施すことにより水を除去して有機電解液を得ることとを含むものである。この製造方法により、本発明の一形態に係るフッ化物イオン伝導性有機電解液を製造することができる（第１形態）。上記フッ化物塩は溶解性が低く、有機溶媒にそのまま溶解しようとしても溶けないというのが従来の常識であった。また、α位水素を有するエステル系／ラクトン系溶媒はフッ化物イオンと相互作用することから多少溶けやすくはなるものの、やはりそのままでは溶けにくいという問題があった。そこで、本発明の製造方法では、上記フッ化物塩が水には良く溶けるという性質を利用し、フッ化物塩を一旦水に溶かして水溶液を得る。その後、α位水素を有するエステル系／ラクトン系有機溶媒またはこれらの混合溶媒と混合して混合溶液（本明細書中、「第１の混合溶液」ともいう）を得る。そして、このようにして得られた第１の混合溶液に加熱処理を施すことにより水を除去する。そうすると、上記有機溶媒にアルカリ金属フッ化物が高濃度で溶解した有機電解液が調製されうるのである。なお、本発明者等の検討によれば、他の有機溶媒を用いた場合にはフッ化物イオンが安定に存在できず、フッ化物塩が再析出しやすくなるため、本発明の製造方法を適用することができないことも判明した。
[Method for Producing Fluoride Ion Conductive Organic Electrolyte]
An embodiment of the method for producing a fluoride ion conductive organic electrolytic solution of the present invention is as described in the above-mentioned [Method for preparing an electrolytic solution]. Specifically, the method for producing a fluoride ion conductive organic electrolytic solution according to another embodiment of the present invention comprises dissolving an alkali metal fluoride in water to obtain an aqueous solution, and an ester-based or lactone having α-hydrogen. It includes mixing a single or mixed organic solvent of the system with the aqueous solution to obtain a first mixed solution, and removing water by heat-treating the mixed solution to obtain an organic electrolytic solution. .. By this production method, the fluoride ion conductive organic electrolytic solution according to one embodiment of the present invention can be produced (first embodiment). It has been a conventional wisdom that the fluoride salt has low solubility and does not dissolve even if it is tried to dissolve in an organic solvent as it is. Further, although the ester / lactone solvent having α-hydrogen interacts with the fluoride ion, it becomes slightly soluble, but there is a problem that it is difficult to dissolve as it is. Therefore, in the production method of the present invention, the fluoride salt is once dissolved in water to obtain an aqueous solution by utilizing the property that the fluoride salt is well dissolved in water. Then, it is mixed with an ester / lactone-based organic solvent having α-hydrogen or a mixed solvent thereof to obtain a mixed solution (also referred to as “first mixed solution” in the present specification). Then, water is removed by heat-treating the first mixed solution thus obtained. Then, an organic electrolytic solution in which the alkali metal fluoride is dissolved in the organic solvent at a high concentration can be prepared. According to the study by the present inventors, fluoride ions cannot be stably present when other organic solvents are used, and fluoride salts are likely to be reprecipitated. Therefore, the production method of the present invention is applied. It also turned out that it couldn't be done.
より詳細に、本実施形態（第１形態）に係るフッ化物イオン伝導性有機電解液の製造方法では、まず、アルカリ金属フッ化物を一旦水（例えば、純水）に数Ｍ以上の高濃度で溶解する。この濃厚水溶液（例えば、１．５Ｍ程度の濃度のもの）をα位水素を有するエステル系／ラクトン系溶媒の過剰量と、水の割合が１０ｖ％（１０体積％）程度になるように混合し、攪拌加熱する。作業雰囲気は大気中でも支障ないし、真空・減圧下で行ってもよい。上記混合溶液（第１の混合溶液）を攪拌加熱すると、液温が１１０℃付近で水の蒸発による発泡が始まる。１２０℃付近（例えば、１２０℃±１０℃の範囲）でこの定常的な蒸発が続くような加熱条件を設定すると、１０分程度で見かけ上、水がほぼ全て蒸発して発泡が収まる。上記の時間の間に、各イオンの周囲では、溶媒和水分子が段階的に徐々にＧＢＬ等の有機溶媒分子で置換される状況が生まれる。このようにして、極度に大きな速度論的バリヤーを伴うことなく、溶媒和構造が水からα位水素を有するエステル系／ラクトン系溶媒に段階的に変換され、最終的に５０ｍＭ程度の熱力学的な上限濃度がスムーズに達成できるのである。第１形態に係る製造方法では、この時点（水の蒸発による発泡が終了した時点）で、加熱処理による水の除去を終了する。このような製造方法によれば、比較的簡便な操作によって、十分に実用的なフッ化物イオン伝導性有機電解液を製造することが可能である。 More specifically, in the method for producing a fluoride ion conductive organic electrolytic solution according to the present embodiment (first embodiment), first, the alkali metal fluoride is once added to water (for example, pure water) at a high concentration of several M or more. Dissolve. This concentrated aqueous solution (for example, one having a concentration of about 1.5 M) is mixed with an excess amount of the ester / lactone solvent having α-hydrogen so that the ratio of water is about 10 v% (10% by volume). , Stir and heat. The working atmosphere does not interfere with the atmosphere, and may be performed under vacuum or reduced pressure. When the above mixed solution (first mixed solution) is stirred and heated, foaming due to evaporation of water starts when the liquid temperature is around 110 ° C. When heating conditions are set so that this steady evaporation continues at around 120 ° C. (for example, in the range of 120 ° C. ± 10 ° C.), almost all of the water evaporates apparently in about 10 minutes and the foaming stops. During the above time, a situation arises in which the solvation water molecules are gradually and gradually replaced with organic solvent molecules such as GBL around each ion. In this way, the solvation structure is gradually converted from water to an ester / lactone solvent having α-hydrogen without an extremely large kinetic barrier, and finally thermodynamically about 50 mM. The upper limit concentration can be achieved smoothly. In the production method according to the first embodiment, the removal of water by the heat treatment is completed at this point (when the foaming due to the evaporation of water is completed). According to such a production method, it is possible to produce a sufficiently practical fluoride ion conductive organic electrolytic solution by a relatively simple operation.
本実施形態のフッ化物イオン伝導性有機電解液の製造方法では、水の蒸発による発泡が終了した時点より後に、さらに加熱温度を上昇させて加熱処理を継続することにより水を追加除去することも好ましい形態である（第２形態）。このような加熱処理の継続による水の追加除去の際には、不活性ガスをバブリングすることにより脱水処理を促進することが好ましい。ここで、上述した水の蒸発による発泡が終了した液には、まだ水分が０．１ｖ％以上のレベルで残存している。そして、本発明者等のけんとうによれば、場合により加熱温度を１５０℃程度（例えば、１５０℃±２０℃の範囲）まで高めたり、不活性ガスの同時バブリングにより脱水を促進する工夫をさらに施すことで、使用目的に合わせた必要なレベルまで水分含有量を低下させることが可能であることが見出されたのである。 In the method for producing a fluoride ion conductive organic electrolytic solution of the present embodiment, water may be additionally removed by further raising the heating temperature and continuing the heat treatment after the time when the foaming due to the evaporation of water is completed. This is a preferred form (second form). When the additional water is removed by continuing the heat treatment, it is preferable to promote the dehydration treatment by bubbling the inert gas. Here, in the above-mentioned liquid in which foaming due to evaporation of water is completed, water still remains at a level of 0.1 v% or more. Then, according to the present inventors, in some cases, the heating temperature may be raised to about 150 ° C. (for example, in the range of 150 ° C. ± 20 ° C.), or the simultaneous bubbling of the inert gas may be further devised to promote dehydration. Therefore, it was found that it is possible to reduce the water content to the required level according to the purpose of use.
また、本実施形態のフッ化物イオン伝導性有機電解液の製造方法では、フッ化物イオン伝導性有機電解液に共溶解可能な任意のリチウム塩および／またはバリウム塩を、α位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒に溶解させてリチウム塩および／またはバリウム塩の溶液を作製し、前記リチウム塩および／またはバリウム塩の溶液と、上記第１又は第２形態の製造方法により得られたフッ化物イオン伝導性有機電解液を所定の比率で混合して希釈し、さらに前記有機溶媒で所望の濃度になるように希釈してもよい。すなわち、本発明のさらに他の形態によれば、上述したフッ化物イオン伝導性有機電解液の製造方法によってフッ化物イオン伝導性有機電解液を作製することと、フッ化物イオン伝導性有機電解液に共溶解可能なリチウム塩および／またはバリウム塩がα位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒に溶解した溶液を前記フッ化物イオン伝導性有機電解液と混合して混合溶液（本明細書中、「第２の混合溶液」ともいう）を得ることと、前記第２の混合溶液を前記有機溶媒で希釈することを含むフッ化物イオン伝導性有機電解液の製造方法もまた、提供される。 Further, in the method for producing a fluoride ion conductive organic electrolytic solution of the present embodiment, any lithium salt and / or barium salt co-dissolvable in the fluoride ion conductive organic electrolytic solution is used as an ester-based ester having hydrogen at the α-position. Alternatively, a solution of a lithium salt and / or a barium salt is prepared by dissolving it in a lactone-based single or mixed organic solvent, and the solution of the lithium salt and / or barium salt is obtained by the above-mentioned production method of the first or second form. The obtained fluoride ion conductive organic electrolytic solution may be mixed and diluted at a predetermined ratio, and further diluted with the organic solvent to a desired concentration. That is, according to still another embodiment of the present invention, the fluoride ion conductive organic electrolyte solution can be produced by the above-mentioned method for producing a fluoride ion conductive organic electrolyte solution, and the fluoride ion conductive organic electrolyte solution can be used. A mixed solution in which a co-dissolvable lithium salt and / or barium salt is dissolved in an ester-based or lactone-based single or mixed organic solvent having α-hydrogen is mixed with the fluoride ion conductive organic electrolytic solution (the present). Also provided is a method for producing a fluoride ion conductive organic electrolyte solution, which comprises obtaining (also referred to as "second mixed solution") in the specification and diluting the second mixed solution with the organic solvent. Will be done.
ここで、リチウム塩およびバリウム塩は、解離溶解したアルカリ金属フッ化物の濃度に対して、いずれも５倍以上の濃度で混合することが望ましい。これは、広い電位領域で様々な金属電極のフッ化・脱フッ化反応を可能にするフッ化物イオン伝導性有機電解液の製造方法では、フッ化物イオン伝導性有機電解液に共溶解可能な任意のリチウム電解液が、アルミニウム、ランタン、セリウム、マグネシウムなどの反応が期待される負高電位領域でフッ化物イオンとその他の溶液種が複雑に関与した不可逆還元反応を引き起こすことがない点で優れている。フッ化物イオン伝導性有機電解液に共溶解可能な任意のリチウム塩および／またはバリウム塩に関しては、上記フッ化物イオン伝導性有機電解液の形態で説明した通りである。 Here, it is desirable that the lithium salt and the barium salt are mixed at a concentration of 5 times or more the concentration of the dissociated and dissolved alkali metal fluoride. This is an arbitrary method for producing a fluoride ion conductive organic electrolyte solution that enables a fluoride / defluorination reaction of various metal electrodes in a wide potential region, and is co-dissolvable in a fluoride ion conductive organic electrolyte solution. Lithium electrolyte is excellent in that it does not cause a complex irreversible reduction reaction involving fluoride ions and other solution species in the negative high potential region where reactions such as aluminum, lantern, cerium and magnesium are expected. There is. Any lithium salt and / or barium salt that can be co-dissolved in the fluoride ion conductive organic electrolyte is as described above in the form of the fluoride ion conductive organic electrolyte.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.
以下に実施例と比較例を示して本発明をさらに具体的に説明する。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
［実施例１］
＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液
＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液は、γ−ブチロラクトンと、セシウムカチオンおよびフッ化物イオンを有するフッ化セシウムと、を含有するフッ化物イオン伝導性有機電解液であり、多段階の溶解処理を経て、代表的なアルカリ金属フッ化物であるフッ化セシウム（ＣｓＦ）がγ−ブチロラクトン（ＧＢＬ）溶媒中に単純溶媒和イオン化解離した電解液である。ただし該溶解処理によって溶媒自身の有意な改質が生じている可能性を示すため、電解液を構成する溶媒名として以後純ＧＢＬ溶媒と区別したＲＢＬ（Ｒｅｆｏｒｍｅｄ Ｂｕｔｙｒｏｌａｃｔｏｎｅ）の名称を用いる。また溶解処理が最小限必要なステップのみを経ていることを示すために、＜ステージＩ＞という調整法類別のための表記を語頭に追加した。詳細には、＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液は、以下のように「多段階の溶解処理を経て」作製した。まず、ＣｓＦを純水に加えて撹拌混合して溶解し、ＣｓＦの１．４Ｍ水溶液を作製した。次に、過剰のＧＢＬと、ＣｓＦの１．４Ｍ水溶液と、を１０：１（体積比）で混合して混合液（混合液中約０．１３ＭのＣｓＦ）を作製し、攪拌加熱した。上記混合液を攪拌加熱すると、液温が１１０℃付近で水の蒸発による発泡が始まり、１２０℃付近でこの定常的な蒸発（による発泡）が続くような加熱条件を設定することで、１０分程度で水がほぼ全て蒸発し発泡が収まった。この発泡が収まった液を、＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液として得た。なお、作業雰囲気は大気中とした。
[Example 1]
<Stage I> CsF / RBL electrolytic solution <Stage I> CsF / RBL electrolytic solution is a fluoride ion conductive organic electrolytic solution containing γ-butyrolactone and cesium fluoride having a cesium cation and a fluoride ion. This is an electrolytic solution in which cesium fluoride (CsF), which is a typical alkali metal fluoride, is simply solvent-harmonized and dissociated in a γ-butyrolactone (GBL) solvent after undergoing a multi-step dissolution treatment. However, in order to show the possibility that the solvent itself is significantly modified by the dissolution treatment, the name of RBL (Reformed Butyrolactone), which is distinguished from the pure GBL solvent, is used as the name of the solvent constituting the electrolytic solution. In addition, a notation for categorizing the adjustment method called <Stage I> was added to the beginning of the word to indicate that the dissolution treatment has undergone only the minimum necessary steps. Specifically, the <Stage I> CsF / RBL electrolyte was prepared "through a multi-step dissolution process" as follows. First, CsF was added to pure water, stirred and mixed to dissolve, and a 1.4 M aqueous solution of CsF was prepared. Next, excess GBL and a 1.4 M aqueous solution of CsF were mixed at a ratio of 10: 1 (volume ratio) to prepare a mixed solution (about 0.13 M CsF in the mixed solution), and the mixture was stirred and heated. When the above mixed solution is stirred and heated, foaming due to evaporation of water starts at a liquid temperature of around 110 ° C., and this steady evaporation (foaming due to) continues at around 120 ° C. for 10 minutes. Almost all of the water evaporated and the foaming subsided. A liquid in which this foaming was contained was obtained as a <stage I> CsF / RBL electrolytic solution. The working atmosphere was in the atmosphere.
＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液の室温でのイオン伝導度の実測値は０．６〜０．８ｍＳ／ｃｍであった。また原子吸光法で定量したＣｓの重量濃度をもとに、等モル量のフッ化物イオンが溶解していると仮定して計算したフッ化物イオンのモル濃度の平均値は５０ｍＭであった。この値は後述するＮＭＲスペクトルの情報とも合致している。また該電解液を調製直後の残留水分の実測値は１００ｐｐｍ未満であった。当該溶媒中の１００ｐｐｍの水分はモル濃度にして約５ｍＭに相当する。 <Stage I> The measured value of the ionic conductivity of the CsF / RBL electrolytic solution at room temperature was 0.6 to 0.8 mS / cm. The average molar concentration of fluoride ions calculated on the assumption that an equal molar amount of fluoride ions was dissolved was 50 mM based on the weight concentration of Cs quantified by the atomic absorption method. This value also matches the information of the NMR spectrum described later. Further, the measured value of the residual water immediately after preparing the electrolytic solution was less than 100 ppm. The water content of 100 ppm in the solvent corresponds to about 5 mM in molar concentration.
＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液の成分分析のため５３２ｎｍ励起ラマンスペクトルを測定したところ、純ＧＢＬ溶媒のそれと完全に重なり両者を区別することはできなかった。そこでラマン分光法よりも感度の高いＦＴ−ＩＲスペクトルを測定したところ、図２に示す結果となり、ＯＨ伸縮振動に相当する高波数領域にのみ純ＧＢＬでは見られないピークが認められた。なお純ＧＢＬで測定した参照スペクトルで同領域に見える小さなピークはカルボニル伸縮振動の倍音であり、また２４００ｃｍ−１付近の信号は大気中の二酸化炭素によるバックグラウンド信号である。＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液のスペクトルではこの部分がバックグラウンド二酸化炭素量の変動のために負のピークとして現れている。 <Stage I> When the 532 nm excited Raman spectrum was measured for component analysis of the CsF / RBL electrolytic solution, it completely overlapped with that of the pure GBL solvent and the two could not be distinguished. Therefore, when the FT-IR spectrum, which is more sensitive than Raman spectroscopy, was measured, the results shown in FIG. 2 were obtained, and a peak not seen in pure GBL was observed only in the high frequency region corresponding to the OH expansion and contraction oscillation. In the reference spectrum measured by pure GBL, the small peak seen in the same region is the overtone of the carbonyl expansion and contraction vibration, and the signal near 2400 cm -1 is the background signal due to carbon dioxide in the atmosphere. <Stage I> In the spectrum of the CsF / RBL electrolyte, this portion appears as a negative peak due to fluctuations in the amount of background carbon dioxide.
上記の成分の正体を明らかにするため、また溶解解離したフッ化セシウムの状態と濃度に関する情報を得るために１Ｈ、１３Ｃ、１９Ｆ、および１３３Ｃｓの４種類のＮＭＲスペクトルを測定した。測定結果を図３に示す。予想どおり、１Ｈおよび１３Ｃスペクトルから、純ＧＢＬ溶媒中には存在しない化学種が１％未満の濃度で存在することがわかった。ＧＣ−ＭＳ法でさらに詳しく分析したところ、この化学種の正体はＧＢＬの加水分解で生成するγ−ヒドロキシ酪酸（分子量１０４）であることがわかった。その濃度は最大で約０．５ｗｔ％、モル濃度に換算すると約５０ｍＭとなり、解離溶解しているＣｓＦのモル濃度に匹敵する。ただし、後述する＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液の分析結果からも証明されるように、該γ−ヒドロキシ酪酸は副次的な生成物に過ぎず、ＣｓＦの解離溶解には関与していない。 Four types of NMR spectra of 1 H, 13 C, 19 F, and 133 Cs were measured in order to clarify the identity of the above components and to obtain information on the state and concentration of cesium fluoride that had been dissolved and dissociated. The measurement results are shown in FIG. As expected, the 1 H and 13 C spectra showed that there were less than 1% concentrations of chemical species that were not present in the pure GBL solvent. Further detailed analysis by the GC-MS method revealed that the true identity of this species was γ-hydroxybutyric acid (molecular weight 104) produced by hydrolysis of GBL. Its concentration is about 0.5 wt% at the maximum, which is about 50 mM when converted to molar concentration, which is comparable to the molar concentration of dissociated and dissolved CsF. However, as evidenced by the analysis results of the <Stage II> CsF / RBL electrolyte solution described later, the γ-hydroxybutyric acid is only a by-product and is not involved in the dissociation and dissolution of CsF. ..
図３に併せて示した１９Ｆと１３３ＣｓのＮＭＲスペクトルは実測された解離ＣｓＦ濃度と合致する強度のシグナルを与える。また、１９Ｆスペクトルは該電解液に特徴的な化学シフト値である−１５０ｐｐｍ付近に数本のピークを示し、フッ化物イオンの溶媒和の状態が必ずしも一様ではないことを示唆する。 The NMR spectra of 19 F and 133 Cs shown together with FIG. 3 give an intensity signal that matches the measured dissociated CsF concentration. In addition, the 19 F spectrum shows several peaks around -150 ppm, which is a chemical shift value characteristic of the electrolytic solution, suggesting that the solvation state of fluoride ions is not always uniform.
＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液の電位窓の広さと各種金属のフッ化・脱フッ化反応に対する可逆性を評価するために、銀線を参照極、白金メッシュを対極とした三極セルでＣＶ（サイクリックボルタンメトリー）波形を測定したところ、亜鉛から金に至る広い電位範囲で、Ｍ＋ｎＦ−⇔ＭＦｎ＋ｎｅ−（Ｍは金属元素を表す）、の反応に対応する電位領域に可逆的な応答が見出された（図４）。図４には示していないが、その他Ｐｂ、Ｂｉ、Ｉｎ、Ｔｉなど、Ｚｎより貴なほぼ全ての金属でも同様な応答が確認された。電位窓の広さは少なくとも３Ｖ以上で、フッ化物イオン電池に必要な電解液の条件を満たしていることがわかった。 <Stage I> In order to evaluate the width of the potential window of the CsF / RBL electrolyte and the reversibility of various metals to the fluorination / defluorination reaction, a triode cell with a silver wire as a reference electrode and a platinum mesh as a counter electrode was used. When the CV (cyclic voltammetry) waveform was measured, a reversible response was made to the potential region corresponding to the reaction of M + nF − ⇔ MF n + ne − (M represents a metal element) in a wide potential range from zinc to gold. Was found (Fig. 4). Although not shown in FIG. 4, a similar response was confirmed for almost all metals noble than Zn, such as Pb, Bi, In, and Ti. It was found that the width of the potential window was at least 3 V or more, which satisfied the conditions of the electrolytic solution required for the fluoride ion battery.
次にモデル電池としてＩＴＯ基板上に平均厚さが、わずか２７ｎｍの銀超薄膜をスパッタ成膜したものを正極、亜鉛線を対極とした二極セルを作製し、充放電試験を行った結果を図５に示す。成膜された銀の重量はごくわずかなので、ここで使用した５μＡの電流値でも充放電レートは非常に大きくなる。それにも拘わらず、充電時間を延長した場合に銀の理論容量にほぼ等しい容量と、ほぼ１００％に近いクーロン効率が得られた。フッ化物イオン電池の電解液として、該電解液が非常に優れた特性を有することを示す端的な事例である。 Next, as a model battery, a bipolar cell having a positive electrode and a zinc wire as a counter electrode was prepared by sputtering a silver ultrathin film having an average thickness of only 27 nm on an ITO substrate, and a charge / discharge test was performed. It is shown in FIG. Since the weight of the formed silver is very small, the charge / discharge rate becomes very large even with the current value of 5 μA used here. Nevertheless, when the charging time was extended, a capacity almost equal to the theoretical capacity of silver and a Coulomb efficiency close to 100% were obtained. This is a simple example showing that the electrolytic solution has very excellent characteristics as an electrolytic solution of a fluoride ion battery.
［実施例２］
＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液
＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液は、＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液にさらに追加処理を加えて、前述の副次物や水分濃度をさらに低下させた電解液である。しかし該電解液の室温でのイオン伝導度の実測値は０．６〜０．８ｍＳ／ｃｍの範囲にあり、ステージＩとほぼ等価であった。図６に示した該電解液のＦＴ−ＩＲスペクトルでは、図２で見られた高波数ピークは消失し、純ＧＢＬに相当する参照スペクトルと全く区別がつかなくなったことから、副次物の濃度が激減していることがわかる。詳細には、＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液は、以下のように、＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液にさらに追加加熱の条件を厳しくした「追加処理を加えて」作製した。まず、実施例１で作製した＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液を、さらに攪拌加熱を加熱温度(液温）を１５０℃程度まで高めて、１０分程度追加加熱を行ったものを＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液とした。なお、作業雰囲気は大気中とした。
[Example 2]
<Stage II> CsF / RBL electrolytic solution <Stage II> CsF / RBL electrolytic solution further reduced the above-mentioned by-products and water concentration by further adding treatment to the <Stage I> CsF / RBL electrolytic solution. It is an electrolytic solution. However, the measured value of the ionic conductivity of the electrolytic solution at room temperature was in the range of 0.6 to 0.8 mS / cm, which was almost equivalent to that of Stage I. In the FT-IR spectrum of the electrolytic solution shown in FIG. 6, the high frequency peak seen in FIG. 2 disappeared, and it became completely indistinguishable from the reference spectrum corresponding to pure GBL. Can be seen to have decreased sharply. Specifically, the <Stage II> CsF / RBL electrolytic solution was prepared by "adding an additional treatment" to the <Stage I> CsF / RBL electrolytic solution with stricter additional heating conditions as follows. First, the <Stage I> CsF / RBL electrolytic solution prepared in Example 1 was further heated by stirring and heating to a heating temperature (liquid temperature) of about 150 ° C., and further heated for about 10 minutes in <Stage II. > CsF / RBL electrolyte was used. The working atmosphere was in the atmosphere.
この事実は、図７に示した＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液のＮＭＲスペクトルからも確認できる。特に１３ＣのＮＭＲスペクトルには拡大スケールを用いても副次物の信号は認められない。一方、１９Ｆと１３３ＣｓのＮＭＲスペクトルにはステージＩのそれと比べて大きな差は見当たらず、１９Ｆスペクトルの特徴的な化学シフトの値も同じ範囲にある。 This fact can also be confirmed from the NMR spectrum of the <Stage II> CsF / RBL electrolytic solution shown in FIG. In particular, no by-product signal is observed in the 13 C NMR spectrum even when the magnifying scale is used. On the other hand, the NMR spectra of 19 F and 133 Cs did not show a large difference from those of stage I, and the characteristic chemical shift values of the 19 F spectra were also in the same range.
また、該電解液を純ＧＢＬ溶媒で様々な濃度に希釈したときのイオン伝導度とモル濃度の１／２乗（平方根）の関係を調べたところ、図８のように低濃度領域で良好な直線関係（Ｋｏｈｌｒａｕｓｈ平方根則）の成立を確認できた。これは該電解液中で解離溶解したＣｓＦが強電解質として振舞うことを意味しており、ＣｓＦが単純溶媒和イオン化解離して該電解液のイオン伝導性を担っていることを間接的に証明している。 Further, when the relationship between the ionic conductivity and the molar concentration to the 1/2 power (square root) when the electrolytic solution was diluted with a pure GBL solvent to various concentrations was investigated, it was found to be good in the low concentration region as shown in FIG. We were able to confirm the establishment of a linear relationship (Kohllution square root rule). This means that CsF dissociated and dissolved in the electrolytic solution behaves as a strong electrolyte, indirectly demonstrating that CsF undergoes simple solvation ionization dissociation and is responsible for the ionic conductivity of the electrolytic solution. ing.
また、該電解液のフッ化物イオン電池用電解液としての特性は、ステージＩのそれと殆ど差はなく、後者に含まれていた副次成分がＣｓＦの溶解解離そのものにも、電気化学的な特性にも、全く関与していないことを証明している。 Further, the characteristics of the electrolytic solution as an electrolytic solution for a fluoride ion battery are almost the same as those of stage I, and the secondary component contained in the latter is also an electrochemical characteristic in the dissolution dissociation of CsF itself. Also proves that he is not involved at all.
さらに、図８のような希釈により実質的なフッ化物イオンの濃度が数ｍＭに低下した電解液を用いた場合にも、図４と同様な可逆動作の発現を確認することができた。すなわち該電解液中でのフッ化物イオン濃度が製造時の１割程度に低下した系でもフッ化物イオン電池の動作は持続する。 Furthermore, even when an electrolytic solution in which the substantial concentration of fluoride ions was reduced to several mM by dilution as shown in FIG. 8 was used, the same reversible operation as in FIG. 4 could be confirmed. That is, the operation of the fluoride ion battery is maintained even in a system in which the fluoride ion concentration in the electrolytic solution is reduced to about 10% at the time of production.
［実施例３］
＜ステージＩＩ＞ＫＦ／ＲＢＬ電解液
＜ステージＩＩ＞ＫＦ／ＲＢＬ電解液は、γ−ブチロラクトンと、カリウムカチオンおよびフッ化物イオンを有するフッ化カリウムと、を含有するフッ化物イオン伝導性有機電解液であり、アルカリ金属フッ化物としてＫＦを用いた以外は＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液と同じ製法で調製した電解液である。＜ステージＩＩ＞ＣｓＦ／ＲＢＬ電解液と比べた場合、室温でのイオン伝導度の実測値は約０．３ｍＳ／ｃｍとなり、フッ化物イオン濃度も有意に減少したが、フッ化物イオン電池を動作させる性能にほとんど差は確認できなかった。
[Example 3]
<Stage II> KF / RBL Electrolyte <Stage II> KF / RBL Electrolyte is a fluoride ion conductive organic electrolyte containing γ-butyrolactone and potassium fluoride having potassium cation and fluoride ions. Yes, it is an electrolytic solution prepared by the same production method as the <Stage II> CsF / RBL electrolytic solution except that KF is used as the alkali metal fluoride. <Stage II> Compared with the CsF / RBL electrolyte, the measured value of ionic conductivity at room temperature was about 0.3 mS / cm, and the fluoride ion concentration was significantly reduced, but the fluoride ion battery was operated. Almost no difference in performance could be confirmed.
また図９に示したように、該電解液の１９Ｆ−ＮＭＲスペクトルが−１５０ｐｐｍ付近にＣｓＦ／ＲＢＬ電解液と同様な複数のピークを与えることも確認できた。 Further, as shown in FIG. 9, it was also confirmed that the 19 F-NMR spectrum of the electrolytic solution gives a plurality of peaks similar to those of the CsF / RBL electrolytic solution in the vicinity of −150 ppm.
［実施例４］
＜ステージＩ＞ＣｓＦ／ε−カプロラクトン電解液
＜ステージＩ＞ＣｓＦ／ε−カプロラクトン電解液は、ε−カプロラクトンと、セシウムカチオンおよびフッ化物イオンを有するフッ化セシウムと、を含有するフッ化物イオン伝導性有機電解液であり、α位水素を有するエステル系／ラクトン系溶媒としてラクトン系に属する他の代表的な溶媒であるε−カプロラクトンを用いた以外は＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液と同じ製法で調製した電解液である。室温でのイオン伝導度の実測値は約０．１５ｍＳ／ｃｍまで低下したが、フッ化物イオン電池を動作させる作用は十分であった。
[Example 4]
<Stage I> CsF / ε-caprolactone electrolyte <Stage I> CsF / ε-caprolactone electrolyte contains fluoride ion conductivity containing ε-caprolactone and cesium fluoride having cesium cations and fluoride ions. The same production method as <Stage I> CsF / RBL electrolyte except that it is an organic electrolyte and ε-caprolactone, which is another typical solvent belonging to the lactone system, is used as the ester / lactone-based solvent having α-hydrogen. It is an electrolytic solution prepared in. The measured value of the ionic conductivity at room temperature decreased to about 0.15 mS / cm, but the action of operating the fluoride ion battery was sufficient.
［実施例５］
広い電位領域で様々な金属電極のフッ化・脱フッ化反応を可能にするＣｓＦ／ＲＢＬ電解液は、アルミニウム、ランタン、セリウム、マグネシウムなどの反応が期待される負高電位領域ではフッ化物イオンとその他の溶液種が複雑に関与した不可逆還元反応を引き起こす。この問題はリチウム塩としてＬｉＦＳＡ、ＬｉＴＦＳＡ、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣｌＯ４のいずれかもしくはそれらの混合物を解離溶解したアルカリ金属フッ化物の濃度に対して少なくとも５倍以上の濃度で混合することにより解決できる。
[Example 5]
The CsF / RBL electrolyte, which enables the fluoride / defluorination reaction of various metal electrodes in a wide potential region, contains fluoride ions in the negative high potential region where reactions such as aluminum, lantern, cerium, and magnesium are expected. Other solution species cause complex irreversible reduction reactions. This problem is solved by mixing LiFSA, LiTFSA, LiBF 4 , LiPF 6 , LiClO 4 or a mixture thereof as a lithium salt at a concentration of at least 5 times or more the concentration of the alkali metal fluoride dissociated and dissolved. it can.
図１０は、一例として純ＧＢＬ溶媒にリチウム塩としてＬｉＴＦＳＡを２Ｍの濃度で溶解させたＬｉ塩溶液と＜ステージＩ＞ＣｓＦ／ＲＢＬ電解液を１：３の容量比で混合した電解液をさらにＧＢＬで３倍に希釈した電解液（ε−カプロラクトンと、セシウムカチオンおよびフッ化物イオンを有するフッ化セシウムと、ＬｉＴＦＳＡと、を含有するフッ化物イオン伝導性有機電解液）中で、アルミニウム薄板を作用極として測定したＣＶ波形である。銀参照電位基準で−２Ｖ付近にＣｓＦ／ＲＢＬ電解液単独では得られない可逆アノードピークが発現し、また電流値がゼロを横切る動的平衡電位はアルミニウムのフッ化・脱フッ化理論平衡電位とほぼ一致した。 In FIG. 10, as an example, an electrolytic solution obtained by mixing a Li salt solution prepared by dissolving LiTFSA as a lithium salt in a pure GBL solvent at a concentration of 2M and a <stage I> CsF / RBL electrolytic solution at a volume ratio of 1: 3 is further added to GBL. In the electrolytic solution diluted 3-fold with (ε-caprolactone, fluoride ion conductive organic electrolytic solution containing cesium fluoride having cesium cation and fluoride ion, and LiTFSA), the aluminum thin plate was used as a working electrode. It is a CV waveform measured as. A reversible anode peak that cannot be obtained by CsF / RBL electrolyte alone appears near -2V based on the silver reference potential, and the dynamic equilibrium potential at which the current value crosses zero is the fluorination / defluorination theoretical equilibrium potential of aluminum. It almost matched.
この有用な混合効果は総合的に見てリチウム塩に特有のものであり、Ｌｉ＋カチオンとＦ−アニオンとの特殊な相互作用を通じて、フッ化物イオンの反応性が好ましい形で制御されることに基づく。ただし、以下の実施例を参照すると、バリウム塩の添加によっても限定的ではあるが類似の効果が得られる。 This useful mixing effect is generally unique to lithium salts, and the reactivity of fluoride ions is preferably controlled through a special interaction between the Li + cation and the F -anion. Based on. However, referring to the following examples, the addition of barium salt also has a limited but similar effect.
［実施例６］
Ｂａ塩混合ＣｓＦ／ＲＢＬ電解液
リチウム塩のＬｉＴＦＳＡに替えてバリウム塩のＢａＴＦＳＡ塩を用いた以外は実施例５と同様な混合電解液としてＢａ塩混合ＣｓＦ／ＲＢＬ電解液（ε−カプロラクトンと、セシウムカチオンおよびフッ化物イオンを有するフッ化セシウムと、ＢａＴＦＳＡと、を含有するフッ化物イオン伝導性有機電解液）を作製した。混合後のＢａＴＦＳＡ濃度は０．５Ｍ、ＣｓＦ濃度は０．０１７Ｍであった。アルミニウム薄板を作用極として測定したＣＶ波形と同じ濃度のＣｓＦのみを含む電解液で測定したＣＶ波形を比較した結果を図１１に示す。図１０とは異なり、可逆アノードピークの発現は認められなかったが、ＣｓＦ単独電解液での顕著な不可逆還元電流は著しく抑制されていることがわかる。
[Example 6]
Ba salt mixed CsF / RBL electrolytic solution Ba salt mixed CsF / RBL electrolytic solution (ε-caprolactone and cesium) as a mixed electrolytic solution similar to Example 5 except that BaTFSA salt of barium salt was used instead of LiTFSA of lithium salt. A fluoride ion conductive organic electrolyte solution containing cesium fluoride having cations and fluoride ions and BaTFSA) was prepared. The BaTFSA concentration after mixing was 0.5 M, and the CsF concentration was 0.017 M. FIG. 11 shows a result of comparing the CV waveform measured with the electrolytic solution containing only CsF having the same concentration as the CV waveform measured with the aluminum thin plate as the working electrode. Unlike FIG. 10, the expression of the reversible anode peak was not observed, but it can be seen that the remarkable irreversible reduction current in the CsF single electrolytic solution was remarkably suppressed.
［比較例１］
ＣｓＦ／ＰＣ：ＥＣ電解液
Ｌｉイオン電池に用いられる代表的な非水有機溶媒を使用した比較例として、ＧＢＬと分子構造は類似しているがα位の水素を持たないＰＣ（プロピレンカーボネート）とＥＣ（エチレンカーボネート）の１：１（容量比）の混合溶媒を用いて、ＣｓＦ／ＲＢＬ電解液と同じ製法でＣｓＦが解離溶解した電解液（ＣｓＦ／ＰＣ：ＥＣ電解液）を作製した。その室温でのイオン伝導度の実測値は１．２ｍＳ／ｃｍという、ラクトン系よりも高い値を示した。
[Comparative Example 1]
CsF / PC: EC electrolyte As a comparative example using a typical non-aqueous organic solvent used in Li-ion batteries, PC (propylene carbonate) having a molecular structure similar to that of GBL but not having hydrogen at the α-position was used. An electrolytic solution (CsF / PC: EC electrolytic solution) in which CsF was dissociated and dissolved was prepared by the same production method as the CsF / RBL electrolytic solution using a 1: 1 (volume ratio) mixed solvent of EC (ethylene carbonate). The measured value of the ionic conductivity at room temperature was 1.2 mS / cm, which was higher than that of the lactone type.
しかしながら、該電解液についてやはり４種類のＮＭＲスペクトルを測定したところ、図１２に示したように、１Ｈと１３Ｃのスペクトルに溶媒分子以外の副次物が溶媒自身の約１割もの強度で観測された。モル濃度に換算すると数Ｍに近い異常に高い濃度である。 However, the measured again four NMR spectrum of the electrolyte solution, as shown in FIG. 12, secondary product other than the solvent molecules in the spectrum of the 1 H and 13 C are in strength as about 10% of the solvent itself It was observed. When converted to molar concentration, it is an abnormally high concentration close to several meters.
この時、１９Ｆ（図１２）のスペクトルは比較的低磁場側に１本、また異常に高い高磁場側に別の１本のピークを示した。フッ化物イオンと副次物の間の複雑な相互作用を反映したもので、この相互作用を介してＣｓＦの解離溶解が進行したものと推定される。 At this time, the spectrum of 19 F (FIG. 12) showed one peak on the relatively low magnetic field side and another peak on the abnormally high high magnetic field side. It reflects the complex interaction between fluoride ions and by-products, and it is presumed that the dissociation and dissolution of CsF proceeded through this interaction.
白金電極を作用極として該電解液の電位窓の広さを確認した結果を図１３に示す。銀参照極に対し負電位側では約−１Ｖまで、正電位側では約１Ｖまでの広さしかなく、亜鉛極の可逆動作はもちろん、この電位窓の中に入る銀正極の反応の可逆性も不十分であった。多量に存在する副次物が関与した不可逆的な酸化および還元反応が原因と推定される。 FIG. 13 shows the result of confirming the width of the potential window of the electrolytic solution using the platinum electrode as the working electrode. The negative potential side has a range of up to about -1V and the positive potential side has a range of up to about 1V with respect to the silver reference electrode. Not only the reversible operation of the zinc electrode, but also the reversibility of the reaction of the silver positive electrode entering this potential window. It was inadequate. It is presumed that the cause is an irreversible oxidation and reduction reaction involving a large amount of by-products.
［比較例２］
ＣｓＦ／グルタル酸／ＧＢＬ電解液
非水有機溶媒にアルカリ金属フッ化物を溶解させる別の手法としては、アニオンアクセプターを利用する先行例の他にも、アルカリ金属カチオンに強く配位する分子（カチオンアクセプター）を用いる方法が考えられる。その一例としてジカルボン酸の一種であるグルタル酸を０．３Ｍの濃度でＧＢＬに溶解させた液にＣｓＦを飽和溶解させた電解液を作製した。
[Comparative Example 2]
CsF / Gluteric Acid / GBL Electrolyte As another method for dissolving alkali metal fluoride in a non-aqueous organic solvent, in addition to the previous example using an anion acceptor, a molecule (cation) that strongly coordinates with an alkali metal cation. A method using an acceptor) can be considered. As an example, an electrolytic solution in which CsF was saturated and dissolved in a solution in which glutaric acid, which is a kind of dicarboxylic acid, was dissolved in GBL at a concentration of 0.3 M was prepared.
該電解液の室温でのイオン伝導度は０．５ｍＳ／ｃｍという比較的高い値を示し、図１４に示したＮＭＲスペクトルもＣｓＦの解離溶解を裏付けるが、１９ＦスペクトルはＣｓＦ／ＲＢＬ電解液とは明確に異なる−１３５ｐｐｍの位置に１本の主要なピークを与えた。 The ionic conductivity of the electrolytic solution at room temperature shows a relatively high value of 0.5 mS / cm, and the NMR spectrum shown in FIG. 14 also supports the dissociation and dissolution of CsF, but the 19 F spectrum is the same as that of the CsF / RBL electrolytic solution. Gave one major peak at a distinctly different -135 ppm position.
さらに比較例１の電解液と同様に、電位窓の広さは高々２Ｖしかなく、亜鉛負極を動作させることはできなかった。該電位窓の中に入る銀正極の反応の可逆性も不十分であった。添加物としてのグルタル酸自身の不可逆的な酸化および還元反応が原因と推定される。 Further, as in the electrolytic solution of Comparative Example 1, the width of the potential window was only 2 V at the most, and the zinc negative electrode could not be operated. The reversibility of the reaction of the silver positive electrode entering the potential window was also insufficient. It is presumed that the cause is the irreversible oxidation and reduction reaction of glutaric acid itself as an additive.
［比較例３］
Ｌｉ塩以外の塩の混合効果
ＮａＦＳＡやＫＦＳＡなど、アニオン種は共通でカチオン種がＬｉ以外の塩をＣｓＦ／ＲＢＬ電解液に混合したところ、負高電位領域での不可逆的還元電流を抑制することはできなかった。さらに比較例１の電解液と同様に、電位窓の広さは高々２Ｖしかなく、亜鉛負極を動作させることはできなかった。
[Comparative Example 3]
Mixing effect of salts other than Li salt Common anion species such as NaFSA and KFSA When a salt other than Li is mixed with a CsF / RBL electrolyte, the irreversible reduction current in the negative high potential region is suppressed. I couldn't. Further, as in the electrolytic solution of Comparative Example 1, the width of the potential window was only 2 V at the most, and the zinc negative electrode could not be operated.
１…負極活物質の還元（金属）層、
２…負極活物質のフッ化物層、
３…電解液層、
４…正極活物質のフッ化物層、
５…正極活物質の還元（金属）層。
1 ... Reduction (metal) layer of negative electrode active material,
2 ... Fluoride layer of negative electrode active material,
3 ... Electrolyte layer,
4 ... Fluoride layer of positive electrode active material,
5 ... Reduction (metal) layer of positive electrode active material.
Claims (16)
アルカリ金属カチオンおよびフッ化物イオンを有するアルカリ金属フッ化物と、を含有することを特徴とするフッ化物イオン伝導性有機電解液。 With an ester-based or lactone-based single or mixed organic solvent having hydrogen at the α-position,
A fluoride ion conductive organic electrolytic solution containing an alkali metal cation and an alkali metal fluoride having a fluoride ion.
α位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒と前記水溶液とを混合して第１の混合溶液を得ることと、
前記混合溶液に加熱処理を施すことにより水を除去して有機電解液を得ることと、
を含むことを特徴とするフッ化物イオン伝導性有機電解液の製造方法。 To obtain an aqueous solution by dissolving alkali metal fluoride in water,
To obtain a first mixed solution by mixing the aqueous solution with an ester-based or lactone-based single or mixed organic solvent having hydrogen at the α-position.
Water is removed by heat-treating the mixed solution to obtain an organic electrolytic solution.
A method for producing a fluoride ion conductive organic electrolytic solution, which comprises.
フッ化物イオン伝導性有機電解液に共溶解可能なリチウム塩および／またはバリウム塩がα位水素を有するエステル系もしくはラクトン系の単独もしくは混合有機溶媒に溶解した溶液を前記フッ化物イオン伝導性有機電解液と混合して第２の混合溶液を得ることと、
前記第２の混合溶液を前記有機溶媒で希釈することと、
を含むことを特徴とするフッ化物イオン伝導性有機電解液の製造方法。 To prepare a fluoride ion conductive organic electrolytic solution by the production method according to any one of claims 12 to 15,
The fluoride ion conductive organic electrolytic solution is prepared by dissolving a solution in which a lithium salt and / or barium salt co-dissolvable in a fluoride ion conductive organic electrolytic solution is dissolved in an ester-based or lactone-based single or mixed organic solvent having α-hydrogen. Mixing with the solution to obtain a second mixed solution,
Diluting the second mixed solution with the organic solvent and
A method for producing a fluoride ion conductive organic electrolytic solution, which comprises.
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