JP4539816B2 - Positive electrode for lithium secondary battery and lithium secondary battery - Google Patents
Positive electrode for lithium secondary battery and lithium secondary battery Download PDFInfo
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- JP4539816B2 JP4539816B2 JP2004044494A JP2004044494A JP4539816B2 JP 4539816 B2 JP4539816 B2 JP 4539816B2 JP 2004044494 A JP2004044494 A JP 2004044494A JP 2004044494 A JP2004044494 A JP 2004044494A JP 4539816 B2 JP4539816 B2 JP 4539816B2
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- 229910052744 lithium Inorganic materials 0.000 title claims description 35
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- 229910052719 titanium Inorganic materials 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 13
- 229910052758 niobium Inorganic materials 0.000 claims description 12
- 229910052707 ruthenium Inorganic materials 0.000 claims description 12
- 229910052721 tungsten Inorganic materials 0.000 claims description 12
- 229910052750 molybdenum Inorganic materials 0.000 claims description 11
- 229910052720 vanadium Inorganic materials 0.000 claims description 10
- 239000002131 composite material Substances 0.000 claims description 9
- 239000007774 positive electrode material Substances 0.000 description 51
- 239000011572 manganese Substances 0.000 description 40
- 239000000463 material Substances 0.000 description 30
- 239000013078 crystal Substances 0.000 description 24
- 239000002994 raw material Substances 0.000 description 24
- 229910001416 lithium ion Inorganic materials 0.000 description 16
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- 239000011230 binding agent Substances 0.000 description 15
- 238000006467 substitution reaction Methods 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 14
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- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
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- 229910018068 Li 2 O Inorganic materials 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
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- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910014689 LiMnO Inorganic materials 0.000 description 1
- 229910002099 LiNi0.5Mn1.5O4 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910012513 LiSbF 6 Inorganic materials 0.000 description 1
- 101100513612 Microdochium nivale MnCO gene Proteins 0.000 description 1
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- BEKPOUATRPPTLV-UHFFFAOYSA-N [Li].BCl Chemical compound [Li].BCl BEKPOUATRPPTLV-UHFFFAOYSA-N 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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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、リチウム二次電池用正極およびそれを使用したリチウム二次電池に関し、特に、高いエネルギー密度の正極活物質を使用したエネルギー密度の高いリチウム二次電池に関する。 The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery using the same, and more particularly to a high energy density lithium secondary battery using a high energy density positive electrode active material.
リチウム二次電池は、小型で大容量であるという特長を有しており、携帯電話、ノート型パソコン等の電源として広く用いられている。ここで述べるリチウム二次電池とは、正極と負極にそれぞれリチウムを吸蔵放出が可能な正極活物質が存在し、電解液内をリチウムイオンが移動することによって、動作する電池のことであり、負極活物質に、炭素材料などのようにリチウムイオンを吸蔵放出する材料のほか、ＬｉやＡｌなどのＬｉと合金を形成する金属材料を使用する場合も含めたもののことである。リチウム二次電池の正極活物質としては、現在、ＬｉＣｏＯ2が主に利用されているが、充電状態の安全性が必ずしも充分ではない上、Ｃｏ原料の値段が高く、現在、これに代わる新たな正極活物質の探索が精力的に進められている。 Lithium secondary batteries have the feature of being small and have a large capacity, and are widely used as power sources for mobile phones, notebook computers and the like. The lithium secondary battery described here is a battery that operates by the presence of a positive electrode active material capable of occluding and releasing lithium in each of the positive electrode and the negative electrode, and movement of lithium ions in the electrolyte. In addition to a material that occludes and releases lithium ions, such as a carbon material, the active material includes a metal material that forms an alloy with Li, such as Li or Al. Currently, LiCoO 2 is mainly used as the positive electrode active material of the lithium secondary battery, but the safety of the charged state is not always sufficient, and the price of the Co raw material is high. The search for a positive electrode active material is energetically advanced.
リチウム二次電池のエネルギー密度を高める方法としては幾つか考えられる。ＬｉＮｉＯ2などのＮｉを主として使用した層状構造の正極活物質が例として挙げられる．この材料の特徴は、２００ｍＡｈ／ｇ以上の放電容量が得られることである。しかしながら、充放電電位が、ＬｉＣｏＯ2と比較して、０．２Ｖほど低いために、実質的な電池で得られる充放電容量が、本来の容量よりも小さくなってしまうことが問題として挙げられる。また、この材料は、４．３Ｖなどで充電した際には、充電時の結晶構造安定性が低く、相転移などを伴って容量が低下する場合がある。また、別の候補としてＬｉＭｎ2Ｏ4に代表されるスピネル構造の材料がある。この材料の特徴はスピネル構造の結晶安定性から、充放電時の結晶構造の安定性が高い。しかし、容量がＬｉＣｏＯ2と比較して小さいために、現状では、工業的な電池での使用は少量にとどまっている。そのほかに、スピネル構造の材料としてＬｉＮｉ0.5Ｍｎ1.5Ｏ4のような高電圧の材料があるが、現時点で電池にした場合に長期の信頼性を得ることが困難である。その他の材料として、ＬｉＭｎＯ2のＭｎを他元素で置換した材料が報告されている。これらの材料は、Ｍｎを主原料としているために、価格の面で有利であり、Ｌｉ［Ｎｉ0.5Ｍｎ0.5］Ｏ2などでは、１６０ｍＡｈ／ｇ以上の高容量が得られている。 There are several methods for increasing the energy density of a lithium secondary battery. An example is a positive electrode active material having a layered structure mainly using Ni, such as LiNiO 2 . The feature of this material is that a discharge capacity of 200 mAh / g or more can be obtained. However, since the charge / discharge potential is about 0.2 V lower than LiCoO 2 , the problem is that the charge / discharge capacity obtained with a substantial battery becomes smaller than the original capacity. In addition, when this material is charged at 4.3 V or the like, the crystal structure stability at the time of charging is low, and the capacity may decrease with a phase transition or the like. Another candidate is a material having a spinel structure typified by LiMn 2 O 4 . This material is characterized by high stability of the crystal structure during charge / discharge due to the crystal stability of the spinel structure. However, since the capacity is small compared with LiCoO 2 , the use in industrial batteries is limited to a small amount at present. In addition, there is a high-voltage material such as LiNi 0.5 Mn 1.5 O 4 as a material having a spinel structure, but it is difficult to obtain long-term reliability when used as a battery at this time. As other materials, materials in which Mn of LiMnO 2 is substituted with other elements have been reported. Since these materials are mainly made of Mn, they are advantageous in terms of price, and Li [Ni 0.5 Mn 0.5 ] O 2 or the like has a high capacity of 160 mAh / g or more.
ＬｉＭＯ2で示される結晶を有する正極活物質のうち、ＭとしてＮｉとＭｎを必須元素として含み、さらに、Ｖ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種が含まれる正極活物質の例として、特許文献１及び２が存在する。特許文献１には、「Ｌｉ1+x+αＮｉ(1-x-y+δ)/2Ｍｎ(1-x-y-δ)/2ＭyＯ2（ただし、０≦ｘ≦０．０５、−０．０５≦α≦０．０５、０≦ｙ＜０．４５、−０．２４≦δ≦０．２４であり、ＭはＴｉ、Ｃｒ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｇｅ及びＳｎからなる群より選択された１種以上の元素）」というような材料が開示されており、特許文献２には「一般式Ｌｉ1+x+αＮｉ(1-x-y+δ)/2Ｍｎ(1-x-y-δ)/2ＭyＯ2［ただし、０≦ｘ≦０．０５、−０．０５≦ｘ＋α≦０．０５、０≦ｙ≦０．４であり、−０．１≦δ≦０．１（ただし０≦ｙ≦０．２のとき）または−０．２４≦δ≦０．２４（ただし０．２＜ｙ≦０．４のとき）であって、ＭはＭｇ、Ｔｉ、Ｃｒ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｇｅ、Ｓｎからなる群から選択された１種以上の元素］」が開示されている。これらの例には、ＬｉＭＯ2で示される結晶におけるＭをＬｉで置換した正極活物質も含まれるが、その置換比率は最大で０．０５とごく少量である。
近年、従来のＬｉＣｏＯ2を正極活物質として使用してきた電池よりも、エネルギー密度の高い電池への要求が高まっている。特許文献１及び２のように、ＬｉＭＯ2のＭのごく少量をＬｉで置換した正極活物質は、蓄積エネルギー密度の面でさらなる改善が望まれていた。また、ＬｉＭＯ2で示される結晶のＬｉをＭと独立して増やした正極活物質は、金属と酸素との組成比が１からずれており、実用的な電流での充放電容量が顕著に低下するという実用上の電池への適応への課題を有していた。 In recent years, there has been an increasing demand for batteries having a higher energy density than batteries using conventional LiCoO 2 as a positive electrode active material. As in Patent Documents 1 and 2, the positive electrode active material obtained by substituting a very small amount of M in LiMO 2 with Li has been desired to be further improved in terms of stored energy density. In addition, the positive electrode active material in which Li of the crystal represented by LiMO 2 is increased independently of M has a composition ratio of metal and oxygen deviated from 1, and the charge / discharge capacity at a practical current is significantly reduced. There was a problem of adapting to practical batteries.
本発明の目的は、従来の電池よりも高いエネルギー密度を実現できるリチウム二次電池用正極に用いる正極活物質を提供することであり、高エネルギー密度化を図ったリチウム二次電池を提供することを目的とする。 An object of the present invention is to provide a positive electrode active material used for a positive electrode for a lithium secondary battery capable of realizing an energy density higher than that of a conventional battery, and to provide a lithium secondary battery with a high energy density. With the goal.
本発明は、下記一般式（Ｉ）
Ｌｉ［ＬｉxＭｎ1-x-y-zＮｉyＺz］Ｏ2 （Ｉ）
（式中Ｚは、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種、０＜ｚ＜０．２、０．１＜ｘ＜０．３、０．１＜ｙ＜０．７、０．２＜ｘ＋ｙ＋ｚ＜１）
で示される単斜晶の構造を有する複合酸化物を活物質として含むことを特徴とするリチウム二次電池用正極およびそれを使用したリチウム二次電池を提供する。
本発明は、下記一般式（Ｉ）
Ｌｉ［Ｌｉ x Ｍｎ 1-x-y-z Ｎｉ y Ｚ z ］Ｏ 2 （Ｉ）
（式中Ｚは、Ｖ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種、０．０５≦ｚ＜０．２、０．１＜ｘ＜０．３、０．１＜ｙ＜０．７、０．２５＜ｘ＋ｙ＋ｚ＜１）
で示される単斜晶の構造を有する複合酸化物を活物質として含むことを特徴とするリチウム二次電池用正極およびそれを使用したリチウム二次電池を提供する。
The present invention relates to the following general formula (I)
Li [Li x Mn 1-xyz Ni y Z z] O 2 (I)
(Wherein Z is, Nb, Mo, Ru, W , at least one of elements selected from Si and Ti, 0 <z <0.2,0.1 < x <0.3,0.1 < y <0.7, 0.2 <x + y + z <1)
A lithium secondary battery using the positive electrode and it for a lithium secondary battery characterized by comprising a composite oxide as an active material having a structure of monoclinic shown in.
The present invention relates to the following general formula (I)
Li [Li x Mn 1-xyz Ni y Z z] O 2 (I)
(Wherein, Z is at least one element selected from V, Nb, Mo, Ru, W, Si and Ti, 0.05 ≦ z <0.2, 0.1 <x <0.3, 0.1 <y <0.7, 0.25 <x + y + z <1)
And a lithium secondary battery using the positive electrode for a lithium secondary battery, comprising a composite oxide having a monoclinic crystal structure as shown in FIG.
第１の効果は、高エネルギー密度の正極活物質を使用することによって、小型化・軽量化された電池を提供することができる。 The first effect is that a battery that is reduced in size and weight can be provided by using a high-energy-density positive electrode active material.
第２の効果は、電池に流せる電流密度が増加することから、高いパワー密度の電池を提供することができる。 The second effect is that since the current density that can be passed through the battery increases, a battery with a high power density can be provided.
以下に本発明を使用したリチウムイオン二次電池の実施の形態について説明する。 Embodiments of a lithium ion secondary battery using the present invention will be described below.
本発明のリチウムイオン二次電池は、リチウム含有金属複合酸化物を正極活物質とした正極と、リチウムを吸蔵放出可能な負極活物質を持つ負極を主要成分とし、正極と負極の間に電気的接続を起こさないようなセパレータが挟まれ、正極と負極はリチウムイオン伝導性のある電解液に浸った状態であり、これらが電池ケースの中に密閉された状態となっているものとすることができる。正極と負極に電圧を印加することにより正極活物質からリチウムイオンが放出し、負極活物質にリチウムイオンが吸蔵され、充電状態となる。また、正極と負極の電気的接触を電池外部で起こすことにより、充電時と逆に、負極活物質からリチウムイオンが放出され、正極活物質にリチウムイオンが吸蔵されることにより、放電が起こる。 The lithium ion secondary battery of the present invention is mainly composed of a positive electrode using a lithium-containing metal composite oxide as a positive electrode active material and a negative electrode having a negative electrode active material capable of occluding and releasing lithium, and electrically connected between the positive electrode and the negative electrode. A separator that does not cause a connection is sandwiched, and the positive electrode and the negative electrode are immersed in a lithium ion conductive electrolyte, and these are sealed in a battery case. it can. When a voltage is applied to the positive electrode and the negative electrode, lithium ions are released from the positive electrode active material, and the lithium ions are occluded in the negative electrode active material, resulting in a charged state. In addition, by causing electrical contact between the positive electrode and the negative electrode outside the battery, lithium ions are released from the negative electrode active material, and lithium ions are occluded in the positive electrode active material, which is opposite to that during charging.
本発明では、正極活物質として、下記一般式（Ｉ）
Ｌｉ［ＬｉxＭｎ1-x-y-zＮｉyＺz］Ｏ2 （Ｉ）
（式中ＺはＶ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種、０＜ｚ＜０．２、０．１＜ｘ＜０．３、０．１＜ｙ＜０．７、０．２＜ｘ＋ｙ＋ｚ＜１）
で示される単斜晶の構造を有する複合酸化物を使用する。このような正極活物質はエネルギー密度が高いので、この活物質を含むリチウム二次電池用正極とすることで、従来の電池よりも高いエネルギー密度を実現できる。
In the present invention, as the positive electrode active material, the following general formula (I)
Li [Li x Mn 1-xyz Ni y Z z] O 2 (I)
(Wherein Z is at least one element selected from V, Nb, Mo, Ru, W, Si and Ti, 0 <z <0.2, 0.1 <x <0.3, 0.1 <Y <0.7, 0.2 <x + y + z <1)
A composite oxide having a monoclinic structure represented by Since such a positive electrode active material has a high energy density, an energy density higher than that of a conventional battery can be realized by using a positive electrode for a lithium secondary battery including the active material.
一般式（Ｉ）で示される正極活物質においては、０．１＜ｘ＜０．３であることが好ましい。ｘが大きいほど、正極活物質の充放電容量は増加するが、電子伝導性は低下する傾向がある。ｘが小さすぎると、正極活物質の充放電容量が小さいために、電池の高エネルギー密度化には十分ではない。ｘが大きすぎると、正極活物質の電子伝導性が顕著に低下するため、電池として使用する通常の電流での動作が困難となる。ｘは０．２５より小さいことがより好ましく、０．２より小さいことがさらに好ましい。 In the positive electrode active material represented by the general formula (I), it is preferable that 0.1 <x <0.3. As x increases, the charge / discharge capacity of the positive electrode active material increases, but the electronic conductivity tends to decrease. If x is too small, the charge / discharge capacity of the positive electrode active material is small, which is not sufficient for increasing the energy density of the battery. When x is too large, the electron conductivity of the positive electrode active material is remarkably lowered, so that it is difficult to operate with a normal current used as a battery. x is preferably less than 0.25, and more preferably less than 0.2.
一般式（Ｉ）で示される正極活物質においては、０．１＜ｙ＜０．７であることが好ましい。ｙが小さすぎると、単斜晶の結晶構造の安定性が低くなるために、Ｌｉの吸蔵放出を繰り返すとスピネル層などに転移し、電池の容量の低下などの原因となる。一方、ｙが大きすぎると、充放電電位の低下を伴うために、電池としての実質的な容量が低下する場合がある。ｙは０．２より大きいことがより好ましい。また、ｙは０．５より小さいことがより好ましい。 In the positive electrode active material represented by the general formula (I), it is preferable that 0.1 <y <0.7. If y is too small, the stability of the monoclinic crystal structure becomes low. Therefore, repeated occlusion and release of Li causes a transition to a spinel layer or the like, leading to a decrease in battery capacity. On the other hand, if y is too large, the charging / discharging potential is decreased, so that the substantial capacity of the battery may be decreased. More preferably, y is greater than 0.2. Further, y is more preferably smaller than 0.5.
一般式（Ｉ）で示される正極活物質においては、０＜ｚ＜０．２であることが好ましい。ｚが大きすぎると、容量が低下する場合がある。Ｚの導入によって、正極活物質の電子伝導性が改善させるような効果があると考えられるが、ｚが小さすぎると添加元素の効果が小さく改善の効果も小さいため、０．０１以上であることがより好ましい。 In the positive electrode active material represented by the general formula (I), 0 <z <0.2 is preferable. If z is too large, the capacity may decrease. The introduction of Z is considered to have the effect of improving the electronic conductivity of the positive electrode active material. However, if z is too small, the effect of the additive element is small and the effect of improvement is small. Is more preferable.
一般式（Ｉ）で示される正極活物質においては、０．２＜ｘ＋ｙ＋ｚ＜１である。 In the positive electrode active material represented by the general formula (I), 0.2 <x + y + z <1.
一般式（Ｉ）で示される正極活物質においては、ＺはＶ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種である。Ｌｉ［ＬｉxＮｉyＭｎ1-x-y］Ｏ2のような結晶においては、導電性の低下が問題であるが、これは、Ｌｉ量が増加した場合に、Ｍｎ４価の状態が支配的となり、価数変化できるエネルギー状態が減少するために、電子伝導性が低下したものと考えられる。このため、Ｍｎを４価以上のイオンで置換することで、導電性の低下を抑制できる。したがって、正極活物質の導電性が向上し、通常の電池で使用される電流値でも高エネルギー密度の電池として動作することが可能となる。ＺはＶ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉのいずれかであることが好ましい。 In the positive electrode active material represented by the general formula (I), Z is at least one element selected from V, Nb, Mo, Ru, W, Si and Ti. In a crystal such as Li [Li x Ni y Mn 1-xy ] O 2 , a decrease in conductivity is a problem. This is because when the amount of Li increases, the Mn tetravalent state becomes dominant. It is considered that the electron conductivity was lowered because the energy state capable of changing the valence decreased. For this reason, substitution of Mn with tetravalent or higher ions can suppress a decrease in conductivity. Therefore, the conductivity of the positive electrode active material is improved, and it becomes possible to operate as a battery having a high energy density even at a current value used in a normal battery. Z is preferably any one of V, Nb, Mo, Ru, W, Si and Ti.
次に正極活物質の作製方法について説明する。 Next, a method for manufacturing the positive electrode active material will be described.
正極活物質の作製原料として、Ｌｉ原料には、Ｌｉ2ＣＯ3、ＬｉＯＨ、Ｌｉ2Ｏ、Ｌｉ2ＳＯ4などを用いることができるが、Ｌｉ2ＣＯ3、ＬｉＯＨなどのリチウム塩が、遷移金属原料との反応性が高く、ＣＯ3基、ＯＨ基は、焼成時にＣＯ2，Ｈ2Ｏの形で揮発し、正極活物質へ悪影響を及ぼさないことから、好ましい。Ｍｎ原料としては、電解二酸化マンガン（ＥＭＤ）・Ｍｎ2Ｏ3、Ｍｎ3Ｏ4、ＣＭＤ等の種々のＭｎ酸化物、ＭｎＣＯ3、ＭｎＳＯ4などを用いることができる。Ｎｉ原料としては、ＮｉＯ、Ｎｉ（ＯＨ）2、ＮｉＳＯ4、Ｎｉ（ＮＯ3）2などが使用可能である。 As a raw material for producing the positive electrode active material, Li 2 CO 3 , LiOH, Li 2 O, Li 2 SO 4 and the like can be used as the Li raw material, but lithium salts such as Li 2 CO 3 and LiOH are transition metals. CO 3 group and OH group are preferable because they are highly reactive with the raw materials, and volatilize in the form of CO 2 and H 2 O during firing and do not adversely affect the positive electrode active material. As the Mn raw material, various manganese oxides such as electrolytic manganese dioxide (EMD) / Mn 2 O 3 , Mn 3 O 4 , CMD, MnCO 3 , MnSO 4 and the like can be used. NiO, Ni (OH) 2 , NiSO 4 , Ni (NO 3 ) 2, etc. can be used as the Ni raw material.
Ｔｉ原料としては、Ｔｉ2Ｏ3、ＴｉＯ2などのＴｉ酸化物、Ｔｉ炭酸塩、Ｔｉ水酸化物、Ｔｉ硫酸塩、Ｔｉ硝酸塩などが使用可能である。Ｓｉ原料としてはＳｉＯ、ＳｉＯ2などの酸化物が使用可能である。Ｖ原料としてはＶ2Ｏ5などの酸化物などが使用可能である。Ｎｂ原料としては、Ｎｂ2Ｏ5などの酸化物などが使用可能である。Ｍｏ原料としては、ＭｏＯ3などの酸化物などが使用可能である。Ｒｕ原料としてはＲｕＯ2などの酸化物などが使用可能である。Ｗ原料としてはＷＯ3などの酸化物などが使用可能である。 As the Ti raw material, Ti oxides such as Ti 2 O 3 and TiO 2 , Ti carbonate, Ti hydroxide, Ti sulfate, and Ti nitrate can be used. As the Si raw material, oxides such as SiO and SiO 2 can be used. An oxide such as V 2 O 5 can be used as the V raw material. As the Nb raw material, an oxide such as Nb 2 O 5 can be used. As the Mo raw material, an oxide such as MoO 3 can be used. As the Ru material, an oxide such as RuO 2 can be used. As the W raw material, oxides such as WO 3 can be used.
これらの原料を目的の金属組成比となるように秤量して、ボールミルなどにより粉砕混合する。混合粉を５００℃から１２００℃の温度で、空気中または酸素中で焼成することによって正極活物質を得る。 These raw materials are weighed so as to have a target metal composition ratio, and pulverized and mixed by a ball mill or the like. A positive electrode active material is obtained by baking the mixed powder at a temperature of 500 ° C. to 1200 ° C. in air or oxygen.
それぞれの正極活物質原料は、焼成時に元素拡散が起こり難くい場合があり、原料焼成後、各元素の酸化物が異相として残留してしまうことがある。また、Ｌｉ原料と他の金属元素は反応しやすく、安定な複合酸化物相を形成する場合があり、想定した固溶体を形成しない場合がある。このため、Ｌｉ以外の各金属元素原料を先に反応させておいて、後でＬｉ原料を加えて、焼成した方が均一な結晶が得られる場合がある。Ｌｉ以外の金属元素の混合は、金属元素原料を混合焼成して複合酸化物を作製する方法や、水溶液中に金属原料を溶解混合させた後、水酸化物、硫酸塩、炭酸塩、硝酸塩などの形で析出させた混合物を原料として用いることも可能である。また、このような混合物を焼成させた複合酸化物を用いることも可能である。このような混合物または複合酸化物を原料として用いて、さらにＬｉ原料を混合して焼成した場合、各元素が原子レベルで良く拡散しており、異相の少ない結晶の作製が容易となる。 Each positive electrode active material raw material may hardly cause element diffusion at the time of firing, and the oxide of each element may remain as a different phase after the raw material firing. Moreover, Li raw material and other metal elements are easy to react, and may form a stable complex oxide phase, and may not form the assumed solid solution. For this reason, there is a case where uniform crystals can be obtained by reacting each metal element raw material other than Li first and then adding the Li raw material later and firing. Mixing of metal elements other than Li is a method of preparing a composite oxide by mixing and firing metal element raw materials, or after dissolving and mixing metal raw materials in an aqueous solution, hydroxide, sulfate, carbonate, nitrate, etc. It is also possible to use a mixture precipitated in the form of It is also possible to use a composite oxide obtained by firing such a mixture. When such a mixture or composite oxide is used as a raw material and further mixed with a Li raw material and fired, each element is well diffused at the atomic level, and it becomes easy to produce a crystal with few different phases.
焼成温度は、各元素を拡散させるためには高温である方が望ましいが、焼成温度が高すぎると酸素欠損を生じたり、活物質が凝集して粉末状態でなくなるために、電池に使用した場合に特性に悪影響となる場合がある。このことから、最終焼成過程では５００℃から１０００℃程度であることが望ましい。 The firing temperature is preferably a high temperature for diffusing each element, but if the firing temperature is too high, oxygen deficiency occurs or the active material aggregates and ceases to be in a powder state. May adversely affect the characteristics. For this reason, it is desirable that the temperature is about 500 ° C. to 1000 ° C. in the final firing process.
得られた複合酸化物の比表面積は０．０１ｍ2／ｇ以上、３ｍ2／ｇ以下であることが望ましく、好ましくは０．１ｍ2／ｇ以上、１ｍ2／ｇ以下である。比表面積が大きいほど、結着剤が多く必要であり、正極の容量密度の点で不利になるからである。また、比表面積が小さすぎると電解液と正極活物質間のイオン伝導が低下する場合がある。リチウム金属複合酸化物の平均粒径は、好ましくは０．１μｍ以上５０μｍ以下であり、さらに好ましくは１μｍ以上２０μｍ以下である。大きいと正極成膜時に正極層に凹凸などの不均一な部分が生じる場合がある。小さいと成膜された正極の結着性が悪くなる場合がある。 The specific surface area of the obtained composite oxide is desirably 0.01 m 2 / g or more and 3 m 2 / g or less, preferably 0.1 m 2 / g or more and 1 m 2 / g or less. This is because the larger the specific surface area, the more binder is necessary, which is disadvantageous in terms of the capacity density of the positive electrode. On the other hand, if the specific surface area is too small, ionic conduction between the electrolytic solution and the positive electrode active material may decrease. The average particle size of the lithium metal composite oxide is preferably 0.1 μm or more and 50 μm or less, and more preferably 1 μm or more and 20 μm or less. If it is large, uneven portions such as irregularities may occur in the positive electrode layer during the positive electrode film formation. If it is small, the binding property of the deposited positive electrode may deteriorate.
このようにして得られた正極活物質を、導電付与材と混合し、結着剤によって集電体上に膜状に形成することで、正極集電体に正極を形成することができる。導電付与材の例としては、アセチレンブラック、カーボンブラック、黒鉛、または、繊維状炭素などの炭素材料の他、Ａｌなどの金属物質、導電性酸化物の粉末などを使用することができる。結着剤としてはポリフッ化ビニリデンなどが用いられる。集電体としてはＡｌなどを主体とする金属薄膜を用いる。 A positive electrode can be formed on the positive electrode current collector by mixing the positive electrode active material thus obtained with a conductivity-imparting material and forming the film on the current collector with a binder. Examples of the conductivity-imparting material include carbon materials such as acetylene black, carbon black, graphite, or fibrous carbon, metal substances such as Al, and conductive oxide powders. As the binder, polyvinylidene fluoride or the like is used. As the current collector, a metal thin film mainly composed of Al or the like is used.
好ましくは導電付与材の添加量は０．５〜３０質量％（正極活物質、導電付与材および結着剤の合計量に対して）程度であり、結着剤の添加量は０．５〜１０質量％（正極活物質、導電付与材および結着剤の合計量に対して）程度である。導電付与材または結着剤の割合があまり小さいと、電子伝導性に劣ったり、電極剥離の問題が生じたりすることがある。導電付与材と結着剤の割合があまり大きいと、電池質量あたりの容量が小さくなることがある。正極活物質の割合は、６９〜９９質量％（正極活物質、導電付与材および結着剤の合計量に対して）であることが好ましい。さらに好ましくは、８５〜９７質量％（正極活物質、導電付与材および結着剤の合計量に対して）である。正極活物質の割合があまり小さすぎると、電池のエネルギー密度の面で不利となることがある。活物質の割合が多すぎると、導電付与材と結着剤の質量あたりの割合が低くなり、電子伝導性に劣ったり、電極剥離しやすくなったりする傾向があるという点で不利である。 Preferably, the addition amount of the conductivity-imparting material is about 0.5 to 30% by mass (relative to the total amount of the positive electrode active material, the conductivity-imparting material and the binder), and the addition amount of the binder is 0.5 to It is about 10% by mass (based on the total amount of the positive electrode active material, the conductivity-imparting material, and the binder). If the ratio of the conductivity-imparting material or the binder is too small, the electron conductivity may be inferior or electrode peeling may occur. If the ratio between the conductivity-imparting material and the binder is too large, the capacity per battery mass may be small. The proportion of the positive electrode active material is preferably 69 to 99% by mass (relative to the total amount of the positive electrode active material, the conductivity-imparting material and the binder). More preferably, it is 85 to 97% by mass (relative to the total amount of the positive electrode active material, the conductivity-imparting material and the binder). If the proportion of the positive electrode active material is too small, it may be disadvantageous in terms of battery energy density. If the proportion of the active material is too large, the proportion per mass of the conductivity-imparting material and the binder is lowered, which is disadvantageous in that the electronic conductivity tends to be inferior or the electrode tends to be peeled off.
本発明における電解液溶媒としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ビニレンカーボネート（ＶＣ）等の環状カーボネート類、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）、ジプロピルカーボネート（ＤＰＣ）等の鎖状カーボネート類；ギ酸メチル、酢酸メチル、プロピオン酸エチル等の脂肪族カルボン酸エステル類；γ−ブチロラクトン等のγ−ラクトン類；１、２−エトキシエタン（ＤＥＥ）、エトキシメトキシエタン（ＥＭＥ）等の鎖状エーテル類；テトラヒドロフラン、２−メチルテトラヒドロフラン等の環状エーテル類；ジメチルスルホキシド、１、３−ジオキソラン、ホルムアミド、アセトアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、プロピルニトリル、ニトロメタン、エチルモノグライム、リン酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、メチルスルホラン、１、３−ジメチル−２−イミダゾリジノン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、エチルエーテル、１、３−プロパンスルトン、アニソール、Ｎ−メチルピロリドン、フッ素化カルボン酸エステルなどの非プロトン性有機溶媒を一種又は二種以上を混合して使用できる。また、ポリマーなどを添加して電解液溶媒をゲル状に固化したものを用いてもよい。これらのうち、高電圧での安定性や、溶媒の粘度の点から、環状カーボネートと鎖状カーボネートを混合して使用することが適している。 Examples of the electrolyte solvent in the present invention include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Chain carbonates such as diethyl carbonate (DEC) and dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate; γ-lactones such as γ-butyrolactone; Chain ethers such as 2-ethoxyethane (DEE) and ethoxymethoxyethane (EME); cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; dimethyl sulfoxide, 1,3-dioxolane, formamide, acetami Dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl A mixture of one or more aprotic organic solvents such as 2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, and fluorinated carboxylic acid ester Can be used. Moreover, you may use what added the polymer etc. and solidified the electrolyte solution solvent in the gel form. Among these, it is suitable to use a mixture of a cyclic carbonate and a chain carbonate from the viewpoint of stability at a high voltage and the viscosity of the solvent.
これらの電解液溶媒にはリチウム塩を電解液支持塩として溶解させる。リチウム塩としては、例えばＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＳｂＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2、低級脂肪族カルボン酸、カルボン酸リチウム、クロロボランリチウム、四フェニルホウ酸リチウム、ＬｉＢｒ、ＬｉＩ、ＬｉＳＣＮ、ＬｉＣｌなどがあげられる。電解質濃度は、たとえば０．５ｍｏｌ／ｌから１．５ｍｏｌ／ｌとする。濃度があまり高すぎると密度と粘度が増加することがある。濃度があまり低すぎると電気伝導率が低下することがある。
In these electrolyte solutions, lithium salts are dissolved as electrolyte solution supporting salts. Examples of the lithium salt include LiPF 6 , LiAsF 6 , LiAlCl 4 , LiClO 4 , LiBF 4 , LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC (CF 3 SO 2 ) 3 , LiN (CF 3 SO 2) 2, LiN (C 2
負極活物質としてはリチウムを吸蔵放出可能な材料が用いられ、グラファイトまたは非晶質炭素等の炭素材料、Ｌｉ金属、Ｓｉ、Ｓｎ、Ａｌ、ＳｉＯ、ＳｎＯなどを単独または混合して用いることができる。 As the negative electrode active material, a material capable of occluding and releasing lithium is used, and a carbon material such as graphite or amorphous carbon, Li metal, Si, Sn, Al, SiO, SnO, or the like can be used alone or in combination. .
負極活物質を導電付与材と結着剤によって集電体上に形成させることにより、負極集電体に負極を形成することができる。導電付与材の例としては、炭素材料の他、導電性酸化物の粉末などを使用することができる。結着剤としてはポリフッ化ビニリデンなどを用いることができる。集電体としてはＣｕなどを主体とする金属薄膜を用いることができる。 A negative electrode can be formed on the negative electrode current collector by forming the negative electrode active material on the current collector with a conductivity-imparting material and a binder. As an example of the conductivity-imparting material, in addition to the carbon material, a conductive oxide powder or the like can be used. As the binder, polyvinylidene fluoride or the like can be used. As the current collector, a metal thin film mainly composed of Cu or the like can be used.
本発明に係るリチウム二次電池は、乾燥空気または不活性ガス雰囲気において、負極および正極を、セパレータを介して積層、あるいは積層したものを捲回した後に、電池缶に収容したり、合成樹脂と金属箔との積層体からなる可とう性フィルム等によって封口することによって電池を製造することができる。 The lithium secondary battery according to the present invention includes a negative electrode and a positive electrode laminated in a dry air or inert gas atmosphere via a separator, or wound in a battery can, A battery can be manufactured by sealing with a flexible film made of a laminate with a metal foil.
本発明は電池形状には制限がなく、セパレータを挟んで対向した正極、負極を巻回型、積層型などの形態を取ることが可能であり、セルには、コイン型、ラミネートパック、角型セル、円筒型セルを用いることができる。図１には、コイン型リチウムイオン二次電池の断面図を示す。その構造は、正極集電体３、正極活物質層となる正極１、セパレータ５、負極２、負極集電体４の順に積層されており、その積層体を絶縁パッキング部８を介して正極外層缶６及び負極外層缶７で密閉されている。
The present invention is not limited in battery shape, and can take the form of a positive electrode and a negative electrode facing each other with a separator in between, a wound type, a laminated type, etc. A cell or a cylindrical cell can be used. FIG. 1 shows a cross-sectional view of a coin-type lithium ion secondary battery. The structure is formed by laminating a positive electrode current collector 3, a positive electrode 1 serving as a positive electrode active material layer, a
〔参考例１〕
図１に示す構成のコイン型リチウムイオン二次電池を作製した。具体的には、以下に示すようにＬｉ量を変えた組成の試料を作製し、これらを正極活物質として含む正極を用いた電池を作製し、評価を行った。
[Reference Example 1]
A coin-type lithium ion secondary battery having the configuration shown in FIG. 1 was produced. Specifically, samples having compositions with different amounts of Li were prepared as shown below, and batteries using positive electrodes containing these as positive electrode active materials were prepared and evaluated.
Ｌｉ［Ｎｉ0.3Ｍｎ0.7］Ｏ2 （試料１）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.95Ｌｉ0.05］Ｏ2 （試料２）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.9Ｌｉ0.1］Ｏ2 （試料３）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.85Ｌｉ0.15］Ｏ2 （試料４）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.8Ｌｉ0.2］Ｏ2 （試料５）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.75Ｌｉ0.25］Ｏ2 （試料６）
Ｌｉ［（Ｎｉ0.3Ｍｎ0.7）0.7Ｌｉ0.3］Ｏ2 （試料７）
（正極作製）
原料Ｌｉ2ＣＯ3、ＭｎＯ2、ＮｉＯを目的の金属組成比になるように秤量した。ＭｎＯ2、ＮｉＯを粉砕混合して、混合後の粉末を９５０℃で４８時間焼成した。次に、得られた粉末と、Ｌｉ2ＣＯ3を粉砕混合した後に、再度８５０℃で４８時間焼成した。得られた結晶構造は、試料２から７においては、単斜晶の結晶構造に帰属されることがわかった。試料１については、α−ＮａＦｅＯ2型の結晶構造に帰属された。試料５のＸ線回折パターンを図２に示す。得られた粉末の比表面積はいずれも約０．５ｍ2／ｇであり、平均粒径はいずれも約１２μｍであった。
Li [Ni 0.3 Mn 0.7 ] O 2 (Sample 1)
Li [(Ni 0.3 Mn 0.7 ) 0.95 Li 0.05 ] O 2 (Sample 2)
Li [(Ni 0.3 Mn 0.7 ) 0.9 Li 0.1 ] O 2 (Sample 3)
Li [(Ni 0.3 Mn 0.7 ) 0.85 Li 0.15 ] O 2 (Sample 4)
Li [(Ni 0.3 Mn 0.7 ) 0.8 Li 0.2 ] O 2 (Sample 5)
Li [(Ni 0.3 Mn 0.7 ) 0.75 Li 0.25 ] O 2 (Sample 6)
Li [(Ni 0.3 Mn 0.7 ) 0.7 Li 0.3 ] O 2 (Sample 7)
(Preparation of positive electrode)
The raw materials Li 2 CO 3 , MnO 2 , and NiO were weighed so as to achieve the target metal composition ratio. MnO 2 and NiO were pulverized and mixed, and the mixed powder was fired at 950 ° C. for 48 hours. Then, the resulting powder, after grinding and mixing the Li 2 CO 3, was calcined for 48 hours at again 850 ° C.. The obtained crystal structure was found to belong to the monoclinic crystal structure in Samples 2 to 7. Sample 1 was assigned to the α-NaFeO 2 type crystal structure. The X-ray diffraction pattern of
得られた正極活物質を導電付与材である炭素を混合し、Ｎ−メチルピロリドン（ＮＭＰ）にポリフッ化ビニリデン（ＰＶＤＦ（結着剤））を溶かしたものに分散させスラリー状とした。導電付与材には炭素材料のうちカーボンブラックを使用した。正極活物質、導電付与材、結着剤の質量比は８８／７／５とした。厚さ２０μｍのＡｌ集電体上にスラリーを塗布した。その後、真空中で１２時間乾燥させた。その後、直径１２ｍｍの円に切り出し、３ｔ／ｃｍ2で加圧成形したものを正極とした。 The obtained positive electrode active material was mixed with carbon, which is a conductivity-imparting material, and dispersed in N-methylpyrrolidone (NMP) in which polyvinylidene fluoride (PVDF (binder)) was dissolved to form a slurry. Among the carbon materials, carbon black was used as the conductivity imparting material. The mass ratio of the positive electrode active material, the conductivity-imparting material, and the binder was 88/7/5. The slurry was applied on an Al current collector having a thickness of 20 μm. Then, it was dried in vacuum for 12 hours. Thereafter, a positive electrode was cut into a circle with a diameter of 12 mm and pressure-formed at 3 t / cm 2 .
（電池の作製及び評価）
負極は、銅集電体上に形成されたＬｉ箔を直径１５ｍｍに切り出したものを使用した。電解液は、電解液溶媒としてエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）を３０：７０（ｖｏｌ．％）で混合したものを用い、電解液支持塩にはＬｉＰＦ6を使用し、支持塩濃度は１ｍｏｌ／ｌとした。
(Production and evaluation of batteries)
As the negative electrode, a Li foil formed on a copper current collector and cut into a diameter of 15 mm was used. The electrolyte used was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at 30:70 (vol.%) As the electrolyte solvent, LiPF 6 was used as the electrolyte support salt, and the support salt concentration was Was 1 mol / l.
正極と負極がセパレータを挟んで電気的接触がない状態に対向配置させ、コインセル内に配置し、電解液を満たして密閉することで電池を作製した。セパレータにはポリプロピレンのフィルムを使用した。 The positive electrode and the negative electrode were placed facing each other with no separator in between and placed in a coin cell, filled with an electrolyte solution and sealed to produce a battery. A polypropylene film was used as the separator.
以上のようにして作製した電池について電池特性を評価した。電池の初期の放電容量は約２ｍＡｈであった。まず、上限電圧を４．７Ｖとして０．０２ｍＡまたは１ｍＡの定電流で充電を行った。次に、下限電圧を３Ｖとして充電と同じ定電流で放電を行った。充放電電流０．０２ｍＡ、１ｍＡは、それぞれ、充放電レート０．０１Ｃ、０．５Ｃに相当する。得られた放電容量を表１に示す。 The battery characteristics of the battery produced as described above were evaluated. The initial discharge capacity of the battery was about 2 mAh. First, charging was performed at a constant current of 0.02 mA or 1 mA with an upper limit voltage of 4.7V. Next, the lower limit voltage was set to 3 V, and discharging was performed at the same constant current as charging. The charge / discharge currents of 0.02 mA and 1 mA correspond to charge / discharge rates of 0.01 C and 0.5 C, respectively. The obtained discharge capacity is shown in Table 1.
以上のように、０．０１Ｃのような低充放電レートにおいては、ＬｉＭＯ2で示される結晶におけるＭのＬｉへの置換比率（ｘ）が０．１５から０．２付近において２００ｍＡｈ／ｇ以上の非常に大きな放電容量が得られた。しかし、０．５Ｃのような実用電池で使用するような充放電レート領域においては、Ｌｉへの置換比率（ｘ）が０．１から０．２の付近で放電容量が極大値となった。Ｌｉ置換比率（ｘ）の増加によって放電容量が増加した理由としては、軽量なＬｉ元素の存在比率の増加によって、質量あたりの放電容量が増加したためと考えられる。一方、Ｌｉ置換比率（ｘ）が０．２よりも大きい場合に、放電容量が低下した理由は、活物質の電子伝導性が低下したために充放電時のＬｉイオンの移動に負荷がかかり、充放電がうまくできなくなったために放電容量が低下したと考えられる。このような結果から、高い放電容量を得るためには、Ｌｉ置換比率（ｘ）は、０．１より大きいことが好ましいが、Ｌｉ置換比率が０．２以上の場合には活物質の電子伝導性を高めるような工夫が必要と考えられる。 As described above, at a low charge / discharge rate of 0.01 C, the substitution ratio (x) of M to Li in the crystal represented by LiMO 2 is 200 mAh / g or more in the vicinity of 0.15 to 0.2. A very large discharge capacity was obtained. However, in the charge / discharge rate region used in a practical battery such as 0.5C, the discharge capacity reached a maximum value when the substitution ratio (x) to Li was near 0.1 to 0.2. The reason why the discharge capacity increased due to the increase of the Li substitution ratio (x) is considered to be that the discharge capacity per mass increased due to the increase of the light Li element existing ratio. On the other hand, when the Li substitution ratio (x) is greater than 0.2, the reason why the discharge capacity is reduced is that the movement of Li ions during charge / discharge is burdened because the electron conductivity of the active material is reduced, and the charge / discharge is reduced. It is thought that the discharge capacity was lowered because the discharge was not successful. From these results, in order to obtain a high discharge capacity, the Li substitution ratio (x) is preferably larger than 0.1, but when the Li substitution ratio is 0.2 or more, the electron conduction of the active material It is considered necessary to improve the performance.
〔参考例２〕
図１に示す構成のコイン型リチウムイオン二次電池を作製した。正極活物質として、以下に示すように、Ｌｉ量を固定して、ＮｉとＭｎの組成比を変えた試料を作製し、これらを正極活物質として含む正極を用いた電池を作製し、評価を行った。正極の作製並びに電池の作製及び評価の方法は参考例１と同じとした。なお、得られた材料の結晶構造は、すべて単斜晶に帰属された。また、得られた粉末の比表面積はいずれも約０．５ｍ2／ｇであり、平均粒径はいずれも約１２μｍであった。結果を表２に示す。
[Reference Example 2]
A coin-type lithium ion secondary battery having the configuration shown in FIG. 1 was produced. As shown in the following, as a positive electrode active material, a Li amount was fixed, a sample having a different composition ratio of Ni and Mn was produced, a battery using a positive electrode containing these as a positive electrode active material was produced and evaluated. went. The method for producing the positive electrode and the method for producing and evaluating the battery were the same as those in Reference Example 1. The crystal structure of the obtained material was all attributed to monoclinic crystals. In addition, the specific surface area of the obtained powder was about 0.5 m 2 / g, and the average particle size was about 12 μm. The results are shown in Table 2.
Ｌｉ［Ｎｉ0.1Ｍｎ0.75Ｌｉ0.15］Ｏ2 （試料８）
Ｌｉ［Ｎｉ0.2Ｍｎ0.65Ｌｉ0.15］Ｏ2 （試料９）
Ｌｉ［Ｎｉ0.3Ｍｎ0.55Ｌｉ0.15］Ｏ2 （試料１０）
Ｌｉ［Ｎｉ0.5Ｍｎ0.35Ｌｉ0.15］Ｏ2 （試料１１）
Ｌｉ［Ｎｉ0.7Ｍｎ0.15Ｌｉ0.15］Ｏ2 （試料１２）
Li [Ni 0.1 Mn 0.75 Li 0.15 ] O 2 (Sample 8)
Li [Ni 0.2 Mn 0.65 Li 0.15 ] O 2 (Sample 9)
Li [Ni 0.3 Mn 0.55 Li 0.15 ] O 2 (Sample 10)
Li [Ni 0.5 Mn 0.35 Li 0.15 ] O 2 (Sample 11)
Li [Ni 0.7 Mn 0.15 Li 0.15 ] O 2 (Sample 12)
以上のように、ＬｉＭＯ2で示される結晶におけるＭのＮｉへの置換比率（ｙ）が小さいと、０．５Ｃレートでの放電容量が顕著に減少した。一方、Ｎｉへの置換比率が多すぎても０．５Ｃレートでの放電容量が低下する傾向であった。このような結果からＮｉへの置換比率は、０．１より大きいことが好ましく、０．７より小さいことが好ましい。また、０．２より大きいことがより好ましく、０．５より小さいことがより好ましい。 As described above, when the substitution ratio (y) of M to Ni in the crystal represented by LiMO 2 was small, the discharge capacity at the 0.5 C rate was significantly reduced. On the other hand, even if the substitution ratio to Ni was too large, the discharge capacity at the 0.5C rate tended to decrease. From these results, the substitution ratio to Ni is preferably greater than 0.1, and preferably less than 0.7. Further, it is more preferably larger than 0.2, and more preferably smaller than 0.5.
〔実施例１〕
図１に示す構成のコイン型リチウムイオン二次電池を作製した。正極活物質として、以下に示すように、Ｖ、Ｎｂ、Ｍｏ、Ｗ、Ｔｉ、Ｓｉ、Ｒｕを含有した試料を作製した。
[Example 1]
A coin-type lithium ion secondary battery having the configuration shown in FIG. 1 was produced. As the positive electrode active material, a sample containing V, Nb, Mo, W, Ti, Si, and Ru was prepared as shown below.
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｖ0.05］Ｏ2 （試料１３）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｎｂ0.05］Ｏ2 （試料１４）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｍｏ0.05］Ｏ2 （試料１５）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｗ0.05］Ｏ2 （試料１６）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｔｉ0.05］Ｏ2 （試料１７）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｓｉ0.05］Ｏ2 （試料１８）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｒｕ0.05］Ｏ2 （試料１９）
（正極作製）
原料としてＬｉ2ＣＯ3、ＭｎＯ2、ＮｉＯ、Ｎｂ2Ｏ5、ＭｏＯ3、ＷＯ3、ＴｉＯ2、ＳｉＯおよび、ＲｕＯ2を使用した。ＭｎＯ2、ＮｉＯと、Ｎｂ2Ｏ5、ＭｏＯ3、ＷＯ3、ＴｉＯ2、ＳｉＯまたは、ＲｕＯ2のうちの一種とを、目的の金属組成比になるように秤量して粉砕混合した後に、９５０℃で４８時間焼成した。次に、得られた粉末と、Ｌｉ2ＣＯ3を粉砕混合した後に、８５０℃で４８時間で焼成した。得られた材料の結晶構造は、すべて単斜晶に帰属された。得られた粉末の比表面積はいずれも約０．５ｍ2／ｇであり、平均粒径はいずれも約１２μｍであった。電池の作製及び評価の方法は参考例１と同じとした。結果を表３に示す。比較として、電池１０のデータも表３に示した。
Li [Ni 0.3 Mn 0.5 Li 0.15 V 0.05 ] O 2 (Sample 13)
Li [Ni 0.3 Mn 0.5 Li 0.15 Nb 0.05 ] O 2 (Sample 14)
Li [Ni 0.3 Mn 0.5 Li 0.15 Mo 0.05 ] O 2 (Sample 15)
Li [Ni 0.3 Mn 0.5 Li 0.15 W 0.05 ] O 2 (Sample 16)
Li [Ni 0.3 Mn 0.5 Li 0.15 Ti 0.05 ] O 2 (Sample 17)
Li [Ni 0.3 Mn 0.5 Li 0.15 Si 0.05 ] O 2 (Sample 18)
Li [Ni 0.3 Mn 0.5 Li 0.15 Ru 0.05 ] O 2 (Sample 19)
(Preparation of positive electrode)
Li 2 CO 3 , MnO 2 , NiO, Nb 2 O 5 , MoO 3 , WO 3 , TiO 2 , SiO and RuO 2 were used as raw materials. After weighing and mixing MnO 2 , NiO and one of Nb 2 O 5 , MoO 3 , WO 3 , TiO 2 , SiO, or RuO 2 to the desired metal composition ratio, 950 Baked for 48 hours at ° C. Next, the obtained powder and Li 2 CO 3 were pulverized and mixed, and then fired at 850 ° C. for 48 hours. The crystal structure of the obtained material was all attributed to monoclinic crystals. The specific surface areas of the obtained powders were all about 0.5 m 2 / g, and the average particle size was about 12 μm. The method for producing and evaluating the battery was the same as in Reference Example 1. The results are shown in Table 3. For comparison, the data of the battery 10 are also shown in Table 3.
以上のように、ＬｉＭＯ2で示される結晶におけるＭの一部を、Ｖ、Ｎｂ、Ｍｏ、Ｗ、Ｔｉ、Ｓｉ、Ｒｕで置換することで、充放電レート０．５Ｃの場合の放電容量が増加する効果があった。これらの元素の存在によって活物質の電子伝導性が改善されたためであると考えられる。このため、Ｖ、Ｎｂ、Ｍｏ、Ｗ、Ｔｉ、Ｓｉ、Ｒｕで置換した場合には、Ｌｉ置換比率（ｘ）を０．２以上に増加させても、高い放電容量が得られるようになる。 As described above, by substituting a part of M in the crystal represented by LiMO 2 with V, Nb, Mo, W, Ti, Si, and Ru, the discharge capacity when the charge / discharge rate is 0.5 C is increased. There was an effect to. This is probably because the presence of these elements improved the electronic conductivity of the active material. Therefore, when V, Nb, Mo, W, Ti, Si, and Ru are substituted, a high discharge capacity can be obtained even if the Li substitution ratio (x) is increased to 0.2 or more.
〔実施例２〕
図１に示す構成のコイン型リチウムイオン二次電池を作製した。正極活物質として、以下に示すようなＭｏを含有した試料でＭｏ組成比を変えた試料を作製し、これらを正極活物質として含む正極を用いた電池を作製し、評価を行った。正極の作製条件並びに電池の作製及び評価の方法は実施例１と同じとした。なお、得られた材料の結晶構造は、すべて単斜晶に帰属された。また、得られた粉末の比表面積はいずれも約０．５ｍ2／ｇであり、平均粒径はいずれも約１２μｍであった。結果を表４に示す。比較として、電池１０のデータも表４に示した。
[Example 2]
A coin-type lithium ion secondary battery having the configuration shown in FIG. 1 was produced. As positive electrode active materials, samples containing Mo as shown below were prepared with different Mo composition ratios, and batteries using positive electrodes containing these as positive electrode active materials were prepared and evaluated. The production conditions for the positive electrode and the method for producing and evaluating the battery were the same as in Example 1. The crystal structure of the obtained material was all attributed to monoclinic crystals. In addition, the specific surface area of the obtained powder was about 0.5 m 2 / g, and the average particle size was about 12 μm. The results are shown in Table 4. As a comparison, the data of the battery 10 are also shown in Table 4.
Ｌｉ［Ｎｉ0.3Ｍｎ0.53Ｌｉ0.15Ｍｏ0.02］Ｏ2 （試料２０）
Ｌｉ［Ｎｉ0.3Ｍｎ0.5Ｌｉ0.15Ｍｏ0.05］Ｏ2 （試料２１）
Ｌｉ［Ｎｉ0.3Ｍｎ0.47Ｌｉ0.15Ｍｏ0.08］Ｏ2 （試料２２）
Ｌｉ［Ｎｉ0.3Ｍｎ0.45Ｌｉ0.15Ｍｏ0.1］Ｏ2 （試料２３）
Ｌｉ［Ｎｉ0.3Ｍｎ0.35Ｌｉ0.15Ｍｏ0.2］Ｏ2 （試料２４）
Li [Ni 0.3 Mn 0.53 Li 0.15 Mo 0.02 ] O 2 (Sample 20)
Li [Ni 0.3 Mn 0.5 Li 0.15 Mo 0.05 ] O 2 (Sample 21)
Li [Ni 0.3 Mn 0.47 Li 0.15 Mo 0.08 ] O 2 (Sample 22)
Li [Ni 0.3 Mn 0.45 Li 0.15 Mo 0.1 ] O 2 (Sample 23)
Li [Ni 0.3 Mn 0.35 Li 0.15 Mo 0.2 ] O 2 (Sample 24)
以上のように、ＬｉＭＯ2で示される結晶におけるＭのＭｏへの置換比率（ｚ）の増加によって充放電レート０．５Ｃの場合の放電容量は増加する効果があったが、Ｍｏへの置換比率が０．２では逆に容量が低下した。このような結果から、Ｍｏへの置換比率は０より大きく０．２より小さいことがより望ましい。 As described above, there was an effect of increasing the discharge capacity when the charge / discharge rate was 0.5 C by increasing the substitution ratio (z) of M to Mo in the crystal represented by LiMO 2. On the other hand, at 0.2, the capacity decreased. From these results, it is more desirable that the substitution ratio to Mo is larger than 0 and smaller than 0.2.
また、同様の検討をＶ、Ｎｂ、Ｗ、Ｔｉ、Ｓｉ、Ｒｕで置換した試料で行った結果、同様の置換比率（ｚ）依存性があることを確認した。 Moreover, as a result of conducting the same examination with the sample substituted by V, Nb, W, Ti, Si, and Ru, it was confirmed that there was the same substitution ratio (z) dependency.
本発明の活用例として、携帯電話、ノートパソコン、自動車、無停電源や携帯用音楽機器に使用される電池が挙げられる。 Examples of utilization of the present invention include batteries used in mobile phones, notebook computers, automobiles, uninterruptible power supplies, and portable music equipment.
１ 正極（正極活物質層）
２ 負極
３ 正極集電体
４ 負極集電体
５ セパレータ
６ 正極外装缶
７ 負極外装缶
８ 絶縁パッキング部
1 Positive electrode (positive electrode active material layer)
2 Negative electrode 3 Positive electrode current collector 4 Negative electrode
Claims (9)
Ｌｉ［ＬｉxＭｎ1-x-y-zＮｉyＺz］Ｏ2 （Ｉ）
（式中Ｚは、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種、０＜ｚ＜０．２、０．１＜ｘ＜０．３、０．１＜ｙ＜０．７、０．２＜ｘ＋ｙ＋ｚ＜１）
で示される単斜晶の構造を有する複合酸化物を活物質として含むことを特徴とするリチウム二次電池用正極。 The following general formula (I)
Li [Li x Mn 1-xyz Ni y Z z] O 2 (I)
(Wherein Z is, Nb, Mo, Ru, W , at least one of elements selected from Si and Ti, 0 <z <0.2,0.1 < x <0.3,0.1 < y <0.7, 0.2 <x + y + z <1)
A positive electrode for a lithium secondary battery, comprising a composite oxide having a monoclinic structure represented by
Ｌｉ［Ｌｉ Li [Li xx ＭｎMn 1-x-y-z1-x-y-z ＮｉNi yy ＺZ zz ］Ｏ] O 22 （Ｉ） (I)
（式中Ｚは、Ｖ、Ｎｂ、Ｍｏ、Ｒｕ、Ｗ、ＳｉおよびＴｉから選ばれる元素のうちの少なくとも１種、０．０５≦ｚ＜０．２、０．１＜ｘ＜０．３、０．１＜ｙ＜０．７、０．２５＜ｘ＋ｙ＋ｚ＜１）(Wherein, Z is at least one element selected from V, Nb, Mo, Ru, W, Si and Ti, 0.05 ≦ z <0.2, 0.1 <x <0.3, 0.1 <y <0.7, 0.25 <x + y + z <1)
で示される単斜晶の構造を有する複合酸化物を活物質として含むことを特徴とするリチウム二次電池用正極。A positive electrode for a lithium secondary battery, comprising a composite oxide having a monoclinic structure represented by
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| JP6941811B2 (en) * | 2016-09-26 | 2021-09-29 | パナソニックＩｐマネジメント株式会社 | Positive electrode active material for batteries and batteries |
| CN109997254A (en) * | 2016-11-22 | 2019-07-09 | 日产自动车株式会社 | Electrical equipment cathode and the electrical equipment for using it |
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| JP2000294242A (en) * | 1999-04-09 | 2000-10-20 | Seimi Chem Co Ltd | Positive electrode active material for nonaqueous electrolyte secondary battery, manufacture therefor and nonaqueous electrolyte secondary battery |
| JP2002145619A (en) * | 2000-09-04 | 2002-05-22 | Mitsubishi Chemicals Corp | Lithium manganese multiple oxide, positive electrode material for lithium secondary cell, positive electrode for lithium secondary cell and manufacturing method of lithium secondary cell and lithium manganese multiple oxide |
| JP2003146662A (en) * | 2001-11-13 | 2003-05-21 | Nikki Chemcal Co Ltd | Lithium-nickel-manganese complex oxide, method for manufacturing the same and use of the same |
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