JP4544250B2 - Non-aqueous electrolyte lithium secondary battery - Google Patents
Non-aqueous electrolyte lithium secondary battery Download PDFInfo
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Description
本発明は、非水電解液リチウム二次電池に関する。 The present invention relates to a non-aqueous electrolyte lithium secondary battery.
近年、従来のサイクル特性に問題のあったリチウム金属またはリチウム合金を負極に用いたリチウム二次電池にかわり、負極活物質として炭素材料を用いた格段にサイクル特性に優れたリチウム二次電池が登場し、携帯電話や携帯式ビデオカメラなどポータブル電気機器用の二次電池として初めてリチウム二次電池が実用化された。しかしながら、充放電を繰り返すことにより容量が次第に低下していくという現象が認められ、サイクル特性については必ずしも満足できるものではなく、さらに一層の特性向上が求められている。
サイクル特性が必ずしも満足できないのは、電極内部での活物質の構造変化と密着性の低下の他に、電池内での電解液溶媒および電解質が化学的変化により減少することと、その変化によって生成される化合物が負極表面に堆積することにより過電圧が増大することが原因と考えられる。
In recent years, lithium secondary batteries using a carbon material as the negative electrode active material have remarkably improved cycle characteristics, replacing the conventional lithium secondary batteries that use lithium metals or lithium alloys that have had problems with cycle characteristics. For the first time, lithium secondary batteries were put to practical use as secondary batteries for portable electric devices such as mobile phones and portable video cameras. However, the phenomenon that the capacity gradually decreases by repeating charge and discharge is recognized, and the cycle characteristics are not always satisfactory, and further improvement in characteristics is required.
The cycle characteristics are not always satisfactory because the electrolyte solution solvent and electrolyte in the battery decrease due to chemical changes in addition to the structural change of the active material inside the electrode and the decrease in adhesion. It is considered that the overvoltage increases due to the deposition of the compound to be deposited on the negative electrode surface.
リチウム二次電池においてサイクル性向上を目的とした電解液の改良は従来より行われており、その一例として、負極活物質として黒鉛系炭素を使用した場合の電解液の成分としてエチレンカーボネート（以下、ＥＣとよぶことがある。）を含有することによりサイクル性が改善するとされ、実用化されている。
しかしながら、ＥＣは融点が室温より高いため電解液の粘度を上げ電導度を下げる。そのため、ＥＣを含有することは大電流充放電特性および低温特性を低下させる一因となる。また、ＥＣを含有することにより過電圧の増大が見られ、それがサイクル劣化の一因ともなっている。
Improvement of the electrolytic solution for the purpose of improving the cycle performance in the lithium secondary battery has been conventionally performed, and as an example, ethylene carbonate (hereinafter, referred to as the component of the electrolytic solution when graphite-based carbon is used as the negative electrode active material). It may be referred to as EC.), And it has been put to practical use because the cycleability is improved.
However, since EC has a melting point higher than room temperature, it increases the viscosity of the electrolyte and lowers the conductivity. Therefore, the inclusion of EC contributes to the deterioration of the large current charge / discharge characteristics and the low temperature characteristics. In addition, an increase in overvoltage is observed due to the inclusion of EC, which contributes to cycle deterioration.
本発明の目的は、低温特性を損なうことなく、サイクル特性および大電流充放電特性を向上させたリチウム二次電池を提供することにある。 An object of the present invention is to provide a lithium secondary battery having improved cycle characteristics and large current charge / discharge characteristics without impairing low temperature characteristics.
このような事情をみて、本発明者らが鋭意検討を行った結果、カーボネート基を持つ高分子材料を含有させた負極を使用することにより、リチウム二次電池のサイクル特性および大電流充放電特性を向上させることができることを見出し、本発明に至った。 In view of such circumstances, as a result of intensive studies by the present inventors, by using a negative electrode containing a polymer material having a carbonate group, cycle characteristics and large current charge / discharge characteristics of a lithium secondary battery Has been found to be improved, and the present invention has been achieved.
すなわち、本発明とは、（１）リチウムイオンをドープ・脱ドープ可能な物質を活物質とする正極と、リチウムイオンをドープ・脱ドープ可能な炭素材料を活物質とする負極と、前記正極、負極の対向面間に挟まれたセパレーターと、リチウム塩からなる溶質を有機溶媒に溶解した電解液とを備えた非水電解液リチウム二次電池において、該負極が下記一般式［Ｉ］で表されるカーボネート構造を有する数平均分子量３００以上２０００００以下の重合体を含む非水電解液リチウム二次電池に係るものである。
さらに、本発明は、（２）重合体が、一般式［Ｉ］で表されるカーボネート構造を含み、かつ含まれるカーボネート構造のうちの５０％以上が該重合体の主鎖に含まれる（１）記載の非水電解液リチウム二次電池に係るものである。
さらに、本発明は、（３）重合体が、一般式［Ｉ］で表されるカーボネート構造を含み、かつ含まれるカーボネート構造のうちの５０％以上が該重合体の側鎖に含まれる（１）記載の非水電解液リチウム二次電池に係るものである。
Further, in the present invention, (2) the polymer contains a carbonate structure represented by the general formula [I], and 50% or more of the contained carbonate structure is contained in the main chain of the polymer (1 ) Described in the non-aqueous electrolyte lithium secondary battery.
Further, in the present invention, (3) the polymer contains a carbonate structure represented by the general formula [I], and 50% or more of the contained carbonate structure is contained in the side chain of the polymer (1 ) Described in the non-aqueous electrolyte lithium secondary battery.
また、本発明は、（４）重合体が、下記一般式［ＩＩ］で表される化学構造を含む（２）記載の非水電解液リチウム二次電池に係るものである。
さらに、本発明は、（５）重合体が下記一般式［ＩＩＩ］で表される繰返し単位からなる（４）記載の非水電解液リチウム二次電池に係るものである。
また、本発明は、（６）重合体が下記一般式［ＩＶ］で表される繰返し単位からなる（４）記載の非水電解液リチウム二次電池に係るものである。
本発明にかかる負極とこれを用いたリチウム二次電池において、電解液にＥＣを含有しない場合、従来の負極を用いたリチウム二次電池に比べて、サイクル性と大電流充放電特性が向上する。また、本発明にかかる負極とこれを用いたリチウム二次電池において電解液にＥＣを含有した場合でも、従来の負極を用いたリチウム二次電池においてＥＣを含有する場合に比べて、サイクル特性は落ちることがなくかつ大電流充放電特性が向上する。
これにより、長寿命かつ大電流充放電特性に優れたリチウム二次電池を提供することができ、工業的価値は極めて大きい。
In the negative electrode according to the present invention and a lithium secondary battery using the same, when EC is not contained in the electrolytic solution, cycle performance and large current charge / discharge characteristics are improved as compared with a lithium secondary battery using a conventional negative electrode. . In addition, even when the negative electrode according to the present invention and the lithium secondary battery using the negative electrode contain EC in the electrolyte, the cycle characteristics are higher than in the case where the conventional lithium secondary battery using the negative electrode contains EC. There is no drop and large current charge / discharge characteristics are improved.
As a result, a lithium secondary battery having a long life and high current charge / discharge characteristics can be provided, and the industrial value is extremely high.
次に本発明を詳細に説明する。
まず、本発明における負極とは、リチウムイオンをドープ・脱ドープ可能な炭素材料を活物質とし、それと一般式［Ｉ］で表されるカーボネート構造を有する重合体と、必要であればポリエチレン、ポロプロピレン、フッ素樹脂等の適当な結着材と、さらに必要であれば導電材とを混合し、塗布、延伸等の方法により集電体シートに固着した構成のものが挙げられる。
該重合体の数平均分子量は、３００〜２０００００であり、好ましくは５００〜１５００００である。
該重合体と結着剤の総重量は、該負極で使用する炭素粉末の合計量１００重量部に対して０．１重量部ないし２０重量部程度とすることが好ましい。さらに好ましくは１重量部ないし１０重量部である。
Next, the present invention will be described in detail.
First, the negative electrode in the present invention includes a carbon material that can be doped / undoped with lithium ions as an active material, a polymer having a carbonate structure represented by the general formula [I], and, if necessary, polyethylene, An appropriate binder such as propylene and fluororesin, and further a conductive material, if necessary, are mixed and fixed to the current collector sheet by a method such as coating or stretching.
The number average molecular weight of the polymer is 300 to 200,000, preferably 500 to 150,000.
The total weight of the polymer and the binder is preferably about 0.1 to 20 parts by weight with respect to 100 parts by weight of the total amount of carbon powder used in the negative electrode. More preferably, it is 1 to 10 parts by weight.
該重合体としては、一般式［Ｉ］で表されるカーボネート構造を含むことを特徴とし、具体的には、該重合体が、一般式［Ｉ］で表されるカーボネート構造を含み、かつ含まれるカーボネート構造のうちの５０％以上が該重合体の主鎖に含まれるものや、該重合体が、一般式［Ｉ］で表されるカーボネート構造を含み、かつ含まれるカーボネート構造のうちの５０％以上が該重合体の側鎖に含まれるものが挙げられる。
これらの中で、含まれるカーボネート構造のうちの５０％以上が該重合体の主鎖に含まれるものが好ましく、特に一般式［ＩＩ］で表される化学構造を持つものが好ましく、Ｒ1 、Ｒ2 、Ｒ3 、Ｒ4 がすべて水素原子であるものがさらに好ましい。
また、一般式［ＩＩＩ］で表される繰り返し単位からなる重合体が好ましく、該重合体として一般式［ＩＶ］で表される繰り返し単位からなるポリエチレンカーボネートが特に好ましい。
本発明におけるポリエチレンカーボネートは、例えば、Ｐｏｌｙｍｅｒ Ｌｅｔｔｅｒｓ，ｖｏｌ．７，２８７ページ（１９６９年）、またはＭａｋｒｏｍｏｌ．Ｃｈｅｍ．，ｖｏｌ．１３０，２１０ページ（１９６９年）に記載される、エチレンオキシドと二酸化炭素を触媒を用いて交互共重合させる方法などによって得られる。
The polymer includes a carbonate structure represented by the general formula [I]. Specifically, the polymer includes and includes a carbonate structure represented by the general formula [I]. 50% or more of the carbonate structure contained in the main chain of the polymer, or the polymer contains a carbonate structure represented by the general formula [I] and 50 of the carbonate structure contained % Or more is included in the side chain of the polymer.
Among these, those containing 50% or more of the carbonate structure contained in the main chain of the polymer are preferred, and those having a chemical structure represented by the general formula [II] are particularly preferred, R 1 , More preferably, R 2 , R 3 and R 4 are all hydrogen atoms.
Moreover, the polymer which consists of a repeating unit represented by general formula [III] is preferable, and the polyethylene carbonate which consists of a repeating unit represented by general formula [IV] as this polymer is especially preferable.
Polyethylene carbonate in the present invention is described in, for example, Polymer Letters, vol. 7, 287 (1969), or Makromol. Chem. , Vol. 130, 210 (1969), and a method of alternately copolymerizing ethylene oxide and carbon dioxide using a catalyst.
本発明における、リチウムイオンをドープ・脱ドープ可能な炭素材料としては、天然黒鉛、人造黒鉛、コークス、カーボンブラック、熱分解炭素、炭素繊維、高分子化合物を焼成して得られた炭素材料などが例示できる。また、これら炭素材料を主成分とする複合材料が例示できる。なかでも単位重量あたりの充放電容量が大きく、充放電中の平均電位が低いという点で黒鉛系材料が含まれることが好ましい。
黒鉛系材料に含まれる黒鉛は、天然黒鉛か、人造黒鉛かは問われない。天然黒鉛としては、スリランカ産黒鉛、マダガスカル産黒鉛、朝鮮産フレーク状黒鉛、朝鮮産土状黒鉛、中国産黒鉛などが挙げられる。また、該天然黒鉛をさらに加熱、加工、変性して得られる黒鉛を用いてもよい。人造黒鉛としては、コークス材料などの黒鉛化品、メソマイクロビーズの黒鉛化品、メソフェーズピッチ系炭素繊維の黒鉛化品などが挙げられる。
Examples of the carbon material that can be doped / undoped with lithium ions in the present invention include natural graphite, artificial graphite, coke, carbon black, pyrolytic carbon, carbon fiber, and a carbon material obtained by firing a polymer compound. It can be illustrated. Moreover, the composite material which has these carbon materials as a main component can be illustrated. Among these, it is preferable that the graphite-based material is contained in that the charge / discharge capacity per unit weight is large and the average potential during charge / discharge is low.
It does not matter whether the graphite contained in the graphite-based material is natural graphite or artificial graphite. Examples of natural graphite include Sri Lankan graphite, Madagascar graphite, Korean flake graphite, Korean soil graphite, Chinese graphite and the like. Further, graphite obtained by further heating, processing and modifying the natural graphite may be used. Examples of the artificial graphite include graphitized products such as coke materials, graphitized products of mesomicrobeads, graphitized products of mesophase pitch-based carbon fibers, and the like.
本発明におけるリチウムイオンをドープ・脱ドープ可能な物質として正極に含まれる活物質としては、いわゆるα−ＮａＦｅＯ2 型構造を母体とする層状リチウム複合酸化物、スピネル型構造を母体とするリチウム複合酸化物、遷移金属カルコゲン化物などが例示できる。特に、高電圧、高エネルギー密度が得られ、サイクル特性にも優れることから、α−ＮａＦｅＯ2 型構造を母体とする層状リチウム複合酸化物が好ましい。
本発明における正極とは、リチウムイオンをドープ・脱ドープ可能な物質を活物質として、さらにポリエチレン、ポロプロピレン、フッ素樹脂等の適当な結着材とさらに導電材粉末とを混合し、塗布、延伸等の方法により集電体シートに固着した構成のものが挙げられる。該導電材粉末としては、導電効果があり、使用する非水電解液に対する耐性や正極での電気化学反応に対する耐性を有するものであればよく、例えば黒鉛粉末、カーボンブラック、コークス粉末、導電性高分子などが挙げられる。
該α−ＮａＦｅＯ2 型構造を母体とする層状リチウム複合酸化物としては、バナジウム、鉄、コバルト、ニッケル等の遷移金属を少なくとも一種含む層状リチウム複合酸化物、およびそれらにマンガンを含む層状リチウム複合酸化物等が例示される。なかでも好ましくはサイクル特性が優れているという点で、リチウム・ニッケル複合酸化物を主体とする層状リチウム複合酸化物が好ましい。
The active material contained in the positive electrode as a material capable of doping and dedoping lithium ions in the present invention includes a layered lithium composite oxide based on a so-called α-NaFeO 2 type structure, and a lithium composite oxidation based on a spinel type structure. And transition metal chalcogenides. In particular, a layered lithium composite oxide based on an α-NaFeO 2 type structure is preferable because high voltage and high energy density can be obtained and cycle characteristics are excellent.
The positive electrode in the present invention is a material capable of doping and dedoping lithium ions as an active material, and further mixed with a suitable binder such as polyethylene, polypropylene, fluororesin, and conductive material powder, and applied, stretched The thing of the structure fixed to the electrical power collector sheet | seat by the method of these etc. is mentioned. The conductive material powder may be any conductive material that has a conductive effect and has resistance to the non-aqueous electrolyte to be used and electrochemical reaction at the positive electrode. For example, graphite powder, carbon black, coke powder, high conductivity Examples include molecules.
The layered lithium composite oxide based on the α-NaFeO 2 type structure includes a layered lithium composite oxide containing at least one transition metal such as vanadium, iron, cobalt, nickel, etc., and a layered lithium composite oxide containing manganese in them. Examples are things. Among these, a layered lithium composite oxide mainly composed of a lithium / nickel composite oxide is preferable because it has excellent cycle characteristics.
本発明におけるリチウム塩としては従来より公知のものがいずれも使用でき、ＬｉＣｌＯ4 、ＬｉＰＦ6 、ＬｉＡｓＦ6 、ＬｉＢＦ4 、ＬｉＣＦ3 ＳＯ3 、ＬｉＮ（ＳＯ2 ＣＦ3 ）2 、ＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 等が例示できる。なかでも電気伝導度が大きいＬｉＰＦ6 、ＬｉＢＦ4 、ＬｉＮ（ＳＯ2 ＣＦ3 ）2 、ＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 等が好ましい。
本発明における電解液は前記リチウム塩の少なくとも１種以上を含み、前記リチウム塩を０．１Ｍ（モル／ｌ）〜２Ｍの濃度範囲で溶解している。なかでも好ましくは０．５Ｍ〜１．５Ｍの濃度範囲が好ましい。
Any conventionally known lithium salt can be used as the lithium salt in the present invention. LiClO 4 , LiPF 6 , LiAsF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 etc. can be exemplified. Of these, LiPF 6 , LiBF 4 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2, etc. having high electrical conductivity are preferable.
The electrolytic solution in the present invention contains at least one of the lithium salts, and the lithium salt is dissolved in a concentration range of 0.1 M (mol / l) to 2 M. Among these, a concentration range of 0.5M to 1.5M is preferable.
本発明におけるセパレーターとしては、フッ素系樹脂やポリエチレン、ポリプロピレンなどのオレフィン系樹脂の多孔体フィルムや、フッ素系樹脂、ポリエチレン、ポリプロピレンなどのオレフィン系樹脂、ナイロンなどの不織布が例示される。 Examples of the separator in the present invention include a porous film of an olefin resin such as fluorine resin, polyethylene, and polypropylene, an olefin resin such as fluorine resin, polyethylene, and polypropylene, and a nonwoven fabric such as nylon.
以下に実施例を挙げて本発明を説明するが、本発明はこれら実施例によりなんら限定されるものではない。
試験に供したリチウム二次電池の正極は、次に述べる方法で得た。
硝酸リチウムと炭酸ニッケルと硝酸ガリウムをＬｉ：Ｎｉ：Ｇａ＝１．０５：０．９８：０．０２となるように混合し、酸素気流中において６６０℃で１５時間焼成して得られたガリウム添加ニッケル酸リチウム粉末８７重量％に、数平均一次粒径が４０ｎｍのアセチレンブラック〔電気化学工業（株）製、商品名：デンカブラック５０％プレス品〕１重量％と、重量平均粒径が７．２μｍの鱗片状人造黒鉛（ロンザ社製、商品名：ＫＳ１５）９重量％を混合したものに対して、バインダーとしてＮ−メチルピロリドンを溶媒としたポリフッ化ビニリデン〔呉羽化学工業（株）製、商品名：ＫＦ♯１３００〕を３重量％相当分加えて充分に混練し、ペーストとした。
EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
The positive electrode of the lithium secondary battery subjected to the test was obtained by the method described below.
Addition of gallium obtained by mixing lithium nitrate, nickel carbonate and gallium nitrate so that Li: Ni: Ga = 1.05: 0.98: 0.02 and firing in an oxygen stream at 660 ° C. for 15 hours 1% by weight of acetylene black (trade name: Denka Black 50% press product, manufactured by Denki Kagaku Kogyo Co., Ltd.) having a number average primary particle size of 40 nm, 87% by weight of lithium nickelate powder, and a weight average particle size of 7. Polyvinylidene fluoride using N-methylpyrrolidone as a binder as a binder (commercially available from Kureha Chemical Industry Co., Ltd.) Name: KF # 1300] was added in an amount corresponding to 3% by weight and kneaded sufficiently to obtain a paste.
上記ガリウム添加ニッケル酸リチウム粉末は、粉末Ｘ線回折によりα−ＮａＦｅＯ2 型構造を有することが確認された。該ペーストを集電体である２０μｍ厚のアルミニウム箔に塗布した後、乾燥、プレスしてシート化した後、１．３×１．８ｃｍの小片に切断して正極を得た。この正極の活物質重量は４０ｍｇ〜４５ｍｇである。
セパレーターとしてはポリプロピレン多孔質フィルム（ダイセル化学社製、商品名：セルガード♯２４００）を用いた
The gallium-added lithium nickelate powder was confirmed to have an α-NaFeO 2 type structure by powder X-ray diffraction. The paste was applied to a 20 μm thick aluminum foil as a current collector, dried and pressed to form a sheet, and then cut into 1.3 × 1.8 cm pieces to obtain a positive electrode. The active material weight of this positive electrode is 40 mg to 45 mg.
A polypropylene porous film (manufactured by Daicel Chemical Industries, trade name: Celgard # 2400) was used as the separator.
負極炭素粉末は次に述べる方法で得た。３０００℃で熱処理した、窒素吸着法による比表面積が９ｍ2 ／ｇ、数平均粒径が１０μｍ、真比重が２．２６、Ｘ線回折における格子面間隔ｄ002 が３．３６Å、灰分が０．０５重量％の天然黒鉛（マダガスカル産）粉末９５重量部に対して、２８００℃で黒鉛化処理した窒素吸着法による比表面積が３０ｍ2 ／ｇ、真比重が２．０４、数平均一次粒子径が６６ｎｍの擬黒鉛質カーボンブラック粉末〔東海カーボン（株）製、商品名：ＴＢ３８００〕５重量％との混合炭素材を用い、シランカップリング剤（日本ユニカー社製、商品名：Ａ１８６）を予め純水に分散したものを１重量部相当分添加して充分混合後、１５０℃で真空乾燥して、シランカップリング剤で処理した炭素粉末を得た。 The negative electrode carbon powder was obtained by the method described below. Heat-treated at 3000 ° C., specific surface area by nitrogen adsorption method is 9 m 2 / g, number average particle diameter is 10 μm, true specific gravity is 2.26, lattice spacing d 002 in X-ray diffraction is 3.36 mm, and ash content is 0.3. A specific surface area of 30 m 2 / g, a true specific gravity of 2.04, and a number average primary particle diameter of 95% by weight of a natural graphite (made in Madagascar) powder of 95% by weight, graphitized at 2800 ° C. by a nitrogen adsorption method. 66nm pseudographitic carbon black powder [trade name: TB3800, manufactured by Tokai Carbon Co., Ltd.] 5% by weight and a silane coupling agent (trade name: A186, manufactured by Nihon Unicar Co., Ltd.) An amount equivalent to 1 part by weight of the dispersion in water was added and mixed well, followed by vacuum drying at 150 ° C. to obtain a carbon powder treated with a silane coupling agent.
得られた電池の放電容量のサイクル性は、室温において以下に述べる条件（１）と（２）を交互に繰り返して試験した。
サイクル性試験条件：
（１）電流密度３．３ｍＡ／ｃｍ2 、充電最大電圧４．２４Ｖ、充電時間３時間の定電流定電圧充電の後、電流密度０．６６ｍＡ／ｃｍ2 、終止電圧２．７５Ｖでの放電を行う。この充電放電を２回連続して行う。
（２）電流密度３．３ｍＡ／ｃｍ2 、充電最大電圧４．２４Ｖ、充電時間１時間の定電流定電圧充電の後、電流密度３．３ｍＡ／ｃｍ2 、終止電圧２．７５Ｖでの放電を行う。この充電放電を２０回連続して行う。
サイクル効率：９０回目の充放電における放電容量を２回目の充放電における放電容量で除した値をサイクル効率とした。
高負荷効率：３回目の充放電における放電容量を２回目の充放電における放電容量で除した値を高負荷効率とした。この高負荷効率の高いものほど大電流充放電特性に優れている。
The cycle characteristics of the discharge capacity of the obtained battery were tested by alternately repeating the conditions (1) and (2) described below at room temperature.
Cycling test conditions:
(1) After a constant current and constant voltage charge with a current density of 3.3 mA / cm 2 , a maximum charging voltage of 4.24 V, and a charging time of 3 hours, discharge at a current density of 0.66 mA / cm 2 and a final voltage of 2.75 V is performed. Do. This charging / discharging is continuously performed twice.
(2) After charging at a current density of 3.3 mA / cm 2 , a maximum charging voltage of 4.24 V, a constant current and constant voltage charging for 1 hour, and discharging at a current density of 3.3 mA / cm 2 and a final voltage of 2.75 V. Do. This charging and discharging is continuously performed 20 times.
Cycle efficiency: The value obtained by dividing the discharge capacity in the 90th charge / discharge by the discharge capacity in the second charge / discharge was defined as the cycle efficiency.
High load efficiency: The value obtained by dividing the discharge capacity in the third charge / discharge by the discharge capacity in the second charge / discharge was defined as the high load efficiency. The higher the load efficiency, the better the large current charge / discharge characteristics.
実施例１
前記シランカップリング剤処理材料９０重量％に対して、Ｎ−メチルピロリドンを溶媒とした数平均分子量５００００のポリエチレンカーボネート（以下、ＰＥＣとよぶことがある。）２重量％相当分とバインダーとしてＮ−メチルピロリドンを溶媒としたポリフッ化ビニリデンを８重量％相当分を加えて充分に混練し、ペーストとした。
該ペーストを集電体である１０μｍ厚の銅箔に塗布した後、乾燥、プレスしてシート化し、１．５×２ｃｍの小片に切断してＰＥＣ含有負極を得た。
非水電解液溶媒としてジメチルカーボネート（以下、ＤＭＣとよぶことがある。）を用い、該溶媒に電解質としてＬｉＰＦ6 を１モル／リットルとなるように溶解した非水電解液を用い、上記のようにして得た正極とＰＥＣ含有負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ａ１を作製した。
サイクル効率と高負荷効率の測定結果を表１に示す。
Example 1
With respect to 90% by weight of the silane coupling agent-treated material, polyethylene carbonate having a number average molecular weight of 50000 using N-methylpyrrolidone as a solvent (hereinafter sometimes referred to as PEC) is equivalent to 2% by weight and N- as a binder. Polyvinylidene fluoride using methylpyrrolidone as a solvent was added in an amount corresponding to 8% by weight and sufficiently kneaded to obtain a paste.
The paste was applied to a 10 μm-thick copper foil as a current collector, then dried, pressed into a sheet, and cut into 1.5 × 2 cm pieces to obtain a PEC-containing negative electrode.
As described above, dimethyl carbonate (hereinafter sometimes referred to as DMC) is used as the non-aqueous electrolyte solvent, and a non-aqueous electrolyte solution in which LiPF 6 is dissolved in the solvent to a concentration of 1 mol / liter is used. The positive electrode thus obtained and the PEC-containing negative electrode were opposed to each other with a separator interposed between them and housed in a stainless steel container to produce a battery A1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
比較例１
前記シランカップリング剤処理材料９０重量％に対して、バインダーとしてＮ−メチルピロリドンを溶媒としたポリフッ化ビニリデンを１０重量％相当分を加えて充分に混練し、ペーストとした。該ペーストを集電体である１０μｍ厚の銅箔に塗布した後、乾燥、プレスしてシート化した後、１．５×２ｃｍの小片に切断して、ＰＥＣを含有しない負極を得た。
非水電解液としては、実施例１と同一の組成のものを用い、前記正極とＰＥＣを含有しない含有負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ｒ１を作製した。この電池の充放電は、前記実施例１と同一条件で行った。
サイクル効率と高負荷効率の測定結果を表１に示す。
Comparative Example 1
To 90% by weight of the silane coupling agent-treated material, polyvinylidene fluoride using N-methylpyrrolidone as a solvent as a binder was added in an amount corresponding to 10% by weight and sufficiently kneaded to obtain a paste. The paste was applied to a 10 μm-thick copper foil as a current collector, dried and pressed to form a sheet, and then cut into 1.5 × 2 cm pieces to obtain a negative electrode containing no PEC.
As the non-aqueous electrolyte, one having the same composition as in Example 1 was used, and the positive electrode and the containing negative electrode not containing PEC were opposed to each other through a separator and housed in a stainless steel container to produce a battery R1. The battery was charged and discharged under the same conditions as in Example 1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
実施例２
非水電解液溶媒として、ＤＭＣとエチルメチルカーボネート（以下、ＥＭＣと呼ぶことがある）との体積比１：１の混合液を用い、該溶媒に電解質としてＬｉＰＦ6 を１モル／リットルとなるように溶解した非水電解液を用い、前記実施例１と同様に作成した正極とＰＥＣ含有負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ａ２を作製した。
この電池の充放電は、前記実施例１と同一条件で行った。
サイクル効率と高負荷効率の測定結果を表１に示す。
Example 2
As a non-aqueous electrolyte solvent, a mixed solution of DMC and ethyl methyl carbonate (hereinafter sometimes referred to as EMC) in a volume ratio of 1: 1 is used, and LiPF 6 is used as an electrolyte in the solvent so as to have a concentration of 1 mol / liter. Using the non-aqueous electrolyte dissolved in, the positive electrode prepared in the same manner as in Example 1 and the PEC-containing negative electrode were opposed to each other through a separator, and housed in a stainless steel container to prepare a battery A2.
The battery was charged and discharged under the same conditions as in Example 1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
比較例２
非水電解液として実施例２と同一組成の溶液を用い、前記比較例１と同様に正極とＰＥＣを含有しない負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ｒ２を作製した。
この電池の充放電は、前記実施例１と同一条件で行った。
サイクル効率と高負荷効率の測定結果を表１に示す。
Comparative Example 2
A solution having the same composition as that of Example 2 was used as the non-aqueous electrolyte, and the positive electrode and the negative electrode not containing PEC were opposed to each other with a separator in the same manner as in Comparative Example 1 and housed in a stainless steel container to prepare battery R2. .
The battery was charged and discharged under the same conditions as in Example 1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
実施例３
非水電解液溶媒として、ＥＣ、ＤＭＣ、ＥＭＣの体積比３０：３５：３５の混合液を用い、該溶媒に電解質としてＬｉＰＦ6 を１モル／リットルとなるように溶解した非水電解液を用い、前記実施例１と同様に作成した正極、ＰＥＣ含有負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ａ３を作製した。
この電池の充放電は、前記実施例１と同一条件で行った。
サイクル効率と高負荷効率の測定結果を表１に示す。
Example 3
As a non-aqueous electrolyte solution, a mixed solution of EC, DMC, and EMC with a volume ratio of 30:35:35 is used, and a non-aqueous electrolyte solution in which LiPF 6 is dissolved in the solvent so as to be 1 mol / liter is used. A positive electrode and a PEC-containing negative electrode prepared in the same manner as in Example 1 were opposed to each other with a separator interposed between them, and housed in a stainless steel container to prepare a battery A3.
The battery was charged and discharged under the same conditions as in Example 1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
比較例３
非水電解液として実施例３と同一組成の溶液を用い、前記比較例１と同様に正極とＰＥＣを含有しない負極をセパレーターを介して対向させ、ステンレス製の容器に収納し電池Ｒ３を作製した。
この電池の充放電は、前記実施例１と同一条件で行った。
サイクル効率と高負荷効率の測定結果を表１に示す。
Comparative Example 3
A solution having the same composition as that of Example 3 was used as the non-aqueous electrolyte, and the positive electrode and the negative electrode not containing PEC were opposed to each other through a separator in the same manner as in Comparative Example 1 and housed in a stainless steel container to prepare battery R3. .
The battery was charged and discharged under the same conditions as in Example 1.
Table 1 shows the measurement results of cycle efficiency and high load efficiency.
従来の負極を用いたリチウム二次電池では、ＤＭＣを電解液に使用した場合は、室温でのサイクル効率は良い（電池Ｒ１）が通常の電池動作範囲の低温域で凝固するため、実用性に欠ける。そのため、ＤＭＣにＥＭＣなどの非対称非環状炭酸エステルを混合することによって凝固しにくくし、実用性を向上させることができる。しかし、一方で、前記非対称非環状炭酸エステルを混合した電解液は、サイクル性が低下する（電池Ｒ２）。その混合電解液にさらにＥＣを混合することにより、サイクル劣化を低減することができる（電池Ｒ３）が、ＥＣ自体、その凝固点が高く粘度も大きいため、ＥＣ混合により大電流充放電特性および低温特性等の好ましい特性が低下する。 In a conventional lithium secondary battery using a negative electrode, when DMC is used as an electrolyte, the cycle efficiency at room temperature is good (battery R1), but solidifies in the low temperature range of the normal battery operating range. Lack. Therefore, it is difficult to solidify by mixing an asymmetric acyclic carbonate such as EMC with DMC, and practicality can be improved. However, on the other hand, the cycle performance of the electrolyte mixed with the asymmetric acyclic carbonate is decreased (battery R2). By further mixing EC with the mixed electrolyte, cycle deterioration can be reduced (battery R3). However, since EC itself has a high freezing point and a large viscosity, large current charge / discharge characteristics and low temperature characteristics are obtained by EC mixing. Such preferable characteristics are deteriorated.
Claims (4)
（Ａ）ジメチルカーボネート(A) Dimethyl carbonate
（Ｂ）ジメチルカーボネートおよびエチルメチルカーボネート(B) Dimethyl carbonate and ethyl methyl carbonate
（Ｃ）エチレンカーボネート、ジメチルカーボネートおよびエチルメチルカーボネート(C) ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate
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| JPS6230147A (en) * | 1985-07-31 | 1987-02-09 | Nissan Chem Ind Ltd | Ion conductive high polymer complex |
| JPS6230148A (en) * | 1985-07-31 | 1987-02-09 | Nissan Chem Ind Ltd | Novel ion conductive high polymer complex |
| JPH08217869A (en) * | 1995-02-10 | 1996-08-27 | Sony Corp | Solid polyelectrolyte |
| JPH08217868A (en) * | 1995-02-10 | 1996-08-27 | Sony Corp | Solid polyelectrolyte |
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| JPS6230147A (en) * | 1985-07-31 | 1987-02-09 | Nissan Chem Ind Ltd | Ion conductive high polymer complex |
| JPS6230148A (en) * | 1985-07-31 | 1987-02-09 | Nissan Chem Ind Ltd | Novel ion conductive high polymer complex |
| JPH08217869A (en) * | 1995-02-10 | 1996-08-27 | Sony Corp | Solid polyelectrolyte |
| JPH08217868A (en) * | 1995-02-10 | 1996-08-27 | Sony Corp | Solid polyelectrolyte |
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