JP5632794B2 - Lithium titanate and method for producing the same, electrode active material containing the lithium titanate, and power storage device using the electrode active material - Google Patents
Lithium titanate and method for producing the same, electrode active material containing the lithium titanate, and power storage device using the electrode active material Download PDFInfo
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Description
本発明は、新規なチタン酸リチウム及びその製造方法に関する。また、前記チタン酸アリチウムを含む電極活物質及びこの電極活物質を用いた蓄電デバイスに関する。 The present invention relates to a novel lithium titanate and a method for producing the same. The present invention also relates to an electrode active material containing the lithium lithium titanate and an electricity storage device using the electrode active material.
リチウム二次電池は、サイクル特性に優れていることから、近年急速に普及している。リチウム二次電池の電極活物質、特に負極活物質としては、エネルギー密度が高く、レート特性に優れたリチウム・チタン複合酸化物が普及しており、一方、放電電位が高く、安全性に優れたチタン酸化合物も注目されている。例えば、Ｌｉ４Ｔｉ５Ｏ１２で表されるスピネル型（特許文献１）、Ｌｉ２Ｔｉ３Ｏ７で表されるラムズデライト型（特許文献２）のチタン酸リチウムや、Ｈ２Ｔｉ１２Ｏ２５で表されるチタン酸化合物（特許文献３）を、電極活物質に用いる技術が知られている。また、電極活物質にＬｉ２Ｔｉ１２Ｏ２５で表されるチタン酸リチウム（特許文献４）を用いる技術も提案されている。あるいは、前記のスピネル型やラムズデライト型のチタン酸リチウムの表面に、酸化銅等の銅酸化物を被覆することで、電解液の分解を低減させ、ガスの発生を抑制する技術も知られている（特許文献５）。 Lithium secondary batteries have been rapidly spreading in recent years because of their excellent cycle characteristics. As an electrode active material of a lithium secondary battery, in particular, a negative electrode active material, a lithium-titanium composite oxide having a high energy density and excellent rate characteristics is widespread, while a discharge potential is high and safety is excellent. Titanate compounds are also attracting attention. For example, a spinel type represented by Li 4 Ti 5 O 12 (patent document 1), a ramsdelite type (patent document 2) lithium titanate represented by Li 2 Ti 3 O 7 , and H 2 Ti 12 O 25. A technique using a titanic acid compound represented by the formula (Patent Document 3) as an electrode active material is known. A technique using lithium titanate (Patent Document 4) represented by Li 2 Ti 12 O 25 as an electrode active material has also been proposed. Alternatively, a technique for reducing the decomposition of the electrolyte and suppressing the generation of gas by coating the surface of the spinel-type or Ramsdelite-type lithium titanate with a copper oxide such as copper oxide is also known. (Patent Document 5).
本発明は、より一層電池特性に優れた、特に、高温サイクル特性に優れたチタン酸リチウムを提供する。 The present invention provides lithium titanate that is further excellent in battery characteristics, in particular, high temperature cycle characteristics.
本発明者らは、鋭意研究を重ねた結果、一般式として（式１）Ｌｉ２ＴｉｘＯ２ｘ＋１（ｘは４以上の偶数）の化学組成をとるチタン酸リチウムに、銅及び／又はスズを含ませ、このチタン酸リチウムを活物質に用いると、優れた電池特性、特に、高温サイクル特性が得られることを見出して、本発明を完成させた。 As a result of intensive research, the present inventors have made copper and / or tin into lithium titanate having a chemical composition of (formula 1) Li 2 Ti x O 2x + 1 (x is an even number of 4 or more) as a general formula. It was found that when this lithium titanate was used as an active material, excellent battery characteristics, particularly high-temperature cycle characteristics were obtained, and the present invention was completed.
即ち、本発明は、
（１）一般式として（式１）Ｌｉ２ＴｉｘＯ２ｘ＋１（ｘは４以上の偶数）の化学組成をとる化合物に銅及び／又はスズを含むチタン酸リチウム。
（２）一般式として（式１）Ｌｉ２ＴｉｘＯ２ｘ＋１（ｘは４以上の偶数）の化学組成をとる化合物に銅及び／又はスズを含むチタン酸リチウムを含有する蓄電デバイス用電極活物質。
（３）正極、負極、セパレーター及び電解質を含む蓄電デバイスにおいて、前記正極または負極が上記（２）項に記載の電極活物質を含有する蓄電デバイス、
である。
That is, the present invention
(1) Lithium titanate containing copper and / or tin in a compound having a chemical composition of (Formula 1) Li 2 Ti x O 2x + 1 (x is an even number of 4 or more) as a general formula.
(2) Electrode active material for an electricity storage device containing lithium titanate containing copper and / or tin in a compound having a chemical composition of (Formula 1) Li 2 Ti x O 2x + 1 (x is an even number of 4 or more) as a general formula .
(3) An electricity storage device including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode or the negative electrode contains the electrode active material according to (2) above,
It is.
本発明のチタン酸リチウムは、電極活物質に用いると、電池特性、特に、高温サイクル特性に優れた蓄電デバイスが得られる。 When the lithium titanate of the present invention is used as an electrode active material, an electricity storage device having excellent battery characteristics, particularly high-temperature cycle characteristics, can be obtained.
本発明のチタン酸リチウムは、一般式として（式１）Ｌｉ２ＴｉｘＯ２ｘ＋１（ｘは４以上の偶数）の化学組成をとる化合物に銅及び／又はスズが含まれる。
（式１）で表される化合物、特に、式１中のｘが４、６、８、１２、１８又は２４である化合物は、その結晶構造が一次元のトンネル構造を有していると推測され、トンネル内に大量のリチウムイオンを吸蔵することが可能となり、また一次元の伝導パスが確保されていることから、トンネル方向へは、イオンの移動が容易であると考えられる。更に、銅及び／又はスズが含まれることで、これらのチタン酸リチウムが改質されて、優れた高温サイクル特性を付与している。
このため、本発明のチタン酸リチウムは、蓄電デバイス用の電極材料の電極活物質として好適である。
（式１）で表される化合物の中でも、一般式として（式１’）Ｌｉ２Ｔｉ１８Ｏ３７（式１中のｘが１８）、（式１”）Ｌｉ２Ｔｉ１２Ｏ２５（式１中のｘが１２）の化学組成をとるものが好ましく、式１’のものが一層好ましい。
In the lithium titanate of the present invention, copper and / or tin is contained in a compound having a chemical composition of (formula 1) Li 2 Ti x O 2x + 1 (x is an even number of 4 or more) as a general formula.
The compound represented by (Formula 1), in particular, the compound in which x in Formula 1 is 4, 6, 8, 12, 18, or 24 is presumed that the crystal structure has a one-dimensional tunnel structure. Therefore, it is possible to occlude a large amount of lithium ions in the tunnel, and since a one-dimensional conduction path is secured, it is considered that ions can be easily moved in the tunnel direction. Furthermore, by including copper and / or tin, these lithium titanates are modified to give excellent high-temperature cycle characteristics.
For this reason, the lithium titanate of this invention is suitable as an electrode active material of the electrode material for electrical storage devices.
Among the compounds represented by (Formula 1), as a general formula, (Formula 1 ′) Li 2 Ti 18 O 37 (x in Formula 1 is 18), (Formula 1 ″) Li 2 Ti 12 O 25 (Formula 1 Among them, those in which x has a chemical composition of 12) are preferred, and those of formula 1 ′ are more preferred.
銅やスズは、（式１）の化合物に、酸化物、水酸化物等の化合物として含まれていても、金属、合金等として含まれていても良い。中でも、銅、スズが、（式１）の化合物の粒子表面に担持された様態で含まれているのが好ましい。その担持様態は、厚みが均一な連続層であても、厚みが不均一な担持層であっても、島状に存在するような不連続な担持層であっても良い。銅及び／又はスズの含有量は、（式１）の化合物に含まれるチタンに対し、銅、スズあるいはそれらの合計量として０．００１／１〜０．１／１の範囲が好ましく、０．００５／１〜０．０５／１の範囲が更に好ましい。 Copper or tin may be contained in the compound of (Formula 1) as a compound such as an oxide or hydroxide, or may be contained as a metal, an alloy, or the like. Among them, it is preferable that copper and tin are contained in a state of being supported on the particle surface of the compound of (Formula 1). The supporting mode may be a continuous layer having a uniform thickness, a supporting layer having a non-uniform thickness, or a discontinuous supporting layer that exists in an island shape. The content of copper and / or tin is preferably within a range of 0.001 / 1 to 0.1 / 1 as copper, tin, or a total amount thereof with respect to titanium contained in the compound of (Formula 1). The range of 005/1 to 0.05 / 1 is more preferable.
（式１）の化合物の平均粒子径（レーザー散乱法によるメジアン径）は、特に制限を受けないが、通常は、０．０５〜１０μｍの範囲にあり、０．１〜２μｍの範囲であれば更に好ましい。また粒子形状は、球状、多面体状等の等方性形状、棒状、板状等の異方性形状、不定形状等、特に制限は無い。このものの一次粒子を集合させて二次粒子とすると、流動性、付着性、充填性等の粉体特性が向上し、電極活物質に用いる場合には、サイクル特性等の電池特性も改良されるので好ましい。本発明における二次粒子とは、一次粒子同士が強固に結合した状態にあり、通常の混合、粉砕、濾過、水洗、搬送、秤量、袋詰め、堆積等の工業的操作では容易に崩壊せず、ほとんどが二次粒子として残るものである。二次粒子の平均粒子径（レーザー散乱法によるメジアン径）は、０.１〜２０μｍの範囲にあるのが好ましい。比表面積（Ｎ２吸着によるＢＥＴ法）は特に制限は無いが、０．１〜１００ｍ２／ｇの範囲が好ましく、１〜１００ｍ２／ｇの範囲が更に好ましい。粒子形状も、一次粒子と同様に制限は受けず、様々な形状のものを用いることができる。 The average particle diameter (median diameter by laser scattering method) of the compound of (Formula 1) is not particularly limited, but is usually in the range of 0.05 to 10 μm and in the range of 0.1 to 2 μm. Further preferred. The particle shape is not particularly limited, for example, isotropic shapes such as spherical and polyhedral shapes, anisotropic shapes such as rod shapes and plate shapes, and irregular shapes. When the primary particles are aggregated into secondary particles, powder characteristics such as fluidity, adhesion, and filling properties are improved, and battery characteristics such as cycle characteristics are improved when used as an electrode active material. Therefore, it is preferable. The secondary particles in the present invention are in a state in which the primary particles are firmly bonded to each other, and are not easily disintegrated by industrial operations such as normal mixing, pulverization, filtration, washing, transport, weighing, bagging, and deposition. Most of them remain as secondary particles. The average particle diameter (median diameter by laser scattering method) of the secondary particles is preferably in the range of 0.1 to 20 μm. Although the specific surface area (N 2 BET method by adsorption) is not particularly limited, preferably in the range of 0.1 to 100 m 2 / g, more preferably in the range of 1 to 100 m 2 / g. The particle shape is not limited as in the case of the primary particle, and various shapes can be used.
（式１）の化合物の一次粒子あるいは二次粒子の粒子表面には、銅やスズの他に、炭素や、シリカ、アルミナ等の無機化合物、界面活性剤、カップリング剤等の有機化合物から選ばれる少なくとも１種の被覆を有していても良い。あるいは、チタン、リチウム以外の異種元素を、前記の結晶形を阻害しない範囲で、その結晶格子中にドープさせるなどして含有させることもできる。 In addition to copper and tin, the surface of the primary particles or secondary particles of the compound of formula (1) is selected from inorganic compounds such as carbon, silica and alumina, and organic compounds such as surfactants and coupling agents. It may have at least one kind of coating. Alternatively, different elements other than titanium and lithium can be contained in the crystal lattice by doping, etc., as long as the crystal form is not inhibited.
本発明のチタン酸リチウムは、（式１）の化合物の粒子表面に、銅及び／又はスズを含ませる工程を含む製造方法によって得られる。銅やスズを含ませるには、ＣＶＤ法、スパッタ法などの乾式被覆法、ゾルゲル法、無電解めっきなどの湿式被覆法、ボールミル法、ジェットミル法などの混合・粉砕複合化処理方法など、種々の方法を被覆種に応じて適宜選択して用いることができる。例えば、（式１）の化合物の粒子表面に銅及び／又はスズの酸化物を担持させるのであれば、式１の化合物を分散させた水性スラリーに、銅やスズの水溶性化合物を添加し、中和することで行える。 The lithium titanate of this invention is obtained by the manufacturing method including the process of including copper and / or tin in the particle | grain surface of the compound of (Formula 1). To include copper and tin, there are various methods such as dry coating methods such as CVD methods and sputtering methods, wet coating methods such as sol-gel methods and electroless plating, mixed and pulverized compound processing methods such as ball mill methods and jet mill methods. These methods can be appropriately selected depending on the coating type. For example, if copper and / or tin oxide is supported on the particle surface of the compound of the formula (1), a water-soluble compound of copper or tin is added to the aqueous slurry in which the compound of the formula 1 is dispersed, This can be done by neutralization.
あるいは、（１）一般式として（式２）Ｈ２Ｔｉｘ−ｙＯ２（ｘ−ｙ）＋１（０≦ｙ＜ｘ、ｘ−ｙ＞２、ｙは整数、但しｘは式１中のｘと同じ数値を取る）の化学組成をとる化合物と銅化合物及び／又はスズ化合物とを、式１の化合物に含まれるチタンに対し銅、スズあるいはそれらの合計量として０．００１／１〜０．１／１の範囲になるように反応させ、反応生成物（Ａ）を得る工程（第一の工程）、（２）反応生成物（Ａ）とリチウム化合物とを、反応生成物（Ａ）に含まれる銅、スズあるいはそれらの合計量に対しリチウムが当量以上となるように液相中で反応させて反応生成物（Ｂ）を得る工程（第二の工程）、（３）反応生成物（Ｂ）を固液分離した後、加熱脱水する工程（第三の工程）、を含む方法、も挙げられる。
この方法によっても、銅及び／又はスズを含む被覆が形成されるか、あるいは銅、スズの大半を含む被覆が形成され、一部が（式１）の化合物の結晶格子中に含まれると考えられる。一次元のトンネル構造を有している化合物であれば、前記の公知の方法では、中和剤に由来する水素イオン、アルカリ金属イオン等のカチオンが、トンネル構造に挿入され易いので、この方法は、特に式１中のｘが４、６、８、１２、１８又は２４である化合物の製造に、中でも銅及び／又はスズを含む（式１’）や（式１”）の化合物の製造に適しており、銅及び／又はスズを含む（式１’）の化合物の製造に一層適している。
Alternatively, (1) as a general formula (Formula 2) H 2 Ti xy O 2 (xy) +1 (0 ≦ y <x, xy> 2, y is an integer, where x is The compound having the chemical composition of (the same numerical value as x) and the copper compound and / or the tin compound are 0.001 / 1 to 0 as copper, tin, or the total amount thereof with respect to titanium contained in the compound of formula 1 A step of obtaining a reaction product (A) by reacting to a range of 1/1 (first step), (2) a reaction product (A) and a lithium compound are reacted with the reaction product (A). Step (second step) for obtaining a reaction product (B) by reacting in a liquid phase so that lithium is equal to or more than the equivalent amount of copper, tin or the total amount thereof contained in (3) reaction product A method including a step (third step) of heat-dehydrating after solid-liquid separation of (B) is also included.
Also by this method, a coating containing copper and / or tin is formed, or a coating containing most of copper and tin is formed, and a part thereof is considered to be included in the crystal lattice of the compound of (Formula 1). It is done. If the compound has a one-dimensional tunnel structure, in the above-described known method, cations such as hydrogen ions and alkali metal ions derived from the neutralizing agent are easily inserted into the tunnel structure. Especially for the production of compounds where x in formula 1 is 4, 6, 8, 12, 18 or 24, especially for the production of compounds of formula (1 ′) or (formula 1 ″) containing copper and / or tin. More suitable for the production of compounds of formula (1 ′) comprising copper and / or tin.
第一の工程で、（式２）の化合物と銅化合物やスズ化合物を反応させるには、これらを液相中で混合するなどして接触させる方法を用いても良く、固相中で混合するなどして接触させ加熱しても良い。液相中で反応を行なう場合、反応はスラリー中で行うのが好ましく、水性媒体を用いたスラリー中で行うのが更に好ましい。水性媒体を用いる場合は、銅化合物としては、塩化銅、塩化銅アンモニウム等の水溶性化合物を用いるのが好ましく、スズ化合物としては、塩化スズ、スズ酸ナトリウム等が好ましい。また、式１’（式１中のｘが１８）の化合物を得る場合には、（式２）の化合物は、一般式として（式２’）Ｈ２Ｔｉ１２Ｏ２５（式２中のｘが１８、ｙが６）の化学組成をとる化合物を用いるのが好ましい。また、（式１”）の化合物を得るにも、（式２’）の化合物を用いるのが好ましい。（式２’）の化合物は、トンネル構造を有し、トンネル内に水素イオンが挿入された化合物であり、（式２’）の化合物と銅化合物、スズ化合物等を前記範囲で反応させると、トンネル構造内の水素イオンの一部が銅イオン、スズイオン等と置換されると推測される。 In the first step, in order to react the compound of (Formula 2) with the copper compound or the tin compound, a method of contacting them by mixing them in a liquid phase may be used. It may be contacted and heated. When the reaction is performed in the liquid phase, the reaction is preferably performed in a slurry, and more preferably in a slurry using an aqueous medium. When an aqueous medium is used, it is preferable to use a water-soluble compound such as copper chloride or copper ammonium chloride as the copper compound, and as the tin compound, tin chloride, sodium stannate or the like is preferable. When obtaining a compound of formula 1 ′ (x in formula 1 is 18), the compound of (formula 2) is represented by the general formula (formula 2 ′) H 2 Ti 12 O 25 (x in formula 2). It is preferable to use a compound having a chemical composition in which y is 18 and y is 6). In order to obtain the compound of (Formula 1 ″), it is preferable to use the compound of (Formula 2 ′). The compound of (Formula 2 ′) has a tunnel structure in which hydrogen ions are inserted into the tunnel. When a compound of (Formula 2 ′) is reacted with a copper compound, tin compound, etc. within the above range, it is presumed that some of the hydrogen ions in the tunnel structure are replaced with copper ions, tin ions, etc. .
第二の工程の反応生成物（Ａ）とリチウム化合物との液相中も反応も、スラリー中で行うのが好ましく、水性媒体を用いたスラリー中で行うのが更に好ましい。水性媒体を用いる場合は、リチウム化合物としては、水酸化リチウム、炭酸リチウム等の水溶性リチウム化合物を用いるのが好ましい。反応温度は、８０℃以上が好ましく、３００℃以下とするのがより好ましく、８０〜２００℃が更に好ましい範囲である。１００℃以上で反応させる場合は、オートクレーブ等の耐圧容器を用いるのが好ましい。反応生成物（Ａ）とリチウム化合物との反応は、反応生成物（Ａ）に含まれる銅、スズあるいはそれらの合計量に対し、リチウムが当量より多くなるように反応量を調整することによって、銅イオン及び／又はスズイオンの全部と水素イオンの一部がリチウムイオンと置換するように調整するのが好ましい。
例えば、（式１’）の化合物を得る場合は、反応生成物（Ｂ）に含まれる水素とリチウムとのモル比が０．５／１〜１．５／１になるように、反応生成物（Ａ）とリチウム化合物とを反応させるのが好ましい。反応生成物（Ａ）とリチウム化合物との反応によって、反応生成物（Ａ）のトンネル構造内の銅イオン、スズイオン等はリチウムイオンと置換する。
トンネル構造内から脱離した銅これらのイオンは、水酸化銅、水酸化スズ等を生成させると考えられる。この第二の工程において、反応生成物（Ｂ）は、トンネル構造内に水素イオンとリチウムイオンが挿入された化合物を主体とする粒子の表面に、生成した水酸化銅、水酸化スズ等が担持された様態か、粒子表面に、生成した水酸化銅、水酸化スズ等の一部が担持され、担持されていない水酸化銅、水酸化スズ等が液相中に存在している様態か、または生成した水酸化銅、水酸化スズ等の全部が液相中に存在する様態のいずれかであると推測される。
液相中の水酸化銅、水酸化スズ等の一部又は全部は、後述の第三の工程で固液分離する際に、前記粒子の表面に担持されると推測される。
The reaction and reaction of the reaction product (A) in the second step and the lithium compound are preferably performed in a slurry, and more preferably in a slurry using an aqueous medium. When an aqueous medium is used, it is preferable to use a water-soluble lithium compound such as lithium hydroxide or lithium carbonate as the lithium compound. The reaction temperature is preferably 80 ° C. or higher, more preferably 300 ° C. or lower, and further preferably 80 to 200 ° C. When making it react at 100 degreeC or more, it is preferable to use pressure-resistant containers, such as an autoclave. The reaction between the reaction product (A) and the lithium compound is carried out by adjusting the reaction amount so that the amount of lithium is greater than the equivalent amount with respect to the total amount of copper, tin, or their contained in the reaction product (A). It is preferable to adjust so that all of copper ions and / or tin ions and a part of hydrogen ions are replaced with lithium ions.
For example, when obtaining the compound of (Formula 1 ′), the reaction product is adjusted so that the molar ratio of hydrogen to lithium contained in the reaction product (B) is 0.5 / 1 to 1.5 / 1. It is preferable to react (A) with a lithium compound. By the reaction between the reaction product (A) and the lithium compound, copper ions, tin ions and the like in the tunnel structure of the reaction product (A) are replaced with lithium ions.
Copper desorbed from within the tunnel structure It is considered that these ions generate copper hydroxide, tin hydroxide and the like. In this second step, the reaction product (B) is supported by the produced copper hydroxide, tin hydroxide, etc. on the surface of particles mainly composed of a compound in which hydrogen ions and lithium ions are inserted into the tunnel structure. Or a state in which a part of the produced copper hydroxide, tin hydroxide, etc. is supported on the particle surface, and an unsupported copper hydroxide, tin hydroxide, etc. are present in the liquid phase, Or it is estimated that all of the produced | generated copper hydroxide, tin hydroxide, etc. exist in any state in a liquid phase.
Part or all of copper hydroxide, tin hydroxide and the like in the liquid phase is presumed to be supported on the surface of the particles when solid-liquid separation is performed in a third step described later.
第三の工程では、得られた反応生成物を固液分離し、加熱脱水する。必要に応じて、洗浄、乾燥等を行なっても良い。次に、好ましくは、３００〜６００℃の範囲の温度で加熱脱水する。加熱脱水により、反応生成物の残りの水素イオンが酸素と共に除去され、チタン酸リチウムが形成されると同時に、反応生成物の粒子表面に担持された水酸化銅や水酸化スズから、酸化銅、酸化スズあるいは金属銅、金属スズ等が生成し、銅及び／又はスズを含む担持層を形成するものと考えられる。加熱温度が３００℃より低い場合は、脱水が不十分で所望の組成のチタン酸リチウムが得られ難く、６００℃より高いと、部分的にブロンズ型、アナターゼ型等の二酸化チタンが生成してしまう。あるいは、粒子同士の凝集の程度に応じて、公知の機器を用いて本発明の効果を損ねない範囲で粉砕してもよい。 In the third step, the obtained reaction product is solid-liquid separated and dehydrated by heating. You may perform washing | cleaning, drying, etc. as needed. Next, heat dehydration is preferably performed at a temperature in the range of 300 to 600 ° C. By heat dehydration, the remaining hydrogen ions in the reaction product are removed together with oxygen to form lithium titanate. At the same time, from copper hydroxide and tin hydroxide supported on the particle surface of the reaction product, copper oxide, It is considered that tin oxide, metal copper, metal tin, or the like is generated to form a support layer containing copper and / or tin. When the heating temperature is lower than 300 ° C., dehydration is insufficient and it is difficult to obtain lithium titanate having a desired composition. When the heating temperature is higher than 600 ° C., titanium dioxide such as bronze type or anatase type is partially generated. . Or you may grind | pulverize in the range which does not impair the effect of this invention using a well-known apparatus according to the grade of aggregation of particle | grains.
（式２）で表される化合物は、公知の方法によって得られるので、所望の組成に応じて適宜製造方法を選択する。例えば、（式２’）の化合物であれば、特許文献３に開示される方法によって得ることができる。即ち、ナトリウム化合物と酸化チタンの混合物を６００℃以上の温度で焼成して、一般式として（式３）Ｎａ２Ｔｉ３Ｏ７の化学組成をとる化合物を得る工程、式３の化合物と酸性溶液を反応させて、一般式として（式４）Ｈ２Ｔｉ３Ｏ７の化学組成をとる化合物を得る工程、（式４）の化合物を空気中又は真空中で１５０℃以上２８０℃未満の範囲の温度で加熱脱水する工程を含む方法によって得ることができる。 Since the compound represented by (Formula 2) is obtained by a well-known method, a manufacturing method is suitably selected according to a desired composition. For example, if it is a compound of (Formula 2 '), it can be obtained by the method disclosed in Patent Document 3. That is, a step of calcining a mixture of a sodium compound and titanium oxide at a temperature of 600 ° C. or higher to obtain a compound having the general formula (formula 3) Na 2 Ti 3 O 7 , a compound of formula 3 and an acidic solution To obtain a compound having the chemical formula of (Formula 4) H 2 Ti 3 O 7 as a general formula, the compound of (Formula 4) in the range of 150 ° C. or more and less than 280 ° C. in air or in vacuum It can be obtained by a method including a step of heat dehydration at a temperature.
本製造法では、（式１）の化合物の二次粒子を得ることもできる。（００１４）段落に記載の方法においては、例えば、（１）第一の工程において、（式２）の化合物の二次粒子と銅化合物及び／又はスズ化合物を反応させる方法、（２）第二の工程において、第一の工程で得られた反応生成物（Ａ）の一次粒子を二次粒子に造粒した後、リチウム化合物と反応させる方法、（３）第三の工程において、反応生成物（Ｂ）の一次粒子を二次粒子に造粒して、加熱脱水する方法、（４）第三の工程によって得られた銅及び又はスズを含む（式１）の化合物の一次粒子を二次粒子に造粒する方法等が挙げられる。
（１）の方法で、（式２）の化合物として（式２’）のものを用いる場合、（式２’）の化合物の二次粒子は、（式２’）の化合物の一次粒子を得た後、二次粒子に造粒しても良く、あるいは、ナトリウム化合物と酸化チタンを二次粒子に造粒した後、焼成し、酸性溶液と反応させ、加熱脱水させる；（式３）の化合物の一次粒子を得た後、二次粒子に造粒し、酸性化合物と反応させ、加熱脱水させる；（式４）の化合物の一次粒子を得た後、二次粒子に造粒し、加熱脱水する等の方法で得ることもできる。造粒には、乾燥造粒、撹拌造粒、圧密造粒等が挙げられ、二次粒子の粒子径や形状を調整し易いので、乾燥造粒が好ましい。乾燥造粒には、（式１）〜（式４）の化合物や、反応生成物（Ａ）及び（Ｂ）、ナトリウム化合物、酸化チタン等を含むスラリーを脱水後、乾燥して粉砕する；前記スラリーを脱水後、成型して乾燥する；前記スラリーを噴霧乾燥する等の方法が挙げられ、中でも噴霧乾燥が工業的に好ましい。
In this production method, secondary particles of the compound of (Formula 1) can also be obtained. In the method described in paragraph (0014), for example, (1) in the first step, the secondary particles of the compound of formula (2) are reacted with a copper compound and / or a tin compound, (2) second In the step, the primary particles of the reaction product (A) obtained in the first step are granulated into secondary particles, and then reacted with a lithium compound. (3) In the third step, the reaction product (B) A method of granulating primary particles into secondary particles, followed by heat dehydration; (4) secondary particles of a compound of formula (1) containing copper and / or tin obtained by the third step; Examples thereof include a method of granulating particles.
In the method of (1), when the compound of (Formula 2 ′) is used as the compound of (Formula 2), the secondary particles of the compound of (Formula 2 ′) obtain primary particles of the compound of (Formula 2 ′). Then, it may be granulated into secondary particles, or after granulating sodium compound and titanium oxide into secondary particles, calcined, reacted with an acidic solution, and heated to dehydrate; compound of (Formula 3) After obtaining the primary particles, the particles are granulated into secondary particles, reacted with an acidic compound, and dehydrated by heating; after obtaining the primary particles of the compound of formula (4), the particles are granulated into secondary particles and dehydrated by heating. It can also be obtained by such a method. Examples of granulation include dry granulation, stirring granulation, compaction granulation, and the like, and dry granulation is preferable because the particle diameter and shape of secondary particles can be easily adjusted. In dry granulation, the slurry containing the compounds of (Formula 1) to (Formula 4), reaction products (A) and (B), sodium compounds, titanium oxide and the like is dehydrated, dried and pulverized; After the slurry is dehydrated, it is molded and dried; a method such as spray drying of the slurry is mentioned, and spray drying is industrially preferable.
噴霧乾燥するのであれば、用いる噴霧乾燥機は、ディスク式、圧力ノズル式、二流体ノズル式、四流体ノズル式など、スラリーの性状や処理能力に応じて適宜選択することができる。二次粒子径の制御は、例えば、スラリー中の固形分濃度を調整する、あるいは、上記のディスク式ならディスクの回転数を、圧力ノズル式、二流体ノズル式、四流体ノズル式等ならば、噴霧圧やノズル径を調整する等して、噴霧される液滴の大きさを制御することにより行える。乾燥温度としては入り口温度を１５０〜２５０℃の範囲、出口温度を７０〜１２０℃の範囲とするのが好ましい。スラリーの粘度が低く、造粒し難い場合や、粒子径の制御を更に容易にするために、有機系バインダーを用いても良い。用いる有機系バインダーとしては、例えば、（１）ビニル系化合物（ポリビニルアルコール、ポリビニルピロリドン等）、（２）セルロース系化合物（ヒドロキシエチルセルロース、カルボキシメチルセルロース、メチルセルロース、エチルセルロース等）、（３）タンパク質系化合物（ゼラチン、アラビアゴム、カゼイン、カゼイン酸ソーダ、カゼイン酸アンモニウム等）、（４）アクリル酸系化合物（ポリアクリル酸ソーダ、ポリアクリル酸アンモニウム等）、（５）天然高分子化合物（デンプン、デキストリン、寒天、アルギン酸ソーダ等）、（６）合成高分子化合物（ポリエチレングリコール等）等が挙げられ、これらから選ばれる少なくとも１種を用いることができる。中でも、ソーダ等の無機成分を含まないものは、加熱処理により分解、揮散し易いので更に好ましい。 If spray drying is performed, the spray dryer to be used can be appropriately selected according to the properties of the slurry and the processing capability, such as a disk type, a pressure nozzle type, a two-fluid nozzle type, and a four-fluid nozzle type. The control of the secondary particle size is, for example, adjusting the solid content concentration in the slurry, or if the above disk type, the rotational speed of the disk, if it is a pressure nozzle type, two fluid nozzle type, four fluid nozzle type, etc. This can be done by controlling the size of droplets to be sprayed by adjusting the spray pressure or nozzle diameter. As the drying temperature, the inlet temperature is preferably in the range of 150 to 250 ° C, and the outlet temperature is preferably in the range of 70 to 120 ° C. An organic binder may be used when the slurry has a low viscosity and is difficult to granulate, or for easier control of the particle size. Examples of the organic binder to be used include (1) vinyl compounds (polyvinyl alcohol, polyvinyl pyrrolidone, etc.), (2) cellulose compounds (hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, etc.), (3) protein compounds ( Gelatin, gum arabic, casein, sodium caseinate, ammonium caseinate, etc.), (4) acrylic acid compounds (sodium polyacrylate, ammonium polyacrylate, etc.), (5) natural polymer compounds (starch, dextrin, agar) , Sodium alginate, etc.), (6) synthetic polymer compounds (polyethylene glycol, etc.), etc., and at least one selected from these can be used. Especially, what does not contain inorganic components, such as soda, is more preferable because it is easily decomposed and volatilized by heat treatment.
また、本発明の銅及び／又はスズを含む（式１）の化合物を電極活物質として含有する電極を構成部材として用いた蓄電デバイスは、高容量で、高温サイクル特性に優れ、かつ可逆的なリチウム挿入・脱離反応が可能であり、高い信頼性が期待できる蓄電デバイスである。 In addition, an electricity storage device using an electrode containing the compound of Formula (1) containing copper and / or tin of the present invention as an electrode active material has a high capacity, excellent high-temperature cycle characteristics, and reversible. It is an electricity storage device that can perform lithium insertion / extraction reactions and can be expected to have high reliability.
蓄電デバイスとしては、具体的には、リチウム電池、キャパシタ等が挙げられ、これらは及び正極、負極、セパレーターと及び電解質を含み、電極は、前記電極活物質にカーボンブラックなどの導電材とフッ素樹脂などのバインダーを加え、適宜成形または塗布して得られる。リチウム電池の場合、前記電極活物質を正極に用い、対極として金属リチウム、リチウム合金など、または黒鉛などの炭素系材料などを用いることができる。あるいは、前記電極活物質を負極として用い、正極にリチウム・マンガン複合酸化物、リチウム・コバルト複合酸化物、リチウム・ニッケル複合酸化物、リチウム・バナジン複合酸化物等のリチウム・遷移金属複合酸化物、リチウム・鉄・複合リン酸化合物等のオリビン型化合物等を用いることができる。また、本発明の電極活物質を、公知の活物質と混合して電極を作製しても良い。キャパシタの場合は、前記電極活物質と、黒鉛とを用いた非対称型キャパシタとすることができる。セパレーターには、いずれにも、多孔性ポリエチレンフィルムなどが用いられ、電解液には、プロピレンカーボネート、エチレンカーボネート、ジメチルカーボネートなどの溶媒にＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＢＦ4などのリチウム塩を溶解させたものなど常用の材料を用いることができる。 Specific examples of the electricity storage device include a lithium battery, a capacitor, and the like. These include a positive electrode, a negative electrode, a separator, and an electrolyte. The electrode includes a conductive material such as carbon black and a fluorine resin as the electrode active material. It can be obtained by adding a binder such as In the case of a lithium battery, the electrode active material can be used for a positive electrode, and metallic lithium, a lithium alloy, or a carbon-based material such as graphite can be used as a counter electrode. Alternatively, the electrode active material is used as a negative electrode, and a lithium / transition metal composite oxide such as a lithium / manganese composite oxide, a lithium / cobalt composite oxide, a lithium / nickel composite oxide, a lithium / vanadine composite oxide, Olivine type compounds such as lithium, iron, and complex phosphate compounds can be used. Further, the electrode active material of the present invention may be mixed with a known active material to produce an electrode. In the case of a capacitor, an asymmetric capacitor using the electrode active material and graphite can be used. For the separator, a porous polyethylene film or the like is used for each of the separators, and for the electrolyte, LiPF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (CF 3 SO 3) are used in a solvent such as propylene carbonate, ethylene carbonate, or dimethyl carbonate. 2 ) A conventional material such as a solution in which a lithium salt such as 2 or LiBF 4 is dissolved can be used.
以下に本発明の実施例を示すが、これらは本発明を限定するものではない。 Examples of the present invention are shown below, but these do not limit the present invention.
参考例１：銅を含むチタン酸リチウム
（第一の工程）
市販のルチル型高純度二酸化チタン（ＰＴ−３０１：石原産業製）１０００ｇと、炭酸ナトリウム４５１．１ｇに、純水１２８４ｇを加え、撹拌してスラリー化した。このスラリーを噴霧乾燥機（ＭＤＬ−０５０Ｃ型：藤崎電気製）を用いて、入口温度２００℃、出口温度７０〜９０℃の条件で噴霧乾燥した。得られた噴霧乾燥品を、電気炉を用い、大気中で８００℃の温度で１０時間加熱焼成し、（式３）の化合物：Ｎａ２Ｔｉ３Ｏ７を得た。
Reference Example 1: Lithium titanate containing copper (first step)
To 1000 g of commercially available rutile type high-purity titanium dioxide (PT-301: manufactured by Ishihara Sangyo) and 451.1 g of sodium carbonate, 1284 g of pure water was added and stirred to form a slurry. This slurry was spray-dried under conditions of an inlet temperature of 200 ° C. and an outlet temperature of 70 to 90 ° C. using a spray dryer (MDL-050C type: manufactured by Fujisaki Electric). The obtained spray-dried product was heated and calcined in the atmosphere at a temperature of 800 ° C. for 10 hours using an electric furnace to obtain a compound of formula (3): Na 2 Ti 3 O 7 .
得られたＮａ２Ｔｉ３Ｏ７１０７７ｇに、純水４３１０ｇを加え、分散スラリーを得た。このスラリー４８４８ｇに６４％硫酸７１１ｇを加え、撹拌しながら５０℃の条件で５時間反応させてから、ろ過水洗した。ろ過ケーキに純水を加え３３７０ｇにしてから再分散させ、６４％硫酸３１．３ｇを加え、攪拌しながら７０℃の条件で５時間反応させてから、ろ過水洗乾燥して（式４）の化合物：Ｈ２Ｔｉ３Ｏ７を得た。 4310 g of pure water was added to 1077 g of the obtained Na 2 Ti 3 O 7 to obtain a dispersed slurry. 711 g of 64% sulfuric acid was added to 4848 g of this slurry, and the mixture was reacted for 5 hours at 50 ° C. with stirring, followed by washing with filtered water. After adding pure water to the filter cake to make 3370 g, redispersed, adding 31.3 g of 64% sulfuric acid, reacting at 70 ° C. for 5 hours with stirring, washing with filtered water and drying (compound of formula 4) : was obtained H 2 Ti 3 O 7.
得られたＨ２Ｔｉ３Ｏ７３００ｇを、電気炉を用い、大気中で２６０℃で１０時間加熱脱水し、式２’の化合物：Ｈ２Ｔｉ１２Ｏ２５（試料ａ）を得た。化学組成の妥当性について、試料の２５０〜６００℃の温度範囲における加熱減量を、示差熱天秤を用いて測定し、加熱減量が構造水に相当すると仮定して算出したところ、Ｈ２Ｔｉ１２Ｏ２５の化学組成が妥当であることが確認された。 300 g of the obtained H 2 Ti 3 O 7 was dehydrated by heating at 260 ° C. for 10 hours in the atmosphere using an electric furnace to obtain a compound of formula 2 ′: H 2 Ti 12 O 25 (sample a). The validity of the chemical composition, where the heat loss in the temperature range of 250 to 600 ° C. samples were measured using a differential thermal balance, heat loss was calculated on the assumption that corresponding to structural water, H 2 Ti 12 O 25 chemical compositions were confirmed to be reasonable.
得られたＨ２Ｔｉ１２Ｏ２５２５８．３ｇを純水１リットルに分散させた後、塩化銅アンモニウム二水和物（Ｃｕ（ＮＨ４）２Ｃｌ２・２Ｈ２Ｏ）１３．２９ｇを純水２００ミリリットルに溶解させた水溶液を添加し（Ｃｕ／Ｔｉ＝０．０１５）、３０分間撹拌して反応させ、反応生成物（Ａ）−（１）を得た。 After 258.3 g of the obtained H 2 Ti 12 O 25 was dispersed in 1 liter of pure water, 13.29 g of copper chloride ammonium dihydrate (Cu (NH 4 ) 2 Cl 2 · 2H 2 O) was purified. An aqueous solution dissolved in 200 ml was added (Cu / Ti = 0.015), and the mixture was stirred for 30 minutes for reaction to obtain a reaction product (A)-(1).
（第二の工程）
得られた反応生成物（Ａ）−（１）のスラリーに、水酸化リチウム一水和物（ＬｉＯＨ・Ｈ２Ｏ）３５．１８ｇを純水３００ミリリットルに溶解させた水溶液を添加した後、オートクレーブに仕込み、撹拌しながら１２０℃で５時間反応させ、反応生成物（Ｂ）−（１）を得た。試料の一部を分取し、Ｃｕ、Ｌｉ、Ｔｉの含有量を分析すると共に、２５０〜６００℃の温度範囲における加熱減量を、示差熱天秤を用いて測定し、加熱減量が構造水に相当すると仮定して算出したところ、モル比でＣｕ／Ｔｉが０．０１５／１、Ｈ／Ｔｉが０．０７４／１、Ｌｉ／Ｔｉが０．０７８／１であることが確認された。
(Second step)
An aqueous solution in which 35.18 g of lithium hydroxide monohydrate (LiOH.H 2 O) was dissolved in 300 ml of pure water was added to the resulting slurry of the reaction product (A)-(1), and then the autoclave The reaction product (B)-(1) was obtained by stirring at 120 ° C. for 5 hours while stirring. A portion of the sample was collected and analyzed for Cu, Li, and Ti contents, and heating loss in the temperature range of 250 to 600 ° C. was measured using a differential thermal balance. As a result, it was confirmed that Cu / Ti was 0.015 / 1, H / Ti was 0.074 / 1, and Li / Ti was 0.078 / 1 in molar ratio.
（第三の工程）
得られた反応生成物（Ｂ）−（１）をろ過水洗乾燥した後、４００℃の温度で１０時間加熱処理して、銅を含むチタン酸リチウムを得た。（試料Ａ）
(Third process)
The obtained reaction product (B)-(1) was washed with filtered water, dried and then heat-treated at a temperature of 400 ° C. for 10 hours to obtain copper-containing lithium titanate. (Sample A)
実施例１：スズを含むチタン酸リチウム
（第一の工程）
参考例１の第一の工程で得られた（式２）の化合物：Ｈ２Ｔｉ１２Ｏ２５１０．２ｇを純水８０ミリリットルに分散させた後、スズ酸ナトリウム三水和物（Ｎａ２ＳｎＯ３・３Ｈ２Ｏ）０．５０ｇを添加した後（Ｓｎ／Ｔｉ＝０．０００５４）、３０分間撹拌して反応させ、反応生成物（Ａ）−（２）を得た。
Example 1: Tin titanate containing tin (first step)
Compound (Formula 2) obtained in the first step of Reference Example 1 10.2 g of H 2 Ti 12 O 25 was dispersed in 80 ml of pure water, and then sodium stannate trihydrate (Na 2 SnO) 3 · 3H 2 O) was added 0.50g (Sn / Ti = 0.00054) , and reacted with stirring for 30 min, the reaction product (a) - to obtain a (2).
（第二の工程）
得られた反応生成物（Ａ）−（２）のスラリーに、水酸化リチウム一水和物（ＬｉＯＨ・Ｈ２Ｏ）１．３９ｇを添加した後、オートクレーブに仕込み、撹拌しながら１２０℃で５時間反応させ、反応生成物（Ｂ）−（２）を得た。Ｓｎ、Ｌｉ、Ｔｉの含有量をＩＣＰ発行分光分析法により分析すると共に、２５０〜６００℃の温度範囲における加熱減量を、示差熱天秤を用いて測定し、加熱減量が構造水に相当すると仮定して算出したところ、モル比でＳｎ／Ｔｉが０．０００５４／１、Ｈ／Ｔｉが０．０７１／１、Ｌｉ／Ｔｉが０．１１２６／１であることが確認された。
(Second step)
Lithium hydroxide monohydrate (LiOH.H 2 O) 1.39 g was added to the resulting reaction product (A)-(2) slurry, then charged into an autoclave and stirred at 120 ° C. for 5 hours. Reaction was carried out for a time to obtain a reaction product (B)-(2). It is assumed that the Sn, Li, Ti content is analyzed by ICP emission spectroscopy, and the heating loss in the temperature range of 250 to 600 ° C. is measured using a differential thermal balance, and the heating loss corresponds to structural water. It was confirmed that Sn / Ti was 0.00054 / 1, H / Ti was 0.071 / 1, and Li / Ti was 0.1126 / 1 in molar ratio.
（第三の工程）
得られた反応生成物（Ｂ）−（２）をろ過水洗乾燥した後、４００℃の温度で１０時間加熱処理して、スズ化合物を含む（式１’）の化合物を得た。（試料Ｂ）
(Third process)
The obtained reaction product (B)-(2) was washed with filtered water, dried and then heat-treated at a temperature of 400 ° C. for 10 hours to obtain a compound of (formula 1 ′) containing a tin compound. (Sample B)
比較例１
参考例１の第一の工程で得られた（式２’）の化合物を比較対象の化合物とした。（試料ａ）
Comparative Example 1
The compound of (Formula 2 ′) obtained in the first step of Reference Example 1 was used as a comparative compound. (Sample a)
比較例２ Comparative Example 2
参考例１の第一の工程で得られた（式２’）の化合物２５８．３ｇに純水１リットルと水酸化リチウム一水和物３５．１８ｇ（ＬｉＯＨ・Ｈ２Ｏ）を純水５００ミリリットルに溶解させた水溶液を添加した後、オートクレーブに仕込み、撹拌しながら１２０℃で５時間反応させ、反応生成物を得た。得られた反応生成物をろ過水洗乾燥した後、４００℃の温度で１０時間加熱処理して、銅、スズ等を含まないチタン酸リチウムを得た。（試料Ｃ） To 258.3 g of the compound of the formula (2 ′) obtained in the first step of Reference Example 1, 1 liter of pure water and 35.18 g of lithium hydroxide monohydrate (LiOH.H 2 O) were added to 500 ml of pure water. The aqueous solution dissolved in was added to an autoclave and reacted at 120 ° C. for 5 hours with stirring to obtain a reaction product. The obtained reaction product was washed with filtered water, dried and then heat-treated at 400 ° C. for 10 hours to obtain lithium titanate containing no copper, tin or the like. (Sample C)
評価１：結晶性の確認
参考例１、実施例１、比較例２で得られた化合物（試料Ａ〜Ｃ）について、粉末Ｘ線回折装置により、Ｘ線回折データを測定したところ、いずれも、良好な結晶性を有する、単斜晶系であることが判った。また、試料Ａ〜ＣのＸ線回折パターンは、ほぼ同一であることから、試料Ａの結晶構造中に銅イオンは存在しておらず、また、試料Ｂの結晶構造中にスズイオンは存在していないと推測される。それぞれのＸ線回折パターンを図１〜３に示す。
Evaluation 1: Confirmation of crystallinity With respect to the compounds (samples A to C) obtained in Reference Example 1, Example 1, and Comparative Example 2, X-ray diffraction data were measured by a powder X-ray diffractometer. It was found to be monoclinic with good crystallinity. In addition, since the X-ray diffraction patterns of Samples A to C are almost the same, copper ions are not present in the crystal structure of Sample A, and tin ions are present in the crystal structure of Sample B. I guess it is not. Each X-ray diffraction pattern is shown in FIGS.
評価２：組成の確認
参考例１、実施例１、比較例２で得られた化合物（試料Ａ〜Ｃ）を弗酸に溶解して、ＩＣＰ発光分析法でチタン、リチウム、銅及びスズの含有量を測定した。また、これらの試料の２５０〜６００℃の温度範囲における加熱減量を、示差熱天秤を用いて測定し、加熱減量が構造水に相当すると仮定して、試料Ａ〜Ｃの加熱減量が０．００重量％であることから、構造水が全て除去され酸化物に転化したと見なした。そして、チタンイオンの欠損は無いものとして、酸素とチタンのモル比を同定し、これと上記のチタン、リチウムの分析値とから化学組成を決定した。結果を表１に示す。実施例１は、所望の化合物が得られていることを確認した。
Evaluation 2: Confirmation of composition The compounds (samples A to C) obtained in Reference Example 1, Example 1 and Comparative Example 2 were dissolved in hydrofluoric acid, and contained titanium, lithium, copper and tin by ICP emission spectrometry. The amount was measured. Moreover, the heating loss of these samples in a temperature range of 250 to 600 ° C. is measured using a differential thermobalance, and assuming that the heating loss corresponds to structural water, the heating loss of samples A to C is 0.00. Since it was% by weight, it was considered that all of the structural water had been removed and converted to oxides. And the molar ratio of oxygen and titanium was identified as a thing without the defect | deletion of a titanium ion, and the chemical composition was determined from this and the analysis value of said titanium and lithium. The results are shown in Table 1. Example 1 confirmed that the desired compound was obtained.
評価３：高温サイクル特性の評価
参考例１、実施例１、比較例１で得られた化合物（試料Ａ、Ｂ、ａ）を、電極活物質として用いて、リチウム二次電池を調製し、その充放電特性を評価した。電池の形態や測定条件について説明する。
Evaluation 3: Evaluation of high-temperature cycle characteristics Using the compounds (samples A, B, and a) obtained in Reference Example 1, Example 1, and Comparative Example 1 as electrode active materials, lithium secondary batteries were prepared. The charge / discharge characteristics were evaluated. The battery configuration and measurement conditions will be described.
上記各試料と、導電剤としてのアセチレンブラック粉末、及び結着剤としてのポリテトラフルオロエチレン樹脂を重量比で５０：４０：１０で混合し、乳鉢で練り合わせ、引き伸ばしてシート状にした。このシートを直径１０ｍｍ、重量１０ｍｇの円形に切り出し、同じく直径１０ｍｍの円形に切り出した２枚のアルミニウム製メッシュの間に挟み、９ＭＰａでプレスして正極を作製した。 Each of the above samples, acetylene black powder as a conductive agent, and polytetrafluoroethylene resin as a binder were mixed at a weight ratio of 50:40:10, kneaded in a mortar, and stretched to form a sheet. This sheet was cut into a circle with a diameter of 10 mm and a weight of 10 mg, sandwiched between two aluminum meshes cut into a circle with a diameter of 10 mm, and pressed at 9 MPa to produce a positive electrode.
この正極を２２０℃の温度で４時間真空乾燥した後、露点−７０℃以下のグローブボックス中で、密閉可能なコイン型セルに組み込んだ。コイン型セルには材質がステンレス製（ＳＵＳ３１６）で外径２０ｍｍ、高さ３．２ｍｍのものを用いた。負極には厚み０．５ｍｍの金属リチウムを直径１２ｍｍの円形に成形したものを銅箔に圧着させて用いた。非水電解液として１モル／リットルとなる濃度でＬｉＰＦ６を溶解したエチレンカーボネートとジメチルカーボネートの混合溶液（体積比で１：２に混合）を用いた。 This positive electrode was vacuum-dried at a temperature of 220 ° C. for 4 hours, and then incorporated in a sealable coin cell in a glove box having a dew point of −70 ° C. or less. A coin type cell made of stainless steel (SUS316), having an outer diameter of 20 mm and a height of 3.2 mm was used. As the negative electrode, a metal lithium having a thickness of 0.5 mm formed into a circle having a diameter of 12 mm was used by being pressed onto a copper foil. As the non-aqueous electrolyte, a mixed solution of ethylene carbonate and dimethyl carbonate (mixed in a volume ratio of 1: 2) in which LiPF 6 was dissolved at a concentration of 1 mol / liter was used.
正極はコイン型セルの下部缶に置き、その上にセパレーターとして多孔性ポリプロピレンフィルムを置き、その上から非水電解液を滴下した。さらにその上に負極と、厚み調整用の０．５ｍｍ厚スペーサー及びスプリング（いずれもＳＵＳ３１６製）をのせ、ポリプロピレン製ガスケットのついた上部缶を被せて外周縁部をかしめて密封した。 The positive electrode was placed in a lower can of a coin-type cell, a porous polypropylene film was placed thereon as a separator, and a nonaqueous electrolyte was dropped from above. Further, a negative electrode, a 0.5 mm-thickness spacer for adjusting the thickness, and a spring (both made of SUS316) were placed thereon, and an upper can with a polypropylene gasket was put on the outer peripheral edge portion and sealed.
調製したリチウム二次電池を、６０℃の高温槽中で、充放電電流を０．２５ｍＡ、カットオフ電位１．０Ｖ〜２．５Ｖ、で５０サイクル充放電させた。２サイクル目と５０サイクル目の放電容量について、（５０サイクル目の放電容量／２サイクル目の放電容量）×１００を高温サイクル特性とした。結果を表２に示す。また、それぞれの容量維持率の推移を図３に示す。本発明が、高温サイクル特性に優れていることが判る。 The prepared lithium secondary battery was charged and discharged for 50 cycles at a charge / discharge current of 0.25 mA and a cut-off potential of 1.0 V to 2.5 V in a high-temperature bath at 60 ° C. Regarding the discharge capacity at the second cycle and the 50th cycle, (discharge capacity at the 50th cycle / discharge capacity at the second cycle) × 100 was defined as the high temperature cycle characteristic. The results are shown in Table 2. Moreover, transition of each capacity maintenance rate is shown in FIG. It can be seen that the present invention is excellent in high-temperature cycle characteristics.
本発明のチタン酸リチウムを電極活物質として電極材料に適用した蓄電デバイスは、可逆的なリチウム挿入・脱離反応が可能で、長期にわたる、しかも高温度下での充放電サイクルに対応可能であり、また高容量が期待できる蓄電デバイスである。 An electricity storage device using the lithium titanate of the present invention as an electrode active material as an electrode material is capable of reversible lithium insertion / extraction reaction, and can be used for a long-term charge / discharge cycle at a high temperature. In addition, it is an electricity storage device that can be expected to have a high capacity.
また、その製造方法も、特別な装置を必要とせず、また、使用する原料も低価格であることから、低コストで高付加価値の材料を製造可能である。 Also, the manufacturing method does not require a special apparatus, and the raw material to be used is low in price, so that a high value-added material can be manufactured at a low cost.
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