JP2013084548A - Lithium secondary battery - Google Patents
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- JP2013084548A JP2013084548A JP2012056160A JP2012056160A JP2013084548A JP 2013084548 A JP2013084548 A JP 2013084548A JP 2012056160 A JP2012056160 A JP 2012056160A JP 2012056160 A JP2012056160 A JP 2012056160A JP 2013084548 A JP2013084548 A JP 2013084548A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 27
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 150000003839 salts Chemical class 0.000 claims abstract description 78
- 239000003792 electrolyte Substances 0.000 claims abstract description 18
- IMBHGOLFXVHBMC-UHFFFAOYSA-N potassium;fluorosulfonyl(trifluoromethylsulfonyl)azanide Chemical compound [K+].FC(F)(F)S(=O)(=O)[N-]S(F)(=O)=O IMBHGOLFXVHBMC-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 4
- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 claims abstract description 3
- OYQRIVAEKUDHBB-UHFFFAOYSA-N cesium fluorosulfonyl(trifluoromethylsulfonyl)azanide Chemical compound [Cs+].FS(=O)(=O)[N-]S(=O)(=O)C(F)(F)F OYQRIVAEKUDHBB-UHFFFAOYSA-N 0.000 claims description 2
- ZIRAMZRKLHPLPK-UHFFFAOYSA-N lithium fluorosulfonyl(trifluoromethylsulfonyl)azanide Chemical compound FS(=O)(=O)[N-]S(=O)(=O)C(F)(F)F.[Li+] ZIRAMZRKLHPLPK-UHFFFAOYSA-N 0.000 claims description 2
- 229910003002 lithium salt Inorganic materials 0.000 abstract description 5
- 159000000002 lithium salts Chemical class 0.000 abstract description 5
- GGYPIUANQNUBOE-UHFFFAOYSA-N n-(trifluoromethylsulfonyl)sulfamoyl fluoride Chemical compound FC(F)(F)S(=O)(=O)NS(F)(=O)=O GGYPIUANQNUBOE-UHFFFAOYSA-N 0.000 abstract 3
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical class [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 15
- 229910001416 lithium ion Inorganic materials 0.000 description 15
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 11
- 238000002844 melting Methods 0.000 description 11
- 230000008018 melting Effects 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 238000012360 testing method Methods 0.000 description 9
- 230000037427 ion transport Effects 0.000 description 6
- 239000007774 positive electrode material Substances 0.000 description 6
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 4
- 229910021383 artificial graphite Inorganic materials 0.000 description 4
- 238000002484 cyclic voltammetry Methods 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 230000032258 transport Effects 0.000 description 4
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 3
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 229920000049 Carbon (fiber) Polymers 0.000 description 2
- 229910013075 LiBF Inorganic materials 0.000 description 2
- 229910013275 LiMPO Inorganic materials 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000004917 carbon fiber Substances 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000000113 differential scanning calorimetry Methods 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 238000006713 insertion reaction Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000010450 olivine Substances 0.000 description 2
- 229910052609 olivine Inorganic materials 0.000 description 2
- 150000002894 organic compounds Chemical class 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical group 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910018871 CoO 2 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910032387 LiCoO2 Inorganic materials 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 229910013528 LiN(SO2 CF3)2 Inorganic materials 0.000 description 1
- 229910014211 My O Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- QTHKJEYUQSLYTH-UHFFFAOYSA-N [Co]=O.[Ni].[Li] Chemical compound [Co]=O.[Ni].[Li] QTHKJEYUQSLYTH-UHFFFAOYSA-N 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- -1 alkali metal (fluorosulfonyl) (trifluoromethylsulfonyl) amide salt Chemical class 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 238000002848 electrochemical method Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000002608 ionic liquid Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Inorganic materials [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 description 1
- 239000002931 mesocarbon microbead Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229910001935 vanadium oxide Inorganic materials 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
Description
本発明は、リチウム二次電池（典型的にはリチウムイオン電池）に関し、詳しくは溶融塩電解質を用いた中温型リチウム二次電池に関する。 The present invention relates to a lithium secondary battery (typically a lithium ion battery), and more particularly to a medium temperature lithium secondary battery using a molten salt electrolyte.
非特許文献１は、アルカリ金属(フルオロスルフォニル)(トリフルオロメチルスルフォニル)アミド塩の合成と単塩の融点・熱分解温度について報告しているが、このアミド塩の混合塩の物性及びリチウムイオン電池の電解質として使用することについては開示していない。
本発明は、従来の蓄電デバイスの性能改善、または新たな電気化学デバイスの開発に資する電解質の開発を行うことを目的とする。 It is an object of the present invention to develop an electrolyte that contributes to improving the performance of a conventional power storage device or developing a new electrochemical device.
本発明は、以下のリチウム二次電池を提供するものである。
項１． フルオロスルホニル（トリフルオロメチルスルホニル）アミドのリチウム塩（ＬｉＦＴＡ）単体の溶融塩、またはＬｉＦＴＡにフルオロスルホニル（トリフルオロメチルスルホニル）アミドのセシウム塩（ＣｓＦＴＡ）及びカリウム塩（ＫＦＴＡ）からなる群から選ばれる少なくとも１種の塩を混合した混合塩の溶融塩を電解質として使用してなるリチウム二次電池。
項２． 前記混合塩が、モル比でＬｉＦＴＡ：ＣｓＦＴＡ／ＫＦＴＡ＝０．２〜０．８：０．８〜０．２である、項１に記載のリチウム二次電池。
The present invention provides the following lithium secondary battery.
本発明は、LiFTAとCsFTA/KFTAを混合することで、低融点の溶融塩を作製した。特に、LiFTA がモル比で０．４である組成の塩は、融点33℃と非常に低融点であった。LiFTAとCsFTA/KFTAの混合塩を電解質に用いたリチウム二次電池を作成した。この溶融塩は5.1V広い電気化学窓を持ち、カソードリミットでリチウム金属が溶解析出する（図4)。この溶融塩を用いたLiCoO2正極, LiFePO4正極, 炭素負極の充放電試験の結果、良好な充放電曲線が得られた。以上の結果から、この溶融塩は、中温作動のリチウム二次電池用の電解質として有用である。 In the present invention, a low melting point molten salt was prepared by mixing LiFTA and CsFTA / KFTA. In particular, a salt having a composition with a molar ratio of LiFTA of 0.4 had a very low melting point of 33 ° C. A lithium secondary battery using LiFTA and CsFTA / KFTA mixed salt as an electrolyte was prepared. This molten salt has a 5.1V wide electrochemical window, and lithium metal dissolves and precipitates at the cathode limit (Fig. 4). As a result of a charge / discharge test of LiCoO 2 positive electrode, LiFePO 4 positive electrode, and carbon negative electrode using this molten salt, a good charge / discharge curve was obtained. From the above results, this molten salt is useful as an electrolyte for a lithium secondary battery operating at a medium temperature.
本発明のリチウム二次電池は、ＬｉＦＴＡ単体の溶融塩またはＬｉＦＴＡとＣｓＦＴＡ／ＫＦＴＡの混合塩を電解質として使用することが特徴である。ここで、「ＣｓＦＴＡ／ＫＦＴＡ」とは、ＣｓＦＴＡとＫＦＴＡの少なくとも１種の塩を示す。本発明の混合塩は、ＬｉＦＴＡとＣｓＦＴＡの混合塩、ＬｉＦＴＡとＫＦＴＡの混合塩、ＬｉＦＴＡとＣｓＦＴＡとＫＦＴＡの３種の混合塩のいずれかを意味する。
前記混合塩は、モル比でＬｉＦＴＡ：ＣｓＦＴＡ／ＫＦＴＡ＝０．２〜０．８：０．８〜０．２であるものが好ましい。前記混合塩は、モル比でＬｉＦＴＡ：ＣｓＦＴＡ／ＫＦＴＡ＝０．２〜０．６：０．８〜０．４であるものがより好ましく、ＬｉＦＴＡ：ＣｓＦＴＡ／ＫＦＴＡ＝０．３〜０．５：０．７〜０．５であるものがさらに好ましく、ＬｉＦＴＡ：ＣｓＦＴＡ／ＫＦＴＡ＝約０．４：約０．６であるものが液相線温度及び固相線温度が低いために特に好ましい。
The lithium secondary battery of the present invention is characterized by using a molten salt of LiFTA alone or a mixed salt of LiFTA and CsFTA / KFTA as an electrolyte. Here, “CsFTA / KFTA” refers to at least one salt of CsFTA and KFTA. The mixed salt of the present invention means any one of a mixed salt of LiFTA and CsFTA, a mixed salt of LiFTA and KFTA, and a mixed salt of LiFTA, CsFTA, and KFTA.
The mixed salt preferably has a molar ratio of LiFTA: CsFTA / KFTA = 0.2 to 0.8: 0.8 to 0.2. The mixed salt is more preferably LiFTA: CsFTA / KFTA = 0.2 to 0.6: 0.8 to 0.4 by molar ratio, and LiFTA: CsFTA / KFTA = 0.3 to 0.5: More preferred is 0.7 to 0.5, and particularly preferred is LiFTA: CsFTA / KFTA = about 0.4: about 0.6 because the liquidus temperature and the solidus temperature are low.
本発明のリチウム二次電池には、さらに他のイオン液体、有機溶媒などを含んでいてもよい。 The lithium secondary battery of the present invention may further contain other ionic liquids, organic solvents, and the like.
本発明で使用するアニオンの構造を以下に示す。 The structure of the anion used in the present invention is shown below.
本発明のリチウム二次電池にはさらにＬｉＣＦ３ＳＯ３、ＬｉＰＦ６、ＬｉＣｌＯ４、ＬｉＩ、ＬｉＢＦ４、ＬｉＢＦ３ＣＦ３、ＬｉＢＦ３Ｃ２Ｆ５、ＬｉＣＦ３ＣＯ２、ＬｉＳＣＮ、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＮ（ＳＯ２ＣＦ３）２などの他のリチウム塩を配合してもよい。 The lithium secondary battery of the present invention further includes LiCF 3 SO 3 , LiPF 6 , LiClO 4 , LiI, LiBF 4 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiCF 3 CO 2 , LiSCN, LiN (SO 2 F ) 2 , LiN (SO 2 CF 3 ) 2 and other lithium salts may be blended.
本発明のリチウム二次電池は、前記混合塩の他に、正極、負極、セパレータなどを含む。 The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator and the like in addition to the mixed salt.
負極の主要構成成分である負極活物質としては、炭素質材料（例えば、石炭、コークス、ポリアクリロニトリル系炭素繊維、ピッチ系炭素繊維、有機物の炭素化品、天然黒鉛、人造黒鉛、合成黒鉛、メソカーボンマイクロビーズ、有機物の黒鉛化品及び黒鉛繊維）、及び、負極特性を向上させる目的でリンやホウ素を添加し改質を行った材料等が挙げられる。炭素質材料の中でも黒鉛は、金属リチウムに極めて近い作動電位を有するので電解質塩としてリチウム塩を採用した場合に自己放電を少なくでき、かつ充放電における不可逆容量を少なくできるので、負極活物質として好ましい。黒鉛結晶には良く知られている六方晶系とその他に菱面体晶系に属するものがある。特に、菱面体晶系の黒鉛は、電解液中の溶媒の選択性が広く、例えば、リチウムイオンと共挿入しやすい有機化合物や、比較的貴な電位で還元分解されやすい有機化合物を、非水電解質の構成材料として用いても、層剥離が抑制され優れた充放電効率を示すことから望ましい。 The negative electrode active material that is the main component of the negative electrode includes carbonaceous materials (for example, coal, coke, polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, organic carbonized products, natural graphite, artificial graphite, synthetic graphite, meso Carbon micro beads, organic graphitized products and graphite fibers), and materials modified by adding phosphorus or boron for the purpose of improving the negative electrode characteristics. Among carbonaceous materials, graphite has a working potential very close to that of metallic lithium. Therefore, when lithium salt is used as an electrolyte salt, self-discharge can be reduced, and irreversible capacity in charge / discharge can be reduced, which is preferable as a negative electrode active material. . Graphite crystals include the well-known hexagonal system and others belonging to the rhombohedral system. In particular, rhombohedral graphite has a wide selectivity for a solvent in an electrolytic solution. For example, an organic compound that easily co-inserts with lithium ions or an organic compound that is easily reductively decomposed at a relatively noble potential can be obtained using a non-aqueous solution. Even when it is used as a constituent material of an electrolyte, it is desirable because delamination is suppressed and excellent charge / discharge efficiency is exhibited.
正極としては、アルミニウム集電体に正極活物質を塗布して得られる正極を用いることが好ましい。正極活物質としては、リチウムイオン電池において用いられる公知の正極活物質を用いることができるが、特に、リチウム基準で３〜５Ｖの電位で作動する活物質を用いることが好ましい。正極活物質の具体例としては、高電圧を得るためには、リチウムコバルト酸化物（ＬｉｘＣｏＯ２、ｘ＝０．４〜１）、リチウムニッケル酸化物（ＬｉｘＮｉＯ２、ｘ＝０．３〜１）、リチウムマンガン酸化物（ＬｉｘＭｎＯ２、ｘ＝０〜１）、遷移金属置換リチウムマンガン酸化物（ＬｉｘＭｎ１−ｙＭｙＯ２、Ｍ＝Ｃｏ、Ａｌ、Ｎｉ、Ｃｒ又はＢｉ、ｘ＝０〜１、ｙ＝０．０１〜０．２５）、リチウムニッケルコバルト酸化物（ＬｉｘＮｉ１−ｙ−ｚＣｏｙＭｚＯ２、Ｍ＝Ａｌ又はＭｎ、ｘ＝０．３〜１、ｙ＝０．１〜０．４、ｚ＝０．０１〜０．２）、オリビン相化合物ＬｉＭＰＯ４（Ｍ＝Ｆｅ又はＣｏ）等を用いることができる。これらの内で、リチウムマンガン酸化物は、スピネル相及び層状構造のいずれでも良く、オリビン相化合物ＬｉＭＰＯ４には、Ｍｎ、Ｎｉ等の遷移金属が少量含まれても良い。また、各酸化物は、異なる組成の酸化物の混合物であっても良い。 As the positive electrode, a positive electrode obtained by applying a positive electrode active material to an aluminum current collector is preferably used. As the positive electrode active material, a known positive electrode active material used in a lithium ion battery can be used. In particular, an active material that operates at a potential of 3 to 5 V based on lithium is preferably used. As a specific example of the positive electrode active material, in order to obtain a high voltage, lithium cobalt oxide (Li x CoO 2 , x = 0.4 to 1), lithium nickel oxide (Li x NiO 2 , x = 0. 3-1), lithium manganese oxide (Li x MnO 2 , x = 0 to 1), transition metal substituted lithium manganese oxide (Li x Mn 1- y My O 2 , M = Co, Al, Ni, Cr Or Bi, x = 0 to 1, y = 0.01 to 0.25), lithium nickel cobalt oxide (Li x Ni 1-yz Co y M z O 2 , M = Al or Mn, x = 0 .3-1, y = 0.1-0.4, z = 0.01-0.2), olivine phase compound LiMPO 4 (M = Fe or Co), etc. can be used. Among these, the lithium manganese oxide may have either a spinel phase or a layered structure, and the olivine phase compound LiMPO 4 may contain a small amount of transition metals such as Mn and Ni. Each oxide may be a mixture of oxides having different compositions.
また、高容量を得るためには、マンガン酸化物ＭｎＯｘ（ｘ＝１．５〜２）、バナジウム酸化物ＬｉｘＶｙＯ５（ｘ＝０〜３、ｙ＝１．５〜３．５）、これらの複合酸化物などを用いることが好ましい。正極活物質は、一種単独又は二種以上混合して用いることができる。 Further, in order to obtain a high capacity, manganese oxide MnO x (x = 1.5~2), vanadium oxide Li x V y O 5 (x = 0~3, y = 1.5~3.5 ) Or a composite oxide of these. A positive electrode active material can be used individually by 1 type or in mixture of 2 or more types.
正極は、常法に従って作製することができる。通常、上記した正極活物質に導電剤、バインダーなどを加え、この混合物を集電体上に塗布し、圧着することによって正極を製造することができる。導電剤、バインダー等は、公知の成分を使用できる。例えば、導電剤としては、アセチレンブラック、天然黒鉛、人造黒鉛、合成黒鉛などを使用できる。 The positive electrode can be produced according to a conventional method. Usually, a positive electrode can be produced by adding a conductive agent, a binder, and the like to the above-described positive electrode active material, applying the mixture onto a current collector, and pressing the mixture. Known components can be used for the conductive agent, binder and the like. For example, acetylene black, natural graphite, artificial graphite, synthetic graphite or the like can be used as the conductive agent.
本発明の混合塩電解質は、通常、セパレーター部分と電極の空隙部分に充填ないし含浸して用いられる。 The mixed salt electrolyte of the present invention is usually used by filling or impregnating the gap between the separator and the electrode.
上記した各構成要素は、コイン型、円筒型、ラミネートパッケージなどの公知の各種電池外装に封入され、密閉されて、リチウム二次電池とすることができる。 Each of the above-described constituent elements can be sealed in a well-known various battery exterior such as a coin type, a cylindrical type, and a laminate package to be a lithium secondary battery.
以下に、本発明を実施例及び比較例に基づき、さらに詳細に説明するが、本発明はこれらの記載により限定されるものではない。 Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these descriptions.
参考例１
公知の様々なリチウムの融点を測定した。結果を図１に示す。図１に示すように、LiFTAは最も融点が低いリチウム塩であった。
Reference example 1
Various known lithium melting points were measured. The results are shown in FIG. As shown in FIG. 1, LiFTA was the lithium salt with the lowest melting point.
実施例１
LiFTAとCsFTAを種々のモル比で混合して、固相線温度及び液相線温度を示差走査熱量分析(DSC)により測定した。結果を図２に示す。なお、固相線温度は混合塩が溶け始める温度であり、融解開始点ともいう。液相線温度は、混合塩が溶け終わり、全て液体になる温度であり、融解終了点ともいう。固相線温度と液相線温度の間では、物体は固体と液体が混在している。
Example 1
LiFTA and CsFTA were mixed at various molar ratios, and the solidus temperature and liquidus temperature were measured by differential scanning calorimetry (DSC). The results are shown in FIG. The solidus temperature is a temperature at which the mixed salt starts to dissolve, and is also referred to as a melting start point. The liquidus temperature is a temperature at which the mixed salt is completely dissolved and becomes all liquid, and is also called a melting end point. Between the solidus temperature and the liquidus temperature, the object is a mixture of solid and liquid.
本発明の混合塩は、LiFTAと比較して融点が大きく低下することが明らかになった。 It has been clarified that the mixed salt of the present invention has a significantly lower melting point than LiFTA.
特に、モル組成xLiFTA = 0.40の組成の塩が低融点(33℃)を持つことが分かった。 In particular, it was found that a salt having a composition of molar composition x LiFTA = 0.40 has a low melting point (33 ° C).
実施例２
LiFTAとCsFTAの混合塩について110℃で導電率とリチウムイオン輸率の測定を行った結果(図3(a))、xLiFTA = 0.40の組成の塩はリチウムイオンの導電率(導電率とリチウムイオン輸率の積)が近傍の組成の塩(xLiFTA = 0.20, 0.60)よりも高いことが分かった(図3(b))
Example 2
As a result of conducting measurements of the conductivity and lithium ion transport number of LiFTA and CsFTA at 110 ° C (Fig. 3 (a)), the salt with the composition of x LiFTA = 0.40 is the lithium ion conductivity (conductivity and lithium ion). It was found that the product of the ion transport number was higher than the salt of the nearby composition (x LiFTA = 0.20, 0.60) (Fig. 3 (b))
実施例３
図2と図3の結果から、液相温度域が広く、リチウムイオン導電率の比較的高いxLiFTA = 0.40の混合塩についてサイクリックボルタンメトリーを行った（図4）。その結果、この溶融塩は5.1 Vと広い電気化学窓を持ち、カソードリミットでリチウム金属が溶解析出することが分かった。
Example 3
From the results in Fig. 2 and Fig. 3, cyclic voltammetry was performed on x LiFTA = 0.40 mixed salt with a wide liquidus temperature range and relatively high lithium ion conductivity (Fig. 4). As a result, it was found that this molten salt has a wide electrochemical window of 5.1 V, and lithium metal dissolves and precipitates at the cathode limit.
実施例４
LiFTA（0.40モル）：CsFTA（0.60モル）の混合塩を電解質に用い、LiFePO4正極(図5(a)), LiCoO2正極(図5(b)))についてそれぞれリチウム金属を対極に用いたハーフセルを作成し、サイクリックボルタンメトリーを行った。それぞれの電位でリチウムイオンの脱離・挿入反応に起因する可逆な酸化還元電流が確認された。
Example 4
LiFTA (0.40 mol): Using a mixed salt of CsFTA (0.60 mol) as the electrolyte, the LiFePO4 positive electrode (Fig. 5 (a)) and the LiCoO2 positive electrode (Fig. 5 (b)) have half cells using lithium metal as the counter electrode. Prepared and subjected to cyclic voltammetry. Reversible redox currents due to lithium ion desorption / insertion reactions were confirmed at each potential.
実施例５
LiFTA（0.40モル）：CsFTA（0.60モル）の混合塩を電解質に用い、LiFePO4正極(図6(a)), LiCoO2正極(図6(b)), 炭素負極(図6(c))についてそれぞれリチウム金属を対極に用いたハーフセルを作成し、充放電試験を行った。その結果、それぞれ良好な充放電曲線が得られ、放電容量もそれぞれの電極の理論容量に近い値が得られた。
Example 5
LiFTA (0.40 mol): LiFePO 4 positive electrode (Fig. 6 (a)), LiCoO 2 positive electrode (Fig. 6 (b)), carbon negative electrode (Fig. 6 (c)) using mixed salt of CsFTA (0.60 mol) as electrolyte A half cell using a lithium metal as a counter electrode was prepared and a charge / discharge test was conducted. As a result, good charge / discharge curves were obtained, and the discharge capacity was close to the theoretical capacity of each electrode.
実施例６
エチレンカーボネート(EC)とジメチルカーボネート(DMC)混合溶媒にLiPF6を添加した(濃度1M)従来の電解液と比較したところ、本発明の混合溶融塩は導電率は低いが(図7(a))、LiFePO4正極を用いた充放電レート試験では非常に高いレート特性を有することが分かった(図7(b))。
Example 6
Compared with a conventional electrolyte in which LiPF 6 was added to a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (
実施例７
LiFTAとCsFTAの混合塩と同様に、LiFTAとKFTAの混合塩においてもLiFePO4正極の充放電試験を行った結果、良好な充放電曲線と理論容量に近い放電容量が得られた（図8）。
Example 7
As with the LiFTA and CsFTA mixed salt, the LiFePO 4 cathode charge / discharge test was also performed on the LiFTA and KFTA mixed salt. As a result, a good charge / discharge curve and discharge capacity close to the theoretical capacity were obtained (Fig. 8). .
実施例８
より高温での電解液特性を調べるため、LiFTA単塩も含めた溶融塩について140℃で輸率測定を行った。ＬｉＦＴＡ：ＣｓＦＴＡ＝０．２〜０．８：０．８〜０．２の混合塩は、図3の110℃における値とほぼ同じであったが、Li塩の割合が0.9以上の溶融塩ではリチウムイオン輸率が特異的に高く、LiFTA単塩の輸率は約0.9であった(図9)。
Example 8
In order to investigate the characteristics of the electrolyte at higher temperatures, the transport number was measured at 140 ° C for molten salts including LiFTA single salt. The mixed salt of LiFTA: CsFTA = 0.2 to 0.8: 0.8 to 0.2 was almost the same as the value at 110 ° C. in FIG. The lithium ion transport number was specifically high, and the transport number of LiFTA monosalt was about 0.9 (Fig. 9).
実施例９
LiFTA単塩の溶融塩においても同様の電気化学測定を行った。CVの結果、測定温度は145℃と混合塩よりも高温になるが、5.0 Vと混合塩とほぼ同等の電気化学窓を有することが分かった（図10）。
Example 9
The same electrochemical measurement was performed on the molten salt of LiFTA single salt. As a result of CV, the measurement temperature was 145 ° C, which was higher than that of the mixed salt, but 5.0 V was found to have an electrochemical window almost equivalent to the mixed salt (Fig. 10).
実施例１０
LiFTA単塩においてもLiFePO4正極の充放電試験を行った結果、作動温度は150℃と混合塩よりも高温であるが、良好な充放電曲線と理論容量に近い放電容量が得られた（図11）。このことから溶媒・他のアルカリ金属等の添加物を一切含まないLiFTA塩単体のみからなる電解液は、150℃という高温環境下でも高容量の充放電が可能であることが確認された。図1〜8の混合溶融塩の実験は、このLiFTAの高い熱的・電気化学的安定性とLiFePO4正極に対する高い容量を保ちつつ、より低温まで作動温度を広げるための試みである。
Example 10
As a result of the LiFePO 4 positive electrode charge / discharge test for LiFTA single salt, the operating temperature was 150 ° C, which was higher than the mixed salt, but a good charge / discharge curve and a discharge capacity close to the theoretical capacity were obtained (Fig. 11). From this, it was confirmed that the electrolytic solution consisting only of the LiFTA salt alone containing no additives such as a solvent and other alkali metals can be charged and discharged with a high capacity even under a high temperature environment of 150 ° C. The mixed molten salt experiments in FIGS. 1-8 are attempts to extend the operating temperature to lower temperatures while maintaining the high thermal and electrochemical stability of this LiFTA and the high capacity for the LiFePO 4 cathode.
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