JPH0377626B2 - - Google Patents
Info
- Publication number
- JPH0377626B2 JPH0377626B2 JP57206573A JP20657382A JPH0377626B2 JP H0377626 B2 JPH0377626 B2 JP H0377626B2 JP 57206573 A JP57206573 A JP 57206573A JP 20657382 A JP20657382 A JP 20657382A JP H0377626 B2 JPH0377626 B2 JP H0377626B2
- Authority
- JP
- Japan
- Prior art keywords
- electrolyte
- electrode
- charge
- charging
- ethylene carbonate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000003792 electrolyte Substances 0.000 claims description 38
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 20
- 229910052744 lithium Inorganic materials 0.000 claims description 15
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 13
- 239000008151 electrolyte solution Substances 0.000 claims description 10
- 239000003960 organic solvent Substances 0.000 claims description 10
- 125000004122 cyclic group Chemical group 0.000 claims description 5
- -1 acyclic ethers Chemical class 0.000 claims description 4
- 229910003002 lithium salt Inorganic materials 0.000 claims description 4
- 159000000002 lithium salts Chemical class 0.000 claims description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 26
- 238000007599 discharging Methods 0.000 description 22
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 17
- 239000012046 mixed solvent Substances 0.000 description 13
- 229910001416 lithium ion Inorganic materials 0.000 description 11
- 239000002904 solvent Substances 0.000 description 11
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 230000005611 electricity Effects 0.000 description 8
- 239000011255 nonaqueous electrolyte Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 description 4
- 238000000151 deposition Methods 0.000 description 4
- 239000002798 polar solvent Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910013684 LiClO 4 Inorganic materials 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 3
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 description 2
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 2
- 125000002015 acyclic group Chemical group 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 150000002170 ethers Chemical class 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- OSNIIMCBVLBNGS-UHFFFAOYSA-N 1-(1,3-benzodioxol-5-yl)-2-(dimethylamino)propan-1-one Chemical compound CN(C)C(C)C(=O)C1=CC=C2OCOC2=C1 OSNIIMCBVLBNGS-UHFFFAOYSA-N 0.000 description 1
- 229910010238 LiAlCl 4 Inorganic materials 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- DHXVGJBLRPWPCS-UHFFFAOYSA-N Tetrahydropyran Chemical compound C1CCOCC1 DHXVGJBLRPWPCS-UHFFFAOYSA-N 0.000 description 1
- KSECJOPEZIAKMU-UHFFFAOYSA-N [S--].[S--].[S--].[S--].[S--].[V+5].[V+5] Chemical compound [S--].[S--].[S--].[S--].[S--].[V+5].[V+5] KSECJOPEZIAKMU-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- LYGJENNIWJXYER-UHFFFAOYSA-N nitromethane Chemical compound C[N+]([O-])=O LYGJENNIWJXYER-UHFFFAOYSA-N 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 150000003346 selenoethers Chemical class 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- XSOKHXFFCGXDJZ-UHFFFAOYSA-N telluride(2-) Chemical compound [Te-2] XSOKHXFFCGXDJZ-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Primary Cells (AREA)
- Secondary Cells (AREA)
Description
本発明は、二次リチウム電池に用いる電解液に
関するものである。
リチウム負極活物質として用いる電池は、小
型・高エネルギ密度を有する電池として研究され
ているが、その二次化が大きな問題点となつてい
る。
二次化が可能な正極活物質として、V2O3、
V6O12等の金属酸化物、TiS2、VS2等の層状化合
物が、Liとの間でトポケミカルな反応をする化合
物として知られており、現在までチタン、ジルコ
ニウム、ハフニウム、ニオビウム、タンタル、バ
ナジウムの硫化物、セレン化物、テルル化物を用
いた電池（米国特許第4089052号明細書参照）等
が開示されている。
しかしながら、このような二次電池用正極活物
質の研究に比して、Li極の充放電特性に関する研
究は充分とはいえず、Li二次電池実現のために
は、充放電効率及びサイクル寿命等の充放電特性
の良好な電解液の探査が重大な問題となつてい
る。Li極の充放電効率を向上させる試みとしては
LiClO4／プロピレンカーボネイトにニトロメタ
ン、SO2等の添加剤を加える試み
〔Electrochimica.Acta.vol.22，第75頁〜83頁
（1977）〕等が行なわれているが必ずしも充分とは
いえず、さらに特性の優れたリチウム二次電池用
電解液が求められている。
また、Liの充放電効率向上と導電率向上を目的
に、プロピレンカーボネートにエーテル類を混合
する試み（例えば、特開昭57−141879号）も行わ
れているが、その値は高くない。さらに、Liの充
放電効率と溶媒構造との関係を明らかにすること
を目的に、テトラヒドロフランおよびその誘導体
を用いてLiの充放電効率を測定した報告もある
が、類似構造であつても系統性がなく、その機構
は複雑で充分には解決されていない（J.
Electrochem.Soc.，127巻、1461〜1467頁、1980
年）。特に、溶媒が変化するとLiの充放電効率は
大きく影響するLi表面膜の特性が変化するため、
この膜の特性を良好にしなければならないと考え
られている。
本発明は、このような現状に鑑みてなされもの
であり、その目的は導電率が高くかつLi極の充放
電特性の優れたリチウム二次電池用比水電解液を
提供することにある。
したがつて、本発明によるリチウム二次電池用
非水電解液はリチウム塩を有機溶媒に溶解させた
非水電解液において、前記非水電解液の有機溶媒
としてエチレンカーボネイトとエチレンカーボネ
イトより低粘度の環状又は非環状のエーテル類を
１種以上混合した事を特徴とするものである。
本発明によれば、有機溶媒として、エチレンカ
ーボネイトとエチレンカーボネイトより低粘度の
環状又は非環状のエーテル類を１種以上混合した
ものを用いる事により、導電率が高く、かつLi極
の充放電特性の優秀なリチウム二次電池用非水電
解液を提供することができる。
本発明を更に詳しく説明する。
リチウム二次電池は、リチウムを負極活物質と
し、Li+イオンに対し、電気化学的に活性で、か
つLi+イオンと可逆的な電気化学反応を行なう物
質を正極活物質とし、リチウム塩を有機溶媒に溶
解させた非水電解液を用いたものであるが、この
リチウム二次電池用の有機溶媒として、本発明に
おいては、エチレンカーボネイトとエチレンカー
ボネイトより低粘度の非プロピレン性極性溶媒の
１種以上との混合溶媒を用いる。Li極の充放電効
率及び電解液の導電率を向上させるためには、Li
から溶媒への電子移動反応性が低い溶媒を選択す
る事や溶媒系中のLi塩が解離し易く、かつLi+イ
オンの移動性が大きい事が必要であると考えられ
る。
エチレンカーボネイトは、高誘電率（89.1，40
℃）であるが、その融点は約36℃であり、常温で
は、単独では使用し難いという欠点を有する。
又、その粘度は高く（1.9cP，40℃）、必ずしも好
ましくはない。そこで、エチレンカーボネイトと
エチレンカーボネイトより低粘度の非プロトン性
極性溶媒との混合溶媒を用いる事により上記要求
を満足する事が期待される。
本発明による電解液の有機溶媒は前述のよう
に、エチレンカーボネイトとエチレンカーボネイ
トより低粘度の環状又は非環状のエーテル類との
混合溶媒であるが、これらに、溶解される溶質は
従来この極の電池に用いられる溶質を自由に用い
ることができる。たとえば、LiClO4，LiBF4，
LiAsF6，LiPE6，LiAlCl4等の無機塩及び
CF3SO3Li，CF3COOLi等の有機塩を用いること
ができる。
これらの溶質は前記有機溶媒に、好ましくは
0.5〜2.5N溶解される。溶解する溶質が0.5N未満
であると、充放電特性が著しく低下し、2.5Nを
越えると、溶質は溶解しないからである。
エチレンカーボネイトと混合するエチレンカー
ボネイトより低粘度の非プロトン性極性溶媒は、
従来この種の電池に用いられる低粘度溶媒を自由
に用いる事ができる。たとえば、テトラハイドロ
フラン、２−メチルテトラハイドロフラン、テト
ラハイドロピラン、１，３−ジオキソラン、１，
２−ジメトキシエタン、ジメチルスルホキシド、
ジエチルエーテル、Ｎ，Ｎ−ジメチルホルムアミ
ド等の中から選ばれた１種以上の溶媒を用いる事
ができる。
エチレンカーボネイト及びエチレンカーボネイ
トより低粘度の非プロトン極性溶媒の混合比は好
ましくは１：９〜９：１、最も好ましくは５：５
前後である。１：９以下の混合比であると両者を
混合した意味が薄くなり、単独系の充放電特性に
近づき充放電特性が悪化するからである。
以下、本発明の実施例を説明する。
実施例 １
Pt極を作用極、対極にLiを参照電極としてLi
を用いた電池を組み、Pt極上にLiを析出させる
ことにより、Li極の充放電特性を測定した。電解
液には、2NLiClO4をエチレンカーボネイト（以
下、ECと略記する）とテトラハイドロフラン
（以下、THFと略記する）の１：１モル比混合溶
媒に溶解させたものを用いた。この電解液の導電
率は10.4×10-3Ω-1cm-1であり、2NLiClO4／
THF単独系の導電率である5.2×10-3Ω-1cm-1よ
り高かつた。
測定は、まず５ｍＡ／cm2の定電流で１分間、
Pt極上にLiを析出させ充電した後、５ｍＡ／cm2
の定電流でPt極上に析出したLiをLi+イオンとし
て放電するサイクル試験を行なつた。充放電効率
は、Pt極の電位変化より求め、Pt極上に析出し
たLiをLi+イオンとしえ放電させるのに要した電
気量とPt極上にLiを析出させるために要した電
気量との比から算出した。
第１図は、充放電効率とサイクル数の関係を示
す図であり、図中のａは上記電解液を用いた場合
であり、ｂは、2NLiClO4／THE単独系の電解液
を用いた場合の充放電特性を参考例として示し
た。第１図から判るように、単独系ｂに比べて、
混合系ａは明らかに、充放電特性は向上してい
る。
実施例 ２
電解液として、2NLiClO4をECと１，３−ジオ
キソラン（以下、DOLと略記する）のモル混合
比１：１の混合溶媒に溶解させたものを用いた以
外は、実施例１と同様にしてLiの充放電特性を測
定した。この電解液の導電率は12.6×10-3Ω-1cm
-1であり、2NLiClO4／THF単独系の導電率であ
る2.1×10-3Ω-1cm-1より高かつた。
第２図は充放電効率とサイクル数の関係を示す
図であり、図中のａは本発明の2NLiClO4／EC／
DOL（モル混合比１：１）を電解液として用いた
場合であり、図中のｂは参考例として、
2NLiClO4／DOL単独溶媒系電解液を用いた場合
のLi極の充放電特性を示したものである。第２図
から判る様に、単独系ｂに比べて、混合系ａは明
らかに充放電特性は向上している。
実施例 ３
電解液として2NLiClO4をECと２−メチルテト
ラハイドロフラン（以下、２−MeTHFと略記す
る）のモル混合比１：１の混合溶媒に溶解させた
ものを用いた以外は実施例１と同様にしてLi極の
充放電特性を測定した。この電解液の導電率は、
9.24×10-3Ω-1cm-1であり、2NLiClO4／
2MeTHF単独系電解液の導電率である1.9×10-3
Ω-1cm-1より高かつた。
第３図はLi極の充放電効率とサイクル数の関係
を示す図であり、図中のａは本実施例の
1NLiClO4／EC／2MeTHF（モル混合比１：１）
を電解液として用いた場合であり、ｂは参考例の
2NLiClO4／2MeTHFを用いた場合の充放電特性
である。
第３図から判る様にECと2MeTHFの混合溶媒
を用いる事によりLi極の充放電特性は著しく向上
している。
実施例 ４
電解液として、2NLiClO4をECと１，２−ジメ
トキシエタン（以下、DMEと略記する）のモル
混合比１：１の混合溶媒に溶解させたものを用い
た以外は実施例１と同様にしてLi極の充放電特性
を測定した。
この電解液の導電率は11.0×10-3Ω-1cm-1と高
い値を示した。
第４図はLi祝の充放電効率とサイクル数の関係
を示す図であり、電解液として本発明の
2NLiClO4／EC／DME（モル混合比１：１）を用
いた場合である。参考例として1NLiClO4／DME
単独溶媒系電解液中でのLiの充放電特性を行なつ
たが、１サイクル目において充放電効率は、ほぼ
０％であつた。これに対して、第４図に示す様
に、本発明のECとDMEの混合溶媒系電解液中で
のLiの充放電特性は極めて良好であつた。
実施例 ５
作用極としてPt極を、対極としてLiをさらに
参照電極としてLiを用いたセルを組み、Pt極上
にLiを析出させる事により、Li極の充放電特性を
測定した。電解液には、ECとTHFをモル混合比
１：９で混合したものに2NのLiClO4を溶解させ
たものを用いた。
測定は、まず0.5ｍＡ／cm2の定電流で20分間、
Pt極上にLiを析出させた後0.5ｍＡ／cm2の定電流
でPt極上に析出させたLiをLi+イオンとして放電
するサイクル試験を行なつた。充放電効率はPt
極の電位変化より求め、Pt極上に析出したLiを
Li+イオンとして放電させるのに要した電気量と
Pt極上にLiを析出させるために要した電気量と
の比から算出した。
第５図は、Li極の充放電効率とサイクル数の関
係を示す図であり、図中ａは本発明の
2NLiClO4／EC／THF（１：９モル混合比）を電
解液として用いた場合であり、図中ｂは
2NLiClO4／THF単独溶媒系電解液を用いた場合
のLiの充放電特性を示したものである。第５図か
ら判る様に、混合系ａでは、単独系ｂに比してLi
の充放電特性は著しく向上している。
実施例 ６
電解液として、1NLiAsF6をECと２−MeTHF
の１：１モル比混合溶媒に溶解させたものを用い
た以外は実施例５と同様にしてLiの充放電特性を
測定した。
第６図はLiの充放電効率とサイクル数の関係を
示す図であり、図は本発明の1NLiAsF6／EC／
2MeTHF（モル混合比１：１）を電解液として用
いた場合であり、Liの充放電特性は極めて良好で
あつた。
実施例 ７
電解液として、2NLiBF4をECと2MeTHFの
１：１モル比混合溶媒に溶解させたものを用いた
以外は、実施例５と同様にして、Liの充放電特性
を測定した。
第７図はLiの充放電効率とサイクル数の関係を
示す図であり、図は本発明の2NLiBF4／EC／
2MeTHF（モル混合比１：１）を電解液として用
いた場合である。Liの充放電特性は極めて良好で
あつた。
実施例 ８
第８図に電解液として本発明の1MLiClO4−
EC／THF〔(a)〕と比較例として1MLiClO4−
PC／THF〔(b)〕を用いた場合の25℃における導
電率とTHF混合量との関係を示す。いかなる
THF混合量においても、ECを用いた本発明の電
解液の方が比較例のPCを用いた電解液より高い
導電率を示すことがわかる。
また、第１表には、各種エーテル類とECを混
合した本発明の電解液の導電率を、PCを混合し
た電解液と比較して示す。いずれの場合も、本発
明のEC混合系電解液の方が高い導電率を示し、
優れた特性を示すことがわかる。
The present invention relates to an electrolytic solution used in a secondary lithium battery. Batteries used as lithium negative electrode active materials are being studied as small-sized batteries with high energy density, but secondaryization has become a major problem. As a positive electrode active material that can be secondaryized, V 2 O 3 ,
Metal oxides such as V 6 O 12 and layered compounds such as TiS 2 and VS 2 are known as compounds that undergo topochemical reactions with Li. Batteries using vanadium sulfide, selenide, telluride (see US Pat. No. 4,089,052), etc. have been disclosed. However, compared to such research on positive electrode active materials for secondary batteries, research on the charging and discharging characteristics of Li electrodes is not sufficient, and in order to realize Li secondary batteries, charging and discharging efficiency and cycle life are The search for electrolytes with good charge-discharge characteristics has become a serious issue. As an attempt to improve the charging and discharging efficiency of Li electrodes,
Attempts have been made to add additives such as nitromethane and SO 2 to LiClO 4 /propylene carbonate [Electrochimica.Acta.vol. 22, pp. 75-83 (1977)], but this is not necessarily sufficient. Furthermore, there is a need for an electrolytic solution for lithium secondary batteries with excellent characteristics. In addition, attempts have been made to mix ethers with propylene carbonate (for example, JP-A-57-141879) for the purpose of improving Li charge/discharge efficiency and conductivity, but the results are not high. Furthermore, there are reports that measured the charge and discharge efficiency of Li using tetrahydrofuran and its derivatives with the aim of clarifying the relationship between the charge and discharge efficiency of Li and the solvent structure, but even with similar structures, there is a systematic The mechanism is complex and not fully understood (J.
Electrochem.Soc., vol. 127, pp. 1461-1467, 1980
Year). In particular, when the solvent changes, the characteristics of the Li surface film change, which greatly affects the Li charging and discharging efficiency.
It is believed that the properties of this film must be improved. The present invention has been made in view of the current situation, and its purpose is to provide a specific water electrolyte for lithium secondary batteries that has high conductivity and excellent charging and discharging characteristics of Li electrodes. Therefore, the non-aqueous electrolyte for lithium secondary batteries according to the present invention is a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent, and the organic solvent of the non-aqueous electrolyte is ethylene carbonate, which has a lower viscosity than ethylene carbonate. It is characterized by a mixture of one or more types of cyclic or acyclic ethers. According to the present invention, by using a mixture of ethylene carbonate and one or more types of cyclic or acyclic ethers having a lower viscosity than ethylene carbonate as an organic solvent, the conductivity is high and the charge/discharge characteristics of the Li electrode are improved. We can provide an excellent non-aqueous electrolyte for lithium secondary batteries. The present invention will be explained in more detail. Lithium secondary batteries use lithium as a negative electrode active material, a positive electrode active material that is electrochemically active toward Li + ions and that undergoes a reversible electrochemical reaction with Li + ions, and a lithium salt as an organic material. This method uses a non-aqueous electrolyte dissolved in a solvent, and in the present invention, as an organic solvent for this lithium secondary battery, ethylene carbonate and a type of non-propylene polar solvent with a lower viscosity than ethylene carbonate are used. A mixed solvent with the above is used. In order to improve the charging and discharging efficiency of Li electrodes and the conductivity of electrolyte, Li
It is thought that it is necessary to select a solvent that has low electron transfer reactivity from to the solvent, that the Li salt in the solvent system is easily dissociated, and that the mobility of Li + ions is high. Ethylene carbonate has a high dielectric constant (89.1, 40
℃), but its melting point is about 36℃, and it has the disadvantage that it is difficult to use alone at room temperature.
Moreover, its viscosity is high (1.9 cP, 40°C), which is not necessarily preferable. Therefore, it is expected that the above requirements can be met by using a mixed solvent of ethylene carbonate and an aprotic polar solvent having a lower viscosity than ethylene carbonate. As mentioned above, the organic solvent of the electrolyte according to the present invention is a mixed solvent of ethylene carbonate and a cyclic or acyclic ether having a lower viscosity than ethylene carbonate. Any solute used in batteries can be used. For example, LiClO 4 , LiBF 4 ,
Inorganic salts such as LiAsF 6 , LiPE 6 , LiAlCl 4 and
Organic salts such as CF 3 SO 3 Li and CF 3 COOLi can be used. These solutes are preferably added to the organic solvent.
0.5-2.5N is dissolved. This is because if the amount of dissolved solute is less than 0.5N, the charge/discharge characteristics will be significantly reduced, and if it exceeds 2.5N, the solute will not dissolve. An aprotic polar solvent with a lower viscosity than ethylene carbonate is mixed with ethylene carbonate.
Low viscosity solvents conventionally used in this type of battery can be freely used. For example, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,
2-dimethoxyethane, dimethyl sulfoxide,
One or more solvents selected from diethyl ether, N,N-dimethylformamide, etc. can be used. The mixing ratio of ethylene carbonate and aprotic polar solvent having a lower viscosity than ethylene carbonate is preferably 1:9 to 9:1, most preferably 5:5.
Before and after. This is because if the mixing ratio is 1:9 or less, the meaning of mixing the two becomes weak, and the charge and discharge characteristics approach those of a single system, resulting in deterioration of the charge and discharge characteristics. Examples of the present invention will be described below. Example 1 Pt electrode is used as a working electrode, Li is used as a counter electrode and Li is used as a reference electrode.
We assembled a battery using Pt and deposited Li on the Pt electrode to measure the charge/discharge characteristics of the Li electrode. The electrolytic solution used was one in which 2NLiClO 4 was dissolved in a mixed solvent of ethylene carbonate (hereinafter abbreviated as EC) and tetrahydrofuran (hereinafter abbreviated as THF) in a molar ratio of 1:1. The conductivity of this electrolyte is 10.4×10 -3 Ω -1 cm -1 and 2NLiClO 4 /
The conductivity was higher than that of THF alone, which was 5.2×10 -3 Ω -1 cm -1 . The measurement was first carried out at a constant current of 5 mA/cm 2 for 1 minute.
After depositing Li on Pt electrode and charging, 5mA/cm 2
A cycle test was conducted in which Li deposited on the Pt electrode was discharged as Li + ions at a constant current of . The charge/discharge efficiency is determined from the potential change of the Pt electrode, and is calculated from the ratio of the amount of electricity required to discharge Li deposited on the Pt electrode into Li + ions and the amount of electricity required to deposit Li on the Pt electrode. Calculated. Figure 1 is a diagram showing the relationship between charge/discharge efficiency and number of cycles. In the figure, a shows the case when the above electrolyte is used, and b shows the case when the electrolyte of 2NLiClO 4 /THE alone is used. The charge/discharge characteristics of are shown as a reference example. As can be seen from Figure 1, compared to independent system b,
Mixed system a clearly has improved charge-discharge characteristics. Example 2 Same as Example 1 except that 2NLiClO 4 was dissolved in a mixed solvent of EC and 1,3-dioxolane (hereinafter abbreviated as DOL) at a molar mixing ratio of 1:1 as the electrolyte. The charge/discharge characteristics of Li were measured in the same manner. The conductivity of this electrolyte is 12.6×10 -3 Ω -1 cm
-1 , which was higher than the conductivity of 2NLiClO 4 /THF alone, which was 2.1×10 -3 Ω -1 cm -1 . FIG. 2 is a diagram showing the relationship between charge/discharge efficiency and cycle number, and a in the figure is 2NLiClO 4 /EC/ of the present invention.
This is the case when DOL (molar mixing ratio 1:1) is used as the electrolyte, and b in the figure is a reference example.
This figure shows the charging and discharging characteristics of Li electrodes when using a 2NLiClO 4 /DOL single solvent electrolyte. As can be seen from FIG. 2, the charging and discharging characteristics of the mixed system a are clearly improved compared to the single system b. Example 3 Example 1 except that 2NLiClO 4 dissolved in a mixed solvent of EC and 2-methyltetrahydrofuran (hereinafter abbreviated as 2-MeTHF) at a molar mixing ratio of 1:1 was used as the electrolyte. The charging and discharging characteristics of the Li electrode were measured in the same manner as described above. The conductivity of this electrolyte is
9.24×10 -3 Ω -1 cm -1 and 2NLiClO 4 /
The conductivity of 2MeTHF single electrolyte is 1.9×10 -3
It was higher than Ω -1 cm -1 . Figure 3 is a diagram showing the relationship between the charging/discharging efficiency of Li electrodes and the number of cycles, and a in the figure is for this example.
1NLiClO 4 /EC/2MeTHF (molar mixing ratio 1:1)
is used as the electrolyte, and b is the reference example.
This is the charge/discharge characteristics when using 2NLiClO 4 /2MeTHF. As can be seen from Figure 3, the charge and discharge characteristics of the Li electrode were significantly improved by using a mixed solvent of EC and 2MeTHF. Example 4 Same as Example 1 except that 2NLiClO 4 was dissolved in a mixed solvent of EC and 1,2-dimethoxyethane (hereinafter abbreviated as DME) at a molar mixing ratio of 1:1 as the electrolyte. The charge and discharge characteristics of the Li electrode were measured in the same manner. The conductivity of this electrolyte was as high as 11.0×10 -3 Ω -1 cm -1 . Figure 4 is a diagram showing the relationship between the charging and discharging efficiency of Liho and the number of cycles.
This is a case where 2NLiClO 4 /EC/DME (molar mixing ratio 1:1) is used. As a reference example, 1NLiClO 4 /DME
The charging and discharging characteristics of Li in a single-solvent electrolyte were investigated, and the charging and discharging efficiency was approximately 0% in the first cycle. On the other hand, as shown in FIG. 4, the charging and discharging characteristics of Li in the mixed solvent electrolyte of EC and DME of the present invention were extremely good. Example 5 A cell was assembled using a Pt electrode as a working electrode, Li as a counter electrode, and Li as a reference electrode, and Li was deposited on the Pt electrode to measure the charge/discharge characteristics of the Li electrode. The electrolyte used was a mixture of EC and THF at a molar mixing ratio of 1:9, with 2N LiClO 4 dissolved therein. The measurement was first carried out for 20 minutes at a constant current of 0.5 mA/ cm2 .
After Li was deposited on the Pt electrode, a cycle test was conducted in which the Li deposited on the Pt electrode was discharged as Li + ions at a constant current of 0.5 mA/cm 2 . Charge/discharge efficiency is Pt
The Li deposited on the Pt electrode was determined from the potential change of the electrode.
The amount of electricity required to discharge Li + ions and
It was calculated from the ratio to the amount of electricity required to deposit Li on Pt. FIG. 5 is a diagram showing the relationship between the charging/discharging efficiency of Li electrodes and the number of cycles;
This is the case when 2NLiClO 4 /EC/THF (1:9 molar mixing ratio) is used as the electrolyte, and b in the figure is
This figure shows the charging and discharging characteristics of Li when using a 2NLiClO 4 /THF single solvent electrolyte. As can be seen from Figure 5, in mixed system a, Li
The charge-discharge characteristics of the battery have been significantly improved. Example 6 1NLiAsF 6 was used as an electrolyte with EC and 2-MeTHF.
The charge-discharge characteristics of Li were measured in the same manner as in Example 5, except that Li was dissolved in a 1:1 molar ratio mixed solvent. FIG. 6 is a diagram showing the relationship between the charge/discharge efficiency of Li and the number of cycles.
This was the case when 2MeTHF (molar mixing ratio 1:1) was used as the electrolyte, and the charging and discharging characteristics of Li were extremely good. Example 7 The charging and discharging characteristics of Li were measured in the same manner as in Example 5, except that 2NLiBF 4 dissolved in a 1:1 molar mixed solvent of EC and 2MeTHF was used as the electrolyte. FIG. 7 is a diagram showing the relationship between the charge/discharge efficiency of Li and the number of cycles.
This is the case where 2MeTHF (molar mixing ratio 1:1) was used as the electrolyte. The charging and discharging characteristics of Li were extremely good. Example 8 Figure 8 shows 1MLiClO 4 − of the present invention as an electrolyte.
EC/THF [(a)] and 1MLiClO 4 − as a comparative example
The relationship between the electrical conductivity at 25°C and the amount of THF mixed when using PC/THF [(b)] is shown. whatever
It can be seen that the electrolytic solution of the present invention using EC exhibits higher conductivity than the electrolytic solution using PC of the comparative example, even in terms of the amount of THF mixed. Table 1 also shows the conductivity of the electrolytic solution of the present invention, which is a mixture of various ethers and EC, in comparison with an electrolytic solution that is a mixture of PC. In either case, the EC mixed electrolyte of the present invention exhibits higher conductivity,
It can be seen that it exhibits excellent characteristics.
【表】【table】
【表】
実施例 ９
電解液として本発明のEC／エーテル混合溶媒
系電解液を用いて、実施例１で述べたものと同じ
セルを用いてリチウムの充放電効率を測定した。
また、比較例として、PC／エーテル類混合系を
用いた場合も測定した。
測定は、まず0.5ｍＡ／cm2の定電流で40分間、
Pt極上にLiを析出させた後、0.5ｍＡ／cm2の定電
流でPt極上に析出させたLiをLi+イオンとして放
電するサイクル試験を行つた。充放電効率はPt
極の電位変化より求め、Pt極上に析出したLiを
Li+イオンとして放電させるのに要した電気量と
Pt極上にLiを析出させるために要した電気量と
の比から算出し、１〜10サイクルの平均値を平均
充放電効率（Ett，10）とした。
結果を第２表に示す。第２表からわかるよう
に、本発明のEC混合系電解液は比較例のEC混合
系電解液より優れた特性を有することがわかる。[Table] Example 9 The lithium charge/discharge efficiency was measured using the same cell as described in Example 1, using the EC/ether mixed solvent electrolyte of the present invention as the electrolyte.
In addition, as a comparative example, measurements were also conducted using a PC/ether mixed system. The measurement was first carried out for 40 minutes at a constant current of 0.5 mA/ cm2 .
After Li was deposited on the Pt electrode, a cycle test was conducted in which the Li deposited on the Pt electrode was discharged as Li + ions at a constant current of 0.5 mA/cm 2 . Charge/discharge efficiency is Pt
The Li deposited on the Pt electrode was determined from the potential change of the electrode.
The amount of electricity required to discharge Li + ions and
It was calculated from the ratio to the amount of electricity required to deposit Li on the Pt electrode, and the average value for 1 to 10 cycles was taken as the average charge/discharge efficiency (Ett, 10 ). The results are shown in Table 2. As can be seen from Table 2, the EC mixed electrolyte of the present invention has better properties than the EC mixed electrolyte of the comparative example.
【表】【table】
【表】
実施例 10
電解液として本発明のEC／エーテル類混合溶
媒系電解液を用いて、実施例１で述べたものと同
じセルを用いてリチウムの充放電効率を測定し
た。また、比較例として、PC／エーテル類混合
系を用いた場合も測定した。
測定は、0.05ｍＡ／cm2〜５ｍＡ／cm2の定電流で
200分〜２分間、Pt極上にLiを析出させた後（い
ずれの電流値でも、Liの析出量は、0.6C／cm2とな
る）、各々、析出電流値と同一の電流値でPt極上
に析出したLiをLi+イオンとして放電するサイク
ル試験を行つた。充放電効率はPt極の電位変化
より求め、Pt極上に析出したLiをLi+イオンとし
て放電させるのに要した電気量とPt極上にLiを
析出させるために要した電気量との比から算出し
た。
結果を第９図に示す。図中の（○）は、本発明
のEC混合系電解液を用いた場合であり、図中の
（●）は比較例のPC混合系電解液を用いた場合で
ある。いずれのエーテル類、およびいずれの電流
値においても本発明のEC混合系電解液を用いた
場合より優れたLiの充放電効率を示すことがわか
る。
以上の説明から明らかなように本発明によれば
リチウム塩を有機溶媒に溶解させた非水電解液に
おいて有機溶媒として、エチレンカーボネイトと
前記エチレンカーボネイトより低粘度の環状ある
いは非環状エーテル類の１種以上を混合したもの
を用いる事により、導電率も高くかつLi極の充放
電特性が優れたリチウム二次電池用非水電解液を
提供する事ができる。[Table] Example 10 The lithium charge/discharge efficiency was measured using the same cell as described in Example 1, using the EC/ether mixed solvent electrolyte of the present invention as the electrolyte. In addition, as a comparative example, measurements were also conducted using a PC/ether mixed system. Measurements are made with a constant current of 0.05mA/ cm2 to 5mA/ cm2.
After depositing Li on the Pt electrode for 200 to 2 minutes (the amount of Li deposited is 0.6C/cm 2 at any current value), depositing Li on the Pt electrode at the same current value as the deposition current value. A cycle test was conducted in which the Li deposited on the substrate was discharged as Li + ions. Charge/discharge efficiency is determined from the potential change of the Pt electrode, and calculated from the ratio of the amount of electricity required to discharge Li deposited on the Pt electrode as Li + ions and the amount of electricity required to deposit Li on the Pt electrode. did. The results are shown in Figure 9. (○) in the figure is the case when the EC mixed electrolyte of the present invention was used, and (●) in the figure is the case when the PC mixed electrolyte of the comparative example was used. It can be seen that Li charging and discharging efficiency is superior to the case where the EC mixed electrolyte of the present invention is used for any ether and at any current value. As is clear from the above description, according to the present invention, in a nonaqueous electrolyte in which a lithium salt is dissolved in an organic solvent, ethylene carbonate and one type of cyclic or acyclic ether having a lower viscosity than ethylene carbonate are used as the organic solvent. By using a mixture of the above, it is possible to provide a non-aqueous electrolyte for lithium secondary batteries that has high conductivity and excellent charging and discharging characteristics of Li electrodes.
第１図〜第９図は本発明による電解液を用いた
場合のLi極の充放電効率とサイクル数の関係を示
す図である。
FIGS. 1 to 9 are diagrams showing the relationship between the charging/discharging efficiency of Li electrodes and the number of cycles when using the electrolytic solution according to the present invention.
Claims (1)
二次電池用電解液において、前記電解液の有機溶
媒として、エチレンカーボネイトとエチレンカー
ボネイトより低粘度の環状又は非環状のエーテル
類を１種以上混合した事を特徴とするリチウム二
次電池用電解液。1. In an electrolytic solution for lithium secondary batteries in which a lithium salt is dissolved in an organic solvent, ethylene carbonate and one or more types of cyclic or acyclic ethers having a lower viscosity than ethylene carbonate are mixed as the organic solvent of the electrolytic solution. An electrolyte for lithium secondary batteries characterized by:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57206573A JPS5996666A (en) | 1982-11-25 | 1982-11-25 | Electrolyte for lithium battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57206573A JPS5996666A (en) | 1982-11-25 | 1982-11-25 | Electrolyte for lithium battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5996666A JPS5996666A (en) | 1984-06-04 |
| JPH0377626B2 true JPH0377626B2 (en) | 1991-12-11 |
Family
ID=16525637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP57206573A Granted JPS5996666A (en) | 1982-11-25 | 1982-11-25 | Electrolyte for lithium battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5996666A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0831338B2 (en) * | 1986-03-25 | 1996-03-27 | 日本電信電話株式会社 | Lithium secondary battery |
| JPS62219475A (en) * | 1986-03-20 | 1987-09-26 | Nippon Telegr & Teleph Corp <Ntt> | Secondary cell of lithium |
| JPS63168969A (en) * | 1986-12-27 | 1988-07-12 | Sanyo Electric Co Ltd | Nonaqueous electrolyte cell |
| JPS63307669A (en) * | 1987-06-08 | 1988-12-15 | Sanyo Electric Co Ltd | Nonaqueous electrolyte cell |
| JPH0616422B2 (en) * | 1987-07-08 | 1994-03-02 | 富士電気化学株式会社 | Non-aqueous electrolyte battery |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57141879A (en) * | 1981-02-24 | 1982-09-02 | Nippon Telegr & Teleph Corp <Ntt> | Electrolyte for lithium secondary battery |
-
1982
- 1982-11-25 JP JP57206573A patent/JPS5996666A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57141879A (en) * | 1981-02-24 | 1982-09-02 | Nippon Telegr & Teleph Corp <Ntt> | Electrolyte for lithium secondary battery |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5996666A (en) | 1984-06-04 |
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