JP2008285372A - Method for producing single-crystal LiMn2O4 nanowire and high-rate Li-ion battery using single-crystal LiMn2O4 nanowire - Google Patents
Method for producing single-crystal LiMn2O4 nanowire and high-rate Li-ion battery using single-crystal LiMn2O4 nanowire Download PDFInfo
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- 239000002070 nanowire Substances 0.000 title claims abstract description 62
- 239000013078 crystal Substances 0.000 title claims abstract description 50
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 13
- 229910002097 Lithium manganese(III,IV) oxide Inorganic materials 0.000 title 2
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 claims abstract description 46
- BNBLBRISEAQIHU-UHFFFAOYSA-N disodium dioxido(dioxo)manganese Chemical compound [Na+].[Na+].[O-][Mn]([O-])(=O)=O BNBLBRISEAQIHU-UHFFFAOYSA-N 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 17
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 15
- 239000011734 sodium Substances 0.000 claims abstract description 15
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims abstract description 10
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 6
- 239000011029 spinel Substances 0.000 claims abstract description 6
- 238000005406 washing Methods 0.000 claims abstract description 6
- 229910013553 LiNO Inorganic materials 0.000 claims abstract description 5
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 4
- 238000001035 drying Methods 0.000 claims abstract description 4
- 239000011230 binding agent Substances 0.000 claims description 8
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000002482 conductive additive Substances 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 2
- 239000007774 positive electrode material Substances 0.000 abstract description 5
- 239000007864 aqueous solution Substances 0.000 abstract description 3
- 239000011572 manganese Substances 0.000 abstract 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 abstract 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract 1
- 239000002253 acid Substances 0.000 abstract 1
- 229910052748 manganese Inorganic materials 0.000 abstract 1
- 229910052708 sodium Inorganic materials 0.000 abstract 1
- 238000007599 discharging Methods 0.000 description 6
- 239000002105 nanoparticle Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000002484 cyclic voltammetry Methods 0.000 description 4
- 239000007772 electrode material Substances 0.000 description 4
- 239000002086 nanomaterial Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 239000004745 nonwoven fabric Substances 0.000 description 2
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910014689 LiMnO Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000002524 electron diffraction data Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
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- 239000011163 secondary particle Substances 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
【課題】Liイオン電池正極材料として、低い出力密度から高い出力密度においても、大きな容量を示し、安定したサイクル特性および安定なプラトーを有する単結晶スピネル型LiMn2O4ナノワイヤーの製造方法、これを使用したハイレート用電極及びＬｉイオン電池の提供。
【解決手段】Mn3O4と１〜２０Mの水酸化ナトリウム水溶液を、１〜５００気圧で、１８０〜２５０℃、６時間〜２４０時間で反応させ、反応物を水洗後乾燥させ、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーとし、さらに、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーを水洗し、乾燥させ、この単結晶マンガン酸ナトリウムと超過のLiNO3/LiClを、４００〜５００℃において反応させた後、水洗し、乾燥させ、７００〜９００℃で熱処理することで単結晶LiMn2O4ナノワイヤーが得られる。
【選択図】図７The present invention relates to a method for producing a single crystal spinel type LiMn 2 O 4 nanowire as a positive electrode material for a Li-ion battery, which exhibits a large capacity even from a low power density to a high power density, and has stable cycle characteristics and a stable plateau Of high-rate electrodes and Li ion batteries using
Mn 3 O 4 and 1-20M sodium hydroxide aqueous solution are reacted at 1 to 500 atm. At 180 to 250 ° C. for 6 to 240 hours, and the reaction product is washed with water and dried to obtain single crystal manganese. Sodium nano-acid (Na 0.44 MnO 2 ) nanowires, and then single-crystal sodium manganate (Na 0.44 MnO 2 ) nano-wires were washed with water and dried, and the single-crystal sodium manganate and excess LiNO 3 / LiCl After reacting at ˜500 ° C., washing with water, drying, and heat treatment at 700 to 900 ° C. yields single crystal LiMn 2 O 4 nanowires.
[Selection] Figure 7
Description
本発明は、単結晶LiMn2O4ナノワイヤーの製造方法及び単結晶LiMn2O4ナノワイヤーを用いたハイレートLiイオン電池に関する。 The present invention relates to a high-rate Li-ion battery using the manufacturing method and a single crystal LiMn 2 O 4 nanowires monocrystalline LiMn 2 O 4 nanowires.
近年、エネルギー、環境問題が盛んに取り上げら、その問題の解決の手段としてクリーンなエネルギーデバイスの開発が必要とされており、交通、物流の手段として重要な自動車を電気エネルギーで稼動させることへの要求は、非常に高まっている。電気自動車用のエネルギー源として、Liイオン電池の有する可能性は高いものがある。何故ならLiイオン電池は、エネルギー密度が高いためである。
しかしながら、Liイオン電池には出力密度が低いという欠点がある。この問題を解決するために、多くの発明者によって電気自動車用のLi貯蔵デバイスの研究が行われてきた。
In recent years, energy and environmental issues have been actively taken up, and it has been necessary to develop clean energy devices as a means of solving these problems. The demand is very high. As an energy source for electric vehicles, there is a high possibility that a Li-ion battery has. This is because Li-ion batteries have a high energy density.
However, Li-ion batteries have the disadvantage of low power density. In order to solve this problem, many inventors have studied Li storage devices for electric vehicles.
Liイオン電池には、正極、負極が必要であるが、本発明では正極材料に注目した。現行のLiCoO2はCoのコストが高いことを考えると今後の自動車用用途（大量に必要）には難しいことが予想される。それに対してMnは安価な材料であることから、普及に関して問題がない。層状構造を持つLiMnO2などのMn化合物が正極材料として研究されているが、電気化学サイクルに対して不安定であるために、充放電を繰り返すことによる容量劣化が問題である。この問題を解決するために、スピネル構造を有する安定なLiMn2O4が研究されている。
また、急速に充電放電ができるハイレートLi貯蔵デバイスの開発のためには、以下の解決すべき、四つの問題がある。
１）活物質材料内でのLiの拡散長を減少させるための粒子径の減少。２）急速な充放電過程における電流密度の減少。３）急速な充放電過程におけるサイクル特性の向上。４）電極材料の電子伝導性の向上の４つの問題である。
つまり、ナノ構造制御を行わなければ、ハイレートデバイスは実現できないのである。
The Li ion battery requires a positive electrode and a negative electrode, but in the present invention, attention was paid to the positive electrode material. Current LiCoO 2 is expected to be difficult for future automotive applications (necessary in large quantities) given the high cost of Co. On the other hand, since Mn is an inexpensive material, there is no problem regarding its spread. Mn compounds such as LiMnO 2 having a layered structure have been studied as positive electrode materials. However, since they are unstable with respect to the electrochemical cycle, capacity degradation due to repeated charge and discharge is a problem. In order to solve this problem, stable LiMn 2 O 4 having a spinel structure has been studied.
In addition, there are four problems to be solved in order to develop a high-rate Li storage device that can rapidly charge and discharge.
1) Reduction of particle size to reduce the diffusion length of Li in the active material. 2) A decrease in current density during a rapid charge / discharge process. 3) Improvement of cycle characteristics in a rapid charge / discharge process. 4) There are four problems of improving the electron conductivity of the electrode material.
In other words, a high-rate device cannot be realized without nanostructure control.
これまで、LiMn2O4の用いた良好なハイレート特性の報告はない。これは、まず一つは、ナノ粒子を作製できたとしても、電極材料として使用する際に、容易に凝集して大きな二次粒子となり、本来のナノ粒子の特性を発揮できないことに起因する。二つ目は、安定な充放電電位を有するためには、高い結晶性を有するLiMn2O4を作製する必要があり、高温での熱処理を行わなければならない。この高温熱処理での粒成長の抑制が困難であり、ハイレートLiイオン電池が必要とするナノ構造を得ることができなかったためと考えられる。
凝集と高温熱処理での粒成長の抑制を考慮すると、ハイレートLiイオン電池電極の作製のためには、ナノ粒子の作製は不適切であり、ナノワイヤーからなる不織布の形態を作製することが適切であると考えられる。なぜならば、ナノワイヤーによって形成された不織布は、すでにワイヤー同士によって固定化されており、ポーラスな構造を持ったまま、凝集することがない。その上、ナノワイヤー同士の接点も、非常に少なく、高温での熱処理によっても、粒成長することなく、ナノワイヤーの構造を維持するからである。したがって、ハイレートLiイオン電池の電極構造に必要なナノ構造を有することができるうえ、単結晶のワイヤー構造であれば、粒界による電気抵抗も軽減され、よりハイレートLiイオン電池電極として最適な構造であることも分かる。
So far, there has been no report of good high rate characteristics using LiMn 2 O 4 . This is because, first of all, even if nanoparticles can be produced, they can be easily agglomerated into large secondary particles when used as an electrode material and cannot exhibit the characteristics of the original nanoparticles. Second, in order to have a stable charge / discharge potential, it is necessary to produce LiMn 2 O 4 having high crystallinity, and heat treatment must be performed at a high temperature. This is probably because it is difficult to suppress the grain growth by this high-temperature heat treatment, and the nanostructure required by the high-rate Li-ion battery could not be obtained.
Considering the suppression of grain growth during agglomeration and high-temperature heat treatment, it is inappropriate to produce nanoparticles for producing high-rate Li-ion battery electrodes. It is believed that there is. This is because the non-woven fabric formed of nanowires is already immobilized by wires and does not aggregate while having a porous structure. In addition, the number of contacts between the nanowires is very small, and the structure of the nanowires is maintained without grain growth even by heat treatment at a high temperature. Therefore, it is possible to have the nanostructure necessary for the electrode structure of a high-rate Li-ion battery, and if it is a single crystal wire structure, the electrical resistance due to the grain boundary is reduced, and the structure is more optimal as a high-rate Li-ion battery electrode I understand that there is.
結晶性が良く、ナノ構造を有する電極材料を作製することができれば、ハイレートにおいても、放電曲線がフラットなプラトーを有する電池特性を示すことも期待される。電池のキャパシタに勝る特性の中で、一つは大容量であり、さらには、安定な電圧を供給することができるという点がある。これまでに報告されているハイレートLi貯蔵デバイスは、ほとんどの報告において、フラットなプラトーを示さず、電池ではなくスーパーキャパシタと呼ばれ、放電曲線キャパシタと同様であり、安定な電圧を供給することができなかった。
現在、負極材料として用いられる、グラファイト電極には、グラファイトの粉と共に、カーボンファイバーを混合することにより、電極活物質の充填率の向上と体積緩和を行い、サイクル特性の向上にも寄与している。
本発明者は、マンガン酸ナトリウム（Na0.44MnO2）単結晶ナノワイヤーを用いて、ハイレート電池の電極をすでに提案している（特願２００７−０６７８３５）。
Currently, graphite electrodes used as negative electrode materials are mixed with carbon powder together with graphite powder to improve the filling rate and volume of the electrode active material, thereby contributing to improved cycle characteristics. .
The present inventor has already proposed a high-rate battery electrode using sodium manganate (Na 0.44 MnO 2 ) single crystal nanowire (Japanese Patent Application No. 2007-067835).
本発明では、立方晶の結晶構造を有する物質の単結晶ナノワイヤーを製造する。単結晶スピネル型LiMn2O4ナノワイヤーを作製し、Liイオン電池正極材料として、低い出力密度から高い出力密度においても、大きな容量を示し、安定したサイクル特性および安定なプラトーを有するLiイオン電池正極材料を提供する。 In the present invention, a single crystal nanowire made of a material having a cubic crystal structure is manufactured. A single-crystal spinel-type LiMn 2 O 4 nanowire is fabricated, and as a Li-ion battery cathode material, it exhibits a large capacity even from low to high power density, and has stable cycling characteristics and a stable plateau. Provide material.
すなわち、本発明は、新規な単結晶LiMn2O4ナノワイヤーである。
また、本発明は、結晶がスピネル型である単結晶スピネル型LiMn2O4ナノワイヤーである。
さらに本発明は、直径が数nmから数百nmである単結晶LiMn2O4ナノワイヤーである。
またさらに、本発明は、Mn3O4と１〜２０Mの水酸化ナトリウム水溶液を、１〜５００気圧で、１８０〜２５０℃、６時間〜２４０時間で反応させ、反応物を水洗後乾燥させ、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーとし、さらに、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーを水洗し、乾燥させ、この単結晶マンガン酸ナトリウムと超過のLiNO3/LiClを、３５０〜６００℃において反応させた後、水洗し、乾燥させ、６００〜１０００℃で熱処理することを特徴とする単結晶LiMn2O4ナノワイヤーの製造方法である。
本発明のナノワイヤーの製造方法では、水洗をイオン交換水で行うことができる。
さらに、本発明は、単結晶LiMn2O4ナノワイヤーと導電助剤と結着材とを混合し、成型したハイレート用電極である。
また、本発明では、単結晶LiMn2O4ナノワイヤー：導電助剤：結着材の質量比が、それぞれ４０〜８５：１０〜５０：５〜１０とすることができる。
さらに本発明では、これらの電極を用いたハイレート用Liイオン電池である。
That is, the present invention is a novel single crystal LiMn 2 O 4 nanowire.
The present invention is also a single crystal spinel type LiMn 2 O 4 nanowire whose crystal is a spinel type.
Furthermore, the present invention is a single crystal LiMn 2 O 4 nanowire having a diameter of several nm to several hundred nm.
Furthermore, the present invention comprises reacting Mn 3 O 4 and 1-20M sodium hydroxide aqueous solution at 1-500 atm, 180-250 ° C., 6 hours-240 hours, washing the reaction product with water and drying, Single-crystal sodium manganate (Na 0.44 MnO 2 ) nanowires, and then the single-crystal sodium manganate (Na 0.44 MnO 2 ) nanowires were washed with water and dried, and this single-crystal sodium manganate and excess LiNO 3 / LiCl Is a method of producing single crystal LiMn 2 O 4 nanowires, characterized by reacting at 350 to 600 ° C., washing with water, drying, and heat-treating at 600 to 1000 ° C.
In the method for producing nanowires of the present invention, washing with water can be performed with ion-exchanged water.
Furthermore, the present invention is a high rate electrode obtained by mixing and molding a single crystal LiMn 2 O 4 nanowire, a conductive additive and a binder.
In the present invention, single crystal LiMn 2 O 4 nanowire: conductive additive: weight ratio of the binder material, respectively 40 to 85: 10 to 50: can be 5-10.
Furthermore, the present invention is a high-rate Li-ion battery using these electrodes.
本発明の製造方法により得られた単結晶LiMn2O4ナノワイヤーは、製造方法が簡単であるばかりか、この単結晶LiMn2O4ナノワイヤーを用いた電極は、大きな容量を示し、安定したサイクル特性および安定なプラトーを有するLiイオン電池正極材料を提供することができる。 The single crystal LiMn 2 O 4 nanowire obtained by the production method of the present invention is not only simple in production method, but the electrode using this single crystal LiMn 2 O 4 nanowire exhibits a large capacity and is stable. Li-ion battery positive electrode materials having cycle characteristics and stable plateaus can be provided.
本発明で用いるMn3O4は、市販品を用いることが出来る。
本発明で用いる水酸化ナトリウム水溶液は、１〜２０Mを用いる必要がある。
１M以下では反応が遅く、２０M以上だと品質の良い単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーが得られない。
また、本発明において、反応圧力は、１〜４００気圧が適当である。
１気圧以下では反応が遅く、５００気圧以上だと品質の良い単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーが得られない。
また、本発明において、反応温度は、１８０〜２５０℃が適当である。
１８０℃以下では反応が遅く、２５０℃以上だと品質の良い単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーが得られない。
さらに、本発明において、反応時間は、６時間〜２４０時間が必要である。
本発明において、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーも、単結晶LiMn2O4ナノワイヤーについても、水洗は純度がよいものなら何でも良いが、水洗をイオン交換水で行うことが望ましい。
A commercial item can be used for Mn 3 O 4 used in the present invention.
The sodium hydroxide aqueous solution used in the present invention needs to use 1 to 20M.
Below 1M, the reaction is slow, and when above 20M, good quality single crystal sodium manganate (Na 0.44 MnO 2 ) nanowires cannot be obtained.
In the present invention, the reaction pressure is suitably 1 to 400 atmospheres.
Below 1 atm, the reaction is slow, and when it is above 500 atm, good quality single crystal sodium manganate (Na 0.44 MnO 2 ) nanowires cannot be obtained.
In the present invention, the reaction temperature is suitably 180 to 250 ° C.
Below 180 ° C, the reaction is slow, and above 250 ° C, good quality single crystal sodium manganate (Na 0.44 MnO 2 ) nanowires cannot be obtained.
Furthermore, in the present invention, the reaction time needs 6 hours to 240 hours.
In the present invention, the single-crystal sodium manganate (Na 0.44 MnO 2 ) nanowire and the single-crystal LiMn 2 O 4 nanowire may be washed with water as long as they have good purity. desirable.
さらに、本発明においては、単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーと超過のLiNO3/LiClを反応させるに際して、３５０〜６００℃の温度が適当であるが、より好ましくは、４５０℃程度が望ましい。
またさらに、本発明においては、この反応生成物を水洗し、乾燥させ、熱処理するが、その温度は６００〜１０００℃が好ましい。より好ましくは、８００℃程度が良く、品質の良い単結晶LiMn2O4ナノワイヤーが得られる。
さらに、本発明においては、導電助剤として周知のモノを用いることが出来るが、炭素材料が好ましく用いることが出来る。
結着材としては、業界周知の結着材を用いることが出来る。
単結晶マンガン酸ナトリウム（Na0.44MnO2）ナノワイヤーと導電助剤と結着材とを混合して、成型することにより、任意の形状のハイレート用電極とすることが出来る。
このような電極を用いて、ハイレート用Liイオン電池を作成することが出来る。
本発明について実施例を用いてさらに詳しく説明するが、本発明はこれら実施例に限定されるものではない。
Furthermore, in the present invention, when the single crystal sodium manganate (Na 0.44 MnO 2 ) nanowire is reacted with excess LiNO 3 / LiCl, a temperature of 350 to 600 ° C. is suitable, but more preferably 450 ° C. Degree is desirable.
Furthermore, in the present invention, the reaction product is washed with water, dried and heat-treated, and the temperature is preferably 600 to 1000 ° C. More preferably, a single crystal LiMn 2 O 4 nanowire having a good quality at about 800 ° C. is obtained.
Furthermore, in the present invention, well-known materials can be used as the conductive assistant, but a carbon material can be preferably used.
As the binder, a binder known in the industry can be used.
A single-crystal sodium manganate (Na 0.44 MnO 2 ) nanowire, a conductive additive, and a binder are mixed and molded to form a high-rate electrode having an arbitrary shape.
Using such an electrode, a high-rate Li-ion battery can be produced.
The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
（単結晶LiMn2O4ナノワイヤーの製造）
Mn3O4を5Mの水酸化ナトリウム水溶液に加え、ステンレス製の密閉容器のテフロン（登録商標）製の内筒に入れ、205℃で四日の水熱反応を行った。作製されたマンガン酸ナトリウム（Na0.44MnO2）単結晶ナノワイヤーはイオン交換水で洗浄し、乾燥させた。このマンガン酸ナトリウムと超過のLiNO3/LiClを450℃において1時間反応させた後、イオン交換水で洗浄し、乾燥させた。これを８００℃で一時間熱処理することにより、単結晶LiMn2O4ナノワイヤーを得た。
（電極の製造）
作製したLiMn2O4を導電助剤であるカーボンと混合した後に、結着材と混合し、SUSメッシュ集電体にプレスし、これを電極とした。
（Li電池の製造）
対極・参照極には金属Liを、電解液には1MのLiClO4を含むEC/DECの混合溶媒を用いて電気化学的評価を行った。
図1に作製されたLiMn2O4のXRDを示す。
JCPDSパターンと一致するスピネル型のLiMn2O4が作製されたことが分かる。
(Manufacture of single crystal LiMn 2 O 4 nanowires)
Mn 3 O 4 was added to a 5M aqueous sodium hydroxide solution, placed in a Teflon (registered trademark) inner cylinder in a stainless steel sealed container, and subjected to a hydrothermal reaction at 205 ° C. for 4 days. The produced sodium manganate (Na 0.44 MnO 2 ) single crystal nanowire was washed with ion-exchanged water and dried. This sodium manganate and excess LiNO 3 / LiCl were reacted at 450 ° C. for 1 hour, then washed with ion-exchanged water and dried. This was heat-treated at 800 ° C. for 1 hour to obtain single crystal LiMn 2 O 4 nanowires.
(Manufacture of electrodes)
The produced LiMn 2 O 4 was mixed with carbon, which is a conductive additive, and then mixed with a binder, and pressed onto a SUS mesh current collector, which was used as an electrode.
(Manufacture of Li batteries)
Electrochemical evaluation was performed using metallic Li for the counter electrode and reference electrode, and an EC / DEC mixed solvent containing 1M LiClO 4 for the electrolyte.
FIG. 1 shows the XRD of LiMn 2 O 4 produced.
It can be seen that spinel-type LiMn 2 O 4 that matches the JCPDS pattern was produced.
実施例１で得られたLiMn2O4の電子顕微鏡（SEM）写真を図２に示す。図２のから数十-150nm程度の直径を持つナノワイヤー構造であることが分かり、アスペクト比も1000以上と非常に大きい。また、ナノワイヤーによって不織布の形態をとり、凝集が抑制される構造となっている。
実施例１で得られたLiMn2O4の電子顕微鏡（TEM）写真と電子線回折を図３に示す。
図３の電子顕微鏡（TEM）写真と電子線回折から、得られたナノワイヤーは単結晶であることが分かる。
An electron microscope (SEM) photograph of LiMn 2 O 4 obtained in Example 1 is shown in FIG. From FIG. 2, it can be seen that the nanowire structure has a diameter of about several tens to 150 nm, and the aspect ratio is very large as 1000 or more. Moreover, it takes the form of a nonwoven fabric with nanowires, and has a structure in which aggregation is suppressed.
The electron microscope (TEM) photograph and electron beam diffraction of LiMn 2 O 4 obtained in Example 1 are shown in FIG.
From the electron microscope (TEM) photograph and electron beam diffraction of FIG. 3, it can be seen that the obtained nanowire is a single crystal.
実施例１で得られたLiMn2O4、本荘化学製（参考例１）LiMn2O4、および三井金属製（参考例２）5wt%-MgドープLiMn2O4の電気化学特性について、二サイクル目のサイクリックボルタンメトリー（0.1mV/s）と充放電曲線（0.1C,1C=100mA/gとした）を図4(a),(b)に示す。サイクリックボルタンメトリーでは、ナノワイヤーを用いたもののみが、Liの脱挿入の二つの電位において鋭いピークを示し、結晶性の高さが分かる。また、充放電曲線からもナノワイヤーを用いた場合、サイクリックボルタンメトリーの結果と同様に、二種類のLiの脱挿入の電位によって二段のプラトーを示し容量も最も大きい。市販の充放電曲線は、二種類の電位が一定でなく、二段のプラトーを示さず、なだらかな充放電曲線を示している。 Regarding the electrochemical characteristics of LiMn 2 O 4 obtained in Example 1, Honjo Chemical (Reference Example 1) LiMn 2 O 4 , and Mitsui Kinzoku (Reference Example 2) 5 wt% -Mg-doped LiMn 2 O 4 The cyclic voltammetry (0.1 mV / s) and charge / discharge curve (0.1 C, 1 C = 100 mA / g) at the cycle are shown in FIGS. 4 (a) and 4 (b). In cyclic voltammetry, only those using nanowires show sharp peaks at the two potentials of Li deinsertion, indicating the high crystallinity. Also, from the charge / discharge curve, when nanowires are used, as with the cyclic voltammetry results, the two-stage plateau is shown by the potential of the two types of Li insertion / desorption, and the capacity is the largest. The commercially available charging / discharging curve shows a gentle charging / discharging curve in which the two kinds of potentials are not constant and does not show a two-stage plateau.
実施例１で得られた電極を用いて、ハイレート（50C）で充放電を行った際の二回目の充放電曲線を図５に示す。
ナノワイヤーを用いた場合、50Cというハイレートにおいても、容量が100mA/gを超える大きな容量を示し、図４の低レートでの容量を維持しているうえに、ハイレートにおいてもプラトーを持つ充放電曲線を示している。市販の容量は、図４の低レートの容量よりも大きく減少し、充放電曲線もプラトーを示すことができない。図６においても、ナノワイヤーを用いた電極は100C,200Cの非常にハイレート下での放電曲線も、フラットなプラトーを示していることがわかる。
FIG. 5 shows a second charging / discharging curve when charging / discharging at a high rate (50 C) using the electrode obtained in Example 1.
When nanowire is used, even at a high rate of 50C, the capacity exceeds 100mA / g, and the charge / discharge curve has a plateau at the high rate while maintaining the low rate capacity shown in FIG. Is shown. The commercial capacity is greatly reduced from the low rate capacity of FIG. 4, and the charge / discharge curve cannot show a plateau. Also in FIG. 6, it can be seen that the electrode using nanowires shows a flat plateau in the discharge curve under very high rates of 100C and 200C.
実施例１で得られた電極を用いて、ナノワイヤーと市販のサンプルの充放電サイクル特性を図７に示す。いずれも50Cのハイレートにおいて、100サイクルを行った場合でも良好なサイクル特性を示しているが、その容量はナノワイヤーを用いた場合が、最も大きな値を示している。LiMn2O4ナノワイヤーは、ハイレートにおいても容量が大きく、サイクル特性も良好であると分かる。
実施例１で得られたナノワイヤーと市販のサンプルで得られた電極を用いて、および、報告されているLiMn2O4ナノ粒子を用いた報告のCレート（1C=100mA/g）と容量の関係を図８に示す。
ナノワイヤーを用いた場合、レートの増加に伴う容量の減少はわずかであり、大きな容量をハイレートにいても維持していることが分かる。市販のサンプルはレートの増加にしたがって容量は減少していることが分かり、ナノ粒子を用いた報告の値は、容量が急激に減少している。このグラフからもナノワイヤーを用いたハイレートLiイオン電池の良好な特性が分かる。
FIG. 7 shows the charge / discharge cycle characteristics of the nanowire and the commercially available sample using the electrode obtained in Example 1. Both show good cycle characteristics even when 100 cycles are performed at a high rate of 50C, but the capacity is the highest when nanowires are used. It can be seen that LiMn 2 O 4 nanowires have a large capacity and good cycle characteristics even at high rates.
Reported C-rate (1C = 100 mA / g) and capacity using nanowires obtained in Example 1 and electrodes obtained with commercial samples and using reported LiMn 2 O 4 nanoparticles The relationship is shown in FIG.
When nanowires are used, the capacity decrease with increasing rate is slight, and it can be seen that a large capacity is maintained even at a high rate. Commercial samples are found to decrease in capacity as the rate increases, and reported values using nanoparticles show a sharp decrease in capacity. This graph also shows the good characteristics of high-rate Li-ion batteries using nanowires.
本発明の製造方法により得られた単結晶LiMn2O4ナノワイヤーは、製造方法が簡単であるばかりか、この単結晶LiMn2O4ナノワイヤーを用いた電極は、大きな容量を示し、安定したサイクル特性および安定なプラトーを有するLiイオン電池正極材料を提供することができるため、産業上極めて利用価値が高いものである。 The single crystal LiMn 2 O 4 nanowire obtained by the production method of the present invention is not only simple in production method, but the electrode using this single crystal LiMn 2 O 4 nanowire exhibits a large capacity and is stable. Since a Li-ion battery positive electrode material having cycle characteristics and a stable plateau can be provided, the utility value is extremely high in the industry.
Claims (8)
A high-rate Li-ion battery using the electrode according to claim 6.
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| JP2011183526A (en) * | 2010-03-10 | 2011-09-22 | Kyushu Univ | Manganese oxide nanowire-coated structure and method for producing the same |
| US20120295147A1 (en) * | 2011-05-18 | 2012-11-22 | Battelle Memorial Institute | Nanomaterials for sodium-ion batteries |
| JP2012232890A (en) * | 2011-05-02 | 2012-11-29 | Samsung Corning Precision Materials Co Ltd | Manganese oxide nano wire, secondary battery containing the same, and method for producing the same |
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| JP2001163700A (en) * | 1999-12-08 | 2001-06-19 | Tohoku Techno Arch Co Ltd | Lithium-based composite metal oxide and method of producing the same |
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