JP3429328B2 - Lithium secondary battery and method of manufacturing the same - Google Patents
Lithium secondary battery and method of manufacturing the sameInfo
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- JP3429328B2 JP3429328B2 JP21641192A JP21641192A JP3429328B2 JP 3429328 B2 JP3429328 B2 JP 3429328B2 JP 21641192 A JP21641192 A JP 21641192A JP 21641192 A JP21641192 A JP 21641192A JP 3429328 B2 JP3429328 B2 JP 3429328B2
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- lithium
- synthesized
- secondary battery
- positive electrode
- licoo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、リチウム二次電池およ
びその製造方法に係わり、さらに詳しくはその正極活物
質の改良に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery and a method for manufacturing the same, and more particularly to improvement of the positive electrode active material.
【０００２】[0002]
【従来の技術】リチウム二次電池の正極活物質として
は、これまで、二硫化チタン、五酸化バナジウム、マン
ガン酸化物、リチウムマンガン酸化物、リチウムコバル
ト酸化物などが提案されてきたが、最近は、ＬｉX Ｃｏ
Ｏ2 などのリチウムコバルト酸化物が約４Ｖという高電
圧を有することから、特に注目されている（たとえば、
米国特許第４３０２５１８号明細書）。2. Description of the Related Art Titanium disulfide, vanadium pentoxide, manganese oxide, lithium manganese oxide, lithium cobalt oxide and the like have been proposed as positive electrode active materials for lithium secondary batteries. , Li X Co
Lithium cobalt oxides such as O 2 are of particular interest because they have a high voltage of about 4V (eg,
U.S. Pat. No. 4,302,518).
【０００３】しかし、ＬｉX ＣｏＯ2 のｘ値が約０．７
以下の領域では、ＬｉX ＣｏＯ2 が有機電解液を酸化す
る反応が徐々に進むと考えられ、充放電サイクルに伴い
容量が劣化する。However, the x value of Li X CoO 2 is about 0.7.
In the following region, it is considered that the reaction of Li X CoO 2 to oxidize the organic electrolyte gradually progresses, and the capacity deteriorates with the charge / discharge cycle.
【０００４】これを詳しく説明すると、上記ＬｉX Ｃｏ
Ｏ2 を正極活物質として用いたリチウム二次電池は、ま
ずＬｉ1 ＣｏＯ2 を合成し、それを正極活物質として用
いて電池を組み立て、電池組立後、充電してＬｉ1 Ｃｏ
Ｏ2 からＬｉを電気化学的に引き抜くことによって、Ｌ
ｉX ＣｏＯ2 （ｘ＜１）としている。To explain this in detail, the above Li X Co
Lithium secondary battery using O 2 as the positive electrode active material by first synthesizing the Li 1 CoO 2, assembled into a battery using it as a positive electrode active material, after cell assembly, to charge Li 1 Co
By electrochemically extracting Li from O 2 , L
i X CoO 2 (x <1).
【０００５】しかし、ＬｉX ＣｏＯ2 は、不安定な４価
のコバルトを含み酸化力が強いため、前記のように有機
電解液を酸化し、その結果、充放電サイクルに伴い容量
が劣化するのである。However, since Li X CoO 2 contains unstable tetravalent cobalt and has a strong oxidizing power, it oxidizes the organic electrolytic solution as described above, and as a result, the capacity deteriorates with charge and discharge cycles. is there.
【０００６】[0006]
【発明が解決しようとする課題】本発明は、上述したよ
うに、ＬｉX ＣｏＯ2 を正極活物質として用いたリチウ
ム二次電池が、ｘの小さな値まで充放電に利用すると充
放電サイクルに伴い容量が劣化するという問題点を解決
し、充放電サイクルに伴う容量の劣化が少ないリチウム
二次電池を提供することを目的とする。SUMMARY OF THE INVENTION As described above, the present invention provides a lithium secondary battery using Li X CoO 2 as a positive electrode active material, which is used for charge and discharge up to a small value of x, and is accompanied by a charge and discharge cycle. It is an object of the present invention to solve the problem of capacity deterioration and provide a lithium secondary battery with less capacity deterioration due to charge / discharge cycles.
【０００７】[0007]
【課題を解決するための手段】本発明は、７００℃以下
で合成したＬｉＣｏＯ2 と、ＭｎＯ2 などのリチウムを
含まないマンガン酸化物との混合物を焼成することによ
って得られるＬｉy （Ｃｏy Ｍｎx ）Ｏ2 （ｘ＋ｙ＝
１）をリチウム二次電池の正極活物質として用いること
により、上記目的を達成したものである。The present invention provides a temperature of 700 ° C. or lower.
Li y (Co y Mn x ) O 2 (x + y = which is obtained by firing a mixture of LiCoO 2 synthesized in 1. above and lithium-free manganese oxide such as MnO 2
The above object is achieved by using 1) as a positive electrode active material of a lithium secondary battery.
【０００８】上記のリチウムを含まないマンガン酸化物
としては、ＭｎＯ2 のほか、たとえばＭｎＯＯＨなどが
挙げられる。Examples of the above-mentioned lithium-free manganese oxide include MnO 2 and MnOOH.
【０００９】７００℃以下で合成したＬｉＣｏＯ2 とリ
チウムを含まないマンガン酸化物との混合物を焼成して
得られる化合物は、上記のようにＬｉy （Ｃｏy Ｍ
ｎx ）Ｏ2 （ｘ＋ｙ＝１）の化学式で表される。このＬ
ｉy （Ｃｏy Ｍｎx ）Ｏ2 で表される化合物の特徴を、
たとえば、Ｍｎを２０ｍｏｌ％添加した場合を例にあげ
て説明すると、Ｍｎを２０ｍｏｌ％添加した場合、上記
化合物はＬｉ0.8 （Ｃｏ0.8 Ｍｎ0.2 ）Ｏ2 になる。The compound obtained by calcining a mixture of LiCoO 2 synthesized at 700 ° C. or lower and lithium-free manganese oxide is Li y (Co y M
n x ) O 2 (x + y = 1). This L
The characteristics of the compound represented by i y (Co y Mn x ) O 2 are
For example, the case where 20 mol% of Mn is added will be described as an example. When 20 mol% of Mn is added, the above compound becomes Li 0.8 (Co 0.8 Mn 0.2 ) O 2 .
【００１０】これまで知られているＬｉＭＯ2 （ＭはＣ
ｏ、Ｍｎ、Ｎｉ、Ｆｅ、Ｖや２種以上の金属）ではＬｉ
が１であるが、本発明で用いるＬｉy （Ｃｏy Ｍｎx ）
Ｏ2ではＭｎの添加量だけＬｉが１より小さくなる。Known LiMO 2 (M is C
Li in O, Mn, Ni, Fe, V and two or more kinds of metals)
Is 1, but Li y (Co y Mn x ) used in the present invention
With O 2 , Li becomes smaller than 1 by the amount of Mn added.
【００１１】そして、上記のようにＬｉが１より小さく
なることから、結晶構造にＬｉの空位が既に合成時から
存在しているものと推測され、それがＬｉ+ イオンの拡
散をスムーズにするものと推測される。また、Ｌｉの空
位があり、かつ後述するようにＭｎが４価であることか
ら、合成時の試料に放電反応によりＬｉを挿入すること
ができるという特性があり、特性面において従来のＬｉ
ＭＯ2 と異なるようになるものと考えられる。Since Li is smaller than 1 as described above, it is presumed that the vacancy of Li is already present in the crystal structure from the time of synthesis, which makes the diffusion of Li + ions smooth. Presumed to be. In addition, since there is a vacancy of Li and Mn is tetravalent as described later, there is a characteristic that Li can be inserted into a sample during synthesis by a discharge reaction.
It is considered that it will be different from MO 2 .
【００１２】上記のようにＬｉが１より小さくなったの
は、４価が安定なＭｎが固溶したためであり、このＭｎ
の固溶が前述したような不安定なＣｏ4+による有機電解
液の酸化を抑制して、充放電サイクルによる容量劣化の
小さい正極活物質になるものと考えられる。The reason that Li becomes smaller than 1 as described above is that the tetravalent stable Mn is solid-dissolved.
It is considered that the above solid solution suppresses the oxidation of the organic electrolyte solution due to the unstable Co 4+ as described above, and becomes a positive electrode active material with a small capacity deterioration due to charge / discharge cycles.
【００１３】上記Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2 は、その
合成にあたって、ＬｉＣｏＯ2 とＭｎＯ2 などのリチウ
ムを含まないマンガン酸化物との混合物を加熱して焼成
するが、１１００℃付近で合成したＬｉＣｏＯ2 を用い
ると、単一相のＬｉy （Ｃｏy Ｍｎx ）Ｏ2 が得られ
ず、ＬｉＣｏＯ2 、Ｃｏ3 Ｏ4 、Ｌｉ2 ＭｎＯ3 などに
相分離してしまう。[0013] The Li y (Co y Mn x) O 2 is lithium of when its synthesis, such as LiCoO 2 and MnO 2
A mixture with a manganese oxide containing no lithium is heated and fired. However, when LiCoO 2 synthesized near 1100 ° C. is used, a single-phase Li y (Co y Mn x ) O 2 cannot be obtained, and LiCoO 2 is not obtained. Phase separation occurs in 2 , Co 3 O 4 , Li 2 MnO 3, etc.
【００１４】しかし、比較的低温の７００℃で合成した
ＬｉＣｏＯ2 を用いると、単一相のＬｉy （Ｃｏy Ｍｎ
x ）Ｏ2 が得られる。However, when LiCoO 2 synthesized at a relatively low temperature of 700 ° C. is used, a single-phase Li y (Co y Mn
x ) O 2 is obtained.
【００１５】また、ＥＳＣＡ（Ｘ線光電子分光法）によ
りＣｏとＭｎの価数を調べたところ、Ｍｎは４価、Ｃｏ
は３価であった。従来のＬｉＭｎＯ2 では、Ｍはすべて
３価であり、４価のものは混入しない。Further, when the valences of Co and Mn were examined by ESCA (X-ray photoelectron spectroscopy), Mn was tetravalent and Co
Was trivalent. In conventional LiMnO 2 , M is trivalent and tetravalent is not mixed.
【００１６】低温で合成したＬｉＣｏＯ2 （３７５〜５
００℃で合成）は、従来の層状構造を有するＬｉＣｏＯ
2 （９００〜１１００℃で合成）とＸ線回折像が若干異
なっており、結晶構造が異なっているものと考えられ
る。LiCoO 2 (375-5) synthesized at low temperature
(Synthesized at 00 ° C.) is LiCoO having a conventional layered structure.
2 (synthesized at 900 to 1100 ° C) and the X-ray diffraction image are slightly different, and it is considered that the crystal structure is different.
【００１７】そのため、上記のように、低温合成品のＬ
ｉＣｏＯ2 と従来の高温合成品のＬｉＣｏＯ2 とでは、
ＭｎＯ2 との混合物を焼成したときに生成物に差が生じ
るものと考えられる。そして、その差が生じる境となる
ＬｉＣｏＯ2 の合成温度は、Ｌｉy （Ｃｏy Ｍｎx ）Ｏ
2 を合成する際の条件によっても変化するものと考えら
れるが、低温の下限と考えられる３７５℃付近に近づく
ほど層状構造が乱れた構造になっている。また、ＬｉＣ
ｏＯ2 の層状構造の乱れの変化は連続的で７００℃では
上記の低温型に近いと考えられる。Therefore, as described above, the low temperature synthetic L
With iCoO 2 and the conventional high temperature synthetic product LiCoO 2 ,
It is considered that when the mixture with MnO 2 is fired, a difference occurs in the products. Then, the synthesis temperature of LiCoO 2 which is the boundary where the difference occurs is Li y (Co y Mn x ) O
It is considered that this also changes depending on the conditions for synthesizing 2 , but the layered structure becomes disordered as the temperature approaches 375 ° C, which is considered to be the lower limit of low temperature. In addition, LiC
It is considered that the change in the disorder of the layered structure of oO 2 is continuous and is close to the low temperature type at 700 ° C.
【００１８】つぎに、Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2 の結
晶構造について述べる。Next, the crystal structure of Li y (Co y Mn x ) O 2 will be described.
【００１９】図２は、７００℃で合成したＬｉＣｏＯ2
とＭｎＯ2 をＣｏ／Ｍｎ＝９／１、８／２、７／３、６
／４（モル比）の割合で混合し、得られた混合物をそれ
ぞれ９００℃で焼成して合成した試料のＸ線回折パター
ンである。FIG. 2 shows LiCoO 2 synthesized at 700 ° C.
And MnO 2 with Co / Mn = 9/1, 8/2, 7/3, 6
4 is an X-ray diffraction pattern of a sample synthesized by mixing at a ratio of / 4 (molar ratio) and firing the resulting mixture at 900 ° C.
【００２０】図３は、１１００℃で合成したＬｉＣｏＯ
2 とＭｎＯ2 を同様にＣｏ／Ｍｎ＝９／１、８／２、７
／３、６／４（モル比）の割合で混合し、得られた混合
物をそれぞれ９００℃で焼成して合成した試料のＸ線回
折パターンである。FIG. 3 shows LiCoO synthesized at 1100 ° C.
2 and MnO 2 are similarly Co / Mn = 9/1, 8/2, 7
3 is an X-ray diffraction pattern of a sample synthesized by mixing the mixture at a ratio of / 3, 6/4 (molar ratio) and firing the obtained mixture at 900 ° C., respectively.
【００２１】図２、図３ともに、ＭｎＯ2 量の増加によ
り格子定数（ａ0 、ｃ0 ）が変化し、ピーク位置が変化
する。2 and 3, the lattice constants (a 0 , c 0 ) change with an increase in the amount of MnO 2 , and the peak position changes.
【００２２】しかし、後者では、図３に示すように、い
ずれも、たとえば２θ＝３１°付近にＣｏ3 Ｏ4 のピー
ク（×印で示す）が観察され、単一相ではなかった。However, in the latter case, as shown in FIG. 3, a peak of Co 3 O 4 (indicated by X) was observed in the vicinity of 2θ = 31 °, which was not a single phase.
【００２３】これに対し、前者では、図２に示すよう
に、Ｃｏ／Ｍｎ＝８／２（モル比）とＣｏ／Ｍｎ＝９／
１（モル比）では２θ＝３１℃付近のピークがなく、単
一の化合物となっていた。図２のＣｏ／Ｍｎ＝８／２
（モル比）とＣｏ／Ｍｎ＝９／１（モル比）のパターン
および図２には図示していないがＬｉＣｏＯ2 のパター
ンより格子定数ａ0 、ｃ0 を求めた結果を図４に示す。On the other hand, in the former, as shown in FIG. 2, Co / Mn = 8/2 (molar ratio) and Co / Mn = 9 /
At 1 (molar ratio), there was no peak around 2θ = 31 ° C., and the compound was a single compound. Co / Mn of FIG. 2 = 8/2
FIG. 4 shows the results of determining the lattice constants a 0 and c 0 from the (molar ratio) and Co / Mn = 9/1 (molar ratio) patterns and the LiCoO 2 pattern (not shown in FIG. 2).
【００２４】図４に示すように、Ｍｎの添加により（図
４では、横軸のｙ値の減少により）格子定数ａ0 が若干
減少し、格子定数ｃ0 は増加している。これよりＭｎが
Ｃｏに固溶しており、混合物ではないことがわかる。こ
のように、４価が安定なＭｎの固溶によって前述したよ
うな不安定なＣｏ4+による有機電解液の酸化を抑制し、
充放電サイクルによる容量劣化の少ない正極活物質とな
るものと考えられる。As shown in FIG. 4, the lattice constant a 0 is slightly decreased and the lattice constant c 0 is increased by the addition of Mn (in FIG. 4, the y value on the horizontal axis is decreased). From this, it is understood that Mn is solid-dissolved in Co and is not a mixture. As described above, the solid solution of Mn having stable tetravalence suppresses the oxidation of the organic electrolyte by the unstable Co 4+ as described above,
It is considered to be a positive electrode active material with less capacity deterioration due to charge / discharge cycles.
【００２５】上記のように、ＬｉＣｏＯ2 としては、７
００℃以下、特に３７５℃〜７００℃で合成したもので
あれば、単一相のＬｉy （Ｃｏy Ｍｎx ）Ｏ2 が得られ
る。As described above, as LiCoO 2 ,
A single-phase Li y (Co y Mn x ) O 2 is obtained if it is synthesized at a temperature of 00 ° C. or lower, particularly 375 ° C. to 700 ° C.
【００２６】上記のように、７００℃以下で合成したＬ
ｉＣｏＯ2 とＭｎＯ2 などのリチウムを含まないマンガ
ン酸化物との混合物の焼成は、通常、７００〜１１００
℃で１〜４８時間行われる。L synthesized at 700 ° C. or lower as described above
Firing a mixture of iCoO 2 and a lithium-free manganese oxide such as MnO 2 is usually 700-1100.
The temperature is 1 to 48 hours.
【００２７】Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2 におけるｘと
ｙはｘ＋ｙ＝１であるが、ｘが０．０５〜０．２０のも
のにおいて特に特性のよいものが得られる。Although x and y in Li y (Co y Mn x ) O 2 are x + y = 1, particularly good characteristics can be obtained when x is 0.05 to 0.20.
【００２８】Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2 の原料となる
ＬｉＣｏＯ2 は、たとえばＣｏ3 Ｏ4 とＬｉＯＨ・Ｈ2
Ｏとの混合物を加熱処理することによって得られる。上
記Ｃｏ3 Ｏ4 は炭酸コバルト（ＣｏＣＯ3 ）の酸素中で
の加熱処理によって得られるものであるが、このＣｏ3
Ｏ4 に代えてＣｏＣＯ3 や２ＣｏＣＯ3 ・Ｃｏ（ＯＨ）
2 などを用いてもよいし、またＬｉＯＨ・Ｈ2 Ｏに代え
てＬｉ2 ＣＯ3 などの他のリチウム塩を用いてもよい。[0028] Li y (Co y Mn x) LiCoO 2 as a raw material for O 2, for example Co 3 O 4 and LiOH · H 2
Obtained by heat treating a mixture with O. Although the Co 3 O 4 are those obtained by heat treatment in an oxygen cobalt carbonate (CoCO 3), the Co 3
Instead of O 4 , CoCO 3 or 2CoCO 3 · Co (OH)
2 may be used, or other lithium salt such as Li 2 CO 3 may be used instead of LiOH.H 2 O.
【００２９】正極は、上記Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2
に、必要に応じて、たとえば黒鉛、アセチレンブラック
などの電子伝導助剤や、たとえばポリテトラフルオロエ
チレンなどの結着剤を加え、混合して正極合剤を調製
し、得られた正極合剤をたとえば加圧成形することによ
って得られる。The positive electrode is made of Li y (Co y Mn x ) O 2 described above.
In addition, if necessary, for example, an electron conduction aid such as graphite or acetylene black, or a binder such as polytetrafluoroethylene is added and mixed to prepare a positive electrode mixture, and the obtained positive electrode mixture is For example, it can be obtained by pressure molding.
【００３０】負極には、リチウム金属、リチウム−アル
ミニウム合金などのリチウム合金、リチウム−炭素材料
（黒鉛など）などのリチウム化合物が用いられる。For the negative electrode, a lithium compound, a lithium alloy such as a lithium-aluminum alloy, or a lithium compound such as a lithium-carbon material (graphite) is used.
【００３１】電解液には、たとえば、ＬｉＣｌＯ4 、Ｌ
ｉＰＦ6 、ＬｉＢＦ4 、ＬｉＣＦ3ＳＯ3 、ＬｉＣ4 Ｆ
9 ＳＯ3 などの電解質の１種または２種以上を、１，２
−ジメトキシエタン、１，２−ジエトキシエタン、プロ
ピレンカーボネート、エチレンカーボネート、γ−ブチ
ロラクトン、テトラヒドロフラン、１，３−ジオキソラ
ンなどの単独または２種以上の混合溶媒に溶解した有機
電解液が用いられる。The electrolytic solution includes, for example, LiClO 4 , L
iPF 6 , LiBF 4 , LiCF 3 SO 3 , LiC 4 F
1 or 2 or more electrolytes such as 9 SO 3
An organic electrolytic solution dissolved in a single solvent or a mixed solvent of two or more kinds such as -dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, and 1,3-dioxolane is used.
【００３２】負極にリチウム−炭素材料を用いる場合に
おいて、電池組立時には炭素材料だけを用い、電池内に
おける電気化学的反応を利用してリチウム−炭素材料と
する場合には、正極活物質にリチウム（Ｌｉ）源となる
物質を混入しておくことが好ましい。たとえば、Ｌｉy
（Ｃｏy Ｍｎx ）Ｏ2 に、Ｌｉ2 ＭｏＯ3 、Ｌｉ2 Ｎｉ
Ｏ2 や、Ｌｉを入れたＮｂ2 Ｏ5 などのＬｉを含み、Ｌ
ｉy （Ｃｏy Ｍｎx ）Ｏ2 より低い電位でＬｉが引き抜
かれて炭素材料中へＬｉが挿入されるものを混合してお
く方法が挙げられる。When a lithium-carbon material is used for the negative electrode, only the carbon material is used when assembling the battery, and a lithium-carbon material is used as the lithium-carbon material by utilizing an electrochemical reaction in the battery. It is preferable to mix a substance as a Li) source. For example, Li y
(Co y Mn x ) O 2 , Li 2 MoO 3 , Li 2 Ni
L containing O 2 and Li such as Nb 2 O 5 containing Li
There is a method of mixing a material in which Li is extracted and Li is inserted into the carbon material at a lower potential than i y (Co y Mn x ) O 2 .
【００３３】さらに、正極活物質と有機電解液の反応を
防ぐため、Ｌｉy （Ｃｏy Ｍｎx ）Ｏ2 粒子の表面をＬ
ｉ4 ＳｉＯ4 ・Ｌｉ3 ＰＯ4 などの固体電解質などでコ
ートしてもよい。また、過電圧を高めるため、ＰｂＯ2
やＩｎ2 Ｏ3 、Ｂｉ2 Ｏ3 などの酸化物を混合してもよ
い。Further, in order to prevent the reaction between the positive electrode active material and the organic electrolytic solution, the surface of the Li y (Co y Mn x ) O 2 particles is covered with L.
i 4 SiO 4 · Li 3 may be coated with such as a solid electrolyte, such as PO 4. Also, in order to increase the overvoltage, PbO 2
Alternatively, an oxide such as In 2 O 3 or Bi 2 O 3 may be mixed.
【００３４】[0034]
【実施例】つぎに実施例をあげて本発明をより具体的に
説明する。ただし、本発明はそれらの実施例のみに限定
されるものではない。EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only those examples.
【００３５】実施例１
まず、以下に示すようにして、従来より低い温度でＬｉ
ＣｏＯ2 を合成した。Example 1 First, as shown below, Li
CoO 2 was synthesized.
【００３６】炭酸コバルト（ＣｏＣＯ3 ）を３７５℃で
２０時間酸素中で加熱し、Ｃｏ3 Ｏ4 を得た。このＣｏ
3 Ｏ4 とＬｉＯＨ・Ｈ2 ＯをＬｉ／Ｃｏ＝１／１（モル
比）で混合し、得られた混合物を７００℃で２０時間酸
素中で加熱して、ＬｉＣｏＯ2 を合成した。Cobalt carbonate (CoCO 3 ) was heated in oxygen at 375 ° C. for 20 hours to obtain Co 3 O 4 . This Co
3 O 4 and LiOH.H 2 O were mixed at Li / Co = 1/1 (molar ratio), and the obtained mixture was heated at 700 ° C. for 20 hours in oxygen to synthesize LiCoO 2 .
【００３７】このようにして合成されたＬｉＣｏＯ2 と
ＭｎＯ2 をＣｏ／Ｍｎ＝９／１（モル比）で混合し、得
られた混合物を９００℃で２４時間焼成して、Ｌｉ0.9
（Ｃｏ0.9 Ｍｎ0.1 ）Ｏ2 を合成した。LiCoO 2 and MnO 2 thus synthesized were mixed at Co / Mn = 9/1 (molar ratio), and the obtained mixture was calcined at 900 ° C. for 24 hours to obtain Li 0.9.
(Co 0.9 Mn 0.1 ) O 2 was synthesized.
【００３８】上記のようにして合成されたＬｉ0.9 （Ｃ
ｏ0.9 Ｍｎ0.1 ）Ｏ2 を正極活物質として用い、これに
電子伝導助剤としてアセチレンブラックおよび結着剤と
してポリテトラフルオロエチレンを８０：１５：５（重
量比）の割合で混合して正極合剤を調製した。Li 0.9 (C
o 0.9 Mn 0.1 ) O 2 was used as a positive electrode active material, and acetylene black as an electron conduction aid and polytetrafluoroethylene as a binder were mixed at a ratio of 80: 15: 5 (weight ratio) to prepare a positive electrode mixture. The agent was prepared.
【００３９】この正極合剤４０ｍｇを金型内に充填し、
１ｔ／ｃｍ2 で直径１０ｍｍの円板状に加圧成形したの
ち、２００℃で熱処理して正極とした。この正極を用
い、図１に示すボタン形のリチウム二次電池を作製し
た。40 mg of this positive electrode mixture was filled in a mold,
After pressure-molding at 1 t / cm 2 into a disk shape having a diameter of 10 mm, it was heat-treated at 200 ° C. to obtain a positive electrode. Using this positive electrode, a button type lithium secondary battery shown in FIG. 1 was produced.
【００４０】図１において、１は上記の正極であり、２
は直径１４ｍｍの円板状のリチウムからなる負極であ
る。３は微孔性ポリプロピレンフィルムからなるセパレ
ータで、４はポリプロピレン不織布からなる電解液吸収
体である。In FIG. 1, 1 is the above positive electrode, and 2
Is a negative electrode made of disc-shaped lithium having a diameter of 14 mm. Reference numeral 3 is a separator made of a microporous polypropylene film, and 4 is an electrolytic solution absorber made of a polypropylene nonwoven fabric.
【００４１】５はステンレス鋼製の正極缶であり、６は
ステンレス鋼製網からなる正極集電体で、７はステンレ
ス鋼製で表面にニッケルメッキを施した負極缶である。
８はステンレス鋼製網からなる負極集電体で、上記負極
缶７の内面にスポット溶接されていて、前記の負極２
は、このステンレス鋼製網からなる負極集電体８に圧着
されている。Reference numeral 5 is a positive electrode can made of stainless steel, 6 is a positive electrode current collector made of a stainless steel net, and 7 is a negative electrode can made of stainless steel and having a surface plated with nickel.
Reference numeral 8 denotes a negative electrode current collector made of a stainless steel net, which is spot-welded to the inner surface of the negative electrode can 7 and is used as the negative electrode 2 described above.
Is crimped onto the negative electrode current collector 8 made of this stainless steel net.
【００４２】９はポリプロピレン製の環状ガスケットで
あり、この電池にはプロピレンカーボネートと１，２−
ジメトキシエタンとの容量比１：１の混合溶媒にＬｉＣ
Ｆ3ＳＯ3 を０．６ｍｏｌ／ｌ溶解した電解液が注入さ
れている。Reference numeral 9 is an annular gasket made of polypropylene. In this battery, propylene carbonate and 1,2-
LiC was added to a mixed solvent of 1: 1 by volume with dimethoxyethane.
An electrolytic solution in which 0.6 mol / l of F 3 SO 3 is dissolved is injected.
【００４３】比較例１
Ｃｏ3 Ｏ4 とＬｉＯＨ・Ｈ2 ＯをＬｉ／Ｃｏ＝１／１
（モル比）で混合し、得られた混合物を９００℃で２４
時間焼成して、ＬｉＣｏＯ2 を合成した。Comparative Example 1 Co 3 O 4 and LiOH.H 2 O were added to Li / Co = 1/1.
(Molar ratio) and the resulting mixture at 900 ° C. for 24 hours.
It was fired for an hour to synthesize LiCoO 2 .
【００４４】上記のようにして合成されたＬｉＣｏＯ2
を正極活物質として用い、それ以外は実施例１と同様に
して、ボタン形のリチウム二次電池を作製した。つま
り、この比較例１の電池は、正極活物質としてＭｎを含
まないＬｉＣｏＯ2 （ただし、この合成は従来の一般的
合成方法にしたがって９００℃で合成した）を用いた以
外は実施例１の電池と同様の構成のものである。LiCoO 2 synthesized as described above
Was used as the positive electrode active material, and in the same manner as in Example 1 except for the above, a button type lithium secondary battery was produced. That is, in the battery of Comparative Example 1, the battery of Example 1 was used except that LiCoO 2 containing no Mn (this synthesis was performed at 900 ° C. according to a conventional general synthesis method) was used as the positive electrode active material. It has the same configuration as.
【００４５】上記実施例１の電池および比較例１の電池
を充放電電流０．７８５ｍＡ（１ｍＡ／ｃｍ2 ）で４．
３〜３．０Ｖの電圧間で充放電した。表１に両電池の充
放電サイクル数と充放電容量との関係を示す。3. The battery of Example 1 and the battery of Comparative Example 1 were charged at a charging / discharging current of 0.785 mA (1 mA / cm 2 ).
The battery was charged / discharged at a voltage of 3 to 3.0V. Table 1 shows the relationship between the number of charge / discharge cycles and the charge / discharge capacity of both batteries.
【００４６】[0046]
【表１】 [Table 1]
【００４７】表１に示すように、充放電が１０サイクル
目までは比較例１の電池の方が実施例１の電池より充放
電容量が大きかったが、２０サイクル目になると実施例
１の電池の方が比較例１の電池より充放電容量が大きく
なり、さらに充放電サイクル数が多くなった４０サイク
ル目や８０サイクル目では、その差が大きくなり、実施
例１の電池が充放電サイクルに伴う容量劣化が少ないこ
とが明らかにされていた。As shown in Table 1, the battery of Comparative Example 1 had a larger charge / discharge capacity than the battery of Example 1 up to the 10th cycle of charging / discharging, but at the 20th cycle, the battery of Example 1 was discharged. Has a larger charge / discharge capacity than the battery of Comparative Example 1, and the difference becomes larger at the 40th cycle and the 80th cycle in which the number of charge / discharge cycles is further increased, and the battery of Example 1 is subjected to charge / discharge cycles. It has been clarified that the accompanying capacity deterioration is small.
【００４８】本発明では、正極活物質としてＬｉy （Ｃ
ｏy Ｍｎx ）Ｏ2 を用いることを必須の要件としている
関係で、７００℃以下で合成したＬｉＣｏＯ2 とＭｎＯ
2 などのリチウムを含まないマンガン酸化物とを加熱下
で反応させているが、マンガン酸化物以外にもＴｉ
Ｏ2 、ＰｂＯ2 、ＳｎＯ2 などの４価金属の酸化物をＬ
ｉＣｏＯ2 と加熱下で反応させて、Ｌｉy （Ｃｏy Ｍｎ
x ）Ｏ2 同様にリチウム二次電池の正極活物質と有用な
化合物が得られるものと期待される。In the present invention, Li y (C
O y Mn x ) O 2 is an essential requirement, and LiCoO 2 and MnO synthesized at 700 ° C. or lower are synthesized.
It reacts with manganese oxide that does not contain lithium such as 2 under heating.
Oxide of tetravalent metal such as O 2 , PbO 2 and SnO 2 is added to L
By reacting with iCoO 2 under heating, Li y (Co y Mn
It is expected that a compound useful as a positive electrode active material for a lithium secondary battery and a useful compound can be obtained similarly to x ) O 2 .
【００４９】また、Ｆｅ、Ｎｉ、Ｉｎ、Ｂｉなどについ
ても、Ｍｎに代えて用いることにより、Ｍｎの場合同様
に、リチウム二次電池の正極活物質として有用な化合物
が得られるものと期待される。Also, for Fe, Ni, In, Bi, etc., it is expected that a compound useful as a positive electrode active material of a lithium secondary battery can be obtained by using Mn instead of Mn, as in the case of Mn. .
【００５０】[0050]
【発明の効果】以上説明したように、本発明では、７０
０℃以下で合成したＬｉＣｏＯ2 とリチウムを含まない
マンガン酸化物との混合物を焼成することによって合成
したＬｉy （Ｃｏy Ｍｎx ）Ｏ2 （ｘ＋ｙ＝１）を正極
活物質として用いることにより、充放電サイクルに伴う
容量の劣化が少ないリチウム二次電池を提供することが
できた。As described above, according to the present invention, 70
By using Li y (Co y Mn x ) O 2 (x + y = 1) synthesized by firing a mixture of LiCoO 2 synthesized at 0 ° C. or lower and a manganese oxide containing no lithium, as a positive electrode active material, It has been possible to provide a lithium secondary battery in which the capacity is less likely to deteriorate due to charge / discharge cycles.
【図１】本発明に係るリチウム二次電池の一例を示す断
面図である。FIG. 1 is a cross-sectional view showing an example of a lithium secondary battery according to the present invention.
【図２】７００℃で合成したＬｉＣｏＯ2 とＭｎＯ2 と
の混合物を９００℃で焼成して合成した試料のＸ線回折
パターンを示す図である。FIG. 2 is a diagram showing an X-ray diffraction pattern of a sample synthesized by firing a mixture of LiCoO 2 and MnO 2 synthesized at 700 ° C. at 900 ° C.
【図３】１１００℃で合成したＬｉＣｏＯ2 とＭｎＯ2
との混合物を９００℃で焼成して合成した試料のＸ線回
折パターンを示す図である。FIG. 3 LiCoO 2 and MnO 2 synthesized at 1100 ° C.
It is a figure which shows the X-ray-diffraction pattern of the sample synthesize | combined by baking the mixture with and at 900 degreeC.
【図４】図２に示すパターンより求めたＬｉy （Ｃｏy
Ｍｎx ）Ｏ2 のｙ値と格子定数との関係を示す図であ
る。FIG. 4 shows Li y (Co y obtained from the pattern shown in FIG.
Is a diagram showing a relationship between Mn x) O 2 of the y values and the lattice constant.
１ 正極 ２ 負極 ３ セパレータ 1 positive electrode 2 Negative electrode 3 separator
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平３−201368（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01M 4/36 - 4/62 H01M 4/00 - 4/04 H01M 10/40 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-201368 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) H01M 4/36-4/62 H01M 4 / 00-4/04 H01M 10/40
Claims (3)
ウム化合物を負極に用いるリチウム二次電池において、
正極活物質として７００℃以下で合成したＬｉＣｏＯ2
とリチウムを含まないマンガン酸化物との混合物を焼成
することによって合成したＬｉy （Ｃｏy Ｍｎx ）Ｏ2
（ｘ＋ｙ＝１）を用いたことを特徴とするリチウム二次
電池。1. A lithium secondary battery using a lithium metal, a lithium alloy or a lithium compound as a negative electrode,
LiCoO 2 synthesized at 700 ° C. or lower as a positive electrode active material
Li y (Co y Mn x ) O 2 synthesized by firing a mixture of lithium and manganese oxide containing no lithium
A lithium secondary battery using (x + y = 1).
ウム化合物を負極に用いるリチウム二次電池の製造にあ
たり、正極活物質として用いるＬｉy （Ｃｏy Ｍｎx ）
Ｏ2 （ｘ＋ｙ＝１）を７００℃以下で合成したＬｉＣｏ
Ｏ2 とリチウムを含まないマンガン酸化物との混合物を
焼成することによって合成することを特徴とするリチウ
ム二次電池の製造方法。2. Li y (Co y Mn x ) used as a positive electrode active material in the production of a lithium secondary battery using lithium metal, a lithium alloy or a lithium compound as a negative electrode.
LiCo synthesized from O 2 (x + y = 1) at 700 ° C. or lower
A method for producing a lithium secondary battery, which comprises synthesizing by firing a mixture of O 2 and a manganese oxide containing no lithium.
ｎＯ2 であることを特徴とする請求項２記載のリチウム
二次電池の製造方法。3. A manganese oxide that does not contain Lithium is M
method for producing a lithium secondary battery according to claim 2, wherein it is nO 2.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21641192A JP3429328B2 (en) | 1992-07-21 | 1992-07-21 | Lithium secondary battery and method of manufacturing the same |
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|---|---|---|---|
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|---|---|
| JPH0644973A JPH0644973A (en) | 1994-02-18 |
| JP3429328B2 true JP3429328B2 (en) | 2003-07-22 |
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ID=16688143
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| JP3536611B2 (en) * | 1997-08-25 | 2004-06-14 | 三菱電機株式会社 | Positive electrode active material, method for producing the same, and lithium ion secondary battery using the same |
| JP3611189B2 (en) * | 2000-03-03 | 2005-01-19 | 日産自動車株式会社 | Positive electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| JP3611188B2 (en) * | 2000-03-03 | 2005-01-19 | 日産自動車株式会社 | Positive electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| JP2001250550A (en) * | 2000-03-03 | 2001-09-14 | Nissan Motor Co Ltd | Positive electrode active material for nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery |
| AU2002214289A1 (en) * | 2000-11-16 | 2002-05-27 | Hitachi Maxell, Ltd. | Lithium-containing composite oxide and nonaqueous secondary cell using the same,and method for manufacturing the same |
| JP4813453B2 (en) * | 2000-11-16 | 2011-11-09 | 日立マクセルエナジー株式会社 | Lithium-containing composite oxide and non-aqueous secondary battery |
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