JP5748178B2 - Molten salt battery - Google Patents
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- JP5748178B2 JP5748178B2 JP2011255985A JP2011255985A JP5748178B2 JP 5748178 B2 JP5748178 B2 JP 5748178B2 JP 2011255985 A JP2011255985 A JP 2011255985A JP 2011255985 A JP2011255985 A JP 2011255985A JP 5748178 B2 JP5748178 B2 JP 5748178B2
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- negative electrode
- molten salt
- current collector
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- salt battery
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- 150000003839 salts Chemical class 0.000 title claims description 66
- 239000011248 coating agent Substances 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 22
- 239000003792 electrolyte Substances 0.000 claims description 22
- 239000011149 active material Substances 0.000 claims description 19
- 239000011734 sodium Substances 0.000 claims description 17
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 16
- 229910052708 sodium Inorganic materials 0.000 claims description 16
- -1 polytetrafluoroethylene Polymers 0.000 claims description 11
- 239000002033 PVDF binder Substances 0.000 claims description 10
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 10
- 229920005989 resin Polymers 0.000 claims description 10
- 239000011347 resin Substances 0.000 claims description 10
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 7
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 7
- 239000004642 Polyimide Substances 0.000 claims description 4
- 239000004743 Polypropylene Substances 0.000 claims description 4
- 229920003020 cross-linked polyethylene Polymers 0.000 claims description 4
- 239000004703 cross-linked polyethylene Substances 0.000 claims description 4
- 229920001721 polyimide Polymers 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- 239000004952 Polyamide Substances 0.000 claims description 3
- 229920002647 polyamide Polymers 0.000 claims description 3
- 239000011230 binding agent Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 9
- 239000007773 negative electrode material Substances 0.000 description 9
- 239000007774 positive electrode material Substances 0.000 description 8
- 238000007599 discharging Methods 0.000 description 7
- BNOODXBBXFZASF-UHFFFAOYSA-N [Na].[S] Chemical compound [Na].[S] BNOODXBBXFZASF-UHFFFAOYSA-N 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000006230 acetylene black Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 239000002482 conductive additive Substances 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 239000008151 electrolyte solution Substances 0.000 description 4
- 239000011888 foil Substances 0.000 description 4
- 239000003273 ketjen black Substances 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052718 tin Inorganic materials 0.000 description 4
- 229910052725 zinc Inorganic materials 0.000 description 4
- 239000011701 zinc Substances 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
- 229910001415 sodium ion Inorganic materials 0.000 description 3
- 239000007784 solid electrolyte Substances 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 239000004962 Polyamide-imide Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000005001 laminate film Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920002312 polyamide-imide Polymers 0.000 description 1
- 239000005373 porous glass Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- MHEBVKPOSBNNAC-UHFFFAOYSA-N potassium;bis(fluorosulfonyl)azanide Chemical compound [K+].FS(=O)(=O)[N-]S(F)(=O)=O MHEBVKPOSBNNAC-UHFFFAOYSA-N 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
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- VCCATSJUUVERFU-UHFFFAOYSA-N sodium bis(fluorosulfonyl)azanide Chemical compound FS(=O)(=O)N([Na])S(F)(=O)=O VCCATSJUUVERFU-UHFFFAOYSA-N 0.000 description 1
- PXLIDIMHPNPGMH-UHFFFAOYSA-N sodium chromate Chemical compound [Na+].[Na+].[O-][Cr]([O-])(=O)=O PXLIDIMHPNPGMH-UHFFFAOYSA-N 0.000 description 1
- GROMGGTZECPEKN-UHFFFAOYSA-N sodium metatitanate Chemical compound [Na+].[Na+].[O-][Ti](=O)O[Ti](=O)O[Ti]([O-])=O GROMGGTZECPEKN-UHFFFAOYSA-N 0.000 description 1
- HYHCSLBZRBJJCH-UHFFFAOYSA-N sodium polysulfide Chemical compound [Na+].S HYHCSLBZRBJJCH-UHFFFAOYSA-N 0.000 description 1
- 229910052979 sodium sulfide Inorganic materials 0.000 description 1
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- KAKQVSNHTBLJCH-UHFFFAOYSA-N trifluoromethanesulfonimidic acid Chemical compound NS(=O)(=O)C(F)(F)F KAKQVSNHTBLJCH-UHFFFAOYSA-N 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
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
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- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Description
本発明は、正極、負極及び溶融塩を備える溶融塩電池に関する。 The present invention relates to a molten salt battery including a positive electrode, a negative electrode, and a molten salt.
近年、太陽光、風力等の自然エネルギーを利用した発電が盛んに行われている。これらの自然エネルギーによる発電は、気候及び天候に左右される要素が多く、電力需要に合わせた発電量の調整ができないため、負荷に対する電力供給の平準化が不可欠となる。この平準化には電気エネルギーを充放電する必要があり、そのための手段として高エネルギー密度・高効率のナトリウム硫黄電池が用いられることがある。ナトリウム硫黄電池は、運用状態において正極活物質の硫黄及び多硫化ナトリウムと負極活物質のナトリウムとが高温で溶融しており、両活物質の間に介在する固体電解質が破損した場合であっても、これらの活物質が混じり合って急速に反応しないようにする必要がある。ナトリウム硫黄電池は、また、複数の単電池を組み合わせて大容量化されることが多い。 In recent years, power generation using natural energy such as sunlight and wind power has been actively performed. Since power generation using these natural energies has many factors that depend on the climate and the weather, and the amount of power generation cannot be adjusted to meet the power demand, it is essential to level the power supply to the load. For this leveling, it is necessary to charge and discharge electric energy, and a high energy density and high efficiency sodium-sulfur battery may be used as a means for that purpose. The sodium-sulfur battery is operated even when the positive electrode active material sulfur and sodium polysulfide and the negative electrode active material sodium are melted at high temperatures and the solid electrolyte interposed between the two active materials is damaged. It is necessary to prevent these active materials from mixing and reacting rapidly. Sodium-sulfur batteries are often increased in capacity by combining a plurality of single cells.
例えば、特許文献１では、ナトリウムイオン透過性の円筒袋状の固体電解質内に設けた安全管の内外に流動抵抗部材を充填することにより、安全管のクラックを通じて溶融ナトリウム極に流入する硫黄の流動速度を低下させ、更に安全管が高温腐食により破損した場合には、安全管の内部に硫黄及び硫化ナトリウムが混入する速度を減少させる技術が開示されている。 For example, in Patent Document 1, the flow of sulfur flowing into the molten sodium electrode through a crack in the safety tube by filling a flow resistance member inside and outside the safety tube provided in a sodium ion permeable cylindrical bag-shaped solid electrolyte. A technique is disclosed in which the speed is reduced, and when the safety pipe is broken due to high temperature corrosion, the speed at which sulfur and sodium sulfide are mixed into the safety pipe is reduced.
また、特許文献２では、多数のナトリウム硫黄電池を複数の電池ブロックに区分し、断熱容器内に各電池ブロックを着脱可能に収容することにより、組立時における単電池の組み付け、及び保守点検時における断熱容器内への単電池の脱着を容易にする技術が開示されている。更に、特許文献３では、ナトリウム硫黄電池の単電池を収容する収容容器の底部に活物質の通過溝を設けることにより、単電池から漏れ出た活物質を安全に溜めおく技術が開示されている。 In Patent Document 2, a large number of sodium-sulfur batteries are divided into a plurality of battery blocks, and each battery block is detachably housed in a heat insulating container, so that the unit cells can be assembled and assembled at the time of maintenance inspection. A technique for facilitating the detachment of the unit cell into the heat insulating container is disclosed. Furthermore, Patent Document 3 discloses a technique for safely storing an active material leaked from a single cell by providing a passage groove for the active material at the bottom of a container for housing a single cell of a sodium sulfur battery. .
特許文献１から３に開示されたナトリウム硫黄電池では、固体電解質として用いたアルミナセラミックスからなる収容容器に溶融したナトリウムが収容されており、セラミックスを用いることによる機械的な脆さを補うために、収容容器の形状を円筒状にせざるを得ないところがある。このため、複数の単電池を組み合わせた場合は、収容容器の径の大小に関わりなく一定の割合でデッドスペースが生じる結果となり、エネルギー密度がその分だけ小さくなる。 In the sodium-sulfur battery disclosed in Patent Documents 1 to 3, molten sodium is contained in a container made of alumina ceramics used as a solid electrolyte, and in order to compensate for mechanical brittleness due to the use of ceramics, There is a place where the shape of the storage container must be cylindrical. For this reason, when a plurality of unit cells are combined, a dead space is generated at a constant rate regardless of the diameter of the container, and the energy density is reduced accordingly.
これに対し特許文献４には、溶融塩を含む電解質をセパレータに含浸させて固定化し、正極及び負極で前記セパレータを挟持することによって、活物質の収容容器を不要にした溶融塩電池が開示されている。 On the other hand, Patent Document 4 discloses a molten salt battery in which an electrolyte containing a molten salt is impregnated in a separator and fixed, and the separator is sandwiched between a positive electrode and a negative electrode, thereby eliminating an active material container. ing.
本発明は、溶融塩電池のサイクル特性を従来のものより向上させ、寿命の長い溶融塩電池を提供することを課題とする。 An object of the present invention is to provide a molten salt battery having a longer life by improving the cycle characteristics of the molten salt battery compared to the conventional one.
本発明者等は上記課題を解決すべく鋭意探求を重ねた結果、電解質にナトリウムを含む溶融塩電池にあっては、充放電を繰り返す過程で電解液の一部が負極の裏面（正極、セパレータと向かい合う側の反対の面）にまで回り込み、該負極の裏面で合金化やナトリウム金属の析出といった反応が生じていること見出した。そして、この合金や析出したナトリウム金属は正極と離れているため放電時に使用されにくく、また一部が脱落することにより電池の不可逆容量の要因となっていることが分かった。更に、負極の集電体の周縁部や集電タブの電解質と接触している部分にもナトリウムが析出、合金化していることが見出された。 As a result of intensive investigations to solve the above-mentioned problems, the present inventors have found that in a molten salt battery containing sodium in the electrolyte, a part of the electrolyte solution is formed on the back surface of the negative electrode (positive electrode, separator) in the process of repeated charge and discharge. It was found that reactions such as alloying and precipitation of sodium metal occurred on the back surface of the negative electrode. It was found that this alloy and the deposited sodium metal are not used during discharging because they are separated from the positive electrode, and part of the alloy falls off causing irreversible capacity of the battery. Furthermore, it has been found that sodium is deposited and alloyed in the peripheral portion of the current collector of the negative electrode and the portion in contact with the electrolyte of the current collector tab.
そこで本発明者等はこれらの問題を解決すべく更なる検討を重ねた結果、以下の発明をするに至った。本発明は以下の構成を有する。
（１）正極と負極とがセパレータを介して配置され、電解質としてナトリウムを含む溶融塩を用いた溶融塩電池であって、
前記負極は集電体と、活物質と、集電タブと、を有してなり、
前記活物質は、前記集電体の少なくとも一部分に保持され、
前記集電体の活物質を保持されていない部分及び／又は前記集電タブに絶縁被膜が形成されており、
更に、前記絶縁被膜が、前記負極の集電体の前記正極と向かい合わない面に形成されていることを特徴とする溶融塩電池。
（２）前記絶縁被膜が、前記負極の集電体の端縁部に形成されていることを特徴とする上記（１）に記載の溶融塩電池。
（３）前記絶縁被膜が、前記負極の集電タブの前記電解質と接触する部分に形成されていることを特徴とする上記（１）又は（２）に記載の溶融塩電池。
（４）前記絶縁被膜がポリフッ化ビニリデン樹脂、ポリテトラフルオロエチレン樹脂、架橋ポリエチレン、架橋ポリプロピレン、ポリイミド、及びポリアミドからなる群より選ばれるいずれか１種以上であることを特徴とする上記（１）〜（３）のいずれかに記載の溶融塩電池。
（５）前記電解質がＮaＦＳＡ及びＫＦＳＡを含むことを特徴とする上記（１）〜（４）のいずれかに記載の溶融塩電池。
Thus, as a result of further studies to solve these problems, the present inventors have made the following invention. The present invention has the following configuration.
(1) A molten salt battery in which a positive electrode and a negative electrode are arranged via a separator, and a molten salt containing sodium as an electrolyte is used,
The negative electrode comprises a current collector, an active material, and a current collecting tab,
The active material is held on at least a portion of the current collector;
An insulating film is formed on the portion of the current collector that is not holding the active material and / or the current collector tab ,
The molten salt battery is further characterized in that the insulating coating is formed on a surface of the negative electrode current collector that does not face the positive electrode .
( 2 ) The molten salt battery as described in (1 ) above, wherein the insulating coating is formed on an edge of the current collector of the negative electrode.
( 3 ) The molten salt battery according to (1) or (2) , wherein the insulating coating is formed on a portion of the current collecting tab of the negative electrode that contacts the electrolyte.
( 4 ) The above-mentioned ( 1 ), wherein the insulating coating is at least one selected from the group consisting of polyvinylidene fluoride resin, polytetrafluoroethylene resin, crosslinked polyethylene, crosslinked polypropylene, polyimide, and polyamide. The molten salt battery according to any one of to ( 3 ).
( 5 ) The molten salt battery according to any one of (1) to ( 4 ), wherein the electrolyte contains NaFSA and KFSA.
本発明により、サイクル特性に優れ、寿命の長い溶融塩電池を提供することができる。 According to the present invention, a molten salt battery having excellent cycle characteristics and a long life can be provided.
本発明に係る溶融塩電池は、正極と負極とがセパレータを介して配置され、電解質としてナトリウムを含む溶融塩を用いた溶融塩電池であって、前記負極は、集電体と、活物質と、集電タブと、を有してなり、前記活物質は、前記集電体の少なくとも一部分に保持され、前記集電体の活物質を保持されていない部分及び／又は前記集電タブに絶縁被膜が形成されていることを特徴とする。 A molten salt battery according to the present invention is a molten salt battery in which a positive electrode and a negative electrode are arranged via a separator, and a molten salt containing sodium as an electrolyte is used. The negative electrode includes a current collector, an active material, The active material is held in at least a part of the current collector and insulated from the current collector tab and / or the current collector tab. A film is formed.
本発明の溶融塩電池の構成の一例として、図１に、１枚の正極の両側にセパレータを介して負極を１枚ずつ配置した例を示す。なお、図１においては集電リード、電極端子の記載は省略している。
負極は、負極の集電体に活物質層が形成されているが、該活物質層は正極と向かい合う側の面に形成されている。そして、負極の、正極と向かい合わない側の面（以下、単に「負極の裏面」ともいう）に絶縁被膜が形成されていることが好ましい。これにより、溶融塩電池の充放電を繰り返すうちに電解液の一部が負極の正極と向かい合わない側の面にまで回り込んだとしても、該面上で電解液中のナトリウムが合金化したり、析出したりすることを抑制することができる。
このため本発明の溶融塩電池は、電解質に含まれるナトリウムの損失が無く、サイクル特性に優れ、長寿命の電池となる。負極の裏面においては、全面に絶縁被膜が形成されていることが好ましいが、裏面の一部に形成されている場合であっても本発明の効果は発揮される。図２に、絶縁被膜が形成された負極に裏面の概略図を示す。
As an example of the configuration of the molten salt battery of the present invention, FIG. 1 shows an example in which one negative electrode is arranged on both sides of one positive electrode via a separator. In FIG. 1, illustration of current collecting leads and electrode terminals is omitted.
In the negative electrode, an active material layer is formed on the current collector of the negative electrode, and the active material layer is formed on the surface facing the positive electrode. An insulating film is preferably formed on the surface of the negative electrode that does not face the positive electrode (hereinafter also simply referred to as “the back surface of the negative electrode”). Thereby, even if a part of the electrolytic solution wraps around the surface of the negative electrode that does not face the positive electrode while repeating charging and discharging of the molten salt battery, sodium in the electrolytic solution is alloyed on the surface, It can suppress that it precipitates.
For this reason, the molten salt battery of the present invention has no loss of sodium contained in the electrolyte, has excellent cycle characteristics, and has a long life. On the back surface of the negative electrode, it is preferable that an insulating film is formed on the entire surface, but the effect of the present invention is exhibited even when it is formed on a part of the back surface. FIG. 2 shows a schematic diagram of the back surface of the negative electrode on which an insulating film is formed.
また、本発明に係る溶融塩電池は、図３に示すように前記負極の端縁部（端面も含む）に絶縁被膜が形成されていることが好ましい。一般に、負極の端縁部には前記活物質層が形成されておらず集電体金属が露出した状態になっているが、該端縁部にも電解液中のナトリウムが合金化したり、析出したりすることが見出された。このため、負極の端縁部にも絶縁被膜を形成して、充電時におけるナトリウムの合金化・析出を防ぐことで、電池の不可逆容量を減らすことができる。
負極の端縁部への絶縁被膜の形成は、図４に示すように、端縁部の一部のみに形成されていても良いし、図５に示すように端縁部全体に形成されていてもよい。
Moreover, as for the molten salt battery which concerns on this invention, as shown in FIG. 3, it is preferable that the insulating film is formed in the edge part (an end surface is also included) of the said negative electrode. In general, the active material layer is not formed on the edge portion of the negative electrode, and the current collector metal is exposed, but sodium in the electrolyte is alloyed or deposited on the edge portion. It was found to be. For this reason, the irreversible capacity | capacitance of a battery can be reduced by forming an insulating film also in the edge part of a negative electrode, and preventing the alloying and precipitation of sodium at the time of charge.
As shown in FIG. 4, the insulating coating may be formed on only a part of the end edge as shown in FIG. 4 or on the entire end edge as shown in FIG. 5. May be.
更に、本発明に係る溶融塩電池は、前記集電タブの前記電解質と接触する部分に絶縁被膜が形成されていることが好ましい。一般に、正極と負極との間に介在するセパレータは正極と負極との接触を防止するため、正極や負極よりも大きいサイズのものが使用されている。このためセパレータは負極に備えられた集電タブと接触する構造になっているが、前述のように、該集電タブ上にもセパレータに含浸された電解液に含まれるナトリウムが合金化したり、析出したりすることが見出された。このため、図２、図４、図５に示すように、負極に形成された集電タブの、少なくとも前記電解質と接触する部分に絶縁被膜が形成されていることが好ましい。
以上のように、本発明に係る溶融塩電池は、負極の集電体の活物質を保持されていない部分及び／又は集電タブに絶縁被膜が形成されていればよい。すなわち、負極の裏面、負極の集電体の周縁部、集電タブのいずれか１つ以上に絶縁被膜が形成されていれば効果が発揮される。
Furthermore, in the molten salt battery according to the present invention, it is preferable that an insulating coating is formed on a portion of the current collecting tab that contacts the electrolyte. In general, a separator interposed between the positive electrode and the negative electrode has a size larger than that of the positive electrode or the negative electrode in order to prevent contact between the positive electrode and the negative electrode. For this reason, the separator has a structure in contact with the current collecting tab provided in the negative electrode, but as described above, sodium contained in the electrolytic solution impregnated in the separator is alloyed on the current collecting tab, It has been found that it precipitates. For this reason, as shown in FIGS. 2, 4, and 5, it is preferable that an insulating coating is formed on at least a portion of the current collecting tab formed on the negative electrode in contact with the electrolyte.
As described above, in the molten salt battery according to the present invention, it is only necessary that the insulating film is formed on the portion where the active material of the negative electrode current collector is not held and / or the current collecting tab. That is, the effect is exhibited if an insulating coating is formed on any one or more of the back surface of the negative electrode, the peripheral portion of the current collector of the negative electrode, and the current collecting tab.
なお、本発明の溶融塩電池においては負極の枚数は特に限定されず、図６に示すように正極の枚数に応じて多い数枚の負極を有していても良い。なお、図６においても集電リード、電極端子の記載は省略している。また、積層数の一例としては、正極が２０枚、負極が２１枚、セパレータが４０枚の構成の溶融塩電池が挙げられる。この場合、２１枚の負極のうち、正極に挟まれる１９枚は負極の両面側に活物質が保持されており、両端の２枚は正極と向かい合う側のみに活物質が保持される。従って、正極に挟まれる１９枚の負極は、集電体の周縁部及び／又は集電タブに絶縁被膜が形成されていればよく、また、両端の２枚は正極と向かい合わない側の面及び／又は集電タブに絶縁被膜が形成されていればよい。 In the molten salt battery of the present invention, the number of negative electrodes is not particularly limited, and as shown in FIG. 6, a large number of negative electrodes may be provided according to the number of positive electrodes. In FIG. 6, the description of the current collecting lead and the electrode terminal is omitted. Moreover, as an example of the number of stacked layers, a molten salt battery having 20 positive electrodes, 21 negative electrodes, and 40 separators can be cited. In this case, of the 21 negative electrodes, 19 sheets sandwiched between the positive electrodes hold the active material on both sides of the negative electrode, and two sheets on both ends hold the active material only on the side facing the positive electrode. Therefore, the 19 negative electrodes sandwiched between the positive electrodes may be formed by forming an insulating coating on the peripheral portion of the current collector and / or the current collecting tab, and the two sheets on both ends are not facing the positive electrode and It suffices if an insulating film is formed on the current collecting tab.
以下に、本発明の溶融電電池の各構成をより詳細に説明する。
（負極）
負極は負極用集電体上に負極活物質を設けてなる。
−負極用集電体−
負極用集電体としては特に限定されないが、例えば、アルミニウム、銅、ステンレス、モリブデン、タングステン、プラチナ及び金、並びにこれらの合金の少なくとも１種を選択することが好ましい。また、負極用集電体の形状は板状（箔状）であることが好ましい。負極用集電体の厚さは特に限定されないが、例えば、１０μｍ〜１００μｍであることが好ましく、２０μｍ〜４０μｍであることがより好ましい。
Below, each structure of the fusion electric battery of this invention is demonstrated in detail.
(Negative electrode)
The negative electrode is formed by providing a negative electrode active material on a negative electrode current collector.
-Current collector for negative electrode-
Although it does not specifically limit as a collector for negative electrodes, For example, it is preferable to select at least 1 sort (s) of aluminum, copper, stainless steel, molybdenum, tungsten, platinum, gold | metal | money, and these alloys. The shape of the negative electrode current collector is preferably a plate shape (foil shape). Although the thickness of the collector for negative electrodes is not specifically limited, For example, it is preferable that they are 10 micrometers-100 micrometers, and it is more preferable that they are 20 micrometers-40 micrometers.
−負極活物質−
負極活物質を負極用集電体上に設ける手段としては、例えば、スズ、亜鉛、鉛、ゲルマニウム等の金属（負極活物質）を負極の集電体上にスパッタリング等の手段によりコーティングする方法が挙げられる。
また、負極活物質を負極集電状に設ける手段としては、他にも、チタン酸ナトリウム、ハードカーボン等の負極活物質の粉末を導電助剤及びバインダーと混合してペースト状にし、これを負極の集電体上に塗布し、調厚後、乾燥させる方法が挙げられる。
-Negative electrode active material-
As a means for providing the negative electrode active material on the negative electrode current collector, for example, a method of coating a metal such as tin, zinc, lead, germanium (negative electrode active material) on the negative electrode current collector by means such as sputtering. Can be mentioned.
In addition, as a means for providing the negative electrode active material in the form of a negative electrode current collector, a powder of a negative electrode active material such as sodium titanate or hard carbon is mixed with a conductive additive and a binder to form a paste, which is The method of apply | coating on this electrical power collector, drying after thickness adjustment is mentioned.
導電助剤としては、例えば、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）といったカーボンブラック等を好ましく用いることができる。負極に用いる導電助剤の含有率は、４０質量％以下であることが好ましく、特に、５〜２０質量％の範囲であることがより好ましい。導電助剤の含有率が前記範囲内であれば、充放電サイクル特性に優れ、高エネルギー密度の電池を得やすい。また、導電助剤は正極の導電性に応じて適宜添加すればよく、必須ではない。 As the conductive assistant, for example, carbon black such as acetylene black (AB) and ketjen black (KB) can be preferably used. The content of the conductive additive used for the negative electrode is preferably 40% by mass or less, and more preferably in the range of 5 to 20% by mass. If the content rate of a conductive support agent exists in the said range, it will be excellent in charging / discharging cycling characteristics, and will be easy to obtain a battery of high energy density. Moreover, what is necessary is just to add a conductive support agent suitably according to the electroconductivity of a positive electrode, and it is not essential.
また、バインダーとしては、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）等を好ましく用いることができる。負極に用いるバインダーの含有率は、４０質量％以下であることが好ましく、特に、１〜１０質量％の範囲であることがより好ましい。バインダーの含有率が前記範囲内であれば、負極活物質と導電助剤とをより強固に固着でき、かつ負極の導電性を適切なものとしやすい。 As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) or the like can be preferably used. The content of the binder used for the negative electrode is preferably 40% by mass or less, and more preferably in the range of 1 to 10% by mass. If the content rate of a binder exists in the said range, a negative electrode active material and a conductive support agent can be fixed more firmly, and it will be easy to make the electroconductivity of a negative electrode suitable.
−絶縁被膜の形成−
本発明の溶融塩電池においては、上記のような構成の負極の裏面に絶縁被膜が設けられていることを特徴とする。また、絶縁被膜は負極の端縁部にも設けられていることが好ましい。
絶縁被膜は、絶縁性を有していて溶融塩と反応しないものであればよく、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）樹脂、ポリテトラフルオロエチレン樹脂、架橋ポリエチレン樹脂、架橋ポリプロピレン樹脂、ポリアミド、ポリイミド等を好ましく利用することができる。
絶縁被膜の形成方法としては、例えば、負極の裏面や、負極の端縁部に前記絶縁性の樹脂を塗布したり、テープ状にして貼付したりする方法が挙げられる。
-Formation of insulation coating-
The molten salt battery of the present invention is characterized in that an insulating coating is provided on the back surface of the negative electrode having the above structure. Moreover, it is preferable that the insulating coating is also provided on the edge of the negative electrode.
The insulating coating may be any insulating coating that does not react with the molten salt. For example, polyvinylidene fluoride (PVdF) resin, polytetrafluoroethylene resin, crosslinked polyethylene resin, crosslinked polypropylene resin, polyamide, polyimide, etc. Can be preferably used.
Examples of the method for forming the insulating coating include a method in which the insulating resin is applied to the back surface of the negative electrode or the edge of the negative electrode, or is applied in a tape form.
本発明の溶融塩電池においては負極の枚数は特に限定されず、図１に示すように正極の両側にそれぞれ１枚ずつ負極が設けられていても良いし、正極の片面側に１枚のみ設けられていてもよい。また、図６に示すように正極の枚数が２枚以上とし、これと対応するように負極の枚数を増やすことも可能である。但し、図６の中央部に示す負極のように、両側に正極が位置し、負極の両面に負極活物質層が設けられている場合には、絶縁被膜は負極の端縁部のみに設けることが好ましい。 In the molten salt battery of the present invention, the number of negative electrodes is not particularly limited. As shown in FIG. 1, one negative electrode may be provided on each side of the positive electrode, or only one may be provided on one side of the positive electrode. It may be done. Also, as shown in FIG. 6, the number of positive electrodes may be two or more, and the number of negative electrodes may be increased to correspond to this. However, when the positive electrode is located on both sides and the negative electrode active material layer is provided on both sides of the negative electrode as in the negative electrode shown in the center of FIG. 6, the insulating coating should be provided only on the edge of the negative electrode. Is preferred.
−負極用の集電タブ−
また、本発明に係る溶融塩電池は、負極が集電タブを有しており、該集電タブ上の電解質と接触する部分に絶縁被膜が形成されていることが好ましい。集電タブとしては、負極の集電体上に別部材によるものが設けられていても良いし、負極の集電体と一体に形成されていてもよい。
集電タブが負極の集電体と異なる部材の場合には、集電タブの材質は負極の集電体と同じであっても、異なっていてもよい。すなわち、導電性のものであれば特に限定されず、例えば、アルミニウム、銅、金、銀等を好ましく用いることができる。また、超音波溶接等により集電体と集電タブとを接続することができる。
なお、負極用の集電タブは集電リード等を介して負極端子と接続される。
-Current collector tab for negative electrode-
In the molten salt battery according to the present invention, it is preferable that the negative electrode has a current collecting tab, and an insulating film is formed on a portion of the current collecting tab that contacts the electrolyte. The current collecting tab may be provided on a negative electrode current collector as a separate member, or may be formed integrally with the negative electrode current collector.
When the current collecting tab is a member different from the negative electrode current collector, the material of the current collecting tab may be the same as or different from the negative electrode current collector. That is, it is not particularly limited as long as it is conductive, and for example, aluminum, copper, gold, silver or the like can be preferably used. Further, the current collector and the current collecting tab can be connected by ultrasonic welding or the like.
The current collecting tab for the negative electrode is connected to the negative electrode terminal via a current collecting lead or the like.
（正極）
正極は正極用集電体上に正極活物質を設けてなる。
−正極用集電体−
正極用集電体としては高電位で腐食、溶出しない材質であれば特に限定されないが、例えば、アルミニウムを好ましく用いることができる。また、正極用集電体の形状は特に限定されず、板状（箔状）であってもよいし、３次元網目状構造を有する多孔体であってもよい。
(Positive electrode)
The positive electrode is obtained by providing a positive electrode active material on a positive electrode current collector.
-Current collector for positive electrode-
The positive electrode current collector is not particularly limited as long as it is a material that does not corrode or elute at a high potential. For example, aluminum can be preferably used. The shape of the positive electrode current collector is not particularly limited, and may be a plate (foil shape) or a porous body having a three-dimensional network structure.
−正極活物質−
正極活物質としては、ナトリウムイオンを可逆的に吸蔵・脱離することができるものが好ましく、例えば、クロム酸ナトリウム（ＮaＣrＯ2）等を好ましく用いることができる。
-Positive electrode active material-
As the positive electrode active material, those capable of reversibly occluding and desorbing sodium ions are preferable. For example, sodium chromate (NaCrO 2 ) or the like can be preferably used.
正極活物質を正極用集電体上に設ける手段としては、例えば、前記正極活物質の粉末を導電助剤及びバインダーと混合してペースト状にし、これを正極用集電体上に塗布し、調厚後、乾燥させる方法が挙げられる。 As a means for providing the positive electrode active material on the positive electrode current collector, for example, the positive electrode active material powder is mixed with a conductive additive and a binder to form a paste, and this is applied on the positive electrode current collector, The method of drying after thickness adjustment is mentioned.
導電助剤としては負極の場合と同様に、アセチレンブラック（ＡＢ）、ケッチェンブラック（ＫＢ）といったカーボンブラック等を好ましく用いることができる。正極における導電助剤の含有率も負極と同様に、４０質量％以下であることが好ましく、特に、５〜２０質量％の範囲であることがより好ましい。導電助剤の含有率が前記範囲内であれば、充放電サイクル特性に優れ、高エネルギー密度の電池を得やすい。また、導電助剤は負極の導電性に応じて適宜添加すればよく、必須ではない。 As the conductive assistant, carbon black such as acetylene black (AB) and ketjen black (KB) can be preferably used as in the case of the negative electrode. Similarly to the negative electrode, the content of the conductive additive in the positive electrode is preferably 40% by mass or less, and more preferably in the range of 5 to 20% by mass. If the content rate of a conductive support agent exists in the said range, it will be excellent in charging / discharging cycling characteristics, and will be easy to obtain a battery of high energy density. Moreover, what is necessary is just to add a conductive support agent suitably according to the electroconductivity of a negative electrode, and it is not essential.
また、バインダーも負極の場合と同様に、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）等を好ましく用いることができる。正極に用いるバインダーの含有率も負極の場合と同様に、４０質量％以下であることが好ましく、特に、１〜１０質量％の範囲であることがより好ましい。バインダーの含有率が前記範囲内であることにより、正極活物質と導電助剤とをより強固に固着でき、かつ正極の導電性を適切なものとしやすい。 As the binder, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) and the like can be preferably used as in the case of the negative electrode. As in the case of the negative electrode, the content of the binder used for the positive electrode is preferably 40% by mass or less, and more preferably in the range of 1 to 10% by mass. When the content rate of the binder is within the above range, the positive electrode active material and the conductive additive can be more firmly fixed, and the conductivity of the positive electrode is easily made appropriate.
−正極用の集電タブ−
負極と同様に正極にも集電タブが接続されていることが好ましい。集電タブとしては、正極の集電体上に別部材によるものが設けられていても良いし、正極の集電体と一体に形成されていてもよい。
集電タブが正極の集電体と異なる部材の場合には、集電タブの材質は正極の集電体と同じであっても、異なっていてもよい。すなわち、導電性を有し、高電位で腐食、溶出しない材質であれば特に限定されず、例えば、アルミニウム等を好ましく用いることができる。また、超音波溶接等により集電体と集電タブとを接続することができる。
なお、正極用の集電タブは集電リード等を介して正極端子と接続される。
-Current collecting tab for positive electrode-
A current collecting tab is preferably connected to the positive electrode as well as the negative electrode. The current collecting tab may be provided on the positive electrode current collector as a separate member, or may be formed integrally with the positive electrode current collector.
When the current collecting tab is a member different from the positive electrode current collector, the material of the current collecting tab may be the same as or different from the positive electrode current collector. That is, the material is not particularly limited as long as it is conductive and does not corrode or elute at a high potential. For example, aluminum or the like can be preferably used. Further, the current collector and the current collecting tab can be connected by ultrasonic welding or the like.
The positive electrode current collecting tab is connected to the positive electrode terminal via a current collecting lead or the like.
（電解質）
電解質の溶融塩としては、動作温度で溶融する各種の無機塩又は有機塩を使用することができる。溶融塩のカチオンとしては、リチウム（Ｌi）、ナトリウム（Ｎa）、カリウム（Ｋ）、ルビジウム（Ｒb）及びセシウム（Ｃs）等のアルカリ金属、ベリリウム（Ｂe）、マグネシウム（Ｍg）、カルシウム（Ｃa）、ストロンチウム（Ｓr）及びバリウム（Ｂa）等のアルカリ土類金属から選択した１種以上を用いることができる。
(Electrolytes)
As the electrolyte molten salt, various inorganic salts or organic salts that melt at the operating temperature can be used. The cation of the molten salt includes alkali metals such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca). One or more selected from alkaline earth metals such as strontium (Sr) and barium (Ba) can be used.
溶融塩の融点を低下させるために、２種以上の塩を混合して使用することが好ましい。例えばカリウムビス（フルオロスルフォニル）アミド＜Ｋ-Ｎ（ＳＯ2Ｆ）2；ＫＦＳＡ＞とナトリウムビス（フルオロスルフォニル）アミド＜Ｎa-Ｎ（ＳＯ2Ｆ）2；ＮaＦＳＡ＞とをＮaＦＳＡ：ＫＦＳＡ＝５６：４４のモル比で組み合わせて使用すると、溶融塩の融点は５７℃となり、電池の動作温度を９０℃以下とすることができる。
溶融塩のアニオンとしては、−ＦＳＡの他、例えば、−ＴＦＳＡ（ビストリフルオロメチルスルフォニルアミド）が適する。この場合、各混合物の溶融塩は、比較的低融点となるので、少ない加熱で溶融塩電池を作動させることができる。
なお、上述した各部の材質・成分や数値は好適な一例であるが、これらに限定されるものではない。
In order to lower the melting point of the molten salt, it is preferable to use a mixture of two or more salts. For example, potassium bis (fluorosulfonyl) amide <K—N (SO 2 F) 2 ; KFSA> and sodium bis (fluorosulfonyl) amide <Na—N (SO 2 F) 2 ; NaFSA> and NaFSA: KFSA = 56: When used in combination at a molar ratio of 44, the melting point of the molten salt is 57 ° C., and the operating temperature of the battery can be 90 ° C. or lower.
Examples of the anion of the molten salt, - other FSA, for example, - TFSA (bis trifluoromethylsulfonyl amide) are suitable. In this case, since the molten salt of each mixture has a relatively low melting point, the molten salt battery can be operated with little heating.
In addition, although the material, component, and numerical value of each part mentioned above are suitable examples, it is not limited to these.
（セパレータ）
セパレータは正極と負極とが接触するのを防ぐためのものであり、ガラス不織布や、多孔質樹脂多孔体等を使用できる。前記の電解質としてナトリウムを含む溶融塩はセパレータ中に含浸される。
(Separator)
A separator is for preventing a positive electrode and a negative electrode from contacting, and a glass nonwoven fabric, a porous resin porous body, etc. can be used for it. The molten salt containing sodium as the electrolyte is impregnated in the separator.
（電池）
上記の負極、正極、溶融塩を含浸させたセパレータを積層してケース内に収納し、各負極集電タブ・正極集電タブを、集電リード等を介してそれぞれ負極端子・正極端子に接続し、電池として使用することができる。
(battery)
The above negative electrode, positive electrode, separator impregnated with molten salt are stacked and stored in the case, and each negative electrode current collecting tab / positive electrode current collecting tab is connected to the negative electrode terminal / positive electrode terminal via a current collecting lead, etc. And can be used as a battery.
以下、実施例に基づいて本発明をより詳細に説明するが、本発明はこれらに限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.
［実施例］
（負極の作製）
負極用集電体として厚さ２０μｍで大きさが１０．５ｃｍ×１０．５ｃｍのアルミニウム箔を使用した。また、集電タブは集電体と一体として形成し、大きさは２ｃｍ×３ｃｍとした。
負極活物質としては、ＳnあるいはＺnを使用した。具体的には、上記アルミニウム箔上にＳnあるいはＺnをスパッタリングによるコーティング層を形成した。Ｓn、Ｚnの厚さはいずれも０．１μｍであった。
[Example]
(Preparation of negative electrode)
As the negative electrode current collector, an aluminum foil having a thickness of 20 μm and a size of 10.5 cm × 10.5 cm was used. The current collecting tab was formed integrally with the current collector, and the size was 2 cm × 3 cm.
Sn or Zn was used as the negative electrode active material. Specifically, a coating layer was formed by sputtering Sn or Zn on the aluminum foil. The thicknesses of Sn and Zn were both 0.1 μm.
（絶縁被膜の形成）
負極の裏面（正極と対向しない側の面）及び辺縁部にテトラフルオロエチレン、架橋ポリエチレン、架橋ポリプロピレン、ポリアミド、又はポリイミドのテープを貼付することにより絶縁被膜を形成した。また、前記負極の集電タブの、電解質が接触し得る部分にはポリフッ化ビニリデンを塗布することにより絶縁被膜を形成した。
(Formation of insulation coating)
An insulating coating was formed by applying a tape of tetrafluoroethylene, crosslinked polyethylene, crosslinked polypropylene, polyamide, or polyimide to the back surface (the surface not facing the positive electrode) and the edge of the negative electrode. In addition, an insulating film was formed by applying polyvinylidene fluoride on the portion of the current collecting tab of the negative electrode where the electrolyte could come into contact.
（正極の作製）
正極用集電体として厚さ２０μｍで大きさが１０ｃｍ×１０ｃｍのＡlを使用した。また、集電タブは集電体と一体として形成し、大きさは２ｃｍ×３ｃｍとした。
正極活物質としては、ＮaＣrＯ2を使用した。また、導電助剤としてはアセチレンブラックを、バインダーとしてはＰＶｄＦを使用した。
そして、正極活物質と、導電助剤と、バインダーとを、８５：１０：５の比率で混合した。この混合物にＮ−メチル−２−ピロリドン（ＮＭＰ）を滴下して混合し、ペースト状にした。該ペーストを上記Ａl（集電体）に塗布して圧着してペーストの厚さを１００μｍとした後、１５０℃で３０分間乾燥させることにより正極を得た。
(Preparation of positive electrode)
As the positive electrode current collector, Al having a thickness of 20 μm and a size of 10 cm × 10 cm was used. The current collecting tab was formed integrally with the current collector, and the size was 2 cm × 3 cm.
As the positive electrode active material, NaCrO 2 was used. In addition, acetylene black was used as the conductive assistant and PVdF was used as the binder.
And the positive electrode active material, the conductive support agent, and the binder were mixed in the ratio of 85: 10: 5. N-methyl-2-pyrrolidone (NMP) was added dropwise to the mixture and mixed to make a paste. The paste was applied to the above Al (current collector) and pressed to make the thickness of the paste 100 μm, and then dried at 150 ° C. for 30 minutes to obtain a positive electrode.
（電解質）
電解質としては、ナトリウムイオンを含有するＮaＦＳＡ−ＫＦＳＡ溶融塩（ＮaＦＳＡ：５６mol％、ＫＦＳＡ：４４mol％）を使用した。この溶融塩の融点は５７℃であった。
この溶融塩をセパレータとなる厚さ２００μｍのガラス製セパレータ（多孔質のガラスクロス）に含浸させた。
(Electrolytes)
As the electrolyte, NaFSA-KFSA molten salt (NaFSA: 56 mol%, KFSA: 44 mol%) containing sodium ions was used. The melting point of this molten salt was 57 ° C.
This molten salt was impregnated into a 200 μm-thick glass separator (porous glass cloth) serving as a separator.
（電池）
上記で作製したセパレータを、上記で作製した負極及び正極の間に配置し、Ａlラミネートフィルム製の電池ケースに収納し、電池１を得た。
(battery)
The separator prepared above was placed between the negative electrode and the positive electrode prepared above and housed in a battery case made of an Al laminate film to obtain a battery 1.
［比較例］
負極の裏面及び端縁部並びに負極用の集電タブ上に絶縁被膜を形成しない以外は上記実施例と同様にして溶融塩電池２を作製した。
[Comparative example]
A molten salt battery 2 was produced in the same manner as in the above example except that the insulating film was not formed on the back surface and edge portion of the negative electrode and the current collecting tab for the negative electrode.
［電池の評価］
上記で作製した溶融塩電池１及び２を加熱した状態で、雰囲気温度９０℃で２．７〜３．２Ｖの間で０．１ｍＡ/ｃｍ2の定電流による充放電サイクルを５００回繰り返した。各充放実施後における容量維持率を測定し、グラフに表したものを図７（実施例）及び図８（比較例）に示す。
なお、上記充放電サイクル試験後に、比較例の溶融塩電池２を分解して負極を観察したところ図９に示すように、負極用の集電タブの電解質と接触していた境界部分にナトリウムが析出していた。
[Battery evaluation]
While the molten salt batteries 1 and 2 produced above were heated, a charge / discharge cycle with a constant current of 0.1 mA / cm 2 was repeated 500 times at an ambient temperature of 90 ° C. between 2.7 and 3.2 V. The capacity retention rate after each charge / release was measured, and the results represented in the graph are shown in FIG. 7 (Example) and FIG. 8 (Comparative Example).
After the charge / discharge cycle test, the molten salt battery 2 of the comparative example was disassembled and the negative electrode was observed. As shown in FIG. 9, sodium was present at the boundary portion in contact with the electrolyte of the current collector tab for the negative electrode. It was precipitated.
これらの評価により、本発明の溶融塩電池はサイクル特性に優れ、寿命が改善されていることが示された。 From these evaluations, it was shown that the molten salt battery of the present invention has excellent cycle characteristics and improved life.
以上、本発明を実施の形態に基づいて説明したが、本発明は上記の実施の形態に限定されるものではない。本発明と同一および均等の範囲内において、上記の実施の形態に対して種々の変更を加えることができる。 While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.
Claims (5)
前記負極は集電体と、活物質と、集電タブと、を有してなり、
前記活物質は、前記集電体の少なくとも一部分に保持され、
前記集電体の活物質を保持されていない部分及び／又は前記集電タブに絶縁被膜が形成されており、
更に、前記絶縁被膜が、前記負極の集電体の前記正極と向かい合わない面に形成されていることを特徴とする溶融塩電池。 A molten salt battery in which a positive electrode and a negative electrode are arranged via a separator, and a molten salt containing sodium as an electrolyte is used,
The negative electrode comprises a current collector, an active material, and a current collecting tab,
The active material is held on at least a portion of the current collector;
An insulating film is formed on the portion of the current collector that is not holding the active material and / or the current collector tab ,
The molten salt battery is further characterized in that the insulating coating is formed on a surface of the negative electrode current collector that does not face the positive electrode .
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